Metamorphic Mineral Assemblages of 

Slightly Calcic Pelitic Rocks in and around tlie 

Taconic Allochthon, Southwestern Massachusetts arid

Adjacent *» Connecticut and New York

GEOLOGICAL StJRVEY PROFESSIONAL PAFER 111
Metamorphic Mineral Assemblages of 

Slightly Calcic Pelitic Rocks in and around the 

Taconic Allochthon, Southwestern Massachusetts and 

Adjacent Connecticut and New York

By E-AN ZEN

GEOLOGICAL SURVEY PROFESSIONAL PAPER 111

A study of progressive regional metamorphism of 

pelitic schists from the Taconic allochthon of 

southwestern Massachusetts and its bearing on 

the geologic history of the area

IMTED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1981
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY 

Doyle G. Frederick, Acting Director

Library of Congress Cataloging in Publication Data

Zen, E-an, 1928-

Metamorphic mineral assemblages of slightly calcic pelitic rocks in and around the Taconic allochthon, southwestern Massachusetts and adjacent Connecticut and New York.

(Geological Survey professional paper ; 1113) 

Bibliography: p.

1. Rocks, Metamorphic. 2. Petrology Taconic Mountains. I. Title. II. Series: United States. Geological Survey. Professional paper ; 1113.

QE475.Z46 552'.4 78-32050

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

Washington, D.C. 20402
CONTENTS

Abstract ______________

Introduction _______________________

Acknowledgments __________________

Summary of regional geology _______

Stratigraphy __________________

Structure ___________•..

Mineralogy and mineral assemblages 

Muscovite _____________________

Paragonite __________________

Biotite _______________________

Chlorite ______________________

Chloritoid _____________________

Staurolite _______________

Garnet _______________________

Kyanite ______________________

Amphiboles ___________________

Tremolite _________________

Cummingtonite _______

Hornblende __________

Epidote ______________________

Plagioclase ___________________

Ilmenite _____________

Magnetite _____________________

Tourmaline ___________________

Quartz _________________

Model mineral compositions _____

Staurolite _________________

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Mineralogy and mineral assemblages—Continued 

Model mineral compositions—Continued

Chloritoid _______———_______________

Garnet _______—_—__________________

Chlorite _______________——_——— 

Biotite ________________————_ 

Muscovite _____-__—_——————

Epidote ___________—_____________

Hornblende _________—_-——————

Plagioclase ___________—___________

Kyanite _____________________________

A model multisystem ________________________

Problematic phase relations ___________________

First appearance of chloritoid _————_———___

The chemography of garnet and the biotite-chloritoid-garnet-chlorite relations _________________

Chloritoid-staurolite relations _———————__ 

Kyanite-bearing assemblage _———____________

Phase relations involving epidote _ — ___ —— — ___ 

Relation between epidote-bearing and hornblendebearing assemblages _______————________

Cummingtonite-bearing assemblages ____________

Conditions of metamorphism _____ —— — _———_ —— _

A retrograde isograd? _——_————_—————___

Geologic implications of overburden pressure during

metamorphism _________——__——_————__

References cited _____——_———_——————————

ILLUSTRATIONS

FIGURE 1. 

2,3.

4.

5.

6.

7. 

8,9.

10.

11.

12.

13.

Generalized geologic map of the study area ____________________—_—_—______

Triangular diagrams of:

2. Ar'-Allv-(Fetotai+Mer) compositions of muscovite analyzed by use of the microprobe ____

3. Atomic A(Al-alkalis)FM for biotite samples analyzed by use of the microprobe _-______

Photomicrograph of sample 376—1, showing ilmenite sandwiched between chlorite plates _____—__

Graphs showing composition profiles across garnet crystals in samples 356-1 and 487-2-4 __________

Photomicrographs of cummingtonite assemblages for samples 170-1 and 487-2 ___________

Graphs showing composition profiles across a hornblende crystal in sample 102-1 _____—______

Photomicrographs of:

8. Coexisting Staurolite and epidote in samples 356-1 and 590-1 _______________—_

9. Triply zoned plagioclase from samples 3-3 and 360-1 _________________——_—— 

Graphs showing composition profiles across zoned plagioclase of samples 3-3, 360-1, and 14-1 ______

Photomicrographs showing extreme habit adaptation of metamorphic plagioclase to the foliation surface of the rock, sample 423-1, and late plagioclase that includes folded foliation defined by dust 

trains, sample 340-1 _____________________________________________________________

Graph showing manganese content of coexisting garnet and ilmenite (as inclusions in garnet) in 

sample 356-1 _____________________________________________

Photomicrographs of zoned tourmaline, sample 509-1, and of a mantle of tourmaline, sample 102-2_

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III
IV CONTENTS

Page 

FIGURES 14,15. Diagrams showing:

14. A closed net for the quinary multisystem AWFeO-MgO-CaO-K^O, for the phases epidotegarnet-plagioclase-chlorite-chloritoid-staurolite-biotite-muscovite in the presence of quartz 

and having H20 and 02 as boundary-value components ———————————————————— 24

15. A part of the multisystematk net of figure 14 containing the four invariant points (St),

(Ep), (Bt),and (Cd) _____________________—————————————————————— 26

16. Photomicrographs of chloritoid-biotite assemblages _———————————————————————————— 28

17. ACFM diagram wherein paragonite is projected to the A apex, for phases in coexistence with epidote 35

18. Graph showing experimental pressure-temperature curves pertinent to the mineral assemblages of

the study area _____________________——————-—————————————————————— 39

19. Photomicrograph of sample 191-1, showing chlorite rimming magnetite ————————————————— 42

TABLES

[Tables follow References Cited]

Page

TABLE 1. Mineral assemblages in samples of rocks from within and around the Taconic allochthon, southwestern Massachusetts and adjacent parts of Connecticut and New York —————————————— 49

2. Localities from which samples were obtained for mineral-assemblage information ———————————— 54

3. Microprobe data on various minerals in samples of rocks from within and around the Taconic

allochthon: 

A. Muscovite ___________________—________—_—————————————————— 57

B. Biotite ______________________________________________———————— 67

C. Chlorite __________________________________________—_——_————— 75

D. Chloritoid ______________________________________________—_————— 81

E. Staurolite ____________________________________________-_—__ 88 

F. Garnet ________________________ __________________——————— 95

G. Kyanite ____________________________________________-__-__ 106

H. Hornblende and cummingtonite ______ — ————————————————————————————— 107

/. Epidote ______________________________-_________________________ 109

J. Plagioclase _________________——————_—_———_—_———————————— 110

K. Ilmenite ____________________________________________________ 117 

L. Magnetite ____________________________________________________ 123

4. Conventional wet-chemical analyses and the number of atoms calculated on the basis of the anhydrous

formulas for selected minerals ___________——________________—_________ 124

5. Comparison of wet-chemical and microprobe analyses and of the calculated chemical formulas of

staurolite from sample 355-1 ____________________________________—__ 126

6. Molar volumes of minerals used to calculate slopes of the univariant curves shown in figure 15 ___ 126

7. Compositions of coexisting chlorite, biotite, chloritoid, and garnet in the presence of muscovite,

plagioclase, and quartz ____________________________________________ 127

8. Partial mineral-assemblage data for samples of epidote-bearing assemblages ______________ 127

9. Compositions of coexisting minerals in three hornblende assemblages ___________________ 128 

10. Estimates of minimum temperature of metamorphism based on the K/(K+Na) ratios of muscovite

compositions and the 2.07-kbar solvus of Eugster and others (1972) and micrroprobe data ——— 128
METAMORPHIC MINERAL ASSEMBLAGES OF 

SLIGHTLY CALCIC PELITIC ROCKS IN AND AROUND 

THE TACONIC ALLOCHTHON, SOUTHWESTERN MASSACHUSETTS AND 

ADJACENT CONNECTICUT AND NEW YORK

By E-AN ZEN

ABSTRACT

The mineral assemblages from metamorphosed slightly 

calcic pelitic rocks of the Taconic Range in southwestern 

Massachusetts and adjacent areas of Connecticut and New 

York were studied petrographically and chemically. These 

rocks vary in metamorphic grade from those below the 

chloritoid zone through the chloritoid and garnet zones into 

the kyanite-staurolite zone. Microprobe data on the ferromagnesian minerals show that the sequence of increasing 

Fe/ (Fe+Mg) value is, from the lowest, chlorite, biotite, hornblende, chloritoid, staurolite, garnet. Hornblende, epidote, 

garnet, and plagioclase are the most common minerals that 

carry significant calcium. Biotite is persistently deficient in 

alkali but is abnormally rich in octahedral aluminum to such 

an extent that the overall charge balance can be ascribed to 

an Al=K+(Fe,Mg) diadochy. Muscovite contains small 

though persistent amounts of iron and magnesium in octahedral positions but has a variable K/Na ratio, which is potentially useful as a geothermometer. One low-grade muscovite is highly phengitic, but the white micas in rocks from 

metamorphic grades higher than chloritoid zone do not contain significant phengite components. Chlorite is persistently 

high in aluminum and so its ratio of divalent ions to aluminum is approximately that of garnet. Many garnets show 

pronounced zoning in manganese and less pronounced zoning 

in calcium. Garnet coexisting with hornblende contains a 

high proportion of the grossularitic component. The calcium 

content is significant in all the analyzed garnets, except 

those from a cummingtonite-bearing sample that is free of 

muscovite. This suggests that in slightly calcic pelitic rocks, 

calcium-free garnet cannot coexist with muscovite.

Most of the mineral assemblages formed in the presence of 

excess quartz and muscovite. The phase-petrologic analysis, 

made with the aid of an eight-phase multisystematic model, 

shows the following major points:

1. Chloritoid and staurolite coexist in a definite interval of 

prograde metamorphism.

2. Biotite-chloritoid does not constitute an alternative assemblage to garnet-chlorite-muscovite, because the 

former combination is found predominantly in the 

presence of the latter combination. Because the garnet 

contains lime, all five phases are stable together in lowlime pelitic rocks.

3. The first appearance of staurolite in the area does not 

correspond to the reaction leading to the first intrinsic

stable existence of this phase. Inasmuch as the first appearance of staurolite is always in chlorite-bearing assemblages, I suggest that the mapped staurolite zone 

marker corresponds to a reaction whereby staurolitechlorite becomes stable. The probable lower grade chemical equivalent, for example, chloritoid-aluminum silicate, however, has not been found in the area of study. 

Several staurolite-forming reactions discussed in the 

literature are ruled out because of the relative siderophility of the minerals. A second staurolite isograd 

involves the reaction, chloritoid+chlorite+muscovite= 

staurolite+biotite. A third isograd involves staurolite+ 

chlorite=biotite+kyanite; this reaction is postulated on 

the basis of the observed assemblage biotite-kyanitestaurolite-garnet-muscovite-plagioclase-quartz-ilmenite. 

4. In low-grade rocks, epidote is stable considerably before 

the first appearance of chloritoid. The nature of the 

high-aluminum phase in low-grade rocks that leads to 

the formation of chloritoid remains obscure. The epidote 

is always rich in ferric iron (pistacite content of about 

1/4 to 1/3). Garnet-bearing assemblages (with or without epidote) are formed next as metamorphic grade increases. The next more calcium-rich silicate is hornblende, and despite the meager data on assemblages 

that include hornblende, the first intrinsic appearance 

of this phase has probably been recorded. At highstaurolite grade, the most calcium-rich assemblage in 

pelitic rocks is hornblende-garnet-biotite-plagioclase 

(bytownite)-chlorite-quartz; except for the details of 

compositions of the phases, this assemblage is not a bad 

approximation of an amphibolite in equivalent metamorphic grade. Thus, the mineral assemblages from the 

area seem to bridge the gap between typical pelitic 

schists and impure amphibolites.

Comparison of the mineral assemblages with hydrothermal 

phase-equilibrium data suggests that the approximate range 

of the temperature of metamorphism was 400°-600° C at a 

pressure not less than that of the triple point of the aluminum silicates, or probably about 4 kbars. The metamorphism 

was an Acadian event. The pressures and temperatures indicate that major differential uplift, on the order of about 15 

km, between parts of the study area and the region of the 

Hudson Valley must have taken place since Acadian metamorphism. The nature and date of this uplift are unknown.
METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

INTRODUCTION

The Taconic Range in the tristate area of Massachusetts, Connecticut, and New York is underlain 

by pelitic rocks that belong to the Walloomsac Formation (Middle and Upper? Ordovician), the Egremont Phyllite (Middle and Upper? Ordovician), and 

the allochthonous Everett Formation (upper Precambrian? and (or) Lower Cambrian?). That these 

rocks have undergone regional metamorphism has 

long been recognized (Hobbs, 1893a, b, and references therein). Agar (1932,1933) described some of 

the metamorphic rocks. His work, however, was 

largely of a reconnaissance type and does not contain 

information on the mineral assemblages or the chemical petrology; it was also not in the context of the 

recent interpretation of the structure and tectonic 

history of the area. Earth (1936) described the 

metamorphic rocks of a similar stratigraphic sequence in the Dutchess County area, New York, 

farther to the south; his work has been revised and 

updated by Bence and Vocke (1974) and Vidale 

(1974a,b).

As part of an effort to study the geologic history 

of the Taconic allochthon, N. M. Ratcliffe and I 

mapped the bedrock geology of the Bashbish Falls 

and Egremont 7^-minute Quadrangles in the tristate area (Zen and Hartshorn, 1966; Zen and Ratcliffe, 1971). In addition, the northwestern half of 

the Sharon Quadrangle and strips of areas adjacent 

to these quadrangles were also mapped (fig. 1).

Many samples of these pelitic rocks, as well as 

samples of the carbonate-rich rocks of the Stockbridge Formation, were studied by use of the microscope, X-ray diffractometer, and electron microprobe 

and by conventional wet-chemical analyses of mineral separates. This paper summarizes the results 

of this study.

The petrographic evidence suggests two episodes 

of regional metamorphism. The earlier episode was 

low grade and has been associated previously with 

the Taconian orogeny (Zen, 1969a, b; 1972a; Ratcliffe, 1972). The metamorphic grade of rocks resulting from the second episode ranges from below the 

biotite zone to the staurolite zone; because the micas 

produced by this episode have yielded K-Ar singlemineral ages of about 360 m.y. (million years) (Zen 

and Hartshorn, 1966), which age is corroborated by 

an argon total-fusion age (M. A. Lanphere and E-an 

Zen, unpub. data, 1967), this second episode is taken 

to be Acadian. The mineral assemblages described in 

this paper are almost exclusively effects of this second metamorphic episode.

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EXPLANATION

Walloomsac Formation (Ordovician)

Egremont Phyllite correlated with the Walloomsac Formation (Ordovician)

Stockbridge Formation (Cambrian and Ordovician)

Cheshire Quartzite and Dalton Formation, undivided 

(Precambrian(?) and Cambrian)

Everett Formation {allochthonous) (Precambrian(?) and

(or) Cambrian)

Contact—Approximately located 

Metamorphic isograd—Approximately located 

Sample locations.

Pseudounivariant assemblage chlorite + muscovite+chloritoid=biotite+staurolite formed in the 

presence of quartz by the reaction (Ep, Pg) of the 

multisystem net (fig. 14)

Assemblage on the low-grade side of the above reaction

Assemblage on the high-grade side of the above reaction

74'

INDEX MAP SHOWING LOCATION 

OF STUDY AREA

FIGURE 1.—Generalized geologic map of the study area, 

showing major formations, contacts, and isograds, as well 

as sample control for the isograd denned by the reaction 

chloritoid+chlorite-fmuscovite=staurolite-fbiotite.
INTRODUCTION

73°30' 73°22'30"

73°30' 73°15'

INDEX OF QUADRANGLES

FIGURE 1.—Continued.
METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

The slightly calcic pelitic schists described here are 

chemically and mineralogically complex. Because 

these rocks are not particularly aluminum rich, the 

aluminum-silicate minerals, even paragonite, are 

rare. The rocks do contain enough calcium, however, 

that this component cannot be ignored in phase analysis. The iron, magnesium, and potassium contents 

are normal, and sulfides are rare and can be ignored 

for the present purpose.

Because of the complexity of the rocks, their study 

needed a guiding framework, or model; devising a 

model implies some simplifications of the perceived 

relations. In published studies of pelitic schists, 

other workers have made one of several possible 

simplifying assumptions. They have assumed the system to be chemically simple, or they have assumed 

the system to be mineralogically simple by limiting 

the number or the permissible variations of the compositions of the minerals. To be sure, one could study 

the detailed chemistry of all the minerals in actual 

contact in each rock and derive precise information 

on the changes of mineral chemistry as the bulk composition and metamorphic grades vary; however, 

such a laborious effort must be a second stage to a 

"detailed reconnaissance" that this study is intended 

to be.

In this study, I adopted the expedient of using a 

model multisystem that contains all the important 

minerals observed and that includes all the major 

chemical components for these minerals. The multisystem, which is a model petrogenetic grid, allows 

study of the reaction relationships and prediction of 

discontinuous changes of phase assemblages that are 

used as isograds. The price one pays for this model 

is to use simple mineral compositions—not endmember compositions but rather fixed compositions 

whose atomic proportions are "averages" of the 

microprobe and wet-chemical analyses of minerals 

reported here. This expedient provides a framework 

whereby the myriad observations successfully find 

their niches, but it sacrifices prospects of understanding the details of the variation in composition 

of coexisting minerals as a function of metamorphic 

grade. The data are not lost; they are in the tables 

of chemical analyses and mineral assemblages and 

are discussed in the text for specific reactions. They 

are, however, not made the center of attention of the 

report. I hope this reconnoitering effort will lead 

others to study the details in the not-too-distant 

future.

ACKNOWLEDGMENTS

Many people have contributed to this study. My 

thanks go first to A. E. Bence, who introduced me to 

the use of the electron microprobe and was responsible for the collection of a substantial part of the 

data. Another who helped materially with the microprobe work was L. B. Wiggins. I must acknowledge 

Robert Meyrowitz for the especially painstaking and 

superb analyses of a garnet and a staurolite. For 

careful mineral separations used for the chemical 

analyses I am deeply indebted to D. E. Lee and 

Cristina S. Zen. Discussions of the petrologic problems with J. B. Thompson, Jr., A. L. Albee, N. M. 

Ratcliffe, and D. R. Wones have been most fruitful. 

S. W. Bailey helped to identify the polytypes of 

analyzed chlorite; Malcolm Ross helped to identify 

the polytypes of mica, and he and J. S. Huebner gave 

invaluable advice and help in X-ray cell measurements and in matters mineralogical in general. The 

contribution during a period of several years of Jane 

G. Hammarstrom, who performed many of the 

tedious laboratory chores, undertook the horrendous 

task of microprobe-data reduction in preautomation 

days and made additional microprobe analyses, cannot be adequately acknowledged; both she and J. L. 

Haas, Jr. also helped with the computer software. To 

all these kind people and many others not specifically 

mentioned, I offer my gratitude. The manuscript was 

reviewed by D. S. Harwood, B. A. Morgan, P. H. 

Osberg, and D. B. Stewart, and I am truly grateful 

to them for their Herculean efforts to make this report better.

SUMMARY OF REGIONAL GEOLOGY

The regional geology of the area is briefly summarized; for more details, the reader is referred to 

Zen and Hartshorn (1966) and Zen and Ratcliffe 

(1971).

STRATIGRAPHY

The Precambrian(?) and Paleozoic section contains a basal arkose, the Dalton Formation, succeeded by a vitreous quartzite, the Cheshire Quartzite. This is followed by a thick succession of 

shallow-water carbonate rocks, the Stockbridge 

Formation. Although heterogeneous in detail and 

subdivided into six members (A to F, from old to 

young), the Stockbridge is predominantly dolomitic 

in the lower part and calcitic in the upper part. 

Quartz-rich nodules in the units could be metamorphosed chert nodules, as equivalent rocks at low 

metamorphic grades contain chert beds or nodules.
SUMMARY OF REGIONAL GEOLOGY

At sufficiently high metamorphic grades, such nodular quartz reacted with the carbonate minerals to 

produce calc-silicate minerals (see also Burger, 

1975).

Above the Stockbridge Formation and an erosional gap representing a Middle Ordovician regional 

unconformity (Zen, 1967), the Walloomsac Forma- I 

tion is present. It is a series of gray to black, locally 

sulfide-rich, micaceous to calcareous pelites. Fine 

silty sandstone beds and silty limestone beds are 

minor components of the formation. The base of the 

Walloomsac Formation is commonly a blue-gray 

limestone rich in silt and mica; more rarely, this 

zone is a ferruginous calcareous siltstone, presumably derived from iron-rich residual soil, which was 

extracted for iron in the 19th century through much 

of the area (Chute, 1945).

The Egremont Phyllite, a dark gray to black 

pelite, is exposed in a large but totally enclosed area. 

For the purpose of this report, this unit is correlated 

with the Walloomsac Formation.

The geometrically highest unit is the Everett Formation, consisting at low metamorphic grades of 

green phyllite, quartzose phyllite, and minor interbedded quartzite, silty limestone, and graywacke. 

Beds that might have been impure volcanic ash (now 

hornblende bearing) and beds composed of a peculiar 

quartzose rock of uncertain original nature that 

carry the assemblage cummingtonite-magnetitegarnet-biotite-quartz are present in a very few 

places in the formation. Purplish low-grade phyllite 

is evident in the northwest part of the Egremont 

Quadrangle and along the Mount Washington road 

east of Mt. Fray. One area of massive graywacke 

mapped near Bashbish Falls east of Copake provided the best examples of the epidote-bearing assemblages below the garnet zone; this graywacke 

is correlated by lithology with the Rensselaer Graywacke in the area farther to the northwest in New 

York State.

Most parts of the Everett Formation at higher 

metamorphic grades are silvery green. Likewise, the 

parts of the Walloomsac Formation that have undergone higher grade metamorphism have become silvery gray, instead of dark gray to black. In both 

instances, the color is imparted principally by grains 

of white mica and feldspar that became coarser. 

Therefore, at higher metamorphic grades (highalmandine to staurolite zones) these two formations 

are locally difficult to distinguish in hand specimens. 

Geologic context may provide a clue for mapping; 

the pelites of the Walloomsac also tend to be more 

calcareous. As seen under the microscope, the centers of crystals from the Walloomsac Formation 

often retain dusty inclusion trains of carbonaceous 

material, which are relicts from lower metamorphic 

grades; these trains help to identify the formation.

The Everett Formation is allochthonous and is a 

slice of the composite Taconic allochthon (Zen, 

1967). The slice is geometrically the highest and 

technically the latest of the allochthon. In the northwest corner of the Egremont Quadrangle, purple 

and green slate that may belong to an earlier, technically lower slice is found geometrically beneath 

most of the Everett and is separated from it by the 

Walloomsac and by slivers of the Stockbridge.

Because the Everett Formation is allochthonous, 

one can ask whether its metamorphism might have 

preceded its tectonic emplacement. The following list 

of observations suggests that this is unlikely: First, 

there is no evidence of any discontinuity in metamorphic grade across the zone of tectonic movement. 

Second, the phyllites of the Everett Formation in the 

northwest corner of the Egremont Quadrangle are 

the product of the early metamorphic event. Here 

the early formed foliation in the allochthonous rock 

can be physically traced into the foliations in the 

carbonate sliver and in the underlying Walloomsac 

Formation; thus, the foliation and associated metamorphism are interpreted to be no older than the 

tectonic emplacement (Zen, 1969a, stop A6). I conclude, therefore, that the mineral assemblages of the 

early metamorphism of the allochthonous rocks can 

be interpreted to be continuous parts of the entire 

rock succession; thus, the mineral assemblages of 

the later Acadian metamorphism must also be continuous through the entire rock succession.

STRUCTURE

The area has been deformed several times. The 

earliest deformation that is readily recognized is a 

group of isoclinal recumbent folds in the Stockbridge 

Formation. The age of these folds is interpreted as 

Early to Middle Ordovician. These large-scale passive-flow folds in the carbonate units apparently 

produced no recognizable metamorphic effect.

The second episode of folding was during the emplacement of the allochthonous rocks, which could be 

a late Taconian event, especially if the upper slices 

of the allochthon were propelled by the nappes forming in the crystalline basement rocks of the Berkshire Highlands; the thrusting of the crystalline 

nappes is tentatively dated as Taconian on the basis 

of the isotope age determination of a syntectonic intrusive rock (Harwood, 1972; Zen, 1976). This episode of folding is interpreted to be about the same
METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

age as the first episode of low-grade metamorphism. 

Ages determined by a variety of isotopic methods on 

rocks from Vermont (Harper, 1968; Lanphere and 

Albee, 1974; M. A. Lanphere and E-an Zen, unpub. 

data, 1967) and from southeastern New York (Long, 

1962; Bence and Rajamani, 1972; N. M. Ratcliffe, 

oral commun., 1975) provide evidence for a late 

Taconian (Late Ordovician to Early Silurian) regional thermal and likely metamorphic event; this 

event is entirely consistent with the local geologic 

evidence for the age of emplacement of the allochthonous rocks. This second episode of folding is 

recorded as overturned to recumbent folds in all the 

rocks (in the Everett Formation, there are local indications of an earlier foliation that is folded by this 

second axial surface, but the evidence is meager, and 

the event remains to be verified).

The last episode of flexural deformation is recorded as relatively small scale, open, upright to locally overturned folds, although some recumbent 

folding is not excluded. The foliation and the axial 

surfaces of the second folding were both folded by 

this late event, although single outcrops rarely show 

folding of both. This late event is associated with 

the Acadian orogenic and metamorphic events. 

These events produced the most significant metamorphic assemblages and all the almandine-grade and 

higher grade assemblages in the area. Isotopic dates 

(Zen and Hartshorn, 1966) by K-Ar method on muscovite (390 m.y.) and by Rb-Sr method on biotite 

(355 m.y.) from both allochthonous and autochthonous rocks gave Acadian ages in the southern part 

of the area.

As shown in the section Geologic Implications of 

Overburden Pressure During Metamorphism, the 

post-Acadian uplift may be on the order of 104 

meters in the area but may amount to only about 

103 m barely 3X104 m to the west. Thus, largescale differential movement, either distributive or 

local, may have taken place.

MINERALOGY AND MINERAL ASSEMBLAGES

The mineral-assemblage data given in table 1 were 

obtained principally by means of the petrographic 

microscope and were supplemented by data from 

X-ray diffraction of the samples. Table 2 gives the 

localities of samples by longitude and latitude, states 

the metamorphic zone and the formation, and indicates whether data from microprobe and (or) wetchemical analyses supplement petrographic microscope data for minerals of a given assemblage.

Many compositions of coexisting minerals were

determined by the electron microprobe. These results, given in table 3, are probably good to ±1 percent for major components and to ±5 percent for 

minor components, though the results are reported 

to more significant figures. A few minerals were also 

analyzed by conventional wet-chemical methods, and 

the results are given in table 4.

A few words of explanation for the acceptability 

of the microprobe analyses recorded in table 3 are in 

order. For hydrous minerals, the analyses have been 

recalculated by adding enough H2 0 to make up the 

fully hydrated formula:

Weight percent H2 0 = 18.016 ((Ohf -0af)/0af) S,

where Ohf is the number of gram atoms of oxygen in 

the hydrous formula for the mineral, Oaf is the number of gram atoms of oxygen in the anhydrous formula, and S is defined as

S=Z Weight percent oxide i/'formula

weight oxide i per gram atom oxygen.

If the analyses are exactly right and the minerals 

are stoichiometric, then the sums ought to be 100 

percent, except for the unresolvable uncertainties of 

the oxidation state of iron in the mineral. (The calculations assume ferrous oxide.)

As the data in table 3 show, many of the sums fail 

to add up to 100±1 percent. Realistic estimates of 

analytical uncertainties lead me to include all data 

having 100±1.5 percent; for some minerals, a cutoff 

of ±2 percent was accepted. Many of the spots yielding poor sums have been reproducibly replicated; 

wave-length scans of selected spots rule out omission of major elements having sufficient atomic numbers to be excited in the detectable region. Because 

all the analyzed spots were chosen to avoid inclusions and poor polish and tend to be away from 

edges and because, wherever possible, only coarse 

grains were used, the defective sums may be real; 

therefore, they are retained, although they are not 

at present explained.

A few of the analyses tabulated do violate the ±2 

percent limit. They are retained because the data are 

in sets showing the compositions of adjacent coexisting grains of different minerals. (Such sets are 

noted in the table.) Thus, because the determinations 

were made at the same time, the relative proportions 

of the elements are presumably correctly depicted 

even though the absolute values may be subject to 

doubt. I could have swept the problem under the rug 

by showing the results only as variation diagrams; 

however, the original data cannot be recovered from 

variation diagrams, and I felt that presentation of
MINERALOGY AND MINERAL ASSEMBLAGES

the original data, warts and all, is much to be preferred. Despite the fact that the data were collected 

on two different microprobes (the State University 

of New York, Stony Brook, probe, A. E. Bence, analyst, and the U.S. Geological Survey, Reston, probe, 

N. L. Hickling, J. G. Hammarstrom, and E-an Zen, 

analysts), the results do not appear to be biased 

thereby. The analyses identified by six-digit numbers were made on the Stony Brook probe; the 

others were made on the Geological Survey's ARLSMX 1 probe.

In all, about 400 thin sections were examined and 

about 600 X-ray patterns of rock samples were taken 

to obtain the data on mineral assemblages. About 30 

of the rocks have had one or (more commonly) more 

minerals analyzed by the microprobe.

MUSCOVITE

Muscovite is present in almost every rock studied. 

The only exceptions are a few marble beds of high 

purity and one or two quartzite beds that contain 

garnet, magnetite, cummingtonite, and trace 

amounts of biotite. Certainly every pelitic rock contains muscovite as an important mineral; so, unless 

otherwise stated, it will be regarded as ubiquitous. 

Texturally, it is most commonly part of the matrix, 

the plates lying in the plane of the principal foliation 

of the rock. Intergrowth of muscovite with biotite is 

not uncommon; intergrowth with chlorite is rarer 

and is observed mostly in microporphyroblasts in 

fine-grained, low-grade rocks. In some rocks where 

the foliation has been crenulated, muscovite lies 

oriented along both foliations; however, microprobe 

data do not suggest any significant compositional differences based on orientation.

Microscopically, iron-free biotite (phlogopite), 

paragonite, and pyrophyllite could be confused with 

muscovite. Paragonite and pyrophyllite are readily 

distinguished by their X-ray diffraction patterns if 

they are present in more than a small part of the 

rock. Paragonite has been found in a few samples 

of low-grade to medium-grade rocks but is never 

quantitatively important; it is never found in the 

absence of muscovite. Pyrophyllite has not been seen. 

Iron-free phlogopite has basal spacings similar to 

those of muscovite, but the (001) / (002) intensity 

ratio is very different, and it can be identified by this 

means if little muscovite is present. Fortunately, 

iron-free phlogopite occurs exclusively in metamorphosed marble; in pelitic rocks, where the biotite is

1 Any use of trade names and trademarks in this publication is for descriptive purposes only and does not constitute endorsement by the U.S. 

Geological Survey.

a normal, iron-bearing, green-brown pleochroic variety, the danger of confusion with muscovite is small.

Table 3, section A, gives the microprobe analyses 

and atomic proportions of 88 muscovite spots from 

23 rock samples. These analyses show that most of 

the muscovite contains minor amounts of iron and 

magnesium, though one sample (1169-1) contains 

these components in significant quantities. The analyses also show a persistent though small deficit in 

alkali. Computation of the mineral formulas for muscovite is made uncertain by this factor, though admixture of phase impurities can probably be excluded. One major problem is the oxidation state of 

the iron, as it could enter the muscovite structure by 

Al = Fe3 + substitution, by Fe2 + +Si = 2 Al substitution, or by 2 Al = 3Fe2+ substitution. Decision on 

this assignment of an oxidation state depends in turn 

on how much one is willing to accept the accuracy 

of the aluminum determinations. Because iron is 

present in small quantities and aluminum in large 

quantities in muscovites, a small error in the determination of aluminum could lead to major relative 

changes in the assignment of iron.

Most of the analyses show small deficiency in the 

alkali content when computed to a basis of 11 oxygens (anhydrous formula). Much of this deficiency 

may be real and is well known to those who study 

mica (Eugster and others, 1972, p. 161; Guidotti, 

1973, and written commun., 1973). The possibility 

that alkali may have volatilized during the microprobe analysis was considered, but test runs on the 

microprobe show that this factor cannot be a major 

source of the observed deficiency.

The data in table 3, section A, show that within 

limits of analytical uncertainty the 2:l-layer composition of muscovite in rocks of different metamorphic grades and (or) assemblages varies no more 

than that of muscovite in different spots in the same 

rock. For example, muscovite in chloritoid- and 

staurolite-bearing samples does not differ sensibly in 

aluminum content and in iron-magnesium content 

from muscovite in hornblende-bearing samples. 

These conclusions are contrary to those of Guidotti 

(1973). To a first approximation, therefore, I assume that muscovite from the study area is a dioctahedral mica having the ideal composition (K, 

Na)Al3Si3Oio(OH)2, and this ideal composition is 

used in calculations in a later section of this report.

The muscovite analyses plotted in figure 2 indicate 

that most of the muscovites are low in phengite. The 

one major exception to this generalization is the 

muscovite from sample 1169-1, which is a graywacke 

in the Everett Formation on the low-grade western
METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

, Ferriphengite 

20A40

FIGURE 2.—AP'-Allv-(Fet otai+Mg) plot of muscovite analyzed by use of the microprobe, in atomic proportions. Each number denotes how many samples plot at the particular point. The end members musoovite, ferrimuscovite, phengite, and 

ferriphengite defined by Ernst (1963) are also plotted on the main diagram. The small triangles represent muscovite 

in sample 1169-1.

side of the area (table 2 and fig. 2 (triangles)). 

Pour analyses (table 3, section A) of the muscovite 

revealed a uniformly high phengitic content, as defined by Ernst (1963).

Because muscovite is nearly ubiquitous in pelitic 

rocks, it has been used widely as a projection point 

for depicting the mineral assemblages (Thompson, 

1957). If, however, the muscovite can be far from 

its ideal composition, use of this phase for projection must be evaluated in each study.

Three wet-chemical analyses of muscovite separates are given in table 4. Samples 355-1 and 356-1 

are coarse-grained staurolite-garnet schists; mineral separation was a straightforward procedure, 

and the chemical analyses show the muscovites to 

be nearly identical and to conform to an ideal formula, with substitution in the alkali position. Alkali 

is weakly deficient and is comparable with alkali 

contents indicated by most of the microprobe data. 

Sample 140-2 is a fine-grained chloritoid-chlorite
MINERALOGY AND MINERAL ASSEMBLAGES

phyllite, and separation of the minerals was difficult; some minor mixture of quartz was possible, 

though mixture of chlorite was considered unlikely 

on the basis of a visual examination of the separate 

and its X-ray pattern. The analysis indicates that 

sample 140-2 is about 10 percent deficient in alkali 

and has some excess silica. If we assume an improbably high upper limit of 5 percent by weight 

of quartz impurity, the atomic silicon content would 

be 3.0, but the alkali content would be increased 

only to 0.93. Thus, the alkali deficiency may be real. 

I had hoped that a comparison of the wet-chemical 

analyses, which distinguished ferric and ferrous 

iron, could provide the basis for the evaluation 

of total iron in the microprobe analyses. All three 

wet analyses of muscovite show the ferrous iron/ 

magnesium atomic ratio to be on the order of unity 

and the sum of the ferrous iron and magnesium 

cations to be a few hundredths of an atom per 11 

oxygen; these micas are thus very weakly phengitic. 

Lumping of ferric and ferrous iron would change 

this ratio, of course, but not so much as to make the 

results incompatible with the range of ratios shown 

by the microprobe data. In the absence of criteria 

based on consideration of atomic site occupancy, 

such as exist for the amphibole minerals (Papike 

and others, 1974), the problem of partition of oxidation states of iron in the microprobe analyses 

of muscovite must remain unresolved.

PARAGONITE

Paragonite is found in some aluminum-rich pelitic 

rocks but not in large enough quantities that it can 

be physically separated from the other minerals for 

detailed study or can even be studied by the microprobe. The presence of this mineral is generally 

inferred on the basis of one or more weak X-ray 

diffraction peaks of the (001) set superimposed on 

the much stronger basal reflections of muscovite. 

Thus, the presence of paragonite was easy to detect, 

but its composition, including possible intergrowth 

with the phengitic sodium-rich mica (Laduron and 

Martin, 1969), could not be determined.

The mineral assemblages including paragonite 

are given in table 1. The rocks run the gamut of 

the entire metamorphic range in the area, and the 

assemblages are entirely consistent with available 

published data (Zen and Albee, 1964; Eugster and 

others, 1972). The presence of paragonite indicates 

that the muscovite is saturated with the sodium 

component and that the assemblage lies on a section 

of the multicomponent solvus between the muscovitic 

and paragonitic end members. The basal spacing

and chemical composition of muscovite can be determined with greater certainty than those of paragonite, which is less abundant; knowledge of the 

muscovite composition allows estimation of the metamorphic temperatures on the basis of the solvus 

calculated by Eugster and others (1972).

BIOTITE

Biotite is a very common mineral in the pelitic 

assemblages above the biotite zone; by definition it 

is not found below that zone. Biotite typically forms 

stout books lying either within or across the conspicuous surfaces of penetrative cleavage. Inclusions 

of zircon are common and show pleochroic halos. 

Dusty inclusions are also found, frequently preserving earlier foliations. Biotite is commonly intergrown with muscovite; microprobe data on intergrown pairs are noted in table 3. Biotite intergrowth with chlorite is also common, though in 

some rocks the chlorite probably resulted from alteration of biotite. The two minerals are probably 

equilibrium phases where they are in fresh and 

sharp intergrown contact along the basal cleavage 

or where they are present as discrete unaltered 

crystals in the rock.

With rare exceptions, biotite in the pelitic rocks 

is pleochroic from brown to light olive brown; only 

rarely is it pleochroic in shades of green. In limesilicate rocks, the biotite is commonly a phlogopite 

showing faint light tan to colorless pleochroism.

The 60 microprobe analyses (table 3, section B) 

show a remarkable uniformity in the general composition of the biotite. The values of Aliv per 11 oxygen (anhydrous formula) are within the range of 

1.17-1.45, and the mean value is 1.33 ± 0.05 (standard deviation). The Alvi value is slightly more 

i variable, the mean and standard deviation being 

I 0.40±0.09 (range, 0.18-0.59). The aluminum content exceeds that for the formula suggested by 

J. B. Thompson, Jr. (oral commun., 1955), which 

i is K(Fe,Mg,Mn) 2 . 67Alvio.33Si 2 . 6 rAliv1 .3 3 01 o (OH) 2 = % 

(K3 (Fe,Mg,Mn) 8Alvi (Si8Al4iv )03o(OH) 6 ). The major deviation is an excess of about 0.1 in Alvi per 

12 oxygen and is almost precisely compensated for 

by a ubiquitous deficiency of potassium and sodium; 

the mean value of the sum of these two elements 

in the same analyses amounts to 0.88 ±0.05. However, individual analyses do not reveal this nice 

correlation of excess Alvi and deficient alkali; only 

the statistical mean values do, and the correlation 

is a weak one.

In addition, one biotite separate (356-1) was 

also analyzed by the wet-chemical method (see table
10 METAMORPHIC MINERAL ASSEMBLAGES, T AGONIC ALLOCHTHON, MASS., CONN., N.Y.

4); this same biotite was used for dating by the 

K-Ar procedure (Zen and Hartshorn, 1966).

Nine microprobe analyses were made on spots 

of biotite crystals immediately adjacent to or in 

parallel growth with muscovite. The average Aliv, 

Alvi, and alkali contents of these biotites are, respectively, 1.35±0.03, 0.45±0.05, and 0.87±0.06 and 

are identical with those of the bulk rock.

Another set of 11 analyses is for biotite in immediate contact with chloritoid. For these, the results are Aliv = 1.35±0.02, Alvi = 0.40±0.03, and 

alkali = 0.87±0.04. These results are not distinguishable from the average or from the results of analyses of biotite in immediate contact with muscovite.

A set of 21 analyses is of biotite in assemblages 

that include staurolite, and the results are Aliv = 

1.34±0.04, Alvi = 0.40±0.07, and alkali = 0.88±0.07. 

These are not distinguishable from the mean. Values of the last set are in full accord with those for 

the few individual analyses of biotite in the immediate vicinity of staurolite crystals.

In contrast, five analyses of biotite in hornblendebearing assemblages give the values Aliv =1.29± 

0.03, Alvi = 0.33 ±0.07, and alkali = 0.87 ±0.05. Seven 2 

analyses of biotite in rocks including an amphibole

2 If six other analyses of biotite associated with amphibole that were 

rejected for other reasons were included, the results would be unaffected.

/to A

as a phase (samples 102-1, 289-2, and 487-2-4) 

give the values of Aliv = 1.26±0.05, Alvi = 0.33±0.06, 

and alkali = 0.88±0.05. These values suggest that 

these biotites have a lower aluminum content, especially octahedral aluminum content, than those in 

the above-mentioned three groups. There is no corresponding effect on the alkali content within the 

limits of uncertainty.

The biotite analyses are plotted on an AFM diagram (fig. 3), where major deviations from the 

tight clustering result from two amphibole-bearing 

rocks.

CHLORITE

Chlorite is a common mineral in the pelitic rocks 

and coexists with every other mineral of the area. 

It is part of the groundmass of the rock, developing parallel to the foliation or foliations. It is also 

present as larger plates, especially in sandwiches 

having ilmenite centers (fig. 4) ; generally, the 

plates are oriented at a sharp angle to the conspicuous foliation plane.

Chlorite interleaved with biotite and muscovite 

may be an alteration product (especially of biotite), 

but its origin is difficult to determine. If the interleaving is poorly defined, if chlorite is spatially always associated with biotite, and, especially, if the

+4

+43+ + 2 + + + 2+

++2222

+22+

.30

V V V V

.10

M .10 .20 .30 .40 .50 .60 .70 .80 .90

FIGURE 3.—Atomic A(Al-alkalis)FM compositions for biotite samples analyzed by use of the microprobe. Scales are shown in 

decimal fractions rather than in percent. The samples from assemblages carrying an amphibole are separately identified 

by dots. A cross ( + ) represents a single analysis of amphibole-free rock. A number instead of a symbol indicates how 

many analyses (all such analyses are of samples from amphibole-free rocks) plot at that point. The "ideal" biotite of 

formula H2K(Fe,Mg) 3AlSi3Oi2 plots along the base line. The biotite composition suggested by J. B. Thompson, Jr., lies 

along the line A=0.2. All the analyzed biotites from amphibole-free rocks plot above this line.
MINERALOGY AND MINERAL ASSEMBLAGES 11

FIGURE 4.—Photomicrograph of sample 376-1 (cross-poianzsd 

light), showing ilmenite (Ilm) sandwiched between chlorite 

(Ch) plates. Also shown is a bent (though not broken) 

ilmenite lath and stress-induced (?) twinning in a zoned 

porphyroblast of plagioclase (Pg).

chlorite shows radiation halos around inclusions of 

zircon, which are common in biotite, then the chlorite is considered to be an alteration product. Such 

chlorite commonly is also sufficiently inhomogeneous 

even within a single platelet to show distinct patchiness in color in plane light and in the anomalous 

color between crossed nicols.

Oxidized chlorite is found in a few rocks but is 

generally in such small amounts that its presence 

can be established with certainty only by microprobe analyses. However, such chlorite tends to be 

strongly pleochroic in murky yellow and brown 

and lacks the luster or the "birds-eye maple" texture of biotite under the microscope. Resemblance 

of oxidized chlorite to stilpnomelane is strong, and 

distinction is not easy. Chatterjee (1966) has discussed the common occurrence of oxidized chlorite 

in many pelitic rocks.

Table 3, section C, lists the results of 51 microprobe analyses of chlorite. All samples show an 

aluminum content in excess of that given by the 

ideal Pauling (1930) formula. (For reference, the 

Fe,Mg/Al ratio for an ideal Pauling chlorite is 2.5; 

for a chlorite whose ratio is equal to that of almandine, the value is 1.5.)

Two chlorite samples were separated for wetchemical analysis; the results are given in table 4. 

Sample 355-1 was a clean separate that could have 

been contaminated only by traces of muscovite, and

the small amount of alkali was so calculated. Sample 

140-2 was very fine grained, and contamination 

was more likely. The phosphorus is probably from 

apatite, and the alkali from potassium-sodium muscovite (the ratio of these two elements in the analysis of chlorite from sample 355-1 very nearly corresponds to that in the analysis of muscovite from 

this rock; see table 4). After subtracting the impurities, one could calculate the chlorite formula 

in several ways, especially by considering the iron 

to be in different oxidation states. However, the 

differences among these calculated chlorite structural formulas are so slight as to suggest that contamination or the assumption regarding the oxidation of iron have little effect on the main features 

of the formula. All these chlorite formulas have 

distinctly high aluminum content in both the f ourand six-fold positions, as do formulas for chlorites 

in other pelitic rocks (Zen, 1960).

CHLORITOID

Chloritoid is present in pelitic rocks showing 

a wide range of metamorphic grades. It is in both 

the Walloomsac and the Everett Formations. In the 

lower grade rocks, its presence is indicated by tiny 

dark-green lustrous specks (Zen, 1960). In the 

higher grade and generally coarser rocks, it forms 

dark greenish-black crystals superficially resembling biotite but having a duller luster and more 

brittleness. It could be confused with platy ilmenite; 

a magnet helps to distinguish them.

In thin section, chloritoid is found typically in 

lath-shaped crystals, commonly showing simple to 

polysynthetic twinning; the composition plane is 

parallel to the long direction (in the (001) plane), 

and extinction positions are at most only slightly 

different from the trace of the composition plane. 

The crystals most commonly have straight, regular 

sides parallel to (001), but the terminations are 

commonly ragged. In some crystals, inclusions of 

tiny grains, especially quartz, give the mineral a 

worm-eaten appearance, though crystal outline can 

almost always be recognized. The pleochroism in 

chloritoid is from bluish-green to straw yellow, 

though some crystals have little or no pleochroism. 

The different pleochroic colors are not reflected in 

the major chemical composition determined on the 

basis of the microprobe data.

Microprobe data on 59 chloritoid analyses are 

given in table 3, section D. Despite the fact that the 

mineral is found in rocks of different metamorphic 

grades, the composition is remarkably uniform. 

Chloritoid has one atom of silicon and two atoms
12 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

of aluminum per six oxygens (anhydrous formula). 

There is no need to assume or evidence for ferric 

iron substitution for aluminum. Four analyses from 

a single rock from below the garnet zone (sample 

140-2) gave Fe/(Fe + Mn+Mg) =0.86±0.01. Sixteen analyses of chloritoid from samples 338-1, 

466-1, 506-1, and 509-1, from the garnet zone and 

the staurolite-garnet transition zone gave the same 

ratio as 0.85±0.01. Ten analyses from the staurolite 

zone but in rocks without that mineral gave the 

ratio as 0.86±0.01. Thirty-five analyses of chloritoid in the matrix and coexisting with staurolite 

gave this ratio as 0.85±0.02. Two analyses of a 

single sample from the staurolite zone in which 

the chloritoid is found only as inclusions in the 

centers of garnet gave this ratio as 0.83 ±0.01. For 

the present, we must assume the chloritoid to be 

constant in composition regardless of grade and 

mineral assemblage; the slightly lower Fe/(Fe + 

Mn + Mg) ratio of the included chloritoid does not 

seem significant, because in several other samples, 

chloritoid within and outside garnet gave identical 

chemical analyses.

Similarly, an effort was made to see if chloritoid 

inside garnet has higher manganese content, as 

cores of garnet commonly are manganese rich. The 

data of table 3, section D, do not show such a trend. 

The chloritoid of sample 140-2 has a higher manganese content than do those of others (about 0.04 

atoms of manganese per six oxygen, anhydrous formula) ; this could well be because the rock is below 

the garnet zone. In rocks containing garnet, the 

chloritoid is depleted of manganese, and this low 

manganese content is maintained in rocks of higher 

grades.

STAUROLITE

Staurolite is a common mineral in the higher 

grade metamorphic pelitic rocks. The assemblages 

that include this mineral are given in table 1. Fiftyeight electron-rmcroprobe analyses of staurolite 

from 13 different rocks are given in table 3, section 

E. In addition, two separates of staurolite from two 

different assemblages and different stratigraphic 

units (355-1 from the Everett Formation and 356-1 

from the Walloomsac Formation, both from near 

Lions Head) were analyzed by the conventional wetchemical methods; the results are given in table 4.

Interpretation of the microprobe analyses is uncertain for several well-known reasons. The oxidation state of iron is uncertain. Because iron is such 

a major component, even a small error in analysis 

could lead to significant differences in site assignment. The amount of structural H2O in staurolite 

has been debated since the reexamination of the 

staurolite structure by Naray-Szabo and Sasvari 

(1958). These workers suggested an ideal end-member formula of HFe2Al9Si4O24 . However, Richardson 

(1968) synthesized staurolite "on composition" with 

an initial mix whose anhydrous formula corresponds 

to FeaAleSis.TsOaa; he thus advocated a formula containing 2 hydrogen per 24 oxygen. Griffen and 

Ribbe (1973) supported this formula, largely on 

the basis of three direct determinations of densities 

of analyzed material and of an assumption that no 

ferric iron was present. Fed'kin (1975) recently 

reviewed the problem of staurolite composition.

Of the two wet-chemical analyses, the one of 

specimen 355-1 was made with special care. The 

result indicates minor substitution of ferric iron for 

aluminum (less than 0.3 out of 9 aluminum sites, 

and 17 atomic percent of total iron as ferric iron). 

The amount of H2O, which was determined by a 

microcombustion train on 200 mg of sample using 

V2O5 flux, was corrected for H2O~ (110° C), and 

the resulting H2O+ gave 1.5 hydrogen per 24 oxygen, exactly halfway between the two formulas.

Sample 355-1 was also studied on the automated 

microprobe; the standard was repeatedly redetermined during the analyses. The results, given in 

tables 3, section E, and 5, show excellent agreement 

with the wet-chemical results. Addition of one mole 

of H2O per 23 oxygens (reckoned in the anhydrous 

formula) to the anhydrous sum would have added 

2.23 weight percent H2O and brought the total of 

the probe result to 101.0 percent (without correcting for ferric iron, which would have added to the 

sum). Addition of 0.5 mole H2O per 23.5 oxygens 

to the anhydrous sum would have brought the sum 

to 99.9 percent. Either sum is acceptable; thus the 

results do not help to resolve the problem, though 

the less hydrous formula seems more appealing. %Another discriminant, though in practice a poor one, 

is to calculate the number of cations per 23.5 oxygen. The Naray-Szabo and Sasvari formula predicts 

15 cations (exclusive of hydrogen), but the Richardson formula predicts 15.07. The 58 probe analyses 

gave a mean of 14.96±0.06, and though far from 

definite, the result does seem to support the idea 

of a less hydrous formula. Without further information and with the indication from Mossbauer spectra (Dowty, 1972, fig. 1) that a slight amount of 

ferric iron may be in the sample, I accept for the 

subsequent calculations the less hydrous formula of 

staurolite proposed by Naray-Szabo and Sasvari 

(1958).
MINERALOGY AND MINERAL ASSEMBLAGES 13

Dowty (1972) also found that the staurolite of 

sample 355-1 shows no evidence that ferrous iron 

occupies the six-fold position. Hollister (1970) 

studied an aliquot of the same sample for the possibility of sectorial zoning and concluded that titanium is preferentially sited on the (010) growth 

face relative to the (100) face by a factor of 1.56 

but that no evidence exists for zoning among aluminum and silicon. Hollister (1970) also studied 

the staurolite from sample 356-1, which showed 

sectorial zoning in titanium by a factor of 1.19 in 

the same zone and no zoning in aluminum or silicon.

Albee (1972) discussed the problem of correlating wet-chemical analyses of staurolite with microprobe data. In addition to the problems outlined 

above, staurolite is a particularly difficult mineral 

to analyze by the conventional methods because of 

its refractory nature; moreover, tiny inclusions are 

common in staurolite, and these may be very difficult to eliminate. The data of table 5, on the other 

hand, seem to indicate that with sufficient care an 

acceptable agreement between these two methods 

of anaylses is attainable.

