The deuterium content of hydrous minerals from the East-Central Sierra Nevada and Yosemite National Park

Geochimica et Cosmochimica Acta, 1962, Vol. 26, pp. 1215 to 1245. Pergamon Press Ltd. Printed in Northern Ireland

The deuterium content of hydrous minerals from the East-Central Sierra Nevada and Yosemite National Park* JOHN D. (Received

11 April

GODFREY

1962; retised

11 May

1962)

Abstract-The experimental procedure for the extraction of hydrogen from natural hydrous silicate minerals is outlined. The D/H ratios, water, and flourine contents have been determined for coexisting biotite, hornblende, and chlorite from rocks of the east-central Sierra Nevada and Yosemite National Park regions. These data are discussed in relation to the petrogenesis of the principal rock types of the regions. Local hydrogen isotopic fractionation and equilibrium between coexisting hydrous silicates were noted.

developments in the application of isotopic abundances have opened new fields of investigation as applied to the study of the crust of the earth. The results of these investigations have appeared in journals and periodicals with Recently, textbooks have been increasing frequency over the past two decades. published summarizing the accumulated data. Numerous geologic processes and problems have been clarified by use of both radiogenic and non-radiogenic isotopes, for example, those of the element hydrogen. Three naturally-occurring isotopes of hydrogen are recognised. Mass one is referred to as protium (H), mass two as deuterium (D), and mass three, the radiogenic isotope of approximate half-life 12.5 years, as tritium (T). The abundance of the stable hydrogen isotopes as given‘by WAY et ccl. (1960) is 0*0156:99*9844 per cent for D:H, which is 6409 for the D:H ratio and -5.14 per cent on our relative scale. * * For comparative purposes, Table 1 gives a list of D/H analyses of natural substances, including rocks and minerals, indicating the widest reported variations in each group. Water extracted from minerals by heating samples under high vacuum was converted to hydrogen by passing over hot uranium and was isotopically analysed by the mass spectrometric method. The concept of juvenile water is a commonly accepted one and is widely referred to in texts and papers in several related fields of geology including igneous petrology, ore deposits, and geochemistry. Juvenile (primitive) water is that water which has been imprisoned in the interior of the earth since the time of the earth’s formation and has never been a part of the general system of groundwater circulation. Magmatic water is derived from a magma and may represent a mixture of juvenile and resurgent waters, the latter originating from an external source RECENT

* This study has been undertaken in partial fulfillment for the degree of Doctor of Philosophy at the University of Chicago. Present address: Research Council of Alberta, Edmonton, Alberta, Canada. * * See footnote to Table 1. 1

1215

JOHN D. GODFREY

1216

Table 1. Distribution of deuterium in natural substances Source Material and Locality

AD%l

National Park Gas 8amples* Spring issuing from Hurricane Vent, Xorris Basin Punch Bowl Spring, Upper Basin

Yellowstone

Natural Waters* Snow Rain Ocean Ocean water average Afeteorites* * Iron meteorites Carbonaceous chondrites2

-46.3 -19.2 0.0 to -26.0 +4.5 to -1.0 +5.5 to $3.0 $4.1 -7.1 $36.0

to -13.4 to -13.0

A-finerals

Hornblende Biotite Chlorite Average hornblende, Sierra Nevada and Yosemite National Park (35 samples) Average biotite, Sierra Nevada and Yosemite National Park (36 samples) Average chlorite, Sierra Nevada and Yosemite National Park (8 samples) Rocks* Obsidian Perlite Basalt 3 and ’ Hawaiian Basalt 1 AD%

=

D/H

sample D/H

D/H

standard

standard

-1.0 -1.4 -2.4

to -14.5 to -14.2 to - 13.7 -5.0 --5.1 -4.9

-5.0 -3.0 -6.2 -1.0

to -12.5 to -16.6 to -15.0 t*o 5.0

x 100; (standard is “standard Michigan water”)

Lake

2 BOATO (1954) 3 KOKUBU, MAYEDA and UREY (1960) * FRIEDMAN (1953, 1958, 1961) * * EDWARDS (1955)

such as buried sediments. Original water is characteristic of and exists in a rock Connate waters are buried with exogenic at the time of the latter’s formation. formations and volcanic rocks, remaining stagnant except when liberated by diagenesis or metamorphism. Meteoric water is a comprehensive term that includes water which has gone through the meteorologic cycle and atmospheric moisture, or surface water, which entered from the surface into voids of the lithosphere. Ground-water (phreatic water) refers to water in the zone of saturation, below the water-table. Vadose water applies to seepage waters occurring below the surface and above the water-table. Usage of this terminology in discussing types of water shows some inconsistencies in the literature and is included above for clarification. Though the primary experimental objective of this st’udy has been the deterof D/H isotopic ratios in minerals, at the same time it has been possible to quantitatively measure the water content. mination

The deuterium content of hydrous minerals

1217

The scope of useful application of this type of study goes beyond the present undertaking, and at this time new information is presented concerning but a few geologic and geochemical concepts and problems such as: (a) the occurrence and extent of local equilibrium in mineral assemblages within systems in a plutonic plutons and the operation of “open” and “closed” environment. (b) the possible identification of juvenile water or water from the interior of the earth held in hydrous minerals in plutonic masses the differentiation of igneous and some metamorphic mineral assemblages ;f;l recrystallization and equilibration in plutonic masses environmental conditions associated with chloritization (4 One of the chief problems connected with this work involves the elimination They may be experimental or geological or evaluation of sources of contamination. in nature. In the latter case one must deal with changes in the original D/H ratios due to secondary fractionating processes. e. g., weathering, oxidation, metamorphism, metasomatism, etc. Experimentally, the main concerns are the separation of adsorbed hydrogen from original hydrogen, and the complete extraction of original water from a given sample. EXPERIMESTAL i. .Ilineral

PROCEDURE

sample preparation

Hand specimens were crushed and sieved into several size categories in the range from ~ 60 to ~ 120 mesh. Mineral separations were processed using the heavy liquids tetrabromeothane, bromoform, and methylene iodide diluted with dimethyl formamide, and where appropriate the minerals were further purified by use of the Franz isodynamic separator. Degree of purity* of the mineral separates was determined by mounting grains in aroclor cement and counting 300 grains, which gives an accuracy of 17 per cent of the amount of impurity present in the 5 per cent abundance range (KRUMBEIN and PETTIJOHN, 1938). Purity of biotite and hornblende concentrates was mostly from 97 to 99 per cent but chlorite was from 70 to 90 per cent. The impurities necessitated only minor adjustments to the data directly obtained in the course of this study, with the exception of chlorite. Determination of the D/H ratio of certain control samples showed that use of heavy liquids did not affect their deuterium content by either adsorption or exchange. ii. Appnmtus Samples contained in a *J. Lawrence Smith platinum crucible within a Vycor tube were heated by a high frequency induction heater coil. Water from hydrous silicate minerals was converted to hydrogen by passing over uranium metal at about 750°C. The complete extraction line shown in Fig. 1 is similar t,o that used by FRIEDMAN (1953). iii. Begussing

technique

A t,horough degassing of the apparatus was undertaken prior to water extraction in order to reduce contamination due to absorbed and adsorbed atmospheric moisture. The extraction system was constantly kept under high vacuum and frequently sparked with a Tesla high voltage coil to check for loads and to dislodge adsorbed particles on the inner surface of the glass lino. The drgassing operat,ion involved heating the Vycor tube and platinum crucible to the extraction * A precise evaluation of the degree of chloritization using an X-ray technique was not, rritical in view of the experimental accuracy which for the water content was about *O.l wright per cent.

JOHN D. GODFREY

1218

Pyrex Graded

5eos

vycor

U i,numcruc,ble

sample

Fig.

