东昆仑卡而却卡铜钼铁多金属矿床成矿年代学:辉钼矿Re-Os和金云母Ar-Ar同位素定年约束

摘要

The Kaerqueka polymetallic deposit is a large-scale skarn deposit with porphyry and hydrothermal mineralization, which is located at the Qimantage, eastern Kunlun. The copper, molybdenum and iron polymetallic mineralization is closely related with porphyritic monzogranite and granodiorite. The skarn type copper and molybdenum ores are composed of grossular, vesuvianite, diopside, scapolite, tremolite, molybdenite and chalcopyrite. The Re-Os dating of molybdenite yielded a weighted mean age of 246.1±1.2 Ma (MSWD=0.92) and an isochron age of 245.5±1.6 Ma (MSWD=1.2). The phlogopite with paragenesis of magnetite in skran type iron ores yield an Ar-Ar plateau age of 233.9±1.4 Ma (MSWD=1.68) and a diverse isochron age of 234.3±1.5 Ma (MSWD=1.58). The ore forming-age of Kaerqueka deposit was the Middle or Late Triassic era. The Re contents of the molybdenite in the Kaerqueka deposit vary from (1.342±0.014)×10?6to (23.86±0.29)×10?6, implying that the ore-forming material was mainly derived from both of crust and mantle. Combing with those available petrogenetic and metallogenic chronological data published recently and regional tectonic research works, it is suggested that the Middle-Late Triassic intrusive rocks in Kaerqueka deposit might be formed by underplating, remelting of ancient crust and magma mixing in the Late Paleozoic to Early Mesozoic collision-post collision stage. The magma mixing at the Middle-Late Triassic era provides a large number of ore-forming materials for large-scale polymetallic mineralization.%卡而却卡矿床位于东昆仑祁漫塔格地区, 达大型规模, 属矽卡岩型矿床, 伴有斑岩型和热液型矿化.区内铜钼铁多金属成矿与似斑状二长花岗岩、花岗闪长岩密切相关.B 区矽卡岩铜钼矿石由钙铁榴石、符山石、透辉石、方柱石、透闪石、辉钼矿、黄铜矿等组成, 辉钼矿Re-Os加权平均年龄为246.1±1.2 Ma(MSWD=0.92), 等时线年龄为245.5±1.6 Ma (MSWD=1.2); B 区深部矽卡岩型铁矿石中磁铁矿与透闪石、金云母等共生, 金云母 Ar-Ar 坪年龄为233.9±1.4 Ma (MSWD=1.68), 反等时线年龄为234.3±1.5 Ma(MSWD=1.58), 成矿时代为中?晚三叠世.卡而却卡矿床辉钼矿的Re含量为(1.342±0.014)×10?6~(23.86±0.29)×10?6, 表明成矿物质为壳幔混合来源.综合区域地质资料, 卡而却卡矿床形成于中?晚三叠世碰撞?后碰撞转换阶段, 与中?晚三叠世壳幔岩浆混合作用密切相关, 壳幔相互作用可能为区域大规模金属成矿提供成矿物质.