The geochemistry of some igneous rock series

Geochimicn

et Cosmochimics

Acta. 1953,

Vol.4, pp. 105to 142. Pergamon PressLtd..Xondon

The ge~he~~ S.

ofsome&mot@

rock

series

R. NOCKOLDS and R. ALLEN

Department of Mineralogy and Petrology, Cambridge,England

(Received 12 DeMnbEf, 1952) ABSTRACT This is the first of four pepem ooncerningthe distribution of some of the commoner trace elements with

respect to the major elements in various igneous rock series. The present communication deals with

certain oak-alkali igneous rock series, namely, the rock8 of the Southern Qblifornia ~tholith, the lavas of Laasen Peak, Crater Lake, the Lesser Antilles, the Medicine Lake Highlands and the East Central Sierra Nevade. These are compered with the Scottish Caledonian igneous rocks.

The object of the present investigation is to study tile behaviour of the trace elements with respect to the major constituents in some well known igneous rock series of talc-alkali, alkali, and tholeiitic character, to determine how their behaviour varies from series to series and from group to group, and to discover what light, if any, they throw on the origin of the three main branches of igneous rock evolution, It is proposed to publish three papers dealing respectively with the talc-alkali group, the alkali group and the tholeiitic group, and to summarize the results and conclusions in a fourth paper. One of us (R.A.) has been responsible for taking the spectrograms and reading the results. The other (S.R.N.) has also read the results and is responsible for the writing of the paper. A semi-quantitative spectrographic method has been used for the determination of the trace elements, the sample under investigation, mixed with an equal quantity of powdered carbon, being pIwed in a carbon electrode of the type devised by AEXENS and LIEBENBERC~(( 19461 type 5, Fig. 2, p. 136). This electrode is made the anode. A large quartz-glass Hilger spe&rograph wu used with & ten-stepped sector rotating in front of the slit. A standard average “igneous rock’? was made up from pure constituents (well mixed, and the whole sintered at 900%) to which known amounts of the trace elements were added. The number of steps in which & given line of an element was visible wae then plotted against the logarithm of the concentrrttion and a kind of working curve, normally a straight line through most of its range, wae obtained. When a line just appeared very faintly in the final step, this was taken aa half a step, and it W&Bfound that results were normlally reproducable to within & half a step. In some oases, the line used for an element filled up all ten steps at quite a low concentration. Another, less sensitive, line of the same element was then used for the higher concentrations. The unknown samples were arced, and the plates developed, under exactly the same conditions M the known st.anderds and the number of steps in which a given line of an element w&8 %ible gave the concent~tion of that element in the unknown sample. In general, the method gives an accuracy of about & 30% which was considered accurrtte enough for the particular purpose in view. All the results given for the trace elements were determined in this way with the exception of Ga, Tl and In. For these the volatile method described by AHRENS (1950) was used and the concentrations determined by visual comparison with known standards. Most of the other elements were determined from lines within the rauge 2800-4000 A, for 105 GA.

4-d

S. R. NOCKOLDS and R.

AI&EN

which Kodak 310 spectrographicplates were used. The arc gap was 10 mm with a current of 8 Amp and the sample was burned to completion. For Cs, Rb, Li, Ba and Sr the glass optical train was utilised, using Kodak 11N spectrographic plates and an arc gap of 14 mm with a current of 8 Amp. The main advantage of using the glass instead of the quartz opticaltrain was that the Cs line 8521 A was much more sensitive and Cs could be determined down to about 16 ppm. Kodak O-O spectrographic plates were used for the determination of Ga, Tl and In, with an arc 6ap of 10 mm and a current of 2.5 Amp, the burn being stopped after 30 seconds. In an investigation of this kind it is important that the results should be comparable in all the rock series investigated. To make sure of this, random samples of other series were taken at the same time as those of any particular series and the results checked with those previously found for the samples in question. For many samples duplicate burns were made and, in every case, the concentrations of the elements were determined independently by both of us. A few determinations of boron were made, using copper electrodes, an arc gap of 5 mm and a current of 2.5 Amp.

List Ofl%&53USed B Pb Sn Be MO V Y Ni Zr co SC Cr La

2497.73, 2496.79 2333.01 2940.0 3130.4, 3131.1 3170.3 3189.4 332738 341477 3452.89 ( > 409 ppm) 3438.23 3453.6 434633 4264.36 4339.45 ( > 400 ppm) 4333.73

1.

A6 In Tl Ga

4101.77 3775.72 4172.06

Sr Ba Li Rb cs

4607.33 4934.09 6707.84 7800.23 8621.1

3382.89

CALC-ALKALIIGNEOUSROCK SERIES

The following igneous rock series of talc-alkali type have been invest+ted: the Southern California batholith; Lassen Peak; Medicine Lake; East Central Sierra Nevada; Crater Lake; Lesser Antilles; while we have for comparison the Scottish Caledonian series already published. (1) The Southern California

batholith

The various intrusions which make up the great South California batholith have been described in detail by LARSEN (1948). A variation diagram showing the relationship between Mg, (Fe” + Fe”‘) and (Na + K) and between Ca, Na and K is given in Fig. 1. It can be seen that the bulk of the rocks fall on a smooth curve in each case until a certain position at the .basio end is reached. Beyond this, there is more or less random sdattering. The basic end of the smooth curves is believed to represent the parental rmzgma, and the scattered points beyond this, all of which represent esrly phases of the batholith, are interpreted as uceumulatiue rocks. ?he average composition of the parental magma will be found in ‘Table 8, column 5 and Table 9, column 4. 106

The gecchemistq of come ignemm rock eerie8

Fig. 1. Vat&ion diagram of the rocks of the Southem Califmia batholith. Smell ~irclee wd the full curve refer to variations in.@’ + Fern), Mg, and (Ne .+ E); crcmm end the Wed CWB refer to v&r&ion in Cs, se, and K; trifbng~ rqmaent fmmn ul8tive rbcke.

Fig. 2.

Variation diagram of the rocka of the Iamen Peak area,

H r&m

to Euknem

bust.

S. R. NOCKOLDS and FL ALLEW

Fig. 3.

Variation diagram of the¢

rocks of the Medicine Lake Highlands.

Fig. 4. As Fig. 3, but with the earlier V~mner bamlts, Lake baaalts and platy andesites of theShield volcano added. Warner basalts represented by triangies, Lake basalts by squares, platy andesites by dots surrounded by circles.

108

The geochemistry of some igneous rock series

(b) Lassen Pmk area The volcanic rocks of the Lassen Peak area have been studied most recently by WIDTHS (1932), and numerous chemical analyses are available. The variation diagram is shown in Fig. 2. Here again, there are the same smooth curves of variation and the same scattering of points at the basic end of the curves. Moreover, both the curves of variation are similar in form to those of the Southern California batholith. The composition of the supposed parental magma is given in Table 8, column 4, and Table 9, column 3.

The lavas of the Medicine Lake Highlands have been discussed by ANDERSON (1941). Only certain of these lavas concern us h&e, namely, the Modoc basalts,

Fig. 5. Variationdiagram of the calc-alkali eeriea of rocks from Eeet CtmWalSierra Nevada.

the basalt inclusion foynd in dacite, the da&es and the rhyo~te-obsi~ans of Glass Xountain. Those belong to a well-marked series (see Fig. 3) to which the earlier Warner basalts, Lake basalts and platy andesites of the Shield volcano do not belong (Fig. 4). We believe the parental magma to have a composition approximating to that given in Table 8, column 2, and Table 9, column 2. (d) Ea.& Central Sierra henna The lavas of the East Central Sierra Nevada have been investigated by HALSEY (1951), CURTIS (1952) and SLEMMONS (1952) who have kindly allowed us to make use of their unpublished chemical analyses. Two series are present-a normal 109

S. R.. NOCIKOLDSand R.

bL.EN

~c-~ series ranging from pyroxene andesite to rhyolite, and a somewhat later latite series. The variation diagram for the former series is shown in Fig. 6. The composition of the supposed parental magma is given in Table 8, column 6 and Table 9,’ column 6. (e) Scotti+& Caledonian and Old

Red Sandstone igneous rock.8

These have already been dealt with elsewhere by ~OCKOLDS and MITCZIXLL(1948) and are inserted here for comparison. The variation diagram, with the. accumulative rocks omitted for the Ca-Na-K portion of the diagram, is shown in Fig. 6 and the composition of the supposed parental ‘magma is given in Table 8, column 1 and Table 9, column 1.

Fii.

6.

Variation diagram of the Scottish Caledonian rocks, for comparison with the others.

It is evident from a study of the variation diagrams t.hat these five examples of calo-alkali rook series are all very similar, the curves of variation having the same form in each ease, in spite of the fact that some series are volcanic, while the &ottish Caledonian series has volcanic, hypabyssal, aud plutonic representatives, and the Southern CaEfornia batholith series is largely plutonic. It seems most unlikely, that a group of rock series showing such similar variation should have formed in quite different ways and it is concluded that all these series are magmatic and have crystallixed from a melt. This being so, the smooth curves of vtiation are believed to represent, in each case, the liquid line of descent of the parental magma, and the rooks whieh we have alreadytermed accumulative represent original magmatic liquid together with a varying amount of aocumulated solid Wj&&lS.

110

The geochemistry of nome igneous rock c&es

.

Alk

bJ3 Fii. 7.