1. Sample preparation

line.

temperature under high vacuum (m lop5 mm Hg). After the crucible had been cooled to room temperature, it was removed from the Vycor tube and a known weight of sample was placed in the crucible. The crucible was handled with forceps during the operation and tho whole unit placed on the vacuum system with as little exposure to the atmosphere as possible. Tho sample and platinum combustion tube were degassed at elevated temperatures and at high vacuum in readiness for water extraction. To test the adequacy of the degassing techniques used for minerals and the possibility of the presence of readily exchanged hydrogen in a hydrous, layer-lattice silicate, special extractions were undert,aken from a muscovite sample. Part of the sample was suspended for a period of 5 months in a deuterium-enriched environment (100 per cent enrichment of deut)erium as compared to the standard Lake Michigan water, which would analyso + 100 per cent on our scale) at room temperature and pressure. A portion of the moisture collected during the latter part of degassing, carried out from 28 to 458°C over 90 min, gave AD = + 11.3 per cent. m-ater of const)itution collected from 458 to 1050°C over 73 min, gave 4.37 per cent H,O and AD = -4.8 per cent. These latter figures compare wit’h 4.4 i 0.1 per cent H,O and AD = -4.5 & 0.4 per cent for six det)erminations of the same sample extracted under standard conditions. It can be seen that the degassing techniques were effective in that all the heavy water had been collected in the degassing interval (28 to 458°C) prior to the extraction proper, and that bonded water in this crystal structure did not, equilibrate or exchange with that in the environment under experimental conditions. The judgement of the degassing conditions was greatly facilitated by a knowledge of decomposition temperatures, differential thermal analysis curves, and the dehydration points (BIRCH, SCHAIRER and SPICER, 1942; KAUFFMAN and DILLING, 1950; and CHOWUBURY, 1941) for the mineral species examined. In general, degassing temperatures were several hundred degrees below the dehydration temperature in order to avoid the loss of bonded hydrogen; e.g., biotito and hornblende were degassod at 165°C.

The deuterium iv. Extraction After

content

of hydrous

minerals

1219

procedure

the degassing

operation,

the temperature

of the sample

and crucible

was gradually

raised by a motorized geared input attached to the induction heater. When the temperature reached about 1000°C the exterior of the Vycor combustion tube was gently heated by an open flame in order to prevent condensation and fixation of alkalic hydroxides on the inside surface. In the course of extraction volatilized alkalies apparently combine with evolved water, which leads to erratic results if the above treatment is not carried out. Maximum temperatures attained in the water extraction of minerals were generally in the range from 1300 to 1500°C. Water drawn through the line A-D-E-F by toepler pump (L) reacts in the uranium furnace (F) to give hydrogen which in turn is transferred through the liquid nitrogen trap (G) into the On completion of the first pass, shown by bot,h constant manometer (M) side of the system. manometer pressure and the lack of gas passing through the toeplcr pump out,let valrc, the extraction tube was cut off from the remainder of the line. A second pass was made using the recycle line (H) in order to check the possibility of unreacted water having been condensed in trap (G). The recycle usually produced either no gas or a negligible number of small hydrogen bubbles, indicating an efficient first pass reaction. Knowing the manometer pressure and the volume of the line between the mercury level in the outlet valve of the Toepler pump (L) and themanomotcr, it was possible to calculate the amount of hydrogen extracted from a given sample. Hydrogen was transferred by Toepler pump (L) to the degassed gas sample tube (N) for the ultimate isotopic analysis by the mass spectrometric method. A routine extraction of a mineral sample, not including degassing, involves a time of l-1/2 to 2-l/2 hr. In general, as large a hydrogen gas sample as possible up to 10 ml. at S.T.P. was extract,ed from minerals in order to minimize contamination errors. The extraction temperatures wore measured by means of an optical pyrometer and the temperature of the uranium reactor by a chromel-alumel thermocouple. The pressure in the vacuum system was shown to be less than IO-* mm of mercury by the thermocouple vacuum guage. About 70 to 90 runs could bc made with a uranium reactor before it was necessary to install a fresh one. To aid in the reproducibility of analytical dat’a obtained from minerals and waters, the ext,raction steps were timed to within 1 min. T’ycor tubes were cleaned with hot aqua regia between runs, and platinurn crucibles were t,reated with hot hydrofluoric acid, then heated to above 1000” C in a strongly oxidising flame. Pyrex gas sample tubes used to transfer hydrogen from the ext,raction system to the mass spectrometer for analysis were cleaned by heating to just below the softening point for about 2 hr under high vacuum. The unheated glass around the greased stopcock was degassed whilst under vacuum by repeated sparking from a Tesla coil until there was no fluorescence. To check daily and long term variations and “drift” both in the extraction system and in the mass spectrometer it was found necessary to process a standard water sample at the beginning and end of each daily series of runs. This procedure provides a satisfactory correlation of experiment’al data obtained over a considerable period of time. The standard water was released into the vacuum system from a sealed capillary after the latter was broken by a falling steel bar upon removal of a horseshoe magnet (FRIEDMAN, 1953). The standard water, introduced via stopcock (B), Fig. 1, was then processed in the usual manner as described above. Duplicate analyses of waters showed that ADoh checked within the limits f 0.10 per cent. Consecutive duplicate runs were made of each mineral sample and those pairs not checking within AD = 0.15 per cent were discarded. Coexisting minerals were always run consecutively and on the same day in order to minimize the effect of experimental “drift” and to provide the best possibility of dotacting a slight deuterium fractionation between these minerals. v. Isotopic

analysis

by the mass spectrometric

method

The hydrogen gas to be analysed is compared to a standard hydrogen sample. The two gases are alternately introduced into the mass spectrometer under the same physical conditions such that any slight change in the conditions of analysis is duplicated from one gas to the other and the changes are thereby compensated.

1220

JOHN

D.

GODFREY

A more complete discussion of the mass spect,rometrie technique and the I&+ ion correction are given in FRIEDMAN (1953). vi. Presentation of data isotopic data are presented in the conventional way:

AD in y. =

D/H sample - D/H standard D/H standard

x 100

and the water content is in weight per cent. The arbitrary standard with which all the isotopic data are compared is a sample of distilled Lake Michigan water, for which ADO,; =z O*OOO,; (E'RIEDMAX, 1953). As the standard is 0.0148 & 0.0001 mole %D, the conversion to mole ‘$i,l> is given by: Mole %D

in sample == 0.0148

i’onversion from mole %D

$- (hydrogen analysis

x, 0*0148) (FRIEDMAN,

to the specific gravity difference scale, in p&s

1953). per million (y),

is given by: 11~ = 0*000927 molo s/oD. 911 anatyt,ical data have been compiled and arc presented in Table 7.*

All fluorine determinations were made following the method outlined by ~~.RIMALDI, ~ORAM ant%CTTLTITTA (1955). In t,his technique the sample is fused with a mixture of sodium carbonate and zinc oxide, leached with water, and filtered. The fluorine in the filtrat,e is dist‘illed diroetly from a perehloric acid-phosphoric acid mixture, and is det,ermined by either microtitration with t,horirrm nitrate or calorimetrically with thoron.

~FLIW~TCINE CONTENT AND D/H RATIOS OF COEXISTING,BIOTITE ANI) HORNBLENDE Because of the similarity in ionic radii and hence the probability of substitution of fluorine and (OH)- ions (l-33 and 1.4 to 1.6 A&respectively, GOLDSCHMIDT.1954), it might be suspected t,hat eo~lsistent bias in fluorine : water ratios between coexisting biotite and hornblende would influence the D/H ratios of the water of constitution of these minerals. Such an effect must be evaluated before geological interpretations can be made from the data, and frequency distributions of the fluorine and water contents of biotite and hornblende from the Sierra Nevada and Yosemite National Park are shown in Figs. 2 and 3. The arithmet,ic means show similar fluorine:water ratios for biotites and hornblendes which suggests that, on the average, fluorine distribution will be proportionate to the amount of water in the hydrous mineral species. F:H,O F: H,O F : H,O

(Biotite) (Biotite) (Hornblellde)

9.4: 100 (including fluorine skew) 7 : 100 (excluding fluorine skew) 7: 100

Wide ranges in the plots of fluorine vs. deuterium and (fluorine: water) vs. deuterium for both biotite and hornblende from the Sierra Pr’evada and Yosemite Nat,ional Park given in Figs. 4, 5, 6 and 7 show no distinct pattern or trend, which suggests a relationship between the fluorine and deuterium contents of these hydrous minerals. * Tut&: 7 appears on p. 1240.

The deuterium 16

I

Fig. 2. Frequency

I

content

of hydrous I

I

1221

minerals I

I

distribution of fluorine for biotite and hornblende Sierra Nevada and Yosemite Xational Park.

from

the

i

1

2.0

Hz0

Fig. 3. Frequency

wt per cent

4c1

3.5

30

2.5

-

distribution of water for biotite and hornblende Sierra Nevada and Yosemite National Park.

from

the

Three biotites and one hornblende (M-842, M-962, Y14 and Y15) with exceptionally high fluorine analyses are regarded as belonging to another population and therefore have been omitted from the statistical calculations. Further, very low fluorine contents are associated with two biotite-hornblende mineral pairs

JOHN D. GODFREY

1222

01 -I

I

-2

I

-3

I

-4

I

-5

I

-6

-1 _ -7

__I__-i___L__

-8

-9

-10

-8,

-12

-13

-14

-AD%

Fig. 4. Flnorine

T A n

@ v

9/;1 vs. AD% for biot,ite and chlorite from the Sierra Nevada Yosemite Kational Park Uiot./Chl. Uiot./Hbl.

