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Trace element partition during olivine fractionation of Hawaiian basalts
C h e m i c a l Geology E l s e v i e r P u b l i s h i n g Company, A m s t e r d a m P r i n t e d in The N e t h e r l a n d s -
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION HAWAIIAN BASALTS
OF
BERNARD M. GUNN D e p a r t m e n t of G e o c h e m i s t r y , U n i v e r s i t y of M o n t r e a l , M o n t r e a l , Que. (Canada) (Received N o v e m b e r 19, 1971) ABSTRACT Gunn, B.M., 1971. T r a c e e l e m e n t p a r t i t i o n d u r i n g olivine f r a c t i o n a t i o n of Hawaiian b a s a l t s . Chem. Geol., 8 (1971): 1--13. A lava s e r i e s f r o m the 1959 Kilauea Iki e r u p t i o n of Hawaii has a c o m p o s i t i o n a l r a n g e of 7.0 to 19.0% MgO which has a l r e a d y been shown to be due to olivine f r a c t i o n a t i o n only. The t r a c e e l e m e n t s Sc, Cr, Ni, Co, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ba, have been d e t e r m i n e d (in addition to the m a j o r e l e m e n t s ) for the s e r i e s to d e l i m i t the effects of olivine c o n t r o l . C r and Ni a r e c o n c e n t r a t e d m a r k e d l y in the o l i v i n e r i c h m e m b e r s , Mg and Co a r e c o n c e n t r a t e d to a l e s s e r d e g r e e . Zn, Fe and Mn a r e p a r t i t i o n e d equally between olivine and liquid, while Sc, Cu, Ga, Rb, Sr, Y. Z r and Ba a r e all c o n c e n t r a t e d e x c l u s i v e l y t o g e t h e r with the o t h e r f e l s i c e l e m e n t s in the r e s i d u a l liquid. C r y s t a l l i n e olivine is s u b j e c t to s u b s o l i d u s r e a d j u s t m e n t but the c o m p o s i t i o n of the o r i g i n a l olivine may be i n f e r r e d by e x t r a p o l a t i o n of the t r e n d s of the bulk lava a n a l y s e s . By t h i s m e a n s an MgO content of 46.0~ + 1 is d e r i v e d . Olivine c o m p o s i t i o n s have also been d e t e r m i n e d by m i c r o p r o b e and olivine f r o m a p r e h i s t o r i c flow in the s a m e r e g i o n has also been a n a l y s e d for t r a c e e l e m e n t s . The r e s u l t s show the bulk of C r to be c o n t a i n e d in C r s p i n e l included in the olivine, and Zn, Co, Mn and Ni to be d i s t r i b u t e d f a i r l y r e g u l a r l y throughout the olivine. The p a r t i t i o n coefficient k, for Ni (ol.)/Ni (liq.) is 10.0, with k (Zn) b e i n g c l o s e to 0.95 c o m p a r e d with p a r t i t i o n c o e f f i c i e n t s of 4.5 for Mg, 3.0 for Co, 1.1 for Fe, and 1.0 for Mn. C o m p a r i s o n with p r e h i s t o r i c Makaopuhi lava lake t r e n d s shows d i f f e r e n t slopes, e s p e c i a l l y for Ni/Mg, C a / K and S r / K , due to c l i n o p y r o x e n e and p l a g i o c l a s e , as well as olivine, b e i n g involved in p r o d u c i n g f r a c t i o n a t i o n . INTRODUCTION In m a n y b a s a l t i c p r o v i n c e s e x t e n s i v e c h e m i c a l m o d i f i c a t i o n of t h e p a r e n t a l b a s a l t i s o f t e n p r o d u c e d b y f r a c t i o n a l c r y s t a l l i z a t i o n of o n e o r more crystal phases formed under low pressure prior to extrusion. If the m i n e r a l s o l i v i n e , c l i n o p y r o x e n e a n d p l a g i o c l a s e , a l l of w h i c h f o r m c o n t i n uous reaction series, are involved, the resulting lava series may not show s i m p l e t r e n d s of c h e m i c a l v a r i a t i o n , e s p e c i a l l y i n t h e c u m u l a t i v e m e m b e r s . A m a g m a s e r i e s c o n t r o l l e d b y t h e f r a c t i o n a l c r y s t a l l i z a t i o n of a s i n g l e p h a s e i s t h e r e f o r e of g r e a t i n t e r e s t , a s t h e r e s u l t i n g t r e n d s f o r b o t h m a j o r a n d t r a c e e l e m e n t s m a y b e f i x e d a n d u s e d in t h e i n t e r p r e t a t i o n of m o r e complex series. The 1959 Kilauea Iki lava series has been described in great detail Chem. Geol.. 8 (1971) 1 - 1 3
2
B.M. GUNN
by M u r a t a and R i c h t e r (1966a,b). T h e c o n t e n t of p h e n o c r y s t o l i v i n e was shown to v a r y d i r e c t l y with the r a t e of m a g m a e x p u l s i o n r e s u l t i n g in a m a g n e s i a c o n t e n t r a n g i n g f r o m 7 to 19%. T h e o t h e r m a j o r e l e m e n t s w e r e shown to v a r y l i n e a r l y and to be s u b j e c t to o l i v i n e c o n t r o l ; that is, any two e l e m e n t s w e r e found to v a r y in such a m a n n e r that the c o m p o s i t i o n of o l i v i n e , p a r e n t a l m a g m a and c u m u l a t i v e and r e s i d u a l l a v a s lay on a s t r a i g h t line. In the s a m e a r e a , on the s o u t h e a s t r i f t z o n e , t h e r e l i e s the 150 ft. deep p r e h i s t o r i c Makaopuhi l a v a lake f o r m e d of s i m i l a r o l i v i n e t h o l e i i t i c b a s a l t . A n o l i v i n e and m a g n e s i a - r i c h zone n e a r the b a s e of the lake has b e e n i n t e r p r e t e d by M o o r e a n d E v a n s (1967) and E v a n s and M o o r e (1968) to have b e e n f o r m e d by the p o s t - e m p l a c e m e n t s i n k i n g of the p h e n o c r y s t o l i v i n e , though d e t a i l e d m ~ c r o p r o b e a n a l y s i s of the o l i v i n e s a l s o showed that e x t e n s i v e m i n e r a l o g i c a l s u b - s o l i d u s r e a c t i o n had o c c u r r e d and f o r m e d s e c o n d a r y h y p e r s t h e n e . T h e bulk c h e m i s t r y s u g g e s t s s o m ~ s e t t l i n g of c l i n o p y r o x e n e and p l a g i o c l a s e with u p w a r d d i s p l a c e m e n t of r e s i d u a l liquid a l s o occurred. T r a c e e l e m e n t a n a l y s i s of a s u i t e of Makaopuhi lava lake s a m p l e s h a s shown that s y s t e m a t i c f r a c t i o n a t i o n of t r a c e e l e m e n t s has a l s o o c c u r r e d c o m p a r e d with the m i n o r d e g r e e of f r a c t i o n a t i o n of the m a j o r e l e m e n t s other than m a g n e s i a . T h i s f r a c t i o n a t i o n i n c l u d e s c h a n g e s in r a t i o of e l e m e n t s not i n c l u d e d in o l i v i n e . T h u s when the u p p e r p a r t of the l a v a lake i s c o m p a r e d with the l o w e r , the l a t t e r not only has h i g h e r F e / T i , M g / S i , and l o w e r M.g/Cr, M g / N i r a t i o s , such a s could be e x p e c t e d to r e s u l t f r o m o l i v i n e a c c u m u l a t i o n , but the C a / N a and N a / K r a t i o s w e r e h i g h e r , w h i l e the K / C a and R b / S r w e r e l o w e r . T h o u g h t h e s e d i f f e r e n c e s a r e s m a l l (see T a b l e III), a l l a r e c o n s i s t e n t with a m o r e b a s i c m a g m a c o m p a r e d to a m o r e highly f r a c t i o n a t e d m a g m a and could not be p r o d u c e d by o l i v i n e f r a c t i o n a t i o n alone. T h e s e d i f f e r e n c e s r a i s e a n i m p o r t a n t q u e s t i o n as to w h e t h e r the i n i t i a l Makaopuhi m a g m a w a s h o m o g e n e o u s , but was s u b s e q u e n t l y m o d i f i e d not only by o l i v i n e s e t t l i n g , but a l s o by s e t t l i n g or f i l t e r p r e s s i n g of c a l c i c p l a g i o c l a s e and m a g n e s i a n p y r o x e n e , as s u g g e s t e d by M o o r e and E v a n s (1967). A l t e r n a t i v e l y , at d i f f e r e n t t i m e s d u r i n g the i n f i l l i n g of the l a v a lake, the m a g m a m a y have v a r i e d not only i n o l i v i n e c o n t e n t but a l s o in o t h e r c h a r a c t e r i s t i c s s u c h a s i t s R b / S r and N a / C a r a t i o s . T h e p a r e n t a l 1959 K i l a u e a Iki l a v a w a s s i m i l a r to the a v e r a g e M a k a o puhi m a g m a , and w a s s a m p l e d at r e g u l a r i n t e r v a l s d u r i n g e m i s s i o n . T h e p r e s e n t study was m a d e to t e s t the t r a c e e l e m e n t h o m o g e n e i t y of this s e r i e s , to i n f e r o l i v i n e - l i q u i d p a r t i t i o n c o e f f i c i e n t s for s o m e t r a c e e l e m e n t s and to c o m p a r e p r e - and p o s t - e f f u s i o n f r a c t i o n a t i o n t r e n d s a s shown by t h e s e two s e r i e s . M e m b e r s of the K i l a u e a V o l c a n o O b s e r v a t o r y p r o v i d e d a p r e v i o u s l y u n a n a l y s e d s u i t e of K i l a u e a Iki s a m p l e s c o v e r i n g a r a n g e of o l i v i n e c o n t e n t w h i l e the p r e h i s t o r i c Makaopuhi s a m p l e s w e r e p r o v i d e d by D r . B. E v a n s .
ANALYTICAL METHODS M a j o r e l e m e n t s MZ, A1, Si, K, Ca, Mn, T i , F e , w e r e a n a l y s e d by X - r a y f l u o r e s c e n c e u s i n g a p o w d e r e d r o c k s a m p l e f u s e d in l i t h i u m t e t r a b o r a t e . M a t r i x c o r r e c t i o n s w e r e m a d e i t e r a t i v e l y by c o m p u t e r . A l l d e t e r m i n a t i o n s
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION w e r e made in d u p l i c a t e , the p r e c i s i o n v a r y i n g from + 0.3% SiO2 to ± 0.002 % K20, MnO and TiO2. Sodium was a n a l y s e d by a t o m i c a b s o r p t i o n and P205 by c o l o r i m e t r y . The t r a c e e l e m e n t s C r , Ni, Co, Cu, Zn, Ga, Rb, Sr, Y and Ba w e r e a l s o d e t e r m i n e d by X . R . F . , the p r e c i s i o n of r e p l i c a t e d s a m p l e s r a n g i n g from + 5 p.p.m, for Ba and Cr to + 0.5 p.p.m. Rb at the 95% confidence level. B e c a u s e of the high Ni and Cr contents, the Twin S i s t e r s Dunite DTS-1 was used as s t a n d a r d for t h e s e e l e m e n t s , the v a l u e s used being 2,348 p . p . m . Ni and 3°030 p.p.m. Cr. F o r other e l e m e n t s two W-1 p e l l e t s w e r e used with the a c c e p t e d v a l u e s of 82 p . p . m . Zn, 110 p . p . m . Cu, 50 p.p.m. Co, 16 p.p.m. Ga, 25 p . p . m . Y, 100 p.p.m. Z r , 34 p . p . m . Sc, 180 p.p.m. S t , 22 p.p.m. Rb and 156 p.p.m. Ba being used. The mineralogical analyses were made using a M.A.C. electron microprobe using pure oxide standards, with intensity data being adjusted using the Philibert absorption correction and the Philibert-Tixieratomic number correction.
