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秦岭造山带区域矿床成矿系列、构造—成矿旋回与演化

Regional Minerogenetic Series, Tectono-Minerogenic Cycles and Evolution in the Qinling Orogen

【作者】 王平安

【导师】 裴荣富; 毛景文; 陈开礼;

【作者基本信息】 中国地质科学院 , 矿床学, 1997, 博士

【摘要】 秦岭造山带具有近30亿年的长期、复杂演化历史,是世界著名大陆造山带之一,也是当今大陆地球科学研究的热门地区之一。此造山带为我国一个重要的构造—成矿带,蕴藏有极其丰富的矿产资源,是研究区域矿床成矿系列的理想地区。作者根据矿床成矿系列学术思想的基本原理,结合秦岭造山带构造演化和成矿演化的具体实际,并根据大量野外地质调查及室内测试和大量学习、吸收前人工作、研究成果,对秦岭造山带区域矿床成矿系列进行了较为全面的综合研究,取得了以下10个方面的主要认识和成果:(1)提出区域矿床成矿系列研究的新思路,即把由时间因素所决定的区域大地构造背景与主要成矿地质作用类型作为建立和划分区域矿床成矿系列的依据,如中、新元古代扬子地块北缘陆缘裂谷和扩张海槽—洋盆演化过程中,由深源岩浆侵入和海相火山(沉积)作用所形成的一组Fe、Cr、Mn、Nb、Ag、Au、Cu、V (Ti)、石墨和硫多金属矿床归入同一个区域矿床成矿系列中,把它们看作是在秦岭造山带地质历史中由陆缘裂谷向多岛小洋盆转变过程中,以张裂背景下幔源岩浆活动为内在联系的构造—岩浆活动的必然产物。突破了原来将三大基本地质作用做为划分和建立矿床成矿系列主要依据的标准。(2)在前人研究基础上,首次对秦岭造山带的区域矿床成矿系列进行了比较全面、系统的研究,建立了18个矿床成矿系列、28个亚系列及其中4个典型系列的区域成矿模式,丰富和深化了矿床成矿系列的研究内容,拓宽了研究领域,增加了研究实例,也填补了本区区域成矿规律方面的一项研究空白。(3)划分秦岭造山带的构造—成矿作用演化历史为六个旋回,即:①新太古代—古元古代早期构造—成矿旋回,②古元古代早期构造—成矿旋回,③中、新元古代构造—成矿旋回,④新元古代—早古生代构造—成矿旋回,⑤晚古生代构造—成矿旋回,⑥中、新生代构造—成矿旋回。(4)开展了区域矿床成矿系列成因研究的探索,指出秦岭造山带各区域矿床成矿系列都有其特定的、与地质历史发展相联系的固有起因;区域矿床成矿系列的成因应从秦岭造山带演化历史中去寻找答案。(5)通过秦岭新元古代区域变质矿床成矿系列的研究,指出秦岭晋宁期构造运动性质以拼合碰撞为主,形成高压亚系列和中低压亚系列;结合对松树沟铬铁矿矿床的研究,认为秦岭板块构造体制肇始于中元古代晚期。(6)前人认为南秦岭泥盆系碳酸盐岩容矿的铅锌矿床为泥盆纪同生沉积成因,锑汞矿床为燕山期热液成因。本文通过对邓家山—磨沟铅锌矿床和公馆—青铜沟锑汞矿床的研究,认为前者应属典型的沉积—改造成因矿床,而后者应以后生为主;铷锶法成矿年代测试分别得到263±9 Ma和250±14 Ma两个年龄值,反映它们主要的成矿时代应为印支期,初始锶同位素比值表明其成矿物质均为地壳来源。(7)对西秦岭南亚带大水式金矿床进行了较为全面的矿床学、年代学、稳定同位素地球化学、流体包裹体和构造控矿方面的研究,结合对白龙江复背斜核部的现代温泉泉华物质组成和稳定同位素测试,认为大水式金矿床为与燕山期浅成—超浅成中酸性岩浆活动有关的热泉成因,提出同成矿期“热水岩溶”容矿的新认识,并建立了大水式金矿床的热泉成因模式。(8)探讨了成矿演化与构造演化的内在关系,划分秦岭造山带构造—成矿作用过程为陆块或板块的开裂、碰撞拼合、陆内滑脱—推覆—拉分—断陷和相对稳定环境四个类型,每一种过程都经历过不止一次。成矿作用具有长期性、多期性、间断性和旋回性特征。最早的矿化发生在25亿年前,最新的为第四纪。许多矿床是在多期成矿作用之下形成的,叠加和改造成矿作用具有突出和普遍意义。指出秦岭中、新元古代和中、新生代两个大的成矿高峰期,分别对应着秦岭造山带两次最重要的构造体制转化时期:一次为由陆缘裂谷向板块构造体制的转化时期,另一次为由板块构造体制向陆内造山体制转化的时期。前一次的成矿作用主要与分异较差的幔源岩浆活动和大陆裂谷—海相火山—洋壳超基性岩浆活动有关,后一次的成矿作用主要与深断裂和大规模推覆—伸展构造机制下幔源碱性—中酸性岩浆侵入和陆相火山活动及陆壳深熔型中酸性岩浆活动有关。(9)通过对不同种类的各种成因类型的矿床的分布特征、时空演化及区域成矿系列的构造—成矿旋回和区域成矿规律的研究,从十个方面论述了秦岭造山带的区域成矿规律。特别是发现秦岭造山带构造—成矿作用的规模和强度在造山带南、北和东、西之间具有振荡性交替演化的特征和规律,认为它不仅对应着构造活动强度的振荡性交替演化,在更深层次上还可能反映秦岭地壳活动和深部地幔物质运动的信息,从而深化了秦岭造山带区域成矿规律及成矿学与大地构造学相结合的理论认识水平,同时对提高区域矿产远景评价和找矿预测的科学性具有实际价值。(10)首次编制了“秦岭造山带主要矿床成矿系列图”,并编写了约13万字的说明书。共编入内生、外生及各种复合成因矿床(点)411个,涉及的矿种有金、银、铜、铅、锌、汞、锑、钼、钨、铁、镍、钛、铬、锰、钒、铀、稀有、稀土、铝土矿、耐火粘土、砷、硫、磷、重晶石、毒重石、金红石、膏盐、石棉、宝(玉)石、萤石、石墨、红柱石、蓝晶石、钾长石、白云母、煤、石油等,包容了除建筑材料及冶金辅助材料之外的所有各矿种。