Fig. 8.

Variation diagram of the rocks of the Leswr Anti&a.

Variation diagram of the roake of Crater Lake and Mount &a&a.

111

!6&1@ 2Wlop 276.10’ 278~10~ eee10 !wlO" 284@ sztw s7.10, Q&10’ Q!&lo” 95.1@ @.~lV SS.l@ 107~1~ 77.10” 7&l@ 54qat 42.M 54.1ot s&M 42.1* 4r1u* 30*10’ l%lQJ lix@ IO@ 11~10’ 11~10 6.10” 20 WI@ 30.3 26~10s ‘27~loa 19,lOS lQ,lC 14.i(P 1010* 8,108 46.1D1 62.10s 4@1P SQbl@ SS,lC 420 350 18,lot 22,ld 24.10, 2Z.lo’ 26,lti 22.10* ZIl*lot Wl@ 2Sld S?lo, 54.108 5&l@ 47,ld 41,ld Ulod 4cHo” zsld .1aM 11810’ lcwo’ 1.3910’ 15&l@ losli 133M 15!?10’ 30 30 1::

: *“k;

%I 25 1::

10 40 20 Ml

50 ; So 110

90 100

5 75

a 50

rii

100 l

25 1S

5 *

50

* *

10

-8.2

Nwlv

l

l

-66

20 I * 1 -6.8

10 . l

1 -8.9

20 r( 1 t -2.9

8. Busrtz.bIotlte.ho~bl~e @XnO. LAR8liFi(lQW, An&I. 4, p. 50. 9. Lr&evlew Modomtslnton&e. LAW&~ (1948), AnaL 7, IJ. 06. 10. arl?en VnlIcy titlallta. LAEsEI (lQW, Anal. 2, p, Se, 11. Ronmll t0naIite. LARSPX(lQ4a1, Anal: 3, 12. La sIeian.%tOr&.e (enrtebed In Phnbxue). P LABSEN (1QW. 2loal., p, 73 (Ime h&b AI and X& Y&y gtwdIo*. LA&s& (IQ@, An&, p. 70. 11* 14. mmmFI @men alley ton9W LWIX?J flQ413I,AmI. 1. P. W. 15. Porpkyritlo gnaodlorlte. lrpsra (1946), An&, p. 93. 18. ~htx&umd dike. Lauur (lQ48), AnaL p. 10‘2. 17. Otnmhilarlte carat of Lake&w. LUsrhl (lQ48), Ad. 1, Q, 65. 18. Quwtz la&e pxtWry. LARUEX(194% Anal..P. 105.

Aommuletird Reck8

1. OIlvIne uotite (wtth hornblemle). Luwci (1948). Anti. 1. p. SO. 2. Nodtlc kornblande gPbbco. LARSW (lQ48), AMI. 4. p. 50. 3. Cal& borntdende abbm Me& In lmn W. LARS~X (IW, An&2 SQ. r.~~te(rlchfn~weI.‘Lma3n(lQ~),An*l.5,pW). 6. TypIuI norIte. LAwiN (194% An&I. 6, p* 60.

. e.d.

lbM~~L49Uidfi!WO~Duat II. C!mrm 9autfiblotIle nafIb. J&TIJI (lQO), Anal. 9, p. 50. 7. RcmmII t.mmIIte, LWEN (184dh AMI. 2, p. 6%

112

20 3

20 2

20 15

+lO.B $10.8

CI1.3

ZD *

+II.8

15 2

15 .

15 c

15 I

15 *

20 1

~12.5

-13.3

$13,9

tl4,6

t14.6

+152

i-31

+I@$

Sl1.i

twti

26

‘2.7

28

eo

50

0.29

osi

D.32

ou

wil

17

18

19 20 -P1__ll_

21

22

23

24

I+25

025

a,26

G+zl

D.21

D.20

0.23

_

027

25 __-~.-rJ?l

Gax lnon:al

(194%), Anal., !&D.86. 19. Itmall tonnlite.LSBEHR Mountaingranodiorlte.“Lb~sl~(1948),Anal. 1, p. 80. 20. Wood&on LIR&y (1943),Anal.,p. 91. 21. Mt. Hole ~~io~le. 29. WoodsonNounlainpranodiorite.UASEN (194E),Anal. 4, P. 80. 23. Coarsepraiuedgraniteof RubldouxMountain.LARSE?i (1846). “4. Robiarleuro~nite. LNISIJ(1043).Anal.,p. 98. 25. Micropeematite granite(altwd). L~nsra (1948), Anal.. p. !N ote lm Li and nreeenee d X0). 16. Finr graikd granite oi Rubidoux Hountnin. LARSEx(lB46). na1.2, p. IDo.

!?!I Lnke V’olford leucopranodiorfteLARSRY (1948), Anal.. p, 85 (statedby Larsen.p. 141.to be not typicalof thisintrusion). 30. WotsleonMal:ntain ~~n~o~te. LAneEX (1943),Anal.2, p. X0.

113

S.

R.

h_OCKOLDS

and R. &mm

H/ Si+’ Ale Ti+’ Fe+s Mg+* Fe+’ Na+’ Ca+= K+’

F0 Mg Alk

8

9

271.1CP 25i.l@ 228,lo” 225*l(r 278.105 291*105 292.lV 32&l@ 296*1W 3:;;; 72.W 98*lV 89.10” 9l.lW 91.10” 87.10” 89*l(r 89.lW 82~10” 40.101 80.10” 50.10’ 40.10’ 4O*lV 20.10’ (20*10’) 25,lV 40*10’ 40.10’ 41.10” l&l@ 6~10~ 11.10’ 16.103 14*l(r 11.1oa 9.10” 23.10” 8.10’ 5*1@ 1o.w 55*101 37.105 33.105 22.10” 20.105 2O.l(r 17*lV 32.10” 67*los 38.105 45.105 30,105 31.10s 19*l(r 22.105 lO*l@ 56.105 22.10” 27.108 25.10% l5.103 32.105 29-10” 26,105 27*1@ 20.105 17.lV 59~10Z 56.10s 51.10’ 23+1* 80.108 45.103 43.105 PI-IO” 15.i1p 69.10” 23,101 2i*1CP lG.loa 17~lOP 10.10s 15-102 13.105 17,103 21&l@ 18.18

B+z Ga+' ck+S ;,:t Ni+’ Co+’ SC+8 Zr+’ y+S La+’ sr+* Pb+* Ba+* Rb+’ C&+1

7

:8

170 20 25 25 910 200 20 65: * 450 100

-

59 12

*

2

6

25 260 200 25

4: 300 1:: 66

z: 25 80 15

8:: 40

loot * 400 40

l& 7; * *

49 38 13

.

-

39 33 28

92 20 150 100 40 50 20 15 100 20 + 1000 * 550 100 -

46 ft

2 20 1:: 45 25 20 20 100 20 * 1000

-ii0 80

100 60 25 :: 80 25 *

20 50 65 50 30 10

5 20

ii 50 40 20 10 15 100 15 1250

70; 80 -

1000 * 1000 100 -

1:: 25 * I250 ?lO 1000 100 -

43 21 36

39 20 41

33 20 47

35 18 47

l

8; 100 -

5: 50 1: * 100 20 * 1500 10 600 60 -

24 6 70

10 20

10 50 50 + * l

120 “(1 1000 25 1000 200 *

26 ::

(f) Lesser Antilles A considerable body of data is available on the lavas of the Lesser Antilles through the pub~~atio~ of LACROIX fl924) and of A. G. MCGREGOR (1938). The variation diagram is given in Fig. 7 and, while the curve of variation for Mg, Fe and Alkalies is not unlike those of the previous series, the curve for Ca, Na and K takes a different course. It should be mentioned that LACROIX describes a number of lavas which have been contaminated. Some of these show grains of quartz surrounded by a corona of pyroxene, others have been affected by argillaceous sediment which may lead to the development of oordierite. In both cases, these lavas lie off the curves of variation and they have been omitted from the figure so as not to cause confusion with the accumulative types. The composition of the supposed parental magma will be found in Table 8, column 10, and Table 9, column 8.

114

The geochemistry of Borneigneoue rock es&a Ta&

Y x lOQO/Ca Sr X lOO/Ca Sr x lOO/Ce + H

o-3 0.9 0.8

o-5 l-3 1-o

Ba x lOQ/K Rb x 100/K

2-8 0.6

O-4

2a.

0;3 1.7 l-4

o-4 :I: 3.7 o-7

$I

l

IAXNIMPeak

a. HUb&t. WlLLIAXS (I%!), AX&. 11, p. 280, (thla rock hea an abnormal compmitlon with respect to bothjta majorand traceelsmentll md doeanot appear to belong to the Lueen Peek e&e@. 1. BeeeM. rather rich in ollvine (accumulative). 1 mile s.E. ofPWIWCreeL.cum (leiw.ha. L. P: 175. 2. Au&e muMite, Hat Creak. WlLTaMS (1982), &ML 15. p. 290. 3. Pyroseue bra&, XI%. of Butte Lake. WII&LMS (lBS2), Anal. 36, p. 388. 4. Pete pyroxene endee&, R. aide of Huckleberry Lake. WILLLMS(1932),Anal. 5, p. 25%

0.4 2-O 1.6

O-6 2-2 l-6

;:; 2.0

f:i

x::

4.8 o-5

o-4 :I: 4.4 0.6

::: 3.3

0.7 0-s 2.4

2-2 O-2

1:;

5. Hyperathene andarite, S. slope. of Dadgw MOUllti. WXLLIAHS (1%X32), Anal. 4. p. 240. 6. Piety pale grey rndcsite. Paddler aaolmtah WILLIAMS (1992), AU. 2, p. 233. 7. Platy pale grey andedite, Cryetal I&e. WlLLsAYS (1952), Anal. 1. p. 223. 8. Hornblende-mica da&e, Raker Peek. WZLLIAXS (19S2). Anal. 26, p. 865. 9. Eombkmde-mice dedte, Leuun Peak . CLAaxr (1915). Anal. A, p. 171.

