中国地质2024，Vol.51Issue(2)：632-649,18.DOI:10.12029/gc20200906003
云南个旧卡房辉绿岩墙锆石U-Pb年龄、地球化学特征及其岩石圈伸展作用
Geochronology,geochemistry and lithosphere extension of Kafang diabase in Gejiu area,Yunnan Province
摘要
Abstract
This paper is the result of geological survey engineering. [Objictive]The exploration of the petrogenesis and tectonic setting of the Kafang diabase is crucial to know about the tectonomagmatic evolution in Gejiu area.[Methods]Based on LA-ICP-MS zircon U-Pb age,whole-rock geochemistry and Sr-Nd-Pb isotope analysis,the formation age,geochemical characteristics and geological significance of Kafang diabase dike are studied.[Results]Zircon U-Pb dating shows that the age of Kafang diabase is 77 Ma.Inherited zircon ages(2409 Ma,2616 Ma,290 Ma)indicate tectono-thermal related Neoarchean and Paleoproterozoic metamorphic basement and the magmatic activity in Early Permian in Gejiu area.The Kafang diabase belongs to the shoshonite series with the characteristics of low SiO2 content and high K2O,TiO2,MgO contents.In primitive mantle normalized trace elements diagram,these samples show similarities with OIB and enriched in LILEs(such as Rb,K,Sr),depleted in HFSEs(such as Nb,Ta,Zr,Hf).High initial 87Sr/86Sr ratios(0.70782-0.70791),positive εNd(t)values(2.07-2.29)and initial Pb isotopic compositions(206Pb/204Pb=18.286-18.465,207Pb/204Pb=15.668-15.717,208Pb/204Pb=37.763-38.830)indicate the enriched mantle(EM2)source.[Conclusions]The petrogenesis of Kafang diabase is that the upwelling of asthenosphere in an extensional setting induced 5%-15%partial melting of garnet lherzolite at a depth of 60-120 km in the lithospheric mantle.The new-formed magma with characteristics of EM2 consists of the primary magma of the Kafang diabase.During the ascent of magma,contamination of the lower crust occurred accompanied by weak fractional crystallization,and then formed the Kafang diabase.关键词
辉绿岩/锆石U-Pb定年/地球化学特征/成岩机制/构造背景/地质调查工程/个旧/云南Key words
diabase/zircon U-Pb dating/geochemistry/petrogenesis/tectonic setting/geological survey engineering/Gejiu/Yunnan Province分类
天文与地球科学引用本文复制引用
尚志,陈永清,童祥,沈思联..云南个旧卡房辉绿岩墙锆石U-Pb年龄、地球化学特征及其岩石圈伸展作用[J].中国地质,2024,51(2):632-649,18.基金项目
国家自然科学基金(41972312,41672329)、国家重点研发计划课题(2016YFC0600509)和中国地质调查局项目(1212011220922)联合资助. Supported by the projects of the National Natural Science Foundation of China(No.41972312,No.41672329),the National Key Research and Development Project of China(No.2016YFC0600509),and China Geological Survey(No.1212011120341). （41972312,41672329）
