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1.
The northwestern corner of New South Wales consists of the paratectonic Late Proterozoic to Early Cambrian Adelaide Fold Belt and older rocks, which represent basement inliers in this fold belt. The rest of the state is built by the composite Late Proterozoic to Triassic Tasman Fold Belt System or Tasmanides.In New South Wales the Tasman Fold Belt System includes three fold belts: (1) the Late Proterozoic to Early Palaeozoic Kanmantoo Fold Belt; (2) the Early to Middle Palaeozoic Lachlan Fold Belt; and (3) the Early Palaeozoic to Triassic New England Fold Belt. The Late Palaeozoic to Triassic Sydney—Bowen Basin represents the foredeep of the New England Fold Belt.The Tasmanides developed in an active plate margin setting through the interaction of East Gondwanaland with the Ur-(Precambrian) and Palaeo-Pacific plates. The Tasmanides are characterized by a polyphase terrane accretion history: during the Late Proterozoic to Triassic the Tasmanides experienced three major episodes of terrane dispersal (Late Proterozoic—Cambrian, Silurian—Devonian, and Late Carboniferous—Permian) and six terrane accretionary events (Cambrian—Ordovician, Late Ordovician—Early Silurian, Middle Devonian, Carboniferous, Middle-Late Permian, and Triassic). The individual fold belts resulted from one or more accretionary events.The Kanmantoo Fold Belt has a very restricted range of mineralization and is characterized by stratabound copper deposits, whereas the Lachlan and New England Fold Belts have a great variety of metallogenic environments associated with both accretionary and dispersive tectonic episodes.The earliest deposits in the Lachlan Fold Belt are stratabound Cu and Mn deposits of Cambro-Ordovician age. In the Ordovician Cu deposits were formed in a volcanic are. In the Silurian porphyry Cu---Au deposits were formed during the late stages of development of the same volcanic are. Post-accretionary porphyry Cu---Au deposits were emplaced in the Early Devonian on the sites of the accreted volcanic arc. In the Middle to Late Silurian and Early Devonian a large number of base metal deposits originated as a result of rifting and felsic volcanism. In the Silurian and Early Devonian numerous Sn---W, Mo and base metal—Au granitoid related deposits were formed. A younger group of Mo---W and Sn deposits resulted from Early—Middle Carboniferous granitic plutonism in the eastern part of the Lachlan Fold Belt. In the Middle Devonian epithermal Au was associated with rifting and bimodal volcanism in the extreme eastern part of the Lachlan Fold Belt.In the New England Fold Belt pre-accretionary deposits comprise stratabound Cu and Mn deposits (pre-Early Devonian): stratabound Cu and Mn and ?exhalite Au deposits (Late Devonian to Early Carboniferous); and stratabound Cu, exhalite Au, and quartz—magnetite (?Late Carboniferous). S-type magmatism in the Late Carboniferous—Early Permian was responsible for vein Sn and possibly Au---As---Ag---Sb deposits. Volcanogenic base metals, when compared with the Lachlan Fold Belt, are only poorly represented, and were formed in the Early Permian. The metallogenesis of the New England Fold Belt is dominated by granitoid-related mineralization of Middle Permian to Triassic age, including Sn---W, Mo---W, and Au---Ag---As Sb deposits. Also in the Middle Permian epithermal Au---Ag mineralization was developed. During the above period of post-orogenic magmatism sizeable metahydrothermal Sb---Au(---W) and Au deposits were emplaced in major fracture and shear zones in central and eastern New England. The occurrence of antimony provides an additional distinguishing factor between the New England and Lachlan Fold Belts. In the New England Fold Belt antimony deposits are abundant whereas they are rare in the Lachlan Fold Belt. This may suggest fundamental crustal differences.  相似文献   