Y Yosemite National Park ;i Lamarck Granodiorito 1 Round Valley Peak Granodioritc 13 Cart,ridge Pass Granodiorite v Cat,hedral Peak Type Quartz Monzonit’e 4- McMurry Meadows Quartz Monzonit.e 7 TVhcelcr Crest Qnart,z Monzonite

Fig. .T. Fluorine

T X :$ - .2

.I

Diorit$r Coyote Flat, Granodiorito .Deep Canyon Cranodiorito Inconsolable Granodiorite Mt. Givens Granodiorit’r Tlmgstcn Hills Qnart)z Jlonzonite

9/,vs. ~1~ O’ ,O for hornblende from the Sierra Nevada Sational Park.

Y yosornite Kat,ional Park ,? Lamarck Granodioritc 0 Cartridge Pass Granodiorite c Round Valley Peak Granodiorit)e ;.: Deep Canyon Granodiorite - - inconsolable Granodiorite

and

and lTosemit,c~

4- Mc?ulurry Nnadows Quartz Monzonitc 1 \Vheoler Crest Quartz Monzonitc T Diorite X Coyote Flat Granodioritc .2 Mt. Givens Granodiorito .I Tnngston Hills Quartz Monzonitc

-I5

1223

The deuterium content of hydrous minerals

.32 c

1

0

I

/ 0

1

0

.04

o-o” i>

0

0 0

7:

0 0

0

0

u

0

1

0 CJ i

Fig. 6. Fluorine:water Sierra Nevada

vs. deuterium for biotite from and Yosemit,e National Park.

the

from Yosemite (YlS and Y19) which also yielded the highest deuterium values These rare values are attributable to special geologic obtained in this study. circumstances, and in general it is held that the fluorine : water ratio in biotite and hornblende does not affect their D/H content. One specific example may serve to illustrate the point. Biotite samples M-133 and MM-133 collected within 1 f ft of each other have fluorine analyses of 0.35 and 0.62 per cent; however their deuterium content remains similar with AD = -10.3 and -9.7 per cent respectively. It is evident from Fig. 8 that the fluorine distribution between coexisting

1224

JOHN

D.

GODFREY

.I6

I

0

2.12

.08: 0 0 0

Q

/_I 0

.-4

-2

-6

-AD

Fig. 7. Fluorine

-8

%

: water vs. deuterium for hornblende Yosemite

-IO

National

from the Sierra Nevada

and

Park.

0.5 -

t wo4m c ci a : a@31 E : 6 023 LL

0

I

I

0. I

0.2

I

I

I

0.3

04

Fluor,ne

I

0.5 %

6,ot,le

0.6

I

0.7

L-~ 0.8

0.9

I

-

Fig. 8. Fluorine content of coexisting biotite and hornblende the Sierra Nevada and Yosemite Xational Park.

from

C

1323

The deuterium content of hydrous minerals

I

I

I

I

I

I

-15 -

Coexisting

biotite

-14

-

Coexisting

bioti

-13

-

-I2

-

0

-I

-2

-3

-4

-5

-tj

I

I

I

I

I

I

I

I/

- hornblende(o) te - chlorl

te

-7

-10 -/,

-8

-9

1x1

-12 -13 -,4

--,5 -16

AD % Blotlie + Fig. 9. Deuterium content of coexisting biotite and hornblende from the Sierra Nevada and Yosemite Kational Park. and hornblende is roughly constant, indicating an approximation to an equilibrium condition, and thus allowing a direct comparison of the D/H ratios without consideration of the fluorine contents. biotite

FRACTIONATION BETWEEN COEXISTING HYDROUS SILICATE MINERALS A plot of D/H ratios for forty coexisting biotite-hornblende pairs (Fig. 9) shows only limited deviation from the 45’ line representing unfractionated values; about 65 per cent of the data,plot beyond the limits ho.5 per cent of the ideal unfractionated values in the range AD = - 1.0 to - 14.5 per cent. Within this range the plotted data can be conveniently divided into five groups (Fig. 9) which will be used for reference later. The plot of eight biotite-chlorite pairs shows that chlorite tends to contain either similar or higher proportions of deuterium compared to coexisting biotite. with but, one exception. Differences in D/H ratios between augite and coexisting biotite and horneblende (Inconsolable granodiorite, 6-103-4, Table 7) are insufficient t’o indicate

a significant

fractionation.

It is tempting to suggest that biotite-horneblende the limits &to.5 per cent of the ideal unfractionated equilibrium are present

conditions. That in groups 1 to 4.

pairs which values could

plot outside of represent non-

is, both equilibrium and non-equilibrium However, there are a sufficient number

pairs from

the same pluton

suggestion

that most of these points

distributed

in both

represent

Group

2 and Group

equilibrium

situations of minerals

3 to allow

conditions

the

and t’hat

JOHN D. GODFREY

1226

slight shifts away from the unfractionated condition have been caused by isotopic fractionation between coexisting bitoite and horneblende. In comparing groups 2 and 3, hornblende is slightly enriched in deuterium relative to biotite in Group 2, whereas biotite is enriched in deuterium relative to hornblende in Group 3 (Table 2). The relative ages of the Sierra Nevada plutons from field relations, as suggested by PAUL BATEMAN (1961),* are given in Fig. 10. Table

2. Comparison

of coexisting Biot,ite

~___ Croup 2 Group 3

D/H

H,O%

-4.0 -6.2

3.4 3.4

* Not including

and hornblende Hornblende

____ FO/o 0.30 0.26

the abnormally

I Cortridse Pou

biotite

Xumber

D,H

H,OO,;

FO,;

-3.9 -6.6

2.1 2.0

0.15 0,12*

high F content

in Groups 2 and 3

mineral

of hornblende

of pairs

26 9 Y15

1

Fig. 10. Diagram showing intrusive relations and probable age sequence of the granitic rocks of the east-central Sierra Nevada, California (modified after HATEMAN 1961). Solid lines indicate observed relations dashed lines indicate inferred relations. * Bateman gives a complete geological description of the rock types mentioned in the present study including their field occurrence and characteristics, petrographic description, classification, radio-actjive age dates, chemical, modal, and normative analyses.

The deuterium

content

of hydrous

1227

minerals

The rock types in Group 3 (Fig. 11) do not represent a particular grouping with regard to time of intrusion, so that these derived D/H ratios are independent of the relative rock ages. If the deuterium content of the vapour phase changed during crystallization of a magma, it may be expected that since hornblende and biotite crystallize over different temperature ranges, they would have different D/H ratios. However, it

c

-7

I 0

Group

/

/

‘T

/

‘-’

1/’ 0

3

I -I

I I.-I

I -2

-3 -

I -4

AD

-‘5

-6

-7

-8

-9

-10

% Blotite

Fig. 11. Douterium content of coexisting biotite and hornblende of certain rock types from the Sierra Nevada and Yosemite National Park. Y Yosemite National Park + McMurry Meadows Quartz Monzonite T A Lamarck Granodiorito 1 Wheeler Crest Quartz Monzonite w 0 Round Valley Peak Granodiorite T Diorite 0 0 Cartridge Pass Granodiorite x Coyote Flat Granodiorite v A Cathedral Peak Type Quartz Monzonite .2 Mt. Givens Granodiorite :.: Deep Canyon Granodiorite . I Tungsten Hills Quartz Monzonite - - Inconsolable Granodiorite

is most likely that the D/H ratio of early-formed hornblende would re-equilibrate with the vapour-phase from which biotite and later-formed hornblende were still actively crystallizing. Data presented in Tables 2 and 3 show there is little difference in the volatile components of the mineral growth environments between Groups 2 and 3. The difference is expressed as a slight decrease in both H,O and F contents in Group 3 relative to Group 2 which suggests crystallization under lower vapour pressures in Group 3. However, it is felt that a slight change of vapour pressure in the range of crystallization temperatures would not be a significant factor in affecting t’he

1228

JOHN

Table

Il. GODFREY

3. Comparison of coexisting biotite and hornblende Sierra Nevada between Groups 2 and 3 Biotite

Group 2 Group 3

D/H

H,O%

-4.1 -6.3

3.5 3.4

Hornblende F%

D,H

0.28 0.25

-4.0 -6.6

from

t,hr

Number

H,OYO

F Yh

2.1 2.0

mineral

0.14 0.12

of pairs

21 8

deut#erium distribution between Groups 2 and 3, but’ that either varied crystallization temperatures or deuterium concentration in the growth environment was the principal factor in creating these marked differences. The frequency distribution of the average AD”/, of coexisting biotite and hornblende from the Sierra Nevada and Yosemite (Fig. 1’) shows Group 2 to be by far the most important group quantitatively, and.it is therefore interpreted a’s representing the primary conditions of mineral formation. Other groups are believed to be derived either in the course of primary crystallization in association with Group 2 or by alteration from this primary condition. 16

I

I

I

I

I

I

I

-. Group2

I 0-2 Fig. 12. Frequency

and hornblende

-4

-6 -AD%

-8

-10

-12

-14

-16

distribution of average dellterium content of coexist,ing biot,itc, from the Sierra Nevada and Yosemite Nat.ional Park.

