GEOLOGICAL SURVEY PROFESSIONAL PAPER 687
Cataclastic Rocks

By MICHAEL W. HIGGINS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 687

Includes field and microscope criteria for 

recognition of cataclastic rock zones, 

petrogenesis of rocks in these zones, and 

description of occurrences in the United States, 

Scotland, and New Zealand

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director

Library of Congress catalog-card No. 71-611932

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price $1.75 (paper cover)
CONTENTS

Abstract.._________________________________________

Introduction.______________________________________

Acknowledgments_ _ _______-_-_-____--_----____

Classification and nomenclature______________________

Fluxion structure________----_-_______-_-_______

Cataclastic rocks without primary cohesion _ _______

Fault breccia.._________-_-__--_-____---____

Fault gouge._________-----__________---____

Cataclastic rocks with primary cohesion. __________

Cataclasis dominant_______________________

Rocks without fluxion structure._________

Series: microbreccia-cataclasite _______

Microbreccia. __________________

Cataclasite... __________________

Rocks with fluxion structure _____________

Series: protomylonite-mylonite-ultramylonite ___-___ _____..____--_____

Protomylonite. _________________

Mylonite_ _____________________

Ultramylcnite_ _________________

Phyllonite; a variety of mylonite and 

ultramylonite. _ __________________

Neomineralization-recrystallization dominant. __

Series: mylonite gneiss (mylonite schist) -

blasto mylonite _______________________

Mylonite gneiss (mylonite schist) _____

Blastomylonite. ____________________

Protoclastic rocks.._________________________

Retrograde Cataclastic rocks_________________

Cataclastic rocks in which fusion or melting was 

important-. _ _____________________________

Pseudotachylite. _______________________

Hartschiefer_ _____________________________

Polycataclastic and polymetamorphic Cataclastic 

rocks.___________________________________

Problems of nomenclature and classification of 

Cataclastic rocks._____________________________

Mineral assemblage and chemical composition. _ 

Petrofabrics._ ______________________________

Approximate percentage and size of porphyroclasts and rock fragments (grain size) _______

Defining degree of neomineralization-recrystallization__ _ _____________________________

Field relations of cataclastic rocks.___________________

Recognition of faults and fault zones._____________

Recognition of cataclastic rocks __________________

Mafic cataclastic rocks._________________________

Association of cataclasis with felsic and silicic 

intrusive rocks.______________________________

Late mineralization of cataclastic rocks and cataclastic rock zones. __-__-_-____-----------_-_-

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Examples of cataclastic rock zones and their interpretation. __________________________________________

The San Andreas fault system, California-_________

The San Andreas fault. _____________________

Other fault zones of the San Andreas system. _ _ 

Cucamonga Canyon_._________________

The Alpine fault zone, New Zealand._____________

Towaliga, Goat Rock, and Bartletts Ferry fault 

zones, Georgia and Alabama.__________________

Towaliga fault zone_________________________

Goat Rock fault zone.______________________

Bartletts Ferry fault zone__________________

Interpretation of the zones.__________________

The Brevard zone, southeastern United States____

The Moine thrust zone, Northwest Highlands, 

Scotland.._ __________________________________

Protoclastic border, Colville batholith, Washington. ______________________________________

A hypothetical fault zone._______________________

Theoretical aspects of cataclastic rocks and processes 

involved in formation-___-____-__.____-___-_____-_

Recrystallization-neomineralization. ______-__-_-__

Relations between different kinds of cataclastic 

rocks._--____-__-_--___-_---___-_.___-__-_--_

Association of blastomylonites and mylonite 

gneisses with protomylonites, mylonites, and 

ultramylonites-. _ ________________--_-_---.

Relation of microbreccias and cataclasites to 

rocks with fluxion structure________________

Development of cataclastic textures.______________

Micas.____________________________________

Quartz._ __________________--__-____-------

Feldspars _____________-__-__-_-_-_---------

Garnet.______________-____-__-__----------

Development of fluxion structure-______-_--------

Development of compositional layering and color 

lamination.__________-___________-_----------

Original grain size differences._______---_---_-

Variable degrees of comminution___-_--_------

Criginal compositional layering_____------_-_-

Glide-fold schistosity.___-___----------------

Cataclastic metamorphic differentiation_--__-_- 

Folds in cataclastic rocks___----__----_----------

Relation of minor to major structure.______--__---

Conditions of cataclastic rock formation.__________

Glossary ________________________--_--_-------------

Annotated bibliography_______________----_---------

References cited.__----_---_------------------------

HI

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IV CONTENTS

ILLUSTRATIONS

Page.

FIGURE 1. Photographs of microbreccias..___________________________________________________________________ 5

2. Photomicrograph of a cataclasite from the Brevard zone near Atlanta, Ga_____________________________ 6

3. Microdrawings of protomylonite__________________________-__-___---__-----_---_--_______________ 8

4. Photomicrographs of protomylonite-__________________--_____-----_-_--------_-__---_--___________ 10

5. Photomicrographs of a mylonite from the San Andreas fault zone_-__-__---__---_--___--__-______-____ 12

6. Photographs and photomicrographs of a suite of four specimens showing progressive mylonitization_______ 15

7. Schematic sketches showing textures of protomylonite, mylonite, and ultramylonite_____________________ 16

8-12. Photomicrographs of:

8. Mylonite_______________________________________________________________________________ 17

9. Lapworth's original "mylonites" and "augen gneisses"______________________________.________ 18

10. Ultramylonites__________________________________________________________________________ 19

11. Phyllonite from the Brevard zone near Atlanta, Ga_-_----------------------_------_-___-____ 20

12. Mylonite gneisses_______________________________________________________________________ 23

13. Diagram showing relations between some mylonite gneisses or mylonite schists and blastomylonite._______ 23

14-17. Photomicrographs of:

14. Blastomylonites-_______________________________-___-_-__-_--___-____--__-______________ 24

15. Diaphthoritic blastomylonites____-_______--__-___--------------------_____-___--__________ 26

16. Pseudotachylites________________________________________________________________________ 28

17. Brecciated mylonite-_______________________-___------------__-____-_-___-___--___-______ 31

18. Photographs of blastomylonites from the Goat Rock fault zone in Alabama_._ _________________________ 34

19. Photographs and photomicrographs of welded tuff from the San Juan Mountains, Colo___ _______________ 36

20. Microdrawings of a metarhyolite from near Waterville, Maine____-_-_-_--______--_-________________ 38

21. Photograph of banded chert from the Mojave Desert in California __________________________________ 39

22. Photograph of quartzo-feldspathic blastomylonite from the Goat Rock fault zone in Alabama.___________ 39

23. Map showing major fault zones of the San Andreas system.._________________________________________ 40

24-28. Generalized geologic maps of:

24. The Cucamonga Canyon area, San Gabriel Mountains, Calif_________________________________ 43

25. The Alpine fault zone, New Zealand_______-______-_____-____-__--_--______-___-___________ 45

26. Towaliga, Goat Rock, and Bartletts Ferry fault zones_______________________________________ 47

27. Brevard zone, southeastern United States_______-______________-----_-_--__---_-___________ 50

28. The Moine thrust zone, Scotland__-__---__--______---_--___--_---_-___--__--_-__-_________ 52

29. Index map and geologic map of the border of the Colville batholith, Washington.______________________ 55

30. Geologic map of a hypothetical fault zone_________________________________________________________ 56

31. Diagrams showing development of a braided fault zone______________________________________________ 58

32. Schematic diagram showing one possible mechanism for production of different types of cataclastic rocks_ 59

33. Diagram showing development of glidefold schistosity_______________________________________________ 62

34. Photographs showing intrafolial folding in blastomylonite.___________________________________________ 66

35. Photographs showing intraf olial folds in obsidian and blastomylonite- _________________________________ 69

36. Drawings showing relations of various cataclastic textures in thin section, hand sample, outcrop, and on map. 70

TABLES

Page. 

TABLE 1. Classification of cataclastic rocks_________________________-__________-____--___-___----___------_- 3

2. Generalized reaction of various minerals to cataclasis______________________________________________ 60
CATACLASTIC ROCKS

By MICHAEL W. HIGGINS

ABSTRACT

Cataclastic rock is a general term for all rocks produced by 

cataclasis. Cataclastic rocks can be divided into two main 

types: (1) those without primary cohesion; and (2) those with 

primary cohesion. Oataclastic rocks without primary cohesion 

are fault breccia and fault gouge. Cataclastic rocks with primary cohesion are basically metamoipMc rocks and owe their 

cohesion to a combination of crystalloblastic and Cataclastic 

processes. They can be divided into two main categories on 

the basis of whether cataclasis was dominant over neomineralization-recrystallization (crystalloblastic processes) in their 

formation, or vice versa. Rocks in which cataclasis was dominant over neomineralization-recrystallization can be further 

divided on the basis of whether or not they possess fluxion 

structure, a cataclastic foliation. Rocks without fluxion structure 

are micro~breccia and cataclasite. Rocks with fluxion structure 

are protomylonite, mylonite, and ultramylonite. Pliyllomte is 

a variety of mylonite or ultramylonite. Rocks in which 

neomineralization-recrystallization was dominant over cataclasis also have fluxion structure. They are mylonite gneiss or 

mylonite schist and T)lastomylonite. All terms in italics are 

defined in this paper.

Protoclctstic rocks are rocks produced by protoclasis, a variety 

of cataclasis. Protoclasis applies to cataclasis of an igneous 

body or parts of an igneous body, resulting from late intrusive 

movements of or within that body, generally before it has 

completely crystallized.

Diaphthoresis or retrograde metamorphism is a process which 

is not necessarily related to or associated with cataclasis. Diaphthorites are retrograde metamorphic rocks.

Pseudotachylite is a rock formed by melting of already-hot 

rocks because of frictional fusion during faulting near igneous 

intrusions.

Rocks which record a history of two or more separate 

periods of metamorphism are poly metamorphic rocks. Rocks 

which have been subjected to two or more periods or episodes 

of cataclasis are poly cataclastic rocks.

Cataclastic rocks can best be classified quantitatively by 

using approximate size of most of the porphyroclasts or fragments combined with approximate percentage of these features.

In outcrop and hand sample cataclastic rocks may be easily 

mistaken for metasedimentary, metavolcanic, volcanic, or finegrained intrusive rocks. In many cases, overlooking the presence 

of cataclastic rocks has led to erroneous interpretations of 

structure, stratigraphy, and geologic history.

Recognition of cataclastic rocks in the field is often closely 

tied with recognition of fault zones, and vice versa. Criteria 

are given for recognition of fault zones and cataclastic rocks

and for distinguishing cataclastic rocks from some of the 

rocks with which they are easily confused. Any rock suspected 

of being cataclastic should be examined in thin section.

Cataclastic rocks are commonly felsic and (or) silicic in composition because the majority of rocks in mobile metamorphic 

terranes are of this composition, and because mafic rocks 

commonly recrystallize so readily that they seldom preserve 

cataclastic textures. Felsic and (or) silicic intrusive rocks 

commonly utilize faults and fault zones as pathways of easy 

intrusion; there is a remarkable coincidence of cataclasis and 

small felsic and silicic intrusive rocks. Late mineralization is 

also common along fault zones, and many cataclastic rocks show 

secondary mineralization.

Examples of cataclastic rock zones are the San Andreas fault 

system, California-Nevada (particularly the San Andreas fault 

and zones in the San Gabriel Mountains), the Alpine fault 

zone, New Zealand; the Towaliga, Goat Rock, and Bartiette 

Ferry fault zones, Georgia and Alabama; the Brevard zone, 

southeastern United States, the Moine Thrust zone, Scotland, 

and the border of Colville batholith, Washington. Brief descriptions of these zones and their rocks are given in this paper. 

A hypothetical zone can be constructed using these zones and 

others as a basis.

Associations of various rocks with fluxion structure, but with 

varying degrees of neomineralization-recrystallization are tentatively interpreted as indicating concurrent formation under 

differing physical and (or) chemical conditions. Rocks without fluxion structure commonly formed later than the fluxion 

structured rocks with which they are associated.

Cataclastic texture develops progressively with increase of 

comminution and shearing and can be demonstrated by different rocks in the same zone. Different minerals react differently, and a crude "cataclastic reaction series" can be constructed 

based on empirical observations.

Fluxion structure should be considered separate from color 

lamination and (or) compositional layering. Fluxion structure 

refers only to cataclastic foliation, developed by shear and flowage. Compositional layering and color lamination probably develop in various ways : by preferred comminution due to original 

grain-size differences, by varying degrees of comminution, by 

original compositional layering, by glide-fold schistosity, and by 

cataclastic metamorphic differentiation.

Cataclastic metamorphic differentiation is a process by which 

minerals react differently to shearing and tend to segregate 

on this basis. It has been proven in a number of cases, where 

compositionally layered cataclastic rocks have been produced 

from unlayered parent rocks.

Folds in cataclastic rocks have been described and illustrated 

by many workers. Most of the cataclastic rocks with folds can
CATACLASTIC ROCKS

be shown to be blastomylonites or mylonite schists or gneisses.

Cataclastic rocks at the thin section or hand sample scale 

may reflect structural patterns at map scale.

Conditions of cataclastic rock formation are largely speculative. Fluid content and pressure may be quite important to 

the formation of cataclastic rocks and to determining the types 

of rocks formed. Experimental data can, at this time, only be 

applied in a very general way when attempting to determine 

the conditions of cataclastic rock formation.

INTRODUCTION

Since Lapworth (1885, p. 559) first used and defined 

the term mylonite (from the Greek "mylon" a mill), 

the terminology of cataclastic rocks has been considered 

by many workers. Three papers in particular Waters 

and Campbell, 1935; Christie, 1960; and Reed, 1964 

have been valuable in reducing the confusion resulting 

from misuse and lack of awareness of terms. Despite 

these papers, a geologist studying cataclastic rocks for 

the first time still finds many confusing terms. He is 

hampered by multiple terms for the same type of rock 

and by single terms for rocks of widely varying characteristics and origins. Even those experienced in cataclastic -rock nomenclature find the classifications and 

terms confusing and difficult to apply. There is no 

single article in the literature where the uninitiated 

can learn cataclastic rock nomenclature, theory, and 

characteristics or where the more experienced worker 

can turn for reference and comparison. The purpose 

here is to provide such a paper.

Few new terms are introduced, but terms already 

in use are selected on the basis of applicability, general 

usage, and historical precedence. In some cases my own 

preferences and prejudices are unavoidably applied.

Probably tlhe greatest source of confusion in geologic 

literature concerning cataclastic rocks (as implied by 

Knopf (1931), and stated by Waters and Campbell 

(1935) and Christie (I960)) is the use of the term 

mylonite in a general or genetic way to include almost 

any cataclastic rock.

Lapworth (1885, p. 559) defined mylonites as "microscopic pressure-breccias with fluxion structure, in which 

the interstitial dusty, siliceous, and kaolinitic paste has 

only crystallized in part," He elaborated on the formation and characteristics of mylonites and made a distinction between this restricted type of cataclastic rock 

and others of general similarity but with different characteristics and origins. Thus Lapwortfh intended, and 

most later workers have agreed, that the term mylonite 

should be restricted to one particular type of cataclastic 

rock. As Waters and Campbell (1935, p. 476) stated, 

although other terms are available for general or tectonic usage, "no other term adequately fills the place 

Lapworth assigned to mylonite." The use of this term

to includs all superficially similar rocks probably results chiefly from lack of a good general term.

Waters and Campbell (1935, p. 476) suggested cataclastic rock as a general term for all rocks produced by 

cataclasis. Many workers have used this term (including Knopf (1931), Hsu (1955a), Eeed and Bryant 

(1964)), sometimes without emphasis. Only Holmquist 

(1910) used it in a more restricted sense. The term has 

disadvantages in that it includes fault breccias and 

gouge formed under conditions generally not considered 

applicable to mylonites, mylpnite gneisses, blastomylonites, cataclasites, and other cataclastic rocks with 

primary coherence. However, usage and the advantage 

of a generally understood term which includes the various rock types under consideration seem to outweigh the 

disadvantages. Definitions of cataclastic vary slightly, 

but the following is typical: "Rock deformation accomplished by fracture and rotation of mineral grains or 

aggregates; granulation." (Am. Geol. Inst, 1957). I 

propose that cataclastic rock be used as a general term 

for all rocks produced by cataclasis including mylonites, 

protomylonites, blastomylonites, fault breccias, etc., and 

that the term mylonite be restricted, as originally intended, to rocks with the characteristics enumerated by 

Lapworth (1885, p. 559), restated by Waters and Campbell (1935, p. 474-475, 478), and described and defined 

in this paper.

ACKNOWLEDGMENTS

Willard H. Grant of Emory University introduced 

me to cataclastic rocks and guided me in their study 

along part of the Brevard zone. It was Grant who first 

suggested that work was needed on their nomenclature 

and classification. I am also indebted to the U.S. Geological Survey for support during my study of the 

Brevard zone, particularly to Jarvis B. Hadley who 

visited me in the field and with whom I discussed many 

aspects of cataclastic rocks.

I am especially indebted to Aaron C. Waters of the 

University of California at Santa Cruz, who furthered 

my interest in cataclastic rocks, made his collection from 

many fault zones available to me, and was always available for discussions during the years 1965-67, when 

I was a graduate student at the University of California, Santa Barbara.

Excellent suites of cataclastic rocks were provided by 

C. B. Sclar, A. R. Philpotts, W. H. Grant, and K. J. 

Hsu. Grant and Hsu guided me on trips to the Towaliga 

fault zone in Georgia and the Cucamonga Canyon fault 

zone in California, respectively; and R. D. Bently 

guided me along the Goat Rock, Towaliga, Bartletts 

Ferry, and Brevard zones in Alabama.

W. H. Grant, A. C. Waters, N. S. MacLeod, and J. B. 

Hadley read early drafts of this paper and made many
CLASSIFICATION AND NOMENCLATURE

valuable suggestions. I wish to express special thanks to 

David A. Brew, whose critical review of the manuscript 

was so complete and constructive that it resulted in a 

complete revision incorporating many of his suggestions. Finally, many geologists provided me with reprints of their papers in some cases their last copy.

CLASSIFICATION AND NOMENCLATURE

My classification of cataclastic rocks is outlined in 

table 1.

These terms are all that are necessary to name and 

classify the known types of cataclastic rocks. The following definitions and discussions are keyed to this 

classification. Terms that I have chosen to eliminate 

from the classification are defined and discussed in the 

glossary.

Most of the basic "structural" terms used in this paper 

are defined by Turner and Weiss (1963). Other terms 

are defined in the glossary. Because the term fluxion 

structure is such an integral part of the classification 

and definitions, it is defined first.

FLUXION STRUCTURE

Definition. Fluxion structure (fluxion texture) : 

Cataclastically produced directed penetrative texture 

or structure commonly involving a family or set of ssurfaces; cataclastic foliation. May be visible megascopically or only microscopically. Does not necessarily 

involve compositional layering or lamination, although 

many examples do show such layering.

Discussion. Lap worth (1885, p. 559) first used the 

term "fluxion structure" in the original definition of 

mylonite. He gave 110 definition of the structure or 

texture other than that incidental to his description of 

mylonite:

* * * a finely-laminated schist * * * the lamination being 

defined in minute inosculating lines (fluxion lines) of kaolin or 

chloritic material and secondary crystals of mica.

Later geologists have used the term without defining 

it, although nearly all have given illustrations showing 

the texture. There is, and has been, confusion as to 

whether or not -fluxion structure requires compositional 

layering or color lamination. As discussed in a later 

section, many mylonites, ultramylonites, and blastomylonites do have such layering, but many protomylonites and mylonite gneisses clearly transitional 

from undeformed, and in many oases unlayered, parent 

rocks into layered cataclastic rocks have only a cataclastic foliation or, in their finer grades, an incipient 

layering. Many mylonites, ultramylonites, blastomyl'onites, and phyllonites have no compositional layering either, but the "tectonic" significance of their 

cataclastic foliation is identical to that of the layered 

varieties.

Technically, -fluxion is a synonym for flow, and indeed 

the fluxion structure of cataclastic rocks commonly 

resembles the flow structure or flow texture common to 

silicic and felsic volcanic rocks. Lapworth's choice of 

the term reflects his idea that the comminuted matrix 

of mylonites "flowed" around the porphyroclasts in 

differentially-moving layers perhaps separated by the 

thin "inosculating lines" marked by concentrations of 

fine micaceous minerals.

Because a definition of -fluxion structure that requires 

the presence of color or compositional lamination 

would necessitate an unnatural separation between rocks 

such as protomylonite and mylonite, where there is 

ample evidence of a gradual transition, and between 

rocks such as layered and unlayered mylonites whose 

fabrics are otherwise identical, and because I consider

TABLE 1. Classification of cataclastic rocks

[Porphyroclastic, protoclastlc, diaphthoritic, pseudotachylitic, polymetamorphic, polycataclastic, phyllitic, and other terms are used as modifiers. See

text and glossary]

porphyroclasts Approximate volume percent 

in fluxion rocks with structure, 

or 

Approximate fragments volume percent fluxion rocks without structure. in

V AOJ (J1 (J\ I-1 h" o

Rocks without 

primary cohesion

Fault breccia

Fault gouge

Rocks with primary cohesion

Cataclasis dominant over 

neomineralization-recrystallization

Rocks without 

fluxion structure

Microbreccia

Cataclasite

Rocks with 

fluxion structure

Protomylonite

Mylonite

Ultramylonite

Phyllonite 

(variety)

Neomineralizationrecrystallization 

dominant over cataclasis

Rocks with 

fluxion structure

Mylonite gneiss 

(mylonite schist)

Blastomylonite

Visible to & * 

naked eye ~£ .o

>0.2mm 

<0.2mm

03 " " 

~c3 o

_fi Z

o "-^ 

a

« S

=5.2 

S X!

S 03

S g 

S.S

All rocks are gradational
CATACLASTIC ROCKS

fimvion structure or c'ataclastic foliation to have a different significance from color or compositional layering or 

laminaition, the two features are separated in this paper 

and the definition above is proposed for fiuseion structure.

CATACLASTIC ROCKS WITHOUT 

PRIMARY COHESION

Near-surface faulting is generally associated with low 

confining pressures and low temperatures and may produce rocks of varying degrees of granulation and brecciation. The degree or fineness of the granulation 

depends on the confining pressure, original character of 

the rock(s) involved, amount of movement, and duration of movement. The resulting disrupted rocks range 

from coarse breccias, in which the original rock is only 

slightly disrupted, to fine gouge, in which the rock is 

reduced to a paste. All of these rocks have one main feature in common: they lack primary cohesion. Except for 

the effects of secondary processes, which may cement 

the disrupted fragments into unified rock they would be 

without cohesion. The rocks involved may be sedimentary, igneous, or metamorphic, but the disruption or 

granulation occurred at low temperatures and pressures. 

Gouge and breccias have been reported along all types of 

faults (see Hill, 1959) and have been mentioned in 

many publications since the early days of geologic 

science.

Such rocks have generally been considered separately 

from mylonites, mylonite gneisses, cataclasites, ultramylonites, etc., because of their lack of primary cohesion and their implied low pressure-low temperature 

origins (see Knopf, 1931; Waters and Campbell, 1935; 

Christie, 1960). They are briefly considered here only 

because there probably exists a complete transition from 

noncohesive to cohesive cataclastic rocks.

FAULT BRECCIA

Definition. Fault breccia: A rock composed of angular to rounded fragments, formed by crushing or grinding along a fault. Most fragments are large enough to be 

visible to the naked eye, and they make up more than 

30 percent of the rock. Coherence, if present, is due to 

secondary processes.

FAULT GOUGE

Definition. Fault gouge: Pastelike rock material 

formed by crushing or grinding along a fault. Most individual fragments are too small to be visible to the

naked eye, and fragments larger than the average 

groundmass grains make up less than 30 percent of the 

rock. Coherence, if present, is due to secondary 

processes.

CATACLASTIC ROCKS WITH 

PRIMARY COHESION

Deep-seated faulting occurs with generally high confining pressures. The rocks produced in the fault zones, 

though extremely granulated, have remained cohesive, 

As with, the noncohesive fault gouges and breccias, 

confining pressure, original character of the rock(s), 

and amount and duration of movement are important 

determinants of the product, but with the cohesive 

cataclastic rocks the effects of temperature, fluids, and 

other variables must also be considered. Regardless of 

the theoretical possibilities and implications of origin, 

the rocks produced have in common a primary coherence they needed no secondary cementation to become indurated. Cataclastic rocks with primary 

cohesion are really metamorphic rocks.

In contrast to the noncohesive gouges and breccias 

which occur in all kinds of terranes, cohesive cataclastic 

rocks are commonly associated with plutonic and metamorphic rocks because of the environment necessary for 

their formation.

Cataclastic rocks with primary cohesion can be divided into three gradational categories (table 1) : (1) 

those in which neomineralization-recrystallization 

(constructive processes), though present, is subordinate 

to cataclasis (destructive processes); (2) those in which 

neomineralization-recrystallization is dominant over 

cataclasis; (3) retrograde cataclastic rocks. In addition, there is a special category of rock that has been 

melted, formed by cataclasis of rock that was hot before 

faulting. This type is not gradational to the others.

CATACLASIS DOMINANT

ROCKS WITHOUT FLUXION STRUCTURE

SERIES: MICROBRECCIA-CATACLASITE 

MlCROBRECCIA

Definition. Microbreccia: An intensively fractured 

but unground (fragments have not rolled) cohesive 

breccia in which the grains and fragments are without 

form orientation. Fragments may range from megascopic to about 0.2 mm and are separated by finer grained 

material. Fragments larger than 0.2 mm make up more 

than about 30 percent of the rock.

Figure 1 shows typical microbreccias.
CLASSIFICATION AND NOMENCLATURE

B

C

FIGURE 1. Microbreccias. A, From a dikelike fault zone in the North Carolina Piedmont, collected by J. F. Conley, Virginia 

Div. Mineral Resources. B, Photomicrograph of a microbreccia from the Brevard zone near Atlanta, Ga.; crossed polarizers. 

Parent rock was probably a "granfe." C, Photomicrograph of a large microfaulted microelme grain in a microbreccia from 

the northwest edge of the Brevard zone near Atlanta, Ga.; crossed polarizers. Note the undirected nature of the cataclasis 

in A and C.
CATACLASTIC ROCKS

FIGURE 2. Photomicrograph of a cataclasite from the Brevard zone near Atlanta, Ga.; crossed polarizers. Note the undirected 

nature of the cataclasis. Grain or fragment size about the same as in mylonites. Parent rock probably a "granite."

Discussion. The term microbreccia was originally 

used by Tyrrell (1926, p. 281-285; he used micro-breccia}. Tyrrell (1926) also used crush-breccia, for essentially the same rocks. Microbreccias might fit into 

Quensel's (1916) definition of kakirite (although microbreccias generally lack lenticularity), but Holmquist (1910) used kakirite almost synonymously with 

mylonite. Microbreccia is an adequate term for the rock 

described and is less exotic than similar terms. The size 

grade has been introduced into the definition in order 

to distinguish microbreccia from cataclasite.

CATACLASITE

Definition. Cataclasite: An aphanitic, structureless 

cohesive cataclastic rock in which most of the fragments 

are less than 0.2 mm, and make up less than 'about 30 

percent of the rock. Essentially like a mylonite but lacks 

fluxion structure.

Figure 2 shows a typical cataclasite.

Discussion. Cataclasite was first defined by Grubenmann and Niggli (1924). Tyrrell (1926, p. 285), following Grubenmann and Niggli (1924), stated:

* * * when the product is a structureless rock powder, in which 

a few porphyroclasts may have survived, the term cataclasite is 

used in preference to mylonite, as the latter connotes a rolling 

out or milling of the material with resulting parallel structure.

The definition given in this paper is essentially that of 

Waters and Campbell (1935, p. 477) ; a size grade has 

been added to differentiate the rock from microbreccia. 

Cataclasite has been used in this sense by most workers 

(Grubenmann and Niggli, 1924; Tyrrell, 1926; Knopf, 

1931; Waters and Campbell, 1935; Christie, 1960, 1963; 

Hsu, 1955b; Reed, 1964; Higgins, 1966). Schoch (1962) 

has used cataclasite both in the sense of this paper and 

as a general term for all cataclastic rocks.
CLASSIFICATION AND NOMENCLATURE

ROCKS WITH FLUXION STRUCTURE

SERIES: PROTOMYLONITE-MYLONITE-ULTRAMYLONITE 

PROTOMYLONITE

Definition. Protomylonite: A coherent crush-breccia 

composed of megascopically visible fragments that are 

generally lenticular and are separated by megascopic 

gliding surfaces filled with finely ground material. The 

fragments, or "megaporphyroclasts," make up more 

than about 50 percent oi the rock. Protomylonite commonly resembles conglomerate or arkose on weathered 

surfaces. Features of the original rock, such as stratification and schistosity, may be preserved in the larger 

fragments.

Figures 3 and 4 show typical protomylonites.

Discussion. Backlund (1918, p. 195-199) created the 

term protomylonite to describe rocks from Cape 

Chelyuskin-Sarya on the northern tip of Asia. Neither 

Lapworth (1885) nor Teall (1918, see following section on mylonite, this paper) mentions any names for 

this type of rock, but from Teall's descriptions and 

photomicrographs, the rocks transitional from Lewisian gneiss to mylonite can be recognized as protomylonites (fig. 9). With one exception (Holmes, 1928, 

p. 190), there has been little disagreement over the 

definition and characteristics of protomylonite. However, some geologists were not aware of the term and 

created new names for the same type of rock. Thus, 

protomylonite is rougK.y equivalent to kakirite as defined by Quensel (1916), to the "nodular mylonite" of 

Eaguin (1926), and to the "fissured and brecciated 

granite" of Termier and Boussac (1911). Protomylonite is preferable to the other terms because it fits 

into the series mylonite-ultramylonite best and is more 

concisely descriptive of the rock represented.

MYLONITE

Definition. Mylonite: A coherent microscopic pressure-breccia with fluxion structure that may be megascopic or visible only in thin section and with porphyroclasts generally larger than 0.2 mm. These porphyroclasts make up from about 10 to about 50 percent of the rock. Mylonites generally show recrystallization and even new mineral formation (neomineralization) to a limited degree, but the dominant texture is 

cataclastic.

Figures 5, 6, 7, 8, 9 show typical mylonites.

Discussion^ The above definition is essentially that 

of Lapworth (1885, p. 559), with modifications based 

on papers by Staub (1928), Knopf (1931), Waters and 

Campbell (1935), and Christie (1960), and on my own

work. The parts of Lapworth's paper dealing specifically with mylonite and related cataclastic rocks are 

quoted below:

The most intense mechanical metamorphism occurs along 

the grand dislocation (thrust) planes, where the gneisses and 

pegmatites resting on those planes are crushed, dragged, and 

ground out into a finely-laminated schist (Mylonite, Gr. mylon, 

a mill) composed of shattered fragments of the original crystals of the rock set in a cement of secondary quartz, the lamination being defined by minute inosculating lines (fluxion lines) 

of kaolin or chloritic material and secondary crystals of mica. 

Whatever rock rests immediately upon the thrust-plane, whether 

Archean, igneous, or Paleozoic, etc., is similarly treated, the 

resulting mylonite varying in colour and composition according to the material from which it is formed.

* * * While the mylonites may (be described as microscopic 

pressure-breccias with fluxion-structure, in 'which the interstitial dusty, siliceous, and kaolinitic paste has only crystallized 

in part; the augen-scMsts are pressure-breccias, with fluxionstructure, in which the whole of the interstitial paste has crystallized out. The mylonites were formed along the thrust-planes, 

where the two superposed rock-systems moved over each other 

as solid masses; the augen-scMsts were probably formed in the 

more central parts of the moving system, where the 'all-surrounding weight and pressure forced the rock to yield somewhat 

like a plastic 'body. Between these augen-schists there appears 

to be every gradation, on the one hand to the mylonites, and 

on the other to the typical mica-schists composed of quartz and 

mica.

Lapworth made no attempt to illustrate mylonites or 

mylonite texture, but Teall (1918, p. 2) published photomicrographs of what might be called the "type mylonite," with the following statement:

During our first day's excursion [in 1883] in the Eribol district he [Lapworth] led us to Arnabol Hill, showed us Archean 

gneiss resting almost horizontally on Cambrian quartzite, explained that this was due to an overthrust fault, and, pointing 

to the lower portion of the gneiss, used words to this effect: If 

you want to study the microscopic structure of rolled out gneiss 

take a specimen from there. That was my first introduction to 

a special type of dynamic metamorphism, and here is the specimen I collected on that occasion. . . . This is the kind of rock 

for which Prof. Lapworth subsequently proposed the term 

mylonite.

Teall's (1918, p. 2) photomicrographs are reproduced 

here as figure 9. He also illustrated and described rocks 

from Lapworth's Eribol district showing the transition 

from Lewisian gneiss to mylonite. Other cataclastic 

rocks from the Eribol district have been sketched by 

Harker (1950, p. 168-169). Harker's illustrations also 

show the complete transition from Lewisian gneiss to 

mylonite.

From Lapworth's (1885) descriptions, Teall's (1918) 

photomicrographs, and Harker's (1950) sketches we 

get a good picture of the rock the original term mylonite was intended to describe.
8

CATACLASTIC ROCKS 

A

Unrecrystallized plagioclase 

grain showing twinning 

and fractures

Bent twin lamellae 

in Unrecrystallized 

plagioclase

Thin "wispy" train 

of muscovite

Muscovite

'Mosaic" of crystal - 

loblastic quartz and 

feldspar

Streak" of finegrained quartz and 

feldspar

1 mm

"Train" of muscovite 

at edge of quartz grain

Quartz grain (note

severe strain and 

"semi-spindle" shape)

Note 

strain

Muscovite

Recrystallized mortar 

(note strain)

Strained quartz grain 1 mm

Rounded quartz grain

Recrystallized quartz, 

mortar

Extremely elongated 

quartz grain
CLASSIFICATION AND NOMENCLATURE 9

The definition of mylonite suggested in this paper 

differs slightly from those of earlier papers (Knopf, 

1931; Waters and Campbell, 1935; Christie, 1960) in 

stressing the presence of neomineralization-recrystallization, in stating that fluxion structure may be visible 

only in thin section, arid in addition of a size grade. Tihe 

neomineralization-recrystallization aspect will be discussed in detail in a later section of this paper. The 

fluxion-structure aspect represents a source of possible 

contention. Was it Lapwortli's intention that mylonite 

be restricted to rocks showing fluxion structure in outcrop, or may this feature be visible only in thin section ? 

Lapworth did not make a clear point of this, and later 

geologists have also neglected to do so (Lapworth, 

1885, p. 559; Knopf, 1931, p. 9-14; Waters and Campbell, 1935, p. 4Y4-4Y6, 478; Christie, 1960, p. 80-85; 

Reed, 1964, p. 648). The "type mylonites" are laminated 

and show fluxion structure in outcrop (Lapworth, 1885; 

Teall, 1918; Christie, 1960). However, although mylonite structure is correctly identifiable in many cases 

without thin section work, it is definitely identifiable 

only in thin section. Kocks with megascopic fluxion 

structure almost invariably have microscopic fluxion 

structure, and fluxion structure that is only visible in 

thin section has the same significance as megascopically visible fluxion structure. It is clear from Lapworth's and most subsequent definitions that fluxion 

structure in thin section is a requisite for a rock to be 

called mylonite. Therefore, I propose that possessing 

microscopic fluxion structure qualifies a rock to be caljled 

mylonite.

ULTRAMYLONITE

Definition. Ultramylonite: A coherent, aphanitic, 

ultra-crushed pressure breccia with fluxion structure, 

in which, most of the porphyroclasts have been reduced 

to breccia streaks and the few remaining porphyroclasts 

are smaller than 0.2 mm. These porphyroclasts make up 

less than about 10 percent of the rock. As in protomylonite and mylpnite, recrystallization-neomineralization 

is present but is subordinate to cataclastic texture. In 

hand specimen and outcrop ultramylonites are commonly homogeneous-appearing rocks (although many 

have compositional layering), easily confused with 

chert, quartzite, or felsic volcanic rock. Ultramylonite 

represents the highest stage in intensity of mylonitization in the series protomylonite-mylonite-ultramylonite.

Figure 10 shows typical ultramylonites.

FIGURE 3. Microdrawings of protomylonite. A, From Moscow 

Mountain, Wash. Parent rock was a "granite." B, Developed 

from micaceous quartzite of the Weaverton Formation in the 

Virginia Blue Ridge. Note lensoid shape of quartz grains and 

the finely comminuted "mortar" in the interstices. Both drawings with polarizers crossed.

Discussion. Ultramylonite was first defined by Staub

(1915) and subsequently elaborated upon by Quensel

(1916). Both authors defined ultramylonite as a rock in 

which all porphyroclasts have been entirely reduced to 

breccia streaks. Staub (1928), however, later reconsidered and refined his definition, stating: "the extreme 

form of ultramylonitization has been reached when the 

matrix appears as a glass-like substance and the porphyroclasts have diminished to a diameter less than 

0.02 mm." (translation). Waters and Campbell (1935, 

p. 481) followed the earlier definitions almost verbatim, 

but their photomicrographs of ultramylonites (p. 489, 

fig. 6; p. 490, fig. 7; p. 492, fig. 8) all show easily identifiable porphyroclasts (see fig. 1TC). In fact, Quensel's 

(1916, PI. 5, fig. 2) photomicrographs (also used by 

Knopf, 1931, p. 11, fig. 3) also show porphyroclasts. 

Perhaps the fact that Staub's (1928) refined definition 

using the 0.02 mm. limit refers to the "extreme form of 

ultramylonitization" has been overlooked. In the ultramylonites that I have studied and in photomicrographs 

of ultramylonites in the literature, the division between 

mylonite and ultramylonite occurs when the porphyroclasts have reached a diameter of about 0.2 mm. I propose that rocks in which most of the porphyroclasts 

are greater than 0.2 mm in diameter should be called 

mylonite, and those in which most of the porphyroclasts 

are less than 0.2 mm in diameter should be called 

ultramylonite.

In addition to the size of the porphyroclasts there is 

the problem of their relative abundance. Hsu (1955b, p. 

251-252) modified Waters'and Campbell's (1935) definitions of protomylonite, mylonite, and ultramylonite 

to include percentage of "aphanitic paste" relative to 

the bulk of the rock. Under his definitions:

Mylonite is a microbreccia produced by the milling down of 

the original rock material into an aphanitic paste which constitutes more than 50 percent, and less than 95 percent, of 

the bulk of the rock."

Protomylonite is a mylonitic rock in which the aphanitic 

paste constitutes less than 50 percent of the bulk of the rock, 

and ultramylonite is a mylonitic rock in which, the aphanitic 

paste constitutes more than 95 percent of the bulk of the 

rock.

However, given the same original rock type, a cataclastic product with only a few percent porphyroclasts 0.21 

mm in diameter in a very finely granulated matrix has 

probably been milled more than one with a large percentage of porphyroclasts 0.15 mm in diameter, and, 

using Hsu's definitions, a rock with only 10 percent 

"aphanitic paste" or matrix, in which the porphyroclasts were all ground down to less than 0.2 mm, has 

probably been milled more than one with 55 percent
10 CATACLASTIC ROCKS

B
CLASSIFICATION AND NOMENCLATURE 11

matrix and large porphyroclasts. The relative percentage of porphyroclasts, or the percentage of matrix, to 

the bulk of the rock, is extremely important in defining 

mylonite and ultramylonite. The percentages added to 

the definitions of all of the rocks are based on my empirical observations.

Neither Staub (1915,1928) nor Quensel (1916) made 

a real point of the presence or absence of lamination 

or fluxion structure in ultramylonites, but all photomicrographs of "typical" ultramylonites show fluxion 

structure (Quensel, 1916, PI. 5, fig. 2; Knopf, 1931, fig. 

3; Waters and Campbell, 1935, figs. 6, 7, and 8; see fig. 

10 of this paper).

PHYLLONITE: A VARIETY OF MYLONITE AND ULTRAMYLONITE

Definition. Phyllonite (phyllite-mylonite) : A rock 

of phyllitic appearance formed by mylonitization of an 

originally coarser grained rock.

Figure 11 shows typical phyllonites. Because of confusion between the terms phyllonite and diaphthorite, 

phyllonite is discussed after diaphthorite, in a later 

section.

NEOMINERALIZATION-RECRYSTALLIZATION 

DOMINANT

SERIES: MYLONITE GNEISS 

(MYLONITE SCHIST)-BLASTOMYLONITE

MYLONITE GNEISS (MYLONITE SCHIST)

Definition. Mylonite gneiss (mylonite schist): A 

coherent rock intermediate between a protomylonite or 

coarse mylonite and a crystalline gneiss or schist because 

its texture is the result of combined cataclastic and 

crystalloblastic processes. Augen structure is characteristic, the augen generally being porphyroclasts or 

crushed aggregates of felsic minerals. The augen, although commonly recrystallized, preserve evidence of 

cataclastic texture by their shapes and by the crush

FIGURE 4. Photomicrographs of protomylonite. A, From Cucamonga Canyon, San Gabriel Mountains, Calif. Large subhedral, zoned feldspars are surrounded by a matrix consisting 

chiefly of quartz and micas, with some finely ground feldspar. 

See Examples section of text (p. 42). Also note "flamboyant" 

quartz, and degree of recrystallization. This rock is fairly well 

recrystallized for a protomylonite. B, From the San Andreas 

fault zone near Crystal Springs Lakes, Calif, (collected by 

A. C. Waters). This rock is relatively fine grained for a protomylonite, and when compared with A, it illustrates the 

range in grain size covered by the term protomylonite. Parent 

rock was a meta-arkose. Both with crossed polarizers.

trails commonly associated with them; the surrounding 

groundmass has been recrystallized and (or) neomineralized, although it also may show palimpsest cataclastic texture. Most of the porphyroclasts are larger 

than about 0.5 mm, and they make up more than about 

30 percent of the rock.

Figure 12 shows typical mylonite gneisses and mylonite schists.

Discussion. Quensel (1916, p. 99, 101-102) introduced the term mylonite gneiss. The term is equivalent 

toLapworth's (1885, p. 559) augen schist (Knopf, 1931, 

p. 12; Waters and Campbell, 1935, p. 477,479; Christie, 

1960, p. 82; Eeed, 1964, p. 650). Lapworth described 

and defined augen schists and contrasted them with 

mylonites. He indicated that there is complete gradation between the two rock types. Lapworth's term takes 

historical precedence over mylonite gneiss, but the use 

of the term augen gneiss might lead to confusion with 

ordinary products of progressive regional metamorphism in which the augen are commonly porphyroblasts.

There is no common agreement among geologists as 

to what kind of rock should be called gneiss and what 

kind should be called schist, despite admirable efforts to 

standardize these terms (see Dietrich and Mehnertv 

1961). Moreover, some rocks would be transitional between gneiss and schist, no matter how strict the definition of these terms. What is termed mylonite gneiss 

may in some cases resemble schist, as most geologists 

use the term more than gneiss. Therefore, mylonite 

schist is proposed here as an alternate term for mylonite gneiss where the rock is more schistose than 

gneissic.

Mylonite schist, as defined here is a new term. Quensel 

(1916) used the term mylonitschiefer, which translates 

roughly as mylonite schist, to distinguish laminated 

mylonites with fluxion structure (his mylonitschiefer) 

from unlaminated cataclastic rocks without fluxionstructure (cataclasites) which (he considered "true 

mylonites" or "mylonites in the strictest sense" (see 

discussion of mylonite) . Therefore, Quensel's mylonitschiefer is essentially synonymous with mylonite 'as defined and used in this paper.

In terms of ponphyroclast size and abundance mylonite schist and mylonite gneiss are equivalent to protomylonite, but they also include rocks equivalent to 

coarse grained mylonite with porphyroclasts larger than 

0.5 mm. However, this may be strictly a textural comparison, because there is a problem regarding the origin of mylonite gneisses and mylonite schists. Some of 

these rocks may actually be equivalent to protomylonite;
12 CATACLASTIC BOCKS

B
CLASSIFICATION AND NOMENCLATURE 13

they may represent the early stages of mylonitization 

with concomitant recrystallization and neomineralization, just as protomylonite represents the early stages 

of the same process, but with less recrystallization and 

neomineralization. Other identical rocks, however, may 

represent more intense stages, somewhat equivalent to 

mylonite or ultramylonite as far as mylonitization or 

comminution is concerned, but in which recrystallization and neomineralization have been sufficiently intense 

to produce a coarse-grained rock. In other words, some 

mylonite gneisses or mylonite schists may represent 

rocks "on their way down" to blastomylonite, while 

others may represent rooks "on their way up" to crystalline schists because neomineralization-recrystallization has "overpowered" or "outdistanced" the cataclasis, 

so to speak. Thus a more accurate representation on a 

classification chart would be somewhat like that shown 

diagrammatically in figure 13.

