Plutonic Rocks of the 

Klamath Mountains, 

California and Oregon

GEOLOGICAL SURVEY PROFESSIONAL PAPER 684-B
Plutonic Rocks of the 

Klamath Mountains, 

California and Oregon

By PRESTON E. HOTZ

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 684-B

Petrography, chemical composition, and age 

of plutons of the Klamath Mountains and 

a comparison with plutons of the east-central 

and western Sierra Nevada

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

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director

Library of Congress catalog-card No. 76-171032

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

Washington, D.C. 20402 - Price 35 cents (paper cover)

Stock Number 2401-1129
CONTENTS

Abstract___ _ ______

Introduction ______

General geology. _ _ 

Plutonic rocks_ __ 

Mafic rocks___ 

Syenodiorite__ 

Quartz diorite. 

Trondhjemite. 

Granodiorite _.

Page

Bl

1

1

3

3

5

5

5

10

Page 

Plutonic rocks Continued

Quartz monzonite and alaskite____________________ Bll

Chemical data and compositional trends.______________ 11

Age_________ _________________________________________ _______ _______________________ 14

Comparison with plutons of western Sierra Nevada. 

Comparison with plutons of central Sierra Nevada _. 

Conclusions.__________________________________

References..__________________________________

14

16

18

19

ILLUSTRATIONS

Page 

FIGURE 1. General geology of the Klamath Mountains. ________________________________________________________ B2

2. Map showing generalized distribution of granitic and gabbroic rocks in plutons of the Klamath Mountains. __ 4 

3-9. Diagrams showing:

3. Classification system used for plutonic rocks of the Klamath Mountains ___-______-__-_-____-_-_-_ 5

4. Modal quartz-plagioclase-potassium feldspar ratio for plutons of the Klamath Mountains ___________ 5

5. Variation of common oxides in plutonic rocks of the Klamath Mountains plotted against SiO2_ _-____- 12

6. Normative quartz-orthoclase-plagioclase (Ab +An) ratio for plutonic rocks of the Klamath Mountains. 12

7. Comparison of modal and normative quartz-orthoclase-plagioclase (Ab + An) ratios for plutonic rocks

of the Klamath Mountains.____-____________________-_____-_____--____--__--__---_---- 13

8. Alk-F-M ratio (cation percent) for plutonic rocks of the Klamath Mountains_____-__-_-_-__-___- 13

9. Sodium-potassium-calcium ratio (cation percent) for plutonic rocks of the Klamath Mountains. ______ 14

10. Map showing distribution of dated plutons in the Klamath Mountains________________________________ 15

11-19. Diagrams showing:

11. Modal quartz-plagioclase-potassium feldspar ratio for plutonic rocks of the western Sierra Nevada___ 16

12. Normative quartz-orthoclase-plagioclase (Ab + An) ratio for plutonic rocks of the western Sierra

Nevada._____________________________________________________________________________ 16

13. Alk-F-M ratio (cation percent) for plutonic rocks of the western Sierra Nevada__________________ 16

14. Sodium-potassium-calcium ratio (cation percent) for plutonic rocks of the western Sierra Nevada___ 16

15. Modal quartz-plagioclase-potassium feldspar ratio for plutonic rocks of the east-central Sierra

Nevada.____________________________________________________________________________ 17

16. Normative quartz-orthoclase-plagioclase (Ab + An) ratio for plutonic rocks of the east-central Sierra

Nevada.____________________________________________________________________________ 17

17. Alk-F-M ratio (cation percent) for plutonic rocks of the east-central Sierra Nevada._____________ 17

18. Sodium-potassium-calcium ratio (cation percent) for plutonic rocks of the east-central Sierra Nevada. 17

19. Variation of K2O/SiO2 (weight percent) for plutonic rocks of the Klamath Mountains-...- ______ 18

TABLE

TABLE 1. Chemical and spectrographic analyses, norms, and modes of plutonc rocks of the Klamath Mountains.. .__

Page 

B6

ni
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, 

CALIFORNIA AND OREGON

By PRESTON E. HOTZ

ABSTRACT

Pre-Cretaceous sedimentary? volcanic, metamorphic, and ultramafic rocks of the Klamath Mountains province, northwestern 

California and southwestern Oregon, are intruded 'by numerous 

plutons which range from small stocklike bodies to masses of 

batholithic proportions. Quartz diorite is the most plentiful 

variety, but the plutons range in composition from diorite and 

gabbro to quartz monzonite, and some are trondhjemitic. Two 

small plutons in the eastern part of the province are Permian. 

All the rest are Middle and Late Jurassic.

Plutons of the Klamath Mountains are similar in composition 

and age to plutons in the western Sierra Nevada, but contrast 

sharply in composition with plutons in the east-central Sierra 

Nevada, which also are generally younger. The fact that the 

Klamath Mountains and western Sierra Nevada plutons are 

more sodic than the plutons of the east-central Sierra Nevada 

possibly reflects fundamental compositional differences in prebatholithic rocks in which magmas were generated by anatexis. 

Alternatively, a hypothesis correlating increase of K2O in volcanic rocks with increased depth of magma generation along 

landward-dipping subduction zones at continental margins may 

be applicable.

INTRODUCTION

The Klamath Mountains geologic province is an elongate north-trending area of approximately 12,000 

square miles in northwestern California and southwestern Oregon. It is bordered on the east by the Cascade province, on the southeast by the Great Valley 

province of California, and on the west and northwest 

by the Coast Range provinces of Oregon and California.

Prior to 1960 approximately 12 analyses of plutonic 

rocks from the Klamath Mountains province had been 

made; thus the size, shape, distribution, number, and 

general composition of the plutons were poorly known. 

In the last decade, however, more attention has been 

focused on the geology of this region, and several plutons have been mapped (Davis, 1963; Davis and others, 

1965; Holdaway, 1962; Hotz, 1967; Lipman, 1963; 

Romey, 1962; Seyfert, 1965). This report summarizes 

presently available data on composition and age of the 

plutons.

GENERAL GEOLOGY

The Klamath Mountains geologic province is divisible into four north-trending arcuate lithologic belts (fig. 

1) : (1) the eastern Paleozoic belt, (2) the central metamorphic belt, (3) the western Paleozoic and Triassic 

belt, and (4) the western Jurassic belt. (See Irwin, 

1960, p. 16-30; 1966, p. 21-25.)

Rocks of the eastern Paleozoic belt range in age from 

early Paleozoic to Jurassic and include typically eugeosynclinal clastic sediments and volcanic rocks. They 

have an aggregate thickness of approximately 40,000- 

50,000 feet.

Two units make up the central metamorphic belt: 

the Salmon Hornblende Schist and Abrams Mica Schist. 

Their metamorphic age is Devonian, as determined by 

rubidium-strontium techniques (Lanphere and others, 

1968).

The western Paleozoic and Triassic belt, the most extensive of the four belts, is an assemblage of fine-grained 

clastic sedimentary rocks, chert, mafic volcanic rocks, 

and lenticular marble. The age of these rocks is poorly 

known, but meager fossil data indicate that they range 

from late Paleozoic to Late Triassic. The rocks of this 

belt are, for the most part, regionally metamorphosed 

and belong to the lower greenschist facies (chlorite subfacies). There are, however, large areas of amphibolites 

and siliceous metasedimentary rocks of the almandineamphibolite facies within this belt, and these may be 

higher grade equivalents of the other rocks. A subcircular "window" of graphitic micaceous schist and 

actinolite schist, called the schists of Condrey Mountain, 

underlies the higher grade metamorphic rocks. The 

schists of Condrey Mountain were metamorphosed in 

Late Jurassic time, but their parental equivalents are 

unknown.

The western Jurassic belt is composed of slate and 

graywacke of the Late Jurassic Galice Formation and

Bl
B2

124

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

123° 122 C

41

FIGURE 1. General geology of the Klamath Mountains. Modified from Irwin (1964, fig. 1), Da vis, Holdaway, Lapman, and Romey

(1965, pi. 1), and Da vis (1968, pi. 1).
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON B3

volcanic rocks that range in composition from basalt to 

dacite and rhyolite.

The four lithologic belts are bounded by thrust faults 

along which each belt overrides its western neighbor. In 

each belt the bedding and (or) metamorphic foliation 

commonly are inclined to the east. The beds are complexly folded, and the axial planes of the folds commonly dip eastward.

Bodies of ultramafic rock (peridotite and serpentinite) occur in all the lithologic belts. They are commonly elongate and concordant with the structural 

grain of the province and range in size from a few 

acres to hundreds of square miles (fig. 1). Several large, 

continuous, apparently tabular bodies occur along the 

boundaries between major lithologic belts. Many small, 

irregularly shaped bodies are possibly remnants of 

formerly more continuous tabular bodies that were 

infolded with the rocks they intrude. Mafic rocks that 

range in composition from diabase to gabbro 

accompany the ultramafic rocks.

PLUTONIC ROCKS

Granitoid plutonic rocks occur throughout the Klamath Mountains province (figs. 1, 2) and intrude 

rocks of all four lithologic belts. They are, however, 

most plentiful in the central metamorphic and western 

Paleozoic and Triassic belts. The plutons range in size 

from stocks less than 1 mile in diameter to batholiths 

with outcrop areas of 100 square miles or more. They 

tend to be elongate with their long axes parallel to the 

north-south arcuate trend of the province. Most have 

been examined only cursorily. Several in the central 

metamorphic belt have, however, been studied in detail 

(Davis, 1963; Davis and others, 1965; Lipman, 1963) ; 

one of these is cylindrical, and the others have domical 

internal structures.

In general, too, the intrusions are concordant with 

the structure of the enclosing rocks. The Vesa Bluffs 

pluton, northwest of Yreka (Hotz, 1967), and the 

heterogeneous plutonic mass in Oregon herein called 

the Chetco River complex (fig. 2), for the major stream 

which drains much of the area in which it occurs, are 

tabular, sill-like bodies. The elongate Ironside Mountain pluton in the southwestern part of the province 

may have a similar geometry.

