扬子克拉通前寒武纪基底对中生代大面积低温成矿的制约

大面积低温成矿主要见于扬子克拉通和美国中西部,且扬子克拉通比美国中西部具有更多的矿床类型,在全球极具特色,是建立大面积低温成矿理论的理想区域。前人对扬子克拉通中生代大面积低温矿作用进行了较系统的研究,在矿床地质特征、矿床物质组成、成矿流体特征、成矿时代和成矿动力学背景等方面,已取得重要进展。进一步的研究表明,扬子低温成矿域不同矿种的矿床组合(Pb-Zn、Au-Hg-Sb-As、Au-Sb等)在地理位置上是分区产出的,而这种不同矿床组合的分区对应着不同类型的前寒武纪基底。初步证据显示,扬子克拉通前寒武纪基底(含寒武纪)富含低温成矿元素,深循环流体浸取基底岩石中的成矿元素发生了大面积低温成矿,而基底岩石成矿元素组成的空间不均一分布则控制了不同区域矿床组合的差异。应指出的是,由于成矿金属元素来源示踪的复杂性,大面积低温成矿的物质基础尚需更系统的研究进一步证实。     

黑龙江省前寒武纪变质地层划分对比研究进展

黑龙江省前寒武纪地层分布广泛,出露零星.通过对黑龙江省前寒武纪地层年代学、沉积建造、发育矿床特征及地层对比的综合分析显示,黑龙江省前寒武纪变质岩系和古生界锆石测年数据中出现有较多的太古宙、古元古代的谐和年龄,在古生代火成岩中也存在太古宙和古元古代捕获锆石的年龄数据信息,且黑龙江省前寒武纪变质基底主要为中—新元古界,产出...     

诸广铀成矿区矿床成因探讨

本文通过对诸广地区内生铀矿床成矿地质背景分析,系统论述了矿区地质特征及矿床地球化学特征,对本区矿床成因进行了探讨,提出诸广地区存在富铀的前寒武纪结晶基底;成矿物质来源于上地幔流体与下地壳富铀前寒武纪结晶基底的混熔交代;成矿作用受晚中生代伸展裂陷构造——深源热流体演化机制控制,形成中高温热流体充填成矿的高品位脉型矿化和中低温热流体交代成矿的较低品位碎裂蚀变岩－微脉浸染型矿化。     

吉尔吉斯金属矿产时间分布

<正>吉尔吉斯地区经历了漫长的地质演化,在地壳发育的不同阶段,由于不同的成矿作用形成了不同规模、不同类型的矿产。吉尔吉斯的矿床主要形成于前寒武纪、加里东、华力西和阿尔卑斯期四大旋回。1前寒武纪前寒武纪成矿期形成的矿床较少,主要分布在中天山。许多矿床产于前寒武纪变质岩中,早前寒武纪仅在变质的结晶基底中有石墨矿产出;晚前寒武纪的裂谷作用形成了里菲-文德纪火山-沉积建造,赋存有杰德姆超大型铁矿床。     

中国铜矿床成矿期划分及其时空分布特征

根据全国1085个主要铜矿床的成矿时代研究,将中国铜矿床划分为前寒武纪、早古生代、晚古生代、三叠纪、侏罗-白垩纪、新生代六个成矿期。统计分析了各成矿期形成的铜矿床数量,在分析各成矿期地质演化历史的基础上,总结了不同矿床类型铜矿床的时间、空间分布特征。     

早前寒武纪热液矿床成矿后岩脉的鉴别

从矿体与岩脉的接触关系,和早前寒武纪热液矿床地质基本特点出发,举出鉴别早前寒武纪热液矿床成矿后岩脉的一系列实例。     

华南重要金属矿床的成矿规律——时代爆发性、空间分带性、基底继承性和热隆起成矿

华南热液矿床形成的时代爆发性、空间分带性及其成矿元素对前寒武纪基底的继承性表明,构成华南基底和含矿建造的前寒武纪地层（主要为元古界）是华南陆内热液成矿作用的主要成矿物质来源,燕山期花岗岩类是热液成矿作用的主要成矿能量来源;华南热液成矿的区域分布趋势、矿床形成过程和成矿岩体演化等,均表现出与构造热隆起动态有关的成矿特征。多期花岗岩类侵入和迅速块断隆升造成地温梯度增高,基底含矿建造提供成矿物质,以及有利的热液通道和扩容空间是造成构造隆起带或盆地“凹中隆”成矿的重要条件。燕山期花岗岩成岩成矿与大陆地壳的多旋回熔融或再循环有密切的成因关系;地震层析图像资料显示,华南中生代软流圈上涌是造成华南陆壳热隆起的动力学因素。但其成因不同于地幔柱机制,具有被动上涌特征,可能与太平洋板块俯冲形成的大型冷幔柱下沉和地幔过渡带崩溃有关。     

