大别造山带的流体系统与成矿作用

大别山是大别造山带的主体部分,流体活动贯穿于俯冲－碰撞－折返整个造山过程。印支期俯冲－碰撞阶段的流体,以具高挥发份、高盐度为特点,流体中保留有原岩在地表时的天水－岩石以及超高压变质过程中的地幔流体－岩石同位素交换的信息。燕山期折返隆升阶段的流体是大量天水与深部流体发生混合的产物,流体中盐度降低,但水－岩相互作用增强。大别造山带的流体系统可称为“天水与深部流体混合系统”,并可分为流体富集区、流体贫乏区和流体排泄区三个部分。成矿作用主要发生在流体富集区。

Fluid System and Mineralization of the Dabie Orogenic Belt

Fluids were active in the whole process of orogenesis of the Dabie orogen. Fluids of the Indosinian subduc-tion and collision stages were characterized by high contents of volatile components and high salinity. Evidence from oxygen isotope values indicates that the protoliths of the ultra-high pressure metamorphic rocks underwent pre-subduction interaction with meteoric water at the surface and were subsequently affected by mantle fluids during subduction, collision and progressive metamorphism. The deep-source fluids were mixed with large quantities of meteoric water during exhumation and uplifting of the orogen, resulting in salinity reduction of the fluids and intensification of water/rock interactions in the Yanshanian stage.Fluids of the Dabie orogenic belt could be considered to have formed a mixed meteoric and mantle fluid system. Based upon the behaviour of fluid activity, the Dabie orogen has been divided into the fluid-rich, fluid-poor and fluid-draining regions. Gold deposits are located mostly within the fluid-rich region.