RESULTS FOR KILAUEAIKI LAVAS The ten new m a j o r e l e m e n t a n a l y s e s (Table I) do not d i f f e r in any way from those m a d e on the s a m e lava s e r i e s r e p o r t e d by M u r a t a and R i c h t e r . S i m i l a r m a g n i t u d e s and r a t i o s obtained for a l l e l e m e n t s except A1203 which is s y s t e m a t i c a l l y 0.3% l o w e r in the X . R . F . r e s u l t s ( F i g . l ) . o
135
~o
120
a X 0
105 \
o
90
~ 7s u.l ~
~ lr
60
45
30
Na
15
~
O0 O0
*-lit K
~ s'o ,o'oP,[o
2o'o 2[0
" . --~_ 3o'o 3s'o ,o'o ,s'o so'o
PERCENT M g O
1959, KILAUEA IKI SERIES
Fig. 1. C o m p u t e r - p l o t t e d Bowen d i a g r a m showing l e a s t - m e a n - s q u a r e regression trend of (from top)A1203, CaO, TiO2, Na20, K20 , P205 for both new analyses and those of Murata and Richter (1967). Solid bar = range of olivine composition found by electron probe. Dashed lines define the inferred range of MgO for olivine causing fractionation. Scatter in AI203 values is due to systematic differences between U.S.G.S. and U. of M. data. Chem. Geol., 8 (1971) 1-13
98.92
51.9
98,92
50.4
Total
An (%)
1,036.4 773.7 95.1 95.0 100.7 13.8 7.8 256.8 137.3 18.8
100.000
46.25 9.41 1.897 12.822 0.155 18.75 8.390 1.731 0.397 0.185
KI0014
2.35 31.39 19.00 9.53 29.74 2.90 3.60 0.40
1,151.8 820.1 96.1 91.8 99.6 12.4 7.0 246.2 130.3 17.7
99.999
46.26 9.06 1.850 12.761 0.156 19.30 8.355 1.732 0.375 0.151
KI1022
2.22 30.49 19.74 8.70 31.04 2.90 3.51 0.53
Qz Or Plag Di Hy O1 Mt ILl Ap
C.I.P.W. norms
1,158.5 804.3 94.8 91.9 98.7 11.2 6.5 246.5 130.8 17.2
99.999
Total
Cr Ni Co Cu Zn Ga Rb Sr Ba Y
46.26 9.06 1.850 12.761 0.156 19.30 8.355 1.732 0.375 0.151
KI0022
SiO 2 A1203 TiO 2 Fe203 MnO MgO CaO Na20 K20 P205
Number 2
K i l a u e a Iki, 1959 l a v a s
50.6
98.92
2.32 31.78 20.44 7.71 29.75 2.90 3.60 0.41
1,020.9 726.7 91.9 95.9 100.3 14.2 6.8 256.6 133.7 19.0
100.000
46.28 9.45 1.898 12.823 0.157 18.30 8.713 1.801 0.392 0.187
KI0003
52.4
98.93
2.51 33.12 20.21 12.19 23.73 2.90 3.85 0.41
982.1 673.9 87.5 101.1 101.1 13.5 8.4 278.0 151.6 19.1
100.000
46.96 9.97 2.029 12:730 0.156 16.83 8.914 1.805 0.424 0.190
KI0036
732.7 530.6 78.5 106.5 102.1 15.7 8.5 298.7 154.7 20.7
100.000
47.52 10.77 2.209 12.640 0.156 14.63 9.527 1.878 0.461 0.213
KI0020
508.7 217.4 62.8 116.0 100.6 16.2 9.3 327.8 167.7 22.9
99.999
49.24 12.12 2.436 12.417 0.156 9.54 11.174 2.176 0.508 0.240
KI0051
52.7
98.96
3.00 40.20 26.10 18.09 3.51 2.90 4.63 0.52
505.6 207.8 60.0 118.3 100.7 16.4 9.8 330.7 167.2 22.4
99.999
49.24 12.12 2.436 12.417 0.156 9.54 11.174 2.176 0.508 0.240
KI1051
52.7
98.96
3.00 40.20 26.10 18.09 3.51 2.90 4.63 0.52
478.0 207.9 61.5 117.2 99.4 16.0 9.3 332.7 170.9 24.4
99.999
49.24 12.12 2.436 12.417 0.156 9.54 11.174 2.176 0.508 0.240
KI2051
52.7
98.93
3.26 42.09 24.71 17.95 2.63 2.90 4.93 0.45
385.8 189.5 59.6 123.8 104.8 18.9 10.3 357.0 177.6 24.3
100.001
49.20 12.70 2.597 12.656 0.157 8.68 10.970 2.282 0.552 0.206
KI0016
T e n n e w m a j o r e l e m e n t a n a l y s e s w i t h 13 t r a c e e l e m e n t a n a l y s e s of nine s a m p l e s f r o m t h e 1959 K i l a u e a Iki s e r i e s 1
TABLE Il
53.5
98.96
0.00 3.11 40.19 29.37 17.99 0.11 2.90 4.81 0.49
393.2 131.9 56.7 119.1 100.2 16.3 9.7 341.0 174.8 23.6
100.000
49.50 12.18 2.531 12.362 0.157 8.37 12.009 2.138 0.526 0.225
KI0037
50.9
98.97
0.00 3.20 41.07 28.88 16.43 1.19 2.90 4.81 0.50
372.6 125.6 56.7 133.2 101.6 17.4 9.9 339.9 175.2 24.5
100.000
49.61 12.27 2.530 12.308 0.156 8.27 11.770 2.313 0.541 0.227
KI0053
51.2
98.97
0.08 3.16 41.35 28.23 17.98 0.00 2.90 4.79 0.50
367.6 124.8 56.2 131.7 101.2 16.3 9.2 337.9 175.7 23.9
99.999
49.83 12.36 2.523 12.245 0.155 8.15 11.661 2.313 0.534 0.227
KI1052
435.2 182.1 133.1 7.9 313.1 110.8
Cr Ni Cu Rb Sr Ba
0.40 2.61 43.26 22.98 21.73 0.00 2.90 4.62 0.50
99.00
53.1
Qz Or Plag Di Hy O1 Mt I1 Ap
Total
An (%)
C.I.P.W. norms
100.001
50.00 12.95 2.435 ][1.979 0.156 8.74 10.752 2.320 0.442 0.230
SiO2 Al203 TiO2 EFe20 3 Mno " MgO CaO Na20 K20 P205
Total
MP0121
Number
100.000
50.64 13.52 2.854 12.255 0.156 6.49 10.855 2.502 0.502 0.230
MP0166
51.9
98.97
2.98 2.97 45.36 23.13 15.72 0.00 2.90 5.42 0.50
55.0
98.91
0.00 2.23 39.86 23.23 18.34 7.52 2.90 4.32 0.50
519.9 271.0 135.0 6.9 297.0 110.8
100.000
48.50 12.03 2.273 12.933 0.164 10.84 10.601 2.050 0.378 0.230
MP0191
56.5
98.96
98.97 53.6
0.00 2.04 38.64 21.49 22.49 6.92 2.90 4.00 0.48
711,9 .352.6 169.2 6.1 274.3 92.7
99.999
48.88 11.74 2.104 12.396 0.155 12.08 10.154 1.920 0.345 0.220
MP0240
0.00 1.95 39.74 22.34 18.33 9.35 2.90 3.96 0.39
672.6 334.9 106.4 5.2 277.6 88.0
100.001
48.78 11.85 2.085 12.324 0.155 11.96 10.220 2.108 0.330 0.180
MP0218
Makaopuhi lava lake
306.2 111.3 157.2 8.4 337.2 124,1
Prehistoric
T A B L E I (continued)
59.0
98.94
0.64 2.30 40.51 21.15 26.51 0.00 2.90 4.43 0.50
533.2 250.8 109,5 7.0 292.5 100.3
100.001
49.60 12.51 2.333 12.600 0.157 9.82 10.468 1.896 0.389 0.230
MP0053
55.0
98.92
0.41 2.54 41.79 23.21 22.67 0.00 2.90 4.88 0.52
403.5 247.9 136.4 7.9 311.0 102.8
100.004
49.49 12.65 2.568 12.804 0.164 8.71 10.799 2.150 0.429 0.240
MP0057
57.1
98.99
2.08 2.44 42.88 21.66 21.88 0.00 2.90 4.66 0.50
392.6 236.9 108.7 7.2 313.6 109.1
99.999
50.26 13.10 2.454 12.086 0.154 8.49 10.715 2.100 0.412 0.230
MP0091
M P 0 1 2 1 : b a s a l t f r o m -- 7 1 f t . , Makaopuhi lava lake. M P 0 1 6 6 = b a s a l t f r o m - - 1 1 3 ft.. Makaopuhi lava lake. MP0191 b a s a l t f r o m - - 1 3 8 ft.. Makaopuhi lava lake. MP0218 b a s a l t f r o m - - 1 6 5 ft.. Makaopuhi lava lake. M P 0 2 4 0 - b a s a l t f r o m - - 1 8 7 ft.. Makaopuhi lava lake. MPO053 = b a s a l t s u r f a c e c r u s t of Makaopuhl prehistomc lava lake. MPO057 b a s a l t f r o m - - 4 ft.. M a k a o p u h l l a v a lake. MPO091 b a s a l t f r o m - - 4 1 ft.. M a k a o p u h i l a v a lake.
1 T o t a l i r o n only i s s h o w n a s F e 2 0 3 a n d r e s u l t s a r e s u m m e d to 100% w a t e r - f r e e . 2 S a m p l e s - KI0022 = b a s a l t s c o r i a , p h a s e 1, 1 1 / 1 8 , 5.00 p . m . KI1022 = b a s a l t , d u p l i c a t e t r a c e e l e m e n t a n a l y s e s of KI0022 KI0014 = b a s a l t s c o r i a , p h a s e 5, 1 2 / 6 , 4.30 p . m . KI0003 = b a s a l t s c o r i a , p h a s e 1. 1 1 / 1 9 , 8.00 a . m . KI0036 = b a s a l t pond, p h a s e 9, 1 2 / 1 3 , 4.00 p . m . KI0020 = b a s a l t s c o r i a , p h a s e 7. 12/8. KI0051 = b a s a l t pond, p h a s e 1, 1 1 / 2 1 , 9.30 a . m . KI1051 = b a s a l t , d u p l i c a t e t r a c e e l e m e n t a n a l y s e s of KI0051. KI2051 = b a s a l t , d u p l i c a t e t r a c e e l e m e n t a n a l y s e s of KI0051. KI0016 = b a s a l t flow, p h a s e 4, 1 2 / 4 , 9.50 a . m . KI0037 = b a s a l t flow, p h a s e 11, 11/14 KI0053 = b a s a l t pond, p h a s e 1, 1 1 / 1 6 , 2.30 p . m . KI1053 = b a s a l t , d u p h c a t e of KI0053.