2.
新疆西天山吐拉苏地区发育的与中酸性火山-次火山岩有关的浅成低温热液-斑岩型金多金属成矿系统,是在晚古生代北天山洋向南部伊犁-中天山板块之下俯冲消减的活动大陆边缘背景下形成的。赋矿的大哈拉军山组火山岩及相关的次火山岩形成于晚泥盆世-早石炭世,岩石总体显示钾质-高钾质、准铝质-过铝质的钙碱性-高钾钙碱性特征,其轻稀土富集、Eu负异常显著、大离子亲石元素富集和高场强元素亏损等,均显示出俯冲带岛弧岩浆作用的特点。阿希(低硫型)和京希-伊尔曼得(高硫型)浅成低温热液金矿床以及塔北、吐拉苏铅锌矿床,受大哈拉军山组火山岩中的断裂破碎带以及具高孔隙度和渗透率的岩性控制;塔吾尔别克斑岩型金矿化主要受斑岩体及火山岩中的断裂和裂隙系统控制,并很可能存在浅成低温热液型金矿化的套合或叠加。硫、铅、碳、氧同位素特征显示,成矿物质主要来自岩浆所分泌的热液和/或赋矿的火山-次火山岩。根据成矿系统形成后的保存和变化情况,认为在吐拉苏盆地内剥蚀程度较低的地区,浅成低温热液型金铅锌矿床具备良好的保存条件,同时在其深部还应注意寻找斑岩型或矽卡岩型铜金矿床。  相似文献   

3.
华北地台北缘内蒙古中部地区晚古生代前发生过造山后伸展作用，在晚泥盆世－早石炭世，本区经厅了短暂的造山作用，形成前陆盆地并推积了滨浅 海相磨拉石建造，同时伴有同碰撞期花岗岩产生。中石炭世一早二叠世，本区进入造山后的陆内伸展作用阶段，并发育大量火山岩。火山岩碱质含量高，碱质成分中Na2O>K2O，且显示双峰分布特征；碎屑岩成分熟度和结构熟度降低，表明中石炭世一早=叠世本区进人陆内伸展构造发育阶段。  相似文献   

4.
武广  陈毓川  陈衍景 《岩石学报》2010,26(12):3683-3695
哈萨克斯坦北东天山地区是中亚造山带重要的浅成低温热液型金矿床产出地区,但其成矿年代学研究非常薄弱。为确定成矿时代,作者运用高精度激光40Ar/39Ar定年法对阿尔哈尔雷金矿床和乌仁科布拉克金矿床的赋矿围岩进行了年龄测定。获得阿尔哈尔雷金矿床安山岩样品20个点40Ar/39Ar等时线年龄为304±7Ma(MSWD=6),乌仁科布拉克金矿床安山玄武岩样品21个点40Ar/39Ar等时线年龄为280±6Ma(MSWD=2.4),表明哈萨克斯坦北东天山地区浅成低温热液型金矿床主要形成于晚石炭世末期-早二叠世。初步的岩石学、地球化学研究表明,哈萨克斯坦北东天山地区晚石炭世末期-二叠纪火山岩主要为流纹岩、粗安岩、玄武粗安岩、玄武安山岩、粗面玄武岩和玄武岩,具双峰式特征,主体属于高钾钙碱性和橄榄玄粗岩系列。哈萨克斯坦北东天山地区晚石炭世末期浅成低温热液型金矿床形成于碰撞晚期向裂谷的转换阶段,而二叠纪浅成低温热液型金矿床产出于陆内裂谷环境。  相似文献   

5.
The Northern, Central, and Southern zones are distinguished by stratigraphic, lithologic, and structural features. The Northern Zone is characterized by Upper Silurian–Lower Devonian sedimentary rocks, which are not known in other zones. They have been deformed into near-meridional folds, which formed under settings of near-latitudinal shortening during the Ellesmere phase of deformation. In the Central Zone, mafic and felsic volcanic rocks that had been earlier referred to Carboniferous are actually Neoproterozoic and probably Early Cambrian in age. Together with folded Devonian–Lower Carboniferous rocks, they make up basement of the Central Zone, which is overlain with a angular unconformity by slightly deformed Lower (?) and Middle Carboniferous–Permian rocks. The Southern Zone comprises the Neoproterozoic metamorphic basement and the Devonian–Triassic sedimentary cover. North-vergent fold–thrust structures were formed at the end of the Early Cretaceous during the Chukchi (Late Kimmerian) deformation phase.  相似文献   

6.
东天山铜金多金属矿床成矿系统和成矿地球动力学模型   总被引：47，自引：2，他引：47  
近年来，在东天山地区地质找矿不断取是突破，一系列大型，中型铜金矿床先后被发现。绝大多数铜金矿床在空间上密集分布于黄山－康古尔缝合－剪切带两侧的岛弧带内，时间上集中在石炭纪－二叠纪。金矿床包括造山型，石英脉型和浅成低温热液型，铜矿床包括斑岩型，夕卡岩型和热液脉型及铜镍硫化物型，金，铜和铜镍矿化各自成系统产出，为板块俯冲晚期和碰撞期大规模镁铁质－超镁铁质和中酸性－酸性花岗质岩浆侵位－喷发事件的产物。  相似文献   

