阿拉伯地盾地质构造演化与关键地质矿产问题浅析

阿拉伯地盾位于阿拉伯板块的西南部,与红海西岸的努比亚地盾共同组成努比亚-阿拉伯地盾,是新元古代东、西冈瓦纳大陆汇聚过程中形成的泛非造山带的重要组成部分。在“沙特阿拉伯地盾精细地质填图”技术标编制过程中,笔者综合分析了该区的地质调查和研究成果,总结了阿拉伯地盾8个次级地体、主要蛇绿岩构造混杂岩带及新元古代沉积盆地的地质特征,并将阿拉伯地盾的地质演化细分为4个构造演化阶段。其中,在新元古代洋-陆转化过程中阿拉伯地盾形成了一系列重要的矿产资源。在此基础上,系统梳理了区内地层、构造、岩浆作用及与成矿相关的地质问题,提出了未来精细地质填图过程中的工作建议。     

哀牢山造山型金成矿系统:复合造山构造演化与成矿作用初探

哀牢山金矿带是我国最重要的喜马拉雅期造山型金矿带,形成于三江特提斯复合造山过程中。论文基于对哀牢山复合造山带区域构造背景、控矿构造系统演化、金成矿期次及其时代的系统研究,从金成矿年代序列、成矿过程构造控制及成矿作用动力学环境三个方面,探讨了复合造山过程中的金矿成矿作用。研究结果表明,哀牢山金矿带发育三期金矿成矿-热事件:早期金成矿作用(61.55～63.09Ma)对应于逆冲推覆构造系统最为发育的时期,与剪切走滑断裂构造的形成同步,显示它们统一受控于印度-亚洲大陆碰撞早期的强烈汇聚挤压构造动力学体制;主期金成矿作用(33.76～36.10Ma)对应于区域挤压构造应力场的相对松弛阶段以及富碱斑岩和剪切走滑断裂构造系统最为发育的时期,受控于印度-亚洲大陆碰撞构造动力学转换体制,并可能受青藏高原物质东向逃逸和软流圈脉动隆起的联合制约,金矿大规模成矿作用与构造动力体制转换过程中的壳幔物质强烈交换与构造变形密切相关;晚期金成矿作用(26.40～30.80Ma)对应于岩石圈伸展作用的发生以及亏损地幔减压熔融产生的板内高钾岩浆岩的就位,受控于印度板块反向旋转拖曳与斜向俯冲回退的综合作用。     

东北非努比亚地盾金矿成矿地质特征与找矿标志

东北非金矿的矿床类型、成矿条件与努比亚地盾演化密切相关.努比亚地盾金矿类型,按成因可分为两大类:一类是与造山带有关的韧性剪切带金矿,即造山型金矿;另一类是弧-弧拼合过程中形成的火山成因块状硫化物金矿,即VMS型铜-金矿.受韧性剪切带控制的造山型金矿形成于闭合-碰撞造山阶段,与弧-弧碰撞缝合带展布方向一致的北东向韧性剪切带为造山型金矿的主要控矿构造,该类型矿床规模以中小型为主.沿韧性剪切带成带分布的火山成因块状硫化物(VMS型)金矿床形成于洋壳俯冲-岛弧的形成阶段,其形成环境为岛弧裂谷或弧后裂谷环境,矿床规模以大型为主,成群分布于5个矿集区内.本文总结了该地区造山带型和VMS型金矿的主要特征,并依此提出在该地区寻找此两种类型金矿的找矿标志.     