6
B.M. GUNN
D o u b l e c h e c k i n g a g a i n s t o t h e r s t a n d a r d s has not a l t e r e d the r e s u l t . T h e P e a r s o n R c o r r e l a t i o n c o e f f i c i e n t s b a s e d on r e g r e s s i o n a n a l y s i s of each e l e m e n t p a i r a s o b t a i n e d by c o m p u t e r , a r e a l s o i d e n t i c a l . If c e r t a i n a s s u m p t i o n s a r e m a d e , i . e . , that the s e r i e s does indeed follow a n o l i v i n e c o n t r o l t r e n d , a n d that the o l i v i n e c o n t a i n s v i r t u a l l y no Na, K, Rb, Ba, P , Ca, A1, etc., the c o m p u t e d i n t e r c e p t of the t r e n d s of any of t h e s e e l e m e n t s when p l o t t e d a g a i n s t a n y e l e m e n t found in o l i v i n e , e.g. SiO2, MgO, F e 203, MnO, C r , Ni, Co, Zn, m a y b e u s e d to e s t i m a t e the c o m p o s i . tion of the o l i v i n e at the t i m e the f r a c t i o n a t i o n took p l a c e . T h e c a l c u l a t i o n i s s i m i l a r in p r i n c i p l e to that u s e d in the B o w e n d i a g r a m which is s i m p l y a g r a p h i c a l s o l u t i o n of the s a m ~ p r o b l e m ( F i g . l ) . Partition coefficients are customarily derived from phenocryst/glass c o m p o s i t i o n s ( H e n d e r s o n a n d D a l e , 1970), but p h e n o c r y s t o l i v i n e s m a y not be in e q u i l i b r i u m with the g l a s s in which they o c c u r and g r o u n d m a s s o l i v i n e s a r e u s u a l l y m o r e i r o n - r i c h and do not have the c o m p o s i t i o n of the o l i v i n e s p r o d u c i n g the f r a c t i o n a t i o n . M a r a t a a n d R i c h t e r (1966) found the m o s t b a s i c g l a s s f r o m both K i l a u e a and M a u n a Loa v o l c a n o e s to have 10% MgO; this c o m p o s i t i o n i s t a k e n to be c l o s e to the p r i m i t i v e p a r e n t a l m a g m a for the r e g i o n . T h e i n f e r r e d and a c t u a l o l i v i n e c o m p o s i t i o n s have a m e a n of a b o u t 43% MgO f r o m which l i q u i d / c r y s t a l d i s t r i b u t i o n c o e f f i c i e n t s for o l i v i n e can be d e r i v e d for a n u m b e r of t r a c e e l e m e n t s a s follows: (a) N i c k e l . F r o m the slope of the M g / N i d i a g r a m ( F i g . 2 ) an a v e r a g e Ni c o n t e n t of 2 , 4 0 0 - 2 , 5 0 0 p . p . m , and a M g / N i r a t i o of 112 m a y be i n f e r r e d for the o l i v i n e . T h e r e was i n s u f f i c i e n t m a t e r i a l to allow s e p a r a t i o n of o l i v i n e for a n a l y s i s f r o m K i l a u e a Iki s a m p l e s . A n o l i v i n e c o n c e n t r a t e f r o m Kona b e a c h sand d e r i v e d f r o m a h i s t o r i c flow of K i l a u e a n r i f t z o n e b a s a l t was a l s o a n a l y s e d for c o m p a r i s o n and this gave 2,428 p . p . m . Ni and a M g / N i r a t i o of 99. We have b e e n u n a b l e to a t t a i n the p r e c i s i o n of m i c r o p r o b e a n a l y s i s r e p o r t e d by H~tkli and W r i g h t (1987) in t h e i r work on the Ni c o n t e n t s of the h i s t o r i c M a k a o p u h i l a v a , but v a l u e s for Ni of 2,950 p . p . m . and 2,350 p . p . m , h a v e b e e n o b t a i n e d by m i c r o p r o b e for the c e n t e r of p h e n o c r y s t s and for g r o u n d m a s s o l i v i n e r e s p e c t i v e l y for Kzlauea Iki ( T a b l e H). 1000 800
600
/
/
200
0
O0
2r5
S'O
7'5 I0'0 17'5 15To PESCENT MgO KILAUEA (o} AND MAKAOPUHI (,)
17'5
~0'0
LAVAS
F i g . 2 . N i c k e l d i s t r i b u t i o n r e l a t i v e to MgO for K i l a u e a Iki ( c i r c l e s ) and the P r e h i s t o r i c l a v a lake ( t r i a n g l e s ) . D i s t r i b u t i o n on X a x i s is e q u i v a l e n t to 1 - 3 0 (/~ o l i v i n e c o n t e n t .
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION
7
TABLE II Results of five analyses of Hawaiian basalts
SiO 2 A1203 TiO 2 FeO MnO MgO CaO
A
B
39.48
41.4
C
0.023 11.0
Cr Co Ni Cu Zn
39.1
37.7
0 12.6
15.8
12.8
45.7
41.7
46.4
0.146 47.83
0.17
0.25 12.6 0.16 45.7
0.123
1.0 0.15
0.51
0.008
0
0.02
0.02
0.12
]?205 Total
E
0.163
Na20 K20
D
98.77 1,020 250 2,920 9 86
99.7
2,950
99.6
2,350
0
97.1 2,840 190 2,430 5 97
A. Olivine from Kona beach sand, Hawaii, analysed by X . R . F . B . Microprobe analysm of phenocryst olivine from 1959 Kilauea Iki basaltic, pumice ejecta. C. Microprobe average of FeO and MgO in Kilauea Iki groundmass olivine. D. Olivine composition inferred from slope and intercept of bulk analyses from Murata and Richter (1966b). E. Olivine composition inferred from new bulk analyses. M g / N i r a t i o s i n c r e a s e f r o m 9 0 - 1 1 0 f o r p u r e o l i v i n e , t h r o u g h 140 for o l i v i n e - r i c h b a s a l t to 345 f o r o l i v i n e - f r e e b a s a l t , the l a t t e r b e i n g e s s e n t i a l l y the M g / N i r a t i o of t h e c l i n o p y r o x e n e . A d i f f e r e n t s l o p e is o b t a i n e d f o r the p r e h i s t o r i c M a k a o p u h i s a m p l e b e c a u s e of s o m e p y r o x e n e c o n c e n t r a t i o n a c c o m p a n y i n g o l i v i n e (Fig.2). N i c k e l f r a c t i o n a t i o n by o l i v i n e has b e e n the s u b j e c t of c o n s i d e r a b l e r e s e a r c h and the a n o m a l o u s p r e f e r e n c e of the o l i v i n e o c t a h e d r a l l a t t i c e s i t e fo r Ni o v e r M g h a s b e e n e x p l a i n e d on the b a s i s of c r y s t a l f i e l d t h e o r y by B u r n s (1970b). Htlkli and W r i g h t (1967) found the o l . - c p x , p a r t i t i o n r a t i o and the t o t a l Ni c o n t e n t to d e c r e a s e s t e e p l y with t e m p e r a t u r e in the r e c e n t M a k a o p u h i l a v a lake. (b) C h r o m i u m . T h e C r o c c u r s m a i n l y in e u h e d r a l c h r o m e s p i n e l i n c l u d e d in o l i v i n e . C h r o m e s p i n e l i s a b s e n t in the g r o u n d - m a s s and is not j a c k e t e d by u l v o s p i n e l - m a g n e t i t e a s o c c u r s in t h e C r o z e t b a s a l t s (Gunn et a l . , 1970}, and in M a k a o p u h i ( E v a n s and M o o r e , 1967). M i c r o p r o b e a n a l y s e s of K i l a u e a s p i n e l s show t h e r e to be an a v e r a g e of 40% C r 2 0 3 p r e s e n t and l e s s than 1% T i O 2 . A s t h e bulk of t h e C r p r e s e n t o c c u r s only in t h e s e s p i n e l s p r e s e r v e d w i t h i n o l i v i n e , (and a s s u m i n g an e v e n d i s p e r s i o n of s p i n e l a s the o l i v i n e c r y s t a l l i z e d } the o r i g i n a l m a g m a m a y h a v e c o n t a i n e d n e a r l y 1% C r .
8
B.M. GUNN
T h e M g / C r d i s t r i b u t i o n in the M a k a o p u h i l a v a l a k e i s s i m i l a r to the Kilauean series. The virtually constant Mg/Cr ratio (Fig.3) suggests c o t e c t i c c r y s t a l l i z a t i o n f o l l o w e d by l o s s by g r a v i t a t i o n a l s e t t l i n g o r r e s o r p t i o n of a n y s p i n e l not i n c l u d e d in o l i v i n e . N e g l e c t i n g the v e r y m i n o r C r p r e s e n t in t i t a n o m a g n e t i t e , an a v e r a g e C r c o n t e n t of 700 p . p . m , m a y be i n f e r r e d for the p y r o x e n e c o m p a r e d with 2,800 p . p . m , i n f e r r e d for the s p i n e l i n c l u d e d in t h e K i l a u e a o l i v i n e and 1,027 p . p . m , o b t a i n e d f o r the K o n a olivine. (c) Cobalt. T h e s l o p e of the M g O - C o d i s t r i b u t i o n i s l e s s t h a n unity, i . e . Co2+ e n t e r s the o l i v i n e l e s s r e a d i l y than d o e s the Mg 2+ ion. T h e M E / C o r a t i o is 1,450 f o r o l i v i n e and c h a n g e s in the l a v a f r o m 1,210 to 860 with d e c r e a s e in o l i v i n e c o n t e n t . T h e o l i v i n e is i n f e r r e d to h a v e 190 p . p . m . Co and the p a r t i t i o n c o e f f i c i e n t Co ( o l . ) / C o (liq.)= 3.0. T h e r a t h e r m o r e m a g n e s i a n Kona o l i v i n e i s s i g n i f i c a n t l y r i c h e r in Co (250 p . p . m . ) . (d) ~'e-Mn-Zn. A l t h o u g h t h e s e t h r e e e l e m e n t s did e n t e r into o l i v i n e , the o l . / l i q , p a r t i t i o n c o e f f i c i e n t w a s v e r y c l o s e to one for Mn, 0.95 for Zn and about 1.1 for F e . Not only h a s l i t t l e r e l a t i v e f r a c t i o n a t i o n t a k e n p l a c e , but MnO for e x a m p l e , d o e s not v a r y by m o r e than 0.002% t h r o u g h o u t . T h e r a t i o s v F e 2 0 3 / M n O = 80 and F e / Z n = 1,244 m u s t a l s o b e c h a r a c t e r i s t i c of the p r i m a r y b a s a l t . (e) S r - R b - B a - C u - G a - Y - Z r . T h e s e t r a c e e l e m e n t s , t o g e t h e r with the m a j o r e l e m e n t s A1, T i , Na, K, Ca, P , b e i n g v i r t u a l l y e x c l u d e d f r o m the o l i v i n e l a t t i c e (with the e x c e p t i o n of a b o u t 10 p . p . m . Cu) have b e e n m e r e l y c o n c e n t r a t e d o r d i l u t e d in the r e s i d u a l l i q u i d a n d t h e i r r e l a t i v e r a t i o s r e m a i n c o n s t a n t . S e m i q u a n t i t i v e d e t e r m i n a t i o n of Sc s h o w s t h a t t h i s e l e m e n t is a l s o m a i n l y c o n c e n t r a t e d in the r e s i d u a l l i q u i d with a m a x i m u m of about 30 p . p . m . Y t t r i u m in i t s g e o c h e m i c a l b e h a v i o r f o l l o w s the r a r e e a r t h e l e m e n t s and p r e d i c t a b l y a p p e a r s to b e e x c l u d e d b~} o l i v i n e . C l a r k e (1970) a l s o found a n e g a t i v e c o r r e l a t i o n of y t t r i u m with o l i v i n e in the Baffin B a y B a s a l t s and a s i m i l a r r a n g e in c o n c e n t r a t i o n . T h e r e m a y be s o m e doubt a s to t h e comI~osition of the p a r e n t a l b a s a l t 1200 o
1000
./
800
600
400
200
•
0 oo
2'5
, 50
715
10'0
PERCENT
, 125
15'0
, 175
, 200
MgO
KILAUEA (o) AND MAKAOPUHI (") LAVAS
Fig.3. Chromium vs. MgO distribution symbolised as in Fig.2. Regression line is drawn through Kilauea Iki samples only.
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION T A B L E III C o m p a r i s o n of d i f f e r e n c e b e t w e e n l a v a s s u b j e c t to o l i v i n e c o n t r o l a n d l a v a - l a k e s u b j e c t to ol. + c p x . + p l a g . c o n t r o l A
B
C
D
SiO 2
48.68
49.80
46.63
49.47
A1203
11.89
13.09
9.70
12.31
TiO 2 Fe203 MnO
2,181 12.58 0.159
2.59
1.98
12.36
12.76
0.159
0.156
2.524 12.40 0.155
MgO
11.66
8.25
17.56
8.60
CaO
10.24
10.80
8.78
11.52
Na20
2.02
2.28
1.83
2.24
K20
0.362
0.444
0.409
0.532
P205
0.22
0.23
0.21
0.23
Total
100.00
99.99
100.01
99.98
Cr
n.d.
n.d.
986
Co
n.d.
n.d.
93
58
Ni
399
277
719
176
406
Cu
130
147
98
125
Zn
n.d.
n.d.
99
100
Ga
n.d.
n.d.
13
17
Rb
5,7
8.3
7.6
258
317
Y
n.d.
n.d.
