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吉龙铜矿位于青藏高原东、北缘三江造山带中段青海玉树地区,其矿化特征和三江南段兰坪盆地内沉积岩容矿脉状铜矿特征相似,对该矿床矿化特征和矿床成因的详细研究有助于理解区域沉积岩容矿脉状铜矿成矿规律,对区域找矿具有重要意义。详细的野外地质考察及室内显微镜下观察发现,吉龙矿床铜矿化以石英-碳酸盐-硫化物脉的形式发育在石炭系杂多群上段灰岩与碎屑岩的岩性分界面上,矿石矿物主要为黄铜矿+斑铜矿+黝铜矿+辉铜矿,脉石矿物以石英+方解石为主。方解石Sm-Nd同位素等时线年代学研究表明,吉龙铜矿形成于34Ma,在大地构造背景下和区域逆冲推覆构造活动间歇期的走滑断裂活动以及相伴随的钾质岩浆活动同期。主成矿阶段成矿流体仅发育富液相LV流体包裹体,流体表现出中温度(230~250℃)、低盐度(3%~6%NaCleqv)性质;δD V-SMOW值分馏较大(-154‰~-80‰),δ18O V-SMOW值分馏较小(7.72‰~10.30‰),反映了开放体系发生去气作用后的残余岩浆热液来源。硫化物沉淀阶段成矿热液S同位素组成一致(3.4‰~11.6‰),较岩浆来源硫分馏大,推测成矿还原硫主要来自赋矿灰岩地层封存硫酸盐的有机质热还原作用;铅同位素组成(206Pb/204Pb、207Pb/204Pb和208Pb/204Pb比值分别为18.668~18.707、15.657~15.792和38.645~38.873)同区域新生代钾质岩浆岩一致,推测成矿金属物质可能来自区域钾质岩浆作用。吉龙铜矿成矿模式可简要归纳为:走滑断裂→钾质岩浆活动,岩浆去气→富金属热液形成,热液运移→与富硫酸盐地层相遇,硫酸盐有机质热还原→还原硫产生,还原硫与金属物质结合→硫化物沉淀。综合对比吉龙铜矿与三江南段兰坪盆地内沉积岩容矿脉状铜矿发现,二者在成矿地质背景、矿床地质特征、成矿流体性质及来源、成矿物质来源上都具有极大相似性,推测吉龙铜矿为三江南段沉积岩容矿脉状铜矿在区域上向中北段的延伸,三江带上有望发现一条上千千米的沉积岩容矿脉状铜矿带。
The JiLong copper deposit is located in the Yushu area of Qinghai province in the middle of the Sanjiang orogenic belt on the eastern and northern margins of the Qinghai-Xizang Plateau. Its mineralization characteristics are similar to those of the volcanic ore-hosting copper deposits in the Lanping basin in the Sanjiang section. The mineralization characteristics of the deposit and its genesis Detailed study is helpful to understand the metallogenetic regularity of vein-type copper deposits in regional sedimentary rocks, which is of great significance for regional prospecting. Detailed field geologic investigation and observation under an indoor microscope showed that the copper mineralization of the Jiulong deposit developed in the form of quartz-carbonate-sulfide veins on the lithologic interface of limestone and clastic rocks in the upper Carboniferous heterogeneous group , Ore minerals are mainly chalcopyrite + beryllium + tetrahedrite + chalcocite, gangue minerals mainly quartz + calcite. The Sm-Nd isotopic dating of calcite shows that the JiLong copper deposit was formed at 34 Ma, and under the background of tectonic setting, the strike-slip faulting activities and the associated karst magmatism activities during the synclinal nappe event . In the main mineralization stage, only the fluid-rich LV fluid inclusions were developed in the ore-forming fluid, and the fluids exhibited moderate (230-250 ° C) and low salinity (3-6% NaCleqv) fluid properties. The δD V-SMOW fractionation was large (-154 ‰ ~ -80 ‰). The δ18O V-SMOW fractional fractionation is small (7.72 ‰ ~ 10.30 ‰), which reflects the source of residual magmatic hydrothermal fluids after degassing in the open system. The S isotopic compositions of the ore-forming hydrothermal fluids are consistent (3.4 ‰ ~ 11.6 ‰) in the sulphide precipitation stage, which is larger than the sulfur fraction in the magma source. It is presumed that the reduced sulfur in the ore-forming mineralization is mainly due to the organic matter thermal reduction of the sealed sulphate in the ore- (206Pb / 204Pb, 207Pb / 204Pb and 208Pb / 204Pb ratios are 18.668 ~ 18.707, 15.657 ~ 15.792 and 38.645 ~ 38.873, respectively) are consistent with the Cenozoic potash magmatic rocks in the area, suggesting that the metallogenic metals may be derived from the regional karstification . The ore-forming patterns of JiLong copper deposit can be summarized as follows: strike-slip faulting → potassic magmatic activity, magmatic degassing → rich metal hydrothermal formation, hydrothermal migration → encounter with sulfate-rich strata, thermal reduction of sulfate organic matter → reduction Sulfur production, sulfur reduction combined with metal → sulfide precipitation. A comprehensive comparison of the vein mineralization of vein-shaped copper deposits in the JiLong copper mine and the LanPing basin in the SanJiangnan section shows that both of them have great potentials in terms of metallogenic geological background, geological characteristics of the deposit, nature and source of ore-forming fluid and source of metallogenic material It is speculated that the JiLong copper deposit is an extension of the vein-type vein-shaped copper-bearing vein in the Sanjiang section to the north-central section in the area. It is expected that a sedimentary rock-hosted vein copper belt with a thickness of 1000 km will be found on the Sanjiang belt.