【摘要】 狮子山矿田内分布着一系列燕山期岩浆岩 ,岩性主要为辉石闪长岩、石英闪长岩和花岗闪长岩。通过岩相学和地球化学研究 ,表明它们属富碱高钾钙碱性岩系 ,并有类似高Ba -Sr花岗岩的地球化学特征 (如Ba ,Sr和LREE含量高 ,Y和HREE含量较低 ,LREE/HREE强烈分离 ,Nb ,Ta ,Ti强烈亏损 ,无明显的Eu负异常 ,Sr-Nd同位素具有EMⅠ型特征 ) ,由此推断它们具有相同岩浆来源。在区域拉张 -伸展构造域中 ,由富集Ba ,Sr的基性岩浆底侵熔融下地壳 ,并发生了结晶分异作用。更多还原

【Abstract】 Baimangshan,Qingshanjiao and Nanhongchong intrusions in the Shizishan orefield,Tongling area,Anhui province,are composed of pyroxene diorite,quartz diorite and granodiorite,respectively. They are predominantly calc-alkine,alkaline-rich,with higher Ba,Sr contents,and share the following similar characteristics with the high Ba-Sr granitoids: higher Ba,Sr and LREE and lower Y and HREE abundances,distinct Nb,Ta and Ti depletion,and absence of negative Sr and Eu anomalies. It is suggested that crystallization differentiation played an important role in evolution of magmas because they have covariant major elements. Fractionation of P- and Ti-bearing accessory minerals,such as apatite,ilmenite and titanite might result in a decrease of P and Ti abundances. The relative depletion in Y and HREE might be caused by hornblende and/or garnet retention,but not intermediate plagioclase in the source. Initial 87 Sr/ 86 Sr (0.7062～0.7101) and 143 Nd/ 144 Nd (0.5116～0.5121) ratios show EMⅠ-type signature,and are negatively correlated. The regional switching from compression to extension in the early Cretaceous in a post-collisional setting might readily trigger a rapid rise of hot Ba- and Sr-enriched upper asthenosphere material and result in widespread melting of lower crust to generate voluminous magmas in the deep-seated magma chamber.更多还原