大别山的构造变形期次和超高压岩石折返的动力学

从构造关系上看,大别山可分为南部,中部和北部3个构造系统,大别山南部构造系统为一套（原地）构造堆叠系统（相对的）,从上到下依次为：（1）未变质的震旦纪一早三叠世沉积盖层,它被造山后的侏罗－白垩纪砂－砾岩不整合覆盖;（2）弱变质的新元古代板岩;（3）高压变质岩系（宿松群）,这些变质岩系大多退变质为绿片岩相;（4）含柯石英榴辉岩超高压变质单元的异地系统;（5）未经历超高压变质作用的原地（相对的）片麻岩系。北西－南东向的拉伸线理在各个地质单元均有表现。从动力学上看,上盘指向NW的剪切运动被后期的褶皱所改变,大别山中部为（混合岩）热穿窿改造系统,系经历了超高压变质作用的地体叠加了混合岩化作用的产物,它与超高压变质地体的界限为一拆离断层,而正是这个拆离断层使超高压变质地体向地表折返并经历了角闪岩相的退变质作用。大别山北部为构造堆叠系统,早期的面理和南北向的挤压线理被轴面北倾的褶皱所改造,这种褶皱对应于大别山中部同折返期的韧性变形的隆升构造。同时建立了地球运力学模型并讨论了逆冲作用和正断层的作用。

Different Deformation Stages of the Dabieshan Mountains and UHP Rocks Exhumation Mechanism

On the basis of the authors' research, the Dabieshan Mountains is divided into three tectonic domains; the South Dabieshan, Central Dabieshan and North Dabieshan domains. The South Dabieshan domain consists of autochthonous stacked strata, which are, from top to bottom, Da sedimentary cover of unmetamorphosed Sinian-Early Triassic series, unconformably overlain by Jurassic sandstone, 2) weakly metamorphosed Neo-Proterozoic slate, 3) " Susong group", most of which had been retrogressed into greenschist facies, 4) al-lochthonous block consisting of gneiss and UHP eclogite, 5) autochthonous gneiss which has never been subjected to UHP metamorphism. All these units exhibit a NW-SE lineation. The NW-directed shearing on the top of the unit was reworked by later folds. The central Dabieshan domain is a migmatitic dome resulting from migmatization that the UHP metamorphosed terrane had experienced. Its boundary with the HUP terrane is a detachment fault, which is responsible for the exhumation of the UHP unit during its retrogression into amphi-bolite facies. In the north Dabieshan domain, early foliation and N-S-trending compressional lineation are deformed by N-verging folds coeval to the syn-exhumation ductile structures of the central Dabieshan domain. A geodynamic model involving coeval thrusting and normal faulting is discussed.