(g) Crater Lake

The lavas of Crster Lake have been described by PATTON(1902) and WILLIAMS (3942). The variation diagram is shown in Fig. 8 and is similar to that for the Lesser Antilles, except that the acid lrtvas are richer in potassium. The estimated composition of the parental magma is given in Table 8, column 8, and Table 9, column 7. The lavas of Mount Shasta (WILLUMS, 1931) also belong here. Both these rock series are volcanic and, again, the curves of smooth variation are interpreted as representing the liquid line of descent during the differentiation of the parental magma.

VARIATIOX

IN

THE

MAJOR

AND

TRACE

ELEMENTS

OF THE

CALC-ALKALI

ROCK

SERIES The data on which the following discussion is based sre given in Tables 1 to 7 ao far as the trace elements are concerned. For the major elements we had, of course, all the chemical. data (which was recalculated on a water-free basis) available for each of the particular series. We shall confine our attention largely 115

S. R. Table 3. A

and R. ALLEN

EOCKOLDS

Rode

of the Medicine 2

B

Lake Highlands 3

4

5

-__ L.___,

Si+l

Al+3 Ti+’ Fe+* Mg+’ Fe+9 XX+ Cat* K+l --B+3 Ga+s cr+s v+3 I&i+’ Ni+* Co+’ sc+s Zr+’ Y+a La+8 Sr+’ Pbf’ Ba+’ Rb” cE+’ Tl+’

6

7

.- --

227.105 274.10s 334.105 ! 256.103 275.109 30i.105 341.10’ 339.105 342.103 342.1@ 97.103 91.108 78*109, 98.10s 95.10s 86.109 74.103 76.10s 75.108 i5.103 54.10” 12.10’ I 54.10’ 18.10’ 18.10’ 18.10’ 18.10’ 48.10’ 42~10~ 42.10’ 7.10’ 42.10’ 21.10’ 105.104 49*10* I 75.10” 35.1oz 49.109 56.10” 56.101 2.10’ 4,105 4.109 35.105 23*105 11.10s 2.108 2.103 54.105 20.105 32*10* 12.103 16.105 19.10” 15.10% 6&105 49.105 16.109 i 46.105 45.10’ 28.10” 26.10a 30.103 i 22-105 24.105 30.105 28,10a 29.103 ml@ 17.10’ X3.108 11.103 11*10~ ll*loj 83.105 48.103 18.105 , 62.103 51.105 26.1@’ 8.10~ 120.10~ 290.102 : 80.100 140-10~ 230.10* 330.102 340.IO’ 330.102 340.10’

_.

-

-

2;: 175 5 225 50 40 50 20 *

49 38 13

-

20 25

15

125 35 1;

g 80 15

25 *

1: 250 25 *

51 :;

85 15

:

25

:

7;;

I /

-

-


15 50 130 40 40 25

15 5 20 80 I *

15 * 1;

- 15

15

* *

;s” *

2:: 25

2; 30

25; 35

t * + 175 35

t 80 * * * 175 35

ii

:i

77 23

83 17

90 10

SO 10

89 11

46 29 25

44 21 35

37 11 52

22

24 7:

24 2 74

23 2 75

* 80 10

to the liquid line of descent, mentioning the accumulative types only when we have sufficient data. We have prepared. diagrams illustrating the behaviour of the major, and some of the minor, elements along the liquid line of descent in the various series and these are given in Fligs. 9, 10, 13 and 14. In these, the amount of a given element is plotted, by a modification of LARSEN’S method (1938) against (@?G+ K) - (Ca + Mg). LARSEN used oxides, and added iron in with calcium and magnesium. But if iron is added, it is impossible to show iron enrichment in a series satisfactorily. This does not affect the talc-alkali series but does arise in the alkali and tholeiitic series which will be the subject of later papers. By adopting the method given above, we are able to use the same basis of comparison for all the different rock series with which we shall deal. The scale for any given element is the same in all the diagrams, so that the behaviour of an element in any given rock series can be compared directly with that in any other.

116

The g~chemist~ Table 3n. A

c

B

1

Medicine Lake Ri&buh 3

2

_.---_.-~

__.__I-.-

of some igneous rook pries

4

6

7

0.20

0.20

/

Ga x lOOO/Al

*

*

i

cr

5.0

4.0

i

lying Li X ~~/Mg Ni x lOOO/Mg Co x loOO/Mg Fe/Mg SC x lOOO/Mg

*

1

Cr

j V x lOOO/Fe

;.;

O-4 * * -3.2 1.4 0.3

!

Co x lOOO/Fe SC x IOOO/Fe -Y x lOOO/Ca Sr x loop

,

8r

4.6 0.8

2.9 0.8

1 Ba x 100/K / Rb x 100/K

5

--____

-___

I

0.15

-

0.2”

o-19

4.2 3.2

1.3 6.2

3.7 7.5

I:; 0.9

*1.7 0.7

203.7 l-2

;::

2.9 1.2

3.2

0.4

2.5 0.7 0.6

;:: O-4

E

0.5 2.1 1.7

0.5

0.7

j

i

020

O-16

2.9 2.9 ::;

2.2 5.6 ::;

o-45 l-8 1

0.7 ;:g

0.9 ;::

* *3.4

1.9

1.0

0.1

0.20 + 2.5 25 I * *4.5

0.20 -_--* 5.0

40 *

50 * *

1; *

10 *

40 * * 10 *

0.5 * *

i.6 t *

f.5 + *

i.5 *

1.1 1.2 0.6

2.7 1.2 0.3

3.2

3.2

l

---

F--__)1.4 t::

0.17

jI + 1.2 / 1.2

8:: 1.5

2.5 * A. Warner besalt, 4 miles S.E. of East Sand Butte. ANDEREON (1941~, Anal. 2. p. 387. B. Platy olivine andesite, hear 9. end of Calmhan. lava flow. ANo~nsoN (194lf, Anal. 1, C. Perlftic rhyolite, 1 mile E ~~~rnrn~t of Mount Hoffmann. ANDERSOR (1941). Anal. 1, p. 399. 1. Basalt, inchrsion in recent da&e of Utass Mountain rhyolite-daclte composite flow. AND&WON (1941), Anal. 3, p. 390. 2. Bawltic andesite, porphyritic Modoc basalt, northern flank of highland. AYDERSON (1941). Anal. 5, p. 390.

.

:.t

.

v

x

mo;3~g

x

x

X

lOOO/Fe

100/b

$

h:

3. Da&e, N.E. tonpue of rhyohtedacitc composite flow. AIDEBSO~’ (1%41), Amt. 1. p. 396. 4. Pumice ejeeta from cone remnant, S. of G?ol*s Mountain. ANDERSON (194lf. Anal. 4, p. 399. 5. Rhyolite glass, summit of Ohms Mount&r. AIDERSON (19411, Anal. 3, p. 899. 6. Ohsidlan from flow, (1941). Anal. 6, p. 39%.

Class

Mountain.

