Platinum-group elements and Os isotopic characteristics of the lower oceanic crust

被引:38
作者
Blusztajn, J [1 ]
Hart, SR [1 ]
Ravizza, G [1 ]
Dick, HJB [1 ]
机构
[1] Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA
基金
美国国家科学基金会;
关键词
platinum group; osmium; rhenium; isotopes; oceanic crust;
D O I
10.1016/S0009-2541(00)00186-8
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We present osmium isotopic compositions and Os, Re and platinum-group element (PGE) contents in the lower oceanic crust gabbros from ODP Site 735B on the Southwest Indian Ridge. The average gabbros are very depleted in PGEs, e.g. the Os concentrations are very low and range from 0.5 to 38 ppt. One troctolite sample is an exception, containing, e.g. 376 ppt Os, 396 ppt Ir and 8 ppb Pd. Re contents are extremely heterogeneous, ranging from 128 ppt to 28 ppb. The present day Os-187/Os-188 varies from 0.140 to 0.467, and correlates with Rb/Cs, suggesting that seawater alteration affected the Os isotopic system. The average Os content in the lower oceanic crust is about 9 ppt while median value for Re is about 487 ppt. Such very high Re/Os is relatively similar to the upper MORB-type oceanic crust, indicating that recycled ocean crust basalts and gabbros will rapidly develop very radiogenic Os isotopic signatures. (C) 2000 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:113 / 122
页数:10
相关论文
共 38 条
[1]  
albarede f, 1995, INTRO GEOCHEMICAL MO, V1st, DOI DOI 10.1017/CBO9780511622960
[2]  
ALT CJ, 1991, P OCEAN DRILL PROGRA, V118, P113
[3]  
COLODNER D, 1993, EARTH PLANET SC LETT, V117, P25
[4]  
DICK HJB, 1991, P OCEAN DRILLING PRO, V0118
[5]  
DICK HJB, 1998, EOS, V79, P40
[6]   PB-SR ISOTOPE VARIATION IN INDIAN-OCEAN BASALTS AND MIXING PHENOMENA [J].
DUPRE, B ;
ALLEGRE, CJ .
NATURE, 1983, 303 (5913) :142-146
[7]   Oxygen isotope variations in ocean island basalt phenocrysts [J].
Eiler, JM ;
Farley, KA ;
Valley, JW ;
Hauri, E ;
Craig, H ;
Hart, SR ;
Stolper, EM .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1997, 61 (11) :2281-2293
[8]  
Greenough JD, 1990, PROC OCEAN DRILL SCI, P71, DOI [10.2973/odp.proc.sr.115.128.1990, DOI 10.2973/ODP.PROC.SR.115.128.1990]
[9]   The fingerprint of seawater circulation in a 500-meter section of ocean crust gabbros [J].
Hart, SR ;
Blusztajn, J ;
Dick, HJB ;
Meyer, PS ;
Muehlenbachs, K .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1999, 63 (23-24) :4059-4080
[10]   Hobbs Coast Cenozoic volcanism: Implications for the West Antarctic rift system [J].
Hart, SR ;
Blusztajn, J ;
LeMasurier, WE ;
Rex, DC .
CHEMICAL GEOLOGY, 1997, 139 (1-4) :223-248