Volatile compositions of the Jinchuan ultra mafic intrusion and associated sulfide ores, western China

摘要

1 IntroelutionThe Jinchuan ultramafic intrusion, western China comprises ultramafic rocks crystallized from a high-Mg basaltic magma (Chai and Naldrett, 1992). It contains the third largest Ni-Cu sulfide deposit in the world. Assimilation of crustal S is widely thought to be critical for the genesis of other world-class Ni-Cu sulfide deposits associated with mafic-ultramafic rocks (e.g., Naldrett, 1999). However, the mechanisms of S transfer from country rocks to magma remains largely unknown. In this study we have used stepwise heating to extract volatiles from sulfide and silicate mineral separates from the Jinchuan Ni-Cu sulfide deposit. The compositions of volatiles released at elevated temperatures are used to evaluate ore genesis and postmagmatic hydrothermal modification.