| 西藏拿若斑岩型铜(金)矿含矿岩体年代学、地球化学及地质意义 |
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| 引用本文： | 丁帅,唐菊兴,郑文宝,杨超,张志,王勤,王艺云.西藏拿若斑岩型铜(金)矿含矿岩体年代学、地球化学及地质意义[J].地球科学,2017,42(1):1-23. |
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| 作者姓名： | 丁帅 唐菊兴 郑文宝 杨超 张志 王勤 王艺云 |
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| 作者单位： | 1.成都理工大学地球科学学院，四川 成都 610059 |
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| 基金项目： | 国土资源部公益性行业科研专项项目201511017 |
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| 摘 要： | 多龙矿集区是班公湖-怒江成矿带最重要的组成部分，其成矿规模巨大、时间跨度较长、成矿过程复杂，因而人们对该区成岩成矿地质背景及岩石成因等问题一直争议不断，值得进一步明确.通过研究矿集区中部拿若斑岩型铜(金)矿与成矿相关的花岗闪长斑岩LA-ICP-MS锆石U-Pb年龄、全岩地球化学特征及Hf同位素组成，并与区域邻近矿床进行详细地对比研究，查明了多龙地区与成矿相关的岩浆岩形成构造背景、岩石成因及深部动力学过程.测试结果表明拿若铜(金)矿形成时代为早白垩世120Ma左右，与多龙地区其他矿床形成时代一致.这些岩浆岩均相对富集轻稀土(LREE)与大离子亲石元素(LILE: Rb, Ba, K等)；亏损重稀土(HREE )与高场强元素(HFSE: Nb, Ta, Zr, Hf等).原位锆石εHf(t)均为正值，为1.38～7.37，Hf同位素两阶段模式年龄tDM2为707～1086Ma，表明多龙矿集区斑岩-浅成低温热液型铜(金)矿形成与早白垩世班公湖-怒江特提斯洋北向俯冲有关.当俯冲洋壳到达地壳50～70km深度时发生不同程度相变，从而导致角闪石等矿物脱水产生的熔体交代楔形地幔，进而诱发幔源物质部分熔融产生弧岩浆，其形成环境类似于南美安第斯成矿带洋陆俯冲背景之下的陆缘弧环境.
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| 关 键 词： | 拿若铜(金)矿 年代学 地球化学 锆石Hf同位素 陆缘弧 亏损地幔 |
| 收稿时间： | 2016-07-15 |
Geochronology and Geochemistry of Naruo Porphyry Cu (Au) Deposit in
Duolong Ore-Concentrated Area,Tibet, and Their Geological Significance |
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| Abstract: | As the most important part of Bangong Lake-Nujiang River metallogenic belt, the Duolong ore-concentrated area is characterized by the occurrence of huge mineralization scale, extended time span and complex forming process, resulting in controversial understanding of its petrogenesis and tectonics and those of related deposits. To address this problem, this study firstly presents new data of LA-ICP-MS zircon U-Pb age, whole-rock geochemistry, and in situ zircon Hf isotopes for the mineralization-associated granite porphyry in Naruo porphyry copper (gold) deposit, and secondly we make a detailed comparison with research results of other porphyry deposits in Duolong area to find out the tectonic setting, petrogenesis and geodynamic processes of the mineralization-associated porphyry in Duolong area. The test results show that the age of the Naruo Cu (Au) deposit formation is consistent with that of other deposits in Duolong area formed at Early Cretaceous about 120Ma. All the main intrusive rocks have similar lithogeochemical characteristics, for they all show the relative enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE: Rb, Ba, K, etc.), relatively depleted in heavy rare earth elements (HREE ) and high field strength elements (HFSE: Nb, Ta, Zr, Hf, etc.). Moreover, the granite porphyry shows positive εHf(t) values between 1.38-7.37, and two-stage model ages of zircons are 707-1086Ma. The results suggest that the formation of porphyry-epithermal copper (gold) deposit in Duolong ore-concentrated area is dominated by northward subduction of the Bangongcuo Tethys plate beneath Qiangtang block at Early Cretaceous. When the subducted oceanic crust reached 50-70km underground and generated different degrees of phase transformation, which leads to melt produced by dehydration of amphibole minerals metasomatized mantle wedge and induced mantle partial melting produced magmatic arc. Those deposits occurred in a continental arc tectonic setting which is similar to the continental margin arc environment of the ocean-continent subduction setting of the Andes metallogenic belt in South America. |
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