Distribution of Minor Elements 

in Biotite Samples From 

Felsic Intrusive Rocks as a 

Tool for Correlation

GEOLOGICAL SURVEY BULLETIN 1314-D

Distribution of Minor Elements 

in Biotite Samples From 

Felsic Intrusive Rocks as a 

Tool for Correlation

By TOM G. LOVERING

CONTRIBUTIONS TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1314-D

Differences in minor-element concentrations in biotite can be used to distinguish 

different intrusives of similar composition 

in the same area

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director

Library of Congress catalogue-card No. 76-183756

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

Washington, D.G. 20402 - Price 25 cents (paper cover)

STOCK NUMBER 2401 1224
CONTENTS

Abstract.. _ _______________________________________

Introduction. _____________________________________

Previous investigations.____________________________

Source and description of samples ___________________

Analytical methods._______________________________

Analytical data and discussion._____________________

Southern Arizona._____________________________

Southern Rocky Mountains, Colo_______________

Great Basin, Nev. and Utah____________________

Northern Rocky Mountains, Idaho and Mont____

Cascade Range, Wash-________________________

Regional variations and variation with age of intrusive. 

Conclusions__ _____________________________________

References cited___________________________________

Page 

Dl

2

4

5

8

9

16

17

22

23

26

26

28

ILLUSTRATIONS

Page 

FIGURE 1. Index map showing locations of study regions and intrusive

rock bodies sampled___________-_______---__-_____--_ D3

2. Graph showing trends in minor-element distributions in 

biotite samples from composite Ruby Star Granodiorite 

stock ______________________________________________ 14

3. Histograms showing titanium content of biotite from felsic

intrusive rocks of various ages__________-_______-____- 27

TABLES

Page 

TABLE 1. Description of biotite samples._________________________ D6

2. Spectrographic analyses of biotite samples from igneous 

rocks of the Sierrita and Santa Rita Mountains of southern 

Arizona.___________________________________________ 10

3. Distinguishing features of minor-element contents of biotite

from igneous intrusives of southern Arizona ____________ 15

4-7. Spectrographic analyses of biotite samples from igneous 

rocks of the:

4. Southern Rocky Mountains, Colo________________ 18

5. Great Basin, Nev. and Utah________.____________ 20

6. Northern Rocky Mountains, Idaho and Mont____ 22

7. Cascade Range, Wash___-____.________________- 24

CONTRIBUTIONS TO GEOCHEMISTRY

DISTRIBUTION OF MINOR ELEMENTS

IN BIOTITE SAMPLES FROM FELSIC

INTRUSIVE ROCKS AS A TOOL FOR

CORRELATION

By TOM G. LOVERING

ABSTRACT

Biotites separated from suites of samples from 20 bodies of felsic intrusive 

rocks in the Western United States were analyzed by a semiquantitative spectrographic method to investigate differences in the minor elements that might characterize the biotites from different intrusives with similar composition in the 

same region. The samples were taken from five regions: southern Arizona, the 

southern Rocky Mountains of Colorado, the Great Basin of Nevada and western 

Utah, the northern Rocky Mountains of Idaho and Montana, and the Cascade 

Range of Washington. The intrusives sampled range in composition from syenite 

to quartz diorite and in age from early Precambrian to Tertiary.

Different intrusives with similar composition in the same region generally 

exhibit characteristic differences in the concentration of one or more minor 

elements in their biotites. Regional differences are more subtle, but there appears 

to be a tendency toward high titanium in biotites from southern Arizona, high 

chromium in those from the southern Rocky Mountains of Colorado, high niobium 

in samples from the northern Rocky Mountains of Idaho and Montana, and low 

strontium in those from the Cascade Range of Washington. Titanium is the only 

minor element whose concentration in biotite appears to be related to the age 

of the rock from which it was taken. Biotite from the Precambrian intrusive 

rock samples generally contains 1 percent or less of this element; biotite from 

samples of Tertiary intrusives commonly contains 1.5 percent or more.

Dl
D2 CONTRIBUTIONS TO GEOCHEMISTRY

INTRODUCTION

The investigation whose results are here summarized was an extension of an earlier study on the minor-element content of biotite samples 

from igneous rocks (Lovering, 1969), in which it was shown that 

biotite may contain many minor elements that range widely in concentration. This observation led to the hypothesis that biotites crystallising from different bodies of magma might exhibit differences in 

their minor-element contents that reflect differences in concentrations 

of these elements in the fluids present in the magma, chambers at the 

time of biotite crystallization.

Biotite was separated from three or more samples of felsic rock 

from each of two or more intrusives in five regions in the Western 

United States (fig. 1) and analyzed by a semiquantitative spectrographic method. The rocks sampled range in composition from syenite, through granite, quartz monzonite, :and granodiorite, to quartz 

diorite. Some of the intrusives represented by these samples are composite plutons of variable composition, some are relatively homogeneous stocks, and a few are separate small intrusives known to have 

had a common magmatic source.

Unfortunately, only the biotite separates were available to the 

author, and therefore no comparison was possible 'between the minorelement content of the biotite separates and that of the parent rock 

samples from which the biotites were derived. However, such comparisons have been published (Nockolds and Mitohell, 1946), and 

they indicate that the concentrations of some minor elements in biotite 

may be very different from those in the host rock and that some rocks 

in a differentiated sequence may actually show trends in the concentrations of certain minor elements that are opposite to trends in the biotite separated from them.

In primary biotite separated from representative samples of the 

same intrusive, the pattern of minor-element distribution varies, but 

certain elements are commonly present in abnormally 'high or abnormally low concentrations, in comparison with concentrations of 

the same elements in biotite from a different intrusive of similar 

composition in the same area. Such characteristic patterns in the 

minor-element content of biotite may be useful for determining the 

magmatic affiliations of small dikes, plugs, and sills, for estimating 

the probable source of float samples in areas that contain numerous 

intrusive bodies, and for interpreting isolated rock outcrops in covered areas.
MINOR-ELEMENT DISTRIBUTION, BIOTITE D3

-T-TMONTANA

^CASCADE I \ 

*21 RANGE I V

^WASHINGTON I \

"~"^ ( vvx:H*:' NORTHERN

/to .,:.-.-:S?;*:-- :: '"ROCKY MOUNTAINS 

/ 18 x;p':- i . 

/ S _rvf

OREGON ') " ' N I IDAHO I

 J T H

' I

WYOMING

ROCKY MOUNTAINS

«.?*:!:

UTAH

10- ^SSSiSi'l 1 li

COLORADO

V ARIZONA

 --Y SOUTHERN 

^--^ ARIZONA

200

r

i i

i NEW MEXICO \ \

400 MILES 

_J

FIGURE 1. Locations of study regions (stippled) and intrusive rock bodies 

sampled. Numbers refer to localities listed in table 1.