老挝琅勃拉邦—泰国黎府成矿带古特提斯构造-岩浆演化与金铜成矿作用

老挝琅勃拉邦—泰国黎府成矿带位于印支板块西北缘,是中南半岛重要的金铜成矿带之一。该带经历了晚古生代—中生代古特提斯构造-岩浆演化作用,成矿活动复杂,形成了斑岩-矽卡岩型金铜矿床、浅成低温热液型金银矿床以及热液脉型金矿床。然而,热液脉型金矿的成因类型仍存在争议,3类金铜矿床与区域构造演化的关系仍缺乏总结。本文通过对前人典型矿床研究资料的整理,并结合成矿流体来源、演化新证据,将带内热液脉型金矿床的成因类型归为造山型金矿。综合区域构造-岩浆-成矿作用研究资料,总结了成矿带内3类金铜矿床的时空分布规律和成矿特征,建立了与古特提斯洋俯冲-闭合及陆陆碰撞过程相关的区域金铜成矿模式,提出了晚二叠世—早三叠世俯冲期浅成低温热液型金银矿床、早中三叠世闭合期斑岩-矽卡岩型铜金矿床、晚三叠世陆陆碰撞期造山型金矿床的成矿规律。     

贵州锦丰(烂泥沟)超大型金矿床构造解析及构造成矿作用

在矿区大比例尺填图的基础上,运用构造解析的理论和方法,对贵州锦丰(烂泥沟)金矿的构造特征、构造演化和构造控矿作用进行了系统的阐述。矿区构造线主要分为近NS向、NW向和NE向3组,其中NW向构造线控制了矿区的构造格架。构造变形主要经历了同生期裂陷、造山期挤压、后碰撞造山侧向挤压和岩石圈伸展等4个阶段。盆地裂陷期间(D2-T2)形成的同生断层为后续的构造活动提供了最初的构造薄弱面,并成为主要的热液通道;造山期挤压期间(T3)形成了矿区最为明显的近NS向和NW向大型倒转褶皱和逆冲断层以及配套的NE向右旋走滑断层;后碰撞造山侧向挤压期间(J1)形成走向NE的叠加褶皱,并在F2-F3"X"型断裂系上形成近EW向的拉张区,矿质沿着拉张的空间沉淀就位;燕山期(J2-K)岩石圈伸展,形成小规模的近水平逆断层。上述4个主要构造变形阶段与右江盆地的裂陷-闭合-坍塌的发展演化历史相吻合,成矿发生在由挤压向拉张过渡的构造体制转换阶段。造山期逆冲作用形成的构造闭圈和后碰撞造山期间挤压向伸展转变的过程中形成的局部张性构造环境是矿质得以大量聚集、沉淀的主要构造控制因素。构造成矿作用是锦丰(烂泥沟)金矿单一矿体垂向延深1000m以上的主要制约因素。构造成矿的观点将为在滇黔桂"金三角"卡林型金矿带的深部找矿提供重要的理论依据。     

非洲基巴拉带东北部卢旺达地层-构造-岩浆演化及成矿作用

卢旺达地处中非基巴拉带东北部(卡拉圭-安科连带),是非洲乃至全球重要的铌-钽-钨-锡成矿区。本文梳理和总结了卢旺达境内的地层层序、岩浆作用、构造属性、地球动力学机制和铌钽钨锡矿产成矿作用特征。卢旺达地层主要由古元古代变质基底和中元古代卢旺达超群组成,少量新近纪火山岩,其中以卢旺达超群最为重要,从底至顶依次由四个群组成:基可勒群、平杜拉群、乔霍哈群和卢各支群。侵入岩主要形成于中-新元古代,以四期花岗岩为代表(G1～G4期),其中G4花岗岩与钨锡铌钽矿成矿作用关系密切。岩浆作用与区内构造活动频繁有关,在元古代经历了四阶段挤压-伸展更替的构造岩浆演化。根据对已有资料的梳理和分析,本次研究认为,岩浆作用更可能形成于"汇聚俯冲+板片拆沉(或弧后伸展)"的动力学背景,即俯冲汇聚大背景下的局部伸展体制。铌钽钨锡矿是卢旺达最为典型和最重要的矿种,主要受G4花岗岩和区域构造的控制,表现为伟晶岩型铌钽锡矿、热液石英脉型钨锡矿和云英岩型锡矿,成岩成矿过程的先后关系总结为:G4花岗岩上涌侵位,形成于986～976Ma→分异演化形成伟晶岩和铌钽矿±锡矿,铌钽矿形成于975～962Ma→形成石英脉和锡矿,锡矿形成...     

