| 西藏南部错那洞矽卡岩型铍钨锡多金属矿体成矿母岩成岩时代及其地球化学特征 |
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| 引用本文： | 夏祥标,李光明,曹华文,梁维,付建刚. 西藏南部错那洞矽卡岩型铍钨锡多金属矿体成矿母岩成岩时代及其地球化学特征[J]. 地球科学, 2019, 44(7): 2207-2223. DOI: 10.3799/dqkx.2019.038 |
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| 作者姓名： | 夏祥标 李光明 曹华文 梁维 付建刚 |
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| 作者单位： | 中国地质调查局成都地质调查中心, 四川成都 610081 |
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| 基金项目： | 中国地质调查局项目DD20160015中国地质调查局项目DD20190147国家重点研发计划项目2018YFC0604103 |
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| 摘 要： | 错那洞穹窿是北喜马拉雅片麻岩穹窿带(NHGD)中发现的新成员，并发育有超大型铍钨锡多金属成矿作用.错那洞矿床铍钨锡多金属矿体赋存于矽卡岩、断裂构造及(伟晶状)花岗岩中，以矽卡岩型矿体为主，形成矽卡岩型矿体的成矿母岩则为一套弱定向二云母花岗岩.针对弱定向二云母花岗岩开展了年代学及地球化学特征研究工作.年代学结果表明，弱定向二云母花岗岩锆石U-Pb年龄为16.5±0.3 Ma，为中新世淡色花岗岩浆活动，表明错那洞超大型铍钨锡多金属矿床形成于中新世，为喜马拉雅碰撞造山过程中伸展阶段的产物.地球化学结果表明，该套成矿弱定向二云母花岗岩具有富硅(73.36%~73.89%)、贫铁(0.96%~1.58%)、强过铝质的钙碱性花岗岩地球化学特征.其稀土元素总量较低，相对富集轻稀土元素，而相对亏损重稀土元素，具有明显负Eu异常，相对富集Rb、Th等大离子亲石元素，相对亏损Zr、Ti等高场强元素，地球化学特征综合显示其为一套高分异淡色花岗岩，可能为变泥质岩重融的产物，与藏南拆离系(STDS)的活动密切相关.
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| 关 键 词： | 错那洞 稀有金属 弱定向二云母花岗岩 成岩时代 地球化学 |
| 收稿时间： | 2018-12-31 |
Petrogenic Age and Geochemical Characteristics of the Mother Rock of Skarn Type Ore Body in the Cuonadong Be-W-Sn Polymetallic Deposit,Southern Tibet |
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| Abstract: | The Cuonadong gneiss dome is a newly discovered dome in the North Himalaya gneiss domes (NHGD) belt. Mineralization of the Cuonadong super-large Be-W-Sn polymetallic deposit is developed in the Cuonadong dome. The Cuonadong Be-W-Sn polymetallic ore bodies exist in skarn, fractures and (giant) granite. The main genetic type of deposit is skarn type, and the mother rock of skarn type ore body is weakly oriented two-mica granite. In this paper, chronology and geochemical characteristics of metallogenic mother rock (weakly oriented two-mica granite) of skarn type ore body in the Cuonadong super-large Be-W-Sn polymetallic deposit are studied. Zircon U-Pb dating results show that the weakly oriented two-mica granite's formation time is 16.5±0.3 Ma, which belongs to magmatic activity of Miocene leucogranite. It shows that the Cuonadong super-large Be-W-Sn polymetallic deposit, which is the product of the extension stage of Himalayan collision orogenic process, was formed in Miocene. Geochemical data show that metallogenic mother rock (weakly oriented two-mica granite) is the calcium alkaline and strong peraluminous granite with high silica (73.36%-73.89%), low iron(0.96%-1.58%). Its total rare earth is relatively low, with enrichment of LREE, depletion of HREE and obvious negative Eu anomaly. The two-mica granite is characterized by an enrichment of some large iron lithophile elements (Rb, Th) and loss of high field strength elements (Zr, Ti).The geochemical characteristics of two-mica granite show that it is a set of highly fractionated leucogranite. The study shows that the weakly oriented two-mica granite may be the product of remelting of metaargillaceous rocks, which is closely related to the activities of the South Tibetan detachment system. |
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