扬子地台西缘海相火山岩建造及其控矿特征

FORMATIONS AND ORE CONTROLLING CHARACTERISTICS OF THE MARINE VOLCANIC ROCKS ON THE WESTERN MARGIN OF THE YANGTZE PLATFORM

扬子地台西缘海相火山岩主要分布在海域裂陷构造、碰撞诱发的裂谷盆地－撞击槽及晋宁－澄江期增生的各类地体中，并以中元古代、二叠－三叠纪最为发育。划分了均一玄武岩组合、玄武岩－安山岩－英安岩－流纹岩组合、玄武岩－流纹岩双峰组合、玄武岩－英安岩－流纹岩－粗面岩组合、细碧角斑岩组合等５种火山岩构造－岩石组合类型。提出以地幔动力部分熔融为主的裂陷－拗拉槽型细碧角斑岩组合和以结晶分异为主岛弧、洋岛、洋脊及部分弧后裂谷型细碧角斑岩组合以及岛弧裂谷（拗拉槽）玄武岩－流纹岩双峰组合是最主要的控制铜多金属矿的构造－火山岩石组合类型。研究表明，碱－偏碱性分异良好的富钠细碧角斑岩系内中酸性火山岩发育的喷发中心相—近火口相、火山喷发旋回末期或喷发间隙期的有利岩石组合是形成中—大型铜多金属矿床的重要条件。

Mainly distributed in the marine taphrogenic tectonics, impactogens rift basins induced by collision and accretional terranes of Jinning Chengjiang period, the marine volcanic rocks on the western margin of the Yangtze platform are well developed in Paleozoic, Permian and Triassic.They are classified into five structure rock associations, i.e., homogeneous basalt combination, basalt andesite dacite rhyolite combination, basalt rhyolite bimodal combination, basalt dacite rhyolite trachyte combination and spilite keratophyre combination, in which the spilite keratophyre combination resulting mainly from mantle dynamic partial melting in the taphrogen aulacogen and from crystallization differentiation in the island arc, ocean island, ocean ridge and partial back arc rift as well as the basalt rhyolite bimodal combination in the island arc and rift are most important structure rock combinations controlling copper polymetallic deposits. Studies show that well developed intermediate acid volcanic rocks in the alkaline slightly alkaline well differentiated sodium rich spilite keratophyre sequence (intermediate basic volcanic rock:(Na 2O+K 2O)>4 8%,Na 2O/K 2O>6,or 4%(Na 2O+K 2O)<4 8%,2 5<Na 2O/K 2O<6),the central or nearly central eruptive facies in the paleovolcanic apparatus and the favorable rock combination of the last stage or the invervals of the volcanic eruptive cycle are most important conditions for the formation of medium and large size copper polymetallic deposits.