Classification. The classification system adopted 

here (fig. 3) is a common one based on the modalmineral ratio of quartz-potassium feldspar (including 

perthite) -plagioclase, recomputed to 100 percent.

Modal composition. Sixty-seven modes plotted in 

figure 4 include data from table 1, data from published 

reports and unpublished theses, and modes determined 

by the author. These data include measurements made

by point counting of thin sections and stained rock 

slabs.

MAFIC ROCKS

Many of the plutons are partly composed of mafic 

rocks whose modal compositions plot near the plagioclase corner of the quartz-plagioclase-potassium feldspar triangular diagram (fig. 4). Some of the mafic 

rocks form relatively small bodies wholly or partly 

enclosed by more f elsic rocks, which constitute the major 

part of a pluton. Some larger bodies are mafic parts of 

composite plutons that are predominantly more silicic. 

The intimate association'strongly, suggests a consanguineous relationship between the mafic and more silicic 

members of a pluton. Some diorites and gabbros associated with the ultramafic bodies have isotopic ages 

that are distinctly older than any of the granitic plutons 

which have been dated (Lanphere and others, 1968, p. 

1043^7; R. G. Coleman, written commun. 1970). These 

older rocks are not described here.

The mafic members are dark medium-grained hypidiomorphic-granular rocks which are classified as gabbros or diorites depending on the anorthite content of 

their plagioclase. Rocks classified as gabbro commonly 

contain 40-60 percent mafic minerals, and the plagioclase is more calcic than An50 . Most diorites contain 

35-60 percent mafic minerals, somewhat less than gabbro, and the plagioclase is less calcic than An50 (35^5 

percent anorthite in most specimens).

Pyroxene is the dominant mafic mineral in some of 

the gabbros, although some hornblende is commonly 

present. Both orthopyroxene and clinopyrpxene are 

generally present. The common varieties of gabbro in 

many composite plutons, however, have hornblende as 

the principal mafic constituent, which may or may not 

be accompanied by pyroxene. Plagioclase is well 

twinned and strongly zoned. Its average composition 

may range from approximately An55 to An80 , but most 

commonly is between An55 and An65 ; the range in zoned 

crystals may be very wide, and An35 to An80 is not unusual. Quartz is a minor constituent (less than 10 percent) of most hornblende gabbros.

Hornblende is the dominant mafic mineral of the 

diorites and is commonly accompanied by small amounts 

of biotite. Pyroxene, generally relict grains enclosed 

by hornblende, occurs in small, variable amounts in 

many specimens. The plagioclase averages about 35 to 45 

percent anorthite, although zoned crystals may range 

from An25 to An50. Small amounts of quartz (less than 

10 percent) are present in many of the diorites. Some 

of these quartz-bearing diorites plot on the lower part 

of the quartz-plagioclase join above the 10-percentquartz boundary on the modal triangular diagram.
B4

42° 

41

124 C

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY,

123° 122 C

.37

Analyzed sample

Number refers to table 1

FIGTIBE 2. Plutons of the Klamath Mountains.
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON B5

Quartz

Quartz 

monzonite 

'C-yGranodiorite/ (adamellite

07 / and

alaskite)

Plagioclase 10 Potassium-feldspar

FIGURE 3. Classification system used for plutonic rocks of 

the Klamath Mountains.

Quartz

Plagioclase

EXPLANATION 

A +

Ironside Mountain Forks of Trondhjemite 

Salmon, and Wildwood plutons

Potassium-feldspar

All others

Castle Crags pluton

FIGURE 4. Modal quartz-plagioclase-potassium feldspar ratio 

for plutons of the Klamath Mountains.

SYENODIORITE

Four specimens collected for age determinations 

(Lanphere and others, 1968) three from the Ironside 

Mountain pluton and one from the Forks of Salmon 

pluton constitute an unusual variety of mafic rock, 

syenodiorite, according to Johannsen's (1939) system of

classification. On the quartz-plagioclase-potassium feldspar diagram (fig. 4), the specimens plot near the plagioclase corner in the syenodiorite and gabbro fields.

The rocks are dark (color index 33-48), fine to medium grained, and hypidiomorphic granular. They contain up to 2 percent interstitial quartz and 46-57 percent plagioclase, which ranges from calcic oligoclase 

(An25 ) to calcic labradorite (An65 ). They also contain 

4-11 percent of anhedral intergranular potassium feldspar. The predominant mafic mineral is anhedral to subhedral pyroxene, most of which is hypersthene and the 

rest augite. Biotite is a minor constituent. In the specimen from the Forks of Salmon pluton, hornblende, 

which has replaced pyroxene, is the chief mafic mineral. 

A similar but lighter rock (color index 21) from the 

Eussiaii Peak pluton was described by Romey (1962) 

as a monzonitic pyroxene-biotite diorite.

QUARTZ DIORITE

Quartz diorite is the commonest plutonic rock of the 

Klamath Mountains. Its color index ranges from less 

than 10 to about 40. Eocks whose dark minerals amount 

to 15-35 percent are most abundant, but light-colored 

varieties whose index is less than 10 are plentiful in 

some plutons. The rocks are hypidiomorphic granular 

and fine to medium grained.

The quartz content ranges from 10 to approximately 

35 percent. Subhedral to euhedral plagioclase amounting to 50-65 percent in most of the quartz diorite is 

generally strongly zoned and ranges in composition 

from approximately Aii20 to An60 (calcic oligoclase to 

medium labradorite; average composition probably is 

in the range of andesine).

Potassium feldspar is a minor constituent in many 

of the plutonic rocks called quartz diorite, but is absent from many others. It occurs interstitially in 

amounts that range from a trace to 5 percent and is usually untwinned, although some shows microcline-type 

grid twinning under the microscope.

Hornblende is the predominant mafic mineral and 

usually occurs as euhedral crystals, although in some 

specimens it forms ragged grains. In some specimens 

it contains cores of partly replaced relict augite. Biotite 

accompanies hornblende, but in somewhat smaller 

amounts. It occurs as discrete plates and as irregular 

masses intergrown with and forming rims around 

hornblende.

TRONDHJEMITE

The younger, innermost parts of some composite and 

zoned plutons are trondlijemitic in composition (Davis, 

1963; Davis and others, 1965; Lipman, 1963). From 

the limited data presently available, it appears that 

trondhjemite plutons are among the youngest in the

424-041 O - 71 - 2
B6 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

TABLE 1. Chemical and spectrographic analyses, norms,

[Analyses from sources given in localities list at end of table, except as follows: Chemical analyses: specimen 45, standard analysis by F. S. Grimaldi; 46, 48-58, rapid analyses 

39 analyzed by W.B. Crandell; 46,48-58 by Chris Heropoulos; 37,38,41-44. 47 by R.E.Mays; 34,40 by C. H. Pickett; results reported to the nearest number in the 

series 1, the quantitative value about 30 percent of the time. Modes: for characterizing accessories, B =biotite, H=hornblende, P=pyroxene, M=muscovite]

Pluton......--.-.-.....-. .................

Specimen No.-...----.-.-. ... . 1

FieldNo .- L-5

Shasta Bally

2

A-5-64

3

D-24 .

4 5

BB-38

Pit River

6

65 

Cle3 .

7 8

Wildwood

9

66

Cle26

Ironside Mountain

10

65

Cle29

11

66

Cle27

12 13

66 65 

Cle 28 Cle 33

Chemical analyses

SiO .__ ._ ........................... 64.5

AljO3-- - ..-. - 16.3

FejOa . 1.6

Total FeasFeO.. .......... . . -....-.-.. (3.9)

FeO... . ___ ... 2.5

MgO.. .. . 2.9

CaO_. ....... ............................ 4.1

N&tO. .................................... 4.0

KjO.. ------ ... 20

HiO-. . . . ......... \ , K

HsO+_. ... . . .. ] 1' 6

TiO2. __ __ ... .- ____ . .- ..-- .48

PsOs. -------.-------.-.-----.-..--.--...-- .10

BaO. - ..... -- . ..

COj... -.... ... . <.05

Total............................... 100.00

67.4 

15.0 

1.3 

(3.5) 

2.3 

2.3 

4.0 

3.2 

2.4 

(.741 

1 13} 

.41 

.09 

.05

.05

99.00

68.0 

16.0 

1.5 

(2.9) 

1.5 

2.0 

4.1 

3.8 

2.2

.56

.33

.09 

.04

<.05 ..

100.00

68.10 

15.18 

1.34 

(2.9) 

1.70 

2.06 

4.66 

3.71 

1.48

.55

.35 

.18 

.20 

.06 .

99.57

70.4 

15.9 

.9 

(2.2) 

1.4 

1.3 

3.2 

4.0 

2.5

.56

.28 

.07 

.04

<.05 .

101.00

71.3 

15.0 

.61 

(2.5) 

1.9 

.8 

3.3 

3.7 

1.8 

( .15 

|l.O 

.25 

.03 ..

.09 ..

100.00

63.09 

16.04 

1.33 

(5.6) 

4.40 

2.48 

5.00 

3.85 

.91 

1.94 

.12 

.53

99.69

63.26 

15.80 

1.45 

(5.4) 

4.07 

2.47 

4.31 

4.53 

1.06 

2.01 

.14 

.48

99.58

50.1 

18.0 

3.4 

(10. 7) 

7.6 

4.8 

9.6 

2.8 

.75 

.13 

1.1 

.79 

.33 

.07

<.05

99.00

50.1 

16.3 

2.1 

(11. 0) 

9.1 

4.8 

8.7 

2.7 

2.1 

.11 

1.5 

1.0 

.5 

.12

<.05

99.00

51.6 

17.5 

2.2 

(9.6) 

7.6 

5.1 

9.7 

2.7 

1.2 

.09 

1.0 

.17 

.32 

.26

<.05

99.00

51. 6 53. 1 

15. 2 14. 9 

2.7 1.4 

(10. 4) (10. 9) 

8. 0 9. 6 

5. 8 5. 3 

10.3 8.4 

2.4 2.5 

1. 7 2. 4 

.05 .11 

.95 .71 

.17 .99 

.31 .37 

.10 .07

<. 05 <. 05

99. 00 100. 00

Semiquantitative spectrographic

B. ........... ............ ... ... . .......

Ba - ... ........ ... .. ......... .-.....