Thanks are given to Richard Marvin, who supplied the biotite 

samples from the northern and southern Rocky Mountains and from 

the Great Basin of Nevada; to Joan Engel, who provided samples 

from the Cascade Range in Washington; to John Cooper and Harald 

Drewes, who collected the rock samples from Arizona; and to George 

Cone, who separated the biotite from the latter samples. I also thank 

Wallace Griffitts for allowing me to use analytical data on biotite 

samples he separated and had analyzed from rocks of the Ibapah stock 

in western Utah.
D4 CONTRIBUTIONS TO GEOCHEMISTRY

PREVIOUS INVESTIGATIONS

The composition of biotite separated from igneous rocks has been 

studied and reported in the literature by many investigators since the 

late 1940's. Some of these investigations concerned the variation in 

composition of biotite from different genetically related composite intrusives, some dealt with partition of elements between biotite and 

host rock or between biotite and other coexisting minerals in the rock, 

some compared the concentrations of certain ore metals in biotite from 

igneous rocks genetically related to deposits of these metals with those 

in biotite from petrologically similar "barren" intrusives, and others 

compared the composition of biotite from igneous intrusives with that 

of biotite from the metamorphic rocks they intrude.

Nockolds and Mitchell (1946) studied the variation of about a dozen 

elements in biotites separated from various facies of several composite 

intrusives in the Scottish Highlands. Barsukov (1957) compared the 

tin content of biotite from tin-bearing granites of Russia with that of 

biotite from granites in the same region that are not associated with 

tin deposits.

Several papers dealing with various aspects of the composition of 

biotite from igneous rocks were published in 1963. Erickson and Blade 

(1963) compared the concentrations of minor elements in biotites from 

the alkalic complex at Magnet Cove, Ark., with those in the host rocks 

for these biotites. Wenk, Schwander, Hunziker, and Stern (1963) 

determined major and minor constituents of biotite from pegmatites 

and various metamorphic rocks in the Tessin Alps of Switzerland. 

Parry and Nackowski (1963) made a statistical study of the distributions of copper, lead, and zinc in multiple samples of biotite from both 

mineralized and unmineralized quartz monzonite stocks of the Basin 

and Range province in Utah and Nevada. They made the important 

observation (p. 1142) that the biotite in each stock has its own characteristic base-metal population. Putman and Burnham (1963) reported the results of a systematic study of the composition of ferromagnesian mineral concentratas taken from samples of seven major 

plutons in northwestern and central Arizona. These concentrates 

consisted largely of biotite, mixed in varying proportions with chlorite, hornblende, and pyroxene. Putman and Burnham noted (p. 74) 

a significant difference in the pattern of minor-element distributions in 

the ferromagnesian mineral concentrates from the various plutons. 

Ishikawa, Shibata, and Negishi (1963) determined the concentrations 

of major constituents plus seven minor elements in biotite separates 

from a succession of related granitic intrusives in the Dando-San 

district of Japan.
MINOR-ELEMENT DISTRIBUTION, BIOTITE D5

Analyses of single biotite separates from several granitic intrusive 

rocks in various parts of Canada and of replicate separates from 

granodiorite and quartz inonzonite f acies of the White Creek batholith 

in British Columbia were reported by Rimsaite (1964).

Physical chemical studies on the partition of specific elements between coexisting biotite and hornblende in igneous rocks in relation 

to the composition of the host rock were made by Gottf ried and Dinnin 

(1965), Greenland, Gottf ried, and Tilling (1968), and Tilling, 

Greenland, and Gottf ried (1969).

Bradshaw (1967) studied the distribution of selected elements in 

biotite, muscovite, and feldspar from several granitic intrusive rocks 

in Great Britain in relation to mineralization.

The variations in compositions of biotites from plutons in the Sierra 

Nevada batholith of California in relation to changes in physical and 

chemical conditions in the magma chambers during the time of biotite 

crystallization were discussed by Dodge and Moore (1968) and Dodge, 

Smith, and Mays (1969). A somewhat similar study of the relationship 

between the composition of biotite and that of its host rock, concerning 

both intrusive and extrusive rocks, was made by Dupuy (1968) on 

granodiorite samples from Elba and ignimbrite samples from Italy.

Sobolev, Sitnin, and Dorokhov (1968) presented data on the variations in concentrations of selected minor elements in biotite, muscovite, and chlorite from different phases of intrusive igneous 

complexes in central Kazakhstan as these variations relate to the 

ages of the intrusives. Haack (1969) and Lovering (1969) summarized the minor-element content in biotite from igneous rocks.

SOURCE AND DESCRIPTION OF SAMPLES

One hundred and five samples of primary biotite representing 20 

felsic intrusive rock bodies in five regions of the Western United 

States were used in this study. Splits of all but the three samples 

representing the Ibapah stock in Utah were examined to determine 

the amount and nature of mineral impurities and the characteristic 

color of the biotite. The locations, ages, and general compositions 

of the parent intrusives are given in table 1 together with the number 

of samples from each intrusive and a brief description of the biotite. 

Locations of the intrusives are indicated by latitude and longitude 

coordinates for a point within each intrusive.

Only the samples from southern Arizona were collected for the 

specific purpose of studying the composition of biotite. Samples 

from the other four regions were taken for age determinations based 

on potassium-argon isotope studies of the biotite. Consequently, the

443-522 O - 71 - 2
D6 CONTRIBUTIONS TO GEOCHEMISTRY

Southern Arizona

TABLE 1. Description

Loc. Name of intrusive 

(fig. 1)

Number 

of Type of rock 

samples

Location of 

intrusive

Lat.N. Long.W.

Geologic age

1 Ruby Star Granodiorite 

2 Do.....................

3 Continental Qranodiorite..

17 Qranodiorite.

5 Quartz monzonite por3 Qranodiorite and quartz 

monzonite.

31°55' 111°09' Paleocene.....

31°53' 111°09' .....do.........

31°48' 110°47' Precambrian..

31°45' IVPBff Late Cretace5 

6

diorite.

Do .........

4

4 Quartz latite porphyry ....

31°54' 

31°52'

110°46' 

110°45'

ous. 

Paleocene- 

.... .do ... ...

Southern Rocky Mountains, Colo.

7 

8

9 

10

11

Boulder Creek Granite.

St. Kevin Granite. ..---.

Do. ...............

7

4

4

3

Granite to quartz 

monzonite. 

.-..do ..................

39°55' 

39°40/

39°20' 

38°18'

38°20'

105°20' 

105°45'

106°30' 

106°56'

105°29'

Precambrian. . 

.-..do ..-..

.....do.... ..

Early Precambrian. 

Late Precambrian.

Great Basin, Nev. and Utah

12 Snake Range stock..

13 Ibapah stock (Utah).

14 Unnamed --.......

15 Climax stock........

16 Unnamed.

5 Quartz monzonite......... 38°50/ IU°W Jurassic.......

3 . do..................... 39°55' 113PBV Tertiary ......

3 Qranodiorite-..--.---.-... 40°45' 118°25' Cretaceous....

5 Quartz monzonite to 37°15' 116°04' Jurassic..... _.

granodiorite. 

4 Qranodiorite- - - - 40°20/ 115°30/ Tertiary ......

Northern Rocky Mountains, Idaho and Mont.

17 Boulder batholith 

(Montana)

18 Idaho batholith (Idaho)...

45°50/ 6 Qranodiorite to quartz

monzonite. 

4 Qranodiorite..---- 45'W 115°25' .....do

Cretaceous. 

Cascade Range, Wash.

