下营坊一带不对称褶曲的构造特征、形成条件及控岩控矿意义

本文着重介绍了下营坊一带主要构造格架—ＮＥ向Ｓ状不对称褶曲的几何特征、形成机制、变形环境及控岩控矿作用。通过区域应力场分析及岩组分析，揭示了该区在ＮＥ向左行斜冲剪切机制下，元古界层状岩层因上、下界面的滑脱剪切所造成的交形效应以及所处的中温低压变形坏境。不对称褶曲的翼部地层的顺层滑脱和转折端部位的虚为本区中酸性岩浆活动提供了侵位通道和空同。向ＳＷＷ倾伏的不对称褶曲的背斜转折端与ＥＷ向及ＮＮＥ向复合构造控制下营坊南梁斑岩型铜矿。

Geological Features,Forming Conditions and Mapmatism and Mineraliation Controlling of S-shaped Asymmetrical Fold in Xiayangfang District,Pingquan,NE Hebei,China

Xiayingfang district, Pingquan, NE Hebei, Called Yongan-Xiayingfang-Maojiagoumetallogenetic belt in which there sxist bedded sedimentary rocks of proterozoic changcheng system and overlyine jurassic volcanoclastic rocks and underlying archean metamorphic crystal base ment with disconformities,is located in the east segment of Yangshan platformat fold belts,N. China platform. And Yangshan conjunct arc passes west to the area. The existent evidence ofan S-shaped aspometrital fold with NE trending is described and its genetic mechanism and deformation environment are discussed in this paper, which shows that the fold resulted from thesinistral shear with oblique thrust on the two disconformities as decollements. Bedding decouplingin the long limbs controls isneors veinS in NE trending and the decoupling in the hinge zones ofthe fold controls intrusion, which shows its intruding atom SWW to NEE along the hinges. Theconjuncted place of plunging Crown of fold and EW trended and NEE trended faults is, therefore,a promosing prospect. The analyses of regional stress field and quartze C-axes of rocks from theasymmetrical fold reveal that the deformation take place in the environment with middle temperature and lOw pressure.