Despite Hollister's (1970) data suggesting minor 

sectorial zoning, staurolite is generally not visibly 

zoned. The microprobe data also indicate that staurolite is considerably more homogeneous, both between grains and within grains, than are garnet 

or hornblende. Staurolite is, however, characteristically rich in mineral inclusions as well as trains of 

dusty particles; these may define a foliation trend 

that may be at angles to the foliation trend in the 

groundmass and that I interpret as rotation after 

growth. Some staurolite crystals have rims relatively free of inclusions, yet others show excessive 

incorporation of the groundmass, mainly quartz, 

in quartz-rich and mica-poor rocks, so the grain 

boundaries are poorly defined.

In garnet-staurolite assemblages, the garnet commonly contains chloritoid and ilmenite as inclusions. 

Interestingly, staurolite never has such inclusions 

even though almost certainly a paragenetic relationship exists between staurolite and chloritoid. 

The common presence of inclusions in garnet is 

correlated with its persistent compositional zoning 

and indicates lack of recrystallizatipn; staurolite, 

despite its refractory nature, may recrystallize more 

readily. The wet-chemical analyses of both staurolites show significant zinc, a fact confirmed by the 

microprobe data on the same samples and by determinations of zinc in staurolite from other localities 

(Hollister, 1970).

GARNET

Garnet appears in pelitic rocks throughout the 

eastern and southern parts of the area, and its 

first detection marks the lower limit of the mapped 

garnet zone. It persists as part of the garnet-staurolite assemblage in the highest grade rocks in the 

area and as garnet-sillimanite rocks in the Canaan 

Mountain Schist of Agar (1932, 1933) in the area 

immediately southeast of the study area.

In mica-rich rocks, garnet is euhedral, although 

commonly the crystals are full of inclusions consisting of quartz, ilmenite, chloritoid, some rare mica 

flakes, and trains of dust. Plagioclase inclusions 

have not been positively identified. Helicitic texture 

has been observed, though not commonly; nothing 

resembling the elegant "rolled garnets" described 

from eastern Vermont (Rosenfeld, 1970) is found 

in the study area. Some euhedral garnets are broken, 

a fact that can be established by observation of truncated crystal outlines or of truncation of zoning or 

by distinctly nonsymmetrical composition profiles 

determined by microprobe analyses across the crystals.

Zoning in garnet is best established by microprobe data (fig. 5). Zones are accented by concentric banding of color and by the zonal arrangement 

of inclusions. The rim is commonly nearly inclusion 

free. Zoning or lack thereof is by and large characteristic of a given rock and thus appears to record 

accurately the history of crystal growth.

In quartzite or very quartz-rich pelitic rocks, 

garnet does not tend to become euhedral and subequant as it does in a more pelitic matrix. Rather, 

it commonly forms anhedral, anastomosing crystals 

in the interstices of quartz grains, thoroughly "wetting" the interface. Garnet in quartzite that has a 

distinct planar fabric may form long stringers. 

These stringers are not zoned; for instance, microprobe analyses indicate that specimen 161-1 (table 

3, section F) is homogeneous. The present shape 

of the crystals is not the result of simple deformation, because these stringers show no evidence of 

crushing or even of fracturing; if crushing was the 

initial cause of the shape, then the crystals must 

have been thoroughly recrystallized subsequently.

Table 3, section F, gives the microprobe analyses 

of 90 garnet spots in different mineral assemblages. 

Table 4 gives the wet-chemical analyses of two garnets from two rocks 1 km apart having different 

mineral assemblages: Sample 355-1 from the Everett Formation is a garnet-staurolite-chlorite-plagioclase-muscovite-ilmenite-quartz rock; 356-1, from
14 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

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MINERALOGY AND MINERAL ASSEMBLAGES 15

the Walloomsac Formation, has the same assemblage plus biotite and epidote but has only trace 

chlorite. These analyses are necessarily on bulk 

separates and thus are "averages" of the zoned 

garnet.

The garnets are all almandine rich. They show 

variable amounts of manganese, which is enriched 

in the cores of garnet but decreases progressively 

outward, in accord with well-established patterns 

(fig. 5). Of considerable interest is the fact that 

calcium as the grossularitic component is found in 

small but significant quantities in all the garnets 

probed. Calcium zoning is not as marked as manganese zoning. The calcium content of garnet seems 

to increase either toward or away from the rim 

in different crystals, but some calcium is generally 

present in the rim (Guidotti, 1970). The calcium 

contents of garnet from hornblende-bearing rocks 

are notably high; calcium may occupy as many as 

one-fourth of the total divalent cation positions. 

The ubiquity and sensitivity of calcium in garnet 

in pelitic rocks may have more petrologic significance than has generally been thought, and this 

topic is considered in other sections.

Several rocks contain garnets that show unexpectedly high contents of ZnO in a few point analyses. The location of zinc in lower grade rocks is 

unclear. Albee (1972) suggested that zinc may be 

concentrated in muscovite. My analytical data do 

not show much zinc in muscovite; a few biotite 

analyses do show ZnO. The analytical data (table 

3, sections K and L) indicate that zinc is not preferentially concentrated in lower grade rocks in magnetite or ilmenite. The concentration of zinc in garnet is intriguing and needs more comprehensive 

study and corroboration.

KYANITE

Agar (1932) reported kyanite from the "Salisbury Schist" in the present study area but gave no 

details. Despite careful search, I have found kyanite 

in only one suite of samples, which is from a hillock 

on the west bank of the Housatonic River at the 

southeast edge of the study area and thus is from 

the area of highest metamorphic grade. The mineral 

assemblage is kyanite-staurolite-garnet-biotite-muscovite-plagioclase-quartz-tourmaline-ilmenite. Four 

different samples from this hillock were examined; 

two (including sample 655-1-1) contain kyanite, 

and only one sample, which is free of kyanite, contains chlorite, obviously of secondary origin. Chlorite and kyanite do not seem to form a compatible 

pair in the presence of staurolite and biotite here.

Microprobe analyses of the kyanite are given in 

table 3, section G.

AMPHIBOLES

Three kinds of amphiboles have been found in 

the area: tremolite-actinolite, cummingtonite, and 

high-aluminum hornblende.

TREMOLITE

Tremolite is found in metamorphosed impure 

dolostones of the Stockbridge Formation, especially 

in unit a 3 (Zen and Hartshorn, 1966), where it 

often grew in clusters around quartz nodules (which 

could be metamorphosed chert). Table 4 gives a 

complete analysis of a colorless tremolite from this 

unit. The analysis indicates that the tremolite has 

a Fe/(Fe + Mg) ratio less than 0.007.

Tremolite commonly forms laths and clusters of 

laths ranging from a few millimeters to several 

decimeters in length. Mineral assemblages that include tremolite are given in table 1 (samples 598-2, 

659-1, 677-1, 1054-1).

CUMMINGTONITE

Cummingtonite has been found in three outcrops 

of quartzose beds in the Everett Formation (tables 

1 and 2, samples 170-1, 170-2, 487-2). The mineral 

is present as radiating sheaves of long laths a fraction of a millimeter across (fig. 6). As seen under 

the microscope, these laths are colorless; individual 

laths are as much as 0.1x0.5 mm. Microprobe data 

on two crystals from sample 487-2-4 are given in 

table 3, section H. These data may be compared 

with data on cummingtonite by Stout (1972). The 

analyses show a near absence of calcium, sodium, 

and aluminum and very low fluorine (about 1 percent of the OH sites). The Fe/(Fe+Mg) ratio is 

about 5/7, so these crystals may be properly called 

grunerite. The assemblages associated with the 

cumming-fconite include an almandine-rich garnet, 

biotite, magnetite, quartz, and traces of muscovite 

and chlorite.

HORNBLENDE

Hornblende is known from three localities in the 

study area: two in the Walloomsac Formation 

(samples 102-1 and 289-2) and one in the Everett 

Formation (sample 161-1). All three hornblende 

samples are highly aluminous (Alvi occupancy about 

1.5/23 oxygen, Aliv = 2). The crystal chemistry, probable oxidation ratio of iron, and mineral assemblages of samples 102-1 and 289-2 are fully discussed elsewhere (Doolan and others, 1978).

3 Mapped at least in part as Unit B by Burger, 1975.
16 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

FIGURE 6.—Photomicrographs of cummingtonite (Cum) assemblages for samples (A) 170-1 (plane-polarized light) 

and (B) 487—2 (plane-polarized light). Other minerals 

present are chlorite (Ch), bdotite (Bt), and garnet (Ga).

Doolan and others (1978) also presented the 

optical data on one hornblende (sample 102-1). 

Both hornblendes from samples 289-2 and 102-1 

are pleochroic from grass green to greenish yellow. 

Hornblende from sample 161-1 is pleochroic from 

blue green to grass green, has the highest Fe/(Fe + 

Mg) ratio, and has the lowest calcium content 

(though sodium contents in the M(4) sites of all 

three samples are about equal). Sample 161-1 is of 

the lowest metamorphic grade (just above the garnet-zone marker), 102-1 is just within the staurolite zone, and 289-2 is well within the staurolite 

zone.

On the scale of microprobe analysis, the hornblende crystals are not uniform in composition, 

either between grains or even within an optically 

homogeneous single grain (Doolan and others, 1978; 

see also table 3, section H, and fig. 7). The withingrain variations are smaller than the between-grain 

variations for the same sample (on the scale of a 

single thin section used for microprobe analysis). 

The variations cannot be related to zoning, to proximity to different phases, or to the stratigraphic 

unit. Perhaps the inhomogeneities can be eventually 

attributed to growth factors analogous to the sectorial zoning in andalusite and staurolite described 

by Hollister (1970); they could be a good fossil 

record of the scale of chemical equilibrium during 

metamorphism.

EPIDOTE

Epidote is a subsidiary mineral in some mineral 

assemblages, primarily those in the lower grade 

rocks (table 1). In lower grade rocks, the relatively 

high refractive indices of epidote make it conspicuous. Epidote in these rocks is colorless to faintly yellow and is pleochroic in this range; it commonly is 

present as apparently subrounded clusters, a millimeter or so across, that are aggregates of finer subhedral crystals. In higher grade rocks (garnet zone 

on up), epidote is present as small, discrete, subhedral to euhedral crystals.

The textural relations of epidote in lowest grade 

rocks show the mineral aggregate to crosscut rock 

foliation; thus, the mineral is nondetrital. The reason for the rounded aggregate shape is unclear; it 

may be pseudomorphous after some preexisting mineral or rock fragment, possibly limy micronodules.

The highest grade rocks that contain epidote are 

samples 356-1 and 590-1, both schists of the Walloomsac Formation found well into the staurolite 

zone (table 2 and fig. 1). The mineral assemblages of 

both include staurolite-garnet-chlorite-epidote-biotite-muscovite-plagioclase-quartz (table 1). These 

are the only instances of coexisting staurolite and 

epidote found in the area (fig. 8). The photomicrograph (fig. 8A) shows these euhedral minerals to be 

in mutual contact; presumably they are equilibrium 

phases.

The microprobe analyses of epidote are given in 

table 3, section /. These analyzed epidotes all contain 

appreciable iron, which on the basis of stoichiometry 

should be computed as ferric iron substituting for
MINERALOGY AND MINERAL ASSEMBLAGES 17

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FIGURE 8. — Photomicrographs of coexisting staurolite (St) 

and epidote (Ep) in (A) sample 356-1 (plane-polarized 

light) and (B) sample 590-1 (plane-polarized light). Other 

minerals present are garnet (Ga), biotite (Bt), and muscovite (Mu).

aluminum (pistacite end member). The extent of 

this substitution is very nearly constant at about 30 

percent of the aluminum positions.

PLAGIOCLASE

Plagioclase is nearly ubiquitous in the pelitic rocks 

and is the only feldspar found in most. Potassic 

feldspar is found only in a few granulites and carbonate rocks, chiefly in the basal part of the Dalton 

Formation (Precambrian? and Cambrian) (tables
18 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

1 and 2). The plagioclase is present in a variety of 

habits:

1. Plagioclase forms microporphyroblasts as much 

a 1 mm across. Such feldspar is readily recognized in hand specimen as white spots scattered throughout the rock. Because the grains 

all have their long dimensions alined parallel to 

the rock cleavage surfaces, the particles on 

these surfaces commonly appear as if smeared 

out. In thin section, these crystals generally 

show rude crystal outlines. These crystals are 

especially well developed in relatively low 

grade pelitic rocks below the garnet zone, 

where the other phases are in fine grains but 

the feldspar is relatively large. These plagioclase crystals are commonly zoned, the center 

having less calcium than the outer zone. Many 

porphyroblasts in samples from the part of the 

study area near the "retrograde" isograd 

mapped on figure 1, however, show an outermost calcium-free zone in fairly sharp contact 

with the calcium-rich zone (fig. 9). In some 

porphyroblasts, the most calcic and spatially 

intermediate zones have altered to a mixture of 

white mica and a very fine grained phase having a high refractive index; presumably, the 

phase is zoisite or epidote. Figure 10 gives 

several microprobe profiles of such triply zoned 

crystals, as well as a profile of a plagioclase 

from a staurolite schist for comparison. Because the electron beam used in the traverses 

across crystals has an effective diameter on 

the order of 10 ^m, actual change of sodium 

content is probably sharper than shown. All 

the plagioclases contain negligible potassium.

2. In higher grade pelitic rocks, plagioclase is present commonly as xenomorphic crystals. These 

are either oval crystals in finer ground mass 

(in which case they show up megascopically as 

white spots) or are part of interlocking systems of crystals in the rock. Such crystals are 

readily identified in thin section by their cloudiness compared with quartz. Zoning is found 

but does not show reversal toward albitic rim 

as in category 1, and the zones are not separated by sharp boundaries. Many rocks showing crenulated foliation defined by mica alinement contain plagioclase that has grown into 

tabular crystals that fill the space defined by 

the warped folia (fig. 11A). Other crystals include dust trains defining an earlier foliation 

surface as relict but show no conformity of

FIGURE 9.—Photomicrographs of triply zoned plagioclase 

from (A) .sample 3-3 (cross-polarized light) and (B) sample 360-1 (cross-polarized light), showing the calcium-free 

rim in sharp contact with a calcium-rich intermediate zone, 

now partly altered to sausserite, and a less calcium-rich 

core. Compare with the profiles shown on figure 10.

the crystal morphology to the folia configuration (fig. 115).

3. Plagioclase forms small crystals that are difficult 

to recognize microscopically and that can be 

identified mainly by the X-ray diffraction pattern and by microprobe analysis. The most 

calcium-rich plagioclase found in the area 

forms small crystals, as in sample 289-2. The 

atomic Ca/(Ca + Na) ratio exceeds 0.9 (table 

3, Section J).
MINERALOGY AND MINERAL ASSEMBLAGES 19

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sample 360-1, and (C) sample 14-1, which does not show reversal and is from a staurolite-bearing rock. An, anorthite 

component.

Special treatment of the analytical data on plagioclase is possible because the site occupancy of various atoms in feldspar is well understood and tests of

reasonableness of analytical data can be applied with 

some confidence. In order to apply these tests and 

avoid excessive round-off errors, the numbers in table
20 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

FIGURE 11.—Photomicrographs showing (A) extreme habit 

adaptation of metamorphic plagioclaise to the foliation surface of the rock, sample 423-1 (cross-polarized light); 

(B) late plagioclase including folded foliation denned by 

dust trains; the sigmoidal fold is in a single crystal, sample 340-1 (plane-polarized light).

3, section /, are carried to more places than are those 

in other parts of table 3 and than are warranted by 

the original data.

The results of three tests are tabulated in table 3, 

section /: the number of tetrahedrally coordinated 

atoms per eight oxygens (Si, Ti, Al) is designated 

Z ; the number of atoms occupying interstices of the 

framework (Ca, Na, K, Ba, Mg, Mn, Fe) is designated X\ and quantity Y is the difference between 

the sum of the numbers of each type of X atom multiplied by its cationic charge and the number of aluminum atoms. A fourth test, that the sums of cationic charges should equal 16, is really a test of 

arithmetic accuracy and is strictly obeyed by all the 

listed data. The role of iron is a problem, as ferric 

iron should be reckoned as a Z atom, but ferrous iron 

should be considered as an X atom. In table 3, section /, iron is taken to be ferrous; to regard it as 

ferric would increase the value of Z, but decrease X 

and Y. Sample computation on the most iron-rich 

sample was made on the basis of the assumption of 

ferric iron and produced negligibly different final 

results.

With a few exceptions that are obvious from table 

3, section /, I have accepted only those analyses that, 

in addition to having good total oxide sums, satisfy 

the three conditions Z = 4.00±0.03, X=1.00±0.04, 

and F=0.0±0.07. The quality of the data, by these 

tests, is comparable to that of data included in the 

compilation of Deer, Howie, and Zussman (1963) 

for plagioclases, as shown by the following average 

data, standard deviations, and ranges (all calculated 

to eight oxygens):

Atom

Deei-, Howie, and

Zussman 

(1963, p. 108-120)

This i-epoi-t 

(table 3, section J)

Z _________

Range in Z 

X _________

Range in X 

Y _________

Range in Y 

Number of 

analyses _

3.993+0.013

3.958-4.020

0.996±0.014

0.968-1.030

-5.8XlO-3+0.037

-0.081-+0.168

87

3.999+0.009

3.979-4.017

1.017+0.023

0.962-1.063

+3.9X10^+0.050

-0.071-+0.082

51

A matter of considerable interest is whether the 

sodium-rich plagioclase in rocks below the staurolite 

zone shows the peristerite miscibility gap. Crawford 

(1966) demonstrated that certain schists from eastern Vermont and from New Zealand show this gap, 

which decreases as metamorphic grade increases 

until it disappears in rocks of the staurolite zone. 

Crawford's data show that at approximately the 

garnet isograd, plagioclase in the bulk composition 

range Ab95-Ab80 does not exist as a single phase; 

instead two plagioclases are present side by side. 

The miscibility gap shows a marked asymmetry toward the sodium end. Orville (1974) suggested that 

instead of being the result of a two-phase solvus, the 

peristerite gap may be the result of a transition loop 

between low albite and high plagioclase that has the 

maximum temperature point anchored at the pure 

albite composition rather than at some intermediate 

composition.

Nord and others (1978) examined several specimens of plagioclase from the report area by detailed
MINERALOGY AND MINERAL ASSEMBLAGES 21

microprobe study and also examined sample 3-3 by 

means of transmission electron microscopy. The 

plagioclase shows concentric zoning; the intermediate zone shows spinodal decomposition into peristerite. The peristerite structure has characteristic 

dimensions of a few hundred angstroms and is found 

only in regions where the microprobe analysis (beam 

size about 5 /^m) shows the composition to be in the 

An5-An2o range. The texture of the exsolution and its 

restriction to zones of suitable composition suggest 

that the zones originally crystallized as a homogeneous phase. Because the rock probably never attained a grade as high as that of the garnet metamorphic zone, crystallization of a homogeneous 

oligoclase instead of a two-phase peristeritic mixture 

was likely metastable, and the reason for this metastable single-phase crystallization is at present 

unknown.

Other plagioclase samples from below the garnet 

and the chloritoid zones studied by Nord and others 

(1978) show a complex range of zoning patterns; 

the reader is referred to their paper for details.

ILMENITE

Ilmenite is the most common and readily identified 

opaque accessory mineral from the rocks of the area. 

It is characteristically platy, a fact that greatly aids 

in identification. In low-grade pelites, it is commonly 

sandwiched between chlorite plates (fig. 4), and locally it is sandwiched between white mica plates.

Microprobe analyses of ilmenite are given in table 

3, section K. Ilmenite grains enclosed in garnet cores 

of sample 356-1 contain more manganese than those 

in the matrix as a result of the exchange equilibrium 

between garnet and ilmenite. The results are shown 

in figure 12. Least squares analysis of the data is 

unsatisfactory because the points fall into two tight 

clusters. However, the line in figure 12, drawn by use 

of coeval fitting (Zen and Albee, 1964), indicates 

that, in atomic proportions, Mn(Ga) = -3.4xlO~3 + 

16.6 Mn(Ilm), r2 (correlation coefficient) = 0.97 on 

the basis of a 12-oxygen formula for garnet and a 

3-oxygen formula for ilmenite.

MAGNETITE

Magnetite is found in some samples, as indicated 

in table 1. Microprobe data for one sample are given 

in table 3, section L. These data and those for ilmenite show that neither mineral is a host for zinc, and 

thus the source of zinc in staurolite remains a 

problem.

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CD

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0 0.01 0.02 0.03 

Mn IN ILMENITE, ATOMS PER 3 OXYGEN

FIGURE 12.—Manganese content of coexisting garnet 

and ilmenite (as inclusions in garnet) in sample 

356-1. The high-manganese points were taken from 

the core of a large garnet; one of the low-manganese 

points was from the rim of the same crystal, and the 

other points were from the rim of another small 

garnet crystal.

TOURMALINE

Tourmaline is a common accessory mineral in the 

pelitic rocks, especially of the Everett Formation. 

These crystals are as much as 0.1 mm across, are 

commonly strikingly zoned, and have a honey-yellow 

core and smoky blue-gray mantle. The cores have 

rounded outlines and presumably were detrital 

heavy-mineral grains in the sediment. However, the 

mantles are metamorphic, because they have irregular, jagged to euhedral outlines and also because 

larger grains actually contain preexisting foliation 

as dusty trains of inclusions (fig. 13).

QUARTZ

Quartz is ubiquitous in the assemblages studied 

(table 1) and is the only polymorph of silica found. 

All mineral assemblages are assumed to have equilibrated with it. In low-grade clastic rocks, some 

quartz-rich layers show marked cataclastic texture. 

In higher grade rocks, on the other hand, such textures are not found, and quartz is present as discrete 

grains; in quartzite beds, it commonly assumes poly-
22 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

FIGURE 13.—Photomicrographs of tourmaline. A, Zoned 

tourmaline characteristic of tourmaline found in the area; 

a light-yellow core having rounded (detrital?) outline is 

mantled by a dark-bluish-gray overgrowth; sample 509-1 

(plane-polarized light). B, A mantle of tourmaline showing 

inclusion of a preexisting metamorphic foliation; sample 

102-2 (plane-polarized light).

gonal contact relations, indicating the approach to 

textural equilibrium.

Veins and stringers of quartz are common in the 

higher grade pelites; these are interpreted as having 

been secreted out of the rock rather than having been 

introduced. In some members of the Stockbridge Formation, vein quartz and nodular quartz are common, 

and these form nuclei for the growth of tremolite. 

Such vein and nodular quartz is never found in the

low-grade stratigraphically equivalent beds. However, these lower grade beds do contain chert nodules 

and even chert beds as much as half a meter thick ; 

the quartz in the higher grades is presumed to be 

metamorphosed chert.

MODEL MINERAL COMPOSITIONS

To facilitate calculations of balanced reactions in 

the subsequent sections of this report, reasonable 

model mineral compositions must be assumed where 

actual data have not been determined or where univariant reactions must be hypothesized on the basis 

of divariant reactant and product assemblages. The 

following sections include the model mineral compositions used. These compositions are based on the 

microprobe data of table 3. Except for the ironmagnesium proportions for the ferromagnesian 

phases and the potassium-sodium proportions of 

white mica and alkali feldspar, the compositions 

probably are good depictions of the actual phases. 

Epidote and hornblende contain ferric iron ; iron in 

the model compositions of the other minerals is 

ferrous.

STAUROLITE

The model staurolite composition used is 

H(Fe,Mg) 2Al9Si4024 .

Iron is variable in the range 1.75-1.85 ; a useful approximation is FeLgsMgo.is.

CHLORITOID

The model chloritoid composition is 

H2 (Fe,Mg)Al2Si07 .

A useful approximation is both ±0.02.

GARNET

The model garnet composition used is 

(Fe,Mg,Ca,Mn) 3Al2Si3 012 .

The divalent cation proportions range widely: Calcium from 0.2 to 0.7, and iron from 2.0 to 2.7. The 

spessartitic component is subtracted out completely 

in the calculations. A useful approximation of the 

Fe/(Fe + Mg) ratio is 0.95.

CHLORITE

The model chlorite composition used is 

H8(Fe,Mg) 4. 5Al3Si2 . 5 018.

This formula differs from the formula of Pauling 

(1930) and the modified formula suggested by 

Thompson and Norton (1968) but seems to accord
A MODEL MULTISYSTEM 23

much better with the chemical analyses of metamorphic chlorites from pelitic rocks (Zen, 1960) and the 

present set of microprobe data. Most of the chlorites 

have a Fe/Mg ratio of 2.5/2, which is a useful approximation. The proportion may deviate from that 

value, and, where available, actual values are used in 

the calculations.

BIOTITE

The model biotite composition used is

H2K0 . 9 (Fe,Mg) 2.66Ali.TTSi 2 .6TOi2.

This formula, based on the microprobe data, balances 

the total cation charge (24) as well as the total number of octahedral and tetrahedral sites occupied (7). 

The Fe/Mg ratio is generally about 1.5/1.1 but 

varies a little (fig. 3).

MUSCOVITE

The model muscovite composition is 

H2KAl3Si3 012 .

The microprobe data show this ideal formula to be a 

good approximation of actual muscovite, the main 

deviations being the phengitic substitution in a few 

low-grade rocks (fig. 2) and the Na=K substitution. 

The paragonitic component, however, is minor.

EPIDOTE

The model epidote composition used is 

HCa2 (Al2Fe3 +)Si3 013 .

This is a good approximation of the actual microprobe analyses. The ferric iron substitution for aluminum is nearly constant at one atom per formula as 

given.

HORNBLENDE

The hornblende from the area is uniformly high in 

the tschermakitic component (Doolan and others, 

1978). The calculations involving hornblende used 

the average analyses for the appropriate rocks, 

slightly simplified (analyses of sample 161-1 are reported in table 3, section H\ analyses of 102-1 and 

289-2 were reported by Doolan and others, 1978) : 

Sample 161-1:

Sample 102-1 : H2Nao.44Ca1 . 63Fe2 +2Mg1 .o2Fe3o+5

Sample 289-2: H2Na0 .39Ca1 . 79Fe2+Mg1 .39Fe3 +

PLAGIOCLASE

Formulas of the end-member components are used 

for plagioclase.

KYANITE

The ideal formula of kyanite, Al2Si05 , is used.

A MODEL MULTISYSTEM

Most of the mineral assemblages observed involve 

various combinations of nine principal minerals: 

garnet, staurolite, chloritoid, chlorite, biotite, musl covite, plagioclase, epidote, and quartz. Other obj served minerals are hornblende, cummingtonite, ilmenite, magnetite, paragonite, kyanite, potassic 

feldspar, and tourmaline. However, if the assemblages restricted to the nine principal minerals are 

explained, the presence of additional minerals can 

be more readily explained by an extension of the 

theory.

If the An end member of plagioclase alone is considered, and if the other minerals are confined to 

those components given by the model compositions, 

then the system can be defined by the eight-component system: Si02 , A12 03 , Fe, MgO, CaO, K2 0, H2 0, 

and 02 . Because quartz is ubiquitous and if both 

H2 0 and oxygen are boundary-value components,4 

the minerals are reduced to a simple quinary multisystem of one negative degree of freedom. Such a 

multisystem has eight invariant points which may 

be labeled by the missing phases as (Ga), (St), 

(Cd), (Ch), (Bt), (Mu), (Pg), and (Ep). These 

points are connected by univariant lines bearing 

symbols of two missing phases, the enclosed divariant areas bear triple labels, and so on. The system 

is degenerate because muscovite and biotite must 

appear in pairs on opposite sides of a reaction and 

because garnet, epidote, and plagioclase (anorthite) 

are the only calcium-bearing phases, so that the 

three invariant points (Ga), (Ep) and (Pg) lie 

on a smooth univariant loop. Mu and Bt are 

not directly connected but are indirectly connected 

through one of the other invariant points (Zen, 

1974). As a result of the degeneracy, only 19 distinct univariant lines are in the multisystem instead 

of the full number of 8!/6!2! = 28 lines. All the 

points except (Mu) and (Bt) have seven univariant 

lines emanating from them; the points (Mu) and 

(Bt) have only six emanating lines.

* The validity of the assumption is, of course, arguable (see Rumble, 

1974). For the volatile HsO, I prefer to retain this assumption and use 

other nonvolatile components such as CaO to explain the observed assemblages, unless it is necessary to do otherwise.
24 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

MM

MM

FIGURE 14.—Closed net for the quinary multisystem Al2Oc-FeO-MgO-CaO-K20 for the phases epidote-garnet-plagioclasechlorite-chloritoid-staurolite-biotite-muscovite in the presence of quartz and having H20 and 02 as boundary-value components. Abbreviations: Ep, epidote; Ga, garnet; Pg, plagioclase; Ch, chlorite; Cd, chloritoid; St, staurolite; Bt, biotite; 

Mu, muscovite; Q, quartz; W, water; and Ox, oxygen. The model compositions of the text were used to balance the reactions. Pseudodivariant fields are labeled with italic letters for easy reference.

The complete closed net for the multisystem is 

shown in figure 14. The figure involves also 15 indifferent crossings. The topology of the net is determined by balancing the 19 univariant reactions. 

Only three distinct reactions are independent, and

these define the entire net; all other reactions are 

linear combinations of these three.

The closed net has a stable part and a metastable 

part, corresponding to the upper and lower parts of 

the representation polyhedron (Zen, 1966). Deter-
A MODEL MULTISYSTEM 25

mination of which set of points constitutes the 

stable part and which constitutes the metastable 

part is straightforward if, for a given choice of 

intensive plotting variables, the values for the conjugate extensive variables are known. For example, 

if we choose the chemical potential of H2 0 and 

total pressure to be the plotting intensive variables 

(isothermal and iso-/*02 sections), the conjugate 

extensive variables are the number of moles of H2 0 

released for a given reaction and the change of volume of the solid phases for the same reaction. The 

former is given directly by the balanced univariant 

reactions; the latter is obtainable from tabulated 

molar volume data for minerals (for example, Robie 

and others, 1967). The molar volumes I used take 

into account the fact that the model compositions 

are generally those of solid solutions; the corrections are simply linear combinations of end-member 

volumes because more refined data are not available 

and constitute second-order corrections. The data 

used are given in table 6, as are the bases for their 

derivation.

Knowledge of the molar volumes and of the amount 

of H2 0 released in the reactions then permits calculation of the slopes of the univariant lines in 

-FV-/AW (pressure on the solid-chemical potential of 

H2 0 ) space and also permits the unambiguous orientations of the Schreinemakers bundles (Zen, 

1974). These bundles consist of invariant points and 

associated univariant lines and belong to one of two 

groups depending on their mutual consistency. The 

closed areas of each partial net constructed from 

the consistent bundles contain phase assemblages 

unique to each partial net, so that comparison with 

observed mineral assemblages decides which is the 

stable and which is the metastable net (Zen, 1974).

By application of this approach, the eight invariant points (fig. 14) are placed into two groups: 

(Mu), (Ch), (Pg), and (Ga) in one group and 

(St), (Bt), (Ep), and (Cd) in the other.5 The

6 For the purpose of this construction, I used for chloritoid the composition appropriate to the analyzed sample from the lowest grade rock 

containing this mineral, namely 140-2, having a (Fe + Mn)/Mg atomic 

proportion of 0.88/0.12 (table 4) instead of the mean value of 0.86/0.14. 

Use of this chloritoid composition enables us to include the invariant 

point (St) on figure 15 without in any way changing the topology of 

the grid at the other invariant points and -with but insignificant changes 

in the values of the slopes around these other points. Inclusion of (St) 

permits the study of low-grade reactions and is thus desr'rable. The drastic 

effect of a small compositional difference of chloritoid on the net is 

more apparent than real and is the result of the facts (1) that the univariant line (Ep, St) is nearly independent of pressure and (2) that a 

slight change in the stoichiometric coefficients of the reaction changes the 

sign of the slope. Note that even though figure 15 uses pressure and 

the chemical potential of HaO as the independent variables, the diagram 

can be qualitatively extended to P-T (pressure-temperature) sections because the main effect of temperature increase is dehydration, precisely 

the same as that of isothermal decrease of the activity of HaO.

closed areas are defined by the labels of the invariant points of each group. The four-point partially 

closed net consisting of (St) (Ep) (Cd) (Bt) has 

these possible unique assemblages:

1. (Ep,Bt,Cd,);

2. (Ep,Bt,St);

3. (Ep,Cd,St); and

4. (St,Bt,Cd).

The other four-point partially closed net has the 

unique assemblages:

5. (Mu,Ch,Pg);

6. (Mu,Ch,Ga);

7. (Mu,Pg,Ga); and

8. (Ch,Pg,Ga).

Assemblages 5, 6, and 7 can be dismissed because 

they cannot coexist with muscovite which is observed in every sample. Assemblage 8 can be dismissed because all observed chloritoid-bearing assemblages have chlorite. On the other hand, assemblages 1 through 4 are all observed (for example, 

sample 355-1 contains assemblage 1, 16-1 contains 

assemblage 2, 370-2 contains 3, and 62-1 contains 

4; see table 1). Therefore, I conclude that this partially closed net is the correct one for the area; this 

is shown in figure 15. The net contains three of the 

fifteen possible indifferent crossings; the others are 

excluded either because they are unique to the other 

net or because the numerical values of the slopes on 

the Ps —fjw projection exclude the intersection of the 

lines.

The net was constructed by assuming that oxygen behaved as a boundary value component. If 

oxygen is an initial value component so that the 

value of its chemical potential is determined by the 

buffered assemblage itself, then the multisystem 

has one more independent component without adding a phase. Because one more phase may be added 

without changing the variance, epidote (of variable 

composition) or another mineral containing ferric 

iron (magnetite, hematite) may be found with the 

assemblages. Alternately, one or more of the other 

minerals may show variable amounts of ferric iron. 

The nature of the mineral assemblages, to be discussed in the following sections, shows that this 

possible interpretation is compatible with the observations but is hardly necessary.

It cannot be overemphasized, as the examnle given demonstrates, that 

the assignment of invariant points and indifferent crossings to the two 

sets depends on numerical values of the slopes, which, given the nature 

of the Schreinemakers bundles, decide the orientations of the bundles 

in the chosen intensive-variable space. These slopes represent differences of 

large numbers, some having large uncertainties. Therefore, if molar 

volumes of the minerals are refined and if different mineral compositions 

are assumed, the results could be changed.
26 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

(Ch)

1 bar

FIGURE 15.—A part of the multisystematic net of figure 14 containing the four invariant points (St), (Ep), (Bt), and 

(Cd). This partial net predicts assemblages in conformity with those observed. The model compositions of the minerals 

(except chloritoid, see footnote, p. 25 for discussion) and the molar volumes given in table 6 were used in orienting 

the diagram and determining the scales. Labels with italic letter® of pseudodivariant fields are same as in figure 14.

PROBLEMATIC PHASE RELATIONS

The mineral assemblages in the study area that 

are summarized in table 1 present a few interesting 

problems. In this part of the paper, these problems 

rather than the details of each mineral assemblage 

are discussed. An understanding of the solutions 

to the problems will greatly aid in clarifying the 

relationships among the mineral assemblages and 

will provide a model describing the progressive 

evolution of these assemblages.

FIRST APPEARANCE OF CHLORITOID

The reaction leading to the first appearance of 

chloritoid is not well understood. Some of the possible reactions have been reviewed by Frey (1969) 

and Zen and Thompson (1974). Thompson (1972)

suggested the reaction chloriteH-hematite=chloritoid + magnetite, thus relating the appearance of 

chloritoid to the change of the rock color from 

purple (chloriteH-hematite) to green, as purple 

rocks seldom lack chlorite. In western Vermont 

(Zen, 1960), as well as in the study area, however, 

many green pelitic rocks, some containing magnetite and some not, do not contain chloritoid; others 

have chloritoid but no magnetite. In western Vermont, rocks stratigraphically equivalent at lower 

grades to these green rocks are purple. Therefore, 

the coupling of the color change and appearance of 

chloritoid cannot be a general phenomenon.

Frey (1969, p. 115) suggested that the reaction 

in the Keuper Formation of central Switzerland 

that led to the formation of chloritoid was between 

an aluminous chlorite and titaniferous hematite to
PROBLEMATIC PHASE RELATIONS 27

form chloritoid, rutile, and a less aluminous chlorite. 

The microprobe data of samples from the study area 

and previously published chemical analyses of chlorite (Zen, 1960) do not show a decrease of aluminum content of chlorite upon the appearance of 

chloritoid; no indication exists that titanium participated in the formation of chloritoid, and no 

rutile is found. Therefore, the reaction suggested 

previously (Zen, 1960) may be valid: chlorite+ 

paragonite = chloritoid+albite. If H2O is assumed 

to be a boundary-value component, this reaction in 

the presence of quartz involves the components 

sodium, iron, magnesium, and aluminum. All four 

phases (and quartz) could coexist under divariant 

conditions. If the plagioclase contains calcium and 

no other calcium mineral is present, the system is 

even trivariant, and the four-phase assemblage may 

be widely expected. In western Vermont, the chloritoid-chlorite assemblage is found only with paragonite, not plagioclase (Zen, 1960). In the present 

study area, both paragonite and plagioclase, together or singly, are found with the chlorite-chloritoid pair (table 1). This coexistence could be 

caused by the addition of the calcium component 

in plagioclase in the Massachusetts rocks but could 

mean that these rocks are more anhydrous (higher 

grade) than those of Vermont.

THE CHEMOGRAPHY OF GARNET AND THE 

BIOTITE-CHLORITOID-GARNET-CHLORITE RELATIONS

In the study area, biotite and chloritoid are commonly found together. They generally form stout 

porphyroblastic laths in intimate association without sign of reaction (fig. 16) or indication that they 

formed during different episodes of metamorphism. 

The presumption must be that these two minerals 

formed together in a state of at least local equilibrium. Albee (1972) and other workers have discussed possible reasons why this biotite-chloritoid 

assemblage is found instead of the common assemblage of almandine-rich garnet, chlorite, and muscovite in pelitic rocks of the garnet zone and the lower 

grade part of the staurolite zone.

Albee (1972) suggested that, in the presence of 

quartz and muscovite, the chlorate-garnet join is 

broken at higher temperature to yield the chloritoidbiotite pair in rocks having the appropriate bulk 

ratio of magnesium to iron. The mineral assemblages 

from the area provide data to test this hypothesis.

Almandine-rich garnet is present in 117 assemblages of the rocks examined petrographically in 

this study (table 1). Without exception, the rocks 

containing garnet are pelitic. All but nine of these

garnetiferous rocks also carry chlorite. Excluding 

rocks that contain chloritoid only as inclusions 

within garnet, which may not have formed in equilibrium with the minerals outside of the garnet, 

14 rocks contain the four-phase association garnetchlorite-chloritoid-biotite (plus quartz, muscovite, 

and plagioclase). Only two assemblages (466-1 and 

466-2) show the chloritoid-biotite-chlorite-muscovite association without garnet; these are found at 

the garnet-staurolite zone boundary. To a good first 

approximation, the biotite-chloritoid association is 

coextensive with the garnet-chlorite-muscovite association and is not complementary to it, as it would 

be if a reactive relation always existed between 

them (both Albee's sample 242-c from "Patterson 

Knob" in his 1972 study and my sample 103-1 are 

from the same outcrop; on the U.S. Geological Survey topographic map of Bashbish Falls Quadrangle 

(1958), it is a knob identified by the triangulation 

station "Patterson").

Of the 14 assemblages of chloritoid-chlorite-biotite-garnet sampled in the area, four have been 

studied by use of the electron microprobe, whereby 

each of the phases was analyzed. The results are 

presented in table 3, but for convenience, these are 

gathered together as average values of cations per 

formula for each mineral from each rock and are 

presented in table 7. In addition, one sample (339-1) 

for which the chloritoid was found only as inclusions in the cores of almandine crystals was also 

analyzed, and the results are given in table 7. Results for sample 466-1, which contains the chloritoid-biotite pair without garnet, are also given in 

table 7 for comparison.

From the data, one could next calculate the balanced chemical reactions involving the transition 

from the garnet-chlorite assemblage to the chloritoid-biotite assemblage. The calculations are analogous to those used for the model multisystem, except 

that the actual iron-magnesium values for garnet 

and biotite (table 6) were used and the system was 

assumed to be lime free. The chlorite formula was 

further tested by using two different versions. 

One formula suggested by Thompson (1957) and 

Thompson and Norton (1968) may be written as 

(Fe,Mg) 4.67Al2 . 67 Si2.67O10 (OH)8; the second, the 

model formula (Fe,Mg) 4.5Al3Si2 .5Oio(OH) 8 , makes 

the (Fe,Mg)/Al ratio of chlorite equal to that of 

almandine-pyrope garnet. Balanced chemical reactions using all five garnet-bearing assemblages of 

table 7 lead to these conclusions:
28 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

FIGURE 16.—Photomicrographs of chloritoid (Cd)-biotite (Bt) assemblages. A, Sample 338-1, with chlorite (Ch), garnet 

(Ga), and muscovite (Mu). B, Sample 234-1, with chlorite (Ch), staurolite (St), muscovite (Mu), plagioclase (Pg), and 

ilmenite (Ilm). C, Sample 103-lA, with garnet. D, Sample 509-lA, with garnet (Ga) and chlorite (Ch). All, plane-polarized light.

1. The proportions of the phases participating in 

each reaction are nearly independent of the 

choice of chlorite formula, although for stoichiometric reasons, the more aluminous formula leads to a constant relation between the 

amount of biotite and the amount of chloritoid 

for all five assemblages.

2. The stoichiometric coefficients of each phase participating in the reaction are nearly independent of the Fe/Mg ratios of the phases.

3. A small amount of quartz (about 2 moles per 

mole of chlorite) is needed on the biotite + 

chloritoid side to balance all five reactions.

4. A small amount of H2O is released (about twothirds mole per mole of chlorite) upon the 

formation of biotite+chloritoid. This release 

of H2O confirms Albee's (1972) conclusion 

that the biotite-chloritoid assemblage is of 

higher grade than the garnet-chlorite assemblage, everything else being equal. The amount 

of H2O released, however, is small.
PROBLEMATIC PHASE RELATIONS 29

In the calculations, the manganese and equivalent 

amounts of aluminum and silicon in the garnet have 

been subtracted. This may seem a bad approximation because the manganese content, in relative 

divalent cation proportions, is an order of magnitude greater in garnet than in the other phases. 

However, the rims of the garnets are considerably 

less manganese rich than are the cores, and the data 

in table 7 are averaged without regard to the position of the analyzed spot in the garnet. I presume 

that the phases that would have reacted initially 

would have had compositions corresponding to those 

of the rims.

The data in table 7 for sample 466-1 show that 

the chloritoid, chlorite, and biotite of this assemblage are not discernibly different from those of 

the other assemblages. The sample came from near 

the boundary of the staurolite-garnet zones and is 

approximately isogradic with specimens 103-1 and 

103-2. Pelitic rocks on both sides of the isograd 

(for example, samples 448-1, 366-2, 463-1, and 

468-1) carry garnet (rtstaurolite). Thus, the lack 

of garnet in samples 466-1 and 466-2 is probably 

due to the bulk composition of the rocks rather than 

to metamorphic grade.

In interpreting the data of table 7, one must remember that the 16 biotite-chloritoid assemblages 

are found evenly distributed in the garnet zone and 

in the lower grade part of the staurolite zone (table 

1). Except for samples 466-1 and 466-2, all these assemblages contain garnet and chlorite, and the minerals show no evidence of disequilibrium and reaction, indicating that these "alternative" assemblages 

are in fact equilibrium assemblages. Moreover, because so many biotite-chloritoid-garnet-chlorite assemblages were found to be widely distributed in the 

study area, the observed relations probably are not 

the result of the samples having been obtained by 

chance on an univariant reaction surface. If the biotite-chloritoid-chlorite-garnet-muscovite assemblages 

are divariant or have even higher variancy, clearly 

more components than K2 0, FeO, MgO, and A12 03 

( + Si02 and H20) must be considered in a model 

multisystem. Possible candidates are Fe2 0a , Ti02 , 

MnO, CaO, and Na2 0.

In the phase rule sense, we may rule out Na20 

because it is an essential component of plagioclase, 

a ubiquitous phase in these assemblages. Ti02 is only 

a trace component in all the phases, and ilmenite 

is generally present in the assemblages. The microprobe data cannot show the amount of ferric iron 

in the phases, and the rocks do not carry hematite 

and rarely carry magnetite, so this component cannot be definitely excluded. The stoichiometric calculations of chloritoid and garnet analyses indicate 

that ferric iron cannot be important in these minerals, but it may be important for biotite and especially chlorite. Although optically the chlorites in 

these assemblages do not appear to be oxychlorites 

(Chatterejee, 1966), ferric iron in fully hydrated 

chlorite cannot be distinguished optically. Hey 

(1954) proposed a regression equation for ferriciron content versus refractive index; however, the 

standard deviation of the results on which the regression was based is about equal to Hey's reported 

total range of iron (0 to about 3 atoms per 18 oxygen), so the use of the equation is not practical. 

(See equation 1, Deer, Howie, and Zussman, 1962, 

p. 152.)

The manganese and (or) calcium content of garnet potentially could explain the assemblages. The 

microprobe and wet-chemical analyses of garnets 

(tables 3, section F, and 4) show that both components are almost never absent from garnet. Manganese is strongly concentrated toward the cores of 

the garnets; calcium content tends to be uniform 

in garnet of a given rock, although it changes sensitively in different rocks and different mineral associations and can occupy as many as one-fourth of 

the total divalent cation positions for hornblendebearing rocks. It is not possible to decide whether 

MnO or CaO is responsible for the assemblages. 

However, because of the factors just mentioned, including the different distribution of manganese and 

calcium in garnet, biotite-chloritoid and garnetchlorite-muscovite are considered not to be alternative assemblages but to represent different chemographic regions, the latter association being in rocks 

containing more calcium than can be absorbed in 

the plagioclase. In pelitic rocks containing the garnet-chlorite-muscovite assemblage, garnet is not a 

phase truly belonging to the AFM projection of 

Thompson (1957) but is interior to a ACFM tetrahedron.6

The conclusions discussed form the principal basis 

for the choice of the model mineral compositions in 

the multisystem shown in figure 14. As shown in 

figure 14, the reaction proposed by Albee (1972), 

now taking into account the effect of calcium in 

garnet, becomes the curve (Ep, St); the chloritoidbiotite-anorthitic plagioclase assemblage is the

6 Table 3, section F, shows in fact that only one rock contains nearly 

calcium-free garnet. This is sample 487-2, whose garnet contains the normal 

allotment of calcium in the core but is nearly free of calcium toward the 

rim. The assemblage is garnet-chlorite-cummingtonite-magnetite-biotitequartz and has only traces of muscovite and no plagioclase.
30 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

drier and denser equivalent of the garnet-chloritemuscovite assemblage.

However, the plagioclase in assemblages from 

the study area is a solid solution rich in the Ab 

component, and the assemblages do not have a second sodium-bearing phase, except the solid solution 

of sodium in muscovite (none of the paragonitebearing rocks have the assemblage being discussed). 

Therefore, the assemblage garnet-chlorite-biotitechloritoid-plagioclase-ttiuscovite-quartz occupies a 

divariant field (fig. 15) and does not lie merely 

along a univariant line. The fields in which the assemblage is stable are below and to the right of the 

lines (Pg, Ep) and (Ep, St).

Sample 466-1, containing the assemblage chloritoid-biotite-muscovite-chlorite-plagioclase-quartz, 

without garnet, is found close to rocks containing 

both garnet and staurolite. The absence of garnet 

is interpreted to reflect composition of the rock 

rather than conditions of metamorphism. Likely 

divariant fields where the assemblage could have 

formed are fields U and R in figure 15.

Crawford's (1974) discussion of the buffer relation between a calcium-bearing garnet and a calcium-bearing plagioclase in pelitic rocks was modeled on the experimental work of Boettcher (1970) 

on the CaO-Al2 03 -Si02-H2 0 system. Reactions suggested by Crawf ord are

low-calcium garnet+calcic plagioclase

= high-calcium garnet+sodic plagioclase

+ aluminum silicate + quartz,

low-calcium garnet+calcic plagioclase + biotite

= high-calcium garnet+ sodic plagioclase 

+ muscovite+chlorite + quartz, 

and

low-calcium garnet + calcic plagioclase+ H2 0

— high-calcium garnet+sodic plagioclase 

+ staurolite + quartz.

None of these reactions as such can be applied to 

our rocks. The possibility of a buffer reaction cannot be adequately represented by the proposed multisystem, which assumes fixed phase compositions. 

A likely reaction might be

low-calcium garnet+calcic plagioclase+biotite 

+ chloritoid + H2 0 + quartz

^high-calcium garnet+sodic plagioclase 

+chlorite + muscovite.

This reaction is analogous to the limiting reaction 

depicted by the line (St, Ep) on figure 15.

In a study of garnet-staurolite-biotite assemblages from Nova Scotia, Phinney (1963) suggested

that the CaO component may significantly affect the 

nature and compositions of the assemblages. Phinney's argument, based on the behavior of tielines 

of coexistent phases, was later shown to be noncompelling (Greenwood and others, 1964). However, Phinney's initial conclusion may remain valid, 

and his assemblages may provide a higher grade 

analogy with the phase relations observe^ in my 

area.

Rumble (1974) studied some pelitic ro^.ks in western New Hampshire that carry assemblages including garnet, chloritoid, chlorite, kyanite, and staurolite. He found apparent crossings of tielines as 

well as too many phases in the AFM projection of 

Thompson (1957). Rumble was able to unscramble 

the tielines by projecting the assemblages through 

muscovite and kyanite or an iron end member of 

staurolite onto the H2 0-FeO-MgO plane. He therefore suggested that the assumption of boundaryvalue component status for H2 0 is invalid and that 

strong gradients in the chemical potential of H2 0 

existed during metamorphism. This suggestion may 

be correct, but the inclusion of another component 

is bound to reduce the problem of excess phases. 

Rumble's projection through muscovite and kyanite 

sidesteps the problem of crossing tielines because 

the problematic assemblages are not visible from 

the kyanite projection point. Projection from an 

idealized iron-staurolite may or may not be valid 

because staurolite is not fixed in composition and 

assemblages including non-end-member compositions of this mineral are those that most commonly 

appear to violate the phase rule. Thus, although 

Rumble's suggestion is stimulating, I have chosen 

not to utilize it in explaining my assemblages because his rationale is not necessary.

CHLORITOID-STAUROLITE RELATIONS

In recent years, many experimental and observational studies have been made on the phase relations 

of coexisting staurolite and chloritoid in metamorphic rocks. Ganguly (1968, 1969, 1972) studied the 

experimental phase equilibrium relations of both 

minerals. Grieve and Fawcett (1974) studied the 

stability relations of chloritoid and revised the earlier results of Halferdahl (1961). Richardson (1968) 

and Hsu (1968) worked on the upper stability of 

staurolite. Hoschek (1967, 1969) studied the stability of staurolite in multicomponent systems approximating the compositions of pelitic rocks. These are 

but some important studies among many.

As use of the electron microprobe has become 

widespread, chemical data on coexisting staurolite
PROBLEMATIC PHASE RELATIONS 31

and chloritoid also have become increasingly available. These data, coupled with the observation that 

chloritoid and staurolite are commonly found together without obvious evidence of one mineral 

growing at the expense of the other, led to the appreciation of the fact that these minerals form coexisting pairs in rocks of suitable composition. The 

compositions of these pairs, as well as their reaction 

relations, are of considerable interest.

Of the mineral assemblages studied, 46 contain 

staurolite. Among these, ten also contain chloritoid 

as a groundmass phase. The compositions of five of 

these coexisting staurolite and chloritoid pairs have 

been studied by use of the microprobe and are given 

in table 3, sections D and E. Sample 339-1 (table 3, 

sections D and E, and table 7) contains staurolite 

in the groundmass, but the chloritoid is present as 

inclusions in the core parts of the garnet. The chemical data are useful for comparison.

Albee (1965, 1972) studied the chemographic relations of chloritoid and staurolite and made good 

use of the graphical technique of Thompson (1957). 

Hoschek (1969), in part on the basis of his experimental phase equilibrium studies, proposed two possible reactions involving chloritoid and leading to 

the appearance of staurolite:

chloritoid+aluminum silicate=staurolite+ 

quartz + H2 0,

chloritoid+quartz=staurolite+garnet+H2 0.