Be.................. 

Co. . .. .............

Or. ... 

Cu..- -- -.-. - .

fi-n

La...... .. . . .

Nb... ----- -.. - ...... . ...

Ni... ...--. . -.................. ........

Pb --- --.- - ...- .

Sr... . ........

V-.-. - -... .... ..... ..._ 

Y.. ........ .

Yb. .-- - - --..- .- . .

Zr. .................................................

Norms (weight

Q. 19.6

C. ......................... ............... .4

or......................................... 11.0

ab. ----------------..--..............-.-_. 34.1

k.......... .........................................

61..... ..... .........................................

liy. ....................................... 9.8

fO........ ...........................................

fa. . 

mt... -- - . .- 2.3

il. ---_-.-......-.... ........ .............. .9

Total--.----.--.-----.-..-----.-.-.- 97.9

27.0 

.2 

14.3 

27.3 

19.1

5.8 .

2.6 .

1.9 

.8 

.2 

.1 .

99.3

25.9

O

12.8 

32.0 

18.9

6.1

2.1 

.6 

.3

99.0

27.54

8.90 

31.44 

20.29

1.84

6.18

1.86 

.91 

.34

99.30

31.2 

1.0 

15.0 

29.9 

15.0

4.4

1.4 

.6 

.3

98.8

33.5 

1.0 -

10.7 

31.4 

16.2

2.0 

2.7

.9 

.5 

.1 -

99.00

19.7

5.3 

32.6 

23.8 

.4 

7.2 

6.1

1.0 

1.9

97.0

17.8

6.2 

38.3 

19.7 

.7 

6.2 

5.5

2.1 

.9

97.4

2.0

4.4 

23.7 

34.3 

4.6 

11.9 

10.0

4.9 

1.5

97.3

12.4 

22.8 

26.2 

5.7 

9.7 

11.0

1.5

1.9

3.0 

1.9 

1.2

97.3

1.2

7.1 

22.8 

32.1 

5.8 

12.7 

12.3

3.2 

.3

.8

98.3

0. 7 1. 4

10. 0 14. 2 

20. 3 21. 2 

25.7 22.3 

9. 8 7. 1 

14. 4 13. 2 

12.4 15.0

3. 9 2. 0 

.3 1.9

.7 .9

98. 2 99. 2

Modes (volume

Quartz.... _ __ .... __ ....._... _ .............

Characterizing accessories. ..........................

32 

8 

47 

13 

B,H

35

6

49

10

B,H

2

65 

33 

P,B

2 

... 6

57 

36 

P,B

<1 1 

6 11 

46 51 

48 36 

. P.B P,B
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON B7

and modes of plutonic rocks of the Klamath Mountains

by P. L. D. Elmore, S. D. Botts, Gillison Chloe, Lowell Artis, James Kelsey, Hezekiah Smith, and J. L. Glenn. Semiquantitative spectrographic analyses: specimens 35, 36, 

0.7, 0.5, 0.3, 0.2, 0.15, and 0.1, etc., which represent approximate midpoints of group data on a geometric scale; the assigned interval for semiquantitative results will include

Forks of Caribou 

Salmon Mountain

14 15

66 

Cle 17 14-33

Deadman Peak

16 17 18 19

3317 3617 272 173

Russian Peak

20 21 22

157 159 175

Craggy 

Peak

23 24

65 

613 Cle 6

Sugar 

Pine

25

65 

Cle 8

Castle 

Crags

26

66 

Clel

English Peak

27 28 29

65 

2-818 2-19 Cle 19

(weight percent)

53.1

16.5

1.8

(8.3)

6.7

5.3

8.6

3.7

1.1

.18 ..

1 9

.76

.11

.07

<.05 ..

68.58

17.10

.76

(2.1)

1.44

1.18

4.40

4.69

.96

.58

.29

.11

.23

58.87

15.82

1.25

(5.9)

4.76

5.34

5.82

3.66

1.44

.35

9 19

.85

QO

.10

67.68

15.89

1.54

(3.3)

1.94

2.04

3.71

4.30

1.62

.28

.68

.45

.17

.05

66.67

15.52

1.74

(3.4)

1.83

2.17

3.79

4.17

1.99

.25

.67

.50

.28

.06

50.64

16.67

3.49

(9.2)

6.07

6.33

10.78

3.19

.18

.14

on

.65

34

.15

53.99

16.85

2.17

(7.8)

5.82

3.90

7.71

4.03

1.64

.44

1.68

.90

.39

.12

56.14

18.01

2.75

(7.1)

4.61

2.50

6.61

4.24

2.16

.36

1 03

.80

.35

.11

64.37

15.77

2.05

(4.4)

2.56

1.62

4.61

4.13

2.56

.23

1 09

.45

99

.07

69.87

16.26

1.09

(2.4)

1.46

.18

2.85

4.77

2.10

.34

.75

.30

11

.04

70.5

16.4

.79

(1.8)

1.1

.87

3.4

4.7

.95

.44

.06

.28

.02

.06

<.05

60.8

16.6

2.4

(5.6)

3.4

3.0

6.0

3.7

1.4

.64

.16

.74

.15

.15

<.05

66.5

17.7

1.0

(2.2)

1.3

.91

3.3

5.2

2.7

.11 ..

.50 ..

.25

.14 ..

.10

<.05 ..

58.0

16.0

1.54

(7. 72)

6.33

4.8

7.8

2.95

1.94

.70

.14

59.0

17.0

1.1

(5.29)

4.2

3.5

6.8

3^3

2.27

.62

.10

61.1

16.5

.84

(5.4)

4.6

3.6

5.8

3.3

1.5

1.0

.16

.69

.14

.10

100.00 100.32 100.60 100.35 9.64 99.53 9.64 99.67 9

7Q 

. /o 100.14 100.00 9.00 100. 00 100. 00 98.00 99.00

analyses (weight percent)

percent)

0.6

6.5 

31.3 

25.2

7.0 ..

13.2 -.

9.7 ..

2.6 

1.4 

.3

25.5 

.61 .-

5.56 

39.82 

20.85

5.14 ..

1.16 

.61 

.34

11.0

8.5 

30.1 

22.9 

1.6 - 13.3

6.5

1.8 

1.6

.8

25.2 

.7

9.6 

36.4 

17.3

5.1

1.6

2.2 

.9 

.4

23.7 

.3 ..

11.8 

35.3

17.0

5.4

1.2

2.5 

1.0 

.7

0.9

1.1 

27 

30.6 

8.6

15.8

7.4

5.1 

1.2

.8

2.1

9.7 

34.5 

22.8 

5.4

9.7

7.6

3.1

1.7 

g

5.5

12.8 

35.9 

23.7 

2.8

6.2

5.1

4.0 

1.5 

.8

18.8

15.1 

34.9 

16.9 

1.9 ..

4.0

2.4

3.0 

.9 

.5

27.5 

1.3

12.4 

40.4 

13.3

.4

1.4

1.6 

.6 

.3

30.7 

1.5 ..

5.6 

40.0 

16.8

2.2

1.0

1.2 

.5

16.6

8.4 

31.6 

24.8 

1.8 ..

7.5

3.3

3.5 

1.4 

.4

17.4 

.6 ..

16.0 

44.2 

15.5

2.3

1.3

1.5 

.5 

.3 ..

8.2

11.4

24.9 

24.6 

5.8

11.9

9.4

2.2 

1.3

10.1

13.7 

29.6 

24.8 

4.0

8.9

6.1

1.6 

1.2

16.2

8.9 

28.29 

26 

.9

9.0

6.8

1.2 

1.3 

.3

99.59 98.1 9.4 98.9 98.5 97.5 98.3 98.4 9.2 99.55 9

0 

. o 9.6 99. 7 100. 00 98.8

percent)

<1

4

50 

46 

P.H

28.6

1.1 .

64.2 

6.1 

B.H

11.3

55.0 

33 

B.H

23.4

5.9

56.1 

15 

B.H

28.5 ..

16.5 ..

42.7 

12 

B.H

60.9 

39 

P.H

2.6

53.8 

43 

P.B.H

1.6

10.2

68.5 

21 

P.B

21.6

10.0

51.8 

16 

B.H

23.7

8.8

56.8 

10 

B

27

1

66 

7 

B

16

4

56 

23 

B.H

11

13

67 

9 

B.H

9.6

3.6

50.4 

36.4 

P.B.H

20.5

9.5

43.2 

26.9 

B.H .

16

Trace

55 

29
B8 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

TABLE 1. Chemical and spectrographic analyses, norms,

[Analyses from sources given in localities list at end of table, except as follows: Chemical analyses: specimen 45, standard analysis by F. S. Grimaldi; 46, 48-58, rapid analyses 

35, 36, 39 analyzed by W. B. Crandell; 46, 48-58 by Chris Heropoulos; 37, 38, 41-44, 47 by R. E. Mays; 34, 40 by C. H. Pickett; results reported to the nearest number in 

will include the quantitative value about 30 percent of the time. Modes: for characterizing accessories, B=biotite, H=hornblende, P=pyroxene, M=muscovite]

Field No---------.---- -.

........ 30

66 

... ...... ClelS

.Peak

31

2-731

Wooley Creek

32

66 

Cle20

33

66 

Cle21

34

CM 

20-62

35

CM 

99-64

36

CM 

100-64

Vesa Bluffs

37

CM 

118-63

38

CM 

109-63

39

CM

89-64

40 41

CM CM 

29-60 108-63

Chemical analyses

SiOj ...........................