A?IDERSOS

7. Pumice from surface of obsidian flow, Glass Uountain. ANDERSOS (1941), Anal. 5, p, 399.

~~~~~0~and Ozggen (Figs. 9a to 9g) In every cafe-alkali rock series investig&ted in the present study, there is & steady rise in’ both silicon and oxygen with increasing positive value’ of the function [(fSi + K) - (Cs + Mg)]. The curves for silicon and oxygen are almost, but not quite, parallel and, in every case, the rat’io of Si to 0 is 1 : 1.8 at the basic end of the liquid line of descent, rising to 1 : 1.4 at the extreme acid end. In terms of atomic proportions this corresponds very closely to a ratio S&O, at the basic end and Si,O, at the acid end, It will be shown in a later paper t.hat these ratios are different for the alkali igneous rock series.

Aluminium and Gallium (Figs. 9a to 9g) The shapes of the curves for Al and Ga are very similar in each series, though the actual amounts of these elements vary to some extent. The ratio Ge/Al remains practically constant throughout, each series and there is little evidence of enrichment in Ga with respect to Al except, in some instances, at the extreme acid end of a series. The average Ga x lOOO~A1 ratio varies a little with the series concerned being 0.20 for the Scottish Caledonian, 0.19 for the Medicine Lake series, 0.21 117

i3, R. Nocno~~s sod R. ALLXW

Fig.

%a. s,

0difOZ-Ili8

b8thO&h.

-so 0

-4s

Fii. %b. Lassen Pe& Oallium.

118

Valuesin weight pemnt,

The gm~chemistry

Fig. Be.

of some igneoue rock

emiee

Fdedicine Lake Highlsncts

35 30 Si 25

20 -

*

- 4s

119

S. R. Nocxoms

and R. ALLEN

The geochemistry

of wme igneous rock eeries

L J

35. 30 si 25, 20

IO Al

5

5

Ga 0

I

L

0

IO

5 Fig. Qg.

IS

Crater Lake.

for Lassen Peak, 0.27 for the Southern California batholith, O-28 for the E. Central Sierra Nevada series, O-23 for Crater Lake and O-25 for the Lesser Antilles. Magnesium, Nickel, Lithium, Iron, Cobalt, Chromium, Vanadium, Titanium, ~c~~~urn (Figs, 10a to log) These elements, with the exception of Li, all behave in the same general way in every series and gradually decrease in amount as the rocks .become more acid. Lithium, on the other hand increases in amount in the same direction. The original parental magmas of the different series vary in their content of Mg and, to a less extent, of Fe (see Tables 8 and 9) and this affects the amounts of Cr, V, Ni and Co present. In general, it may be stated, that the contents of Cr and Ni tend to be relat,ively high in the more magnesian parent magmas and to decrease in amount as the parent magma becomes less magnesian. Mo~~ver;the decrease is greater than it would be for a member of a more magnesian series having the same content of Mg. This is clearly shown in Figs. 11 and 12 where the contents of Cr, V, Ni, Co and Fe are plotted against Mg for the different series. V increases in amount as the parental magma becomes less magnesian. Co does not vary much in absolute amount but the ratio Co/Mg tends to be greater as the Mg content of the parental magma decreases. The decreasing content of Ni, and increasing content of Co in relation to Mg in the parental magmas, has an interesting effect on the behaviour of the curves for Ni and Co in the variation diagrams. In the series with the most magnesian parental magma (Scottish Caledonian, Fig. 10e) the curve for Ni lies above that for Co, until the extreme acid end of the diagram is reached where they both drop 121 GA. 4-3

S. R. NOCXOLDS and R. ALLEN Tabk4.

Bts &+a Ck+” V+’

Et’

E~tCentmlbnaNeva&(&-dMi&)

-

1

2

3

4

6

6

7

271*1(r lOl*l(r 36*l(r 24.10” 2*1p 29*101 27*l(r 46.w 13.w

293-10s SS*l@ 3&l@ 7.10” 14.16 29-w 24*l(ts 35-w 21*18

302.W 97*l(r 36.10’ 18.101 7-l@ 14.1v

344.109 79.10” 12*lW 4.10” 2-w 11.m 24.101 lO*l(r 33.105

353.105 tw1cP 6.10’ 4.1p 5.1w S.l(r 25.10’ 6.10” 42.10”

3E: * 6.W 3*1@ l*l(r 3.W 27.10’ 6*io” 3?*loa

30

30

35

30

TO

A0

?O

2z 20

200 25 25

1: 15

80 6 25

30 * 50

* 3:

* 50

;: * 125 20

2:

30 16

10 5 * 100 20

* * ix

*

*

1; 30 1:

5;; *

I Si+‘ Al+’ Ti+’ Fe+’ lag+* Fe+; Na+’ GE+ K+l

Rocka of

EE: 42.10’ 17.10 27.w 50.10= 27.w 56.1w l@f(r

::::’f 17*1cT

8

373-l@ 66-l@ 6.10’ l*l(r 3.10’ 20.1@ 13.1(r 2,l(r 39*10”

i -_

-

Ni+* Co+’ SC+’ Zr+’ Y+’ Le+’ sr+* Pb+’ Be+’ Rb” CS+’

1000 50 *

1601t St

l&G 200 ?

1500 100 *

2s 250 ?15

zz

Poe&ion

+1*1

-i-3*7

+7-o

-t-7.7

+ 13.6

+ 15.0

ld

l

2; 1500 3:

150 20 * 1500

910

15;

1OZ

20

60 ?

10 2: 60 + * * 50 . I 50

60 3: 3; 15 + 15.1

;:

;:

;:

82 18

88 12

;t

86 14

;:

47

38 16

39

20

15 6

8

28

:I

47

5:

7;

79

9:

__-.-

12::: 125 *

+ 16.1 99 1

29 tr. 71

below the limits of sensitivity. In the next most mrtgnesian series (Medicine Lake H~~&n~, Fig. 10~; and Cr&er Lake, Fig. log) Ni still lies above Co but both drop below the limits of sensitivity at &n earlier stage. Next comes the Lassen Peak series (Fig. lob) where the curves are closer together and where the Ni curve falls below the Co curve just before the limit of sensitivity is reached. In the case of the S. California batholith (Fig. 10a) Ni starts above Co, but the ourve soon falls below the Co curve. In the two least magnesia-n series fE. Central Sierra Nevada, Fig. .lOd and Lesser Antilles, Fig. fOf) the Co curve lies above the Ni curve throughout. Moreover, the distance apart of the curves is greater in the Lesser Antilles series than in the East Central Sierra Nevada series. One further result should be noted, namely that Ni falls below the limits of sensitivity earlier and earlier in each series. Scandium follows iron, in the sense thet-it tends to be slightly more &bundant in the least msgnesisn parental magmas. But in every series it soon falls below the limits of sensitivity, so that its behaviour cannot be’traced satisfactorily. 122

OS x 1000~Al

O-18

cr x lOOO/aag v x loo%/M.6

GJ.7 167

Li X lOOO/Mg Xi x 1000/I&

l

7:0 *

Cr x 1OOO~Fe V x lOO%/Fe Co x HMO/Fe SC x WOO/Fe Y x lOOop.% 4 x lOO/ca 6r x lO%jc~+ K Be x ldO]K

Rb x 100/K

o-5 3-8 o-4 +

‘2’;’ * 0.4 *

0.2

O-4

l-8 l-5

O-6 3-3 2-6

O-6 4.3 2.7

0.6 ;:;

10-o

11.6

7.1

;I; 3-o l

0.5

0.4

g:; +

1.0

;:;

~WM uide&a fnt~&oz~ fCII%l%S,Xo. S-B-46.) Pyroserkesndmke flow. fCmws, Ro. 7-24-46.) Da&a bomb. WUMIS, Ro. 17-28-46). Da&e dome. (Cwwrm.No. 22-28-45.) Late? rhyolite flow. (CURTIS,No. 15-H-156.)

l

l

*

2-o

o-4

l

l

l

l

* 1:: 2-3 ;:“B

L 6-O ;:i

;:;

l

1.0

1

l

l

l

* 0.04 0.0%

* :.: .*

0.01 0.8

3.2 0.3

6. Older rh&ite flow. (SLswaorS, No. 1-177.) 7. Lateat rbyolite dome. ~IKALSDY, No. 1GC.) 8. 8Ulcmn~ Wwtdon in rbyollta dome (Ued off the UquldUne of dcscsnt). K%!‘BTI&No. M-1.)

Turning now to the relationship between the trace elements and the major constituents, the general behaviour is the s&me ti each series (Tables le, to 7a). The ratios Cr/Mg, Ni/Mg, CrjFe, VfFe decrease in every case as we pass to more acid rocks. The ratio V/Mg is somewhat variable but shows a tendency to increase in the same direction. CojMg and Co/Fe remain more or less oonstant but show a slight tendency to decrease as the more acid rocks in eech series%re approached. Moreover, the average ratio Co x 1OOO~~ghas praetiealiy the same value (about 0.9) in each series, which agrees well with the rstio Co/ItfgO = 0~00086 found by SANDXLL and GOLDICH (1943) who were the first to notice the uonstanay of this ratio. The ratio Co x lOOO/Fe (total) averages O-4 for ea6h series, the range being O-34 to 049. The ratio Li/Mg increases steadily in each series in the same dire&ion (STROCK,1936). These ohanges are what would be expeoted to oo-cur on the basis of the size and valency of the ions concerned. C&&n

