辽东半岛中生代韧性剪切带特征及其地质意义

CHARACTERISTICS OF DUCTILE SHEAR ZONES OF MESOZOIC IN EASTERN LIAONING PENINSULA AND THEIR GEOLOGICAL IMPLICATIONS

辽东半岛韧性剪切带可分为两种类型,一类为低角度逆冲推覆型,多为北东—南西向或北北东—南南西走向,大致分布于辽东半岛东南边缘;另一类为高角度近水平剪切滑动型,多分布于半岛内部的a线理及运动学特征指示这些剪切带的总体应力场这由南东东向北西西推覆、挤压。剪切带的形成时间大多在中生代末期。辽东半岛金矿大多与这次韧性剪切活动有关,由剪切活动产生的一些韧-脆性的变形带很可能即是环太平洋成矿作用的容矿构造。

Ductile shear zones developed in the Archaean-Mesozoic rocks in Eastern Liaoning Peninsula arc divided into two types: thrust shear zones, gently dipping and NE-to SW-or NNE-to SWW-trending, extending on the southeastern margin of the peninsula; strike-slip shear zones, high-angle dipping and extending in the centre of the peninsula.They are characterized by mylonitic schistosity(Sm), shear plane(C), sheath fold and stretching lineation.The stretching lineation, S—C relationship, asymmetric pressure shadow suggest a late Mesozoic SEE-to NWW-napping and compressing, related to underthrust of the Pacific Ocean Plate. Most of gold deposits discovered in the peninsula are hosted by the shear zones, which can be the channel and space of Au-bearing fluid.Therefore, the author pointed out that the ductile-brittle shearing zones are the host of gold deposits in the Peripheral Pacific Metallogcnic Belt and the ductile shear zones, especially the thrust shear zones are the prospect for further exploration.