摘要
新疆萨尔托海铬铁矿是一个典型的与蛇绿岩有关的高铝型豆荚状铬铁矿,其中矿石铬尖晶石发生了明显的热液蚀变,发育了富Cr的蚀变环边,形成高铁铬铁矿,Cr#在蚀变后升高,发生了Cr元素的次生富集。在矿石颗粒间隙中的Fe-Ni-As-S矿物组合主要为镍黄铁矿-赫硫镍矿-针镍矿-砷镍矿。围岩纯橄岩普遍发育强烈的蛇纹石化,其中的Fe-Ni-As-S矿物组合为赫硫镍矿-镍黄铁矿-砷镍矿,还有少量的针镍矿和铜矿物。通过对硫化物的成分对比分析,认为矿石中的镍黄铁矿和赫硫镍矿都属于岩浆演化的产物(>600℃),与赫硫镍矿和针镍矿一样,均从贫S的母岩浆中通过岩浆熔离过程形成。围岩和矿石中的含砷矿物以及围岩中的镍黄铁矿都是晚期热液活动的结果,其中砷镍矿具有特殊的蠕虫状-乳滴状结构,与围岩中的赫硫镍矿和镍黄铁矿共生。围岩和矿石中Fe-Ni-As-S矿物组合的形态和成分差异,说明金属矿物的整体演化从岩浆期到热液期经历了从贫S到富As的环境变化,最终形成了现在所观察到的复杂Fe-Ni-As-S矿物组合。
Sartohay chromite deposit is located on the Darbut ophiolitic belt in Xinjiang,which is a typical high-Al podiform chromite deposits related to ophiolite.The Cr-spinel ores have experienced obvious hydrothermal alteration,developing a rim of ferricchromite.The Fe-Ni-As-S mineral assemblage in ore spinels inter-cumulates is mainly composed of pentlandite-heazlewoodite-milleritemaucherite.The wall-rock dunite develops extensive serpentite alteration,and the Fe-Ni-As-S mineral assemblage includes heazlewoodite-pentlandite-maucherite,rarely millerite and copper minerals.Through the data comparison of the sulfide composition,it could be deduced that the pentlandite and heazlewoodite are originated from high-temperature magma,the disequilibrium structure and the high Ni content in pentlandite implies that it is formed above 600℃,forming immiscible droplets from an S-poor parent magma.All arsenides and pentlandite in wall rocks are the results from late-stage hydrothermal fluids,in which the maucherite develops a special worm-like structure,coexisting with heazlewoodite and pentlandite in wall rock.The differences of appearance and composition of the Fe-Ni-As-S mineral assemblages in ore and wall rock show that the whole evolvement of metal-rich minerals starts from an Sundersaturated magma in high temperature and involved an As-rich fluid in hydrothermal environment,forming the complicated current Fe-Ni-As-S mineral assemblages.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第8期2264-2274,共11页
Acta Petrologica Sinica
基金
国家自然科学基金重点项目(40730314)资助
