陕西陈家坝变质火山体系

陈家坝变质火山体系位于太古代扬子陆壳西北边部康略勉初始裂谷，是在裂谷纪大陆拉张后期所生成的一个浅海海底中－酸性火山体系，它包括同源成串的裂隙式火山机构、火山塌陷构造和塌陷被动侵位的岩塞。火山机构的五次喷发堵塞阶段与刘家沟组凝灰岩系的五个喷发沉积阶段，岩段之间有着明显的成因对应关系，原岩属于陆壳来源型的富镁安山岩－英安岩－流纹岩组合。在较厚的近火山灰锥锥坡海底洼地相的角斑质火山尘凝灰岩层中，夹有含金

METAMORPHOSED VOLCANIC EDIFICE OF CHENJIABA AREA,SOUTHWESTERN SHANXI PROVINCE,CHINA

Located in Kang-Lue-Mian primitive rift aaalong the NW margin of Archaean Yangtze platform .the metamorphosed volcanic edififce of Chenjiaba area is intermediate-acidic volcanic edifice formed in shallow submarine water during the late stage of contine ntal distension in proterzoic Riftian. It consists of clustered comagmatic source volcanic apparatuses of fissutr type,volcanic collapse structure and glug of passive emplacement,There are five eruptive depositional and oruptive filling stages,The primary rocks of the volcanic edifice belong to Mg-rich andesite-decite-rhyolite association of continental crust source.Only in keratophyric dust-tuff tayers near volcanic cones of comparatively thick submarine depression factes,there exist intercalates of borititic lenses of polymatallic sulphidc deposits ,containing An and Ag.i. e. .An and Ag-bearing exhalative-sedimentary deposits,And only in brinepools of submarine pit-crater collapse.there exist volcnogenic massive sulphide deposits(VMS).