青海省化隆县沙加含铜镍矿基性杂岩体地质特征及Re-Os同位素研究

摘要

沙加岩体是化隆基性-超基性岩带中的一个含铜镍硫化物的基性杂岩体,其岩体规模较小,岩相分带弱,矿体呈透镜状产于岩体中,苏长岩为主要赋矿岩相.对其进行岩石地球化学及硫化物Re-Os同位素测试,结果表明:岩体属钙碱性、铁质系列,富集轻稀土元素,亏损Nb、Ta等高场强元素.硫化物187Os/188Os初始值为0.346 9～0.407 1,yOs为180～228,说明岩体遭受了显著的地壳混染作用,地壳物质加入比例大于30％.地壳混染可能在岩浆达到S饱和进而熔离出硫化物熔体的过程中起到了重要作用.%Shajia Cu-Ni ore-bearing basic complex is one of the intrusive rocks in Hualong basic-ultrabasic rocks belt, it is small scale, weak lithological zoning, Orebody are lenticular in the intrusion, and norite is the main host rock for the Cu-Ni ores- The analysis on rock geochemistry indicate that the intrusive is calc-alkaline, iron series, rich in LREE, depleted in high field strength elements such as Nb, Ta. The analysis on the sulfide display that the initial 187Os/188Os ratios are from 0. 346 9 to 0. 407 1, the γo2 values are from 180 to 228, which suggest that abundant crustal material was mixed with the magma, and the content of crust-derived Os was estimated to ＞30%. The contamination by crustal material probably played an important role in triggering the sulfide saturation and segregation.