| 西藏浦桑果铜多金属矿床中酸性岩石成因及动力学背景:年代学、地球化学及Sr-Nd-Pb-Hf同位素约束 |
| |
| 引用本文： | 李壮,郎兴海,章奇志,何亮.西藏浦桑果铜多金属矿床中酸性岩石成因及动力学背景:年代学、地球化学及Sr-Nd-Pb-Hf同位素约束[J].岩石学报,2019,35(3):737-759. |
| |
| 作者姓名： | 李壮 郎兴海 章奇志 何亮 |
| |
| 作者单位： | 中国地质科学院矿产资源研究所, 自然资源部成矿作用与资源评价重点实验室, 北京 100037;中国地质大学(北京)地球科学与资源学院, 北京 100083,成都理工大学地球科学学院, 成都 610059,西藏自治区地质矿产勘查开发局第六地质大队, 拉萨 851400,成都理工大学地球科学学院, 成都 610059;西藏自治区地质矿产勘查开发局第六地质大队, 拉萨 851400 |
| |
| 基金项目： | 本文受国家重点研发计划项目（2018YFC0604106）、中国地质调查局地质调查项目（121201103000150004）和国家自然科学基金项目（41403040）联合资助. |
| |
| 摘 要： | 浦桑果矿床位于拉萨地块冈底斯成矿带中段,为侵入岩体与钙质围岩接触带内形成的矽卡岩型高品位铜多金属矿床(Cu@1. 42%,Pb+Zn@2. 83%),是冈底斯成矿带目前唯一一个大型富铜铅锌(钴镍)矿床。本文以浦桑果矿床相关中酸性侵入岩体(黑云母花岗闪长岩和闪长玢岩)为主要研究对象,开展LA-ICP-MS锆石U-Pb年代学、全岩主微量元素、全岩SrNd-Pb及锆石Lu-Hf同位素研究,旨在厘定侵入岩体的形成时代、岩石成因及成岩成矿的动力学背景。LA-ICP-MS锆石U-Pb定年结果表明,黑云母花岗闪长岩和闪长玢岩侵位年龄分别为13. 6～14. 4Ma和13. 6～14. 6Ma,岩体形成时代均属中新世。岩石地球化学特征表明,闪长玢岩和黑云母花岗闪长岩均属高钾钙碱性I型花岗质岩石;岩石普遍具高Sr含量(599×10~(-6)～1616×10~(-6))、高Sr/Y(48. 2～132. 3)和高(La/Yb)N(19. 6～25. 4)比值特征,具低Y(10. 38×10~(-6)～12. 70×10~(-6))和Yb含量(0. 79×10~(-6)～1. 17×10~(-6))特征,表现出埃达克质岩的地球化学属性。全岩稀土元素表现为明显富集轻稀土元素(LREEs)和大离子亲石元素(LILEs),而相对亏损重稀土元素(HREEs)和高场强元素Nb、Ta、P、Ti等(HFSE)。全岩Sr-Nd-Pb及锆石Hf同位素分析结果表明,浦桑果矿床相关中酸性岩石与冈底斯成矿带中新世大多斑岩-矽卡岩矿床紧密相关的埃达克质侵入岩体具相似的同位素组成特征,指示岩石具同源岩浆特征且埃达克质岩浆主要起源于拉萨地块加厚新生下地壳。浦桑果矿床中酸性岩体主要形成于后碰撞伸展的构造背景,因碰撞挤压向后碰撞伸展背景的构造转换,引起印度大陆岩石圈发生拆沉(42～25Ma)及拉萨地块中富集岩石圈地幔发生部分熔融,从而形成富含Cu、Co等基性岩浆熔体底侵加厚新生下地壳(25～18Ma),导致拉萨地块加厚新生下地壳中部分石榴子石角闪岩相发生部分熔融,最终形成闪长质熔体于浦桑果矿区有利构造部位形成具埃达克质属性的中酸性侵入岩体(13～14Ma)和矽卡岩型铜多金属矿体。
|
| 关 键 词： | 浦桑果 矽卡岩矿床 埃达克质侵入岩 岩石成因 动力学背景 西藏 |
| 收稿时间： | 2018/9/28 0:00:00 |
| 修稿时间： | 2019/1/2 0:00:00 |
Petrogenesis and geodynamic settings of the intermediate-acid intrusions related to the Pusangguo copper-dominated polymetallic deposit in Tibet: Constraints from geochronology, geochemistry and Sr-Nd-Pb-Hf isotopes |
| |
| LI Zhuang,LANG XingHai,ZHANG QiZhi and HE Liang.Petrogenesis and geodynamic settings of the intermediate-acid intrusions related to the Pusangguo copper-dominated polymetallic deposit in Tibet: Constraints from geochronology, geochemistry and Sr-Nd-Pb-Hf isotopes[J].Acta Petrologica Sinica,2019,35(3):737-759. |
| |
| Authors: | LI Zhuang LANG XingHai ZHANG QiZhi and HE Liang |
| |
| Institution: | MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;School of Earth Sciences and Resources, China University of Geosciences, Beijing 10008,School of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China,No.6 Geological Party, the Bureau of Geological Exploration and Mineral Resources, Lhasa 851400, China and School of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China;No.6 Geological Party, the Bureau of Geological Exploration and Mineral Resources, Lhasa 851400, China |
| |