7.
东天山大南湖岛弧带石炭纪岩石地层与构造演化   总被引：5，自引：0，他引：5  
详细的地质解剖工作表明,东天山地区大南湖岛弧带石炭纪出露4套岩石地层组合,即早石炭世小热泉子组火山岩、晚石炭世底坎儿组碎屑岩和碳酸盐岩、晚石炭世企鹅山组火山岩、晚石炭世脐山组碎屑岩夹碳酸盐岩。根据其岩石组合、岩石地球化学、生物化石、同位素资料以及彼此的产出关系,认为这4套岩石地层组合的沉积环境分别为岛弧、残余海盆、岛弧和弧后盆地。结合区域资料重塑了大南湖岛弧带晚古生代的构造格架及演化模式。早、晚石炭世的4套岩石地层组合并置体现了东天山的复杂增生过程。  相似文献   

8.
阿尔泰山南缘晚古生代火山岩十分发育,从早泥盆世到早二叠世均有发育。其中中泥盆世北塔山组为一套中基性火山岩,并且底部含有厚度超过100m的苦橄岩;中泥盆世蕴都喀拉组为一套浅海相细碎屑沉积岩夹中性、中基性火山岩;晚泥盆世江孜尔库都克组为火山碎屑岩夹中基性和中酸性火山岩组合;而晚石炭世巴塔玛依内山组以玄武岩和玄武安山岩为主,夹凝灰岩、粉砂岩和炭质页岩。对这4个组火山岩的主要元素、微量元素地球化学特征研究表明,北塔山组和蕴都喀拉组为拉斑和钙碱性系列,并且均具有大离子亲石元素(LILE)富集,而高场强元素与MORB相当,说明其为岛弧环境。江孜尔库都克组火山岩为钾玄岩系列,并且具有较高的LILE富集,表明其形成于岛弧演化的晚期阶段;巴塔玛依内山组火山岩为碱性系列,并且具有强烈富集LILE的特征,指示了其形成于大陆板内环境。因此,从火山岩的时间和空间演化来看,本区晚古生代火山岩与准噶尔洋板块向北的俯冲有关,西伯利亚板块和准噶尔板块的碰撞发生在早石炭-晚石炭世。  相似文献   

9.
New data on the ages of detrital zircons from folded basement rocks and cover sediments of the Severnaya Zemlya archipelago and Izvestiy TSIK islands have been obtained. The basement age is defined as Cambrian (pre-Ordovician). The Ordovician and Silurian sandstones were mainly formed by erosion of the basement rocks. The Devonian sandstones were formed by debris sourced from the Caledonian orogen. The Carboniferous–Early Permian molasse was formed simultaneously with the erosion of the Carboniferous granitoids and weathering of the Ordovician volcanic arc rocks and the Cambrian basement. The North Kara basin was formed in the Ordovician as a back-arc basin. It experienced its main compression deformations at the boundary of the Devonian and Carboniferous and in the Carboniferous.  相似文献   

10.
In this paper we discuss the timing of final closure of the Paleo-Asian Ocean based on the field investigations of the Carboniferous–Permian stratigraphic sequences and sedimentary environments in southeastern Inner Mongolia combined with the geology of its neighboring areas. Studies show that during the Carboniferous–Permian in the eastern segment of the Tianshan-Hinggan Orogenic System, there was a giant ENE–NE-trending littoral-neritic to continental sedimentary basin, starting in the west from Ejinqi eastwards through southeastern Inner Mongolia into Jilin and Heilongjiang. The distribution of the Lower Carboniferous in the vast area is sparse. The Late Carboniferous or Permian volcanic-sedimentary rocks always unconformably overlie the Devonian or older units. The Upper Carboniferous–Middle Permian is dominated by littoral-neritic deposits and the Upper Permian, by continental deposits. The Late Carboniferous–Permian has no trace of subduction-collision orogeny, implying the basin gradually disappeared by shrinking and shallowing. In addition, it is of interest to note that the Ondor Sum and Hegenshan ophiolitic mélanges were formed in the pre-Late Silurian and pre-Late Devonian respectively, and the Solonker ophiolitic mélange formed in the pre-Late Carboniferous. All the evidence indicates that the eastern segment of the Paleo-Asian Ocean had closed before the Late Carboniferous, and most likely before the latest Devonian (Famennian).  相似文献   