BLASTOMYLONITE

Definition. Blastomylonite: A coherent rock intermediate between medium- to fine-grained mylonite or 

ultramylonite and a crystalline schist or gneiss because 

its texture is the result of combined cataclastic and crystalloblastic processes. It is not produced by later reorystallization or neomineralization of a previously 

mylonitized rock; cataclasis and neomineralization-recrystallization are concurrent, which produces a rock in 

which crystalloblastic texture appears to have overprinted the basic mylonite texture. Porphyroclasts in 

blastomylonite are generally smaller than about 0.5 mm 

and may show recrystallization. They make up less than 

about 30 percent of the rock.

Figure 14 shows typical blastomylonites.

Discussion. Sander (1912, p. 250) first used the term 

blastomylonite to describe rocks from the Tauernwestend, Austria. Knopf (1931, p. 12) introduced the term 

to English-speaking geologists. The definition above is 

essentially a rewording of Knopf's definition. Her definition (which most later papers follow) includes the 

phrase: "Neomineralization is so far advanced that the 

mylonitization can only be recognized with difficulty." 

This phrase has been removed from the definition because the degree of difficulty obviously depends on the

FIGURE 5. Photomicrographs of a mylonite (collected by A. C. 

Waters), from the San Andreas fault zone near Crystal 

Springs Lakes, Calif., in plane-polarized light (A) and with 

crossed polarizers (J5). Note the fluxion structure and the 

trails of crushed particles in the pressure shadows of porphyroclasts. The porphyroclasts are chiefly feldspar. Also note 

how the trails of finely comminuted dark minerals (much 

of this is magnetite) help define the fluxion structure. The 

parent rock was a meta-arkose.

observer and his knowledge of the rock and its field relations. In fact, Knopf (1931, p. 14) states in a later 

sentence: "The characteristic feature wherein mylonites 

differ from cataclastic rocks in general is in their ultracataclasis or intensive rolling out, so that even where 

much neomineralization accompanies the process as in 

blastomylonites the texture is still characteristic."

The size grade for porphyroclasts is based on my 

data. Blastomylonite is equivalent in terms of porphyroclast size to medium- and fine-grained mylonite and 

ultramylonite; it thus includes all rocks with porphyroclasts less than 0.5 mm. where neomineralization-recrystallization dominates over cataclasis.

PROTOCLASTIC ROCKS

Protoclastic deformation, or protoclasis, is a type of 

cataclastic deformation. It applies to cataclasis of an 

igneous body, or parts of an igneous body, due to late 

intrusive movements of, or within, that body, generally 

before it has completely crystallized. The products of 

protoclasis are called protoclastic rocks, and may be 

indistinguishable texturally from other cataclastic 

rocks, except for their intimate association with, or localization within, the parent igneous body.

Brogger (1890, p. 105) was apparently the first to 

use the term protoclastic (protoklastisch). The meaning 

and use of the term has changed little since it was first 

defined. Thus, my definition above is essentially the 

original translated into modern terms.

Protoclastic rocks can be considered special varieties 

of cataclastic rocks; thus, there seems no need for sepjarate nomenclature. However, the term protoclastic 

should be used as a prefix to the cataclastic rock name, 

(for example: protoclastic mylonite).

Despite the fact that protoclastic rocks are cataclastic rocks, they differ from the latter in one important 

respect; protoclastic rocks are formed by deformation of magmatic rocks which are not completely solidified at the time of deformation, although the percentage 

of unsolidified material may be extremely small. Some 

crystallization must therefore occur during, or even 

slightly after the protoclastic deformation. This crystallization is reflected in the textures of the protoclastic 

rocks, and consequently most of these rocks fit best into 

the series mylonite gneiss (mylonite schist)-blastomy* 

lonite.

Waters and Krauskopf (1941) have given perhaps 

the best and most detailed description of an occurrence 

of protoclastic rocks at the Colville batholith, Washington. The protoclastic rocks of the Colville batholith 

are discussed in this paper at the end of the section, 

Examples of cataclastic rock zones and their interpretation, (p. 53-56).

420-478 O - 71 - 2
14 CATACLASTIC ROCKS

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CLASSIFICATION AND NOMENCLATURE 15

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16 CATACLASTIC ROCKS

FIGURE 7. Schematic sketches showing textures of protomylonite (A), mylonite (B), and ultramylonite (C). The white 

represents porphyroclasts and "breccia streaks" or trails from

RETROGRADE CATACLASTIC ROCKS

Retrograde or diap'hthoritic cataclastic rocks are the 

products of retrograde metamorphism (diaphthoresis) 

occurring concurrently with cataclasis. They are in a 

sense simply variations of the basic cataclastic rocks already defined. However, their common occurrence in 

major fault zones (see bibliography) makes it desirable 

to include them in any general classification of cataclastic rocks.

Diaphthoresis is a process not necessarily related to 

or associated with cataclasis. A diaphthoritic rock or 

diaphthorite has relict minerals of a higher grade or 

facies of metamorphism which have been elsewhere in 

the rock changed or partially changed by retrogressive 

metamorphism (diaphthoresis) to minerals of a lower 

grade or facies of metamorphism. Such rocks are commonly but not necessarily phyllitic in appearance, which 

has led to confusion and misuse of the terms phyllonite 

and diaphthorite.

The concept of diaphthoresis was first introduced by 

Becke (1909) to account for relict high-grade minerals 

in low-grade rocks of the High Tauern Alps of the 

Austrian Tyrol. E. B. Knopf (1931) introduced the 

concept of diaphthoresis, the concept of phyllonitization, and the terms diaphthorite and phyllonite (originally defined by Sanders, 1911, p. 301) into English 

geological literature. She emphasized the distinction between phyllonites (which may or may not be retrogressive) and diaphthorities (which may or may not be 

cataclastic). She listed (1931, p. 19) the following criteria for the recognition of phyllonites:

(1) Phyllitic appearance accompanied by the characteristic 

lenticular structure, either megascopic or microscopic.

(2) A completely phyllonitized rock does not show cleavage 

that cuts the old S-planes because its phyllitic texture is the 

result of a refolding and transportation of the old S-planes of 

the rock.

(3) Adjacent lenses are of different sizes but the individuals 

in each lens are of similar grain size.

(4) All the individuals in one lens show subparallel optical 

orientation.

Knopf (1931, p. 14) defined phyllonite as follows:

* * * a rock of phyllitic appearance that as a rule is indistinguishable from a normal phyllite. Unlike normal phyllites, however, it has been formed not by the crystallization of new 

mineral constituents, progressively increasing in grain size, but 

by the mylonitic degradation of an originally coarser-grained 

rock.

porphyroclastic material; the black represents finely comminuted material and dark minerals. All three represent 

rocks produced from the same parent, coarse-grained 

"granite."
CLASSIFICATION AND NOMENCLATURE 17

FIGURE 8. Photomicrographs of mylonite. Above: From Scotland (collected by A. C. Waters) ; plane light. The porphyroclasts are 

chiefly plagioclase. Note the "flow" of the finely comminuted matrix around them. This photomicrograph also illustrates compositional layering, probably due to cataclastic metamorphic differentiation. Effects of recrystallization-neomineralization can 

be seen in the matrix, but the dominant texture is cataclastic. Parent rock was a gneiss. Below: From the San Andreas fault 

zone near Crystal Springs Lakes, Calif. (collected by A. C. Waters) ; crossed polarizers. Note fluxion structure. Parent rock 

was probably a meta-arkose.
18 CATACLASTIC ROCKS

^

FIGURE 9. Teall's (1918, pi. 1) photomicrographs of Lapworth's original "mylonites" and "augen gneisses" from the Eribol district 

of northwest Scotland. Presumably under plane-polarized light. No scale given. According to Teall (1918, p. 2), 3 is least 

mylonitlzed Lewisian gneiss, 2 is more mylonitized Lewisian gneiss;, and 1 is typical of mylonite produced from Lewisian 

gneiss. Four is a mylonitized metasediment which Teall presented to show that the effects of mylonitization were the same 

regardless of the rock type.
CLASSIFICATION AND NOMENCLATURE 19

(7

FIGURE 10. Ultramylonites. A, From a fault zone in Cucamonga 

Canyon, San Gabriel Mountains, Calif. Note layering separating coarser ultramylonite at left from fine variety at right. 

B, From New London County, Conn, (collected by C. B. Sclar, 

Battelle Memorial Institute) ; photomicrograph with polarizers crossed. Well-developed compositional layering resulted

from cataclastic metamorphic differentiation. The parent rock 

is a nonlayered biotite-cummingtonite-hornblende gneiss. 

C, From Scotland (collected by A. C. Waters) ; photomicrograph taken in plane-polarized light. The blurring is partly 

due to the high magnification. Note lack of compositional 

layering. Parent rock probably a gneiss.
20 CATACLASTIC ROCKS
CLASSIFICATION AND NOMENCLATURE 21

She also stated (1931, p. 19-20): |

Unfortunately the term phyllonite is often used in the litera- ' 

ture without a clear distinction as to what it implies, and it is 

a common error among writers on metamorphism to make phyllonite synonymous with diaphthorite even where no evidence 

is produced to show the retrogressive metamorphism in the 

mylonitized rock. Unless the correct meaning of phyllonitization is appreciated, a misinterpretation of tectonic history is 

likely to result, because phyllonitization does not necessarily 

mean retrogressive metamorphism, although many phyllonites 

are also diaphthoritic. For example, a phyllonite may be derived 

by the mylonitization of a porphyritic granite or conglomerate. 

Obviously the resultant rock has not been produced by retrogressive metamorphism because the original rock was unmetamorphosed to begin with. Moreover, a phyllonite may be formed 

by the degradation of a highly crystalloblastic schist and yet 

not be, as tacitly assumed by some geologic writers, diaphthoritic. * * * Thus a biotite phyllonite derived from a biotite 

schist or a chlorite phyllonite derived from a chlorite-sericite 

schist is not diaphthoritic, but a chlorite-sericite phyllonite produced from a garnetiferous biotite schist does show a retrogression in metamorphism. In general a diaphthorite must be 

sufficiently crystalloblastic to show mineral retrogression, while 

a phyllonite must be sufficiently cataclastic to reveal its mylonitic 

origin.

Knopf (1931) made two important points regarding 

diaphthorites: (1) they must have relict minerals of a 

higher grade or facies of metamorphism; (2) they 

commonly have a phyllitic appearance and a "diseased 

look" in outcrop. She also stated that most diaphthorites 

are in fact tectonites. Knopf did not emphasize one important point strongly enough thalt any retrogressively metamorphosed rock can be a diaphthorite even 

though it is not cataclastic. For example, diaphthorite 

can be produced where igneous intrusions cause retrogressive contact metamorphism of previously metamorphosed rocks.

From the above it is seen that phyllonite should be 

used for phyllitic mylonitic cataclastic rocks (those 

with fluxion structure as denned in the glossary); 

diaphthorite for retrograde rocks (phyllitic or not; 

cataclastic or not); phyllitic diaphthorite for noncataclastic retrogressive rocks that have the appearance of 

phyllites; and diaphthoritic phyllonite for retrogressive 

mylonitic cataclastic rocks with the appearance of 

phyllites. Diaphthoritic can be used as a modifier of

FIGURE 11. Phyllonite from the Brevard zone near Atlanta, 

Ga. A, Hand specimen with "eyes" of porphyroclastic 

muscovite. B, Photomicrograph of same rock. The spindle-shaped, bent, and twisted porphyroclasts of muscovite 

give the phyllonite the appearance of having fish scales on 

its cataclastic foliation planes. The rock is not a diaphthorite. 

Parent rock was probably a gneiss. Plane-polarized light.

any of the other cataclastic rock names (see table 1). 

Figure 15 shows some diaphthoritic rocks,

CATACLASTIC ROCKS IN WHICH FUSION OR 

MELTING WAS IMPORTANT

In addition to the more common types of cataclastic 

rocks already defined, there are some in which fusion 

or melting played an important role. In some cases, 

melting has virtually erased most of the cataclastic 

texture, and other criteria must be used to identify and 

classify the rocks.

PSEUDOTACHYLITE

Definition. Pseudotachylite: A glassy rock generally 

resembling tachylite, commonly of intrusive habit, and 

closely associated with faults or fault zones. The groundmass of the rock is composed mainly of glass, which in 

some cases contains microlites of feldspar, vesicles, 

spherulites, amygdules, or partially melted rock and 

mineral fragments. The rock fragments may be cataclastic or undeformed. Pseudotachylite probably forms 

by melting resulting from frictional fusion during 

faulting of already-hot rocks.

Figure 16 shows typical pseudotachylite.

Discussion. Dark, glassy rocks of intrusive habit 

occur in many fault zones, particularly those closely 

associated in time and space with plutonic activity. 

Commonly, these rocks have the aspects of thin basaltic 

(dolerite) dikes: they are definitely of intrusive habit 

(fig. 165); they are glassy; they may have finer-grained 

margins; they may contain microlites ('chiefly of feldspar) , skeletal crystals, vesicles, spherulites, amygdules, 

and partly melted (embayed) or corroded minerals and 

mineral fragments (fig. 16J., B). However, they also 

have aspects of cataclastic rocks: they are invariably 

closely associated with faults or fault zones; many are 

gradational to mylonites, ultramylonites, cataclasites, 

or other types of cataclastic rock; some have recognizable porphyroclasts; in most, the mineral fragments 

are chiefly quartz and feldspar, and the rock fragments 

are from the host rock (fig. 166") ; commonly, the plagioclase microlites are more sodic than andesine; and, 

where chemical analyses have been made, almost all 

of the glassy rocks have the approximate chemistry of 

their intermediate to felsic host rocks (Shand, 1917; 

Hall and Molengraaff, 1925; Salop, 1949; Philpotts, 

1964). These glassy rocks have been called by several 

names, and various origins have been proposed for 

them.

Shand (1917, p. 199) introduced the term pseudotachylite for 'branching, glassy, dikelike rocks associated
22 CATACLASTIC ROCKS
CLASSIFICATION AND NOMENCLATURE 23

FIGURE 12. Mylonite gneisses. A, Outcrop of coarse-grained 

mylonite gneiss in the Towaliga fault zone near Auburn, 

Ala. (coin is 1.9 cm in diam.). The structure in this outcrop 

is strikingly like the texture of a mylonite in thin section 

(compare with fig. IB). The giant porphyroclasts are feldspar. B, Photomicrograph of specimen from northwest edge 

of the Brevard zone near Atlanta, Ga.; crossed polarizers. 

Note high degree of neomineralization-recrystallization. Despite this, the fluxion structure is still visible. This rock is 

finer grained than the one shown in C, illustrating the range 

in grain size covered by the term "mylonite gneiss." The range

Parent rock

I

Mylonite gneiss or mylonite schist

I

Blastomylonite

I

Mylonite gneiss or mylonite schist

FIGURE 13. Diagram showing relations between some mylonite 

gneisses or mylonite schists and blastomylonite.

is about the same as that of protomylonites. Parent rock was 

probably a coarse-grained "granite." C, Photomicrograph of 

specimen from the northwest edge of the Brevard zone near 

Atlanta, Ga.; crossed polarizers. Note relatively high degree of 

neomineralization-recrystallization of the matrix. This is a 

fairly coarse-grained mylonite gneiss, comparable in grain size 

with coarser protomylonites. Note the "roundnesis" of the large 

feldspar porphyroclast (lower right). Fuzzy grain boundaries 

in photomicrograph are natural and not due to poor photographic focus.

with granitic rocks in the Vredefort dome of the Parijs 

(Parys) region of South Africa. He came to the tentative conclusion (1917, p. '219) that "* * * the pseudotachylite has originated from the granite itself through 

melting, cause'd not by Shearing but by shock, or, alternatively, 'by gas-fluxing." Several geologists at that 

time agreed with Shand; others offered different explanations (see Shand, 1917, p. 220-221, discussion). 

Similar rocks had been described earlier (King and 

Foote, 1864, p. 271; Holland, 1900, p. 198-248) from 

southern India, where they were called trwp-shotten 

gneiss, and from Scotland (Clough, 1888; Clough and 

others, 1909; Peach and others, 1907), where they were 

called flinty crush^rock*
24 CATACLASTIC ROCKS

FIGURE 14. Blastomylonites. (All photomicrographs with 

crossed polarizers.) A, Porphyroclastic, crudely laminated 

blastomylonite from the Towaliga fault zone in Alabama. 

The large porphyroclasts are K-feldspar. B, Photomicrograph 

of a blastomylonite from the Brevard zone near Atlanta, Ga. 

Note high degree of neomineralization-recrystallization of the 

matrix. The fuzziness is natural and is not due to poor focus; 

it is common in blastomylonites, and probably results from 

the fine-grained neomineralization. The porphyroclasts are 

feldspars. Parent rock was possibly a micaceous gneiss. C, 

Photomicrograph of a blastomylonite from tlhe Brevard zone

near Atlanta, Ga. Note the relatively high degree of neomineraMzation-recrystallizatiou of the matrix. Despite this, the 

fluxion structure and "flow" of trails of recrystallized material around the rounded porphyroclast are visible. Parent rock 

was a "granite." D, Photomicrograph of a porphyroclast and 

surrounding matrix in a blastomylonite from the Brevard 

zone near Atlanta, Ga. This view shows the neomineralized-recrystallized character of the matrix; note particularly the 

small micas. Fuzziness in photomicrograph is due to high magnification. Parent rock was probably a "granite."
CLASSIFICATION AND NOMENCLATURE 25
26 CATACLASTIC ROCKS

Quartz porphyroclast

Chlorite Recrystallized "crush 

train" or trail?

Garnet

Fine, partly recrystallized 

quartz-feldspar mortar

Recrystallized 

"crush trail"

Recrystallized 

quartz stringer

Biotite streak

Note how recrystallized 

quartz-feldspar mortar 

trail "flows" around 

porphyroclast

Plagioclase

B

Biotite

Garnet partly altered 

to chlorite and biotite

Garnet

"Crush" or mortar from 

the K-feldspar

K-feldspar, note "fine, 

fingerlike perthite"

K-feldspar fragments

FIGUBE 15. Diaphthoritic blastomylonites. A, B, Layered, diaphthoritic blastomylonile from near Tlrschneim, Germany. A shows texture 

common in mylonites and blastomylonites, as well as compositional 

layering. In the microdrawing (B), note the garnets partly altered 

to biotite and chlorite, and the K-feldspar partly altered to muscovite.

Muscovite aggregate 

with pieces of K-feldspar remaining

The background mosaic, while still preserving the cataclastic flow 

texture, is thoroughly recrystallized. Drawing with crossed polarizers. C, Photomicrograph of a diaphthoritic blastomylonite from New 

London County, Conn, (collected by C. B. Sclar), crossed polarizers. 

Note the general neomineralization-recrystallization of the matrix.
CLASSIFICATION AND NOMENCLATURE 27

.*-. *.

i

Despite this, the cataclastic texture and fluxion structure are well 

preserved. D, Photomicrograph of a diaphthoritic blastomylonite 

from New London County, Conn, (collected by C. B. Sclar), planepolarized light. The large garnet porphyroclast in the center has been 

retrogressively altered to chlorite at its borders and along fractures.

The fluxion structure of the groundmass and the trails of retrogressively altered and crushed particles of garnet extending from 

either side of the porphyroclast help define the fluxion structure. 

Parent rock was a gneiss.
28 CATACLASTIC ROCKS

FIGURE 16. Pseudotachylites. A-C from Vredefort dome in South 

Africa, collected by Bailey Willis, and furnished by A. C. 

Waters. A, Pseudotachylite dike and stringers in "granitic" 

host. Note thin stringers of pseudotachylite in the country 

rock. B, Pseudottachylite dike cutting "granitic" host rock. 

Note the sharp contacts of the dike, and the inclusions of 

"granitic" host rock in it. Many of these inclusions are cor-

, ' * * 

B

roded quartz grains. C, Pseudotachylite and "granitic" host 

rock. Note inclusion of fractured "granitic" host rock in the 

black pseudotachylite. D, Photomicrograph of pseudotachylite 

from the Belleau-Desaulniers area, Quebec (collected by A. B. 

Philpotts, McGill Univ.) ; plane-polarized light. Note the 

branching intrusive nature of the malterial, and its isiotropic 

character.

The term -flinty crush-rock was first used by Clough 

(1888, p. 22) for dark veinlike rocks along fault zones 

in the Cheviot Hills of Scotland. It was subsequently 

used by Peach and others (1907, p. 124, 141, 151-153, 

190, 196, 214-216, 244-250) for rocks associated with 

thrust faults in the Northwest Highlands of Scotland; 

by dough and others (1909, p. 629-631) for rocks associated with the ring fault at Glen Coe, Scotland; by 

Backhmd (1913) for glassy rocks associated with fault 

zones in Argentina; by Jehu and Craig (1923, p. 430- 

436; 1925, p. 629-630) and Dougal (1928) for rocks 

associated with thrust faults in the Outer Hebrides;

and by Scott and Drever (1953) for rocks associated 

with a Himalayan thrust fault.

In most of the early papers flinty crush-rock was used 

as a field name for many varieties of cataclastic rock. 

Thus, as Shand (1917, p. 209-210) noted, dough's 

(1888) flinty crush-rocks include dark, flinty mylonites, 

ultramylonites, and cataclasites, as well as rocks that 

show evidence of fusion and melting, and the same is 

true of most of the flinty crush-rocks of later geologists.

Pseudotachylite (byname) has been described by Hall 

and Molengraaff (1925), Hammer (1930), Bearth 

(1933), Nockolds (1940), Goldschmidt (1943), Salop
CLASSIFICATION AND NOMENCLATURE 29

D

(1949),Dietrichson (1953), Bryn (1959), Park (1961), 

and Philpotts (1962, 1964).

Holland (1900) was perhaps the first to give serious 

consideration to the origin of fused, intrusive cataclastic 

rocks.1 He crushed a sample of the charnokite host rock 

from one of the pseudotachylite localities in southern 

India and heated it until fusion took place. He stated 

(1900, p. 200) :

The result was a fritted black cake having the lustre of a 

tachylite and showing in thin section a black structureless matrix including angular fragments of quartz; in fact, the fritted 

charnokite powder very closely resembled the so called strings 

of trap in these breccia bands.

Knopf (1931, p. 13) thought pseudotachylite was 

"possibly produced by fritting or by fusion under local 

development of intense heat." She presented a photomicrograph (1931, fig. 5) showing its "pseudoeruptive" 

nature. Cirickmay (1933, p. 166-170) described intrusive 

"mylonites" (dike-mylonites) which he considered to

and Foote (1864) thought that the rocks studied by Holland 

were basaltic dikes. Hence their terminology trap-shotten gneiss.

be pseudotachylites, but which showed no fusion. Waters 

and Campbell (1935) gave an excellent summary of 

the various theories for the origin of pseudotachylite 

and compared pseudotachylites with mylonites and 

ultramylonites from the San Andreas fault zone. They 

tentatively concluded that pseudotachylite formed not 

by fusion but by extreme crushing of the rock material. 

However, in their definition (1935, p. 479-480) they retained the prerequisite of fusion as a distinctive property of pseudotachylite. Dietrichson (1953) and Bryn 

(1959) described and analyzed pseudotachylites from 

Norway and concluded that they formed by fusion at 

local hot spots produced by friction. Scott and Drever 

(1953) were the first to give convincing evidence of f rictional fusion in the rocks they called flinty crush-rocks, 

cryptomylonites, and Jiyalomylonites. They described a 

glassy rock which is vesicular and has a refractive index of 1.5. The rock occurs in a thrust fault, where complete gradation can be traced from the glassy rock 

through mylonite into undeformed rock. This was the 

first convincing evidence that sufficient frictional heat 

could be produced in a fault zone to cause the rock to

420-478 O - 71 - 3
30 CATACLASTIC ROCKS

melt, though Bowden and others (1947) and Bowden 

and Thomas (1954) had shown experimentally that two 

polished surfaces rubbed together at speeds as low as 

1 to 2 feet per second under a load of 1,000 grams can 

develop visible hot spots.

Reynolds (1954, p. 591-595) suggested fluidized solidgas systems (fluidization) as an explanation, for the 

origin of pseudotachylite. After studying the South 

African pseudotachylites (also studied by Shand and 

by Hall and Molengraaff), she concluded that they 

were originally composed of finely ground particles 

transported in suspension by rapidly moving gases from 

the underlying magma to their present locations. 

Christie (1960, p. 84) accepted Reynolds' "fluidization 

hypothesis" for the origin of pseudotachylite. Fluidization as a major process producing such large features as 

the Vredefort dome (and thereby the pseudotachylite 

also) was subsequently discounted by McBirney (1963, 

p. 227-231), who showed by calculations the improbability of rapid release of the huge volumes of gases 

required.

The most satisfactory explanation for the origin of 

pseudotachylite .resulted from Philpotts' (1964) complete study of Canadian and South African pseudotachylites. He carefully considered and eliminated most 

of the existing hypotheses of origin and gave good field, 

petrographic, X-ray, chemical, and petrologic evidence 

to support the interpretation that pseudotachylite 

forms by melting due to frictional heating during faulting of rocks already at temperatures above 400° C. 

Generally, these rocks are near igneous intrusions, and 

commonly the time of intrusion of tihe igneous mass 

can be shown to be quite close to tihe time of faulting 

and formation of pseudotachylite. According to Philpotts, the melted material is forced into fractures 

where it begins to cool. As the melt moves along the 

fractures, it differentiates, becoming progressively 

(though only slightly) enriched in the low-melting 

fractions. This is shown by chemical analyses along 

a single dike.

The definition of pseiidotachylite used in this paper 

is based on the work of Philpotts (1964). Because it 

has so often been used as a general field term for various kinds of cataclastic rocks and because there is confusion regarding its meaning, even in the strictest sense, 

-flinty crush-rock is not used in my classification (table 

1). However, all gradations probably exist from 

pseudotachylite in which a large proportion of the rock 

has been melted, through partially melted cataclastic 

rock, to only slightly fused cataclastic rock, and some 

way to designate such rocks is desirable. Naming these 

rocks can be iaccomplished by using pseudotachylitic as 

a modifier of the cataclastic rock names already 'defined 

(table 1).

HARTSCHIEFER

The term "hartschiefer" was popularized by Holmquist (1910, p. 945), but had previously been in general 

use by Scandinavian geologists. There has been much 

disagreement over the characteristics and especially the 

origin of hartschiefer. Holmquist first favored the idea, 

that they are sedimentary, chiefly because of the unusually straight and regular lamination. Quensel (1916, 

p. 100, 113-116) favored a caitaclastic origin. Knopf 

(1931, p. 10) considered hartschiefer equivalent to 

ultramylonite. Waters and Campbell (1935, p. 477-478, 

480) favored a cataclastic origin, and stated:

In the opinion of most Swedish geologists they differ from 

ultramylonite, which they resemble rather closely, in the remarkable banding, a feature that is regarded to be the result 

of metamorphic differentiation, and in the much more thorough 

recrystalliziation, crystalloblastic structures commonly predominating over cataclastic.

Christie (1960, p. 82) essentially concurred with Waters 

and Campbell. Reed (1964, p. 650-651) considered most 

hartschiefer to be well-banded blastomylonites.

Descriptions and illustrations of hartschiefer (Holmquist, 1910; Quensel, 1916; Knopf, 1931) and my study 

of samples, kindly furnished by A. C. Waters, from 

Scandinavian localities which include Holmquist's 

Tornetrask area, lead me to conclude that the term 

"hartschiefer" comprises a variety of coherent cataclastic rocks. Most of these are well-banded (layered), 

neomineralized or recrystallized blastomylonites, but 

some are only slightly neomineralized or recrystallized 

and should be called ultramylonite and mylonite. Other 

"hartschiefer" are very probably thinly bedded metasedimentary rocks. Hartschiefer is therefore not used in 

my classification (table 1); the rocks to which it pertains are considered covered by the other terms.

POLYCATACLASTIC AND POLYMETAMORPHIC 

CATACLASTIC ROCKS

Coherent cataclastic rocks are an integral part of the 

metamorphic terranes in which they occur, and the 

metamorphic and deformational histories of the metamorphic terranes generally apply in some manner to 

the cataclastic rocks as well. Many metamorphic terranes have been subjected to multiple metamorphic 

events and to multiple deformations, and polycataclastic 

rocks and polymetamorphic cataclastic rocks are relatively common.

Following Read (1949) and Hsu (1955a), polymetamorphic rocks are those that record a history of two 

or more separate periods of metamorphism; or as Hsu 

(1955a, p. 238) stated: ". . . periods of metamorphism 

that present no obvious genetic connection." Rocks re-
CLASSIFICATION AND NOMENCLATURE 31

metamorphosed during different stages or episodes of 

one single period of metamorphism are monometamorphic (Read, 1949; Hsu, 1955a). However, modern studies (particularly those including radiometric age dating) of several metamorphic terraces that have undergone only one major period of metamorphism show that 

there are generally distinct episodes within the single 

metamorphic period (Johnson, 1961, 1963; Steiger, 

1963; Button, 1963). Perhaps these monometamorphic 

rocks should be called polyepisodic. These terms can be 

used as modifiers to the cataclastic rock names; for example: polymetamorphic mylonite or polymetamorphic ultramylonite.

The term blastomylonite does not apply to polymetamorphic mylonites or even to polyepisodic monometamorphic mylonites; a 'blastomylonite is not a metamorphosed mylonite. Blastomylonite applies only to 

rocks in which the cataclasis and the neomineralizationrecrystal'lization were essentially concurrent, though 

possibly also recurrent.

Polycataclastic rocks are those that have been subjected to two or more periods or episodes of cataclasis.

Most major fault zones have long histories of repeated movements for example, the Caledonian thrust 

belt (Johnson, 1961, 1963; Holgate, 1963; Christie, 

1960); the Alpine fault zone (Eeed, 1964; Suggate, 

1963); the Brevard fault zone (Eeed and Bryant, 1964; 

Higgins, 1966,1968) ; the San Andreas fault zone (Hill 

and Dibblee, 1953; Crowell, 1962,1966); the Cucamonga 

fault zone (Hsu, 1955b); the Great Glen fault zone 

(Kennedy, 1946) ; the Towaliga fault zone (Grant. 

1967, 1968). Many of the rocks in these zones are polycataclastic. Generally, if the latest cataclasis was equal 

to or greater in intensity than the earlier episodes, then 

the earlier textures will have been obliterated and the 

rock will appear to be monocataclastic. However, if, as 

is often the case, the later cataclasis was weaker, then 

the resulting rock may have a polycataclastic texture.

Any of the rocks defined thus far could be affected by 

a second period or phase of cataclasis. For these polycataclastic rocks, combinations of terms can be used. For 

instance, a mylonite affected by a later, weaker cataclasis 

might result in a coherent breccia of mylonite fragments 

which should be called brecciated mylonite (fig. 17).

'.i"Ii«»Jl ' Jl *v^w, *

iif" ft? \ >-^* 3^ ^"*\t, ; * 

FIGURE 17. Photomicrograph of a brecciated mylonite from the Brevard zone near Atlanta, Ga. ; plane-polarized light. Note the

"broken" fluxion structure.
32 CATACLASTIC ROCKS

PROBLEMS OF NOMENCLATURE AND CLASSIFICATION OF CATACLASTIC ROCKS

The definitions and classification proposed in this 

paper are for the most part qualitative. Texture, including degree of recrystallization-neomineralization, 

is the chief basis for classifying most cataclastic rocks. 

Approximate porphyroclast size combined with the 

approximate percentage of porphyroclasts, compared 

with photomicrographs of what may be called "standards," is the only quantitative parameter used. Because 

the various cataclastic rock types grade into one another, any classification is more or less arbitrary. Although coherent cataclastic rocks are really metamorphic rocks, problems of their nomenclature and classification have much in common with those of sedimentary 

rocks. Cataclastic rocks cannot be defined and classified by Ithe parameters used to classify most other 

kinds of rocks.

MINERAL ASSEMBLAGE AND CHEMICAL COMPOSITION

We define and classify noncataclastdc metamorphic 

rocks chiefly on the basis of their mineral assemblages 

and igneous rocks largely on the basis of their mineral 

assemblages, mineral compositions, and bulk chemical 

compositions. Cataclastic rocks are produced from 

rocks of diverse type; therefore mineral assemblages, 

mineral compositions, and bulk chemical compositions 

have little value in defining and classifying them. For 

example, a mylonite can be formed from granite, schist, 

conglomerate, gabbro, or almost any other rock. In fact, 

a mylonite can be formed from more than one parent 

rock. In this respect, cataclastic rocks are somewhat 

like sedimentary rocks.

PETROFABRICS

Petrofabric analysis has been made on many types 

of cataclastic rocks from many different areas. The results indicate that commonly all of the coherent cataclastic rocks of one deformation and the noncataclastic 

rocks of the same deformation within an area have essentially the same fabrics (Christie, 1963, p. 402-407 

and fig. 23). Petrofabric analysis can be used in some 

cases to separate cataclastic rocks of different deformations in the same area (Grant, 1968), but not to develop 

general definitions and an overall classification of cataclastic rocks.

APPROXIMATE PERCENTAGE AND SIZE OF

PORPHYROCLASTS AND ROCK

FRAGMENTS (GRAIN SIZE)

In attempting to apply some quantitative criteria to 

definition and classification of cataclastic rocks, I measured porphyroclast and fragment size and determined 

the approximate percentage of porphyroclasts or fragments in eight or more thin sections of the cataclastic 

rock types in which grain size is a criterion.

DEFINING DEGREE OF 

NEOMINERALIZATION-RECRYSTALLIZATION

One of the chief problems in any classification of 

cataclastic rocks is that of defining the arbitrary separation between rocks of the sequence protomylonitemylonite-ultramylonite and rocks of the sequence 

mylonite gneiss (mylonite schist)-blastomylonite. The 

problem is essentially one of recognizing degrees of recrystallization and (or) neomineralization. Most former 

workers have faced this problem by defining the two 

sequences of rock types as end members (Knopf, 1931; 

Waters and Campbell, 1935; Christie, 1960). Thus, 

mylonite and related rocks were defined as totally unrecrystallized or un-neomineralized, and blastomylonite 

and related rocks as nearly completely recrystallized 

and (or) neomineralized, so that their cataclastio texture was recognizable only with great difficulty. My 

study indicates that such end members are rare. Accordingly, I lhave chosen to define the two rock sequences so that the distinction between them depends on 

what has most influenced their present texture, the destructive process of cataclasis or the constructive process of neomineralization and (or) recrysta'llization, 

(table 1).

Thus defined, the separation must depend on some 

kind of standards to represent, as much as possible, the 

various degrees of neomineralization-recrystallization 

in natural cataclastic rocks. This is accomplished by 

means of photographs and photomicrographs of "typical" examples of the various rock types. It should be 

noted that the degree of neomineralization-recrystallization focuses attention primarily on the groundmass. 

There are numerous rocks for which a decision is extremely difficult, or even impossible, and a rock classified by one geologist as >a 'mylonite might be classified by 

another as a blastomylonite. Therefore, detailed descriptions and photomicrographs are advisable, particularly 

when dealing with "borderline" rocks.

FIELD RELATIONS OF CATACLASTIC 

ROCKS

In outcrop and hand sample, cataclastic rocks may be 

easily mistaken for metasedimentary, metavolcanic, 

volcanic, or fine-grained intrusive rocks. In fact, many 

of the original definitions of cataclastic rocks include 

descriptive phrases such as "quartzite-like," "flinty," 

"felsitic," and "cherty."
FIELD RELATIONS OF CATACLASTIC ROCKS 33

In many cases, overlooking the presence of cataclastic 

rocks has led to erroneous interpretations of structure, 

stratigraphy, and geologic history. In other studies, the 

various types of cataclastic rocks have been "lumped" 

together, in mapping and in description, under one 

term, such as mylonite. This too has led to oversimplified 

and erroneous interpretations in many areas.

Recognition of cataclastic rocks in the field is often 

difficult, and study of thin sections is the only positive 

method of recognizing them. Because cataclastic rocks 

are intimately associated with faults and fault zones, 

in many cases it is the suspicion of or recognition of the 

the existence of these structural breaks which leads one 

to suspect the presence of cataclastic rocks. The reverse 

is equally true; the recognition of cataclastic rocks 

has often led to recognition of major structural breaks.

In this section, criteria are given for the recognition 

of faults, fault zones, and cataclastic rocks, with examples described. Since this report is for the student as 

well as for the more experienced geologist, some of the 

more elementary aspects of field problems concerning 

cataclasis are considered.

RECOGNITION OF FAULTS AND FAULT ZONES

Faults or fault zones and belts of cataclastic rocks 

in crystalline terranes may be suspected where there 

are: (1) alinements of topographic features, springs, 

or marshy areas; (2) abrupt changes in attitude of 

bedding or foliation; ('3) abrupt terminations of folds, 

dikes, faults, or other structural features; (4) changes 

in dips or in direction of joints or lineations; (5) offsets of map unit contacts; (6) repetition or omission 

of rock units; (7) blocks of float foreign to the underlying rock units; (8) lineaments in, or changes in the 

style of, magnetic or gravity anomalies; (9) steep 

gradients on magnetic or gravity maps; (10) anomalous 

changes in metamorphic zones or facies; (11) linear 

zones of mineralization, silicification, or alteration.

'Steeply dipping fault zones are commonly marked 

by linear topographic alinements. Drainage may follow these lineaments because cataclastio rocks are commonly either less resistant or more resistant to weathering than the surrounding noncataclastic rocks. The 

more resistant varieties tend to block and divert small 

streams, so that these streams flow parallel to the cataclastic rock bands and then cross them at high angles 

when a zone of less resistant rock is reached. The less 

resistant cataclastic rocks tend to provide easily eroded 

streambeds, so that the streams follow the cataclastic 

rock bands. Marshy areas are relatively common on 

the upslope side of resistant cataclastic rock bands.

RECOGNITION OF CATACLASTIC ROCKS

Once the presence of fault zones or cataclastic rocks 

is suspected, there are certain general criteria which 

help to identify cataclastic rocks and to distinguish 

them from noncataclastic rocks.

(1) Textural contrast. Cataclastic rocks are often 

recognizable in the field by their contrast with the noncataclastic rocks around them. This is especially true of 

phyllonites and of diaphthoritic cataclastic rocks, but 

it also applies to most of the other cataclastic rocks. For 

example, a fine-grained, laminated mylonite in mediumgrained or coarse-grained schist or gneiss would be 

conspicuous.

(2) Differential weathering. Weathering differences 

between cataclastic rocks and noncataclastic rocks can 

help in recognition of cataclastic rocks.

(3) Gradational nature. The gradational nature into 

and out from crystalloblastic metamorphic rocks often 

helps to distinguish the cataclastic rocks (see Crickmay, 

1933). Such gradation is especially useful in distinguishing cataclastic rocks from metavolcanic rocks.

(4) Presence of porphyroclasts or visible -fluxion 

structure. Except for microbreccias and cataclasites, 

coherent cataclastic rocks are commonly recognizable 

by the presence of porphyroclasts and streaking or other 

visible fluxion structure (fig. 18). They can be confused with porphyritic volcanic or metavolcanic rocks, 

but porphyroclasts tend to be rounded, whereas euhedral or subhedral shapes are more common for phenocrysts in volcanic and metavolcanic rocks (figs. 19 and 

20). This criterion should be used with caution, however, because euhedral and subhedral porphyroclasts 

are not unknown (fig. 6; also see Hsu, 1955b), and 

rounded phenocrysts do occur in some volcanic and 

metavolcanic rocks (figs. 19J., B and 20), particularly 

in tuffaceous rocks and welded tuffs. Moreover, round 

or nearly round porphyroblasts are also known.

Cataclastic rocks may also be confused with flint, 

dhert, slate, or fine-grained quartzite (figs. 21 and 22) 

(see Crickmay, 1933). Here again, the presence of porphyroclasts (fig. 22) may be the distinguishing feature, 

though rounded clastic grains may be mistaken for 

porphyroclasts.

Perhaps as important as the shapes of porphyroclasts 

in distinguishing them from most phenocrysts and porphyroblasts is their mineralogy. It is well-known that 

quartz is ground down more readily than feldspars during cataclasis and that most porphyroclasts are feldspar. Porphyroclasts of quartz are rare in cataclastic 

rocks, but quartz phenocrysts are fairly common in 

volcanic, metavolcanic, and intrusive igneous rocks.
34 CATACLASTIC ROCKS

FIGUEE 18. Blastomylonites from the Goat Rock fault zone in 

Alabama. A, Porphyroclastic blastomylonite with rounded 

feldspar porphyroclasts. B, Laminated blastomylonite. This 

rock is similar in appearance to some kinds of metamorphosed TOlcanic rocks with thin layering and phenocrysts. 

However, the rounded feldspars are porphyroclasts, and the 

streaking and layering are parallel to fluxion structure.

(5) Zones of mineralization and alteration. Cataclastic rocks particularly those in the sequence microbreccia-cataclasite are commonly zones of mineralization and alteration. Consequently, they may be marked 

by discoloration and stains due to the mineralization or 

to weathering of the minerals. This is especially true 

where the mineralization involves sulfides.

(6) Presence of mica masses. Micas in cataclastic 

rocks commonly occur in clotlike masses or in spindleshaped lenses and generally are bent or smeared (fig. 

11). On surfaces parallel to ithe fluxion structure or

foliation, these mica masses commonly give the rock the 

peculiar appearance of having "eyes," or of being 

smeared with fish scales (fig. 11). The mica lenses have 

been called "buttons," "eyes," and "fish-scale structures," 

and the rocks "button schists," "eyed schists," "eyed 

phyllonites," "phyllonitic schists," and "curly schists" 

(see Crickmay, 1952; Reed and Bryant, 1964; Reed, 

1964; Higgins, 1966). This feature is most common in 

phyllonites and blastomylonites.

(7) Association with fault zones. Field relations 

(map relations) are most important in recognition of
FIELD EELATIONS OF CATACLASTIC EOCKS 35

cataclastic rocks. Although the kinds of rocks with 

which cataclastic rocks are commonly confused may be 

found in fault zones, they will generally also be found 

away from fault zones as well. Cataclastic rocks may 

thus be suspected simply by their intimate association 

with fault zones.

(8) Catalastic texture in thin section. The primary 

rule for recognition of cataclastic rocks is that they are 

positively identifiable only in thin section. Any rock 

suspected of being cataclastic should be examined 

in thin section.

MAFIC CATACLASTIC ROCKS

It has long been recognized that most cataclastic 

rocks are felsic or silicic. This has been such a 

common observation that it was included in many of 

the definitions of cataclastic rocks. However, cataclastic 

rocks formed from mafic rocks are known and are not 

really rare. Waters and Campbell (1935, p. 484, 489) 

described basalt and diabase mylonites. Sclar (1958, p. 

70-75) described mylonites and ultramylonites formed 

from mafic gneiss. Prinz and Poldervaart (1964) decribed mylonite formed from metadolerite. Dunite 

mylonites have been described from St. Paul's Rocks 

(Tilley, 1947), and from New Zealand (Turner and 

Verhoogen, 1960, p. 633; Williams and others, 1954, p. 

77-78).

The fact that the greater proportion of cataclastic 

rocks are of "granitic" composition probably results 

from several factors. First, because cohesive cataclastic 

rocks form under conditions of relatively high confining 

pressure and moderate to high temperatures, they are 

mostly limited to metamorphic-plutonic terranes. 

"Granites" constitute 90 percent of the intrusive rocks 

in these terranes (Daly, 1933, chap. 3; Read, 1957, p. 

70-82), and a large proportion of sedimentary and 

metasedimenitary rocks in orogenic belts are felsic or 

silicic. Therefore, a large percentage of cataclastic rocks 

are necessarily "granitic." Secondly, as Waiters and 

Campbell noted (1935, p. 489) :

* * * under the pressure-temperature conditions that result 

in the formation of a mylonite from quartzite or graywacke, 

basalts and diabases are partially recrystallized, and serpentine is entirely recrystallized and converted into schist.

ASSOCIATION OF CATACLASIS WITH FELSIC 

AND SILICIC INTRUSIVE ROCKS

Felsic and silicic dikes, veins, and thin sills are common features of most crystalline terranes. Faults coincident with these bodies are also common. In the 

Northwest Highlands of Scotland, minor fault zones 

and felsic and silicic dikes have a remarkable coincidence. In their classic memoir on this region, Peach and 

others (1907) describe no fewer than 18 cases of cataclastic zones in dikes (p. 116,122,124,141,145,148-149, 

152-153,173, 202, 209, 213-214, 244, 248, 263, 470). The 

following two examples (1907, p. 153, 213) are typical:

In the last two localities this type of deformation [mylonitization] occurs in dikes * * *. It is evident that the dikes formed 

lines of weakness along which movements were repeated.

* * * * *

Zones of mylonised pegmatite are common * * *. The pegmatites near Ooppachy have more often been mylonised than the 

adjacent rocks * * *.

The association of dikes and lava-feeding fissures 

with faults is common in volcanic terranes (for example 

see Waters, 1962). Generally, repeated igneous activity 

has alternated with fault movement along these fissures. 

Dikes, veins, and sills in metamorphic terranes formed 

zones of easiest movement during directed stress, particularly if they were not quite completely solidified. 