19 Chilliwack batholith.

20 Ten Peak pluton....

21 Mount Stuart batholith_

22 Similkameen batholith.-...

5 Quartz monzonite to 48°52' 121°30/ Tertiary.. 

granodiorite. 

3 Quartz monzonite.----...- 48°00' 121°00' Cretaceous..-.

6 Quartz diorite -- . 47°30' 121°00' .....do.........

4 Syenite to quartz diorite.. 48°45' 119°45' Cretaceous (?).

1 Color terms are from Qoddard and others (1948).
MINOR-ELEMENT DISTRIBUTION, BIOTITE D7 

of biotite samples

Mineral impurities 

Color of biotite i

Mineral grains in samples Mineral inclusions in biotite

Southern Arizona Continued

Dark brown (SYR 3/2) to med- Chlorite, hornblende, sphene ±10 Apatite, rutile, ilmenite, zircon ±5

ium olive brown (5F 4/4). percent. percent. 

Dark brown (5KB 3/2)______ Chlorite, sphene ±10 percent_... Apatite, ilmenite, rutile, zircon

±10 percent. 

Medium olive brown (5F4/4)____ None. __-_.-.______..-.___.. Minor chlorite <5 percent.

Medium brown (5FB 3/4)_.__ Hornblende 10 percent, chlorite Ilmenite, sphene ±10 percent.

10 percent. 

Dark yellowish brown (10YR 4/2). Chlorite, sphene, plagioclase 10 Hematite, apatite, zircon ±5

percent. percent. Medium brown (SYR 4/4)-.----.- Cnlorite, sphene ±10 percent___ Apatite, rutile, ilmenite ±5 percent

Southern Rocky Mountains, Colo. Continued

Medium olive brown (5F4/4),-.. Chlorite, feldspar <5 percent__. None, 

-----do__-___---.__._.- Muscovite <5 percent............. Apatite, zircon <5 percent.

Medium brown (SYR 4/4)..._.. None_._.___...__.__ Apatite <5 percent. Medium olive brown (5F4/4).... Feldspar <5 percent- ______ Apatite, rutile <5 percent.

Light brown (5KB 5/6)_.___ Hornblende, feldspar, chlorite Do.

<5 percent.

Great Basin, Nev. and Utah Continued

Medium yellowish brown Horblende, feldspar ±10 percent.. None.

(10FR5/4).

No information.___.___.. No information....._..----._. No information. 

Medium olive brown (5F 4/4).... Hornblende, chlorite ±5 percent.. Rutile <5 percent. 

__do..___..._._...__ Chlorite ±10 percent__._____ Rutile, apatite, ilmenite ±5

percent, 

.-...do.-.- __.________ None......--._.______._ Apatite <5 percent.

Northern Rocky Mountains, Idaho and Mont. Continued

Medium brown (SYR 3/4)_..... Chlorite ±10 percent_____._ Rutile, apatite, ilmenite ±5

percent. 

.._do.... __..._.____ Chlorite <5 percent______... None.

Cascade Range, Wash. Continued

Variable_____..-.______ Magnetite, hornblende <5 per- Apatite, chlorite <5 percent.

cent. 

Light brown (SYR 5/6)____... Hornblende, chlorite, hematite Apatite, zircon, rutile <5 percent.

<5 percent. Medium brown (5FR 4/4)____ Hornblende, chlorite <5 percent.. None.

Medium olive brown (5Y 4/4)__ Hornblende, chlorite ±5 percent.. Apatite, sphene, hematite <5

percent.
D8 CONTRIBUTIONS TO GEOCHEMISTRY

nature and distribution of the rock bodies represented in these four 

regions were determined by the availability of replicate samples, 

and the bodies are more widely separated geographically than those 

in southern Arizona.

The intrusive bodies sampled are medium- to coarse-grained alkalic plutonic rocks except for the quartz latite porphyry from Arizona, which consists of three genetically related hypabyssal intrusive 

pipes. Most of the intrusives range in age from Jurassic to Tertiary, 

but one in Arizona and all in Colorado are Precambrian.

The color of the biotite ranges from olive brown through medium 

brown to dark brown. Grains of chlorite, hornblende, feldspar, 

sphene, magnetite, hematite, or muscovite are present in some of the 

mineral separates, and the biotite flakes commonly contain inclusions 

of apatite, rutile, sphene, zircon, hematite, or ilmenite; some of the 

biotite flakes show partial alteration to chlorite. The total amount 

of such mineral impurities ranges from <5 to about 20 percent.

ANALYTICAL METHODS

All the biotite samples were analyzed in the Analytical Services 

Laboratories of the U.S. Geological Survey in Denver, Colo., by a 

semiquantitative spectrographic method in which concentrations of 

an element are reported as the midpoints (0.1, 0.15, 0.2, 0.3, 0.5, 0.7, 

and 1.0, and so forth) of six geometric intervals per order of magnitude. Precision of the reported value is approximately plus or minus 

one interval at 68-percent confidence and plus or minus two intervals 

at 95-percent confidence. The method is a refinement of the three-step 

method described by Myers, Havens, and Dunton (1961). Sensitivity 

of the method varies from element to element.

ANALYTICAL DATA AND DISCUSSION

Analytical data on the biotite samples from igneous rocks in each 

of the five regions southern Arizona, southern Rocky Mountains, 

Great Basin, northern Rocky Mountains, and Cascade Range are 

presented and discussed separately to facilitate the comparison of 

minor-element suites in biotite from different rock bodies of similar 

composition in the same area. The smallest region, and also the one 

best represented both by number of rock bodies and by number of 

biotite samples, comprises the Sierrita and Santa Rita Mountains of 

southern Arizona.
MINOR-ELEMENT DISTRIBUTION, BIOTITE D9 

SOUTHERN ARIZONA

Primary biotite was separated from unaltered samples of three distinct but closely related rock types of the composite Ruby Star 

Granodiorite pluton on the east flank of the Sierrita Mountains; 

biotite was also separated from samples of three unrelated intrusive 

plutonic rock bodies that are similar in composition to each other 

and to the Ruby Star Granodiorite and from samples of several 

hypabyssal quartz latite porphyry plugs in the Santa Rita Mountains, 

a larger mountain range about 15 miles east of the Sierrita Mountains 

across the Santa Cruz River valley. Analytical data on the biotite 

samples from these rocks are presented in table 2.

The Ruby Star Granodiorite in the Sierrita Mountains is a large 

composite southward-plunging stock of Paleocene age composed predominantly of three rock types: an equigranular border facies of 

granodiorite, a porphyritic core facies of granodiorite, and a quartz 

monzonite porphyry at the south end of the stock. The porphyry has 

intrusive contacts with the granodiorite in some places and gradational contacts in others. The large disseminated-copper ore bodies 

of the Esperanza and Sierrita mines are near the southern edge of 

the quartz monzonite.

Samples of biotite from these rocks provide an opportunity to investigate progressive changes in the composition of this mineral during 

the crystallization and differentiation of a rather large magmatic 

body, in which the equigranular border facies of the granodiorite is 

the oldest facies, the porphyritic core facies is intermediate, and the 

quartz monzonite porphyry is the youngest.

Some of the minor elements show progressive changes in concentration through the three rock types, some show distinctly different 

concentrations in one rock type relative to the other two, and some 

show little difference in concentration among the three rock types. 

