铬铁矿预富集和上地幔部分熔融关系的实验研究  

EXPERIMENTAL STUDY ON THE RELATIONSHIP OF PARTIAL MELTING IN THE UPPER MANTLE TO CHROMITE PRECONCENTRATION

作　　者：金振民[1] Quan Bai D.L.Kohlstedt 金淑燕[1] 

机构地区：[1]中国地质大学 [2]UNIVERSITY OF MINNEASOTA MINNEAPOILS,USA

出　　处：《地质论评》1996年第5期424-429,共6页Geological Review

基　　金：中国自然科学基金(编号4913009);美国自然科学基金(编号Ear-9018323)

摘　　要：用合成地幔岩为原始材料,在温度1225°C和严格控制氧分压10^(-5)-10^(-12)atm条件下,对上地幔部分熔融作用与铬铁矿预富集关系进行实验研究。实验结果表明:(1)在达到稳态熔融结构时,5％-8％的玄武质硅酸盐熔体主要赋存在矿物三联点之间,它为铬元素从地幔岩中萃取运移和预富集提供了先决条件;(2)在部分熔融过程中原岩的尖晶石和辉石(铬透辉石和顽火辉石)提供的铬元素相结合,形成了富铬尖晶石和铬铁矿(Cr_2O_3可达38％-47％)。上地幔部分熔融作用不仅控制了上地幔岩石类型演化(二辉橄榄岩→方辉橄榄岩→纯橄榄岩),同时它对铬铁矿的预富集起着关键作用。In order to investigate the relationship of partial melting in the upper mantle with chromite preconcentration, experiments have been performed on synthetic pyrolite at a temperature of 1225℃ and the controlled oxygen fugacity of 10-5-10-12atm. Experimental results suggest that 5 % - 8 % basaltic silicate melts mainly occurred at triple-junctions of olivine minerals which provided the prerequisite for extraction of chromium element from pyrolite their transport and preconcentration. Combination and concentration of the chromium element coming from spinel and pyroxene (chromium diopsite and enstatite) of the protolith during the process of partial melting resulted in the formation of Cr-rich spinel and chromite (Cr2O338% -47%). The partial melting of the upper mantle not only controlled the evolution of mantle rock types (lherzolite→harzber-gite→dunite) but also played a critical role for chromite preconcentration.

关 键 词：地幔岩 部分熔融 铬铁矿 高温实验研究 

分 类 号：P578.8[天文地球—矿物学]