Als03 -- . .._ ..

YeiOt...... .......................

Total Fe as FeO _ . FeO....... ........... -..-......

MgO..... .........................

CaO-.-. .-.-_ -----_ ...

NajO... ........... ...............

KjO- ....... _. ... ...........

H2 0-_ __ ........................

HsO<...... ...... ...................

Ti02 _. _-_.--_ .................

FtOt........... ...................

MnO...... .......

BaO..... . .................. _.

COz...... ............... ....

Total.. --------

..--.- 68.3

 .... . 15.3

----- 1.0

... .. . (3.3)

----- 2.4

_.---. 1.4

 ...... 4.1

 ...... 3.0

.... ..... 2.7

 .... . .07 .

 .73 .

-.._. . .27

... ...... .04 .

 ..... .07

 <.05 .

..-. . 99.00

74.0 

14.0 

.37 

(1.92) 

1.59 

.78 

2.4 

3.65 

3.70

.22

.05

101.00

56.4 

15.6 

.89 

(8.0) 

7.1 

4.8 

8.0 

2.4 

1.8 

.11 

1.1 

.77 

.15 

.11

.11

99.00

64.6 

15.4 

1.2 

(4.6) 

3.5 

2.4 

4.8 

3.1 

2.5 

.12 

1.1 

.43 

.08 

.13

<0.05

99.00

46.5 

18.0 

2.9

(11.1)

8.5 

6.2 

10.9 

2.7 

.50 

.07 

2.2 

.94 

.36 

.21

<.05

100.00

50.9 

18.7 

1.4 

(7.6) 

6.3 

4.5 

10.5 

3.5 

1.0 

.19 

1.6 

.73 

.18 

.14

.19

100.00

53.9 

16.2 

2.4 

(7.9) 

5.7 

5.4 

10.0 

2.7 

1.1 

.09 

1.3 

.65 

.15 

.16

.11

100.00

60.0 

17.2 

1.7 

(6.0) 

4.5 

2.9 

6.8 

2.8 

1.4 

.19 

1.7 

.39 

.23 

.15

<.05

100.00

61.1 

17.2 

2.6 

(5.7) 

3.4 

2.3 

7.5 

3.2 

1.1 

.10 

.95 

.29 

.35 

.14

<.05

100.00

63.5 

16.4 

.79 

(4.8) 

4.1 

2.0 

4.6 

3.9 

2.5 

.12 

1.2 

.49 

.14 

.15

.05

100.00

64. 2 74. 6 

16. 9 14. 6 

2.4 .53 

(4.9) (0.6) 

2. 7 .16 

1. 9 .26 

6. 2 .10 

2. 8 4. 7 

1. 6 4. 6 

.11 .12 

1.0 .65 

.33 .04 

.17 .01 

.14 .03

<. 05 <. 05

100. 00 100. 00

Semiquantitative spectrographic

B.. ...................... ._._._.-

Ba..... ........................ ..

Be... ........................... .

Co................. ...... ....

Cr. ...................... -.. 

Cu...... ................. ........

Oa...... ..................... 

La............... .................

Nb ...........................

Ni. ........ ............ . -...

Pb... ...... ........ .......... 

Sc

81.... ............................

V. . .... ..

Y. ... . ... . .

Yb ................. 

Zr ............. ...... .-......-

<0. 003 .

.02

.003 

.002 

.07 

.0015

.003 

.002 .

.003 

.1 

.03 

.003 

.0003 .

.003

0.03

.003 

.007 

.0015 

.0015

.005

.003 

.07 

.02 

.0007

.003

0.05

.002 

.003 

.01 

.001

.005

.003 

.05 

.02 

.001 

.0001 

.001

0.07

.0015 

.0007 

.007 

.0015

.0005

.0015 

.15 

.015 

.0015 

.0002 

.005

0.05

.0015 

.0017 

.007 

.0015

.0005

.0015 

.1 

.015 

.0015 

.0002 

.007

0.1

.001 

.002 

.001 

.001

<.003

.001 

.05 

.01 

.0007

.007

. <0.003 ....... 

.1 0. 01 

_.--.--. .0003

.0015 ...........

. 002 . 0002 

. 003 . 0005 

. 0015 . 0015

.003 .... .... ...

.0015 _--.--..---

.15 .007 

.015 ...........

.002 ...........

. 0002 . 0001 

.01 .01

Norms (weight

C ...

ab ................. ..--_._.-

fs... ............ ......... ........

di--~ ~----

hy.. - ..... .

fO---- 

fa. -.- .. 

il... ........ ........ ..........

Total-....--..-.--..--.

----- 28.5

......... .1 .

... ... ... 16.1

..... .... 25.6

_.--.- 20.2

 . 3.5

-_.--. 3.3

----- 1.5

-.-...-. .1 .

....-_ 99.4

31.2

21.7 

30.6 

10.8 

.4 

1.9 

2.3

.5 

.4

99.8

9.4

10.7 

20.5 

26.7 

4.8 

12.0 

11.3

1.3 

1.5

.4

98.8

21.8

14.9 

26.4 

20.9 

1.1 

6.0 

5.0

1.8 

.8 

.2

98.9

3.0 

22.8 

35.5 

6.8 

5.6 

4.4

6.9 

5.9 

4.2 

1.8 

.8

97.7

5.9 

29.6 

32.4 

7.2 

7.1 

6.0

2.9 

2.7 

2.0 

1.4 

.4 

.4

98.0

5.8

6.5 

22.8 

28.8 

8.0 

13.5 

7.7

3.5 

1.2

.4 

.2

98.4

17.6

8.3 

23.7 

30.3

.8 

7.2 

6.5

2.5 

.7 

.5

98.1

19.2

6.5 

27.1 

29.3 

2.3 

5.7 

3.9

3.8 

.6 

.8

99.2

16.4

14.8 

33.0 

19.9 

.7 

5.0 

6.3

1.1 

.9 

.3 

.1

98.4

25. 1 29. 1 

.... ... .... . 1.7

9. 4 27. 2 

23. 7 39. 8 

28. 8 .4 

.3 ..... ......

4.7 .6 

2.7 ..

3.5 .5 

.6 .1 

.4 <.l

99. 2 99. 4

Modes (volume

Characterizing accessories ...

-.-.--. 31

... . 7

----- 51

......... 11

33.8 

20.2 

37.5 

8.5 

B P

10 

2 

53 

35 

.B.H

25 

13 

43 

19 

B.H

1

44 

50 

H

59 

41 

H

7

43

50 

H

16 

1 

56 

25 

B.H

17

57 

24 

B.H

22 

5 

52 

20 

B.H

24 33 

1 24 

51 40 

24 3 

B.H M
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON B9

and modes of plutonic rocks of the Klamath Mountains Continued

by P. L. D. Elmore, S. D. Botts, Gillison Chloe, Lowell Artis, James Kelsey, Hezekiah Smith, and J. L. Glenn. Semiquantitative spectrographic analyses: specimens 

the series 1, 0.7, 0.5, 0.3, 0.2, 0.15, and 0.1, etc., which represent approximate midpoints of group data on a geometric scale; the assigned interval for Semiquantitative results

Ashland

42 43

CM CM 

27-63 59-63

44

CM 

26-63

45

PEH 

116-38

46

ASH

7-67

47

CM 

77-63

Jacksonville

48

MED1-67

Gold 

Hill

49

MED3-67

Squaw 

Peak

50

TL

2-67

Greyback

51

OC1-67

52

OC2-67

Grants 

Pass

53

GP 1-67

White Rock Chetco River complex

54

WI8-67

55 50 57

WI- GAL- PP9-67 11-67 1-67

58

GAL12-67

(weight percent)

49. 5 52. 1 

13. 8 10. 7 

1.0 1. 2 

(10. 7) (7. 5) 

9. 8 6. 4 

8. 6 11. 7 

11. 4 12. 6 

1. 6 1. 7 

.44 .82 

.12 .34 

1. 2 1. 1 

1. 4 .78 

.60 .16 

.21 .15

<. 05 <. 05

100. 00 100. 00

57.9 

14.9 

1.2 

(7.7) 

6.6 

6.1 

7.9 

2.5 

1.2 

.16 

.52 

.84 

.34 

.13

<.05

100.00

57.85 

17.57 

1.98 

(7.0) 

5.22 

3.42 

7.06 

3.27 

1.29 

.07 

.33 

1.04 

.36 

.12

.14

99.72

62.3 

16.3 

1.3 

(4.5) 

3.2 

3.3 

5.4 

3.5 

2.9 

.05 

.54 

.66 

.35 

.13

<.05

100.00

63.3 

15.8 

1.3 

(4.2) 

3.0 

3.4 

6.1 

3.9 

1.4 

.20 

1.0 

.48 

.26 

.10

,17

100.00

65.0 

16.7 

1.8 

(3.6) 

1.9 

2.2 

3.8 

4.9 

1.8 

.11 

.51 

.56 

.17 

.11

<.05

100.00

68.1 

16.1 

1.2 

(2.6) 

1.4 

1.4 

2.8 

5.1 

2.5 

.09 

.55 

.40 

.12 

.07

<.05

100.00

58.2 

18.0 

3.2 

(6.7) 

3.7 

2.9 

7.0 

3.0 

1.7 

.17 

1.2 

.49 

.16 

.17

<.05

100.00

48.7 

16.4 

2.3 

(11. 2) 

8.9 

9.0 

11.3 

1.3 

.14 

.07 

.45 

.76 

.08 

.22

.11

100.00

66.0 

16.4 

1.8 

(4.4) 

2.7 

1.0 

4.8 

3.8 

1.4 

.27 

.93 

.46 

.12 

.10

.05

100.00

69.4 

15.9 

.86

L3 

2.6 

4.6

2.4 

.10 

.82 

.28 

.11 

.08

.05

100.00

69.2 

17.6 

1.0 

(2.1) 