Schreyer and Chinner (1966) made microprobe 

studies of the Fe/Mg ratios of some coexisting 

chloritoid and staurolite from Big Rock, N. M., and 

concluded that chloritoid is slightly more siderophile than the coexisting staurolite. This relation, 

if true, would seem to suggest that Hoschek's second 

reaction for the derivation of staurolite is more 

probable. However, Rumble (1970, 1974), also using 

the microprobe, found that coexisting staurolite and 

chloritoid from a single formation from western 

New Hampshire have identical Fe/Mg ratios in the 

presence of garnet; however, in assemblages without garnet, the chloritoid is more magnesium rich 

than is the coexisting staurolite. Because the garnet 

that coexists with chloritoid and staurolite shows the 

highest Fe/Mg ratio of the three minerals, Rumble 

(1970) advocated a reaction of the type

quartz+chloritoid+aluminum silicate

=garnet+staurolite+H2 0.

In fact, however, the chemographic relations given 

by Rumble show that the components of garnet+

staurolite and chloritoid+aluminum silicate are 

mutually indifferent in the AFM projection.

Fox (1971), Albee (1972), and Fed'kin (1975, p. 

74) produced new microprobe data on coexisting 

staurolite and chloritoid from different metamorphic 

areas. Albee showed that for the samples analyzed, 

staurolite always has a higher Fe/Mg ratio than the 

coexisting chloritoid does and that this ratio is even 

higher in the coexisting garnet. Average Fe/Mg 

ratios and standard deviations of these coexisting 

minerals in my study area were calculated from the 

data given in table 3, sections D, E, and F, and are 

presented, as follows (figures in parentheses are the 

numbers of ratios averaged) :

Sample Chloritoid Staurolite Garnet

234-1 

331-1 

369-1 

463-1 

506-1

5.3±0.5 (2) 

5.7±0.3(8) 

6.4+0.2(4) 

5.7+0.3(6) 

6.4+0.2(4)

7.7+0.9(3) 

7.2+0.5(6) 

8.7+0.3(2) 

6.3+0.4(2) 

7.5+0.6(3)

11.6+1.1(2) 

11.9+1.0(9) 

14.4+1.9(4) 

11.3+1.5(3) 

12.1+0.4(4)

Thus, my data, as well many of Rumble's new 

(1974) data, are entirely in accord with Albee's 

conclusions. The data indicate that none of the 

three reactions listed above could account for the 

first appearance of staurolite because opposite sides 

of each reaction form compositionally indifferent 

systems.

The contradiction between Albee's, Fox's, and 

my data and those of Schreyer and Chinner remains 

unexplained. Taking the different chemical data 

together, one might be tempted to conclude that the 

relations indicate an extremal type of phase relations between chloritoid and staurolite (see summary by Khlestov, 1972); however, the evidence is 

permissive at best, and such a conclusion seems to 

be premature. Another possible explanation is that 

different extents of ferric iron substitution for aluminum might affect the Fe/Mg ratios, because 

nearly all the data are derived by the microprobe. 

Albee's data (1972) do not readily lend themselves 

to sorting out possible Fe3+ =Al substitution. However, on the basis of stoichiometry, the data of table 

3 and of Fox (1971) show that these chloritoids are 

virtually free of ferric iron. If ferric iron is important in staurolite, then the correct Fe2 +/Mg ratio 

would show staurolite to be less siderophile than 

indicated by the microprobe data, thus conforming 

better with the results of Schreyer and Chinner 

(1966). Staurolite from sample 355-1, already discussed, does not support the idea of significant 

ferric-iron contribution. The microprobe data also 

calculate out to a nearly full complement of alu-
32 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

minum (9 per 24 oxygens). On the basis of these 

data, as well as those of Fox (1971), ferric iron 

does not seem to be an important component of 

staurolite in coexistence with chloritoid, and the 

relatively higher Fe/Mg ratio in staurolite seems 

real.

The very lowest grade appearance of staurolite 

(or the very highest grade disappearance of chloritoid) in pelitic schists must involve a reaction or 

reactions in which, except for phases in excess, 

staurolite appears alone on the product side (or 

chloritoid appears alone on the reactant side). Considering the chemical compositions of coexisting 

chloritoid, staurolite, and garnet, and ignoring for 

now the calcium and manganese contents of garnet, 

the most likely reaction for the lowest grade appearance of staurolite in rocks from the study area 

seems to be of the type 

chloritoid + garnet + aluminum silica te=staurolite.

Using the calcium- and manganese-free model 

composition of phases, a possible balanced reaction 

for the above is

chloritoid + garnet+7 pyrophyllite

= 2 staurolite+ 3 quartz+ 7 H2O.

In this reaction, muscovite cannot be a reactant 

because otherwise biotite would have to be formed, 

contrary to hypothesis. The paragonitic component 

or paragonite (Pa) as a phase could participate, 

however; a schematic reaction, using the model compositions of phases, is

4 quartz + chloritoid + garnet+ 7 paragonite

= 2 staurolite+ 7 albite + 7 H2O.

Muscovite can appear on the product side, and 

so a possible reaction is

garnet+biotite + aluminum silicate

= staurolite+ muscovite

However, such a reaction would imply the absence 

of the staurolite-chloritoid join upon the first appearance of the former, which seems to contradict 

petrographic observations. It also requires a biotitealuminum silicate assemblage, which has not been 

observed, below the staurolite zone.

Reaction among biotite, chloritoid, and aluminum 

silicate is chemically indifferent to staurolite in the 

AFM projection, as is a reaction involving chlorite 

in place of an aluminum silicate polymorph; neither 

reaction can lead to the first appearance of staurolite.

After staurolite becomes intrinsically stable, its 

appearance in rocks of suitable composition can result from switching one or more tielines. If staurolite formed originally in the chloritoid-garnetaluminum silicate compositional field as postulated, 

then the next higher grade reaction may be of the 

sort

chloritoid + aluminum silicate = chlorite + staurolite. 

(See also discussions by Thompson and Norton, 

1968.)

Three reactions that can be written using the 

model compositions are

23.35 pyrophyllite+ 25.58 chloritoid

= 10.54 staurolite + chlorite+ 39.65 H2O

+ 74.31 quartz,

23.35 kyanite +25.58 chloritoid

= 10.54 staurolite+chlorite +16.31 H2O

+ 4.27 quartz,

and

23.35 paragonite+ 25.58 chloritoid+ 19.08 quartz

= 10.54 staurolite+chlorite+ 23.35 albite

+ 39.65 H2O.

Note that chlorite is the prograde mineral despite 

its high degree of hydration. These reactions are 

analogous to that for the staurolite-chlorite isograd 

proposed by Fox (1971) and may reasonably be 

supposed to describe the formation of much of the 

staurolite marking the staurolite zone mapped in 

figure 1. Because paragonite has been observed in 

the garnet zone (tables 1 and 2), the reaction involving paragonite may be the one that actually 

took place.

The nature of the mineral assemblages observed 

and the compositions of individual minerals show 

that the next plausible reaction is as follows, where 

the stoichiometry is based on the model compositions used previously:

chlorite+ 2.01 muscovite+ 4.21 chloritoid

= 2.23 biotite+1.50 staurolite + 7.23 H2O

+ 0.78 quartz.

This reaction is (Ep, Pg) = (Ep, Ga) of figure 15 

(the Fe/Mg ratios of the phases can change rather 

extensively without affecting the qualitative nature 

of the reaction). This reaction belongs strictly to 

the AFM projection on the basis of considerations 

already given to the mineral compositions. It constitutes a tieline switch above the staurolite-chlorite 

isograd that breaks up the chloritoid-chlorite compatibility. Each of the three-phase subsystems derived from the above tieline switch can have garnet 

as another phase to form two sets of two assemblages each. Before chloritoid-chlorite (-muscovite) 

ceases to be stable, the possible assemblages are (1)
PROBLEMATIC PHASE RELATIONS 33

garnet-chloritoid-chlorite-biotite and (2) garnei>- 

chloritoid-chlorite-staurolite; afterwards, these are 

(3) garnet-chloritoid-staurolite-biotite and (4) 

garnet-chlorite-biotite-staurolite.

Reference to table 1 shows that of the four assemblages (all in the presence of quartz, muscovite, 

and plagioclase), all but assemblage 3 is found in 

the area. The absence of this assemblage may result 

from incomplete sampling or from a lack of the 

necessary restricted bulk composition.

The distribution of assemblages 2 and 4 on the 

isograd map (fig. 1, samples indicated by triangles 

and squares, respectively) is well ordered and defines a second staurolite zone, marking the reaction 

given above.7

As shown in figure 1 (samples indicated by circles), four assemblages carry all five phases, chloritoid, chlorite, staurolite, biotite, and garnet; these 

assemblages are probably truly fortuitous findings 

of pseudounivariant assemblages. Except the assemblage of sample 331-3, the five-phase assemblages 

occur between assemblages 2 and 4.

Because the chloritoid-staurolite pair is stable 

for a finite range of rock compositions as well as 

of external conditions these minerals must show 

ranges of Fe/Mg ratios. The composition of the 

chloritoid in equilibrium with the first staurolite 

will be different from that of the last chloritoid in 

equilibrium with staurolite. Unfortunately, my data 

do not indicate clearly whether the chloritoid coexisting with staurolite becomes more magnesian 

in rocks of higher or lower grade. Sample 339-1 

contains chloritoid relicts in garnet only and thus 

presumably the rock is above the zone in which 

chloritoid is a stable phase for the active bulk composition. This chloritoid is also the most magnesian 

of those described in table 7 but is not significantly 

so (compare ranges of compositions for samples 

331-1, 463-1, and 509-1 for both chloritoid included 

in garnet and stout crystals in the groundmass, 

table 3, section D). The least magnesium chloritoids 

listed in table 3, section D, are from 45-1, 140-2, 

338-1, 466-1, and 515-1. Samples 45-1 and 140-2 

are of rocks below the garnet zone, and 338-1 and 

466-1 are from just below the staurolite zone; sample 515-1, however, is from well in the staurolite 

zone just before the disappearance of chloritoid, 

as far as can be judged.

7 Figure 15 indicates that the reaction (Ep, PI) takes place at a 

higher grade than does (Ep, Bt), which describes the reaction of chloritoid with anorthite to form staurolite+firaraet+chlorite; however, this 

fact need not unduly disturb us because in actual rocks the plagioclase 

is an Ab-rich plagioclase, not anorthite.

How does chloritoid finally disappear from the 

assemblages? I do not have definite information. 

However, one of these reactions seems plausible: 

(1) chloritoid+muscovite=biotite+staurolite+calcium-free garnet or (2) chloritoid=staurolite+ 

chlorite+calcium-free garnet. Both reactions to the 

right consume quartz but release large amounts of 

H2 0. In calcium-bearing rocks, the reaction is either 

(3) chloritoid+calcium-plagioclase+quartz=staurolite +garnet+chlorite+sodium-plagioclase ((Ep, 

Bt) of fig. 15) or (4) chloritoid+calcium-plagioclase = staurolite + chlorite + epidote + quartz 

+ sodium-plagioclase ((Ga, Bt) of fig. 15); reaction 

4 is followed by (5) chloritoid+epidote = staurolite 

+garnet+chlorite ((Bt, Pg) of fig. 15). All three 

reactions release H2 0 to the right. In sample 355-1, 

chloritoid is abundant in cores of garnet but never 

in the matrix and could be a record of reactions 

3 or 5.

After the disappearance of chloritoid from rocks 

typified by sample 355-1, the system of four phases 

(chlorite-staurolite-biotite-garnet, for example, 

sample 356-1) and "five components acquires an 

extra degree of freedom; each phase may therefore 

have one compositional variability that is of course 

correlated among the phases. Depending on the 

CaO and MnO contents of the effective rock composition, the apices of the four-phase hypervolume 

may vary. Moreover, three-phase assemblages, for 

instance chlorite-staurolite-garnet (sample 355-1) 

and biotite-staurolite-garnet, can exist under external conditions similar to those acting on the fourphase assemblage. These three-phase assemblages 

will occupy hypervolumes in the compositional space 

and, for arbitrary effective rock compositions, can be 

realized. This existence of the hypervolumes apparently explains why rocks having few of the ACFM 

phases, such as sample 355-1, are commonly found 

in the area.

KYANITE-BEARING ASSEMBLAGE

One kyanite-bearing mineral assemblage has been 

found in the study area. Sample 655-1-1 is from 

the southeastern extremity of the area and represents rocks of the highest metamorphic grade. The 

assemblage is kyanite-staurolite-biotite-garnet-plagioclase-quartz-tourmaline-muscovite-ilmenite; primary chlorite is not found in the several slides 

examined. The assemblage clearly cannot be discussed in terms of the model multisystem. However, 

in view of the nature of the mineral assemblages 

just below this grade, discussed in the previous sec-
34 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

tions, a plausible reaction leading to the assemblage 

may be

staurolite+chlorite + muscovite

= biotite+kyanite + quartz + H2 0

This reaction may mark the final disappearance of 

the staurolite-chlorite pair in the presence of muscovite. Using the model compositions, the balanced 

reaction is

staurolite+4.96 chlorite+ 8.55 muscovite

= 9.5 biotite+ 16.38 kyanite+ 0.33 quartz

+ 19.4H2 0.

The main geologic interest in the kyanite-bearing 

assemblage in the area is in the implication of minimum rock pressure during metamorphism, as is 

discussed in another section of this study (p. 42).

PHASE RELATIONS INVOLVING EPIDOTE

Epidote is found in rocks ranging from below 

the biotite zone through the lower part of the staurolite zone. Together with garnet, hornblende, and 

plagioclase, it is an important calcium-bearing 

phase; its relations with the other minerals thus 

are of interest. The assemblages that include epidote 

are given in table 1; table 8 summarizes the data 

and includes information on the metamorphic zones.

At low metamorphic grades, the pelitic rocks 

show very simple mineral assemblages: muscovite, 

chlorite, a sodium-rich plagioclase, quartz, and ilmenite are common, and a carbonate mineral (calcite) and (or) epidote are added phases. The simplicity of these prevalent assemblages has been a 

puzzle, and I suggested (Zen, 1960) that chlorite 

may be sufficiently variable in composition to account for this assemblage. The microprobe data on 

sample 1169-1 (table 3, section A; fig. 2) indicate 

that for this, and presumably for other rocks, the 

muscovite is phengitic. The variable composition 

of muscovite, coupled with variable composition of 

chlorite along both the Fe = Mg and (Fe,Mg)+Si 

=A1 + A1 coordinates, could explain the simple assemblages, though whether this is the principal 

explanation remains to be proven.

A divariant reaction of illite+chlorite + calcite 

to form phengite + epidote seems possible in view 

of the chemography of the phases. Using the iron 

end member for chlorite, an illite composition of 

H2Ko.sAl2 .2Fe3 +o.3Si3.50i2, a phengite composition of 

H2KAl2. 2Fe2 +o.54Si3 .33012 , and the model epidote composition, the reaction is

8.52 illite + chlorite+ 6.75 calcite + 0.84 02 

+ 0.5 quartz

= 3.38 epidote+ 6.82 phengite + 6.75 C02 + 4.02 H2 0. 

If hematite participates in the reaction but no redox 

change is included, then the reaction is

chlorite+ 34.1 illite+ 4.5 hematite+ 18 calcite

= 9 epidote+27.3 phengite+6.32 H2 0 + 18 C02

+ 4 quartz.

Both reactions seem plausible in view of the nature 

of the assemblages and the associations of epidote 

and phengite in sample 1169-1. Both reactions involve strong evolution of mixed volatile components 

in the system C-H-0 for the reaction to proceed 

to the right.

| In fact, of course, Fe2 +-Mg substitutions are important, and both reactions are at least divariant, 

so that no phase needs to disappear in the reaction; 

rather, both chlorite and the muscovite-phengite 

solid solutions slide along a univariant compositional trend to adjust to the bulk composition for a 

given set of external variables.

In progressive metamorphism, garnet is the next 

calcium-bearing phase to appear, and the fact that 

higher grade rocks contain increasing garnet and 

diminishing epidote suggests a reaction relation

j between these two minerals. Five of the 19 epidotebearing pelitic rocks mapped as being above the 

garnet isograd do not contain garnet, but three of 

these contain paragonite (tables 1 and 2). If we 

assume that paragonite can be projected to the A 

apex of the ACFM compositional space, then figure 

17A shows that two of the possible assemblages are 

epidote-garnet-chlorite-chloritoid and epidote-chlorite-chloritoid-paragonite (all + plagioclase+quartz 

+muscovite). These divisions are compatible with 

the data in table 1.

Figure VIA shows that a third four-phase assemblage, epidote-chlorite-garnet-biotite (+muscovite 

+ plagioclase+quartz) is compatible with the tieline relations depicted. Because of the chemographic 

relation of epidote in the ACFM diagram (whether 

ferric iron is reckoned as belonging to the F apex 

or not), the assemblages including this phase do 

not involve the biotite-chloritoid tieline. Indeed, the 

assemblage data (table 1) show that although epidote is found with either biotite or chloritoid, it is 

not found with both, despite the common coexistence 

of these two phases and garnet, as discussed in 

another section (p. 27).

According to these observed relations, the reactions involving garnet and epidote may be

chloritoid+iron oxide+chlorite+epidote

= garnet + oxygen,
CONDITIONS OF METAMORPHISM 35

Pa 

(1,0,0,0)

Cd 

(0.66,0,0.29,0.05)

Ep 

(0.4,0.4,0.2,0)

Ga 

(0.40,0.04,0.53,0.03)

St 

(0.82,0,0.17,0.01)

B

FIGURE 17.—The ACFM diagram wherein paragonite is 

projected to the A apex, for phases in coexistence with 

epidote. The numbers in parentheses after each phase name 

refer to the atomic percent of the four apical components 

in the order of A, C, F, and M. Assemblages are for the 

presence also of muscovite, plagioclase (albite), and quartz. 

A, Below the chloritoid-out isograd. B, Above the chlo<ritoidout isograd. Epidote is reckoned such that ferric iron is 

plotted as if it were ferrous iron. Phase symbols: Ep, 

epidote; Pa, paragonite: Ch, chlorite; Cd, chloritoid; Ga, 

garnet; Bt, biotite; and St, staurolite.

chlorite + iron oxide + muscovite + epidote

= biotite + garnet+oxygen,

and

paragonite + magnetite+epidote + chlorite

=garnet+albite.

If the detailed compositions of the phases are 

known, then balanced reactions can be written 

(Thompson and Norton, 1968; Thompson, 1976). 

If magnetite is the iron-oxide phase and the silicate 

phases have model compositions, these reactions 

would be as follows:

65.6 chloritoid+ 43.8 magnetite + chlorite 

+ 7.5 epidote+133.3 quartz

= 74.6 garnet+ 73.4 H2 0 + 23.7 02 , 

chlorite+2.0 magnetite +1.4 muscovite

+ 0.25 epidote+ 4.1 quartz

= 1.5 biotite+2.5 garnet+4.0 H2 0 +1.1 02 ,

and

10.5 paragonite+ 10.5 magnetite + chlorite 

+ 1.3 epidote+ 33.5 quartz

= 13.3 garnet+ 15.2 H2 0 + 10.5 albite+5.6 02 .

All three reactions involve devolatilization and dehydration as garnet is formed. The first and the 

third reactions truly mark the first appearance of 

garnet in this chemographic system. The second 

reaction is of the "tieline switch" type (the tieline 

garnet-biotite versus the plane chlorite-magnetiteepidote). This reaction could be a petrographic 

marker for the garnet zone for rocks of appropriate 

compositions. The reactions predict major consumption of magnetite; interestingly, the modal content 

of magnetite drops abruptly at about the lower 

limit of the garnet zone.

Another reaction involving epidote and garnet is

chloritoid + epidote + iron oxide + albite + quartz

=garnet + paragonite+H2 0 + 02 ;

for instance,

2.0 chloritoid+ 0.2 epidote + magnetite+0.3 albite 

+ 3 quartz

= 1.8 garnet+0.3 paragonite+ 0.602 +1.8 H2 0.

However, the lack of coexistence of paragonite, garnet, and epidote in the rocks suggests that this 

reaction did not obtain, although for other assemblages lacking epidote, the garnet-paragonite association is found and shows that the association can 

be stable for rocks of appropriate, probably lowcalcium, compositions.

The relatively small amount of epidote in all the 

observed rocks, compared with the large amount 

of garnet in many, indicates that the reactions involving epidote cannot be the major reactions lead-
36 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

ing to garnet. Other plausible garnet-forming reactions are discussed elsewhere in this study.

Another caveat is that the plagioclase in all epidote-garnet-plagioclase rocks of the area is not 

anorthite but a solution relatively rich in the Ab 

component, so the simple model is not strictly applicable. As the An component is formed in a given 

reaction, it is diluted by Ab, and the chemical potential of calcium in this phase decreases approximately according to Raoult's Law; thus, the calcium 

content of garnet must also decrease in general to 

maintain equilibrium. If we assume the epidote to 

be fixed in composition (not strictly true, but the 

change in Al/Fe ratio may not greatly affect the 

chemical potential of calcium in the phase), then 

this phase will remain unchanged in composition 

but will diminish in amount so the components may 

dissolve in the garnet and plagioclase to maintain 

the equality of the chemical potential of calcium 

in all phases until epidote disappears.

After the disappearance of chloritoid by the reaction (Bt, Ep), (Bt, Ga) or (Bt, Pg), as discussed 

on page 33, the assemblage staurolite-garnet-chlorite-epidote becomes stable together with plagioclase, muscovite, and quartz (fig. 171?).

We have few probe data on the compositions of 

garnet and plagioclase that coexist with epidote. Although the An content of the plagioclase is nearly 

constant, the calcium content of garnet decidedly 

is not. Part of the problem may be in analyzing for 

the zoned garnet; one must be certain that the correct zone (presumably the rim) that equilibrated 

with plagioclase and epidote is tabulated, an impossible task. The compositions of these coexisting 

phases at specified temperatures, pressures, oxygenbuffer conditions, and chemical potentials of H20 

need to be calibrated under laboratory conditions; 

when the coexisting compositions are determined, 

these phases can be used in the study of natural 

assemblages.

Samples 356-1 and 590-1 contain staurolitegarnet-epidote-chlorite-biotite (plus muscovite, plagioclase, and quartz) and are intriguing because 

in the ACFM projection they contain five phases. 

One could argue that in this assemblage ferric iron 

should be considered an independent component; 

although the point is debatable, the rarity of the 

staurolite-epidote assemblage (and presence of five 

phases in the ACFM system) suggests that this 

may be a truly univariant reaction of the type

garnet+chlorite + muscovite

= biotite+staurolite+epidote.

Balanced reaction using the model compositions 

yields

0.383 garnet+0.505 chlorite+ 0.9 muscovite 

+ 0.012 02

= biotite + 0.344 staurolite+ 0.0575 epidote 

+ 1.718 H2 0 +0.893 quartz.

This reaction yields a large amount of H2 0. In the 

section, Chloritoid-Stauro'ite Relations (p. 30), I 

suggested that samples 355-1 and 356-1 were probably formed under similar external conditions; reference to figure 15 suggests that they may have 

formed in field £ Both samples 356-1 and 590-1 

could have formed along the univariant line (Cd, 

Pg), but 356-1 seems more likely to have formed 

near the invariant point (Cd) itself.

RELATION BETWEEN EPIDOTE-BEARING AND 

HORNBLENDE-BEARING ASSEMBLAGES

Samples of three rocks in the garnet and staurolite zones have been found to contain hornblende. 

Of these, sample 161-1 is from just above the lower 

limit of the garnet zone, 102-1 is from just above 

the lower limit of the staurolite zone, and 289-2 is 

from well into the staurolite zone. The first two 

rocks were probably originally impure tuffaceous 

sediments (161-1, in the allochthonous Everett Formation, and 102-1 in the autochthonous Walloomsac Formation). Sample 289-2 is from a highly 

calcareous pelite at the base of the Walloomsac, 

presumably originally in part a residual soil rich 

in aluminum and containing calcium. Rather exceptional compositions are needed to cause hornblende 

| to appear in the pelitic rocks, and a high calcium 

content seems to be required. The compositions of 

phases in these three specimens are summarized in 

table 9.

The mineral assemblages including hornblende 

(table 1) suggest that a single phase volume in the 

ACFM projection—hornblende-garnet-biotite-chlorite (plus muscovite, plagioclase, quartz, ilmenite, 

and (or) magnetite)—suffices to account for the 

assemblages. As discussed by Doolan and others 

(1978), the apices of this phase volume shift presumably in response to different metamorphic 

grades; sample 289-2 moreover has a highly magnesian biotite and is without chlorite, so that its 

assemblage occupies the three-phase "plane"—actually a wedge-shaped volume—that is opposite the 

phase volume including chlorite.

In the section, Phase Relations Involving Epidote 

(p. 34), the assemblage epidote-chlorite-biotitegarnet was shown to form a phase volume in the
PROBLEMATIC PHASE RELATIONS 37

ACFM projection. The Fe/Mg ratio of hornblende 

from sample 161-1 is sufficiently high that the composition of this hornblende may be within this volume.8 The appearance of hornblende in 161-1, then, 

could be related to the reaction written as follows, where the actual compositions of phases from 

this rock (tables 3, and 9) as well as a model 

composition of biotite were used:

0.65 garnet+0.23 chlorite + 0.28 biotite 

+ 0.64 epidote + 0.1 albite + 0.38 quartz 

= 0.25 muscovite +hornblende+ 0.26 H2O + 0.11 O2 .

The first appearance of hornblende apparently 

nearly corresponds to the petrographic garnet-zone 

marker.

As the metamorphic grade increases, the composition of the hornblende changes. Sample 102-1 was 

collected nearly 2 km east of sample 161-1 and is 

of higher grade; the compositions of all the phases 

of sample 102-1 are significantly different from 

those of sample 161-1 (table 9). On the basis of 

the microprobe data for these phases, the reaction 

involving the same phases must be written

0.99 epidote + 0.34 biotite+ 0.60 chlorite + 0.4 albite 

+ 1.08 quartz

= 0.27 garnet+hornblende+0.31 muscovite 

+ 1.91 H2O + 0.15 O2 .

The chemographic relations now are qualitatively 

different, and the appearance of hornblende in this 

rock is of the tieline switch type. In between the 

two sample localities, the hornblende composition 

relative to those of the other participating phases 

must have changed so that hornblende became momentarily coplanar with the phases epidote, biotite, 

and chlorite (and albite), but the exact point of 

that degeneracy is as yet undefined.

It seems reasonable to suppose that the hornblende compositional volume is a continuous one 

extending from within the epidote-chlorite-biotitegarnet (plus albite) volume to that corresponding 

to sample 102-1. One puzzle is that a rock (sample 

590-1) about 5 km south-southeast of sample 102-1 

but considerably upgrade from it and roughly isogradic with the rock of sample 289-1 contained 

this four-phase assemblage in which all phases are 

euhedral and groundmass phases are apparently 

in equilibrium. Because formation of hornblende 

from this four-phase assemblage involves consid8 Sample 161-1 does not actually include biotite; what at first appeared 

to be biotite was proved by microprobe analysis to be oxychlorite (Chatterjee, 1966). However, we can assume a wide range of biotite compositions 

and still define, together with the other minerals, a phase volume that 

would contain the composition of the hornblende of sample 161-1.

erable devolatilization, it seems improbable that the 

four-phase assemblage could be stable in rocks of 

higher grade than those containing hornblende, 

even if the boundary of the hornblende phase volume in the ACFM projection can be assumed to 

have receded entirely outside of that phase volume. 

One possibility is that the value of /*w in sample 

590-1 may have been considerably higher than in 

102-1 (the latter might have had appreciable CO2 

dilution), so the reaction in 590-1 was retarded. 

This, however, is speculation.

Another reaction leading to the formation of 

hornblende that is conceivable, though not observed 

in this area, involves the five phases epidote, garnet, .chlorite, hornblende, and chloritoid. Clearly 

this reaction would have to take place at higher 

grade than that corresponding to sample 161-1 

because that assemblage represents the first appearance of hornblende and because the reaction involving chloritoid must be of the tieline switch type. 

Using the mineral compositions for 102-1, the balanced reaction is:

0.838 epidote+ 0.4 albite+ 0.176 garnet

+ 0.741 chlorite+ 0.482 quartz

-hornblende+ 0.652 chloritoid+ 1.731 H2O + 0.11 O2 .

After the appearance of staurolite and disappearance of chloritoid, another appropriate reaction 

would be approximately

0.918 epidote+ 0.745 chlorite + 0.4 albite 

+ 0.716 quartz

= 0.113 staurolite+ 0.051 garnet+hornblende

+ 2.382 H2O + 0.13 O2 .

Neither the hornblende-staurolite nor the hornblende-chloritoid assemblage has been observed in 

the area: both, however, have been found elsewhere (Frey. 1974, p. 495 and quoting J. S. Fox, 

p. 498; Fed'kin, 1975, p. 75).

CUMMINGTONITE-BEARING ASSEMBLAGES

| Several samples from two widely separated localities have yielded the assemblage quartz-almandine 

garnet-cummingtonite. One locality (487-2) is south 

of Wachocastinook Brook about 1 km southwest of 

Lions Head. The other locality (170-1) is on the 

south slope of Bear Mountain. Both are in the Bashbish Falls Quadrangle, and the rocks are in the

] allochthonous Everett Formation (tables 1 and 2).

| The rocks are dense, fine grained, and pinkish gray 

(the pink hue is due to almandine) and contain 

scattered plumose olive-green fibrous clusters of 

cummingtonite. The sample from Bear Mountain
38 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

contains epidote in addition to garnet, quartz, and 

cummingtonite (fig. 6A). Feldspar is absent from 

these rocks, and muscovite, biotite, and chlorite are 

exceedingly rare; chlorite is present mainly as alteration rims around garnet. This assemblage, which 

is virtually alkali free, is the only one found in 

which the garnet rim is also virtually calcium free; 

the garnet is rich in manganese, especially in the 

core, where manganese occupies as much as 15 percent of the divalent cation positions. The coexisting 

cummingtonite is virtually aluminum and calcium 

free, is very low in manganese, and has a Fe/Mg 

ratio of about 5/2. Thus, the mineral chemistry 

indicates that the rock is rich in silica and contains 

a major amount of iron and alumina but very little 

else. The protolith could have been saprolitic 

material.

CONDITIONS OF METAMORPHISM

Although quantitative estimates of the temperature and pressure values of metamorphism across 

the area are difficult to make, helpful estimates of 

approximate values can be made, largely on the basis 

of existing experimental studies of phase-stability 

relations in pertinent systems.

Holdaway (1972) and Liou (1973) studied the 

stability of epidote in oxygen-buffered systems. Liou 

used several buffer systems, HM (hematite-magnetite), NB (nickel-bunsenite), and QFM (quartzfayalite-magnetite), and determined the maximum 

stability limits of epidote of specific compositions 

(Fe/Al = i/2 for HM, =% for NB and QFM) that 

are similar to the compositions of epidote from the 

area. The upper thermal stability of Liou's epidote, 

therefore, should correspond to the upper limit for 

the metamorphism of epidote-bearing rocks. The 

oxygen fugacity of the rocks is unknown. The lowest grade rocks contain hematite, and higher grade 

rocks (below the garnet zone) contain magnetite; 

thus, presumably somewhere in the less metamorphosed part of the chloritoid zone, the HM buffer 

surface intersects the land surface at its present 

level of erosion. Higher grade rocks probably were 

metamorphosed under more reducing conditions. Because lower oxygen fugacity reduces the stability 

field of epidote, everything else being equal, the 

curve of Liou based on the HM-buffered system can 

truly be considered the upper limit of metamorphism (fig. 18; compare curve 3 with curves 4 and 

5).

In figure 18, curves 1 and 2 show the phase 

diagrams for the aluminum silicate polymorphs according to Richardson and others (1969) and to 

Holdaway (1971), respectively. Kyanite is found 

in the study area. Sillimanite is a major rock-forming mineral in sillimanite-muscovite-garnet-quartz 

(with or without staurolite) associations in the "Canaan Mountain Schist" a few kilometers southeast 

of the present study area (Agar, 1932, 1933; D. S. 

Harwood, oral commun., 1975). If the kyanite and 

sillimanite formed roughly simultaneously, their 

stability boundary passed between the Taconic 

Range and Canaan Mountain. The pressure of overburden in the area must have been no less than that 

corresponding to the triple point of the aluminum 

silicate polymorphs, about 3.8 kbar according to 

Holdway (1971) and about 5.5 kbar according to 

Richardson and others (1969).

Day (1973) and Chatterjee and Johannes (1974) 

studied the upper thermal stability limit of stoichiometric muscovite in the presence of quartz. 

Their curves do not differ significantly, and figure 

18, curve 13, shows that of Chatterjee and Johannes. 

Because muscovite-quartz is a nearly ubiquitous 

association in the area, the limit imposed on the 

stability of the association—assuming that the relatively small departures from stoichiometry of most 

of the muscovites may be ignored—is useful and 

restricts the temperature to lower values than those 

indicated by Liou's (1973) work on epidote stability in HM-buffered systems.

A few rocks, especially at lower metamorphic 

grades, contain small amounts of paragonite (table 

1) This phase has not been chemically analyzed 

and is identified only by the X-ray pattern. The 

basal spacings indicate that the paragonite is approximately potassium free (Zen and Albee, 1964; 

Eugster and others, 1972) ; thus, the upper thermal 

stability of the paragonite-quartz assemblage studied by Chatterjee (1972; this report, fig. 18, curve 

12) is an approximate limit of the temperature at 

which paragonite in the study area formed. For a 

given total pressure and H2 0 activity, the highest 

temperature at which the paragonite-quartz assemblage is stable is lower by about 100° C than the 

corresponding temperature for the muscovite-quartz 

assemblage. For a Ptotai = -PHoo of 4 kbar, the thermal 

limit is about 570° C for the paragonite-quartz 

assemblage.

Many rocks at higher metamorphic grades contain staurolite and quartz. Staurolite is a phase 

of variable composition, and its stability may be 

affected by the oxygen fugacity. Therefore, Richardson's (1968) experimental results for staurolite 

of the specific composition H4Fe4Al18Si7 .5048 in a
CONDITIONS OF METAMORPHISM 39

16

12

CO 

DC

CO

O

^ 8

LU 

DC 

D 

CO 

CO 

LU 

DC 

Q_

EXPLANATION

9.

10.

Al-silicate polymorphs. Richardson and others, 1969. 

Al-silicate polymorphs according to Holdaway, 1971. 

Upper stability of epidote, HM buffer; epidote has pistacite

(Ps)=0.33. Liou, 1973.

Upper stability of epidote, NB buffer, Ps=0.25. Liou, 1973. 

Upper stability of epidote, QFM buffer, Ps=0.25. Liou, 1973. 

Staurolite+quartz=almandine+sillimanite+W, QF^ buffer. Richardson, 1968. 

Staurolite+quartz=Fe-cordierite+sillimanite+W, QFM

buffer. Richardson, 1968. 

Chloritoid+sillimanite+quartz=staurolite+W, QFM buffer.

Richardson, 1968. 

Chloritoid+oxygen=staurolite+magnetite+quartz+W,

HM buffer. Ganguly and Newton, 1968. 

Chloritoid=Fe-cordierite+hercynite ss , NB buffer. Grieve

and Fawcett, 1974. 

10a. Chloritoid=AI-Fe anthophyllite+staurolite+hercynite, NB

buffer. Grieve and Fawcett, 1974. 

10b. AI-Fe anthophyllite+hercynite=almandine+staurolite+W,

NB buffer. Grieve and Fawcett, 1974.

11. 11a, lib. Same as the corresponding reactions 10, lOa, 10b, 

QFM buffer. Grieve and Fawcett, 1974.

12. Paragonite+quartz=andalusite+albite+ W. Chatterjee,

1972. 

12a. Paragonite+quartz=kyanite+albite+W. Chatterjee, 1J972_

13. Muscovite+quartz=andalusite+sanidine+W. 'Chatterjee

and Johannes, 1974. 

13a. Muscovite+quartz=sillimanite+sanidinei+ W. Chatferjee

and Johannes, 1974. 

Quartz+muscovite+Mg-chlorite=phlogopite+cordierite+

W. Seifert, 1970. 

Mg-chlorite+muscovite=phlogopite+kyanite+quartz+W.

Bird and Fawcett, 1973. 

Daphnite=fayalite+Fe.-cordierite+hercynite+W, MW

buffer. Turnock, 1960. 

Daphnite=mullite+hematite+magnetite+quartz+W, HM

buffer. Turnock, 1960. 

Clinochlore=forsterite+cordierite+spinel+W. Chernosky,

1974. 

Clinochlore+quartz=talc+cordierite+W. Chernosky,, 1978.

15

10a

19.

400 500 600

TEMPERATURE, IN DEGREES CELSIUS

700 800

FIGURE 18.—Experimental pressure-temperature curves pertinent to the mineral assemblages of the study area. Righthand side of reactions 6 to 9 are high-temperature assemblages. W, H2O. Buffer systems: HM, hematite-magnetite; 

NB, nickel-bunsenite; QFM, quartz-fayalite-magnetite; MW, magnetite-wustite.

QFM-buffered system can be applied only with considerable skepticism, especially because we do not 

yet have any thermochemical data to calculate the 

effects of composition changes such as magnesium 

substitution for iron. Nevertheless, the upper limit 

(staurolite + quartz = Fe-cordierite + sillimanite 

+ H2 0, or =almandine+sillimanite+H2 0, fig. 18,

curves 6 and 7) obtained by extrapolating Richardson's (1968) results is consistent with those based 

on Liou's (1973) epidote study or Chatterjee's and 

Johannes' (1974) muscovite-quartz study; the limit 

indicates that temperatures were less than about 

650°-700° C for pressures of about 4 kbar during 

this reaction.
40 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

Another limit supplied by Richardson (1968) is 

the lower thermal stability limit for staurolite according to the reaction chloritoid + sillimanite + 

quartz = staurolite+ H2 0 in a QFM-buffered system 

(fig. 18, curve 8). The limit gives the lowest temperature at which staurolite is stable; other reactions leading to staurolite must be at higher temperatures when other conditions are equal. However, 

for H2 0 fugacity less than full load pressure, the 

curve would be shifted to lower temperatures, so 

again the limit is only approximate. For 4 kbar, the 

temperature given by Richardson is about 530° C, 

and the curve has a very steep slope. The curve 

intersects the kyanite-andalusite curve at about 4.5 

kbar, according to Richardson and others (1969), 

or the kyanite-sillimanite curve at about the same 

pressure, according to Holdaway (1971).

Ganguly (1968) and Ganguly and Newton (1968) 

studied the oxidation of chloritoid to staurolite + 

quartz + magnetite under HM- and NB-buffer conditions, and Ganguly (1968) studied the reaction 

chloritoid + quartz = garnet + staurolite + H2 0, under 

the NB-buffer condition. As in Richardson's (1968) 

experiments, the reactions refer strictly to the ferrous end members of the phases; the natural materials all show significant amounts of magnesium 

(plus calcium and manganese for garnet), and the 

reactions are not univariant. These reactions do 

supply estimates of the upper stability of the chloritoid-quartz pair, at least approximately. Unfortunately, the reactions were run at pressures in excess of 10 kbar and application to the study area 

most likely requires extensive extrapolation. Figure 

18, curve 9, shows the HM-buffered data; extrapolation of the curve suggests that temperatures not 

greater than about 550° C at 4 kbar for stability 

of the chloritoid-quartz pair is indicated; these are 

not inconsistent with the estimates based on the 

lower thermal stability of staurolite.

Grieve and Fawcett (1974) reported on the upper 

thermal stability of ferrochloritoid, using both NB 

and QFM buffers. The reactions they investigated 

are: chloritoid = Fe-cordierite + hercynite (low pressures ) ; chloritoid = Fe-anthophyllite + staurolite + 

hercynite; and Fe-anthophyllite+ hercynite=almandine + staurolite + H2 0. The system is free of quartz, 

and thus the stability limit of chloritoid is a maximum value. Their reactions (fig. 18, curves 10, lOa, 

lOb, 11, lla, and lib) can be compared with the estimated curve of Ganguly (1969) for chloritoid 

+ quartz=staurolite+almandine+H2 0 (not shown 

on fig. 18). Ganguly's quartz-saturated reaction occurs at about 50° C lower (for beginning of chloritoid breakdown) to 100° C lower (for completion 

of staurolite+ almandine reaction; these two are described as a single step by Ganguly without intermediate anthophyllite) than those of Fawcett and 

Grieve. This difference could be consistent with the 

effect of excess quartz in reducing the stability field 

of chloritoid. However, because data are lacking, 

nothing more can be stated. The uncertainty regarding the compositions of the phases involved in 

the different studies, especially the composition of 

staurolite, makes comparison even more hazardous.

Fawcett and Yoder (1966) studied the upper 

thermal stability of the magnesium chlorite clinochloreMg5Al2Si3 010 (OH) 8 ; Chernosky (1974) added 

new and improved data (this report, fig. 18, curve 

18). Turnock (1960) gave preliminary results on 

the upper thermal stability of two aluminum-rich 

iron chlorites, daphnite Fei. 8Al2 . 4Si2 .8(0,OH)i8 and 

pseudothuringite Fe4 . 2Al3 .6Si2 . 2 (0,OH)i8 , using both 

the magnetite-hematite and the magnetite-wiistite 

buffer systems. Hsu (1968) studied the upper stability of iron-chlorite Fe4 .5-4.oAl 3-4Si2.5-2.o(0,OH)i8 

plus quartz in a system buffered by iron-quartzfayalite; he also studied these phases plus magnetite 

using the iron-magnetite, iron-wiistite, QFM, and 

NB buffer systems. Although the stability limit of 

chlorites intermediate in iron-magnesium compositions and for different aluminum contents has not 

been determined, the available data (Fawcett and 

Yoder, 1966; Turnock, 1960; Hsu, 1968) do provide rough estimates of the upper limits for these 

! intermediate chlorite compositions in the presence 

of quartz; these estimates are particularly useful 

because the chlorite-quartz assemblage is common. 

Turnock's (1960) experimental data are shown in 

figure 18, curves 16 and 17.

Bird and Fawcett (1973) and Seifert (1970) 

studied the upper thermal stability of the muscoviteclinochlore assemblage in the presence of quartz; 

Seifert studied the reaction to cordierite + phlogopite, and Bird and Fawcett studied the reaction to 

phlogopite + kyanite. Chernosky (1978) studied the 

reaction of clinochlore +quartz to talc + cordierite. 

Although the product assemblages are not found in 

the area, the widespread and common presence of 

the reactant assemblages allows me to form veryuseful estimates of maximum temperatures, especially as the presence of iron-bearing chlorite should 

lower the limit of stability of the reactant assemblage. Their results, plotted in figure 18, curves 

14,15, and 19, suggest that the mineral assemblages 

in the study area formed at temperatures of less than
REFERENCES CITED 41

640° C at ^ 6 kbar, 580° C at 4 kbar, or 520° C at 

2 kbar. A condition of metamorphism where -PH2o 

<-Ptotai would, of course, also further lower these 

maximum temperature values.

Another way to establish minimum temperature 

estimates is through the muscovite-paragonite pair. 

Equations correlating the basal spacings of these 

micas with their compositions, have been published 

by Zen and Albee (1964), Guidotti and Crawford 

(1968), and Eugster and others (1972).9 These 

equations can be used in combination with the data 

of Eugster and others (1972) on the muscoviteparagonite solvus to estimate temperatures of formation of coexisting muscovite-paragonite pairs. 

For rocks containing muscovite but not paragonite, 

these equations can be used to estimate minimum 

temperatures because if equilibrium is attained, the 

range of single-phase muscovite composition in 

terms of K/(K+Na) ratios increases monotonically 

with temperature. One shortcoming of this method 

is that the basal spacings of muscovite and paragonite depend not only on the K/(K+Na) ratios but 

on traces of the calcium end member, on the phengitic component (Ernst, 1963), and possibly on 

other factors such as alkali deficiency or hydronium 

substitution for alkalis in the interlayer position.

X-ray diffraction data are used to determine 

whether a muscovite is coexisting with paragonite 

and is thus on a section of the multicomponnt muscovite-paragonite solvus. Microprobe data on one or 

both of the white micas are then used to determine 

the K/(K+Na) ratio of each white mica and 

whether the micas lie approximately on the binary 

join (K,Na)Al3Si:}Oio(OH) 2 , thus permitting the 

use of the temperature-pressure-composition diagram for this binary solvus as proposed by Eugster 

and others (1972). This procedure therefore circumvents the uncertainties caused by using the 

existing regression equations (Zen and Albee, 1964; 

Guidotti and Crawford, 1968; Eugster and others, 

1972).

Table 10 gives the temperatures of metamorphism 

estimated on the basis of microprobe analyses of 

muscovite. The muscovite from each sample showed 

a small range in K/(K+Na) values; the analysis 

showing the lowest value (that is, the maximum 

solution) is taken because that value presumably

0 The Muscovite from Methuen County, Ontario, used by Zen and Albee 

(1964) was reported by Hurlbut (1956, p. 896) to have ca = 20.01 A, 

/3 = 96°, corresponding to an anomalously low basal spacing (dooi=9.950 A) 

for its composition. Cell dimensions of another sample from the same 

locality have been carefully measured (Robie and others, 1976, p. 632), 

indicating that dooi = 9.985 A and removing this anomaly.

is closest to the solvus. The minimum temperature 

estimate is made by assuming the muscovite composition having the lowest K/(K+Na) ratio to be 

actually on the solvus. If the rock also contains 

paragonite, the assumption is better justified. The 

pressure effect is another reason that the temperature estimate thus obtained is minimal. Eugster and 

others (1972) suggested on the basis of volume data 

on the muscovite-paragonite solid solution that increasing pressure increases the critical temperature 

of the solvus. The solvus of Eugster and others was 

derived for 2.07 kbar. Because the mineral assemblages suggest that the higher grade part of the 

study area was metamorphosed at pressures in excess of about 4 kbar, application of a pressure correction from 2 to 4 kbar would increase the estimated minimum temperature.10 For the lower grade 

areas, the amount of the pressure correction cannot 

be directly obtained. However, the lower grade area 

is less than about 10 km from the higher grade 

area and was probably shallower by no more than 

5 km. A difference of 5 km of overburden would 

correspond to a pressure correction of less than 2 

kbar, and the qualitative aspects of the conclusions 

do not appear to be affected.

The temperature estimates given in table 10 

should be compared with the experimental phase 

equilibrium studies summarized in figure 18. The 

set of minimum temperatures derived from muscovite composition and the set of maximum temperatures previously discussed barely overlap. Eugster and others (1972) also commented on the fact 

that the temperatures based on their solvus seem 

excessively high and suggested that hydronium substitution in the interlayer position might explain 

some of the discrepancies. This uncertainty and the 

uncertainties in the microprobe analytical data 

doubtless both play important parts in the calibration curve of Eugster and others (1972) and in its 

application to my samples. The measured basal spacings and microprobe data on compositions of muscovite from the area do not conform to the regression equation correlating composition and basal 

spacing as proposed by Eugster and others (1972). 

Thus, significant revisions of the solvus in P-T space 

may have to be made and may lead to different estimates of temperatures on the basis of muscovite 

compositions.

10 Chatterjee and Froese (1975) disagreed with this conclusion. Their 

data suggest that the critical temperature should be nearly independent 

of pressure.
42 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

A RETROGRADE ISOGRAD?

A possible retrograde isograd passes through the 

center of the studied area, from northeast to the 

southwest (fig. 1). Evidence for this has been reported previously (Zen, 1969b). It is indicated 

mainly by calcium-free rims of albite on preexisting plagioclase for which the calcium content increases outward. In many instances, the calciumrich zones have been altered to sausserite (fig. 9). 

One specimen contains magnetite that has been 

peripherally altered to chlorite (fig. 19); the same 

specimen shows "ghosts" of a preexisting mineral 

having the habit of chloritoid but now is a fine mixture of minerals showing no constant or rational 

chemical composition.

Although the earlier metamorphic event cannot 

be dated, regional relations indicate that a chloritoid-grade metamorphic event prevailed through the 

Taconic region during the Taconian orogeny (Zen, 

1974). Therefore, the low-grade earlier metamorphism is presumed to be a record of this event. 

The rate of increase of metamorphic grade resulting from the Acadian event is interpreted to have 

been faster than that resulting from the Taconian 

event in the study area; thus, the mineral assemblages on the northwest side of the line marked 

"retrograde isograd" on figure 1 were mainly the 

result of the earlier event. All the higher grade

FIGURE 19.—Photomicrograph of sample 191-1, showing 

chlorite (Ch) rimming magnetite (Mt) (plane-polarized 

light). A "ghost" crystal of chloritoid ("Cd") is also 

shown. The magnetite and chloritoid are interpreted to be 

relicts of an earlier episode of metamorphism.

zones, including all garnet-bearing assemblages and 

also many assemblages from below the garnet zone, 

were produced during the later event, which obliterated evidence for the earlier metamorphism. None 

of these higher grade rocks have yielded evidence 

of retrograde zonation of plagioclase. The one plagioclase from these higher grade rocks that was 

traversed by the microprobe (fig. 10C) showed no 

albite rim but only steady outward increase of calcium content and thus supports the interpretation.

GEOLOGIC IMPLICATIONS OF OVERBURDEN 

PRESSURE DURING METAMORPHISM

The conclusion, based on mineral-assemblage data, 

that the pressure of Acadian metamorphism was as 

high as 4 kbar and that the temperatures were as 

high as possibly 600°-650° C has interesting geologic consequences. At Mt. Ida and Becraft Mountain, about 35 km northwest of the study area, 

Silurian and Devonian sedimentary rocks are apparently unaffected by metamorphism and probably 

were not buried under more than the normal stratigraphic thickness (about 1 km) of pre-Acadian 

sedimentary rocks. In the study area, the overburden (the nature of which is a mystery) must have 

been somewhat thicker than 10 km. Thus, a load 

gradient (assuming no post-Acadian crustal shortening) of about 30 percent is required, suggesting 

major differential uplift since Acadian time. The 

structural evidence for this is not yet in. It is, however, consistent with the idea of major uplift in 

the intervening area, as concluded by Ratcliffe and 

Bahrami (1976).

Likewise, the average temperature gradient must 

have been on the order of 500° C in 35 km or about 

15° C per kilometer in what is now a horizontal 

direction. Translating into depth for horizontal isotherms, this would be something like 50° per kilometer, a rather steep gradient, but not impossible in 

an area of active orogeny and metamorphism.

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of Science, ser. 5, v. 23, no. 133, p. 31-48.

———— 1933, Further notes on the Salisbury district of Connecticut: American Journal of Science, ser. 5, v. 25, no. 

149, p. 385-389.

Albee, A. L., 1965, A petrogenetic grid for the Fe-Mg silicates 

of pelitic schists: American Journal of Science, v. 263, 

no. 6, p. 512-536.
REFERENCES CITED 43

———— 1972, Metamorphism of pelitic schists; reaction relations of chloritoid and staurolite: Geological Society of 

America Bulletin, v. 83, no. 11, p. 3249-3268.

Earth, T. F. W., 1936, Structural and pstrologic studies in 

Dutchess County, New York; Pt. 2, Petrology and metamorphism of the Paleozoic rocks: Geological Society of 

America Bulletin, v. 47, no. 6, p. 775-850.

Bence, A. E., and Rajamani, V., 1972, ""Ar/^Ar incremental 

heating "ages" of muscovites and biotites from a progressive metamorphic terrain [abs.]: Geological Society 

of America Abstracts with Programs, v. 4, no. 7, p. 

449.

Bence, A. E., and Vocke, R. D., 1974, Low grade metamorphic 

reactions in pelitic schists, Dutchess County, N.Y. [abs.] : 

EOS (American Geophysical Union Transactions), v. 55, 

no. 4, p. 449.

Bird, G. W., and Fawcett, J. J., 1973, Stability relations of 

Mg-chlorite-muscovite and quartz between 5 and 10 kb 

water pressure: Journal of Petrology, v. 14, no. 3, p. 

415-428.

Boettcher, A. L., 1970, The system CaO-Al203-SiO2-H20 at 

high pressures and temperatures: Journal of Petrology, 

v. 11, no. 2, p. 337-379.

Burger, H. R., 1975, General geology of the Stockbridge Valley marble belt, in New England Intercollegiate Geological Conference, 67th Annual Meeting, Great Barrington, 

Mass., Oct. 10-12, 1975, Guidebook for field trips in western Massachusetts, northern Connecticut, and adjacent 

areas of New York: New York, City College of City 

University of New York, Department of Earth and 

Planetary Science, p. 261-273.

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———— 1972, The upper stability limit of the assemblage 

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82.

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44 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

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p. 259-272.
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Review of Earth and Planetary Science, v. 2, p. 179-212.