18
24
79
101
142
174
527
444
447
455
28
24
21
21
Ba K/Rb CaO/K20 CaO/Na20 Na20/K20 -
~Fe3+/MnO K/Rb Rb/Sr Mg/Ni Ca/K
5.1 5.6
4.7 5.1
268
9.7
Sr
4.8 4.5
341
5.1 4.2
79
78
82
79
527
444
447
455
0.022
0,026
0.028
0,028
176
180
147
295
28
24
21
21
A. A v e r a g e of 5 a n a l y s e s f r o m t h e l o w e r 105 ft. of M a k a o p u h i l a v a l a k e . B. A v e r a g e of 5 a n a l y s e s f r o m t h e u p p e r 120 ft. C. A v e r a g e of 5 h i g h m a g n e s i a p h a s e s of t h e 1959 K i l a u e a Iki l a v a . D. A v e r a g e of 5 low m a g n e s i a p h a s e s of t h e e r u p t i o n .
C h e m . G e o l . , 8 (1971} 1 - 1 3
10
B.M. GUNN
of K i l a u e a but b e c a u s e of the lack of r e l a t i v e f r a c t i o n a t i o n of this group of e l e m e n t s , the p a r e n t a l m a g m a m'ast have had K / R b = 450, R b / S r = 0.028, K / B a = 32, N a 2 0 / K 2 0 = 4.3, C a O / N a 2 0 = 5.0, A 1 / G a = 3,330 (see T a b l e III). A l l t h e s e r e s i d u a l e l e m e n t s show high d e g r e e s of m u t u a l p o s i t i v e c o r r e l a t i o n . COMPARISON WITH MAKAOPUHI LAVA LAKE TRENDS T h e m e a n s of the o l i v i n e - r i c h and o l i v i n e - p o o r m e m b e r s of both the K i l a u e a s e r i e s and the M,~kaopuhi s e r i e s a r e c o m p a r e d in T a b l e I. T h e slope of the M~,-Cr t r e n d i s i d e n t i c a l in both l a v a s u i t e s due to the d o m i n a n c e of Mg f r a c t i o n a t i o n by o l i v i n e and of the C r by the i n c l u d e d s p i n e l . T h e M ~ / N i t r e n d shows d i s t i n c t l y d i f f e r e n t slope, the K i l a u e a t r e n d b e i n g e s s e n t i a l l y a p a r t i a l s e r i e s b e t w e e n the end m e m b e r s o l i v i n e - l i q u i d , w h e r e a s in Makaopuhi Ni and Mg a r e a f f e c t e d by two c r y s t a l l i z i n g p h a s e s , o l i v i n e and c l i n o p y r o x e n e , the l a t t e r with m a r k e d l y l o w e r Ni c o n t e n t r e l a t i v e to Mg. T h e s e r a t i o s m a y be c a l c u l a t e d for the o l i v i n e a s M g O / N i = 180 and for c l i n o p y r o x e n e a s M g O / N i = 800. T h e two s e r i e s a l s o d i f f e r in t h e i r K / C a and K / S r d i s t r i b u t i o n (Fig.4,5). In both c a s e s the K i l a u e a Iki s e r i e s show no r e l a t i v e f r a c t i o n a t i o n a n d e x t r a p o l a t e d i r e c t l y t o w a r d s o l i v i n e c o m p o s i t i o n while the Makaopuhi shows h i g h e r Ca and S r at low K i n d i c a t i n g p l a g i o c l a s e f r a c t i o n a t i o n . T h e d i f f e r e n c e in K / R b r a t i o is b a r e l y s i g n i f i c a n t ( F i g . 6 ) the m e a n b e i n g 450. T h e fact that Makaopuhi i s s l i g h t l y l o w e r in both Rb and Ba r e l a t i v e to K m a y be a t t r i b u t e d to the s e p a r a t i o n of g r a n o p h y r e v e i n s in Makaopuhi (Fig.7). C o p p e r shows a s i m p l e o l i v i n e c o n t r o l d i s t r i b u t i o n in K i l a u e a but a m u c h m o r e e r r a t i c d i s t r i b u t i o n in Makaopuhi s u g g e s t i n g s o m e s u b s o l i d u s m i g r a t i o n (Fig.8).
60
400
45
300 -
o
2
o~ ~
2OO-
c~ lOO
0 oo
, 20
,40
, 60
PERCENT
0 80
100
120
CaO
KILAUEA (o) AND MAKAOPUHI (-) LAVAS
,
, I
, 2 PERCENT
, 3
, 4
- - 1 5
6
K~O
KILAUEA (o) AND MAKAOPUHI (-) LAVAS
F i g . 4 . D i s p a r i t y b e t w e e n n o n - f r a c t i o n a t e d K i l a u e a Iki, and f r a c t i o n a t e d M,~kaopuhi l a v a for K 2 0 vs. CaO. F i g . 5 . D i s p a r i t y in Sr v s . K 2 0 t r e n d s for K i l a u e a Iki ( n o n - - f r a c t i o n a t e d ) and M,~kaopuhi ( f r a c t i o n a t e d ) .
TRACE E L E M E N T PARTITION DURING OLIVINE FRACTIONATION
11
IBO
MnO
~'9o-- o
-o o--O-o~o
150 O ¢j
EFe
r~ 120
Zn
0
60
0 c
3o
0 oo
, 25
, so
, 75
. 100
.
. 125
PERCENT
. 150
. 175
200
MgO
1959. KILAUEA IKI SERIES
F i g . 6 . D i s t r i b u t i o n s l o p e s for p e r c e n t M . 1 0 x 1 0 0 0 , F e 3+ x 10, Z n
(p.p.m.) and Co (p.p.m.) ~20
o03
IOO o
~
80
8a
S: °
O 6O Z
g: 4o 2O
Rb
I
2
3
PERCENT
_~__o f
o~°
4
S
6
K20
KILAUEA (o) AND MAKAOPUHI (*) LAVAS Fig.7. R b and B a distribution relative to K20. Circles = Kilauea ]~i, t r i a n g l e s M a k a o p u h i , f i l l e d c i r c l e = o l i v i n e . N o t e l a c k of r e l a t i v e f r a c t i o n a tion. 200
)so
d ~
Io0o 50
O. O0
25
SO
7$
I00
PERCENT
125
ISO
175
200
MgO
KILAUEA (o) AND MAKAOPUHI (-) LAVAS
F i g . 8 . Cu d i s t r i b u t i o n s y m b o l i s e d a s for F i g . 7 . N o t e the m o r e e r r a t i c d i s t r i b u t i o n in the l a v a l a k e s a m p l e s . Chem. Geol.. 8 (19711 1 - 1 3
12
B.M. GUNN
D~CUSSION
T h e r e s u l t s p r e s e n t e d h e r e show that for the K i l a u e a Iki o l i v i n e s , the o c t a h e d r a l s i t e p r e f e r e n c e s for the t r a n s i t i o n m e t a l s a r e in the o r d e r Ni ) Mg ~ Co ~ F e > M~I > Zn. In the c a s e of Mn the slope of the d i s t r i b u tion c o e f f i c i e n t k is 1 w h a t e v e r the c o m p o s i t i o n of the p r i m a r y m a g m a . M u r a t a and R i c h t e r (1967) p r e s e n t c o n s i d e r a b l e e v i d e n c e to show that the p r i m a r y t h o l e i i t i c m a g m a in M a u n a L o a and K i l a u e a v o l c a n o e s r e m a i n s c o n s t a n t at 10% MgO. We c a n t h e r e f o r e i n f e r d i s t r i b u t i o n c o e f f i c i e n t s of a p p r o x i m a t e l y k(Ni) = 10, k(Mg) = 4.5, k(Co = 3.0, k (Fe) = 1.1, k(Mn) = 1.0, k (Zn) = 0.95. T h e s e v a l u e s a r e in g e n e r a l s i m i l a r in o r d e r but at v a r i a n c e in m a g n i t u d e with t h o s e d e r i v e d by o t h e r m e a n s . T h u s H e n d e r s o n and D a l e (1970) find v a l u e s of k(Ni) 4 . 9 - 1 8 . 6 , k(Co) 1 . 1 - 1 . 8 and k ( F e ) 1 . 4 - 3 . 0 , k(Mn) 1 . 1 - 1 . 8 , for g r o u n d m a s s o l i v i n e - g l a s s f r o m l a v a s of R e u n i o n , the S o l o m o n s and J u a n F e r n a n d e z . H o w e v e r it m u s t be p o i n t e d out that such s t u d i e s a r e b a s e d on c r y s t a l - r e s i d u a l g l a s s e q u i l i b r i a e x i s t i n g at l o w e r , p o s s i b l y s u b s o l i d u s t e m p e r a t u r e s . T h e s a m e w r i t e r s quote o c t a h e d r a l s i t e p r e f e r e n c e e n e r g i e s ( k c a l . / m o l e ) a s Ni 2+ = 20.G, Co 2+ = 7.4, F e 2+ = 4.0, M 12+ = 0, w h i c h a r e c o m p a t i b l e with the d i s t r i b u t i o n s of the K i l a u e a t r a n s i tion e l e m e n t s . T h e s l o p e s of the d i s t r i b u t i o n of M g / N i , M g / C o , M g / M n , etc. and the r a t i o s of the r e s i d u a l e l e m e n t s a r e c o n s i d e r e d to be, a s a r e s u l t of the a b o v e work, of c o n s i d e r a b l y m o r e v a l u e in c l a s s i f y i n g a p e t r o g r a p h i c p r o v i n c e than a r e a b s o l u t e e l e m e n t a b u n d a n c e s or v a r i a t i o n t r e n d s .
ACKNOWLEDGMENTS T h e c h e m i c a l a n a l y s e s w e r e m a d e u n d e r s u p p o r t p r o v i d e d by C.N.R. g r a n t No. A - 3 8 3 4 . D r . R. C o y - Y l l c a r r i e d out the m i c r o p r o b e a n a l y s e s . D r . H. S c h m i n k e b r o u g h t the K i l a u e a Iki s a m p l e s f r o m Hawaii and the Makaopuhi s a m p l e s w e r e p r o v i d e d by D r . B. E v a n s . T h e c o o p e r a t i o n of m e m b e r s of the U.S. G e o l o g i c a l S u r v e y , e s p e c i a l l y D r s . D. S w a n s o n , J. M o o r e , T. W r i g h t and D. P e c k is g r a t e f u l l y a c k n o w l e d g e d , the l a t t e r e s p e c i a l l y for g u i d a n c e in the field.
REFERENCES Burns, R.G., 1970a. Site preferences of transition metal ions in silicate crystal structures. Chem. Geol.. 5(4): 275-283. Burns, R.G., 1970b. Mineralogical Applications of Crystal Field Theory. Cambridge University Press, London,in press. Clarke, D.B., 1970. Tertiary basalts of Baffin Bay: Possible primary magma from the mantle. Contr. Mineral. Petrol., 25: 2-3, 224. Evans, B.W. and Moore, J.G., 1968. Mineralogy as a function of depth in the prehistoric Makaopuhi tholeiitic lava lake, Hawaii. Contr. Mineral. Petrol., 17: 85-115. Gunn, B.M., Coy-Yll, Ramon, Watkins, N.D., Abranson, C.E. and Nougier, J., 1970. Geochemistry of an oceanite-ankaram}te-basalt suite from East Island, Crozet Archipelago. Contr. Mineral. Petrol., 28: 319-339.
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION
13
H~kli, T.A. and Wright, T . L . , 1967. The f r a c t i o n a t i o n of nickel between olivine and augite as a g e o t h e r m o m e t e r . Geochim. C o s m o c h i m . Acta, 31: 877-884. H e n d e r s o n . P. and Dale, I.M., 1970. The p a r t i t i o n i n g of s e l e c t e d tranMtion e l e m e n t ions between olivine and g r o u n d m a s s of oceanic b a s a l t s . Chem. Geol., 5(4): 267-274. Murata, K.J. and R i c h t e r , D.H., 1966a. The s e t t l i n g of olivine in m a g m a as shown by lavas of the 1959 eruption. Am. J. Sci., 264: 194-203. Murata, K.J. and R i c h t e r , D.H., 1966b. C h e m i s t r y of the lavas of the 1959-1960 eruption of Kilauea Volcano, Hawaii. U.S. Geol. Surv. P r o f e s s . P a p e r , 537-A. Moore, J.G. and Evans, B.W., 1967. The r o l e of olivine in the c r y s t a l l i z a t i o n of the p r e h i s t o r i c Makaopuhi tholeiitic Lava Lake, Hawaii. Contr. M i n e r a l . P e t r o l . , 15: 202-223.
