伸展型脆-韧性剪切带对沃溪钨锑金矿床的构造控制

STRUCTURAL CONTROL OF THE EXTENSIONAL BRITTLE-DUCTILE SHEAR ZONE ON WOXI W-Sb-Au DEPOSIT IN WESTERN HUNAN PROVINCE

湘西沃溪钨锑金矿床受控于一条伸展型顺层脆—韧性剪切带。带内岩石在非共轴顺层剪切构造动力作用下发生变形分解 ,形成泥质构造板岩强变形带和砂质构造板岩弱变形域。泵吸中心—弱变形域中的承压矿液沿砂质构造板岩的ab面发生水力压裂而产生“D”型张剪裂隙。构造—流体双重动力系统的周期性振荡使主裂隙系统发生周期性的破裂—愈合作用而形成条带状复脉。矿液是通过隐蔽的低角度正断层、强变形带内的构造面理及弱变形域中的微裂隙系统运移的 ,说明在靠近滑脱面的弱变形域中水力压裂作用会增强 ,其矿化类型将以蚀变岩型为主、脉型为辅。

Woxi W-Sb-Au deposit, western Hunan Province ,was contro ll ed by the extensional beded brittle-ductile shear zone.Under the tectonic dynam ics of beded uncoaxial shear, the rocks produced deformation partitioning to for m the strong-deformation zone consisting of pelitic tectonic slate and the weak- deformation domain consisting of sandy tectonic slate respectively. The confined fluids in the pumping centre ofweak-deformation domain developed hydrofracturi ng along ab tectonic foliation , producing D-type tenso-shear fractures. The per iodic vibration of the dual-dynamics system ,formed by the tectonic dynamics and the fluid dynamics, caused the main fracture system to develop periodic rupture -healing and form banded composite veins. The ore-bearing fluids flowed through the blind detachment fault, the tectonic foliations in the strong-deformation zo ne and the minute fissure system in the weak-deformation domain. It is indicated that hydrofracturing started to be strengthened in the weak-deformation domain near detachment fault where the mineralization type would be characteristic prin cipally of the alteration type, and secondarily of the vein type.