TABLES 1-10

tOI-'OOO OOoOO «D«O«D«D«D «D «D 00 OO OO OO OO -q -q -q -q -q -q O5 O5 O5 O5 O5 O5 O5 O5 Ol Ol Ol Ol C?i i)i. i)i. Ji. CO CO tO |-i I-1 1-1 I-1 1-1 1-^ I-1 ^ 

OtO-q-qCO CO tO to I-1 h-1 «D CO tO tO H* OOCnO^I-1 h-iOOOOO-q -q -q CO OO -q -q Ol Ol *>• CO tO «O <O OO <Sn en en CO o ?o O5 Cn «D 00 -q Ci <35 en it*, tj^. CO CO CO C

CO tO

X XXX -o X X X X -= "=

xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxx

xxxxx x! ! xx xxxxx ! xxx ! xxx xxxx! xx x j | !

IIIII 1 III IIIII IIIII IIIII III 1 1 III III 

III 1 1 III IIIII 1 III IIIII II 1 IIIII III

jxxxx xxxxx x xx x| j xxx!!! xxxxj xxjxxxj

lliil yl li 11111 i i- i i i i i i 1 y yl yyy i yl i yi i i 

III 1 1 AI 111 ii III 1 i 1 A AI AAA | A , i A i

IN3 K-L K-L M tO h-L

xxxx

y 1 1 1 A | i

1 1 1

1 1 1

1 y ' 1 A |

! ! xx

xxxxx xxxxx xxxxx xxxxx xxx! x xxx! ! x-^xx xxxxx xxxxx

I 1 1 1 1 1 III IIIII IIII IIIII IIIII IIIII 1 1 1 NX NX 1 1 1 1

III I I III I III III I ill III I iill I 1 A A i i i i

xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx

III 1 1 III 1 III III NX 1 1 I 1 1 NX 1 1 1 1 1 IIII III

II 1 1 II 1 III III A | i i i 1 i A IIII llli ill"3

1-1 l~t|~t|~M_* N^^i-Li^ OiCTCCt

•^X XX 

X X XXXXX XXXX

I y y i fto'l I I I I 

1 1 A | A | ^ | 1 1 | | 

111 i i y y i 1111

ill i i A A i 1111

111 i y y y i i i i

II | A A A iiii

1 lllll llll 

1 1 llll llll

xxx! xxx j xx!

y i i 111 1111

A 1 1 III llll

! xxx xxxxx xxxx

1 1 1 1 II 1 1 1 NX 1 

ii I ill i i A i 

xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxx

11111 11111 11111 11111 11111 ii i i 111 i i i i NX NX i i i yyyi ' i i i i NX i i i i 11111 i I I lllii 11111 11111 11111 i ill i i i A A i i i AA A'I i 111 X i i i |

III 1 IIII IIIII || 1 IIII IIIII 1 1 1 1 1 1 1 y 1 1 1 N/ 1 1 1 1 1 1 1 1 I 1 1 I 

III 1 III 1 IIIII I|l|l III 1 III 1 1 1 II A , , | , A| III IIIII IIII

Illyyylyll ly ly'yly.^ 1 I I '' II ' ' ' y y ' ' ^ ' I I I I y 1 1 1 NX l IINXNX IIIIN

1 1 I A A A | A | | |A |A A i A "" i i i | ii ii i I I A A ii"3 ! 1 1 1 1 A i | | A ( t | A A i i i 

III 1 II yl y I I II llll lllll II yyy 1 - -I ' yl III II .NX' 1 1 I I i NX y y 1 ' III NX 

Illll I i A | A i i ii 1111 lllll iiAAAi"3 "3 !! AIIII i i "* A i lllii AAA| i i i A 

iiiii ii NX i ' yyi y ' i ' ' ' i i i i i i i i i i yyi i i i i i i i i i i i i i i i i i i NX i i i i i 

lllll III AI 1 AA| A |||I 1 III III 1 1 AA| lllll II llll lllll A| llll

tu IT^ CQ

if" "^

"5

o

%* E
50 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 1.—Mineral assemblages in samples of rocks from within and around the Taconic allochthon, southwestern Massachusetts and adjacent parts of Connecticut and New York—Continued

Sample

(128-1) _ __ _

128-2 _ _

129-1 __ __ __.

130-1 _ __ _

131-1 __ _ __

(140-1) __ _ ___

140-2 __ _ __ __

144-1 ____ __

152-1 _ _ _ _ _

161-1 __ __

162-1 __ _ _ _

163-1 __ _ _ _.

166-1 _ _.

167-1 _ _____

(167-2) __ ____

167-3 __ __ _.

170-1 __

170-2 __ _ _.

172-1 __

172-2 _ __

178-1 __ _

182-1 __ _

188-1 __ __

188-2 _ _ _ _

189-1 _ __ _ _

191-1 _

195-1 __ __ _

196-1 __

208-1 __ __ __

208-2 __ _ _

214-1 _ _ _

214-2 _ __ ___

215-1 _ _____

223-1 __

(223-2)

224-1

232-1 _ __ _

234-1 _ __ __

235-1 __ _

237-1 _ _ _

238-1 _

238-2 _ _

242-1 ______

243-1

243-2 _ _____

247-1 _

247-2 __ _ _

250-1 _ __ _

268-1 _

272-1 __ _ __

272-2 _ _ __ _

274-1 __ _

278-3 __ _

289-2 _

290-1 _ _ _

290-2 _ _ ____

291-1 _ _

297-1 . —

298-1 __

298-2 ______

300-1 _ __ _

309-1 __ __ __

331-1 _ __ _

331-3 _ __ _

333-1 __ ______

Bt

X

?

X

?

X

X

_ _ X

X

?

X

X

__ X

X

X

X

X

X

__ X

X

X

X

X

_ X

Ch

X 

X 

X 

X 

X

X 

X

X 

X

X 

X 

X 

X 

X

X 

X 

X 

X 

X

X 

X

XXXXXXX 

X

X 

X

X

X 

X

"x

9

"x

X 

X

Cd

--

X

X 

X

X 

X 

X 

X 

X

X

~x

X

—

?

"x

X 

X 

X

x"

X

X

X

X 

X 

X 

X 

X

X 

X

X

~x

--

—

--

~x

X 

X

st

—

—

—

—

--

"x

~x

X 

X

X

X 

X

Ga

x~

--

--

X

x~

X 

X 

X

X 

X 

X

x~

X 

X

--

X

X

X 

X

X 

X

X

X 

X

X

Ep

—

X

--

X

--

X 

X

X

—

X 

X

x~

X

--

--

—

—

—

—

—

Pg

X 

X 

X

X 

X 

X

X

X 

X 

X 

X

X

><

X

~x

X 

X

x"

X 

X 

X

X 

X 

X 

X 

1

X 

X 

X 

X

X

~x

X 

X

X

X

X

X 

X

X 

X

X 

X 

X 

X 

X

X 

X 

X 

X 

?

Ksp

--

—

—

~

—

~x

x:

X

X 

X

Mu

XXXXXX XX

XXXXXXXX 

X 

X

X 

X 

X

X 

X 

X 

X 

X

Pa

—

~x

--

X 

X 

X

X

—

—

—

1

X 

X

—

—

—

—

--

—

—

Q Cc

X __ 

X X 

X — 

X __ 

X __

X __ 

X 

X __ 

X

X __

X __ 

X 

X 

X 

X

X __ 

X 

X __ 

X __ 

X

X

X __ 

X X 

X X

x

X

X _

X __ 

X

X

X __ 

X __ 

X __ 

X __ 

X

X __ 

X __ 

X

X __ 

X

X __ 

X 

X 

X 

X __

X 

X 

X X 

X X 

X

X X 

X _

X X 

X __ 

X __

X __ 

X

X X 

X 

X

X X 

X 

X __ 

X __ 

X __

Dol Ilm

II "x 

II ><

X __

X

__ X 

X

__ __

__ __

__ X

II ?

__ X

_ X

__ X

II x~

__ X 

__ X

__ X 

__ X

__ X

II ><

II >< 

>< II

_ X

__ X 

X __

X

— —

X

~I ><

II ><

Mt Tour

— —

T ~x

X __

>< II 

x: —

?

_'_ X

__ X 

X

II ><

X

II ><

__ X 

__ X

~x

__ X 

__ X

II ~x

__ X 

__ X

__ __

X -_

__ __

" x"

— X

Other

Zs 

Hb

Cum 

Cum, Ap

Stp?

S'iderite 

Stp?

Hb 

Zs
TABLES 51

TABLE 1.—Mineral assemblages in samples of rocks from within and around the Taconic allochthon, southwestern Massachusetts and adjacent parts of Connecticut and New York—Continued

Sample

336-1

337-1 ______

338-1 __ _

339-1 _

(340-2) _

(344-1) _

344-2 _ _

345-1

346-1

350-1

350-2

352-1

352-3

355-1

356-1

358-1 _ _

360-1

(361-1) _

(363-1) __ __

365-1 _ __ __ .

366-1

366-2 _ _

366-3

369-1

370-1 _ _ _

370-2 _

373-1

373-2

(375-1) __ _

376-1-1 _

376-1-2 -

376-1-3

383-1 _ _

384-1

385-1 _

391-1

394-1 __ _ _

400-1

401-1

(401-2)

401-3

405-2

405-3 _ _

406-1

407-1

407-3

410-1

(412-1) _ __ _

(414-1)

417-1 __

421-1 _ __

(421-2) __

421-3 _

423-1 _ _

429-1 _ ___ _

444-1 _ _

448-1 _ _

456-1

457-1

463-1 __ _ _

464-1 _ _ _

466-1

466-2 _ _ .

468-1 _ _ _

473-1 __

Bt

X

X

X

X

X

X

X

X

X

__ X

X

X

7

X

9

X

X

X

X

Ch

X

X

X

X

X

X

X

X

X

y

X

X

y

x

x

x

x

V

x

X

x

x

x

x

X

x

V

x

X

y

x

x

V

x

V

x

V

x

x

X

x

x

X

x

x

x

X

V

x

V

x

V

X

x

V

Cd

X

X

1 O*Q

x

x

1 O*Q

X

1 O*Q

X

X

X

X

1 O*Q

x

X

X

X

X

X

st

X

X

X

X

X

X

X

X

X

X

X

Ga

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Ep

X

X

X

X

X

X

X

X

Pg

9

X

X

x

V

V

x

V

V

x

X

x

X

f

X

x

V

x

V

V

X

x

x

X

x

V

x

x

X

X

x

X

X

x

V

x

x

X

x

x

X

x

X

x

V

X

X

x

x

V

y

Ksp Mu

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Pa

X

X

X

X

X

X

Q Cc

X __

X

X

X

X

X __

X

X

X

X

X _

X

X

X

X

X X

X

X

X

X

X _

X

X

X _

X

X

X

X

X

X

X

X

X

X _

X

X X

X

X __

X

X

X

X

X __

X

X

X X

X

X ?

X

X __

X

X _

X

X _

X

X __

X

X X

X __

X __

X

X X

Dol Ilm

X

X

X

_ X

X

X

X

X

X

X

X

X

X

X

X

X

_ X

7

X

X

X

X

7

X

X

X

X

X

X

X

X

_ X

X

__ X

X

X

X

Mt Tour Other

X

X Ap

X

Stp, Zs

X

X

X

X

X

X Sph

X

X

- - Py

? X

X

X

X

X

X

_ X

_ X

_ X

_ X

9

__ X Stp

_ x

Act

__ X

__ X

_ X
52 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 1.—Mineral assemblages in samples of rocks from within and around the Taconic allochthon, southwestern Massachusetts and adjacent parts of Connecticut and New York—Continued

Sample

476-1

478-1 _ _ _ _.

479-1 _ _ __ _.

486-1 __ _ __.

487-1 ___ ___

487-2

488-1 _

488-2 _ _ _ . 495-1 __ _ _ __.

496-1 _

497-2 __

499-1 _ _ _ _ _

504-1

505-1 _

506-1

506-2 _ _

509-1 _ _ _

513-1 __ _ _ . 515-1 _ _

515-2 _ __ _

517-2 _ _ __ ___

543-1 _ _ _

563-1 __ _ _

569-1 __ __

581-1 _ _ _ _ _

581-2 __ _ _ _.

588-1 _ _ _ _

590-1 _ _ __

590-2

591-1 __ _ _

CQC 1

598-2 _ _

603-1

609-1 __ _ __

614-1 _ ___ _

626-1 ____ _

630-1 __ _ _

638-1 __ _ ____

641-1

649-1 _ __ ___

650-1 ____ _

652-1 __ __ __

655-1-1 _____

658-1 __ _ __

659-1 __ __ __

677-1 __ _ ____

677-2

690-1 ____ __

693-1 ____ __

701-1 __

709-2 _ __ _

715-1 _ ___

715-2 __

715-3 __ __ _

(715-4) __ _

749-1 ___ ___

749-2 _ __ _

750-1 _______

753-2 _ ___ _

806-1 __ __ __

808-1 _ _ __ _

813-1 _ _

885-1 __

893-1 _ ___

Bt

_ _ X

X

— X

X

X

X

_ _ X

__ X

X

__ X

-_ X

X

X

X

X

X

X

_ _ X

X

x

.__ X

X

__ X

_ X

X

7

x

X

__ X

__ X

X

__ X

__ X

__ X

X

__ X

__ X

X

__ X

X

X

__ X

__ X

_- X

__ X

Ch

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Cd

iga

iga

X

X

X

X

X

iffa

isra

X

iga

iga

st

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Ga Ep

X _

v

X

X

v

X

X

X

X _

X

X __

X

X

X X

X

X

x

X __

y

X

X __

X _

X X

X _

X

X

X

X _

x

X

__ X

X

X _

X

X

X __

X

X _

X

Pg

X

v

X

x

X

X

X

X

v

X

X

7

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Ksp

X

X

X

Mu Pa

X

X

X _

X

X

7

X

X

X

X

X _

X _

X

X

X

X _

X _

X __

x

X _

X

X

X

X

X

X

X _

X

X __

7

7

X

X

X

X

X

X

X

X

X

X

x

X

x

X

X _

X

X

X

X

X

X

X

X

X

X __

X __

Q

v

x

X

x

x

x

x

X

x

x

x

X

x

x

X

X

x

x

X

X

v

x

x

x

X

x

X

X

x

X

x

X

x

X

X

x

X

x

X

x

x

X

x

X

x

X

x

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Cc

X

X

X

X

X

X

7

7

X

X

X

X

X

X

X

X

X

X

X

Dol

X

7

X

X

X

X

X

X

Em

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

_

Mt

v

7

_

Tour

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

_

Other

Sph?

Cum

Hem

Dp, Trem

Fibrolite?

Kyanite

Sph, Trem,?

Sph, Trem

Stp?
TABLES 53

TABLE 1.—Mineral assemblages in samples of rocks from within and around the Taconic allochthon, southwestern Massachusetts and adjacent parts of Connecticut and New York—Continued

Sample

906-1 _

912-1 _ _

(918-1) __ _

941-1 _ _ _ __

959-1 __ _____

967-1 __

986-1 _ __

994-1 _____

999-1 _ __ __ _.

(1000-1) __ _ _

1009-1 _ __ __

1014-1 _ __ __

1014-2

1019-1 _ _______

1023-1

1032-1 _________

1032-2 __ __ _

1040-1 _ __ __

1052-1 _ ____

1052-2 _ _____

1054-1 __ _____

1073-1 __ _ __

1087-1

(1087-1-2) __ __

1087-2 _ _ _

1087-3 __ _ _____

1089-1 _ _ ______

1100-1 _________

1100-2 _________

1100-3 __ __

1102-1 __________

1106-1 __ ____ ,

(1106-2) __ _____

1107-1

1114-1 ____ _

(1115-1) _________

(1115-2) _

(1115-3) _____

1118-1

1129-1 _ ____

1139-1 _ __ _____

1143-1 _ __ _

1144-1 _ _ _____

1146-1 _ __ ___

1147-1 _ ___

1165-1

1169-1 __ _

1170-1 _ _ _ __

1173-1 _ ______

1180-1 __ __

1189-1-1 _ ______

1189-1-2

1192-1

120&-1

1204-1

1208-1 _ _ ____

1208-2 __ _____

1216-1

Bt

__ X

9

_ X

_ X

__ X

_ _ X

__ X

9

_ _ X

Ch Cd St

X X __

X __ __

X __ __

X _

X _

X _

X __ _

X __ _

X

X X __

X _ X

X X

X _

X

X _

X __ _

X __

X _

X

X _ _

X _ __

X _ __

X _ _

X __

X __ __

X

X __ _

X __

X _

X _

X _

9

X

X X

X

X

X

X

X

X

X _

Ga Ep

X

X

X

X __

__ X

X

__ X

X

X

Pg

X

X

X

X

9

X

X

X

X

X

9

X

X

X

X

X

9

9

X

X

X

X

X

X

X

X

X

9

X

9

9

X

X

X

X

X

X

X

X

X

Ksp

X

X

X

9

X

9

Mu

X

X

9

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

y

X

X

X

X

X

X

X

X

X

?

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

x

x

Pa

X

x

x

x

X

9

9

X

X

Q

x

x

x

X

x

X

x

X

X

X

x

x

x

X

x

x

X

X

X

X

x

X

-V

X

x

x

X

x

x

X

x

x

X

x

x

X

X

x

X

x

x

x

x

x

x

x

x

X

x

X

X

X

X

x

x

Cc

X

X

X

9

9

X

X

X

X

X

9

x

x

x

x

x

Dol Urn Mt Tour

9

X -

X _ _ —

._ _ X

__ _ X

? __ X

_ __ X

X

X _

_ __ X

__ X X

9

__ X

X __ _

__ _ X

__ _ _ X

__ — X

? __ X

X _ __ __

X __ __ __

X __

X X

X X

_ X X

X __ _ __

__ X

X __

X X

__ __ X

X

_ __ _ X

X __ __

__ X

Other

Sph?

Trem

Stp?

Stp

Stp? Sph

Tourmaline vein

Pv

Trem, Sph, Dp

Stp?

Stp?

Stp?

Hem

Stp?

Stp?

Stp

Stp, Hem
54 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 2. — Localities from which samples were obtained for

mineral-assemblage information

[The availability of data from microprobe and wet-chemical analyses is

indicated by footnote reference. Quadrangle: EGM, Egremont Quadrangle, Mass.-N.Y.; CPE, Copake Quadrangle, N.Y.-Mass.; BBF, Bashbish Falls Quadrangle, Mass.-Conn.-N.Y.; ASF, Ashley Falls Quadrangle,

Mass.-Conn.; HDL, Hillsdale Quadrangle, N.Y.; STL, State Line Quadrangle, N.Y.-Mass.; MLT, Millerton Quadrangle, N.Y.-Conn.; SHN, 

Sharon Quadrangle, Conn.-N.Y.; GBR, Great Barrington Quadrangle,

Mass. Formation: Ev, Everett Formation ( allochthonous ) ; W, Walloomsac Formation (autochthonous); W(ls), limestone in Walloomsac 

Formation; W(Eg), Egremont Phyllite, correlated with Walloomsac 

Formation (autochthonous); SB-a, SB-b, ***, SB-f Stockbridge Formation, unit a, unit b, ***, unit f (autochthonous); Sb-brec, Stockbridge

Formation, breccia ( parautochthonous at base of the Taconic allochthon);

Dal, Dalton Formation (autochthonous); W/Sb, on contact between Walloomsac and Stockbridge Formations. Zone: — Ga, below garnet zone; 

Ga, garnet zone; +Ga, at or near garnet zone lower boundary; +Ga, 

high-grade part of garnet zone; Ga/St, at or near garnet-staurolite

zone boundary; St, staurolite zone; +St, high-grade part of staurolite 

zone. Metamorphic zone designations for samples from the Stockbridge 

Formation are extrapolated from zones in the pelitic rocks]

Location

Sample Quad- Long. Lat. tfnT" Zone 

rangle 73° W+ N

3-1 __ EGM 28'00" 42°09'37" Ev -Ga

3-2 __ EGM 27'57" 09'37" Ev -Ga

3-3 1 __ EGM 27'53" 09'36" Ev -Ga

3-5 __ EGM 27'45" 09'35" Ev -Ga

3-6 __ EGM 27'40" 09'33" Ev — Ga

4-1 __ EGM 28'39" 10'22" W -Ga

14-1 * __ SHN 26'33" 41°59'48" W St

15-1 __ BBF 27'0'3" 42°00'03" W St

16-1 __ BBF 27'56" 00'44" Ev Ga/St

16-2 __ BBF 27'56" 00'44" Ev Ga/St

17-1 __ BBF 28'01" 02'27" Ev Ga

18-1 __ BBF 27'59" 04'17" W(Eg) -Ga

19-1 __ BBF 27'51" 04'52" W(Eg) -Ga

25-1 __ EGM 25'36" 10'56" SB-e Ga

36-1 __ EGM 26'57" 09'58" SB-c -Ga

39-1 __ EGM 26'22" 08'38" Ev -Ga

40-2 __ EGM 25'54" 07'52" Ev Ga

43-1 __ BBF 26'01" 07'13" Ev Ga

45-1 ^ _ EGM 26'33" 08'45" Ev -Ga

55-1 __ BBF 24'05" 0>6'43" SB-e Ga

55-2 __ BBF 24'05" 06'41" SB-e Ga

58-1 __ EGM 26'13" 08'36" Ev +Ga

59-2 __ EGM 26'08" 08'25" Ev +Ga

59-3 __ EGM 26'05" 08'24" Ev +Ga

62-1 __ EGM 25'45" 07'43" Ev +Ga

63-1 __ EGM 25'53" OS'00" Ev +Ga

64-1 __ BBF 25'23" 06'33" Ev Ga

65-1-2 __ BBF 25'37" 06'24" Ev Ga

65-1-3 __ BBF 25'37" 06'24" Ev Ga

67-1 __ BBF 25'59" 06'08" Ev Ga

67-2 __ BBF 25'53" 06'04" Ev Ga

68-1 __ BBF 26'12" 06'22" Ev Ga

73-1 __ BBF 26'14" 06'02" Ev Ga

77-1 __ BBF 24'52" 06'18" W Ga

77-2 __ BBF 24'55" 0>6'18" Ev Ga

77-3 __ BBF 25'07" 06'16" Ev Ga

78-1 __ BBF 25'22" 06'19" Ev Ga

78-2 __ BBF 25'22" 06'19" Ev Ga

80-1 __ BBF 25'08" 05'42" Ev Ga

81-1 __ BBF 25'03" OS'41" Ev Ga

81-2 __ BBF 25'03" 05'41<" Ev Ga

84-1 __ BBF 25'22" 07'25" Ev Ga

85-1 __ BBF 25'17" 07'17" Ev Ga

90-1 __ BBF 25'08" OS'19" Ev Ga

90-2 __ BBF 25'06" 05'21" Ev Ga

91-1 __ BBF 25'27" 05'22" Ev Ga

92-1 __ BBF 25'42" OS'03" Ev Ga

92-2 __ BBF 25'47" 04'58" Ev Ga

93-1 __ BBF 25'55" 04'47" Ev Ga

99-1 __ BBF 26' 10" 03'45" Ev Ga/St

TABLE 2. — Localities from which samples were

minera l-assem b lage

Sample

101-1 ___

101-2 __ _

102-1 1 __ 

102-2 __

103-1 1 _

103-2 1 ___ 

107-1 __ 

107-2 __

112-1 __ 

120-1 __

128-1 __ 

128-2 __ 

129-1 __

130-1 __

131-1 __

140-1 __

140-2 12 _

144-1 __

152-1 __

161-1 * ——

162-1 __

163-1 __

166-1 __

167-1 __

167-2 __

167-3 __

170-1 ....

170-2 __

172-1 __

172-2 ____

178-1 __

182-1 __

188-1 __

188-2 __

189-1 __

191-1 ' __

195-1 __

196-1 __

208-1 __

208-2 __

214-1 __

214-2 __

215-1 __

223-1 __

223-2 __

224-1 __

232-1 __

234-1 1 __

235-1 __

237-1 __

238-1 __

238-2 __

242-1 __

243-1 __

243-2 __

247-1 __

247-2 __

250-1 __

268-1 __

272-1 __

272-2 __

274-1 ____

278-3 __

Quadrangle

BBF

BBF

BBF 

BBF

BBF

BBF 

BBF 

BBF

BBF 

BBF

•RTJTP r>or 

BBF 

BBF

UT3T3 DOT1

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

EGM

EGM

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

CPE

CPE

CPE

BBF

BBF

BBF

BBF

BBF

BBF

EGM

BBF

BBF

BBF

BBF

Location

Long.

rrqo ^rr [ 1 O VV T"^

26'55"

26'55"

26'21" 

26'12"

25'58"

25'53" 

26'15" 

26'03"

26'05" 

27'20"

9S'fl^" £O UO 28'OS" 

27'50"

orrM C" ^ /lb 27'14"

27'33"

27'43"

28' 10"

28'04"

27'33"

28'36"

28'54"

28'59"

28'31"

28'31"

28 '31"

27'22"

27'22"

28'01"

28'01"

27'54"

27'04"

28'51"

29'06"

29' 16"

29'04"

29' 57"

29'50"

28'46"

28'05"

26'06"

26'06"

26 '38"

29'53"

29'54"

29' 57"

26'35"

25 '05"

25 '30"

30'01"

30'18"

30 '11"

29'10"

29'30"

29'36"

24'56"

24'58"

24'45"

24'15"

26'16"

26'21"

25'59"

24'25"

obtained for

information — Continued

Lat.

N

42°03'21"

03'21"

03'07" 

03'16"

03' 19"

03 '20" 

04'30" 

04'31"

04' 11" 

02 '43"

07'fiQ" U 1 Uc7 07'03" 

07' 05"

nQ/K/y> UO OV 03'56"

05'05"

05' 04"

05'42"

06'04"

03 '23"

02'57"

03'08"

03' 52"

03'45"

03'45"

03'45"

02'25"

02'21"

02'24"

02'24"

08'51"

08'02"

OS'45"

OS'42"

OS'42"

05'59"

06'58"

06'54"

04'13"

04' 17"

02'56"

02'56"

02'53"

06'15"

06'07"

05 '57"

06'22"

04'54"

04'56"

05 '08"

OS'14"

05'31"

02'23"

02 '20"

02'30"

OS'41"

05'44"

06'11"

08'49"

03'01"

03'04"

03'23"

04'35"

Formation

Ev

Ev

W 

W

W

W 

Ev 

Ev

Ev 

Ev

W(Eg) 

W(Eg) 

W(Eg)

Ev

Ev

Ev

Ev

W(Eg)

W(Eg)

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

W(Eg)

W(Eg)

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

W

Ev

W

Ev

Ev

Ev

Ev

Ev

Ev

Ev

SB-f

SB-c

W

W

WSB-b

Zone

Ga

Ga

Ga/St 

St

St

St 

Ga 

Ga

Ga 

Ga

-f-fj,fl HHjrd

±Ga 

Ga

Ga

Ga

-Ga

-Ga

-Ga

-Ga

Ga

±Ga

-Ga

— Ga

-Ga

-Ga

-Ga

Ga

Ga

Ga

Ga

-Ga

-Ga

— Ga

-Ga

-Ga

— Ga

-Ga

-Ga

-Ga

-Ga

St

St

St/Ga

-Ga

— Ga

-Ga

Ga

St

Ga

-Ga

-Ga

— Ga

-Ga

-Ga

-Ga

Ga

Ga

Ga

Ga

St

St

St

St
TABLES 55

TABLE 2. — Localities from which samples

mineral-assemblage

Sample

289-2 * __

290-1 x __

290-2 __

291-1 __

297-1 __

298-1 __

298-2 __

300-1 __

309-1 __ 

331-1 1 __ 

331-3 __ 

333-1 __

336-1 __

337-1 __

338-1 a __ 

339-1 * __

340-2 __

344-1 __

344-2 __

345-1 __

346-1 __

350-1 __

350-2 __

352-1 __

352-3 __

355-1 12 __

356-1 1 a __

358-1 __

360-1 1 __

361-1 __

363-1 __

365-1 __

366-1 __

366-2 __

366-3 __

369-1 1 __

370-1 __

370-2 __

373-1 __

373-2 __

375-1 __

376-1-1 _

376-1-2 _

376-1-3 __

383-1 ____

384-1 __

385-1 __

391-1 __ 

394-1 __

400-1 __ 

401-1 __ 

401-2 __

401-3 __ 

405-2 __

405-3 __ 

406-1 ____ 

407-1 __

407-3 __

410-1 __

412-1 __

414-1 __

417-1 __

421-1 __

421-2 __

Quadrangle

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

EGM 

BBF 

BBF 

BBF

BBF

BBF

BBF 

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

SHN

BBF

BBF

SHN

BBF

CPE

BBF

BBF

SHN

SHN

SHN

BBF

BBF

BBF

HDL

HDL

CPE

CPE

CPE

CPE

CPE

CPE

CPE

BBF 

CPE

BBF 

BBF 

BBF

CPE 

BBF

BBF 

BBF 

CPE

CPE

CPE

BBF

CPE

CPE

CPE

CPE

Location

Long.

73° W +

23'34"

23'32"

23'31"

23'13"

25' 15"

25'03"

25'05"

25'03"

22'32" 

26 '24" 

26'40" 

27'22"

26' 53"

26'59"

27'20" 

26'42"

26'24"

28'28"

28'37"

29'13"

29'44"

26'54"

26'54"

27'46"

27' 17"

26 '47"

26'11"

25'54"

29'20"

30'04"

29'46"

29 '40"

28'10"

28'10"

28 '10"

27' 08"

27'04"

27'04"

30'18"

30'27"

30'44"

30' 57"

30' 57"

30'57"

31 '40"

SI'00"

30'35"

29'51" 

30'54"

29'36" 

29'53" 

29'56"

SO'Ol" 

29'48"

29'48" 

29 '49" 

30 '07"

30'16"

30 '32"

28 '27"

30'05"

31 '59"

30'06"

30'02"

were obtained for

information — Continued

Lat.

N

42° OS'0©"

OS'01"

OS'01"

OS'13"

02'24"

02'03"

02'22"

02'40"

09'44" 

01 '51" 

01 '55" 

01 '37"

01'43"

Ol'll"

01 '09" 

00'28"

00'32"

01 '37"

01 '37"

01 '43"

01 '44"

00'25"

00'40"

OO'Ol"

41°59'57"

42°00'25"

00'04"

41°59'31"

42°04'36"

04'45"

05'16"

05 '39"

41°59'40"

59'37"

59'37"

42° OO'SO"

OO'SO"

OO'SO"

07'47"

07' 54"

0'6'39"

06'22"

06'22"

06'22"

Formation

w

w

w

w

SB-fc

SB-b

SB-b

SB-b

Dal 

W 

Ev 

Ev

Ev

Ev

Ev 

Ev

W

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

W

SB

Ev

Ev

Ev

Ev

W

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

Ev

05'31" SB-brec 05'31"

04'36"

03 '38" 

04' 03"

0'2'50" 

02'28" 

02 '27"

02'26" 

01 '52"

01'52^' 

01 '03" 

01 '07"

01 '07"

01 '31"

02'37"

04'23"

04'29"

00'19"

00'17"

Ev

Ev

Ev 

SB

Ev 

Ev 

Ev

Ev 

Ev

Ev 

Ev 

Ev

Ev

SB

Ev

Ev

SB

Ev

Ev

Zone

+st +st

+st +st

St

St

St

St

Ga

St 

St 

Ga/St

Ga/St

Qf J3l

Ga/St 

St

q+ ot

Ga

Ga

Ga

Ga

St

St

St

St

St

St

St -Ga

-Ga

-Ga

-Ga

St

St

St

St

St

St

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga 

-Ga

-Ga 

-Ga 

-Ga

-Ga 

±Ga

±Ga 

Ga 

Ga

Ga

±Ga

±Ga

-Ga

-Ga

Ga

Ga

TABLE 2. — Localities from which samples

mineral-assemblage

Sample

421-3 __

423-1 __

429-1 ____

444-1 __

448-1 __

456-1 __

457-1 __

463-1 * __

464-1 ____ 

466-1 ' __ 

466-2 __ 

468-1 __

473-1 __

476-1 ____ 

478-1 __

479-1 ____

486-1 __

487-1 __

487-2 1 __

488-1 __

488-2 __

495-1 __

496-1 __

497-2 __

499-1 ____

504-1 __

505-1 __

506-1 a __

506-2 __

509-1 x __

513-1 __

515-1 1 __

515-2 __

517-2 __

543-1 __

563-1 __

569-1 __

581-1 __

581-2 __

588-1 __

590-1 __

590-2 ____

591-1 __

595-1 ____

598-2 __

603-1 __

609-1 __ 

614-1 __

626-1 __ 

630-1 __ 

638-1 __

641-1 __ 

649-1 __

650-1 __ 

652-1 __ 

655-1 1 __

658-1 __

659-1 __

677-1 __

677-2 __

690-1 __

693-1 __

701-1 __

Quadrangle

CPE

MLT

EGM

SHN

SHN

EGM

EGM

SHN

SHN 

SHN

SHN 

SHN

SHN

SHN

SHN

SHN

SHN

SHN

BBF

SHN

SHN

SHN

SHN

SHN

SHN

SHN

SHN

SHN

SHN

BBF

BBF

BBF

BBF

EGM

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

BBF

ASF

SHN

BBF 

ASF

SHN 

BBF 

BBF

BBF 

ASF

ASF 

ASF 

ASF

ASF

ASF

SHN

SHN

EGM

EGM

EGM

Location

Long.

73° W +

30'09"

30 '03"

28'55"

29'59"

29 '27"

29 '02"

28'21"

28'26"

28'30" 

28'50" 

28'50" 

28'01"

27' 52"

27'03" 

27'05"

27'29"

25'43"

27'27"

27'27"

27'36"

27'36"

28 '49"

29'05"

29'14"

28 '32"

28'52"

28'57"

39 '05"

29'14"

24'54"

26'43"

26'13"

26'08"

26'09"

24'16"

22 '50"

22 '46"

24' 06"

24'08"

25'06"

24'26"

24' 26"

24'35"

23 '56"

21 '22"

29'10"

23'23" 

22'14"

25'52" 

25'52"

25'47"

24' 47" 

21 '37"

21 '19" 

21'11" 

20 '54"

20'46"

21 '16"

22 '55"

22'55"

27'24"

27'29"

27'12"

were obtained for

information — Continued

Lat.

N

42°0'0'19"

41° 59 '41"

42°09'25"

41° 59 '24"

59'01"

42°10'13"

10'19"

41°58'21"

58'17" 

59 '04" 

5©'04" 

58'55"

5S'01"

59'47" 

59'18"

59 '09"

59'14"

59'55"

42°00'02"

41° 58 '17"

58'17"

56'02"

55'41"

55'55"

56'54"

56'15"

55'42"

55'13"

55'09"

42°05'38"

02'50"

02'28"

02'28"

08 '33"

06'21"

03 '28"

05'22"

01 '35"

01 '41"

01'42"

00 '44"

00 '44"

OO'IO"

00'09"

04' 07"

41°54'11"

42°00'27" 

02 '24"

41°59'27" 

42° 03' 53" 

04'20"

05'49" 

02'18"

02'45" 

01 '42" 

02'21"

0'2'56"

01'15"

41° 59 '42"

59'42"

42°12'15"

11 '41"

Formation

Ev

W

Ev

Ev

Ev

Ev

W

W

SB 

Ev 

Ev 

Ev

W

Ev 

W

W

W

Ev

Ev

W

W

W

Ev

Ev

W

W

W(ls)

Ev

Ev

W

Ev

Ev

Ev

Ev

SB-c

W

W

W

WSB-b

W

W

W

WSB-a

Ev

W 

W

W 

W 

Ev

W 

W

W 

W 

W

W

SB

W/SB

W/SB

Ev

Ev

12'34" SB-brec

Zone

Ga

Ga

-Ga

Ga

Ga

-Ga

-Ga

St

St

Ga/St 

Ga/St 

St

St

St 

St

St

St

St

St

St

St

Ga/St

Ga/St

Ga

St

Ga/St

Ga/St

Ga/St

Ga

Ga

Ga/St

St

St

Ga

Ga

+st

St

St

St

St

St

St

St

+st

+St

Ga/St

+St

+st

St

Ga/St 

Ga/St

Ga +st

+st +st +st +st

+st

+st +st

-Ga

-Ga

-Ga
56 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 2. — Localities from which sample

mineral-assemblage

Sample Quad709-2

715-1

715-2 

715-3 

715-4

717-2

749-1

749-2 

750-1 

753-2

806-1

808-1

813-1 

885-1 

893-1

906-1

912-1

918-1 

941-1 

959-1

967-1

986-1

994-1

999-1

1000-1

1009-1

1014-1

1014-2

1019-1

1023-1

1032-1 

1032-2 

1040-1

1052-1 

1052-2

1054-1

1 07Q 1 JLU (o — X

1087-1

rangle

__ EGM

__ EGM

__ EGM 

__ EGM 

__ EGM

__ HDL

__ ASF

__ ASF 

__ ASF 

__ ASF

__ EGM

__ EGM

__ EGM 

__ EGM 

__ EGM

__ BBF

__ GBR

2 _ EGM 

__ GBR 

__ EGM

__ EGM

__ EGM

__ STL

__ EGM

__ EGM

__ STL

__ EGM

__ EGM

__ STL

__ STL

__ EGM 

__ STL 

__ STL

__ SHN 

1 _ SHN

__ SHN

__ EGM 

__ EGM

Location

Long.

73° W +

29 '04"

29'03"

29 '00" 

28'59" 

29'04"

30'09"

21 '41"

21 '46" 

22'07" 

21'29"

25'19"

24'20"

23'31" 

26'17" 

25'08"

25'07"

22'29"

22'43" 

22'00" 

25'36"

25'39"

26'27"

29'24"

29 '26"

29'24"

28'03"

29 '46"

29 '40"

29'03"

29'02"

26'54" 

26'48" 

25'56"

23'15" 

23'17"

22'33"

28'13" 

28'28"

s were obtained for

information — Continued

Lat.

N

42°14'33"

14'29"

14'26" 

14'25" 

14'31"

14'31"

06' 50"

06 '43" 

06'54" 

05'47"

12'57"

12'57"

11'17" 

08'20" 

07'49"

07'19"

08'17"

09 '30" 

12'06" 

14'03"

14'31"

13'51"

15'08"

14'12"

14'10"

22'24"

14'51"

14' 52"

15 '28"

15'19"

14'55" 

15 '03" 

15 '03"

41° 59 '55" 

59 '58"

59'33"

42°13'00" 

11 '52"

Formation

Ev

Ev

SB-brec 

W 

SB-brec

W(ls)

Ev

Ev 

Ev SB-a

Ev

W(ls)

SB-b 

Ev SB-c

SB-f

SB-b

SB-a 

Dal 

Ev

SB-brec SB-d

Ev

Ev

Ev

Ev

Ev

Ev

SB-brec

Ev vein

Ev 

Ev 

Ev

W 

W

W/SB

TTSr JiiV 

W

Zone

— Ga

-Ga

— Ga 

-Ga 

-Ga

-Ga

St

St 

St 

St

Ga

Ga

Ga 

Ga 

Ga

Ga

Ga

St 

Ga 

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

— Ga

-Ga

-Ga

-Ga

-Ga

-Ga 

— Ga 

-Ga

+st 

+st

-f-St

-Ga 

— Ga

TABLE 2. — Localities from which sample

mineral-assemblage

Sample

1087-1-2 _

1087-2 ____

1087-3 __ 

1089-1 ____ 

1100-1 ____

1100-2 __

1100-3 __

1102-1 __ 

1106-1 __ 

1106-2 ____

1107-1 __

1114-1 __

1115-1 __ 

1115-2 __ 

1115-3 __

1118-1 __

1129-1 __

1139-1 __ 

1143-1 __ 

1144-1 __

1146-1 __

1147-1 __

1165-1 ____

1169-1 * __

1170-1 ____

1173-1 __

1180-1 ____

1189-1-1 _

1189-1-2 _

1192-1 __ 

1200-1 __ 

1204-1 __

1208-1 __ 

1208-2 __

1216-1 __

Quadrangle

EGM

EGM

EGM 

EGM 

CPE

CPE

CPE

EGM 

EGM 

EGM

EGM

EGM

HDL 

HDL 

HDL

EGM

EGM

EGM 

EGM 

EGM

EGM

EGM

HDL

CPE

CPE

EGM

EGM

EGM

EGM

EGM 

EGM 

EGM

EGM 

EGM

EGM

Location

Long. 73° W-f

28'28"

28'28"

28'24" 

28'43" 

30'01"

30'01"

30'09"

28'02"

27'45" 

27' 45"

28'06"

29 '56"

30 '16" 

30'15" 

30'16"

29 '41"

29 '43"

29'07" 

29 '54" 

29'49"

28' 38"

28'10"

31 '28"

30' 20"

30'47"

28'05"

27'32"

28'21"

28'21"

29 '06"

28'45" 

28'19"

27'30" 

27'39"

27'06"

s were obtained for

information — Continued

Lat.

N

42°11'52'"

11 '52"

11'53" 

12'00" 

06'57"

06'57"

06'59"

12'46" 

13 '24" 

13'24"

13'20"

10'Sl"

10'48" 

10'04" 

10 '04"

10' 35"

09'44>"

09'05" 

08'03" 

07'39"

09 '07"

12'36"

OS'01"

07'28"

07'06"

11'06"

12'06"

13'39"

13'39"

09 '44" 

08'49" 

08'26"

07'56" 

07'47"

14'06"

Formation

W

W

W 

SB-brec 

Ev

Ev

Ev

Ev 

SB-brec 

SB-brec

Ev

Ev

SB-b 

SB-b SB-b

W

W

Ev 

Ev 

Ev

Ev

Ev

SB-d

Ev

Ev

W

SB-brec

Ev

Ev

Ev 

W 

Ev

Ev 

Ev

Ev

Zone

-Ga

-Ga

-Ga 

-Ga 

-Ga

-Ga

— Ga

— Ga 

-Ga 

-Ga

-Ga

-Ga

-Ga 

-Ga 

— Ga

-Ga

-Ga

-Ga 

-Ga 

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga

-Ga 

— Ga — Ga

-Ga 

— Ga

-Ga

1 Probe data are available 

2 Wet-chemical data are available.
TABLES 57

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon

A. Muscovite 

E. Staurolite

7. Epidote

B. Biotite 

F. Garnet

J. Plagiodase

List of sections of table

C. Chlorite 

G. Kyanite

K. Ilmenite

D. Chloritoid

H. Hornblende and

Cummingtonite 

L. Magnetite

[Both the chemical analyses and the number of atoms are based on the anhydrous formulas. Total iron is calculated as FeO. The excess oxygen 

equivalent to analyzed fluorine and chlorine has been subtracted from the sums and subsums of the analyses. The amount of water has been 

determined by converting the anhydrous mineral formula to the hydrous mineral formula and by considering the iron to be ferrous (see page 

6 for details). Accuracy for major components is ±1 percent; for minor components, it is ±5 percent. Mineral assemblages are given in 

table 1; sample localities are given in table 2. nd, not determined. Abbreviations of mineral names: Bt, biotite; Ga, garnet; Pg, plagioclase; 

Urn, ilmenite; Ch, chlorite; Cd, chloritoid; St, staurolite; Ep, epidote; Hb, hornblende; Mu, muscovite. Analyses of some spots mentioned in 

the notes are not included in table 3 because their sums are outside the 10J±2 percent limit (see page 6 for discusson)]

A. MUSCOVITE

Sample _ —— _ — _ _ .__

Spot .. ___________

14-1

15 19 042008

102-1

042009 051008 051009

103-1

051010 052002

Weight percent

Si02 __ ___ ___ __

Ti02 _ _ __

A12 03 _ _ __ _

FeO _ __ _ _____

MnO __ _ _ __

MgO _ _ _ _____

CaO ___ __ _

Na20 __ _ _ __

K20 ______________

F __ __ _

Subsum

H20 ______________

42.57 

.38 

37.05 

.84 

.01 

.35 

.07 

1.36 

10.25 

.00

92.88 

4.37

97.25

44.57 

.25 

35.12 

1.14 

.14 

.30 

.00 

1.58 

9.62 

.20

92.75 

4.39

97.14

44.89 

.20 

35.33 

1.46 

.08 

.65 

.00 

1.19 

9.29 

nd

93.04 

4.41

97.45

44.93 

.14 

35.68 

1.33 

.04 

.58 

.00 

1.13 

9.08 

nd

92.91 

4.42

97.33

45.30 

.25 

35.30 

1.67 

.02 

.44 

.00 

1.30 

8.74 

nd

93.02 

4.43

97.45

45.46 

.17 

34.51 

2.23 

.04 

.72 

.00 

1.38 

8.99 

nd

93.50

4.42

97.92

46.42 

.31 

34.89 

2.23 

.03 

.93 

.00 

.94 

9.20 

nd

94.95 

4.50

99.45

45.19 

.27 

35.07 

2.00 

.04 

.49 

.03 

1.16 

8.89 

nd

93.14

4.42

97.56

Number of atoms

Sd _________ _

Ti __ ____ _

Al _ __ _ _

Fe _____ _ _ Mn _ ___________

Mg ________ — ____

Ca _ _ _ _______

Na _____ __ _

K _ __ __ __ _

F __ _ _ __ _

Cation sum _

2.92 

.02 

2.99 

.05 

.00 

.04 

.01 

.18 

.90 

.00

7.11

3.05 

.01 

2.83 

.06 

.01 

.03 

.00 

.21 

.84 

.04

7.04

3.05 

.01 

2.83 

.08 

.00 

.07 

.00 

.16 

.81 

nd

7.01

3.05 

.01 

2.85 

.08 

.00 

.06 

.00 

.15 

.79 

nd

6.99

3.06 

.01 

2.83 

.09 

.00 

.04 

.00 

.17 

.75 

nd

6.95

3.08 

.01 

2.76 

.13 

.00 

.07 

.00 

.18 

.78 

nd

7.01

3.09 

.02 

2.74 

.12 

.00 

.09 

.00 

.12 

.78 

nd

6.96

3.07 

.01 

2.81 

.11 

.00 

.05 

.00 

.15 

.77 

nd

6.97

Notes

Spots 042008 and 042009 

are in same crystal

Next to 

Bt 

051011

Next to 

Ga 

052001; 

near 

Urn 

052003
58 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE—Continued

Sample —————————______103-1—Continued

Spot ————————————— 052004 052007

Si02 __________ 46.02 45.41

Ti02 _________ .18 .24

A1203 ________ 35.05 34.71

FeO __________ 2.08 2.62

MnO ________ .02 .05

MgO _________ .48 .59

CaO _________ .01 .01

Na20 ________ .67 1.06

K2 0 __________ 8.65 7.98 

F ________________nd_____nd

Subsum ___ 98.16 92.67

H20 __________ 4.44_____4.41

____Sum ____ 97.60 97.08

Si __________ 3.11 3.09

Ti __________ .01 .01

Al __________ 2.80 2.78

Fe __________ .12 .15

Mn _________ .00 .00

Mg __________ .05 .06

Ca __________ .00 .00

Na _________ .09 .14

K ___________ .74 .69 

F __________________nd_____nd

Cation sum _ 6.92 6.92

103-2

061011 061014 061017 062003 062010

161-1

Weight percent

44.23

.17

35.49

1.94

.06

.54

.00

1.29

9.60

nd

45.01

.27

34.56

2.03

.03

.91

.03

1.02

9.94

nd

45.51

.17

34.48

1.91

.05

.68

.04

1.03

9.81

nd

46.47 

.20

32.66

1.89

.04

.59

.00

.93

9.76

nd

45.40

.24

35.00

1.96

.04

.48

.00

1.31

9.57

nd

93.32

4.40

93.80

4.42

93.68

4.42

92.54

4.38

94.00

4.44

97.72 98.22 98.10 96.92 98.44

45.32

.46

35.29

2.57

.00

.55

.09

.71

8.34

.00

93.33

4.44

97.77

44.04

.63

37.20

2.14

.00

.43

.13

.68

8.36

.30

93.66

4.46

98.12

Number of atoms

3.02 

.01

2.85 

.11 

.00 

.06 

.00 

.17 

.83 

nd

3.06 

.01

2.77 

.12 

.00 

.09 

.00 

.13 

.86 

nd

3.09 

.01

2.76 

.11 

.00 

.07 

.00 

.14 

.85 

nd

3.18 

.01

2.64 

.11 

.00 

.06 

.00 

.12 

.85 

nd

3.07 

.01

2.79 

.11 

.00 

.05 

.00 

.17 

.83 

nd

7.05 7.04 7.03 6.97 7.03

3.06

.02

2.81

.15

.00

.05

.01

.09

.72

.00

6.91

2.97

.03

2.95

.12

.00

.04

.01

.09

.72

.06

6.93

Notes

Next to 

Bt

052008

In Pg 

061018

Next to Bt 

062002 

and 

062004
TABLES

TABLE 3. — Microprobe data on various minerals in samples of rocks from within and around the Taconic