In many cases, the intrusive bodies may have first been 

emplaced along fault planes, or in fault zones, only to be 

deformed by later fault movements. If confining pressures were great enough, cataclastic rocks might be 

produced preferentially in these igneous bodies. Alternatively, perhaps some of the cataclastic dikes are the result 

of protoclastic deformation.

Phillips (1945, p. 214-215) noted faulted and cataclastically deformed pegmatite dikes and veins in the 

Moine Schist. Read (1951) noted cataclastic zones 

which appear to be localized in "acidic dikes." Johnson 

(1961, p. 425) noted that: "Lewisian pegmatites have 

been selected for intense shearing during the Caledonian 

movements."

There are also examples from the United States. In 

his study of the Swakane Biotite Gneiss, Entiat Mountains, Wash., Waters (1932) noted preferential cataclasis of pegmatites. Alf (1948) has described preferential cataclasis (producing protomylonites, mylonites, 

and ultramylonites) of quartz monzonite sills and dikes 

in granulites of the San Gabriel Mountains, Calif, (see 

Hsu, 1955b, p. 256-258, 273-274, for an alternate hypothesis). Higgins (1966, p. 40-42) has described "blastomylonite dikes," which were probably originally 

pegmatite, in Georgia.
36 CATACLASTIC ROCKS

FIGURE 19. Welded tuff from the San Juan Mountains, Colo. 

All photographs from Ratte and Steven, 1967 (A, fig. 4A-C; 

B, flg. 7; O, fig. 5B, C). A, Hand samples of welded tuff. Note 

similarity to some cataclastic rocks. Final forward creep of 

the welded tuff sheet produces structures resembling flow

structure of some mylonites. Draping of flattened pumice 

lapilli around phenocrysts and rock fragments produces structures similar to those around porphyroclasts in fluxion-structured cataclastic rocks. B, Fluidal welded tuff. Note similarity 

to hand samples of some cataclastic rocks, and the rounded
FIELD RELATIONS OF CATACLASTIC ROCKS 37

phenocrysts visible on right end. C, Microscopic structures in 

welded tuff. Left: Eutaxitic structures1 showing weak fluidal 

characteristics, upper half of welded tuff member (Willow 

Creek Member of Bachelor Mountain Rhyolite). Note euhedral 

plagioclase phenocrysts 'and embayed quartz phenocrysts.

Right: Fluidal structure in lower part of the welded tuff 

member. Note similarity to cataclastic texture. The euhedral 

and subhedral plagioclase phenocrysts and the angular quartz 

phenocrysts distinguish this rock from cataclastic rocks in 

thin section. Both with crossed polarizers.
CATACLASTIC ROCKS 

A

Flow of crystallites 

around grain

Euhedral plagioclase 

crystal

Flow bands defined 

by orientation of crystallites and by crystallite-rich and -poor alter 

nations

Chlorite; these bands 

probably represent 

"sperulite zones"

Shear plane?

Recrystallized material (crystalloblastic)

Quartz, feldspar, sericite, and chlorite

1 mm

Some plagioclase 

shows "complex" 

twinning

Sericite

1mm

FIGUKE 20. Microdra wings of metarhyolite from near Waterville, Maine, A, Plane-polarized light; B, crossed polarizers. The 

rock superficially resembles a mylonite or blasitomylonite, but the euhedral phenocrysits of plagioclase identify it as a 

metavolcanic rock. In A, crystallites (some are sericite) are shown in black which tends to exaggerate them. In B, note 

recrystallization followsi same lines as crystallites (old flow lines). Sample from collection of A. C. Watem
FIELD RELATIONS OF CATACLASTIC ROCKS 39

LATE MINERALIZATION OF CATACLASTIC 

ROCKS AND CATACLASTIC ROCK ZONES

Late mineralization is common along many fault 

zones and accounts for secondary minerals in many cataclastic rocks. The most common products of secondary 

mineralization in cataclastic rocks are sulfide minerals, 

carbonate minerals, silica minerals, magnetite, and 

hematite (Crickmay, 1933, p. 174-175; Waters and 

Campbell, 1935, p. 491-^92; Hsu, 1955b, p. 307-308; 

Sclar, 1958, p. 66, 68, 76; Reed, 1964, p. 670, 672, 675; 

Conley and Drummond, 1965, p. 204-206; Higgins, 1966, 

p. 27-28). Secondary carbonate minerals and silica generally occur as veins cutting the cataclastic rocks. Magnetite and pyrite commonly occur as euhedral crystals 

unaffected by the cataclasis. Hematite may be produced 

still later from secondary magnetite.

Most geologists have proposed that the secondary 

mineralizations in cataclastic rocks are due to hydrothermal activity selectively concentrated in the fault 

zones.

FIGURE 21. Banded chert from the Mojave Desert in California. Note the gross similarity to the banding of some cataclastic rocks.

FIGURE 22. Quartzo-feldspathic blastomylonite from the Goat Rock fault zone in Alabama. This rock strikingly resembles finegrained metaquartzite, but the tiny porphyroclasts of feldspar (p) and the field relations indicate it is cataclastic. Thin 

sections show that it is a blastomylonite.

EXAMPLES OF CATACLASTIC ROCK 

ZONES AND THEIR INTERPRETATION

THE SAN ANDREAS FAULT SYSTEM, CALIFORNIA

The San Andreas fault system (Hill, 1966; Hamilton 

and Myers, 1966a) consists of thousands of anastomosing lateral faults in a belt approximately 600 miles long 

and 300 miles wide in California and western Nevada 

(fig. 23). Hamilton and Myers (1966b, p. 516) state:

Some minor faults of the San Andreas system are single 

breaks, but most of the major faults are zones as much as a 

few kilometers wide of anastomosing nearly parallel breaks of 

varying age. Some breaks are moving now but others have been 

long inactive. Gouge and breccia are typically present along

the faults, but mylonite and blastomylonite have been exposed 

along others.

According to Hill (1966, p. 240) :

The system appears to be typified by right-slip on northwest 

trending faults and by left-slip on some of the east-northeast 

trending faults.

The major faults of the system are shown by name on 

figure 23.

THE SAN ANDREAS FAULT

The San Andreas fault, the best known and largest 

fault of the San Andreas system in length and probable 

displacement, is continuous for more than 600 miles, 

from south of the Mexican border to the vicinity of
40 CATACLASTIC ROCKS

124 C 122° 120" 118° 116° 114°

Fault 

Dashed where approximately located

Areas discussed in detail in text 

Crystal Springs Lakes area 

Cucamonga Canyon area

Santa Rosa 

Island

Santa Cruz 

Island

36

34° 

FIGURE 23. Major fault zones of the San Andreas system. Modified from U.S. Geological Survey and American Association of

Petroleum Geologists (1961).
EXAMPLES OF CATACLASTJC ROOK ZONE'S AND THEIR INTERPRETATION 41

Point Arena, north of San Francisco (fig. 23). It has 

been suggested that it extends for at least another 100 

miles offshore to the north (Tocher, 1956; Shepard, 

1957; Curray and Nason, 1967) and into and perhaps 

through the Gulf of California to the south (Hamilton, 1961). There are wide differences of opinion on 

both the sense and amount of movement on the San 

Andreas. Some workers contend that the main movement has been primarily vertical (Buwalda, 1937; 

Clark, 1929; Willis, 1929; Weaver, 1949; Oakeshott, 

1966); others contend that the main sense is strike-slip 

(Noble, 1926; Waters and Campbell, 1935; Wallace, 

1949; Hill and Dibblee, 1953; Moody and Hill, 1956; 

Hamilton, 1961; Dibblee, 1962; Crowell, 1962, 1966; 

Hamilton and Myers, 1966a, b; Hill, 1966). Vickery 

(1925), Noble (1926), Waters and Campbell (1935), 

and Wallace (1949) suggested strike-slip of 12 to 25 

miles; Reed and Hollister (1936), Taliaferro (1943), 

and Oakeshott (1966) would restrict strike-slip to lees 

than a mile; and Hill and Dibblee (1953), Moody and 

Hill (1956), Hamilton (1961), Dibblee (1962), Crowell 

(1962, 1966), Hill (1966), and Hamilton and Myers 

(1966a, b) suggest more than 200 miles of displacement. 

Most proponents of strike-slip movement agree on 

right-lateral displacement, with nearly 1 mile of rightlateral slip (based chiefly on stream offsets) having 

occurred since Pleistocene time. Historic displacements 

are right-lateral and measurable in tens of feet.

Lawson and others (1908), Noble (1926), Wiaters and 

Campbell (1935), Wallace (1949), Crowell (1962), and 

others have described the surface features of the San 

Andreas fault. In brief, it is commonly a zone more 

than half a mile wide marked by scarps, scarp lines, 

slice ridges, sag ponds, shutter ridges, irregular topography, and offset streams.

The fault zone cuts rocks of widely varying age and 

character along its course through California (U.S. 

Geol. Survey and California Div. Mines and Geology, 

1966; Crowell, 1962). Depths of exposure resulting 

from erosion also vary greatly along the zone. Consequently, a great range of cataclastic rock types is found 

along the fault zone. In many places along the zone, 

movements have been distributed through unindurated 

or poorly-indurated rocks. These rocks are deformed 

and jumbled but are certainly not cataclastic. In other 

places, the zone is one of anastomosing shears filled 

with gouge or breccia. In still other places, the zone 

consists of coherent cataclastic rocks and is more than 

half a mile wide.

Waters and Campbell (1935, p. 482-484) have described the San Andreas fault zone and its cataclastic 

rocks in the vicinity of Crystal Springs Lakes, about 30 

miles south of San Francisco:

The rocks along this zone are much sheared and broken, and 

fragments derived from every formation in the region from the 

oldest to the youngest have been brought together in a chaotic 

jumble. At some localities these blocks are sufficiently large to 

be mapped as separate fault slivers, but elsewhere they have 

been ground down until the entire zone can be designated only 

as a heterogeneous fault breccia. ... A great number of different rock varieties are found in this breccia, but the most 

common ones are serpentine, feldspathic sandstone and siltstone, 

altered basialt or diabase, quartz diorite and diorite, quartzite, 

graywacke, impure calcareous rocks, and a well-laminated black 

rock with aphanitic texture which the microscope shows to be a 

true mylonite * * *.

Unlike the other rock varletiesi of the fault breccia, the 

mylonite occurs not in distinct blocks but as a sort of matrix 

which encloses the other rock varieties. Locally it forms great 

tabular masses many feet in thickness. It grades into all the 

other rock varieties and in this transition gradually takes on 

the properties and appearance of the rock with which it is in 

contact. Thus adjacent to the altered basalt the normally black 

color of the mylonite shades off into dark green until the rock 

is indistinguishable from 'schistose, chloritized basalt. Or it may 

grade into quartzite or feldspathic sandstone by a gradual 

increase in granularity and simultaneous decrease in the degree 

of lamination. Similar gradations are shown against quartz 

diorite, and at one place there is an even alternation of black 

mylonite with layers of antigorite schist, the individual layers 

locally averaging less than an inch in thickness. At some places 

minute veinlets of quartz ramify through the rock, some of them 

following the lamination, others cutting across it at all angles. 

The lamination is exceptionally well developed and, produces 

a rock cleavage similar to that of slate or phyllite. The attitude 

of the lamination is highly variable. At Locality 2 it strikes 

parallel with the fault zone and dips vertically though local 

variations appear. At Locality 1 both .strike and dip are highly 

variable, although the strike is prevailingly in the same direction as that of the fault, and the dip is commonly at a low angle. 

Although the lamination is straight at most places, it is locally 

highly contorted, the folds ranging in amplitude from microscopic dimensions to structures a few inches across. Many faults 

of small displacement are also visible in these plicated zones. At 

one place the rock shows two distinct banded structures, one 

dipping at a low angle, the other standing practically vertically. 

The rock splits readily into thin plates along either of these. 

Another curious feature of the lamination is the presence in the 

rock of minute elliptical spots pulled out parallel with the 

laminlation. The true nature of these spots is seldom recognizable 

to the unaided eye, but with a hand lens one can see that they 

are eye^shaped mineral aggregates, or porphyroclasts1 , which 

have survived the complete pulverization of the groundmass, 

and which remind one on a minature scale of 'the 'augen' in a 

typical augen gneiss. Although the rock cleaves into thin plates 

as easily as schist or phyllite, the eye-sihaped jspots, local contortion, and other irregularities cause the lamination to resemble 

the flow structure of an acidic lava as much as it does the foliation of a metamorphic rock. The lustre of the rock may be like 

slate or may be subvitreous like chert or tachylyte.

They go on (p. 484-495) to describe and illustrate 

the mylonites, and ultramylonites in detail.
42 CATACLASTIC ROCKS

OTHER FAULT ZONES OF THE SAN ANDREAS SYSTEM

CUCAMONGA CANYON

Two major and several subsidiary fault zones pass 

through the San Gabriel Mountains, east of Los Angeles 

(fig. 23). Cataclastic zones are well exposed in the steep 

canyons that drain the western slopes of the San Gabriels (Alf, 1948; Hsu, 1955b). The cataclastic rocks 

of Cucamonga Canyon (fig. 24) are particularly 

interesting.

In the Cucamonga Canyon and Aurela Ridge groups 2 

(fig. 24), cataclastic rocks are commonly associated with 

thrust faults on which the sense of movement is readily 

demonstrated by drag folds in the adjacent rocks. The 

zones or layers of cataclastic rocks attending the thrusts 

range from about a foot to several tens of feet in thickness. Thinner layers of cataclastic rock are also present 

in the country rocks away from the easily demarked 

thrust zones. The Sarac Ridge group (fig. 24), about 

3,000 feet in apparent thickness, consists almost entirely 

of cataclastic rocks.

Protomylonite, mylonite, ultramylonite, mylonite 

gneiss, and blastomylonite are all represented in Cucamonga Canyon. There are also some polycataclastic 

rocks. Hsu (1955b, p. 281) stated:

Mylonites in zones of later faulting are brecciated and recemented by secondary minerals, namely clinozoisite penninite.

Some of the cataclastic rocks of the canyon are peculiar for several reasons: (1) Their modal and chemical compositions more closely match those of nearby 

plutons than they do those of the adjacent country rocks 

(see Alf, 1948); (2) Porphyroclasts of feldspars in some 

of these cataclastic rocks show the well-developed zoning common to igneous rocks, and some of the porphyroclasts are euhedral or subhedral (fig. 6B; also see Hsu, 

1955b, p. 337); (3) The cataclastic rocks are interlay - 

ered with siliceous and felsic gneisses of the granulite 

facies of metamorphism, but also with rocks of the 

amphibolite facies.

A\f (1948) thought the cataclastic rocks were derived from the nearby intrusive rocks. He stated (1948, 

p. 1117) :

The thick, steeply north-dipping sheet of Black Belt mylonite [Hsu's Sarac Ridge group! suggests formation along a 

fault zone. If the 2000 feet of mylonite and mylonite gneiss

2 In the discussion of the Cucamonga Canyon that follows, all geologic 

names are informal and are from Hsu (1955b) unless otherwise noted. 

Pertaining to the use of the term "group," Hsu (1955b, p. 230) states :

"Ais the term 'zones' has been commonly used by petrologists to 

designate zones of different P-T X conditions during progressive 

metamorphism * * * I choose to use the term group to designate bodies 

of polymetamorphic rocks whose differences in structures and textures 

resulted from localization of stress rather than from differences in 

temperature and pressure (hydrostatic) conditions. The term 'group' 

as applied to the polymetamorphic rocks of the area does not have the 

connotations commonly implied by stratigraphers * * *."

were formed by crushing and milling of the formations now 

adjacent to the Belt, its chemical composition might be expected to be intermediate between that of the quartz diorite 

gneiss [Hsu's El Dorado Ridge gneissose quartz diorite] and 

that of the pyroxene dioritic gneiss [Hsu's Aurela Ridge group] 

(or locally the Oucamonga Complex) [Hsu's Cucamonga Canyon group]. But, as shown, chemical analyses and all other 

available information indicate that the Black Belt rocks have 

compositions close to that of the quartz diorite gneiss, and more 

siliceous than most of the pyroxene dioritic gneiss. Perhaps at 

depth the Black Belt is walled on both sides by quartz diorite 

gneiss, and was produced chiefly by the grinding up of a single 

rock type.

The hypothesis of origin of the Black Belt from the crushing 

of solid, dark quartz diorite gneiss has two defects. First, the 

quartz diorite gneiss appears to intrude the Black Belt mylonite, 

and thus to have been at least locally semi-liquid after the mylonite had formed. Second, narrow dike-like streaks of pale 

analysed quartz monzonite mylonite cut the main mass of the 

Black Belt. This pale mylonite has neither the composition of 

the enveloping rock nor a simply related composition (e.g., 

merely more siliceous). The existence of two types of mingled 

mylonite, each with the composition of a plutonic rock present 

in the area, suggests that the main mass of mylonite may have 

been formed by the crushing of a barely consolidated upper 

layer of a quartz diorite batholith and that the bands of quartz 

monzonite mylonite may have resulted from the streaking out 

of plutonic dikes while they were more plastic than the surrounding rock, perhaps before crystallization was entirely 

completed.

Hsu (1955b) disagreed with Alf. He thought the 

cataclastic rocks were derived from the granulites and 

had been metasomatized (1955b, p. 256) :

* * * their composition is so varied that they could not have 

been derived from a homogeneous "igneous" body and probably 

not from the Stoddard Canyon quartz monzonite, which has 

a rather uniform composition over the area.

The field occurrence suggests that cataclasis was synchronous 

with the thrusting of the Aurela Ridge granulites. If the cataclastic rocks were derived from "igneous" rocks, one has to assume that "igneous" rocks occurred as dikes where thrusting 

subsequently took place. Such a coincidence seems highly improbable, especially when one takes into consideration the 

remarkable preferred orientation of the cataclastic "dikes."

The chemical and mineralogical compositions of the cataclastic rocks indicate that they are not simply mylonitized 

granulites; they are richer in potash feldspar and poorer in 

pyroxene than the granulites. Only in one or two specimens 

is a trace of relict pyroxene found. Such a discrepancy in composition, nevertheless, can be readily explained by assuming 

metasomatism accompanying cataclasis.

Of the feldspars Hsu stated (1955b, p. 256-257):

The origin of the large plagioclase crystals in cataclastics is 

somewhat puzzling. Many of them are not severely strained. 

Their idiomorphic outline, straight twinning lamellae, and clear 

appearance are in remarkable contrast to the angular or lenticular outline, the bent and broken twinning lamellae, and the dusty 

apperance of the strained plagioclase crystals. Whether these 

little strained crystals are porphyroclasts or porphyroblasts is 

still debatable, although it seems highly improbable that any 

crystal a few millimeters long could survive cataclasis, with its
EXAMPLES OF CATACLASTIC ROCK ZONES AND THEIR INTERPRETATION 43

A : : /:Qf-. ;.;:; ; : 

EXPLANATION

NO STRATIGRAPHIC ORDER IMPLIED 

ALL NAMES INFORMAL*

Qt, Other Quaternary deposits

Stoddard Canyon quartz monzonite

El Dorado Ridge gneissose quartz diorite

Chiefly cataclastic rocks; some amphibolites

Hypersthene arnphibolites and altnandineCucamonga Canyon group

Cataclastic rocks, amphibnlites, and marble

Contact between Quaternary rocks and 

older rocks

1000 0 1000 2000 3000 4000 FEET

500 

I i

500 1000 METERS

Contact 

Dashed where approximately located

Fault

Dashed where approximately located; 

queried where doubtful

Thrust fault

Dashed where approximately located;

short dashed where inferred. Saioteeth on upper plate

 X- Group is not used in formal stratigraphic 

sense. As used here it applies to rocks 

with similar structure and texture resulting from localization of stress

FIGURE 24. Geologic map of the Oucamonga Canyon area, San Gabriel Mountains, Oalif. (see fig. 23 for location). Generalized

from Hsu (1955b).

idiomorphic outline preserved and showing little evidence of 

strain, while other crystals are broken into fragments 0.01 to 

0.001 mm. in size. Broken porphyroclastic crystals are common. 

On the other hand, some crystals containing trains of inclusions, 

which may be relic foliation, are probably porphyroblasts. The 

fact that the relic foliation (?) in some plagioclase crystals is 

tilted at an angle to the foliation of the enclosing matrix and

that the corners of some plagioclase porphyroblasts are sheared 

off indicate that some deformation occurred after the recrystallization of the plagioclase. It seems therefore that some crystals 

were pulverized by cataclastic deformation, others were recrystallized, and that recurrent movement caused repeated 

cataclasis. These observations and deductions indicate a 

synkinematic crystallization of plagioclase.
44 CATACLASTIC ROCKS

Potash feldspar probably crystallized from introduced ichors 

(hydrothermal or pegmatitic solutions). Textural criteria suggest a period of potash feldspar replacement subsequent to the 

crystallization of plagioclase. The fllling-in of the cracks of 

broken plagioclase by aggregates of potash feldspar dates the 

metasomatic process as synkinematic. Myrmekite may have resulted from synkinematic or postkinematic metasomatic activities, and granoblastic quartz was probably formed in the waning 

phase of cataclasis.

I regard the origin of these cataclastic rocks as unsolved, but favor the hypothesis of Alf (1948). Hsu's 

point regarding the dikes is not convincing; as noted 

elsewhere in this paper (p. 35) the coincidence of 

cataclasis and dikes is common. It also seems that the 

feldspars can more simply be explained by cataclasis of 

incompletely crystallized dikes than by an exotic scheme 

of metasomatism; from what is known of protoclastic 

rocks the existence of euhedral porphyroclasts is not 

completely anomalous. Hsu does make a good point regarding Alf's scant chemical data, but his statement 

regarding the variation in composition is based on little 

evidence, because he presented no new analyses.

Regardless of arguments concerning ultimate origin, 

the rocks of Cucamonga Canyon are impressive because of their variety and good exposure and because 

it can be readily demonstrated that they formed by 

faulting under conditions of amphibolite facies metamorphism.

Other fault zones of the San Andreas system and the 

cataclastic rocks in them have been described by Noble 

1954 (1954), Dibblee (1954,196T),Mann (1955), Alien 

(1957), Ehlig (1959), Proctor (1962), Theodore 

(1966), and Sharp (1967).

THE ALPINE FAULT ZONE, NEW ZEALAND

The South Island of New Zealand is transected by a 

great fault zone (fig. 25) known as the Alpine fault 

(Wellman and Willett, 1942) or the Alpine fault zone 

(Eeed, 1964). This fault zone has long been known to 

extend from Milford Sound on the southwest coast to 

near Lake Eotoroa, southeast Nelson, in the northern 

part of the island (Wellman and Willett, 1942). Recently, Suggate (1963) and Reed (1964) have shown 

that it is continuous with the Wairau fault, and by this 

connection reaches Cook Strait near the mouth of Wairau River (fig. 25). The fault zone probably continues 

into the North Island also (Wellman, 1956; Suggate, 

1963; Reed, 1964).

Through most of its length the Alpine fault zone is 

marked by a conspicuous topographic and geologic lineament, according to Cotton (1947, p. 369), "the most remarkable lineament in the geology of New Zealand." 

Apparent stratigraphic offset along the fault zone is 

readily seen even on small scale geologic maps (fig. 25:

also see New Zealand Geol. Survey, 1958). Suggate 

(1963) discussed alternative possibilities for the 280- 

to 300-mile right-lateral shift first proposed by Wellman (1955) but presented good evidence that the shift 

is probably real (also see Reed, 1964). As much as 60,- 

000 feet of vertical movement has also taken place on 

the fault zone, but the amount probably varies considerably along its course (Suggate, 1963; Reed, 1964). 

Reed (1964) has given an excellent description of the 

cataclastic rocks in the Alpine fault zone. He stated 

(pp. 645, 672) :

The cataclastic rocks along the Alpine Fault can be readily 

classified into three distinct groups: an incoherent group of 

fault pug [fault gouge in my classification table 1], fault 

breccia, and shattered rock; a cataclasite group of brecciated 

rock, mortared rock, [both micro'breccia, in my classification] 

and cataclasite; and a mylonite group comprising augen 

mylonite [3] , mylonite, ultramylonite, and blastomylonite.

The first group is common along the line of Quaternary movement of the Alpine Fault, the fault pug and fault breccia being 

a few feet to more than 100 ft wide, and the zone of shattered 

schist several chains t*J or more in width.

* * * The second group is conspicuous in .the granitic rocks, 

the structureless cataclasite being 100-200 ft. thick, and the 

zone of brecciated and mortared granite a mile or more in 

width. The mylonite group is characterized by fluxion banding 

and forms a belt 1,000-2,500 ft. wide, largely within the granite.

And concerning the mylonite group (p. 675) :

The composite picture obtained from study of all the sections 

is of a mylonite belt 1,000-2,500 ft. in width, of which 600-2,000 

ft. is augen mylonite and mylonite, 300-1,000 ft. blastomylonite, 

and 100-300 ft. schist derived mylonite.

Reed also describes specific sections of cataclastic 

rocks in the zone; the following is typical (1964, p. 672- 

673) :

* * * the passage between schist and mylonite is well displayed in a continuous section in the Saddle Creek tributary of 

Canada Creek; about 1,300 ft. of augen mylonite and mylonite 

passes eastward into about 600 ft. of blastomylonite, and this 

in turn into garnetiferous "curly" schist. These three rock types 

form distinct bands except for some minor interfingering of 

blastomylonite with augen mylonite and mylonite.

Reed (1964, p. 676) also notes cataclasites formed 

from mylonites (polycataclastic rocks). He describes 

all of the cataclastic rocks well, and his illustrations are 

particularly good. However, nothing would be gained 

here by quoting his descriptions, because the rocks are 

all similar to those defined, described, and illustrated 

elsewhere in this paper.

3 Reed (1964, p. 657-659) uses this term for mylonites with large 

porphyroclasts. It is not equivalent to mylonite gneiss. Perhaps porphyroclastic mylonite would serve better.

4 1 chain equals 66 feet.
EXAMPLES OF OATAOLASTIO ROOK ZONES AND THEIR INTERPRETATION 45

NORTH 

ISLAND

TASMAN SEA

EXPLANATION

MOST ROCKS YOUNGER THAN 

JURASSIC NOT SHOWN

Upper Cretaceous(?) and Lower

Nelson and Red Mountain ultramafic

SOUTH ISLAND

BANKS 

PENINSULA

Triassic and Jurassic rocks

Chiefly sedimentary rocks

Lower Mesozoic and upper Paleozoic rocks

Otago, Alpine, and Marlborough schists

Permian and Carboniferous rocks

Chiefly sedimentary rocks, some tuffs

Pre-Carboniferous rocks

Chiefly metamorphic and plutonic rocks

Inferred contact

Fault

Dotted where concealed; 

queried where doubtful

20 0 20 40 60 80 100 KILOMETERS 

STEWART i > 11 i i i i i i

ISLAND

20 0 20 40 60 80 100 MILES 

l____l____I l

FIGURE 25. Greneralized geologic map showing the Alpine fault zone, New Zealand (modified from New Zealand Geol. Survey,

1958).

420-418 O - 71 - 4
46 CATACLASTIC ROCKS

TOWALIGA, GOAT ROCK, AND BARTLETTS 

FERRY FAULT ZONES, GEORGIA AND ALABAMA

There are three major fault zones near the southern 

margin of exposed Piedmont crystalline rocks in 

Georgia and Alabama (fig. 26). Two of these, the 

Towaliga and Goat Rock zones, have been known since 

the early 1930's (Crickmay, 1933); the Bartletts Ferry 

has only recently been recognized (Bentley, 1969). The 

Towaliga and Goat Rock zones were long interpreted 

as thrust faults (Crickmay, 1933, 1939, 1952; Clarke, 

1952), but recent work suggests that they probably 

have complicated movement histories involving thrust, 

normal, and strike-slip displacements (W. H. Grant, 

1967, 1968, and oral commun., 1965-69; R. D. Bentley, 

oral commun., 1969). Bentley (1969) interprets displacement on the Bartletts Ferry zone as predominantly right lateral. All three zones are marked by 

thick assemblages of various types of cataclastic rocks.

Microscopic descriptions of various cataclastic rocks 

in the Towaliga and Goat Rock fault zones have been 

published by Crickmay (1933), Clarke (1952), and 

Grant (1968). They are not quoted or described here 

because the rocks are similar to those defined, described, 

and illustrated elsewhere in this paper.

TOWALIGA FAULT ZONE

The Towaliga zone (fig. 26) has been traced from 

Ocmulgee River, east of Barnesville, Ga., to near Auburn, Ala., where it disappears beneath Cretaceous 

rocks of the Gulf Coastal Plain (Crickmay, 1933, 1939; 

Bentley, 1969; W. H. Grant, oral commun., 1969). It 

probably extends farther east in Georgia (as dashed on 

fig. 26), and possibly into South Carolina.

Near Ocmulgee River, the main zone of the Towaliga 

is characterized by dense mylonite which Crickmay 

(1933, p. 172) described as follows:

* * * the mylonite looks like a volcanic rock; it contains feldspar porphyroclasts in a dark gray to black, aphanitic groundmass 'that simulate phenocrysts in an extrusive, and it possesses 

a fluidal structure that is strongly reminiscent of the flow banding in certain rhyolites,

Near Barnesville, Ga., the main zone, about 100-400 

feet thick, is marked by mylonite, blastomylonite, and 

microbreccia. According to Grant (1968), the mylonite 

and the microbreccias are relatively continuous, whereas the discontinuous blastomylonite recurs along the 

zone. Crickmay (1933, p. 171) described a mylonite in 

the zone near Barnesville as follows:

The rock might easily be mistaken for the Hollis quartzite, 

which crosses the highway three-quarters of a mile south, but 

for the presence of rather characteristic banding and small 

porphyroclasts of feldspar. Through most of the mylonite the

porphyroclasts are absent and the rock is aphanitic, but in 

certain thin layers, which have not been crushed to the same 

extent as the main mass, porphyroclasts are abundant and indicate at once the origin of the rock.

The rocks for several miles on either side of the main 

zone in the Barnesville area have been affected by intense penetrative deformation, and small en echelon 

fault zones, marked by mylonite or, more commonly, 

by microbreccia, are common within a mile or two of 

the main zone.

West of Barnesville the main zone gradually thickens, 

and polycataclastic rocks, chiefly brecciated mylonites, 

appear. Near the Alabama line the main zone is more 

than half a mile wide, and is occupied chiefly by "dense 

gray mylonites with abundant porphyroclasts" (Crickmay, 1933, p. 171), blastomylonites, and subordinate 

amounts of aphanitic ultramylonite. On either side of 

this main band are zones of mylonite gneiss up to threequarters of a mile thick.

The whole zone continues to thicken to the west in 

Alabama, and near Auburn (fig. 26) it is a zone approximately 6 miles wide of blastomylonites and porphyroclastic mylonite gneisses interspersed with at least three 

mylonite bands and containing slices of metaquartzite, 

marble, and schist (Bentley, 1969).

GOAT ROCK FAULT ZONE

The Goat Rock zone (fig. 26) has been traced from 

near Talbotton, Ga., to southwest of Salem, Ala., where 

it is covered by Cretaceous rocks (Crickmay, 1933,1939; 

Bentley, 1969; W. H. Grant, oral commun., 1969). On 

the Geologic Map of Georgia, Crickmay (1939) showed 

the fault curving northeast just east of Talbotton, and 

he extended it as a dashed line to Flint River. Actually, 

the Goat Rock zone extends east along Crickmay's contact between his biotite gneiss and schist unit and his 

augen gneiss unit at least as far as Flint River, and it 

may continue along this relatively straight contact for 

some distance to the east (fig. 26).

Through most of its known extent in Georgia, the 

Goat Rock is a zone, 2 to 4 miles wide, of mylonite, ultramylonite, blastomylonite, and mylonite gneiss. Microbreccias and polycataclastic rocks are also present but 

are subordinate in volume to the varieties listed above. 

Like the Towaliga, the Great Rock has a main, or central 

zone, as much as a mile thick, of mylonite, blastomylonite, and ultramylonite bordered on each side by zones of 

blastomylonite and mylonite gneiss. As Crickmay (1933, 

p. 173-174) recognized, these outer zones are gradational into crystalloblastic augen gneisses by decrease 

in cataclastic texture and increase in crystalloblastic 

texture.
EXAMPLES OF CATACLASTIC ROOK ZONES AND THEIR INTERPRETATION 47
48 CATACLASTIC ROCKS

Crickmay (1933, p. 174) gave a good description of a 

mylonite (my classification, table 1; he refers to it as 

an ultra-mylonite) in the Goat Rock zone:

The ultra-mylonite is well exposed near Piny Grove Church, 

about ten miles north-northwest of Columbus, near the center of 

the mylonitized zone. The rock has the apperance of a black 

argillite with a poorly developed slaty cleavage, which dips 35° 

southeast. The cleavage surfaces are dull, perfectly regular, 

and are commonly coated with a dendritic growth of manganese 

oxides. In the groundmass are embedded numerous rounded 

porphyroclasts of feldspar averaging .5 mm. and rarely more 

than 2.5 mm. in diameter.

Bentley (1969) has described the Goat Rock in Alabama as a vertical to steeply southeast dipping zone, at 

least three miles wide, with a central band about a mile 

wide, characterized by ultramylonite, mylonite, and 

blastomylonite, and marginal bands, each nearly a mile 

wide, of "flaser gneisses and augen gneisses." The latter 

are mostly mylonite gneiss.

BARTLETTS FERRY FAULT ZONE

The Bartletts Ferry zone (fig. 26) was recognized 

and mapped in Alabama by R. D. Bentley. It has not 

yet been mapped in Georgia, but it extends across the 

State line (R. D. Bentley, oral commun., 1969). Where 

the zone crosses the Chattahochee River into Georgia it 

approximates Crickmay's (1939) contact between his 

Manchester schist and Sparks schist unit and his augen 

gneiss unit. These units are similar to belts of rocks 

separated by the fault zone in Alabama (Bentley and 

Deininger, 1969). Possibly then, the Bartletts Ferry 

zone may follow Crickmay's contact, thus bounding 

the Pine Mountain sequence on the south as the Towaliga fault zone bounds it on the north (Crickmay, 

1939). This would account for the cataclastic rocks near 

Flint River, east of Pleasant Hill, which caused Crickmay to curve the Goat Rock fault to the northeast on 

the Geologic Map of Georgia (Crickmay, 1939).

Bentley (1969) describes the Bartletts Ferry fault 

zone in Alabama as follows:

The middle zone (Bartlets [sic] Ferry fault) trends N3OE 

N5OE and is nearly vertical throughout. This zone is characterized by 200 feet of ultramylonite, which is bordered on 

the southeast by several thousand feet of mixed mylonite, 

blastomylonite and porphyroclastic gneiss.

INTERPRETATION OF THE ZONES

The history of interpretation of the Towaliga and 

Goat Rock fault zones is particularly interesting 

because it illustrates how recognition and study of cataclastic rocks can influence geologic maps and interpretations of the geologic and tectonic history of an area.

Galpin (1915, p. 74r-76) first recognized the peculiar 

nature of the rocks along the Towaliga fault zone with

respect to the rocks on either side of the zone. He interpreted the rocks as volcanic. They do superficially 

resemble volcanic rocks (Crickmay, 1933, p. 171-173).

None of the fault zones are shown on the geologic 

map of Alabama (Smith, 1926).

Crickmay (1933, p. 171-175) recognized the rocks 

of the Towaliga and Goat Rock zones as cataclastic. 

Concerning the rocks in the Towaliga zone, he stated 

(p. 173) :

They are mylonites derived from a coarse biotite augen gneiss 

in which neomineralization is very minor or entirely absent 

They might easily be mistaken for a quartzite or volcanic rock, 

from which they may be distinguished in the field by their mode 

of occurrence (e.g., they occur close to the Towaliga fault; they 

are gradational into cataclastic augen gneiss), and by the 

presence of feldspar porphyroclasts.

Because cataclastic rocks were then known to occur 

only in conjunction with thrust faults, or supposed 

thrust faults such as the "Brevard thrust" (Jonas, 

1932), Crickmay (1933,1939) interpreted the Towaliga 

and Goat Rock fault zones as thrusts.

Clarke (1952) studied the Towaliga and Goat Rock 

zones in the Thomaston, Ga., area. However, what 

Clarke mapped as the Goat Rock fault may be an extension of the Bartletts Ferry fault zone. He agreed with 

Crickmay, and interpreted both of the zones as thrusts. 

In addition, he expanded Crickmay's tectonic interpretations and postulated that the Towaliga, Goat Rock, 

and Brevard faults are the same folded thrust. This 

would make the whole Georgia and Alabama central 

Piedmont (Dadeville Belt of Crickmay, 1952) a klippe.

Since the early 1960's, the Towaliga fault zone has 

been studied by W. H. Grant of Emory University and 

his students. Grant (1968) stated:

Three distinct periods of movement are recognized. The 

earliest is recognized by a blastomylonite in which considerable 

recrystallization is svident. These outcrops are very sparse 

hence reconstruction of the blastomylonite producing fault is 

not feasible. Recrystallization of biotite shows this movement 

overlaps with the later phases of metamorphism which raised 

the surrounding rocks to sillimanite and kyanite grade.

The second movement period is seen in the main (strike N. 

70° E.) mylonite zone. These mylonites are only slightly recrystallized. Dips on these easily traceable fault surfaces ramge 

up to 80° to the north. The mlajor movement appears1 to have 

been (Strike slip as indicated by displacement of minor structures. This movement is also indicated by petrof abric data which 

sihow a strong maxima for quartz in the strike slip direction.

Striations, at right angles to the fault and the rotation of 

joints formed in the mylonite, are evidence of the third movement This indicates a. dip slip movement, and appears to be the 

last

Bentley (1969) reports evidence of lateral movement 

on all three fault zones in Alabama. Of the Goat Rock 

fault zone he states:
EXAMPLES OF CATACLAST1C ROCK ZONES AND THEIR INTERPRETATION 49

Most minor folds and local faults suggest a right lateral 

displacement along the zone.

Of the Bartletts Ferry fault zone:

Horizontal mineral lineations are only locally developed along 

this fault. Minor folds and faults and strained clasts all indicate a right lateral displacement.

And of the Towaliga fault zone:

Similar to the Goat Rock fault this zone shows a well developed, nearly horizontal mineral lineation. Drags of mapped 

units along the northern edge of the zone suggest right lateral 

regional 'displacements. The amount of displacement cannot 

be determined.

As I stated earlier, all three fault zones have probably had complicated movement histories with more 

than one sense of displacement.

THE BREVARD ZONE, SOUTHEASTERN 

UNITED STATES

The Brevard zone is a belt about 1 to 5 miles wide 

of cataclastic and low-grade metamorphic rocks that 

extends northeast in a nearly straight line from eastern 

Alabama nearly to Virginia (fig. 27). Throughout this 

course the zone is bordered on either side by plutonic 

and higher grade metamorphic rocks. Approximately 

coincident with the belt from near Wilkesboro, N.C., 

to about Tallapoosa River in Alabama is a marked 

topographic lineament (see U.S. Army Map Service 

plastic relief 1: 250,000-scale series maps: Atlanta NI 

16-9; Greenville NI 17-4; Knoxville NI 17-1; Charlotte NI 17-2; and Winston-Salem NJ 17-11). A 

distinctive magnetic lineament is also coincident with 

the Brevard zone for at least part of its course (Philbin 

and others, 1964). The southern end of the Brevard 

zone in Alabama was assumed to bend to the south 

near Tallapoosa River to reach the edge of the Coastal 

Plain just northeast of Montgomery (U.S. Geol. Survey 

and Am. Assoc. Petroleum Geologists, 1961; King, 

1964; Reed and Bryant, 1964; Bayley and Muehlberger, 

1968). However, recent work in that area shows that 

the zone probably splays southwest of Tallapoosa River; 

subsidiary zones bend gradually south, but the main 

zone continues on its southwest course to pass beneath 

the edge of the Coastal Plain near Central, Ala. (Bentley, 1969; Bentley and Deininger, 1969; Bentley, oral 

commun., 1969; fig. 27). A somewhat similar situation 

exists for the northern end of the Brevard zone, in 

North Carolina. On most maps (U.S. Geol. Survey and 

Am. Assoc. Petroleum Geologists, 1961 King, 1964; 

Reed and Bryant, 1964), the Brevard zone is shown 

continuing along a straight northeast course past Mount

Airy and into Virginia, but recent work (Dunn and 

others, 1966; Espenshade, 1967; Butler and Dunn, 1968; 

Centini, 1968) indicates that the zone begins to splay 

near Wilkesboro. One branch bends east to become the 

Stony Ridge fault zone; another branch bends eastward toward Pilot Mountain; and still another branch 

bends slightly eastward and follows a conspicuous topographic lineament through Ararat, between Mount Airy 

and Pilot Mountain (fig. 27).

From near Wilkesboro, to near Fletcher, N.C. (fig. 

27) the Brevard zone is a belt of phyllonite, blastomylonite, and mylonite gneiss, about a mile wide, near 

the northwest edge of a zone of shearing and retrogressive metamorphism about 5 miles wide (see Reed and 

Bryant, 1964). Rocks quite similar to those in the segment from Wilkesboro to Fletcher occupy the two westernmost branches or splays northeast of Wilkesboro; 

the easternmost branch, the Stony Ridge fault zone, is 

characterized chiefly by microbreccia. The description 

of the Wilkesboro to Fletcher segment of the zone also 

fits the segment from Fletcher southeast to near Flowery Branch, Ga., except that this segment also contains 

discontinuous lenses of dolomitic marble, which Reed 

 and Bryant (1964) consider "exoitic tectonic lenses." 

Southwest of Flowery Branch, at least to Tallapoosa 

River in Alabama, phyllonites, blastomylonites, and 

mylonite gneisses identical to those in the zone to the 

northeast are joined by thin, discontinuous, and commonly en echelon bands of mylonite, protomylonite, 

ultramylonite, microbreccia, and cataclasite. Polycataclastic rocks, chiefly brecciated mylonite, are also present in this segment. In Georgia, the main band of 

cataclastic rocks is locally more than 2 miles wide, but 

the zone of shearing and retrogressive metamorphism is 

generally thinner than in North Carolina. Southwest 

of Tallapoosa River the Brevard zone and its branches 

have not yet been studied in detail, but it appears that 

the rocks there are similar to those of the Flowery 

Branch to Tallapoosa River segment.

The character and origin of the Brevard zone is currently in dispute. Some geologists have presented evidence that it is a great strike-slip fault with some 

vertical displacement (Reed and others, 1961; King, 

1964; Reed and Bryant, 1964; Higgins, 1966); others 

believe it is an "alpine type root zone" or zone of 

"Verschluckung" (Burchfiel and Livingston, 1967, 

1968; Livingston and Burchfiel, 1968); still others recognize sedimentary characteristics in the zone (Hurst 

and Crawford, 1964; Dunn, Butler, and Justus, 1968; 

Dunn, Butler, and Weigand, 1968). Nevertheless, the 

presence of cataclastic rocks in the zone is indisputable.
50 CATACLASTIC ROCKS

EXPLANATION

Tertiary and Cretaceous

sedimentary rocks

Unmetamorphosed Paleozoic

sedimentary rocks

Paleozoic and Precambnan 

metamorphic and plutonic rocks

Thrust fault

Sawteeth mi upper plate; many thrusts

Normal fault 

Ticks on downthrwn side

Steeply dipping major fault

zone

Width of line approximates width 

ofcatada.itic rock zone

50 KILOMETERS

FIGTJEE 27. Generalized geologic map of the Brevard zone, southeastern United States (modified from Fisher and

others, 1970).
EXAMPLES OF CATACLASTIC ROCK ZONES AND THEIR INTERPRETATION 51

Reed and Bryant (1964, p. 1182-1183) gave a vivid 

"verbal cross section" of the southeast border of the 

Brevard zone in North Carolina:

The rocks of the Inner Piedmont more than 5 miles southeast 

of the Brevard zone are all of high metamorphic grade and 

display no conspicuous cataclastic features. The plagioclase is 

generally andesine; aluminous rocks contain sillimanite, and 

calcareous rocks contain diopside. Foliation has diverse strikes 

and low to moderate dips, generally to the south or southeast. 

Lineation is marked by alignment of fibrous sillimanite and 

prismatic hornblende, by elongate clots of biotite, and by crenulations in foliation planes and generally plunges gently or moderately eastward. The mineral alignment is apparently due to 

growth parallel to crenulation axes.

About 4 miles from the Brevard zone the metamorphic grade 

is lower. Sillimanite disappears, although staurolite and kyanite 

are found locally; polymetamorphic textures become increasingly apparent. Foliation assumes a consistently northeast 

strike, parallel to the Brevard zone, and sufohorizontal cataclastic lineation parallel to the strike becomes prominent. This 

lineation is marked by streaks of fine recrystallized mica on 

foliation planes, crushed and drawn out feldspar porphyroclasts, and aligned aggregates of recrystallized quartz. Long 

axes of boudins of amphibolite and of competent lime-silicate 

rocks in the gneisses are generally parallel to it. Axes of isoclinal 

folds also generally trend northeast, but many display steeper 

and more erratic plunges. Within 2-3 miles of the Brevard 

rocks of the Inner Piedmont belt are conspicuously cataclastic and polymetamorphic. The schists contain porphyroclasts of muscovite, plagioclase, and locally of staurolite and 

kyanite set in a matrix of fine-grained, recrystallized quartz, 

biotite, muscovite, epidote, and plagioclase. Both the plagioclase 

porphyroclasts and the fine-grained recrystallized plagioclase 

are either oligoclase or sodic andesine, indicating recrystallization under medium-grade conditions.

