| 拉萨地块北部~90Ma斑岩型矿床年代学及成矿地质背景 |
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| 引用本文： | 王保弟,许继峰,刘保民,陈建林,王立全,郭琳,王冬兵,张万平.拉萨地块北部~90Ma斑岩型矿床年代学及成矿地质背景[J].地质学报,2013,87(1):71-80. |
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| 作者姓名： | 王保弟 许继峰 刘保民 陈建林 王立全 郭琳 王冬兵 张万平 |
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| 作者单位： | 成都地质矿产研究所，成都，610081；;中国科学院广州地球化学研究所同位素年代学和地球化学重点实验室，广州，510640；;西藏地勘局区域地质调查大队，拉萨，850000;中国科学院广州地球化学研究所同位素年代学和地球化学重点实验室，广州，510640；;成都地质矿产研究所，成都，610081；;西藏地勘局区域地质调查大队，拉萨，850000;成都地质矿产研究所，成都，610081；;成都地质矿产研究所，成都，610081； |
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| 基金项目： | 国家自然科学基金项目（面上项目，重点项目，重大项目） |
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| 摘 要： | 近年来青藏高原多个大型—超大型斑岩Cu-Mo-Au矿床的发现已引起人们广泛的关注,现有研究显示这些含矿斑岩和斑岩型矿床的形成年龄主要集中在120～110Ma、～90Ma、54～45Ma和18～12Ma4个阶段,其中90Ma左右的斑岩型矿床的成矿地质背景仍存在很大争议。本文报道拉萨地块北部尼玛县拔拉扎斑岩型矿床含矿斑岩的LA-ICPMS锆石U-Pb定年以及辉钼矿Re-Os定年结果,并分析了该期的成矿地质背景。两件花岗闪长斑岩锆石206Pb/238U加权平均年龄分别为92.1±1.2Ma、93.8±1.2Ma,代表了岩浆的结晶时代;而辉钼矿Re-Os模式年龄为88.2～89.6Ma,代表了拔拉扎矿床的成矿年龄。依据区域地质资料,本文认为拉萨地块北部～90Ma岩浆活动和成矿作用既不可能是雅鲁藏布江结合带所代表的新特提斯洋平板俯冲或洋脊俯冲的产物,也不可能是班公湖-怒江洋盆南向俯冲消减直接的产物,而很可能是班公湖-怒江洋盆俯冲消减闭合之后碰撞过程的产物。因此本文认为拉萨地块中北部地区～90Ma的岩浆作用及其成矿作用是形成于碰撞的构造背景。
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| 关 键 词： | 碰撞型矿床 90Ma成矿作用 斑岩矿床 拉萨地块 |
| 收稿时间： | 2011/10/19 0:00:00 |
| 修稿时间： | 5/7/2012 12:00:00 AM |
Geochronology and Ore-forming Geological Background of ~90Ma Porphyry Copper Deposit in the Lhasa Terrane, Tibet Plateau |
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| WANG Baodi,XU Jifeng,LIU Baomi,CHEN Jianlin,WANG Liquan,GUO Lin,WANG Dongbing and ZHANG Wanping.Geochronology and Ore-forming Geological Background of ~90Ma Porphyry Copper Deposit in the Lhasa Terrane, Tibet Plateau[J].Acta Geologica Sinica,2013,87(1):71-80. |
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| Authors: | WANG Baodi XU Jifeng LIU Baomi CHEN Jianlin WANG Liquan GUO Lin WANG Dongbing and ZHANG Wanping |
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| Institution: | Chengdu Institute of Geology and Mineral Resources, Chengdu, 610081;;Key Laboratory of Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640;;Regional Geological Surveying Party of the Tibet Bureau of Geology and Exploration, Lhasa, 851400;Key Laboratory of Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640;;Chengdu Institute of Geology and Mineral Resources, Chengdu, 610081;;Regional Geological Surveying Party of the Tibet Bureau of Geology and Exploration, Lhasa, 851400;Chengdu Institute of Geology and Mineral Resources, Chengdu, 610081;;Chengdu Institute of Geology and Mineral Resources, Chengdu, 610081; |
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| Abstract: | A number of large - very large porphyry Cu-Mo-Au deposit was discovered in Tibetan plateau, which has rised widespread concern in recent years. It is commonly argumed that the periods of ore-bearing porphyries and porphyry deposits mainly composed of four stages in Tibetan Pleteau, i.e., 120 ~ 110 Ma, ~ 90 Ma, 54 ~ 45 Ma and 18 ~ 12 Ma of them, the ore-forming geological background of second stage (90Ma) porphyry deposits is still controversial and hotly debated. The zircon U-Pb and Molybdenites Re-Os ages are reported in this study, with the geodynamic setting in Balazha porphyry deposits in northern Lhasa terrane. LA-ICPMS U-Pb zircon dating of two granodioritic porphyry samples concordant 206Pb/238U age of 92.1 ± 1.2 Ma and 93.8 ± 1.2 Ma, respectively, which probably record the magmatic crystallization. Molybdenites Re-Os isotopic dating shows that the molybdenite is formed at 88.2 ~ 89.6Ma, which probably represent the age of mineralization of Balazha porphyry deposits. These geochemical features, combined with other characteristics of Late Cretaceous lavas in mid-northern Lhasa terrane, indicate that ~90Ma magmatism and mineralization did not result from melting of seafloor subduction or ocean ridge subduction of the Yarlung-zangbo Ocean, or from erther southward subduction of the Bangong co-Nujiang Ocean. This mineralization may be produced in collision process, which subduction closed of the Bangongco-Nujiang Ocean. So we suggest that ~90Ma magmatism in northern Lhasa terrane and its mineralization is formed in the collision of tectonic environment. |
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| Keywords: | Collision type deposit Mineralization period about 90Ma Porphyry deposit Lhasa terrane |
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