and ~~r~~~~

(Figs. 13a to 13g)

With the exoeption of the S. California batholith, wbiGh is remarkably low in strontium, the Ca and Sr contents dF the p&rental magmas do not show s great deal of variation (Table 9). Calclium deoreases steadily in every eeriea aa the value of the function [(aa + K) - (b + Wdl inomea, and the decrease is virtually linear. Stron-

123

S. R. NOCKOLDS end R. AUEN Table 6.

I Sif’ Al+* Ti+* Fe+8 I+@+’ Fe+’ IV&+’ Ca+’ K+l _-__ B+” Ga+* cr+a v+” Li+l Ni+’ co+* SC+” Zr+O Y+a La+s Sr+’ Pb+’ Be+’ Rb+’ cw TI+’

1

3

4

5

6

7

8

9

10

11

12

244,105 248.10” 263.105 267-W 276*10” 280.10s 282.10s 287.10s 2SS*10s 294.108290+1@ 283.10’ 31 98.105 99.10” 97.105 96.10’ 94*10s 94.10” 91.105 93.105 109.10’ : 102*10” 104.1W 91.W 54.10’ ‘72.10’ 42.10’ 24.10’ 30.10’ 30.10’ 24.10’ 3010’ 18.10’ 24.10’ 36.10’ 36*10” 20.10s 27.loI 17.10” l&10’ 17*lW 16.18 15.105 15.1W 9*1W 15.10’ 27.105 : 19*1p 23-l@ 25.W 22.10” 20.10’ 17.10” 18.10s 19*10” 14-l@ 15.1~ 14*1@ 5.10” 33*1p 45.19’ 2&l(r 39-W 3&l@ 34*1e 32-l@ 33.105 33*1p 33.105 32.1V 9.10” 44,101 2&l@ 22.18 20.10” 17.101 23-l@ 22-l@ 21-l@ 27.10* 24.10a 2&l@ 26-W ! 19.10s 69.1p 7O.W 62*1@ 68.10’ 54,105 54.103 47*1@ 46-l@ 49*10* 46.103 54.19 a 76.1W 83.10’ 75.10’ 58.10’ 75.10* 58.10’ 83.10’ 91.10’ 83.10’ 108.10” 83.102 103.10” ! 66.10’ I

* 30 *z 2: 35 60 ;: *

Position

5 25 30: 20 5 30 20 85 20 l

x: 20 160 20 6 25 30 100 26 * 400 10 400 50 t *

2; 15

200 15

:: 30 100 20 *

5

25

1560 15 5

158 30

* 25 5 170 30

15 *

2; *

zx 100 20 *

300

250 *

15: 20 * *

150 22

-2.1

750 * 100 20 + + ---0.2

+0-l

+l*l

+2.2 --

!E

-74 26

68 32

;:

25

500 * 7s 10 * * .‘e

Fe f W -Fe Mg Alk

-1

oft& LeaeerAnti&a

Rocks

54 ::

27

100 20 30; * 150 20

125 25 + 400

---

-&j * 100 45 1; * 100 20 30;

+2.8

2: 25 * * -----i-3.0

-f-3.9

;8”

::

;t

72 28

:: 25

52 18 30

49

l

*

*

::

2: 35 * *

49 19 32

0

25 *

25

100 45

lb0 40

1; 45

1;

1; +

1; *

:: * 5 t

9: 20 *

s8

75 20

75 25

300 10 150 35 t z

3; 10 200 45 * *

30; 10 200 30 *

35; 15 250 45 * *

*

+4.4 ---;; -~___50

l

f25 *

+4+

j-4.5

+4.6

;:

E

88 12

46

P9

46

:t

tium, however, behaves in two different ways. It may increase gradually in amount to a maximum value and then decrease rapidly to a very low value, as the value of the function [(@i + K) - (Ca + Mg)] increases. This is shown by the E. Central Sierra Nevada series (Fig. 13d), by the Scottish Caledonian series (Fig. 13e) and probably would be shown also by the Lassen Peak se’ries (Fig. 13b) but, u~o~unately, we have no analysed specimens of the most acid rocks to test this. On the other hand, strontium may decrease, like Ca, as the function [Wi + K) - @a + Mg )I increases, and the curves for Ca and Sr tend to converge 8,s the more acid rocks are approached. This state of affairs is shown by the Medicine Lake Highlands series (Fig. 13c), the S. California batholith (Fig. 13a), the Cfatir Lake Series (Fig. 13g) and that of the Lesser Antilles (Fig. 13f) though here, again, we have been unable to obtain a sample of the most acid rock type described. 124

-

The geochemistry of came ignecw rock series

1

2

3

4

5

Gs x MOO/Al

0.29

0.24

0.27

0.26

0.25

Cr x lOOO/Mg v x 1~~~ Li x lOOO/Mg Ni x lOOO/Mg Co x looO/Mg Fe/W SC x 1~jMg

1:’ o-15

A2*

6 038

0.7 9

O-25 7-5 *9

8::

0.2 @8

0.7 0.5

0.8 0.25

cr x 1OOOpe V x lOOO/Fe Co x .lOOO/Fe So x 1OOQ~Fe

O-6 6.3

0.6 lil 1.9 1.5

6

7

8

9

10

11

12

13

0.27

0.22

0.27

0.27

0.23

0.22

0.3 9

t5.3

t7

a

I

*

*

1.8 *

1.7 t

2.4 *

3.2 l

i.7 *

i.2 *

0.7 2~8 l

0.7 34 *

7.2 1-o * * :::

O-26 0.26

l&) +

i(.:

:9 0.9

2-1 I.0 1.2

2.6 L-1 1.4

2.5 1-O ,.9

O-9 3.0 *

2.6 1.1 *

O-8 2.5

0.4 2.8 0.5 0.6

0.3 3.6 0.4 0.6

0.1 2.9 0.4 0.4

* 2.9 0.3 *

o-1 3-6 0.4 c

* 2.1 0.3 t

l

I.4

i-1

;:;

0.1 4.6 05 (j.3

2-l 0.3 *

0.2 *

0.2 *

*

2.5 0.2 +

Y x l~/~

Sr x 1oOpJ sr x lOO/Ca $ K

0.3 0.7 0.6

0.3 1.1 1-o

o-4 O-6 0.5

0.3 0.6 0.4

0.3 0.4 0.4

o-4 0.5 o-5

o-5 0.7 0.6

o-4 0.6 0.5

0.4 o-7 O-6

0.4 0.6 0~5

0.4 O-7 0.6

0.5 0.6 0.5

0.5 O-6 0.5

Ba x 100/K Rb x 100/K

1.1 0.2

1-2 0.2

(5.3) (O-7)

2.6 0.3

2.0 0.3

2.6 0.3

2.4 o-3

2.2 0.4

1.8 0.4

1.9 0.4

2.4 0.4

2-3 0.4

3.3 0.4

1. Olivine baeelt (w?mmlatIve), S. ofSouf?Sem HULXtmt8ermt. KACOREOOR (1988),Anal. 7, p. 74. 2. Oliviw be&t, 500 yde. W. of E&e Ftock, ?donteermt. DIA~ORB~OII ilQS@t,AI&. 6, p. 74. 3. Dacltoid, near Mom dea Csdeb, Xartirdque. L~cFtoIx (1924), p* 304. 4. ~~ne.ban~~, CeutreHills, &m&err& ~~~~0~ (1038).Anal. 5, p. 74. 5. Pyroxeue bendnile, Silver Hill, Monteerrat. MdcQmxx (ISQS),Anal. 4+$x74. 6.Ifornble e-pyroxene bandaite, Cratks Peak, Xonteemt. MAC~XXOO~ (19381,Anal. 3, p, 74. 7. Homble~~p~x~e br~nd&e, near Old Fork Point, Xonherrat.hf~Qap00R (1936).AM. 2, p. 74.

l

3.4 l-1 *

l

8.I)act&ld, summitof Mt.P&e, Martinique.Lbcltolx (IBZJ). p. 304. 9. Dacitoid pumice, eruption of July 19% Mt. P&e, Marfinique. LACXOIXUQ34),p. 394. 10. De&e, emptlon of January 1909, It. Pelk Martinique. LACaOlX (IQ!&),p. 394. 11. Decide. eruption of 1906, Mt. PeMe, Eartiniqus. (UapnbIlehed melyele by J. 3. SCOON.) 12. De&e, neiShbourhc@d of St. Pierre, Martbdque. (Unpubiiied nnalysiaby J. Ii. SiXoN.) IS. Acid ~mblende-p~xene baud&e, near Landing Bay, Montsenot. %A&XXQOR (1933).AnaL1, p. 74.

This difference of behaviour must be correlated with the removal of Sr by early crystallizing minerals, in effect by pla~ocl~e, as the ~a-bea~ng fe~omagne~a~ minerals carry very little Sr (NOCKOLDS and MJTCHELL, 1948). If much early crystallizing plagioolase feldspar is removed from the system, then the Sr will decrease in the residual liquid, whereas if relatively little is being removed, then the Sr content of the residual liquid will increase. The ratio Sr/Ca increases continuously in the E. Central Sierra Nevada series, the Scottish Caledonian series, the rocks of&e S. California batholith, the Lassen Peak series (as far as traced) and the Crater Lake series, but falls at the extreme acid end of the first two. It remains more or less constant in the Medicine Lake Highlands series and in that of the Lesser Antilles (as far as traced). The ratio Sr/Ca + K increases in the case of the Lassen Peak series (as far as traced), the E. Central Sierra Nevada series, the rocks of the S. California batholith and the Scottish Caledonian series, but decreases in the last three as the more acid rocks are approached. In the Medicine Lake Highlands series the ratio remains more or less constant at first, but decreases again when the more acid rocks are reached.

125

i.3 3-l *

S. R. ;NOCKOLDS and R. ALLEN

Rackaof Cm&r Laxcc,Creqm

Table 7. 2

I 26O.W 89.W 7-l@ 27rW

Si*’ Al” l-i+*

Fe+'

S’

ZG 27-l@ 6l‘W 108.10’

Na+l

cw ’ K+l B+’

Qa+’

0 300 130

cl+’

v+* 1 +1 XI -*

CO+’

se-

Zr ’

LUu

lg 30 110 160 lb 16Oz + MO 16

sr+’ Pb*’ Bau

Rb+’ C!S+l

l l

n41

Poaition

3

4

6

6

7

8

9

10

11

12

267*1@ 268.W 276.W’ 282*16 28O.W ZSB*lfF 291.10’ 317.10”.322.105329-l@ 333-W : QWlO’ QS*lV 98.10’ 95.10’ 98.W 96*105 Ql.lW 84*10* 84*l(r 81-W 79*l(r 6.W 7.lW 4*1(r 3.w 2-w 4.101 4.10” 4.10” $*l(r 3.1(r 2*l(r 16.1p 2O.W 19.W 14.W 13*1W 13.101 17*1V 13*1V 16.10” 13.1(r 10*1(r 8.10” 0.10” 4.10” &I@ 20.W 24.W 22*1(r 2l.W lQ.l(r 17*10’ 1Q.W 33.10” 26.W 26-W 27.W 30.10’ 26.10” 21.18 14.W 7.10” 9.10’ 1O.W 2Q,l(r 30.10s 29.16 31.1~ 33.10’ 33.10’ 30.10’ 33*1[r 39.10” 39.lW 39-l@ 64.W 52.101 49.103 46.10’ 4f&tot 41*X0” 41-l@ 24.10’ 2&l@ lS*W 15.101’ 66.10’ lOO*lO* 100~10’ 108.10’ 108.1Q’ 116*10’ i41.10’ 199.10’ 207-10’ 216*KO*224.10’ 2