Adjacent to the Brevard zone the medium-grade polymetamorphic rocks are retrogressively metamorphosed to low grade: 

plagioclase is partly or completely altered to albite, and biotite 

is replaced by chlorite. The textural contrasts, as the Brevard 

zone is approached, are particularly conspicuous in the Henderson Gneiss. Fine-grained biotite-quartz monzonite gneiss containing large augen of microcline is reduced to blastomylonitic 

gneiss [mylonite gneiss of my classification; table 1] and finally 

to blastomylonite in and near the Brevard zone.

For the most part, the rocks in the Brevard zone are 

typical cataclastic rocks like those defined, described, 

and illustrated elsewhere in this paper. However, two 

types of rock in and near the zone are particularly interesting, chiefly because identical rocks occur in association with the Brevard throughout its extent: (1) 

Porphyroclastic phyllonites, called "phyllonitic schists" 

by Reed and Bryant (1964, p. 1181), and "muscoviteeyed phyllonites" by Higgins (1966, p. 27-28), occur 

intermittently in the Brevard zone from Alabama to 

northern North Carolina. These rocks typically have a 

lustrous gray, silvery-gray, gray-green, or blue-green 

phyllitic groundmass and contain bent porphyroclasts 

of muscovite or sericite, which have a "fish-scale" appearance on foliation planes and a ragged, "flagellate"

appearance in cross section. These bent porphyroclasts 

of mica give the foliation planes a "curly" or "wavy" 

appearance. Reed and Bryant (1964, p. 1189) cited evidence that some of these rocks are diaphthoritic in the 

Grandfather Mountain Window area, but near Atlanta, 

Ga., they may be simply phyllonitic (Higgins, 1956, p. 

27); (2) Rocks called "button schists" by Higgins (1966, 

p. 27), and simply "polymetamorphic schists" by Reed 

and Bryant (1964) are intimately associated with the 

Brevard zone throughout its extent and have a remarkably identical appearance all along the zone. These rocks 

are not strictly cataclastic, because they have crystalloblastic textures, but it is obvious that they have been 

much sheared and recrystallized, and, in fact, they may 

be blastomylonites in which the crystalloblastic process 

has completely dominated cataclasis. They are characterized by two subparallel cleavages that cause distinctive buttons upon weathering (Crickmay, 1952, p. 26).

THE MOINE THRUST ZONE, NORTHWEST 

HIGHLANDS, SCOTLAND

The Moine thrust zone angles across northwest Scotland in a sinuous course from Whiten Head to Point of 

Sleat, Isle of Skye (fig. 28). This thrust zone is probably the best known and most closely studied fault zone 

in the world, and it was here that much of the geology 

of the Northwest Highlands was first unraveled (Peach 

and others, 1907). It was also along the Moine thrust 

zone that mylinites were first recognized, described, and 

defined (Lapworth, 1885; Peach and others, 1907). In 

fact, this zone and the adjacent areas have probably had 

more influence on geology, particularly structural 

geology, than any other area of comparable size on 

earth.

The Moine thrust zone is a belt of two to four major 

overlapping thrust faults (fig. 28; Peach and others, 

1907; Bailey, 1935; WiMnson, 1955; Johnson, 1957; 

Christie, 1963; Barber, 1965) and numerous minor 

faults. The basic geology of the zone has been known 

for more than 60 years (Peach and others, 1907); recent work has chiefly added details and refined interpretation. Although Christie's (1963) proposal of 6 miles 

of strike-slip movement was strongly opposed by Johnson (1965) and by Barber (1965), all who have studied 

the zone agree that the major component is thrust. Each 

of the thrusts in the zone appears to be overlapped in 

turn by the overlying one (Peach and others, 1907; 

Christie, 1963; Barber, 1965), and the Moine thrust, 

generally regarded as the most important, locally overlaps them all and carries crystalline schists of the Moine 

series over Lewisian, Torridonian, and Cambrian rocks 

to the west (fig. 28). Both imbricate structure, or
52 CATACLASTIC ROCKS

NORTH A TLANTIC 

OCEAN

10 5 0 10 KILOMETERS 

111 I

EXPLANATION

STRATIGRAPHIC SEQUENCE NORTH

OF THE MOINE THRUST 

(Includes units not shown separately on map)

Cambrian, Torridonian, and 

Lewisian rocks

Moine thrust zone

Thrust.faults and 

cataclastic rocks

Chiefly metasandstones

Approximate contact

Short dashed where inferred

Lewisian rocks

Gneisses and metamorphosed Major thrust fault 

Teeth on upper plate

CROSS SECTION OF THE MOINE THRUST

LOCH BROOM 

From Peach and others (1907)

(Torridonian rocks not shown)

Lewisian gneiss

FIGURE 28. Generalised geologic map of the Moine thrust zone, Northwest Highlands, Scotland. Modified from Christie (1968)

and Peach and others (1907).
EXAMPLES OF CATACLASTIC ROCK ZONES AND THEIR INTERPRETATION 53

Schuppen /Struktur, and nappe structure are locally developed along the zone.

Excellent reviews of the history of interpretation and 

research on the Moine thrust zone have been published 

by Mclntyre (1954) and Christie (1963).

Cataclastic rocks are found all along the Moine thrust 

zone, and all of the major rock groups in the thrust 

zone, Lewisian, Moinian, Torridonian, and Cambrian 

have locally been cataclastically deformed. Generally, 

the most intensively deformed rocks occur in narrow 

bands immediately adjacent to the thrust planes, 

whereas less intensively deformed, more recrystallized 

and neomineralized rocks occur in broad zones 

between and structurally above the faults. Near 

the Moine thrust, the Moine schists are retrogressively metamorphosed.

Barber has described the gradational cataclasis in the 

Kishorn nappe of Lochalsh and Lochcarron (1965, p. 

217-219):

Specimens of Torridonian Sandstones, collected, across the 

outcrop in Lochalsh, show increasing signs of cataclasis from 

west to east. In the west, sandstones of the Applecross Group 

have a typical sedimentary texture, with only occasional fractured felspar grains. Further east the sandstones develop a 

'mortar' texture with large fragmented felspar grains embedded in a fine-grained groundmass. Towards the contact with 

the overlying Lewisian the texture in the Torridonian becomes 

lenticular, with shear surfaces developed around the original 

grains, which are now lozenge-shaped and enclosed by groundmass minerals to form augen structures. At the contact with 

the Lewisian, the Torridonian Sandstones have been completely converted to mylonite.

Throughout the Torridonian the minerals in the groundmass 

are quartz, white mica and chlorite. The major differences in 

the groundmass, seen in thin sections taken across the area, 

from west to east are; that the groundmass makes up an 

increasing portion of the whole rock; and that the flaky constituents have an increasingly parallel orientation. The end 

products of these trends are most fully developed in the mylonites, where relict felspar grains are scattered through a finegrained groundmass. The minerals of the groundmass have a 

strong preferred orientation, giving the rock a pronounced 

fissility.

* * * * *

Every stage of deformation from unaltered Lewisian rocks 

to their mylonitic derivatives occurs in the Kishorn Nappe. The 

most highly deformed rocks occur at the contact with the 

Torridonian, but the amount of deformation decreases rapidly 

eastwards through the Lewisian.

Christie (1963) has given detailed descriptions of the 

cataclastic rocks of the Moine thrust in the Assynt 

region (fig. 28). The following generalized description, 

using my terminology,5 is paraphrased from his 

numerous local descriptions (1963, p. 357, 362, 364, 369, 

375, 378, 410) :

6 Christie (1960, 1963) devised a system of terminology in which 

"mylonitic rock" is used as a general term for all cataclastic rocks, 

mon,ocataclastic rocks are called "primary mylonitic rocks," and polycataclastic rocks are called "secondary mylonitic rocks."

The horizon or "surface" mapped as the Moine thrust 

is commonly not a faiult surface, but a boundry between 

rocks of different composition and original age, with 

similar fabric and texture, in a zone of extensive 

penetrative movement; only locally is it a sharply defined "surface." Cataclastic rocks of various types are 

commonly developed both above and below the "surface" mapped as the Moine thrust. Generally, the most 

intensively mylonitized rocks, including protomylonites, 

mylonites and phyllonites, ultramylonites, blastomylonites, and mylonite gneisses, occur in a zone 100^ 

250 feet thick above the thrust "surface," and for a few 

feet below it.

Within the upper zone there is a gradation; the most 

intensively mylonitized rocks occur in the lower part 

and grade upward by increase in grain size, decrease in 

degree of lamination, and increase in degree of neominerailization and recrystallization, across an arbitrary 

contact, into phyllonitic and diaphthoritic schists of the 

Moine series. These schists, called "crumpled schists," 

"frilled schists," "puckered schists," and "oyster-shell 

rock" by Peach and others (1907, p. 481, 502, 505, 598), 

are remarkably similar to the "button schists," 

"phyllonitic schists," "curly schists," and "wavy schists" 

bordering fault zones in other parts of the world (Crickmay, 1933, 1952; Eeed and Bryant, 1965; Reed, 1964; 

Higgins, 1966). The foliation of the cataolastic rocks 

and of the Moine schists is parallel to the Moine thrust. 

The thinner zone of cataclastic rocks beneath the thrust 

"surface" shows a gradation similar to that of the upper 

zone, except that the gradation is ultimately into normal 

gneisses and quartzites.

Polycataclastic rocks are also present along the Moine 

thrust. According to Christie (1963, p. 369) "The effects 

of secondary deformation increase toward the Moine 

thrust." Brecciated mylonites, brecciated blastomylonites, and even mylonitized mylonites occur locally 

within the zones of monocataclastic rocks. There are 

also separate zones east of the Moine thrust composed 

almost entirely of polycataclastic rocks chiefly phyllonitized mylonites. Some of these are locally more than 

half a mile wide.

The effects of cataclasis generally decrease gradually 

in the Moine schists east of the Moine thrust, and in 

most areas the schists a mile or so away from the thrust 

show little evidence of abnormal penetrative movement.

PROTOCLASTIC BORDER, COLVILLE 

BATHOLITH, WASHINGTON

The Mesozoic Colville batholith (Waters and Krauskopf, 1941) is a complex plutonic mass that occupies 

the region between the Okanogan and Columbia Rivers 

in northern Washington (fig. 29). The batholith
54 CATACLASTIC ROCKS

intrudes folded late Paleozoic and Triassic metasedimentary and metavolcanic rocks, but although the 

contact is markedly discordant, contact metamorphic 

effects are slight or absent. The central parts of the 

batholith are not unusual, being chiefly structureless 

granodiorite similar to numerous other batholiths and 

plutons of this general region. However, this central 

mass grades outward into a belt of complexly foliated 

and swirled gneiss, which in turn grades outward into 

a remarkable border phase that resembles a fault zone 

more than part of an igneous intrusion. This is the 

classic protoclastic harder of the Colville batholith 

(Waters and Krauskopf, 1941), probably the largest, 

best exposed, and best known occurrence of protoclastic 

rocks in the world. The rocks of this border are cataclastic rocks, but rather than being formed in a fault 

zone, propelled by tectonic forces during metamorphism, they were produced when the almost solid intrusive body rose and pulverized its own nearly crystallized border.

Waters and Krauskopf (1941) divided the eastern 

part of the batholith into three facies (fig. 29) : (1) the 

"gneissic and protomylonitic facies," consisting chiefly 

of markedly foliated gneisses and rocks with cataclastic 

textures, in a peripheral zone from a few yards to about 

4 miles wide; (2) the "swirled and porphyritic gneiss 

facies," consisting chiefly of protoclastic gneisses, augen 

gneisses, and migmatitelike "swirled" gneisses, in a zone 

about 1 to 5 miles wide; and (3) the "homophanous 

granodiorite facies," consisting of structureless, or 

nearly structureless, granodiorites, in the central parts 

of the batholith. They emphasized (p. 1379) that all 

of the contacts are arbitrary and gradational, and that 

each of the facies contains some rocks characteristic of 

the others.

Waters and Krauskopf (1941) presented good evidence that the batholith deformed its own nearly solid 

periphery as it rose, and that the deformation was not 

a later metamorphic or tectonic event. Of the protoclastic rocks in the gneissic and mylonitic facies they 

stated (1941, p. 1406) :

During the rise several definite autometamorphic rock types 

were produced. Local areas of protomylonite and some rare 

thin bands of lustrous material approaching pseudotachylite, are 

present. . . . The mylonites usually show effects due to recrystallization in greater or less degree, and commonly grade 

into rocks best described as blastomylonites. These in turn grade 

into coarser-grained rocks with granoblastic texture which may 

or may not show a gneissic banding. . . . All of the various 

metamorphic rock varieties mentioned, and particularly the 

more siliceous granoblastic types, show every transition into 

definite igneous rocks, and indeed are in many cases so permeated with magmatic material as to make their classification 

as igneous or metamorphic a purely arbitrary matter.

They (Waters and Krauskopf, 1941) described rocks 

resembling ordinary cataclastic rocks in the field, except for the gradation into plutonic rocks, and the confinement to and conformity with the batholith's border 

(fig. 29). Many of these rocks have porphyroclasts of 

feldspar with crush trails, megascopic fluxion structure, and a fine-grained groundmass. However, the 

microscopic textures of these rocks are unusual. According to Waters and Krauskopf (1941, p. 1407- 

1408) :

Microscopic study reveals a quartz-orthoclase mesostasis permeating the rock, filling cracks and openings1 in broken porphyroclasts, and wandering along the crush bands. Locally this 

mesostasis collects in pools from which irregular ramifications 

go forth into the pulverized rock. The quartz-orthoclase liquid 

seems to have been, active chemically and apparently has 

greatly aided recrystallization of the adjacent mylonitic

* * * evidence clearly shows that at the time of their development magmatic juices and fluids still formed at least a part 

of the rock that was being deformed; rock fiowage was accomplished in a crystal mesh which still contained a small 

proportion of interstitial liquids * * *

*****

Only rarely are mylonitic rocks found completely free of 

new minerals developed by recrystallization of the cataclastic 

paste.

In summary they say (p. 1392) of some of the more 

recrystallized protoclastic rocks:

At all events, the rock described seems best classified as an 

igneous rock. Most of it has been formed by direct precipitation 

from a magmatic solution, but the course of the solidification 

was interrupted by a period of mechanical movement which 

deformed and partially granulated, the early solidified components. These strained components1 were then partially recrystal-
W P3 & a

5 Q

(P Q

Q 3!

VI g.

P rt-

& 2

P- S

II

I

COLVILLE BATHOLITH
56 CATACLASTIC ROCKS

lized and were also cemented by final crystallization of the still 

liquid residuum.

The crucial point is that these granulated rocks have 

been cemented and made coherent by crystallization 

from magmatic solutions.

A HYPOTHETICAL FAULT ZONE

Figure 30 shows the relations of different kinds of 

cataclastic rocks in a hypothetical fault zone, based on 

zones described in the literature and on my own observations.

1 MILE 

I

1 .5 0 1 KILOMETER

rea of figure

INDEX

EXPLANATICJN 

All contacts gradational

Protomylonite, mylonite, and ultramylonite

(includes phyllonite)

Blastomylonite; some mylonite

Mylonite gneiss and mylonite schist; some

Button schist; some mylonite schist

Normal" schist and gneiss

Microbreccia and cataclasite

Polycataclastic rocks: brecciated mylonite, 

brecciated blastomylonite

FIGURE 30. Greologic map of a hypothetical fault zone showing typical relations of various types of cataclastic rock.
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 57

THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES 

INVOLVED IN FORMATION

Theories of cataclasis and related metamorphic processes are as yet incompletely formulated, and experimental study in this area has lagged far behind studies 

of other rock-forming processes. Therefore, the statements and conclusions presented here are largely qualitative, tentative, and somewhat speculative.

RECRYSTALLIZATION-NEOMINERALIZATION

In his definition of mylonite, Lapworth (1885, p. 559 

see p. 7 this paper), referred to secondary crystals

of quartz and mica in mylonites, and noted that the

"interstitial paste" had "only crystallised in part."

Knopf (1931, p. 10-11) followed Lapworth, stating:

Although a true mylonite is dominantly cataclastic, even

ultra-cataclastic, nevertheless there is a variable amount of

newly formed minerals in mylonitic rocks dependent upon the

conditions under which the deformation has taken place and

upon the constitution of the rock that is mylonitized.

Knopf (1931, p. 5) also distinguished between recrystallization and neomineralization:

* * * a combination of the old constituents into new minerals 

is usually called recrystallization by English-speaking writers 

on metamorphic geology. However, the so-called recrystallization 

is generally a development of new minerals from the original 

constituents * * * the term recrystallization is only justified 

where certain constituents such as calcite and quartz have 

newly crystallized without change of chemical constitution. It 

has been suggested by A. Knopf that neomineralization be used 

to denote the transformation of the old mineral constituents 

into minerals of new and different composition.

Waters and Campbell (1935) made it clear that there 

was some recrystallization-neomineralization in mylonite, as they used the term, but in their discussion of 

coherence they made the following statement (1935, p. 

475):

The retention of coherence in the rock during crushing may 

be due not so much to the welding together of the broken particles by newly formed minerals as Lapworth emphasized, as it 

is to the fact that the rock was fractured under such great 

confining pressure that the surfaces of movement never opened 

widely enough to break the molecular bonds between them.

Some later workers have overlooked all but the first 

part of this statement, and have given mylonite the connotation of completely lacking recrystallization.

All the cataclastic rocks (excepting gouge and fault 

breccia) that I have seen, and all those shown in photomicrographs in the literature, show some degree of recrystallization-neomineralization. Certainly there is less 

recrystallization-neomineralization in rocks of the sequence protomylonite-mylonite-ultTamylonite than in

the sequence mylonite gneiss (mylonite schist)-blastomylonite, and, in fact, this difference in degree of recrystallization-neomineralization is used to distinguish 

between them, but all are to some degree recrystallized 

and (or) neomineralized. The molecular bonds in mylonites have been broken, and the particles have been 

disjoined and partially rehealed by concurrent recrystallization-neomineralization. This has in effect overprinted but not destroyed the cataclastic texture.

I disagree with Waters and Campbell (1935, p. 475) 

regarding the coherence of cataclastic rocks. I believe 

the retention of coherence is due primarily to the metamorphic "welding" effect of recrystallized and newly 

formed minerals. This growth takes place concurrently, 

and probably repeatedly, with the granulation. Of 

course the coherence does result from high confining 

pressures, but not simply or directly from this alone. 

Eather, the confining pressure, along with the effects 

of high temperature, fluid content, and shearing, causes 

the new mineral growth and recrystallization of old 

minerals. Thus, coherent cataclastic rocks are basically 

metamorphic rocks and are limited to metamorphic and 

plutonic terranes.

RELATIONS BETWEEN DIFFERENT KINDS 

OF CATACLASTIC ROCKS

Major fault zones generally contain more than one 

kind of cataclastic rock. Most zones contain rocks of 

the series protomylonite-mylonite-ultramylonite, the 

series mylonite gneiss-J)lastomylonite-, and the series 

microbreccia-cataclasite, and many contain, in addition, 

retrograde cataclastic rocks and polycataclastic rocks 

(see section on examples of cataclastic rock zones, p. 

39). Commonly, these different kinds of rock are intimately associated in the zone; contacts are gradational 

and mappable units are intricately intercalated (fig. 

30). The relationships and characteristics of these different kinds of rock are important in interpreting the 

conditions and time of their formation and in interpreting fault zones.

ASSOCIATION OF BLASTOMYLONITES AND MYLONITE

GNEISSES WITH PROTOMYLONITES, MYLONITES,

AND ULTRAMYLONITES

When blastomylonites and mylonite gneisses are present in the same zone with protomylonites, mylonites, 

and ultramylonites, both groups of rocks tend to occur 

in parallel or subparallel outcrop bands whose borders 

are gradational and ill defined (fig. 30). Fluxion structure in both groups commonly has the same trend and 

dip (Clarke, 1952; Hsu, 1955b; Sutton ,and Watson, 

1959; Christie, 1960, 1963; Eeed, 1964; Barber, 1965;
58 CATACLASTIC ROCKS

Bentley, 1969), and the same minor structures (folds 

and kinks, etc.) are generally common to both (Hsu, 

1955b; Christie, 1963; Barber, 1965). Both groups may 

have mineral assemblages of the same metamorphic 

facies, or even the same mineral assemblages (Clarke, 

1952; Hsu, 1955b; Sutton and Watson, 1959; Christie, 

1960,1963; Reed, 1964). What factors, then, account for 

the different manner in which the rocks of the two 

groups have reacted to cataclastic metmorphism in the 

same zone ? Do the blastomylonites and mylonite gneisses 

represent an earlier period, episode, or phase of metamorphism, as some have suggested? Or do they represent a later period, episode, or phase, as suggested by 

Johnson (1961), Sutton and Watson (1959), and Barber 

(1965)?

Evidence from many fault zones favors the idea that 

the blastomylonites and mylonite gneisses formed at 

essentially the same time as the protomylonites, mylonites, iand ultramylonites (Sander, 1912; Knopf, 1931; 

Crickmay, 1933; Waters and Campbell, 1935; Clark©, 

1952; Hsu, 1955b; Christie, 1960,1963; Reed and Bryant, 1964; Reed, 1964; and others). Blastomylonites are 

not mylonites which have been later recrystallized. This 

is demonstrated by the fact that blastomylonites and 

mylonites are commonly found adjacent to each other 

in a single fault zone; contacts are gradational and even 

intercalated; and the rocks are in the same metamorphic 

facies. Moreover, the mylonites have the same recrystallized and neomineralized texture as the blastomylonites, 

only to a lesser degree. If a later period, episode, or 

phase of metamorphism caused the recrystallizationneomineralization of the blastomylonites, then it should

have affected the mylonites to the same degree. The 

blastomylonites commonly pass by gradation into mylonite gneisses. If one assumed that a later metamorphism formed the blastomylonites, then one could also 

assume that the mylonite gneisses represent still a third 

episode, period, or phase of metamorphism.

Probably the most feasible explanation for the essentially simultaneous formation of the two different 

groups of rocks in a single zone is that the rate or intensity of cataclasis (or both of these) was different. 

Thus, although both groups of rocks were being metamorphosed under the same conditions of temperature, 

confining pressure, and fluid pressures, and under the 

same chemical conditions, the protomylonites, mylonites, 

and ultramylonites were formed in sub-zones of more 

intense cataclasis, or in subzones where the rate of 

cataclasis was greater, or both.

Alternatively, perhaps the blastomylonites and mylonite gneisses did form slightly earlier than the protomylonites, mylonites, and ultramylonites, but within the 

same phase, period, and episode of metamorphism. Perhaps the subzones of most intense, or higher rate, cataclasis shifted from time to time (figs. 31, 32), the least 

recrystallized-neomineralized rocks representing the last 

location of the subzones.

RELATION OF MICROBRECCIAS AND CATACLASITES TO 

ROCKS WITH FLUXION STRUCTURE

In contrast to the relationship between different 

kinds of rocks with fluxion structure, the relationship 

between rocks with fluxion structure and rocks of the 

series microbreccia-cataclasite is commonly clear; the

EXPLANATION

POLYCATACLASTIC ROCKS OCCUR ALONG BOUNDARY 

LINES AND PARTICULARLY AT INTERSECTIONS

Pr 

anc

;YfY:

otomylonite, Blastomylonite 

mylonite, and 

ultramylonite mylonite 

gneiss

<{'»«' ^

Microbrecci 

and 

cataclasite

FIGURE 31. Development of a braided fault zone. Differences in lithology produce frictional differences and uneven movements, 

thus creating undulations. Continued movements give rise to alternating areas of relative tension and compression (A-C, from 

Kingma, 1958). D, shows the theoretical distribution of types of cataclastic rock in a system like that hypothesized by Kingma 

(1958). The various types would be formed at about the same time, and the difference in effects of cataclasis would be the 

result of differences in relative tension and compression.
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 59

(Mylonite and blastomylonite)

(Myloniteand ultramylonite)

(Mylonite gneiss and blastomylonite)

FIGURE 32. Schematic diagram of one possible mechanism for 

producing different types of cataclastic rock in a single fault 

zone during a single period of movement. The zone of most 

intense cataclasis shifts or jumps, and movement o-a' (which 

does not necessarily involve 3) is earlier than movement 6-6', 

but with within the same period. Further shifts would produce 

polycataclastic rocks, as would overlaps of zones of most 

intense cataclasis.

latter are generally younger (Peach and others, 1907, 

called them "crush breccias" and "crush conglomerates"; Grubenmann and Niggli, 1924; Hsu, 1955b; 

Johnson, 1957,1961; Christie, 1960,1963; Schoch, 1962; 

Keed, 1964; Higgins, 1966, 1968; Grant, 1967, 1968; 

Dalziel and Bailey, 1968). The contacts O'f microbreccias 

and (or) cataclasites with the fluxion-structured rocks 

in a fault zone, and with crystalloblastic rocks outside 

the fault zone, are generally discordant, and the trend 

of bands of these "structureless" cataclastic rocks may 

be at high angles to the zone, to the fluxion structure or 

lamination of the other rocks in the zone, and to the 

foliation of rocks outside the zone. Quite commonly, it 

can be shown that microbreccias and cataclasites are 

polycataclastic, proving that they are younger because 

they formed by brecciation of the other rocks. Moreover, 'there is general agreement that the microbreccias 

and cataclasites formed under less intense conditions of 

cataclasis than the rocks with fluxion structure, and 

also under less intense metainorphic conditions (see 

Christie, 1960, p. 90-91, and Reed, 1964, p. 675-676). 

The manner of deformation is different. For example, 

as Christie (1960, p. 90) noted, quartz and feldspar 

alike are deformed by cataclastic breakdown to the same 

degree. Reed (1964, p. 676) stated:

. . . the mylonites are characterised by fluxion banding presumably produced by long-continued movement in. one direction, whereas the structureless cataclasites were probably 

produced by repeated movements in different directions.

Also, there are obvious fabric differences between the 

two groups of rocks; rocks with fluxion structure have 

directed fabrics (anisotropic), whereas microbreccias 

and cataclasites tend to have isotropic fabrics.

DEVELOPMENT OF CATACLASTIC TEXTURES

Waters and Campbell (1935, p. 484-488) gave a detailed description of the development of cataclastic textures in San Andreas fault zone rocks near Crystal 

Springs Lakes, Calif. :

Under the microscope every stage in the demolishing of original coarse grained rocks to an ultramicroscopic paste can be 

seen. ... In general, crushing begins by the fracturing of the 

rock into a coherent breccia or protornylonite whose fragments 

are megascopically visible. Pronounced strain shadows appear 

in the quartz even though little shearing is visible in thin section. Further movement results in the formation of a thin film 

of crush powder ibetweeii the mineral grains forming typical 

"mortar structure." The next stage is the development of a 

closely spaced series of microscopic shears in the individual 

mineral grains. With further crushing, films of pulverized material form along the microscopic shears and grow at the expense of the mineral grains until finally the uncrushed material 

between adjacent shears is isolated as streaks, lenticles, and 

irregular masses in the powdery groundmass. Complete rolling out of the rock to an ultramicroscopic powder in which 

none of the eye-shaped porphyroclasts are left is rare. 'The small 

round particles resist further milling to an unusual degree and 

even in those cases where the groundmass has been reduced to 

such small fragments that it becomes practically isotropic some 

of the porphyroclasts commonly survive. Feldspar seems to be 

more resistant to crushing than quartz, as shown by the fact 

that feldspar porphyroclasts are relatively more abundant in 

the more completely pulverized mylonites.

Similar descriptions have been written by nearly all 

who have seriously considered cataclastic rocks (for 

example, see Quensel, 1916; Crickmay, 1933; Clarke, 

1952).

Different minerals react differently to cataclasis. 

Some minerals are apparently easily granulated or 

sheared, whereas others resist comminution and form 

porphyroclasts; some recrystallize, whereas others preserve their cataclastic shapes. It is possible to construct 

a generalized "cataclastic reaction series" based on empirical observations (table 2).

MICAS

Micas are apparently easily deformed and are commonly the first minerals affected by cataclasis. Generally, the micas recrystallize as the cataclasis proceeds, 

but their new "aberrant" shapes record the deformation. 

Large micas are first deformed into lens- or spindleshaped masses. As cataclasis proceeds, these are ground 

down, and fine recrystallized micas are streaked out 

along the fluxion planes and around porphyroclasts of
60 CATACLASTIC ROCKS

TABLE 2. Generalised reaction of various minerals to cataolasis

1. Easily deformed minerals which generally deform by recry'Stallization and. preserve little or no evidence of cataclasis :

Carbonate minerals 

Epidote minerals 

Some amphiboles

2. Minerals which generally deform by comminution and recrystallization, but which preserve evidence of cataclasis:

Micas

Many amphiboles 

Some quartz

3. Minerals which deform chiefly by comminution with good 

preservation of cataclastic textures: 

Most quartz 

Plagioclase

Garnet

One can construct a generalized "cataclastic reaction series" 

based on empirical observations :

Most easily 

comminuted

Micas

Quartz

Feldspar

Garnet

w

&

Tendency to 

form porphyroclasts

other minerals. These fine micas may be further comminuted, or may be kinked or bent. Some large micas 

may remain as recrystallized porphyroclasts.

Biotite seldom undergoes cataclasis without chemical 

change. Iron is commonly expelled from biotite to form 

magnetite, which occurs in thin streaks along fluxion 

planes and helps define them. The optical characteristics 

of the biotite in cataclastic rocks commonly indicate that 

it is poorer in iron than that of the undeformed parent 

rock. Titanium may also be expelled from biotite during cataclasis to enter sphene (see Hsu, 1955b, p. 253).

QUARTZ

Quartz, like the micas, is one of the first minerals affected by cataclasis. It first becomes elongated and 

strained; undulatory extinction and fine deformation 

lamellae appear. After this initial stage, which appears 

to be common to all kinds of quartz-bearing rocks, the 

behavior of quartz seems to follow two different patterns in different kinds of rock. In very quartz rich 

rocks, such as orthoquartzites and protoquartzites, the 

quartz further elongates, becomes lens-shaped, and 

granulates at the edges so that a fine quartz mortar fills 

the sheared interstices between the fractured and deformed grains. The mortar is generally slightly recrystallized. In less quartz rich rocks, such as metagraywacke or granite, the quartz grains become increasingly 

shattered throughout, but comminution of the grains is 

not so much a gradual process from the outside inward.

Perhaps this difference is due to the presence of feldspars in the less quartz rich rocks, which act as resistant 

masses and prevent the quartz from deforming in a 

partially plastic manner. After this "second stage" the 

behavior of quartz again is similar in all kinds of rock. 

With increasing cataclasis, the quartz fragments disintegrate by fracturing, seemingly "all at once," into 

a fine granular mass which forms much of the matrix 

and is arranged in fluxion bands or stringers around 

porphyroclasts of other minerals. Only rarely are porphyroclasts of quartz larger than the general matrix 

size observed. Commonly, some of the quartz is recrystallized into thin "flamboyant" stringers which undulate with, and help to define, the fluxion structure. 

Generally, the recrystallized quartz of these stringers 

is itself severely strained.

FELDSPARS

In marked contrast to quartz, feldspars are notably 

resistant to crushing during cataclasis, and as a result 

comprise the most common porphyroclasts in cataclastic 

rocks. Comminution of feldspar grains is from the outside inward and generally starts in most grains only 

after comminution of quartz is well advanced. First, 

the corners of a crystal, or any projections from an irregularly shaped grain are broken or ground off. These 

small feldspar fragments join the quartz in the fine matrix, and become rounded by granulation. Further comminution of the main feldspar grain is by attrition, as it 

rolls between differentially moving fluxion planes or 

bands, until the porphyroclast is round or oval. Some 

large porphyroclasts may separate along flaws or along 

well developed cleavage planes, to begin the rounding 

process all over again. As cataclasis proceeds still further, the feldspar porphyroclasts continue to comminute by rounding until there is complete reduction. 

Round, as opposed to irregularly shaped or oval, porphyroclasts are most common in ultramylonites.

GARNET

Garnet generally appears to be quite resistant to cataclasis. In some cataclastic rocks where the matrix is 

extremely fine grained and even the feldspar porphyroclasts are few and small, large garnet porphyroclasts 

survive. Comparison with cataclastically undeformed 

garnets in the parent rocks shows that the garnets in 

the cataclastic rocks have merely had their corners 

rounded off and have been little reduced in size. Garnets 

apparently react to cataclasis by rolling between dif-
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 61

ferentially moving fluxion planes or layers. Under conditions in which quartz and some feldspar recrystallize 

and deform in a partially plastic manner by elongation, 

as in many blastomylonites and mylonite gneisses, garnets may also be elongated or even smeared. In the most 

intensively mylonitized rocks, garnets may be cracked 

and separated, the cracks commonly being filled by a 

"mortar" of quartz and feldspar, but seldom are they 

completely ground down and the pieces streaked out 

along fluxion planes. Are garnets so resistant to cataclasis because, being initially nearly round, they can 

easily roll and thus escape much further comminution; 

or, is there simply a relative difference in relation to 

quartz and to a lesser extent feldspar ?; or, do the 

garnets continually recrystallize as the comminution 

takes place?

Probably each factor is the most important in 

certain rocks, and in some rocks all three may be important. That garnets have commonly been rotated and 

rolled during deformation is well documented for noncataclastic rocks (Peach and others, 1912; Schmidt, 

1918; Becke, 1924; Miigee, 1930; Guilluly, 1938; Knopf 

and Ingerson, 1938; Fairbairn, 1949; McLachlan, 1953; 

Spry, 1957, 1963; Eosenfeld, 1960, 1968; Peacey, 1961; 

Hopson, 1964; and others) and for cataclastic rocks 

(Crickmay, 1933; Clarke, 1952; Sclar, 1958; Sutton and 

Watson, 1959; Johnson, 1961; and others). Many garnets in cataclastic rocks (particularly in mylonites and 

ultramyloniteis) have a rounded cataclastic shape (for 

example, see: Crickmay, 1933, p. 168; Sutton and Watson, 1959, pi. 1; Sclar, 1958, p. 78, 79), 'but nearly 

euhedral garnets are seen in some oataclastic rocks 

(chiefly in blastomylonites, but in some mylonites also), 

and Sutton and Watson (1959) have described and 

illustrated garnets in recrystallized cataclastic rocks 

(chiefly blastomylonites) that have a round porphyroclastic core surrounded by a euhedral shell riddled with 

tiny inclusions from the cataclastic matrix.

DEVELOPMENT OF FLUXION STRUCTURE

There are several hypotheses and much confusion 

regarding the origin of what has been called "fluxion 

structure." Most of the confusion has stemmed from 

lack of proper definition of the terms fluxion structure, 

compositional layering, and color lamination. As a 

result, some geologists have considered the origin of 

color lamination or compositional layering, calling them 

fluxion structure, whereas others considered the origin 

of cataclastic foliation, with or without color lamination or compositional layering. Fluxion structure, as 

used in this paper, is defined 011 page 3, and refers only

to cataclastic foliation. Compositional layering, defined 

in the glossary (p. 72), refers only to layering in which 

adjacent layers differ in mineral and chemical composition. Color lamination, also defined in the glossary, generally includes compositional layering, but refers only 

to color differences in adjacent layers, which in some 

cases may be due simply to grain size.

The generally accepted hypothesis of the origin of 

fluxion structure is essentially that envisioned by Lapworth (1885) and expounded by Waters and Campbell 

(1935, p. 482-484); see quote p. 59 of this paper). 

According to this hypothesis, fluxion structure is really 

flow structure. It is the textural expression left by differentially moving fine planar masses of comminuted 

material developed and propelled by shearing. These 

masses or layers flowed around obstructions or porphyroclasts in a manner similar to highly viscous siliceous lavas flowing around phenocrysts and inclusions. 

Just as microlites and crystallites in the lava tend to 

concentrate between laminar flow layers or within certain thin layers, the finer mineral fragments (particularly of metallic and micaceous minerals) in the cataclastic rocks tend to concentrate between the laminar 

flow layers of the cataclastic matrix, thus defining these 

laj/ 3rs. The process starts with lenselike and wavy shear 

planes, grades with further cataclasis into subparall 

shear planes, and finally into laminar flow layers. As 

large porphyroclasts are ground down betweien the 

moving layers, the ground-off material is streaked out 

between the layers, further defining the fluxion structure by streaky compositional differences. The process 

in this stage is essentially one of milling.

DEVELOPMENT OF COMPOSITIONAL LAYERING 

AND COLOR LAMINATION

Compositional layering and color lamination are 

common to many mylonites, ultramylonites, and blastomylonites and have been confused with fluxion structure. There are several hypotheses regarding1 the origins 

of these features.

ORIGINAL GRAIN SIZE DIFFERENCES

Crickmay (1933, p. 170) proposed that the color 

lamination in some mylonites and ultramylonites originated because of grain size differences in the parent 

gneiss. He thought that cataclasis started at first in 

the finer grained layers of the gneiss, providing these 

layers with a "head start," so to speak, which was maintained as cataclasis proceeded through the mylonite and 

into the ultramylonite stage. This produced mylonites 

and ultramylonites in which some layers are more finely 

comminuted than others and hence of different color.

420-478 O - 71 - 5
62 CATACLASTIC ROCKS

VARIABLE DEGREES OF COMMINUTION

Waters and Krauskopf (1941, p. 1407), in discussing 

some of the protoclastic rocks in the border zone of the 

Colville batholith, stated:

The banding so conspicuous in hand specimen is due to variable 

degrees of crushing in different layers.

Crickmay (1933, p. 176) also noted that the layering 

in some mylonites and ultramylonites is due to: "the 

interlayering of completely and incompletely crushed 

material."

Variable degrees of comminution in different 

"layers" accounts for the color lamination of some 

mylonites, ultramylonites, and blastomylonites in the 

Brevard zone, in the Towaliga fault zone, and in the 

Cucamonga Canyon zones (also see Hsu, 1955b). This 

is illustrated in figure 10.

ORIGINAL COMPOSITIONAL LAYERING

Original compositional layering in the parent rocks 

may account for the color lamination and cataclastic 

compositional layering of some cataclastic rocks. Sclar 

(1958, p. 66) stated this possibility for some mylonites 

and ultramylonites near Preston City, Conn.

GLIDE-FOLD SCHISTOSITY

Christie (1963, p. 383-384) suggested that "glidefold schistosity" or "G-leitfaltscMej'erung" (Kienow, 

1953) was probably important in producing the color 

lamination of some mylonites, ultramylonites, and 

blastomylonites. Under this mechanism, to paraphrase 

Christie, slip surfaces become unstable during movement and bend into intrafolial flexural slip folds, which 

become overturned in a direction related to the sense of 

shear. A new schistosity develops by shearing of the 

limbs of the smallest scale folds. This schistosity is more 

stable than the original, but it is rapidly rotated toward 

the plane of the latter (fig. 33).

CATACLASTIC METAMORPHIC DIFFERENTIATION

The term metamorphic differentiation was introduced 

by Stillwell (1918) for processes by which contrasting 

mineral assemblages develop from an initially uniform 

rock during metamorphism. Stillwell and many later 

workers (Eskola, 1932; Read, 1933) considered metamorphic differentiation as almost purely a chemical 

process. Others (Harker, 1932) discounted its importance entirely. Sander (1930, p. 269-275) believed that 

there is an interplay of mechanical and chemical activity in the process of metamorphic differentiation, but 

he assigned an auxiliary role to the mechanical factor.

FIGURE 33. Development of "glide-fold schistosity." A, Diagram 

showing development of "glide-fold schistosity." B, Analysis of 

movement in "glide folding." Long arrows indicate the sense 

of shear; short arrows denote axes of "compression" and 

"tension." The stable glide-fold schistosity (b-b) is rotated in 

the direction shown by the arrow (R) to the unstable orientation (a-a). C, The sense of slip indicated by intraf olial folds. 

From Christie, 1963, figure 19.

In 1932, Schmidt (p. 183-187) proposed a hypothesis 

of purely mechanical metamorphic differentiation. He 

showed that rolled wrought iron consists of alternating layers of perlite and ferrite produced mechanically 

by the rolling process and suggested that slip surfaces 

formed in the early stages of deformation of a heterogeneous rock are irregular, discontinuous, and commonly 

located within crystals or crystal aggregates of those 

minerals that can readily adjust their lattices to the 

imposed stresses by translation gliding, twin gliding, or 

recrystallization. Minerals less susceptible to such deformation may at first form "projections" interrupting 

the early formed slip surfaces, but as deformation 

proceeds, the obstructions are mechanically eliminated
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 63

and segregated. Penetrative movement in major 

slip surfaces rolls out the easily deformable minerals 

(quartz, calcite, plagioclase) into continuous bands. The 

platy or prismatic minerals are drawn into subparallel 

position (crystal form orientation) by flow movement 

involved in the deformation.

Turner and Verhoogen (1960, p. 586) stated:

Schmidt's hypothesis explains how two physically dissimilar 

sets of minerals tould be separated from one another; but to 

what extent thi^ mechanism actually operate® in metamorphism remains dubious in view of the undoubted fact that 

solution and crystallization usually play an important role in 

shaping the fabric of deformed rocks, and in the absence of 

experimental proof that under metamorphic conditions quartz 

and albite are more ductile than mica, chlorite, and epidote. ... It would seem, then, that development of laminated 

structure in regionally metamorphosed rocks is a complex process involving solution, crystallization, and mechanical deformation, acting together or in alternating combinations as the 

selective agents of metamorphic differentiation.

In 1916 (before Stillwell named the process of 

metamorphic differentiation), Quensel (1916, p. 95-97, 

103-105, 107-116) had considered JiartscMefer (in my 

classification a variety of blastomylonite] as partially 

recrystallized ultramylonite that had undergone strong 

chemical changes during crushing and recrystallization 

to bring about marked chemical differences between the 

different bands. He described bands of felsic minerals 

alternating with bands rich in chlorite and micas, and 

suggested that the differences were brought about during crushing and recrystallization (neomineralization).

Wenk (1934, p. 221-226) described layered mylonite 

associated with its nonlayered parent in the Silvretta 

gneiss of Switzerland. The compositionally layered 

cataclastic rocks (mylonite and ultramylonite) occur as 

relatively thin zones at or near the contacts of the allochthonous gneiss block. Wenk concluded that mechanical processes had transformed the augen gneiss into 

layered cataclastic rocks.

In 1935, Waters and Campbell (p. 478), referring to 

hartschiefer, stated:

In the opinion of most Swedish geologists they differ from 

ultramylonite, which they resemble rather closely, in the remarkable banding, a feature that is regarded to be the result 

of metamorphic differentiation.

In their discussion of the San Andreas cataclastic 

rocks, they (1935, p. 482-494) noted:

* * * at one place there is an even alteration of black 

mylonite with layers of antigorite schist, the individual layers 

locally averaging less than an inch in thickness.

They also described (1935, p. 482,488-494) rocks that 

were originally "altered basalts or diabases" but are 

now laminated mylonites and ultramylonites. After describing (p. 490) mylonites with alternating "dark-colored bands" and "quartzose layers," they stated (p. 

491):

If chemical differentiation of material during mylonitization 

does take place, it may well be that the rocks from the San 

Andreas fault zone showing these peculiar layers of quartz 

rich material represent an early stage in the transformation of 

a crushed rock to a chemically differentiated "hartschiefer."

Turner (1941), in his often cited paper describing 

metamorphic differentiation in the Otago schists, emphasized the great amount of shearing involved in their 

formation and, in fact, called them "blastophyllonites." 

Although he dwelt upon the chemical factors of the 

differentiation, the great amount of shearing and mechanical deformation involved in the production of the 

banded rocks from massive parent rocks is quite clear 

from his descriptions.

Sclar (1950, 1958, p. 64-66, 70-75) described layered 

cataclastic rocks derived from nonlayered parent rocks. 

Regarding the origin of a layered ultramylonite developed from nonlayered biotite-cummingtonite-hornblende gneiss he stated (1958, p. 74-75) :

Metamorphic differentiation resulting from the solubility 

factor alone is ruled out in this case by the fact that shearing 

stress was the 'triggering' mechanism for metamorphic differentiation of the gneiss, and the observation that metamorphic 

differentiation increases with increasing cataclasis. Therefore, 

in the light of present knowledge the question of the mechanism (s) by which metamorphic differentiation of the gneiss was 

accomplished may be resolved into a discussion of the relative 

importance of the mechanical factor as opposed to the chemical 

factor. In other words, was the layering produced because of 

the difference in mechanical behavior of light and dark minerals 

under shearing stress (Schmidt-Wenk hypothesis) or was the 

layering produced by the interplay of cataclasis and chemical 

activity in which a critical grain size is reached through granulation, resulting in increased chemical activity that promotes 

segregation of light and dark minerals by means of the solubility 

principle (Sander-Turner hypothesis) ? The writer believes that 

the weight of evidence supports the Schmidt-Wenk hypothesis. 