59

allochthon — Continued

A. MUSCOVITE— Continued

Sample _ - _ __ .._

Spot . ________

191-1

1 2

234-1

4 i

290-1

2 3 091004

331-1

091006 092002

Weight percent

Si02

Ti02 _____ ___ ___

A12 03

FeO _ __ _ ,

MnO

MgO _

CaO ___ _ _ _

Na20

K2 0 ______________

F _

Subsum _

H20 ____ _ ____

Sum

45.03 

.20 

35.80 

3.45 

.07 

.32 

.00 

1.25 

8.69 

.00

94.81 

4.47

99.28

45.59 

.24 

34.78 

3.07 

.00 

.43 

.01 

1.30 

8.62 

.00

94.04 

4.45

98.49

48.00 

.38 

37.73 

.87 

.03 

.48 

.02 

.87 

8.77 

.00

97.15 

4.67

101.82

46.74 

.13 

37.66 

1.03 

.01 

.33 

.02 

1.66 

8.54 

.00

96.12 

4.60

100.72

46.52 

.25 

36.12 

1.20 

.00 

.61 

.00 

1.36 

8.46 

.14

94.54 

4.52

99.06

46.88 

.31 

36.46 

.91 

.00 

.34 

.02 

1.71 

8.62 

.00

95.25 

4.56

99.81

46.64 

.21 

36.55 

1.27 

.03 

.49 

.00 

1.88 

7.42 

nd

94.49 

4.54

99.03

45.67 

.24 

36.93 

1.07 

.04 

.36 

.00 

2.02 

7.82 

nd

94.15 

4.51

98.66

45.73 

.30 

36.53 

1.66 

.05 

.52 

.00 

1.90 

7.92 

nd

94.61

4.52

99.13

Number of atoms

Si __ ___ _ _______

Ti

Al _ _ _

Fe _ _ __ _ __

Mn _ __ __

Mg _______________

Ca _ _ __ _ _

Na

K _ _ __

F _ _ _ _ _

Cation sum ___

3.02 

.01 

2.83 

.19 

.00 

.03 

.00 

.16 

.74 

.00

6.98

3.07 

.01

2.77 

.17 

.00 

.04 

.00 

.17 

.74 

.00

6.97

3.08 

.02 

2.85 

.07 

.00 

.05 

.00 

.11 

.72 

nd

6.90

3.05 

.01 

2.89 

.06 

.00 

.03 

.00 

.21 

.71 

.00

6.96

3.08 

.01 

2.82 

.07 

.00 

.06 

.00 

.17 

.72 

.03

6.93

3.09 

.02 

2.83 

.05 

.00 

.03 

.00 

.22 

.72 

.00

6.96

3.08 

.01 

2.84 

.07 

.00 

.05 

.00 

.24 

.63 

nd

6.92

3.04 

.01 

2.89 

.06 

.00 

.04 

.00 

.26 

.66 

nd

6.96

3.04 

.01 

2.86 

.09 

.00 

.05 

.00 

.24 

.67 

nd

6.96

Notes

Next to 

Ch 

091005

Next to 

Ch 

091007

Next to 

Urn 

092001
60 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE— Continued

Sample __ _ . ______ _

Spot ______ _________

331-1 — Continued

092003 092009 093007 093012 101003 101005

338-1

101006 101007 102003

Weight percent

Si02 ______

Ti02

A1203 _ __ _ __

FeO _ __ __ __

MnO . __ _

MgO ____ _ _____

CaO _ _ __ __ __

Na20 __ _ _ _

K2 0 _ _ __ _

F __ _ __

Subsum _

H_0 ______________

Sum _ _ _

46.02 

.24 

37.05 

1.08 

.11 

.41 

.00 

2.24 

7.91 

nd

95.06 

4.55

99.61

45.65 

.19 

37.31 

1.09 

.05 

.32 

.00 

2.33 

8.09 

nd

95.03 

4.54

99.57

45.60 

.21 

36.55 

1.26 

.05 

.43 

.00 

1.71 

7.78 

nd

93.59 

4.49

98.08

46.04 

.26 

36.43 

1.23 

.02 

.45 

.00 

1.80 

7.52 

nd

93.75 

4.50

98.25

45.33 

.24 

35.12 

2.19 

.04 

.64 

.00 

1.35 

8.81 

nd

93.72

4.44

98.16

45.22 

.17 

36.59 

1.58 

.03 

.36 

.00 

1.87 

8.46 

nd

94.28 

4.49

98.77

46.24 

.18 

35.29 

2.15 

.05 

.56 

.00 

1.62 

8.92 

nd

95.01 

4.50

99.51

45.55 

.23 

36.46 

1.57 

.05 

.40 

.00 

1.40 

8.77 

nd

94.43 

4.49

98.92

46.10 

.21 

35.98 

2.10 

.04 

.49 

.00 

1.28 

8.73 

nd

94.93 

4.56

99.49

Number of atoms

Sd _ __ __ _

Ti _____

Al _

Fe ______

Mn __ — _ _ _ _

Mg ______ _ _ _

Ca _ __ _ __ _

Na __ _ __ __

K _ _ _ __

F _ _

Cation sum _ .,

3.04 

.01 

2.88 

.06 

.01 

.04 

.00 

.29 

.67 

nd

7.00

3.02 

.01 

2.91 

.06 

.00 

.03 

.00 

.30 

.68 

nd

7.01

3.05 

.01 

2.88 

.07 

.00 

.04 

.00 

.22 

.66 

nd

6.93

3.07 

.01 

2.86 

.07 

.00 

.04 

.00 

.23 

.64 

nd

6.92

3.06 

.01 

2.80 

.12 

.00 

.06 

.00 

.18 

.76 

nd

6.99

3.02 

.01 

2.88 

.09 

.00 

.04 

.00 

.24 

.72 

nd

7.00

3.08 

.01 

2.77 

.12 

.00 

.06 

.00 

.21 

.76 

nd

7.01

3.04 

.01 

2.87 

.09 

.00 

.04 

.00 

.18 

.75 

nd

6.98

3.06 

.01 

2.82 

.12 

.00 

.05 

.00 

.17 

.74 

nd

6.97

Notes

Next to 

Ilm 

092001 

and Ch 

092004

Next to 

St 

093004, 

Ch 

093005, 

and Cd 

093006

Near Next to 

St Cd 

093004 101002 

and Bt 

101001

Next to 

Bt 

101004

Next to 

crystal 

containing Mu 

101005

Next to 

Bt 

101008
TABLES 61

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE— Continued

Sample _ _______

Spot _ ____ __ ______

338-1 — Continued

102004 102009 102013 102014 101101 111025

339-1

111029 112007 112008

Weight percent

SiO. _ __ _ __

TiO, _ _ _ _

Al_0a __ _. __ _

FeO _ _ _ __ _ MnO ___ _____

MgO ____ _ _

CaO __ __ _

Na.O _ _ __ _

K.O ___ ____ __

F _ ______ __

Subsum _ _

H.O ______________

Sum _ _ _

46.33 

.34 

35.18 

2.34 

.03 

.71 

.00 

1.17 

8.56 

nd

94.66 

4.50

99.16

46.41 

.24 

34.51 

2.19 

.02 

.76 

.00 

1.15 

8.92 

nd

94.20 

4.47

98.67

45.76 

.22 

35.11 

1.99 

.04 

.62 

.00 

1.40 

9.21 

nd

94.35

4.47

98.82

46.37 

.20 

34.69 

1.89 

.03 

.72 

.00 

1.24 

9.02 

nd

94.16 

4.47

98.63

46.16 

.30 

35.29 

4.67 

.07 

1.21 

.03 

1.03 

8.08 

nd

96.84 

4.56

101.40

46.47 

.18 

36.53 

1.26 

.03 

.56 

.00 

1.98 

8.22 

nd

95.23 

4.55

99.78

46.70 

.24 

36.49 

1.16 

.04 

.51 

.00 

2.01 

8.60 

nd

95.75 

4.57

100.32

46.52 

.19 

37.32 

1.03 

.02 

.55 

.03 

1.74 

8.50 

nd

95.90 

4.59

100.49

46.18 

.20 

36.85 

.91 

.02 

.40 

.00 

1.97 

8.34 

nd

94.87 

4.54

99.41

Number of atoms

Si __ _

Ti _ _ _ _

Al _ _ _ __

Fe _ _ __ __

Mn _ _ _ _ _ Mg __ _ ___ _

Ca _ __ _ _ _

Na _______

K _ _____

F _ _ _____

Cation sum ___

3.09 

.02 

2.76 

.13 

.00 

.07 

.00 

.15 

.73 

nd

6.95

3.11 

.01 

2.73 

.12 

.00 

.08 

.00 

.15 

.76 

nd

6.96

3.07 

.01 

2.78 

.11 

.00 

.06 

.00 

.18 

.79 

nd

7.00

3.11 

.01 

2.74 

.11 

.00 

.07 

.00 

.16 

.77 

nd

6.97

3.04 

.02 

2.74 

.26 

.00 

.12 

.00 

.13 

.68 

nd

6.99

3.06 

.01 

2.84 

.07 

.00 

.05 

.00 

.25 

.69 

nd

6.97

3.07 

.01 

2.83 

.06 

.00 

.05 

.00 

.26 

.72 

nd

7.00

3.04 

.01 

2.88 

.06 

.00 

.05 

.00 

.22 

.71 

nd

6.97

3.05 

.01 

2.87 

.05 

.00 

.04 

.00 

.25 

.70 

nd

6.97

Notes

Next to 

Ilm 

102002

Between

Cd 

102005, 

Cd 

102008, 

and Bt 

102010

Spots 102013 and 102014 

are in same crystal

Next to 

Em 

111024

Next to 

St 

111028

In Pg 

next to 

Ch 

112004
62 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE— Continued

Sample . _____ _. _ _

Spot ___________ 19

355-1

20 21 27 29 30

356-1

31 34

Weight percent

Si02

Ti02 ______ ___

AU>3 _______ _

FeO _ _________

MnO __ _ __ __

MgO _____________

CaO — __ __ __

Na20 __ _____

K2 0 ____ __

F _ _ __ _

Subsum _ __

H20 _____ _____

Sum ______

46.26 

.29 

34.89 

1.89 

.00 

.38 

.00 

2.27 

7.70 

.00

93.68

4.47

98.15

45.38 

.31 

35.22 

1.72 

.03 

.42 

.00 

2.21 

8.37 

.37

93.72

4.45

98.17

45.30 

.25 

36.09 

1.70 

.04 

.39 

.00 

2.26 

7.75 

.00

94.10

4.47

98.57

46.13 

.29 

37.16 

.89 

.03 

.40 

.00 

1.67 

8.33 

.00

94.90 

4.55

99.45

46.22 

.30 

36.42 

1.24 

.03 

.55 

.00 

1.69 

8.57 

.02

95.82 

4.55

100.37

46.93 

.20 

35.78 

.63 

.00 

.50 

.00 

1.58 

7.95 

.00

93.57 

4.51

98.08

46.64

.41 

36.51 

.71 

.03 

.38 

.00 

1.90 

7.97 

.10

94.57 

4.54

99.11

47.91 

.15 

38.53 

.64 

.04 

.37 

.00 

1.46 

7.96 

.61

97.16 

4.68

101.84

Number of atoms

Si_ _ — _____

Ti _ ___ _____

Al _ __ _____

Fe __ _ ___

Mn _ ______ __

Mg _______________

Ca _ _ __________

Na _

K _ __ __ ______

F __ _ _ _ __

Cation sum _

3.10 

.01 

2.76 

.11 

.00 

.04 

.00 

.29 

.66 

.00

6.97

3.06 

.02 

2.80 

.10 

.00 

.04 

.00 

.29 

.72 

.08

7.03

3.04 

.01 

2.85 

.10 

.00 

.04 

.00 

.29 

.66 

.00

7.01

3.04 

.01 

2.89 

.05 

.00 

.04 

.00 

.21 

.70 

.00

6.94

3.04 

.01 

2.83 

.07 

.00 

.05 

.00 

.21 

.72 

.00

6.97

3.12 

.01 

2.80 

.03 

.00 

.05 

.00 

.20 

.67 

.00

6.88

3.08 

.02 

2.84 

.04 

.00 

.04 

.00 

.24 

.67 

.02

6.93

3.07 

.01 

2.91 

.03 

.00 

.03 

.00 

.18 

.65 

.12

6.88

Notes

ZnO=0.00 ZnO=0.00 Weight ZnO=0.00 Weight 

percent percent 

sum in- sum includes eludes 

0.32 0.80 

ZnO; ca- ZnO; cation tion 

sum in- sum includes eludes 

0.02 0.04 

atom atom 

Zn Zn

ZnO=:0.00 ZnO=0.00
TABLES 63

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE— Continued

Sample __ _________ ___

Spot . ... ____ ____ 121008

360-1

122005 122006 131015

369-1

132004 132007 141010

463-1

141011 142002

Weight percent

Si02 _ __ _ __ _

TiO2 _ _____

A1203 ___ ___ _

FeO _ __ ___

MnO _ _ __ _

MgO ____________

GaO ____ __ _

Na.0 ______ ______

K2O __ _ _ _ __

F _____ __ ___

Subsum _ _ _

H2O _ ___ __

Sum _ __

45.46 

.20 

35.95 

2.23 

.07 

.27 

.00 

1.57 

9.03 

nd

94.78 

4.48

99.26

45.17

.23 

35.94 

2.56 

.06 

.28 

.00 

1.33 

9.05 

nd

94.62

4.47

99.09

45.60 

.36 

35.98 

2.23 

.05 

.28 

.00 

1.37 

9.96 

nd

95.83 

4.51

100.34

45.76 

.30 

36.52 

1.04 

.03 

.04 

.00 

1.87 

8.44 

nd

94.00 

4.49

98.49

46.12 

.38 

36.71 

1.12 

.02 

.36 

.00 

1.95 

8.27 

nd

94.93 

4.54

99.47

45.70 

.21 

37.82 

1.30 

.02 

.33 

.00 

1.92 

8.24 

nd

95.54 

4.56

100.10

45.69 

.20 

36.89 

.99 

.04 

.36 

.00 

2.17 

7.85 

nd

94.19 

4.51

98.70

46.31 

.24 

36.97 

1.02 

.05 

.30 

.00 

2.05 

7.98 

nd

94.92 

4.55

99.47

45.16 

.17 

37.09 

1.15 

.02 

.30 

.01 

2.16 

8.37 

nd

94.43 

4.50

98.93

Number of atoms

Si _ _ _ _______

Ti ______ _ _

Al ___ _ _______

Fe _____ _ ______

Mn __ __________

Mg ______________

Ca ___ __ ________

Na __ __ _ ____

K _____ ________

F __ __ __ ____

Cation sum _ _

3.04 

.01 

2.84 

.12 

.00 

.03 

.00 

.20 

.77 

nd

7.01

3.03 

.01 

2.84 

.14 

.00 

.03 

.00 

.17 

.77 

nd

6.99

3.03 

.02 

2.82 

.12 

.00 

.03 

.00 

.18 

.85 

nd

7.05

3.06 

.02 

2.87 

.06 

.00 

.00 

.00 

.24 

.72 

nd

6.97

3.05 

.02 

2.86 

.06 

.00 

.04 

.00 

.25 

.70 

nd

6.98

3.00 

.01 

2.93 

.07 

.00 

.03 

.00 

.24 

.69 

nd

6.97

3.04 

.01 

2.89 

.06 

.00 

.04 

.00 

.28 

.67 

nd

6.99

3.05 

.01 

2.87 

.06 

.00 

.03 

.00 

.26 

.67 

nd

6.95

3.01 

.01 

2.91 

.06 

.00 

.03 

.00 

.28 

.71 

nd

7.01

Notes

Next to 

Ch 

122004

Next to 

Ch 

132006

Next to 

Pg 

141012

In Bt

142003
64 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE— Continued

Sample . _ _ __ _

Spot ____ __________ 151002 151006 152002

466-1

152004 153001 153002 172010

506-1

172012 172018

Weight percent

Si02 __ _____

Ti02 __ ___ __

ALA, _ _ _

FeO _ ___ _

MnO _____________

MgO __ __ _

CaO _ __ _

Na_0 ___ ____ ____

K20 ___ __ _ ______

F __ _

Subsum _ __

H20 _ ______ _____

Sum _ _

46.04 

.18 

35.59 

1.66 

.03 

.95 

.00 

1.04 

8.77 

nd

94.26 

4.49

98.75

45.43 

.13 

36.84 

1.48 

.05 

.34 

.00 

1.96 

8.39 

nd

94.62

4.51

99.13

45.94 

.21 

36.36 

1.28 

.03 

.41 

.00 

1.82 

8.73 

nd

94.78 

4.51

99.29

45.55 

.20 

37.14 

1.25 

.05 

.36 

.00 

1.73 

8.82 

nd

95.10 

4.53

99.63

47.33 

.21 

35.91 

1.33 

.03 

.41 

.00 

1.75 

8.56 

nd

95.53 

4.56

100.09

46.34 

.22 

36.56 

1.11 

.04 

.47 

.00 

1.85 

8.57 

nd

95.16

4.54

99.70

45.29 

.22 

36.25 

1.42 

.04 

.51 

.05 

1.66 

8.26 

nd

93.70

4.47

98.17

45.40 

.23 

36.38 

1.10 

.06 

.40 

.01 

1.28 

8.50 

nd

93.36 

4.46

97.82

45.63 

.26 

36.48 

1.02 

.04 

.43 

.00 

1.85 

8.42 

nd

94.13 

4.49

98.62

Number of atoms

Si _ _ _ _ _

Ti _ _ _

Al _ _ _ __

Fe __ _ _____

Mn _ __ _ _____

Mg ______________

Ca _ _ _ _

Na _ ____ __

K __ __ __ __

F

Cation sum _ _

3.07 

.01 

2.80 

.09 

.00 

.09 

.00 

.13 

.75 

nd

6.94

3.02 

.01 

2.89 

.08 

.00 

.03 

.00 

.25 

.71 

nd

6.99

3.05 

.01 

2.85 

.07 

.00 

.04 

.00 

.24 

.74 

nd

7.00

3.02 

.01 

2.90 

.07 

.00 

.04 

.00 

.22 

.75 

nd

7.01

3.11 

.01 

2.78 

.07 

.00 

.04 

.00 

.22 

.72 

nd

6.95

3.06 

.01 

2.85 

.06 

.00 

.05 

.00 

.24 

.72 

nd

6.99

3.04 

.01 

2.87 

.08 

.00 

.05 

.00 

.22 

.71 

nd

6.98

3.05 

.01 

2.88 

.06 

.00 

.04 

.00 

.17 

.73 

nd

6.94

3.05 

.01 

2.87 

.06 

.00 

.04 

.00 

.24 

.72 

nd

6.99

Notes

Next to 

Cd 

151001

Next to 

Bt 

151005

Next to Next to 

Pg Ch 

152003 153003

Next to 

Cd 

172008 

and 

172009

Next to 

Ga 

172013
TABLES 65

TABLE 3.—Microprobe data on various minerals in samples of rooks from within and around the Taconic allochthon—Continued

A. MUSCOVITE—Continued

Sample _____________ 506-1—Con. ________

Spot ————— ——————— _ 174003 181002

Si02 __________ 45.52 45.54

Ti02 ________ .26 .15

A1203 _________ 36.86 35.85

FeO __________ 1.03 1.44

MnO _________ .01 .04

MgO _________ .39 .55

CaO ________ .00 .00

Na20 ________ 1.98 1.36

K20 __________ 8.08 9.01 

F _______________nd_____nd

Subsum ____ 94.08 93.94

HS0 __________ 4.50_____4.47

Sum ____ 98.58 98.41

Si __________ 3.03 3.06

Ti __________ .01 .01

Al __________ 2.89 2.84

Fe __________ .06 .08

Mn __________ .00 .00

Mg __________ .04 .06

Ca __________ .00 .00

Na __________ .26 .18

K ___________ .68 .77 

F _______________nd_____nd

Cation sum __ 6.97 7.00

509-1

181004 181008 182001 182004 182014

515-1

191003 191013

Weight percent

46.07

.17

36.23

1.26

.03

.47

.00

1.25

8.45

nd

46.42

.17

36.53

1.28

.01

.50

.00

1.55

8.69

nd

46.58 

.19

34.95

1.35

.03

.83

.00

.98

9.30

nd

47.05 

.22

34.94

1.24

.03

.56

.01

.92

9.35

nd

46.11

.17

36.06

1.47

.04

.49

.00

1.37

8.96

nd

93.93

4.49

95.15

4.54

94.21

4.49

94.32

4.50

94.67

4.51

98.42 99.69 98.70 98.82 99.18

45.28

.30

36.41

1.12

.01

.47

.03

1.39

8.58

nd

93.59

4.47

98.06

46.58

.25

36.57

1.17

.05

.49

.00

1.61

8.81

nd

95.53

4.56

100.09

Number of atoms

3.07 

.01

2.85 

.07 

.00 

.05 

.00 

.16 

.72 

nd

3.07 

.01

2.84 

.07 

.00 

.05 

.00 

.20 

.73 

nd

3.11 

.01

2.75 

.08 

.00 

.08 

.00 

.13 

.79 

nd

3.13 

.01

2.75 

.07 

.00 

.06 

.00 

.12 

.79 

nd

3.07 

.01

2.83 

.08 

.00 

.06 

.00 

.18 

.76 

nd

6.93 6.97 6.95 6.93 6.98

3.04 

.01

2.88 

.06 

.00 

.05 

.00 

.18 

.73 

nd

6.95

3.07 

.01

2.84 

.06 

.00 

.05 

.00 

.21 

.74 

nd

6.98

Notes

Next to 

Cd

181001 

and Bt 

181003

Next to 

Bt

181003; 

with 

Mu

181002 

forms a 

Mu-BtMu 

sandwich

Next to 

Ch

181007 

and Cd 

181001 

and 

181005

Next to 

Cd 

182003

Next to 

Bt 

182013

Next to 

Ilm 

191001

Outside 

of Ga

191004.

191005. 

191007, 

ancj 

191012
66 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

A. MUSCOVITE— Continued

Sample ———— __._ — __

Spot ____________

515-1 — Continued

191016 191017 192003

1052-2

1 26 211002

1169-1

213005 213006 215003

Weight percent

SiOa __ _______

Ti02 _ ___ __

A1203 _ ___ _____

FeO ____ _____

MnO _ _ ____ __

MgO _____________

CaO __ __ _____

NaaO __ _ ________

K20

F _ __ ___________

Subsum _____

H20 __ ___________

Sum _ _ ___

46.44

.28 

36.66 

1.33 

.02 

.47 

.00 

1.69 

8.66 

nd

95.55 

4.56

100.11

45.61 

.24 

36.30 

1.04 

.03 

.51 

.02 

1.64 

8.97 

nd

94.36 

4.49

98.85

46.04 

.30 

35.45 

1.26 

.04 

.54 

.01 

1.36 

8.64 

nd

93.64

4.47

98.11

46.17 

.51 

37.23 

1.13 

.00 

.33 

.02 

1.46 

8.89 

nd

95.74

4.57

100.31

47.25 

.55 

37.05 

.89 

.06 

.33 

.00 

1.32 

8.98 

nd

96.43 

4.61

101.04

48.57 

.16 

26.38 

4.66 

.07 

2.67 

.00 

.21 

9.39 

nd

92.11 

4.31

96.42

47.19 

.16 

28.76 

4.34 

.06 

2.57 

.00 

.26 

10.44 

nd

93.78 

4.36

98.14

49.45 

.17 

25.51 

4.37 

.09 

2.83 

.00 

.24 

10.55 

nd

93.21 

4.34

97.55

48.31 

.17 

26.84 

4.94 

.09 

2.38 

.00 

.29 

10.32 

nd

93.34 

4.33

97.67

Number of atoms

Si _ ____ _ __

Ti — _ _ _____

Al __ __ ___

Fe ____ ________

Mn ___ ________

Mg _ ___________

Ca ___ ____________

Na __ ________

K

F _ __ _ _

Cation sum _ _

3.06 

.01 

2.84 

.07 

.00 

.05 

.00 

.22 

.73 

nd

6.98

3.05 

.01 

2.86 

.06 

.00 

.05 

.00 

.21 

.76 

nd

7.00

3.09 

.01 

2.80 

.07 

.00 

.05 

.00 

.18 

.74 

nd

6.94

3.03 

.03 

2.88 

.06 

.00 

.03 

.00 

.19 

.74 

nd

6.96

3.07 

.03 

2.84 

.05 

.00 

.03 

.00 

.17 

.74 

nd

6.93

3.38 

.01 

2.16 

.27 

.00 

.28 

.00 

.03 

.83 

nd

6.96

3.25 

.01 

2.33 

.25 

.00 

.26 

.00 

.03 

.92 

nd

7.05

3.42 

.01 

2.08 

.25 

.01 

.29 

.00 

.03 

.93 

nd

7.02

3.34 

.01 

2.19 

.29 

.01 

.25 

.00 

.04 

.91 

nd

7.04

Notes

Next to 

Ch 

191014

Next to 

Urn 

192001

Next to 

Ep 

211001

Next to 

Ep 

213002, 

and 

213004

Next to 

crystal 

containin? Mu 

213005

Next to 

Dm 

215001 

and Ep 

215002
TABLES 67 

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

B. BIOTITE

Sample _. ____ __ __ ...

Spot ____ ___________

14-1

3 14 18 20

102-1

043001 043002 051004

103-1

051005 051006

Weight percent

Si02 ______ _ _

Ti02 __ __ ___

A12 0;) _ _ _ __

FeO _____ _

MnO _ __ _______

Mg-0 _____________

CaO ___ __ ___

Na_0 __ _ _____

K2 0 ___ __

F _ _ _ ___ _

Subsum _ _ _

H_O _ __ __ _

Sum _ _

33.39 

1.87 

19.84 

21.00 

.07 

9.13 

.01 

.30 

7.77 

.57

93.70 

3.85

97.55

33.73 

1.96 

19.75 

20.75 

.00 

8.82 

.00 

.35 

9.31 

.32

94.72 

3.88

98.60

33.35 

1.95 

18.68 

21.14 

.00 

8.66 

.27 

.38 

8.08 

.30

93.69 

3.81

97.50

35.59 

2.08 

17.34 

19.89 

.00 

9.18 

.06 

.34 

9.21 

.45

94.72 

3.88

98.60

34.07 

1.81 

18.08 

22.94 

.16 

8.51 

.09 

.10 

7.88 

nd

93.64 

3.82

97.46

34.80 

1.87 

18.40 

22.39 

.14 

8.51 

.02 

.11 

8.27 

nd

94.51 

3.87

98.38

33.89 

1.61 

18.52 

25.53 

.09 

6.61 

.07 

.28 

8.42 

nd

95.02 

3.82

98.84

33.77 

1.56 

18.53 

25.26 

.09 

6.58 

.08 

.28 

8.30 

nd

94.45 

3.80

98.25

33.51 

1.65 

19.00 

25.01 

.10 

6.26 

.06 

.30 

8.13 

nd

94.02 

3.79

97.81

Number of atoms

Si _______________

Ti _ _ ____ _

Al _ _ _ _ _____

Fe

Mn _ ____ __ _

Mg ______________

Ca ____ ___ __ -

Na ______

K _ __ _

F _ _ _ _ _____

Cation sum _

2.60 

.11 

1.82 

1.36 

.00 

1.06 

.00 

.04 

.77 

.14

7.77

2.61 

.11 

1.80 

1.34 

.00 

1.02 

.00 

.05 

.92 

.08

7.85

2.62 

.11 

1.73 

1.39 

.00 

1.01 

.02 

.06 

.81 

.07

7.81

2.75 

.12 

1.58 

1.28 

.00 

1.06 

.00 

.05 

.91 

.11

7.80

2.60 

.11 

1.67 

1.51 

.01 

1.00 

.01 

.01 

.79 

nd

7.71

2.70 

.11 

1.68 

1.45 

.01 

.99 

.00 

.02 

.82 

nd

7.78

2.66 

.10 

1.72 

1.68 

.01 

.77 

.01 

.04 

.84 

nd

7.83

2.67 

.09 

1.72 

1.67 

.01 

.77 

.01 

.04 

.84 

nd

7.82

2.65 

.10 

1.77 

1.66 

.01 

.74 

.01 

.05 

.82 

nd

7.81

Notes

Weight 

percent 

sum 

includes 

ZnO = 

0.23; 

Cation 

sum 

includes 

0.01 

atom 

Zn

ZnO=0'.00 Weight 

percent 

sum 

includes 

ZnO = 

1.13; 

Cation 

sum 

includes 

0.06 

atom 

Zn

Weight 

percent 

sum 

includes 

ZnO = 

0.96; 

Cation 

sum 

includes 

0.05 

atom 

Zn

Spots 043001 

043002 are 

crystal

and 

in same

Next to 

Cd 

051001; 

in same 

crystal 

as spot 

051006

In same 

crystal 

as spot 

051005
68 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

B. BIOTITE— Continued

Sample ____ _____ _ _ _

Spot ____ ___________

1 03-1 — Continued

051007 051011 052005 052006 052008 061001

103-2

061008 061010 1

Weight percent

Si02 _ _

Ti02 _ _ _____

A1203 ______

FeO _ _ _ __

MnO _____________

MgO _ __ _ __

CaO

Na20 _ __ _ ___

K20 ________

F __ ____

Subsum _ _

H20 ___ __ _ ______

Sum _____

33.37 

1.76 

18.42 

25.57 

.13 

6.64 

.08 

.30 

8.03 

nd

94.30 

3.79

98.09

33.94 

1.64 

19.30 

25.20 

.13 

6.59 

.01 

.27 

8.57 

nd

95.65 

3.85

99.50

33.51 

1.64 

19.41 

26.23 

.13 

6.68 

.03 

.27 

8.70 

nd

96.60 

3.86

100.46

33.29 

1.85 

19.13 

25.25 

.12 

6.20 

.01 

.27 

8.31 

nd

94.43 

3.80

98.23

33.76 

1.52 

19.12 

25.28 

.11 

6.44 

.17 

.29 

7.98 

nd

94.67 

3.82

98.49

33.25 

1.72 

18.67 

22.73 

.11 

7.79 

.02 

.26 

8.95 

nd

93.50 

3.78

97.28

33.20 

1.70 

19.45 

21.96 

.14 

7.50 

.00 

.21 

9.00 

nd

93.16 

3.79

96.95

33.61 

1.55 

18.97 

22.54 

.11 

7.12 

.08 

.25 

8.71 

nd

92.94 

3.78

96.72

36.55 

1.50 

20.55 

21.82 

.04 

7.52 

.02 

.21 

9.06 

.28

97.31 

4.01

101.32

Number of atoms

Si _ __ _ _____

Ti _

Al

Fe _______________

Mn _ _ __ __

Mg ___ __ ______

Ca _______________

Na _ _______

K _____

F _ _ _

Cation sum _ __

2.64 

.10 

1.72 

1.69 

.01 

.78 

.01 

.05 

.81 

nd

7.81

2.64 

.10 

1.77 

1.64 

.01 

.76 

.00 

.04 

.85 

nd

7.81

2.60 

.10 

1.78 

1.70 

.01 

.77 

.00 

.04 

.86 

nd

7.86

2.63 

.11 

1.78 

1.67 

.01 

.73 

.00 

.04 

.84 

nd

7.81

2.65 

.09 

1.77 

1.66 

.01 

.75 

.01 

.04 

.80 

nd

7.78

2.63 

.10 

1.74 

1.51 

.01 

.92 

.00 

.04 

.91 

nd

7.86

2.63 

.10 

1.81 

1.45 

.01 

.88 

.00 

.03 

.91 

nd

7.82

2.67 

.09

1.78 

1.50 

.01 

.84 

.01 

.04 

.88 

nd

7.82

2.73 

.08 

1.81 

1.36 

.00 

.84 

.00 

.03 

.86 

.07

7.71

Notes

Next to 

Cd 

051001 

and 

051002

Next to 

Mu 

051009

Next to 

Mu 

052007

Next to 

Cd 

061002

Next to 

Mu 

061007

Next to 

Cd 

061009
TABLES 69

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

B. BIOTITE— Continued

Sample __ — . — —— _

Spot ____ ._ ________

103-2 — Continued

2 062008 062012

234-1

14 081001

289-2

081008 081013

Weight percent

Si02 _ _ _ _

Ti02

A1203 _____ ________

FeO __ __ _

MnO __ __ __

MgO _ _ _

CaO _ __ __

Nsu.0

K20 _

F _ _

Subsum

H20 ___ _____ ___

Sum

36.06 

1.43 

19.65 

21.80 

.09 

7.79 

.02 

.22 

8.91 

.24

96.01 

3.95

99.96

33.94 

1.76 

18.55 

23.28 

.12 

7.74 

.03 

.18 

7.92 

nd

93.52 

3.81

97.33

33.61 

1.79 

18.82 

23.36 

.16 

7.52 

.01 

.25 

8.79 

nd

94.31 

3.82

98.13

33.70 

2.07 

20.00 

20.47 

.01 

9.13 

.02 

.21 

7.99 

.32

93.65 

3.87

97.52

35.19 

1.99 

16.06 

19.07 

.17 

11.77 

.09 

.12 

8.76 

nd

93.22 

3.85

97.07

35.10 

2.03 

18.16 

17.05 

.20 

11.42 

.08 

.22 

9.03 

nd

93.29 

3.90

97.19

36.36 

1.86 

18.30 

17.73 

.16 

11.30 

.07 

.15 

9.07 

nd

95.00 

-3.97

98.97

Number of atoms

Si _ _ _ ___

Ti ______ _

Al _____

Fe __ __

Mn _ __

Mg ______________

Ca __ _ __ __ _

Na __ _

K _ __ ___ __

F _

Cation sum _ _

2.74 

.08 

1.76 

1.38 

.00 

.88 

.00 

.03 

.86 

nd

7.73

2.67 

.10 

1.72 

1.53 

.01 

.91 

.00 

.03 

.80 

nd

7.77

2.64 

.11 

1.74 

1.54 

.01 

.88 

.00 

.04 

.88 

nd

7.84

2.61 

.12 

1.83 

1.32 

.00 

1.05 

.01 

.03 

.79 

.21

7.76

2.74 

.12 

1.47 

1.10 

.01 

1.37 

.01 

.02 

.87 

nd

7.71

2.70 

.12 

1.65 

1.21 

.01 

1.31 

.01 

.03 

.89 

nd

7.93

2.75 

.11 

1.63 

1.12 

.01 

1.27 

.01 

.02 

.87 

nd

7.79

Notes

Next to 

Cd 

062007

Next to 

Cd 

062011

Next to 

Hb 

081007

Next to 

Pg 

081012
70 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

B. BIOTITE— Continued

Sample ———— __ __. — .

Spot __________________ 4

290-1

5 6

331-1

093002

338-1

093003 101001 101004 101008 102010

Weight percent

Si02 _ ___________

Ti02 _ _______ _

A1203 ____ _ _

FeO ______________

MnO ______

MgO _ ___________

CaO _____________

Na.O ______ __

K20 ______________

F ___ __ _ _

Sufosum _____

H20 __ ________

Sum __ __

34.71 

2.11 

18.98 

20.16 

.00 

9.16 

.00 

.36 

8.96 

.00

94.56 

3.89

98.45

34.18 

2.21 

18.32 

21.42 

.00 

8.46 

.00 

.30 

9.00 

.00

93.89 

3.84

97.73

33.91 

2.18 

20.10 

20.99 

.01 

9.58 

.00 

.27 

7.74 

.00

94.78 

3.92

98.70

34.90 

2.05 

20.07 

20.02 

.09 

8.65 

.00 

.28 

8.24 

nd

94.30 

3.92

98.22

35.06 

2.22 

19.90 

20.70 

.07 

8.49 

.00 

.28 

8.28 

nd

95.00 

3.93

98.93

34.02 

1.82 

19.48 

23.68 

.09 

6.86 

.03 

.22 

8.52 

nd

94.72 

3.85

98.57

33.58 

1.67 

19.43 

24.07 

.08 

6.67 

.05 

.25 

8.63 

nd

94.43 

3.82

98.25

33.99 

1.70 

19.65 

23.02 

.10 

6.90 

.05 

.23 

8.84 

nd

94.48 

3.84

98.32

33.20 

1.75 

19.33 

25.17 

.10 

7.17 

.04 

.18 

8.06 

nd

95.00 

3.83

98.83

Number of atoms

Si ________________

Ti _______ _

Al _______________

Fe _ _ __ _ __

Mn __ _________

Mg ______________

Ca _ __ ________

Na _______________

K ______ ______

F __ ____________

Cation sum _

2.67 

.12 

1.72 

1.30 

.00 

1.05 

.00 

.05 

.88 

.00

7.79

2.67 

.13 

1.69 

1.40 

.00 

.99 

.00 

.04 

.90 

.00

7.82

2.59 

.12 

1.81 

1.34 

.00 

1.09 

.00 

.04 

.75 

.00

7.74

2.67 

.12 

1.81 

1.28 

.01 

.99 

.00 

.04 

.81 

nd

7.73

2.67 

.13 

1.79 

1.32 

.00 

.96 

.00 

.04 

.81 

nd

7.72

2.65 

.11 

1.79 

1.55 

.01 

.80 

.00 

.03 

.85 

nd

7.79

2.64 

.10 

1.80 

1.58 

.00 

.78 

.00 

.04 

.87 

nd

7.81

2.66 

.10 

1.81 

1.50 

.01 

.80 

.00 

.03 

.88 

nd

7.79

2.60 

.10 

1.79 

1.65 

.01 

.84 

.00 

.03 

.81 

nd

7.83

Notes

Weight 

percent 

sum 

includes 

ZnO = 

0.12

ZnO=0.00 ZnO=0.00 Spots 093002 and 093003 

are in the same 

staurolite crystal 

093004

Next to 

Cd 

101002

Next to 

Mu 

101005

Next to 

Mu 

101007

Next to 

Cd 

102006, 

Mu 

102009; 

in same 

crystal 

as spots 

102011 

and 

102012
TABLES 71

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

Sample ____ _ __ _ _

Spot ____ ___________

H. BIOTITE— Continued

338-1 — Continued

102011 102012 101103 101105

33&-1

111010

356-1

26 28

Weight percent

SiC-2 _ _

TiO2 __ _ _

A12O3 _ _ _ __

FeO _____„ _____

MnO ___ __ _

MgO ___ ___

CaO __ _ _

Na.0 __ _____ _ _

K_0 __ _ _ ____ _

F ________

Subsum ___

H20 ___ _ ___ ___

34.18

1.77 

19.78 

24.01 

.09 

6.92 

.04 

.28 

8.77 

nd

95.84 

3.88

99.72

34.18 

1.70 

20.02 

23.84 

.09 

7.20 

.03 

.26 

8.86 

nd

96.18 

3.90

100.08

33.38 

1.55 

19.24 

23.98 

.08 

6.76 

.09 

.17 

8.02 

nd

93.27 

3.78

97.05

34.28 

1.53 

19.06 

23.74 

.12 

6.67 

.04 

.19 

8.39 

nd

94.02 

3.82

97.84

35.62 

1.75 

20.19 

19.57 

.08 

9.56 

.01 

.29 

8.55 

nd

95.62 

3.98

99.60

35.55 

1.39 

19.36 

19.09 

.00 

10.00 

.00 

.32 

8.00 

.06

94.08 

3.93

98,01

35.77 

1.45 

19.08 

19.59 

.00 

10.39 

.00 

.34 

7.86 

.34

94.53 

3.95

98.48

Number of atoms

Si __ ___ _

Ti _ ______

Al

Fe _ __ _ _

Mn __ _ _ _

Mg ______________

Ca _ __ _ __ __

Na _____

K _ __

F ______ _

Cation sum _

2.64 

.10 

1.80 

1.55 

.01 

.80 

.00 

.04 

.86 

nd

7.80

2.63 

.10 

1.82 

1.53 

.01 

.83 

.00 

.04 

.87 

nd

7.83

2.65 

.09 

1.80 

1.59 

.01 

.80 

.01 

.03 

.81 

nd

7.79

2.69 

.10 

1.76 

1.56 

.01 

.78 

.00 

.03 

.84 

nd

7.77

2.68 

.10 

1.79 

1.23 

.01 

1.07 

.00 

.04 

.82 

nd

7.74

2.71 

.08 

1.74 

1.22 

.00 

1.14 

.00 

.04 

.78 

.01

7.73

2.72 

.08 

1.71 

1.24 

.00 

1.18 

.00 

.05 

.76 

.08

7.74

Notes

In same 

crystal 

as spots 

102010 

and 

102012

In same 

crystal 

as spots 

102010 

and 

102011

Next to 

Ga 111001- 

111004 

and 

Ch 

111011

Weight 

percent 

sum includes 

ZnO 

= 0.36; 

cation 

sum includes 

0.02 

atom 

Zn

ZnO = 0.00
72 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

B. BIOTITE— Continued

Sample _ ___ _ _____ ___

141005 141006

463-1

141016 142003 142004

466-1

151005

487-2-4

1 2

Weight percent

Si02 _

Ti02 __ ___ __

AW), ______

FeO

MnO __ __ __

MgO _ __ __ ____

CaO ______ _

Na_0 _ __ __ _

K20 ___ _ ___ __ _

K

Subsum _ _ _

H20

Sum _

Si _ _ __ _

Ti ___ — _ _____

Al _ _ __

Fe _ ___ _ _____

Mn __ ___ __

Mg ______________

Ca __ _______ __

Na

K __ _ _ __

F

Cation sum ___

33.37 

1.72 

18.47 

21.81 

.15 

7.71 

.09 

.21 

8.17 

nd

91.70 

3.75

95.45

2.67 

.10 

1.74 

1.46 

.01 

.92 

.01 

.03 

.83 

nd

7.77

34.52 

1.78 

18.57 

23.44 

.13 

7.86 

.04 

.21 

8.13 

nd

94.68 

3.86

98.54

2.69 

.10 

1.70 

1.53 

.01 

.91 

.00 

.03 

.81 

nd

7.78

34.10 

1.59 

19.20 

22.61 

.12 

8.07 

.07 

.20 

7.86 

nd

93.82 

3.84

97.66

Number of

2.66 

.09 

1.77 

1.48 

.01 

.94 

.01 

.03 

.78 

nd

7.77

34.31 

1.61 

19.24 

21.88 

.09 

8.14 

.04 

.25 

8.30 

nd

93.86 

3.85

97.71

atoms

2.67 

.09 

1.77 

1.43 

.01 

.95 

.00 

.04 

.83 

nd

7.79

34.34 

1.60 

19.92 

21.53 

.10 

8.02 

.03 

.40 

8.67 

nd

94.61 

3.88

98.49

2.66 

.09 

1.86 

1.39 

.01 

.92 

.00 

.06 

.86 

nd

7.85

34.57 

1.21 

19.91 

22.29 

.14 

7.28 

.00 

.39 

6.92 

nd

92.71 

3.83

96.54

2.71 

.07 

1.84 

1.46 

.01 

.85 

.00 

.06 

.69 

nd

7.69

34.99 

.97 

15.88 

29.77 

.08 

4.10 

.03 

.12 

8.79 

.05

94.74 

3.72

98.46

2.82 

.06 

1.51 

2.01 

.00 

.49 

.00 

.02 

.91 

.01

7.82

34.81 

1.51 

16.78 

30.18 

.11 

4.31 

.09 

.07 

8.67 

.08

96.54 

3.79

100.33

2.76 

.09 

1.56 

2.00 

.01 

.51 

.01 

.01 

.87 

.02

7.82

Notes

Between 

Cd 

141002 

and Ga 

141015

Next to 

Cd 

141007

Bt 142003 and Bt 142004 

are in the same crystal 

and Bt 142003 is near 

Mu 142002

Next to 

Mu 

151006
TABLES 73

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

B. BIOTITE— Continued

Sample _ — .__ — __

Spot _ .. . _ _________

509-1

1 2 3 4 181003 182006 182007 182012

Weight percent

Si02 __ _ _____

Ti02 _ _ ._ _

A1203 _ _ —

FeO _ __ ________

MnO _ _____ _ MgO __ ___ _ _____

CaO __ _ _ _

NasO __ _ _ _ _

KaO ___________

F

Subsum _ _

H2 0 ______________

Sum __ _

Si ______ __ _ _____

Ti _ _ __

Al _ __ _ __

Fe _ __ _ ____

Mn __ _ _ __ _

Mg ______________

Ca _ _ _______

Na

K __ __ _ __ _

F _ _ _ _____

Cation sum _ _

36.74 

1.54 

20.76 

20.68 

.01 

7.99 

.02 

.18 

7.74 

.18

95.69 

4.00

99.69

2.75 

.09 

1.83 

1.29 

.00 

.89 

.00 

.02 

.74 

.04

7.61

36.46 

1.46 

20.50 

20.05 

.04 

8.25 

.02 

.32 

8.61 

.42

95.78 

3.99

99.77

2.74 

.08 

1.82 

1.26 

.00 

.92 

.00 

.05 

.83 

.10

7.70

37.15 

1.35 

20.04 

18.38 

.00 

8.57 

.03 

.09 

8.75 

.42

94.43 

3.97

98.40

Number of

2.81 

.08 

1.78 

1.16 

.00 

.96 

.00 

.01 

.84 

.10

7.64

37.21 

1.57 

20.53 

18.91 

.00 

8.67 

.13 

.04 

8.62 

.44

95.75 

4.02

99.77

atoms

2.78 

.09 

1.81 

1.18 

.00 

.96 

.01 

.00 

.82 

.10

7.65

34.60 

1.67 

19.91 

22.15 

.11 

8.29 

.04 

.20 

8.26 

nd

95.23 

3.91

99.14

2.65 

.10 

1.80 

1.42 

.01 

.95 

.00 

.03 

.81 

nd

7.77

34.71 

2.11 

19.98 

20.99 

.11 

8.19 

.00 

.23 

8.69 

nd

95.01 

3.91

98.92

2.66 

.12 

1.80 

1.35 

.01 

.94 

.00 

.03 

.85 

nd

7.76

35.96 

1.75 

20.94 

20.89 

.10 

8.22 

.01 

.18 

8.51 

nd

96.56 

4.01

100.57

2.69 

.10 

1.85 

1.31 

.01 

.92 

.00 

.03 

.81 

nd

7.72

34.95 

1.61 

20.20 

21.16 

.11 

8.31 

.02 

.26 

8.83 

nd

95.45 

3.93

99.38

2.67 

.09 

1.82 

1.35 

.01 

.95 

.00 

.04 

.86 

nd

7.79

Notes

Next to 

Mu 

181002, 

Mu 

181004, 

and Cd 

181001

Next to 

Ch 

181007

Next to 

Ga 

182009, 

182010, 

and 

182011
74 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

Sample ______ __ __ _

Spot __________ _

SiO2 ______ __

Ti02 _____ ____

A12O3 __ _ _______

FeO __ _ ____ _ _

MnO _ __ _____

MgO _____ _ __

CaO ____ __ _

Na2O _____ ___

K2O _ __________

F _______ _ __

Subsum

H20 _ _________

Sum _ _ _

Si _____ _ ______

Ti _______________

Al _ ___ ____

Fe _______________

Mn _______ __

Mg __________ __

Ca _______________

Na _ _____________

K ____ ________

F ____ __ _____

Cation sum _ _

z

27

35.40

2.17

19.11

18.57

.03

9.68

.00

.21

9.96

.44

95.20

3.94

99.14

2.70

.12

1.71

1.18

.00

1.10

.00

.03

.97

.11

7.81

;nO = 0.00

1052-

28

33.97

2.41

19.11

19.76

.01

9.67

.05

.29

9.93

.29

95.25

3.90

99.15

2.61

.14

1.73

1.27

.00

1.11

.00

.04

.97

.07

7.87

ZnO = 0.00

B. BIOTITE— Continued

-2

29

Weight percent

34.13

2.15

17.95

20.77

.01

9.68

.00

.22

9.40

.19

94.34

3.85

98.19

Number of atoms

2.66

.13

1.65

1.35

.00

1.12

.00

.03

.93

.05

7.87

Notes

ZnO = 0.00
TABLES 75

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

C. CHLORITE

Sample ___. _ _._._..__

Spot _ __________

Si02 __ _ ___

Ti02 ________

A1203 ._„ _____

FeO

MnO __ ___ ___

MgO _____________

CaO ______ _

NasO _ __ __ __

K20 ______ ________

F

Subsum _ ____

H20 ___ ________

Sum ____

Si -__-_--____-___

Ti _ ______ _

Al _______________

Fe _________ _ Mn ______ _

Mg ___ ________

Ca __ ____________

Na — __._

K ______ ____

F _________ _

Cation sum _

14-1

9

24.05 

.13 

23.80 

26.71 

.00 

12.47 

.02 

.07 

.00 

.00

87.27 

11.26

98.53

2.56 

.01 

2.99 

2.38 

.00 

1.98 

.00 

.01 

.00 

.00

9.93

102-1

041005

24.51 

.13 

21.67 

26.97 

.14 

14.01 

.06 

.00 

.00 

nd

87.49 

11.24

98.73

2.62 

.01 

2.73 

2.41 

.01 

2.23 

.01 

.00 

.00 

nd

10.02

041006

Weight

25.05 

.00 

21.64 

26.63 

.21 

14.59 

.00 

.00 

.00 

nd

88.12 

11.36

99.48

Number

2.65 

.00 

2.69 

2.35 

.02 

2.30 

.00 

.00 

.00 

nd

10.01

041007

percent

24.31 

.10 

21.93 

26.11 

.15 

14.48 

.04 

.00 

.00 

nd

87.12 

11.24

98.36

of atoms

2.59 

.01 

2.76 

2.33 

.01 

2.30 

.00 

.00 

.00 

nd

10.00

042005

24.82 

.14 

22.88 

26.17 

.10 

14.10 

.04 

.00 

.00 

nd

88.25 

11.43

99.68

2.61 

.01 

2.83 

2.30 

.01 

2.21 

.00 

.00 

.00 

nd

9.97

103-1

052011

22.15 

.00 

22.80 

31.63 

.12 

9.44 

.02 

.00 

.00 

nd

86.16 

10.74

96.90

2.48 

.00 

3.00 

2.96 

.01 

1.57 

.00 

.00 

.00 

nd

10.02

103-2

2

22.30 

.09 

23.87 

29.42 

.16 

11.33 

.00 

.00 

.15 

.01

87.32 

11.02

98.39

2.43 

.01 

3.06 

2.68 

.01 

1.84 

.00 

.00 

.02 

.00

10.05

3

23.17 

.05 

22.75 

28.94 

.12 

11.90 

.02 

.04 

.15 

.03

87.14 

11.03

98.17

2.52 

.00 

2.91 

2.63 

.01 

1.93 

.00 

.01 

.02 

.01

10.03

Notes

Weight 

percent 

sum includes 

ZnO= 

0.02

Next to 

crystal 

containing Ch 

041005

Next to 

Hb 

042006
76 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

C. CHLORITE— Continued

Sample __________ _ _ _

Spot ____ _______ _ 4

161-1

5 6

191-1

1 2

234-1

6 091005

331-1

091007 092004

Weight percent

Si02 _ __

Ti02 __ __ _ __

AloOs ______ _._

FeO __ _ ____ _

MnO ______ _

MgO ______ _._

CaO ____ __ __

Na.0 _ _ _____

K_0 _ _ _ _ _

F _ __ _ __ _ _

Subsum

H20 __ __ _

Sum _ _ _

24.46 

.07 

27.05 

30.05 

nd 

10.98 

.06 

.02 

.00 

.19

92.72 

11.86

104.58

26.60 

.04 

24.67 

29.33 

nd 

11.81 

.06 

.00 

.00 

.19

92.54 

11.92

104.46

24.42 

.00 

27.15 

29.46 

nd 

10.73 

.02 

.08 

.00 

.00

91.86 

11.79

103.65

22.56 

.04 

23.77 

30.55 

.66 

10.18 

.05 

.02 

.13 

.00

87.96 

11.02

98.98

22.77 

.11 

22.76 

30.93 

.63 

10.09 

.02 

.01 

.13 

.04

87.46 

10.92

98.38

24.00 

.16 

21.79 

29.00 

.02 

11.95 

.02 

.06 

.00 

.02

87.00 

11.05

98.05

23.71 

.07 

23.47 

28.11 

.07 

12.04 

.00 

.00 

.02 

nd

87.49 

11.19

98.68

22.99 

.0<0 

23.71

27.75 

.09 

11.56 

.00 

.00 

.00 

nd

86.10 

11.01

97.11

24.93 

.17 

24.68 

27.80 

.08 

11.93 

.00 

.00 

.12 

nd

89.71 

11.56

101.27

Number of atoms

Si __ _ _ _ _._

Ti ____ ___ _ _____

Al _ _ ______

Fe ___ _ _ __

Mn _ _ _ _

Mg ______________

Ca _ ___ __ __

Na _ _ ___________

K _____ _____

F _ _ __ _

Cation sum ___

2.47 

.01 

3.22 

2.54 

nd 

1.65 

.01 

.00 

.00 

.06

9.90

2.67 

.00 

2.92 

2.47 

nd 

1.77 

.01 

.00 

.00 

.06

9.84

2.49 

.00 

3.26 

2.51 

nd 

1.63 

.00 

.01 

.00 

.00

9.90

2.46 

.00 

3.05 

2.78 

.06 

1.65 

.00 

.00 

.02 

.00

10.02

2.50 

.01 

2.95 

2.84 

.06 

1.65 

.00 

.00 

.02 

.01

10.03

2.60 

.01 

2.79 

2.63 

.00 

1.93 

.00 

.01 

.00 

.01

9.97

2.54 

.01 

2.97 

2.52 

.01 

1.92 

.00 

.00 

.00 

nd

9.97

2.51 

.00 

3.05 

2.53 

.01 

1.88 

.00 

.00 

.00 

nd

9.98

2.59 

.01 

3.02 

2.41 

.01 

1.84 

.00 

.00 

.02 

nd

9.90

Notes

Samples from 161-1 could be partially 

oxidized to oxychlorite, and assignment of H»O may be too high, leading to high oxide sums and low 

cation sums

ZnO = 0.00 Next to 

Mu 

091004

Next to 

Mu 

091006

Next to 

Mu 

092003 

and Ilm 

092001
TABLES 77

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

C. CHLORITE— Continued

Sample ____ _ ______ _

Spot ____________

331-1 — Continued

093005 093011 111011 111012

339-1

111013

360-1

111019 112004 122004 122008

Weight percent

SiOa _ __ ______

Ti02 ____________

A12 03 _ __ _ ______

FeO __ __________

MnO ____ _ _..

