夹皮沟金矿带韧性剪切变形中的水岩反应及物质组分变化规律

FLUID ROCK INTERACTIONS AND CHEMICAL COMPONENTS VARIATIONS DURING DUCTILE DEFORMATION IN THE JIAPIGOU GOLD BELT

夹皮沟金矿北西向剪切带存在着长英质和镁铁质两类糜棱岩系列岩石，韧性变形中伴随的大量流体与糜棱岩之间发生了强烈的水岩反应：斜长石绢云母化和钠化，暗色矿物绿泥石化，以及大范围强烈的碳酸盐化。韧性剪切变形为一近等体积过程（ｆｖ≈１）．随韧性剪切作用增强，两类糜棱岩系列岩石中ＳｉＯ２均带出，而ＣＯ２和Ｈ２Ｏ等挥发分及Ａｕ、Ｓ等成矿元素明显富集。释放出的ＳｉＯ２呈胶体态赋存在流体中，并吸附Ａｕ等成矿物质，后在脆性构造中重结晶为含金石英脉。流体包裹体研究显示成矿流体主要由大气降水组成，其温度、压力和盐度分别为２４５～２９２℃、９５．４～１３１．７ＭＰａ和１２．８８～１６．３３ｗｔ％ＮａＣｌ。

Two mylonite series rocks, felsic and mafic, have been recognized in the NW striking shear zone of the Jiapigou gold mine During the ductile deformation, the accompanying fluid interacted intensively with the mylonite series rocks, resulting in sericitization of plagioclases, chloritization of dark minerals and extensive carbonatization The ductile dcformation was approximately an isovolume process ( f v≈1) Duing the deformation, SiO 2 in rocks of the two mylonite series was depleted, while volatile components, such as CO 2 and H 2O, and some ore forming elements, such as Au and S, were enriched obviously The SiO 2 released from fluid rock interactions occurred in the form of colloid, absorbed gold in the fluids, and then recrystallized to form auriferous quartz veins in the brittle structure Fluid inclusions studies show that the ore forming fluid was composed mainly of meteoric water with its temperature, pressure and salinity being 245￣292℃, 95.4￣137.7 MPa and 12.88￣16.33wt% NaCl respectively