陕南地区前寒武纪基底与金铜铅锌矿床分布关系

依据陕南秦岭造山带区域地质及重力资料，按是否露出地表将前寒武纪基底划分为出露基底和隐伏基底两种类型。其中，圈定出露基底15处，解译推断隐伏基底6处。小秦岭—北秦岭地区的基底大多露出地表，其总体具典型华北地块基底特征；南秦岭、勉略阳及北大巴山地区的出露基底则呈较零散的孤岛状分布，而隐伏基底向南、北两侧扩展延伸范围较大且基本连为一体，基底性质总体具典型扬子地块双层基底特征。区内已知大—中型金、铜、铅锌矿床(田)及Au、Ag、Cu、Pb、Zn元素化探异常密集区(带)的分布大多与前寒武纪基底有关。前寒武纪基底与上述矿产和化探异常间的分布关系，无疑为今后本区贵金属及有色金属矿产勘查评价及成矿预测提供了新的思路。     

试论新疆成矿体系与时空演化模式

文章探讨了成矿体系的内涵,在以往研究成果和编制1∶1 500 000中国新疆维吾尔自治区矿床成矿系列图的基础上,根据先时间、后空间、再成因的总体思路,完善了新疆前寒武纪、早古生代、晚古生代、中生代、新生代五个时段成矿体系,初步构建了各时段成矿体系的时空演化模式,总结出5个时段成矿体系的特点是:前寒武纪为基底陆壳的形成与发展各具特色的成矿体系;早古生代板块体制早期发育具中亚成矿域特色的成矿体系;晚古生代板块体制晚期发育具中亚成矿域特色的成矿体系;中生代新疆北部发育板内西域成矿特色的成矿体系和新疆南部发育特提斯成矿域特色的成矿体系;新生代发育板内西域成矿特色的大陆成矿体系。     

铅同位素的研究

对地表铁帽或矿石矿物的铅进行铅同位素分析.可以找到矿床并查明其成因.成果的推断解释取决于异常铅与普通锅的识别及其成因关系与空间分布.在研究矿床成因方面,主要用途是确定矿石中铅的来源并估计成矿年代.例如,同位素铅证明:密苏里州西南部显生宙方铅矿矿石的铅来自寒武纪砂岩含水层,部分可能来自前寒武纪基底和古生代碳酸岩母岩;爱达荷州克达伦地区的矿石年代是前寒武纪,并非过去认为的新生代.铅有三种兹射性同位素,具有高的原子量(对天然的、依赖质量的分馏方法不灵     

Gold in Madagascar

Gold is commonly found throughout the Precambrian basement exposed in the eastern two-thirds of Madagascar, composed of Archean and Proterozoic greenstone belts and metasediment belts. Gold occurs in four main kinds of deposits:- as a diffuse component of the crystalline basement rocks, - in concordant quartz veins within the metamorphic rocks of the Precambrian basement, - in recent discordant veins, - and in recent and ancient alluvial deposits.The initial gold mineralisation is probably in relation with the greenstone belt formation, and many have been formed and/or reworked during different metamorphic and magmatic events. It is therefore difficult to obtain an accurate age of the different kinds of deposits.     

