大别山北淮阳带奥陶纪花岗岩的厘定及其对北秦岭东延的启示

详细的野外地质调查以及锆石SHRIMP U-Pb定年和初步的岩石学研究表明,大别山北淮阳带东段发育早古生代奥陶纪花岗岩。这些花岗岩经过了强烈的构造变形、局部发育片麻理和绿帘角闪岩相变质作用,形成时代为457±2 Ma,与北淮阳带西段马畈闪长岩的形成时代以及北秦岭?桐柏造山带一期与大洋俯冲相关的早古生代岛弧岩浆作用时代一致。结合区域地质背景和盆地沉积分析,证明北秦岭古生代俯冲增生造山带至少向东延伸到大别山北淮阳带的金寨及相邻地区。研究区古生代花岗岩及相关岩石的进一步研究,将为大别山碰撞造山带的古生代构造演化以及华南与华北板块之间的汇聚?拼贴过程提供新的制约。

Confirmation of the Ordovician Granite from the Beihuaiyang Zone in the Dabie Orogen: Insight into Eastern Extension of the Northern Qinling Orogen

Detailed field investigation,zircon SHRIMP U-Pb dating and preliminary petrographic observation affirm for the first time that the Early Paleozoic granite occurs in the eastern Beihuaiyang zone of the Dabie orogen.In addition,the granite is strongly deformed with local foliation and epidote-amphiboilite facies metamorphism,and its formation time is 457±2 Ma.The age of the granite is similar to those of the Mafan diorites from the western segment of the Beihuaiyang zone and the early Paleozoic arc rocks related to oceanic subduction in the northern Qinling-Tongbo orogen.Combined with regional geological background and the related basin sediments,it is indicated that the northern Qinling orogen easterly extends to the Jinzhai and the adjacent area in the eastern segment of the Beihuaiyang zone,the Dabie orogen.Further integrated researches on the Paleozoic granites and related rocks in the study area will provide new constraints on the Paleozoic tectonic evolution of the Dabie collisional orogen,and the convergent-amalgamate processes between the North and South China Blocks.