岩浆铜镍硫化物矿床中地壳硫的深部来源:来自黄山东矿床的证据OA北大核心CSTPCD
Deep source of crustal sulfur in magmatic Cu-Ni sulfide deposits:Evidence from the Huangshandong deposit
岩浆铜镍硫化物矿床的含硫化物的直接围岩对成矿的贡献一直是研究的热点.本文以黄山东岩浆铜镍硫化物矿床中围岩与岩体中不同产状的硫化物进行微量元素分析与原位S同位素分析,并结合黄山东岩体与围岩的微量元素分析,讨论黄山东岩体的直接围岩中磁黄铁矿的成因机制,并探讨其直接围岩对成矿的贡献.黄山东岩体的直接围岩为含硫化物的干墩组碳质板岩与灰岩,远离岩体的碳质板岩中硫化物为较为自形的黄铁矿,而紧邻岩体的碳质板岩中硫化物为不规则团块状的磁黄铁矿.碳质板岩中的磁黄铁矿的Co/Ni比值(平均值为0.71)高于岩体中熔离成因的磁黄铁矿(平均值为0.02),并且具有更低的Se元素含量(平均含量为37.53×10-6)与更高的Pb元素含量(平均含量为116.36×10-6),其地球化学特征与Duluth岩体中围岩热接触变质带中的磁黄铁矿较为相似,指示黄山东矿床中碳质板岩中的磁黄铁矿是由地层中原有的黄铁矿受到岩体中热液改造形成,而不是岩体中硫化物向下渗滤.在黄山东岩体直接围岩中,碳质板岩中硫化物已经交代形成磁黄铁矿,而灰岩中的硫化物仍为自形黄铁矿,指示了还原性物质对黄铁矿的相变过程有着促进作用.黄山东岩体的S/Se比值大于地幔范围,指示了富S地层的同化混染,而黄山东矿床的围岩中的硫化物S同位素值为-12.25‰～-11.95‰,岩体中磁黄铁矿的S同位素值为+0.91‰～+2.10‰,指示了黄山东矿床岩浆并没有大规模地同化混染直接围岩,岩浆中壳源S的加入更有可能发生在深部.
It is a critical question whether the sulfide⁃bearing country rocks play an important role in the sulfide saturation of magmatic copper⁃nickel sulfide deposits.In this paper,semimetals of whole rocks,trace elements and in situ sulfur isotope for sulfide in intrusive rocks,and country rocks of Huangshandong deposit were analyzed to discuss the genesis of pyrrhotites in country rocks of Huangshandong deposit and its contribution to Ni⁃Cu mineralization.The country rocks of Huangshandong intrusion are limestone and carbonaceous slate of Gandun Formation.The sulfides in the carbonaceous slate far away the intrusion are euhedral pyrites,while the sulfides in carbonaceous slate are irregular clumpy pyrrhotites.Compared to the country rocks,pyrrhotites in the intrusive rocks and sulfide ores have lower Co/Ni ratios,higher Se content and lower Pb content.The geochemical compositions of the pyrrhotite in the country rocks from the Huangshandong deposit are similar to the pyrrhotites in the thermal contact metamorphic zone of country rocks in Duluth intrusion,indicating that the pyrrhotite in the Huangshandong country rocks is formed by hydrothermal metasomatism of the original pyrite,rather than the infiltration of sulfide melts from the intrusion.The sulfide in the carbonaceous slate are pyrrhotites,but the sulfide in the limestone is mainly idiomorphic pyrite,indicating that the reducing substances have a promoting effect on the hydrothermal metasomatism of pyrite.The S/Se ratio of the Huangshandong sulfide ores is larger than the mantle range,indicating assimilation of the crustal sulfur.The S isotopes of pyrites in the country rocks of Huangshandong deposit range from-12.25‰ to-11.95‰,while the S isotopes of pyrrhotites in the sulfide ores range from+0.91‰ to+2.10‰,which is obviously different from those of the country rocks,indicating that there is no large⁃scale contamination with country rock in the Huangshandong deposit,and the addition of crust sulfur in the magma is more likely to occur in the deep.
曹盛轩;哈依热提;邓宇峰;韦帅;袁峰;李卫东;谭治雄;韩建军
合肥工业大学资源与环境工程学院 合肥 230009新疆地质矿产勘查开发局第六地质大队 新疆 哈密 839000合肥工业大学资源与环境工程学院 合肥 230009合肥工业大学资源与环境工程学院 合肥 230009||中国科学院地球化学研究所,矿床地球化学国家重点实验室 贵阳 550081合肥工业大学资源与环境工程学院 合肥 230009新疆地质矿产勘查开发局第六地质大队 新疆 哈密 839000新疆地质矿产勘查开发局第六地质大队 新疆 哈密 839000青海省地质调查局 西宁 810001
地质学
黄山东岩浆铜镍硫化物矿床磁黄铁矿直接围岩同化混染
Huangshandong magmatic sulfide depositPyrrhotiteCountry rocksCrustal contamination
《地质科学》 2024 (6)
1588-1602,15
国家自然科学基金项目(编号:42272083,U1803113)和第二次青藏高原综合科学考察研究项目(编号:2019QZKK0708)资助
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