冀东长城式金矿构造地质特征及构造演化与金矿化的关系

长城式金矿是产在中晚元古宇碳酸岩中的一种新类型金矿,本文从金矿床的构造地质特征及其演化的角度,阐述了长城式金矿构造与金矿化的独特关系。     

祁连造山带构造演化与新生代变形历史

祁连造山带位于东特提斯北缘,蛇绿混杂岩带、(超)高压变质岩和弧岩浆岩等广泛发育,是前新生代华北克拉通与柴达木古地块之间多期次俯冲、碰撞和造山形成的复合造山带。现今的祁连山是青藏高原北缘高原隆升与扩展的关键构造带,具有复杂的陆内变形构造和深部结构,记录了新生代高原生长过程中不同阶段的构造变形和盆-山演化历史。本文在区域地质研究资料的综合分析基础上,讨论祁连造山带元古宙变质基底属性、新元古代—古生代古海洋演化和中—新生代构造变形特征,探讨祁连(山)造山带的构造演化过程和陆内变形历史。祁连造山带发育新元古代早期和早古生代两期岩浆弧,分别代表了古祁连洋和(南、北)祁连洋的俯冲-碰撞事件;亲华北的基底属性指示了祁连洋实属陆缘海。新生代青藏高原东北缘发育两阶段构造变形和盆-山演化,在中新世完成了由新生代早期以逆冲断裂活动为主向走滑断裂和逆冲断裂共同作用的转变,随着东昆仑山的快速隆起将古近纪大盆地隔开成两个盆地,即现今的柴达木盆地和可可西里盆地。中新世中晚期以来,青藏高原东北缘的构造格局主要受控于东昆仑和海原两个近乎平行的大型转换挤压构造系统的发育、顺时针旋转和侧向生长。大型走滑断裂系统在造山带内的...     

尼泊尔及南侧邻区元古宙以来的构造-沉积演化

迄今,尼泊尔及其南侧邻区元古宙以来的构造-沉积演化尚缺乏系统性研究.为了促进区域地质认识,结合前人研究成果及新的研究发现,对尼泊尔低喜马拉雅带及以南的构造-沉积演化首次进行系统性总结与讨论.结果表明:尼泊尔低喜马拉雅带及以南与印度地盾北缘在地质历史中的构造-沉积演化息息相关,且自元古宙以来,发育了被动大陆边缘→陆内裂谷→被动大陆边缘→前陆盆地等不同构造演化阶段的沉积响应;尼泊尔西部的Dailekh群属于~1.8 Ga以前或前哥伦比亚超大陆之前的被动大陆边缘沉积;Vindhyan超群为下断上坳的陆内裂谷沉积,尼泊尔境内的Lakharpata群相当于下Vindhyan群;Gondwana超大陆裂解导致由北往南形成一系列初始发育时间越来越晚的裂谷盆地;Surkhet群至Siwalik群为被动大陆边缘至前陆盆地沉积,其中,Surkhet群Swat/Subathu组是喜马拉雅南侧地质历史上最后一套海相沉积地层,也是被动大陆边缘向前陆盆地转换期的沉积响应;Siwalik群大规模的磨拉石建造标志着喜马拉雅快速和大幅度隆升,该群沉积成岩后,印度-欧亚板块进一步的挤压作用导致了地质历史上迄今为止最后一次强烈的构造运动,形成MFT与Siwalik褶皱带,并奠定了喜马拉雅带现今构造格局.      

藏东类乌齐-左贡成矿带构造演化与成矿作用

藏东类乌齐-左贡成矿带(简称类-左带)是三江特提斯成矿域内一条重要的成矿带,其整体的研究较为薄弱、零散。本文基于最新的研究成果,按照成矿时代、地质背景、成矿作用及成矿元素组合将带内矿床划分为了6个成矿系列,包括：(1)印支期晶质石墨矿系列;(2)印支期蛇绿岩相关风化淋滤型菱镁矿系列;(3)印支期沉积-改造型Fe-Cu多金属系列;(4)燕山期与中酸性岩浆岩相关的W-Sn-Mo-Cu多金属系列;(5)燕山期热液脉型Pb-Zn多金属系列;(6)喜山期MVT型Pb-Zn多金属系列。针对每一个成矿系列,作者选取了典型矿床对其成矿地质特征进行了简要论述,并对其成因机制进行了重点剖析。此外,作者深入探讨了类-左带内区域构造演化与成矿作用之间的关系,指出各类矿床在带内大量发育是古、中、新特提斯构造长期演化的结果。本项研究有助于深入认识类-左带内的成矿作用与成矿规律,并对区内未来的找矿勘查工作具有重要的参考价值。     

