大别岳西地区花岗岩类岩石学及其成因

Petrology and Genesis of the Yuexi Granitoids in Eastern Dabie,China

岳西地区花岗岩类主要由主簿原和白马尖二长花岗岩－正长花岗岩岩基、花岗闪长岩－石英二长闪长岩小岩体和晚期的淡色碱长花岗岩岩体组成。主要岩体形成于燕山晚期，为造山后花岗岩。岩基中花岗岩的暗色矿物为黑云母，主簿原花岗岩含有褐帘石，岩石化学显示为过铝质（Ａ／ＣＮＫ约为１．１），稀土配分为右倾的、中等负铕异常（Ｓｍ／Ｅｕ为０．１６～０．２５）曲线。花岗闪长质的、没有变形的小岩体中普遍含有角闪石和榍石，岩石化学表现为准铝质（Ａ／ＣＮＫ为０．８～０．９，Ａ／ＮＫ为１．５～１．８），稀土配分为右倾的无铕异常（或略有正铕异常）的曲线，但其形成时代和εＮｄ（０）值与主要岩基相同。花岗岩类的εＮｄ（０）值均为较大的负值（－１７～－２６），在εＮｄ（０）－εＳｒ（０）图上，表现为一条水平带状分布，显示其源岩为存留时间很长的古老地壳。

A suite of plutonic rocks from Yuexi in eastern Dabie is intruded in the North Dabie metamorphic complex. The igneous suite is characterized by monzogranite syenogranite,granodiorite quartz monzodiorite and alkali granite. Petrographical and geochemical charactes indicate that they were emplaced in the post orogenic regimes. The granites batholiths containing biotite are peraluminous (A/CNK 1 1±), an undeformed granodiorite quartz monzodiorite shows that rock types are metaluminous(A/CNK 0 8￣0 9, A/NK 1 5￣1 8) and REE plots exhibit a smaller Eu anomally (Eu/Sm 0 31). All granitoids from the Yuexi district have early Cretaceous emplacement ages and negative ε Nd (0) (-17 ￣ -26). Sr and Nd isotope results may be plotted forming a horizontal zone on ε Nd (0) ε Sr (0) diagramn , that suggests that the source rock of these granitoids is an old earth crust.