1.1 

.69 

3.6 

4.8 

.84 

.09 

.67 

.24 

.09 

.06

<05

100. 00

70. 8 49. 6 52. 9 

17. 5 17. 7 17. 7 

.33 1. 1 4. 3 

(1.2) (8.9) (10.4) 

.88 7. 7 6. 3 

.41 7. 9 4. 5 

3. 4 11. 6 8. 7 

4. 7 1. 4 2. 5 

.95 .06 .20 

.07 .22 .21 

.52 1. 9 .78 

.13 .40 .75 

.04 .13 .15 

.05 .20 .21

<. 05 <. 05 <. 05 

100. 00 100. 00 99. 00

62.1 

17.5 

2.5 

(5.2) 

2.8 

2.0 

5.8 

3.3 

1.4 

.12 

1.1 

.61 

.24 

.17

<.05

100. 00

analyses (weight percent)

.......... 0.0007

0. 02 . 03

.003 .003 

.07 .02 

. 007 . 015 

. 0015 . 001

. 01 . 015

.003 .005 

.1 .05 

.03 .03 

.002 .002 

. 0002 . 0002 

.......... .01

0.0015 

.05

.002 

.03 

.01 

.0015

.003

.002 

.07 

.02 

.002 

.0003 

.01

0.002 

.1 

.0003

.002 

.007 

.005 

.0015 

.005

001

.005 

.002 

.002 

.1 .01' 

.002 

.0002 

.015

0.0015 

.07

.001 

.003 

.005 

.0015

.001 

.002 

.0015 

.15 

.01 

.002 

.0002 

.01

0.05 

.00015 

.001 

.005 

.0007 

.002

.0007 

.002 

.001 

.001 

.1 

.007 

.002 

.0002 

.007

0.001 

.05 

.0002 

.0007 

.003 

.0005 

.0015

.0007 

.002 

.001 

.0007 

.07 

.005 

.001 

.0001 

.01

0.0015 

.05

.002 

.001 

.01 

.0015

.0007 

.001 

.002 

.07 

.02 

.002 

.0002 

.003

0.01

.007 

.015 

.03 

.0015

!(X)7

.007 

.07 

.07 

.001 

.0015 

.0015

0.001 

.07

.0007 

.0005 

.0015 

.002 

.003 -

.001

.001 

.0015 

.05 

.005 

.002 

.0002 

.02

0. 0015 

.1 

.00015 ..

.0007 

.003 

.005 

.002

.0007 .-

.0015 

.002 

.001 

.1 

.005 

.0007 

.0001 

.007

0.001 

.03

.0005 

.001 

.0015 

.002

.0005 

.0007 

.0005 

.1 

.005 

.0007 

.0007 

.01

0.0015 ....................

. 03 0. 003 0. 01 

.0001 ....................

. 0002 .005 .005 

. 0005 . 005 . 0007 

.001 .01 .02 

. 0015 . 0015 . 002

........... .001 .-... .

. 0001 . 005 . 0015 

.001 -......-...-.-..-...

.......... .007 .002

.1 .05 .07 

. 0015 .03 .01 

.......... .0015 .002

_-..---- .0002 .00015

. 007 . 0007 . 015

0.07

.0015 

.001 

.0015 

.002 

.005 

.0015 

.0005 

.001 

.002 

.07 

.01 

.002 

.00015 

.015

percent)

1.1 ..........

2. 6 4. 8 

13. 5 14. 4 

29. 2 19. 1 

9. 8 17. 7 

21. 4 28. 6 

15. 2 9. 6

11.6

7.1 

21.2 

25.9 

4.6 

15.2 

10.0

12.63

7.62 

27.67 

29.45 

.98 

8.52 

6.46

14.5

17.2

29.6 

20.2 

1.8 

8.2 

4.0

17.9

8.3 

33.0

21.5 

2.5 

8.5 

3.8

18.2 

.2 

10.7 

41.7 

17.8

5.5 

1.3

20.7 

.2 

14.8 

43.3 

13.1

3.5 

1.0

14.4

10.1 

25.5 

30.7 

1.3

7.2 

3.7

0.8

.8 

11.0 

38.6 

6.8 

22.5 

13.6

26.0 

.3 

8.3 

32.3

22.8

2.5 

2.9

25.7 

1.4 

14.2 

39.0 

11.9

3.2 

1.6

29.2 

2.5 

5.0 

40.7 

17.3

1.7 

.9

31. 6 2. 3 10. 7 

2.7 ..-....-...-.......-

5. 6 .4 1. 2 

39. 9 11. 9 21. 4 

16. 6 42. 0 36. 8 

........... 6.2 2.4

1.0 19.7 11.3 

1. 2 13. 0 7. 2

21.8 

.6 

8.3 

28.1 

27.3

5.0

2.4

.......... .4

.......... .1

1. 4 1. 7 

2. 7 1. 5 

1.4 .4

98. 3 98. 3

1.7 

1.6 

.8

99.7

2.87 

1.98 

.85 

.32

99.35

1.9 

1.3

.8

99.5

1.9 

.9 

.6

99.3

2.6 

1.1 

.4

99.5

1.7 

.8 

.3

99.4

4.6 

.9 

.4

98.8

3.3 

1.4 

.2 

.2

99.2

2.6 

.9 

.3

.1

99.0

1.2 

.5 

.3

99.1

1.4 

.5 

.2

99.4

.5 1. 6 6. 3 

.3 .8 1. 4 

.1 .3 .4

99. 5 98. 2 99. 1

3.6

1.2 

.6

98.9

percent)

Trace 2

40 19 

60 68 

P,H P,H

12

49 

39 

P,B,H

14

56 

30

13 

16 

48 

23 

P,H

18 

Trace 

54 

27 

P,H

20 

4 

61 

15 

B,H

22 

14 

56 

8 

B,H

18 

5 

53 

24

49 

51

31 

1

57 

12 

B,H

26 

25

42 

7 

B,H

31

61 

8 

B,M

35 8 12

60 39 54 

5 53 35 

B,M H P,H

26 

2 

62 

10 

B,H

(For locality descriptions, see following page.)
BIO SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

LOCALITIES FOR TABLE 1

1. Quartz diorite; 40°30'30" N., 122°40'30" W. (Albers, 1964, 

table 2).

2. Granodiorite; 40°40' N., 122°47' W. (Lanphere and others, 1968, 

table 8, sample 35).

3. Quartz diorite; 40°34' N., 122°44' W. (Albers, 1964, table 2).

4. No name given; approximately 40°29' N., 122°37' W. (Albers, 

1964, table 2, sampie A).

5. Quartz diorite; 40°36' N., 122°39' W. (Albers, 1964, table 2).

6. Granodiorite; 40°45' N., 122°li9' W. (Lanphere and others, 1968, 

table 5, sample 22).

7. Quartz diorite; 40°44' N., 122°19' W. (Hinds, 1935, p. 345).

8. No name given ; 40°44' N., 122°19' W. (Hinds, 1935, p. 345).

9. Pyroxene diorite; 40°27' N., 123°4' W. (Lanphere and others, 1968, 

table 6).

10. Syenodiorite; 40°47' N., 123°25' W. (Lanphere and others, 1968, 

table 6, sample 23).

11. Syenodiorite; 40°35' N., 123°15' W. (Lanphere and others, 1968, 

table 6).

12. Syenodiorite; 40°36' N., 123°16' W. (Lanphere and others, 1968, 

table 6).

13. Syenodiorite; 41°05'30" N., 123°34' W. (Lanphere and others, 

1968, table 6, sample 24).

14. Syenodiorite; 41°16' N., 123°18'30" W. (Lanphere and others, 

1968, table 6, sample 25).

15. Calcic trondhjemite; approximately 41°!' N., 122°58' W. (Davis, 

1963, p. 344).

16. Quartz diorite; approximately 41°12' N., 122°58' W. (Holdaway, 

1962).

17. Quartz diorite; approximately 41°10' N., 122°58' W. (Holdaway, 

1962).

18. Granodiorite; approximately 41°8' N., 122°58' W. (Holdaway, 

1962).

19. Pyroxene diorite; approximately 41°17' N., 122°54'30" W. (Romey, 

1962).

20. Diorite; approximately 41°16' N., 122°57'30" W. (Romey, 1962).

21. Quartz diorite; approximately 41°16' N., 122°57'30" W. (Romey, 

1962).

22. Granodiorite; approximately 41°17'30" N., 122°54'30" W. (Romey, 

1962).

23. Granodiorite; approximately 41°24' N., 122°57' W. (Romey, 1962).

24. Trondhjemite; 41°13'30" N., 122°43' W. (Lanphere and others, 

1968, table 8, sample 33).

25. Quartz diorite; 40°41' N., 122°45' W. (Lanphere and others, 1968, 

tables, sample 34).

26. Granodiorite; 41°11'30" N., 122°19' W. (Lanphere and others, 

1968, table 5, sample 21a).

27. Quartz diorite; 41°20' N., Ii23°12' W. (Seyfert, 1965, p. 80).

28. Granodiorite; 41°24' N., 123°13' W. (Seyfert, 1965, p. 80).

29. Quartz diorite; 40°41' N., 122°45' W. (Lanphere and others, 

1968, table 8, sample 36).

30. Granodiorite; 40°41' N., 122°45' W. (Lanphere and others, 1968, 

table 7).

31. Granodiorite; 41°22' N., 123°15' W. (Seyfert, 1965, p. 80).

32. Diorite; 41°20'30" N., 123°22'30" W. (Lanphere and others, 

1968, table 7).

33. Granodiorite; 41°21' N., 123°24' W. (Lanphere and others, 1968, 

table 7).

34. Gabbro; 41°47'30" N., 122°50' W. (Lanphere and others, 1968, 

table 7).