Chromium and nickel seem to decrease and zirconium, strontium, 

copper, niobium, and tin seem to increase progressively in biotites 

from the border facies granodiorite through the core facies granodiorite to the quartz monzonite porphyry (fig. 2). Copper shows a 

tremendous variation in samples from the two granodiorite facies; 

the concentration of this element in the biotite seems to decrease 

systematically outward from a center of copper mineralization in the 

quartz monzonite porphyry, as shown previously by Lovering, Cooper, 

Drewes, and Cone (1970).
D10 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 2. Spectrographic analyses (in percent) of biotite samples from 

[Analysts, J. L. Finley and E. H. Heldel. N, looked for but not detected; D, detected but below threshold

Element (threshold of detection in parentheses) Rock body and rock type Sample 

No. Ca Na Ti Mn 

(0.005) (0.05) (0.0002) (0.0001)

Sierrita Mountains

Paleocene Ruby Star Granodlorite; equigranular border facies.

Paleocene Ruby Star Granodiorite; porphyritic

core facies.

Paleocene Ruby Star Granodiorite; quartz monzonite porphyry at south end of pluton.

T9

T6

T91

T165

T7

T8

1-3-5

T166

T452

T453

T454

T455

T92

T465

T466

T456

T457

T94

T467

T468

T469

T470

0.1

1.0

.2

.3

.7

1.0

.2

.2

.2

.2

.2

.07

.2

.2

.1

.3

.2

.5

.2

.7

.2

.7

0.3

.3

.5

.3

.2

.3

.3

.5

.2

.2

.3

.2

.5

.3

.3

.3

.3

.7

.5

.7

.5

.5

1.0

3.0

2.0

3.0

3.0

1.5

1.0

1.0

1.5

1.5

1.5

2.0

3.0

2.0

2.0

3.0

2.0

3.0

3.0

1.5

2.0

2.0

0.3

.15

.1

.2

.15

.15

.5

.5

.3

.2

.5

.3

.2

.15

.2

.1

.07

.1

.07

.1

.07

.07

Santa Rita Mountains

Precambrian Continental Granodiorite; granodiorite and quartz monzonite.

Late Cretaceous Madera Canyon Granodiorite;

granodiorite.

Unnamed Paleocene quartz monzonite porphyry.

Unnamed Paleocene quartz latite porphyry.

65D994

66D1046

66D1043

65D769

65D837

63D316

66D1163

66D1313

66D1375

66D1403

66D921

66D1098

66D1185

66D1245

0.2

.3

.7

.5

1.0

1.0

.1

1.5

1.5

2.0

1.5

.2

.3

.5

0.2

.3

.2

.3

.3

.7

.3

.7

.7

.5

.7

.7

1.0

.7

0.7

.7

1.0

3.0

3.0

2.0

3.0

2.0

3.0

3.0

2.0

2.0

2.0

2.0

0.3

.3

.2

.1

.15

.03

.7

.7

.15

.5

.15

.3

.3

.3

Calcium is lower and shows less variation in biotite samples from 

the core facies of the granodiorite than in those from the other two 

rock types. This may reflect varying contamination by older, more 

calcic rocks near the intrusive contacts of the granodiorite and quartz 

monzonite, an effect from which the core facies would be well insulated. 

Manganese is lower in samples from the quartz monzonite than in 

those from either of the granodiorite facies, and both sodium and 

lead are higher in the quartz monzonite biotites than in the granodiorite biotites.

Titanium, barium, cobalt, lithium, scandium, vanadium, yttrium, 

and gallium show no significant difference in concentration in biotite
MINOR-ELEMENT DISTRIBUTION, BIOTITE Dll

igneous rocks of the Sierrita and Santa Rita Mountains of southern Arizona 

of sensitivity; leaders (....) in figure columns, not looked for. Other element looked for but not detected: Zn] 

Element (threshold of detection in parentheses) Continued

Ba Be Ce Co Cr Cu Ga La 

(0.0002) (0.0001) (0.015) (0.0003) (0.0001) (0.0001) (0.0005) (0.003)

Li

(0. 01)

Sierrita Mountains Continued

0.05

.07

.1

.15

.2

.15

.07

.07

.07

.05

.05

.05

.07

.15

.15

.1

.1

.15

.15

.15

.15

.3

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

JV

N

N

N

D

N

N

N

N

N

0.05

N

N

D

N

N

N

.03

N

D

0.007

.007

.005

.007

.005

.002

.007

.01

.01

.01

.003

.005

.003

.005

.005

.0015

.0015

.005

.003

.005

.002

.003

0.007

.05

.005

.005

.015

.01

.0015

.002

.002

.003

.002

.002

.003

.001

.001

.003

.001

.003

001

.0005

.0007

.0005

0.003

.001

.0005

.0005

.002

.5

.001

.0015

.002

.002

.015

.1

.07

03

.07

.5

.07

.5

1

.7

.1

.5

0.005

.007

.005

.001

.007

.005

.007

.01

.015

.01

.015

.015

.005

.007

.007

.007

.007

.015

.007

.007

.007

.007

N

N

N

N

N

N

N

N

N

N

N

N

0.03

N

N

.07

N

.007

N

.015

N

.003

0.05

.03

.01

N

N

.01

.05

.015

.05

.05

.03

.02

.015

.01

.02

.02

.02

.02

.01

.015

.01

Santa Rita Mountains Continued

0.1

.07

.15

.3

.3

.15

.16

.07

.15

.15

.3

.2

.15

.15

N

N

N

N

N

N

0.0001

.0002

N

.0001

N

N

.0001

N

N

N

N

N

N

N

0.015

.07

N

.07

.03

.03

N

N

0.007

.007

.003

.007

.005

.007

.003

.007

.007

.005

.005

.005

.003

.005

0.0015

.002

.001

.003

.003

.003

.0015

.0007

.003

.0015

.001

.0015

.0015

.001

0.003

.007

.005

.02

.01

.02

.007

.007

.007

.015

.07

.1

.5

.1

0.007

.007

.005

.007

.007

.003

.007

.007

.007

.007

.005

.007

.007

.005

N

0.007

.003

N

N

.003

.015

.05

.007

.03

.015

.015

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

(Table 2 continued on next page.)

samples relative to rock type. Cerium, lanthanum, and molybdenum 

were detected in too few samples to provide information on their 

relative abundance in biotites from the different rocks of this stock. 

Dodge and Moore (1968, p. B8-B9) studied the variation in minorelement content of biotite from a small pluton in the Sierra Nevada 

that is compositionally zoned from a porphyritic quartz monzonite core 

to an equigranular quartz diorite border facies. They concluded that 

chromium, nickel, and vanadium are more abundant in biotites from 

the more mafic border f acies but that scandium, strontium, and zinc 

are more abundant in samples from the quartz monzonite core. Nockolds and Mitchell (1948, p. 566) reported the composition of biotites
D12 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 2. Spectrographic anlysis (in percent) of biotite samples from igneous

Rock body and rock type Sample 

No.

