Re-Os isotopic evidence for genesis of Archaean nickel ores from uncontaminated komatiites

被引:162
作者
Foster, JG
Lambert, DD
Frick, LR
Maas, R
机构
[1] WESTERN MIN CORP PROPRIETARY LTD,KAMBLADA NICKEL MINES,KAMBALDA,WA 6442,AUSTRALIA
[2] LA TROBE UNIV,SCH EARTH SCI,VICTORIAN INST EARTH & PLANETARY SCI,MELBOURNE,VIC 3083,AUSTRALIA
关键词
D O I
10.1038/382703a0
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
THE late Archaean greenstone terranes of Western Australia contain abundant komatiites (high-MgO lavas) hosting magmatic sulphide deposits rich in nickel, copper and platinum-group elements, Thermal erosion and assimilation of sulphidic sea-floor sediments has been proposed as a mechanism by which the komatiites were brought to sulphide saturation(1-4), Such models have important implications not only for the genesis of these sulphide ores, but also for interpreting the magnitude and extent of isotopic heterogeneity in the Archaean mantle, Here we report that massive, matrix and disseminated sulphide ores and a komatiite from Western Australia yield a magmatic Re-Os isochron age of 2,706 +/- 36 Myr and a near-chondritic initial Os-187/Os-188 ratio of 0.10889 +/- 0.00035, whereas a proposed sulphidic sedimentary contaminant has an extremely radiogenic Os-187/Os-188 of 1.0983 at 2,706 Myr, These data demonstrate that the ore-forming komatiites were derived from the upper mantle without significant contamination by radiogenic crust either before eruption or during turbulent how at the surface, Thus, ground melting and assimilation of sulphidic sediments may not be as important in ore genesis as current theories suggest.
引用
收藏
页码:703 / 706
页数:4
相关论文
共 36 条