黑龙江省东部早古生代地层的确定:地质与碎屑锆石U-Pb年代学证据

通过研究黑龙江省东部早古生代地层晨明组和宝泉组碎屑锆石的U-Pb定年结果,讨论了晨明组和宝泉组的所属时代和物源.大多数锆石呈自形-半自形晶,显示出典型的岩浆生长环带或条痕状吸收,暗示其岩浆成因,极少数的锆石具有经变质作用形成的暗色增生边.定年结果表明:采自晨明组上部长石石英砂岩中碎屑锆石59个分析点产生了以下年龄组:561 Ma、621 Ma、683 Ma、752 Ma、803 Ma、822 Ma、851 Ma、900 Ma、922 Ma、954 Ma、1 781 Ma、1 865 Ma和1 933 Ma,这表明晨明组沉积于561 Ma之后.而以不整合接触关系覆盖于晨明组之上的宝泉组底部泥质板岩中碎屑锆石60个分析法点产生了425 Ma、450 Ma、485 Ma、900 Ma和1 750 Ma年龄众数.由上述地质关系和年代学测定结果,结合晚古生代地层中碎屑锆石的年龄组合,可以判定位于黑龙江省东部地区晨明组的形成时代介于561~510 Ma之间,这是首次在黑龙江省东部确定的具有确切年代学证据的早古生代地层.上述年龄组碎屑锆石的存在,表明其物源主要为该区新元古代和古元古代的地质体,这进一步揭示在早古生代期间,松嫩-张广才岭地块东缘可能存在前寒武纪残片.      

敦煌复合造山带前寒武纪地质体的组成和演化

敦煌复合造山带位于塔里木克拉通东端,是连接塔里木克拉通和华北克拉通的重要纽带。近年来,敦煌基础地质研究取得了重大进展。本文简要回顾了敦煌基础地质研究历史和现状,系统归纳了区内前寒武纪地质单元时空分布特征及前寒武纪构造-热事件序列,初步讨论了前寒武纪大陆地壳形成和演化规律、前寒武纪结晶基底亲缘性及构造演化过程,提出:(1)敦煌造山带前寒武纪结晶基底形成于ca.3.1~1.6Ga,构造-热事件主要划分为新太古代(ca.2.7~2.6Ga和2.6~2.5Ga)、古元古代晚期(ca.2.0~1.8Ga)和中元古代早期(1.8~1.6Ga)三个阶段;(2)新太古代早期(ca.2.7~2.6Ga)和新太古代晚期(2.6~2.5Ga)是敦煌造山带大陆地壳形成的主要阶段;古元古代晚期(ca.2.0~1.8Ga)和中元古代早期(1.8~1.6Ga)主要是古老大陆地壳物质再循环阶段,也有少量新生陆壳物质的形成;(3)敦煌造山带前寒武纪结晶基底最初拼合事件可能发生在新太古代末期(~2.5Ga),之后经历了古元古代晚期(ca.2.0~1.8Ga)汇聚、碰撞造山过程,直到中元古代早期(1.8~1.6Ga),造山活动结束,前寒武纪结晶基底最终固结,进入稳定发展阶段;(4)前寒武纪结晶基底最终稳定固结之后,即～1.6Ga之后,敦煌前寒武纪结晶基底可能进入长达12亿年的静寂期,一直处于稳定状态,目前没有发现相关的岩浆-变质-沉积记录(类似于地盾状态),直至古生代志留纪开始活化(～440Ma),卷入古亚洲洋南缘俯冲、碰撞造山过程并被强烈改造。     

The Early Baikalian crystalline complex in the basement of the Dzabkhan microcontinent of the Early Caledonian orogenic area, Central Asia

Fragments of continental blocks or microcontinents are represented in the Early Caledonian orogenic area of Central Asia (or Early Caledonian superterrane); the largest of these are the Dzabkhan and Tuva-Mongolian microcontinents, with Early and Late Precambrian crystalline basements, respectively. In the linkage zone of these microcontinents, crystalline rocks of the Tarbagatai and Songino blocks that are considered as units of the Early Precambrian ensialic basement of the superterrane are also known. They are composed of strongly metamorphosed rocks formed during the Early Baikalian orogeny about 790 to 820 Ma. U-Pb zircon dating and Nd isotope studies revealed, within the northwestern Dzabkhan microcontinent, the Dzabkhan-Mandal zone of crystalline rocks associated with the Riphean crust-forming process. The age of the gneiss substrate of this zone is estimated as 1.3 to 0.86 Ga. An early episode of metamorphism is dated at about 856 ± 2 Ma. The data available so far indicate a heterogeneous structure of the Dzabkhan microcontinent basement represented by Early Precambrian and Early and Late Baikalian crystalline formations.     