Element (threshold of detection in parentheses) 

Continued

Mo 

(0.0003)

Nb 

(0.001)

Nd 

(0.007)

Ni 

(0.0003)

Sierrita Mountains Continued

rpo

T6

T91

T165

T7

T8

1-3-5

T166

T452

T453

T454

T455

T92

T465

T466

T456

T457

T94

T467

T468

T469

T470

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

0.02

N

.003

N

.0015

N

N

N .......

N .......

N .......

N .......

N .......

N .......

0.001 .......

N .......

N .......

N .......

.001 .......

.001 .......

N .......

.002 .......

.001 .......

.001 .......

.001 .......

.007 .......

.002 .......

.0015 .......

.0015 .......

.0015 .......

..... 0.01

..... .015

..... .01

..... .015

..... .015

..... .015

. . . .007

..... .01

..... .01

..... .015

..... .005

..... .01

..... .007

..... .007

..... .005

..... .01

..... .005

..... .003

..... .003

..... .003

.002

..... .002

Santa Rita Mountains Continued

Precambrian Continental Qranodiorite; granodiorite and quartz monzonite.

Late Cretaceous Madera Canyon Qranodiorite;

granodiorite.

Unnamed Paleocene quartz monzonite porphyry.

Unnamed Paleocene quartz latite porphyry.

65D994

66D1046

66D1043

65D769

65D837

63D316

66D1163

66D1313

66D1375

66D1403

65D921

66D1098

66D1185

66D1245

N

N

N

N

N

N

N

N

N

N

0.0015

.0015

.003

N

N

N

N

0.003

.002

.002

.015

.007

.005

.015

.002

.005

.005

.003

N

N

N

N

N

0.007

.015

.015

.007

.03

.015

.015

N

N

.003

.003

.002

.01

.003

.015

.003

.0015

.005

.003

.003

.003

.003

.003

from various facies of several Caledonian igneous intrusive complexes 

in Scotland. They found a systematic decrease in the chromium, 

vanadium, copper, nickel, cobalt, 'and strontium contents of biotite 

from the oldest rocks to the youngest in the Garabal Hill-Glen Fyne 

complex, which ranges in composition from a pyroxene-mica diorite 

(oldest) to a porphyritic granodiorite (youngest). However, in the 

Ben Nevis complex the strontium relations are reversed strontium is 

markedly higher in biotite samples from the younger granite than in 

those from the older granodiorite. In a similar study of biotites from 

a series of granitic intrusive rocks from the Dando-San district in 

Japan, Ishikawa, Shibata, and Negishi (1963, p. 69, 74) found a 

decrease in contents of magnesium, manganese, chromium, vanadium, 

nickel, and cobalt in biotite from the older to the younger rocks. 

Although these previous investigators vary somewhat in their con-
MINOR-ELEMENT DISTRIBUTION, BTOTITE D13

rocks of the Sierrita and Santa Rita Mountains of southern Arizona Continued 

Element (threshold of detection in parentheses) Continued

Pb

(0.001)

Pr 

(0.01)

Sc 

(0.0006)

Sn 

(0.001)

Sr 

(0.0006)

V 

(0.0007)

Y

(0.001)

Yb 

(0.0001)

Zr

(0.001)

Sierrita Mountains Continued

N ........

N ........

N ........

N ........

N .......

N .......

D ........

N ........

N ........

N ........

N ........

N ........

N ........

N ........

N ........

N ........

N ........

0.005 ........

D ........

.001 ........

.001 ........

.002 .......

..... 0.006

..... .003

..... .003

..... .005

..... .003

..... .007

..... .005

..... .006

..... .005

..... .003

..... .007

..... .01

..... .01

..... .007

..... .007

..... .006

..... .007

..... .007

..... .007

..... .006

..... .005

.005

N

N

N

N

N

N

N

N

N

N

N

N

N

0.001

N

.002

.002

.001

.003

.003

.002

.001

0.0005

.003

D

N

.0007

.0015

.003

.002

.001

.001

.0005

.0005

.002

.001

.0005

.003

.001

.015

.002

.015

.006

.03

0.06

.06

.03

.06

.06

.06

.03

.06

.05

.05

.015

.02

.02

.06

.03

.05

.06

.02

.05

.02

.06

.05

N ........

0.002 ........

N ........

.0015 ........

.0015 ........

.002 ........

.001 ........

.001 ........

N ........

N ........

.002 ........

N ........

.001 ........

.002 ........

.0015 ........

.006 ........

.002 ........

.005 ........

.002 ........

.003 ........

.001 ........

.003 ........

0.005

.005

.001

.001

.006

.... .005

.01

.007

.006

.001

.005

.003

.015

.01

.005

.01

.005

.02

.01

.02

.007

.02

Santa Rita Mountains Continued

0.001

.0015

.001

.001

N

.001

.003

.006

.0015

.003

.0015

.006

.0015

.0015

N

N

N

N

N

0.01

N

.015

.01

N

N

N

0.003

.007

.007

.0015

.002

.002

.007

.015

.007

.007

.007

007

.007

.007

N

N

N

N

N

N

N

N

N

0.002

N

N

N

N

0.003

.003

!(K)3

.003

.003

.015

.007

.015

.015

.03

.015

.003

.0015

.006

0.02

.02

.02

.03

.03

.03

.02

.015

.03

.015

.03

.03

.015

.015

0.0015

.0015

.0015

.001

.001

.001

.02

.03

.01

.03

.003

.007

.007

.007

0.0003

.0003

.0003

.0001

.0001

.0001

.002

.003

.001

.003

.0003

.0007

.001

.001

0.015

.607

.015

.007

.015

.02

.03

.05

.03

.06

.03

.03

.03

.03

elusions, they all concur with my observation that nickel and chromium 

in biotite decrease systematically with decreasing age of the rock f acies 

in a composite intrusive complex.

The four intrusive rock bodies in the Santa Kita Mountains are of 

three different ages and are not closely related, although they are 

grossly similar in composition to each other and to the composite stock 

in the Sierrita Mountains. These four intrusives are represented by 

fewer biotite samples than the Ruby Star Granodiorite, and, therefore, 

apparent differences in minor-element contents of these biotite suites 

may not be representative of differences in composition of all the 

biotite in these bodies. Nevertheless, where the range of concentration 

of an element is small in all the samples from a given body and where 

this range differs appreciably from that in biotites from another body, 

a real difference is strongly implied.

443-522 O - 71 - 3
1.0

Cr Nl Zr Sr 

0.1

O 0.01

0.001

0.0001

Tt

1 2 3 123 1 2 3 1 2 3 1 

FIGTTBE 2. Trends in minor-element distributions in biotite samples from com

indicates range, and tick indicates median; light line indicates geometric dev

1, Border facies granodiorite (oldest) ; 2, porphyritic core facies granodiori

(youngest).
MINOR-ELEMENT DISTRIBUTION, BIOTITE D15

As a group, the biotites from rocks of the Santa Eita Mountains 

appear to differ from those of the Sierrita Mountains in the absence 

of detectable lithium.