11.
准噶尔盆地的类型和构造演化   总被引：35，自引：1，他引：34  
张晓东 《地学前缘》2000,7(4):431-440
准噶尔盆地的早二叠世属于裂谷还是前陆盆地 ,存在意见分歧 ;晚二叠世—老第三纪盆地的性质也不确定。文中通过对盆地构造几何学、沉降史、热史及火山岩的综合分析研究 ,对盆地类型和构造演化获得了一些新的认识 :( 1)准噶尔盆地在早二叠世为裂谷 ,晚二叠世为热冷却伸展坳陷 ,三叠纪—老第三纪为克拉通内盆地 ,新第三纪至今 ,由于印度板块与亚洲大陆碰撞才形成陆内前陆盆地。 ( 2 )对石炭纪—早二叠世的岩浆活动结合区域构造资料的研究表明 ,准噶尔地区古生代的板块运动和造山作用具软碰撞特点 ,早二叠世的裂谷盆地是在软碰撞背景下造山带伸展塌陷的产物。 ( 3)地幔热对流作用可能是软碰撞造山后伸展塌陷的主要深部动力学机制。  相似文献   

12.
老爷庙-额仁山一带发育3套性质不同的火山岩，通过对其岩石组合、岩相、古火山机构特征的详细观察及岩石学、岩石化学、地球化学的研究，晚泥盆世老爷庙组火山岩为玄武岩-安山岩组合，发育盾状和层状火山，属海相环境，为板块消减带岛弧型高铝玄武岩；晚石炭世-早二叠世哈尔加乌组火山岩为陆相火山岩，岩石组合为安山岩．英安岩-流纹岩，以爆发相为主，常形成破火山及锥状火山机构，为陆-陆碰撞造山期火山岩；早二叠世中晚期卡拉岗组火山岩为一套以酸性为主的陆相火山岩，喷溢相发育，常形成穹状古火山机构，岩石组合为英安岩-流纹岩，为造山期弛张期火山岩，3套火山岩为板块不同阶段的火山岩，从老爷庙组火山岩→哈尔加乌组火山岩→拉岗组火山岩，岩石向酸性演化，地壳成熟度愈来愈高，南混合壳转化为陆壳．  相似文献   

13.
研究表明,阿尔泰南缘和准噶尔北缘晚古生代大地构造演化及成矿作用均受古亚洲洋形成与演化的控制。晚古生代该地区经历了3个不同性质的构造演化阶段,同时伴有不同的多金属成矿作用。早泥盆世,由于古亚洲洋板块的俯冲,在阿尔泰南缘形成了一系列陆缘断陷盆地,并伴随以铅、锌、铜、铁多金属为主的矿化;同时,俯冲的古亚洲洋板块发生部分熔融,形成了埃达克岩及与其有关的铜矿床。随着板块俯冲的继续,中泥盆世出现了前弧盆地,并形成了铜-铅-锌多金属矿床。至石炭纪,西伯利亚板块与哈萨克斯坦-准噶尔板块发生碰撞,在额尔齐斯缝合带附近出现了由于挤压作用而形成的金矿床,同时,在缝合带北侧(阿尔泰地区),由于壳型花岗岩的广泛发育,形成了稀有金属矿床。早二叠世,在额尔齐斯缝合带附近又发生了碰撞后的板内拉张作用,从而诱发了一系列与地幔作用有关的岩浆活动,形成了以喀拉通克为代表的铜-镍矿化。因此,阿尔泰南缘和准噶尔北缘晚古生代多金属找矿远景区包括:阿勒泰南缘早泥盆世火山-沉积盆地内铅、锌、铜及铁多金属矿床和准噶尔北缘早泥盆世与埃达克岩有关的铜矿床;中泥盆世前弧盆地内的铜多金属矿床;石炭纪额尔齐斯缝合带内与碰撞有关的金矿床及稀有金属矿床;早二叠世与板内拉张有关的铜-镍多金属矿床。  相似文献   