Several models are considered in a general approach t#o the possible fractionation of deuterium between two c?.existing hydrous silicates d and B in equilibrium The schemat’ic curves in Fig. in an aqueous environment at various temperatures. 13 represent open system conditions (infinite water reservoir) where the isotope

The deuterium content of hydrous minerals

1229

ratio is the same in all phases at high temperatures, and hence a plot of the D/H ratios for coexisting minerals A and B (Y) formed at high temperature would fall on the line of non-fractionation (OW). Quadrants C and F would only be entered either in open systems where silicates A and B have opposing effects in the partition of deuterium with respect to the aqueous phase. or in closed systems where water was absent or formed a minor constituent.

0

-

AD%

S,l,cate

A

Fig. 13. Model open system showing change in deuterium content for coexisting silicate minerals A and B with temperature.

In the case where silicate A concentrates deuterium with respect to silicate B the possible paths of equilibrium fractionation with falling temperature are YP and YS. In considering the equilibrium fractionation of silicates with water, if water concentrates deuterium the fractionation path follows YP, but if silicates concentrate deuterium the fractionation path follows YS. In the case where silicate B concentrated deuterium with respect to silicate A, the corresponding paths are YQ and YR. Figs. 14, 15, and 16 represent models where equilibrium fractionation is (D/H) silicate > 1 operative at lower temperatures and (D/H) environment ’ Fig. 14 represents equilibrium fractionation between silicate minerals and an aqueous environment in a system of infinite reservoir. In geological terms this situation is equivalent to an open system where the deuterium content of the water will not change with temperature, and the difference in deuterium ratios between

JOHK D. GODFREY

1230

water and silicate at a particular temperature is a function of both the isotopic equilibrium content and the deuterium concentration in the water. However, the difference in deuterium concentration between coexisting silicates at a particular temperature is a function of the isotopic equilibrium constant alone. Fig. 15 represents equilibrium fractionation between silicate minerals and the aqueous environment in a system of finite reservoir, equivalent to a closed system in geological terms. Differences in deuterium concentration between silicate-water, and silicate-silicate at a particular temperature are a function of the isotopic

High

A

Temperature

Fig. 14. Model open system of infmite reservoir u-here

(D/H) silicate (D/H)

environment

.I.

equilibria constants alone. The symmetrical shape of the curves in Fig. 15 indicate equal amounts of water present in the environment and in the silicat,e phase. The approach of either of the curves to the horizontal dashed line means a greater amount of water in the corresponding phase. while the curve for the remaining phase moves away from the horizontal dashed line as its D/H ratio becomes more extreme. At any temperature the maximum AD deviation of the silicate phase from t,he initial composition 0 is represented by the silicate curve in Fig. 14. Under these circumstances the ratio of water in the environment to that held in the silicate is so large that the reservoir is essentially infinite. and hence approximates the conditions illustrated in Fig. 14. Fig. 16 represents fractionation between silicate and the aqueous environment in a system of finite reservoir where only partial equilibrium is attained in the course of removal of early-formed minerals which do not re-equilibrat’e with the remainder of the system. Geologically, this condition is equivalent to progressive crystallization in a cooling magma where early-formed minerals segregate and thus are prevented from re-equilibrating with the aqueous environment at lower temperatures. The shape of the curves in Fig. 16 are schematic since they are dependent on the relative amounts of water in the fractionating phases, the amount of silicate mineral removed from the system, and the stages at which silicate is removed in the cooling history. Differences in the deuterium content of coexisting silicate minerals in equilibrium with the aqueous environment at a given temperature are dependent only on the isotopic fractionation constants of the minerals involved. However, the absolute D/H ratios are also determined by the amount of deuterium in the equilibrating system, and this factor could be greatly influenced by the effectiveness in removal of the early-formed deuterium-enriched minerals. Perspective diagram Fig. 17 illustrates the same system which is represented in Fig. 16, but in addition separates two silicate components A and B from the

The deuterium

Fig.

content

of hydrous

15 e” H

.

.

‘\Slltcato

! 1 High

-

F,n,te vopour (eorlv-formed

Fig.

Fig.

LOW

Tempera+urc

reservo,r.closed s~kate

system.

removed)

16

ri gh

Fig.

1231

minerals

-

Temoerature

15. Model closed system of finite reservoir 16. Model

closed system

where early-formed

where

of 6.nite vapour

silicate removed

LOW

(D/H) silicate (D/H)

environment

reservoir and partial (D/H) silicate and (D/H) environment

> 1.

equilibrium > 1.

Fig. 17. Model closed system of finite vapour reservoir and partial equilibrium showing change in deuterium content for coexisting silicate minerals A and I3 in aqueous environment with temperature where early-formed silicate minerals and (D/H) silicate A (D/H) silicate 1 1. > 1; removed and (D,H) environment, (D/H) silicate B

JOHN

1132

II. GODFREY

aqueous el~vironmeI~t. The AD% variation for each silicate mineral and the Removal of early-formed silicates environment is traced with falling temperature. enriched in deuterium allows only partial equilibrium amongst the remaining component,s of a deuterium-depleted system. Thus, the final phase in the equilibrating system at low temperatures are considerably deuterium-depleted and fall towards the end of the curves YH and YM. Again, differences in ADY” for coexisting mineral phases are dependent on the isotopic fractionation constants: but the absolute D/II rat,ios are also a function of the amount of deuterium in the equilibrating system. Construction of this figure fits tbe condition that isotopic fractionation between silicate A and the environment increases with decreasing temperature, and hence the interval 1 t,o 1’ < 2 to 2’ < 3 to 3’ < 4 to 4’. > I. it is based on the assumption that --.__ (D/H)R apparent that the generation of a highly deuterium-depleted aqueous environment could be most readily achieved by the removal of early-formed hydrous silicate from t,he system, corresponding to the situation representBed in Fig. 16. d somewhat deuterium-depleted aqueous environment would be formed in the case represented in Fig. 15, but the degree of deuterium depletion is limited by the isotopic equilibrium constant,. Deuterium depleted aqueous phases could be effective in producing minerals low in deuterium either by exchange with earlier-formed minerals or by participation in the crystallization of newly-formed minerals. Progressive crystallization, fractionation and crystal segregation in a closed system of the type shown in Fig. 16 could produce hydrous minerals of a Dfr-2 ratio beyond the lowest values recorded in this study. Thus, the formation of deuterium-depletion silicates by fractionation in the course of crystallization (such as those represented in Groups 4 and 5) suggests the operation of systems which are locally closed with respect to t,he aqueous phase, but where early-formed hydrous silicates may be segregated and do not re-equilibrate with the aqueous phase. Closed systems may be locally realized within a magma chamber where connection with the main aqueous reservoir is ineffective. Under these cir~urnstal~~es varied degrees of deuterium-depleted are possible at different locations dependent upon conditions of temperature change, crystal segregation, relative amounts of aqueons phase and hydrous silicate, and the nature of the system wit,h regard to spatial continuity of the aqueous phase in time. Since the process of deuterium-depletion of an aqueous phase by isotopic fractionation could be effected so readily in localized closed systems, it seems possible that this condition would be repeated at several locations within the same pluton. and further, within several plutons. Under these conditions it can be inferred that parts of at least three plutons-Round Valley granodiorite, Cartridge Pass granodiorite and Lamarck granodiorite-have contained closed systems in which fractionation and deuterium depletion of the aqueous phase has been achieved. It is quite possible that Group 3 is derived from Group 2 by deuterium-depletion through fractionation, which would bring the total to eight affected plutons. However, this stage must take place at lower temperatures where a new isotopic From t,he foregoing

discussion

The deuterium content of hydrous minerals

1’33

equilibrium constant between biotite and hornblende prevails in which biotite preferentially concentrates deuterium, and Group 3 moves laterally from the condit’ion of non-fractionation, (Fig. 11); note that Group 2 is more symmetrically posit’ioned along the line of non-fractionation. Silicates of low deuterium content such as Groups 4 and 5 may also form from water of different origin and history such as magmatic waters contaminated by exTwo contrasting mamlers of ternal waters which are relatively low in deuterium. dilution are examined here: firstly, the formation of an aqueous phase of varied nature. in which intermittent mixing of magmatic waters with new external waters is

