西大别造山带早白垩世花岗岩地球化学特征与成矿

摘要

西大别造山带早白垩世花岗岩广泛发育,具有高硅(SiO272.94％～77.56％),富碱(K2O+ Na2O 7.06％～8.78％),高K2O/Na2O(1.12％～2.12％),贫镁(MgO 0.13％～0.80％),贫钙(CaO 0.32％～0.96％)的特征.主量元素质量平衡模拟计算表明,西大别花岗岩形成于大别角闪石片麻岩的部分熔融,并有较多的角闪石和少量石榴石残留,结合中稀土出现一定的亏损,指示重熔作用很可能发生于增厚下地壳的环境.早白垩世岩浆活动与成矿,构成了对中国东部中生代大规模岩石圈减薄、拆沉的响应.%Early Cretaceous granites are widespread in western Dabie orogen, characterized by high-silica ( SiO2 72. 94% ~ 77. 56% ) , high alkaline ( K2O + Na2O 7. 06% - 8. 78% ) and high K2O/Na20 ratios( 1. 12% - 2. 12% ) , and depleted in MgO (0. 13% - 0.80% ) and CaO (0.32% -0.96% ). Mass balance modeling of major elements suggests that heavy melting may occur in the thicken crust due to the granites in western Dabie orogen derived from the partial melting or anatexis of am phi bole gneisses of Dabie core complexes, the residue of many hornblendes and a few garnets, and combined with some wanity of rare earth. Early Cretaceous magmatism and mineralization could be ascribed to Mesozoic regional largescale lithospheric thinning and delamination throughout East China.