【作者】 王勇；

【导师】 张荣华； 裴荣富； 胡书敏；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2002， 博士

【摘要】 西秦岭造山带为秦岭造山带的西段，是该造山带一个重要的矿集区。西秦岭地区的研究工作历来是以铅锌矿、金矿的研究为主的。但大量研究表明，矿床的形成与区域构造演化有着非常重要的关系。本文对西秦岭地区的构造演化及其与矿床的形成和分布的关系等问题作了探讨性的研究工作。秦岭的大地构造格局是以南北两条缝合带(商丹带和勉略带)为界与南北两大板块(扬子板块和华北板块)分开，中间则作为一个独立的板块—秦岭微板块。本文研究表明，东西秦岭存在很大的差别，结合前人在东秦岭的研究成果，本文建议将西秦岭独立出来，作为一个独立的地块，称为西秦岭地块。秦岭沉积盆地的范围位于南部志留系和北部李子园群之间，这样，西秦岭是一个由南北基底、中间盆地组成的一个统一的演化体系。晚古生代盆地研究表明，本区盆地具有南浅北深南缓北陡的不对称形态、偏离沉降中心的热活动、向南倾、向北发展的主同生断裂活动等特征，属于一种伸展构造产生变质核杂岩的盆地模式，吴家山背斜核部对应于变质核杂岩的隆升部位。本文将该盆地称为伸展盆地。晚泥盆世开始西秦岭北部发育前陆盆地，从而形成了一个北部前陆盆地、南部伸展盆地的盆地组合。从晚泥盆世后，本区始终处于一种东部不断抬升、盆地不断向西部发展的状态之中。中三叠世，由于古特提斯洋的俯冲，本区盆地内发生了一次强烈的裂陷活动。整个盆地属于一个统一的盆地演化系统。本文建立了该盆地的演化模式并分析了其完整的演化过程。逆冲推覆构造是西秦岭造山的主要构造形式，东部复杂，强烈，南北各有一个独立的逆冲推覆构造系统。西部简单，强度稍弱，是一种单向逆冲推覆构造。造山期后伸展以走滑作用为主，伴随大规模岩浆活动。岩体分布总体受盆地演化期两组同生断裂的控制。本文还讨论了地层元素地球化学微量元素的分布特征，进行了不同时代、不同岩性、不同构造部位等地层中的成矿元素与微量元素含量等的对比工作。研究了逆冲推覆构造和水热事件对元素分布的影响，发现逆冲推覆构造能导致地层中的流体活动引起多数元素向逆冲前锋迁移。在地球化学动力学实验研究的基础上，本文对重点铅锌矿床进行了研究。结果表明：本区重要的变质水热事件可分为三期，流体有地壳和地幔两种来源；厂坝铅锌矿床的形成与深部岩浆和热液流体有关；气体可携带金属从深部进入浅部。并且通过微量元素分析认为变质作用能使含矿元素迁移，有利于矿床形成。伸展盆地的变质核杂岩演化规律、同生断裂活动的特征等方面制着热水沉积型铅锌矿床的形成，中泥盆统地层是有利的赋矿层位。综合分析石炭系和二叠系的沉积特征，表明在盆地西部的石炭系和二叠系地层内形成这种类型铅锌矿的可能性很小。本区金矿按基本成矿机制可以分为构造控矿型和岩体控矿型两种。前者主要是在构造作用下形成，主要形成于强构造变形区。后者主要与岩体有密切的关系，受岩体侵位裂隙控制，区域分布与岩体分布特征相似。总结起来，金矿的形成主要是受印支期造山作用及印支—燕山期造山期后伸展作用控制。总体来说，本文系统地研究了从盆地到造山至造山后的伸展整个过程中的构造演化、地球化学特征、成矿等几个重要的课题，取得了一些创新性的成果，同时也为西秦岭地区的基础研究、地调及找矿工作提供了一种新的思维和研究视野。更多还原