MgO _____________

CaO ___ _ _______

NasO ___ __ _

K20 _ _ __________

F _ ____________

Subsum _ __

H20 __ ____ _ _ _

Sum _ __

23.29 

.08 

23.89 

27.82 

.07 

12.14 

.02 

.00 

.00 

nd

87.31 

11.17

98.48

23.28 

.00 

23.62 

27.72 

.06 

11.86 

.01 

.00 

.00 

nd

86.55 

11.08

97.63

24.39 

.00 

23.89 

26.45 

.03 

13.43 

.01 

.00 

.00 

nd

88.20 

11.41

99.61

24.13 

.00 

24.08 

26.15 

.04 

14.06 

.01 

.00 

.00 

nd

88.47 

11.45

99.92

24.14

.08 

23.32 

26.21 

.05 

13.34 

.05 

.00 

.15 

nd

87.34 

11.27

98.61

23.42 

.00 

23.50 

27.16 

.07 

12.65 

.04 

.00 

.00 

nd

86.84 

10.81

97.65

23.64 

.09 

23.74 

27.93 

.02 

12.36 

.04 

.00 

.02 

nd

87.84 

11.25

99.09

22.01 

.03 

23.09 

34.14 

.45 

7.24 

.01 

.03 

.02 

nd

87.02 

10.68

97.70

22.45 

.08 

22.87 

34.60 

.48 

7.36 

.03 

.02 

.04 

nd

87.93 

10.78

98.71

Number of atoms

Si _ - _ ____ ___

Ti _____ ___________

Al ___ _ ______

Fe _ _ __ __

Mn _ __ __ __

Mg ______________

Ca __ __ _______

Na __ ____ _

K _ _ __________

F __ __ ____ _

Cation sum _ _

2.50 

.01 

3.02 

2.50 

.01 

1.94 

.00 

.00 

.00 

nd

9.98

2.52 

.00 

3.02 

2.51 

.01 

1.92 

.00 

.00 

.00 

nd

9.98

2.56 

.00 

2.96 

2.32 

.00 

2.10 

.00 

.00 

.00 

nd

9.94

2.53 

.00 

2.97 

2.29 

.00 

2.19 

.00 

.00 

.00 

nd

9.98

2.57 

.01 

2.92 

2.33 

.00 

2.11 

.01 

.00 

.02 

nd

9.97

2.52 

.00 

2.98 

2.44 

.01 

2.03 

.00 

.00 

.00 

nd

9.98

2.52 

.01 

2.99 

2.49 

.00 

1.97 

.00 

.00 

.00 

nd

9.98

2.47 

.00 

3.06 

3.21 

.04 

1.21 

.00 

.01 

.00 

nd

10.00

2.50 

.01 

3.00 

3.22 

.04 

1.22 

.00 

.01 

.01 

nd

10.01

Notes

Next to 

St 

093004, 

Cd 

093006, 

and Mu 

093007

Next to 

St 

093010

Next to 

Bt 

111010

Next to Next to 

Ga Ga 

111001- 111001- 

111004 111004; 

not in 

same 

crystal 

as spot 

111012

In Pgr 

next to 

Pgr

112003 

and Mu 

112007

Next to 

Mu 

122005
78 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

C. CHLORITE— Continued

Sample ..__ _ _.... _

Spot ___ ______ .. i

31

131006

59-1

132003

463-1

132006 1 2 141017 141018

466-1

151007

Weight percent

Si02 ___ __ _

Ti02 __ __

A12O3 _ _ _ __

FeO _

MnO __ _ __

MgO __ __ __

CaO

Na2O __ _ __ __

K20 ______ _ _

F __

Subsum _

H20 __ ____ _ _

Sum __

22.63 

.20 

24.72 

28.09 

.01 

11.55 

.02 

.00 

.14 

nd

87.36 

11.14

98.50

23.45 

.10 

23.88 

27.48 

.07 

10.89 

.04 

.00 

.02 

nd

85.93 

11.02

96.95

22.79 

.05 

23.75 

29.00 

.05 

11.20 

.00 

.00 

.02 

nd

86.86 

11.02

97.88

23.26 

nd 

23.27 

29.18 

.07 

11.47 

.00 

nd 

nd 

nd

87.2'5 

11.07

98.32

22.26 

.21 

25.00 

27.63 

.14 

11.71 

.00 

.00 

.14 

nd

87.09 

11.12

98.21

23.16 

.11 

24.40 

27.18 

.11 

11.82 

.05 

.00 

.17 

nd

87.00 

11.15

98.15

23.20 

.17 

23.42 

28.49 

.15 

11.51 

.00 

.00 

.05 

nd

86.99 

11.07

98.06

23.62 

nd 

23.46 

28.79 

.13 

11.59 

.01 

nd 

nd 

nd

87.60 

11.16

98.76

23.40 

nd 

23.19 

30.88 

.20 

10.55 

.00 

nd 

nd 

nd

88.22 

11.10

99.32

Number of atoms

Si __ _ __ __ Ti _ _ ______

Al _ _ _ _____

Fe _ _ __ _. _____

Mn __ ___ _

Mg _ __ _________

Ca __ _ _______

Na _

K _ _____

F _

Cation sum ___

2.43 

.02 

3.13 

2.52 

.00 

1.85 

.00 

.00 

.02 

nd

9.97

2.55 

.01 

3.06 

2.50 

.01 

1.77 

.00 

.00 

.00 

nd

9.90

2.48 

.00 

3.05 

2.64 

.00 

1.82 

.00 

.00 

.00 

nd

9.99

2.52 

nd 

2.97 

2.64 

.01 

1.85 

.00 

nd 

nd 

nd

9.99

2.40 

.02 

3.18 

2.49 

.01 

1.88 

.00 

.00 

.02 

nd

10.00

2.49 

.01 

3.09 

2.44 

.01 

1.89 

.00 

.00 

.02 

nd

9.95

2.51 

.01 

2.99 

2.58 

.01 

1.86 

.00 

.00 

.01 

nd

9.97

2.54 

nd 

2.97 

2.59 

.01 

1.86 

.00 

nd 

nd 

nd

9.97

2.53 

nd 

2.95 

2.79 

.02 

1.70 

.00 

nd 

nd 

nd

9.99

Notes

Next to 

Ga 

131007

Next to 

St 

132002

Next to 

Mu 

132007

Spots 141017 a 

are in same

ind 141018 

crystal
TABLES 79

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

C. CHLORITE— Continued

Sample ___ ._.___ _____

Spot . _ ____ _ ..

466-1 — Continued

152005 152006 153003 172004

506-1

172005 172017 181007

509-1

181009 182016

Weight percent

Si02 __ __ _..__

Ti02 __ __ _ _______

A12 03 _ __ _ _ _

FeO _ _

MnO _ ___ _______

Mg-0 _ _ _ _-

CaO ____ _

Na_O ____ _

K2 0 __ ___ __ ____

F __ __ _ _ -

Subsum

H,0 _

Sum _ _

23.38 

.12 

23.62 

29.57 

.23 

10.53 

.00 

.00 

.30 

nd

87.75 

11.08

98.83

23.07 

nd 

23.43 

29.37 

.22 

10.85 

.00 

nd 

nd 

nd

86.94 

11.01

97.95

23.73 

.16 

23.92 

28.90 

.20 

10.24 

.00 

.00 

.09 

nd

87.24 

11.11

98.35

23.42 

.09 

23.61 

28.12 

.08 

11.84 

.01 

.00 

.05 

nd

87.22 

11.14

98.36

23.01 

nd 

23.39 

27.63 

.06 

11.95 

.01 

nd 

nd 

nd

86.05 

11.00

97.05

25.71 

nd 

24.76 

26.81 

.03 

10.50 

.02 

nd 

nd 

nd

87.83 

11.43

99.26

24.05 

.07 

22.97 

28.22 

.10 

12.55 

.00 

.02 

.07 

nd

88.05 

11.24

99.29

24.63 

.10 

21.70 

28.08 

.09 

12.61 

.01 

.00 

.05 

nd

87.27 

11.15

98.42

23.87 

.15 

23.34 

27.43 

.10 

12.24 

.02 

.02 

.61 

nd

87.78 

11.19

98.97

Number of atoms

Si _ __ - _

Ti _ _ ____ _____

Al _ _ _

Fe __

Mn __

Mg- ______________

Ca ___ __ _ __

Na _______ ___ _

K _ _

F ______

Cation sum _

2.53 

.01 

3.01 

2.67 

.02 

1.70 

.00 

.00 

.04 

nd

9.98

2.51 

nd 

3.01 

2.68 

.02 

1.76 

.00 

nd 

nd 

nd

9.98

2.56 

.01 

3.04 

2.61 

.02 

1.65 

.00 

.00 

.01 

nd

9.90

2.52 

.01 

3.00 

2.53 

.01 

1.90 

.00 

.00 

.01 

nd

9.98

2.51 

nd 

3.01 

2.52 

.01 

1.94 

.00 

nd 

nd 

nd

9.99

2.70 

nd 

3.06 

2.35 

.00 

1.64 

.00 

nd 

nd 

nd

9.75

2.56 

.01 

2.89 

2.52 

.01 

1.99 

.00 

.00 

.01 

nd

9.99

2.65 

.01 

2.75 

2.53 

.00 

2.02 

.00 

.00 

.01 

nd

9.97

2.55 

.01 

2.94 

2.45 

.01 

1.95 

.00 

.00 

.08 

nd

9.99

Notes

Next to 

Mu 

153001

Next to Next to 

St St 

172001, 172006 

and 

172002

Next to 

Bt 

181006 

and Mu 

181008

Next to 

Bt 

181006
80 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rooks from within and around the Taconic allochthon—Continued

C. CHLORITE— Continued

Sample __ ___ __ ______

Spot __ __„_.________

515-1

191014 192002 30

1052-2

31

1169-1

32 213012 215004

Weight percent

Si02 _ _ ____

Ti02 _______ __

A1203 _ _ _

FeO _ _ MnO _ _ _ __

MgO __ __ _.

CaO _ _ _ _

Na»0 _ _ _

K2 0 _

F _ __

Subsum _ _

H2 0

Sum _ _

22.98 

.41 

23.68 

29.51 

.05 

10.99 

.02 

.02 

.05 

nd

87.71 

11.10

98.81

22.67 

.23 

23.66 

29.76 

.04 

10.92 

.03 

.00 

.04 

nd

87.35 

11.03

98.38

24.86 

.16 

22.64 

24.43 

.04 

14.83 

.01 

.01 

.00 

.04

86.99 

11.36

98.35

24.91 .11

22.81 

25.16 

.02 

14.64 

.00 

.00 

.00 

.04

87.66 

11.42

99.08

24.31 

.09 

23.61 

25.52 

.04 

13.74 

.02 

.08 

.00 

.05

87.62 

11.35

98.97

23.73 

.04 

22.03 

28.71 

.44 

11.91 

.02 

.03 

.01 

nd

86.92 

11.02

97.94

24.52 

.04 

21.73 

28.56 

.43 

12.54 

.05 

.01 

.02 

nd

87.90 

11.19

99.00

Number of atoms

Si

Ti _ _ _ __

Al _ _ ____

Fe __ __ _ __

Mn _ _____

Mg ______________

Ca _ __ _ _____

Na - _

K _

F __ _ _ _ ____

Cation sum ___

2.48 

.03 

3.01 

2.67 

.00 

1.77 

.00 

.00 

.01 

nd

9.97

2.46 

.02 

3.03 

2.71 

.00 

1.77 

.00 

.00 

.01 

nd

10.00

2.62 

.01 

2.81 

2.16 

.00 

2.33 

.00 

.00 

.00 

.01

9.93

2.62 

.01 

2.82 

2.21 

.00 

2.29 

.00 

.00 

.00 

.01

9.95

2.57 

.01 

2.94 

2.25 

.00 

2.16 

.00 

.02 

.00 

.02

9.97

2.58 

.00 

2.83 

2.61 

.04 

1.93 

.00 

.01 

.00 

nd

10.00

2.63 

.00 

2.75 

2.56 

.04 

2.01 

.01 

.00 

.00 

nd

10.00

Notes

Next to 

Ilm 

191015 

and Mu 

191016

Next to 

Ilm 

192001

ZnO = 0.00 ZnO^O.OO Weight 

percent 

sum includes

o'.20; 

cation 

sum includes 

0.02 

atom Zn

Next to 

Ep 

215002
TABLES 81

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID

Sample ________________________45-1______

Spot _.___...______ 1 3

SiO2 _________ 23.76 23.38

TiO2 ________ .00 .01

A1.O3 _________ 40.59 41.80

FeO __________ 25.32 25.10

MnO ________ 1.16 1.36

MgO ________- 1.41 1.22

CaO _________ .02 .02

NaaO ________ .00 .00

K2 0 _________ .16 .13 

F ________________nd_____nd

Subsum ____ 92.42 93.02

H2O __________ 7.18_____7.23

Sum ____ 99.60 100.25

Si __________ 0.99 0.97

Ti __________ .00 .00

Al __________ 2.00 2.04

Fe ____________ .88 .87

Mn _________ .04 .05

Mg __________ .09 .08

Ca __________ .00 .00

Na __________ .00 .00

K __________ .00 .00 

F ________________nd_____nd

Cation sum __ 4.00 4.01

103-1 103-2

051001 051002 061002 061005 061009 062006 062007

Weight percent

23.74

.06

39.57

25.55

.29

2.02

.03

.05

.05

nd

23.78 

nd

39.80

25.73

.30

1.95

.03

nd

nd

nd

23.62

.02

39.86

24.71

.40

2.18

.04

.04

.02

nd

24.06

.04

39.97

24.46

.41

2.46

.01

.03

.00

nd

23.59 

nd

40.01

24.53

.43

2.34

.03

nd

nd

nd

91.36

7.11

91.59

7.13

90.89

7.10

91.44

7.17

90.93

7.12

98.47 98.72 97.99 98.61 98.05

23.29 

nd

39.07

24.57

,44

2.26

.07

nd

nd

nd

89.70

7.00

96.70

23.69 

nd

40.30

24.53

.38

2.27

.00

nd

nd

nd

91.17

7.14

98.31

Number of atoms

1.00 

.00

1.97 

.90 

.01 

.13 

.00 

.00 

.00 

nd

1.00 

nd

1.97 

.91 

.01 

.12 

.00 

nd 

nd 

nd

1.00 

.00

1.98 

.87 

.01 

.14 

.00 

.00 

.00 

nd

1.01 

.00

1.97 

.86 

.01 

.15 

.00 

.00 

.00 

nd

0.99 

nd

1.99 

.86 

.02 

.15 

.00 

nd 

nd 

nd

4.01 4.01 4.00 4.00 4.01

1.00 

nd

1.97 

.88 

.02 

.14 

.00 

nd 

nd 

nd

4.01

1.00 

nd

1.99 

.86 

.01 

.14 

.00 

nd 

nd 

nd

4.00

Notes

Average 

of 3 

determinations

Average 

of 3 

determinations

Next to 

Bt

051005, 

and 

051007; 

in same 

crystal 

as spot 

051002

Next to 

Bt

051007; 

in same 

crystal 

as spot 

051001

Next to 

Bt 

061001

In Ga

061006

In contact 

with 

Bt 

061010

In contact 

with 

Bt

062002

In contact 

with 

Ch

062009 

and 

Bt 

062008
82 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID—Continued

Sample ——————————— 103-2—Continued

Spot ____________ 062011

Si02 ________ 23.52

Ti02 ________ nd

AI2 03 ________ 39.65

FeO __________ 24.78

MnO ________ .36

MgO ________- 2.23

CaO ________ .03

Na20 ________ nd

K20 _________ nd 

F __________- _______nd

Subsum ____ 90.57

H20 ________________7.08

Sum __________97.65

Si __________ 1.00

Ti __________ nd

Al __________ 1.98

F« __________ .88

Mn __ __ __ _ .01

Mg __________ .14

Ca __________ .00

Na __________ nd

K __________ nd

F __________________nd

Cation sum _ 4.01

140-2 234-1

15 16

Weight percent

24.03

.09

40.15

24.33

1.36

1.32

.04

nd

nd

.00

23.41

.02

41.14

24.06

1.36

1.23

.05

nd

nd

nd

24.01

.00

40.36

23.61

1.19

1.65

.05

nd

nd

.00

23.96

.04

41.46

23.87

1.15

1.61

.02

nd

nd

.00

91.32

7.13

91.71

7.15

90.87

7.13

92.11

7.23

98.45 98.86 98.00 99.34

24.34

.00

40.38

24.75

.13

2.48

.00

.04

.00

nd

92.35

7.24

99.59

23.39

.06

40.73

23.96

.03

2.64

.04

.01

.00

.00

90.86

7.15

98.01

Number of atoms

1.01 

.00

1.99 

.85 

.05 

.08 

.00 

nd 

nd 

.00

0.98 

.00

2.03 

.84 

.05 

.08 

.00 

nd 

nd 

nd

1.01 

.00

2.00 

.83 

.04 

.10 

.00 

nd 

nd 

.00

0.99 

.00

2.03 

.83 

.04 

.10 

.00 

nd 

nd 

.00

3.98 3.99 3.98 3.99

1.01 

.00

1.97 

.86 

.00 

.15 

.00 

.00 

.00 

nd

4.00

0.98

.00

2.01

.84

.00

.17

.00

.00

.00

.00

4.00

Notes

In contact

with Bt 

062012

ZnOrrO.OO Weight 

percent 

sum 

includes 

ZnO = 

0.44; 

cation 

sum 

includes 

0.01 

atom 

Zn

= 0.00 Weight 

percent 

sum 

includes 

ZnO = 

0.23; 

cation 

sum 

includes 

0.01 

atom 

Zn
TABLES 83

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID— Continued

Sample — __.---._ ______

Spot __________________ 091001 091003 092005 092006

331-1

092007 092010 092011 093006

Weight percent

SiO3 _ _ ____ __

TiO2 __ ________

A12O3 __

FeO _ .___ _______

MnO _____________

MgO _ ______ -

CaO _ _ __ __

Na.O _ __________

K.O ______ _

F ___ __ _ -

Subsum _

H.O ___ _ ____ _

Sum ______

Si __ _ ______

Ti ______________

Al _ __ __

Fe ___ ______

Mn _ _ ___ __

Mg ______________

Ca __ ___ __ __

Na _ _____ _

K _ _ ________

F _ __ _ __

Cation sum _

23.91 

.12 

39.95 

24.89 

.20 

2.38 

.00 

.03 

.02 

nd

91.50 

7.16

98.66

1.00 

.00 

1.97 

.87 

.01 

.15 

.00 

.00 

.00 

nd

4.00

24.15 

nd 

40.03 

24.92 

.18 

2.49 

.00 

nd 

nd 

nd

91,77 

7.19

98.96

1.01 

nd 

1.97 

.87 

.01 

.16 

.00 

nd 

nd 

nd

4.02

24.32 

nd 

40.75 

25.08 

.19 

2.38 

nd 

nd 

nd 

nd

92.72

7.27

99.99

Number of

1.00 

nd 

1.98 

.87 

.01 

.15 

nd 

nd 

nd 

nd

4.01

23.91 

.03 

40.61 

24.62 

.20 

2.36 

.00 

.03 

.02 

nd

91.78 

7.20

98.98

atoms

1.00 

.00 

1.99 

.86 

.01 

.15 

.00 

.00 

.00 

nd

4.01

23.80 

nd 

40.73 

24.84 

.18 

2.39 

nd 

nd 

nd 

nd

91.94 

7.20

99.14

0.99 

nd 

2.00 

.86 

.01 

.15 

nd 

nd 

nd 

nd

4.01

24.31 

.06 

40.69 

23.95 

.63 

2.63 

.00 

.03 

.00 

nd

92.30

7.26

99.56

1.01 

.00 

1.98 

.83 

.02 

.16 

.00 

.00 

.00 

nd

4.00

23.91 

nd 

40.70 

24.57 

.28 

2.39 

nd 

nd 

nd 

nd

91.85 

7.21

99.06

1.00 

nd 

2.00 

.86 

.01 

.15 

nd 

nd 

nd 

nd

4.02

24.19 

nd 

40.18 

24.73 

.17 

2.19 

.01 

nd 

nd 

nd

91.47 

7.18

98.65

1.01 

nd 

1.98 

.86 

.01 

.14 

.00 

nd 

nd 

nd

4.00

Notes

Next to 

Urn 

091002

Spots 092006 and 

092007 are in 

same crystal

In Ga In Ga Next to 

St 

093004, 

Ch 

093005, 

and Mu 

093007
84 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID— Continued

Sample _ __ __- _ _

Spot ____________ 101002 102005

338-1

102006

339-1

102007 102008 111005 111006

369-1

131001 131002

Weight percent

Si02 ____ ______

Ti02 _ _ _____

AlsOs _ _ -

FeO _ _____

MnO _ _ _ __ -

Mg-0 __ __ __

CaO

Na20 _- __ _

K2 0 _ _____

F _ ________

Subsum _ __

H20 _____ ________

24.07 

.05 

40.37 

25.12 

.16 

2.01 

.00 

.07 

.08 

nd

91.93 

7.19

99.12

23.94 

.06 

40.48 

25.61 

.23 

1.99 

.00 

.04 

.03 

nd

92.38 

7.21

99.59

23.69 

nd 

40.01 

25.62 

.23 

2.05 

nd 

nd 

nd 

nd

91.60 

7.14

98.74

23.31 

nd 

40.17 

25.75 

.24 

2.00 

nd 

nd 

nd 

nd

91.47 

7.12

98.59

24.12 

nd 

40.24 

25.57 

.24 

1.97 

nd 

nd 

nd 

nd

92.14 

7.19

99.33

24.33 

.05 

40.72 

24.37 

.35 

2.65 

.02 

.04 

.00 

nd

92.53

7.27

99.80

24.16

nd 

40.57 

24.45 

.48 

2.60 

.04 

nd 

nd 

nd

92.30

7.24

99.54

24.04 

.02 

40.53 

24.17 

.99 

2.15 

.00 

.04 

.01 

nd

91.95 

7.20

99.15

24.22 

nd 

40.78 

24.47 

1.12 

2.17 

nd 

nd 

nd 

nd

92.76 

7.26

100.02

Number of atoms

Si _ - _ _ __

Ti _ __ _ _

Al _ _

Fe

Mn _ _ __ _

Mg ______________

Ca _ _ _ __ _

Na _ _ _

K __

F

Cation sum _

1.00 

.00 

1.98 

.88 

.01 

.12 

.00 

.00 

.00 

nd

3.99

1.00 

.00 

1.99 

.89 

.01 

.12 

.00 

.00 

.00 

nd

4.01

1.00 

nd 

1.98 

.90 

.01 

.13 

nd 

nd 

nd 

nd

4.02

0.98 

nd 

2.00 

.91 

.01 

.13 

nd 

nd 

nd 

nd

4.03

1.01 

nd 

1.98 

.89 

.01 

.12 

nd 

nd 

nd 

nd

4.01

1.00 

.00 

1.98 

.84 

.01 

.16 

.00 

.00 

.00 

nd

3.99

1.00 

nd 

1.98 

.85 

.02 

.16 

.00 

nd 

nd 

nd

4.01

1.00 

.00 

1.99 

.84 

.04 

.13 

.00 

.00 

.00 

nd

4.00

1.00 

nd 

1.99 

.85 

.04 

.13 

nd 

nd 

nd 

nd

4.01

Notes

Next to 

Bt 

101001 

and Mu 

101003

Next to 

Ilm 

102001 

and Mu 

102009; 

in same 

crystal 

as spots 

102006- 

102008

Next to 

Bt 

102010; 

in same 

crystal 

as spots 

102005, 

102007 

and 

102008

On rim Next to 

of Mu 

crystal 102009; 

contain- in same 

ing crystal 

spots as spots 

102005, 102005- 

102006, 102007 

and 

102008

In Ga 

crystal 

containing 

spots 111001- 

111004, 

in contact 

with Ga 

111004

In same 

Ga as 

spot 

111005; 

next to 

Ga 

111007

In rim 

of Ga

Next to 

Ga 

131003; 

in. same 

crystal 

as spot 

131001, 

nearer 

rim of 

Ga
TABLES 85

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID— Continued

Sample ________ _ __

Spot ____ ________

369-1 — Continued

131004 131010 141002 141003

463-1

141004 141007 141008 141024

466-1

151001

Weight percent

Si02 __ _ ________

Ti02 __ _ _ _

Ala03 _____________

FeO _. __ __

MnO ________

MgO __ ___ ____

CaO _ _ __

Na20 __-__ _ _ ___

K2 0 __ __ _ __

F _ _ _ _

Subsum

H20 ____ ____ ____

Sum

23.73 

nd 

40.67 

24.47 

.99 

2.22 

.01 

nd 

nd 

nd

92.09 

7.20

99.29

24.21 

nd 

40.38 

24.58 

1.05 

2.16 

.01 

nd 

nd 

nd

92.39 

7.22

99.61

24.18

.32 

40.90 

24.26 

.35 

2.41 

.00 

.04 

.04 

nd

92.50

7.27

99.77

23.95 

.09 

40.65 

24.52 

.38 

2.29 

.00 

.04 

.05 

nd

91.97 

7.21

99.18

23.87 

nd 

40.54 

24.51 

.35 

2.35 

nd 

nd 

nd 

nd

91.62 

7.18

98.80

24.25 

nd 

40.54 

24.14 

.33 

2.54 

nd 

nd 

nd 

nd

91.80 

7.22

99.02

23.79 

nd 

41.03 

24.33 

.34 

2.49 

nd 

nd 

nd 

nd

91.98 

7.22

99.20

24.34 

nd 

41.14 

24.44 

.36 

2.40 

nd 

nd 

nd 

nd

92.68 

7.29

99.97

24.38 

.04 

40.60 

24.96 

.63 

2.09 

.00 

.08 

.03 

nd

92.81 

7.26

100.07

Number of atoms

Si ______

Ti _ _

Al __ ______

Fe __ _ _

Mn ___ _ _ _

Mg

Ca _ ___ _

Na _ __ _____

K _ _ _

F _ _ __ ____

Cation sum ___

0.99 

nd 

2.00 

.85 

.04 

.14 

.00 

nd 

nd 

nd

4.02

1.01 

nd 

1.98 

.85 

.04 

.13 

.00 

nd 

nd 

nd

4.01

1.00 

.01 

1.99 

.84 

.01 

.15 

.00 

.00 

.00 

nd

4.00

1.00 

.00 

1.99 

.85 

.01 

.14 

.00 

.00 

.00 

nd

3.99

1.00 

nd 

1.99 

.86 

.01 

.15 

nd 

nd 

nd 

nd

4.01

1.01 

nd 

1.99 

.84 

.01 

.16 

nd 

nd 

nd 

nd

4.01

0.99 

nd 

2.01 

.85 

.01 

.15 

nd 

nd 

nd 

nd

4.01

1.00 

nd 

2.00 

.84 

.01 

.15 

nd 

nd 

nd 

nd

4.00

1.00 

.00 

1.98 

.86 

.02 

.13 

.00 

.01 

.00 

nd

4.00

Notes

Center 

of Ga; 

next to 

Ga 

131005

In Ga 

131011, 

near 

rim

Near Bt 

141005 

and 

next to 

Ilm 

141001; 

in same 

crystal 

as spots 

141003, 

141004, 

141007, 

and 

141008

In same On twin 

crystal boundas spots ary in 

141002, same 

141004, crystal 

141007, as spots 

and 141002, 

141008 141003, 

141007, 

and 

141008

Next to 

Bt 

141006; 

in same 

crystal 

as spots 

141002, 

141003, 

141004, 

and 

141008

In same 

crystal 

as spots 

141002, 

141003, 

141004, 

and 

141007

Next to 

Mu 

141023

End of 

crystal 

next to 

Mu 

151002; 

in same 

crystal 

as spot 

151008
86 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID— Continued

Sample _.__ _ __ ..._

Spot ._ _____ ______

466-1 — Continued

151008 152001 172008

506-1

172009 172011 174005 181001

509-1

181005 182003

Weight percent

Si02 _ _ _ —

Ti02 _____________

A1203 _ __ ___ -

FeO _ _ _ __

MnO _ _ _ ___ -

MgO ___ _ __ ___

CaO _ __

Na20

K.O __ __ _ ____

F _ _ __ _ _

Subsum

H.O _ ___________

Sum _ _

24.28 

nd 

40.29 

25.11 

.62 

2.12 

.00 

nd 

nd 

nd

92.42 

7.22

99.64

24.07 

.03 

40.70 

25.13 

.73 

1.87 

.00 

.03 

.05 

nd

92.61 

7.23

99.84

24.34 

.06 

40.03 

24.92 

.15 

2.12 

.02 

.02 

.05 

nd

91.71 

7.18

98.89

24.06 

nd 

40.23 

25.09 

.15 

2.22 

.02 

nd 

nd 

nd

91.77 

7.18

98.95

23.55 

nd 

40.30 

24.97 

.15 

2.21 

.00 

nd 

nd 

nd

91.18 

7.13

98.31

24.09 

.04 

39.79 

25.02 

.15 

2.22 

.02 

.04 

.07 

nd

91.44 

7.15

98.59

24.50 

.04 

40.05 

24.81 

.29 

2.41 

.00 

.03 

.06 

nd

92.19 

7.22

99.41

24.19 

.03 

40.48 

24.68 

.22 

2.49 

.01 

.04 

.03 

nd

92.17 

7.23

99.40

24.34 

.02 

40.64 

24.26 

.20 

2.56 

.00 

.04 

.05 

nd

92.11

7.24

99.35

Number of atoms

Si — _ __ _

Ti _ ____ — -

Al _ ___ _____

Fe

Mn _________

Mg ______________

Ca __ ___ _

Na ___ _ __

K

F _ _

Cation sum ___

1.01 

nd 

1.97 

.87 

.02 

.13 

.00 

nd 

nd 

nd

4.00

1.00 

.00 

1.99 

.87 

.03 

.12 

.00 

.00 

.00 

nd

4.01

1.02 

.00 

1.97 

.87 

.01 

.13 

.00 

.00 

.00 

nd

4.00

1.00 

nd 

1.98 

.88 

.01 

.14 

.00 

nd 

nd 

nd

4.01

0.99 

nd 

2.00 

.88 

.01 

.14 

.00 

nd 

nd 

nd

4.02

1.01 

.00 

1.97 

.88 

.01 

.14 

.00 

.00 

.00 

nd

4.01

1.02 

.00 

1.96 

.86 

.01 

.15 

.00 

.00 

.00 

nd

4.00

1.00 

.00 

1.98 

.86 

.01 

.15 

.00 

.00 

.00 

nd

4.00

1.01 

.00 

1.98 

.84 

.01 

.16 

.00 

.01 

.01 

nd

4.02

Notes

In same 

crystal 

as spot 

151001

Center 

of 

crystal

Next to 

St 

172001 

and Mu 

172010

Next to Near Ga 

St 172013 

172001 and 

and Mu next to 

172010 Ga 

172014

Next to 

Bt 

181003, 

and Mu 

181002 

and 

181008; 

in same 

crystal 

as spot 

181005

Near Bt 

181006 

and 

next to 

Mu 

181008; 

in same 

crystal 

as spot 

181001

Next to 

Bt 

182005 

and Mu 

182004
TABLES 87

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

D. CHLORITOID— Continued

Sample ——————————— 509-1 — Continued

Spot ______ __ _ 182008 191008 191010 191018

515-1

191021 191104 191105 191106

Weight percent

Si02 _ ___ _

Ti02 ________

Al20-i

FeO __ _____ __

MnO _ _____ -

MgO _ _ __ _

CaO _ __

Na20 - _ _ _

K20 ______ __

F _ _ __ __ _

Subsum _

H20 _ ___ __ _ _

Sum _ _

24.03 

.05 

40.47 

24.13 

.22 

2.48 

.00 

.03 

.01 

nd

91.42 

7.19

98.61

23.61 

.22 

40.16 

25.11 

.36 

2.41 

.06 

.04 

.00 

nd

91.97 

7.18

99.15

23.82 

.01 

40.93 

25.03 

.60 

2.49 

.04 

.03 

.01 

nd

92.96 

7.26

100.22

24.21 

.02 

40.73 

25.61 

.14 

2.14 

.01 

.03 

.05 

nd

92.94 

7.26

100.20

23.88 

.03 

40.29 

25.43 

.13 

2.20 

.02 

.04 

.01 

nd

92.03 

7.19

99.22

24.34 

nd 

40.31 

26.02 

.13 

1.82 

.07 

nd 

nd 

nd

92.69 

7.23

99.92

24.45 

nd 

40.10 

26.07 

.16 

1.95 

.01 

nd 

nd 

nd

92.74 

7.23

99.97

24.39 

nd 

40.69 

25.67 

.14 

2.20 

.02 

nd 

nd 

nd

93.11

7.28

100.39

Number of atoms

Si

Ti _ ___________

Al _ __ _ ________

Fe _ __ _ __

Mn __ _ _ _

Mg ____ _ ______

Oa _ _____________

Na ___ _ ______

K _ __ ___ __

F _____ _____

Cation sum _

1.00 

.00 

1.99 

.84 

.01 

.15 

.00 

.00 

.00 

nd

3.99

0.99 

.01 

1.98 

.88 

.01 

.15 

.00 

.00 

.00 

nd

4.02

0.98 

.00 

1.99 

.84 

.02 

.15 

.00 

.00 

.00 

nd

3.98

1.00 

.00 

1.98 

.88 

.00 

.13 

.00 

.00 

.00 

nd

3.99

1.00 

.00 

1.98 

.89 

.00 

.14 

.00 

.00 

.00 

nd

4.01

1.01 

nd 

1.97 

.90 

.00 

.11 

.00 

nd 

nd 

nd

3.99

1.01 

nd 

1.96 

.90 

.01 

.12 

.00 

nd 

nd 

nd

4.00

1.01 

nd 

1.98 

.88 

.00 

.13 

.00 

nd 

nd 

nd

4.00

Notes

At rim of 

Ga near 

spot Ga 

182009

In Ga 

containing spot 

Ga 

191004; 

next to 

Ihn 

191009

In Ga 

containing spot 

Ga 

191004; 

near Ga 

191012

In contact 

with St 

191019, 

in parallel 

orientation

Spots 191104, 

are in

191105, and 191106 

same crystal
88 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE

Sample _ _ _ ______ _ _

i 2

14-1

3 4 5 1

234-1

2 9

Weight percent

SiO2 _ __ _ __

TiO2 ____ __ __

A12O3 _- . _

FeO __ ____

MnO _ _ — -

MgO _ __

CaO _____

Na20 _ - _____

K2O — _ _ __

F _ _

Subsum _ _

H.0 1 __ _ __ _

Sum

Si

Ti _

Al __ _ _____

Fe __ __

Mn __ _ —

Mg ___________ ——

Ca

Na _____

K _ ___ _

F _ _

Cation sum _

27.72 

.57 

52.88 

14.04 

.06 

1.53 

.01 

.00 

nd 

.00

97.11 

1.05

98.16

3.97 

.06 

8.92 

1.68 

.01 

.32 

.02 

.00 

nd 

.00

15.01

28.43 

.75 

53.72 

13.38 

.02 

1.37 

.01 

.00 

nd 

.00

97.88 

1.06

98.94

4.01 

.08 

8.94 

1.58 

.00 

.29 

.00 

.00 

nd 

.00

14.92

27.58 

.73 

52.78 

14.18 

.02 

1.37 

.00 

.00 

nd 

.00

97.10 

1.05

98.15

Number of

3.96 

.08 

8.92 

1.70 

.00 

.29 

.00 

.00 

nd 

.00

15.00

29.11 

.42 

53.37 

14.33 

.08 

1.43 

.00 

.00 

nd 

.20

98.91

1.07

99.98

atoms

4.07 

.04 

8.79 

1.67 

.01 

.30 

.00 

.00 

nd 

.09

14.89

28.31 

.66 

53.73 

14.31 

.05 

1.37 

.00 

.00 

nd 

.08

98.64 

1.07

99.71

3.98 

.07 

8.91 

1.68 

.01 

.29 

.00 

.00 

nd 

.04

14.96

28.41 

.76 

51.55 

14.36 

.00 

1.05 

.00 

.00 

.00 

.59

96.79 

1.04

97.83

4.09 

.08 

8.75 

1.73 

.00 

.22 

.00 

.00 

.00 

.27

14.93

27.75 

.39 

52.00 

14.13 

.05 

.94 

.02 

.00 

.00 

.26

96.23 

1.03

97.26

4.02 

.04 

8.89 

1.71 

.00 

.20 

.00 

.00 

.00 

.12

14.96

28.07 

.58 

53.21 

12.89 

.12 

1.07 

.05 

nd 

nd 

nd

95.99 

1.04

97.03

4.03 

.06 

9.01 

1.55 

.01 

.23 

.00 

nd 

nd 

nd

14.89

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.30; 

cation 

sum includes 

0.03 

atom 

Zn; 

average 

of 3 

analyses

Weight 

percent 

sum includes 

ZnO 

= 0.20; 

cation 

sum includes 

0.02 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.44; 

cation 

sum includes 

0.05 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.14; 

cation 

sum includes 

0.01 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.20; 

cation 

sum includes 

0.02 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.57; 

cation 

sum includes 

0.06 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.91; 

cation 

sum includes 

0.10 

atom 

Zn

See footnotes at end of table, p. 123.
TABLES 89 

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE— Continued

Sample _ _ ___. _ ._ _ _ _

Spot _. ________ _ 14

290-1

15

331-1

16 091008 091009 091010 093004 093009 093010

Weight percent

Si02 _ _____

Ti02

A12 03 __ __ __

FeO _ _

MnO

MgO

CaO _ _ __

NasO

K20 __ ___ __ __

F

Subsum _ __

H»0 1

Sum _ _ _

28.36 

.50 

52.81 

13.61 

.07 

1.31 

.02 

.02 

nd 

.03

97.13 

1.05

98.18

27.83 

.51 

53.34 

12.78 

.02 

1.49 

.01 

.02 

nd 

.09

96.24 

1.05

97.29

28.75

.35 

53.45 

12.96 

.01 

1.59 

.01 

.07 

nd 

.13

97.55 

1.06

98.61

28.06 

.52 

54.78 

13.53 

.12 

1.00 

.00 

.01 

.01 

nd

98.03 

1.06

99.09

27.80 

.46 

54.91 

13.38 

.11 

.99 

.00 

.00 

.00 

nd

97.65 

1.06

98.71

27.93 

nd 

54.45 

13.26 

.14 

1.15 

.00 

nd 

nd 

nd

96.93 

1.05

97.98

27.60 

.58 

54.00 

13.76 

.15 

1.10 

.00 

.00 

.00 

nd

97.19 

1.05

98.24

26.89 

.52 

54.10 

13.47 

.14 

1.10 

.00 

.00 

.00 

nd

96.22 

1.04

97.26

26.94 

nd 

54.64 

13.33 

.14 

1.00 

.00 

nd 

nd 

nd

96.05 

1.04

97.09

Number of atoms

Si _

Ti

Al _

Fe _ __ _ __

Mn __ _ _ _

Me

Ca _

Na ____

K _

F _ _ _ __

Cation sum ___

4.05 

.05 

8.89 

1.63 

.01 

.28 

.03 

.00 

nd 

.01

14.99

3.99 

.06 

9.01 

1.53 

.00 

.32 

.00 

.00 

nd 

.04

14.93

4.0<7 

.04 

8.93 

1.54 

.00 

.34 

.00 

.00 

nd 

.01

14.95

3.96 

.06 

9.10 

1.60 

.01 

.21 

.00 

.00 

.00 

nd

14.94

3.93 

.05 

9.15 

1.58 

.01 

.21 

.00 

.00 

.00 

nd

14.93

3.98 

nd 

9.14 

1.58 

.02 

.24 

.00 

nd 

nd 

nd

14.96

3.94 

.06 

9.08 

1.64 

.02 

.23 

.00 

.00 

.00 

nd

14.97

3.87 

.06 

9.18 

1.62 

.02 

.24 

.00 

.00 

.00 

nd

14.99

3.88 

nd 

9.27 

1.60 

.02 

.21 

.00 

nd 

nd 

nd

14.98

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.43; 

cation 

sum includes 

0.05 

atom 

Zn; 

average 

of 3 

analyses

Weight 

percent 

sum includes 

ZnO 

= 0.23; 

cation 

sum includes 

0.02 

atom 

Zn; 

average 

of 3 

analyses

Weight 

percent 

sum includes 

ZnO 

= 0.34; 

cation 

sum includes 

0.03 

atom 

Zn; 

average 

of 3 

analyses

Next to 

Cd 

093006, 

Ch 

093005, 

Bt 

093003, 

and Mu 

093007; 

in same 

crystal 

as spot 

093009

In same 

crystal 

as spot 

093004

Next to 

Ch 

093011

See footnotes at end of table, p. 123.
90 METAMOBPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE— Continued

Sample ______ _ _ __ _

Spot __________________

339-1

111015 111016 111018 111028 1 2

355-1

3 4 5

Weight percent

Si02 _ _ _ __ _ _

TiO2 _ ____ _ __

A1_O3 _ ____ —

FeO __ __ _

MnO _ __ __

MgO _ _ _

CaO ._ _ __ __

Na20 _ __ ______

K20 ______________

F __ _

Subsum _ _

H.0 1 _ _ ___ __ __

Sum _ _____

27.07 

.57 

53.74 

15.17 

.09 

1.17 

.00 

.00 

.02 

nd

97.83 

1.05

98.88

27.88

nd 

53.99 

15.09 

.10 

1.40 

.02 

nd 

nd 

nd

98.48 

1.06

99.54

27.97 

.49 

53.72 

14.96 

.07 

1.34 

.01 

.00 

.00 

nd

98.56 

1.06

99.62

27.85 

nd 

53.51 

14.88 

.10 

1.34 

.02 

nd 

nd 

nd

97.70 

1.05

98.75

28.33 

.64 

54.79 

14.25 

.07 

1.07 

.00 

nd 

nd 

nd

99.15 

1.07

100.22

27.75 

.60 

54.52 

13.% 

.04 

1.05 

.00 

nd 

nd 

nd

98.49 

1.06

99.55

28.12 

.36 

53.31 

14.23 

.02 

1.05 

.02 

nd 

nd 

nd

97.44 

1.05

98.49

27.73 

.77 

54.64 

14.04 

.07 

1.07 

.00 

nd 

nd 

nd

99.09 

1.07

100.16

28.48 

.75 

55.71 

13.80 

.07 

.99 

.00 

nd 

nd 

nd

99.89 

1.08

100.97

Number of atoms

Si ___ _ _______

Ti _____ ______

Al _______ ___

Fe ______ _ _

Mn ____ ______

Mg- ______________

Ca _ _____________

Na

K

F ___

Cation sum ___

3.87 

.06 

9.05 

1.81 

.01 

.25 

.00 

.00 

.00 

nd

15.05

3.95 

nd 

9.01 

1.79 

.01 

.30 

.00 

nd 

nd 

nd

15.06

3.95 

.05 

8.95 

1.77 

.01 

.28 

.00 

.00 

.00 

nd

15.01

3.97 

nd 

8.99 

1.77 

.01 

.28 

.00 

nd 

nd 

nd

15.02

3.96 

.06 

9.03 

1.67 

.00 

.22 

.00 

nd 

nd 

nd

14.94

3.92 

.06 

9.07 

1.65 

.00 

.22 

.00 

nd 

nd 

nd

14.98

4.01 

.04 

8.96 

1.70 

.00 

.22 

.00 

nd 

nd 

nd

14.96

3.90 

.08 

9.05 

1.65 

.01 

.22 

.00 

nd 

nd 

nd

14.99

3.94 

.08 

9.09 

1.60 

.01 

.20 

.00 

nd 

nd 

nd

14.93

Notes

Next to 

Ga 

111014; 

in same 

crystal 

as spot 

111016

In same 

crystal 

as spot 

111015

Next to 

Mu 

111029

ZnO = 0.00 

Samples 

1-5, inclusive, 

used in 

comparison 

with 

wetchemical 

analysis 

(table 

5); 

probe 

done on 

aliquot 

of mineral separate

Weight 

percent 

sum includes 

ZnO 

= 0.57; 

cation 

sum includes 

0.06 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.33; 

cation 

sum includes 

0.03 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.77; 

cation 

sum includes 

0.08 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.09; 

cation 

sum includes 

0.01 

atom 

Zn

See footnotes at end of table, p. 123.
TABLES 91

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE— Continued

Sample _______ _ _ _ _ _ _

Spot _____________

355-1 — Continued

17 18 20 21

356-1

22

369-1

23 24 132001 132002

Weight percent

Si02 _ _ _

Ti02 _. __ ______

A12(X

FeO __ _ __ __

MnO _ __ _ _

MgO __ _____

CaO __ __ _

Na20 _ _ __ _

K20

F ___ __ __

Subsum _ _

H20 a _ _ _____

Sum _ _

27.40 

.76 

51.14 

14.2-9 

.04 

1.02 

.00 

.00 

.00 

.00

94.83 

1.02

95.85

28.07 

.71 

53.63 

14.46 

.09 

.99 

.00 

.00 

.00 

.00

98.02 

1.06

99.08

28.73 

.65 

53.91 

13.96 

.05 

1.52 

.01 

.00 

nd 

.00

99.16 

1.07

100.23

27.97 

.50 

54.11 

13.30 

.04 

1.52 

.01 

.00 

nd 

.26

97.95 

1.06

99.01

27.97 

.52 

53.50 

13.66 

.05 

1.59 

.00 

.00 

nd 

.10

97.46 

1.06

98.52

28.87 

.62 

53.74 

13.74 

.02 

1.43 

.00 

.00 

nd 

.00

98.77 

1.06

99.83

28.05 

.63 

52.51 

13.28 

.10 

1.46 

.03 

.00 

nd 

.00

96.16 

1.04

97.20

27.53 

.54 

54.46 

12.87 

.11 

.86 

.00 

.04 

.00 

nd

96.41 

1.05

97.46

27.51

nd 

54.59 

12.66 

.07 

.81 

.00 

nd 

nd 

nd

95.64 

1.04

96.68

Number of atoms

Si _ _ __ _ ___

Ti _______ ___

Al _______________

Fe _ _ ___________

Mn __ _ __ _

Mg ______________

Ca __ __ _ ______

Na _ _ _______

K __ _______ _

F _ _ __

Cation sum _ _

4.03 

.08 

8.85 

1.76 

.00 

.22 

.00 

.00 

.00 

.00

14.96

3.98 

.08 

8.96 

1.71 

.01 

.21 

.00 

.00 

.00 

.00

14.96

4.02 

.07 

8.90 

1.64 

.01 

.32 

.00 

.00 

nd 

.00

14.99

3.94 

.05 

9.00 

1.57 

.00 

.32 

.00 

.00 

nd 

.12

14.93

3.97 

.06 

8.96 

1.62 

.01 

.34 

.00 

.00 

nd 

.05

14.98

3.96 

.07 

9.00 

1.64 

.00 

.30 

.00 

.00 

nd 

.00

15.01

4.04 

.07 

8.91 

1.60 

.01 

.31 

.00 

.00 

nd 

.00

14.95

3.94 

.06 

9.18 

1.54 

.01 

.18 

.00 

.01 

.00 

nd

14.92

3.96 

nd 

9.25 

1.52 

.01 

.17 

.00 

nd 

nd 

nd

14.91

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.18; 

cation 

sum includes 

0.02 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.07; 

cation 

sum includes 

0.01 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.33; 

cation 

sum includes 

0.03 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.46; 

cation 

sum includes 

0.05 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.15; 

cation 

sum includes 

0.02 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.35; 

cation 

sum includes 

0.04 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.10; 

cation 

sum includes 

0.01 

atom 

Zn; 

average 

of 2 

analyses

In same 

crystal 

as spot 

132002

On rim of 

crystal 

containing spot 

132001; 

next to 

Ch 

132003

See footnotes at end of table, p. 123.
92 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE— Continued

Sample _ _ _ _ _ _______

Si02 _ __ „

Ti02 _ _ _ _

AlsO. _____ _

FeO _ _ __ __

MnO __________

MgO ___ _

CaO __ _ __ __

Na2O __ _ __

K20 _

F ______

Subsum _

EsQ 1 __ ___ __

Sum

Si _ _ _ — __

Ti ___ __

Al _ _ __ _ _

Fe __ ___

Mn _ _ __

Mg _ __ ___ ___

Ca __ ______

Na __ __ _ __

K _ __ _ _

F _ _

Cation sum _ _

463-1

142010

27.09 

.43 

53.18 

15.60 

.24 

1.44 

.00 

.00 

.01 

nd

97.99 

1.05

99.04

3.88 

.05 

8.97 

1.87 

.03 

.31 

.00 

.00 

.00 

nd

15.11

142011

26.99 

nd 

53.58 

15.50 

.23 

1.30 

.00 

nd 

nd 

nd

97.60 

1.05

98.65

3.87 

nd 

9.06 

1.86 

.03 

.28 

.00 

nd 

nd 

nd

15.10

1

Weight

29.15 

.55 

53.52 

11.78 

.10 

.94 

.00 

.00 

nd 

.30

96.50 

1.06

97.56

Number

4.13 

.06 

8.93 

1.39 

.01 

.20 

.00 

.00 

nd 

.13

14.76

506-1

2

percent

28.66 

.61 

53.75 

11.76 

.05 

.88 

.00 

.00 

nd 

.00

96.08 

1.05

97.13

of atoms

4.09 

.07 

9.05 

1.41 

.01 

.19 

.00 

.00 

nd 

.00

14.86

172006

27.52 

nd 

53.48 

12.71 

.08 

.88 

.01 

nd 

nd 

nd

94.68 

1.03

95.71

4.00 

nd 

9.17 

1.55 

.01 

.19 

.00 

nd 

nd 

nd

14.92

191019

28.00 

.38 

54.32 

11.92 

.09 

.72 

.00 

.06 

.04 

nd

95.53 

1.04

96.57

4.02 

.04 

9.19 

1.43 

.01 

.15 

.00 

.02 

.01 

nd

14.87

515-1

191020

27.73 

.40 

54.35 

11.83 

.08 

.71 

.01 

.07 

.02 

nd

95.20 

1.04

96.24

3.99 

.04 

9.22 

1.42 

.01 

.15 

.00 

.02 

.00 

nd

14.85

191022

27.94 

.37 

54.48 

11.98 

.08 

.73 

.01 

.08 

.02 

nd

95.69 

1.05

96.74

4.00 

.04 

9.20 

1.43 

.01 

.16 

.00 

.02 

.00 

nd

14.86

Notes

On rim of 

crystal 

containing spot 

142011

In same 

crystal 

as spot 

142010

Weight 

percent 

sum includes 

ZnO 

= 0.41; 

cation 

sum includes 

0.04 

atom 

Zn; 

average 

of 2 

analyses

Weight 

percent 

sum includes 

ZnO 

= 0.37; 

cation 

sum includes 

0.04 

atom 

Zn; 

average 

of 3 

analyses

Next to 

Ch 

172005

Next to 

Cd 

191018; 

in same 

crystal 

as spots 

191020 

and 

191022

In same 

crystal 

as spots 

191019 

and 

191022

In contact 

with 

Cd; in 

same 

crystal 

as spots 

191019 

and 

191020

See footnotes at end of table, p. 123.
TABLES 93

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE—Continued

Sample ———— —————— _____________515-1—Continued_____________ __________________655-1________________ 1052-2 

Spot __——— ————— — 192004______192005 192006 192007 ___1 ________2__________3_________4_________16

Weight percent

SiO2 __________ 27.93 27.05 27.38 27.64 27.84 28.05 27.66 27.71 27.55

TiO2 _________ .60 .47 .48 .46 .76 .69 .73 .64 .63

A12O3 _________ 54.38 54.12 54.45 54.57 50.91 52.79 52.72 53.12 51.88

FeO __________ 11.65 11.99 12.03 11.52 14.89 14.85 14.68 14.53 15.08

MnO _________ .10 .13 .11 .12 .05 .07 .07 .05 .02

MgO _________ .75 .81 .72 .78 1.41 1.45 1.46 1.41 1.52

CaO __________ .01 .00 .02 .00 .00 .04 .07 .00 .00

NaaO ________ .09 .08 .10 .06 nd nd nd nd nd

K2O __________ .02 .01 .02 .03 nd nd nd nd nd 

F __—_—___—_____nd_____nd_____nd_____nd_____nd_____nd______nd_____nd_____nd

Subsum ____ 95.53 94.66 95.31 95.18 95.86 97.94 97.39 97.46 96.68

H2O 1 _________ 1.05_____1.03_____1.04_____1.04_____1.03_____1.05______1.05_____1.05_____1.04

Sum ____ 96.58 95.69 96.35 96.22 96.89 98.99_____98.44 98.51 97.72

Number of atoms

Si ___________ 4.00 3.93 3.95 3.97 4.05 3.99 3.96 3.96 3.98

Ti __________ .06 .05 .05 .05 .08 .07 .08 .07 .07

Al __________ 9.19 9.26 9.25 9.25 8.73 8.85 8.90 8.94 8.83

Fe __________ 1.40 1.45 1.45 1.38 1.81 1.77 1.76 1.73 1.82

Mn __________ .01 .02 .01 .01 .00 .01 .01 .00 .00

Mg __________ .16 .18 .15 .17 .30 ,30 .31. .30 .33

Ca __________ .00 .00 .00 .00 .00 .00 .01 .00 .00

Na _________ .03 .02 .03 .02 nd nd nd nd nd

K ___________ .00 .00 .00 .01 nd nd nd nd nd 

F ______________nd______nd______nd______nd______nd______nd______nd______nd______nd

Cation sum __ 14.85 14.91 14.89 14.86 14.97 14.99 15.03 15.00 15.03

Notes

Spots 192004 and 192005 

are in same crystal

See footnotes at end of table, p. 123.
94 METAMOBPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

E. STAUROLITE— Continued

Sample _ _ _ ____ _ _ _

Spot

1052-2— Continued

17 18 19 20 21 22

Weight percent

Si02 _________

Ti02 _____ __

A1203 _____ -

FeO __ _________

MnO _ _ _ __

MgO __ __ _

CaO ________ _

NasO ____________

K20

F _______________

Subsum ______

HsO 1 ____ ___

Sum _ _ _

27.73 

.47 

52.86 

15.04 

.07 

1.56 

.00 

nd 

nd 

nd

97.73 

1.05

98.78

27.66 

.97 

52.86 

15.85 

.02 

1.66 

.03 

.00 

.00 

.00

99.12 

1.06

100.18

27.37 

.77 

53.21 

14.44 

.04 

1.57 

.03 

.00 

.00 

.13

97.55 

1.05

98.60

28.52 

.71 

50.76 

14.59 

.03 

1.29 

.03 

.00 

.00 

.00

96.16 

1.04

97.20

27.30 

.74 

53.02 

15.36 

.04 

1.23 

.00 

.02 

.00 

.23

98.05 

1.05

99.10

28.64

.86 

53.38 

14.91 

.09 

1.33 

.01 

.00 

.00 

.32

99.66 

1.07

100.73

Number of atoms

Si _ ___ ______

Ti _ _____ _

Al ______ __

Fe __ _ __________

Mn _____________

Mg _ _ _

Ca _______________

Na _ ____ _ __

K

F ______ ______

Cation sum _

3.95 

.05 

8.89 

1.79 

.00 

.33 

.00 

nd 

nd 

nd

15.01

3.91 

.10 

8.82 

1.87 

.00 

.35 

.00 

.00 

.00 

.00

15.05

3.90 

.08 

8.95 

1.72 

.00 

.33 

.00 

.00 

.00 

.06

14.99

4.13 

.08 

8.66 

1.76 

.00 

.28 

.00 

.00 

.00 

.06

14.93

3.90 

.08 

8.93 

1.83 

.00 

.26 

.00 

.00 

.00 

.10

15.03

4.01 

.09 

8.81 

1.74 

.01 

.28 

.00 

.00 

.00 

.14

14.98

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.07

Weight 

percent 

sum includes 

ZnO 

= 0.10; 

cation 

sum includes 

0.01 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.23; 

cation 

sum includes 

0.02 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.30; 

cation 

sum includes 

0.03 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.39; 

cation 

sum includes 

0.04 

atom 

Zn

See footnotes at end of table, p. 123.
TABLES 95

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET

Sample __.._. _ — _ __.

