安徽沿江地区燕山期火成岩成岩成矿地质背景

安徽沿江地区位于长江中下游Cu,Fe成矿带的中段。通过区内变质基底类型、时代和地球物理、地球化学资料等综合研究,证明该区存在一元古宙基底缝合带,即“古岩石圈尺度不连续”,燕山期的强烈构造-岩浆-成矿活动是“古岩石圈尺度不连续”的“再活化”的表现。燕山期火成岩岩石构造组合以及岩浆作用有关的矿种组合表征它也是深达地幔的岩石圈尺度不连续,实质上岩石圈尺度不连续为区内的重要控岩、控矿构造,而燕山期挤压加厚环境中形成的高钾钙碱性系列火成岩及对应的Cu,Au组合、橄榄安粗岩系列火成岩及对应的Fe,S组合是岩浆成矿受壳幔相互作用和幔源物质贡献等因素控制的直接反映。同时,文中还利用了Nd-Sr同位素示踪体系对区内中、新生代地幔类型进行了初步研究,论证了中-新生代岩石圈/软流圈发生了灾变事件,区内晚中生代属富集型地幔(EMⅡ),火成岩为富集型地幔(EMⅡ)与亏损地幔(DM)或下地壳(IC)相互作用的结果,新生代则成为亏损型地幔(DM),这种地幔类型的变化是导致中国东部燕山期大规模岩浆成矿作用和岩石圈减薄的

PETROGENIC AND METALLOGENIC SETTINGS OF AREA ALONG YANGTZE RIVER IN YANSHANIAN,ANHUI PROVINCE

The area along Yangtze River of Anhui Province is the central segment of the iron-copper-met-allogenesis belt of the Middle-Lower Yangtze River. The synthetical studies in this paper deal with the types and chronology of the metamorphic basement, the data of geophysical and geochemical researches. It is proved that there is a basement suture zone of Proterozoic era in the area along Yangtze River metal-logenic belt in Anhui Province, known as the "old lithospheric discontinuities". The strong tectono-magma-metallogenesis in Yanshanian stage is the reactivation of the "old lithosphere discontinuities". The character of igneous petrotectonic assemblage and deposit associations related with magmatism in Yanshanian stage also proved that it is a lithosphere scale discontinuity deep to the mantle,and it is the major structure controlling the petrogenesis and metallogenesis in this area. The high-K calc-alkaline series igneous rocks which formed in the compressive thickened environment in Yanshanian stage and the parallelism Cu, Au association, the shoshonite series igneous rocks and the correspondent Fe, S association, directly indicate that the magmatic metallogenesis is controlled by crust-mantle interaction and the contribution of mantle material. In addition, this paper deals with the mantle types in Mesozoic and Ce-nozoic based on the Nd-Sr isotope tracer, and with the catastrophic events of lithosphere/asthenosphere in Mesozoic and Cenozoic. There was the enriched mantle (EM Ⅱ) in Later Mesozoic, and the igneous associations were formed by the interaction the enriched mantle (EMⅡ) with the depleted mantle (DM) and the lower crust (LC). And there was the depleted mantle (DM) in Cenozoic. The variations in the types of mantle are the key factors which lead to the large scale magmatic-metallogenesis and lithosphere thinning in Yanshanian stage in eastern China.