14.
The general structure of the Chinese Altai has been traditionally regarded as being formed by five tectono-stratigraphic ‘terranes’ bounded by large-scale faults. However, numerous detrital zircon studies of the Paleozoic volcano-sedimentary sequences shown that the variably metamorphosed Cambro-Ordovician sequence, known as the Habahe Group, is present at least in four ‘terranes’. It structurally represents deepest rocks unconformably covered by Devonian and Carboniferous sedimentary and volcanic rocks. Calc-alkaline, mostly Devonian, granitoids that intruded all the terranes revealed their syn-subduction related setting. Geochemistry and isotope features of the syn-subduction granitoids have shown that they originated mainly from the melting of youthful sediments derived from an eroded Ordovician arc further north. In contrast, Permian alkaline granitoids, mostly located in the southern part of the Chinese Altai, reflect a post-subduction intraplate setting. The metamorphic evolution of the metasedimentary sequences shows an early MP-MT Barrovian event, followed by two Buchan events: LP-HT mid-Devonian (ca. 400–380 Ma) and UHT-HT Permian (ca. 300–270 Ma) cycles. The Barrovian metamorphism is linked to the formation of a regional sub-horizontal possibly Early Devonian fabric and the burial of the Cambro-Ordovician sequence. The Middle Devonian Buchan type event is related to intrusions of the syn-subduction granitoids during an extensional setting and followed by Late Devonian-Early Carboniferous NE-SW trending upright folding and crustal scale doming during a general NW-SE shortening, responsible for the exhumation of the hot lower crust. The last Permian deformation formed NW-SE trending upright folds and vertical zones of deformation related to the extrusion of migmatites, anatectic granitoids and granulite rocks, and to the intrusions of gabbros and granites along the southern border of the Chinese Altai. Finally, the Permo-Triassic cooling and thrust systems affected the whole mountain range from ca. 265 to 230 Ma. In conclusion, the Chinese Altai represents different crustal levels of the lower, middle and upper orogenic crust of a single Cambro-Ordovician accretionary wedge, heterogeneously affected by the Devonian polyphase metamorphism and deformation followed by the Permian tectono-thermal reworking event related to the collision with the Junggar arc. It is the interference of Devonian and Permian upright folding events that formed vertical boundaries surrounding the variously exhumed and eroded crustal segments. Consequently, these crustal segments should not be regarded as individual suspect terranes.  相似文献   

15.
北天山上石炭统奇尔古斯套组中发现早二叠世珊瑚化石   总被引：3，自引：1，他引：3  
新近于北天山艾维尔沟北原划为上石炭统的奇尔古斯套组火山岩系所夹灰岩中,采到了结节脊板杯珊瑚Cy-athocariniatuberculataSoshkina,其时代属于早二叠世,表明该区奇尔古斯套组的一部分应属下二叠统。另外,于头屯河原划为上石炭统的奇尔古斯套组火山-碎屑岩系所含灰岩砾石中,采到伊万诺夫格鲁特珊瑚GrootiaivanoviDubrolyubova,时代属于晚石炭世,与达拉阶(即莫斯科阶)相当,故地层时代应晚于晚石炭世达拉期,根据区域对比推测该地层的一部分也应属于下二叠统。艾维尔沟一带早二叠世珊瑚化石的发现,表明北天山石炭纪强烈的拉张事件可以持续到早二叠世。  相似文献   

16.
南秦岭勉略古缝合带非史密斯地层和古海洋新知   总被引：12，自引：3，他引：9  
南秦岭勉略古缝合带是一个构造混杂岩型非史密斯地层区,由不同时代的原地地层系统和异地地层系统的构造岩片构成。泥盆纪—石炭纪硅质岩的常量元素、稀土元素分析结果指示了勉略小洋盆的存在。区域背景分析表明晚震旦世到早寒武世,南秦岭为扬子板块北部边缘的一部分,中、晚寒武世以后开始分裂形成南秦岭裂陷槽。该海槽于中、晚志留世萎缩但未关闭,泥盆纪又进一步开裂逐渐形成大陆边缘裂谷盆地,晚泥盆世后期到早石炭世早期形成一开放小洋盆。早石炭世后期出现洋壳俯冲,从而转化为活动大陆边缘盆地。该洋盆可能持续到二叠纪,并于印支期最终关闭、碰撞和造山。  相似文献   

