【摘要】 针对黔西普安铅锌矿区内的辉绿岩脉进行锆石U-Pb年代学与地球化学研究,结果表明其主量元素以高w(TiO2)(4.12%~4.18%)、高w(CaO)(7.46%~8.63%)和低w(MgO)(4.59%~5.02%)、低碱且Na2O>K2O为特征,ΣREE总量较高,LREE明显富集。与原始地幔相比,明显富集Rb,Ba,Th等大离子亲石元素,而高场强元素(HFSE)Nb,Zr,Hf等略为亏损,并出现K,Sr和P亏损。主量元素特征和微量元素标准化图解显示,普安辉绿岩属于拉斑玄武岩系列,具有洋岛玄武岩(OIB)的特征,与峨眉山玄武岩为同源产物,具有密切的成因关系。微量元素示踪表明,岩浆来源于富集地幔,具有地幔柱成因特征。LA-ICP-MS锆石U-Pb定年结果表明辉绿岩形成年龄为263 Ma±10 Ma,代表了峨眉山地幔柱的启动时间。更多还原

【Abstract】 Zircon U-Pb dating and geochemical analysis was performed on diabase dykes in the Pu′an area,west Guizhou.The major elements of the diabase are characterized by high w(TiO2)(4.12%~4.18%),high w(CaO)(7.46%~8.63%),low w(MgO)(4.59%~5.02%),low alkali and Na2O>K2O.It is showed that the diabase dykes are enriched in light rare earth elements with abundance rare earth elements.Compared with the primitive mantle,they are distinctly enriched in large-iron-lithophile elements,such as Rb,Ba and Th,slightly depleted of high-field-strength element,Nb,Zr and Hf for instance,and depleted of K,Sr and P.On the basis of major and trace elements patterns,it is demonstrated that the diabase dykes belong to tholeiitic basalt series in lithology and present OIB(Ocean island basalts)features in accordance with Emeishan basalts.Trace elements tracing indicates that the magma originated from an enriched mantle source and possesses origin of mantle plume.LA-ICP-MS method of zircon U-Pb dating shows that the diabase dykes formed at 263 Ma±10 Ma,representing the activating time of Emeishan mantle plume.更多还原