中条裂谷的幔柱构造与成矿

Mantle plumes and ore genesis in Zhongtiaoshan area

中条山地区的地球物理场具有"三低一高"(低波速、低密度、低黏度及高地热异常)特点,变质核杂岩中赋存有科马堤岩并具"双层"结构,火成岩呈"双峰"状态,变质期的古地温为522～608℃,压力0.3～0.73GPa,地热梯度23℃/km,表明中条山地区为新太古代—元古宙的大陆裂谷-地幔热柱构造。其成矿作用存在着"四代同堂"的成矿模式,成矿期与岩浆侵入期的时差甚小;成矿空间上,大多数矿床沿着裂谷内两组断裂呈X型"对称式"展布,有益元素矿物组合及成矿温度自中心向周围呈有规律降低趋势。由于在新太古代以前,富铜的扬子板块俯冲至华北板块之下,促使中条裂谷的地壳加厚,形成丰富的成矿物质场,因为地幔热柱脉动式隆升,热液在运移过程中不断萃取地壳的铜质,故成为区域内独特的铜矿集中区。

Geophysics characterized by low seismic velocity, low density, low viscosity and high geother- mal gradient, metamorphic core complex with komatiite and a two-layer structure pattern, and occurrence of large bimodal igneous province and paleo-geothermal features estimated at 522-608℃, 0.3-0.73 GPa and 23℃/kin indicate that Neoarchean-Proterozoic mantle plume were developed in the Zhongtiaoshan re- gion. Metallogeny here shows co-existence pattern of four ore generations. Temporally, the ore formation is close to magma intrusion. Spatially, most deposits occur symmetrically along two crosscutting sets of faults in the rift zone. Ore-forming elements and mineral components and the ore-forming temperature de- crease outward from the center. Before Neoarchean the Cu-rich Yangtze plate underthrusted under North China plate leading to thickening of crust at Zhontiaoshan rift area and abundant ore material field. Pulse rising of the mantle plume carried hydrothermal fluid upward and extracted Cu and Zhongtiaoshan area be- eames the copper ore deposit-clustered area.