17.
《Gondwana Research》2014,25(1):48-102
The Asian continent formed during the past 800 m.y. during late Neoproterozoic through Jurassic closure of the Tethyan ocean basins, followed by late Mesozoic circum-Pacific and Cenozoic Himalayan orogenies. The oldest gold deposits in Asia reflect accretionary events along the margins of the Siberia, Kazakhstan, North China, Tarim–Karakum, South China, and Indochina Precambrian blocks while they were isolated within the Paleotethys and surrounding Panthalassa Oceans. Orogenic gold deposits are associated with large-scale, terrane-bounding fault systems and broad areas of deformation that existed along many of the active margins of the Precambrian blocks. Deposits typically formed during regional transpressional to transtensional events immediately after to as much as 100 m.y. subsequent to the onset of accretion or collision. Major orogenic gold provinces associated with this growth of the Asian continental mass include: (1) the ca. 750 Ma Yenisei Ridge, ca. 500 Ma East Sayan, and ca. 450–350 Ma Patom provinces along the southern margins of the Siberia craton; (2) the 450 Ma Charsk belt of north-central Kazakhstan; (3) the 310–280 Ma Kalba belt of NE Kazakhstan, extending into adjacent NW Xinjiang, along the Siberia–Kazakhstan suture; (4) the ca. 300–280 Ma deposits within the Central Asian southern and middle Tien Shan (e.g., Kumtor, Zarmitan, Muruntau), marking the closure of the Turkestan Ocean between Kazakhstan and the Tarim–Karakum block; (5) the ca. 190–125 Ma Transbaikal deposits along the site of Permian to Late Jurassic diachronous closure of the Mongol–Okhotsk Ocean between Siberia and Mongolia/North China; (6) the probable Late Silurian–Early Devonian Jiagnan belt formed along the margin of Gondwana at the site of collision between the Yangtze and Cathaysia blocks; (7) Triassic deposits of the Paleozoic Qilian Shan and West Qinling orogens along the SW margin of the North China block developed during collision of South China; and (8) Jurassic(?) ores on the margins of the Subumusu block in Myanmar and Malaysia. Circum-Pacific tectonism led to major orogenic gold province formation along the length of the eastern side of Asia between ca. 135 and 120 Ma, although such deposits are slightly older in South Korea and slightly younger in the Amur region of the Russian Southeast. Deformation related to collision of the Kolyma–Omolon microcontinent with the Pacific margin of the Siberia craton led to formation of 136–125 Ma ores of the Yana–Kolyma belt (Natalka, Sarylakh) and 125–119 Ma ores of the South Verkhoyansk synclinorium (Nezhdaninskoe). Giant ca. 125 Ma gold provinces developed in the Late Archean uplifted basement of the decratonized North China block, within its NE edge and into adjacent North Korea, in the Jiaodong Peninsula, and in the Qinling Mountains. The oldest gold-bearing magmatic–hydrothermal deposits of Asia include the ca. 485 Ma Duobaoshan porphyry within a part of the Tuva–Mongol arc, ca. 355 Ma low-sulfidation epithermal deposits (Kubaka) of the Omolon terrane accreted to eastern Russia, and porphyries (Bozshakol, Taldy Bulak) within Ordovican to Early Devonian oceanic arcs formed off the Kazakhstan microcontinent. The Late Devonian to Carboniferous was marked by widespread gold-rich porphyry development along the margins of the closing Ob–Zaisan, Junggar–Balkhash, and Turkestan basins (Amalyk, Oyu Tolgoi); most were formed in continental arcs, although the giant Oyu Tolgoi porphyry was part of a near-shore oceanic arc. Permian subduction-related deformation along the east side of the Indochina block led to ca. 300 Ma gold-bearing skarn and disseminated gold ore formation in the Truong Son fold belt of Laos, and along the west side to ca. 250 Ma gold-bearing skarns and epithermal deposits in the Loei fold belt of Laos and Thailand. In the Mesozoic Transbaikal region, extension along the basin margins subsequent to Mongol–Okhotsk closure was associated with ca. 150–125 Ma formation of important auriferous epithermal (Balei), skarn (Bystray), and porphyry (Kultuminskoe) deposits. In northeastern Russia, Early Cretaceous Pacific margin subduction and Late Cretaceous extension were associated with epithermal gold-deposit formation in the Uda–Murgal (Julietta) and Okhotsk–Chukotka (Dukat, Kupol) volcanic belts, respectively. In southeastern Russia, latest Cretaceous to Oligocene extension correlates with other low-sulfidation epithermal ores that formed in the East Sikhote–Alin volcanic belt. Other extensional events, likely related to changing plate dynamics along the Pacific margin of Asia, relate to epithermal–skarn–porphyry districts that formed at ca. 125–85 Ma in northeastmost China and ca. 105–90 Ma in the Coast Volcanic belt of SE China. The onset of strike slip along a part of the southeastern Pacific margin appears to correlate with the giant 148–135 Ma gold-rich porphyry–skarn province of the lower and middle Yangtze River. It is still controversial as to whether true Carlin-like gold deposits exist in Asia. Those deposits that most closely resemble the Nevada (USA) ores are those in the Permo-Triassic Youjiang basin of SW China and NE Vietnam, and are probably Late Triassic in age, although this is not certain. Other Carlin-like deposits have been suggested to exist in the Sepon basin of Laos and in the Mongol–Okhotsk region (Kuranakh) of Transbaikal.  相似文献   