Chem. Geol., 8 (1971) 1-13
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION HAWAIIAN BASALTS
OF
BERNARD M. GUNN D e p a r t m e n t of G e o c h e m i s t r y , U n i v e r s i t y of M o n t r e a l , M o n t r e a l , Que. (Canada) (Received N o v e m b e r 19, 1971) ABSTRACT Gunn, B.M., 1971. T r a c e e l e m e n t p a r t i t i o n d u r i n g olivine f r a c t i o n a t i o n of Hawaiian b a s a l t s . Chem. Geol., 8 (1971): 1--13. A lava s e r i e s f r o m the 1959 Kilauea Iki e r u p t i o n of Hawaii has a c o m p o s i t i o n a l r a n g e of 7.0 to 19.0% MgO which has a l r e a d y been shown to be due to olivine f r a c t i o n a t i o n only. The t r a c e e l e m e n t s Sc, Cr, Ni, Co, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ba, have been d e t e r m i n e d (in addition to the m a j o r e l e m e n t s ) for the s e r i e s to d e l i m i t the effects of olivine c o n t r o l . C r and Ni a r e c o n c e n t r a t e d m a r k e d l y in the o l i v i n e r i c h m e m b e r s , Mg and Co a r e c o n c e n t r a t e d to a l e s s e r d e g r e e . Zn, Fe and Mn a r e p a r t i t i o n e d equally between olivine and liquid, while Sc, Cu, Ga, Rb, Sr, Y. Z r and Ba a r e all c o n c e n t r a t e d e x c l u s i v e l y t o g e t h e r with the o t h e r f e l s i c e l e m e n t s in the r e s i d u a l liquid. C r y s t a l l i n e olivine is s u b j e c t to s u b s o l i d u s r e a d j u s t m e n t but the c o m p o s i t i o n of the o r i g i n a l olivine may be i n f e r r e d by e x t r a p o l a t i o n of the t r e n d s of the bulk lava a n a l y s e s . By t h i s m e a n s an MgO content of 46.0~ + 1 is d e r i v e d . Olivine c o m p o s i t i o n s have also been d e t e r m i n e d by m i c r o p r o b e and olivine f r o m a p r e h i s t o r i c flow in the s a m e r e g i o n has also been a n a l y s e d for t r a c e e l e m e n t s . The r e s u l t s show the bulk of C r to be c o n t a i n e d in C r s p i n e l included in the olivine, and Zn, Co, Mn and Ni to be d i s t r i b u t e d f a i r l y r e g u l a r l y throughout the olivine. The p a r t i t i o n coefficient k, for Ni (ol.)/Ni (liq.) is 10.0, with k (Zn) b e i n g c l o s e to 0.95 c o m p a r e d with p a r t i t i o n c o e f f i c i e n t s of 4.5 for Mg, 3.0 for Co, 1.1 for Fe, and 1.0 for Mn. C o m p a r i s o n with p r e h i s t o r i c Makaopuhi lava lake t r e n d s shows d i f f e r e n t slopes, e s p e c i a l l y for Ni/Mg, C a / K and S r / K , due to c l i n o p y r o x e n e and p l a g i o c l a s e , as well as olivine, b e i n g involved in p r o d u c i n g f r a c t i o n a t i o n . INTRODUCTION In m a n y b a s a l t i c p r o v i n c e s e x t e n s i v e c h e m i c a l m o d i f i c a t i o n of t h e p a r e n t a l b a s a l t i s o f t e n p r o d u c e d b y f r a c t i o n a l c r y s t a l l i z a t i o n of o n e o r more crystal phases formed under low pressure prior to extrusion. If the m i n e r a l s o l i v i n e , c l i n o p y r o x e n e a n d p l a g i o c l a s e , a l l of w h i c h f o r m c o n t i n uous reaction series, are involved, the resulting lava series may not show s i m p l e t r e n d s of c h e m i c a l v a r i a t i o n , e s p e c i a l l y i n t h e c u m u l a t i v e m e m b e r s . A m a g m a s e r i e s c o n t r o l l e d b y t h e f r a c t i o n a l c r y s t a l l i z a t i o n of a s i n g l e p h a s e i s t h e r e f o r e of g r e a t i n t e r e s t , a s t h e r e s u l t i n g t r e n d s f o r b o t h m a j o r a n d t r a c e e l e m e n t s m a y b e f i x e d a n d u s e d in t h e i n t e r p r e t a t i o n of m o r e complex series. The 1959 Kilauea Iki lava series has been described in great detail Chem. Geol.. 8 (1971) 1 - 1 3
2
B.M. GUNN
by M u r a t a and R i c h t e r (1966a,b). T h e c o n t e n t of p h e n o c r y s t o l i v i n e was shown to v a r y d i r e c t l y with the r a t e of m a g m a e x p u l s i o n r e s u l t i n g in a m a g n e s i a c o n t e n t r a n g i n g f r o m 7 to 19%. T h e o t h e r m a j o r e l e m e n t s w e r e shown to v a r y l i n e a r l y and to be s u b j e c t to o l i v i n e c o n t r o l ; that is, any two e l e m e n t s w e r e found to v a r y in such a m a n n e r that the c o m p o s i t i o n of o l i v i n e , p a r e n t a l m a g m a and c u m u l a t i v e and r e s i d u a l l a v a s lay on a s t r a i g h t line. In the s a m e a r e a , on the s o u t h e a s t r i f t z o n e , t h e r e l i e s the 150 ft. deep p r e h i s t o r i c Makaopuhi l a v a lake f o r m e d of s i m i l a r o l i v i n e t h o l e i i t i c b a s a l t . A n o l i v i n e and m a g n e s i a - r i c h zone n e a r the b a s e of the lake has b e e n i n t e r p r e t e d by M o o r e a n d E v a n s (1967) and E v a n s and M o o r e (1968) to have b e e n f o r m e d by the p o s t - e m p l a c e m e n t s i n k i n g of the p h e n o c r y s t o l i v i n e , though d e t a i l e d m ~ c r o p r o b e a n a l y s i s of the o l i v i n e s a l s o showed that e x t e n s i v e m i n e r a l o g i c a l s u b - s o l i d u s r e a c t i o n had o c c u r r e d and f o r m e d s e c o n d a r y h y p e r s t h e n e . T h e bulk c h e m i s t r y s u g g e s t s s o m ~ s e t t l i n g of c l i n o p y r o x e n e and p l a g i o c l a s e with u p w a r d d i s p l a c e m e n t of r e s i d u a l liquid a l s o occurred. T r a c e e l e m e n t a n a l y s i s of a s u i t e of Makaopuhi lava lake s a m p l e s h a s shown that s y s t e m a t i c f r a c t i o n a t i o n of t r a c e e l e m e n t s has a l s o o c c u r r e d c o m p a r e d with the m i n o r d e g r e e of f r a c t i o n a t i o n of the m a j o r e l e m e n t s other than m a g n e s i a . T h i s f r a c t i o n a t i o n i n c l u d e s c h a n g e s in r a t i o of e l e m e n t s not i n c l u d e d in o l i v i n e . T h u s when the u p p e r p a r t of the l a v a lake i s c o m p a r e d with the l o w e r , the l a t t e r not only has h i g h e r F e / T i , M g / S i , and l o w e r M.g/Cr, M g / N i r a t i o s , such a s could be e x p e c t e d to r e s u l t f r o m o l i v i n e a c c u m u l a t i o n , but the C a / N a and N a / K r a t i o s w e r e h i g h e r , w h i l e the K / C a and R b / S r w e r e l o w e r . T h o u g h t h e s e d i f f e r e n c e s a r e s m a l l (see T a b l e III), a l l a r e c o n s i s t e n t with a m o r e b a s i c m a g m a c o m p a r e d to a m o r e highly f r a c t i o n a t e d m a g m a and could not be p r o d u c e d by o l i v i n e f r a c t i o n a t i o n alone. T h e s e d i f f e r e n c e s r a i s e a n i m p o r t a n t q u e s t i o n as to w h e t h e r the i n i t i a l Makaopuhi m a g m a w a s h o m o g e n e o u s , but was s u b s e q u e n t l y m o d i f i e d not only by o l i v i n e s e t t l i n g , but a l s o by s e t t l i n g or f i l t e r p r e s s i n g of c a l c i c p l a g i o c l a s e and m a g n e s i a n p y r o x e n e , as s u g g e s t e d by M o o r e and E v a n s (1967). A l t e r n a t i v e l y , at d i f f e r e n t t i m e s d u r i n g the i n f i l l i n g of the l a v a lake, the m a g m a m a y have v a r i e d not only i n o l i v i n e c o n t e n t but a l s o in o t h e r c h a r a c t e r i s t i c s s u c h a s i t s R b / S r and N a / C a r a t i o s . T h e p a r e n t a l 1959 K i l a u e a Iki l a v a w a s s i m i l a r to the a v e r a g e M a k a o puhi m a g m a , and w a s s a m p l e d at r e g u l a r i n t e r v a l s d u r i n g e m i s s i o n . T h e p r e s e n t study was m a d e to t e s t the t r a c e e l e m e n t h o m o g e n e i t y of this s e r i e s , to i n f e r o l i v i n e - l i q u i d p a r t i t i o n c o e f f i c i e n t s for s o m e t r a c e e l e m e n t s and to c o m p a r e p r e - and p o s t - e f f u s i o n f r a c t i o n a t i o n t r e n d s a s shown by t h e s e two s e r i e s . M e m b e r s of the K i l a u e a V o l c a n o O b s e r v a t o r y p r o v i d e d a p r e v i o u s l y u n a n a l y s e d s u i t e of K i l a u e a Iki s a m p l e s c o v e r i n g a r a n g e of o l i v i n e c o n t e n t w h i l e the p r e h i s t o r i c Makaopuhi s a m p l e s w e r e p r o v i d e d by D r . B. E v a n s .
ANALYTICAL METHODS M a j o r e l e m e n t s MZ, A1, Si, K, Ca, Mn, T i , F e , w e r e a n a l y s e d by X - r a y f l u o r e s c e n c e u s i n g a p o w d e r e d r o c k s a m p l e f u s e d in l i t h i u m t e t r a b o r a t e . M a t r i x c o r r e c t i o n s w e r e m a d e i t e r a t i v e l y by c o m p u t e r . A l l d e t e r m i n a t i o n s
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION w e r e made in d u p l i c a t e , the p r e c i s i o n v a r y i n g from + 0.3% SiO2 to ± 0.002 % K20, MnO and TiO2. Sodium was a n a l y s e d by a t o m i c a b s o r p t i o n and P205 by c o l o r i m e t r y . The t r a c e e l e m e n t s C r , Ni, Co, Cu, Zn, Ga, Rb, Sr, Y and Ba w e r e a l s o d e t e r m i n e d by X . R . F . , the p r e c i s i o n of r e p l i c a t e d s a m p l e s r a n g i n g from + 5 p.p.m, for Ba and Cr to + 0.5 p.p.m. Rb at the 95% confidence level. B e c a u s e of the high Ni and Cr contents, the Twin S i s t e r s Dunite DTS-1 was used as s t a n d a r d for t h e s e e l e m e n t s , the v a l u e s used being 2,348 p . p . m . Ni and 3°030 p.p.m. Cr. F o r other e l e m e n t s two W-1 p e l l e t s w e r e used with the a c c e p t e d v a l u e s of 82 p . p . m . Zn, 110 p . p . m . Cu, 50 p.p.m. Co, 16 p.p.m. Ga, 25 p . p . m . Y, 100 p.p.m. Z r , 34 p . p . m . Sc, 180 p.p.m. S t , 22 p.p.m. Rb and 156 p.p.m. Ba being used. The mineralogical analyses were made using a M.A.C. electron microprobe using pure oxide standards, with intensity data being adjusted using the Philibert absorption correction and the Philibert-Tixieratomic number correction.
