| 西藏中部塔吉冈矿区早白垩世花岗岩成因及地质意义 |
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| 引用本文： | 刘海永,唐菊兴,曾庆高,华康,赵洪飞,王雨,央宗.西藏中部塔吉冈矿区早白垩世花岗岩成因及地质意义[J].地球科学,2022,47(4):1217-1233. |
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| 作者姓名： | 刘海永 唐菊兴 曾庆高 华康 赵洪飞 王雨 央宗 |
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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： | 中国地质调查项目(No.DD20190167)； |
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| 摘 要： | 塔吉冈铜多金属矿位于南羌塘地块的南缘，是认识班公湖-怒江成矿带构造-岩浆-成矿作用的理想窗口.以塔吉冈铜多金属矿区内出露的花岗岩为研究对象，对其进行了系统的锆石U-Pb定年、全岩地球化学和锆石原位Hf同位素研究.结果显示塔吉冈花岗岩形成于早白垩世晚期（120~118 Ma），岩石地球化学具有高SiO2、高碱（Na2O+K2O）、低P2O5的特征，铝饱和指数（A/CNK）为0.78~1.02，整体显示偏铝质钙碱性Ⅰ型花岗岩的特征.塔吉冈花岗岩具有正的锆石εHf（t）值（+3.9~+7.2）、年轻的地壳模式年龄（TDMC=717~926 Ma）以及与陆壳相似的Zr/Hf（26.88~38.65）、Nb/Ta（7.01~13.61）、Sm/Nd（0.17~0.21）、Nb/La（0.32~0.58）等特征元素比值，指示其起源于新生的火成岩下地壳部分熔融.对比研究区域地质资料，塔吉冈花岗岩形成于拉萨与南羌塘地块碰撞的构造背景，并显示与区域同时期成矿相关岩体一致的地球化学与同位素组成，均为西藏中部新生下地壳部分熔融的产物.考虑到新生地壳通常富含铜金等金属元素，研究提出西藏中部大规模发育的新生地壳熔融成因的花岗岩体具有一定的成矿条件，是今后寻找斑岩型铜金矿重点勘查方向.
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| 关 键 词： | 青藏高原 班公湖-怒江成矿带 塔吉冈矿区 早白垩世 岩石学 |
| 收稿时间： | 2021-05-24 |
Petrogenesis and Geological Significance of Early Cretaceous Granites in Tajigang Mining Area,Central Tibet |
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| Liu Haiyong,Tang Juxing,Zeng Qinggao,Hua Kang,Zhao Hongfei,Wang Yu,Yang Zong.Petrogenesis and Geological Significance of Early Cretaceous Granites in Tajigang Mining Area,Central Tibet[J].Earth Science-Journal of China University of Geosciences,2022,47(4):1217-1233. |
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| Authors: | Liu Haiyong Tang Juxing Zeng Qinggao Hua Kang Zhao Hongfei Wang Yu Yang Zong |
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| Abstract: | Tajigang copper polymetallic ore is located in the south margin of southern Qiangtang terrane, providing an ideal window for understanding the tectonic-magmatic activities and mineralization of Bangong Co-Nujiang metallogenic belt. In this paper, it focuses on the granites in Tajigang mining area and reports their zircon U-Pb ages, geochemical and zircon Hf isotopic data. These granite rocks were dated as Early Cretaceous (120-118 Ma) and characterized by high SiO2, total alkali (Na2O+K2O), and low P2O5 contents, with aluminum saturation index (A/CNK) of 0.78-1.02, suggesting geochemical affinity to calc alkaline Ⅰ-type granite. Furthermore, the granites display positive εHf(t) values (+3.9-+7.2) with relatively young crustal model age (TDMC=717-926 Ma) and show similar Zr/Hf (26.88-38.65), Nb/Ta (7.01-13.61), Sm/Nd (0.17-0.21), and Nb/La (0.32-0.58) ratios to crust, indicating a magma source of juvenile igneous lower crust. Together with data from the recent literature, it proposes that the Tajigang granites formed in a collision setting of Lhasa and southern Qiangtang terranes. In addition, the Tajigang granites show similar geochemical and isotopic compositions with the regional simultaneous metallogenic related rocks which were derived by partial melting of juvenile lower crust. In general, the juvenile crust was enriched in Cu, Au and other elements. Thus, our research proposes that these widely exposed juvenile-crust derived granitic rocks of central Tibet have certain metallogenic conditions and are the key exploration direction for prospecting porphyry Cu-Au deposits in the future. |
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