The critical evidence is as follows: 1) the exceedingly finegrained apparently cataclastic fabric of the light-colored laminae, 

and 2) the increase in metamorphic differentiation toward the 

bottom of the gneiss block.

With respect to the first point, if sufficient aqueous pore solutions were available to promote solution of the quartz and 

plagioclase, and redeposition in layers parallel to the active 

s-planes after the rock was reduced to a critical grain size, then 

it is difficult to understand why the ultramylonite did not become 

a coarse-grained laminated blastophyllonite similar to those 

described by Turner (1941). It cannot be claimed that temperatures were too low to allow the comminuted paste to attain a 

moderate grain size. Temperatures during mylonitization were 

high enough to prevent diaphthoresis, and the deformation therefore took place under at least low-rank mesozonal conditions. 

Thus it appears more probable that lack of pore solutions rather 

than lack of heat to promote chemical activity was responsible 

for failure of the rock to become a coarse-grained laminated 

blastophyllonite. If this is correct, then Schmidt's mechanical 

process of metamorphic differentiation is favored.
64 CATACLASTIC ROCKS

The mylonite layers in the gneiss, the mylonite that grades into 

the ultramylonite, and the ultramylonite itself are all almost 

submicroscopic in grain size. Nevertheless, neither the mylonite 

nor the mylonite layers in the gneiss are laminated. As increasing movement from top to bottom of the block parallel to the 

foliation of the gneiss is indicated by increasing pulverization 

of the gneiss in the same direction, a second approximation may be made by correlating metamorphic differentiation with the distance traveled by different parts of the 

block. This satisfies the observation that metamorphic differentiation increases from top to bottom of the block, and suggests 

that metamorphic differentiation can be correlated with granulation only because increasing transport of minerals under 

shearing stress has resulted in increasing cataclastic reduction. 

The writer therefore concludes that the degree of perfection of 

the lamination is probably a function of the kinematics of the 

gneiss during mylonitization.

In a later paper Sclar (1965, p. 612) stated:

Mechanical metamorphic differentiation is likely to be restricted 

to narrow fault zones of intense penetrative movement of limited 

thickness, whereas chemical or chemical-mechanical metamorphic differentiation is more likely to be widespread and 

even regional in exltent

* * * pre-existing mixtures of rock-forming phyllosilicates 

and/or inosilicates with tectosilicates that are involved in deepseated zones of penetrative movement may be segregated into 

phyllosilicate and/or inosilicalte layers1 and itectosilicate layers 

as a result of differences in mechanical behavior between contrasting crystal structures under high confining pressure and 

intense shearing stress.

Figure 105 is a photomicrograph of one of the rocks 

described by Sclar.

Prinz and Poldervaart (1964) described a 15-footthick zone of compositionally layered mylonite in a 

150-foot-thick metadolerite dike. They described how 

the metadolerite grades into partly mylonitized rocks 

and finally into layered mylonite, and gave (p. 743) 

chemical analyses of the original unsheared rock and 

the light and dark layers of the mylonite. By comparing the sum of empirically observed percentages of light 

layer and dark layer analyses with the chemical composition of the unsheared metadolerite, they showed 

that the layered mylonite was produced from the unlayered metadolerite. Their evidence for metamorphic 

differentiation due to mechanical factors is quite strong. 

Eegarding minerals they stated (p. 743) : "Petrographic observations indicate that in the mylonitization 

of metadolerite, pyroxenes were more ductile than 

plagioclase, which was brittle."

In surveying the literature, one becomes aware that 

where the case for metamorphic differentiation is strong, 

evidence for shearing deformation and great penetrative movement is also strong; conversely, where the 

case for metamorphic differentiation is weak, the lack 

or weakness of deformation or shearing is apparent.

Therefore, it appears that mechanical factors are much 

more important in metamorphic differentiation than has 

previously been acknowledged by most geologists.

Examination of cataclastic rock suites from the San 

Andreas fault zone, the Tornetrask region, the Brevard 

fault zone, and other areas shows that as granulation 

increases, lamination or banding due to compositional 

differences also becomes more pronounced. Ultramylonites show more precise compositional banding than 

mylonites. The nature of this banding, where determiiiaKLe, involves segregation of framework silicate minerals from layer and (or) chain silicates, although it 

generally involves partial rather than complete 

segregation.

In summary, the banding common to many cataclastic 

rocks probably results from cataclastic metamorphic 

differentiation progressing with the granulation.

FOLDS IN CATACLASTIC ROCKS

Small-scale folds, with amplitudes generally less than 

2 feet (61 cm), are relatively common in some fluxionstructured cataclastic rocks (Peach and others, 1907, 

p. 506-507; Eead, 1931, p. 10; Wilson, 1953; Mclntyre, 

1954; Hsu, 1955b, p. 281,287-288,342, 346-347; Wilkinson, 1955; Johnson, 1957, 1961; Christie, 1963; Barber, 

1965; Dalziel and Bailey, 1968; Bentley, 1969). Although various names have been applied to the cataclastic rocks in which the folds occur, almost all are 

recognizable, either through microscopic study or 

through descriptions and (or) illustrations in the literature, as blastomylonites with varying degrees of recrystallization and neomineralization. In fact, some authors 

have commented on the large degree of recrystallization and neomineralization in these rocks (Hsu, 1955b, 

p. 281; Johnson, 1957, p. 263, 1961, p. 419, 422-423; 

Christie, 1960, p. 87,1963, p. 358; Barber, 1965, p. 224- 

225; Dalziel and Bailey, 1968, p. 543). As far as I can 

determine, very few (if any?) folds have been observed 

in rocks, which should be called protomylonite, mylonite, or ultramylonite.

Most of the folds in cataclastic rocks are similar slip 

folds (Ramsay, 1967; Whitten, 1966), and many are 

intrafolial (see Christie, 1963, p. 363, 367, 371, 377, 383- 

84, 423, 425; Hsu, 1955b, p. 281, 347; see also fig. 34). 

In some folds, particularly from the Moine thrust zone 

(see Christie, 1963), fluxion structure is axial-planar 

to the compositional layering that defines the folds. 

Johnson (1957, 1961, 1965) interprets this as resulting 

from more than one phase or episode of deformation; 

Christie (1963) interprets it as resulting from glide 

folding. Wilson (1953), Mclntyre (1954), and Christie 

(1963) have noted the contrast between the "brittle"
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 65

style of deformation in cataclastic rocks and the "plastic" style of folding in crystalloblastic rocks away from 

fault zones.

Perhaps the fact that cataclastic rocks with folds are 

nearly always blastomylonites (includes rocks that some 

workers have termed phyllonites) , is significant with 

regard to the style of folding. Blastomylonites with 

their concomitant cataclasis and recrystallization-neomineralization would be expected to submit to shearing by transposition of earlier formed planar features. 

Thus, "drag" between differentially moving fluxion 

planes or fluxion layers might fold the material between the planes to produce small folds with the fluxion 

structure axial-planar. This could occur during a single 

phase of deformation.

The style of most folds in cataclastic rocks is remarkably similar to that of folds in obsidian flows (fig. 

354), and in some cataclastic rocks (fig. 355, C) it can 

be shown that the folds developed because of the "drag" 

of differentially moving fluxion planes. This is accentuated where less mobile parts of the rock (porphyroclasts, phenocrysts, etc.) have added to the drag. Some 

folds in obsidian flows even have axial-plane "foliation" (fig. 35Z>), similar to that of some folded cataclastic rocks. Perhaps then, the folds, the axial-plane 

foliation, and the oithorhombic fabric of some cataclastic rocks (see Johnson, 1967) are caused by differential movement in more than one direction, just as 

it is in large obsidian flows. The internal movements 

in cataclastic rocks with fluxion structure may be remarkably similar to the internal movements in obsidian 

flows.

Another important point regarding folds in cataclastic rocks is their orientation with respect to the 

fault zone and the direction of tectonic transport. In 

the cataclastic rocks of the Moine thrust zone (chiefly 

blastomylonites), the axes of small folds commonly 

trend approximately normal to the trend of the fault 

zone and plunge down the dip of the overriding block 

(Johnson, 1957; Christie, 1963, p. 359, 360-361, 370- 

371, 374, 376). Christie (1963) interprets this as evidence of some strike-slip displacement along the zone 

to provide some tectonic transport approximately normal to the fold axes. Johnson (1957, 1961, 1965) and 

Barber (1965) interpret these folds as secondary features imposed on features of the main, earlier thrust 

deformation and find no evidence of strike-slip displacement.

Few other fault zones have been studied in as much 

detail, throughout so much of their extent, or by as 

many different workers, as the Moine thrust zone. However, Bentley (1969) reports early "drag" folds with

steeply plunging axes in blastomylonites along the 

Goat Kock, Towaliga, and Bartletts Ferry fault zones 

in Alabama (fig. 26), and interprets them as resulting 

from strike-slip displacements, and Grant (1968) reports bending of early fold axes by strike-slip displacements along the Towaliga fault zone in Georgia. Folds 

in blastomylonites are also found in the Brevard zone 

near Atlanta, Ga. There, most of the folds have axial 

planes striking roughly parallel to the trend of the 

zone and dipping steeply to the southeast.

RELATION OF MINOR TO MAJOR STRUCTURE

Pumpelly, Wolff, and Dale (1894, p. 158) long ago 

recognized that minor structure commonly reflects major structure. This may also be true with regard to cataclastic structures and textures. Relations and features 

seen in thin sections of cataclastic rocks commonly reflect in a general way those seen in hand sample, outcrop, and at map scale (fig. 36). In some thin sections 

and hand samples, the intercalation of finely comminuted cataclastic rocks with coarser varieties and of 

less recrystallized types with recrystallized and even 

totally crystalloblastic rocks is commonly matched by 

the map patterns of major cataclastic zones. Minor 

structures in cataclastic rocks of a zone may be matched 

by major features of a larger area containing the zone.

CONDITIONS OF CATACLASTIC 

ROCK FORMATION

The variables generally considered to control metamorphism are: temperature, lithostatic pressure, fluid 

pressure, shearing stress, rock composition, reaction 

rates, and fugacities of oxygen and carbon dioxide 

(Yoder, 1955; Hsu, 1955b; Turner and Verhoogen, 

1960; Turner, 1968). Cataclastic rocks are primarily 

metamorphic rocks, and all these variables must influence their genesis. In cataclastic rocks, however, we must 

add the factors of differences in amount of deformation 

and differences in the reaction of different minerals 

to stress.

In 1932, Harker (1950) was one of the first to consider some of the variables controlling cataclastic rocks. 

He thought that cataclasis could be classed separately 

from other types of metamorphism, as is evident from 

the following statement (1950, p. 169) :

Mylonitization, as contrasted with brecciation of a less 

drastic kind, requires a notable pressure, implying a considerable depth of cover. At such a depth the temperature too must 

doubtless be above the ordinary, but it does not appear that 

the elevation of temperature is such as to remove the process 

from the category of purely dynamic metamorphism as here 

understood.
66 CATACLASTIC ROCKS
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 67

Harker was puzzled because the cataclastic rocks 

obviously formed at relatively high temperatures, yet 

were not recrystallized or neomineralized to the degree 

common to normal crystalloblastic rocks formed under 

similar temperatures. Hsu (1955b) faced similar problems in his study of the Cucamonga Canyon area in 

California. There, cataclastic quartz-feldspar rocks and 

crystalloblastic amphibolites are intimately interlayered 

and show evidence of being syngenetic. Hsu (1955b, p. 

272) stated:

Apparently, the Cucamonga Canyon mylonites and amphibolites are syngenetic; while the quartz-feldspar granulites 

were being deformed cataclastically to form mylonites the pyroxene-rich granulites were deformed through neomineralization 

and recrystallization to form amphibolites; both processes took 

place under the P-T-X conditions represented by the amphibolite facies and under intense shearing stress.

Hsu (1955b, p. 272) explained the occurrence as 

follows:

The fact that the amphibolites are predominantly granoblastic, 

whereas the interlayered and quartz-feldspar rocks are predominantly mylonitic, may not be coincidental. The H2O component in 

a metamorphic system takes part in mineral reactions: it could 

promote the formation of biotite through reactions with hypersthene and/or garnet; it could promote the uralitization of pyroxenes ; it could promote the epidotization of plagioclase; and it 

could promote the chloritization of various f erromagnesian minerals. The P-T-X conditions determine in which mineral reaction 

the Hj.O component should participate. Under the conditions 

represented by the amphibolite facies, the uralitization of pyroxenes in rocks of gabbroic bulk composition is the most favorable 

reaction; the felsic rocks of the granulite facies contain mineral 

assemblages that are stable also in the amphibolite facies. Thus 

a thermodynamic potential was set up so that the H2O component 

migrated into the mafic rocks to promote the amphibolitizatioii 

of pyroxenes, whereas the felsic parts of the Cucamonga Canyon

FIGURE 34. Intrafolial folding in blastomylonites. A, Photomicrograph showing intricate "plastic style" intrafolial folding in a poly cataclastic blastomylonite from >a fault zone near 

the northwestern edge of 'Straight Fork window, eastern 

Great 'Smoky Mountains, North Carolina (furnished by J. B. 

Hadley, U.S. Geological Survey) ; plane^polarized light. Most 

of the porphyroclasts are feldspar. "The large light areas are 

cataclasite; they are virtually "megaporphyroclasts" in the 

polycataclastic, blastomylonitic matrix. 'The rock is fairly 

well recrystallized. Parent rock was a biotite-plagioclasepotassium feldspar gneiss (see Ravensford body, Hadley and 

Goldsmith, 1963, p. 816). B, Overturned, isoclinal, intrafolial 

folds in blastomylonite from the Goat Rock fault zone, near 

Goat Rock Dam, Alabama. Note style of folding, and compare with Plate Ib, 'Christie (1963, p. 423).

system became, or remained, poor or deficient in HaO. Consequently, active synkinematic neomineralization was possible in 

mafic rocks, forming granoblastic amphibolites; at the same 

time, the felsic rocks underwent cataclastic deformation under 

a dispsenic [sic should read dipsetic] condition, the little H2O 

that was present promoting the incipient neomineralization.

Hsu (1955b, p. 312) also proposed that:

* * * the partial pressure of the hydrous phase, rather than the 

amount of water present, plays a vital role in determining the 

nature of the equilibrium assemblage for a rock of a given bulk 

composition.

Hsu's (1955b, p. 312) variables would therefore be: 

temperature, hydrostatic pressure, partial pressure of 

the hydrous phase, and "other factors (X)."

Hsu's work emphasized the importance of water content and PH2o in determining the formation and mineralogy of cataclastic rocks. More recent work has 

shown that the chemical activities of various elements 

and compounds are also important in metamorphism, 

and therefore in cataclastic rock formation as well 

(see Turner, 1968).

Experimental studies of rock deformation are not 

yet sufficiently far advanced to warrant quantitative 

statements regarding the physical and chemical conditions of cataclasis. We do know that: (1) increase in 

confining pressure without temperature change causes 

increase in ultimate strength, strain, and commonly in 

conjugate shear angle; (2) increase in temperature 

without change in confining pressure causes decrease in 

ultimate strength, but not necessarily increase in strain. 

We know that the main effect of increasing confining 

pressure in triaxial-test experiments is to cause a significant increase in amount of flow before rupture and 

a significant increase in the rupture strength of the 

material.

Experimental data suggest that cataclasis operates by 

uniform flow (Badgley, 1965, p. 25), at least in the 

finer-granulated rocks. Therefore it may be classed as 

plastic deformation and considered graphically. If we 

use this approach, published curves can give us a general idea of the conditions of cataclasis (see Griggs and 

others, 1960). It must be emphasized, however: (1) that 

these curves do not depict all the conditions of natural 

cataclasis, but only give a general idea of these conditions; and (2) that most of the experiments have been 

conducted using marbles, limestones, shales, and other 

easily deformed rocks, whereas most cohesive cataclastic rocks were formed from felsic or siliceous rocks.
68 CATACLASTIC ROCKS
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 69

Elongated sperulite

Note orientation of 

jrt-=~--^^s ^O" =?" ^rT^ir^-^^*jx crystallites *"' y ° lcl ''' LC ° in axis

^H^S^K^^^ Crystallite

 zjj

2^ Flow of crystallites 

Ground rotated(?) sperulite

7

Sperulite in which crystallites 

pass through

FIGUEE 35. Intrafolial folds in obsidian and blastomylonite. A, 

Overturned, isoclinal fold in flow banded obsidian from Big 

Obsidian Flow, Newberry Caldera, central Oregon. The light 

layers are pumiceous obsidian; the dark layers are glassy 

obsidian. Movement direction is to the left in this photograph, 

but a prominent lineation on flow band surfaces, caused by 

elongated vesicles (the black holes visible in cross section 

here), indicate that movement also occurred normal to the 

main movement or flow direction (that is, movement in B). 

The round shape of many of the vesicles in cross section shows 

that the movement was not chiefly a flattening component, but 

more like a spreading. There is also a grooving lineation 

parallel to the main movement direction (A). The fold is of 

the "intrafolial" type, similar to folds common in cataclastic 

rocks. B, C, Blastomylonite from the Towaliga fault zone 

in Alabama. B shows hand sample with straight fluxion 

structure overall and parallel color and compositional layering. C is an enlargement of part of B, showing intrafolial 

folds (f), and disruption of fluxion structure and layering 

around porphyroclasts. The swirled area(s) is a fold formed 

by differentially moving planes and then further rotated 

and "rolled up." JD, Microdrawing of obsidian from Obsidian 

Canyon, Yellowstone National Park, showing an intrafolial 

style fold with crystallites oriented parallel to the axial plane. 

Elongated spherulites suggest late movement when the obsidian was in a semicrystalline state.
70 CATACLASTIC ROCKS

A

1MM

B

i o 4 INCHES

5

L_u 5 CENTIMETERS

FIGUBE 36. Relations of various cataclastic texturesi in tMn section (A), hand sample (B), outcrop (C), and on map (D). 1, Coarser graine

catclastic rocfi: chiefly blastomylonite (note biotite (b) in A and B) ; 4, fine- to very fine graine
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 71

1000 0 4000 FEET

I I i l i l

1 METER

1 KILOMETER

jataclasitic rock chiefly protomylonite; 2, medium- to fine-grained cataclastic rock chiefly mylonite; 8, recrystallized-neomineralized 

jataclastic rock chiefly ultramylonite. Rock in all cases was originally a coarse-grained gneiss.
72 CATACLASTIC ROCKS

GLOSSARY

(Lower case boldface type is used for the cataclastic rock 

terms of table 1, Classification of Cataclastic Rocks, when they 

are defined in the glossary. Hock terms not used in the classification are in italics. Other terms are not in bold type or 

italics.)

"allure lenticulaire" (Knopf, 1931) : The lenticular structure 

caused by isoclinal folding and cataclastic shearing-out 

(both generally and on a microscopic scale) of relatively 

resistant beds or layers of a rock during phyllonitization.

augen: A lenticular or rounded mineral or aggregate of min 

erals larger than the general groundmass grain size of a 

rock. Auge is German for eye, and augen in rocks are commonly eye-shaped, the spindle-shaped ends extending parallel to the foliation. Augen are most commonly of feldspar 

(particularly K-feldspar), and are most commonly present 

in gneisses. They may be porphyroblastic or porphyrociastic.

augen gneiss: A gneiss characterised by augen. Most augen 

gneisses are crystalloblastic and essentially noncataclastic ; 

some are actually mylonite gneisses.

auffen schist (Lapworth, 1885) : Equivalent to mylonite gneisis. 

See mylonite gneiss.

compositional banding: See color lamination and layering.

Bewegungsbild (Sander, 1930) : "Movement-picture". See movement picture.

blastomylonite: A coherent, rock intermediate between mediumto fine-grained mylonite or ultramylonite and a crystalline 

schist or gneiss because its texture is the result of combined cataclastic and crystalloblastic processes. It is not 

produced by later recrystallization or neomineralization of 

a previously mylonitized rock; cataclasis and neomineralization-recrystallization -are concurrent, producing a rock in 

which crystalloblastic texture appears to have overprinted 

the basic mylonite texture. Porphyroclasts in blastomylonite 

are generally smaller than about 0.5 mm and may show 

recrystallization. They make up less than about 30 percent 

of the rock. Discussion p. 13.

Uastomylonitic gneiss (Reed and Bryant, 1964, p. 1181) : ". . a 

gneissic rock consisting of 10-90 per cent porphyroclasts set 

in a matrix of blastomylonite."

blastophyllonite (Turner, 1941) : Turner used this term for 

phyllonites with a high degree of neomineralization and 

recrystallization. The rocks are covered by the term blastomylonite as defined in this paper.'

firecciated mylonite: A fault breccia composed of fragments of 

mylonite a polycataclastic rock formed by the action of 

a second phase, episode, or period of cataclasis on a mylonite. Brecciated ultramylonite is similarly defined.

"button scMst": A common field term for rocks in which micaceous porphyroclasts or porphyroblasts form button-like 

structures upon weathering. It is also used for rocks in 

which two cleavages intersect at an angle to produce button 

shaped or lens-shaped fragments (See Crickmay, 1952; 

Reed and Bryant, 1964; Higgins, 1966) . Similar rocks have 

been called "wavy schist," 'frilled schist," "curly schist,"

"phyllonitic schist," "crumpled schist," "puckered schist," 

"eyed schist," "eyed phyllonite," "fish-scale schist," and 

"oyster-shell rock."

cataclasis: The process by which rocks are broken and granuulated due to stress and movement during faulting; granulation or comminution. See p. 2.

cataclasite: An aphanitic, structureless cohesive cataclastic rock 

in which most of the fragments are less than about 0.5 mm, 

and make up less than about 30 percent of the rock. Essentially like a mylonite but lacking fluxion structure. Discussion p. 6.

cataclastic: Pertaining to rocks affected by cataclasis. 

cataclastic foliation: Fluxion structure. See fluxion structure.

cataclastic metamorphic differentiation: metamorphic differentiation produced by cataclasis. See metamorphic differentiation.

cataclastic rock: A general term for any rock produced by 

cataclasis, regardless of whether or not the rock is coherent.

cohesion (coherent, cohesive) : In this paper cohesion pertains 

to primary cohesion. See primary cohesion.

color lamination : Layering due to color differences, regardless of 

origin, in adjacent layers of rock whether on a megascopic or 

microscopic scale.

comminution: Reduction in size of the constituents of a rock 

due to cataclasis.

compositional layering: Layering due to chemical and mineralogical differences in the adjacent layers, regardless of 

origin. May include color lamination.

confining pressure: An equal, all-sided pressure. In the crust of 

the earth it is lithostatic pressure resulting chiefly from the 

load of overlying rocks. In experimental work it is a hydrostatic pressure, commonly produced by liquids.

"crumpled schist": A fairly common field name for phyllonitic 

rocks in which the lenticular structures may give rise to 

an uneven wavy surface. See "button schist."

crush-breccia (Tyrrell, 1926) : Equivalent to microbreccia. See 

microbreccia.

crush-rock: A field term used by early workers for many different 

kinds of cataclastic rock, but particularly for those without 

fluxion structure.

cryptomylonite (Scott and Drever, 1953) : Essentially equivalent 

to flinty crush rock. See flinty crush-rock. Also see hyalomylonite.

crystalloblastic (Becke, 1904) : A crystalline texture due to metamorphic growth of minerals in solid rocks by recrystallization and/or neomineralization. In this texture the essential 

constituents have crystallized simultaneously and not in 

sequence. A constructive texture as opposed to cataclastic 

texture which is chiefly destructive.

"curly schist": A fairly common field term for phyllonitic rocks 

in which lenticular structures may give the rock an uneven 

wavy surface upon weathering (see Reed, 1964). See "button 

schist."
THEORETICAL ASPECTS OF CATACLASTIC ROCKS AND PROCESSES INVOLVED IN FORMATION 71

1 METER

1000 0 4000 FEET

l l i i i i

1 KILOMETER

cataclasitic rock chiefly protomylonite; 2, medium- to fine-grained cataclastic rock chiefly mylonite; 3, recrystallized-neomineralized 

cataclastic rock chiefly ultramylonite. Rock in all cases was originally a coarse-grained gneiss.
72 CATACLASTIC EOCKS

GLOSSARY

(Lower case boldface type is used for the cataclastic rock 

terms of table 1, Classification of Cataclastic Bocks, when they 

are defined in the glossary. Rock terms not used in tihe classification are in italics. Other terms are not in bold type or 

italics.)

"allure lenticulaire" (Knopf, 1931) : The lenticular structure 

caused by isoclinal folding and cataclastic shearing-out 

(both generally and on a microscopic scale) of relatively 

resistant beds or layers of a rock during phyllonitization.

augen: A lenticular or rounded mineral or aggregate of rain 

erals larger than the general groundmass grain size of a 

rock. Auge is German for eye, and augen in rocks are commonly eye-shaped, the spindle-shaped ends extending parallel to the foliation. Augen are most commonly of feldspar 

(particularly K-feldspar), and are most commonly present 

in gneisses. They may be porphyrccblastic or porphyrociastic.

augen gneiss: A gneiss characterised by augen. Most augen 

gneisses are crystalloblastic and essentially noncataclastic; 

some are actually mylonite gneisses.

augen schist (Lapworth, 1885) : Equivalent to mylonite gneisis. 

See mylonite gneiss.

compositional banding: See color lamination and layering.

Bewegungsbild (Sander, 1930) : "Movement-picture". See movement picture.

blastomylonite: A coherent rock intermediate between mediumto fine-grained mylonite or ultramylonite and a crystalline 

schist or gneiss because its texture is the result of combined cataclastic and crystalloblastic processes. It is not 

produced by later reerystallization or neomineralization of 

a previously mylonitized rock; cataclasis and neomineralization-recrystallization -are concurrent, producing a rock in 

which crystalloblastic texture appears to have overprinted 

the basic mylonite texture. Porphyroclasts in blastomylonite 

are generally smaller than about 0.5 mm and may show 

reerystallization. They make up less than about 30 percent 

of the rock. Discussion p. 13.

Wastamylonitic gneiss (Reed and Bryant, 1964, p. 1181) : ". . a 

gneissic rock consisting of 10-90 per cent porphyroclasts set 

in a matrix of l>lastomylonite."

llastophyllonite (Turner, 1941) : Turner used this term for 

phyllonites with a high degree of neomineralization and 

recrystallization. The rocks are covered by the term blastomylonite as defined in this paper.'

Irecciatea mylonite: A fault breccia composed of fragments of 

mylonite a polycataclastic rock formed by the action of 

a second phase, episode, or period of cataclasis on a mylonite. Brecciated ultramylonite is similarly defined.

"button schist": A common field term for rocks in which micaceous porphyroclasts or porphyroblasts form button-like 

structures upon weathering. It is also used for rocks in 

which two cleavages intersect at an angle to produce button 

shaped or lens-shaped fragments (See Crickmay, 1952; 

Reed and Bryant, 1964; Higgins, 1966) . Similar rocks have 

been called "wavy schist," 'frilled schist," "curly schist,"

"phyllonitic schist," "crumpled schist," "puckered schist," 

"eyed schist," "eyed pfayllonite," "fish-scale schist," and 

"oyster-shell rock."

cataclasis: The process by which rocks are broken and granuulated due to stress and movement during faulting; granulation or comminution. See p. 2.

cataclasite: An aphanitic, structureless cohesive cataclastic rock 

in which most of the fragments are less than about 0.5 mm, 

and make up less than about 30 percent of the rock. Essentially like a mylonite tout lacking fluxion structure. Discussion p. 6.

cataclastic: Pertaining to rocks affected by cataclasis. 

cataclastic foliation: Fluxion structure. See fluxion structure.

cataclastic metamorphic differentiation: metamorphic differentiation produced by cataclasis. See metamorphic differentiation.

cataclastic rock: A general term for any roick produced by 

cataclasis, regardless of whether or not the rock is coherent.

cohesion (coherent, cohesive) : In this paper cohesion pertains 

to primary cohesion. See primary cohesion.

color lamination : Layering due to color differences, regardless of 

origin, in adjacent layers of rock whether on a megascopic or 

microscopic scale.

comminution: Reduction in size of the constituents of a rock 

due to cataclasis.

compositional layering: Layering due to chemical and mineralogical differences in the adjacent layers, regardless of 

origin. May include color lamination.

confining pressure: An equal, all-sided pressure. In the crust of 

the earth it is lithostatic pressure resulting chiefly from the 

load of overlying rocks. In experimental work it is a hydrostatic pressure, commonly produced by liquids.

"crumpled schist" : A fairly common field name for phyllonitic 

rocks in which the lenticular structures may give rise to 

an uneven wavy surface. See "button schist."

crush-breccia (Tyrrell, 1926) : Equivalent to microbreccia. See 

microbreccia.

crush-rocJc: A field term used by early workers for many different 

kinds of cataclastic rock, but particularly for those without 

fluxion structure.

cryptomylonite (Scott and Drever, 1953) : Essentially equivalent 

to flinty crush rock. See flinty crush-rock. Also see hyalomylonite.

crystalloblastic (Becke, 1904) : A crystalline texture due to metamorphic growth of minerals in solid rocks by recrystallization and/or neomineralization. In this texture the essential 

constituents have crystallized simultaneously and not in 

sequence. A constructive texture as opposed to cataclastic 

texture which is chiefly destructive.

"curly schist": A fairly common field term for phyllonitic rocks 

in which lenticular structures may give the rock an uneven 

wavy surface upon weathering (see Reed, 1964). See "button 

schist."
GLOSSARY 73

diaphthoresis (Becke, 1909) : Retrogressive metamorphism. See 

p. 4(M4.

diaphthorite: A. rock with relict minerals of a higher grade or 

facies of metamorphism which have been changed or partly 

changed elsewhere in the rock by retrogressive metamorphism (diaphthoresis) to minerals of a lower grade or 

facies of metamorphism. Diaphthorites are not necessarily 

cataclastic. See p. 16-21.

diaphthoritic: Pertaining to rocks affected by diaphthoresis. 

See diaphthoresis.

diaphthoritic phyllonite: A phyllonite that shows evidence of 

diaphthoresis. See 16-21.

dike-mylonite (Hammer, 1914) : An ultramylonite or mylonite 

that shows intrusive relations to the adjacent rock. The 

intrusive habit is due to flowage of crushed rock powder 

during cataclasis (see Crickmay, 1933; Knopf, 1931; Higgins, 1966) or to selective cataclasis of igneous dikes (see 

Peach and others, 1907). This term should not be used as 

a rock name because it merely denotes mode of occurrence.

dipsetic: dry; a condition of thirst; producing thirst. See Hsu 

(1955b, p. 272).

en echelon: Parallel but offset structural features; parallel 

features not in the same line.

episode: One of two or more divisible time or feature-producing 

units of a period of metamorphism or a period of deformation.

"eyed phyllonite": See "eyed schist."

"eyed, schist" (Knopf, 1931) : A cataclastic schistose or phyllonitic rock in which porphyroclasts or porphyroblastsJ, generally of mica, appear as "eyes" in the finer grained matrix. 

This is a fairly common field term, equivalent to "fish-scale 

phyllonite," to some "button schists," "curly schists," "wavy 

schists," and "oyster-shell rocks," and to the "phyllonitic 

schist" of Reed and Bryant (1964). See "button schist."

fabric: (Paterson and Weiss, 1961; Turner and Weiss, 1963) 

The fabric of a body is ". . . the internal geometric configuration of its elementary parts and of any characteristic 

features to which the arrangement of these parts gives 

rise." (Turner and Weiss, 1963, p. 19).

fault breccia : A rock composed of angular to rounded fragments, 

formed by crushing or grinding along a fault. Most fragments are large enough to be visible to the naked eye, and 

they make up more than. 30 percent of the rock. Coherence, 

if present, is due to secondary processes.

fault gouge: Pastelike rock material formed by crushing and 

grinding along a fault. Most individual fragments are too 

small to be visible to the naked eye, and fragments larger 

than the average groundmass grains make up less than 30 

percent of the rock. Coherence, if present, is due to secondary processes.

fault pug: Reed (1964, p. 652-654) used this term for shattered, 

altered, structureless rocks similar to fault gouge, but 

formed from schistose rocks. According to Reed, the rocks 

are incoherent, and are in the same category as fault breccias and fault gouge with regard to conditions of formation.

fault zone: As opposed to a fault which is by definition a plane 

)Of movement, a fault zone is a zone of faulting. A fault zone 

may consist of many separate fault planes concentrated in 

a relatively narrow zone or may be a zone of distributed 

movements with few or no distinct fault planes.

felsic: Refers to quartz, feldspars, and feldspathoids. The U.S. 

Geological Survey recommends the terms felsic and (or) 

silicic in place of "acid," because the former are more 

precise. For example, quartzites are silicic; rhyolites and 

granites are felsic.

"fish^scale phyllonite" : See "eyed schist."

fissility (fissile) : A property of splitting easily along closely 

spaced planes which may be parallel or may lie at low 

angles to one another. A rock with fissility is described as 

fissile.

"fissured and brecaiated granite" (Termier and Boussac, 1911) : 

Descriptive phrase used by some early workers for cataclastic rocks.

"flamboyant quartz" : A descriptive term for the wavy stringers 

of strained or granulated quartz common to many blastomylonites and mylonite gneisses, and present in some 

mylonites.

fiaser gneiss (Tyrrell, 1926) : As Tyrrell used this term it is 

equivalent to mylonite gneiss and to some protomylonite. 

Tyrrell (1926, p. 286) defined fiaser rocks as ". . . rocks in 

which lentioles of relatively-unaltered material are preserved in a finely crushed and partially-recrystallized 

matrix." Fiaser is German for streaks or lenticles, and 

many geologists have used flaser gneiss, flaser rock, flaser 

gabbro, etc., for any streaked rock, regardless of the origin 

of the streaky, lenticular structure. (See Heinrich, 1956.)

flaser structure: See flaser gneiss.

flinty crush-rock (Clough, 1888, p. 22) : Used by most early 

workers (see Clough, 1888; Peach and others, 1907, p. 124, 

141, 151-153, 190, 196, 214-216, 244-250; Clough and others, 

1909, p. 629-631; Jehu and Oraig, 1923, p. 430-436, 1925, 

p. 629-630; Dougal, 1928) as a field term for many varieties 

of fine-grained, aphanitic, flinty-appearing cataclastic rock. 

Generally defined as a dark-colored, flinty or glassy rock 

found as veins and stringers associated with fault zones 

and formed by ultracrushing and partial fusion of finely 

comminuted rock powder along the fault zone. Some of the 

rocks called flinty crush-rock are intrusive (and even 

nonintrusive) finely comminuted mylonites and ultramylonites; others are pseudotachylite. Where melting or 

fusion can be proved, the term pseudotachylite should be 

used; where melting or fusion are absent, an applicable 

name from the classification (table 1) should be used, 

regardless of intrusive relationships. See discussion p. 21-30.

flow structure (flow-structure) : See fluxion structure.

fluidization (Reynolds, 1954) : An industrial process whereby 

gas is passed through fine-grained particles to facilitate 

movement or chemical reaction. Reynolds (1954) and 

Christie (1960) considered pseudotachylite a result of 

fluidization. See p. 30.

fluxion banding : See fluxion structure.
74 CATACLASTIC ROCKS

fluxion lines: Lines of minerals, grains, etc. denning fluxion 

structure. See fluxion structure.

fluxion structure (fluxion texture) : Cataclastioally produced 

directed penetrative texture or structure commonly involving a family or set of s-surfaces; cataclastic foliation. 

May be visible megascopically or only microscopically. Does 

not necessarily involve compositional layering or lamination, although many examples do show such layering. Discussion p. 3, 61. See color lamination and compositional 

layering.

foliation: Any type of recognizable s-surfaces of metamorphic 

(includes coherent cataclasis) origin.

form orientation: (after Sander, 1930) Directed penetrative 

texture; the fabric of a tectonite.

"frilled schist": See "button schist."

gangmylonite (Hammer, 1914) : Equivalent to dike-mylonite. 

See dike-mylonite.

glide-fold schistosity (Gleitfaltschieferung) : (Kienow, 1953; 

Christie, 1963) A schistosity developed by shearing of the 

limbs of small-scale folds. This schistosity is rapidly rotated toward the plane of the original schistosity. See 

p. 62 and figure 33.

gouge: See fault gouge.

gneiss: Relatively coarse grained metamorphic rock in which 

the schistosity and foliation are less well denned than in 

schist because of the preponderance of felsic minerals over 

micaceous minerals. Most gneisses are granitic in composition. Irregular to regular banding is common, but not requisite for use of the term "gneiss." Some gneisses are 

plutonic and should be so designated. Distinction from 

schist on one hand, and from granite on the other is arbitrary and gradational.

"granite": A general term referring to any medium- to coarsegrained, quartz- and feldspar-bearing, hypabyssal or plutonic-appearing rock.

granite: Specific name for a medium- to coarse-grained rock 

consisting of potassium feldspar and quartz with sodic 

plagioelase, typically oligoclase, present in distinctively 

lesser amounts than the potassium feldspar (according to 

Williams and others (1954), alkali feldspar constitutes 

more than two-thirds of the total feldspar) ; biotite, and 

(or) hornblende, and (or) muscovite are commonly present 

in accessory amounts. (See Dietrich and Mehnert, 1961).

granitic rock ("granitic rock") : General term for "granites." 

See "granite."

hartschiefer (Holmquist, 1910) : Originally used for blastomylonites with well-developed parallel compositional layering 

or color lamination. Hartschiefer has also been used for 

rocks that are probably metamorphosed sediments, and for 

layered mylonites and ultramylonites. Discussion p. 30.

hyalomylonite (Scott and Drever, 1953) : Essentially equivalent to pseudotachylilte. Scott and Drever (1953, p. 123) 

stated: "The terms 'cryptomylonite' and 'hyalomylonite' will 

be used, respectively, for material the determination of 

which is hampered by its relative opacity, and to material 

characterised by an abundance of easily determinable 

glass." See pseudotachylite and discussion p. 21-30.

intrusive: Applies to a rock body that has moved from its place 

of origin into another rock.

kaJcirite (Svenonius, 1892) : Svenonius used this term for many 

different kinds of cataclastic rock. Holmquist (1910) used 

it for cataclastic rocks without "parallel structure," and 

stated that kakirite has the structure of a "microbreccia." 

Holmquist's photomicrographs of "kaMrilte" (1910, p. 939) 

appear to be cataclasite. Quensel (1916, p. 100) stated that 

he agreed with Svenonius and Holmquist on, the definition 

of kakirite, but defined it (1916, p. 99) as: "In einem in 

miakroskopischen Dimensionen brecciierten Gesltein sind die 

relativ weniger zertrummerten Bruchstiicke des Ausgangsmateriales auf alien Seiten von Rutsch- oder Kluftflachen 

umgeben, in denen eine intensive Zermahlung neben Mineralneubildung sich geltend macht." Translated into English this would imply that (there are shear planes or gliding 

surfaces in the rock (see Waters! and Campbell, 1935, p. 

478; Christie, 1960, p. 83), thus making it more like protomylonite than like cataclasite.

lamination: See color lamination, 

layering: See compositional layering.

lenticular structure (lenticular texture) : Structure or texture 

characterized by lenses or lentils of rock material separated and defined by s-surfaces having doubly-convex relationships.

mafic: Refers to the dark minerals of a rock; minerals rich 

in iron and magnesium. The U.S. Geological Survey recommends the term mafic in place of basic, because it is more 

precise. For example, gabbros and basalts are mafic rocks.

"mashed gneiss": Field term used by early workers for various 

kinds of cataclastic rocks.

metamorphic differentiation (Stillwell, 1918) : Refers to variouis processes by which contrasting mineral assemblages 

develop from an initially uniform rock during metamorpihism. Discussion p. 62-64.

microbreccia: An intensively fractured but unground (fragments have not rolled) cohesive breccia in which the grains 

and fragments are without form orientation. Fragments 

may range from megascopic to about 0.2 mm and are separated by finer grained material. Fragments larger than 0.2 

mm make up more than about 30 percent of the rock. Discussion p. 6.

micro-breccia (Tyrrell, 1926) : Equivalent to microbreccia. See 

microbreccia.

monocataclastic: Applies to rocks that have been affected by 

only one episode, phase, or period of cataclasis.

monometamorphic: Applies to rocks that have been affected 

by only one episode, phase, or period of metamorphism.

mortar (Tornebohm, 1880) : From Swedish Murbrulc (mortar). 

Refers to fine-grained rock powder between porphyroclasts 

or within shears in a rock; like mortar between stones or 

bricks.

mortar structure (mortar texture) (Tb'rnebohm, 1881) : Refers 

to a structure or texture in rocks characterized by mortar 

between and around porphyroclasts, or filling shears between unground fragments of the rock. See mortar.
GLOSSARY 75

movement picture (Sander, 1930) : The kinematic concept that 

the nature of the geometric order of a body reflects the 

geometric order of the differential displacements, rotations, and strains that must be present during deformation 

of a real polycrystalline body. See Turner and Weiss 

(1963, p. 9, 367-378).

mylonite: A coherent microscopic pressure-breccia with fluxion 

structure which may be megascopic or visible only in thin 

section and with porphyroclasts generally larger than, 0.2 

mm. These porphyroclasts make up about 10 to 50 percent 

of the rock. Mylonites generally show recrystallization and 

even new mineral formation (neomineralization) to a limited degree, but the dominant texture is cataclastic. Discussion p. 7.

mylonite gneiss (mylonite schist): A coherent rock intermediate 

between a protomylonite or coarse mylonite and a crystalline gneiss or schist because its texture is the result of 

combined cataclastic and crystalloblastic processes. Augen 

structure is characteristic, the augen generally being 

porphyroclasts or crushed aggregates of felsic minerals. 

The augen, although commonly recrystallized, preserve evidence of cataclastic texture by their shapes and by the 

crush trails commonly associated with them; the surrounding groundmass has been recrystallized and or neomineralized, although it too may show palimpsest cataclastic 

texture. Most of the porphyroclasts are larger than about 0.5 

mm and they make up more than about 30 percent of the 

rock. Discussion p. 11-13.

mylonitschiefer (Quensel, 1916) : Essentially equivalent to 

mylonite schist. See mylonite gneiss (mylonite schist). Also 

see discussion p. 11-13.

mylonitic: Meaning mylonitelike. Pertains only to protomylonites, mylonites, and ultramylonites.

mylonitization: The process by which mylonites are formed; a 

subdivision of the process of cataclasis which pertains only 

to the production of protomylonites, mylonites, and ultramylonites.

neomineralization: The process of metamorphic transformation 

of the old mineral constituents of a rock into new minerals 

of different composition; new mineral growth. Discussion 

p. 57.

neomineralization-recrystallization: Used in this paper for neomineralization and (or) recrystallation.

"nodular mylonite" (Baguin, 1926) : Raguin used this term for 

course megascopic breccias. It is essentially equivalent to 

protomylonite. See protomylonite.

"oyster-shell rock" (Peach and others, 1907, p. 598) : Essentially 

equivalent to "eyed schist." See "eyed schist" and "button 

schist."

period: Time or event of metamorphism or of deformation; 

separated from other periods by times of distinct nondeformation or nonmetamorphism; generally represents a long 

time and may be divisible into episodes, which may in turn 

be divisible into phases. See episode and phase.

phacoidal structure (Peach and others, 1907) : Lenticular structure at outcrop scale, in which large lenticular (doubly convex) masses of unfoliated to poorly foliated rock are enclosed in sheared well-foliated rock. A sort of "mega-flaser 

structure." Well described (1907, p. 149, 169, 263, 504) and 

well illustrated (1907, p. 29) by Peach and others. Heinrich 

(1956) has used phacoidal in a macroscopic sense for the 

textures of mylonite gneisses and related rocks. However, 

Peacih and others (1907) apparently limited the term to outcrop-scale features, which seems desirable as there are other 

terms for the miscroscopic textures.

phase: Theoretically, the smallest divisible time or feature-producing unit of metamorphism or deformation; two or more 

phases form an episode. Something like a "pulse" of activity 

within the larger, longer event. See episode and period.

phyllitic: Phyllite-like; having the appearance of a phyllite.

phyllitic diaphthorite: A retrogressive metamorpihic rock with 

the appearance of a phyllite. Not necessarily a cataclastic 

rock. Seep. 16-21.

phyllonite: Phyllite-mylonite; A rock of phyllitic appearance 

formed by mylonitization of an originally coarser grained 

rock. See p. 16-21.

phyllonitic schist (Reed and Bryant, 1964) : Reed and Bryant 

(1964, p. 1181) define phyllonitic schist as: "... a schist 

partly retrogressively metamorphosed to phyllonite and 

containing 10-90 percent porphyroclasts (chiefly of mica) 

in a matrix of phyllonite." They probably coined this term 

to avoid using such names as "eyed schist," "eyed phyllonite," and "button schist," previously used for rocks along 

the Brevard zone (see p. 49-51, this paper), and to express the retrogressive nature of the rocks. However, their 

definition carries the unfortunate connotation that phyllonites are produced by retrogressive metamorphism (see 

p. 11, 16-21, this paper). Phyllonitic schist is essentially 

equivalent to diaphthoritic phyllonite. See diaphthoritic 

phyllonite, and phyllonite.

phyllonitization: The cataclastic process by which phyllonite 

is produced. Essentially, mylonitization of a schistose or 

micaceous rock. Does not necessarily involve diaphthoresis. 