Late Neoproterozoic adakitic magmatism of the eastern Arabian Nubian Shield

Late Neoproterozoic adakitic magmatism within the Eastern Arabian Nubian Shield has been dated at633.2±9.0 Ma(2σ).These magnas intrude the forearc Ad Dawadimi Basin,which is composed of metapelitic schists and greywacke along with ophiolitic melanges of boninitic affinity which underwent inversion and deformation by~620 Ma.This adakitic magmatism,while intruding parts of the Ad Dawadimi Basin,predates this deformation,but is possibly coincident with basin closure.As adakitic magmatism requires melting of an amphibolite or eclogitic source,empirical and experimental constraints require anomalously hot supra-subduction zone mantle.Considering that this magmatism immediately predates basin inversion,these magmas possibly pinpoint the timing of the slab breaking,marking the terminal stages of arc magmatism,terrane accretion and the influx of hot oceanic asthenospheric mantle.This influx of hot asthenospheric mantle may also be responsible for postcolltsional A-type magmatism.     

小秦岭金矿田构造演化与金矿成矿作用

依据小秦岭金矿田的地质构造穿插关系和同位素年龄资料,建立了本区构造、岩浆、成矿事件序列。在此基础上,将小秦岭地区的构造演化划分为６个阶段：褶皱变质、韧性剪切变形、稳定升降、韧－脆性断裂转化、断裂活动、抬升剥蚀阶段。对小秦岭金矿田的成矿时代,成矿深度、矿床成因等地质问题,给出了构造地质学方面的判据。     

Metallogeny of gold in relation to the evolution of the Nubian Shield in Egypt

Gold mineralization in the Eastern Desert of Egypt is confined, almost completely, to the basement rocks of the Nubian Shield that was cratonized during the Panafrican orogeny.Island-arc, orogenic and post-orogenic stages are indicated for the tectonic-magmatic evolution of the Nubian Shield in Late Proterozoic times. Different styles of gold mineralization recognised in the Eastern Desert are inferred to have developed during these stages.In the island-arc stage, which is characterized by volcanic and volcaniclastic rocks in an ensimatic environment, gold mineralization is hosted in stratiform to strata-bound Algoma-type BIF and associated tuffaceous sedimentary rocks. Both types represent exhalative deposits, formed during breaks in sub-marine basaltic and bastalic–andesite volcanic eruptions. The volcanic rocks have a tholeiitic affinity and reflect an immature arc stage. Gold hosted in massive-sulphide deposits within calc-alkaline rhyolites represents another style of gold mineralization connected with mature island arc stage.During the orogenic-stage, ophiolites and island arc volcanic and volcaniclastic rocks were thrust onto the Pre-Panafrican continental margin. Subduction was active beneath the continent while the thrusting was still operative. A phase of calc-alkaline magmatic activity developed during this stage and the compressional deformation event was synchronous with regional metamorphism (greenschist–amphibolite facies). Extensional shear fractures (brittle–ductile shear zones) were broadly contemporaneous with the intense compressional tectonic regime. These fractures opened spaces in which the mineralizing fluids penetrated.Gold mineralization associated with the orogenic-stage is represented by vein-type mineralization that constituted the main target for gold since Pharaonic times. Other styles of gold mineralization during this stage are represented by altered ophiolitic serpentinites (listwaenites), Gold mineralization associated with intrusion related deposits (possibly porphyry copper deposits), as well as, auriferous quartz veins at the contacts of younger gabbros and G-2 granites.The post-orogenic stage is characterized by the dominance of intra-plate magmatism. Small amounts of the element in disseminations, stockworks and quartz veins of Sn–W–Ta–Nb mineralization represent gold mineralization connected with this stage.The link between these tectonic–magmatic stages and gold mineralization can be used as a criterion at any exploration strategy for new targets of gold mineralization in Egypt.     