100 16 ;z

1::

70 160

20 g

;;

?lO 70 1;

?lO 100 20 c

I6 TlO 120 20

1200 * 260 10 * *

1000 * 46Q 2:

&

*

360 20 l

+

l

160 20 :z

120 20 20 40

1:: :: 15

1:: 26 .E

2 20 IO 6 110 200 2:

?lO 100 2z

?lO 120 20

?lO 100 25)

110 160 2:

1000 * 660 26 + *

7,@

800 *

760 *

6:

z

l

600 20

* .

l

*-

l l

700 * 366 * +

2x 6 z 6 l

17; 22 700 * 750 100 l l


20 + 30 40 * * 1;; 3:

660 650 ?lO rio SO@& ‘O&I L *

-1.0

‘+I*6

+2*3

+3*1

+3+8

+3-Q

+6-O

+6.1

+9.4

+10+2

z

::

E

67 33

::

if

3:

::

23 77

;f

86 16

86 I5

;:

86

37

:40

41 18

44 3Q 17

43 38 19

60 31 9

26 RI 7

70 26 6

72 “:

PO ;:

+11.2

* + +Il.C

-t

Having regard to the ionic radii of Sr and Ca, it may be expected that Sr, present for the meet part in plagioolase among the &-bearing minerals, would be concentrated relative to Ca in the later rocks of a series. On the othei hand Sr enters certain potassium-bearing minerals, especially powh feldapars, and then it would be expected to concentrate in the early formed potash feldsparbr.It is the interplay of these two factors that is responsiblefor the behavionr of the Sr/Crt + K ratio, the first being dominant in the earlier atagea, the second becoming gradually more important and finally dominant in the latest stages thue leading to a decrease in the Sr/Ca + K ratio. The ratio SrjCa + K remains practically constant throughout .in the Crater Lake series and in that of the Lesser Antilles (as far as traced). This ie due to the fact that potassium is not concentrated to the Irame extent in these two series aain

126

!rd& 7a. cmtsr LA I

1

2

3

0.25

0.20

7.0 4*2

4

6

6

7

8

9

10

11

12

13

OCi6 0.21

0.28

0.26

0.22

0.24

0.24

0.25

0.26

0319

333 6.0

3.2 6.8

2.9 7.1

3.2 8.3

2.4 is1

4~2

1.2

0.8

0.25

*

;:i 97 1.3 -

0.6 2.7 2.1 0.8 I.0 &8 1.8 l-9 --------•

2.3 o-7 97 2.0

2.4 1.0 1.0 2.0

2.1 I.1 1-l 2.3

1.8 1.2 0.9 2.3

2.6 I.1 2~0

1.2 0.6 3.4

0.7 * 3.8

l

*

if

i:f

1.6 3.3 0.3

1.5 3-i a.5

1.4 2.8 0*5

I Ga x lOOSpI

CT x MOO/Fe V x looO/Fe Co x lOOO/Fe SC x IooO~Fe

_-

0x5 -

1.7 2-6 0.5 0.4 ----_---*

i.5 l

1.0 3.1 0.4

2.1 3.9 0.5

o-4 2.2 0.2

o-2 2.2 l

* 2.0 l

l

5.0 * ;.5 +

* * 6~7 * I I.8 l

*

l

*

-/ O-25 2.5 2.1

Y x 1~~~ sr x loo/c8

Srx1oo/catK Ba x 100/K Rb x MO/K

0.22

I

;I:

2.0

o-4 1.B 1.8

0.4 I.8 1.5

o-4 2.2 1.8

o-4 I.6 1.3

o-5 I.95 l-5

0.5 l-8 l-4

0.8 2.9 1.6

1.0 3.6 1.7

I.3 4.1 1.7

2.0 4.3 1.8

2.7 5.5 I*8

E

;:;

3.5 0.2

be0 0.2

4.5 0.2

4.3 0.2

3.6 o-2

4.2 0.3

3.6 0,5

3.7 @3

4-5 o-5

6.4 @4

1 O-3 / 2.2

1. Baealt faccumuWve).baneof Red Cone. CCAXKE(1915). Anal. J, p. 188. 2. Hllpsrsthene baa&,Anna Creek. CLANX (1915). Anal. K, p. 200. 3. Dnrk aecmtlon. oummlt of Llaa Bwk. CLARKE(1915).

8. Pyresens nude&e, Pelbmdes.N.E. twr&m of crater rim. CUEKI (1815). Anal. H, p. 199. 9. Light cokwed secretion,aouthetnrim of cmter. CraBu 11915),Anal. N, p. 200. 10. H mtheme da& near “Wine Olnaa” Qwtto Cave. ClapKE%5). Anal. B, p.‘lSS. 11. Hppemthsae da&e, bead of Cketwood Cove. Cuxex (1915), Anal. D, p. 198. 12.HWhane da&e, 5. edsf: of Us0 Bwk La. CLIlanz (1915), Anal. A, II. 1913. 13. Hypaathen~da&e, small dyke. below Us0 Rock. CLAB~E f1915), Aosl. c, p. 159.

_ , .__ene andesite, crater rim, just 9. of ‘The Ws4chmnn.” CL&EKE (1#15),Anal. 0, P. 180.

the others, with the result that the effect of Sr substitution of K in potash feldspar does not become dominant over the Sr substitution of Ca in plq$oelase feldspar.

The Scottish CaJedonim series caslnot be used for a discussion of yttrium, as the limit of sensitivity for the method of determination used for that series is 30 ppm and the yttrium content rarely rises above this. But in all the other series the Y/Ca ratio increases steadily as the more acid rocks are approached. With regard to the absolute amounts of yttrium present, this tends to be constant throughout a large portion of the r&nge of any one series, though in some series it increases at the acid end (Medicine Lake Highlands, S. Ctilifornia batholith, Crater Lake). There is, however, a decrease at the extreme acid end of the E. Central Sierra Nevada series, The initial yttrium content of the parental magma is apptlrently & function of the Fe/Mg ratio, and yttrium falls below the limits of sensitivity in the more magnesian parental magmas (see Table 9).

127

IO Cr 0 IO Li 0

.

-+-yz--~.!

IO -

5 Ni ca 0

Fe

oIO V I

I

to

5 Fig. 1Oa.

0

1

I

0

0

15

S. California batholith. -2 !O

- II3 : 4,r -c 1

IO

- I(3 : IL i

4

-C 1

0 i 3 yi

IO

30 -: 1

Fe

0 IO V 1

0

1

I

I

5

10

15

Fig. lob. Fig. 10 a-g.

0

Lassen Peak. :

Variation in Chromium, Lithium, Magnesum+ Nickel, CobsIt, Iron and Vanadium. Values in weight percent, with Cr, Li, Ni, Co and V x 1000.

128

-v 1

‘

s

0

Fig.

IO

lCh_i. E. Central Sierra Nevada.

I5

-0

4

CJ

5

10

I3

6f Borne igneous rook

The geoohemistry

series 20

IO Ct

IO

0 IO Li

M9

.

+-+.-I

-

Li

l-.

0 0 5 Ni

IO

2 Fe

l --•<-_

0

t0 V 1

1

0

5

I

IO

0

IS

Fig. 1Og. Crater L+ke.

Lanthanum Lanthanum rarely rises above the limit of sensitivity (40 ppm) in any of the rock series under investigation. It does, however, appear in the most acid members of the E. Central Sierra Nevada series, the Southern California batholith series, and the Scottish Caledonian series. Sodium (Figs. 13a to 13g) Sodium behaves in the same way in the Medicine Lake Highlands series, the Lassen Peak series, the S. California batholith, the Central Nevada series and the Scottish Caledonian series. In each of these the sodium content is nearly, but not quite, constant throughout the whole range, reaching a feeble maximum in the intermediate members of the series. The close approach to a constant value for sodium in all the members of a talc-alkali rock series was long ago remarked upon by BOWEN (1927, p. 100). The Crater Lake and Lesser Antilles series, characterised by their lower content of potassium, show a different behaviour for sodium. Here, the sodium content shows a small but steady rise throughout. This leads to higher values of Na at the acid end than in the other series.

131

S. R. NOCKOLD~and R.

ALLEN

Although the amounts of potassium in the parental magmas are somewhat variable‘; the behaviour of t,his element is the same in all the series except those of Crater Lake and the Lesser Antilles. Potassium increases in amount throughout any given series, the increase being more marked at the acid end. The Crater

6 S 4 k 3

I

1

4

2

MO

2

I

4

0

Fig. 11.

s

*

=*

2

I

1

1 0

Fig. 12.

Fig. 11. Variation of Cr, V, Ni, Co and Fe with respect to Mg. 1, Scottish Caledonian; 2. Medicine Leke Highlands; 3. Lsasen Peak; 4. Southern California Batholith; 5. East Central Sierra Nevada (talc-alkali). Values for trace elements in ppm; values for Mg and Fe in weight percent. Fig. 12.

Variation of Cr, V, Ni, Co and Fe with respect to Me;. 1. Crater Lake; 2. Lesser Antilies. Values for tr@e elements in ppm; valtlss for Mg and Fe in weight prcent.

Lake and Lesser AntilEesseries both have slightly lower initial amounts of potassium and the amount of potassium shows a steady increase in the Crater Lake series (and in that of the Lesser Antilles as far as it can be traced) with no more marked increase at the acid end of the series. Thus these series remain relatively low in potassium throughout. 132

The geochemistry of Borneigneous rock series

- IO

sr

. -0

- IO - 01 0 -

s

.

Rb

-L 01

I

0 Fig. 13a.

,

,

I

s

IO

IS

