青海锡铁山铅锌矿床喷流沉积后的构造再造过程

本文提出锡铁山矿区早期属伸展构造体制,形成加里东期变质核杂岩;晚期属收缩构造体制,形成海西期褶皱冲断岩片。认为基底剥离断层(F1)与上剥离断层(F2)所夹绿色变质岩系(O3tna -b)属绿片岩相顺层正滑韧性剪切带,带内基性 -中酸性火山岩所夹灰岩层经变形分解作用形成大理岩构造透镜体群,并在递进变形过程中经水力压裂作用在其中形成系列雁行排布的Y或R型张裂构造,而原先赋存于海相火山岩中由喷流沉积作用形成的层控铅锌矿体则完全从高应变带内迁出,继而沉淀于低应变的透镜化大理岩中及其附近的新生容矿空间中。重点阐述了大理岩透镜体的几何特征,并依此提出预测隐伏铅锌矿体的地质依据

TECTONIC RECONSTRUCTION OF THE XITIESHAN Pb-Zn DEPOSIT AFTER SPOUT SEDIMENTATION, QINGHAI PROVINCE

The Xitieshan mine area showed extensional structure regime in early stage,in which formed Caledonian metamorphic core complexes,and compressional structure regime in late stage,in which formed Hercynian fold-thrust rock flake.The green metamorphic rocks(O3tna-b) between the base detachment fault (F1) and the upper detachment fault (F2) were a downslide bedded ductile shear zone in greenschist facies,in which the limestone among basic-neutroacidic volcanic rocks formed marble tectonic lens group through deformation partitioning and in marble lens formed en echelon D or R style gaping tectonics through hydrofracturing in the process of progressive deformation.In the meantime,the early stratabound Pb-Zn orebodies in marine volcanic rocks,which formed by spout sedimentation,were thoroughly taken out from a high strain zone and lately deposited in the new tectonic space in the marble lenses and their vicinity.The paper specially describes the geometric features of marble lens and presents a geological basis for forecasting buried Pb-Zn orebodies according to the mentioned above.