川西北哲波山金矿床构造演化与成矿

印支中－晚期区域构造演化形成了一套巨厚的浊积岩系，为金矿的初始富集期。印支晚期－燕山早期的多期次构造深化导致矿区内岩浆侵位，控矿构造的最终形成以及Au的活化。迁移、沉淀、富集。该期应力作用表现为先压、后剪、再张的过程。燕山早期后的构造演化结果是矿体被抬升、破碎、位错及氧化次生富集。     

Sub‐Cambrian pedogenesis recorded in weathering profiles of the Arabian‐Nubian Shield

Altered crystalline rocks occur at the peneplain exposed in southern Israel and in other localities across North Africa and Arabia where they underlie an extensive blanket of Cambro–Ordovician sandstones. This study focuses on the petrography, mineralogy and geochemistry of top basement rocks of the northern Arabian‐Nubian Shield. The altered rocks are shown to be weathering profiles that can be subdivided into three horizons interpreted as apparently unweathered granite, or saprock, which grades upwards to a saprolite, topped by a thin clayey plasmic zone. The plasmic zone is enriched in iron and aluminium and is depleted in silicon, calcium, magnesium and potassium relative to the underlying saprolite. The chemical index of alteration increases upward, but does not exceed 90 and, therefore, lags behind values observed in strongly leached present‐day tropical soils. Petrographic examinations reveal iron mobility under local fluctuating redox conditions, similar to modern and Proterozoic soils. A variety of birefringence fabrics induced by shrinkage and expansion of clays during wetting and drying cycles and clay illuviation strongly indicate pedogenic processes rather than a post‐depositional alteration. Illite and ordered illite‐smectite phases coexist with smectitic illite‐smectite in the lower part of the saprolite and with kaolinite in the plasmic zone, in line with increasing chemical index of alteration. Observations are in accordance with the current profile being a remnant of a thick weathering profile whose top was truncated by fluvial incision just prior to deposition of the overlying Early Cambrian sequence. A previously documented Devonian thermal event reaching temperatures of at least 200°C overprinted the studied rocks. During burial diagenesis, illitization affected original smectite rather than kaolinite. However, in spite of the elevated temperatures, illitization was incomplete implying restricted potassium addition. The sub‐Cambrian weathering reflects warm and humid conditions in a tropical or sub‐tropical climate, in line with several plate reconstructions placing Israel at low latitudes during Cambrian time.     

Origin,age and petrogenesis of Neoproterozoic composite dikes from the Arabian‐Nubian Shield,SW Jordan

The evolution of a Pan‐African (c. 900–550 Ma) suite of composite dikes, with latite margins and rhyolite interiors, from southwest Jordan is discussed. The dikes cut the Neoproterozoic calc‐alkaline granitoids and high‐grade metamorphic rocks (c. 800–600 Ma) of the northern Arabian‐Nubian Shield in Jordan and have been dated by the Rb‐Sr isochron method at 566±7 Ma. The symmetrically distributed latite margins constitute less than one‐quarter of the whole dike thickness. The rhyolite intruded a median fracture within the latite, while the latter was still hot but completely solidified. The dikes are alkaline and bimodal in composition with a gap in SiO₂ between 61 and 74 wt%. Both end members display similar chondrite‐normalized rare earth element patterns. The rhyolites display the compositional signature of A‐type granites. The (La/Lu)_N values are 6.02 and 4.91 for latites and rhyolites, respectively, and the rhyolites show a pronounced negative Eu anomaly, in contrast to the slight negative Eu anomaly of the latites. The chemical variability (e.g. Zr/Y, Zr/Nb, K/Rb) within and between latites and rhyolites does not support a fractional crystallization relationship between the felsic and mafic members of the dikes. We interpret the magma genesis of the composite dikes as the result of intrusion of mantle‐derived mafic magma into the lower crust in an extensional tectonic regime. The mafic magma underwent extensive fractional crystallization, which supplied the necessary heat for melting of the lower crust. The products of the initial stages of partial melting (5–10%) mixed with the fractionating mafic magma and gave rise to the latite melts. Further partial melting of the lower crust (up to 30%) produced a felsic melt, which upon 50% fractional crystallization (hornblende 15%, biotite 5%, feldspars 60%, and quartz 20%) gave rise to the rhyolitic magma. Copyright © 2004 John Wiley & Sons, Ltd.     