【Abstract】 Qinling orogen, a famous continental orogen in the world with a long and complexgeologic history, is one of hot points for studies on continental geosciences, and also is animportant tectono-minerogenic belt enriched in mineral resources, which makes it an idealdistrict for the study of regional minerogenetic series(RMS). Based on the principles ofminerogenetic series, integrated with detailed analysis of tectonic and metalogenic evolution, theregional minerogenetic series(RMS), tectono-minerogenic cycles and evolution of the Qinlingorogen are studied. The main results and achievements are as follows:(1) The basis and criterion for differenting and establishing regional minerogenetic series(RMS) are regional tectonic settings and major mineralizing process (or genetic type) decidedby time factor, rather than the three basic geological agents.(2) 18 RMSes, 28 sub-RMSes and 4 regional minerogenetic models of typical RMSes areestablished in this paper.(3) More than 400 mineral deposits in the Qinling mmerogenic belt were formed in the 6tectono-minerogenic cycles(TMC):①Ar-Pt11 TMC,②Pt1 TMC,③Pt2-Pt3 TMC,④Pt3-Pz1TMC,⑤Pz2 TMC, and⑥Mz-Kz TMC.(4) Every RMS in the Qinling orogen has its specific origin connected with the specialstage in the evolutionary history.(5) Based on the study of RMS related to the Pt3 regional metamorphism (the V RMS) andthe Songshugou chromite deposit associated with ophiolite (belong to theⅢRMS), the authorsuggests that the Qinling orogen began to be part of a plate regime m the end of the Middle tothe Late Proterozoic.(6) The Pb-Zn deposits in the carbonate rocks of the South Qinling zone were mainlyformed by hydrothermalism in the Early Mesozoic, two Rb-Sr isotopic ages from theDengjiashan-Mogou Pb-Zn deposit in Gansu province and the Gongguan-Qingtonggou Sb-Hgdeposit in Shanxi province are 263±9Ma and 250±14Ma, respectively.(7) The Dashui-type gold deposits in the south sub-zone of the western Qinling folded beltwere formed by hot-spring related to the Yanshanian alkali-intermediate to acidic pyrogenesis,most of the ores are actually synore ’hot water karst’ formed by ore-forming fluids, hosted in theDevonian to the Triassic carbonate rocks, and a hot-spring metallogenic model is established inthis paper.(8) The relationship between evolution of metallogeny and tectonics is grouped into 4process-types:①rifting and splitting of land blocks or plates,②subduction-collision betweenland blocks or plates,③intracontinental postorogenic detachment, nappe, pull-apart and rift- faulting and④relatively stable environment process-type. Each process-type took place for atlest twice. Metallogeneses in this area is characterized by inheritance, polyphasees, polysourcespolygeneses and cyclicity. There are two important metallogenic periods: one is the MiddleProterozoic-Early Paleozoic during which the metallogenetic processes are related to thespreading rifting, the minerogenetic series of deposits are related genetically to the basic-ultrabasic intrusions and the bimodality pattern marine volcanism resulting from spreadingrifting and deep faulting; the other, related to the intracontinental subduction, is the Mesozoic,the minerogenetic series of deposits are related genetically to the intermediate-acid intrusionsand terrestrial volcanism, generated by postorogenic tectonism.(9) The tectono-mineralization associated with volcanism and splitting would haveexperienced a vibration between the north and south Qinling orogen through out the geologicalhistory.(10) "Minerogenetic Series Map of Main Deposits in the Qinling Orogen" (Scale: 1/1 000000) is drawn up, and its directions about 130 000 Chinese characters with 411 mineral depositsis also compiled.

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