河南省前河构造蚀变岩型金矿的矽卡岩化及其找矿意义

Skarnization of Qianhe structural alteration type gold deposit in Henan Province and its ore-prospecting significance

前河金矿床位于秦岭造山带内,矿体赋存于低绿片岩相变质的中元古界熊耳群安山质火山岩地层中,严格受断裂控制。通过对前河金矿深部和外围找矿工作发现,石家岭矿段发育有矽卡岩化岩石,主要发育于合峪花岗岩体北部赋存金矿体的F4断裂附近,围岩是低绿片岩相的安山质火山岩,并且在前河大桥附近有石榴子石脉产出;岩相学特征及电子探针成分分析表明,该矽卡岩化岩石由钙铁石榴子石、透辉石-钙铁辉石、绿帘石、绿泥石、阳起石、石英和方解石等矿物组成,经历了干矽卡岩阶段、湿矽卡岩阶段以及石英硫化物阶段这一典型演化过程;褐帘石电子探针成分和穆磁铁矿具赤铁矿的假象表明,湿矽卡岩阶段具有还原性特征。因此,前河金矿矽卡岩化可能由附近合峪花岗岩岩浆热液交代形成。

The Qianhe gold deposit in the Xiong＇ ershan area of Henan Province was previously regarded as a hydrothermal alteration-type gold deposit. Gold mineralization is strictly controlled by fractures and hosted in metaandesitic rocks of the Middle-Proterozoic Xiong＇ er Group which has undergone low-greenschist facies regional metamorphism. It is notable that some skarn minerals such as garnet, diopside, epidote, chlorite and actionlite were locally discovered in the Shijialing segment of the Qianhe gold deposit in recent years, suggesting typical skarn-forming processes of prograde, retrograde and sulfide stages with relative reduction characteristics. In addition, the wall rocks of Qianhe skarn are meta-andesitie rocks rather than carbonates. The Qianhe skarn minerals might result from the interaction of hydrotherrnal fluids derived from the near-by Heyu granite plutonism with meta-andesites of the Xiong＇ er Group, and their development is valuable to the understanding of Qianhe gold mineralizeation as well as to the follow-up exploration in this area.