35. Diorite; 41°48' N., 122°51'30" W. (Lanphere and others, 1968, 

table 7).

36. Quartz diorite; 41°47'30" N., 122°51'30" W. (Lanphere and others, 

1968, table?).

37. Quartz diorite; 41°48' N., 122°56' W. (Lanphere and others, 1968, 

table 7).

38. Quartz diorite ; 41°48'30" N., 122°45'30" W. (Lanphere and others, 

1968, table?).

39. Quartz diorite; 41°46'30" N., 122°54'30" W. (Lanphere and others, 

1968, table 7).

40. Quartz diorite ; 41°49' N., 122°46' W. (Lanphere and others, 1968, 

table 7, sample 32).

41. Quartz monzonite; 41°48'30" N., 122°45'30" W. (Lanphere and 

others, 1968, table 7).

42. Gabbro; 41°56'45" N., 122°45'45" W. (Lanphere and others, 1968, 

table 7).

43. Gabbro; 41°58'45" N., 122°46'30" W. (Lanphere and others, 1968, 

table 7).

44. Quartz diorite ; 41°56'45" N., 122°45'15" W. (Lanphere and others, 

1968, table 7, sample 31).

45. Quartz diorite; approximately 42°1'30" N., 122°47' W.; new 

analysis.

46. Granodiorite; 42°10'30" N., 122°44'30" W.; new analysis.

47. Granodiorite; 41°58'15" N., 122°46'15" W. (Lanphere and others, 

1968, table 7, sample 30).

48. Quartz diorite; 42°20' N., 122°58'30" W.; new analysis.

49. Granodiorite; 42°26'30" N., 122°59'45" W.; new analysis.

50. Quartz diorite; 42°7'45" N., 122°59'45" W.; new analysis.

51. Gabbro; 42°9'30" N., 123°19'30" W. ; new analysis.

52. Quartz diorite; 42°8'30" N., 123°21'30" W.; new analysis.

53. Quartz monzonite; 42°28'45" N., 123°21' W. ; new analysis.

54. Trondhjemite; 42°41' N., 123°2'30" W.; new analysis.

55. Trondhjemite; 42°39'30" N., 123°3' W.; new analysis.

56. Quartz gabbro; 42°33'15" N., 123°41' W.; new analysis.

57. Quartz gabbro; 42°22'30" N., 123°48'30" W. ; new analysis.

58. Quartz diorite; ;4i2°3i3' N., 12'3°42' W.; new analysis.

Klamath Mountains. Most of them occur in the Trinity 

Mountains plutonic belt (fig. 10; Lanphere and others, 

1968), where they range in age from 127 to 140 m.y. 

(million years). Only one, the White Eock pluton, has 

been recognized in Oregon. Muscovite from this pluton 

yielded a potassium-argon age of 138 m.y.

The trondhjemites are essentially light-colored 

oligoclase-quartz diorites. Those whose plagioclase is 

andesine, Davis (1963) called calcic trondhjemite. 

Mica is the predominant mafic mineral. In the California plutons, biotite is the chief mica and is accompanied by some muscovite; however, muscovite is 

the predominant mica in the White Rock pluton. Hornblende is either absent or present in subordinate 

amounts.

The Mule Mountain stock in the southern Klamath 

Mountains is mostly trondhjemite (Kinkel and others, 

1956, p. 43^8). It is extensively altered and silicified 

and is associated with albite granite that may have 

been formed by albitization of the trondhjemite (Albers, 1964, p. J34). The Mule Mountain trondhjemite 

has been interpreted to have formed in large part by 

metasomatism (Albers, 1964, p. J35).

On the modal quartz-plagioclase-potassium feldspar 

diagram (fig. 4) the trondhjemites plot in the upper 

part of the quartz diorite field near and on the 

quartz-plagioclase join.

GRANODIORITE

Rocks classified as granodiorite seem less abundant 

than quartz diorite, but this may be because of inadequate sampling and insufficient mapping of most of the 

Klamath plutons. In some of the larger plutons that 

have been more thoroughly studied, granodiorite is predominant. For example, the rock type of about twothirds of the English Peak (Seyfert, 1965), the Russian 

Peak (Davis and others, 1965), and the Shasta Bally 

(Albers, 1964) plutons is granodiorite. The central part 

of these plutons is granodiorite; the outer parts are 

composed of quartz diorite or more-mafic rocks.

The granodiorites are typically medium-grained 

hypidiomorphic-granular rocks which are slightly 

porphyritic in places. Their color index is commonly 

about 10, but ranges from as little as 5 to as much as 30. 

The quartz content is greater than 10 percent and is 

as high as approximately 30 percent. The ratio of 

potassium feldspar to total feldspar is from about 

one-tenth to one-third.

Plagioclase, the most abundant light-colored constituent, is subhedral to euhedral, well twinned, and 

zoned. Most commonly it is fresh, although the internal 

parts of crystals may be somewhat saussuritized. The 

composition of individual crystals varies widely, but 

the average anorthite content is most commonly 

An2 o-An4 o (medium oligoclase to medium andesine).
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON Bll

Quartz is in anhedral interstitial grains, and almost 

all is strained. Anhedral potassium feldspar occurs 

interstitially also, and commonly it markedly embays 

and encloses plagioclase. Some of the granodiorite 

from the Castle Crags pluton is porphyritic, with subhedral to euhedral phenocrysts of potassium feldspar 

poikilitically enclosing corroded grains of plagioclase. 

The potassium feldspar most commonly appears as untwinned microperthitic bodies, but in some specimens 

it shows microcline twinning. Myrmekite is common on 

the boundaries between potassium feldspar and 

plagioclase.

The chief mafic minerals are green hornblende and 

biotite. Biotite is commonly more plentiful than hornblende, but in some specimens the two are of approximately equal abundance. Biotite is anhedral, and 

hornblende subhedral to euhedral. Biotite is partly 

replaced by chlorite in some specimens.

Clinopyroxene (augite) is a minor constituent of 

a few of the granodiorites. Almost invariably it is 

rimmed by hornblende. An unusually pyroxene-rich 

granodiorite occurs apparently as a small satellitic body 

in the southern part of the Ashland pluton. Specimens 

of this rock, which contain about 11 percent quartz, 

10-13 percent potassium feldspar, and approximately 

45 percent zoned plagioclase (An60-An40 ), contain as 

much as 12 percent pyroxene, including hypersthene 

and augite. In one specimen the pyroxene occurs as 

small phenocrysts. Hornblende and biotite are also 

present, the hornblende partly replacing pyroxene.

Other common accessory minerals are magnetite, 

sphene, and apatite. A few small grains of zircon are 

present.

QUARTZ MONZONITE AND ALASKITE

Kocks classified as quartz monzonite (adamellite) 

are apparently rare, but may be more common than 

the limited sampling indicates.

A sample from the central part of the Grants Pass 

pluton is a medium-grained hypidiomorphic-granular 

rock with a color index of 7. Its quartz content is 26 

percent, potassium feldspar 25 percent, and plagioclase 

42 percent. Plagioclase crystals are subhedral and well 

twinned and show oscillatory zoning. The central parts 

range from An25 to An29 , and the rims are sodic 

oligoclase (An15 ). Some zones are saussuritized. Large 

anhedral plates of generally untwinned white potassium feldspar wrap around and poikilitically enclose 

the plagioclase. Quartz forms large anhedral grains. 

Biotite, partly altered to chlorite, is the principal mafic 

mineral, but small amounts of pale-green hornblende 

also are present. Metallic opaque minerals are minor.

A small alaskitic pluton cuts quartz diorite in the eastern part of the Vesa Bluffs pluton. This light-colored 

pinkish fine-grained hypidiomorphic-granular rock contains only about 3 percent dark minerals. Subhedral 

slightly zoned plagioclase (An34 ) is surounded and embayed by anhedral quartz and potash feldspar. The 

potash feldspar all shows microcline twinning. Quartz 

amounts to about 33 percent of the rock, potassium feldspar 24 percent, and plagioclase 40 percent; white mica 

and less than 1 percent of pyrite constitute the balance. 

The mica is in the form of tiny flakes in plagioclase 

(sericite) and as a few larger interstitial flakes of 

muscovite.

The central part of the predominantly granodioritic 

English Peak pluton grades to quartz monzonite (Seyfert, 1965), which constitutes 8 percent of the exposed 

area of the batholith. Quartz ranges from 31 to 34 

percent, potassium feldspar 20 to 24 percent, and 

plagioclase (An2 o-An2 3) 35 to 39 percent. Biotite (5-7 

percent) is the principal mafic mineral and is partly 

chloritized. Hornblende amounts to less than 1 percent.

CHEMICAL DATA AND COMPOSITIONAL 

TRENDS

Fifty-eight chemical analyses of samples from plutons 

in the Klamath Mountains are given in table 1. In addition to analyses of "granitic rocks," some more-mafic 

rocks including diorite and gabbro, which are believed 

to be consanguineous, are also included. The sampling 

is unevenly distributed. Some plutons are represented 

by several analyses, while only a single analysis is 

available for others. The data are probably sufficient, 

however, to demonstrate the broad chemical features 

of the rocks and to illustrate the general trend of their 

variation.

In figure 5 the major oxides are plotted on standard 

silica-variation diagrams. For rocks containing 55 percent SiO2 or more, the trends of the oxides are fairly definite and expectable: as SiO2 increases, A12O3 , total Fe, 

MgO, and CaO decrease, while Na2O and K2O increase. 

The trondhjemitic rocks are, however, obvious exceptions to these general trends: A12O3 is higher than average for the high-silica rocks, Na2O is slightly higher, and 

K2O is markedly below the average. Below 55 percent 

SiO2 the points for A12O3 , total Fe, and MgO are so 

scattered that the trend for these oxides cannot be defined. Obviously, however, some of the specimens from 

the Ironside Mountain pluton contain greater-thanaverage K2 O compared with the other rocks in this silica 

range. The silica-variation diagrams, as applied to these 

rather heterogeneous data, are less informative than 

plots of ternary ratios between various components, 

which are considered in the succeeding discussion.
B12 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

AI 2 03

10

Total Fe 

as FeO

Z

UJ

o

Q£

HJ 10 

Q.