See mylonitization.

phyilonitized: Applies to a rock that has undergone phyllonitization. See phyllonitization.

plastic deformation: A permanent, nonelastic, change in shape 

of a solid that does not involve failure by rupture. It may 

involve recrystallization, gliding within individual crystals or grains, and rotation of grains. Dlagrammaitically, 

it is nonelasitic deformation past the yield point.

''plicated schist": See "button schist."

polycataclastic: Applies to rocks that have been affected by 

more than one period or episode of cataclasis (as opposed 

to monocataclastic). See p. 30-31.

polyepisodic: Applies to rocks remetamorphosed during two 

or more episode® of metamorphism (polyepisodic metamorpihic rocks), or to rocks affected by two or more episodes of cataclasis (polyepisodic cataclastic rocks).

polymetamorphic: Applies to rocks that have been affected by 

more than one period of metamorphism (as opposed to 

monometamorphic). See p. 30-31.
76 CATACLASTIC ROCKS

porphyroblast: A relatively large crystal or mineral grain developed during metamorphism by neomineralization and 

(or) recrystallization. Porphyroblasts are larger than the 

matrix which encloses them.

porphyroclast: A relatively large fragment of a crystal, mineral 

grain, or aggregate of crystals or grains, in a cataclastic 

rock. Porphyroclasts are not produced by neomineralization 

or recrystallization (as opposed to porphyroblasts), but 

may be recrystallized in blastomylonites and mylonite 

gneisses.

primary cohesion: Refers to congenital coherence of a rock, as 

opposed to that produced by secondary cementation. Essentially metamorphic cohesion.

protoclasis: Cataclasis of an igneous body, or parts of an igneous 

'body, due to late intrusive movements of, or within, that 

body, generally before it has completely crystallized. See 

p. 13.

protoclastic rocks: The products of protoclasis are called protoclastic rocks. They may be indistinguishable from other cataclastic rocks, except for their intimate association with, or 

localization within, the parent igneous body. See p. 13.

protomylonite: A coherent crush-breccia composed of megascopically visible fragments which are generally lenticular 

and are separated by megascopic gliding surfaces filled with 

finely ground material. The fragments, or "megaporphyroclasts," make up more than about 50 percent of the rock. 

Protomylonite commonly resembles conglomerate or arkose 

on weathered surfaces. Features of the original rock, such 

as stratification and schistosity, may be preserved in the 

larger fragments. Discussion p. 7.

pseudoeruptive: Early workers used this term for cataclastic 

rocks showing intrusive relationships. Same as intrusive. 

See* intrusive.

pseudointrusive: Early workers used this term for cataclastic 

rocks showing intrusive relationships. Same as intrusive. 

See intrusive.

pseudotachylite: A glassy rock generally resembling tachylite, 

commonly of intrusive habit and closely associated with 

faults or fault zones. The groundmass of the rock is composed mainly of glass which in some cases contains microlites 'Of feldspar, vesicles, spherulites, amygdules, or partially melted rock and mineral fragments. The rock fragments may toe cataclastic or undeformed. Pseudotachylite 

probably forms by melting due to frictional fusion during 

faulting of already-hot rocks; generally rocks heated by 

igneous intrusions. Discussion, p. 21-30.

"puckered schist": See "button schist."

purge parfaite (Termier and Boussac, 1911) : Termier and 

Boussac used this term, which means "perfect soup," for 

rocks that are compact, finely-ground "microbreccias" in 

which the particles are so fine grained that the rocks resemble chert or hard wax. Essentially equivalent to cataclasite. See cataclasite.

recrystallization: Metamorphic crystallization of new mineral 

grains from old minerals of the same chemical constitution 

(for example, quartz from quartz) ; as opposed to neomineralization. See neomineralization.

retrograde: Applies to the products of retrograde metamorphism. See retrograde metamorphism.

retrograde metamorphism: The process by which rocks of a 

higher grade or facies of metamorphism are changed or 

partially changed to rocks of a lower grade or facies of 

metamorphism; diaphthoresis. The process is not necessarily related to or associated with cataolasis. 'See diaphthoresis and discussion p. 16-21.

retrograde rocks: iSee diaphthorite, 

retrogressive: Retrograde.

s-surface ('Sander, 1911) : Any kind of penetrative planar 

structure in rocks.

schist: A schistose metamorphic rock whose main constituent 

minerals are visible in hand sample with the naked eye; 

platy and (or) micaceous minerals are generally the most 

important and abundant constituents. See gneiss.

schistosity: Foliation defined by platy and (or) micaceous minerals. See foliation.

"shatter granite": Field term used by early workers for various kinds of cataclastic rocks.

shear: The effect produced by action of a shearing stress. 

Verb : to subject a body to shear.

shearing stress: A stress causing or tending to cause two adjacent parts of a solid to slide past one another parallel 

to the plane of contact.

shear zone: A zone of shearing in rocks; essentially like a 

fault zone, but more specific because it excludes zones of 

faulting not associated with shear. See Sutton and Watson (1959, p. 4r-5). See fault zone.

silicic: Refers to silica minerals, chiefly quartz; rocks are silicic if characterized by quartz. The U.S. Geological Survey 

recommends the term silicic in place of acid, because it is 

more precise. See felsic and mafic.

strain: Deformation resulting from applied force; the changes 

in geometric properties induced in a body in response to

stress.

stress: Force per unit area of the surface to which it is applied; a body in equilibrium under the action of a system 

of forces is said to be in a state of stress (Turner and 

Weiss, 1963, p. 259).

structure: The mutual relationships in space (geometric configuration) of various components of a rock (crystals, parts 

of crystals, multigranular aggregates, or microscopically 

irresolvable groundmass materials), and any characteristic features to which the arrangement of these parts gives 

rise. Europeans have traditionally used texture for what 

Americans call structure, and vice versa. Here, following 

Turner and Verhoogen (1960), the two terms are considered interchangeable when applied to metamorphic rocks.

tachylite (tachylyte) : Dark basaltic glass. 

tectonic breccia: Same as fault breccia. See fault breccia.

texture: Interchangeable with structure with regard to metamorphic rocks. See structure.
GLOSSARY 77

tectonite (Sander, 1912, 1930) : A rock whose "fabric clearly 

displays coordinated geometric features related to continuous flow during its formation." (Turner and Weiss, 

1963, p. 39).

transposition foliation: See Umf altungs-cleavage.

trap-shotten gneiss (King and Foote, 1864) : A term used by 

early workers for dark-colored cataclastic rocks that show 

intrusive habit. See flinty crush-rock and discussion of 

pseudetachylite p. 21-30.

ultimate strength: The greatest stress that a substance can 

stand under normal short-time experiments. The highest 

point on a stress-strain curve.

ultramylonite: A coherent, aphanitic, ultracrushed pressure 

breccia with fluxion structure, in which most of the porphyroclasts have been reduced to breccia streaks and the 

few remaining porphyroclasts are smaller than 0.2 mm. 

These porphyroclasts make up less than about 10 percent 

of the rock. As in protomylonite and mylonite, recrystallization-neomineralization is present but is subordinate to cataclastic texture. In hand specimen and outcrop, ultramylonites are commonly homogeneous-appearing rocks (although 

many have compositional layering), easily confused with 

chert, quartzite, or felsic volcanic rock. Ultramylonite represents the highest stage in intensity of mylonitization in 

the series protomylonite-mtylonit0-ultramylontite. Discussion 

p. 9-11.

Unfaltungs-cleavage (Umfaltungsclivage Sander, 1911, 1923) : 

(Knopf, 1931) The final stage of strain-slip cleavage in 

which the old s-planes are completely transposed by folding 

and shearing. (Turner and Weiss, 1963, p. 92) ", . . transposition of an initial layering or foliation from one dominant 

orientation to another, with the appearance of what is effectively a new foliation discordant to the rotated gross 

orientation of the initial layering." See glide-fold schistosity

uniform flow: Macroscopically homogeneous plastic deformation. The part of the stress-strain curve past the yield point

"wavy schist": See "button schist"

ANNOTATED BIBLIOGRAPHY

Like most bibliographies this one is incomplete. I 

have made no attempt to include every publication in 

which cataclastic rocks are mentioned but not described. 

In addition, I have undoubtedly missed many publications in which cataclastic rocks are described as part 

of a general study of an area or problem. Many Bussian and Italian contributions have probably also been 

overlooked.

No attempt is made to completely abstract the articles 

in this bibliography. The annotations are, in most cases, 

intended only to give the user an idea of what the 

article is about and to cite, where possible, some of its 

chief contributions.

It is not the purpose of this bibliography to cover 

all the experimental work that might be related to 

cataclastic rocks. Generally, studies of specific minerals 

have been excluded; most of the references included 

pertain to rock deformation. Many of the experimental 

references are not annotated, either because the title 

is sufficient, or because the data are so voluminous 

as to make annotation impractical.

Adams, F. D., 1896, Geology of a portion of the Laurentian area 

lying to the north of the island of Montreal: Canada Geol. 

Survey Ann. Kept., v. 8, pt. J, 184 p.

Granulated anorthosites are attributed to protoclasis. Of 

historical interest as the first description of cataclastic 

rocks in Canada. See especially p. 106-115.

 1910, An experimental investigation into the action of 

differential pressure on certain minerals and rocks, employing the process suggested by Professor Kick: Jour. Geology, v. 18, p. 489-525.

One of the earliest experimental studies; chiefly of historical interest.

Adams, F. D., and Bancroft, J. A., 1917, On the amount of internal friction developed in rocks during deformation and 

on relative plasticity of different types of rocks: Jour. 

Geology, v. 25, p. 597-637.

Chiefly of historical interest. One of the first references to 

experimentally produced mylonitic texture. Deformed rocks 

at room temperature under confining pressure.

Alf, B. M., 1943, Mylonites in the eastern San Gabriel Mountains: California Jour. Mines and Geology, v. 39, no. 2, 

p. 144-151.

Brief field and petrographic description of protomylonites, 

mylonites, and ultramylonites in Evey Canyon, San Gabriel 

Mountains, Calif.

 1948, A mylonite belt in the southeastern San Gabriel 

Mountains, California: Geol. Soc. America Bull., v. 59, no. 

11, p. 1101-1120.

Describes protomylonites, mylonites, and ultramylonites in 

several cataclastic rock zones in a 50-square-mile area of the 

southeastern San Gabriel Mountains, including Cucamonga 

and San Antonio Canyons. Mylonite is used as a general 

term. "Chemical analyses and other data indicate that 

the mylonites were derived chiefly from a dark quartz diorite, and to a lesser extent from a paler quartz monzonite, 

without much mixing of the two source materials. The mylonite zones were intruded by the quartz monzonite and 

probably by the quartz diorite. Possibly the main mass of 

mylonite was formed by tlhe crushing of a barely consolidated upper portion of a quartz diorite pluton, as one or 

more tectonic episodes during the general period of plutonic intrusion" (part of author's abstract). Good photomicrographs. See also Hsu, 1955b.

Aloisi, Piero, 1910. Le cosi-dette Miloniti dell' Isola d'Elba: Soc. 

toscana di. Sci. Nat., Atti, Mem. 27, p. 3-16.

Description of cataclastic rocks in a zone on the island of 

Elba. Disagrees with Termier (1909a, b, c) with regard to 

the thickness of the zone and the conditions of cataclasis.

420-478 O - 71 - 6
78 CATACLASTIC ROCKS

Ambrose, J. W., 1936, Progressive kinetic metamorphism in 

the Missi Series, near Flinflon, Manitoba: Am. Jour. Sci., 

5th ser., v. 32, no. 190, p. 257-286.

Attributes progressive metamorphism (garnet grade) to 

heat developed by shearing.

Anderson, G. H., 1934, Pseudo-eataclastic texture of replacement origin, in igneous rocks: Am., Mineralogist, v. 19, no. 

5, p. 185-193.

Good discussion of cataclastic textures. Describes pseudocataclastic textures in which there is commonly corrosion 

of primary grains by solutions instrumental in depositing 

the matrix. Grain boundaries and contacts are not formed 

by pressure alone. New minerals are abundant. Plagioelase 

twin lamellae and quartz grains show little or no evidence 

of strain. "* * * pseudocatJaclastic texture is often welldeveloped where evidences of mechanical stress are absent'' 

(p. 191).

Andreatta, Giro, 1952, Polymetamorphose und Tektonik in der 

Ortlergruppe (Vortragsinholt, Bonner Kolloquim 1951) : 

Neues Jahrb. Mineralogie, Monatsh., no. 1, p. 13-28.

 1954a, Stoffmobilisterungen und Stoffbewegungen bei der 

tektonischen Metamorphose: Neues Jahrb. Mineralogie, 

Monatsh., no. 1-2, p. 2-17.

Deals with chemical changes during metamorphism due to 

tectonic movements ("tectonic metamorphism").

 1954b, Appunti sul metamorfismo; I, Mobilizzazione e 

movimenti di materia nel metamorflsmo tettonico: Soc. 

Miner. Italiana, Rend. an. 10, p. 45-61.

Concludes that during tectonic metamorphism ions and 

groups of ions move in aqueous solutions from one place 

in a rock mass to another and form crystal structures 

oriented by pressure.

 1954c. Bemerkungen iiber die Metamorphose; 1, Stoffmobilisierung und Stoffbewegungen bei der tektonischen 

Metamorphose: Fortschr. Mineralogie, v. 32, p. 56-57.

Attempts to define the conditions under which changes of 

structure and composition of rocks can take place during 

metamorphism caused by tectonic activity.

Andreatta, Giro, 1962. Id polymetamorfismo nel quadro dei problemi concernenti la poligenesl della rocce. Der Polymetamorphismus im Rahmen der Probleme, welche die Polygenesis 

der Gesteine betreffen: Acta. Geol. Alpina, no. 8, p. 81-92.

Good discussion of polymetamorphism.

Angel, Franz, 1931, Einige neuerliche Pseudotachylytefunde in 

den ostereichischen Zentralalpen; Geol. Bundensanst. Wien 

Verh., p. 143-153.

Describes partially fused cataclastic rocks in the Alps.

 1965, Retrograde Metamorphose und Diaphthorese: 

Neues Jahrb. Mineralogie Abb.., v. 102, p. 123-176.

Mineralogical and chemical discussion of retrogressive 

metamorphism. "There exist several kinds of retrograde 

metamorphism, of which diaphthoresis is but a special case, 

and progressive-final-retrograde metamorphism another" 

(part of author's abstract). He questions the classical 

"depth-zone" concepts.

Armstrong, Elizabeth, 1941, Mylonization of hybrid rocks near 

Philadelphia, Pennsylvania: Geol. Soc. America Bull., v. 52, 

no. 5, p. 667-694.

Describes "vertical, winding myonite zones" which "outline 

lenticular masses of less sheared rocks and in, some places 

attain ia thickness of a quarter of a mile" (part of author's 

abstract). Notes presence of some porphyroblasts in the 

cataclastic rocks (p. 679). Describes folds in the mylonites 

(p. 680). Uses mylonite as a general term for various 

cataclastic .rocks, most of which appear to be blastomylonites. Photomicrographs and outcrop photographs.

Backlund, H. (Helge) G., 1913, Algunas observaciones sobre 

rocas notables, provenientes de Olavarrla (Buenos Aires) : 

Argentine Republic Direcci6n General de Minas, Geologia 

e Hidrologia, Bol. no. 2, ser. B, 37 p.

Describes intrusive phenomena shown, by a thick band of 

mylonites and ultramylonites south of Buenos Aires, Argentina. Suggests fusion as an explanation for the black, cherly 

crush rocks produced from red and gray granites. Good review of other cataclastic rock zones known at that time, 

and good discussion of various cataclastic rocks and their 

nomenclature. Hand-sample photographs. It should be noted 

that Waters and Campbell (1935, p. 481) confuse this reference with Baklund (1924).

Backlund, H. (Helge) G., 1918, Petrogenetische Studien an 

Taimyrgesteinen: Geol. Foren. Stockholm Forh., v. 40, p. 

101-203.

Discusses some of the thicker mylonite units described at 

that time and the confusion resulting from mistaking these 

bands of cataclastic rock for stratigraphic horizonst

Backlund, H. G., 1924; see Baklund, O. O., 1924.

Bailey, S. W., Bell, R. A., and Peng, C. J., 1958, Plastic deformation of quartz in nature: Geol. Soc. America Bull., v. 69, no. 

11, p. 1443-1466.

Baklund, O. O. [Backlund, H. (Helge) G.], 1924, O milonitakh. i 

tektonitakh [On mylonites and tectonites] : Mineralogicb.eskoe Obshchestvo, Leningrad, Zapiski, ser. 2, v. 52, p. 145-168.

Original definition of protomylonite. Describes protomylonites on Cape Ghelyuskin-Sarya, IT.S.S.R., on the northern 

tip of Asia. Emphasizes the coarse brecciation and the resemblance to conglomerate. Implies in the prefix proto that 

the rock is first in a series (protomylonite-mylonite-ultramylonite). Helge G. Backlund was called O. O. Baklund by 

the Russians; see note under Backlund (1913) regarding 

confusion of references.

Barber, A. J., 1965, The history of the Moine thrust zone, Lochcarron and Lochalash, Scotland : Geologists' Assoe. Proc., v. 

76, pt. 3, p. 215-242.

Describes mylonites, phyllonites, and brecciated mylonites. 

Notes that most of the cataclastic rocks are recrystallized. 

Good description of the gradation between unmylonitized 

metamorphosed sandstone and the same sandstone after 

mylonitization. Folded eataclastic rocks are also described.

Bateman, J. D., 1940, An Archean mylonite from northwestern 

Ontario: Am. Jour. Sci., v. 238, no. 10, p. 742-750.
ANNOTATED BIBLIOGRAPHY 79

Describes a 1,500-foot-wide zone of cataclastic rock. Chemical analyses of parent rock and cataclastic rocks indicate 

that loss of silica was the only bulk chemical change during 

cataclasis.

Bearth, Peter, 1933, Uber Gangmylonite der Silvretta : Schweizer. 

Mineralog. Petrog. Mitt., v. 13, p. 347-355.

Describes pseudotachylite veins ("gangmylonite") in amphibolites and paragneisses at the base of the Silvretta 

nappe. Does not accept the idea of fusion in their genesis.

Becke, Frederich, 1909, Uber Diaphthorite: Tschermaks mineralog. Petrog. Mitt., v. 27, p. 369-377.

First recognition of retrograde metamorphism. Describes 

diaphthoritic phyllonites produced from high-grade gneisses. 

First definition of diaphthorite from the Greek root, meaning "to destroy." Defines as diaphthorites those crystalline 

schists in which the index minerals of a lower grade (zone) 

have been developed at the cost of minerals peculiar to an 

upper zone.

 1913, Ubersicht der petrographischen Verhaltnisse, in 

Becke, Frederich, Himmelbauer, A., Reinhold, O., and Gorgey, R., Das niederosterreiche Waldviertel: Tschermaks 

mineralog. Petrog. Mitt., v. 32, p. 185-217.

Discusses the chemical-mineralogical objections to explaining the chemical changes in the Moldanubian block described and discussed by Suess (1913) and Kolbl (1922) as 

due to mechanical disturbance. Interprets the mica schists 

and gneiss as belonging to the same formation, but differing in reaction to the primary metamorphism because they 

represent layers originally of different composition. Good 

discussion of chemical changes during dynamic metamorphism.

Becke, Frederich, 1916, Fortschritte auf dem Gebiete Metamorphose : Fortschr. Mineralogie, Kristallographie, Petrographie, v. 5, p. 210-264.

Discusses posisible chemical changes due to mylonitization. 

See particularly p. 234-238.

Bennington, K. O., 1956, Role of shearing stress and pressure 

in differentiation as illustrated by some mineral reactions 

in the system BgO-SiotrELO: Jour. Geology, v. 64, no. 6, 

p. 558-577.

Proposes a mechanism for differentiation due to shearing. 

The development of layering and more massive lenticular 

differentiation under prolonged shearing stress and high 

pressure is considered. Suggests that shear-differentiation 

accounts for the areal distribution of many serpentinites 

and dunites.

Bentley, R. D., 1969, Strike slip faults in Lee County, Alabama 

[abs.]; Geol. Soc. America, Abstracts with Programs for 

1969, pt. 4, p. 5.

Describes three major fault zones, Towaliga, Goat Rock, 

and Bartletts Ferry fault zones, in the Alabama Piedmont, 

and the cataclastic rocks found in these zones (see Examples section of text).

Berg, George, 1912, Die krystallinen Schiefer des ostlichen 

Riesengebirges: Preussische geol. Landesanst. Abh., new 

ser., v. 68, p. 1-188.

See comment after entry of Berg, 1923.

 1923, Der Granit des Riesengebirges und seine Ganggesteine: Preussische geol. Landesanst. Abh., new ser., v. 

94, p. 1-90.

This paper and Berg (1912) give results of a study of the 

Riesen area, Germany. Description of epizonal diaphthoresis 

of the metamorphosed margin of a granite pluton.

Beringer, C. C., 1943, Geologisches Worterbuch: Stuttgart, 

Ferdinand Enke Verlag, 154 p.

Defines diaphthorite on p. 28.

Bisschoff, A. A., 1963, The pseudotachylite of the Vredefort 

dome: Geol. Soc. South Africa Trans., v. 65, p. 207-230.

Suggests gas-fluxing as origin of pseudotachylite.

Bonney, T. G., 1886, The anniversary address of the president, 

Prof. T. G. Bonney: Geol. Soc. London Quart. Jour., v. 42, 

Proc., p. 38-115.

"Pressure Metamorphism" p. 94-101; excellent descriptions 

and discussions of cataclastic rocks, in England and continental Europe. Describes phylliites (phylloniltes) produced 

by comminution of granitic gneisses.

 1902, On the relation of certain breccias to the physical 

geography of their age: Geol. Soc. London Quart. Jour., 

v. 58, p. 185-203.

Borg, I. Y., and Handin, John, 1966, Experimental deformation 

of crystalline rocks: Tectonophysics, v. 3, no. 4 (spec, 

issue), p. 249-368.

Describes deformation under "shallow" conditions (1kb, 

150°O) of 18 igneous and meltamorphic rocks, and under 

"deep" conditions (5kb, 500°C) of the minerals biotite and 

plagioclase.

Borg, I. Y., and Turner, F. J., 1953, Deformation of Yule Marble, 

Part VI, Identity and significance of deformation lamellae 

and parting's in calcite grains: Geol. Soc. America Bull., v. 

64, no. 12, pt. 1, p. 1343-1352.

Born, Axel, 1925. Gefugesftudien an Gesteinen des Varistischen 

Gebirges: Neues Jahrb. Mineralogie, Beilage-Bd., v. 52, Abt 

B, p. 123-161.

Describes slaty cleavage and its development Good discussion of neomineralization.

Bowden, F. P., Stone, M. A., and Tudor, G. K., 1947, Hot spots 

on rubbing surfaces and the detonation of explosives by friction: Royal Soc. (London) Proc., v. 188, p. 329-349.

Frictional production of hot spots on moving surfaces.

Bowden, F. P., and Tabor, D., 1950, The friction and lubrication 

of solids: Oxford, Oxford Univ. Press, 372 p.

Detailed consideration of friction.

Bowden, F. P., and Thomas, P. H., 1954, The surface temperature of sliding solids: Royal Soc. (London) Proc., v. 223, 

p. 29-40.

If two polished surfaces are rubbed together at speeds as 

low as 1 or 2 feet per second, and under a load of 1,000 

grams, visible hot spots will appear.

Bowen, N. L., and Aurousseau, M., 1923, Fusion of sedimentary 

rocks in drill holes; Geol. Soc. America Bull., v. 34, no. 3, 

p. 431-448.
80 CATACLASTIC ROCKS

Describes rocks fused by rotation of the core barrel of a 

rotary oil drill, giving chemical analyses and results of 

various laboratory tests.

Bridgman, P. W., 1935, Effects of high shearing stress combined 

with high hydrostatic pressure: Phys. Rev., v. 48, p. 825- 

847.

 1936, Shearing phenomena at high pressure of possible 

importance to geology: Jour. Geology, v. 44, no. 6, p. 653-

Brogger, W. O., 1890, Die Mineralien der Syenitpegmatitgange 

de Siidnorwegischen Augit- und Nephelinsyenite; allgemeiner Teil: Zeit Krystallographie u. Mineralogie, v. 16, p. 

104-120.

First used the word protoclastio, p. 105.

Bryant, Bruce, 1966, Formation of phyllonites in the Grandfather Mountain area, northwestern North Carolina: U.S. 

Geol. Survey Prof. Paper 550-D, p. D144-D150.

Detailed discussion of chemical conditions and changes during phyllonitization. Also describes physical aspects of 

phyllonitization.

Bryn, K. O., 1959, Et funn av pseudotachylitt i S. Tr0ndelag, og 

en teori for dannelson: Norges Geol. Unders0kelse, no. 211 

(Arbokl959),p. 8-17.

Describes and gives analyses of pseudotachylltes from localities in Norway and concludes that they formed by fusion of 

the rocks at local "hot spots" in a fault zone. Gives no 

proof of fusion.

Buddington, A. F., 1939, Adirondack igneous rocks and their 

metamorphism: Geol. Soc. America Mem. 7, 354 p.

Detailed descriptions of cataclastic and protoclastic rocks. 

Definitions (in the sense he uses them, p. 252-253) : mortar 

gneiss, auffen gneiss, mylonite, ultramylonite, ultraoataclastio mylonite, flaser gneiss, granoblastio gneiss. Uses ultramylonite for rocks without fluxion structure, and ultraoataclastic mylonite for finely comminuted rocks with 

fluxion structure. Good discussions of recrystallization and 

crystalloblastic growth. Notes a concentration of magnetite 

in many of the cataclastic rocks (p. 317).

Burton, C. K, 1965, Wrench faulting in Malaya: Jour. 

Geology, v. 73, no. 5,781-798.

Describes major wrench-faults with shearing and chloritization of the rocks along them.

Butler, J. B., and Dunn, D. E., 1968, Geology of the Sauratown 

Mountains anticlinorium and vicinity, North Carolina: 

Southeastern Geology, Spec. Pub. 1, p. 19-47.

Describes the Stony Ridge fault zone in North Carolina. 

Microbreccias and cataclasites, which are referred to as 

mylonites, are described and illustrated in drawings (p. 

33). Some of the rocks appear to be polycataclastic.

Carstens, C. W., 1925, Zur Frage der Genesis der Eisenerzvorkommen von Fosen, Norwegen: Zeit. Praktisch Geologie, v. 

33, p. 94-102.

Discusses the possibility of chemical changes during mylonitization. Concludes that some changes can generally be 

noted between cataclastic rocks and their parent rocks 

but gives no satisfactory explanation for the changes.

Carter, N. L., Christie, J. M., and Griggs, D. T., 1964, Experimental deformation and recrystallization of quartz: Jour. 

Geology, v. 72, no. 6, p. 687-733.

Carter, N. L., and Friedman, MeMn, 1965, Dynamic analysis of 

deformed quartz and calcite from the Dry Creek Ridge 

anticline, Montana: Am. Jour. Sci., v. 263, no. 9, p. 747-

785.

Case, J. B., 1922, Notes on the use of core barrel with rotary 

tools: California State Mining Bur. Summary of Operations 

California Oil Fields, v. 7, no. 9, p. 6-7.

Brief description of fused rocks produced by friction from 

rotation of the core barrel of a rotary drill.

Christie, J. M., 1958, Dynamic interpretation of the fabric of 

dolomite from the Moine thrust-zone in north-west Scotland : 

Am. Jour. Sci., v. 256, no. 3, p. 159-170.

 1960, Mylonitic rocks of the Moine thrust-zone in the 

Assynt region, north-west Scotland: Edinburgh Geol. Soc. 

Trans., v. 18, pt. 1, p. 79-93.

Considers the terminology, classification, and characteristics 

of cataclastic rocks. Uses mylonitic rooks as a general term 

for all catiaclastic rocks. Descriptions, illustrations, and 

theories of the origin of cataclastic rocks in the Moine 

thrust area. Quoted and cited widely in this text.

 1963, The Moine thrust zone in the Assynt region, northwest Scotland: California Univ. Pubs. Geol. Sci., v. 40, no. 6, 

p. 345-419.

Detailed description, petrofabric study, and petrogenetic 

consideration of cataclastic rocks in the Moine thrust zone. 

Uses nomenclature of Christie, 1960. Quoted and cited widely 

in this text.

 1967, The structure of mylonite zones and their tectonic 

implication [at>s.] : Am. Geophys. Union Trans., v. 48, p. 214.

In many fault zones, high-grade mineral assemblages 

crystallized during deformation. The mylonite zones formed 

contemporaneously with regional metamorphism of the 

rocks on one or both sides of the zone. Interprets the structure of "mylonite zones" in terms of a model in which 

subcrustal convection is the cause of orogeny.

Clarke, J. W., 1952, Geology and mineral resources of the 

Thomaston quadrangle, Georgia : Georgia Geol. Survey Bull. 

59, 99 p.

Describes and illustrates cataclastic rocks along the 

Towaliga and Goat Rock fault zones in the Georgia Piedmont. Good descriptions of progressive cataclasis of several 

types of rock, and the reactions of various minerals to this 

comminution. Describes and illustrates "button schists." 

Quoted and cited in this text.

Clough, C. T., 1888, The geology of the Cheviot Hills: England 

and Wales Geol. Survey Mem., 60 p.

(especially p. 22-24). First definition of flinty crush-rock as 

"A dark-colored flinty, or quartzite-like rock found as veins 

and stringers adjacent to fault zones, and formed by ultracrushing and perhaps partial fusion of the finely comminuted rock powder aiong the fault" (p. 22). Also uses flinty 

crush-rock as a general term for many types of cataclastic 

rock.
ANNOTATED BIBLIOGRAPHY 81

Clough, C. T., Maufe, H. B., and Bailey, E. B., 1909, The cauldron 

subsidence of Glen Coe, and the associated igneous phenomena : Geol. Soc. London Quart. Jour., v. 65, p. 611-676,

Describes cataclastic rocks in conjunction with study of the 

caldera in the Northwest Highlands of Scotland. In the Glen 

Ooe "flinty crush-rocks," fragments of quartz embedded in 

a fine-drained groundmass showing perfect flow structure 

are commonly free from any strain shadows. Concludes 

that the rock has been partially fused, and suggests that 

small microlites in the groundmass developed by contact 

metamorphism due to later intrusions.

Conley, J. F., and Drummond, K. M., 1963, Brecciated dikes 

in the southern Piedmont and mountain regions of North 

Carolina [abs.] : Geol. Soc. America, Spec. Paper 76, p. 241.

See Conley and Drummond, 1965.

 1965, Ultramylonite zones in the western Oarolinas: 

Southeastern Geology, v. 6, no. 4, p. 201-211.

Describes and illustrates cataclastic rocks occurring as 

dikelike bodies as much as 27 miles long. The terms mylonite and ultramylonite are incorrectly used for microbreccias and catadasites. Except for this inaccuracy, the 

descriptions are good.

Conybeare, C. E. B., and Campbell, C. D., 1951, Petrology of 

the red radioactive zones north of Goldfields, Saskatchewan: Am. Mineralogist, v. 36, nos. 1-2, p. 70-79.

Good descriptions1 of cataclastic rocks.

Cornelius, H. P., 1925, Tiber einige Gesteine der 'Fedozserie' 

aus dem Disgraziagebiet (Bhatische Alpen) : Neues Jahrb. 

Mineralogie Beilage Bd,, v. 52, Abt. A, p. 1-50.

Describes pseudotachylite.

Corstorphine, G. S., 1897, Report of the Geologist to the Commission: Cape of Good Hope Geol. Comm. Ann. Kept, p. 

3-43.

Summary of geologic knowledge of southwestern Cape of 

Good Hope area, South Africa, to 1897. Mentions sheared 

granites and states that the shearing is " * * * due most

probably to movement while consolidation was going on

* * #_»

Crickmay, G W., 1933, The occurrence of mylonites in the 

crystalline rocks of Georgia: Am. Jour. ScL, 5th ser., v. 26, 

no. 152, p. 161-177.

Describes cataclastic rocks from several Georgia fault zones. 

Well illustrated. Describes intrusive, branching, dikelike, 

unfused "mylonites." Notes resistance of feldspar to comminution as opposed to quartz and attributes the difference to original larger grain size of the feldspar, so that 

". . . preferential cataclasis proceeds to reduce the smaller 

grains first to the state of a mylonite" (p. 177). Good discussions of cataclasis. Gives some criteria for distinguishing cataclastic rocks from volcanic rocks. Quoted and cited 

widely in this text.

 1952, Geology of the crystalline rocks of Georgia: 

Georgia Geol. Survey Bull. 58,54 p.

Describes several cataclastic rock zones1 in Georgia. Good 

description of "button schists."

Dalziel, I. W. D., and Bailey, S. W., 1968, Deformed garnets 

in a mylonitic rock from the Grenville Front and their 

tectonic significance: Am. Jour. Sci., v. 266, no. 7, p. 542- 

562.

Terminology of Christie (1960) for cataclastic rocks is 

used. Brief description of blastomylonitesi along the Grenville Front in Canada. X-ray study of garnets in blastomylonites along with detailed structural information. 

". . . the deformation of garnet in the mylonitic rocks 

near Coniston must have taken place tinder relatively high 

temperature/low strain rate conditions" (p. 560). Conclude that garnets may be of use as1 deformation ellip^ 

soids: "The crystals have no crystallographic preferred 

orientation, but where bend axes in the structure can be 

detected on Laue photographs, they consistently lie in the 

mylonitic foliation nearly normal to a prominent regional 

lineation (elongation of quartz and porphyroclastic feldspar grains)" (authors' abstract). It should be noted that 

the "porphyroclastic feldspar grains" appear recrystallized 

in their photomicrographs; in fact, the rocks appear to be 

blastomylonites.

Demay, A., 1927, La zone mylonitique de Grimaud, et la tectonique du massif des Maures: Geol. Soc. France Bull., ser. 4, 

v. 27, p. 279-336.

Describes a 100-meter-thick band of "mylonite" derived 

from gneiss in the Pyrenees. Good petrographic descriptions.

de Sitter, L. U., 1964, Structural geology (2d ed.) : New York, 

McGraw-Hill Book Co., 530 p.

Describes and defines some cataclastic rocks (p. 77-78) : 

tectonic breccia, mylomte, ultramylomte, pseudotachylite. The definitions are very general. Gives examples of 

some cataclastic ("mylonite") zones (p. 78-79, 164, 414- 

418).

Dibblee, T. W., Jr., 1967, Areal geology of the western Mojave 

Desert, California: U.S. Geol. Survey Prof. Paper 522, 

153 p.

Several zones of "mylonitic rocks" are described (p. 9).

Dietriehson, Brynjulf, 1953, Pseudotachylit fra de kaledonske 

skyvesoner i Jotunheimens forgarder, Gudbrandsdalen, 

og deres dannelsesbetingelser: Norges Geol. Unders0kelse, 

no. 184, p. 23-70.

Describes pseudotachylites from localities in Norway.

Dougal, J. W., 1928. Observations on the geology of Lewis (Outer 

Hebrides) : Edinburgh Geol. Soc. Trans., v. 12, p. 12-18.

Describes a thick zone of "flinty crush-rock." Concludes that 

the rock formed by fusion during Caledonian thrusting. 

Good photomicrographs of stellate groupings of hornblende 

crystals in some of the "flinty crush-rocks."

Eskola, Pentti, 1920, Mineral facies of rocks: Norsk Geol. Tidsskr., v. 6, p. 143-194.

Describes "armored relics" of garnet enveloped in chlorite 

and explains how the retrogression at first tends1 to destroy the garnet, but the product of the retrogression (chlorite) protects the garnets from further destruction and 

preserves them as evidence of a higher grade. This enables 

recognition of the diaphthoresis.
82 CATACLASTIC ROCKS

 1932, On the principles of metamorphic differentiation: 

Finland Comm. Ge~ol. Bull. 97, p. 68-77.

A classic discussion of metamorphic differentiation. Particularly good for chemical considerations.

 1939, in Barth, T. F. W., Correns, C. W., and Eskola, 

Pentti, Die Entstehung der Gesteine: Berlin, Springer, 

p. 263-407.

Classic discussion of metamorphic principles, including 

retrogressive metamorphism.

Byles, V. A., and MacGregor, A. G., 1932, 'The Great Glen crushbelt : Geol. Mag., v. 89, no. 6, p. 426-436.

Essentially a reply to Shand (1951), this paper describes 

the cataclastic zones and rocks in the Great Glen fault 

zone, Scotland.

Fairbairn, H. W., 1939, Hypothesis of quartz orientation in 

tectonites: Geol. Soc. America Bull., v. 50, no. 10, p. 1475- 

1491.

 1949, 'Structural petrology of deformed rocks [2d ed.]: 

Cambridge, Mass., AddisonJWesley 'Press, 344 p.

 1950, Pressure shadows and relative 'movement in a 

shear zone: Am. Geophys. Union Trans., v. 31, no. 6, p. 

914-016.

Fairbairn, H. W., and Hawkes, H. E., Jr., 1941, Dolomite orientation in deformed rocks: Am. Jour. Sci., v. 239, no. 9, 

p. 617-632.

Flett, J. S., 1912, Geology of the Lizard and Meneage: England 

and Wales Geol. Survey Mem., Explanation 'Sheet 359, 

280 p.

Describes protoclastic gabbro, p. 88-90.

Flinn, Derek, 1961, On deformation at thrust planes in Shetland and the Jotunheim area of Norway: Geoi. Mag., v. 

98, no. 3, p. 245-256.

Brief description of cataclastic rocks associated with thrust 

faults in the (Shetland Islands of Scotland and with the 

Jotun thrust in Norway.

Friedman, Melvin, 1963, Petrofabric analysis of experimentally 

deformed calcite-cemented sandstones: Jour. Geology, v. 

71, no. 1, p. 12-37.

 1964, Petrofabric techniques for the determination of 

principal stress directions in rocks, in Judd, W. R., ed., 

State of stress in the earth's crust: New York. Ab. Elsevier Pub. Co., p. 450-552.

Gangiopadhyay, P. K., and Johnson, M. R. W., 1962. A study of 

quartz orientation and its relation to movement in shear 

folds: Geol. Mag., v. 99, no. 1, p. 69-84.

Gives petrofabric data and interpretation on a folded 

mylonite and cataclastic quartzites from the Moine area, 

Scotland.

Gavelin, A. O., 1910. Oin relationera mellan graniterna, groutsternarna och kvartsit-leptit-serien inom Loftahammaromradet: Sveriges geol. Unders0kning, Ser. C., Afhandlingar 

och Uppsatser, no. 224,116 p.

Describes cataclastic rocks in the Rapatales region of 

Sweden. See Hamberg, 1910.

Goldschmidt, V. M., 1921, Geologische-petrographische Studien 

im Hochgebirge des siidlichens Norwegens; V. Die Injektionsmetamorphose im Stavanger-Gebiete: Vidensk.-selsk. 

Skr., Kristiania, 1,1920, no. 10,142 p.

Both retrogressive and progressive metamorphism have 

affected the Stavanger district, Norway. Goldschmidt distinguishes between chlorite of progressive metamorphism 

and chlorite of retrogressive metamorphism and gives criteria for the recognition of each type.

Goldschmidt, V. M., 1943, Om friksjonsglass (pseudo-tachylitt) 

i fjelkjeden: Geol. Foren. Stockholm Forh., v. 65, no. 1, 

p. 83-84.

A field and petrographic study of pseudotachylite.

Grant, W. H., 1967, Geology of the Barnesville area and Towaliga fault, Lamar County, Georgia: Atlanta, Georgia 

Geol. Soc., Guidebook 2nd ann. field trip, 16 p.

Descriptions, field relations, petrofabrics, and interpretations of various cataclastic rocks in the Towaliga fault 

zone of Georgia. See Examples section of this paper.

 1968, Movements in the Towaliga fault zone, Pike and 

Lamar Counties, Georgia [abs.]: Geol. Soc. America, Southeastern Sect. 17th Ann. Mtg. Program, p. 40-41.

Interprets cataclastic rocks and their petrofabrics along 

the Towaliga fault zone of Georgia. Concludes there has 

been a complex sequence of movement. See Examples section of this paper.

Griggs, D. T., 1936, Deformation of rocks under high, confining 

pressure: Jour. Geology, v. 44, no. 5, p. 541-577.

Rocks under high confining pressure are capable of sustaining shearing stress many times greater than those under 

atmospheric pressure.

 1940a, Experimental flow of rocks under conditions favoring recrystallization: Geol. Soc. America Bull., v. 51, no. 

7, p. 1001-1022.

 1940b, Experiments in dynamic metamorphism [aba]: 

Geol. Soc. America Bull., T. 51, p. 1928.

Griggs, D. T., and Blacic, J. D., 1964, The strength of quartz in 

the ductile regime [abts.]: Am. Geophy& Union Trans., v. 

45, no. 1, 1021-103.

Griggs, D. T., and Miller, W. B., 1951, Deformation of Yule 

Marble, Part I, Compression and extension experiments on 

dry Yule Marble at 10,000 atmospheres confining pressure, 

room temperature: Geol. Soc. America Bull., v. 62» no. 8, p. 

853-862.

Griggs, D. T., Turner, F. J., Borg, Iris, and Sosoka, John, 1951, 

Deformation of Yule Marble, Part IV, Effects at 150° C: 

Geol. Soc. America Bull., v. 62, no. 12, pt. 1, p. 1385-1406.

 1953, Deformation of Yule Marble, Part V, Effects at 

300° C: Geol. Soc. America Bull., v. 64, no. 12, pt. 1, p. 1327- 

1342.

Griggs, D. T., Turner, F. J., and Heard, H. C., 1960, Deformation of rocks at 500° to 800° C, in Griggs, D. T., and Handin, 

J. W., eds., Rock deformation, a symposium: Geol. Soc. 

America Mem. 79, p. 39-104.
ANNOTATED BIBLIOGRAPHY 83

The most complete published experimental study to date 

pertaining to the conditions of mylonitization.

Grubenmann, U., and Niggli, Paul, 1924, Die Gestelnsmetamorphose: Berlin, Borntrager, 539 p.

Especially p. 219-223. Original definition of cataclasite. Discussion of mylonite with emphasis on fluxion structure. 

Other aspects of metamorphism, cataclasis, and diaphthoresis are also discussed in this classic work.

Hadley, J. B., and Goldsmith, Richard, 1963, Geology of the 

eastern Great Smoky Mountains, North Carolina and Tennessee: U.S. Geol. Survey Prof. Paper 349-B, 118 p.

Describes augen gneisses, "zones of shearing," and "mylonites" (especially p. 87-88). Good outcrop photographs. 

"The fact that the mylonite cuts across older structural 

features and is not greatly recrystallized indicates that it 

formed relatively late in the deformation of the region." 

(p. 88).

Hall, A. L., and Molengraaff, G A. F., 1925, The Vredefort 

mountain land in the southern Transvaal and the northern 

Orange Free State: Koninkl. Akad. Wetensch. Amsterdam 

Verh., (sec. 2), v. 24, no. 3, 183 p.

Includes a detailed study of the pseudotachylites described 

by Shand (1917). Textural, field, and analytical data support Shand's contention that the pseudotachylite is similar 

in composition to the rock in which it occurs. Chilled borders 

on some pseudotachylite dikes are described.

Hamberg, Axel, 1910, Gesteine und Tekonik des Sarekgebirges: 

G«ol. Foren. Stockholm Forh., v. 32, p. 725-749.

Describes cataclasis in the Rapatales region, Sweden. "The 

least metamorphism is seen in numerous rocks where narrow oblique cracks can be perceived along the borders of 

the mineral grains. * * * By more through-going cataclasis the cracks become covered with muscovite, biotite, 

amphibole, chlorite, etc. * * * The greatest transformation is shown in the completely laminated rocks in which 

orthoclase, microcline, soda-potash feldspar and augite are 

missing, but in which muscovite, albite, zoisite, and hornblende appear. * * * Such beds show such a complete planeparallel structure that one may confuse them with sediments if one has not perceived their genetic association 

and the fact that they are composed of the same materials 

as the associated igneous rocks." (literal translation, 

p. 733).

Hammer, Wilhelm von, 1915, Das Gebiet der Bundnerschiefer im 

Tirolischen Oberinntal: Geol. Reichsanstalt, Wien, Jahrb., 

v. 64, p. 443-567.