Fig.

closed system of finite vaIlour reservoir and Ijartial oyuilibrilml (D/H) silicate X’ 1. where early-formed silicate removed and (1)/H) environment

18. Model

combined with a changing pattern of aqueous phase circulation. Together, these factors would be expected to produce a spectrum of D/H values in hydrous silicates. which, however, does not fit the distribution shown in Fig. 9. A second manner of dilution involves the formation of a uniform aqueous phase in which mixing is rest,ricted to a relatively short time, followed by an essentially closed system. These condit.ions would be expected to produce closely grouped D/H values in coexisting hydrous silicates within a limited area. The latter case fits the conditions necessary for a D/H shift of parts of plutonic masses from Group 1 to Groups 3. 4 and 5. and possibly to other hitherto undetected groups. Let us consider the application of the alternate assumption that deuterium is concentrated in the aqueous environment relative to the coexisting silicate phases. Fig. 18 represents the analogous case to Fig. 16 i.e., removal of early-formed minerals in a closed system to permit, only partial equilibrium, but here deuterium is concentrated in the environment relative to the coexisting silicate phase. The net result is the production of a deuterium-enriched residual environment. Similarly, Fig. 19 is analagous to Fig. 17, except that again deuterium is concenbrat’ed in the environment relative to the coexisting silicate phases. (D/H) silicate Under the prevailing assumption that < 1, Groups 3, 4 and (D/H) environment 5 must be formed by a mechanism other than isotopic fractionation of magmatic water, and the most likely would seem to involve mixing of magmatic with external waters of low deuterium content.

JOHN

D.

GODFREY

Y

-

AD%

Su!rcote A and

0

Environment

Fig. 19. Model closed system of finite vapour reservoir and partial eyuilibrium showing change in deuterium content for coexisting silicate minerals A and 13 in aqncous environment with temperature where early-formod silicate minerals removed

and

__

(D/H) silicate

(D/H)

Fig.

~n~ironrllent,

<

1.

and

’

@I%? silicate A

. , 1,

(U/H) silicate B

20. Schematic diagram of deuterium aureoles to groups 1 to Ei within a pluton.

corresponding

The deuterium

content

of hydrous

1235

minerals

The skew character of Fig. 12 indicates the operation of a process (or processes) in addition to those concerned with the primary crystallization of Group 2 materials which is responsible for the low deuterium content of some minerals and where the most negative values represent an extreme development of that process. The process could essentially be the dilution of magmatic wat’ers by “light” external (D/H) silicate > 1 holds true, isotopic waters. However, if the assumption (D/H) environment fractionation in aureoles or zones is favoured, where progressively smaller equilibrating volumes, corresponding to progressively more restricted circulating systems, result in greater deuterium depletion in the residual system. A schematic representation is shown in Fig. 20. An appropriate suite of samples from a Group 4 or 5 location would readily test the possibility of a concentric arrangement of “deuterium zones”. Irregularities and imperfect aureoles may be found in nature due to changing circulat,ion patterns of solutions and porosity of rocks in response to stress adjustments and chemical activity.

This process occurs late in the petrogenetic evolution of magmatic plutonic rocks and is customarily associated with the pneumatolytic-deuteric stages. From this point of view the D/H ratio and fluorine conOent of secondary chlorite, mainly after biotite, is of interest. Seven of eight chlorite samples have an equivalent or greater deuterium content that the coexisting biotite, and the exception. which is based on a single isotopic analysis, is regarded as being possibly anomalous. The three chlorite samples with fluorine analyses show a reduced fluorine content and hence a greatly increased fluorine : wat’er ratio compared to that of t’he coexisting biotite (Fig. 4, Table 4). The average fluorine:water weight per cent Table

4. Comparison

of analytical

data for coexisting

Riotite

Chlorite

D/H

H,O%

F%

-5.0

3.6

1.0

0.278

-4.7

3.8

0.55

4.3(?)

0.23

14.2

F/H,0

biotite

_____

H,O %

F%

-3.6

10.6

0.31

0.028

0.145

-3.6

9.4

0.10

0.011

0.053

- 13.7

10.0

0.14

0,014

D/H

and chlorite

Rock

type

F/H,0 Cathedral Peak type quart’2 monzonite Cartridge Pass granodiorit’e Lamarck granodiorite

ratios for all analysed biotites, hornblendes, and chlorites are ‘71100, 71100, and l.S/lOO respectively; and the average fluorine weight percentages are 0.25, 0.15, and 0.18 respectively. These values show a consistent fluorine: water ratio in biotite and hornblende, suggesting that these minerals crystallized under similar physico-chemical conditions and approximated equilibrium. The fluorine: water ratio for chlorite is in marked contrast to that in the coexisting

1236

JOHN

D.

GODFREY

biotite and hornblende which would not seem to be accounted for an the basis of crystal chemistry alone as chlorite and biotite are phyllosilicates of similar chemistry. If there is no great difference in the fluorine attraction by chlorite and biot’ite in similar environments, then the observed significant differences in fluorine : water ratios and in the fluorine contents of these minerals are best explained as a function However, if the approximat,ion is not valid. of varied cryst.allization conditions. t,hen environmental conditions cannot be isolated as the major factor in accounting These chlorites have lower fluorine for the differences in fluorine distribution. contents t’han expected in view of their high water content, the ease of substitution of fluorine and the hydroxyl ion (ionic radii I .33 and 1.4 to 1.6 A respectively, GOLDSCHMIDT, 1954) and the relat’ively high fluorine content of coexist,ing biotites. From the foregoing considerations it is evident that conditions during chloritization were proba’bly quite different from those prevailing in the crystallization of biotite and hornblende such that: 1. The fluorine content of the chloritization solutions was probably low compared ho that in the solutions of primary crystallizat’ion. However. it is generally accepted t’hat fluorine and other volatiles are concentrated rather than depleted in t,he course of magmatic evolution and reach a maximum in magmatic pneumatolytic products (GOLUSCIUVIIDT, 1954). 2. The high fluorine : water rat,ios in secondary chlorites is probably due to both low fluorine contents in the chloritization solutions and to different I’T conditions prevailing during primary crystallization. 3. The fluorine content of biotite and hornblende coexisting with chlorite was apparently unaffect.ed and did not re-equilibrate in t’he course of chlorit’ization. This. however, was not the case for the deuterium content’ of t,hese minerals, see Lamarck granodi0rit.e B&102-2. Table 7, where the D/H rnt,ios for coexisting biotite hornblende. and chlorite are similar a,nd far removed from the D/H ratios typical of other samples from this pluton. 4. Considerable fluorine was released to the environment during chloritization of biot’ite. Such fluorine would be a contributory fact’or in any general rock alt’eration which is known to commonly accompany chloritization. In the case of Group 2 and adjoining chlorites (Fig. 9), i.e. the majority of chlorites examined in this study, it is suggest,ed that chloritization was related to late-stage primary crystallization because of the coincidence of deuterium concentrations with those of biotite and hornblende. (Many biotit’e and hornblende separates which fall in Group 2 are fresh and show no alteration or tendency to form chlorite; thus we may assume that D/H ratios of Group 2 represent deuterium concentrations which are typical of primary crystallization conditions rather than a re-equilibration with chloritization solutions of a subseqent period of alteration). The D/H rat’ios of four chlorites which plot on or close to the zero fractionation line (Fig. 9) have probably been unaltered since formation. but three other chlorites are notably heavier than their coexisting biotite. The high deuterium content of these three chlorites may have resulted either from a low temperature fractionation which favoured chlorite, or from a process which preferentially affect,ed the generally more loosely held water of chloribe as compared to that held in biotite.