MgO 

n I a 

r Jq i i i

X

O 10

» 

.

 * 

* A . A 

1*1 I .l«wf b I d *

I I I

50 55 60 65 70 

SiO2 CONTENT, IN WEIGHT PERCENT

EXPLANATION

Pyroxene diorite and syenodiorite 

from Ironside Mountain, Forks of 

Salmon, and Wildwood plutons

Trondhjemites from Caribou Mountain, Craggy Peak, and White Rock 

plutons

FIGURE 5. Variation of common oxides in plutonic rocks of 

the Klamath Mountains plotted against SiO2 .

The ternary ratios of the normative minerals quartzorthoclase-piagioclase, derived from the analyses (table 

1), are plotted in figure 6. For comparison, norms of 

some of Nockolds' (1954) average rocks and two of 

Goldschmidt's (1916, p. 79; 1921, p. 20) trondhjemites 

are also plotted on the diagram. The granitic rocks 

(quartz> 10 percent) have a fairly well defined trend 

and plot somewhat closer to average tonalite (quartz 

diorite) and the trondhjemites than to granodiorite. 

Only one rock plots near average adamellite (quartz 

monzonite). The four trondhjemites with their relatively low normative orthoclase are clearly separated 

from other rocks which have approximately equivalent normative quartz and plagioclase. Norms of analyzed specimens from the Ironside Mountain pluton 

and of one specimen from the Forks of Salmon pluton 

fall near the plagioclase-orthoclase join, two near average diorite and one near average mangerite.

In figure 7 both modal and normative quartz-orthoclase-piagioclase of chemically analyzed rocks are 

plotted. With a few exceptions, the modes and norms 

are rather widely separated, and in nearly every instance the normative plot is displaced toward the orthoclase corner. In other words, the analyses show more 

normative orthoclase than modal potassium feldspar.

Ab+An

EXPLANATION

Ironside Mountain, Forks of 

Salmon, and Wildwood plutons

+

Trondhjemites from Caribou Mountain, Craggy 

Peak, and White Rack 

plutons

Average rocks (of Nockolds, 

1954, unless otherwise noted)

All others

FIGURE 6. Normative quartz-orthoclase-piagioclase (Ab+An) 

ratio for plutonic rocks of the Klamath Mountains.
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON B13

EXPLANATION

Ab + An 

(Plagioclase) t Potassium-feldspar)

FIGURE 7. Comparison of modal and normative quartz-orthoclase-plagioclase (Ab+An) ratios for plutonic rocks of the 

Klamath Mountains.

Presumably this is because K2O of biotite and, to a 

lesser extent, of plagioclase and hornblende is calculated 

as normative orthoclase, and the amount of albite in 

solid solution in modal potassium feldspar is insufficient 

to counterbalance this effect. A notable exception is the 

sample from the Grants Pass pluton, whose modal constituents plot in the quartz monzonite field but whose 

normative orthoclase is approximately 11.5 percent 

lower than modal potassium feldspar, which possibly 

contains albite in solid solution. The potassium feldspar, however, shows no perthitic intergrowths under 

the microscope. For about six rocks the plagioclasepotassium feldspar ratio is fairly constant between 

norm and mode, but modal quartz is greater than quartz 

in the norm. The difference is only a few percent for 

most, but for two it is more than 10 percent. The discrepancies probably result from inhomogeneities in the 

material selected for chemical and modal analyses, or 

inadequate sampling, or both.

Two other ternary ratios, Alk-F-M and sodiumpotassium-calcium (figs. 8, 9), illustrate some features 

of the rock chemistry which are not so apparent in the 

normative quartz-orthoclase-plagioclase (Ab + An) diagram and are useful in making comparisons with rocks 

from other provinces. The Alk-F-M diagram shows 

a fairly well defined trend, and the data suggest that 

different plutons and groups of plutons may have 

slightly different chemical characteristics. Analyses for

F=Fe+3 +Fe+2+Mn

Alk = Na+ K M = Mg

EXPLANATION

Ironside Mountain, Forks of Salmon, 

and Wildwood plutons

Ashland and other Oregon 

plutons

Vesa Bluffs pluton

Russian Peak pluton

Trondhjemite

Shasta Bally, Caribou 

Mountain, Deadman 

Peak, Sugar Pine, and 

Craggy Peak plutons

pit River pluton

 

Castle Crags pluton

English Peak and Wooley 

Creek plutons

FIGURE 8. Alk-F-M ratio (cation percent) for plutonic rocks 

of the Klamath Mountains.

the Ironside Mountain and related plutons (Forks of 

Salmon and Wildwood) group closely together in the 

mafic part of the diagram, however, possibly because 

sampling has been insufficient to discover more alkaline 

members of the suite.

The generally sodic composition of the rocks and the 

very slight potassium enrichment along the trend from 

right to left are apparent in the sodium-potassiumcalcium diagram (fig. 9). The trondhjemites are well 

below the general trend, toward the sodium corner, as 

if they were the terminal product of a subsidiary 

branch. Da vis (1963, p. 346-347), Da vis, Holdaway, 

Lipman, and Romey (1965, p. 962) and Lipman (1963, 

p. 1277-1279), on the basis of limited data, first called 

attention to the divergence of quartz dioritic rocks of 

the south-central Klamath Mountains from the calcalkaline trend toward what they called a trondhjemitic 

trend. A similar observation was made by Larsen and 

Poldervaart (1961) for the Bald Rock batholith in the 

northwestern Sierra Nevada.
B14 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

EXPLANATION

Ironside Mountain, Forks of 

Salmon, and Wildwood plutons

Ashland and other Oregon 

plutons

Vesa Bluffs pluton

Russian Peak pluton

T 

Trondhiemite

-AShasta Bally, Caribou 

Mountain, Deadman 

Peak, Sugar Pine, and 

Craggy Peak plutons

Pit River pluton

Castle Crags pluton

English Peak and Wooley 

Creek plutons

FIGURE 9. ScwUum-potassi urn-calcium ratio (cation percent) 

of plutonic rocks of the Klamath Mountains.

AGE

Stratigraphic evidence for the age of the Klamath 

Mountains plutons is sparse. The youngest rocks they 

intrude are of Late Jurassic (Kimmeridgian) age. The 

oldest strata, which lie depositionally on eroded granitic 

plutons, are of Early Cretaceous (Hauterivian) age in 

the southeastern part of the province and of Late Cretaceous (Cenomanian and Turonian) age in the northeastern part of the province. Potassium-argon mineral 

ages have been determined, however, for specimens 

from most of the plutons in the California and Oregon 

parts of the Klamath Mountains (Lanphere and others, 

1968, 1969). In the southern Klamath Mountains, granitic plutons form three fairly well denned belts that are 

differentiated on the basis of age (fig. 10). The oldest 

granitic rocks occur in the eastern Paleozoic belt, where 

the Pit River stock has a minimum age of 246 m.y. 

(Permian). Grouped with this stock is the Castle Crags 

pluton, for which a discordant pattern of mineral ages, 

ranging from 133 to 224 m.y., was obtained. The next 

younger group of plutons includes the Ironside Mountain, Forks of Salmon, and Wildwood plutons. These 

occur in the southwestern part of the province and are 

collectively called the Ironside Mountain plutonic belt. 

They yield ages of 165 to 167 m.y. Between the eastern 

and Ironside Mountain belts and occupying the southcentral part of the province is the Trinity Mountains 

plutonic belt, from which dates of from 127 to 140 m.y. 

were determined. In the central and northern part of 

the province (the northern plutonic area), no clear beltlike distribution is apparent. The mineral ages deter-- 

mined on specimens from the plutons range from 136 

to 160 m.y. Thus, the ages determined from the Klamath 

Mountains plutons, excluding the Pit River and Castle 

Crags bodies, are Middle and Late Jurassic.

COMPARISON WITH PLUTONS OF THE 

WESTERN SIERRA NEVADA

Modal and chemical data are scanty for plutons exposed in the western foothills of the Sierra Nevada. 

Most of the data are for the Merrimac (Hietanen, 1951) 

and Bald Rock (Compton, 1955; Larsen and Poldervaart, 1961) plutons at the north end of the western 

Sierra belt. Data for the small Rocky Hill stock in the 

southern part of the western Sierra belt are also available from a study by Putnam and Alfors (1965). A few 

analyses were obtained from a report by Turner (1894), 

and unpublished data were supplied by L. D. Clark 

(written commun., 1970).

The available modal data are summarized in a ternary diagram (fig. 11) for quartz-plagioclase-potassium-feldspar. The data fall predominantly in the 

quartz diorite and granodiorite fields. The trondhjemitic character of plutons in the northwestern Sierra 

Nevada was observed (Hietanen, 1951; Compton, 1955; 

Larsen and Poldervaart, 1961) before trondhjemites 

were recognized in the Klamath Mountains.

Chemical data for western Sierra plutons are somewhat more abundant than modal data. A normative 

quartz-orthoclase-plagioclase (Ab + An) plot (fig. 12) 

of western Sierra rocks occupies a field essentially like 

that for plutons of the Klamath Mountains (fig. 6), and 

the average trend is also similar. Furthermore, the fields 

on Alk-F-M and sodium-potassium-calcium plots (figs. 

13, 14) are essentially alike for the western Sierra and 

Klamath Mountains.

The ages of plutons in the western Sierra Nevada correspond in general to dates obtained from samples of 

Klamath Mountains plutons. Plutons in the northern 

part of the western Sierra Nevada, west of the Melones 

fault and Mother Lode belt, range from 126 to 146 m.y. 

