辽东三股流岩体是否为五龙金矿成矿提供必要的能量?

Whether Sanguliu Granite Provided Energy Required for Forming Wulong Gold Deposit,Liaoning Province,China?

辽东地区五龙金矿是华北克拉通东部一个典型的石英脉型金矿床,其成矿过程尚存争议.多种证据表明五龙金矿成矿流体属于岩浆热液,成矿时代又与距离较近的三股流岩体的侵位年龄接近,因而有一种观点认为二者密切相关.目前尚未有充足的地质证据表明三股流岩体释放了五龙金矿成矿所需要的含金岩浆热液,那么三股流岩体是否为其提供必要的能量呢?利用现有的地球化学和地球物理数据,建立三股流岩体仅作为热源驱动大气降水和释放岩浆热液的对流数值模型,模拟三股流岩体周边的流场和温度场.数值模拟结果表明,三股流岩体自侵位后可在其周边1 km范围内形成300℃以上的热场,并维持数十万年,因而有利于形成岩浆热液型矿床.然而,五龙金矿所在的位置受三股流岩体侵位后的热场影响不显著.如果三股流岩体释放了充足的岩浆热液,岩浆热液可在岩体边缘和接触带形成热液蚀变和金矿化,这与现有的地质证据不符.故五龙金矿可能与三股流岩体没有直接成因关系,而金成矿热液来源仍需深入研究.

The Wulong gold deposit located in Liaoning Province is a typical vein-type gold deposit in the eastern part of the North China craton,but how this large-scale gold deposit formed remains controversial.This deposit was interpreted to be genetically related to the Sanguliu granite because they are spatially close and have close chronological ages and the mineralizing fluids have a magmatic-hydrothermal origin.There is no sufficient evidence supporting that the Sanguliu granite provided the gold-bearing magmatic-hydrothermal fluids required for forming the Wulong deposit,so did the former provide sufficient energy for the latter?In order to answer this question,numerical modeling of heat-driven convection of meteoric water and magmatic-hydrothermal fluids released by the Sanguliu granite was built based on its geochemical and geophysical characteristics to simulate the evolution of fluid flow and temperature after emplacement of the granite.Numerical results indicate that the temperatures within 1 km of the Sanguliu granite were elevated to over 300℃for hundreds of thousands of years.This long high temperature filed favors formation of magmatic-hydrothermal deposits.In contrast,the position of the Wulong deposit received insignificant energy from the Sanguliu granite.If magmatic-hydrothermal fluids were released from the Sanguliu granite,those magmatic-hydrothermal fluids should have caused alteration and minerlization at the granite margin and the contact between the granite and its wallrock.However,these phenomena have not been identified in the field.Therefore,there is probably no genetic relationship between the large-scale Wulong deposit and the Sanguliu granite,and further investigations are needed to identify the source for Au-mineralizing fluids.