Biotite samples from the Precambrian Continental Granodiorite are 

characterized by a deficiency in sodium and titanium relative to biotite samples from the other intrusive bodies in the Santa Eita Mountains. Biotite samples from the Cretaceous Madera Canyon Granodiorite have an excess of chromium and nickel and a deficiency of 

manganese and scandium relative to the others. Samples from both 

the Paleocene rocks, the quartz monzonite porphyry and the quartz 

latite porphyry, are enriched in the rare-earth elements cerium, lanthanum, neodymium, praseodymium, and ytterbium, as well as in 

yttrium and zirconium, relative to samples from the older intrusives, 

and these elements appear to be somewhat higher in biotites from the 

quartz monzonite than in those from the quartz latite porphyry. Biotite samples from the Paleocene quartz monzonite are also enriched in 

beryllium and niobium relative to those from the other intrusives. 

Samples from the quartz latite porphyry are distinctively enriched in 

sodium, copper, and molybdenum as compared with samples from 

other intrusives in the Santa Eita Mountains.

Biotites from each of the seven intrusive bodies (including three 

forming a composite body) sampled in southern Arizona seem to have 

certain characteristics in their minor-element contents that distinguish 

them from biotites from all other intrusives in the region. These characteristics are summarized in table 3.

A systematic screening based on the criteria provided by table 3 

will allocate any biotite sample to the correct igneous intrusive on 

the basis of the concentrations of not more than four elements in the 

sample. If chromium is ^0.005 percent, the sample is from the border 

facies of the Euby Star Granodiorite stock. If chromium is <0.005

TABLE 3. Distinguishing features of minor-element contents of biotite from igneous 

intrusives of southern Arizona

Intrusive rock Distinctive minor elements in biotite

Ruby Star Granodiorite stock: 

Border facies . . .-.-................. Chromium >0.005 percent.

Core facies ...........___............... Chromium <0.005 percent, nickel >0.005 percent, lithium

>0.01 percent. 

Quartz monzonite porphyry...._......... Chromium <0.005 percent, nickel <0.005 percent, lithium

>0.01 percent, tin >0.001 percent. 

Continental Granodiorite..................... Lithium not detected, yttrium <0.003 percent, titanium

<1.5 percent, scandium >0.003 percent. 

Madera Canyon Granodiorite-.--.--......--.. Lithium not detected, yttrium <0.003 percent, titanium

>2 percent, scandium <0.003 percent. 

Paleocene quartz monzonite porphyry........ Lithium not detected, yttrium >0.003 percent, copper

<0.03 percent. 

Paleocene quartz latite porphyry..._....... Lithium not detected, yttrium >0.003 percent, copper

>0.03 percent.
DIG CONTRIBUTIONS TO GEOCHEMISTRY

percent and lithium is ^0.01 percent, the sample is from one of the 

other two facies of this stock; if, in addition, nickel is ^0.005 percent, 

the sample is from the core f acies; if nickel is <0.005 percent, the 

sample is from the quartz monzonite porphyry. If chromium is <0.005 

percent and lithium is <0.01 percent (not detected), the sample is from 

one of the intrusives in the Santa Rita Mountains. If, in addition, 

yttrium is <0.003 percent, the sample is from one of the two older 

intrusives; scandium ^0.003 percent indicates the Continental Granodiorite, and scandium <0.003 percent indicates the Madera Canyon 

Granodiorite. Chromium < 0.005, lithium <0.01, and yttrium ^0.003 

percent allocate the sample to one of the two types of Paleocene intrusive. If, in addition copper is <0.03 percent the sample represents 

the quartz monzonite porphyry; if copper is ^0.03 percent, the sample 

is from the quartz latite porphyry.

SOUTHERN ROCKY MOUNTAINS, COLO.

Biotite separates from five different intrusive bodies, all of Precambrian age, in the southern Eocky Mountains of Colorado were 

analyzed for this study. The Boulder Creek Granite iand the Silver 

Plume Granite intrude the Front Range of the Rocky Mountains west 

and northwest of Denver, east of the Continental Divide. The St. 

Kevin Granite is in the northern Sawatch Range in Eagle County, 

west of Denver and west of the Continental Divide. The unnamed 

lower Precambrian syenite is in southeastern Gunnison County, Colo., 

about 100 miles south of the St. Kevin Granite locality. The unnamed 

upper Precambrian mafic syenite forms small intrusive 'bodies in the 

Wet Mountains of southern Fremont County, about 100 miles east of 

the Gunnison County syenite locality.

The Boulder Creek, Silver Plume, and St. Kevin Granites range in 

composition from granite to granodiorite but are largely quartz monzonite. The syenite in Gunnison County is a true syenite, but the 

syenite in Fremont County is variable in composition from a silicadeficient mafic nepheline syenite to a true syenite.

Analytical data on the biotites separated from samples of these 

rocks are presented in table 4.

Minor elements in the biotites of the Silver Plume and St. Kevin 

Granite samples show a marked similarity in concentration. Although 

these two bodies are about 50 miles apart, they are nearly the same 

age and are also similar in appearance and composition. The Boulder 

Creek Granite, on the other hand, is at least 300 million years older 

than the Silver Plume and St. Kevin Granites, and the concentrations 

of several minor elements in the Boulder Creek Granite are distinctly 

different from those in the Silver Plume and St. Kevin Granites.
MINOR-ELEMENT DISTRIBUTION, BIOTITE D17

Niobium, tin, and yttrium and the rare-earth elements cerium, lanthanum, neodymium, and ytterbium are higher and nickel and 

vanadium are lower in biotite from the Silver Plume and St. Kevin 

rock samples than they are in biotite from the Boulder Creek rock 

samples.

A comparison of the minor-element concentrations in biotite from 

the older Precambrian syenite samples from Gunnison County with 

those in biotite from the younger Precambrian syenitic rock of the Wet 

Mountains also shows some distinguishing patterns. Sodium, titanium, 

manganese, and niobium are distinctly lower in the Gunnison County 

biotites, and beryllium, vanadium, and zirconium are higher.

Similarly, certain characteristics distinguish biotite of each intrusive from that of any other intrusive, with the exception of the 

Silver Plume and St. Kevin bodies. Although the overall patterns 

of biotite content of the Boulder Creek Granite and of the syenites 

from Gunnison County are similar, there are noticeable differences 

in sodium, manganese, and barium concentrations. The high rareearth content of the Silver Plume and St. Kevin biotites distinguishes 

them from biotites of both of the syenites as well as those of the 

Boulder Creek Granite, and the Boulder Creek biotites differ from 

biotites of the syenite from the Wet Mountains in their lower titanium 

and higher vanadium contents.

GREAT BASIN, NEV. AND UTAH

The five intrusive bodies in the Great Basin that are represented 

in this study range in composition from quartz monzonite to granodiorite. They range in age from Jurassic to Tertiary and are widely 

separated geographically; therefore each is related to a magmatic 

source entirely separate from any of the others. The Snake Range 

stock is in southeastern White Pine County, Nev.; the Ibapah stock is 

in northwestern Juab County, Utah, about 80 miles north-northeast 

of the Snake Range stock; and the Climax stock is near the east edge 

of the southern part of Nye County, Nev., nearly 150 miles southwest 

of the Snake Range stock. One of the unnamed granodiorite stocks 

is in southern Elko County, Nev., about 100 miles west of the Ibapah 

stock; the other is nearly 150 miles farther west, in northern Pershing 

County, Nev.