2 10 11

14-1

12 13 22 041001

102-1

041003 041004

Weight percent

Si02 _ ___ __

TiO2 __ ________

Al2Oa __ __ _ __

FeO ___ „ _____

MnO __ __

MgO __ _ _ _

CaO _ — __

Na2O __ _ ________

K2O _ _ ___ _

F ______ __ _

Sum _ _ __

38.57 

.01 

20.42 

38.48 

.60 

1.94 

1.11 

.05 

.00 

nd

101.18

36.15 

.02 

20.52 

37.35 

.84 

2.22 

1.84 

nd 

nd 

nd

99.19

34.98 

.20 

21.17 

36.23 

.63 

2.18 

2.09 

.04 

.00 

nd

98.81

34.16 

.00 

21.32 

36.49 

.98 

2.01 

2.43 

.04 

.00 

nd

98.47

36.89

.05 

20.93 

36.96 

1.11 

2.29 

2.21 

nd 

nd 

nd

100.47

35.38 

.00 

20.66 

38.23 

.63 

1.87 

1.53 

.08 

.00 

nd

99.53

36.49 

.04 

21.13 

28.06 

4.44 

1.41 

8.68 

.00 

.00 

nd

100.25

36.33 

nd 

20.73 

28.34 

6.89 

1.16 

7.02 

nd 

nd 

nd

100.47

36.60 

nd 

21.13 

29.33 

4.55 

1.52 

8.12 

nd 

nd 

nd

101.25

Number of atoms

Si __ _ ___ —

Ti _ __ __ _____

Al ___ _ _ __

Fe _ _ ______

Mn ______ ____

Mg ______________

Ca __ _ _ __ ____

Na __ ___ __

K __ __ __

F __ _ __ __

Cation sum _ _

3.08 

.00 

1.93 

2.57 

.04 

.23 

.09 

.Ul 

.00 

nd

7.95

2.97 

.02 

1.99 

2.57 

.06 

.27 

.16 

nd 

nd 

nd

8.05

2.90 

.01 

2.06 

2.51 

.04 

.27 

.19 

.00 

.00 

nd

8.06

2.85 

.00 

2.10 

2.55 

.07 

.25 

.22 

.01 

.00 

nd

8.11

2.98 

.00 

1.99 

2.50 

.08 

.28 

.19 

nd 

nd 

nd

8.02

2.92 

.00 

2.01 

2.64 

.04 

.23 

.13 

.01 

.00 

nd

8.05

2.94 

.00 

2.01 

1.89 

.30 

.17 

.75 

.00 

.00 

nd

8.06

2.94 

nd 

1.98 

1.92 

.47 

.14 

.61 

nd 

nd 

nd

8.06

2.93 

nd 

1.99 

1.96 

.31 

.18 

.70 

nd 

nd 

nd

8.07

Notes

ZnO = 0.00 Rim of 

crystal 

containing 

spots 11 

and 12; 

weight 

percent 

sum includes 

ZnO 

= 0.25; 

cation 

sum includes 

0.01 

atom 

Zn

Part way 

into 

crystal 

containing 

spots 10 

and 12; 

weight 

percent 

sum includes 

ZnO 

= 1.29; 

cation 

sum includes 

0.08 

atom 

Zn

Further Core of 

into crystal 

crystal containcontain- ing 

ing spots 10- 

spots 10 12; 

and 11; weight 

weight percent 

percent sum insum in- dudes 

eludes ZnO 

ZnO = 0.03 

= 1.04; 

cation 

sum includes 

0.06 

atom 

Zn

Near Ga 

10; 

wefght 

percent 

sum includes 

ZnO 

=1.15: 

cation 

sum includes 

0.07 

atom 

Zn

In same 

crystal 

as spots 

014003 

and 

041004

On rim of 

crystal 

containing 

spots 

041001 

and 

041004

Center of 

crystal 

containing 

spots 

041001 

and 

041003
96 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET—Continued

Sample ———————————____102-1—Continued

Spot .--_.._-________ 043008 043009

Si02 __________ 36.60 36.95

Ti02 _________ .38 nd

A1203 _________ 20.81 21.18

FeO __________ 29.34 29.23

MnO _________ 4.43 4.67

MgO _________ 1.27 1.34

CaO __________ 7.88 7.93

Na20 ________ .01 nd

K2O __________ .00 nd

F ___________ nd______nd

Sum ____ 100.72 101.30

Si ___________ 2.94 2.95

Ti __________ .02 nd

Al __________ 1.97 1.99

Fe __________ 1.97 1.95

Mn __________ .30 .32

Mg __________ .15 .16

Ca __________ .68 .68

Na ___________ nd nd

K ___________ nd nd

F __________ nd_____nd

Cation sum _ 8.03 8.05

103-1

052001 052014 052015 052016 061004

103-2

061006 061020

Weight percent

36.19

.00

20.96

36.87

3.03

1.37

1.47

.01

.05

nd

36.33 

nd

20.95

37.13

3.16

1.14

1.34

nd

nd

nd

36.16 

nd

20.73

36.06

4.00

1.37

1.68

nd

nd

nd

36.95

.24

20.81

35.10

4.34

1.45

1.76

.01

.04

nd

36.20

.01

20.79

34.09

3.97

1.47

3.01

.02

.04

nd

99.95 100.05 100.00 100.70 99.60

36.51

.10

20.64

33.87

4.10

1.58

3.15

.01

.01

nd

99.97

36.16 

nd

20.44

34.43

4.24

1.38

2.65

nd

nd

nd

99.30

Number of atoms

2.96

.00

2.02

2.53

.21

.17

.13

.00

.00

nd

2.97

nd

2.02

2.54

.22

.14

.12

nd

nd

nd

2.96

nd

2.00

2.47

.28

.17

.15

nd

nd

nd

2.99

.01

1.99

2.38

.30

.17

.15

.00

.00

nd

2.97

.00

2.01

2.34

.28

.18

.26

.00

.00

nd

8.02 8.01 8.03 7.99 8.04

2.97

.01

1.98

2.31

.28

.19

.27

.00

.00

nd

8.01

2.98

nd

1.98

2.37

.30

.17

.23

nd

nd

nd

8.03

Notes

Center of 

crystal 

containing 

spot 

043009

Rim of 

crystal 

containing 

spot 

043008

Near Ilm 

052003; 

in same 

crystal 

as spots

052014.

052015.

and

052016

Rim of 

crystal 

containing 

spots 

052001, 

052015, 

and 

052016

Part way 

into 

crystal 

containing 

spots 

052001, 

052014, 

and 

052016

Near core 

of

crystal 

containing 

spots 

052001, 

052014, 

and 

052015

Contact 

with Cd 

061003

Encloses 

Cd 

061005
TABLES 97

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET—Continued

Sample _______________________161-1 

Spot __________________1_________2

Si02 _________ 38.01 37.45

TiOa ________ .00 .09

AUOs ________ 20.31 20.38

FeO ________ 29.81 31.68

MnO _________ 5.73 4.70

MgO ________ 1.20 1.20

CaO _________ 4.15 5.93

Na20 ________ .03 .04

K20 _________ .00 .00

F __________ nd_____nd

Sum _____ 99.24 101.47

Si __________ 3.08 3.00

Ti __________ .00 .00

Al __________ 1.94 1.92

Fe __________ 2.02 2.12

Mn _________ .39 .32

Mg__________ .14 .14

Ca __________ .36 .51

Na __________ .00 .00

K __________ .00 .00

F __________ nd_____nd

Cation sum _ 7.93 8.01

234-1 289-2

082001 082002 082003 082005

Weight percent

38.60

.20

20.82

28.02

5.25

1.22

5.82

.04

.00

nd

38.25

.00

18.99

38.22

1.23

1.99

1.99

.02

.00

nd

37.20

.08

21.38

36.65

1.89

1.66

1.89

nd

nd

nd

36.39

.26

20.46

27.28

6.55

1.67

7.20

.01

.00

nd

36.75

.20

20.84

27.18

7.35

1.67

6.42

.01

.00

nd

36.66 

nd

20.80

27.08

6.93

1.73

7.07

nd

nd

nd

99.97 100.92 100.75 99.82 100.42 100.27

37.23

.04

21.00

27.77

4.95

2.09

7.62

.01

.00

nd

100.71

Number of atoms

3.08

.01

1.96

1.87

.35

.15

.50

.00

.00

nd

3.09

.00

1.81

2.58

.08

.24

.17

.00

.00

nd

3.00

.00

2.03

2.47

.13

.20

.16

nd

nd

nd

2.95

.02

1.96

1.85

.45

.20

.63

.00

.00

nd

2.96

.01

1.98

1.83

.50

.20

.55

.00

.00

nd

2.96

nd

1.98

1.83

.47

.21

.61

nd

nd

nd

7.92 7.98 7.99 8.06 8.03 8.06

2.97

.00

1.98

1.85

.33

.25

.65

.00

.00

nd

8.03

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.23; 

cation 

sum includes 

0.01 

atom Zn

Center of 

crystal 

containing 

spots

082002.

082003.

and

082005

In same 

crystal 

as spots 

082001, 

082003, 

and 

082005

Near rim 

of

crystal 

containing 

spots

082001.

082002.

and

082005

On rim of

crystal 

containing 

spots

082001.

082002.

and

082003
98 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET— Continued

Sample ____ _________

Spot ___________________

290-1

11 i 2 3

331-1

4 5 6 7

Weight percent

Si02 __ _ _____

Ti02 _ _ _____

A1203 ____________

FeO _ ______

MnO _ _ __ _

MgO _ _ _

CaO _ ________

Na20 ___ _______

K20 ____ _______

F __ _ _____ _

Sum __ __ _

Si __ ___ —

Ti _ ____

Al __ ___ ____

Fe ____ __

Mn _ _____ __

Mg ______ __ ___

Ca _ _ _____ __

Na ____ _ ____

K ___ _ _____

F _ ___ ________

Cation sum _

36.60 

.05 

20.91 

36.43 

.91 

1.40 

2.51 

.01 

.00 

nd

98.82

3.00 

.00 

2.02 

2.50 

.06 

.17 

.22 

.00 

.00 

nd

7.97

36.93 

.04 

21.13 

35.11 

3.89 

1.84 

1.48 

nd 

nd 

nd

100.42

2.99 

.00 

2.01 

2.38

.27 

.22 

.13 

nd 

nd 

nd

8.00

36.63 

.00 

20.91 

37.03 

2.10 

1.61 

1.39 

nd 

nd 

nd

99.67

Number of

2.99 

.00 

2.01 

2.53 

.14 

.19 

.12 

nd 

nd 

nd

7.98

37.26

.00 

20.50 

35.89 

3.06 

1.79 

1.47 

nd 

nd 

nd

99.97

atoms

3.03 

.00 

1.96 

2.44 

.21 

.21 

.13 

nd 

nd 

nd

7.98

35.71 

.04 

20.81 

31.75 

6.45 

1.59 

1.75 

nd 

nd 

nd

98.10

2.96 

.00 

2.04 

2.20 

.45 

.19 

.15 

nd 

nd 

nd

7.99

36.00 

.00 

20.54 

36.78 

2.09 

1.51 

1.43 

nd 

nd 

nd

98.35

2.99 

.00 

2.01 

2.55 

.15 

.19 

.13 

nd 

nd 

nd

8.02

36.43 

.12

21.28 

31.62 

7.06 

1.54 

1.85 

nd 

nd 

nd

99.90

2.96 

.01 

2.04 

2..15 

.48 

.19 

.16 

nd 

nd 

nd

7.99

36.77 

.00 

21.08 

36.41 

2.16 

1.66 

1.51 

nd 

nd 

nd

99.59

3.00 

.00 

2.02 

2.48 

.15 

.20 

.13 

nd 

nd 

nd

7.98

Notes

Core of 

crystal 

containing 

spots 2 

and 3

Rim of Near the 

crystal rim of 

contain- crystal 

ing containspots 1 ing 

and 3 spots 1 

and 2

Core of 

crystal 

containing 

spots 5, 

6, and 7

Rim of 

crystal 

containing 

spots 4, 

6, and 7

Core of 

crystal 

containing 

spots 4, 

5, and 7

Rim of 

crystal 

containing 

spots 4, 

5. and 6
TABLES 99

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET— Continued

Sample ___________ — ___

SiC-2 _ — ———

TiO_ __ __ _ _ -_

A1203 _ _______

FeO ___ ______

MnO ________

MgO _____ -

CaO ____ _ _

Na20 _ „ _____

K20 _ __ _____

F

331-1 —— Continued

8

37.34 

.03 

20.29 

35.26 

3.34 

1.82 

1.42 

nd 

nd 

nd

99.50

9

36.46 

.00 

20.14 

37.20 

2.05 

1.78 

1.37 

nd 

nd 

nd

99.00

111002

Weight

37.47 

nd 

21.11 

37.83 

.95 

1.90 

1.50 

nd 

nd 

nd

100.76

111004

percent

37.42 

.02 

21.25 

34.03 

4.25 

1.66 

3.04 

.00 

.01 

nd

101.68

339-1

111007

37.65 

.06 

21.12 

35.13 

3.02 

1.85 

2.76 

.03 

.01 

nd

101.63

111022

36.97 

nd 

21.38 

37.94 

1.06 

1.97 

2.21 

nd 

nd 

nd

101.53

1

36.29 

.25 

21.24 

36.90 

1.34 

1.70 

1.51 

.01 

.00 

nd

99.24

355-1

2

36.81 

.11 

21.18 

36.03 

2.04 

1.95 

1.72 

.00 

.00 

nd

99.84

Number of atoms

Si __ ____ _ -

Ti ______

Al _______________

Fe _____________

Mn __ _ _____

MeCa _ __ ____ _

Na ____ __ ____

K __ ________

F

Cation sum _

3.05 

.00 

1.95 

2.40 

.23 

.22 

.12 

nd 

nd 

nd

7.97

3.01 

.00 

1.96 

2.57 

.14 

.22 

.12 

nd 

nd 

nd

8.02

3.02 

nd 

2.00 

2.55 

.06 

.23 

.13 

nd 

nd 

nd

7.99

2.99 

.00 

2.00 

2.27 

.29 

.20 

.26 

.00 

.00 

nd

8.01

3.00 

.00 

1.99 

2.34 

.20 

.22 

.24 

.00 

.00 

nd

7.99

2.96 

nd 

2.02 

2.54 

.07 

.24 

.19 

nd 

nd 

nd

8.02

2.97 

.01 

2.05 

2.52 

.09 

.21 

.13 

.00 

.00 

nd

7.98

2.99 

.00 

2.03 

2.45 

.14 

.24 

.15 

.00 

.00 

nd

8.00

Notes

Core of 

crystal 

containing 

spot 9

Rim of 

crystal 

containing 

spot 8

On rim of 

crystal 

containing 

spots 

111004 

and 

111007

In core of 

crystal 

containing 

spots 

111002 

and 

111007; 

next to 

Cd 

111004, 

Bt 

111010, 

and 

Ch 

111012 

and 

111013

Near Cd 

111006; 

in same 

crystal 

as spots 

111002 

and 

111004

Next to 

Dm 

111021- 

111023

ZnO = 0.00 ZnO = 0.00
100 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET—Continued

Sample ———————————______S55-1—Continued

Spot .———_______—— 4

SiO_ _________ 36.48

Ti02 ________ .68

AU>3 ________ 20.60

FeO ________ 33.91

MnO ________ 2.84

MgO ________ 1.80

CaO _________ 2.02

Na_0 ________ .00

K20 _________ .00 

F ________________nd

Sum _____ 98.33

Si __________ 3.00

Ti __________ .04

Al __________ 1.99

Fe __________ 2.33

Mn _________ .20

Mg__________ .22

Ca __________ .18

Na __________ .00

K ___________ .00 

F _______________nd

Cation sum __ 7.96

356-1

11 12 14

Weight percent

36.96 

.17 

21.66 

34.64 

3.29 

1.86 

2.03 

.02 

.00 

nd

36.83

.02

21.25

36.88

.50

2.41

2.09

.00

.00

nd

37.12

.09

19.53

37.63

.58

2.07

2.62

nd

nd

nd

36.22

.30

21.37

33.58

3.93

1.10

3.09

.00

.00

nd

36.68

.09

19.68

34.99

3.07

1.17

3.50

nd

nd

nd

100.63 100.25 99.66 99.59 99.25

36.93

.03

20.54

37.14

1.50

1.61

3.03

.00

.00

nd

100.78

36.20

.11

21.39

36.73

.65

1.99

2.91

nd

nd

nd

100.28

Number of atoms

2.97 

.01 

2.05 

2.33 

.22 

.22 

.17 

.00 

.00 

nd

2.97

.00

2.02

2.49

.03

.29

.18

.00

.00

nd

3.04

.00

1.88

2.57

.04

.25

.23

nd

nd

nd

2.96

.02

2.05

2.29

.27

.13

.27

.00

.00

nd

3.02

.00

1.91

2.41

.21

.14

.31

nd

nd

nd

7.97 7.99 8.01 7.99 8.00

2.99

.00

1.96

2.52

.10

.19

.26

.00

.00

nd

8.02

2.93

.00

2.04

2.49

.04

.24

.25

nd

nd

nd

8.01

Notes

ZnO = 0.00 ZnO = 0.00 Weight 

percent 

sum includes 

ZnO 

= 0.27; 

cation 

sum includes 

0.01 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.02

ZnO—0.00 Weight 

percent 

sum includes 

ZnO 

= 0.07

ZnO=0.00 Weight 

percent 

sum includes 

ZnO 

= 0.30; 

cation 

sum includes 

0.02 

atom 

Zn
TABLES 101

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET—Continued

Sample ———————————_____________356-1—Continued

Spot _____________ 15 42

Si02 __________ 36.48 36.32

TiOa __——————__ .06 .20

A1203 ________ 21.27 20.65

FeO ________ 37.50 35.62

MnO ________ .75 2.52

MgO ________ 2.20 1.50

CaO _________ 1.80 3.37

NaaO ________ nd nd

K20 _________ nd nd 

F _______________nd______nd

Sum ____ 100.44 100.42

Si ___________ 2.95 2.95

Ti __________ .00 .01

Al __________ 2.03 1.98

Fe __________ 2.54 2.42

Mn _________ .05 .17

Mg__________ .26 .18

Ca __________ .15 .29

Na _________ nd nd

K __________ nd nd 

F _______________nd______nd

Cation sum _ 8.00 8.01

369-1

46 131003 131005 131007 moii

463-1

141013

Weight percent

36.24

.05

21.27

37.72

.60

2.16

2.85

nd

nd

nd

37.35

.10

20.95

30.05

9.77

1.12

2.94

.01

.01

nd

36.59 

nd

21.16

29.04

8.83

1.11

3.30

nd

nd

nd

36.92

.02

21.28

36.30

2.82

1.79

2.48

.01

.01

nd

101.04 102.30 100.03 101.63

36.05

nd

21.39

29.28

9.73

1.11

3.05

nd

nd

nd

100.61

36.80

.01

19.79

36.30

3.32

1.85

1.37

.04

.01

nd

99.49

Number of atoms

2.92

.00

2.02

2.54

.04

.26

.25

nd

nd

nd

2.99

.01

1.97

2.01

.66

.13

.25

.00

.00

nd

2.98

nd

2.03

1.98

.61

.13

.29

nd

nd

nd

2.96

.00

2.01

2.44

.19

.21

.21

.00

.00

nd

8.04 8.02 8.02 8.02

2.93

nd

2.05

1.99

.67

.13

.27

nd

nd

nd

8.04

3.02

.00

1.92

2.49

.23

.23

.12

.01

.00

nd

8.02

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.38; 

cation 

sum includes 

0.02 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.24; 

cation 

sum includes 

0.01 

atom 

Zn

Weight 

percent 

sum includes 

ZnO 

= 0.15; 

cation 

sum includes 

0.01 

atom 

Zn

Next to 

Cd

131002 

and near 

rim of 

crystal

Next to 

Cd

131004 

and at 

core

On rim; 

next to 

Ch 

131006

Near rim; 

next to 

Cd 

131010

On rim of 

crystal 

containing 

spots

141014 

and

141015
102 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET— Continued

Sample _.._ _ .... _____

Spot ___ -_—._________

463-1 — Continued

141014 141015 1

487-2-4

3

506-1

4 172013 172014 172015 172016

Weight percent

Si02 _ _ ___

TiO2 ____ _____

A1803 ______ __

FeO __ ____________

MnO ___________

MgO _____________

CaO _____________

NaaO

K20 __ ___ __

F

Sum ___ _

36.59 

nd 

21.38 

35.93 

3.49 

1.95 

1.24 

nd 

nd 

nd

100.58

36.58 

nd 

21.06 

36.48 

3.96 

1.59 

1.19 

nd 

nd 

nd

100.86

36.59 

.08 

20.93 

40.75 

1.32 

1.09 

.37 

nd 

nd 

nd

101.15

35.70 

.12 

20.32 

37.25 

4.26 

.84 

.74 

nd 

nd 

nd

99.89

36.62 

.11 

20.40 

33.01 

7.68 

.60 

2.58 

nd 

nd 

nd

101.00

35.86 

.02 

20.89 

37.88 

1.66 

1.84 

1.65 

.01 

.00 

nd

99.81

36.48 

nd 

21.26 

37.80 

1.46 

1.73 

1.76 

nd 

nd 

nd

100.49

36.28 

nd 

21.06 

35.71 

3.44 

1.69 

1.73 

nd 

nd 

nd

99.91

36.64 

.05 

21.13 

35.11 

4.10 

1.55 

1.60 

.02 

.01 

nd

100.21

Number of atoms

Si _____ __ _

Ti

Al __ ___ ____

Fe __ __________

Mn ______________

Mg _________

Ca _______________

Na _ _ ___________

K _ _ __ ___

F

Cation sum ___

2.96 

nd 

2.04 

2.43 

.24 

.24 

.11 

nd 

nd 

nd

8.02

2.97 

nd 

2.01 

2.48 

.27 

.19 

.10 

nd 

nd 

nd

8.02

2.98 

.00 

2.00 

2.77 

.09 

.13 

.03 

nd 

nd 

nd

8.00

2.96 

.01 

1.98 

2.58 

.30 

.10 

.06 

nd 

nd 

nd

8.03

2.99 

.00 

1.96 

2.25 

.53 

.07 

.23 

nd 

nd 

nd

8.03

2.94 

.00 

2.02 

2.60 

.12 

.22 

.15 

.00 

.00 

nd

8.05

2.96 

nd 

2.03 

2.57 

.10 

.21 

.15 

nd 

nd 

nd

8.02

2.96 

nd 

2.03 

2.44 

.24 

.21 

.15 

nd 

nd 

nd

8.03

2.98 

.00 

2.02 

2.39 

.28 

.19 

.14 

.00 

.00 

nd

8.00

Notes

Near rim 

of 

crystal 

contain 

ing 

spots 

141013 

and 

141015

Near Bt 

141005; 

on rim 

of 

crystal 

containing 

spots 

141013 

and 

141014

On rim of 

crystal 

containing 

spots 3 

and 4; 

weight 

percent 

sum includes 

ZnO 

= 0.02

Most of Core of 

way crystal 

toward containcore of ing 

crystal spots 1 

contain- and 3; 

ing ZnO = 0 

spots 1 

and 4; 

weight 

percent 

sum includes 

ZnO 

= 0.66; 

cation 

sum includes 

0.04 

atom 

Zn

On rim, 

next to 

Mu 

172012

Next to 

Cd 

172011; 

on rim 

of 

crystal 

containing 

spots 

172015 

and 

172016

Farther 

into 

crystal 

containing 

spots 

172014 

and 

172016 

than 

spot 

172014

Farther 

into 

crystal 

containing 

spots 

172014 

and 

172015 

than 

spot 

172015
TABLES 103

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET— Continued

Sample .-_.-._ -_ _ __

Spot ________ _______ 182009

509-1

182010

515-1

182011 191004 191005 191007 191012

Weight percent

Si02 __ ________

Ti02 _ _

A1203 _ — _______

FeO _ _ __________

MnO __ _______

MgO _ __ _ __

CaO

NasO _ ________

K20 ___ __ ________

F ____

Sum _

36.73 

.02 

21.09 

35.98 

2.18 

1.71 

2.67 

.00 

.01 

nd

100.39

37.28 

.03 

21.19 

35.17 

2.53 

1.46 

3.43 

.01 

.01 

nd

101.11

37.38 

.04 

20.90 

34.31 

3.46 

1.30 

3.33 

.00 

.01 

nd

100.73

36.95 

.01 

21.25 

37.70 

1.55 

1.62 

2.59 

.01 

.02 

nd

101.70

37.17 

.07

21.71 

37.39 

1.93 

1.56 

2.65 

.00 

.01 

nd

102.49

37.41 

. .04 

21.32 

33.21 

5.02 

1.50 

3.57 

.00 

.00 

nd

102.07

37.23 

.06 

21.18 

32.42 

6.17 

1.33 

3.42 

.02 

.01 

nd

101.84

Number of atoms

Si

Ti _ _ _ _ __

Al _ __ __ __

Fe ______ ____

Mn ___ __ ___

Mg ______________

Ca ____ __ _

Na _ ___________

K __ ____ __

F

Cation sum _

2.98 

.00 

2.01 

2.44 

.15 

.21 

.23 

.00 

.00 

nd

8.02

2.99 

.00 

2.00 

2.36 

.17 

.17 

.29 

.00 

.00 

nd

7.98

3.01 

.00 

1.99 

2.31 

.24 

.16 

.29 

.00 

.00 

nd

8.00

2.96 

.00 

2.01 

2.53 

.11 

.19 

.22 

.00 

.00 

nd

8.02

2.96 

.00 

2.03 

2.49 

.13 

.19 

.23 

.00 

.00 

nd

8.03

2.98 

.00 

2.00 

2.21 

.34 

.18 

.30 

.00 

.00 

nd

8.01

2.98 

.00 

2.00 

2.17 

.42 

.16 

.29 

.00 

.00 

nd

8.02

Notes

In contact 

with 

Cd 

182008; 

next to 

Bt 

182012; 

on rim 

of 

crystal 

containing 

spots 

182010 

and 

182011

Next to Bt 

182012; 

Part 

way 

into 

crystal 

containing 

spots 

182009 

and 

182011

Next to Bt 

182012; 

farther 

into 

crystal 

containing 

spots 

182009 

and 

182010 

than 

spot 

182010

Rim of 

crystal 

containing 

spots 

191005 

and 

191007

Part way 

into 

crystal 

containing 

spots 

191004 

and 

1910D7

Farther 

into 

crystal, 

containing 

spots 

191004 

and 

191005 

than 

spot 

191005

Center of 

crystal; 

near Cd 

191010 

and Dm 

191011
104 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET— Continued

Sample ——— —————— _

Spot ____ . ___________

655-1

1 2 3 4 2 3

1052-2

4 5 6

Weight percent

Si02 _ ______ _

Ti02

Al_03 _____ _ _ '

FeO ______________

MnO ____________

MgO _____________

CaO

Na.0 _ ___________

K20 ______________

F _ ______ _

Sum _______

37.54 

.09 

21.34 

34.30 

.73 

1.79 

5.29 

nd 

nd 

nd

101.08

37.18 

.14 

20.57 

35.18 

.50 

1.27 

5.38 

nd 

nd 

nd

100.22

37.27 

.11 

21.10 

33.72 

1.88 

.98 

5.46 

nd 

nd 

nd

100.52

36.94 

.03 

20.76 

36.34 

1.48 

2.07 

2.27 

nd 

nd 

nd

99.89

36.69 

.01 

21.13 

37.17 

1.73 

1.99 

1.17 

nd 

nd 

nd

99.89

37.19 

.02 

20.85 

37.12 

1.87 

2.46 

1.37 

nd 

nd 

nd

100.88

35.86 

.05 

21.95 

32.54 

3.48 

1.28 

4.86 

.03 

.00 

nd

100.05

36.98 

.15 

21.21 

30.34 

6.45 

.69 

5.09 

nd 

nd 

nd

100.91

35.48 

.23 

21.56 

26.00 

7.98 

.84 

6.30 

.04 

.00 

nd

98.43

Number of atoms

Si _ — — — _ -

Ti _________ -

Al _ _ _ ______

Fe __ __________

Mn _ _ ______

Mg ______________

Ca — _ _

Na _ _ _________

X. __ _ _

F __ __ ____

Cation sum _

2.99 

.00 

2.00 

2.28 

.05 

.21 

.45 

nd 

nd_

nd

7.98

3.01 

.00 

1.96 

2.38 

.03 

.15 

.47 

nd 

nd 

nd

8.01

3.00 

.00 

2.00 

2.27 

.13 

.12 

.47 

nd 

nd 

nd

7.99

3.00 

.00 

1.99 

2.47 

.10 

.25 

.20 

nd 

nd 

nd

8.01

2.98 

.00 

2.02 

2.53 

.12 

.24 

.10 

nd 

nd 

nd

7.99

2.99 

.00 

1.98 

2.50 

.13 

.30 

.12 

nd 

nd 

nd

8.02

2.91 

.00 

2.10 

2.21 

.24 

.15 

.42 

.00

nd

8.03

2.98 

.01 

2.01 

2.04 

.44 

.08 

.44 

nd 

nd 

nd

8.00

2.92 

.01 

2.09 

1.79 

.55 

.10 

.55 

.00 

.00 

nd

8.01

Notes

ZnO = 0.00 ZnO = 0.00
TABLES 105

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

F. GARNET—Continued

Sample _____ ——— — ._.__________ 

Spot ____________________7

Si02 ______— 36.90

Ti02 ________ .24

A1203 ________ 21.18

FeO _________ 25.11

MnO ________ 10.55

MgO ________ .44

CaO _________ 5.58

Na_0 _______ nd

K20 _________ nd 

F _______________nd

____Sum ____ 100.00

Si __________ 2.99

Ti ________— .01

Al _________- 2.02

Fe __________ 1.70

Mn _________ .72

Mg _________ .05

Ca _________- .48

Na _________ nd

K __________ nd 

F _______________nd_

Cation sum __ 7.97

1052-2—Continued

9 10

Weight percent

36.09

.12

20.75

26.09

9.45

.49

6.79

.03

.00

nd

37.32

.23

20.62

29.74

6.24

.89

5.85

nd

nd

nd

36.87

.14

20.87

34.34

2.10

2.05

3.29

.04

.00

nd

36.43

.00

21.14

37.70

1.47

1.79

1.61

.05

.00

.00

99.84 100.89 99.70 100.19

Number of atoms

2.95

.01

2.00

1.78

.65

.06

.59

.00

.00

nd

3.00

.01

1.95

2.00

.42

.11

.50

nd

nd

nd

2.99

.01

2.00

2.33

.14

.25

.28

.00

.00

nd

2.96

.00

2.03

2.56

.10

.22

.14

.00

.00

.00

8.04 7.99 8.00 8.01

Notes

Weight 

percent 

sum includes 

ZnO 

= 0.03

ZnO = 0.00 ZnO = 0.00
106 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

Sample _____________ _ _

Spot _____________

Si02 — _____

Ti02 _____________

A12 03 ___ __________

FeO ___ __ __

MnO ______ _______

MgO ___ _ _______

CaO

Na20 __ __ _______

K20 ____ __ _____

F _____ _ _ _

Sum _ ____

Si _ __ _ _____

Ti _ _ ____ __

Al __ __ _ _ ___

Fe _____ ___

Mn _ _ __ _

Mg ______________

Ca _ _ __ _____

Na _____ _ ______

K _ ___ _ ___

F _ _ _ ______

Cation sum _ _

i

37.21

.03

60.43

.15

.00

.00

.07

nd

nd

nd

98.07

1.02

.00

1.96

.00

.00

.00

.00

nd

nd

nd

2.99

Weight 

percent 

sum includes 

ZnO 

= 0.18; 

cation 

sum includes 

0.01 

atom 

Zn

655-1

2

37.60

.04

60.86

.64

.03

.00

.04

nd

nd

nd

99.51

1.02

.00

1.95

.01

.00

.00

.00

nd

nd

nd

2.99

Weight 

percent 

sum includes 

ZnO 

= 0.30; 

cation 

sum includes 

0.01 

atom 

Zn

G. KYANITE

Weight percent

37.69

rvq

61.23

.16

.00

.00

fYK

nd

nd

nd

99.16

Number of atoms

1.02

.00

1.96

.00

.00

.00

.00

nd

nd

nd

2.98

Notes
TABLES 107

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

H. HORNBLENDE 2 and CUMMINGTONITE

Sample _ ____ .. — _

Spot ______ ____ .

161-1 (hornblende)

1 2 3 4 5

Weight percent

Si02 ______________

Ti02 ___ _______

A1203 _ ___________

FeO __ _________

MnO _ __ ____

MgO ____ ____

CaO _ _ ___ __

Na20 _____________

K20 ______________

F _____ _______

Subsum _ __

H20 ________ __

Sum _ _ _

39.39 

.16

19.50 

23.49 

1.48 

3.46 

9.88 

1.30 

.05 

.28

98.83 

1.97

100.80

39.35

.05 

19.96 

21.86 

.00 

3.55 

9.98 

1.34 

.00 

.13

96.24 

1.95

98.19

38.55

.22 

18.36 

23.62 

.13 

3.62 

9.85 

1.53 

.00 

.22

95.94 

1.92

97.86

40.45 

.07 

18.03 

22.61 

1.77 

3.57 

10.30 

1.31 

.11 

.29

98.30 

1.97

100.27

39.66

.25 

18.55 

22.43 

1.05 

3.35 

10.06 

1.29 

.00 

.17

96.70 

1.95

98.65

Number of atoms

Si ______ ______

Ti _ ___ __

Al _ ___________

Fe ____ _______

Mn ______________

Mg _______________

Ca _ _____________

Na _ __ _ _______

K _ _ __________

F ________ __

Cation sum _

5.98 

.02 

3.49 

2.98 

.19 

.78 

1.60 

.38 

.01 

.13

15.43

6.04 

.00 

3.61 

2.81 

.00 

.81 

1.64 

.40 

.00 

.06

15.31

6.02 

.02 

3.38 

3.08 

.01 

.84 

1.65 

.46 

.00 

.11

15.46

6.16 

.00 

3.24 

2.88 

.23 

.81 

1.68 

.38 

.02 

.14

15.40

6.11 

.03 

3.37 

2.89 

.14 

.77 

1.66 

.38 

.00 

.08

15.35

Notes

BaO = 0; 

weight 

percent 

sum includes 

Cl 

= 0.14; 

Fluorine 

cation 

sum 

includes

o.oa

atom Cl

Weight 

percent 

sum includes 

BaO 

= 0.09 

and Cl 

= 0.08; 

Fluorine 

cation 

sum 

includes 

0.02 

atom Cl

BaO = 0; 

weight 

percent 

sum includes 

Cl 

= 0.04; 

Fluorine 

cation 

sum 

includes 

0.01 

atom Cl

BaO = 0; BaO = 0; 

weight weight 

percent percent 

sum in- sum includes dudes 

Cl Cl 

= 0.07; =0.06; 

Fluorine Fluorine 

cation cation 

sum sum 

includes includes 

0.02 0.01 

atom Cl atom Cl

See footnotes at end of table, p. 123.
108 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

H. HORNBLENDE 2 and CUMMINGTONITE—Continued

Sample ————__ — ——____487-2-4 (cummingtonite)

Spot _„_________ 1 2

Si02 __________ 47.82 48.30

TiO3 ________ .16 .00

A1203 ________ .35 .98

FeO _________ 36.69 36.82

MnO ________ .00 .55

MgO ________ 8.13 8.39

CaO _________ .23 .13

Na2 0 ________ .03 .05

K2 0 _________ nd nd 

F ________________.14_____.02

Subsum ____ 93.43 95.22

HB0 _________ 1.82______1.86

Sum ____ 95.25 97.08

Si __________ 7.88 7.81

Ti ___________ .02 .00

Al __________ .06 .18

Fe __________ 5.05 4.97

Mn __________ .00 .07

Mg __________ 2.00 2.02

Ca __________ .04 .02

Na __________ .00 .00

K __________ nd nd 

F _______________.07_____.01

Cation sum _ 15.05 15.07

Weight percent

Number of atoms

See footnotes at end of table, p. 123.
TABLES 109

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

/. EPIDOTE

Sample _.—_—________________116&-1

Spot ————————— .— 211001_____213002

SiO2 _________ 37.15 37.06

TiO2 ________ .08 .24

A12O3 _________ 24.75 24.52

FeO _________ 10.59 11.34

MnO ________ .13 .21

MgO ________ .05 .14

CaO _________ 23.34 22.92

Na2O ________ .02 .03

K2O _________ .06 .01 

F _______________nd_____nd

Subsum ___ 96.17 96.47

H2O __________ 3.85_____3.65

Sum ____ 99.82 100.12

Si ___________ 2.93 2.93

Ti __________ .00 .01

Al __________ 2.30 2.28

Fe __________ .70 .75

Mn __________ .01 .01

Mg __________ .01 .02

Ca __________ 1.97 1.94

Na __________ .00 .00

K __________ .00 .00 

F _______________nd_____nd

Cation sum _ 7.92 7.94

213003

Weight percent

36.34 

.13

23.79

12.71 

.20 

.06

21.31 

.04 

.00 

nd

94.58

3.57

98.15

Number of atoms

2.94 

.01

2.27 

.86 

.01 

.01

1.86 

.01 

.00 

nd

7.97

Notes

Iron computed as 

ferric; 

next to 

Mu 

211002

Iron computed as 

ferric; 

next to 

Mu 

213005

Iron computed as

ferric
110 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

J. PLAGIOCLASE

Sample _____________ _ _

Spot ———— . ___________

3-3

2a 3 4 4a 4

14-1

5

103-1

21 052009 052010

Weight percent

Si02 _ _ _ ________

TiO2

A1203 ___ _ ___ _

FeO ____ _ _

MnO _ _ _ _ _ _

MgO _ _ _________

CaO __ __ __

Na20 _ __ ________

K20 _ _ ___ __

F _ _ _ _ _

Sum _______

66.89

nd 

20.58 

nd 

nd 

nd 

.95 

11.14 

.00 

nd

99.56

66.58 

nd 

20.59 

nd 

nd 

nd 

.67 

11.33 

.01 

nd

99.18

66.83 

nd 

19.80 

nd 

nd 

nd 

.48 

11.34 

.00 

nd

98.45

64.18

nd 

21.39 

nd 

nd 

nd 

2.22 

10.45 

.00 

nd

98.24

62.64 

nd 

24.41 

nd 

nd 

nd 

5.14 

8.68 

.02 

nd

100.89

62.23 

nd 

25.01 

nd 

nd 

nd 

5.17 

8.78 

.02 

nd

101.21

61.14

nd 

24.06 

nd 

nd 

nd 

5.20 

8.66 

.03 

nd

99.09

64.74 

.03 

21.83 

.13 

.00 

.03 

2.46 

9.95 

.09 

nd

99.26

66.80 

.00 

20.39 

.16 

.02 

.01 

.76 

11.38 

.09 

nd

99.61

Number of atoms

Si ______ ___ _ .___

Ti__ __ _____ _

Al __ _ _

Fe _ _____________

Mn ___ ____________

Mg ___ ________

Ca _ _________

Na _ _ _ _

K ____ ____

F _ _ __ _ __

Cation sum _

2.941 

nd 

1.066 

nd 

nd 

nd 

.045 

.949 

.000 

nd

5.001

2.939 

nd 

1.071 

nd 

nd 

nd 

.032 

.969 

.001 

nd

5.012

2.968 

nd 

1.036 

nd 

nd 

nd 

.023 

.976 

.000 

nd

5.003

2.874 

nd 

1.129 

nd 

nd 

nd 

.106 

.907 

.000 

nd

5.016

2.748 

nd 

1.262 

nd 

nd 

nd 

.242 

.738 

.001 

nd

4.991

2.725 

nd 

1.290 

nd 

nd 

nd 

.242 

.745 

.001 

nd

5.003

2.736 

nd 

1.269 

nd 

nd 

nd 

.249 

.751 

.002 

nd

5.007

2.868 

.000 

1.139 

.005 

.000 

.002 

.117 

.854 

.00>5 

nd

4.990

2.941 

.000 

1.058 

.006 

.000 

.000 

.036 

.971 

.005 

nd

5.017

Notes

z* ....................

X ........... . .... .....

Y ... __ .... __ ... ___

4.007 

.994

ft97

4.010 

1.002 

— .038

4.004 

.999 

— .014

4.003 

1.013 

— .010

4.010 

.981 

— .039

4.015 

.988 

-.059

4.005 

1.002 — .018

4.007 

.983 

— .032

3.999 

1.018 

+ .002

See footnotes at end of table, p. 123.
TABLES 111

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

/. PLAGIOCLASE— Continued

Sample _ _ _ _ _____ _ _ _

Spot ____________ 061015 061016

103-2

061018

161-1

062013 062014 i 2

Weight percent

Si02 ______________

Ti02 ____________

A1203 _____________

FeO ______________

MnO ____ _____

MgO ___ __ _____

CaO ______________

Na20 _____________

K20 ______________

F

Sum _ _____

59.56 

.12 

24.70 

.37 

.00 

.02 

6.30 

7.73 

.06 

nd

98.86

59.82 

.03 

24.53 

.17 

.06 

.01 

5.70 

8.75 

.05 

nd

99.12

61.25 

.00 

23.77 

.19 

.01 

.03 

5.17 

9.15 

.06 

nd

99.63

59.53 

.02 

24.80 

.17 

.01 

.03 

6.60 

8.14 

.08 

nd

99.38

59.52 

.01 

25.40 

.10 

.00 

.00 

6.57 

8.40 

.07 

nd

100.07

58.84 

nd 

25.52 

nd 

nd 

nd 

6.74 

7.81 

.18 

nd

99.09

58.65 

nd 

25.64 

nd 

nd 

nd 

6.65 

8.13 

.11 

nd

99.18

Number of atoms

Si __ ______________

Al _______________

Fe _ __ ____ _

Mn ________ __

Mg ____________ __

Ca ______________

Na _ ____ _ ___

K _ _ ____ _

F _________ __

Cation sum _ _

2.683 

.004 

1.311 

.014 

.000 

.001 

.304 

.675 

.003 

nd

4.995

2.691 

.004 

1.300 

.006 

.002 

.001 

.275 

.763 

.003 

nd

5.045

2.735 

.000 

1.251 

.007 

.000 

.000 

.247 

.792 

.003 

nd

5.035

2.674 

.001 

1.312 

.006 

.000 

.000 

.317 

.708 

.005 

nd

5.023

2.656 

.000 

1.336 

.000 

.000 

.000 

.314 

.726 

.004 

nd

5.036

2.649 

nd 

1.354 

nd 

nd 

nd 

.325 

.681 

.010 

nd

5.019

2.641 

nd 

1.360 

nd 

nd 

nd 

.321 

.709 

.006 

nd

5.037

Notes

X .....................

Y .....................

Next to 

Mu 

061014 

in 

crystal 

containing 

spot 

061016 

3.998 

.997 

+ .005

Near core 

of 

crystal 

containing 

spot 

061015

3.995 

1.050

+ .033

Next to 

Mu 

061017

3.986 

1.049 

+ .052

Spots 062013 and 062014 

are in the same crystal

3.987 3.992 

1.086 1.044 

+ .047 +.022

4.003 

1.016 

— .013

4.001 

1.036 

+ .007

Sec footnotes at end of table, p. 123.
112 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

/. PLAGIOCLASE— Continued

Sample ________________

Spot ______ .. ________ 2 3 3A

234-1

17 17A 18 4

289-2

6 8

Weight percent

Si02 _____________

Ti03 ____„_______

A1203 _ _ _______

FeO __ _ _ __ __

MnO ________

MgO ___ _______

CaO ______________

Na20 ___ ______

K20 ___ __ __

F

Sum ___ _

56.77 

nd 

26.82 

.09 

nd 

nd 

7.52 

7.11 

.04 

nd

98.35

58.86 

nd 

26.15 

.09 

nd 

nd 

7.45 

7.26 

.05 

nd

99.86

60.07

nd 

24.66 

nd 

nd 

nd 

6.33 

8.08 

.00 

nd

99.14

58.43 

nd 

25.58 

nd 

nd 

nd 

7.05 

7.54 

.02 

nd

98.62

60.49 

nd 

25.02 

nd 

nd 

nd 

6.74 

8.00 

.03 

nd

100.28

60.83 

nd 

24.95 

nd 

nd 

nd 

5.63 

8.16 

.03 

nd

99.60

44.20

nd 

34.77 

nd 

nd 

nd 

18.58 

.86 

.17 

nd

98.58

44.86

nd 

33.92 

nd 

nd 

nd 

18.33 

.82 

.16 

nd

98.09

46.40 

nd 

35.26 

nd 

nd 

nd 

17.33 

1.66 

.17 

nd

100.82

Number of atoms

Si _________

Ti _______________

Al ___ _________

Fe _______________

Mn ______________ MsCa ______________

Na _______________

K ________________

F __

Cation sum ___

2.581 

nd 

1.437 

.003 

nd 

nd 

.366 

.626 

.002 

nd

5.015

2.630 

nd 

1.377 

.003 

nd 

nd 

.356 

.629 

.003 

nd

4.998

2.695 

nd 

1.304 

nd 

nd 

nd 

.304 

.702 

.000 

nd

5.005

2.642 

nd 

1.363 

nd 

nd 

nd 

.341 

.661 

.001 

nd

5.008

2.686 

nd 

1.309 

nd 

nd 

nd 

.320 

.688 

.002 

nd

5.005

2.708 

nd 

1.309 

nd 

nd 

nd 

.268 

.704 

.002 

nd

4.991

2.072 

nd 

1.920 

nd 

nd 

nd 

.933 

.078 

.010 

nd

5.013

2.109 

nd 

1.879 

nd 

nd 

nd 

.923 

.075 

.010 

nd

4.996

2.116 

nd 

1.895 

nd 

nd 

nd 

.847 

.147 

.001 

nd

5.006

Notes

Zs ...... . .............

X .....................

Y .

4.018 

.997 

— .071

4.007 

.991 — .027

3.999 

1.006 

+ .006

4.005 

1.003 

— .018

3.995 

1.010 

+ .021

4.017 

.974 

—.067

3.992 

1.021 

+ .034

3.988 

1.008 

+ .052

4.011 

.995 

— .054

See footnotes at end of table, p. 123.
TABLES 113

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

J. PLAGIOCLASE— Continued

Sample ________________ 338-1

101204 112002

339-1

112003 112006

356-1

3

360-1

2 3

Weight percent

SiO2 ________ ______

TiO2 _____________

Al_03 ____________

FeO _______ —

MnO _____________

MgO — _____ — _

CaO ______________

NaaO _____

K20 ______________

F ________________

Sum _ — _

66.94 

.02 

21.77 

.16 

.03 

.01 

1.54 

11.13 

.12 

nd

101.72

61.36 

.03 

26.08 

.12 

.01 

.03 

5.86 

8.83 

.06 

nd

101.38

61.47

.02 

25.00 

.17 

.02 

.02 

5.83 

8.78 

.07 

nd

101.38

60.77

.02 

24.93 

.12 

.01 

.03 

5.97 

8.59 

.06 

nd

100.50

64.88 

nd 

21.24 

.12 

nd 

.00 

3.01 

10.25 

0.16 

nd

99.81

64.35 

nd 

22.19 

nd 

nd 

nd 

2.52 

10.15 

.23 

nd

99.44

63.74

nd 

22.77 

nd 

nd 

nd 

3.28 

9.75 

.00 

nd

99.54

Number of atoms

Si __ _ _______

Ti ______________

Al _______________

Fe _ _____________

Mn ___________

Mg _ _

Ca _______________

Na

K __ ___________

F

Cation sum _

2.894 

.001 

1.109 

.006 

.001 

.001 

.071 

.932 

.007 

nd

5.022

2.695 

.001 

1.298 

.004 

.000 

.002 

.276 

.752 

.003 

nd

5.031

2.700 

.001 

1.294 

.006 

.001 

.001 

.274 

.747 

.004 

nd

5.028

2.693 

.000 

1.302 

.004 

.000 

.002 

.283 

.738 

.003 

nd

5.025

2.873 

nd 

1.108 

.004 

nd 

.000 

.143 

.880 

.009 

nd

5.017

2.850 

nd 

1.158 

nd 

nd 

nd 

.120 

.871 

.013 

nd

5.012

2.822 

nd 

1.188 

nd 

nd 

nd 

.156 

.836 

.000 

nd

5.002

Notes

Z3 .....................

X .....................

Y .....................