(Curtis and others, 1958; Evernden and Kistler, 1970).
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON

124° 123° 122 C

B15

42

EXPLANATION

Potassium-argon age, m millions 

of years

H, determined on hornblende 

B, determined on biotite

Oregon ages, M. A. Lanphere, 

oral commun., 1970

California ages, Lanphere, 

Irwin, and Hotz (1968)

41° 

FIGUKE 10. Distribution of dated plutons in the Klamaith Mountains.
B16 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Quartz

Plagioclase Potassium-feldspar

FIGUBE 11. Modal quartz-plagioclase-potassium-feldspar ratio 

for plutonic rocks of the western Sierra Nevada.

COMPARISON WITH PLUTONS OF THE 

CENTRAL SIERRA NEVADA

Previously published modal and chemical data for the 

east-central Sierra Nevada plutons are summarized in 

figures 15-18. The contrast in modal and chemical 

composition between the K-lamath Mountains and eastcentral Sierra Nevada plutons is obvious. In general, the 

rocks of the east-central Sierra Nevada are more potassic, and granodiorite and quartz monzonite are predominant (fig. 15). The averaged trend line of 

normative quartz-orthoclase-plagioclase (fig. 16) for

EXPLANATION

From chemical analysis

Computed from mode 

(Larsen and Poldervaart, 

1961)

Average rocks (of Nockolds, 

1954, unless otherwise noted)

.

/\ Trondhjemite 

N (Goldschmidt, 1916)

FIGUBE 12. Normative quartz-orthoclase-plagioclase (Ab+ 

An) ratio for plutonic rocks of the western Sierra Nevada.

= Fe+3+Fe+2

Alk = Na+ K M=Mg

FIGUBE 13. Alk-F-M ratio (cation percent) for plutonic rocks 

of the western Sierra Nevada.

the east-central Sierra is straight and bisects the diagram from the direction of the plagioclase corner toward the center, and thus the ratio between quartz and 

orthoclase is essentially constant 1:1. This trend contrasts sharply with the trend for the Klamath Mountains plutons, which parallels the quartz-plagioclase 

join to about 30 percent quartz and then bends sharply 

toward the center (fig. 6). The well-defined field of the 

east-central Sierran rocks also encloses the plotted positions of Nockolds' (1954) average granodiorite, adamellite, and granite, whereas the field of the Klamath MounEXPLANATION

+ 

Trondhjemite

FIGURE 14. Sodium-potassium-calcium ratio (cation percent) for plutonic rocks of the western Sierra Nevada.
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON

Quartz F=Fe+3+Fe+2 +Mn

B17

Plagioclase Potassium-feldspar

FIGUBB 15. Modal quartz-plagioclase-potassium feldspar ratio 

for plutonilc rocks of the east-central Sierra Nevada (Bateman 

and others, 1963, fig. 15, p. D30).

tains plutons is more diffuse and enclose average 

tonalite and trondhjemite and just barely encloses average granodiorite. The difference in composition of 

plutonic rocks from the two provinces is also clearly 

illustrated by comparing (figs. 9,18) plots of the ratios 

sodium-potassium-calcium which show the more potassic character of the east-central Sierran rocks.

Bateman and Dodge (1970) recently summarized the 

chemical constitution of the central Sierra Nevada 

batholith from the White Mountains east of the main

EXPLANATION

Average rocks (of Nockolds, 

1954, unless otherwise noted)

FIGURE 16. Normative quartz-orthoclase^plagioclase (Ab+An) 

ratio for plutonic rocks of the east-central Sierra Nevada 

(Bateman and others, 1963, fig. 14, p. D30).

Alk = Na + K M = Mg

FIGURE 17. Alk-F-M ratio (cation percent) for plutonic 

rocks of the east-central Sierra Nevada (computed from 

Bateman and others, 1963, table 3, p. D29).

Sierra Nevada to the western foothills. They tentatively 

assigned the plutons to eight comagmatic sequences 

which were emplaced during five intrusive episodes established by Evernden and Kistler (1970) and which 

range in age from 210 to 79 m.y. ago Late Triassic to 

early Late Cretaceous. The composition of the plutonic 

rocks changes systematically across the Sierra Nevada 

batholith (Bateman and Dodge, 1970) : from east to 

west K2O clearly decreases, Fe2O3 and TiO2 also decrease, and FeO, MgO, and CaO increase. The plutons

FIGURE 18. Sodium-potassium-calcium ratio (cation percent) 

for plutonic rolcks of the east^central Sierra Nevada (computed from Bateman and others, 1963, table 3, p. D-29-).
B18 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

east of the western foothills are obviously more potassic than Klamath Mountains plutonic rocks (fig. 19). 

The limited data from Klamath Mountains plutons do 

not show any east-west compositional trends comparable with those of the Sierra Nevada. The plot of the 

K2O/SiO2 ratios for the Klamath Mountains plutons 

(fig. 19) suggests, however, that within the Klamath 

Mountains province there may be compositionally similar groups of plutons. Certainly, thelronside Mountain 

plutonic belt contrasts sharply with other plutonic belts 

in the Klamath Mountains.

CONCLUSIONS

Plutonic rocks of the Klamath Mountains and the 

northwestern Sierra Nevada have many features in

common. In both provinces the plutons intrude country 

rocks dominated by mafic volcanic rocks and eugeosynclinal sedimentary rocks. Bodies of ultramafic rock are 

abundant in both terranes. The plutonic rocks of both 

provinces have similar compositions, and their ages are 

in general the same. The petrologic and age data add 

support to the concept that the Klamath Mountains 

province is a northwestern continuation of the northwestern Sierra Nevada (Irwin, 1966, p. 28; Davis, 

1969). Equivalents of the more potassic central and 

eastern Sierra plutons are lacking, however, and no 

Klamath Mountains plutons are as young as the Late 

Cretaceous plutons of the east-central Sierra Nevada. 

The few Klamath Mountains plutons that have been 

studied in detail show compositional variations which

EXPLANATION

A

Ironside Mountain, Forks of Salmon, and Wildwood plutons

o

Ashland and otheOregon plutons

 

Vesa Bluffs pluton

V 

Russian Peak pluton

English Peak and Wooley 

Creek plutons

Shasta Bally, Caribou Mountain, 

Deadman Peak, Sugar Pi n e, and 

Craggy Peak plutons

D 

Pit River pluton

 

Castle Crags pluton

A

V

O 

A O

A 

v+

 <!>- O O 

O

Trondhjemites

n 

n

60 80

SiO 2 CONTENT, IN WEIGHT PERCENT 

FIGURE 19. Variation of K2O/SiO2 (weight percent) for plutonic rocks of the Klamath Mountains.
PLUTONIC ROCKS OF THE KLAMATH MOUNTAINS, CALIFORNIA AND OREGON B19

have been attributed to magmatic differentiation, multiple intrusion, assimilation of country rocks, or a combination of these (Davis and others, 1965, p. 962). A 

trend toward rocks of trondhjemitic composition is 

typical of the variation in several plutons; however, 

some have an almost normal calc-alkaline variation 

from diorite or gabbro to quartz monzonite.

Klamath Mountains plutons are relatively small, 

widely scattered bodies which vary considerably in texture and composition. Limited isotopic data suggest, 

however, that they can be assigned to three or possibly 

four groups according to age (Lanphere and others, 

1968; 1969). Most of the plutonism occurred during the 

Middle and Late Jurassic Nevadan orogeny, during 

which there was also widespread regional metamorphism. Two small plutons in the eastern part of the 

province are pre-Nevadan and may be late Paleozoic. 

An older metamorphic event (Devonian) for which no 

contemporaneous plutonism has been recognized is recorded by rocks of the central metamorphic belt.

Moore (1959) called attention to fundamental differences in the composition of granitic rocks in the western United States on the basis of their geographic distribution and proposed the concept of the "quartz 

diorite boundary line." Granitic rocks west of the line 

are dominantly quartz diorite, and those to the east are 

dominantly quartz monzonite and granodiorite. The 

Klamath Mountains province and the western Sierra 

Nevada are west of the quartz diorite line, and their 

plutons have quartz diorite affinities.

Differences in composition east and west of the quartz 

diorite line have been attributed to fundamental compositional differences in the crust existing before emplacement of the granitic rocks: rocks east of the line 

were generated in a thick sialic layer with an initially 

higher K2O content, whereas rocks west of the line originated in the sima or a thinner sialic layer with abundant geosynclinal sediments and volcanic rocks (Moore, 

1959). It has also been suggested that age of emplacement may have been the factor controlling the difference 

in composition between the plutons of the Klamath 

Mountains and the central Sierra Nevada (Davis, 1963, 

p. 347; Davis and others, 1965, p. 963). As more data 

become available, however, it appears that composition 

is more dependent on position than on time of intrusion 

(Bateman and Dodge, 1970; Evernden and Kistler, 

1970 ;Eoss, 1969).

Bateman and Eaton (1967) postulated that granitic 

magmas of the Sierra Nevada were formed by anatexis 

in axial parts of a complex synclinorimn on the margins 

of the continent. Westward decrease of K2O in the plutonic rocks reflect progressive changes in composition

of the geosynclinal rocks from epiclastic and carbonate 

sediments in the east to mafic volcanic and volcanicderived sediments in the west. An alternate explanation 

for the observed change in K2O content of the plutonic 

rocks from west to east is offered by recently published 

hypotheses correlating increase of K2O in volcanic 

rocks toward the continents with increased depths of 

magma generation along or above landward-dipping 

subduction zones at continental margins (Dickinson, 

1968; Dickinson and Hatherton, 1967; Hatherton and 

Dickinson, 1969). Applied to the California plutonic 

belt, these hypotheses would suggest that plutonic rocks 

of the Klamath Mountains and western Sierra crystallized from magmas generated at shallower depths along 

an eastward-dipping subduction zone than magmas 

which formed the central and eastern Sierra Nevada 

plutons.

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