RESULTS FOR KILAUEAIKI LAVAS The ten new m a j o r e l e m e n t a n a l y s e s (Table I) do not d i f f e r in any way from those m a d e on the s a m e lava s e r i e s r e p o r t e d by M u r a t a and R i c h t e r . S i m i l a r m a g n i t u d e s and r a t i o s obtained for a l l e l e m e n t s except A1203 which is s y s t e m a t i c a l l y 0.3% l o w e r in the X . R . F . r e s u l t s ( F i g . l ) . o
135
~o
120
a X 0
105 \
o
90
~ 7s u.l ~
~ lr
60
45
30
Na
15
~
O0 O0
*-lit K
~ s'o ,o'oP,[o
2o'o 2[0
" . --~_ 3o'o 3s'o ,o'o ,s'o so'o
PERCENT M g O
1959, KILAUEA IKI SERIES
Fig. 1. C o m p u t e r - p l o t t e d Bowen d i a g r a m showing l e a s t - m e a n - s q u a r e regression trend of (from top)A1203, CaO, TiO2, Na20, K20 , P205 for both new analyses and those of Murata and Richter (1967). Solid bar = range of olivine composition found by electron probe. Dashed lines define the inferred range of MgO for olivine causing fractionation. Scatter in AI203 values is due to systematic differences between U.S.G.S. and U. of M. data. Chem. Geol., 8 (1971) 1-13
98.92
51.9
98,92
50.4
Total
An (%)
1,036.4 773.7 95.1 95.0 100.7 13.8 7.8 256.8 137.3 18.8
100.000
46.25 9.41 1.897 12.822 0.155 18.75 8.390 1.731 0.397 0.185
KI0014
2.35 31.39 19.00 9.53 29.74 2.90 3.60 0.40
1,151.8 820.1 96.1 91.8 99.6 12.4 7.0 246.2 130.3 17.7
99.999
46.26 9.06 1.850 12.761 0.156 19.30 8.355 1.732 0.375 0.151
KI1022
2.22 30.49 19.74 8.70 31.04 2.90 3.51 0.53
Qz Or Plag Di Hy O1 Mt ILl Ap
C.I.P.W. norms
1,158.5 804.3 94.8 91.9 98.7 11.2 6.5 246.5 130.8 17.2
99.999
Total
Cr Ni Co Cu Zn Ga Rb Sr Ba Y
46.26 9.06 1.850 12.761 0.156 19.30 8.355 1.732 0.375 0.151
KI0022
SiO 2 A1203 TiO 2 Fe203 MnO MgO CaO Na20 K20 P205
Number 2
K i l a u e a Iki, 1959 l a v a s
50.6
98.92
2.32 31.78 20.44 7.71 29.75 2.90 3.60 0.41
1,020.9 726.7 91.9 95.9 100.3 14.2 6.8 256.6 133.7 19.0
100.000
46.28 9.45 1.898 12.823 0.157 18.30 8.713 1.801 0.392 0.187
KI0003
52.4
98.93
2.51 33.12 20.21 12.19 23.73 2.90 3.85 0.41
982.1 673.9 87.5 101.1 101.1 13.5 8.4 278.0 151.6 19.1
100.000
46.96 9.97 2.029 12:730 0.156 16.83 8.914 1.805 0.424 0.190
KI0036
732.7 530.6 78.5 106.5 102.1 15.7 8.5 298.7 154.7 20.7
100.000
47.52 10.77 2.209 12.640 0.156 14.63 9.527 1.878 0.461 0.213
KI0020
508.7 217.4 62.8 116.0 100.6 16.2 9.3 327.8 167.7 22.9
99.999
49.24 12.12 2.436 12.417 0.156 9.54 11.174 2.176 0.508 0.240
KI0051
52.7
98.96
3.00 40.20 26.10 18.09 3.51 2.90 4.63 0.52
505.6 207.8 60.0 118.3 100.7 16.4 9.8 330.7 167.2 22.4
99.999
49.24 12.12 2.436 12.417 0.156 9.54 11.174 2.176 0.508 0.240
KI1051
52.7
98.96
3.00 40.20 26.10 18.09 3.51 2.90 4.63 0.52
478.0 207.9 61.5 117.2 99.4 16.0 9.3 332.7 170.9 24.4
99.999
49.24 12.12 2.436 12.417 0.156 9.54 11.174 2.176 0.508 0.240
KI2051
52.7
98.93
3.26 42.09 24.71 17.95 2.63 2.90 4.93 0.45
385.8 189.5 59.6 123.8 104.8 18.9 10.3 357.0 177.6 24.3
100.001
49.20 12.70 2.597 12.656 0.157 8.68 10.970 2.282 0.552 0.206
KI0016
T e n n e w m a j o r e l e m e n t a n a l y s e s w i t h 13 t r a c e e l e m e n t a n a l y s e s of nine s a m p l e s f r o m t h e 1959 K i l a u e a Iki s e r i e s 1
TABLE Il
53.5
98.96
0.00 3.11 40.19 29.37 17.99 0.11 2.90 4.81 0.49
393.2 131.9 56.7 119.1 100.2 16.3 9.7 341.0 174.8 23.6
100.000
49.50 12.18 2.531 12.362 0.157 8.37 12.009 2.138 0.526 0.225
KI0037
50.9
98.97
0.00 3.20 41.07 28.88 16.43 1.19 2.90 4.81 0.50
372.6 125.6 56.7 133.2 101.6 17.4 9.9 339.9 175.2 24.5
100.000
49.61 12.27 2.530 12.308 0.156 8.27 11.770 2.313 0.541 0.227
KI0053
51.2
98.97
0.08 3.16 41.35 28.23 17.98 0.00 2.90 4.79 0.50
367.6 124.8 56.2 131.7 101.2 16.3 9.2 337.9 175.7 23.9
99.999
49.83 12.36 2.523 12.245 0.155 8.15 11.661 2.313 0.534 0.227
KI1052
435.2 182.1 133.1 7.9 313.1 110.8
Cr Ni Cu Rb Sr Ba
0.40 2.61 43.26 22.98 21.73 0.00 2.90 4.62 0.50
99.00
53.1
Qz Or Plag Di Hy O1 Mt I1 Ap
Total
An (%)
C.I.P.W. norms
100.001
50.00 12.95 2.435 ][1.979 0.156 8.74 10.752 2.320 0.442 0.230
SiO2 Al203 TiO2 EFe20 3 Mno " MgO CaO Na20 K20 P205
Total
MP0121
Number
100.000
50.64 13.52 2.854 12.255 0.156 6.49 10.855 2.502 0.502 0.230
MP0166
51.9
98.97
2.98 2.97 45.36 23.13 15.72 0.00 2.90 5.42 0.50
55.0
98.91
0.00 2.23 39.86 23.23 18.34 7.52 2.90 4.32 0.50
519.9 271.0 135.0 6.9 297.0 110.8
100.000
48.50 12.03 2.273 12.933 0.164 10.84 10.601 2.050 0.378 0.230
MP0191
56.5
98.96
98.97 53.6
0.00 2.04 38.64 21.49 22.49 6.92 2.90 4.00 0.48
711,9 .352.6 169.2 6.1 274.3 92.7
99.999
48.88 11.74 2.104 12.396 0.155 12.08 10.154 1.920 0.345 0.220
MP0240
0.00 1.95 39.74 22.34 18.33 9.35 2.90 3.96 0.39
672.6 334.9 106.4 5.2 277.6 88.0
100.001
48.78 11.85 2.085 12.324 0.155 11.96 10.220 2.108 0.330 0.180
MP0218
Makaopuhi lava lake
306.2 111.3 157.2 8.4 337.2 124,1
Prehistoric
T A B L E I (continued)
59.0
98.94
0.64 2.30 40.51 21.15 26.51 0.00 2.90 4.43 0.50
533.2 250.8 109,5 7.0 292.5 100.3
100.001
49.60 12.51 2.333 12.600 0.157 9.82 10.468 1.896 0.389 0.230
MP0053
55.0
98.92
0.41 2.54 41.79 23.21 22.67 0.00 2.90 4.88 0.52
403.5 247.9 136.4 7.9 311.0 102.8
100.004
49.49 12.65 2.568 12.804 0.164 8.71 10.799 2.150 0.429 0.240
MP0057
57.1
98.99
2.08 2.44 42.88 21.66 21.88 0.00 2.90 4.66 0.50
392.6 236.9 108.7 7.2 313.6 109.1
99.999
50.26 13.10 2.454 12.086 0.154 8.49 10.715 2.100 0.412 0.230
MP0091
M P 0 1 2 1 : b a s a l t f r o m -- 7 1 f t . , Makaopuhi lava lake. M P 0 1 6 6 = b a s a l t f r o m - - 1 1 3 ft.. Makaopuhi lava lake. MP0191 b a s a l t f r o m - - 1 3 8 ft.. Makaopuhi lava lake. MP0218 b a s a l t f r o m - - 1 6 5 ft.. Makaopuhi lava lake. M P 0 2 4 0 - b a s a l t f r o m - - 1 8 7 ft.. Makaopuhi lava lake. MPO053 = b a s a l t s u r f a c e c r u s t of Makaopuhl prehistomc lava lake. MPO057 b a s a l t f r o m - - 4 ft.. M a k a o p u h l l a v a lake. MPO091 b a s a l t f r o m - - 4 1 ft.. M a k a o p u h i l a v a lake.
1 T o t a l i r o n only i s s h o w n a s F e 2 0 3 a n d r e s u l t s a r e s u m m e d to 100% w a t e r - f r e e . 2 S a m p l e s - KI0022 = b a s a l t s c o r i a , p h a s e 1, 1 1 / 1 8 , 5.00 p . m . KI1022 = b a s a l t , d u p l i c a t e t r a c e e l e m e n t a n a l y s e s of KI0022 KI0014 = b a s a l t s c o r i a , p h a s e 5, 1 2 / 6 , 4.30 p . m . KI0003 = b a s a l t s c o r i a , p h a s e 1. 1 1 / 1 9 , 8.00 a . m . KI0036 = b a s a l t pond, p h a s e 9, 1 2 / 1 3 , 4.00 p . m . KI0020 = b a s a l t s c o r i a , p h a s e 7. 12/8. KI0051 = b a s a l t pond, p h a s e 1, 1 1 / 2 1 , 9.30 a . m . KI1051 = b a s a l t , d u p l i c a t e t r a c e e l e m e n t a n a l y s e s of KI0051. KI2051 = b a s a l t , d u p l i c a t e t r a c e e l e m e n t a n a l y s e s of KI0051. KI0016 = b a s a l t flow, p h a s e 4, 1 2 / 4 , 9.50 a . m . KI0037 = b a s a l t flow, p h a s e 11, 11/14 KI0053 = b a s a l t pond, p h a s e 1, 1 1 / 1 6 , 2.30 p . m . KI1053 = b a s a l t , d u p h c a t e of KI0053.
