| 大别造山带银水寺铅锌矿区正长花岗斑岩脉锆石U-Pb年代学、地球化学特征和地质意义 |
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| 引用本文： | 吴皓然,谢玉玲,钟日晨,王莹.大别造山带银水寺铅锌矿区正长花岗斑岩脉锆石U-Pb年代学、地球化学特征和地质意义[J].地球科学,2020,45(3):910-929. |
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| 作者姓名： | 吴皓然 谢玉玲 钟日晨 王莹 |
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| 作者单位： | 北京科技大学土木与资源工程学院, 北京 100083 |
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| 基金项目： | 自然资源部公益性行业基金项目201011011中国地质调查局项目2014-01-020-010 |
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| 摘 要： | 银水寺铅锌矿床位于大别造山带北缘，是大别山地区最大的矽卡岩型矿床.目前对矿区岩浆作用时限、岩石地球化学、岩石形成环境等方面的研究较为薄弱，在一定程度上制约了对该区铅锌成矿规律的认识.在详细野外地质调查的基础上，对矿区出露的正长花岗斑岩脉的岩石学、成岩年代学、岩石化学和同位素地球化学进行了系统研究.结果表明，银水寺矿区正长花岗斑岩脉锆石LA-ICP-MS U-Pb年龄为125.4±0.4 Ma，表明其形成时代为早白垩世.全岩地球化学分析显示，正长花岗斑岩脉表现为高硅（SiO2=71.43%~72.71%）、高钾（K2O=4.62%~4.88%）、富碱（7.47%~7.81%）、弱过铝质（A/CNK=1.03~1.06）、富Fe低Ca，贫Sr、Ba、Ti、P，轻稀土富集、重稀土亏损，具Eu负异常，Ce异常不明显，稀土配分图呈典型的右倾型，显示出A型花岗岩的特征.岩石具有富集的Sr-Nd-Hf同位素组成:全岩（87Sr/86Sr）i值为0.710 21~0.710 53，εNd（t）值在-20.0~-19.2之间；锆石εHf（t）值为-26.7~-23.8，位于地幔演化线之下；TDM2值变化于2 663~2 845 Ma之间，指示其起源于大别杂岩与扬子板块北缘的古老下地壳物质的混合.结合区域地质背景，认为矿区正长花岗斑岩脉形成于扬子克拉通与华北克拉通碰撞造山后的大规模伸展环境，软流圈地幔上涌作用于减薄的岩石圈，与西向俯冲的古太平洋板片俯冲角度改变造成的强烈弧后拉张有关.
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| 关 键 词： | 银水寺铅锌矿 正长花岗斑岩脉 地质年代学 地球化学 地质背景 大别造山带 |
| 收稿时间： | 2019-01-29 |
Geochronology,Geochemistry and Geological Significance of the Syeno-Granite Porphyry from Yinshuisi Pb-Zn Deposit,Dabie Orogenic Belt |
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| Abstract: | The Yinshuisi Zn-Pb deposit,located in the north border of Dabie Orogen Belt,Jinzhai County,Anhui Province,is the largest skarn deposit in the Dabieshan region. Previous studies on chronology,geochemistry and petrogenesis of intrusions are few,which has restricted the understanding of lead-zinc metallogenic regularity. Detailed geochronology,geochemistry,and isotopic data for ore-related syeno-granite were analyzed in this study.LA-ICP-MS U-Pb dating of zircon from Yinshuisi syeno-granite porphyry yields age of 125.4±0.4 Ma,suggesting that it resulted from Early Cretaceous magmatism.According to the geochemical analysis,Yinshuisi syeno-granite porphyry has high SiO2 (71.43%-72.71%),K2O (4.62%-4.88%) and ALK (K2O+Na2O=7.47%-7.81%),but weakly peraluminous (A/CNK=1.03-1.06). The rock is enriched in Fe,Rb,Th,U and LREE,depleted in Ca,Sr,Ba,Ti,P and HREE with negative Eu anomalies,which indicates that Yinshuisi syeno-granite porphyry belongs to aluminous A-type granite.The Yinshuisi syeno-granite porphyry has highly enriched Sr-Nd-Hf isotopic compositions: (87Sr/86Sr)i=0.710 21-0.710 53,εNd(t)=-20.0—-19.2. The εHf(t) value ranges from -26.7 to -23.8,lying below the depleted mantle line.The TDM2 value ranges from 2 663 Ma to 2 845 Ma,which indicates that the syeno-granite porphyry derived from dominantly the mixing of Yangtze's lower crust with the Dabie Complex. Yinshuisi syeno-granite porphyry was emplaced after the major collisional period of the North China Block and Yangtze Block,in a post-collisional or intracontinental extensional setting under the regional extension mechanism,which has the capacity to cause the regional upwelling of the asthenospheric mantle. The thinned lithospheric mantle was exposed to the upwelling asthenopsheric mantle,leading to intensive magmatism,which was related to the rollback of westward subducting Paleo-Pacific Plate beneath the Asian continent. |
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