Metallogeny and tectonic development of the tasman fold belt system in tasmania

In western Tasmania, Precambrian sedimentary sequences form the basement for narrow trough accumulations of Eocambrian and younger sequences. The main trough, the meridional Dundas Trough, is flanked to the west by the Rocky Cape region of Precambrian rocks within which major, apparently stratiform, exhalative magnetite-pyrite deposits are intercalated with metabasaltic volcanics and ultramafic bodies.The Eocambrian-Cambrian troughs apparently developed during extension of Precambrian continental crust. Early shallow-water deposition includes thick dolomite units in some troughs. Deepening of the troughs was accompanied by turbidite sedimentation, with minor limestone, and submarine basaltic volcanism with associated minor disseminated native copper. Ultramafic and related igneous rocks were tectonically emplaced in some troughs during a mild compressional phase. They contain only minor platinoids, copper-nickel sulphides and asbestos, but are source rocks for Tertiary secondary deposits of platinoids, chromite and lateritic nickel.In the Dundas Trough, Eocambrian-Early Cambrian rocks are separated by an inferred erosional surface from structurally conformable overlying Middle to Late Cambrian fossiliferous turbidite sequences. The structural conformity continues through overlying Ordovician to Early Devonian terrestrial and shallow-marine stable shelf deposits.A considerable pile of probable Middle Cambrian felsic volcanics accumulated between the sedimentary deposits of the Dundas Trough and the Tyennan region of Precambrian rocks to the east. A lava-dominated belt within the volcanics hosts major volcanogenic massive sulphide deposits, including those of the exhalative type, which in the south are enriched in copper, gold and silver, whereas in the north they are rich in zine, lead, copper, gold and silver. Cambrian movements along faults near the margin of the Tyennan region resulted in erosion of the mineralized volcanics, locally exposing sub-volcanic granitoids. Above the local unconformities occur unmineralized volcaniclastic sequences that pass conformably into Ordovician to Early Devonian shelf deposits. Ordovician limestone locally hosts stratabound disseminated and veined base metal sulphide deposits.Pre-Middle Devonian rocks of western Tasmania differ, for most part, from those in the northeast where deeper marine turbidite quartz-wacke sequences were deposited during the Ordovician and Early Devonian.The Eocambrian to Early Devonian rocks of Tasmania were extensively deformed in the mid-Devonian. The Precambrian regions of western Tasmania behaved as relatively competent blocks controlling early fold patterns. In northeastern Tasmania, folding is of similar age but resulted from movements inconsistent with those affecting rocks of equivalent age in western Tasmania.The final metallogenic event is associated with high-level granitoid masses emplaced throughout Tasmania during the Middle to Late Devonian. In northeastern Tasmania, extensive I-type granodiorite and S-type granite, with alkali-feldspar granites, are associated with mainly endogranitic stanniferous grelsens and wolframite ± cassiterite vein deposits. In contrast, scheelite-bearing skarns and cassiterite stannite pyrrhotite carbonate replacement deposits are dominant in western Tasmania, associated mainly with S-type granites. Several argentiferous lead-zinc vein deposits occur in haloes around tin-tungsten deposits. A number of gold deposits are apparently associated with I-type granodiorite, but some have uncertain genesis.The contrasting regions of western and northeastern Tasmania have probably been brought together by lateral movement along an inferred fracture. Flat-lying, Late Carboniferous and younger deposits rest on the older rocks, and the only known post-Devonian primary mineralization is gold associated with Creta ceous syenite.     

黑龙江多宝山成矿区金矿成矿规律及找矿方向

通过对黑龙江多宝山成矿区内典型金矿床的地质及地球化学特征的研究和对区域上金矿床（点）的分布特点和成因特征的总结,分析了研究区金矿成矿规律,并明确了找矿方向.研究表明：研究区内金矿床（点）主要受控于NW向和NE向菱（环）形构造,其中以NE向断裂为主,而且由西向东金矿化具有不断加强的趋势.矿体主要赋存于中奥陶世和燕山早期火山岩中,成矿物质主要来源于燕山期岩浆岩及其围岩,成矿流体主要来源于大气降水,流体包裹体均一温度均值在133~267℃之间,属于浅成中-低温热液矿床.     