First use of the term gangmylonite (or dike-mylonite) for 

cataclastic rocks showing intrusive relations to their country rocks. According to Hammer, there is no evidence of 

fusion, the intrusive habit being due to fiowage of crushed 

rock powder during cataclasis. Photomicrographs are presented which were later used by Knopf (1931, p. 14) to illustrate pseudotachylite.

 1930, tiber Pseudotachylyt in den Ostalpen: Geol. Bundesanst, Wien, Jahrb., v. 80, 571-585.

Field and petrographic description of pseudotachylite.

Handin, J. W., 1957, Experimental deformation of rocks and 

minerals: Colorado Sch. Mines Quart., v. 52, no. 3, p. 75-98.

Handin, J. W., and Fairbairn, H. W., 1955, Experimental deformation of Hasmark dolomite: Geol. Soc. America Bull., 

v. 66, no. 10, p. 1257-1273.

Handin, J. W., and Griggs, D. T., 1951, Deformation of Yule 

Marble, Part II, Predicted fabric changes: Geol. Soc. America Bull., v. 62, no. 8, p. 863-886.

Handin, J. W., and Haeer, R. V., 1957, Experimental deformation of rocks under confining pressure; tests at room temperature on dry samples: Am. Assoc. Petroleum Geologists 

Bull., v. 41, no. 1, p. 1-50.

 1957, Experimental deformation of rocks at high temperature ; tests at high temperature: Am. Assoc. Petroleum 

Geologists Bull., v. 52, no. 12, p. 2892-2934.

Handin, J. W., Higgs, D. V., and O'Brien, J. K., 1960, Torsion of 

Yule Marble under confining pressure, in Griggs, D. T., and 

Handin, J. W., eds., Rock deformation, a symposium: Geol. 

Soc. America Mem. 791, p. 245-274.

Barker, Alfred, 1950, Metamorphism: London, Methuen, 362 p.

First edition published in 1932. Good discussion of cataclasis. Definitions of some cataclastic rocks: crush breccia, 

crush conglomerate, mylonite. Excellent drawings, including some of Lapworth's (1885) original mylonite and of 

various stages of cataclasis of the Lewisian gneiss. See particularly p. 165-169. Discusses retrograde metamorphism 

(p. 344-358). Regarding flow structure in mylonite (p. 168- 

169) : "A laminated structure results, closely resembling the 

flow-structure in a rhyolitic lava, emphasized by trains of 

magnetite-dust or thin streaks of colour representing the 

breaking down of some particular mineral of the original 

rock."

 1964, Petrology for students [8th ed.]: Cambridge, Cambridge Univ. Press, 283 p.

Discusses various occurrences of cataclastic rocks, and 

gives descriptions of many British occurrences. Dynamic 

metamorphism is discussed on p. 268-277.

Hatheway, R. B., 1969, Cataclastic rocks in southwestern Maine 

[abs.] : Geol. Soc. America, Abstracts with Programs 1969, 

[v. 1], pt. 1, p. 26-27.

Good brief description of cataclasites, mylonites, and ultramylonites that occur in a fault zone 15 miles long and up to 

4 miles wide.

Hawkes, Leonard, 1929, Pseudotachylyte: Geol. Mag., v. 66, p. 

143-144.

Considers pseudotachylite to result from the grinding and 

polishing of material caught between moving fault surfaces.

Heard, H. C., 1963, Effect of large changes in strain rate in the 

experimental deformation of Yule Marble: Jour. Geology, 

v. 71, no. 2, p. 162-195.

Heard, H. C., and Carter, N. L., 1968, Experimentally induced 

"natural" intragranular flow in quartz and quartzite: Am. 

Jour. Sci., v. 266, no. 1, p. 1-42.

Heim, Albert, 1900, Gneissfaltelung in alpinem Centralmassiv, 

ein Beitrag zur Kenntnis der Stauungsmetamorphose: 

Naturf. Gesell. Zurich, Vierteljahrsschr., v. 45, p. 205-226.
84 CATACLASTIC ROCKS

Describes various stages in development of Umfaltungsclivage, so common in phyllites and particularly in phyllonites. 

Calls the first stage Ausweichungsclivage (cleavage that 

follows the direction of yielding under pressure). Detailed, 

well-illustrated study of this phenomenon in the Tessin 

gneiss of Switzerland.

Heinrich, B. W., 1956, Microscopic petrography: New York, 

McGraw-Hill Book Go., 296 p.

Describes, defines, and illustrates several types of cataclastic rocks (p. 184-187). Divides cataclastic rocks into 

four categories: brecciated rocks, phacoidal rocks, mylonitic 

rocks, vitrified rocks. Discusses cata clastic textures (p. 

176), and crystalloblastic textures (p. 176-178). Uses the 

term "phacoidal rocks" (p. 185) : "In phacoidal rocks the 

characteristic textural feature consists of ellipsoidal or 

lensoid units in a finer-grained matrix that is brecciated 

and sheared." Also uses the term "blastocataclasites": 

"Oataclasites that show some recrystallization effects have 

been termed blastocataclasites."

Higgins, M. W., 1966, The geology of the Brevard lineament near 

Atlanta, Georgia: Georgia Geol. Survey Bull. 77, 49 p.

Describes and illustrates various rocks in the Brevard zone 

(p. 27-42). Photomicrograph of a polycataclastic rock (p. 

34). Some of the rocks are incorrectly named. See Examples 

section of this paper.

Hinterlechner, Karl, 1913. Review of Suess: Geol. Reichanst, 

Wien, Verh., Jahrg. 1913, p. 72-74.

Objects to Suess' idea of "deep-seated' diaphthoresis.

Holland, T. H., 1900, The charnockite series, a group of Archean 

hypersthenic rocks in peninsular India : India Geol. Survey 

Mem. 28, pt. 2,249 p.

Especially p. 198-202. Describes "trap-shotten" charnokite 

gneisses. Holland crushed a sample of the host rock, and 

heated it until "* * * a very imperfect fusion * * *" occurred. 

"The result [p. 200] was a fritted black cake having the 

lustre of a tachylite and showing in thin section a black 

structureless matrix including angular fragments of quartz: 

in fact, the fritted charnokite powder very closely resembled the so-called strings of trap in these breccia bands."

Holmes, Arthur, 1928, The nomenclature of petrology [2d ed.]: 

London, Thomas Murby & Co., 284 p.

Defines many cataclastic rocks. Does not consider lamination or flow structure necessary to use the term mylonite.

Holmquist, P. J., 1903, En geologisk profil 6'fver den skandinaviska fjallkedjan vid Tornetrask: Geol. Foren. Stockholm Fo'rh., v. 25, p. 27-78.

One of the earliest published references to hartschiefer 

which Holmquist considers cataclastic rocks. "The laminated Hantschiefers are opaque granulitic rocks that show 

a remarkable similarity to certain schistose-quartzites. 

* * * Under the microscope they appear as quartz and 

feldspar rich rocks with a variable content of mica * * *

From these circumstances I reach the conclusion that the 

schistose Hartschiefer are (granitic) mylonites" (literal 

translation, p. 27, 73). He goes on to give textural, chemical, 

and field evidence to support his conclusion.

 1910, Die Hochgebirgsbildungen am Tornetrask in 

Lappland: Geol. Foren. Stockholm Forh., v. 32, p. 913-983.

A detailed study of the Tornetrask rocks. Uses cataclastic 

rock and mylonite as synonyms. The more or less clearly 

schistose and laminated rocks are grouped as hartschiefer. 

Holmquist questions his earlier interpretation (1903) and 

considers that the hartschiefer may be metamorphosed 

sedimentary rocks. He ascribes the fabric and neomineralization of the hartschiefer and amiphibolites to "Differential Gleitungen" (p. 954). See discussion of hartschiefer in 

text.

Hsu, K. J., 1955a, Monometamo'rphism, polymetamorphism, and 

retrograde metamorphism: Am. Jour. Sci., v. 253, no. 4, 

p. 237-239.

Comprehensive discussion of the terms in the title and their 

meanings. "Only rocks which record a history of two or 

more periods of metamorphism, that present no obvious 

genetic connection are polymetamorphic. * * * Rocks that 

have been reconstituted repeatedly during different 'Stages 

of one single period of metamorphism should be known, as 

monometamorphic. * * * For diaphthoretic changes in response to falling temperatures during monometamorphism 

we might use the term monometamorphic diaphthoresis. 

* * * For diaphthoretie changes1 in response to rising or 

falling temperatures during a later period of metamorphisim 

we might use the term polymetamorphic diaphthoresis * * *" 

(p. 238-239). See discussion of polycataclastic and polymetamorphic rocks in this text (p. 30).

 1955b, Granulites and mylonites of the region about 

Cucamonga and San Antonio Canyons, San Gabriel Mountains, California: Calif. Univ. Pubs. Geol. Sci., v. 30, no. 

4, p. 223-352.

Very comprehensive study with, definitions, discussions, 

illustrations, classification, and some analyses. States1 that 

the term mylonite should not specify that the rock must 

retain its coherence at the time of cataelasis, but that 

it might be later recrystallized enough to make it coherent and still be a mylonite. Uses coarse1-, medium-, and 

fine-grained mylonite, based on matrix grain sizes, and 

also, protocataclasite, and ultracataclasite. (See especially 

p. 251-252). Quoted and cited widely in this text; see Examples section.

Humphrey, F. L., and Allard, G. O., 1968, The Propria geosyncline, a newly recognized Precambrian tectonic province in 

the Brazilian shield: Internat. Geol. Cong., 23d, Prague, 

1968, Rept, Proo. of Sec. 4, p. 123-139.

Especially p. 130-132. Describes "shear zones" and "mylonitized zones" as much as 20 km long and as much as 

60 m wide.

Jeffreys, Harold, 1942, On the mechanics of faulting: Geol. 

Mag., v. 79, no*. 5, p. 291-295.

"Along a belt of overthrusting fu'sed and partly fused 

rocks may have a wide distribution and such, pseudotachylytes are held to have been made amorphous by heat generated by friction. * * * Consideration of the temperature 

attainable should therefore give a maximum time of formation for any dislocation containing pseudotachylyte" 

(p. 291). Attempts to quantify rate of faulting based on 

pseudotachylite, but notes that faults containing pseudo-
ANNOTATED BIBLIOGRAPHY 85

tachylite are comparatively rare, meaning "* * * that this 

is a special faster than average type of faulting" (p. 291). 

See discussion of pseudotachylite in this text.

Jehu, T. J., 1925, Observations on flinty crush-rocks: Geol. Soc. 

Edinburgh Trana, v. 11, p. 405-406.

Considers flinty crush-rock and pseudotachylite to originate 

when rock material is caught between moving fault surfaces and "vitrified."

Jehu, T. J., and Craig, R. M., 1923, Geology of the Outer Hebrides. Part 1, The Barra Isles: Royal Soc. Edinburgh Trans., 

v. 53, p. 419-441.

Describes extensive occurrences of flinty crush-rocks which 

are directly associated with faulting. Attributes origin of 

flinty crush-rocks to fusion during thrusting. Cites spherulites and corroded quartz grains in the rocks as evidence 

of fusion. See especially p. 430-436.

 1925, Geology of the Outer Hebrides. Part 2, South Uist 

and Eriskay: Royal Soc. Edinburgh Trans., v. 53, p. 615- 

641.

Describes flinty crush-rocks and gives evidence of fusion 

for their origin. Evidence includes; (1) an isotropic groundmass which the authors contend is vitreous; (2) corroded 

quartz grains ; (3) spherulites and incipient crystals in the 

"glassy" groundmass.

 1933, Geology of the Outer Hebrides. Part 5, North Harris 

and Lewis: Royal Soc. Edinburgh Trans., v. 57, p. 839- 

875. 

Good descriptions of flinty crush-rocks.

Johannsen, Albert, 1931, A descriptive petrography of the igneous rocks; Volume I, Introduction, textures, classifications, 

and glossary: Chicago, Univ. of Chicago Press, 267 p.

Definitions (p. 163-237) : autoclastic (p. 168), dynamometamorphism (p. 174), groundmass (p. 179), metamorphism (p. 

185), porphyroblast (p. 193), aphanitic (p. 201), augen 

(p. 202), autoclastic (p. 203), cataclastic (p. 204), crystalloblastic (p. 207), flasrig (p. 211), fluxion (p. 212), 

granoblastic (p. 213), mortar (p. 224), mylonitic (p. 224), 

palimpsest (p. 226), protoclastic (p. 230).

Johnson, M. R. W., 1957, The tectonic phenomena associated 

with the post-Cambrian thrust movements at Coulin, Wester 

Ross; Pt. 2. The structural geology of the Moine thrust 

zone in Coulin Forest, Wester Ross; Geol. Soc. London 

Quart. Jour., v. 113, pt. 2, no. 450, p. 241-270

Chiefly a structural study, but descriptions of cataclastic 

rocks near thrust planes are included. Folds in cataclastic 

rocks are described.

 1961, Polymetamorphism in movement zones in the Caledonian thrust belt of northwest Scotland: Jour. Geology, 

v. 69, no. 4, p. 417-432.

Detailed descriptions and illustrations of a variety of cataclastic rocks. Cataclastic events are integrated by petrographic and petrofabric analysis into the interpretation of 

the geologic history. Evidence is given for four phases in 

the structural-metamorphic history, with cataclastic rocks 

f different types produced by at least three of these phases. 

Notes selective cataclasis of pegmatites. Good descriptions 

of cataclastic differences being dependent on original

rock type. Most rocks described are recrystallized and 

neomineralized.

 1962, Relations of movement and metamorphism in the 

Dalradians of Banffshire: Edinburgh Geol. Soc. Trans., 

v. 19, pt. 1, p. 29-64.

Gives textural evidence for polymetamorphism.

 1963, Some time relations of movement and metamorphism 

in the Scottish Highlands: Geol. en Mijnbouw, v. 42, no. 5, 

p. 121-142.

Gives evidence that deformation is "* * * a promoter of 

metamorphic reactions * * *" (p. 127) and that strong 

tectonism aids attainment of chemical equilibrium. Discusses retrogressive metamorphism. Attempts to place mylonitization in a time-sequence of events.

 1967, Mylonite zones and mylonite banding: Nature, v. 

213, no. 5073, p. 246-247.

Interprets mylonite zones and mylonite banding as surfaces 

of flattening strain and relates the banding to slaty cleavage 

in origin.

Johnson, R. J., and McConnell, R. B., 1951, Notes on the geology 

of the northern part of the Ruwenzori Mountains: Geol. 

Mag., v. 88, no. 4, p. 249-256.

Description of mylonites and other cataclastic rocks in a 

thick zone in Africa.

Jonas, A. I., 1932, Structure of the metamorphic belt of the 

southern Appalachians: Am. Jour. Sci., ser. 5, v. 24, p. 

22&-243.

Brief description of retrogressive cataclastic rocks and 

polymetamorphic rocks along the Brevard zone. See examples section of this text.

Jung, Jean, 1925, Sur quelques types de roches 6crasees des 

Vosges: Acad. Sci., Paris, Cbmptes Rendus, v. 180, p. 839- 

840.

Field and petrographic description of cataclastic rocks from 

the Vosges, France.

 1928, Contribution a la geologic des Vosges Hercyniennes 

d'Alsace: Service Carte Geol. Alsace et Lorraine Mem. 2, 

p. 1-481

Description of some Alsatian cataclastic rocks, chiefly mylonites and "flinty crush-rocks." Notes spherulitelike aggregates of chlorite in the "flinty crush-rocks," and formation 

of new minerals (quartz and feldspar) in some of the 

mylonites.

Kalkowsky, E., 1886, Review of Kjerulf (1885) : Neues Jahrb., 

ser. II, ref. 244. 

Uses the term Kataklas-Structure.

Kennedy, W. Q., 1946, The Great Glen fault: Geol. Soc. London 

Quart. Jour., v. 102, pt. 1, no. 405, p. 41-72.

Study of a major fault zone with emphasis on determination 

of offset. Field description of cataclastic rocks, chiefly 

mylonite.

Kienow, Sigismund, 1953, Uber Gleitfaltung und Gleitfaltschieferung: Geol. Rundschau, v. 41, p. 110-128.
86 CATACLASTIC ROCKS

Detailed discussion, explanation, and illustrations of glidefold schistosity and its development. See also Christie (1963, 

p. 382-384) and section on glide-fold schistosity in this 

text.

Kieslinger, Alois, 1926, Geologie und Petrographie der Koralpe, 

I: Akad. Wiss., Wien, Sitzsungsber., Math. Naturwiss. Kl., 

v. 135, p. 1-42.

"* * * diaphthoresis is only recognizable where it is incomplete, and where a metamorphic facies of the lower zone 

is completely transformed into an upper zone facies the new 

rock can no longer be distinguished from a primary phyllite." (literal translation, p. 8) The zones refer to depth 

zones.

 1928, Tiber Diaphthorese mit Beispielen aus dem Ostalpinen Kristallin: Tschermaks mineralog. petrog. Mitt., v. 

39, p. 12-15.

Good description of the diaphthoritic zone associated with 

the "old crystalline" of the Kor Alps. Cites remnants of 

biotite in chlorite, and chess-board albite as relicts of higher 

metamorphism. Gives a valuable list of new "typomorphic 

minerals" and the old minerals from which they formed.

King, P. B., and Ferguson, H. W., 1960, Geology of northeasternmost Tennessee: U.S. Geol. Survey Prof. Paper 311, 136 p.

Describes "niylonites," "phyllonites," "flaser gneisses," and 

"mortar gneisses" in fault zones in northeast Tennessee. 

Good outcrop photographs. Defines terms (above) as used 

(P. 17).

King, W., Jr., and Foote, R, B., 1864, On the geological structure of the districts of Trichinopoly, Salem, etc., Madras: 

India Geol. Survey Mem. 4, p. 223-379.

Especially p. 271. Describes "trap-shotten gneiss." See discussion of pseudotachylite in this text.

Kjerulf, Th., 1885, Grundf jeldprofilet red Mjosens sydende: Nyt 

Mag. iNaturvidenskaberne, v. 29, p. 215-294.

First use of the word cataclastic. "* * * applies to a texture characterized by crushed, fragmentary, deformed, and 

strained crystals." (Literal translation from p. 288.) It 

is in part synonymous with "mortar-structure," but is a 

broader term.

Knopf, E, B., 1931, Retrogressive metamorphism and phyllonitization: Am. Jour. Sci., ser. 5, v. 21, p. 1-27.

Review, discussion, definition, and classification of the processes in the title, of cataclastic rocks, and of polymetamorphic and polycataclastic rocks. A classic paper on cataolastic and polymetamorphic rocks. Quoted and cited widely 

in this text. See especially the section of this paper on 

phyllonitesi and diaphthorites (retrograde rocks).

Knopf, B. B., and Ingerson, Earl, 1938, Structural petrology: 

Geol. Soc. America Mem. 6, 270 p.

A comprehensive work on structural petrology, with a large 

amount of petrofabric data on cataclastic rocks. Good discussions of cataclastic textures and processes. Especially 

valuable because it presents many of Sander's ideas and 

techniques in English.

Konigsberger, J. G., 1912, Die kristallinen schiefer der Zentralschweizerischen Massive und Versuch einer Einteilung der

kristallinen Schiefer: Internat. Geol. Cong., llth, Stockholm, 1910, Comptes rendus, v. 1, p. 639-671.

Proposes a classification of crystalline .schists, with a group 

called dynamo-metamorphic schists which "includes mylonites."

Kolbl, Leopold, 1922, Zur Deutung der moldanubischen Gliminerschieferzone im niederosterreichischen Waldviertel: Geol. 

Bundesanst, Wien, Jahrb, v. 72, p. 81-104.

A study of "deep-seated diaphthorites" in the mica schist 

zone described by Suess (1913). The mica schist diaphthorites lack the diseased or weathered appearance characteristic of the "upper-zone" diaphthorites.

Lambert, I. B., and White, A. J. R., 1965, The Berridale wrench 

fault; a major structure in the Snowy Mountains of New 

South Wales: Geol. Soc. Australia Jour., v. 12, pt. 1, p. 

25-34.

Brief field description of cataclastic rocks incidental to 

description of a major fault zone.

Laniplugh, G. W., 1903, The geology of the Isle of Man: Great 

Britain Geol. Survey Mem., 620 p.

Describes "crush-conglomerates" developed in a banded 

series of alternating grits and shalesi (p. 55-58).

Lapworth, Charles, 1885, The Highland controversy in British 

geology; its causes, course, and consequences: Nature, v. 32, 

p. 558-559.

Original use and definition of the term mylonite. Mylonites 

and related rocks, such as augen schists, are described. See 

discussion of mylonite.

Imbrock, H., 1925, Geologisch-Letrographische Beobachtungen 

im siidostlichen Teil der Bohmischen Masse zwischen Marbach und Sarmingstein a.d. Donau: Geol. Bundesanst., 

Wien, Jahrb. 75, p. 129-180.

Objects to the idea of "deep-seated diaphthoresis" (see 

Kolbl, 1922; Suess, 1913, 1918), and claims that the conditions along the eastern edge of the Moldanubian block are 

abnormal from the point of view of the depth-zone concept 

of metamorphism, because the epizone Moravian phyllites 

underlie the mesozone mica schists.

Lundgren, Lawrence, Jr., 1969, Cataclastic deformation of the 

Hebron Formation, southeastern Connecticut [abs.]: Geol. 

Soc. America, Abstracts with Programs 1969, [v. 1] pt 1, 

p. 38.

Describes "blastomylonitic quartz-biotite schists" with "ultramylonite sheets." Describes kink folds in blastomylonite, 

and folds "* * * formed during ductile faulting when 

horizontal movement was accommodated by pervasive 

granulation of quartz and biotite (but not plagioclase) 

* * *. Notes that * * * "the last formed (ultramylonite) 

behaved much like intrusive basaltic magma."

MacGregor, A. G., 1952, Metamorphism in the Moine nappe of 

northern Scotland: Edinburgh Geol. Soc. Trans., v. 15, p. 

241-257.

Brief descriptions of cataclastic rocks, chiefly blastomylonites. Description of folds in these cataclastic rocks.
ANNOTATED BIBLIOGRAPHY 87

Magnusson, N. H., 1937, Den centralvarmlandska niylonitzonen 

och dess Fortsattning i Norge: Geol. Foren. Stockholm 

Forh., no. 409, v. 59, no. 2, 205-228.

Describes mylonite and other cataclastic rocks in a thick 

Norwegian fault zone (p. 205).

Malaroda, Roberto, 1946, Revisione e aggiornamento della 

sistematica delle tettoniti a deformazione post-cristallina: 

Soc. Mineralog. Italiana Rend., v. 3, no. 3, p. 150-171.

Describes and discusses a large "mylonite" zone in northern Italy. Theoretical aspects and definitions are discussed. 

Malaroda devises a workable classification of cataclastic 

rocks. Well illustrated. Very good bibliography.

Marshall, P., 1904, Magnesian rocks at Milford Sound: New 

Zealand Inst. Trans., v. 37, p. 481-484.

Describes mylonitized peridotites and discusses the cataclastic textures.

Martin, Henno, 1935, Bruchtektonik und Mylonite in Siidschwedan [abs.]: Geol. Rundschau, v. 26, no. 1-2, p. 144-145.

Maske, S., 1957, The diorites of Yzerfontein, Darling, Cape 

Province: Stellenbosch Univ. Ann., v. 33, Sec. A, nos. 1-11 

(1957), p. 23-69.

Describes "crush breccias" intimately associated with "fine 

black mylonites."

McOallien, W. J., 1934, Metamorphic diffusion: Finland Comm. 

g£ol. Bull. 104, p. 11-27.

Mclntyre, D. B., 1954, The Moine thrust its discovery, age, 

and tectonic significance: Geologists Assoc. (London) 

Proc., v. 65, pt. 3, p. 203-219.

Brief description of cataclastic rocks along the Moine 

thrust in Scotland, chiefly blastomylonites. Description of 

folds in blastomylonites.

Michel-Levy, A., 1928, Sericitoschistes des chaines du MontBlanc et des Aiguilles Rouges qui sont des Mylonites recristallise'es poste"rieures au granite: G§ol. Soc. France Bull., 

ser. 4, v. 28, p. 255-260.

Description of a complex "unit" in the Alps called the 

"protogene," with many kinds of cataclastic rocks showing 

varying degrees of crushing, neomineralization, and recrystallization.

Nel, L. T., 1927, Geology of the country around Vredefort; An 

explanation of the geological map: South Africa Geol. Survey, 130 p.

Includes a comprehensive chapter on pseudotachylite occurrences in the classic Vredefort area, South Africa. Good 

descriptions of pseudotachylite. Concludes that the mylonites, flinty crush-rocks, and pseudotachylites are the products of mechanical stresses, culminating in fusion. Considers 

the enstatite granophyre to be a recrystallized pseudotachylite.

Noble, L. F., 1926, Report of t!he California Earthquake Commission : Carnegie Inst. Washington Year Book 25, p. 415.

Brief description of crushed and shattered rocks in the San 

Andreas fault zone.

Nockolds, S. R., 1940, Petrology of rocks from Queen Mary 

Land: Australasian Antarctic Exped., 1911-1914, Sci. Repts., 

ser. A, v. 4, pt. 2, p. 15-86.

Describes a granitic boulder from a moraine on Cape Charcot, Queen Mary Land, Antarctica, cut by a vein of pseudotachylite that resembles very closely the pseudotachylite 

of Parys (Parijs), Orange Free State, South Africa (see 

Shand, 1917), but which contains elliptical vesicles that 

indicate the igneous nature of the rock. This is the first 

report of such vesicles in pseudotachylite. See discussion 

of pseudotachylite in this text. There is no field evidence 

that the rock described by Nockolds actually is pseudotachylite and not an igneous rock.

Norton, W. H., 1917, A classification of breccias: Jour. Geology, 

v. 25, p. 160-194.

Oulianoff, Nicola s, 1942, Effet de P4crasement natural et experimental: Lausanne Univ. Lab. GSologie, Geographie 

Physique, Min6ralogie, et Paleontologie Bull. 76, 7 p.

Discusses some of the crushed rocks produced experimentally and attempts to relate them to naturally produced 

cataclastic rocks.

 1955, Ecrasement sans trituration et mylonitisation des

roches: Eclogae Geol. Helvetiae, v. 47, p. 377-381. 

Discussion of cataclastic rocks, cataclasis, and faulting.

Park, R. G., 1961, The pseudotachylite of the Gairloch district, 

Ross-Shire, Scotland: Am. Jour. Sci., v. 259, no. 7, p. 542- 

550.

Describes pseudotachylites and shows that they contain 

spherulites and relict glass, the presence of which proves 

that some Scottish flinty crush-rocks were once molten. 

Photomicrographs.

Peach, B. N., Home, John, Gunn, W., Clough, C. T., and Hinxnian, L. W., 1907, The geological structure of the Northwest Highlands of Scotland: Great Britain Geol. Survey 

Mem., 668 p.

Many types of cataclastic rocks are described and discussed in this thorough and classic account of Highland 

geology. The authors conclude that "flinty crush-rocks" 

(a term used both for rocks showing evidence of fusion 

and as a general field term for dense, flinty cataclastic 

rocks of various types) and mylonites were "* * * formed 

simultaneously in different parts of the same line of movement" (p. 153). There is a detailed description of Lapworth's 

(1885) Eireboll district and its rocks. Conditions of cataclasis are discussed (p. 598). The intimate relationship between various types of dikes and faulting with cataclasis 

is repeatedly mentioned. The ideas and nomenclature of 

this 1907 paper have greatly influenced later thought retgarding cataclastic rocks and many other aspects of geology. 

Quoted and cited widely in this text.

 1913, The geology of central Ross-shire: Scotland Geol. 

Survey Mem., 114 p.

Occurrences of cataclastic rocks are described and discussed, but most of the ideas are the same as those expressed in Peach and others (1907).
88 CATACLASTIC ROCKS

Peach, B. N., and Home, John, 1930, Chapters on the geology 

of Scotland: London, Oxford Univ. Press, 232 p.

Brief accounts of the more important fault zones, including 

summarized descriptions of cataclastic rocks.

Phillips, F. C., 1937, A fabric study of some Moine schists and 

associated rocks: Geol. Soc. London Quart. Jour., v. 93, 

pt. 4, no. 372, p. 581-616.

See Phillips, 1945.

 1945, The micro-fabric of the Moine schists: Geol. Mag., 

v. 82, no. 5, p. 205-220.

Good petrofabric data on cataclastic rocks. "In a crushed 

quartzose rock * * * lenticular grains of highly strained 

quartz lie in a fine-grained mylonitic matrix. These lenticular grains show a concentration of optic axes nearly 

normal to the schistosity. If it can be reasonably supposed 

that the original rock showed the normal type of girdle, this 

mylonite presents an interesting example of the differential 

yield of quartz grains to the shearing according to the 

attitude of their internal structure in relation to the impressed shear planes" (p. 213-214). "I would draw a careful 

comparison between the readiness with which quartz suffers recrystallization and the reluctance which it shows 

to undergo reorientation" (p. 219). Notes faulted pegmatites 

and veins (p. 214-215) in noneataclastie rocks.

Philpotts, A. B., 1964, Origin of pseudotaehylites: Am. Jour. Sci., 

v. 262, no. 8, p. 1008-1035.

Comprehensive field, petrographic, petrologic, mineralogic, 

and chemical study of pseudotachylite.

Offers abundant evidence that pseudotachylite forms by 

complete melting of already-hot rocks during faulting. 

Gives criteria for distinguishing pseudotachylite from other 

similar cataclastic rocks. See discussion of pseudotachylite 

in this text.

Philpotts, A. B., and Miller, J. A., 1963, A Pre-Cambrian glass 

from St. Alexis-des-Monts, Quebec: Geol. Mag., v. 100, no. 4, 

p. 337-344.

Good description of pseudotachylite.

Pitcher, W. S., Elwell, B. W. D., Tozer, C. F., and Cambray, 

F. W., 1964, The Leannan fault: Geol. Soc. London Quart 

Jour., v. 120, pt. 2, no. 478, p. 241-273.

Brief description of "mylonites" and "tectonic breccias" incidental to the discussion of a large wrench-fault in Ireland.

Pochin Mould, D. D. C., 1946, Geology of the Foyers granite: 

Geol. Mag., v. 72, p. 249-265.

Brief description of "crush zones and movement lines" in 

Foyers granite, near the Great Glen of Scotland.

Preclik, Karl, 1930, Zur Genesis einiger Moldanubischer Gesteins 

typen I: Centralblatt Mineralogie, Geologie, Palaontologie, 

Jahrg. 1930-A, p. 61-78.

Bestudy of the area in Austria studied by Suess (1913). 

Gives evidence to support retrogressive origin of the rocks.

Prinz, Martin, and Poldervaart, Arie, 1964, Layered mylonite 

from Beartooth Mountains, Montana: Geol. Soc. America 

Bull., v. 75, no. 8, p. 741-744.

Describes a metadolerite dike traversed by a fault /one. 

Gives conclusive petrographic, petrologic, and chemical evidence of cataclastic metamorphic differentiation producing 

compositional layering from the nonlayered parent rock. See 

section on cataclastic metamorphic differentiation in this 

text.

Quensel, Percy, 1913, Die Quartzporphyr- und PorphyroidFormation in Siidpatagonien und Feuerland: Upsala Univ, 

Geol. Inst Bull., v. 12, no. 2, p. 9-40.

Describes mylonitization of a "quartz porphyry" and discusses the chemical changes occurring during mylonitization, as shown by chemical analyses.

 1916, Zur Kenntnis der Mylonitbildung, erlautert an Material aus dem Kebnekaisegebiet: Upsala Univ., Geol. 

Inst. Bull., v. 15, p. 91-116.

Comprehensive discussion and classification of cataclastic 

rocks, with many definitions. Original definition of JcaJcirite 

(see glossary of this paper). Detailed discussion of ultramylonite (see discussion of iiltramylonite in this text). 

Original use of the term mylonite gneiss (see discussion 

of mylonite in this text). Quensel used the term mylonite 

schist for laminated cataclastic rocks; unlaminated cataclastic rocks were considered mylonite (also see Knopf, 

1931). Considered hartschiefer to be chemically differentiated, recrystallized mylonitic rocks. His definitions and 

photomicrographs have been widely used by several later 

workers (for example, see Knopf, 1931).

Baguin, E., 1926, Au sujet de divers genres de "mylonites 

granitiques" le long des lignes de dislocation de 1'Quest du 

Plateau Central: France Serv. Carte G6ol. Bull., v. 29, no. 

261, p. 213-230.

One of the early attempts at a classification of cataclastic 

rocks. Good field descriptions of cataclastic rocks along a 

fault zone in France.

Bamberg, Hans, 1952. The origin of metamorphic and metasomatic rocks: Chicago, Univ. Chicago Press, 317 p.

Discusses chemical principles of metamorphic differentiation (p. 212-228). Mechanical differentiation is discussed on 

p. 226, "* * * it is empirically found that although there 

are variations in details as to the minerals which tend to 

cosegregate, it appears to be generally true that minerals 

which go together in concretionary growth also go together in secretionary growth or in banded growth under 

shearing."

Bamsay, J. G., 1958, Moine-Lewisian relations at Glenelg, Inverness-shire : Geol. Soc. London Quart. Jour., v. 113, pt. 4, 

p. 487-523.

Especially p. 494-495. Describes cataclastic rocks (chiefly 

blastomylonites) in the Moine thrust zone, Scotland. Also 

describes minor folds in these cataclastic rocks.

Bead, H. H., 1931, The geology of central Sutherland: Scotland 

Geol. Survey Mem., 238 p.

Brief description of cataclastic rocks associated with thrust 

faults.

 1933, On quartz-kyanite rocks in Unst, Shetland 

Islands, and their bearing on metamorphic differentiation: 

Mineralog. Mag., v. 23, p. 317-328.
ANNOTATED BIBLIOGRAPHY 89

Detailed discussion of the origin of kyanite-quartz bands 

and veins in pelitic schists on Unst. Suggests that the bands 

are the result of metamorphic differentiation.

 1934, Age problems of the Moine Series of Scotland: 

Geol. Mag., v. 71, no. 841, p. 302-317.

Uses the term "dislocation metamorphism" to denote the 

cataclastic action in the vicinity of thrust faults.

 1937, Metamorphic correlation in the polymetamorphic 

rocks of the Valla Field block, Unst, Shetland Islands: 

Royal Soc. Edinburgh Trans. v. 59, pt. 1, p. 195-221.

In the Valla Field block, a first metamorphic episode resulted in the production of garnet-staurolite-kyanite-biotite 

gneiss. It was followed by a second episode during which 

this assemblage was not stable, and a chloritoid-chloritemuscovite schist was formed from the gneiss. In the Saxa 

Vord structural unit, a first metamorphism produced staurolite, andalusite, and garnet. On this a second metamorphism 

was superposed, characterized by the formation of chloritoid and kyanite. Along the mechanical junction of the 

two structural units, all pelitic rocks adjacent to the belt 

of special movement were converted into chlorite-sericite 

phyllites a type example of metamorphic convergence.

1951, Mylonitisation and cataclasis in acidic dikes in the 

Insch (Aberdeenshire) gabbro and its aureole: Geologists' 

Assoc. (London) Proc., v. 62, pt. 4, p. 237-247.

Describes cataclastic rocks localized in dikes.

 1957, The granite controversy: London, Murby, 430 p.

Good discussion of diaphthoresis (p. 296-300), and of polymetamorphism versus monometamorphism (p. 305-308). 

Numerous scattered descriptions of cataclastic rocks, processes, and zones, many of which are associated with intrusive phenomena. (See mylonites in Read's index).

Reed, J. C., Jr., and Bryant, Bruce, 1964, Evidence for strikeslip faulting along the .Brevard zone in North Carolina: 

Geol. Soc. America Bull., v. 75, no. 12, p. 1177-1196.

Good descriptions of cataclastic and polytmetamorphic 

rocks along the Brevard zone (see Examples .section of this 

text). "The nomenclature of polymetamorphic cataclastic 

rocks is complex and confusing, so we therefore define the 

following terms in the sense used in this paper:" (p. 1180). 

Definitions of porphyroolcust, l)lastomylonite, 'blastomylonitic 

gneiss, phyllonite, and phyllonitic schist are given (see 

Glossary of this paper). They use phyllonite for rocks that 

should he called diaphthoritic phyllonite (see discussion of 

retrograde cataclastic rocks in this paper). Excellent photO'- 

micrographs. Good descriptions of relations between various kinds of rocks in the zone 'and on either side. See Examples section of this text.

Reed, J. J., 1957, Fault zones in part of the Rimutaka Range: 

New Zealand Jour. Sci. and Technology, ser. B, v. 38, no. 7, 

p. 686-«87.

Describes a 5,000-foot-thick zone of "autoclastic breccia," 

which he states is a possible example of protomylonite.

 1964, Mylonites, cataclasites, and associated rocks along 

the Alpine fault, South Island, New Zealand: New Zealand 

Jour. Geology and Geophysics, v. 7, no. 4, p. 645-684.

Good detailed descriptions, illustrations, and discussions 

of all types of cataclastic rocks. Classification is particularly good. Describes retrogressive metamorphism of cataclastic rocks. (Suggests that the silicification common to 

many cataclastic rocks may be a retrograde feature. Divides rocks along Alpine fault zone into "augen mylonite 

and mylonite," blastomylonite, and "schist-derived mylonite." The three groups are interpreted as having formed 

at three distinct levels within the earth's crust, so that 

their juxtaposition along the Alpine fault is evidence of 

three distinct periods of movement (p. 675). States that 

mylonites pass into Haast :Schist, and concludes that the 

type of metamorphism changed, so that mylonite-iblaistomylonite-schist are gradational. Good definitions. See Examples section of this text.

Reinhard, Martin, and Preiswerk, H., 1927, Uber Granitmylonite 

im Aiguilles-Rouges-Massiv (Westliches Wallis) : Naturf. 

Gesell. Basel Verh., v. 38, p. 188-200.

Describes mylonite and several dther types of cataclastic 

rock.

Reynolds, D. L,, 1954, Fluidization as a geological process, and 

Its bearing on the problem of intrusive granites: Am. 

Jour. Sci., v. 252, no. 10, p. 577-614.

Describes and explains the process of fluidization. Concludes, from recent work on "fiuidized" solid-gas systems, 

that the South African pseudotachylites were originally 

composed of finely ground particles (transported to their 

present location as a suspension in rapidly moving gas. This 

process was thought to explain the extreme mobility commonly demonstrated by the intricate narrow networks of 

veins of pseudotachylite, and the nondilational form of some 

of the dikes. (See McBirney, 1963; Philpotts, 1964.) See 

discussion of pseudotachylite in this text

Rogers, A. W., 1897, report on the survey of the Stellenbosch 

district: Cape of Good Hope Geol. Oomm. Ann. Rept, 1897, 

p. 45-49.

Regarding a granite mass in the Stellenbosch area of South 

Africa "along a few planes parallel with the general foliation, the rock resembles a very fine-grained slate. This finegrained rock may be the result of crushing. The foliated 

granite passes into normal rock by insensible gradations * * *" (p. 48).

 1905, An introduction to the geology of Cape Colony: 

London, Longmans, Green and Co., 463 p.

Especially p. 32r-53. Describes a protoelastic border of a 

gneissic granite and states that some of the rocks are 

mylonite.

 1911, Geological Survey of parts of Van Rhyns Dorp 

and Namaquialand divisions: Cape of Good Hope Geol. 

Comm. 16th Ann, Rept., 1911, p. 9-84.

Especially p. 29. Describes thin pseudotachylite veins in 

a gneiss.

Ruger, L., 1928, Uber Blastomylonite in Grundgebirge des Odenwaldes: Verein Erdkunde Darmstadt Notizblatt, 1927, ser. 5, 

p. 219-231.

Salop, L. I., 1949, Psevdotakhitity iz Pribaikalya i zapadnogo 

Zabaikalya i problema ikh genezisa: [Pseudotachylites
90 CATACLASTIC ROCKS

from the cis-Baikal and western trans-Baikal regions and 

the problems of their genesis] : Akad. Nauk SSSR, Izv., Ser. 

GeoL, no. 5, p. 40-56.

Describes pseudotachylites in amphibolites. The pseudotachylites contain microlites of feldspar and extremely embayed fragments of quartz, both well illustrated in the 

paper. Chemical analyses show the similarity in composition between the pseudotachylites and the rocks in which 

they occur. Concludes that the pseudotachylites were formed 

by melting of the host rocks along a thrust fault.

Sander, Bruno, 1911, tJber Zusammenhange zwischen Teilbewegung und Gefiige in Gesteinen: Tschermaks mineralog. 

petrog. Mitt., v. 30, p. 281-314.

Discusses some of the fundamental principles involved in 

the origin of fabric. Mrst use of the term phyllonite for 

phyllite-mylonite. See discussion of phyllonite in this text.

Sander, Bruno, 1912, tJber einige Gesteinsgruppen des Tauernwestendes: Geol. Reichsanst., Wien, Jahrb., v. 62, p. 219- 

228.

Original use and definition of the term Wastomylonite (see 

discussion of blastomylonite in this text). First use and 

definition of tectonite, as a metamorphic rock deformed by 

differential movements that integrate into the tectonic 

movement as a whole.

 1914, Bemerkungen iiber tektonischen Gesteinsfazies und 

Tektonik des Grundgebirges: Geol. Reichsanst., Wien, 

Verh., Jahrg. 1914, no. 9, p. 220-240.

Points out that the existence of an abnormal metamorphic 

facies relation along the Moldanubian-Moravian contact 

zone cannot be cited as a reasonable objection to the hypothesis of deep-seated diaphthoresis because the hypothesis 

was itself advanced in an attempt to explain the abnormalities (see Suess, 1913, 1918; Limbrock, 1925).

 1914, BeitrSge aus den Zentralalpen zur Deutung der 

Gesteinsgef uge: Geol. Reichsanst., Wien, Jahrb., v. 64, p. 

567-634.

In the biotite phyllonite of a Tauern gneiss near Brenner, 

"* * * there is no reversion of lower zone typoxnorphic 

minerals to those of a higher zone . . ." (meaning depth 

zones not grades) so a phyllonite may be formed by the 

degradation of a highly crystalloblastic schist, ard yet 

not be diaphthoritic." (p. 584).

 1930, Gefugekunde der Gesteine: Vienna, Springer, 352 

P.

A classic study of petrofabric theory and techniques. Contains fabric analysed of cataclastic rocks and discussion 

of their origins.

 1950, Einfiihrung in die Gefugekunde der geologisehen 

KSrper; II, Die Korngefuge: Vienna, Springer-Verlag, 409 

P.

Scheumann, K. H., 1961, Mineralfazies und Kinematik: Neues 

Jahrb. Mineralogie, Mh. 6, p. 121-123.

Schmidt, Walter, 1932, Tektonik und Verformungslehre: Berlin, Borntraeger, 208 p.

Proposes and explains a purely mechanical hypothesis of 

metamorphic differentiation. Uses data from experimental

work with metals, as examples. See discussion of cataclasitic 

metamorphic differentiation in this text.

Schoch, A. El., 1962, The caitaclasites of Northwest Bay: Stellenbosch Univ. Annals, v. 37, ser. A, no. 10, p. 659-808.

Detailed descriptions and statistical structural analysis of 

varioute types of cataclastic rocks in South Africa, "The 

cataclastic deformation features, which were mapped in 

detail, are of three types, namely a coarse bodily shattering of the granite, numerous vertical black streaks of 

mylonitisation, and broad zones of comminution up to six 

hundred feet in width" (part of author's abstract). Proposes a complex partially quantitative classification with 

numerous terms. Useis cataclasite both as a specific term 

and as a general term for all cataclastic rocks.

Scholtz, D. L., 1946, On the youngei* pre-Cambrian granite 

plutons of the Cape Province [presidential address]: Geol. 

Soc. South Africa Trans. and Proc., v. 49, p. 35-82.

Describes crush zones in some plutons and mylonite zones 

crossing othens1 . States (p. 65) that stress was responsible 

for the development of local gneissic granite with mortar 

structures and anastomosing veins of mylonite, "* * * 

while zones of black cataclasite up to five hundred feet in 

width occur in the older granite at Northwest Bay." See 

Schoch, A. E. (1962).

Schwartz, G. M., and Todd, J. H., 1941, Comments on retrograde metamorphism: Jour. Geology, v. 49, no. 2, p. 177- 

189.

(p. 178) "In many instances the terms 'retrograde metamorphism,' 'regressive metamorphism,' and 'diaphthoresis' 

are not 'being used in precise accordance with their original 

connotations." Gives a very complete list of mineral changes 

attributed to retrograde metamorphism (p. 179). Notes 

that hydrothermal changes are often retrogressive, and 

many retrogressive changes involve a hydration. "It seems 

permissible to question the validity of the general statement that temperatures (usually) drop so rapidly as to 

greatly inhibit retrograde reactions. It seems more likely 

that the failure to react is due to the absence of some essential component rather than merely to temperature conditions." (p. 185). Also seeKnopf (1931) and Hsu (1955a).