| Abstract: | Located in the middle part of the Gangdese metallogenic belt in the Lhasa block, the Pusangguo deposit is a high-grade skarn type copper polymetallic deposit (Cu@1.42%, Pb+Zn@2.83%) formed in the contact zone between magma and the calcareous surrounding rocks and is the only large-scale Cu-Pb-Zn-(Co-Ni) deposit in the Gangdese metallogenic belt. Taking the intermediate-acid intrusions (biotite granodiorite and dioritic porphyrite) as the main research object, this study primarily carried on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb chronology on the zircon, whole-rock geochemistry, whole-rock Sr-Nd-Pb and zircon Hf isotopic study, aiming to confirm the timing and discuss the petrogenesis and geodynamic settings of the intrusions in Pusangguo. The results of LA-ICP-MS zircon U-Pb dating show that the biotite granodiorite and dioritic porphyrite were emplaced in 13.6~14.4Ma and 13.6~14.6Ma, respectively. The intrusions in Pusangguo deposit were formed in Miocene. Geochemically, these intrusions belong to high-K calc-alkaline I-type granitoids. Both the biotite granodiorite and dioritic porphyrite are characterized by high Sr content (599×10-6~1616×10-6), high Sr/Y ratio (48.2~132.3) and high La/Yb ratio (27.4~35.4), low Y content (10.38×10-6~12.7×10-6) and Yb content (0.79×10-6~1.17×10-6), showing the geochemical properties of adakitic rocks. In terms of whole-rock rare earth elements, the biotite granodiorite and dioritic porphyrite are enriched in light rare earth elements (LREEs) and large-ion-lithophile elements (LILEs), and are depleted in high-field-strength elements (HFSE) such as the element Nb, Ta, P, and Ti. The compositions of Sr-Nd-Pb and zircon Hf isotopes, which are closely related to the intrusions associated with the Miocene porphyry-skarn deposits in the Gangdese metallogenic belt, have similar isotopic composition characteristics, indicating that they probably have the similar magmatic origin and are mainly derived from the thickened juvenile lower crust. The Pusangguo deposit adakitic intrusions were mainly formed in the post-collisional extensional tectonic setting. The transformation of collision extruding tectonic setting to post-collisional stretching background eventually led to the delamination of the continental Indian lithosphere (42~25Ma) and the partial melting of enriched lithospheric mantle in Lhasa block and the formation of the Cu(Co)-bearing basic magmatic melts to underplate the thickened juvenile lower crust in Lhasa block (25~18Ma). Then, the underplating of the basic magmatic melts could directly cause the partial melting of the garnet-bearing amphibole lithofacies in the thickened juvenile lower crust and then form the adakitic dioritic magmatic melts, which eventually formed the adakitic intermediate-acid intrusions invaded (13~14Ma) in the favorable structures and the skarn-type copper polymetallic orebodies in Pusangguo deposit. |
| |
| Keywords: | Pusangguo Skarn deposit Adakitic intrusion Petrogenesis Geodynamic setting Tibet |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《岩石学报》浏览原始摘要信息 |
| 点击此处可从《岩石学报》下载免费的PDF全文 |
|