I

5. California batholith.

20 5 JO

Cb

sr

0

0

10

s

0a 0

N4

s

0

Rb

5

0

K 0 gig. I3b. Fig. 13 a-g.

Lassen Peak.

Variation in Calcium, Strontium, Barium, Sodium, Rubidium and Valuesinweight percent, Sr, Be and Rb x 100.

133

S. R. NOCXOLDS and R, AIAXB

5

C8

5

.Rb 0

Fig. 13~. Medioine Lake Highlends.

20 5

IO C8

s? 0

0

IO 08 0 5

.Rb 0

K . Ok 0

IO

5

F_ig.lad.

E. Central Sierra New&de. 134

15

The geoohemietry of Borne igneousrock aerien

-lo

*sr -0

. -0

01

* 0

I

5

IO

Fig. 13~1. Scottish Celedonisn

Fig. Hf.

Leseer Anti&s.

IS

Rb

S.

R.

~OCEOLDS

and R. ALLEN

5

c8 0

-lo 5 N8 0

. Rb

5 K 0

I

0

I

5 Fig. 13g.

I

IO Creter Lake.

I

I5

Barium The South California batholith, Medicine Lake series, Lassen Peak series and Scottish Caledonian series all have approximately the same initial amounts of Ba, but this element is definitely greater in amount in the E. Central Sierra Nevada series. In all these, Ba rises steadily in amount as the more acid rocks are approached. But in the E. Central Sierra Nevada series, as in.the Scottish Caledonian series, there is a sudden drop in the Ba content at the extreme acid end. These two series have more highly differentiated end products than the others and the final residual magma is depleted in Ba. The Lassen Peak series would probably show the same feature, but unfortunately we have not been able to test this. The Ba/K ratios do not show, in general, a great deal of change in any one series. There is a tendency for a slight rise at the beginning of a series, followed by a period in which the ratio remains more or less constant, and finally the ratio may fall-as in the Lassen Peak series and the Scottish Caledonian series. The E. Central Sierra Nevada series, however, shows a fall in the Ba/K ratio throughout. The Crater Lake series shows a slow increase in the Ba content, tending to become greater as the more acid rocks are reached, but the Ba/K ratio remains more or less unchanged throughout. The same remarks apply to the Lesser Antilles series, as far as we have traced it. Rubidium The most striking feature here is the almost complete parallelism of the curves for Rb and K in all the series, indicating the constancy of the Rb/K ratio. In the early stages of each series, the Rb/K ratio tends to be a little lower than the 136

The geochemimy of swuc igneous rock series

average, but it is only at the ext,reme acid end of the Scottish Caledonian series. representing residual aplites, that there is any appreciable rise in the rat’io. Having regard to the ionic radii of the two elements, one would expect the Rb/K ratio to increase in the later rocks, but it is evident that such an increase must be very small and only becomes appreciable at the final residual &age. This censtancy of the Rb/K ratio has been observed also by AHRENS, PIE;SOSa,nd KEARSS (1952). But although the ratio is constant in each series its value is not the same in all. The average ratio Rb x 100/K is 0.84 for the Scottish Caledonian, 0.76 for the Medicine Lake series, O-59 for Lassen Peak, 0.81 for the Southern California batholith and 0.61 for the East Central Sierra Nevada series. For the two series less rich in potassium, hamely Crater Lake and Lesser Antilles, the ratio is definitely lower’ being 0.28 and 0.36 respectively. These values may be compared with the average rat,io of O-82 for the Skaergaard rocks and wit,h the average ratio 0.9 for all igneous rocks as given by AHRENS,PIXSOS and KEARWS. Caesium

In most of t,he rocks where Cs has been sought it lies below t*helimits of sensitivity (15 ppm) and it is only at the extreme acid end of certain series (S. California batholith, E. Central Sierra Nevada, Scottish Caledonian) that it can be detected and even then it lies only just above the sensitivity limit. Thallium Thallium behaves in the same way as caesium and is normally not found even in the most acid rocks, although the sensitivity limit is much lower (2 ppm). The recent work by SHAW (1952) on the geochemistry of this element has shown that for most rocks the amount present is below our limit, of sensitivity and only rises above this for certain granites and rhyolites. Lead Lead is present in small amounts (10 to 15 ppm) in the rocks of most of the series and often falls below the limits of sensitivity at the more basic end. It only becomes appreciable in amount at the acid end of the more potassic series where it normally ranges from 30 to 50 ppm. In the less potassic series of Crater Lake it remains low throughout, and this is true of the Lesser Antilles series too, as far as it can be traced.

Boron, Zirconium Boron This element has been determined for a number of samples in certain of the rock series, using copper electrodes. The results are difficult to interpret. In the Lassen Peak series, the B content appears to rise as the rocks become more acid. But in the case of the S. California batholith and the Crater Lake series it occurs sporadically throughout and does not seem to be following any particular trend. G.A.4-3

137

S.

R.

NOCKOLDS

and

Ji.

ALLIS

On the other hand, the boron content of the Scottish Caledonian series decreases as the rocks become more acid. Zirconium

(Fig. 14)

Zirconium behaves in much the same way in every series, though the.amount of Zr present varies from series to series. In general, the Zr content is low at the basic end of each series and then tends to rise, after which it seems more or less constant until the extreme acid end when it tends to fall.

Molybdenum,

Tin, Cerium, Germanium,

Beryllium

and In&urn

Molybdenum (sensitivity 2 ppm) was detected only in one altered rock (No. 25, Table 1) from the South California batholith. A noteworthy feature is the absence of appreciable tin (sensitivity 5 ppm) in every series even in the most acid rocks. Cerium (sensitivity 300 ppm), germanium (sensitivity 15 ppm), beryllium (sensitivity 5 ppm) and iridium (sensitivity 1 ppm) were not observed in any of the samples. SANDELL’S(1952) work on the geochemistry of beryllium shows that basic igneous rocks have, on the average, about 1 ppm and granitic rocks about 3 ppm, values below our limit of sensitivity. Again, SHAW’S (1952) study on the geochemistry of indium indicates that the indium content of our rocks would be below our limit of sensitivity for this element.

THE ACCUMULATIVE ROCKS Attention has been directed so far to those members of each series which lie on smooth curves on the variation diagram and which are believed to be representative of the liquid line of descent. We have, however, determined the trace element content of a few samples which occur at the basic end of the series, do not lie on the curves, and are believed to be due to a certain amount’of crystal accumulation. Five samples come from the S. California batholith (Nos. 1 to 5, Table l), one from Lassen Peak (No. 1, Table i), one from Crater Lake (No. 1, Table 7) and one from the Lesser Antilles (No. 1, Table 6). In general, all these rocks show varying degrees of enrichment in Mg and Ca and sometimes, also, in Fe or Al. They are impoverished in Si, K and Na and. sometimes, in Al. Among the trace elements there is enrichment in Cr, V, Ni, Co and SC, and impoverishment in Li, Ba, Rb and sometimes Zr. Sr may show enrichment when plagioclase accumulation occurred (i.e. in those rocks enriched in Al) or it may show impoverishment when accumulation of dark minerals took place (i.e. in those rocks impoverished in Al). Similar results have been obtained already from a study of the accumulat,ive rocks of the Scottish Caledonian series (NOCKOLDSand MITCHELL,1948) and are, indeed, what would be expected if these rocks represent early liquids enriched to a greater or less extent by the accumulation of early formed crystals of the ferromagnesian minerals and/or early formed plagioclase feldspar. 138