The deuterium

content

of hydrous

1237

minerals

The latter possibility seems more likely in the event of local thermal effects or by exchange with a localized heavy water. The previously mentioned anomalous “light” chlorite could be included here as the result of exchange with a “light” water. The extremely low deuterium concentrations in the hydrous minerals of sample BB-102-2 are best accounted for either by re-equilibration with an influx of external waters or by extreme fractionation of locally contained magmatic waters such that the residual solutions were deut’erium depleted. In summary, chloritization has taken place at the late primary crystallization or pneumatolytic stage, in waters of Group 2 composition, and where the fluorine content was low. Chlorites enriched in deuterium relative to the coexisting biotites may have resulted either from exchange with heavy water or from a low temperature isotopic fractionation which favoured chlorite. The fluorine content of biotite seems to remain unaffected in the course of partial chloritization, while its deuterium cont’ent has been changed in at least one instance. Release of fluorine to the environment accompanies chloritization of biotite. CARTRIDGE PASS GRANODIORITE This pluton is of special interest since it has been shown by James G. Moore to be distinctly zoned on the basis of specific gravity, colour index, plagioclase composition, and plagioclase, quartz, and K-feldspar cont’ent. From margin to core the rock types become more acidic. To test the possibility that this zoning may also pertain to the D/H rat,io of the hydrous minerals, seven samples, representing a cross-section from margin to core of the pluton have been studied, and the results are presented in Table 5. These data show a lack of systematic change of D/H ratio, water content, or the index of biotite with the spatial distribution. The refractive index of biotite would be expected to reflect the chemistry of the mineral, in particular the Fe3+:Fe2+ and Table

5. Coexisting

biotite

and hornblende

from the zoned

Biotite AD%

3320%

Cartridge

Hornblende F%

AD%

H,O%

Pass granodiorite Befractive Index Biotite

F%

(Exterior) M-127

-4.1

lM-131 M-139 MM-139

-4.4 -3.4 -3.5

3+* 3.7 3.5 3.5

0.21 0.36 0.40 0.45

M-135 MM-135 M-109

-4.1 -4.7 -3.6

3.5 3.8 4.0

0.55 0.55 0.92

-10.3 -9.7 -3.7

3.8 3.7 3.6

0.35 0.62

M-133 MM-133 B-720 (Interior) * Purity

of mineral

sample

-3.7 -4.2 -3.3 -3.6

-10.7

not evaluated,

2.2* 2.2 2.3 2.3

2.2

and H,O%

0.13

0.14

1.630 & 0.005 1.632 i 0.005 1.630 + 0.005 1.625 & 0.005 1.625 1.625 1.628 1.627 1.625 1.635

not reliable.

f + h h f +

0.005 0.005 0.005 0.005 0.005 0.005

1238

JOHN 1). GODFREY

Fe:Mg ratios. However, there is a definite increase in the fluorine content of These data should fit the petrobiotite from exterior to interior of the pluton. genetic picture of the Cartridge Pass granodiorite as indicated from other petrologic factors mentioned above. Like several other plutons in the Sierra Navada the Cartridge Pass granodiorite was locally affected by a later re-equilibration and biotite and hornblende from samples M-133 have considerably “lighter” water than samples from other zones of the pluton. The three ‘MM’ samples (duplicates of the ‘M’ samples, collected up to 2ft apart) establish the range of isotopic variation to be expected between hand specimens These variations range up to O.G’$&in the D/H collected from a small outcrop. ratio for biotite. Further, the samples &I-133 and MM-133 give some idea of the minimum distance involved in areas of isotopic re-equilibration as indicated by deuterium-depletion in coexisting biotite and hornblende. COMPARISON OF SOME ROCK TYPES FROM THE SIERRA NEVAU~~

AND THE YOSEMITE NATIONAL PARK It is immediately apparent from the Fig. 21 that the coexisting biotite and hornblende from the Yosemite plutons are considerably enriched in deuterium compared to those from the east-central Sierra Nevada plutons. This cont’rast in D/H ratios may be a consequence of such factors as isotopic fractionation on a gross scale, the degree of mixing of magmatic and resurgent waters, or simply that all magmatic waters do not have the same isotopic composition. In the Yosemite group only the two samples of Cathedral Peak quartz monzonite and one of Half Dome quartz monzonite have AD?/, values which overlap those of the Sierra Nevada rocks. As in the case of the Sierra Nevada examples, the low negative ADo/, values of Yosemite minerals may represent secondary effects resulting from local fractionation and re-equilibration, or from dilut’ion of magmatic waters. The magmat,ic complex of the Yosemite rocks appears to have crystallized from a relatively deuterium-rich, and fluorine-rich environment (Table 7). However, if the earlier discussion concerning the derivation of Group 1 rocks has any validity, some aspects of petrogenesis dealing with deuterium and fluorine concentrations of the Sierra Nevada and Yosemite rocks will be quite similar. The distribution of D/H ratios of one rock type in more than one group indicates a complex. diverse history and renders any attempt to use averages of all data of a rock type quite invalid. The present interpretation would regard averages from only Group 3 to have any validity in t#erms of primary isotopic distributions. Ext’remely high or low fluorine contents of hydrous silicat’es of bot,h t,he Sierra Nevada and Yosemite are associated with abnormal deuterium concentrations and coincide n-it’h discontinuit’ies in t’he trends presented in Fig. :! 1. The smaller number of Yosemite plutons and the relatively high proportion of “unusual” fluorine values do not permit satisfactory trend lines to be sketched in Fig. 21. This figure also shows that hornblende has a slight preference for deuterium in Group 2 (high temperature fractionation?) while biotite has a preference for deuterium in Groups 3. 4. and 5 (lower temperature fract,ionation?).

The douterium

content

of hydrous

minerals

1239

0 Hornblende

Fig. 21. Deuterium content of coexisting biotite and hornblende from rock types of the Sierra Nevada and Yosemite National Park in chronological sequence.

There appears to be no marked trend (Big. 21) relating t,he deuterium content of biotite and hornblende with the age (MATTHES. 1930; CVRTIS. et al.. 1958) of the parent rock. One outstanding peculiarity is the exceptionally high fluorine content of biotite and hornblende in the Cathedral Peak quartz monzonite of Yosemite and in the Cathedral Peak type rocks of the Sierra Nevada which are regarded by Bateman and co-workers as lithologic equivalents. The fluorine content of biotite and hornblende in these rocks is higher than those in all other plutons studied by a factor of two or three, and of course these minerals are also among those which are lowest in water content. It is apparent that the geologic evolut,ion of the Sierra Nevada and Yosemite complexes have followed similar paths in producing a Cathedral Peak type rock late in the sequence where abnormally high fluorine concentrations were present in the residual volatiles. There has not been a gradual build-up of fluorine concentration in the course of evolution in these complexes; in each case the high fluorine concentration is unique to the Cathedral Peak type rocks. This type of rock must represent a stage at which the vapour pressure of fluorine was exceptionally high, perhaps in a locally restricted system, such that older, adjacent plutons were not affected and did not re-equilibrate with the residual volatiles.

