陕西凤太矿集区铅锌矿床的成矿模型及其找矿意义

A new metallogenic model and its significance in search for Zn-Pb deposits in Fengtai(Fengxian-Taibai)polymetallic ore concentration area,Shannxi Province

陕西凤太(凤县-太白)矿集区是南秦岭铅锌金多金属成矿带的重要组成部分,区内发育7个大中型铅锌矿床以及许多小型矿床(点)。关于铅锌矿床成因前人提出了多种观点,这些成因认识的根本分歧在于是同生成矿还是后生成矿,是一期成矿还是两期成矿。多年来笔者在凤太矿集区开展了比较全面的研究工作,文章综合这些研究成果,并结合近十年来有关的区域地质、矿产研究和找矿勘查工作等方面的新进展,系统论述了铅锌成矿地质特征、控矿因素、成矿流体和成矿元素来源,厘定成岩成矿时代和成矿动力学背景,建立成矿模型,并提出新的找矿方向。笔者认为凤太矿集区铅锌矿床形成于晚三叠世秦岭造山运动的后碰撞阶段,是区域大规模构造变形变质-岩浆作用-流体活动的产物,是同一期成矿事件中后生成矿流体在不同构造扩容空间充填交代形成不同矿化类型铅锌矿体,共同组成了一个多源流体成矿系统。根据成矿模型,提出了中泥盆世古道岭组灰岩的内部及灰岩与中酸性岩体接触带附近是今后深部找矿勘查的新目标。

The Fengtai(Fengxian-Taibai)polymetallic ore concentration area in Shaanxi Province is an important part of the South Qinling Zn-Pb-Au polymetallic metallogenic belt,and there are seven large and medium-sized Zn-Pb deposits and lots of small deposits developed in this ore concentration area.Various views on the ore genesis of the Zn-Pb deposits have been proposed in previous studies,and the main controversies of these views of genesis are whether the Zn-Pb deposits were syngenetic or epigenetic,and whether they were formed in one or two mineralization episodes.The authors carried out comprehensive research work in Fengtai ore concentration area for years,and here synthesizes the achievements of these work,combining the new progress in regional geology,ore deposits,and prospecting work during the past decade,for the purpose of①depicting systematically the Zn-Pb mineralization characteristics,including ore geology,ore-controlling factors,sources of ore-forming fluids and elements,②clarifying the ages of igneous rocks and Zn-Pb deposits,and the geodynamic setting of the mineralization,③establishing proper metallogenic model,and④proposing new prospecting targets.The authors hold that Zn-Pb deposits in Fengtai ore concentration area were formed during the post-collision stage of the Qinling orogenic belt in Late Triassic,being the products of large-scale tectonic deformation,dynamic metamorphism,magmatism,and hydrothermal fluid activities in this area.The Zn-Pb deposits were developed in a single metallogenic episode,and were formed by filling and replacing action of epigenetic ore-forming fluids within different structural dilational spaces in host rocks to form different types of Zn-Pb ore bodies,thus comprising a multi-sourced hydrothermal ore system.It is held that the interior of the limestone of the Middle Devonian Gudaoling Formation and the vicinity of the contact zone between the limestone and the felsic-intermediate intrusion are the new targets for deep prospecting work in the future.