Sclar, C. B., 1950, Origin of a layered ultramylonite from 

southeastern Connecticut [abs.] : Geol. Soc. America Bull., 

v. 61, p. 1501.

Ascribes origin of tne layered rock to cataclastic metamorphic differentiation.

 1958, The Preston gabbro and the associated metamorphic gneisses, New London County, Connecticut: Connecticut Geol. Nat. History Survey Bull. 88, 136 p.

Good descriptions and discussions of cataclastic rockfc. 

Well illustrated. Excellent discussion of and evidence for 

cataclastic metamorphic differentiation. Quoted and cited 

extensively in this text; see section on cataclastic metamorphic differentiation.

 1965, Layered mylonites and the processes: of metamorphic differentiation: Geol. Soc. America Bull., v. 76, no. 

5, p. 611-612.
ANNOTATED BIBLIOGRAPHY 91

Gives good evidence supporting cataclastic metamorphic 

differentiation, with discussion of the theory. Quoted extensively in this text; see section on cataclastic metamorphic differentiation.

Scott, J. S., and Drever, H. I., 1953, Frictional fusion along a 

Himalayan thrust: Royal Soc. Edinburgh Proc., sec. B, v. 65, 

pt, 2, p. 121-140.

Describes a glassy rock formed by frictional fusion. The 

glass is vesicular, has a refractive index of 1.5. and occurs 

in the plane of a thrust fault. A gradation can be traced from 

unideformed rock through mylonite to the fused rock. This 

is the first conclusive proof of sufficient frictional heat produced in a fault zone to produce melting of the rock. Wellillustrated. The terms cryptomylonite and hyalomylonite are 

used (see Glossary of this text). See discussion of pseudotachylite in this text.

Sederholm, J. J., 1913, On regional granitization (or anatexis) : 

Internat. Geol. Cbng., 12lth, Toronto, 1913, Comptes rendus, 

p. 319-324.

"Oataclasis is in general a destructive process; it is not 

creating new minerals or rocks. The use of the term 

'dynamometamiorphism' for every metamorphic change 

which cannot otherwise be accounted for should be discontinued as not warranted by facts," (p. 323).

Seidlitz, W. von 1910, Ueber Granit-mylonit und ihre tektonische 

Bedeutung: Geol. Rundschau, v. 1, p. 188-197.

Discusses chemical changes during myloaitization.

Semenenko, N. P., 1960, Theory of metamorphisin of mobile 

zones: Internat. Geol. Gong., 21st Copenhagen, 1960, Rept. 

pt. 14, p. 62-71.

Shand, S. J., 1917, The pseudotachylytte of Parijs (Orange Free 

State), and its relation to "trap-shotten-gneiss" and "fiintycrush-rock": Geol. Soc. London Quart. Jour., v. 72, pt. 3, p. 

198-221

Introduction of the term pseudotachylyte, for dark, 

aphanitic rocks found as veins and networks in the 

granite near Parijs (Parys) Orange Free State, Africa. 

Shand thought that the rupturing of the rock was due to 

sihock rather than shearing and that incandescent gases 

had produced the pseudotachylite. Good descriptions and 

illustrations of the rocks. Discussion at the end of article 

contains comments and alternate hypotheses by several 

geologists. See discussion of pseudotachylite in this text.

 1951, Mylonite, slickensides, and the Great Glen fault: 

Geol. Mag., v. 88, no. 6, p. 423-428.

Cursory discussion of some of the aspects of mylonite formation. Concludes that the general absence of mylonite 

along the fault zone invalidates Kennedy's (1946) strikeslip hypothesis. Clearly, Shand expected to find veinlike 

cataclastic rocks resembling pseudotachylite. See Byles and 

MacGregor's (1952) reply to Shand.

Smyth, C. H., Jr., 1896, Metamorphisxn of a gabbro occurring in 

St. Lawrence County, New York: Am. Jour. Sci., 4th ser., 

v. 1, p. 273-281.

Describes cataclasis in the gabbro: "In the first type, the 

rock as a whole retains its original structure, the outlines 

of the different minerals being slightly changed; but all of 

the constituents are, at the same time, reduced to fine

grains, giving a cataclastic structure (except for residual 

cores of the feldspars). As the crushing becomes more intense, the mineral outlines change, and a more or less pronounced parallel structure results. In this stage the rock is 

made up of very fine grains of pyroxene, hornblende, feldspar and scapolite * * * In the other type of secondary 

structure the rock is a well defined gneiss. It is apparently 

much finer grained than the previous variety, but in reality 

is coarser, the individual grains being many times larger 

than in the cataclastic rock. * * * This rock is composed 

of feldspar, with pyroxene or hornblende, or more generally, 

both. Between this phase of the rock and that with cataclastic structure intermediate phases occur, showing that 

the development of cataclastic structure is the first step in 

the process of converting gabbro into gneiss" (p. 277).

Snook, J. R., 1965, Metamorphic and structural history of "Oolville batholith" gneisses, north-central Washington: Geol. 

Soc. America Bull., v. 76, no. 7, p. 759-776.

Describes and illustrates mylonites, mylonite gneisses, and 

microbreccias in the border area of the Colville batholith. 

Disagrees with Waters and Krauskopf (1941), and proposes 

that rather than being protoclastic, the rocks are cataclastic and produced by a later deformation. See Examples 

section of this text.

Staub, Rudolf, 1915, PetrograpMsche Untersuchungen im Westlichen Berninagebirge: Naturf. Gesell. Zurich Vierteljahrsschrift, v. 60, p. 55-336.

Especially p. 71-91. Extensive consideration of cataclastic 

rocks, with a proposed classification. "The formation of mylonites is not considered as an act of metamorphism due 

to recrystallization and remineralization, but as a purely 

mechanical rock forming process in which crushing and 

especially rolling, play a significant role. Where the rolling 

process has failed, the rocks can just as well be considered 

as merely cataclastic. Mylonites are always laminated 

rocks, (literal translation.) Divides mylonites into six 

types on the basis of grain size.

 1928, Der Bewegungsmechanismus der Erde dargelegt 

am bau der irdischen gebirgssyteme: Berlin, Gebriider 

Borntraeger, 270 p.

Describes cataclastic rocks. According to Staub, the extreme form of ultramylonitization has been reached when 

the matrix appears as a glasslike substance and the porphyroclasts have diminished to a diameter less than 0.02 mm. 

See discussion of ultramylonite in this text.

Stillwell, F. L., 1918, The metamorphic rocks of Adelie Land: 

Australasian Antarctic Exped., 1911-1914; Sci. Repts., ser. 

A, v. 3, pt. 1, p. 1-230.

First use of the term metamorphic differentiation, for v^rious processes by which contrasted mineral assemblages develop during metamorphism from an initially uniform rock. 

See discussion of cataclastic metamorphic differentiation 

in this text.

Suess, F. E., 1913, Die moravischen Fenster und ihre Beziehungen zum Grundgebirge des Hohen Gesenkes: Akad. 

Wiss., Wien, Math.-Naturwiss. Klasse, Denkscnr., v. 88, 

p. 541-631.

First noted that retrogression need not go "all the way," 

that Kata-zone rocks might go to "Meso-zone rocks" under 

"Meso-zone conditions" and never reach the "Epizone"
92 CATACLASTIC ROCKS

stage. Good description and interpretive discussion of a 

diaphthoritic zone in the Austrian Waldviertel. See Becke 

(1913), Suess (1918), Kolbl (1922), Limbrock (1925), and 

Preclik (1930) for discussions of this controversial zone.

 1918, Bemerkungen zur neueren Literatur iiber die moravischen Fenster; Geol. Gesell Wien, Mitt, v. 11, p. 108-104.

Eeply to Becke (1913) (see Suess, 1913). Ascribes the 

formation of mica schists in the Moldanubian block to 

deep-seated diaphthoresis of highly potassic argillaceous 

layers whose composition was peculiarly susceptible to retrogression. The "schiefer gneiss" intercalations are regarded as relics of the original "Katagneiss."

Suggate, R. P., 1963, The Alpine fault: Royal Soc. New Zealand 

Trans. Geology, v. 2, no. 7, p. 105-129.

Cataclasis and mylonitization (p. 115-116) are described 

along with detailed description and discussion of the Alpine 

fault zone of New Zealand. Good brief description of the 

field relations of some of the rocks and their relation to 

the fault movements (see also Reed, 1964). See Examples 

section of this text.

Sutton, John, and Watson, Janet, 1951, The pre-Torridonian 

metainorphic history of the Loch Torridon and Scourie 

areas in the north-west Highlands, and its bearing on 

the chronological classification of the Lewisian: Geol. Soc. 

London Quart. Jour., v. 104, p. 241-307.

Describes "shear belts" with various cataclastic rocks. 

Also describes "mylonite belts."

 1959, Metamorphlism in deep-seated zones of transcurrent movement at Kungwe Bay, Tanganyika Territory: 

Jour. Geology, v. 67, p. 1-13.

One of the most detailed descriptions of blastomylonites. 

Other cataclastic rocks are also described. Wide "shear 

belts" and thin "mylonite belts" are distinguished and 

mapped. Good descriptions of the mlneralogical changes 

in some of the shear belts. "The mylonite gneisses can be 

arranged in a series showing increasingly complete mechanical breakdown, while the noncataclastic types form a second series which appears to show increasing degrees of 

crystallization. * * * The end point of the first series is1 a 

minutely granular rock which does not differ greatly from 

the starting point of the second series." (p. 6). Describes 

blastomylonite in which recrystallization-neomineralization has allowed growth of sulbhedral mineral rims crowded 

with, inclusions of the cataclastic matrix material of the 

rock. The rims of the minerals are of the same material 

as the relict rounded cores. There was no retrogression. 

Very well illustrated.

Svenonius, F., 1892, Om berggrunden i Norrbottens lan och 

untsigterna till brytvarda Apatitforekomster derstades: 

Sveriges Geol. Unders., ser. G, Afhandlingar och Uppsateer, 

no. 126, 43 p.

Describes cataclastic rocks in a thick zone.

 1900, Oversikt af Stora Sjofallets och angransande 

Fjalltrakters geologi: Geol. Foren. Stockholm Forh., v. 22, 

p. 273-322.

First use of the term kakirite for the strongly brecciated 

rocks that lie above the Silurian crystalline rocks in the 

region of Storce, Sweden. Good descriptions.

Taubeneck, W. H., 1967, Notes on the Glen Coe caldron subsidence, Argyllshire, Scotland: Geol. Soc. America Bull., 

v. 78, no. 11, p. 1295-1316.

Describes and discusses the flinty crush-rocks at Glen 

Coe (p. 1307-1308). Attributes origin of the rocks to fluidization and denies cataolasis.

Teall, J. H. H., 1918, Dynamic metamorphism; a review, mainly 

personal: Geologists Assoc. (London) Proc., v. 29, p. 1-15.

Descriptions and photomicrographs of Lap worth's (1885) 

original mylonites. Quoted in this text. See discussion of 

mylonite in this text.

Termier, Pierre, 1909a, Sur les nappes de 1'ile d'Elbe: Acad. 

Sci., Paris, Comptes rendus, v. 148, p. 1648-1651.

Brief description of a thick band of cataclastic rocks on 

the island of Elba.

 1909b, Sur les relations tectoniques de 1'ile d'Elbe avec 

la Corse et sur la situation de celle-ci dans la chaine alpine: 

Acad. Sci., Paris, Comptes rendus, v. 149, p. 11-14.

Describes a band of cataclastic rocks on Elba, and a similar 

band on Corsica. Relates the cataclastic zones to the tectonics of the islands and to the Alps.

 1909c, Sur les granites, les gneiss et les porphyres ^erases 

de 1'ile d'Elbe: Acad. Sci., Paris, Comptes rendus, v. 148, 

p. 1441-1445.

A more detailed description of the cataclastic rocks of Elba 

described in two previous papers1 (1909a, b).

Termier, Pierre, and Boussac, J., 1911, Sur les mylonites de la 

region de Savone: Aead. Sci., Paris, Comptes rendus, v. 

152, p. 1550-1556.

Describes a complete transition between undeformed 

granite and mylonite. According to the degree of mylonitization, they differentiate: (1) fissured and brecciated 

granite; (2) granite incompletely crushed, but laminated; 

(3) granite with lamination more intense; (4) crushing 

incomplete, without lamination; (5) crushing more complete no mineral discernible to naked eye; (6) Puree Parfaite "perfect soup" ; (7) lamination of the preceding soup, 

(literal translation).

Termier, Pierre, and Maury, E., 1928, Nouvelles observations 

ge"ologiques dans la Corse Oriental; Phenome'nes d'ecrasement et de laminage; mylonites et bre'ches tectoniques: 

Acad. Sci., Paris, Oomptes rendus, v. 186, p. 1247-1251.

Field and petrographic description of a complex 24-km-wide 

band of cataclastic rocks on Corsica. They use the term 

mylonite in a general rather than specific way, to include 

all materials formed by crushing, regardless of their nature.

Theodore, T. G., 1966, The fabric of a high-grade mylonite zone 

in southern California [abs.] : Am. Geophys. Union Trans., 

v. 47, no. 3, p. 491-492.

"Phase petrology of the nonmylonitic rocks indicates almandine-amphibolite facies metamorphism. Subsequent granitic 

intrusives caused a breakdown of biotite and muscovite 

to give sillimanite, K feldspar, and iron ores. The mylonitic 

rocks contain the same mineral assemblages as the 

others, with no evidence of retrogressive metamorphism. 

The nature of the folds suggests that pervasive lateral 

shear movements, normal to the lineation but without con-
ANNOTATED BIBLIOGRAPHY 93

stant sense, have affected the mylonite zone. The predominant type of quartz fabric has orthorhombic symmetry and 

consists of crossed girdles of c axes, intersecting in the 

plane of the foliation, normal to the lineation; a single or 

divided maximum occurs at the girdle intersection. The 

orthorhombic quartz fabrics suggest flattening normal to 

the foliation planes and elongation parallel to the lineation. Analysis of preferred orientation of quartz in a fold 

suggests: (1) that the shear folding continued while the 

orthorhombic quartz fabrics were developing, or (2) intermittent shear displacements, perhaps along zones at 

high angles to the maximum compressive stress, have occurred after initiation of the flattening. It appears that 

the complexly deformed mylonite zone formed at depth in 

a mobile region of the Earth's crust undergoing hightemperature metamorphism * * *" (part of author's 

abstract).

Thoreau, J., 1935, Contribution a 1'etude des roches du substratum cristallin des foassins Lulua Bushimail au sud du 7e 

parallele: Louvain Univ., Inst. geol. Mem., v. 8, p. 293-326.

Describes thick zones of blastomylonites in the Belgian 

Congo.

Tilley, C. E., 1947, The dunite-mylonites of St. Paul's Rocks 

(Atlantic) : Am. Jour. Sci., v. 245, no. 8, p. 483-491.

Describes dunite and peridotite cataelastic rocks, chiefly 

mylonites. Well illustrated. The textures in these rocks 

were formerly thought to be volcanic flow features. Notes 

regeneration of fosterite veins after mylonitization.

 1966, A note on the dunite (peridotite) mylonites of 

St Paul's Rocks (Atlantic) : Geol. Mag., v. 103, no. 2, p. 

120-123.

Brief description of the cataelastic rocks. See Tilley, 

1947.

Tornebohm, A. E., 1880, Nagra ord om granit och gneis: Geol. 

Foren. Stockholm Forh., v. 5, p. 233-248.

First use (p. 244) of the term mortar structure (Murbruk 

Swedish for mortar).

Tullis, Jan, 1968, Preferred orientation in experimental quartz 

mylonites tabs.]: Am. Geophys. Union Trans., v. 49, no. 4, 

p. 755.

Turner, F. J., 1941, The development of pseudo-stratification by 

metamorphic differentiation in the schists of Otago, New 

Zealand: Am. Jour. Sci., v. 239, no. 1, p. 1-16.

A classic paper on metamorphic differentiation. Deals 

mainly with the chemical factors of differentiation, but also 

describes the great amount of shearing and mechanical deformation involved, and calls the rocks "blastophyllonites." 

See section on cataelastic metamorphic differentiation in 

this text.

 1942, Preferred orientation of olivine crystals in peridotites, with special reference to New Zealand examples: 

Royal Soc. New Zealand Proc. and Trans., v. 72, pt. 3, p. 

280-300.

Describes and discusses the fabric of a cataelastic dunite. 

"Complete lack of orientation of the space-lattice is attributed to the destructive process of cataclasis as opposed to 

plastic deformation of other rocks." (p. 292).

 1948, Mineralogical and structural evolution of the 

metamorphic rocks: Geol. Soc. America Mem. 30, 342 p.

Defines (Maphthoresis (p. 6) : "A metamorphic assemblage 

of minerals formed at high temperature is converted to an 

assemblage stable at lower temperatures." Also good petrofabric data.

 1968, Metamorphic petrology; mineralogical and field 

aspects: New York, McGraw-Hill Book Co., 403 p.

Good discussion of metamorphic conditions which can be 

used to imply, very generally, conditions of formation of 

some cataelastic rocks. Good discussion of retrograde metamorphism.

Turner, F. J., and Ohih, C. S., 1951, Deformation of Yule Marble, 

Part III, Observed fabric changes dues to deformation at 

10,000 atmospheres confining pressure, room temperature, 

dry : Geol. Soc. America Bull., v. 62, no. 8, p. 887-906.

Turner, F. J., Griggs, D. T., Clark, R. H., and Dixon, R. H., 

1956, Deformation of Yule Marble, Part VII, Development 

of oriented fabrics at 300° G-5000 C: Geol. Soc. America 

Bull., v. 67, no. 9, p, 1259-1294.

Turner, F. J., Griggs, D. T., Heard, H. C., and Weiss, L. E., 1954, 

Plastic deformation of dolomite rock at 380° C.: Am. Jour. 

Sci., v. 252, no. 8, p. 477-488.

Turner, F. J., and Verhoogen, John, 1960, Igneous and metamorphic petrology [2d ed.] : New York, McGraw-Hill Book 

Co., 694 p.

This classic book has excellent discussions of the conditions 

of metamorphism. Some cataelastic rocks are defined in 

a general way (p. 452-454). There are good discussions of 

petrofabrics, origin of structural features (foliation, cleavage, etc.), metamorphic differentiation, and retrogressive 

metamorphism.

Turner, F. J., and Weiss, L. E., 1963, Structural analysis of 

metamorphic tectoniltes: New York, McGraw-Hill Book Co., 

545 p.

A comprehensive textbook on petrofabrics and the geometry 

of rock deformation. Contains1 many references to and discussions of cataelastic rocks and their fabrics, as well as 

good discussions of the origin and development of structural features. The chapter (8) on experimental deformation of minerals and rocks is particularly valuable.

Tweto, Ogden, and Sima, P. K, 1963, Precambrian ancestry of 

the Colorado mineral belt: Geol. Soc. America Bull., v. 74, 

no. 8, p. 991-1014.

Describes various cataelastic rocks along shear zones in the 

Rocky Mountains. Describes a "new" biotite gneiss formed 

from mylonitic rock. The gneiss contains relict fragments 

of mylonite as inclusions. Describes late breccias and gouge 

formed from older cataelastic rocks. Especially good for 

descriptions of poly cataelastic rocks.

Tyrrell, G. W., 1924, the geology of Prince Charles Foreland, 

Spitsbergen: Royal Soc. Edinburgh Trans., v. 53, p, 443-478.

Describes and illustrates "hartschiefer" formed from banded 

siltstones, quartzites, and "crush breccias." Other cataelastic rocks are briefly described.

420-478 O - 71 - 7
94 CATACLASTIC ROCKS

 1926, The principles of petrology: London, Methuen, 

349 p.

Definitions, descriptions, drawings, and discussions of many 

types of cataclastic rocks. Defines (p. 271-272) : cataclastic 

structure, porphyroclastic structure; (p. 281-288) crushbreccia, micro-breccia, flayer-rocks, mylonite, kakirite, crushconglomerate, cataclasite, mylonite-schist, ultramylonite, 

flinty crush rock, and hartschiefer. See Glossary this text.

Van Bemmelen, R. W., 1936, Over de zoogenaamde "Smeltmylonieten" (=pseudotachylieten) : Geol. Mijnbouw, v. 

15, no. 9, p. 74-79.

Good discussion of pseudotachylite.

Van Diver, B. B., 1967, Contemporaneous faulting-metamorphism in Wenatchee Ridge area, northern Cascades, Washington : Am. Jour. Sci., v. 265, no. 2, p. 132-150.

Describes and illustrates Various cataclastic rocks. "It 

should be noted that schistosity, on the whole, is largely a 

phenomenon of fine compositional layering produced by 

direct shearing, rather than strong form or situation of 

crystals" (p. 140). Describes and discusses compositional 

adjustment accompanying cataclasis; "* * * ferromagnesian 

content is directly proportional to the degree of cataclasis" 

(p. 143). Gives two "tenable" explanations: "(1) Selective 

shearing of more mafic original rock types; and (2) basification of original quartz diorite or leuco-dioritic material, 

principally by hydrothermal leaching of silica and alkalies 

during syn-metamorphicfaulting." (p. 143).

Vogel, D. E., 1967, Petrology of an eclogite- and pyrigarnetbearing polymetamorphic rock complex at Cabo Ortegal, 

N.W. Spain: Leidse geol. Mededel., v. 40, p. 121-213.

Von Seidlitz, W., 1910, Ueber Granit-mylonit und Hire tektonische Bedeutung: Geol. Rundschau, v. 1, p. 188-197.

Discusses chemical changes during mylonitization.

Waters, A. C., 1932, A petrologic and structural study of the 

Swakane gneiss, Bntiat Mountains, Washington: Jour. 

Geology, v. 40, no. 6, p. 604-633.

Petrographie and field descriptions of cataclastic rocks, and 

of their gradational characters into noncataclastic rocks. 

Notes preferential cataclasis of pegmatites. Notes preferential demolition of quartz relative to feldspar.

 1938, Petrology of the contact breccias of the Chelan 

batholith: Geol. Soc. America Bull., v. 49, no. 5, p. 763-794.

Waters, A. C., and Campbell, C. D., 1935, Mylonites from the 

San Andreas fault zone: Am. Jour. Sci., 5th ser., v. 29, no. 

174, p. 473-503.

Probably the most comprehensive review of cataclastic 

rock nomenclature in the literature. Cataclastic rocks are 

described, illustrated, discussed, analyzed, and classified. 

Extensively and widely quoted and cited in this text. See 

particularly the Examples section (San Andreas fault zone) 

of this text.

Waters, A. C., and Krauskopf, K. B., 1941, Protoclastic border 

of the CoMlle batholith: Geol. Soc. America Bull., v. 52, no. 

9, p. 1355-1418.

Classic account of protoclasisi. Describes, illustrates, and interprets the protoclastic rocks of the batholith. Conceptual

discussions are particularly valuable. See Examples section of this text.

Wegmann, C. E., 1935, Preliminary report on the Caledonian 

orogeny in Christian X's Land (north-east Greenland) : 

Medd. om Gr0nland, v. 103, no. 3, 59 p.

Good descriptions of mylonites. Considers mylonitization 

along thrusts later than the crystallization of the rocks 

that are thrust.

 1938, Geological investigations in southern Greenland; 

Part I. On the structural divisions of southern Greenland: 

Medd. om Gr0nland, v. 113, no. 2, 148 p.

Devises a schematic correlation chart (flg. 15) for temperature and movement phases during metamorphism in 

southern Greenland. Considers mylonitic activity as the last 

phase.

Wegmann, Eug6ne, 1963, Note sur les mylonites du type de Sidi 

Ferruch (Algerie) : Geol. Rundschau, v. 53, p. 314-324.

Description and interpretation of cataclastic rocks along <a 

major north African fault zone. Uses the term mylonite for 

several different types of cataclastic rock.

Wenk, Edward, 1934, BeitrSge zur Petrographie und Geologie 

des Silvretta Kristallins: Schweizer. Mineralog. Petrog. 

Mitt., v. 14, no. 1, p. 196-278.

Describes layered mylonite associated with its nonlayered 

parent rock in the Silvretta gneiss and concludes that mechanical processes have transformed the unlayered augen 

gneiss into layered cataclastic rocks. Good description of 

cataclastic rocks. See section on cataclastic metamorphic 

differentiation in this text.

 1937, Zur Genese der BSndergneise von Orno' Huvud: 

Upsala Univ. Geol. Inst. Bull., v. 26, p. 53-89.

Gives evidence that a banded gneiss (mylonitic) developed 

from unlayered parent rock through mechanical metamorphic differentiation. See section on cataclastic metamorphic differentiation in this text.

Wilkinson, P., 1955, The structural history of the region east 

of Loch Briboll, Sutherland, in Phillips, F. C., Structural 

petrology and problems of the Caledonides: Advancement 

Sci., London, v. 12, no. 49, p. 573-574.

Good, brief description of folds in cataclastic rocks (blastomylonites?).

Willemse, J., 1936, On the old granite of the Vredefort region: 

Univ. of Zurich, Inaugural Dissert.

See Willemse, 1938.

 1938, On the old granite of the Vredefort region and some 

of its associated rocks: Geol. Soc. South Africa Trans., 

v. 40, p. 43-119.

Restudy of theParijs (Parys) rocks (see Shand, 1917; Hall 

and Molengraaff, 1925). Concludes that there is evidence 

for nothing more than extreme crushing of the rocks, with 

a small amount of recrystallization to produce the spherulites and microlites.

Williams, Howel, Turner, F. J., and Gilbert, C. M., 1954, Petrography An introduction to the study of rocks in thin 

sections: San Francisco, W. H. Freeman and Co., 406 p.
ANNOTATED BIBLIOGRAPHY 95

Definitions, discussions, and drawings of many types of 

cataclastic rocks. Good general discussion of cataclastic 

and crystalloblastic deformation (p. 199-200). Divides cataclastic rocks into three categories (p. 199-208) : cataclasites, 

mylonites, phyllonites. Defines: mylonite (p. 200-201), 

pseudotachylite (p. 201), augen gneiss (p. 203), cataclasite 

(p. 204-205), phyllonites (p. 206-208). Discusses flaser 

granite and flaser gabbro (p. 204). All definitions relatively 

general.

Wilson, Gilbert, 1953, Mullion and rodding structures in the 

Moine series of Scotland: Geologists' Assoc. London Proc., v. 

64, pt. 2, p. 118-151.

Describes minor folds in cataclastic rocks (chiefly blastomylonites). Contrasts the "plastic" style of folding in the 

Moine schists with the "brittle" style of folding in the 

blastomylonites of the Moine thrust zone.

Wiseman, J. D. H., 1932, A. contribution to the petrology of 

the metamorphic rocks of East Greenland: Geol. Soc. London Quart. Jour., v. ?8, pt. 3, p. 312-349.

Suggests (p. 335) that the metamorphism of the sedimentary rocks resulted from heat generated by thrust 

movements.

Wurm, A., 1935, Uber tektonische Ausschmelzungsgesteine und 

ihre Bedeutung: Zeitchr. Vulkanologie, v. 16, no. 2, p. 98- 

119.

Good descriptions and discussions of pseudotachylites.

Zawadynski, L., 1952, Geologisch-petrographisc'he Untersuchungen in der Valle Onsernone (Tessin) ; zur Petrographie 

der KataMasite: Sehweizer. Mineralog. Petrog. Mitt, v. 32, 

no. 1, p. 1-110.

Describes brecciated cataclastic rocks recemented by secondary mineralization (p. 19). Terms them "secondary 

kakirites."

Zwart, H. J., 1968, On the determination of polymetamorphic 

mineral associations: Geol. Rundschau, v. 52, p. 38-65.

REFERENCES CITED

[Not in annotated 'bibliography]

Alien, C. R., 1957, San Andreas fault zone in San Gorgonio 

Pass, southern California: Geol. Soc. America Bull., v. 68, 

no. 3, p. 315-350.

American Geological Institute, 1957, Dictionary of geological 

termsi: Garden City, N.Y., Doubleday and Co., 545 p.

Badgley, P. C., 1965, Structural and tectonic principles: New 

York, Harper and Row, 521 p.

Bailey, E. B., 1955, Moine tectonics and metamorphism in 

Skye: Edinburgh Geol. Soc. Trans., v. 16, pt. 2, p. 93-166.

Bayley, R. W., and Muehlberger, W. R., comps., 1968, Basement rock map of the United States (exclusive of Alaska 

and Hawaii) : Washington, D.C., U.S. Geol. Survey, 2 sheets, 

scale 1:2,500,000.

Becke, Frederich, 1904, Uber Mineralbestand und Struktur der 

kristallinischen Schiefer: Internat Geol. Cong., 9th, Vienna. 

1903, Comptes rendus, p. 533-570.

 1924. Structur und Kluftung: Fortschr. Mineralogie, 

Kristailographie, Petrographie, v. 9, p. 185-220.

Bentley, R. D., and Deininger, R. W., 1969, Granitic plutons in 

the Alabama Piedmont [abs.]: Geol. Soc. America, Southeastern Sec., 18th Ann. Mtg., Abstracts with Programs for 

1969, Pt. 4, p. 4-5.

Burchfiel, B. O., and Livingston, J. L., 1967, Brevard zone compared to Alpine root zones: Am. Jour. Sci., v. 265, no. 4, p. 

241-25&

 1968, Brevard zone compared to Alpine root zones;

Reply: Am. Jour. Sci., v. 266, p. 219-220. 

Buwalda, J. P., 1937, Recent horizontal shearing in the coastal

mountains of California [afas.] : Geol. Soc. America Proc.,

1936, p. 341. 

Centini, B. A., 1968, Structural interpretation of the Hanging

Rock area, Stokes County, North Carolina [abs.]: Geol. Soc.

America, Southeastern Sec., 17th Ann. Mtg., Program, p.

26-27. 

Clark, B. L., 1929, Tectonics of the Valle Grande of California:

Am. Assoc. Petroleum Geologists Bull., v. 13, no. 3, p. 199-

238.

Cotton, C. A., 1947, The Alpine fault of .the South Island of

New Zealand from the air: Royal Soc. New Zealand Trans.

and Proc., v. 76, pt 3, p. 369-372. 

Crickmay, G. W., 1939, Geologic map of Georgia: Georgia Geol.

Survey, scale 1: 500,000. 

Crowell, J. C., 1962, Displacement along the San Andreas fault,

California: Geol. Soc. America Spec. Paper 71, 61 p.

 1966, San Andreas fault system through time [abs.]: 

Geol. Soc. America, 1966 Ann. Mtg., San Francisco, Program, p. 46.

Curray, J. R., and Nason, R. D., 1967, San Andreas fault north 

of Point Arena, California: Geol. Soc. America Bull., v. 78, 

no. 3, 413-118.

Daly, R. A., 1933, Igneous rocks and the depths of the earth: 

New York, McGraw Hill Book Co., 508 p.

Dibblee, T. W., Jr., 1954, Geology of the Imperial Valley region, 

California, in Jahns, R. H., ed., Geology of southern California : California Div. Mines Bull. 170, p. 21-28.

 1962, Displacements on the San Andreas rift zone and 

related structures in Carrizo Plain and vicinity, in Geology 

of Carrizo Plain and San Andreas fault Guidebook, 1962: 

Bakersfield, Calif., San Joaquin Geol. Soc., p. 5-12.

Dietrich, R. V., and Mehnert, K. R., 1961, Proposal for the 

nomenclature of migmatites and associated rocks, in Sorensen, H., ed., Symposium on migmatite nomenclature: Internat. Geol. Cong., 21st, Copenhagen, 1960, Rept, Pt. 26, Supp. 

Vol., Sec. 14, p. 56-68.

Dunn, D. E., Butler, J. R., and Centini, B. A., 1966, Brevard fault 

zone, North Carolina; New interpretation [abs.]: Geol. 

Soc. America Spec. Paper 87, p. 247.

Dunn, D. E., Butler, J. R, and Justus, P. S., 1968, Brevard zone 

compared to Alpine root zones; Discussion: Am. Jour. Sci., 

v. 266, p. 215-219.

Dunn, D. E., Butler, J. R., and Weigand, Peter, 1968, Lithology 

and structural style of the Brevard zone, North Carolina 

[abs.]: Geol. Soc. America, Southeastern Sec., 17th Ann 

Mtg., Program, p. 33-34.
96 CATACLASTIC ROCKS

Ehlig, P. L., 1959, Relationship of the Pelona Schist and Vincent thrust in the San Gabriel Mountains, California [abs.]: 

Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1717.

Espenshade, G. H., 1967, Reconnaissance geologic map of the 

Yadkin Valley region, North Carolina: U.S. Geol. Survey 

open-file map, scale 1: 250,000.

Fisher, G. W., Pettijohn, F. J., Reed, J. C., Jr., and Weaver, 

K. N., eds., 1970, Studies of Appalachian geology central 

and southern: New York Interscience Publishers, 460 p.

Galpin, S. S., 1915, A preliminary report on the feldspar and 

mica deposits of Georgia: Georgia Geol. Survey Bull. 30, 

190 p.

Gilluly, James, 1938, in Lovering, T. S., and others, Report of the 

committee on structural petrology: Washington, D.C., Natl. 

Research Council, Div. Geology and Geography, p. 52-58.

Hamilton, Warren, 1961, Origin of the Gulf of California : Geol. 

Soc. America Bull., v. 72, no. 9, p. 1307-1318.

Hamilton, Warren, and Myers, W. C., 1966a, Cenozoic tectonics 

of the western United States, in The world rift system 

Internat. Upper Mantle Comm. Symposium, Ottawa, 1965: 

Canada Geol. Survey Paper 66-14, p. 291-306.

 1966b, Cenozoic tectonics of the western United States: 

Rev. Geophysics, v. 4, no. 4, p. 509-549.

Higgins, M. W., 1968, Geologic map of the Brevard fault zone 

near Atlanta, Georgia: U.S. Geol. Survey Misc. Geol. Inv. 

Map 1-511, scale 1:48,000.

Hill, M. L., 1959, Dual classification of faults: Am. Assoc. Petroleum Geologists Bull., v. 43, vol. 1, p. 217-221.

 1966, The San Andreas system, California and Mexico, in 

The world rift system Internat. Upper Mantle Comm. Symposium, Ottawa, 1965: Canada Geol. Survey Paper 66-14, p. 

239-245.

Hill, M. I/., and Dibblee, T. W., Jr., 1953, San Andreasi, Garlock, 

and Big Pine faults, California a study of the character, 

history, and tectonic significance of their displacements: 

Geol. Soc. America Bull., v. 64, no. 4, p. 443-458.

Holgate, Norman, 1963, The Cabot and Great Glen faults: 

Nature, v. 197, no. 4868, p. 680-681.

Hopson, C. A., 1964, The crystalline rocks of Howard and Montgomery Counties, in The geology of Howard and Montgomery Counties: Baltimore, Maryland Geol. Survey, p. 

27-215.

Hurst, V. J., and Crawford, T. J., 1964, Exploration of mineral 

deposits in Habersham County, Georgia: Washington, D.C., 

U.S. Dept. Commerce, Area Redevel. Adm., 180 p.

Johnson, M. R. W., 1965, The Moine thrust: A discussion: Jour. 

Geology, v. 73, no. 4, p. 672-676.

King, P. B., 1964, Further thoughts on tectonic framework of 

southeastern United States, in Lowry, W. D., ed., Tectonics 

of the southern Appalachians: Virginia Polytech. Inst., 

Dept. Geol. Sci. Mem. 1, p. 5-31.

Kingma, J. T., 1958, Possible origin of piercement structures, 

local unconformities, and secondary basins in the eastern 

geosyncline, New Zealand: New Zealand Jour. Geology and 

Geophysics!, v. 1, no. 2, p. 269-274.

Lawson, A. C., and others, 1908, The California earthquake of 

April 18, 1906. Report of the State Earthquake Investigation Commission: Carnegie Inst. Washington Pub. 87, v. 1, 

pt 1, p. 1-254, pt. 2, p. 255-451.

Livingston, J. L., and Burchfiel, B. C., 1968, The root interpretation of the Brevard zone [abs.]: Geol. Soc. America, 

Southeastern Sec., 17th Ann. Mtg., Program, p. 53.

Mann, J. F., Jr., 1955, Geology of a portion of the Elsinore fault 

zone, California: California Div. Mines Spec. Rept. 43, 22 p.

McBirney, A. R, 1963, Breccia pipe near Cameron, Arizona; 

Discussion: Geol. Soc. America Bull., v. 74, no. 2, p. 227- 

232.

McLachlan, G. R., 1953, The bearing of rolled garnets on the 

concept of 6-lineation in Moine rocks: Geol. Mag., v. 90, no. 

3, p. 172-176.

Moody, J. D., and Hill, M. J., 1956, Wrench-fault tectonics: Geol. 

Soc. America Bull., v. 67, no. 9, p. 1207-1246.

Miigge, 6., 1930, Bewegungen von Porphyroblasten in Phylliten 

und ihre Messung: Neues Jahrb. Mineralogie, Beil.-Bd., 61A, 

p. 469-510.

New Zealand Geological Survey, 1958, Geological map of New 

Zealand: Wellington, scale 1:2,000,000.

Noble, L. F., 1954, The San Andreas fault zone from Soledad 

Pass to Oajon Pass, California, in Jahns, R. H., ed., Geology 

of southern California: California Div. Mines Bull. 170, 

p. 37-48.

Oakeshott, G. B., 1966, Geologic evidence for displacement on the 

San Andreas fault, California [abs.]: Geol. Soc. America, 

1966 Ann. Mtg., San Francisco, Program, p. 151-152.

Paterson, M. S., and Weiss, L. E., 1961, Symmetry concepts in the 

structural analysis of deformed rocks: Geol. Soc. America 

Bull., v. 72, no. 6, p. 841-882.

Peacey, J. S., 1961, Rolled garnets from Mofrar, Inverness-shire: 

Geol. Mag., v. 98, no. 1, p. 77-80.

Peach, B. N, Gunn, W.f Clough, C. T., Hinxman, L. W., Crampton, C. B., Anderson, E. M., and Flett, J. S., 1912, The geology 

of Ben Wyvis, Carn Chuinneag, Inchbae, and the surrounding country, including Garve, Evanton, Alness, and 

Kincardine (explanation of sheet 93) : Scotland Geol. Survey Mem., 189 p.

Peterson, N. V., 1965, Newberry Volcano area field trip Geologic summary, in Peterson, N. V., and Groh, E. A., eds., 

State of Oregon Lunar Geological Field Conference, Big 

Bend, Oreg., 1965, Guidebook: Oregon Dept. Geology and 

Mineral Industries Bull. 57, p. 11-18.

Philbin, P. W., Petrafeso, F. A., and Long, C. L., 1964, Aeromagnetic map of the Georgia Nuclear Laboratory area, 

Georgia: U.S. Geol. Survey Geophys. Inv. Map GP-488.

Philpotts, A. R., 1962, Preliminary report on the Belleau-Desaulniers area, Counties of St. Maurice, Maskinonge", and Laviolette: Quebec Dept. Nat. Resources Prelim. Rept. 480, 7 p.

Proctor, R. J., 1962, Geologic features of a section across the Casa 

Loma fault, exposed in an aqueduct trench near San Jacinto, 

California: Geol. Soc. America Bull., v. 73, no. 10, p. 1298- 

1296.

Pumpelly, Raphael, Wolff, J. E., and Dale, T. N., 1894, Geology 

of the Green Mountains in Massachusetts: U.S. Geol. Survey Mon. 23, 206 p.

Ramsay, J. G., 1967, Folding and fracturing of rocks: New 

York, McGraw-Hill Book Co., 568 p.

Ratte", J. C., and Steven, T. A., 1967, Ash flows and related volcanic rocks associated with the Creede caldera, San Juan 

Mountains, Colorado: U.S. Geol. Survey Prof. Paper 524-H, 

58 p.

Read, H. H., 1949, A contemplation of time in plutonism: Geol. 

Soc. London Quart. Jour., v. 105, pt. 1, no. 417, p. 101^156.

Reed, J. C., Jr., 1968, The Brevard zone in the Grandfather 

Mountain area, North Carolina; a re-interpretation: Geol. 

Soc. America, Southeastern Sec., 17th Ann. Mtg., Program, 

p. 63-64.
REFERENCES CITED 97

Beed, J. C., Jr., Johnson, H. S., Jr., Bryant, Bruce, Bell, Henry, 

3d, and Overstreet, W. C., 1961, The Brevard fault in North 

and South Carolina: U.S. Geol. Survey Prof. Paper 424-C, 

p. C67-C70.

Reed, R. D., and Hollister, J. S., 1936, Structural evolution of 

southern California: Am. Assoc. Petroleum Geologists Bull., 

v. 20, no. 12, p. 1529-1704.

Rosenfeld, J. L., 1960, Rotated garnets and the diastrophicmetamorphic sequence in southeastern Vermont [abs.]: 

Geol. Soc. America Bull., v. 71, no. 12, pt. 2, p. 1960.

 1968, Garnet rotations due to the major Paleozoic deformations in southeast Vermont, in Zen, E-an, White, W. S., 

Hadley, J. B., and Thompson, J. B., Jr., eds., Studies of 

Appalachian geology northern and maritime: New York, 

Interscience Publishers, p. 185-202.

Schmidt, Walter, 1918, Bewegungsspuren in Porphyroblasten 

Kristalliner Schiefer: Akad. Wiss., Wien, Sitzungsber., v. 

127, p. 293.

Sharp, R. V., 1967, San Jacinto fault zone in the Peninsular 

Ranges of southern California: Geol. Soc. America Bull., v. 

78, no. 6, p. 705-730.

Shelton, J. S., 1966, Geology illustrated: San Francisco, W. H. 

Freeman and Co., 434 p.

Shepard, F. P., 1957, Northward continuation of the San Andreas fault: Seismol. Soc. America Bull., v. 47, no. 3, p. 263- 

266.

Smith, E. A., 1926, Geologic map of Alabama: Alabama Geol. 

Survey, scale 1: 500,000.

Spry, Alan, 1957, Precambrian rocks of Tasmania, Part II, Mt. 

Mary area: Royal Soc. Tasmania Papers and Proc., v. 91, 

p. 95-108.

 1963, The origin and significance of snowball structure 

in garnet: Jour. Petrology, v. 4, no. 2, p. 211-222.

Steiger, R. H., 1963, Use of K-Ar ages of hornblende for dating 

phases of Alpine orogeny [abs.] : Geol. >Soc. America, Ann. 

Mtg., New York, 1963, Program, p. 157A-158A.

Sutton, John, 1963, Some recent advances in our unders'tanding 

of the controls of metamorphism, in Pitcher, W. S., and 

Flinn, G. W., eds., Controls of metamorphism: Edinburgh, 

Oliver & Boyd, p. 22-45.

Taliaferro, N. L., 1943, Geologic history and structure of the central Coast Ranges of California: California Div. Mines Bull. 

118, p. 119-163.

Tocher, Don, 1956, Earthquakes off the north Pacific Coast of 

the United States: Seismol. Soc. America Bull., v. 46, no. 3, 

p. 165-173.

U.S. Geological Survey and American Association of Petroleum 

Geologists, 1961, Tectonic map of the United 'States, exclusive of Alaska and Hawaii: Washington, D.C., 2 sheets, 

scale 1:2,500,000.

U.S. Geological Survey and California Div. Mines and Geology, 

1966, Geologic map of California: U.S. Geol. Survey Misc. 

Geol. Inv. Map 1-512.

Vickery, F. P., 1925, The structural dynamics of the Livermore 

region: Jour. Geology, v. 33, no. 6, p. 608-628.

Wallace, R. E., 1949, Structure of a portion of the San Andreas 

rift in southern California: Geol. Soc. America Bull., v. 60, 

no. 4, p. 781-806.

Waters, A. C., 1962, Basalt magma types and their tectonic associations ; Pacific Northwest of the United States, m The 

crust of the Pacific Basin: Am. Geophys. Union Mon. 6 

(Natl. Acad. Sci.-Natl. Research Council Pub. 1035), p. 158- 

170.

Weaver, C. E., 1949, Geology of the Coast Ranges immediately 

north of the San Francisco Bay region, California: Geol. 

Soc. America Mem. 35, 242 p.

Wellman, H. W., 1955, New Zealand Quaternary tectonics: Geol. 

Rundschau, v. 43, no. 1, p. 248-257.

 1956, Structural outline of New Zealand: New Zealand 

Dept. Sci. and Indus. Research Bull. 121, 36 p.

Wellman, H. W., and Willett, R. W., 1942, The geology of the 

west coast from Abut Head to Milford Sound, Part I: Royal 

Soc. New Zealand Trans. and Proc., v. 71, pt. 4, p. 282-306.

Whitten, E. H. T., 1966, Structural geology of folded rocks: 

Chicago, Rand McNally, 663 p.

Willis, Bailey, 1929, San Andreas rift, California: Jour. Geology, 

v. 46, no. 6, p. 793-827.

Yoder, H. S., Jr., 1955, Role of water in metamorphism, in 

Poldervaart, Arie, ed., Crust of the earth a symposium: 

Geol. Soc. America Spec. Paper 62, p. 505-523.

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