新疆准噶尔北缘托斯巴斯套铁铜金矿床矽卡岩和磁铁矿矿物学特征及其地质意义

Mineralogical Characteristics of Skarn in Tuosibasitao Iron-Copper-Gold Deposits of the Northern Margin of Junggar,Xinjiang,and Their Geological Significance

托斯巴斯套铁铜金矿床赋存于中泥盆统北塔山组火山岩与闪长(玢)岩的接触带中,矿体呈脉状、透镜状,矿体及其周围发育大量矽卡岩。本文分别利用电子探针、电感耦合等离子体质谱法(ICP-MS),对托斯巴斯套铁铜金矿附近的石榴子石、辉石、绿帘石的化学组分及磁铁矿的主量及微量元素开展研究。结果表明:矽卡岩矿物中石榴子石端员组分以钙铝榴石-钙铁榴石系列为主,辉石端员组分以透辉石为主,绿帘石化学成分富铁富钙,这些特点表明矿区矽卡岩具有钙矽卡岩特征。矽卡岩是由岩浆热液流体交代北塔山组基性火山岩而形成的,磁铁矿的形成与矽卡岩的退化变质作用有关。在石英-硫化物-碳酸盐阶段形成铜和金矿化。

The Tuosibasitao Fe-Cu-Au mineral deposit mainly occurs in the contact zone between the diorite porphyrite and basaltic volcanic rock of Middle Devonian Beitashan Formation in the forms of massives, heterogeneous gobbets, veinlets, breccia and veinlet-disseminated. The ore bodies in the ore deposit occur as stratoids or lenses, surrounded by skarn. The major and trace elements in magnetite, and chemical components in garnet, chinopyoxene and epidote from Tuosibasitao deposit were studied by Inductively Coupled Plasma-Mass Spectrometry （ICP-MS） and Electron microprobe analyse. The results demonstrate that the end member of garnet is mainly grossularite and andradite. The composition of pyroxene was mainly diopside, with a small amount of augite. The epidote was enriched in Fe and Ca. The composition of these skarn minerals suggest that skarn in Tuosibasitao ore deposit is calcic skarn. In combination with the geological characteristics, it is possible that the skarns are formed by hydrothermal interaction with metamorphic volcanic, and the formation of magnetite is related to the retrogressive metamorphism of the skarn. Copper and gold mineralization occurred during the quartz-sulphide- carbonate period.