西大别横穿造山带实测地质剖面的基本构造样式

Basic structural pattern along a measured geological profile across the Dabie orogen in the western Dabie area

在高压、超高压变质岩出露齐全的西大别地区精确测制了一条比例尺为1∶1万的横穿造山带地质剖面。根据岩石组合、变质程度和变形样式,将剖面经过的区域从北到南划分出南湾、八里畈、浒湾、新县、红安、七角山、桐柏集和木兰山等8个岩石构造单元。区域构造变形解析表明,在西大别造山带剥露过程中,早期以多幕挤压褶皱和逆冲推覆变形占主导地位,晚期则主要表现为韧性伸展滑脱、正断和走滑改造。结合由榴辉岩推导的热结构特征,认为西大别造山带的基本构造样式是一个规模宏伟的、以超高压变质岩为核部并向西倾伏的不对称背形构造,后期的伸展滑脱使其发展成现今所展示的穹隆。

A1:10000-scale geological profile across the Dabie orogen was accurately measured in the west-ern Dabie area where high-and ultrahigh-pressure(UHP )metamorphic rocks are completely exposed.According to the rock associations ,metamorphic grades and deformational patterns ,eight petrological-tec-tonic units,i.e.the Nanwan,Balifan,Huwan,Xinxian,Hong'an,Qijiaoshan,Tongbaiji and Mulanshan units,are distinguished from north to south along the profile.Regional structural analysis suggests that dur-ing the exhumation of the western Dabie orogen multi-stage compressional folding and thrusting predomi-nated in the early stage,which were modified by extensional ductile shearing,normal faulting and strike slip in the late stage.On that basis,combined with the thermal structure deduced from eclogites,it is be-lieved that the basic structural pattern of the western Dabie orogen is marked by a large-scale,west-dip-ping,and UHP-cored asymmetrical antiform,which developed into a domal structure as a result of ex-tensional detachment at the late stage of exhumation.