Disintegration And Tectonic Attribute Of Devonian "Daminshan Formation" In Yakeshi

Original Devonian Daminshan formation of Yakeshi area is located in the Toudaoqiao-Wunver fracture and its North West.Through systematic field survey and comprehensive study,the original "Daminshan formation" disintegrate into two rock units:narrow Daminshan formation and ophiolite quality melange.The narrow Daminshan formation is in the upper middle devonian series(D2-3d),consists of two lithologic section:the lower part of 1st segment is metamorphic sandstone and slate,the upper part is main of meta-basalts and meta-tholeiite,with a small amount of thin slate and radiolarian cherts;2nd segment is a set of meta-rhyolite(meta-rhyolite,meta-rhyolitic ignimbrite and breccia tuff)with meta-packsand lenses,the top of it is mainly of brecciat tuff and clip packsand and mudstone.Ophiolitic quality melange is mainly distributed in the Toudaoqiao-Wunver fracture,including meta-basalts,radiolarian siliceous rocks,gabbro of heap crystal structure and dolerite rock wall.Rock assemblage and geochemical features indicate that the tectonic environment of Daminshan formation is island arc.Appear of ophiolite quality melange shows that the area has been the oceanic crust,the tectonic environment is arc-back extensive ocean-basin The distribution of ophiolitic quality melange also instruct the Toudaoqiao-Wunver fracture is an important structural belt.This paper summarizes the copper ore-controlling factors of Daminshan formation,and pointed out the prospecting criteria.The upper of 1st segment Daminshan formation is important copper layer,it mineralization on ductile deformation superimposed parts is relatively better.The copper content of two mines have been found is generally 0.2-0.3%,to the highest is 1.7%,pointed out the direction of spilite angle porphyry copper for the area in future.