1240

JOHN

Table

6. Comparison

of Yosemite, Average

Complex Tosemitje

Southern

y

California

Average

Age 88 nl

II. GODFREY

Range

AD% (1)

-2.7

Sierra Nevada

108 m y (2)

-4.0 (-5.o)***

._

--3.3 to -4.7

-3.7*

109 m y (2)

Plutonic (:omplexes

Minerals Analysod Uiotite Horneblende

AD%

(--3.3)** Southern (Talifornia

and Sierra Nevada

(-1.0

to -5.8)

(10;

~~1.5 t,o -3.5

8

-3.3 (-3.3

*

t>o -5.0 t>o -14.8)

8 21

(4%fl . (31)

* Samples of (iroup 2 only ** Including samples in Croups 1, 2 and 3 *** Including samples in Groups 2, 3, 4 and 5 (1) CCRTIS ct al. (1958) (2) ,JAFFE et ul. (1959)

Table

7. Composite

table

of D/H, H,O% and FO/;, for all minerals Nevada and Yosemite _Vat,ional Park Hornblende

Biotite D/H

H&J%

F%

SIERRA N’EI-ADA Cathedml Peak type quartz monzonite -5.9 3.1 1.5 ill-842 -5.0 3.6 1.0 M-962 -5.3 3.8 0.62 PB-1 -8.0 3.8 0.54 CP-1 Tungsten Hills quartz monzonite -4.3 3.2 I’B-2 Curtridge Pass grunodiorite -4.1 3.8* 0.21 M-127 -4.4 3.7 0.36 M-131 -3.4 3.5 0.40 M-139 -3.5 3.5 0.45 MM-139 -4.1 3.5 0.55 M-135 -4.7 3.8 0.55 MM- 135 -3.6 4.0* 0.92 M-109 -10.3 3.8 0.35 M-133 -9.7 3.7 0.62 MM-133 -3.7 3.6 B-720 Coyote Flat granodiorite -4.4 3.3 0.18 6-124-10 -6.4 3.0 0.17 6-124-9

D/H

H,O%

I?%

2.0

-3.7 -4.2 -3.3 -3.6

2.2* 2.2 2.3 2.3

- 10.7

-3.7 3.0 -6.0 3,2* 0.24 MCiWUWay Meadows quartz monzonite -4.3 3.2 0.22 6-153-2 -5.1 3.1* 0.47 12-10-3 Deep Canyon granodiorite -3.3 3.0 0.26 98-69-19

the Sierra

H&O/,

Fo/,

10.6

0.31

-3.6 -2.4

9.4 11.7

0.10

-3.8

13.6

D/H

-3.6

-4.5

from

Chlorite

0.13

0.14

2.2

-3.8 -6.1

2.3 2.2

0.10 0.10

-3.7 -7.0

2.1 1.9

0.05 0.16

-4.1 -6.1

2.0 2.0*

0.16 0.21

-4.0

2.1

0.13

IlioritP 6-65-4 6-g-6-

analysed

The deuterinm

content Table

6-103-f I?ound 6-3-l 6-5-6 6-5-5 6-3-2

D/H

3.2* 3.i

0.30 0.30

-4.1 -7.2

granodiorite -3.8 3.3* -5.5 3.4*

0.30 0.23

-3.9 -6.3

2.0* 1.ci*

0.09

0.13

-7.2

1.9

0.10

__3.7 --4.4 --3.7 -9.4

1.9 2.2 2.2* 2.0*

0.13 O-22 0.27 0.13

-3.5 -4.8

2.3 2.0*

0.06

-3.8 -6.6

Inconsolable 6-141-4 6-103-4

Chlorite

Hornblende F%

D/H

~-98-69-15 98-20-l

-7.5

SO%

3.4

1241

minerals

7 (Contd).

Biotitc

_

of hydrous

H,O -2.0” 2.1

F%

D/H

0.14 0.14

H,O%

F%

-5.7

0.8

0.04

-6.4

9.4

-13.7

10.0

-2.6

8.2

-3.0

9.5

~ (Angite)

Peak gravaodiorite -3.7 3.4 0.18 -4.3 3.5 0.47 -4.6 3.5* 0.45 -9.6 3.8* 0.25 Wheeler Crest quartz monzovkite 98-72-7 -3.7 3.5 0.28 98-23-l -4.6 3.9 0.09 95-44-48 -4.8 3G3* T7dlr!~

Lam.arck granodiorite B6-102-21 -3.2 6-71-3 -4.1 6-70-l -5.0 6-72-U -6.3 6-71-11 -- 7.2 B6-102-2 -14.2 Jft. Gioens granodiorite KP-4 -4.6 Ab-3 -4.6

3.5 3.7 3.8 3.4* 3.6 4.3*

0.21 0.31 0.29 0.21 0.21 0.23

--3.0 -4.1 -4.5 m-6.5 -6.8 -14.5

2.1 2.1* 2.1 2,1* 2.2 2.3*

0.12 0.15 0.16 0.14 0.15 0.15

3.5* 3.3

0.21

-4.5 -4.6

2.2 2.1

0.16 0.17

-5.8

2.1*

0.55

-3.3

2.0*

0.15

-3.6 -3.1

2.0* 2.0”

0.21

YOSEXITE XA TIOVAL f’A RK Cathedral Peak quartz monzonite Y14 -4.5 3.1* 0.92 Y15 -5.3 3.9* Quartz dioritc Yl6 -3.3 3.4* 0.24 El Cap&an granite Y17 -3.5 3.1* 0.37 Y20 -3.8 3.2* 0.55 Y22 -2.4 3.0* 0.57 Sentinel granodiorite Y18 -1.7 3.0* 0.18 Y21 -3.3 3.8* 0.30 Doloritc: Y19 -1.4 3.2* 0.13 Half Dome quartz monzonite D-922 -4.7 3.5* 0.31 * Purity

of mineral

separate

-1.0 -3.0

1.9* 2.1*

-1.3

2.2*

-4.3

2.2*

not evaluated

0.06 0.15

0.14

0.12

and H,Oo/o

not reliable.

Table 0 presents data for a comparison of the Yosemite, Sierra Nevada and Southern California batholiths. Preliminary data on the latter are from a paper in preparation by Miss Betsy Levin and I. Irving Friedman of the U.S. Geological Survey.

1242

JOHN

D. GODFREY

Comparison of data believed to be the most representative of primary crystallization conditions, i.e., Group 2, points to similarities between Yosemite and Sierra Nevada in contradistinction to the Southern California complex. In view of the lack of adequate, comparable data the ultimate meaning of these averaged data is not clear but it is suggested that differences may reflect regional fractionation or mixing with varied amounts of resurgent water. In the latter case, since the average of present-day ocean water is +- 4.1 %D, the Southern California batholith would appear to be least representative of AD% values of magmatic, or mixtures containing significant amounts of magmatic, and juvenile waters.

The st,rict temperature dependence of t’he fractionation of the D/H ratio between hydrous silicates and the growth environment leads to the possibility of a useful geological thermometer in which the temperature of the last equilibrium would be recorded. Because of the lack of knowledge of the deuterium cont,ent of the aqueous growt,h environment in equilibrium with a hydrous mineral, it is necessary to study two or more coexisting hydrous silicates which have equilibrated with the same aqueous environment, since the isotopic fract’ionation between the minerals is independent of the environment composibion. Data from the present study are inadequate, and t’his interesting possibility remains to be tested by an appropriabe series of critically selected suites of samples. Either metamorphic t,hermal gradients or products formed at various stages in the cooling history of igneous plutonic masses would provide a suitable geological setting for such an examination. SUMMARY ANI) CONCLIJSIONS 1. Coexisting biotite-hornblende from plutons of the Sierra Sevada and Yosemite National Park have been divided into five groups on the basis of their D/H ratios. The five-fold division of the mineral pairs bears no relationship to the ages of the corresponding plutons. The majority of D/H ratios for these mineral pairs show little or no isotopic fractionation between biotite and hornblende. 2. The plutons represented in Group 2 are believed to have crystallized from large, spatially continuous reservoirs (i.e. simulating open-system conditions) where a fairly constant deuterium concentration was maintained throughout the periods of primary crystallization in the Sierra Nevada and Yosemite magmatic complexes. The mineral pairs of Group 2 may represent equilibrium fract’ionation under conditions of biotite crystallization, i.e., a relatively high temperature. 3. Coexisting biotite and hornblende of Group 2 have comparable D/H ratios and it is felt that this non-fractionation is associated with high temperature equilibration. 4. Coexisting bitoite and hornblende of Group 3 show a tendency for biotite to be enriched in deuterium, i.e., represented by a lateral shift from the line of nonfractionation (Fig. 10) and it is suggested that this condition arises from an equilibrium fractionation at lower temperatures. 5. Group 2 represents minerals in their primary state of formation, while Groups 1, 3, 4, and 5 represent minerals which have either grown in a deuteriumdepleted or deuterium-enriched environment relative to that of Group 2, or have