6
B.M. GUNN
D o u b l e c h e c k i n g a g a i n s t o t h e r s t a n d a r d s has not a l t e r e d the r e s u l t . T h e P e a r s o n R c o r r e l a t i o n c o e f f i c i e n t s b a s e d on r e g r e s s i o n a n a l y s i s of each e l e m e n t p a i r a s o b t a i n e d by c o m p u t e r , a r e a l s o i d e n t i c a l . If c e r t a i n a s s u m p t i o n s a r e m a d e , i . e . , that the s e r i e s does indeed follow a n o l i v i n e c o n t r o l t r e n d , a n d that the o l i v i n e c o n t a i n s v i r t u a l l y no Na, K, Rb, Ba, P , Ca, A1, etc., the c o m p u t e d i n t e r c e p t of the t r e n d s of any of t h e s e e l e m e n t s when p l o t t e d a g a i n s t a n y e l e m e n t found in o l i v i n e , e.g. SiO2, MgO, F e 203, MnO, C r , Ni, Co, Zn, m a y b e u s e d to e s t i m a t e the c o m p o s i . tion of the o l i v i n e at the t i m e the f r a c t i o n a t i o n took p l a c e . T h e c a l c u l a t i o n i s s i m i l a r in p r i n c i p l e to that u s e d in the B o w e n d i a g r a m which is s i m p l y a g r a p h i c a l s o l u t i o n of the s a m ~ p r o b l e m ( F i g . l ) . Partition coefficients are customarily derived from phenocryst/glass c o m p o s i t i o n s ( H e n d e r s o n a n d D a l e , 1970), but p h e n o c r y s t o l i v i n e s m a y not be in e q u i l i b r i u m with the g l a s s in which they o c c u r and g r o u n d m a s s o l i v i n e s a r e u s u a l l y m o r e i r o n - r i c h and do not have the c o m p o s i t i o n of the o l i v i n e s p r o d u c i n g the f r a c t i o n a t i o n . M a r a t a a n d R i c h t e r (1966) found the m o s t b a s i c g l a s s f r o m both K i l a u e a and M a u n a Loa v o l c a n o e s to have 10% MgO; this c o m p o s i t i o n i s t a k e n to be c l o s e to the p r i m i t i v e p a r e n t a l m a g m a for the r e g i o n . T h e i n f e r r e d and a c t u a l o l i v i n e c o m p o s i t i o n s have a m e a n of a b o u t 43% MgO f r o m which l i q u i d / c r y s t a l d i s t r i b u t i o n c o e f f i c i e n t s for o l i v i n e can be d e r i v e d for a n u m b e r of t r a c e e l e m e n t s a s follows: (a) N i c k e l . F r o m the slope of the M g / N i d i a g r a m ( F i g . 2 ) an a v e r a g e Ni c o n t e n t of 2 , 4 0 0 - 2 , 5 0 0 p . p . m , and a M g / N i r a t i o of 112 m a y be i n f e r r e d for the o l i v i n e . T h e r e was i n s u f f i c i e n t m a t e r i a l to allow s e p a r a t i o n of o l i v i n e for a n a l y s i s f r o m K i l a u e a Iki s a m p l e s . A n o l i v i n e c o n c e n t r a t e f r o m Kona b e a c h sand d e r i v e d f r o m a h i s t o r i c flow of K i l a u e a n r i f t z o n e b a s a l t was a l s o a n a l y s e d for c o m p a r i s o n and this gave 2,428 p . p . m . Ni and a M g / N i r a t i o of 99. We have b e e n u n a b l e to a t t a i n the p r e c i s i o n of m i c r o p r o b e a n a l y s i s r e p o r t e d by H~tkli and W r i g h t (1987) in t h e i r work on the Ni c o n t e n t s of the h i s t o r i c M a k a o p u h i l a v a , but v a l u e s for Ni of 2,950 p . p . m . and 2,350 p . p . m , h a v e b e e n o b t a i n e d by m i c r o p r o b e for the c e n t e r of p h e n o c r y s t s and for g r o u n d m a s s o l i v i n e r e s p e c t i v e l y for Kzlauea Iki ( T a b l e H). 1000 800
600
/
/
200
0
O0
2r5
S'O
7'5 I0'0 17'5 15To PESCENT MgO KILAUEA (o} AND MAKAOPUHI (,)
17'5
~0'0
LAVAS
F i g . 2 . N i c k e l d i s t r i b u t i o n r e l a t i v e to MgO for K i l a u e a Iki ( c i r c l e s ) and the P r e h i s t o r i c l a v a lake ( t r i a n g l e s ) . D i s t r i b u t i o n on X a x i s is e q u i v a l e n t to 1 - 3 0 (/~ o l i v i n e c o n t e n t .
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION
7
TABLE II Results of five analyses of Hawaiian basalts
SiO 2 A1203 TiO 2 FeO MnO MgO CaO
A
B
39.48
41.4
C
0.023 11.0
Cr Co Ni Cu Zn
39.1
37.7
0 12.6
15.8
12.8
45.7
41.7
46.4
0.146 47.83
0.17
0.25 12.6 0.16 45.7
0.123
1.0 0.15
0.51
0.008
0
0.02
0.02
0.12
]?205 Total
E
0.163
Na20 K20
D
98.77 1,020 250 2,920 9 86
99.7
2,950
99.6
2,350
0
97.1 2,840 190 2,430 5 97
A. Olivine from Kona beach sand, Hawaii, analysed by X . R . F . B . Microprobe analysm of phenocryst olivine from 1959 Kilauea Iki basaltic, pumice ejecta. C. Microprobe average of FeO and MgO in Kilauea Iki groundmass olivine. D. Olivine composition inferred from slope and intercept of bulk analyses from Murata and Richter (1966b). E. Olivine composition inferred from new bulk analyses. M g / N i r a t i o s i n c r e a s e f r o m 9 0 - 1 1 0 f o r p u r e o l i v i n e , t h r o u g h 140 for o l i v i n e - r i c h b a s a l t to 345 f o r o l i v i n e - f r e e b a s a l t , the l a t t e r b e i n g e s s e n t i a l l y the M g / N i r a t i o of t h e c l i n o p y r o x e n e . A d i f f e r e n t s l o p e is o b t a i n e d f o r the p r e h i s t o r i c M a k a o p u h i s a m p l e b e c a u s e of s o m e p y r o x e n e c o n c e n t r a t i o n a c c o m p a n y i n g o l i v i n e (Fig.2). N i c k e l f r a c t i o n a t i o n by o l i v i n e has b e e n the s u b j e c t of c o n s i d e r a b l e r e s e a r c h and the a n o m a l o u s p r e f e r e n c e of the o l i v i n e o c t a h e d r a l l a t t i c e s i t e fo r Ni o v e r M g h a s b e e n e x p l a i n e d on the b a s i s of c r y s t a l f i e l d t h e o r y by B u r n s (1970b). Htlkli and W r i g h t (1967) found the o l . - c p x , p a r t i t i o n r a t i o and the t o t a l Ni c o n t e n t to d e c r e a s e s t e e p l y with t e m p e r a t u r e in the r e c e n t M a k a o p u h i l a v a lake. (b) C h r o m i u m . T h e C r o c c u r s m a i n l y in e u h e d r a l c h r o m e s p i n e l i n c l u d e d in o l i v i n e . C h r o m e s p i n e l i s a b s e n t in the g r o u n d - m a s s and is not j a c k e t e d by u l v o s p i n e l - m a g n e t i t e a s o c c u r s in t h e C r o z e t b a s a l t s (Gunn et a l . , 1970}, and in M a k a o p u h i ( E v a n s and M o o r e , 1967). M i c r o p r o b e a n a l y s e s of K i l a u e a s p i n e l s show t h e r e to be an a v e r a g e of 40% C r 2 0 3 p r e s e n t and l e s s than 1% T i O 2 . A s t h e bulk of t h e C r p r e s e n t o c c u r s only in t h e s e s p i n e l s p r e s e r v e d w i t h i n o l i v i n e , (and a s s u m i n g an e v e n d i s p e r s i o n of s p i n e l a s the o l i v i n e c r y s t a l l i z e d } the o r i g i n a l m a g m a m a y h a v e c o n t a i n e d n e a r l y 1% C r .
8
B.M. GUNN
T h e M g / C r d i s t r i b u t i o n in the M a k a o p u h i l a v a l a k e i s s i m i l a r to the Kilauean series. The virtually constant Mg/Cr ratio (Fig.3) suggests c o t e c t i c c r y s t a l l i z a t i o n f o l l o w e d by l o s s by g r a v i t a t i o n a l s e t t l i n g o r r e s o r p t i o n of a n y s p i n e l not i n c l u d e d in o l i v i n e . N e g l e c t i n g the v e r y m i n o r C r p r e s e n t in t i t a n o m a g n e t i t e , an a v e r a g e C r c o n t e n t of 700 p . p . m , m a y be i n f e r r e d for the p y r o x e n e c o m p a r e d with 2,800 p . p . m , i n f e r r e d for the s p i n e l i n c l u d e d in t h e K i l a u e a o l i v i n e and 1,027 p . p . m , o b t a i n e d f o r the K o n a olivine. (c) Cobalt. T h e s l o p e of the M g O - C o d i s t r i b u t i o n i s l e s s t h a n unity, i . e . Co2+ e n t e r s the o l i v i n e l e s s r e a d i l y than d o e s the Mg 2+ ion. T h e M E / C o r a t i o is 1,450 f o r o l i v i n e and c h a n g e s in the l a v a f r o m 1,210 to 860 with d e c r e a s e in o l i v i n e c o n t e n t . T h e o l i v i n e is i n f e r r e d to h a v e 190 p . p . m . Co and the p a r t i t i o n c o e f f i c i e n t Co ( o l . ) / C o (liq.)= 3.0. T h e r a t h e r m o r e m a g n e s i a n Kona o l i v i n e i s s i g n i f i c a n t l y r i c h e r in Co (250 p . p . m . ) . (d) ~'e-Mn-Zn. A l t h o u g h t h e s e t h r e e e l e m e n t s did e n t e r into o l i v i n e , the o l . / l i q , p a r t i t i o n c o e f f i c i e n t w a s v e r y c l o s e to one for Mn, 0.95 for Zn and about 1.1 for F e . Not only h a s l i t t l e r e l a t i v e f r a c t i o n a t i o n t a k e n p l a c e , but MnO for e x a m p l e , d o e s not v a r y by m o r e than 0.002% t h r o u g h o u t . T h e r a t i o s v F e 2 0 3 / M n O = 80 and F e / Z n = 1,244 m u s t a l s o b e c h a r a c t e r i s t i c of the p r i m a r y b a s a l t . (e) S r - R b - B a - C u - G a - Y - Z r . T h e s e t r a c e e l e m e n t s , t o g e t h e r with the m a j o r e l e m e n t s A1, T i , Na, K, Ca, P , b e i n g v i r t u a l l y e x c l u d e d f r o m the o l i v i n e l a t t i c e (with the e x c e p t i o n of a b o u t 10 p . p . m . Cu) have b e e n m e r e l y c o n c e n t r a t e d o r d i l u t e d in the r e s i d u a l l i q u i d a n d t h e i r r e l a t i v e r a t i o s r e m a i n c o n s t a n t . S e m i q u a n t i t i v e d e t e r m i n a t i o n of Sc s h o w s t h a t t h i s e l e m e n t is a l s o m a i n l y c o n c e n t r a t e d in the r e s i d u a l l i q u i d with a m a x i m u m of about 30 p . p . m . Y t t r i u m in i t s g e o c h e m i c a l b e h a v i o r f o l l o w s the r a r e e a r t h e l e m e n t s and p r e d i c t a b l y a p p e a r s to b e e x c l u d e d b~} o l i v i n e . C l a r k e (1970) a l s o found a n e g a t i v e c o r r e l a t i o n of y t t r i u m with o l i v i n e in the Baffin B a y B a s a l t s and a s i m i l a r r a n g e in c o n c e n t r a t i o n . T h e r e m a y be s o m e doubt a s to t h e comI~osition of the p a r e n t a l b a s a l t 1200 o
1000
./
800
600
400
200
•
0 oo
2'5
, 50
715
10'0
PERCENT
, 125
15'0
, 175
, 200
MgO
KILAUEA (o) AND MAKAOPUHI (") LAVAS
Fig.3. Chromium vs. MgO distribution symbolised as in Fig.2. Regression line is drawn through Kilauea Iki samples only.
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION T A B L E III C o m p a r i s o n of d i f f e r e n c e b e t w e e n l a v a s s u b j e c t to o l i v i n e c o n t r o l a n d l a v a - l a k e s u b j e c t to ol. + c p x . + p l a g . c o n t r o l A
B
C
D
SiO 2
48.68
49.80
46.63
49.47
A1203
11.89
13.09
9.70
12.31
TiO 2 Fe203 MnO
2,181 12.58 0.159
2.59
1.98
12.36
12.76
0.159
0.156
2.524 12.40 0.155
MgO
11.66
8.25
17.56
8.60
CaO
10.24
10.80
8.78
11.52
Na20
2.02
2.28
1.83
2.24
K20
0.362
0.444
0.409
0.532
P205
0.22
0.23
0.21
0.23
Total
100.00
99.99
100.01
99.98
Cr
n.d.
n.d.
986
Co
n.d.
n.d.
93
58
Ni
399
277
719
176
406
Cu
130
147
98
125
Zn
n.d.
n.d.
99
100
Ga
n.d.
n.d.
13
17
Rb
5,7
8.3
7.6
258
317
Y
n.d.
n.d.
