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首页> 中文期刊> 《地球学报》 >西藏革吉县尕尔穷铜金矿床地质特征及其成因意义

西藏革吉县尕尔穷铜金矿床地质特征及其成因意义

         
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位于西藏阿里地区革吉县的尕尔穷铜金矿床是班公湖-怒江成矿带西段首个达到详查程度的大型铜金矿床.矿区发育三条断裂,其中F1和F2断层呈北东-南西向展布,F3断层为南北向展布.F1断裂产状复杂、延伸大于3000 m,破碎带内发育的铜金矿体严格受其控制.目前,矿床主要由斑岩型钼(铜、金)矿体、接触带矽卡岩型铜金矿体、F1断裂破碎带内似IOCG型铁铜金矿体组成.不同矿体特征差别显著,斑岩型矿体主要产于石英闪长岩、花岗斑岩中,金属矿物以网脉状辉钼矿主,次为黄铜矿、磁铁矿、黄铁矿；矿物组合有磁铁矿+黄铁矿、黄铜矿+辉钼矿.矽卡岩型矿体主要产于石英闪长岩、花岗斑岩与碳酸盐岩接触带,呈层状、似层状,金属矿物主要为细脉-网脉状黄铜矿、斑铜矿、辉铜矿、铜蓝、自然铜、自然金、自然银,矿物组合为黄铜矿-磁铁矿-自然金、黄铜矿-斑铜矿-磁铁矿-自然金-银、黄铜矿-赤铁矿-自然金、辉钼矿、黄铜矿-自然金.破碎带内似IOCG型铁铜金矿体产于F1断裂破碎带,呈似层状,金属矿物以细脉-网脉状矿石和角砾状赤铁矿、磁铁矿、黄铜矿、斑铜矿、辉铜矿、铜蓝、自然金为主；矿物组合为黄铜矿-自然金、黄铜矿-斑铜矿-自然金-银矿、赤铁矿-磁铁矿-自然金、黄铜矿-自然金.根据矿床地质特征,综合前人研究资料,本文对矿床的成因进行了进一步探讨,认为尕尔穷铜金矿床是晚白垩世班怒洋关闭后南羌塘-三江复合板片与冈底斯-念青唐古拉板片之间弧-陆碰撞阶段形成的,具有与钾玄岩-高钾钙碱性闪长类岩体、陆-陆同碰撞钾玄岩-高钾钙碱性重熔型花岗斑岩有成因密切联系的构造-岩浆岩“三位一体”的成矿特征,即主矿体赋存于斑岩、矽卡岩、构造破碎带中形成的“斑岩-矽卡岩-似IOCG”型铜金矿床.%The Ga'erqiong Cu-Au deposit in Ge'gyai County of Ngari area in Tibet is the first large-size Cu-Au deposit based on detailed survey. The ore district has three fractures, in which fractures F1 and F2 are NE-SW trending whereas F3 is NS- extending. The attitude of F1 is very complex, and the extension is longer than 3000 m. The Cu-Au ore body in this fracture zone is strictly controlled by the fracture. The deposit consists of porphyry Mo-(Cu, Au) ore body, skarn Cu-Au ore body in contact zone and IOCG-like Fe-Cu-Au ore body in F1 fracture zone. Different ore bodies have marked differences. Porphyry ore body is mainly developed in quartz diorite and granite-porphyry, in which metallic minerals are mainly stockwork molybdenite, and subordinately chalcopyrite, magnetite, pyrite; the mineral assemblages are composed of magnetite-pyrite and chalcopyrite-molybdenite. The skarn ore body is mainly developed in the zone where quartz diorite and granite-porphyry are in contact with carbonatite, and the shapes are lamellar and lamellar; the main metallic minerals are veinlet-stockwork chalcopyrite, bornite, chalcocite, covellite, native copper, native silver and native gold. The IOCG-like Fe-Cu-Au ore body occurs in F1 fracture zone, its shape is lamellar and the leading metallic minerals are veinlet-stockwork ore and brecciated hematite, magnetite, chalcopyrite, bornite, chalcocite, covellite, native gold; the mineral assemblages are chalcopyrite-native gold, chalcopyrite-bornite-native gold-silver, and hematite-magnetite-native gold. Based on the geological characteristics of the ore deposit in combination with the data available, this paper discusses the geological characteristics of the ore deposit, and holds the view that the Ga'erqiong Cu-Au deposit was formed after the closure of the Bannu Ocean in late Cretaceous period, and by the collision of arc-continent between the southern Qiangtang-Sanjiang complex slab and the Gangdise-Nyanqentanglha slab, showing the tripartite metallogenic characteristics genetically closely related to potassic basalt-high potassic calc-alkaline diorite-lithosome and continent-continent co-collision potassic basalt-high potassic calc-alkaline remelted granite-porphyry. That is to say, the host ore body existed in porphyry, skarn, and structural fracture zone, thus forming the "porphyry-skarn-IOCG-like" Cu-Au deposit.

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