Geochronology in the southern Midyan terrane: a review of constraints on the timing of magmatic pulses and tectonic evolution in a northwestern part of the Arabian Shield

The southern Midyan terrane is a composite Tonian to Ediacaran tectonostratigraphic crustal block in the northern Arabian Shield that prior to Red Sea opening was contiguous with coeval rocks in the Eastern Desert of Egypt and Sinai. Ion microprobe (sensitive high-resolution ion microprobe [SHRIMP]) dating of 12 rock samples described here and the results of other dating programmes establish a clear timeframe for depositional, intrusive, and structural events in the region and provide a chronology of tectonism in this part of the Arabian-Nubian Shield. Deposition of Zaam and Bayda group volcanosedimentary rocks and emplacement of mafic-ultramafic complexes and TTG-type diorite, tonalite, and granodiorite denote formation of the Tonian (780–715 Ma) Zaam arc and fore-arc ophiolite above a possible west-dipping subduction system in the southern part of the Midyan terrane. Convergence with the Hijaz terrane farther south and obduction of ophiolite nappes resulted by ~700 Ma in development of the Yanbu suture. Ongoing or a new subduction system led to a ~705–660 Ma Cryogenian pulse of magmatism represented by I-type calc-alkaline diorite, granodiorite, and granite that have volcanic-arc and syn-collisional granite affinities. This was followed, after a brief end-Cryogenian hiatus, by a 635–~570 Ma period of Ediacaran magmatism marked by monzogranite, syenogranite, and minor gabbro and diorite. These rocks are reported to have within-plate to volcanic-arc and syncollision chemical characteristics but their precise tectonic setting is uncertain. Structurally, the intrusions are diapiric and were evidently emplaced in an extensional regime consistent with an overlap between intrusion and Najd faulting associated, at this time, with transpressional collision and northward extension through much of the ANS. Terminal magmatism in the southern Midyan terrane postdated cessation of Najd faulting at ~575 Ma and resulted in the emplacement of undeformed within-plate A-type alkali-feldspar granites and mafic (lamprophyre) and felsic dikes.     

南秦岭夏家店卡林型金矿床构造特征与成矿关系

从地质背景、矿床地质、控矿构造分析了夏家店金矿床特征及其形成过程及成矿机理;矿床产于南秦岭陡岭古隆起边缘寒武系-震旦系碳-泥-硅质板岩及白云岩中;控矿构造具有二次韧性剪切变形、二次构造角砾岩化及二次脉体矿化的特征,显示出式样多种、性质多样、形式多变、活动期次与阶段多次叠加的特点;具体阐述了各构造作用阶段与矿化蚀变之间的关系,建立了地层建造-剪切与张裂构造-热液渗流的成矿系统.属于沉积岩系、构造、热液活动3种地质作用叠加改造的卡林型金矿床.     

金山金矿K—Ar年龄及其对赣东北构造演化的指示意义

金山金矿位于我国著名的德兴铜金矿集区内，是一个与韧性剪切带有关的金矿床。成矿流体作用过程的水－岩反应产物伊利石K－Ar年龄的测试结果表明，金山金矿地区存在着明显的晚古生代构造热事件，金山金矿的成矿作用与这次热事件活动有关，成矿年龄为269．9－317．9Ma；燕山期岩浆活动对金山金矿的影响不太明显。结合前人的研究成果，认为赣东北地区甚至整个华南地区在海西期不仅有明显的岩浆活动，而且海西期也是一次重要的金矿成矿期。