陕西凤县—山阳泥盆系同沉积断裂砾岩

THE CONGLOMERATES CONTROLLED BY SYNSEDIMENTARY FAULTS OF THE DEVONIAN IN THE FENGXIAN-SHANYANG,SHAANXI PROVINCE

陕西凤县—山阳泥盆系发育的砾岩 ,包括泥砾岩、钠长石砾岩、白云岩砾岩和砾质矿石 ,不仅空间上与热水沉积体密切相关 ,岩石化学成分也受到热水活动影响。通过对该类砾岩岩石学和岩石化学研究 ,认为其形成受控于成矿期的同沉积断裂。沿同沉积断裂发育海底滞流深水洼地 ,同沉积断裂亦触发海底重力流。这些砾岩即是在这些洼地中形成的重力流砾岩。此外 ,同沉积断裂作为热水上升的通道 ,提供同沉积期矿化作用的热水介质 ,这些砾岩中的铅锌矿床即是这些同生期热水沉积作用的产物。通过柞山矿田西部池沟组 (D2 ch)分布的泥砾岩岩石学和岩石化学研究 ,结合区内矿床同位素测年资料和地层地球化学资料 ,笔者认为柞山矿田大西沟组 (D2 d)中赋存的菱铁矿—银—多金属—金热水沉积矿床系列 ,具有二次热水沉积特点。

The conglomerates of the Devonian in the Fengxian Shanyang area,Shaanxi Province, include mud conglomerates, dolostone conglomerates, ore conglomerates, and albite conglomerates. These conglomerates are closely associated with hydrothermal sedimentary bodies in space. Their petrochemical compositions were also affected by hot water activity. The petrological and petrochemical characteristics indicate that the formation of these conglomerates was controlled by synsedimentary faults during the metallogenic epoch. These synsedimentary faults not only resulted in formation of the deep water basin where the conglomerates were deposited as a result of deep water mass flows, but also carried heat flows for the mineralisation of these conglomerates. The lead zinc deposits are products of the synsedimentary hydrothermal sedimentation. Through studying petrology and petrochemistry (including isotope dating) of mud conglomerates in the Chigou Formation (D 2 ch ), the author suggests that the hydrothermal ore deposit series (siderite silver multimetal gold deposits) in the Daxigou Formation (D 2 d ) should be of natures of secondary hydrothermal sedimentation.