The deuterium content of hydrous minerals

1243

undergone alteration involving isotopic fractionation such as exchange and reequilibration with deuterium-depleted or deuterium-enriched waters, or partial dehydration-rehydration. 6. Group 1 minerals with the greatest deuterium concentration of all minerals analysed occupy a unique position within the scope of this study. They formed either from a growth environment which became enriched in deuterium as crystallization progressed or by later exchange with a deuterium-enriched environment. 7. The deuterium-depleted waters equivalent to Groups 3,4, and 5 are believed to have formed either by isotopic fractionation of magmatic water in a closed system where segregation and isolation of the initial solid phase permitted only partial equilibrium, or by limited mixing of magmatic and external waters which were low in deuterium. 8. AD:/’ mineral values of Groups 3,4, and 5 are not due to secondary effects such as partial dehydration resulting from local reheating as we should observe cases where one mineral in a coexisting association has been preferentially affected because of their different ranges of dehydration temperatures. I). The D/H ratio of biotite, hornblende and chlorite is generally independent of their fluorine content. 10. Extremely low concentrations of fluorine coincide with high deuterium concentrations in two biotite and hornblende pairs of Group 1. Since high fluorine concentrations do not consistently correlate with low deuterium contents, and a general relationship between fluorine and deuterium is lacking, it must be concluded that two independent processes were at work in the same environment. 11. Biotite and hornblende from Cathedral Peak quartz monzonite and Cathedral Peak type quartz monzonite plutons have abnormally high fluorine concentrations which suggest consolidation under considerable fluorine pressure in a restricted or closed system. The deuterium contents of these minerals do not appear to be abnormal, falling in the region of the Group P/Group 3 margin, and hence special conditions of crystallization or recrystallization are not otherwise indicated. 12. Chronologically, chloritization preceded the deuterium exchanges which resulted in the distribution of mineral D/H ratios between Groups 3, 4, and 5. This conclusion arises from the occurrence of most chlorites in the neighbourhood of Group 2. and it seems reasonable that the Lamarck chlorite shifted to the Group 5 position at the same time as the coexisting biotite and hornblende. An alternative explanation would involve two stages of chloritization; first, a general chloritization with D/H ratios in the Group 2 range, and second, a more restricted chloritization with D/H ratios in the Group 5 range, causing isotopic re-equilibration in the coexisting biotite and hornblende. 13. Chloritization most likely took place at the end of primary crystallization while the D/H ratios were still in the Group 2 range, but also overlapping the early deuteric stage where the fluorine concentration was beginning to be built up (Lamarck chlorite). 14. During chloritization of the Lamarck granodiorite the D/H ratios of coexisting biotite and hornblende re-equilibrated with the aqueous environment; however, t’heir fluorine content remained unaffected (B6-102-2).

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JOHN D. GODFJLEY

16. Chlorites relatively high in deuterium content compared t’o the coexisting biotite probably represent re-equilibration with waters enriched in deuterium. 16. D/H ratios in some coexisting hydrous silicat’es (e.g. M-133 aud MM-133. BG-10%2) show that local isotopic equilibria are import,ant in an igneous plutonic environment: and point to the existence of small closed systems, (at lea’st 2 ft’ in diameter), particularly in t)he deuteric stage of batholithic formation. I ‘i. Magmatic waters are appa,rent’ly “light” (-4.0) compared to t,he present)day ocean water average (-t4.1). These data concur with proposals by UREY (1953) and others that hydrogen has been lost from the earth’s atmosphere through geologic time, and hence juvenile waters which make up a pa,rt of magmatic waters should be relatively light. If t,hat part of magmat’ic water made up of resurgent, wat’er falls in the range AD = -- 4.0 to -l-4*1’;‘,. t,hen juvenile waters should be somewhat less than -4*OO;, in order to arrive at’ appropriate 409’0 values of magmatic water. FRIEDMAN (1953) has suggest’ed thah juvenile wat*er is depleted in deuterium relative to the average of present-day surface waters. The problem of identifying juvenile water may be best approached by a study of fresh volcanic materials in ocean basins. where the complicat,ions of secondary processes in a plutonic environment are avoided. 18. The range of deuterium concentrat,ions appea,rs to be from - I .O to -5.0 (or ~ 14.5 including secondary processes) in igneous plutonic complexes ; from -6.2 to ~ 15.0 in extrusive rocks; and since present-day ocean water ranges from -t-3+ to -t-15*5, it may be possible to distinguish between metamorphic rocks arising from the transformat’ion of marine sediments as compared to t’hose from igneous and meta-igneous plutonic or extrusive bodies. Acknouledgements-I should like to acknowledge my indebtedness t*o 1. IRVING F~IJX~MAN, who has encouraged this work and made suggestions at ovcry point). InSal studies wt’re carried out in the laboratories of HAROLD C. UREY at the Enrico Fermi Institut,e, University of Chicago. The experiment,s were completed in the laboratorios of I. IR~IS~ FRIEDMAN, by invitation of the U.S. Geological Survey, at the Kational Bureau of Standards, TVashington, D.C. Special t,hanks are due to J~SEPII HARRIS, assisted by X~R~IK Z/ZACK,who carried out the tlificult fluorine analyses, BETSY LEVIN, ~VAYR’E E. HALL, and other members of t.he U.S. Geological Sltrl-cly who so kindly received and helped me in FVashington, D.C. PAUL PATENAN and colleagues of tho U.S. Geological Survey supplied critically chosen samples for laboratory examination from areas recently studied in the Sierra Ksvada. The Research Council of Alberta made 1)ossible the visit to Washington, D.C., and beneficial discussions were held with several of it,s staff members, particularly ARTHCR T. BLADES and LUBISMW A. B_~YRo~K. I. IR~IK;~: FRIE:U_MAN, GEORGE \Y. DE VORE, JULIAN R. GOLDSMITH, HANS RAMBEM: ant1 HAROLD (‘. UHF,Y ha\-v read and contributed to the improvement, of t)his manuscriptj. REFERENCES BATEMAN I’. C. (1961) Granitic formations in the east,-central Sierra Scvada near Bishop, California. G’eol. Sot. Amer. Bull. $2, 1521-1538. BIRCH V., SCHAIRER J. F. and SPICER H. C. (1942) Handbook of physical const,ant,s. Geol. SOC. Amer. (Special paper Ko. 36) 325. BOATO G. (1954) The isotopic composition of hydrogen and carbon in t,he carbonaceolls chondrites. Ceochim. et Cosmochim. Acta 6, 209-220. CHOWDBTTRYR. R. (1941) Handbook of mica. Chemical Publishing Co. New York. CRAIG H. (1957) New research methods in hydrology. Comm. on research in. water ~SOZITCPW, Univ. of California, 37.

The deuterium

content

of hydrous

C. H., EVERNDEN J. F. and LIPSON J. (1958) in California by the pot,assium-argon method. ural Resources, p. 16 (Special report 54).

C'URTIS

minerals

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Age determination of some granitic rocks St,ate of California, Department of Nat-

EDWARDS G. (1955) Isotopic composition of meteoritic hydrogen. Nature Land. 176,109. FRIEDMAN I. I. (1953) Deuterium content of natural water and other substances. Geochim. et Cosmochim. Acta 4, Nos. l/2, 89-103. FRIEI~MAN I. and SMITH R. L. (1958) The deuterium content of water in some volcanic glasses. GeoclLim. et Cosmochim. Acta 15, No. 3, 218-228. GOLDSCHMIDT 1’. M. (1954) CT’eochemistryOxford University Press, p. 730. GRI~IALDI F. S., ITGRAM B. and CUTTITTA F. (1955) Determination of small and large amounts of fluorine in rocks. Analyt. Chew&. 27, 918. .JAFFE H. W., GOTTFRIEU D., WARING C. L. and WORTHI~‘G H. VT. (1959) Lead-alpha age determinations of accessory minerals of igneous rocks (1953-1957). U.S.G.S. Bull. 1097-B, p.148. KAUFFMAN A. J., Jr. and DILLIXG E. D. (1950) Differential thermal curves of certain hydrous and anhydrous minerals, with a description of the apparatus used. Eco~a. Geol. 45, So. 3. KOI~UBTT,HOBI~HIDE, MAYEDA T. and UREY H. C. (1961) Deuterium content of minerals, rorks and liquid inclusion from rocks. Geochim. et Cosmochim. Acta 21, 247-266. KRUMBEIN W. C. and PETTIJOHN F. J. (1938) LWanuaZ of sedimelztary petrography. p. 549. Appleton-Century-Crofts, New York. MATTHES F. E. (1930) Geologic i&tory of the Yosemite l.aZZey, U.S.G.S. Prof. paper 160, p. 137. UREY 1-I. C. (1953) Chemical evidence regarding the earth’s origin. XIII Internation,aZ Congress of Pure and Applied Chemistry. Plenary Lectures, p. 188-214. A collection of experimental WAY K., FANO I,., SCOTT M. H. and THEW K. (1950) Nuclear data. values of half-lives, radiation energies, relative isotopic abundances, nuclear moments and cross sections. Sational Bureau of Standards. Circ. 499.