18
24
79
101
142
174
527
444
447
455
28
24
21
21
Ba K/Rb CaO/K20 CaO/Na20 Na20/K20 -
~Fe3+/MnO K/Rb Rb/Sr Mg/Ni Ca/K
5.1 5.6
4.7 5.1
268
9.7
Sr
4.8 4.5
341
5.1 4.2
79
78
82
79
527
444
447
455
0.022
0,026
0.028
0,028
176
180
147
295
28
24
21
21
A. A v e r a g e of 5 a n a l y s e s f r o m t h e l o w e r 105 ft. of M a k a o p u h i l a v a l a k e . B. A v e r a g e of 5 a n a l y s e s f r o m t h e u p p e r 120 ft. C. A v e r a g e of 5 h i g h m a g n e s i a p h a s e s of t h e 1959 K i l a u e a Iki l a v a . D. A v e r a g e of 5 low m a g n e s i a p h a s e s of t h e e r u p t i o n .
C h e m . G e o l . , 8 (1971} 1 - 1 3
10
B.M. GUNN
of K i l a u e a but b e c a u s e of the lack of r e l a t i v e f r a c t i o n a t i o n of this group of e l e m e n t s , the p a r e n t a l m a g m a m'ast have had K / R b = 450, R b / S r = 0.028, K / B a = 32, N a 2 0 / K 2 0 = 4.3, C a O / N a 2 0 = 5.0, A 1 / G a = 3,330 (see T a b l e III). A l l t h e s e r e s i d u a l e l e m e n t s show high d e g r e e s of m u t u a l p o s i t i v e c o r r e l a t i o n . COMPARISON WITH MAKAOPUHI LAVA LAKE TRENDS T h e m e a n s of the o l i v i n e - r i c h and o l i v i n e - p o o r m e m b e r s of both the K i l a u e a s e r i e s and the M,~kaopuhi s e r i e s a r e c o m p a r e d in T a b l e I. T h e slope of the M~,-Cr t r e n d i s i d e n t i c a l in both l a v a s u i t e s due to the d o m i n a n c e of Mg f r a c t i o n a t i o n by o l i v i n e and of the C r by the i n c l u d e d s p i n e l . T h e M ~ / N i t r e n d shows d i s t i n c t l y d i f f e r e n t slope, the K i l a u e a t r e n d b e i n g e s s e n t i a l l y a p a r t i a l s e r i e s b e t w e e n the end m e m b e r s o l i v i n e - l i q u i d , w h e r e a s in Makaopuhi Ni and Mg a r e a f f e c t e d by two c r y s t a l l i z i n g p h a s e s , o l i v i n e and c l i n o p y r o x e n e , the l a t t e r with m a r k e d l y l o w e r Ni c o n t e n t r e l a t i v e to Mg. T h e s e r a t i o s m a y be c a l c u l a t e d for the o l i v i n e a s M g O / N i = 180 and for c l i n o p y r o x e n e a s M g O / N i = 800. T h e two s e r i e s a l s o d i f f e r in t h e i r K / C a and K / S r d i s t r i b u t i o n (Fig.4,5). In both c a s e s the K i l a u e a Iki s e r i e s show no r e l a t i v e f r a c t i o n a t i o n a n d e x t r a p o l a t e d i r e c t l y t o w a r d s o l i v i n e c o m p o s i t i o n while the Makaopuhi shows h i g h e r Ca and S r at low K i n d i c a t i n g p l a g i o c l a s e f r a c t i o n a t i o n . T h e d i f f e r e n c e in K / R b r a t i o is b a r e l y s i g n i f i c a n t ( F i g . 6 ) the m e a n b e i n g 450. T h e fact that Makaopuhi i s s l i g h t l y l o w e r in both Rb and Ba r e l a t i v e to K m a y be a t t r i b u t e d to the s e p a r a t i o n of g r a n o p h y r e v e i n s in Makaopuhi (Fig.7). C o p p e r shows a s i m p l e o l i v i n e c o n t r o l d i s t r i b u t i o n in K i l a u e a but a m u c h m o r e e r r a t i c d i s t r i b u t i o n in Makaopuhi s u g g e s t i n g s o m e s u b s o l i d u s m i g r a t i o n (Fig.8).
60
400
45
300 -
o
2
o~ ~
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0 oo
, 20
,40
, 60
PERCENT
0 80
100
120
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KILAUEA (o) AND MAKAOPUHI (-) LAVAS
,
, I
, 2 PERCENT
, 3
, 4
- - 1 5
6
K~O
KILAUEA (o) AND MAKAOPUHI (-) LAVAS
F i g . 4 . D i s p a r i t y b e t w e e n n o n - f r a c t i o n a t e d K i l a u e a Iki, and f r a c t i o n a t e d M,~kaopuhi l a v a for K 2 0 vs. CaO. F i g . 5 . D i s p a r i t y in Sr v s . K 2 0 t r e n d s for K i l a u e a Iki ( n o n - - f r a c t i o n a t e d ) and M,~kaopuhi ( f r a c t i o n a t e d ) .
TRACE E L E M E N T PARTITION DURING OLIVINE FRACTIONATION
11
IBO
MnO
~'9o-- o
-o o--O-o~o
150 O ¢j
EFe
r~ 120
Zn
0
60
0 c
3o
0 oo
, 25
, so
, 75
. 100
.
. 125
PERCENT
. 150
. 175
200
MgO
1959. KILAUEA IKI SERIES
F i g . 6 . D i s t r i b u t i o n s l o p e s for p e r c e n t M . 1 0 x 1 0 0 0 , F e 3+ x 10, Z n
(p.p.m.) and Co (p.p.m.) ~20
o03
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~
80
8a
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g: 4o 2O
Rb
I
2
3
PERCENT
_~__o f
o~°
4
S
6
K20
KILAUEA (o) AND MAKAOPUHI (*) LAVAS Fig.7. R b and B a distribution relative to K20. Circles = Kilauea ]~i, t r i a n g l e s M a k a o p u h i , f i l l e d c i r c l e = o l i v i n e . N o t e l a c k of r e l a t i v e f r a c t i o n a tion. 200
)so
d ~
Io0o 50
O. O0
25
SO
7$
I00
PERCENT
125
ISO
175
200
MgO
KILAUEA (o) AND MAKAOPUHI (-) LAVAS
F i g . 8 . Cu d i s t r i b u t i o n s y m b o l i s e d a s for F i g . 7 . N o t e the m o r e e r r a t i c d i s t r i b u t i o n in the l a v a l a k e s a m p l e s . Chem. Geol.. 8 (19711 1 - 1 3
12
B.M. GUNN
D~CUSSION
T h e r e s u l t s p r e s e n t e d h e r e show that for the K i l a u e a Iki o l i v i n e s , the o c t a h e d r a l s i t e p r e f e r e n c e s for the t r a n s i t i o n m e t a l s a r e in the o r d e r Ni ) Mg ~ Co ~ F e > M~I > Zn. In the c a s e of Mn the slope of the d i s t r i b u tion c o e f f i c i e n t k is 1 w h a t e v e r the c o m p o s i t i o n of the p r i m a r y m a g m a . M u r a t a and R i c h t e r (1967) p r e s e n t c o n s i d e r a b l e e v i d e n c e to show that the p r i m a r y t h o l e i i t i c m a g m a in M a u n a L o a and K i l a u e a v o l c a n o e s r e m a i n s c o n s t a n t at 10% MgO. We c a n t h e r e f o r e i n f e r d i s t r i b u t i o n c o e f f i c i e n t s of a p p r o x i m a t e l y k(Ni) = 10, k(Mg) = 4.5, k(Co = 3.0, k (Fe) = 1.1, k(Mn) = 1.0, k (Zn) = 0.95. T h e s e v a l u e s a r e in g e n e r a l s i m i l a r in o r d e r but at v a r i a n c e in m a g n i t u d e with t h o s e d e r i v e d by o t h e r m e a n s . T h u s H e n d e r s o n and D a l e (1970) find v a l u e s of k(Ni) 4 . 9 - 1 8 . 6 , k(Co) 1 . 1 - 1 . 8 and k ( F e ) 1 . 4 - 3 . 0 , k(Mn) 1 . 1 - 1 . 8 , for g r o u n d m a s s o l i v i n e - g l a s s f r o m l a v a s of R e u n i o n , the S o l o m o n s and J u a n F e r n a n d e z . H o w e v e r it m u s t be p o i n t e d out that such s t u d i e s a r e b a s e d on c r y s t a l - r e s i d u a l g l a s s e q u i l i b r i a e x i s t i n g at l o w e r , p o s s i b l y s u b s o l i d u s t e m p e r a t u r e s . T h e s a m e w r i t e r s quote o c t a h e d r a l s i t e p r e f e r e n c e e n e r g i e s ( k c a l . / m o l e ) a s Ni 2+ = 20.G, Co 2+ = 7.4, F e 2+ = 4.0, M 12+ = 0, w h i c h a r e c o m p a t i b l e with the d i s t r i b u t i o n s of the K i l a u e a t r a n s i tion e l e m e n t s . T h e s l o p e s of the d i s t r i b u t i o n of M g / N i , M g / C o , M g / M n , etc. and the r a t i o s of the r e s i d u a l e l e m e n t s a r e c o n s i d e r e d to be, a s a r e s u l t of the a b o v e work, of c o n s i d e r a b l y m o r e v a l u e in c l a s s i f y i n g a p e t r o g r a p h i c p r o v i n c e than a r e a b s o l u t e e l e m e n t a b u n d a n c e s or v a r i a t i o n t r e n d s .
ACKNOWLEDGMENTS T h e c h e m i c a l a n a l y s e s w e r e m a d e u n d e r s u p p o r t p r o v i d e d by C.N.R. g r a n t No. A - 3 8 3 4 . D r . R. C o y - Y l l c a r r i e d out the m i c r o p r o b e a n a l y s e s . D r . H. S c h m i n k e b r o u g h t the K i l a u e a Iki s a m p l e s f r o m Hawaii and the Makaopuhi s a m p l e s w e r e p r o v i d e d by D r . B. E v a n s . T h e c o o p e r a t i o n of m e m b e r s of the U.S. G e o l o g i c a l S u r v e y , e s p e c i a l l y D r s . D. S w a n s o n , J. M o o r e , T. W r i g h t and D. P e c k is g r a t e f u l l y a c k n o w l e d g e d , the l a t t e r e s p e c i a l l y for g u i d a n c e in the field.
REFERENCES Burns, R.G., 1970a. Site preferences of transition metal ions in silicate crystal structures. Chem. Geol.. 5(4): 275-283. Burns, R.G., 1970b. Mineralogical Applications of Crystal Field Theory. Cambridge University Press, London,in press. Clarke, D.B., 1970. Tertiary basalts of Baffin Bay: Possible primary magma from the mantle. Contr. Mineral. Petrol., 25: 2-3, 224. Evans, B.W. and Moore, J.G., 1968. Mineralogy as a function of depth in the prehistoric Makaopuhi tholeiitic lava lake, Hawaii. Contr. Mineral. Petrol., 17: 85-115. Gunn, B.M., Coy-Yll, Ramon, Watkins, N.D., Abranson, C.E. and Nougier, J., 1970. Geochemistry of an oceanite-ankaram}te-basalt suite from East Island, Crozet Archipelago. Contr. Mineral. Petrol., 28: 319-339.
TRACE ELEMENT PARTITION DURING OLIVINE FRACTIONATION
13
H~kli, T.A. and Wright, T . L . , 1967. The f r a c t i o n a t i o n of nickel between olivine and augite as a g e o t h e r m o m e t e r . Geochim. C o s m o c h i m . Acta, 31: 877-884. H e n d e r s o n . P. and Dale, I.M., 1970. The p a r t i t i o n i n g of s e l e c t e d tranMtion e l e m e n t ions between olivine and g r o u n d m a s s of oceanic b a s a l t s . Chem. Geol., 5(4): 267-274. Murata, K.J. and R i c h t e r , D.H., 1966a. The s e t t l i n g of olivine in m a g m a as shown by lavas of the 1959 eruption. Am. J. Sci., 264: 194-203. Murata, K.J. and R i c h t e r , D.H., 1966b. C h e m i s t r y of the lavas of the 1959-1960 eruption of Kilauea Volcano, Hawaii. U.S. Geol. Surv. P r o f e s s . P a p e r , 537-A. Moore, J.G. and Evans, B.W., 1967. The r o l e of olivine in the c r y s t a l l i z a t i o n of the p r e h i s t o r i c Makaopuhi tholeiitic Lava Lake, Hawaii. Contr. M i n e r a l . P e t r o l . , 15: 202-223.
Chem. Geol., 8 (1971) 1-13