安徽碧溪岭地区超高压变质地质演化——1∶10000填图初步总结

ULTRA-HIGHPRESSUREMETAMORPHISMANDGEOLOGICALEVOLUTIONINTHE BIXILINGAREA,ANHUI－APRELIMINARYSUMMARYOF1∶10000MAPPINGWORK

通过对大别山碧溪岭地区1∶10000地质填图，基本查明了区内地质体的分布特征及地质演化历史。该区的UHP变质岩系主要由浅色榴辉岩系、深色（基性）榴辉岩系及（石榴）斜长片麻岩系列组成，其原岩相当于一套中基性火山－沉积岩系。未受UHP变质的花岗质岩石主要为片麻状花岗岩、花岗闪长斑岩，与UHP变质岩系呈构造拼置关系，其原岩可能为花岗闪长斑岩经不同程度的糜棱岩化改造，再经深熔－交代作用形成。地质演化事件可概括为：在中－晚元古代一套火山－沉积表壳岩岩系经再循环作用被带到上地幔－下地壳，经历UHP变质作用；随后在7亿年左右，花岗闪长斑岩侵位，并在后期的大规模韧性剪切作用下与超高压变质岩构造拼置在一起；在印支期发生深熔交代作用，形成半原地型的花岗岩系，并上升到地壳浅部。

Basically this paper describes the distribution and evolution history of geologic bodies on the basis of 1:10000 geological mapping in the Bixiling area,Dabie Mts.The ultra- high pressure (UHP) metamorphic rock series,whose protolith is equivalent to a suite of intermediate－ basic volcanics- sedimentary rock series,mostly consists of light- colored,dark(basic)eclogites and (garnet )plagiogneiss series.The granitic rocks that have not been subjected to UHP metamorphism include gneissic granite and granodiorite porphyry,structurally juxtaposing with UHP metamorphic rock series. Their protolith may be resulted from granodiorite porphyry that underwent mylonitization reworking and ana- metasomatism.The geological evolution events are summed up as:in the mid- late Proterozoic a suite of volcanics- sedimentary crustoses were taken to upper mantle- lower crust by recycling process,then went through UHP etamorphism;subsequently,ca 700 Ma granodiorite porphyry emplaced and structurally juxtaposed with UHP metamorphic rock series by the later large ductile shearing;in the Indosinian period the rocks experienced ana- metasomatism to form semi- in- situ- type granites and rose to the shallow level of the crust.