新疆阿尔泰什根特铁矿床地质特征及成矿机制

Geological characteristics and metallogenic mechanism of the Shigente iron deposit in Altay,Xinjiang

什根特铁矿赋存于康布铁堡组火山沉积岩系中,矿体呈层状、透镜状、脉状,受地层控制。同时发育矽卡岩及磁铁矿化。矿床形成经历了火山沉积期(主成矿期),岩浆热液期(矽卡岩型矿化)和区域变质期。火山沉积期和岩浆热液期退化蚀变阶段的磁铁矿均具有富Fe,贫Si、Ti、V、Mg、Mn特点;磁铁矿稀土元素配分模式和原始地幔标准化蛛网图具有相似曲线变化特征,指示火山沉积期和退化蚀变阶段的铁矿化具有相同的物质来源,即来自基性火山岩。早期矽卡岩阶段石榴子石中流体包裹体均一温度为160~403℃,集中在180~260℃,盐度集中在5%~9%(质量分数,Na Cleq,下同),δD介于-134‰^-125‰,δ18OH2O值为4.7‰~8.6‰,表明流体为岩浆水。石英碳酸盐阶段流体包裹体均一温度为140~536℃,主要集中在160~340℃,盐度集中在6%~16%,表明流体具有从高温演化到低温、中低盐度和中低密度的特征,石英的δD介于-98‰^-95‰,δ18OH2O值为-0.6‰~2.0‰,表明该阶段流体来自岩浆水混合大气降水。

The Shigente iron deposit is hosted in the volcano-sedimentary rocks of the Kangbutiebao Formation. The orebodies occur in bedding, lenticular, and vein forms, bounded by the strata. Skarnization and magnetite mineralization are both present in the ore district. The ore-forming process can be divided into volcanic sedimentary （the main mineralization period）, magmatic hydrothermal （skarn-type mineralization period）, and regional metamorphic periods. Magnetite in the volcanic sedimentary period and the retrograde alteration stage of the magmatic hydrothermal period is rich in Fe and depleted in Si, Ti, V, Mg, Mn. The chondrite-normalized REE patterns and primitive mantle-normalized trace element spider diagrams of magnetite show similar characteristics, which indicates that the iron mineralization in the volcanic sedimentary period and the retrograde alteration stage had the same metal source, namely the mafic volcanic rocks. Homogenization temperatures of fluid inclusions of garnets at the early skarn stage vary from 160 to 40312, generally in the range of 180 to 260 12. Salinities range from 5 % to 9 % NaCleq;δD values range from - 134%o to - 125‰, and δ18OH2O values are between 4.7‰ and 8.6‰, implying that the fluids were derived from magmatic fluids. Homogenization temperatures of fluid inclusions in the quartz-carbonate stage vary from 140 to 53612, mainly in the range of 160 to 340℃, and the salinities range from 6 % to 16 % NaCleq, which indicates that the fluids are characterized by the evolution from high to low temperatures, moderate-low salinities, and moderate-low densities. 81） values of quartz range from -98‰ to -95‰, and δ18OH2O values are between -0.6‰ and 2.0‰, showing that the fluids in this stake were derived from magmatie fluids, with some contributions from the meteoric water.