4.004 

1.018 — .014

Rim of 

crystal 

containing 

spots 

112003 

and 

112006

3.994 

1.037 

+ .022

Next to Core of 

Ch crystal 

112004; containin ing 

crystal spots 

contain- 112002 

ing and 

spots 112003 

112002 

and 

112006 

3.994 3.995 

1.034 1.030 

+ .020 +.017

Weight 

percent 

sum 

includes 

BaO= 

0.15

3.981 

1.036

+ .075

4.008 

1.004 

—.035

4.010 

.992 

040

See footnotes at end of table, p. 123.
114 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

/. PLAGIOCLASE—Continued

Sample ——————_________________________360-1—Continued________________ ________369-1______ _______463-1______

Spot ————————__... 121001 121003 121004 122002 122003 131013 131014______141009______141012

Weight percent

Si02 __________ 67.23 64.15 63.63 62.81 67.89 62.33 61.62 64.25 62.72

Ti02 _________ .04 .05 .04 .06 .04 .07 .03 .01 .03

A12 03 _________ 20.67 22.80 23.36 23.73 20.50 23.87 23.96 22.52 23.70

FeO __________ .17 .20 .10 .16 .17 .32 .23 .31 .16

MnO _________ .02 .04 .03 .03 .03 .03 .00 .01 .01

MgO _________ .02 .05 .03 .05 .05 .00 .03 .01 .02

CaO __________ .85 3.85 3.85 4.39 .58 5.40 5.06 2.95 4.30

Na20 _________ 10.73 10.09 9.77 9.66 11.84 8.80 8.84 10.09 9.38

K2 0 __________ .05 .05 .06 .05 .05 .04 .04 .07 .06 

F —____________nd_____nd______nd_____nd_____nd_____nd_____nd______nd_____nd

Sum _____ 99.78 101.28 100.87 100.94 101.15 10'0.86 99.81 100.22 100.38

Si __________ 2.946 2.814 2.791 2.761 2.945 2.746 2.740 2.831 2.768

Ti __________ .001 .000 .001 .002 .001 .002 .001 .000 .001

Al __________ 1.067 1.180 1.207 1.229 1.048 1.239 1.256 1.169 1.232

Fe __________ .006 .007 .004 .006 .006 .012 .009 .011 .006

Mn __________ .001 .001 .001 .001 .001 .001 .000 .000 .000

Mg __________ .001 .003 .002 .003 .003 .000 .002 .001 .001

Ca __________ .040 .159 .181 .207 .027 .255 .241 .139 .203

Na __________ .911 .858 .830 .823 .995 .751 .762 .861 .802

K ___________ .003 .003 .003 .003 .003 .002 .002 .004 .003 

F ———__________nd_____nd______nd_____nd_____nd_____nd_____nd______nd_____nd

Cation sum __ 4.976 5.025 5.020 5.035 5.029 5.008 5.013 5.016 5.016

Number of atoms

Notes

On rim 

of

crystal 

containing 

spots 

121003 

and 

121004; 

next to 

spot 

121003

4.014

.962

— .057

In crystal 

containing 

spots 

121001 

and 

121004; 

next to 

spot 

121001 

and 

Hm 

121007 

3.994 

1.031 

+ .025

Just outside 

core 

zone of 

crystal 

containing 

spots 

121001 

and 

121003

3.999

1.021

+ .002

Core of 

crystal 

containing 

spot 

122003

3.992

1.043

+ .030

Rim of 

crystal 

containing 

spot 

122002

3.994

1.035

+ .025

Rim of 

crystal 

containing 

spot 

131014

3.987

1.021

+ .050

In crystal 

containing 

spot 

131013

3.997

1.016

+ .012

Next to 

Cd 

141008

4.000

1.016

— .001

Next to 

Mu 

141010

4.001

1.015

— .005

See footnotes at end of table, p. 123.
TABLES 115 

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

/. PLAGIOCLASE— Continued

Sample ________________

Spot __________________

463-1 — Continued

141021 142008

466-1

152003

506-1

174001 174002

515-1

191002

655-1

3

Weight percent

Si02 __ ____ __

Ti02 __ ________

A1203 _____________

FeO _____________

MnO _______ _

MgO _____________

CaO ______________

NasO ______ _

K20 ______________

F _ ________ _

Sum _ _____

64.97 

.16 

22.23 

.27 

.01 

.02 

3.12 

10.21 

.08 

nd

101.07

63.03 

.02 

23.32 

.24 

.01 

.03 

4.16 

9.66 

.09 

nd

100.56

66.54 

.01 

21.16 

.15 

.01 

.01 

1.11 

11.77 

.08 

nd

100.84

61.42 

.14 

23.33 

.19 

.00 

.01 

5.02 

9.36 

.07 

nd

99.54

62.20 

.07 

23.41 

.15 

.00 

.01 

4.82 

9.47 

.03 

nd

100.16

61.61 

.08 

24.03 

.21 

.07 

.01 

5.04 

9.11 

.07 

nd

100.23

60.03 

nd 

25.02 

nd 

nd 

nd 

5.73 

8.16 

.12 

nd

99.06

Number of atoms

Si ____________

Ti ____ _______

Al ______ _ _____

Fe __ __ _ _____

Mn ——________

Mg ___________ _

Ca _______________

Na _ _—____.__

K ______________

F ________________

Cation sum _

2.840 

.005 

1.145 

.010 

.000 

.001 

.146 

.805 

.004 

nd

5.016

2.779 

.001 

1.212 

.009 

.000 

.002 

.196 

.825 

.005 

nd

5.029

2.904 

.000 

1.008 

.005 

.000 

.001 

.052 

.995 

.004 

nd

5.049

2.746 

.005 

1.229 

.007 

.000 

.001 

.240 

.811 

.004 

nd

5.043

2.759 

.002 

1.223 

.006 

.000 

.001 

.229 

.814 

.002 

nd

5.036

2.732 

.003 

1.257 

.008 

.003 

.001 

.239 

.783 

.004 

nd

5.030

2.692 

nd 

1.322 

nd 

nd 

nd 

.275 

.709 

.007 

nd

5.005

Notes

z« _______ _. ___

X .....................

Y ........ . . .. .

Next to 

Dm 

141020

3.990 

1.026 

+ .039

In rim of 

crystal

3.991 

1.038 

+ .034

In core 

next to 

Mu 

152004

3.992 

1.057 

+ .028

In rim of 

crystal 

containing 

spot 

174002 

3.980 

1.063 

+ .082

Core of 

crystal 

containing 

spot 

174001 

3.984 

1.052 

+ .062

Next to 

Ilm 

191001 

3.992 

1.038 

+ .030

Next to 

kyanite

4.014 

.991 

— .056

Sec footnotes at end of table, p. 123.
116 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

J. PLAGIOCLASE—Continued

Sample ___________ 1052-2 ______1169-1______

Spot —————_____... 13 213008 213011

Si02 __________ 65.84 68.19 68.09

Ti02 ________ nd .07 .00

A1203 _________ 21.07 19.83 19.74

FeO _________ nd .22 .14

MnO ________ nd .02 .03

MgO ________ nd .00 .05

CaO _________ 1.32 .02 .04

Na2 0 ——______ 11.46 11.91 12.10

K20 _________ .17 .03 .03

F —_—______ nd_____nd______nd

____Sum ____ 99.86 100.29 100.22

Si __________ 2.901 2.976 2.975

Ti __________ nd .002 .000

Al __________ 1.094 1.019 1.016

Fe __________ nd .008 .005

Mn —_______ nd .001 .001

Mg _________ nd .000 .003

Ca ___________ .062 .001 .002

Na __________ .979 1.007 1.025

K —________ .010 .000 .002

F ————————_ nd_____nd______nd

Cation sum _ 5.046 5.014 5.029

Weight percent

Number of atoms

Notes

3.995

1.051

+ .019

Next to

Urn

213007 

3.997 

1,017

+ .009

3.991

1.038

+ .033

See footnotes at end of table, p. 123.
TABLES 117

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around tlte Taconic allochthon—Continued

K. ILMENITE

Sample ——— .. ——— _

Spot ____________

14-1

6 1

102-1

2 3

103-1

052003

103-2

061013 062005

290-1

7 8

Weight percent

Si02 ______ _

Ti02

A1203 _____________

FeO _______ __

MnO _____________

MgO _____________

CaO

NasO _____________

K20 _._ __ _______

F _ _ ________

Sum ______

Si ________________

Ti ___ _______

Al _______________

Fe __ ____________

Mn

Mg ______________

Ca _ ___ ____

Na ____________

K ____ __ __

F __ _ _______

Cation sum _

nd 

53.94 

nd 

45.81 

nd 

.02 

nd 

nd 

nd 

nd

99.77

nd 

1.02 

nd 

.96 

nd 

.00 

nd 

nd 

nd 

nd

1.98

0.85 

52.38 

.06 

45.99 

.62 

.10 

.02 

nd 

nd 

nd

100.09

0.02 

.99 

.00 

.96 

.01 

.00 

.00 

nd 

nd 

nd

1.98

0.39

52.17 

.10 

46.77 

.70 

.13 

.06 

nd 

nd 

nd

100.35

0.01 

.99 

.00 

.98 

.01 

.00 

.00 

nd 

nd 

nd

1.99

0.15

52.46 

.13 

45.72 

.55 

.14 

.26 

nd 

nd 

nd

99.41

Number of

0.00 

1.00 

.00 

.97 

.01 

.01 

.01 

nd 

nd 

nd

2.00

0.23 

52.22 

.51 

46.65 

.58 

.11 

.08 

.00 

.10 

nd

100.48

atoms

0.01 

.98 

.01 

.98 

.01 

.00 

.00 

.00 

.00 

nd

1.99

0.11

52.24 

.37 

47.07 

.63 

.34 

.06 

.00 

.01 

nd

100.83

0.00 

.98 

.01 

.98 

.01 

.01 

.00 

.00 

.00 

nd

1.99

0.19 

53.22 

.45 

46.21 

.91 

.07 

.05 

.00 

.06 

nd

101.16

0.00 

.99 

.01 

.96 

.02 

.00 

.00 

.00 

.00 

nd

1.98

0.22 

52.94 

.12 

46.89 

.00 

.11 

.06 

nd 

nd 

nd

100.28

0.01 

1.00 

.00 

.98 

.00 

.00 

.00 

nd 

nd 

nd

1.99

0.30 

52,59 

.12 

46.76 

.02 

.17 

.04 

nd 

nd 

nd

100.00

0.01 

.99 

.00 

.98 

.00 

.01 

.00 

nd 

nd 

nd

1.99

Notes

ZnO = 0.00 Weight 

percent 

sum includes 

CraOs 

= 0.07

Weight 

percent 

sum includes 

CraOs 

= 0.03

CraOs=0 Near Mu 

052002 

and Ga 

052001
118 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

K. ILMENITE—Continued

Weight percent

Sample ___________ 290-1—Con. _____________331-1_______________ __________338-1_________ _______339-1

Spot ———————.—————_______10______ 091002 092001 093008 102001 102002 I

Si02 __________ 0.23 0.18 0.17 0.10 0.11 0.15 0.05 0.13

Ti02 _________ 52.76 54.72 54.34 54.40 52.91 53.13 53.32 52.81

A12 03 _________ .13 .45 .47 .53 .49 .46 .16 .23

FeO __________ 47.53 45.69 45.87 44.51 48.07 48.30 47.0'5 46.24

MnO _________ .07 .48 .54 .54 .41 .38 .09 .16

MgO _________ .13 .18 .16 .13 .07 .20 .18 .06

CaO _________ .07 .00 .00 .02 .02 .01 .02 .03

Na2 0 ________ nd .02 .01 .00 .03 .00 nd nd

K2 0 _________ nd .02 .03 .02 .04 .05 nd nd 

F ___________———_____nd______nd______nd______nd______nd______nd______nd______nd

Sum ____ 100.92 101.74 101.59 100.25____102.15 102.68_____100.93_____99.66

Number of atoms

Si ___________ 0.01 0.00 0.00 0.00 0.00 0.00 0.00

Ti __________ .99 1.01 1.01 1.02 .98 .98 1.00

Al __________ .00 .01 .01 .02 .01 .01 .00

Fe __________ .99 .94 .94 .92 .99 .99 .98

Mn _________ .00 .01 .01 .01 .01 .01 .00

Mg __________ .00 .01 .01 .00 .00 .00 .01

Ca __________ .00 .00 .00 .00 .00 .00 .00

Na __________ nd .00 .00 .00 .00 .00 nd

K __________ nd .00 .00 .00 .00 .00 nd 

F _______________nd______nd______nd______nd_____ nd______nd_______nd

Cation sum _ 1.99 1.98 1.98 1.97 1.99 1.99 1.99

0.00 

1.00 

.01 

.97 

.00 

.00 

.06 

nd 

nd 

nd

1.98

Notes

Next to 

Cd 

091001

Next to 

Mu 

092002

Next to 

Cd 

102005

Next to 

Mu 

102004

Weight 

percent 

sum includes 

Cr2Os 

= 0.06

CraOs

= 0.00
TABLES 119

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

Sample ———————— ____

Spot ____________ 3

K.

4

ILMENITE— Continued

339-1 — Continued

5

355-1

6 7 7 8

Weight percent

Si02

Ti03 __ _ __

Al20s

FeO ___ __ _____

MnO _ _ __ _ __

MgO _ — _ _

CaO _____________

K20 _ ___________

F _ __ __________

Sum _ _____

0.14 

52.77 

.25 

45.84 

.14 

.06 

.00 

nd 

nd 

nd

99.19

0.22 

53.12 

.16 

44.71 

.32 

.36 

.03 

nd 

nd 

nd

98.95

0.18 

53.62 

.12 

45.19 

.35 

.30 

.00 

nd 

nd 

nd

99.77

0.23 

53.61 

.39 

44.70 

.12 

.22 

.00 

nd 

nd 

nd

99.32

0.14 

52.13 

.13 

45.53 

.13 

.37 

.02 

nd 

nd 

nd

98.45

nd 

51.76 

nd 

47.40 

nd 

.33 

nd 

nd 

nd 

nd

99.49

nd 

50.91 

nd 

48.63 

nd 

.37 

nd 

nd 

nd 

nd

99.91

Number of atoms

Si _ ______________

Ti _ _ __ ____

Al _ ______ _

Fe _ ___________

Mn _ _________

Mg __ _ ______

Ca _ _ _______

Na

K _ _ ________

F _ _ _ _ ___

Cation sum _ _

0.00 

1.00 

.01 

.97 

.00 

.00 

.00 

nd 

nd 

nd

1.98

0.01 

1.01 

.00 

.94 

.01 

.01 

.00 

nd 

nd 

nd

1.98

0.00 

1.01 

.00 

.95 

.01 

.01 

.00 

nd 

nd 

nd

1.98

0.01 

1.01 

.01 

.94 

.00 

.01 

.00 

nd 

nd 

nd

1.98

0.00 

1.00 

.00 

.97 

.00 

.01 

.00 

nd 

nd 

nd

1.98

nd 

0.99 

nd 

1.01 

nd 

.01 

nd 

nd 

nd 

nd

2.01

nd 

0.98 

nd 

1.04 

nd 

.01 

nd 

nd 

nd 

nd

2.03

Notes

CrsOs 

= 0.00

Weight 

percent 

sum includes 

CraOs 

= 0.03

Weight 

percent 

sum includes 

CraOa 

= 0.01

Weight 

percent 

sum includes 

CraOa 

= 0.05

=6.00 ZnO = 0.00 ZnO = 0.00
120 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

K. ILMENITE— Continued

Sample _ ______________

Spot __________________

355-1 — Continued

16a 16 16 17 18

356-1

25 36 37 38

Weight percent

Si02 _________

Ti02 __ ___ _ ___

A120S ______ — _

FeO ______________

MnO _____________

MgO _____________

CaO _ ______ __

Na_0 _____

K20 __ _ _______

F

Sum _ _ —

Si _____ ______

Ti ___ __ ______

Al _ __________

Fe _ __ ______

Mn __ ___________

Mg ______________

Ca _____________

Na _ ________

K __ _

F ______ _

Cation sum _

nd 

52.58 

nd 

46.68 

nd 

.00 

nd 

nd 

nd 

nd

99.26

nd 

1.00 

nd 

.99 

nd 

.00 

nd 

nd 

nd 

nd

1.99

nd 

51.78 

nd 

46.29 

nd 

.00 

nd 

nd 

nd 

nd

98.07

nd 

1.00 

nd 

1.00 

nd 

.00 

nd 

nd 

nd 

nd

2.00

0.21 

52.87 

.20 

46.38 

.74 

.22 

.02 

.04 

.00 

nd

100.78

0.01 

.99 

.01 

.97 

.02 

.01 

.00 

.00 

.00 

nd

2.01

0.33 

49.74 

.36 

47.13 

.85 

.24 

.18 

.00 

.00 

nd

98.83

Number of

0.01 

.96 

.01 

1.01 

.02 

.01 

.00 

.00 

.00 

nd

2.02

0.47

51.62 

.23 

47.77 

.20 

.46 

.07 

.00 

.00 

nd

100.82

atoms

0.01 

.97 

.01 

1.00 

.00 

.02 

.00 

.00 

.00 

nd

2.01

0.24

53.93 

.25 

46.51 

.16 

.21 

.02 

.00 

.00 

nd

101.53

0.01 

1.00 

.01 

.96 

.00 

.01 

.00 

.00 

.00 

nd

1.99

0.48 

53.97 

.38 

47.20 

.13 

.14 

.00 

.06 

.00 

nd

102.43

0.01 

.99 

.01 

.96 

.00 

.01 

.00 

.00 

.00 

nd

1.98

0.21 

49.53 

.19 

48.74 

.14 

.42 

.00 

.04 

.00 

nd

99.64

0.01 

.95 

.01 

1.04 

.00 

.02 

.00 

.00 

.00 

nd

2.04

0.22 

52.13 

.23 

47.84 

.19 

.47 

.00 

.02 

.00 

nd

101.30

0.01 

.98 

.01 

1.00 

.00 

.02 

.00 

.00 

.00 

nd

2.02

Notes

ZnO

=0.00

ZnO

= 0.00

In Ga containing 

spot 

Ga 9; 

weight 

percent 

sum includes 

ZnO 

= 0.10

ZnO

= 0.00; 

in Ga 

containing 

spot 

Ga 8

ZnO

= 0.00; 

in Ga 

containing 

spot 

Ga 3

In matrix; 

weight 

percent 

sum includes 

ZnO 

= 0.21

In matrix; 

weight 

percent 

sum includes 

ZnO 

= 0.07

In Ga containing 

spot 

Ga 45; 

weight 

percent 

sum includes 

ZnO 

= 0.37; 

cation 

sum includes 

0.01 

atom 

Zn

In Ga containing 

spot 

Ga 40; 

weight 

percent 

sum includes 

ZnO 

= 0.20
TABLES 121

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

K. ILMENITE— Continued

Sample ______ _______

101006

360-1

121007

S69-1

122001 i 2

463-1

3 4

Weight percent

Si02 ____ _ ______

Ti02 _____________

A1203 _____________

FeO ______________

MnO _____________

MgO _____________

CaO _ _

Na_0

K2 0 ______________

F

Sum _______

0.32 

49.57 

.45 

46.16 

1.90 

.13 

.12 

.04 

.03 

nd

98.72

0.22 

51.82 

.49 

45.46 

2.16 

.12 

.10 

.02 

.03 

nd

100.42

1.85

50.29 

.49 

46.28 

1.99 

.09 

.06 

.02 

.04 

nd

101.11

0.26 

51.58 

.09 

46.95 

.23 

.11 

.05 

nd 

nd 

nd

99.27

0.77 

51.41 

.20 

46.25 

.20 

.11 

.14 

nd 

nd 

nd

99.08

0.16 

52.12 

.20 

45.85 

.71 

.01 

.00 

nd 

nd 

nd

99.05

0.21 

51.25 

.31 

47.27 

.63 

.OS 

.02 

nd 

nd 

nd

99.72

Number of atoms

Si ________________

Ti _______________

Al ______________

Fe _______________

Mn ________ _

Mg ___________ __

Ca ___________

Na

K _______________

F _ _

Cation sum _

0.01 

.96 

.01 

.99 

.04 

.00 

.00 

.00 

.00 

nd

2.01

0.01 

.98 

.01 

.96 

.05 

.00 

.00 

.00 

.00 

nd

2.01

0.05 

94 

.01 

.96 

.04 

.00 

.00 

.00 

.00 

nd

2.00

0.01 

.99 

.00 

1.00 

.00 

.00 

.00 

nd 

nd 

nd

2.00

0.02 

.98 

.01 

.98 

.00 

.00 

.00 

nd 

nd 

nd

1.99

0.00 

1.00 

.01 

.97 

.02 

.00 

.00 

nd 

nd 

nd

2.00

0.01 

.98 

.01 

1.00 

.01 

.00 

.00 

nd 

nd 

nd

2.01

Notes

Next to 

Pg 

121003
122 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

K. ILMENITE— Continued

Sample _------_-_ ___ .

Spot ____________ 191001 191009 191011

515-1

191027

1169-1

1 2 3 215001 3

Weight percent

Si02 _ _ __________

Ti03 ______ __

A1203 _____________

FeO ___ _______

MnO __________

MgO _____________

CaO

Na2 0 _ __ _______

K20 ____ ______

F _ __ ________

Sum _______

0.15 

52.34 

.42 

46.94 

.35 

.21 

.03 

.00 

.04 

nd

100.48

0.17 

53.06 

.39 

47.44 

.35 

.22 

.08 

.00 

.02 

nd

101.73

0.14 

53.63 

.43 

46.09 

1.16 

.20 

.10 

.05 

.02 

nd

101.82

0.17 

53.06 

.59 

46.72 

.48 

.12 

.02 

.05 

.08 

nd

101.29

0.13 

51.61 

.23 

47.37 

.25 

.09 

.00 

nd 

nd 

nd

99.68

0.19 

51.50 

.14 

46.84 

.26 

.13 

.03 

nd 

nd 

nd

99.09

0.24 

51.26 

.18 

46.26 

.35 

.11 

.02 

nd 

nd 

nd

98.42

0.25 

52.29 

.48 

45.47 

2.97 

.07 

.03 

.04 

.04 

nd

101.64

0.33

50.76 

.07 

44.75 

2.79 

.00 

.02 

nd 

nd 

nd

98.72

Number of atoms

Si _ ______________

Ti _ __ __ ______

Al _ _ ________

Fe __ _ __ _______

Mn ______________

Mg ______________

Ca _____________ _

Na __ ___ ____

K __ _ _ __

F

Cation sum _

0.00 

.99 

.01 

.98 

.01 

.01 

.00 

.00 

.00 

nd

2.00

0.00 

.99 

.01 

.98 

.01 

.01 

.00 

.00 

.00 

nd

2.00

0.00 

.99 

.01 

.95 

.02 

.01 

.00 

.00 

.00 

nd

1.98

0.00 

.99 

.02 

.97 

.01 

.00 

.00 

.00 

.00 

nd

1.99

0.00 

.98 

.01 

1.01 

.01 

.00 

.00 

nd 

nd 

nd

2.01

0.00 

.99 

.00 

1.00 

.01 

.00 

.00 

nd 

nd 

nd

2.00

0.01 

.99 

.01 

.99 

.01 

.00 

.00 

nd 

nd 

nd

2.01

0.01 

.98 

.01 

.94 

.06 

.00 

.00 

.00 

.00 

nd

2.00

0.01 

.98 

.00 

.96 

.06 

.00 

.00 

nd 

nd 

nd

2.01

Notes

In Pg containing 

spot Pg 

191002; 

next to 

Mu 

191003

In Ga containing 

spot Ga 

191004; 

next to 

Cd 

191008

In Ga containing 

spot Ga 

191004; 

near Ga 

191012

Next to 

Mu 

215003
TABLES 123 

TABLE 3.—Microprobe data on various minerals in samples of rocks from within and around the Taconic allochthon—Continued

Sample —————— _ _____

Spot __________________

SiO2 ______________

TiO2 ____ _

A12O3 _______ _

FeO ______________

MnO _______ _

MgO ____ _ ______

CaO ___________

Na80 _____________

K20 __________ __

F ____ _________

Sum _ _____

Si _ ____________

Ti ________ _

Al __ ____________

Fe ________ __

Mn ______________

Mg ____ ______

Ca _ _____________

Na __________

K __________

F ______________

Cation sum _

191-1

nd

0.03

nd

90.77

nd

.00

nd

nd

nd

nd

90.80

nd

.00

nd

3.00

nd

.00

nd

nd

nd

"Off nd

ZnO

= 0.00; 

sum is 

97.51 

when calculated as 

Fes04; 

cation 

sum 

based 

on 4 

oxyg«n 

per 

formula 

and % 

FeOiotai 

as Fe20.3

L. MAGNETITE

Weight percent

Number of atoms

Notes

1 The "calculated weight percent HaO" of the staurolite analyses is based on an anhydrous formula of 23.5 oxygen atoms per formula of 24 

oxygens. To obtain the calculated weight percent H_0 on the basis of an .anhydrous formula of 23 oxygen atoms, multiply the HsO value by 2.04.

2 Microprobe data for hornblende from samples 102-1 and 289-2 are given in Doolan and others (1978).

3 For definition of Z, X, and Y, see p. 20.
124 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 4.—Conventional wet-chemical analyses and the number of atoms calculated on the basis of the anhydrous formulas

for selected minerals

[nd, not determined]

Sample no. — ———— .

SiOs ______ - _ .

TiOa _________ ..

Al2Os _________

FeO ___ _________

MnO _______________

MgO _ ____________

CaO _______ _ . NaaO _________ . K2O _________ _.

HaO+ _______________

H_O- _________ .

COa ._.... _ __„___.

PaOs _______________

ZnO —_._________„

Si __________ __

Ti

Al __ . ___ __ ______

Fe3+ _______________ Fe2*

Mn ___________ . Mg

Ca _______ ____

Na

K __ . ____________

Zn ___________ . H17 ________________

Stau

355-1 B

28.55

.41

53.54

2.54

11.42

.08

1.06

.09

nd

<.05

1.61

.02

<.02

.03

.26

«99.61

( 7 ) 

4.02

.04

8.89

.27

1.35

.01

.22

.01

nd

<.01

.03

1.5

rolite

356-1

29.45 

.58 

52.88 

1.1 

12.8 

nd 

1.55 

.09 

nd 

nd 

1.19 

<.02 

nd 

nd 

.23

"99.9

(') 

4.13 

.06 

8.73 

.12 

1.50 

nd 

.32 

.01 

nd 

nd 

.02 

1.1

355-1 B

Weight

37.46 

.10 

20.64 

.48 

33.91 

3.28 

1.75 

2.11 

.05 

<.01 

<.05 

.03 

<.01 

.04 

nd

6 99.85

Number

(8 )

3.04 

.01 

1.97 

.03 

2.30 

.23 

.21 

.18 

.00 

.00 

.00

Garnet 

(almandine)

356-1

percent

37.95 

.09 

21.87 

2.3 

32.6 

.92 

2.29 

2.55 

nd 

nd 

nd 

nd 

nd 

nd 

nd

100.57

of atoms

(8 )

3.01 

.01 

2.04 

.14 

2.16 

.05 

.27 

.22 

nd 

nd 

nd

355-1

45.5 

.23 

36.4 

2.0 

.40 

.03 

.44 

.15 

2.3 

7.9 

4.5 

.08 

<.05 

.00 

nd

100.0

(9) 

3.01 

.01 

2.84 

.10 

.02 

.00 

.04 

.01 

.29 

.67 

nd

Muscovite l

356-1

46.7 

.23 

37.0 

.41 

.35 

.04 

.41 

.0 

2.0 

8.5

}4.7

nd .05' 

nd

100.4

( 8) 

3.06 

.01 

2.86 

.02 

.02 

.00 

.04 

.00 

.25 

.71 

nd

140-2

47.3 

.18 

35.3 

1.2 

.56 

.03 

.5 

.0 

1.4 

8.4 

4.4 

.04 

nd 

.04 

nd

99.4

(B) (-0)

3.12 

.01 

2.75 

.06 

.03 

.00 

.05 

.00 

.18 

.71 

nd

Optical data

[Refractive index; estimated uncertainties in parentheses; sodium light]

j9 -———_,—-_..

*V

2Vobs _______ .

2Vcalc

1.742

(±.002) 

1 747

(±.002) 

1.754

(±.001) 

H —— 80'°

I q-i °

1.739 1.815 1.807

(±.002) (±.005) (±.005) 

1.745

(±.001) 

1.754

(±.002)

H —— 80°

4-70°

(r>v)

1.564

(±.002) 

1.597

(±.002) 

1.603

(±.001)

— 45°

1.568

(±.005) 

1.591

(±.002) 

1.598

(±.002) 

nd— 57°

nd

1.595

(±.002)

1.598

( ±.002) 

nd

nd

Cell data

[Cell edges in angstroms; standard error in parentheses; interaxial angles in degrees, minutes, and fractions of minutes; cell volumes in cubic angstroms; molar volumes in cubic centimeters]

b _______ -._— ___

c

)3 -—_—___— ______

Molar volume _ _ ___ _

Specific gravity

7.864

(±.001) 

16.617

(+.002)

5.659

(+.001) 90°

90°

90°

739.5

(±.2) 

222.7

(+..D 

3.78

7.866

(±.002) 

16.631

(+.005)

5.658

(+.002) 90°

90°

90°

740.2

(±.3) 

222.9

(+..1)

o 77

11.549

( ±.001)

1540.4

(±.5) 

115.96

(±.04) 

4 19

11.549

(±.001)

1540.3

(±.4) 

115.96

(±.04) 

4.13

5.169

(±.013) 

9.002

(+.020)

19.923

(+.022) 90°

95°34.0'

(-no-oo90°

922.7

(±2.2) 

138.9

(±.3)

2.85

5.183

(±.004)

8.979

(+.006)

lfl.964

(+.005) 90°

95°45.6'

(+1.7') 90°

924.3

(±.6) 

139.2

(+..1)

2.83

5.180

(±.003) 

9.013

( +.005)

20.001

(+.006) 90°

95°43.0'

(+2.7')

90°

929.1

(±.5) 

139.9

(±.1)

2.82

1 Muscovite is indexed on the basis of 2Mi polytype.

2 Biotite is indexed on the basis of 1M polytype.

3 Chloritoid is indexed on triclinic cell.

4 Chlorite is the lib polytype.

s Special precision analyses by Ellen Lillie under supervision of Robert 

Meyrowitz, both of the U.S. Geological Survey. Approximately 6 mg of a 

sample was decomposed by fusion with NaOH in a silver crucible at 800° C; 

the melt was dissolved in dilute HC1; aliquots of this solution were used 

for the determination of SiCh and AhOs. SiOa was determined spectrophotometrically by the molybdenum blue procedure using l-amino-2-naphthol-4- 

sulfonic-acid-sulfite as the reducing agent. AhOs was determined spectrophotometrically by the alizarin red S-calcium procedure; the standard solutions contained approximately the same concentration of total iron present 

in the sample solution. Approximately 50 mg of sample was decomposed 

by fusion at 900° C with Na2COs; the melt was leached with water and

treated with HF and HCICU to remove silica; aliquots of this solution were 

used for the determination of total iron, MgO, CaO, K2O, TiOa, P-Os, MnO, 

and ZnO. Total iron was determined spectrophotometrically with o-phenanthroline; the Fe2Os equivalent of FeO present in the sample was subtracted from the total iron \alue to give Fe2Os. MgO was determined by 

atomic-absorption spectrophotometry; lanthanum was used as a releasing 

agent; the standard solutions contained approximately the same concentration of HC1O4 and sodium present in the sample solution. CaO was determined by atomic-absorption spectrophotometry; lanthanum was used as 

a releasing agent; the standard solutions contained approximately the same 

concentration of HClOi, sodium, and MgO present in the sample solution. 

KsO and ZnO were determined by atomic-absorption spectrophotometry; the 

standard solutions contained approximately the same concentration of HClOi 

and sodium present in the sample solution. TiOa was determined spectrophotometrically by the "Tiron" procedure. PaOs was determined spectrophotometrically by the heteropoly blue procedure. MnO was determined by
TABLES 125

TABLE 4.—Conventional wet-chemical analyses and the number of atoms calculated on the basis of the anhydrous formulas

for selected minerals—Continued

Biotite -

356-1

Chloritoid a

140-2

Chlorite *

355-1

Hmenite

140-2 355-1 140-2

Tremolite

918-1

Weight percent

SiO2 ______________

TK>2 ______ ___.

AhOs _____ _ _

FeO __ __ _ __

MnO ______________

MgO _____________

CaO ______________

NasO _____________

K.O ... __ __..___

H.O+ _____________

H2O- _____________

COa _______________

PsOs ______________

ZnO ______________

Sum _ __ _ ____

36.8

1.6

20.4

1.6

16.6

.02

9.3

.00

.44

8.3

\ A*

} 4'3

nd

.12

nd

99.5

26.8 

1.0 

38.2 

5.3 

18.3 

1.3 

1.8 

.00 

.09 

.12 

6.7 

.10 

nd 

.17 

nd

99.9

25.8 

.21 

24.2 

2.8 

24.7 

.05 

10.3 

.00 

.22 

.56 

10.0 

.70 

nd 

.15 

nd

99.7

24.4 

.15 

23.3 

3.2 

29.1 

.40 

8.0 

1.0 

.08 

.20 

10.0 

.07 

nd 

.13 

nd

100.0

1.2 

46.8 

2.0 

11.6 

36.6 

.05 

.23 

.15 

.00 

.14 

.37 

.02 

<.05 

.02 

nd

99.2

3.2

48.7 

4.4 

2.2 

38.6 

1.2 

.28 

.00 

.28 

.20 

.30 

.00 

nd 

.19 

nd

99.6

58.2)5 

.04 

.53 

.08 

.24 

.01 

24.46 

13.47 

.20 

.04 

2.03 

.01 

nd 

.00 

nd

99.48

Number of atoms

Si ________ _____

Ti ________ _____

Al ______ — —— -

Pe3+ _ _

Fe2* ______ —— -

Mn ____________

Mg ________ ____

Ca ________ _.__

Na _______ — —

K ________ __._

Zn __________ _

H" ________ ____

( 9 )

o frr

09

i 8n

09

1.04

.00

i n^i

.00

.06

7Q

nd

(U) (12)

1.09 

.03 

1.83 

.16 

.62 

.04 

.11 

.00 

.01 

.01 

nd

(13) (B

2.69 

.02 

2.97 

.22 

2.15 

.00 

1.60 

.00 

.04 

.07 

nd

i) (U)

2.59 

.01 

2.92 

.26 

2.59 

.04 

1.27 

.11 

.02 

.03 

nd

(IS)

0.03 

.87 

.06 

.22 

.76 

,00 

.01 

.00 

.00 

.00 

nd

(15)

0.08 

.89 

.13 

.04 

.78 

.02 

.01 

.00 

.01 

.01 

nd

(M) 

7.930 .000' 

.085

.008 

.027 

.001 

4.960 

1.964 

.055 

.007 

nd 

1.933

Optical data

[Refractive index; estimated uncertainties in parentheses; sodum light]

0 __——__—__-_—

2Vobs _______________

2Vcalc _______________

[Cell edges in angstroms;

b

0 -_——_—-_-—

Specific gravity 

calculated _________

1.588 

(+.002)

1.629 

(+.002)

1.633 

(+.003)

^17°

standard error

5.346 

(±.002) 

9.214 

(+.008)

10.234 

(+.005) 90°

100°10.9' 

(±8.5') 90°

496.2 

(±.3)

74.7 

(±.1)

2.98

1.722 

(±.002) 

1.725 

(±.003) 

1.730

+~60°

+ 76°

nd 

nd 

1.634 

(±.002) 

nd 

nd

nd

Cell

in parentheses; interaxial angles 

stroms; molar volumes

9.444 

(±.028) 

5.520 

(±.007) 

9.154 

(+.002) 96°19.9' 

(+7.7')

101°53.5' 

(±12.9') 90°53.7' 

( +9.1')

463.8 

(±1.8) 

34.9

(±.1)

3.25

5.378 

(±.002) 

9.320 

(±.004) 

14.218 

(±.006) 90°

96°56.7' 

(±2.2') 90°

707.4 

(±.4) 

106.5 

(±.1)

2.95

nd 

nd 

1.644 

(+002) 

nd 

nd 

nd 

nd

data

in degrees, minutes, and 

in cubic centimeters]

5.418 

(±.001) 

9.385 

(+.004)

28.610 

( ±.002) 90°

96°54.7' 

(+1.1') 90°

717.6 

(±.3) 

108.0 

(±.1)

2.99

fractions of

5.094 

(±.004)

14.129 

(+017) 90°

90°

120°

317.5 

(±.5) 

31.87 

(±.05)

4.61

nd

minutes; cell volumes

5.088 

(±.001)

14.093 

( ±.004) 90°

90°

120°

316.0 

(±.1) 

31.72 

(±.01)

4.55

nd 

nd 

1.616 

( +.002)

18 1.628 

( +.002) —— 90° 

nd

in cubic ang9.836 

(±.001) 

18.045 

(±.002) 

5.278 

( ±.002) 90°

104°45.3' 

(±.9') 90°

905.9 

(±.2)

272.8 

(±.1)

2.98

atomic-absorption spectrophotometry; the standard solutions contained approximately the same concentraton of HClOi, sodium, and total iron present in the sample solution. FeO was determined volumetrically, the sample 

was decomposed by fusion with (NaF)2B2Os in an atmosphere of argon; 

the melt was dissolved in an excess of standard potassium dichromate, and 

the excess dichromate was titrated with standard ferrous ammonium sulfate in the presence of phosphoric acid using sodium diphenylamine-sulfonate as indicator; the sample size was approximately 30 mg. Total water 

and COa were determined simultaneously on a sample of approximately 200 

mg using a microcombustion train; VzOs was used as a flux; the value for 

H2O- was subtracted from the total water value to give H2O+. Approximately 500 mg of sample was heated to constant weight at 110°+5° C to 

determine EkO-.

6 Reported values preceded by "less-than" signs «) are not included 

in the sum.

7 Anhydrous formula; 23.5 oxygen.

8 Anhydrous formula; 12 oxygen. 

'Anhydrous formula; 11 oxygen.

10 Impure separate probably containing quartz.

11 Anhydrous formula; 6 oxygen.

12 Impure separate probably containing chlorite and quartz; see microprobe data (table 3, section D).

M Anhydrous formula; 14 oxygen.

14 Impure separate.

13 Anhydrous formula; 3 oxygen.

M Anhydrous formula; 23 oxygen. Chemical analysis includes 0.21 percent 

fluorine, <0.01 percent chlorine; weight percent sum has been corrected 

for F-equivalent oxygen; number of atoms includes 0.090 fluorine.

17 H is calculated only for two staurolite samples and the tremolite sample.

18 Value is 7' measured on fragment lying on the cleavage; Z' A C=16°.
126 METAMORPHIC MINERAL ASSEMBLAGES, TACONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 5.—Comparison of wet-chemical and microprobe analyses (A), in weight percent, and of the calculated chemical formulas (B) of staurolite from sample 355-1

SiO»

Ti03 ______ _ _____

A1203 _ ____ _____

Fe203 _ ____ __

FeO _ _ __ .. _

MnO _ _ __ __,

MgO ___ ___ __ _

CaO ______ _

Na20 ___ _ __ _ __ . K20 ____ ____ _ ____

ZnO __ __ _ __ _

H20+ _ _ _ __ __ __.

H20- __ _ ______ . C02 __ __ __ _

P205 ________________

Sum _ _ _ _

Wet 

Chemical *

— _ 28.55

__ .41

_ _ 53.54

— - 2.54 \

_ __ 11.42 }

.08

_ _ 1.06

.09

nd

<.05

.26

1.61

.02

<.02

.03

99.61

A. Analyses 

[nd, not determined]

Microprobe 2

OQ n,Q

.62

54.59

14.06

.05

1.05

.00

nd

nd

.35

(1.07)

nd

nd

nd

98.80

/QQ Q7\

B. Formulas 

[FeT, total iron]

Mcroprobe 

data including Fe3+

(3)

28.08

.62

54.59

(

O £"! \ 2.61^

11.71 )

.05

1.05

.00

nd

nd

.35

(1.07)

nd

nd

nd

99.06

(100.13)

Range of 

microprobe data

27.73-28.48

0.86- 0.77

53.31-55.71

13.80-14.25

0.02 0.07

0.99- 1.07

0.00- 0.02

nd

nd

0.00- 0.77

nd

nd

nd

97.44-99.89

1. Formula of staurolite according to wet-chemical analysis, 

based on 23.5 oxygens for anhydrous formula :

(Als.seFe VnJg.ooSii.osOzs.s

(predicted H20+ is 1.06 weight percent) ; FeT/ (FeT 

+Mg)=0.88.

2. Formula of staurolite according to microprobe analysis, 

both ferric and ferrous iron present [FeT/(FeT+Mg)] 

=0.88:

7go.22 no.oino.o4eo.28 o.o7 1.97

Ols.92O23.5

3. Formula of staurolite according to microprobe analysis, 

only ferrous iron present:

1 Analysis from table 4. that the anhydrous formula contains 23.5 oxygen atoms. Total iron is

2 Average of analyses 1-5, table 3, section E, that were made by using calculated as FeO.

the automated ARL-SMX probe of the U.S. Geological Survey in Reston, 3 Total iron partitioned according the atomic ratio of the wet-chemical

Va. H2O+ figure in parentheses and sum in parentheses are calculated on analyses. Figures in parentheses have the same meaning as do those in

the basis of a hydrous formula containing 24.0 oxygen atoms, assuming the preceding column.

TABLE 6.—Molar volumes of minerals used to calculate slopes of the univariant curves shown in figure 15

Mineral

Garnet ______

Staurolite _ 

Chloritoid _ 

Chlorite _____

Biotite _ _ _

Muscovite _ 

Anorthite __ _

Epidote _____

Quartz _ _ _

Formula

(Fe2+ Me Cao )AL>SiO

H(Fe2+,Mg) ^198140.4 

H2 (Fe2%Mg)Al2SiOT 

H8 (Fe2%Mg)4.5Al3Si2 . B018

H2Ko. 9 (Fe^sMgLoo) AlLTTSia.ajO^

CaAl2Si208 _

Si02

Molar 

volume 

(cm»)

1 1 C QC

223.0 

69.6 

ona f\

1 co c

140.71 

100.79

1 qo 7

22.688

Notes and sources

Robie and others, 1967; linear interpolation of end

members. See also table 4. 

Robie and others, 1967; on natural sample of uncertain 

composition. See also table 4. 

Robie and others, 1967; on natural sample of uncertain 

composition. See also table 4. 

Zen, 1972b, table 2.

Robie and others, 1967; linear interpolation of phlogopite and annite. 

Robie and others, 1967. 

Robie and others, 1967. 

Robie and others, 1967.

Robie and others. 1967.
TABLES 127

TABLE 7.—Compositions of coexisting chlorite, biotite,

chloritoid, and garnet in the presence of muscovite,

plagioclase, and quartz, in number of cations

per formula a

TABLE 8.—Partial mineral-assemblage data for samples of 

epidote-bearing assemblages

[Complete assemblage data are in table 1. +, mineral is present in assemblage; —, mineral is absent from assemblage. Ga, garnet; Pa, paragonite; 

Bt, biotite; Cd, chloritoid; Pg, plagioclase]

[Figures are mean number of cations computed from data in table 3; 

figure in parentheses, standard deviation. Leaders in parentheses ( —— ) 

indicate only one analysis was done for this mineral. Sample 339-1 

contains chloritoid in garnet only; sample 466-1 does not contain garnet, 

nd, not determined]

Cation 103-1 103-2 463-1 509-1 339-1 466-1

Chlorite

Si ________

Ti .. ____..

Fe __ —

Mn _______

Mg . ______

Ca _______

K ________

2.48 2.48 2.51

(...) (.06) (.02) .00 .01 .00

(...) (.01) (.01)

(—) (.11) (.03) 

2.96 2.66 2.59

(...) (.04) (.01) .01 .01 .01

(...) (.00) (.00) 

1.57 1.89 1.86

(...) (.06) (.01) 

_ nd nd nd

2.59 

(.06) 

.01 

(.00) 

2.86 

(.10) 

2.50 

(.04) 

.01 

(.01) 

1.99 

(.04) 

nd 

nd 

.05 

(.06)

2.54 2.53 

(.02) (.02) 

.00 .01 

(.01) (.01) 

2.96 3.00 

(.03) (.04) 

2.37 2.69 

(.09) (.08) 

.00 .02 

(.01) (.00) 

2.08 1.70 

(.08) (.05) 

nd nd 

nd nd 

nd nd

Biotite

Si ________

Ti __ - ___

Al __ . _

Fe . ______

Mn _______

Mg _______

Ca _______

Na

K ______..

2.64 2.64 2.67

(.02) (.04) (.01) .10 .10 .09

(.01) (.01) (.01)

1 7K 1 78 1 77

(.03) (.06) (.06) 1.67 1.51 1.46

(.02) (.03) (.05) .01 .01 .01

(.00) (.00) (.00)

7fi SQ QQ

(.02) (.03) (.02)

.04 .04 .04

(.00) (.01) (.01) 

.83 .85 .82

(.02) (.07) (.03)

2.70 

(.04) 

.10 

(.01) 

1.81 

(.02) 

1.33 

(.07) 

.01 

(.00) 

.94 

(.01) 

nd 

.03 

(.01) 

.82 

(.04)

2.68 2.71 

".10 "07 

1~79 1~84 

1~23 1~46 

".01 "6l 

l"07 ".85

nd nd 

.04 .06 

(---) (—)

.82 .69

Chloritoid

Si ________

Ti ________

Al ........ 

Fe _______

Mn _______

Mg _______

Ca __ ...

Na .... ___

K _ . ____

1.00 1.00 1.00

(.00) (.01) (.01) 

— nd nd nd

1.97 1.98 2.00 

(.00) (.01) (.01)

(.01) (.01) (.01) 

.01 .01 .01

(.00) (.00) (.00) .13 .14 .15

(.01) (.00) (.01)

1.01 

(.01) 

nd 

1.98 

(.01) 

.85 

(.01) 

.01 

(.00) 

.15 

(.01) 

nd 

nd 

nd

1.00 1.00 

(.00) (.01) 

nd nd 

1.98 1.98 

(.00) (.01) 

.85 .87 

(.01) (.01) 

.02 .02 

(.01) (.01) 

.16 .12 

(.00) (.01) 

nd nd 

nd nd 

nd nd

Garnet

Si .. ______

Ti __ -__.

Al ....._._

Fe __ —

Mn ___ __

Mg _______

Ca _______

Na ... ____

K . _ . ___

2.97 2.97 2.98

(.01) (.01) (.03) 

.00 .00 .00

(.01) (.01) (.00) 

2.01 1.99 1.99

(.02) (.02) (.06)

2.48 2.34 2.47

(.07) (.03) (.03) 

.25 .29 .25

(.04) (.01) (.02) 

.16 .18 .22

(.02) (.01) (.0,3) 

.14 .25 .11

(.02) (.02) (.01)

2.99 

(.02) 

.00 

(-00) 

2.00 

(.01) 

2.37 

(.07) 

.19 

(.05) 

.18 

(.03) 

.27 

(.03) 

nd 

nd

1 Formula computed on the anhydrous basis of 14 

chlorite, 11 oxygen atoms for biotite, 6 oxygen atoms 

12 oxygen atoms for garnet.

2.99 

(.02) 

.00 

(.00) 

2.00 

(.01) 

2.45 

(.12) 

.14 

(.09) 

.23 

(.02) 

.20 

(.05) 

nd 

nd

oxygen atoms for 

for chloritoid, and

Sample Ga Pa Bt Cd Pg

Below garnet zone

39 1 __ — ?

182-1 __ __ - - - - 

195 1 ____ +

196-1 _ __ - - — -

365-1 __ _____

373 1 ____

373 2 ____

376-1-2 __ - - — - 

376-1-3 __ _ — - — —

385-1 _ __ - - + -

1014-1 __ - - - - 

1014-2 1 __ ? -

1100-1 __ ____ + _

1100-2 __ __ - - + -

1100-3 - - - -

1169-1 x __ - - ? -

1208-2 __ __ - - - -

+

7

Garnet zone

40-2 __ - + - -

62-1 ____ + - - - 

65-1-3 __ + - - - 

67-2 - + - -

68-1 ____ + - - + 

73-1 _ __ + - - +

77-2 + - - +

77-3 __ - - - +

131-1 __ - + - +

161-1 2 __ + - - -

170 1 s 4-

170 2 3 +

232 1 ____ + + 

346-1 ____ + - - -

KAfi O4- J

641-1 ____ - - + -

1

+

Staurolite zone

102-2 4 __ + +

356-1 B ___ + - + - 

590-1 B _ __ + - + -

2 Contains hornblende. 

3 Contains cummin gtonite. 

4 Does not contain staurolite. 

5 Contains staurolite.

I
128 METAMOEPHIC MINERAL ASSEMBLAGES, T AGONIC ALLOCHTHON, MASS., CONN., N.Y.

TABLE 9.—Compositions of coexisting minerals in three hornblende assemblages

[The number of the sample analyzed is given below the mineral name. Figures are number of cations per formula calculated on the basis of anhydrous versions of formulas given on p. 22-23; figures in parentheses, standard deviation. Compositions of hornblende from samples 102-1 and 289-2 

are given by Doolan and others (1978). All other compositions are averages of data in table 3, parts A (muscovite), B (biotite), C (chlorite), 

F (garnet), and H (hornblende), nd, not determined. Sample 289-2 does not contain chlorite or muscovite; sample 161-1 does not contain 

biotite]

Cation

Si ___ _

Ti _____

Al _ __ _

Fe _ __

Mn _____

Mg _ _

Ca ______

Na _ _

K _ _ _

102-1

6.08

(.12) 

.03

(.00) 

__ _ 3.27

(.27) 

__ 2.36

(.09) 

__ .03

(.01) 

__ 1.24

(.25) 

__ 1.73

(.08) 

__ .35

(.03) 

__ .06

(.00)

Hornblende

161-1

6.06 

(.07) 

.02 

(.01) 

3.42 

(.14) 

2.93 

(.11) 

.11 

(.10) 

.80 

(.03) 

1.65 

(.03) 

.40 

(.03) 

.01 

(.01)

Chlorite

289-2

6.09 

(.11) 

.05 

(.01) 

3.14 

(.16) 

2.13 

(.04) 

.04 

(.01) 

1.55 

(.14) 

1.77 

(.03) 

.33 

(.03) 

.09 

(.01)

102-1

2.62 

(.03) 

.01 

(.01) 

2.75 

(.06) 

2.35 

(.05) 

.01 

(.01) 

2.26 

(.05) 

.00 

(-01) 

.00 

(.00) 

nd

161-1

2.54 

(.11) 

.00 

(.01) 

3.13 

(.19) 

2.51 

(.04) 

nd

1.68 

(.08) 

.01 

(.01) 

.00 

(.01) 

.00 

(.00)

102-1

2.94 

(-01) 

.01 

(.01) 

1.98 

(.02) 

1.94 

(.03) 

.36 

(.08) 

.16 

(.02) 

.68 

(.05) 

nd

nd

Garnet

161-1

3.05 

(.05) 

.00 

(.01) 

1.94 

(.02) 

2.00 

(.13) 

.35 

(.04) 

.14 

(.01) 

.46 

(.08) 

.00 

(.00) 

.00 

(.00)

Biotite

289-2

2.96 

(.01) 

.01 

(.01) 

1.98 

(.01) 

1.84 

(.01) 

.43 

(.07) 

.22 

(.02) 

.62 

(.04) 

nd

nd

102-1

2.65 

(.07) 

.11 

(.01) 

1.68 

(.01) 

1.48 

(.03) 

.01 

(.00) 

.99 

(.01) 

.01 

(.01) 

.02 

(.01) 

.81 

(.02)

289-2

2.73 

(.03) 

.12 

(.01) 

1.59 

(.05) 

1.16 

(.06) 

.01 

(.00) 

1.32 

(.05) 

.01 

(.00) 

.02 (.01)

.88 

(.01)

Muscovite

102-1

3.05 

(.00) 

.01 

(.00) 

2.84 

(.01) 

.08 

(.00) 

.00 

(.00) 

.07 

(.01) 

.00 

(.00) 

.16 

(.01) 

.80 

(.01)

161-1

3.02 

(.06) 

.03 

(.01) 

2.88 

(.10) 

.13 

(.02) 

.00 

(.00) 

.05 

(-01) 

.01 

(.00) 

.09 

(-00) 

.72 

(.00)

TABLE 10.—Estimates of minimum temperature of metamorphism based on K/(K-|-Na) ratios of muscovite compositions

and the 2.07-kbar solvus of Eugster and others (1972)

and microprobe data

[ +, mineral is present; —, mineral is absent. Complete assemblage data 

are in table 1. K/(K + Na) ratios are based on data in tables 3, section A, and 4. Cd, chloritoid; St, staurolite; Ch, chlorite; Pa, paragonite]

Sample 

No.

140-2 ... 

360-1 _ 

509-1 ... 

102-1 ... 

338-1 ... 

466-1 ... 

506-1 ...

103-1 ... 

103-2 ... 

331-1 ... 

339-1 ... 

355-1 ...

356-1 ... 

369-1 ... 

463-1 ... 

515-1 ... 

290-1 ... 

1052-1 ...

Zone 1

-Ga 

— Ga 

Ga

Ga/St 

Ga/St 

Ga/St 

Ga/St

St 

St 

St 

St 

St

St 

St 

St 

St +st 

+st

Minerals

Cd

+ 

+

i

associated

St

++++++ ++I11

with muscovite figg^

Ch Pa + N-)

+ — 0.80

+ + .79 

+ — .78 

+ - .84 

+ — .75 

+ - .74 

+ — .72

+ — .81 

— .83 

— .69 

— .73 

— .70

+ — .74 

+ — .74 

+ — -71 

+ — .77 

+ — .77 

+ — .80

Estimated 

temperature, 

in

540 

550 

570 

480 

610 

620 

640

590 

500 

670 

640 

670

620 

620 

650

580 

580 

540

1 —Ga, below garnet zone; Ga, garnet zone; Ga/St, at or near the 

boundary between the garnet and staurolite zones; St, staurolite zone; 

+ St, high-grade part of the staurolite zone.

£ U.S. GOVERNMENT PRINTING OFFICE: 1981 - 34I-6I4'I37