山东沂南金-铜-铁矿床成矿条件分析——兼论不整合面的控矿作用

山东沂南金-铜-铁矿床中与成矿有关的岩体为燕山期多期次浅成侵入的钙碱性杂岩体，岩性主要为闪长玢岩类和花岗斑岩类，属相对富含硅质、碱质和磁铁矿并通常与氧化型含金矽卡岩有关的侵入岩系列。新元古界一寒武系碳酸盐岩与碎屑岩的频繁互层，为含矿气水热液的运移和顺层交代提供了良好的围岩条件，在靠近岩体接触带部位形成了多层矽卡岩矿体。区域性断裂控制了含矿岩体的侵位，而接触带、捕虏体、层间破碎带以及不整合面等构造控制了矿体的空间定位。成矿在中低压力的中浅成至浅成条件下进行，主成矿阶段的含矿流体具有中高温、高盐度的特点，流体的沸腾可能是金-铜-铁等成矿物质大量沉淀的主要原因。接触带的矽卡岩型Au—Cu—Fe矿化与内接触带的斑岩型Cu—Mo矿化、外接触带的热液充填一交代型Au—Cu矿化，以及岩体边部的隐爆角砾岩型Au—Cu矿化一起，构成了一个中酸性岩浆-热液成矿系统。作为一种容易失稳的构造薄弱带和地球化学屏障，不整合面极易产生破碎和滑脱，从而有利于岩浆及其所分泌的含矿气水热液的贯入和成矿，这是沂南矿床中新发现的一种具有重要找矿前景的控矿构造类型。

Ore-forming Conditions and Significance of Unconformity in the Mineralization of the Yi'nan Au-Cu-Fe Deposit, Shandong, China

The Au-Cu-Fe mineralization in the Yi'nan deposit was related to the multiple-intruded,calc-alkaline,shallow Yanshanian complex plutons of porphyritic dioritoid and granotoid.The intrusions are relatively silicic,alkalic,and magnetite-bearing and are broadly similar to the reduced,Au skarn-related plutons.The Neoproterozoic to Cambrian wall rocks of carbonates interbeded with clastic rocks provided a favorable condition for the transport and metasomatism of ore-bearing hydrothermal fluids,which formed multiple layers of skarn orebodies at the contact zone.The emplacement of ore-forming intrusions was controlled by regional faults,while the skarn orebodies were controlled by the structures of contact zones,carbonate xenoliths,interlayer fractures and unconformity surfaces.The mineralization took place in a medium to shallow environment with moderate to low pressures.The hydrothermal fluids during the major mineralization stage were high saline with moderate to high temperatures.Boiling was most probably responsible for the deposition of Au,Cu and Fe.Mineralization of skarn-type Au-Cu-Fe at the contact zone,porphyry-type Cu-Mo within the intrusions,hydrothermal filling-and replacement-type Au-Cu in the wall rocks as well as locally developed breccia-type Au-Cu constitutes a complex magmatic-hydrothermal metallogenic system.As a weak tectonic zone and a geochemical barrier,the unconformity surface is ready to be fractured and glided during later tectonic activity and magmatic intrusion,thus resulting in the filling and mineralization of magmas and related hydrothermal fluids.It is an important ore-controlling structure recently discovered in the Yi'nan deposit.