【作者】 梁清玲；

【导师】 江思宏；

【作者基本信息】 中国地质科学院 ， 矿物学岩石学矿床学， 2013， 硕士

【摘要】 福建紫金山地区的罗卜岭斑岩铜钼矿床、紫金山高硫型铜金矿床和悦洋低硫型银矿床组成了-个斑岩-浅成低温热液成矿系统,其中紫金山铜金矿床是我国最大的高硫型浅成低温热液铜金矿床,赋矿围岩为燕山早期的紫金山岩体,而与成矿有关的是燕山晚期的次火山岩。LA-MC-ICP-MS锆石U-Pb测年显示紫金山岩体形成于165～157Ma之间,为中-晚侏罗世花岗岩,岩体属高钾或钾玄岩系列,具火山弧花岗岩或者活动大陆边缘花岗岩的特征,Sr-Nd-Pb-Hf同位素特征表明其岩浆主要来源于古元古代基底地壳物质。紫金山地区与成矿有关的侵入-火山岩年龄为102～112Ma,形于早白垩世；早白垩世岩浆岩属高钾或钾玄岩系列,同样具火山弧花岗岩或者活动大陆边缘花岗岩的特征,Sr-Nd-Pb-Hf同位素特征显示早白垩岩浆岩岩浆源区为地幔和中元古代基底的混合。紫金山铜矿体成矿流体从早阶段的CO2-H2O-NaCl体系向晚阶段简单的H20体系演化。流体从中高温(均一温度320～380℃)中低盐度(3.06～14.57wt%NaCl.eqv)向中温流体(均一温度240～320℃)高盐度(1.91～33.48wt%NaCl.eqv)演化,到晚阶段的低温(160～200℃)、低盐度(3.87～10.49wt%NaCl.eqv)流体。较高的均一温度显示深部铜矿体成矿作用可能不是属于浅成低温热液型,可能为中高温热液型,反映成矿可能与深部岩体直接相关。氢氧同位素特征显示紫金山铜金矿成矿流体水主要来自岩浆水,混合少量大气水：悦洋银矿床以大气降水为主,有少量的岩浆水加入。硫化物硫同位素和铅同位素特征显示紫金山铜金矿床成矿物质主要来源于岩浆,混合少量地壳基底物质；悦洋银矿床成矿物质主要来源于岩浆和沉积围岩或地壳基底。综合研究表明,紫金山地区从中-晚侏罗世时期开始,由于古太平洋板块的俯冲导致古元古代基底地壳物质部分熔融形成紫金山花岗岩体,此阶段无矿化。早白垩世时期,板块继续俯冲,导致地幔物质上涌和古洋壳物质的加入,与中元古代基底形成混合岩浆区,复杂的壳幔作用过程使得紫金山地区从106Ma(罗卜岭斑岩铜钼矿床辉钼矿Re-Os年龄)开始了大规模的Cu-Au-Mo-Ag成矿作用,并可能一直持续到92Ma。更多还原

【Abstract】 Zijinshan mineral field is a large porphyry-epithermal Cu-Au-Mo-Ag mineralizationsystem located in thesouthwestern Fujian province, which containsLuoboling porphyry Cu-Mo deposit, Zijinshan high-sulfidation epithermalCu-Au deposit and Yueyang low-sulfidationepithermalAg-Au-Cu deposit, etc. The ZijinshanCu-Au depositis the China’s largest high-sulfidation epithermal Cu-Au deposit, with the Zijinshan granite being the wall rock and vocanic rocksof the late Yanshanian related to mineralization. LA-MC-ICP-MS zircon U-Pb dating results and petrol geochemical characteristicsshow that the Zijinshan graniteformed in Middle-Late Jurassic (165-157Ma), and belongs to high potassium or shoshonitic series, with the characteristics of volcanic-arc granite or active continental margin granite. Sr-Nd-Pb-Hf isotopic features show that the granite was originated from Paleoproterozoic basement crust material. The intrusive-volcanic rocks related to the Cu-Au-Mo-Ag mineralization were formed in102to112Ma, and belongs to high potassium or shoshonitic series, with the characteristics of volcanic-arc granite or active continental margin granite. Sr-Nd-Pb-Hf isotopic features suggested that they were derived from the mixing of partial melting of the Mesoproterozoic basement and mantle-derived melts.According to the analysis of fluid inclusions in quartz veins, the ore-forming fluids of copper ore body in Zijinshan Cu-Au deposit was CO2-H2O-NaCl system, with the late stage of evolution simple H2O system. The homogeneous temperatures of ore fluid change from320～380℃to240～320℃. and finally to160～200℃, with the salinities from3.06～14.57NaCl.eqv to1.91～33.48NaCl.eqv, and to3.87-10.49NaCl.eqv respectively. Higher homogenization temperature display deep copper mineralization may not belong to the epithermal-type and reflect mineralization may be directly related to magmatic. The hydrogen and oxygen isotopic composition of quartz in Zijinshan Cu-Au deposit suggest that the ore-forming fluid was mainly derived from magmatic water, mixing a small amount of meteoric water, while the hydrogen and oxygen isotopic composition inYueyang deposit imply that the ore-forming fluid was mainly derived from meteoric water, mixing a small amount of magmatic water. The sulfur and lead isotopic characteristics of various metallic sulfides in Zijinshan Cu-Au deposit suggest that the ore-forming materials were mainly dereived from the magma, mixing a small amount of crustal base material, and the ore-forming materialsof Yueyang deposit derived from the magma and sedimentary wall rocks or crustal basement. It is therefore suggested that the Middle-Late Jurassic and the Early Cretaceous magmatic rocks in the Zijinshan region are the result of an active continental-margin setting related to the subduction of thePaleo-Pacific Plate beneath the Eurasian continent. Because of the continuous subduction andmixing of mantleand ancient oceanic crustmaterial, it makes a large-scale mineralization beganin the Zijinshan regionfrom106Ma (Re-Os age of the molybdenite from the Luoboling Cu-Mo deposit) to92Ma.更多还原