Analyses of biotite separated from samples of these intrusives 

(table 5) suggest distinctive differences in the minor-element contents 

of biotite samples from each of the intrusives. The presence of detectable zinc (^0.02 percent) distinguishes Ibapah stock biotite samples from all the others. Lithium was detected only in samples from 

the Snake Range and Ibapah stocks and the granodiorite of Pershing
D18 CONTRIBUTIONS TO GEOCHEMISTRY

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- .3

I 'S

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B *

11A &

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IJN 

CQ ft

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 fcfc fcfcfc

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Precambrian Silver Plume Granite;

granite to quartz monzonite.

Precambrian St. Kevin Granite; granite

to quartz monzonite.

Mountains) .

ST3

ST8

432

434

435

324B

433B

220B

431 

ST11

C2

C3

C21

C25

2G3200

G3730N

BSJ139

BSJ140

WM62-115

WM66-116C

WM62-143

Element (threshold of d

Li 

(0.01)

N

N

N

N

N

D

D

D

D 

D

D

D

N

D

N

N

N

N

N

N

N

Nb 

(0.001)

N

0.003

N

N

N

N

N

.007

.007 

.005

.007

.007

.005

.007

N .

.001 .

.001 .

N .

.002 .

.002 .

.002

Nd 

(0.007)

N

N

N

N

N

N

N

0.01

.02 

.007

.015

.007

.02

.03

Ni 

(0.0003)

0.005

.007

.02

.03

.05

.02

.02

.007

.007 

.005

.005

.005

.002

.003

.015

.015

.05

.05

.007

.03

.0007

Pb

(0.001)

N .

N .

N -

N .

N

N

N

N

0.002 

.002

N

N

N

N

D .

.001 .

N .

N .

N .

N .

N

Pr

(0.01)

N

N

N

N

N 

N

N

N

N

N
D20 CONTRIBUTIONS TO GEOCHEMISTRY

s

 a 

8 

e

QQ -p

1 n « si

1 1"8

.1 ll

-sl

Si -

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OS

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t~- t~. I-IM

^H^H^ OiHIM

QQQ 333

So .

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§2 5^ 3-3

. 

ll

Si: cJ

P P
MINOR-ELEMENT DISTRIBUTION, BIOTITE

SSi ,* - 

eg ^8-

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D21

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 c .

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D22 CONTRIBUTIONS TO GEOCHEMISTRY

County. Biotite from the Snake Range intrusive contains detectable 

beryllium, whereas that from the granodiorite of Pershing County 

does not. Biotite samples lacking detectable zinc or lithium characterize the Climax stock and the granodiorite of Elko County; samples 

from the Climax stock contain <0.3 percent barium, and those from 

the granodiorite of Elko County contain ^0.3 percent barium.

NORTHERN ROCKY MOUNTAINS, IDAHO AND MONT.

Only two rock bodies in the northern Rocky Mountains are represented by suites of analyzed biotite samples: the Idaho batholith in 

Idaho and the Boulder batholith in Montana, both of Cretaceous age. 

Both these batholiths are large, and they range in composition from 

granite to granodiorite. Only six biotite samples are available from 

the Boulder batholith, and only four from the Idaho batholith far 

too few to adequately represent such vast and complex bodies. The 

analytical data on these 10 samples are presented in table 6, but until 

more data are acquired, apparent differences in the minor-element 

contents of the two analyzed suites must be regarded as merely suggestive of possible differences in the biotite of the two batholiths.

TABLE 6. Spectrographic analyses (in percent) of biotite samples from igneous 

rocks of the northern Rocky Mountains, Idaho and Mont.

Analysts, A. L. Sutton, Jr., and Barbara Tobin. N, looked for but not detected; leaders (..) in figure 

columns, not looked for. Other elements looked for but not detected: Be, Ce, Pb, Sn, and Znl

Rock body 

and rock type

Cretaceous Boulder 

batholith; granodiorite to quartz 

monzonite.

Cretaceous Idaho 

batholith; 

granodiorite.

Sample 

No.

280 

247B 

273B 

274B 

275B 

276B

308 

134 

135 

137

Element (threshold of detection in parentheses)

Ca 

(0.005)

0.7 

.15 

1. 

.2 

.7 

.1

.03 

.3

.7 

.2

Na 

(0. 05)

0.7 

.3 

.7 

.5 

.5 

.3

.3 

.2 

.3 

.3

Ti Mn Ba Co Cr Cu Ga 

(0. 0002) (0. 0001) (0. 0002) (0. 0003) (0. 0001) (0. 0001) (0. 0005)

3.0 

1.5 

1.5 

1.5 

1.5 

1.5

1.5 

2.0 

2.0 

2.0

1.5 

.2 

.5 

.3 

.3 

.7

.3 

.15 

.2 

.3

0.3 

.05 

.1 

.15 

.1 

.2

.2 

.3 

.2 

.1

0.005 

.003 

.007 

.01 

.007 

.007

.0015 

.003 

.002 

.002

0.001 

.002 

.003 

.003 

.003 

.001

.0015 

.003 

.003 

.005

0. 0015 

.003 

.015 

.002 

.015 

.001

N 

.0007 

.0005 

.0005

0.005 

.007 

.007 

.007 

.007 

.007

.01 

.01 

.015 

.01

Rock body 

and rock type

Cretaceous Boulder 

batholith; granodiorite to quartz 

monzonite.

Cretaceous Idaho 

batholith; 

granodiorite.

Sample 

No.

280 

247B 

273B 

274B 

275B 

276B

308 

134 

135 

137

Element (threshold of detection in parentheses) Continued

La

(0.003)

N 

N 

N 

N 

N 

N

0.003

N

N 

N

Nb 

(0. 002)

0.005 

.01 

.005 

.002 

.002 

.003

.003 

.007 

.01 

.015

Ni Sc Sr V 

(0. 0003) (0. 0005) (0. 0005) (0. 0007)

0.003 

.005 

.007 

.007 

.007 

.002

N 

.0015 

.0015 

.002

0.003 

.007 

.003 

.001 

.0015 

.002

.003 

.005 

.0015 

.002

0.01 

.002 

.003 

.002 

.003 

.001

.0015 

.003 

.005 

.003

0.03 

.03 

.05 

.05 

.05 

.02

.02 

.007 

.003 

.015

Y 

(0. 001)

N 

0.002 

.001 

N 

.001 

N

N 

N 

N 

N

Yb Zr 

(0. 0001) (0. 001)

0.0003

N

N 

N 

N

.0003

0.01 

.03 

.015

N 

.007

N

.01 

.01 

.01 

.01
MINOR-ELEMENT DISTRIBUTION, BIOTITE D23

The biotite samples from the Boulder batholith contain appreciably 

more copper, and most of the samples also contain more cobalt, nickel, 

and vanadium, than do the biotite samples from the Idaho batholith. 

On the other hand, the analyzed samples from the Idaho batholith 

are richer in gallium than are the samples from the Boulder batholith. 

It is highly probable, however, that different rock facies within each 

batholith differ in the minor-element content of their biotites. More 

data are needed to determine whether these differences are characteristic of biotites from the entire batholiths or merely of biotite from 

certain facies within them.

CASCADE RANGE, WASH.

