西秦岭西成和凤太矿集区三叠纪多金属成矿作用特征、规律及找矿方向

近十几年来,在西秦岭地区陆续开展的找矿勘查、成矿研究和同位素年龄精测等工作,取得了许多找矿新发现和成矿理论新认识,尤其是获得了一批精细的成岩成矿年龄数据,逐渐揭开了区内三叠纪多金属成矿作用的面纱,显示出三叠纪成矿作用的普遍性和多样性,并指示了巨大的成矿潜力。在西秦岭东段的西成和凤太矿集区中,三叠纪发育的矿种主要包括铅锌、金、银、铜,其次还有钨、钼、铁等,其中铅锌和金是区内的优势矿产。最新的研究进展表明:区内多金属矿床的年龄为231~197 Ma,集中于220~200 Ma;岩浆岩的年龄为248~195 Ma,集中于230~200 Ma。多金属成矿作用与岩浆活动在时间上相耦合,二者的峰期为220~210 Ma。矿床类型主要有与岩浆活动和变质作用有关的热液充填交代型,与岩浆热液成矿系统有关的斑岩型、矽卡岩型和云英岩型等。构造活动及其产物是多金属成矿作用的主导控矿因素,各种类型、不同尺度的构造直接控制了各类矿体的产出位置、形态、产状和规模大小等。区内的多金属成矿作用形成于秦岭造山带印支期造山过程的后碰撞阶段,是晚三叠世区域广泛而强烈的变形变质-岩浆活动-流体耦合作用的产物。基于研究区的成矿地质条件、成矿作用特征、矿床成因、控矿因素和成矿规律,初步提出进一步的找矿方向,以期助推区内今后的深部找矿勘查工作取得新突破。

Characteristics and Metallogeny of Triassic Polymetallic Mineralization in Xicheng and Fengtai Ore Cluster Zones,West Qinling,China and Their Implications for Prospecting Targets

In recent a dozen years,the mineral exploration,research on mineralization and precise measurement of isotopic age have been carried out continuously in West Qinling,which have achieved a lot of new discoveries in exploration and some new understandings of metallogeny.Especially,a quantity of high accuracy isotopic age data of igneous rocks and polymetallic mineralization,have gradually uncovered the veil of Triassic polymetallic mineralization in West Qinling,showing the universality and diversity of Triassic mineralization,and indicating the huge metallogenic potential.Xicheng and Fengtai ore cluster zones,located in the eastern part of West Qinling,where the predominant Triassic minerals of Pb-Zn,Au,Ag and Cu are well developed with lesser minerals of W,Mo and Fe;and Pb-Zn and Au are the superior mineral resources in the ore cluster zones.The latest research achivements show that the ages of the polymetallic deposits in the area range from 231 Ma to 197 Ma,concentrated in 220-200 Ma;the ages of magmatic rocks range from 248 Ma to 195 Ma,concentrated in 230-200 Ma.The polymetallic mineralization and magmatic activity are temporal coupling with the peak of 220-210 Ma.The main types of polymetallic deposits include the hydrothermal filling and replacing ore deposits related to the magmatic activity and metamorphism,the porphyry,skarn and greisen ore deposits associated with magmatic-hydrothermal mineralization system.The tectonic activity and its product are the dominant ore-controlling factors of polymetallic mineralization,and the structures of the various types and different scales directly control the occurrence,form,attitude and size of the orebodies.The polymetallic mineralization in the area developes in the post-collision stage of Indosinian orogenic process in Qinling orogeny,which is the product of the extensive and intense coupling process of deformation and metamorphism,magmatic activity and fluid flow in Late Triassic.Based on the metallogenic geological conditions,mineralization characteristics,ore genesis,ore-controlling factors and ore-forming regularities,some further prospecting targets are suggested preliminarily to promote the prospecting and exploration works at depth in this area to make new achievements.