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尼雄矿田位于隆格尔-工布江达断隆带,是措勤-申扎铁铜多金属成矿带的重要组成部分。滚纠铁矿位于矿田西北端,矿体主要产于花岗闪长岩和二长花岗岩与二叠系敌布错组的接触带及敌布错组层间破碎带中。矿区主要金属矿物有磁铁矿、穆磁铁矿、赤铁矿、磁赤铁矿及少量的褐铁矿、针铁矿等,夕卡岩矿物有石榴石、透辉石、金云母、蛇纹石、绿帘石、阳起石等,其中金云母与磁铁矿密切伴生,本文对其进行电子探针成分分析和40Ar-39Ar同位素测年。电子探针成分分析表明金云母富镁贫铁,Mg/(Fe+Mg+Mn+Ti)介于0.90~0.94之间;金云母40Ar-39Ar同位素测年获得总气体年龄(Total age)为112.3 Ma,与成矿相关的花岗闪长岩(113.6±1.6 Ma)和二长花岗岩(112.6±1.6 Ma)年龄在误差范围内一致,指示矿床形成于早白垩世晚期(113 Ma)。与铁矿化时代不同,矿田内铜矿化主要发生在晚白垩世早期(87 Ma)。结合区域地质资料,认为滚纠铁矿的形成与班公湖-怒江洋壳的向南俯冲关系密切,冈底斯陆壳和羌塘陆壳在约113 Ma对接碰撞,已俯冲的班公湖-怒江洋壳在俯冲惯性和/或重力拖拽作用下发生板片回转,导致软流圈地幔流体上涌,热的软流圈地幔流体携带的巨大热能引发岩石圈地幔和上覆地壳发生部分熔融,形成以壳源为主的壳幔混源岩浆,在弧后拉张区上侵形成花岗闪长岩和二长花岗岩。同时,遭遇下拉组和敌布错组地层,与之发生接触交代作用并形成磁铁矿床。
Nixon ore field is located in Longgeer - Gongbu Jiangda uplift belt, is the Qin-Qin iron Tiemuo metallogenic belt an important part. The ore body is mainly located in the contact zone of granodiorite and monzogranite with the Permian Ubufu fault group and the intergranular fault zone of the Ubuji fault. Mine main metal minerals are magnetite, mu magnetite, hematite, maghemite and a small amount of limonite, goethite, etc., skarn minerals are garnet, diopside, phlogopite, snake Serpentine, epidote, cristobalite, etc., in which phlogopite and magnetite are closely related. In this paper, the electronic probe composition analysis and 40Ar-39Ar isotope dating. Electron probe composition analysis showed that phlogopite is rich in magnesium and poor in Fe, Mg / (Fe + Mg + Mn + Ti) is between 0.90 and 0.94. Total gas age of 40Ar-39Ar isotope dating of phlogopite is 112.3 Ma. The ages of granodiorite (113.6 ± 1.6 Ma) and monzogranite (112.6 ± 1.6 Ma) related to metallogenesis are within the error range, indicating that the deposit was formed in the late Early Cretaceous (113 Ma). Unlike the iron mineralization, copper mineralization in the orefield occurred mainly in the early Late Cretaceous (87 Ma). Combined with the regional geological data, it is considered that the formation of the Au-Gantang iron ore is closely related to the southward subduction of the Bangong-Nujiang oceanic crust. The collision between the Gangdese continental crust and the Qiangtang continental crust at about 113 Ma collided with the subducted Bangong Lake - The Nujiang oceanic crust turns under the action of dive inertia and / or gravity drag, resulting in upwelling of asthenospheric mantle fluid. The huge thermal energy carried by the hot asthenospheric mantle fluid causes the lithospheric mantle and the overlying crust to occur Melted to form crust-mantle mixed-sourced magma that is dominated by the crust, and invaded to form granodiorite and monzonitic granite in the extensional arc back-tension zone. In the meantime, it encountered formations of the pull-down group and the enemy cloth-fault group, contacting with them and forming a magnetite deposit.