大别造山带天柱山中生代中酸性岩成因的REE配分定量模拟  

Quantitative REE Modeling for Genesis of Mesozoic Intermediate-Felsic Rocks at Tianzhushan in the Dabie Orogen

作　　者：徐小军[1] 赵子福[1] 郑永飞[1] 魏春生[1] 

机构地区：[1]中国科学院壳幔物质与环境重点实验室

出　　处：《地球科学（中国地质大学学报）》2005年第6期721-728,770,共9页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(Nos.40303002;40334036).

摘　　要：大量的同位素地质年代学和地球化学研究表明,大别山中生代中酸性岩为俯冲扬子陆壳再循环的产物.REE配分的定量模拟计算结果表明,与基性下地壳相似的北大别基性闪长质片麻岩部分熔融并经过结晶分异能够形成与天柱山中性岩类似的稀土元素组成,而与中性地壳相似的北大别中性灰色片麻岩部分熔融能够形成与天柱山花岗岩类似的稀土元素组成.残留相微量元素定量计算结果表明,大别山现今出露的中基性麻粒岩不是部分熔融后形成的残留体.早白垩世地幔超柱事件热扰动所引起的加厚地壳部分熔融后的残留体可能由于比重较大而拆离进入地幔,从而发生去山根作用和造山带的大面积隆起.A large number of studies of geochronology and geochemistry indicate that Mesozoic intermediate-felsic rocks from the Dabie orogen have originated from recycling of the subducted Yangtze continental crust itself. A REE partition simulation suggests that the Tianzhushan intermediate rocks can be generated by partial melting, in coupling with fractional crystallization, of dioritic gneiss which is similar in chemical compositions to the mafic rocks in the lower crust in North Dabie; partial melting of intermediate grey gneiss which is similar in chemical compositions to the middle crust in North Dabie can generate the Tianzhushan felsic rocks. Quantitative calculation of trace element content for the residue after partial melting suggests that intermediate-mafic granulites outcropped in the Dabie orogen are not the residue of partial melting. The residue formed by partial melting of thickened crust due to anomalous heat supply by mantle superwelling at Early Cretaceous is possibly easy to detach from the crust because of its high density, leading to the remove of mountain root and large scale uplift of the orogen.

关 键 词：中酸性岩 中生代 稀土元素 模拟计算 大别造山带 

分 类 号：P588.12[天文地球—岩石学]