塔里木克拉通基底古隆起构造-热事件及其结构与演化

通过盆地内部锆石U-Pb测年分析表明,塔里木克拉通基底存在2950～ 3100Ma、2100 ～ 2400Ma、1900～2000Ma、1300～1600Ma、900 ～ 950Ma、700～800Ma、540 ～ 560Ma、400～ 500Ma和270～290Ma等9期构造-热事件.中央航磁异常带井下花岗岩锆石SHRIMP U-Pb年龄测定发现1908.2±8.6Ma前寒武纪基底,表明盆地内部可能存在古元古代构造-热事件形成的古老花岗岩基底.结合新的地质与地球物理资料综合分析,塔里木盆地前寒武纪具有不同年代、不同类型的基底结构,北部为中-新元古代中浅变质岩基底、中部为古元古代花岗岩基底、南部为新元古代早-中期岩浆岩与变质岩基底、东南部为遭受早志留纪区域变质改造的变质岩基底.井震结合发现塔里木盆地寒武系/前寒武系发育广泛分布的大型不整合,形成塔北与塔南两大前寒武纪基底古隆起,可能与550Ma“泛非运动”相关.塔里木盆地基底古隆起主要经历5期演化,古元古代中期形成克拉通化基底,新元古代早期形成统一的变质结晶基底,寒武纪沉积前两大基底古隆起形成,加里东晚期五大基底古隆起基本定型,海西期以来发生局部调整改造.     

登封地区早前寒武纪地壳演化—地球化学和锆石SHRIMP U-Pb年代学制约

河南中部登封地区早前寒武纪基底主要由新太古代登封群、古元古代嵩山群和早前寒武纪花岗质岩石组成.登封群主要由斜长角闪岩、角闪变粒岩、黑云变粒岩、云母石英片岩及少量磁铁石英岩(BIF)组成,变质原岩主要为基性火山岩、中酸性火山岩和碎屑沉积岩.3个登封群变质酸性火山岩样品给出2.51～2.53 Ga岩浆锆石年龄,存在2.61～2.69 Ga残余锆石.它们高SiO2,tDM(Nd)和εNd(t)分别为2.52～2.79 Ga和0.51～4.41.嵩山群主要由石英岩和片岩组成,经受绿片岩相变质.石英岩碎屑锆石年龄峰值为2.5 Ga,与华北克拉通孔兹岩系变泥砂质岩石中存在大量2.1～2.3 Ga碎屑锆石明显不同.石英岩中可靠的最年轻碎屑锆石年龄为2.45 Ga,部分碎屑锆石年龄大于2.65 Ga,最大达3.26 Ga.会善寺奥长花岗岩、大塔寺英云闪长岩、路家沟钾质花岗岩和石秤二长花岗岩形成时代分别为2.55 Ga、2.53 Ga、2.51 Ga和1.78 Ga,会善寺奥长花岗岩中存在2621～2638 Ma残余锆石,并有～2.51 Ga变质增生边存在.花岗质岩石在元素地球化学组成上存在较大变化,但具有类似Nd同位素组成,tDM(Nd)为2.60～2.80 Ga(钾质花岗岩样品除外).根据研究,可得出如下结论和认识:①登封群形成于新太古代末期(2.51～2.53 Ga),与前人认识一致.②不同类型花岗质岩石,与登封群表壳岩一道,形成于一个相对较小的时间范围(2.50～2.55 Ga),结合岩石组合和地球化学组成特征,推测其形成与板底垫托作用有关.③在岩石组合和形成时代等方面,五台和箕山地区花岗绿岩带与登封地区的十分类似,可能为同一大型花岗绿岩带的不同部分.④可把嵩山群形成时代限制在2.0～2.45 Ga之间,与五台地区高凡群(2.14～2.47 Ga)或滹沱群(2.08～2.14 Ga)对比.⑤石秤花岗岩是华北克拉通古元古代之后拉张构造体制下壳内岩浆作用的产物.     

我国早前寒武纪变质岩中金矿床深延问题初探

本文通过国内外绿岩带及其中的金矿床对比研究,说明我国早前寒武纪变质岩系的原岩层序和岩性特征与世界各绿岩带是可以对比的;我国早前寒武纪变质岩系中的金矿床在赋矿围岩、控矿构造及产出形式诸方面与绿岩型金矿也是可以对比的。从其成矿机理及基本事实出发,指出在我国早前寒武纪变质岩分布区及已知老矿区寻找深部矿体的可能性。