Suites of biotite samples from four intrusives in the Cascade Range 

of northern Washington represent a region slightly smaller than the 

southern Rocky Mountains in Colorado and range in age from cretaceous (?) to Tertiary. The Chilliwack batholith in Whatcom County 

near the Canadian line is a composite intrusive of Tertiary age composed of quartz monzonite and granodiorite. The Ten Peak pluton, 

about 100 miles to the southeast, in northwestern Chelan County, is 

Cretaceous and is composed largely of quartz monzonite. The Mount 

Stuart batholith, about 50 miles farther south, is also Cretaceous and 

is largely quartz diorite. The Similkameen batholith, in northern 

Okanogan County, about 100 miles east of the Chilliwack batholith, 

is also composite and ranges in composition from syenite to quartz 

diorite. The age of the Similkameen batholith is in doubt, but it is no 

younger than Cretaceous. Analyses of biotite samples from these four 

intrusive bodies are presented in table 7.

The biotite suites representing the four intrusives in the Cascade 

Range can be most readily distinguished by their titanium, strontium, 

and scandium contents. Biotites from the rocks of the Chilliwack 

batholith consistently contain 2 percent titanium, and none of the 

other biotites contain more than 1.5 percent. If a sample contains <2 

percent titanium and 0.002 percent strontium, it represents the 

Similkameen batholith; samples from both the Mount Stuart batholith 

and the Ten Peak pluton contain ^0.0015 percent strontium. Samples 

from the Ten Peak pluton can be distinguished from those of the 

Mount Stuart batholith on the basis of scandium content. Mount Stuart 

samples generally contain 0.001 percent scandium, whereas those 

from Ten Peak contain < 0.001 percent.
TABLE 7. Spectrographic analyses (in percent) of biotite samples from 

[Analyst: Harriet Neiman. N, looked for but not detected; D, detected but below threshold of sensitivity; 

for but not detected: Ce, La, and Mo]

Rock body and rock type

Tertiary Chilliwack batholith; quartz monzonite to 

granodiorite.

Cretaceous Mount Stuart batholith; quartz diorite. .

Cretaceous(?) Similkameen batholith; syenite to 

quartz diorite.

No.

RWT474-67 

RWT475-67 

RWT476-67 

RWT480-67 

75R-66

60-62 

JE-15-67 

JE-16-67

JE-12A-67 

JE-13-67 

JE-14-67 

JE-20-fi7 

JE-21-67 

JE-22-67

L277Z 

L301 

L589 

L618

Element 

Ca 

(0.005)

0.15 

.2 

.15 

.15 

.05

.1 

.1 

.15

.15 

.1 

.15 

.15 

.2 

.1

.1 

.15 

.5 

.2

Na 

(0.05)

0.2 

.2 

.3 

.5 

.3

.3 

.3 

.3

.2 

.3 

.2 

.5 

.5 

.2

.2 

.3 

.3

.7

Ti 

(0.0002)

2.0 

2.0 

2.0 

2.0 

2.0

1.0 

.7 

1.0

1.0 

1.5 

1.0 

1.0 

1.5 

1.5

1.0

.7 

.7 

.7

Mn 

(0. 0001)

0.1 

.15 

.5 

.1 

.07

.1 

.1 

.15

.15 

.2 

.1 

.15 

.05 

.07

.07 

.1 

.3 

.5
MINOR-ELEMENT DISTRIBUTION, BIOTITE D25

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888 ggg

'fcfclz; 12; ' ' '

Sg * ' ' ' *

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_- oj 1"' f-<f-«=>f-*r-< f-tf-tf-t ZZ^^^23 

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3 X»S ****:z; 5^;^; 55^^^^^

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a 

^-o !5 

ssr

SSS ' ' "

0.2
D26 CONTRIBUTIONS TO GEOCHEMISTRY

REGIONAL VARIATIONS AND VARIATION WITH AGE 

OF INTRUSIVE

When all the biotite analyses are grouped by region, the concentration ranges of the elements overlap to such an extent that no element 

is distinctively higher or lower in the biotite of any one region compared with the biotite in any other. However, there are differences in 

the regional median values for certain elements that may reflect 

regional tendencies toward concentration or impoverishment of these 

elements in the biotite. The median concentration of titanium in the 

biotite samples from southern Arizona is twice as much as it is in the 

samples from any other region except the northern Rocky Mountains; 

chromium has its highest median in samples from the southern Rocky 

Mountains; niobium has its highest median value in samples from the 

northern Rocky Mountains; and the median for strontium is distinctly lower in samples from the Cascade Range than in those from 

any other region. None of the other minor elements show any 

appreciable differences on a regional basis.

If the samples are classified broadly by age into Precambrian, Mesozoic, and Cenozoic, only two elements, titanium and chromium, show 

consistent trends relative to the age of the samples. Titanium has a 

rather narrow concentration range and increases progressively from 

Precambrian to Cenozoic (fig. 3). The median values for chromium in 

the samples trend in the opposite direction; they are 0.01 percent for 

the Precambrian, 0.003 percent for the Mesozoic, and 0.002 percent for 

the Cenozoic. The range in concentration of chromium in these samples is so great, spanning two orders of magnitude, that a far larger 

and more representative suite of samples would be needed to adequately 

test the hypothesis of a relationship between the age of a biotite and 

its chromium content. Although there is considerable overlap in the 

titanium values for biotite of various ages, titanium covers a mutch 

narrower range and is more consistent in its distribution than 

chromium. All the biotite samples that contain >1.5 percent titanium 

are from Mesozoic or younger rocks, and all those that contain <1 

percent titanium are from rocks older than Cenozoic (fig. 3).

CONCLUSIONS

Rock samples from unrelated felsic igneous intrusive bodies of 

similar composition in the same area can commonly be distinguished 

by the patterns of minor-element distributions in their biotites. Such 

patterns provide evidence for the parent affiliation of small satellite 

bodies such as dikes, sills, and plugs in an area characterized by
MINOR-ELEMENT DISTRIBUTION, BIOTITE

60 -i

D27

PRECAMBRIAN

TITANIUM, IN PERCENT

0.5 0.7 1 1.5 2 

TITANIUM, IN PERCENT

40n

30-

20-

10-

0.5 0.7 1 1.5 2 3 

TITANIUM, IN PERCENT

FIGURE 3. Titanium content of biotite from felsic intrusive rocks 

of various ages.
D28 CONTRIBUTIONS TO GEOCHEMISTRY

multiple intrusives of different ages. They may also indicate the probable source rock for float samples or detrital cobbles, and they may aid 

the correlation of isolated outcrops in a covered area.

Biotite separates from different facies of a composite intrusive may 

show consistent trends in the concentrations of certain minor elements 

relative to the ages of these facies. Such trends can be useful in helping 

to establish the intrusive sequence from a common center in areas where 

the observable field relations are not diagnostic.

Although the data of this paper are insufficient to establish regional 

differences in the composition of biotite from igneous intrusives, they 

do suggest the possibility that such differences may exist. A possible 

trend toward enrichment of titanium in Tertiary biotite as contrasted 

with Precambrian biotite is worthy of more systematic investigation.

REFERENCES CITED

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MINOR-ELEMENT DISTRIBUTION, BIOTITE D29

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