【Abstract】 The west Qinling orogenic belt is an important mineralization area in Qinling oregen. Itsformer research works were focused on the Pb-Zn、Au deposits. But all researches showed that theore formation had very important relationship with the evolution of the regional tectonics.Established in scientific research project, this paper did some researches on some important issuessuch as the tectonic evolution of the west Qinling and the relationship between it and the oreforming processes and distribution of these deposits.Qinling microplate was a separated plate between Yangtze plate and North China plate,separated by two main suture zones—Shangdan zone and Mianlue zone. This paper indicated thatthere existed big differences between the east an the west Qinling. So this paper suggested to treatthe West Qinling as an separated geological unit and name it "the west Qinling block".The sedimentary basin in the west Qijnling lied between the Silurian in the south andLiziyuan group in the north. The west Qinling is an unified system composed of the north andsouth basement and the sedimentary basin in the central.This research on the late Paleozoic basin indicated the characteristics of the basin. The basinhad an asymmetry shape as deep and steep in the north and shallow and gentle in the south. Themain growth faults had south forward direction of dip and north forward development. The heatactivity occurred not in the sedimentary center but in the shallow and gentle slope. The basinbelonged to a model of extensional structure producing Metamorphic core complex. The locationof metamorphic core complex was corresponding to the core of Wujiashan anticline. In this paper,we call this kind basin extensional basin. From the upper Devonian, the western part of the westQinling developed foreland basin and from then composed a basin combination of two kinds ofbasins—foreland basin in the north and extensional basin in the south. After late Devonian, theeast part of the west Qinling uplifted constantly and the basin had a west forward constantlydevelopment. In middle Triassic, there took place a violently rift faulting because of subduction bythe old Tethys. The west Qinling basins in all periods belonged to a whole basin evolution system.This paper established the model of basin evolution and analyzed the whole process of theevolution.The nappe and thrust was the main structural pattern of the oregenic movement of the westQinling. The structure in the east part was complex and violence and existed two separated nappeand thrust systems respectively formed in the north and south area. The structure in the west wassimple and a little feeble. There formed a nappe and thrust with a single direction. Followed bycosmically magmatic activities, the strike-slip movement was the main pattern of the postorogenicextension. The distribution of the rock bodies was controlled by two group of growth faultsformed in the period of basin evolution.This paper also discusses the distribution characteristics of the ore-forming elements and thetrace elements, and carries through the contrast work of the content of elements distributed instrata of different periods and different lithology and also of different tectonic positions. Thispaper also researches the affect of nappe and thrust and hydrothermal events to the distributionelements and found that the nappe and thrust could make fluid in the strata move and then carrieda lot of elements toward the forebelt of thrusting. Based onthe experiments of geochemical kinetics, this paper did some research on the mainPb-Zn ore deposit and achieved some important conclusions. In the west Qinling, the mostimportant metamorphic events included three periods. The metamorphic fluid had two originrespectively became from the crust and the mantle. The forming of Changba Pb-Zn ore depositwas related to the magma and hydrothermal fluid in the deep.The vapor could carry metals fromthe deep into upper crust. The regional metamophism and water-heat process could make theore-forming elements move and so they are propitious to form deposits.Some aspects, such as the regularity of metamorphic core complex evolution and thecharacteristics of the growth fault activity in the extensional basin, controlled the forming of theheat-water sedimentary Pb-Zn deposits. This study shows that there is little possibilities to findthis kind of Pb-Zn deposits in the Permo-Carboniferious strata in the west of basin. The possibilityexisted in Devonian, the east part of basin.There were two kinds of gold deposits in the west qinling according to the basic ore-formingmechanism: structure-controled Au-deposits and rock body-controled Au-deposits. The formerwas mainly formed in the tectogenesis and distributed in the violent tectonically deforming area.The latter was mainly related to the rock bodies and was controlled by the structure formed in theintrusion of the rock bodies. Its distribution character was the same of the rocks. In a word, theforming of gold deposits was controlled by the oregenesis in Yinzhi period and thepost-orogenesis extension in Indosinian-Yanshanian period.In sum, this paper systematically investigates some important projects as the tectonicevolution, hydrothermal events, the geochemistry and the mineralization in the whole processfrom basin formation to orogenesis and then to the post-orogenesis extension. It produced a newthought and a new research direction to the research works on the west Qinling, and it wouldprobably promote the geological work on the west Qinling.更多还原