THE PAREXTALMAGNAS The approximate chemical compositions of the supposed parental magmas of the various rock series dealt with in t.his paper are collected. together in Table 8, together with one or two other analyses for comparison. They all bear a close resemblance to one another, and the only essential difference between analyses 1 to 6, and analyses ‘7 to 10 lies in the slightly lower K20 content of the latter. This difference, although small, is apparently sufficient to account for the difference in the potassium cont*ent which is observable throughout the different,iation of the two groups. That this is not the complete explanation is shown by the Santorin lavas which differentiate in the same way as the Crater Lake group. The analysis of the Paricutin lava is of great interest, showing a close relation to the parental magmas of Crater Lake, the High Cascades and the Lesser Antilles but with a lower Fe/Mg ratio.*

1

2

3

4

5

6

7

8

8:: 25.2 33.9 14-5 3.5

0.4 2;:; 29.5 1:::

2.1 2El 31.1 13.7 5.1

;:; 26.2 29.7 11.7 3-6

2.6 , 3E 32.5 11.2 2.2

;:;

G?+EO,

1E 29.3 24.5 11.5

30.4 30.0 17.5 3.9

5.0 6.9 28.8 31.1 13-b 4.3

8-8 l-6

il ap

9.1 2.3 2-o 0.7

6.9 ;:;

;:;

0.5

6.6 46 O-8 0.5

2.1 0.3

8-7 3.5 l-4 0.5

60 40

61 39

66 34

66 34

69 31

71 29

9

10

SiO,

TiOl AlsO, Fe,O, Fe0 MnO MgO CaO Na,O GO P,Os q= Or

ab

MgSiO, FeSiO, mt Fe Mg

;:;

1. ScottimCalcdani~n.Averageof four analyses of pyrorane-mica diorite, ~W~~OLDY (1941). A, of Table 4. 2. Medicine Lake Hi&Isnds. Basalt inclusion in recent dacite of Glass Mountain, AXDESSO% (1941). Anal. 3, p. 390. 3. Santorin. Basic inclusion in ltitenas lava-lioa’. GEORQALAS anti PAIUSTMMTIO~ (1951). AMI. 4. p. 36. 4. Lassen Peak region. AversIIe of two analyses (has&s. Shasta County. CLARKE(1915). Anal. N and 0, ,\ 15z.1 “. ‘&“G. California batholith. Average of three am&sea (quartz-biotite norites. LAXJE.S(194Sf. Anal. 8 and 9, p. 50, and “l~onsall tonatite,~ LbRzjgx (lQ4S). Anal. 2, p. 66). 6. East Central Smra Nevada. Pyroxene andesite introsion (CVSTIS, No. 9-28-45). *

It is

somewhat

;:“6 f:i ::

1*3 ’ 336.00 30.0 1;:;

5.8 * 2:.: 35.3 10.0 4.2

2.6 b-6 1.5 0.5

6-7 3-7 24 0.7

A.5 4.6 2.1 0.3

64 36

67 33

74 26

7. Paricutin, We&o, eruption of 1944. (~npublisl~~ analysis by J. H. Scoor%recakulatsd on a water-free basis.) 8. Crater Lake. Olivine basalt, X. base of Union Peak, WILUAXS (1942). Anal. 4, p. 148. 9. High Cascades lnvas. A~rage of two analyses (Basalt of liato type, TIIAYEX(1937). p. 16% and micronortte related to Ninto basalt, T~YER (lQ3i), p. 1WS). 10. Lesser Antilles. Arerags of Phree analyses (basalt, S. Soufriere Hill. Nontserrat JfACcOxltGoa(l!X%%x), “labradorite I,” St. Kitt’s LSCXO~X(KM), “dadtold,” basaltic type, Old Scmma. Soufriere, St. Vincent, LacxoIx (lW4), p. 4031.

richer in Mg than the endyaes listed

139

by

WXLLUMS (1950).

8.

R.

s

0

Fig. 14.

Table 9.

-

and R. ALLEX

??oaiot~s

IO

IS

Variation in Zirconium; Values in ppm.

Content

of certain trace ehnenta in patvnhl magma

1

?

3

4

254.1W 87.1W 6-l@ 11.10” 4o.w SO.l@ 26.W 56-W 14.1P

256*109 98.10s 5.101 8*1P 35*1* 46*1@ 22.105 62.10a 8.108

260.10” 97*1(r 3.1w 23.10’ 33.10” 42*1(r 2&l@ 64*1* 9*1@

263.10’ 92.w 7-w 13.10 2&W 49.10” 23-W 66.10’ iO*l@

6

6

7

8

262*.l(r 93.10’ 6.10’ 12.1P 42.10’ 47*lP 27.10’ 68*l(r 6.10’ -~

256.10’ 90.10” b-10” 27.101 32.105 29.w 2 *l(r 6f *loS 7.10~ -.-.-.

249*10a lOl*lP 7.103 22.10’ 24*1P 46.10” 23.16 66.16 7.103

i Si+‘ Al+” Tit’ Fe+’

$.+-is Ne+’ GE+* K+’

Get’ Cr+*

2:: 100 25

v+=

Li+’ Nit* Co+= Y+l sr+* Ba+* Rb+’

l”o

---

14 400 100 ::

1% 100

252.l(r 102~10” 4*lP 17.w 27.10’ 6O.W 2%10” 56-I@ 10*10*

iti

50

200 20

:: t 750 250 50

z 20 1000 1000 SO

61 39

250 100 66 34

69 31

I. swttistI Caledolltan. 2. Medicine Lake Hi2hlsnda. 3. Lamen Peak region (trace &mex~?rextn~pol~ted from variation diagrams). 4. 9. Californta batbdth.

140

71 29 ; yJiIaiI

2:: 160 15 150 46 l

800 150 l

68 42

(26)

25

I:::; (15) f86i i3oj

2:x 20 6

(15) “(:iJ P) t%4 36

i:

760 100 20 :Q

Sierra rTeva&.

71 Crater I& (tmca elementa extr4polatad vari*ti0n diagNlu). 8. Lesmr AntIM.

from

The geochemistryof some igneousrock Reries

Fig. 15.

Diqram showingvariationin composition of parental magmas.

It will be noticed that, in both groups of analyses, there is some variation in the ratio of total iron to magnesium and, indeed, the analyses are found to lie on a smooth curve when plotted to show the variation between magnesium, t,otal iron, and total alkalies (Fig. 15). As already mentioned, when considering the trace elements concerned, the content of Cr, V, Ni and Co is closely related to the Fe/Mg ratio (Table 9). Yttrium, too, falls below the limit of sensitivity in the more magnesian parental magmas but occurs in small amounts in the more ferriferous ones. Strontium varies little, except in the case of the parental magma of the Southern Californian batholith, where it is unduly low. Rubidium more or less follows potassium, but the barium content is variable in the first group of analyses, though nearly constant in the second. We wish to express our gratitude to Prof. E. S. LARSEN, Prof. H. WILLIAMS, Prof. J. ORCEL, Dr. C. A. ANDERSON, Mr. J. H. HALSEY, Mr. G. H. CURTIS, Mr. D. B. SLEMMMONS, Dr. A. G. MACGREOOR, Dr. W. F. FOSHAU and for providing us wit.h samples of rocks which had already been analysed for their major constit~lents. Ac finowledgmenti-

REFERENCES AHRENS, L. H. and LIEBEXBERQ, W. R.

1946

AHRENS, L. H. LARSEN, E. 8. %~XLLIA?&S, H.

1956 1948 1932

ANDERSON, C. A.

1941

141

49, 133-154 SpectrochemicalAnalysis, p. 148

Trans. Geol. Sot. S. Af’rioa Geol.

Sot. America

Mem. B

Univ. Californis Publ. Bull. Dept. Geol. Sci. 21, X0. 8, 195 Univ. Caiifornia Publ. Bull. Dept. Geol. Sci. 86, 347-422

S. R. SOCXOLDSand R. ALLEN: The pochcmistry PATTOX, H. B. LAC’RofS, A. XAVC:HECOR,A. G. SOCLOLDS, S. R. and MITCHELL, R. L. WILLIAMS, H. LA~SEX, E. S. ?%-ILLIAMS,H. SANDELL,E. B. and GOLDICH,S.S. STROCK.L. W.

1902 1924 1938 1948 1934 1938 1942 1943 1936

BOWEN, N. L. AHRENS, L. II., PINSON, W. H. and KEARNS, AI. &l. SHAW, D. al. SANDELL,E. B. SHAW, D. Bl. TEUYER, T. P. AERENS, L. H. NOCKOLDS,S. R. GEORQALAS,G. C. and PAPASTAXST~O~,J. CLARIiE, F. W. WILLIAMS, FL CURTIS, G. H.

1927 1952

fhEXXONS,

I).

HALSEY, J. H.

B.

1952 1962 1952 1937 1962 1941 1951 1915 1950 1951 1952 1952

142

of some igneous rock series

U.S. Grol. Surv. Prof. Paper 3, 69 Sot. Geol. Belg. Livre .Jubilaire 1,387 Phil. Trans. Roy. Sot., Ser. B 229, 1 Trans. Roy. Sot. Edinburgh 61,533-575 Zeit. Vulk. 15,225-253 J. Geol. 48, 505-515 Carnegie lnst, Washington, Publ. MO J. Geol. 51, 167 Nach. Ges. d. Wiss. Gbttingen, Math. Phys. Kl. 1,171 Evolution of the Igneous Rocks, Princeton Geochim. et Cosmochim. Acta 2, 229-242 Geochim. et Cosmochim. Acta 2, 116-l 54 Geoohim. et Cosmochim. Acta 2, 211-216 Geochim. et Cosmochim. Acta 2, 185-206 Bull. Geol. Sot. Amer. 48, 1611 Geochirn. et Cosmochim. Acta 2, 155-169 Quart. J. Geol. Sot. Ml, p. 497 Bull. Voleanol. 11,l-37 U.S. Geol. Survey Bull. 591 U.S. Geol. Survey Bull. B66-B Unpublished Ph.D. Thesis. Univ. of California Unpublished Ph.D. Thesis, Univ. of California Unpublished Ph.D. Thesis, Univ. of California