18.
North Xinjiang, Northwest China, is made up of several Paleozoic orogens. From north to south these are the Chinese Altai, Junggar, and Tian Shan. It is characterized by widespread development of Late Carboniferous–Permian granitoids, which are commonly accepted as the products of post-collisional magmatism. Except for the Chinese Altai, East Junggar, and Tian Shan, little is known about the Devonian and older granitoids in the West Junggar, leading to an incomplete understanding of its Paleozoic tectonic history. New SHRIMP and LA-ICP-MS zircon U–Pb ages were determined for seventeen plutons in northern West Junggar and these ages confirm the presence of Late Silurian–Early Devonian plutons in the West Junggar. New age data, combined with those available from the literature, help us distinguish three groups of plutons in northern West Junggar. The first is represented by Late Silurian–Early Devonian (ca. 422 to 405 Ma) plutons in the EW-striking Xiemisitai and Saier Mountains, including A-type granite with aegirine–augite and arfvedsonite, and associated diorite, K-feldspar granite, and subvolcanic rocks. The second is composed of the Early Carboniferous (ca. 346 to 321 Ma) granodiorite, diorite, and monzonitic and K-feldspar granites, which mainly occur in the EW-extending Tarbgatay and Saur (also spelled as Sawuer in Chinese) Mountains. The third is mainly characterized by the latest Late Carboniferous–Middle Permian (ca. 304 to 263 Ma) granitoids in the Wuerkashier, Tarbgatay, and Saur Mountains.As a whole, the three epochs of plutons in northern West Junggar have different implications for tectonic evolution. The volcano-sedimentary strata in the Xiemisitai and Saier Mountains may not be Middle and Late Devonian as suggested previously because they are crosscut by the Late Silurian–Early Devonian plutons. Therefore, they are probably the eastern extension of the Early Paleozoic Boshchekul–Chingiz volcanic arc of East Kazakhstan in China. It is uncertain at present if these plutons might have been generated in either a subduction or post-collisional setting. The early Carboniferous plutons in the Tarbgatay and Saur Mountains may be part of the Late Paleozoic Zharma–Saur volcanic arc of the Kazakhstan block. They occur along the active margin of the Kazakhstan block, and their generation may be related to southward subduction of the Irtysh–Zaysan Ocean between Kazakhstan in the south and Altai in the north. The latest Late Carboniferous–Middle Permian plutons occur in the Zharma–Saur volcanic arc, Hebukesaier Depression, and the West Junggar accretionary complexes and significantly postdate the closure of the Irtysh–Zaysan Ocean in the Late Carboniferous because they are concurrent with the stitching plutons crosscutting the Irtysh–Zaysan suture zone. Hence the latest Late Carboniferous–Middle Permian plutons were generated in a post-collisional setting. The oldest stitching plutons in the Irtysh–Zaysan suture zone are coeval with those in northern West Junggar, together they place an upper age bound for the final amalgamation of the Altai and Kazakhstan blocks to be earlier than 307 Ma (before the Kaslmovian stage, Late Carboniferous). This is nearly coincident with widespread post-collisional granitoid plutons in North Xinjiang.  相似文献   

19.
黑龙江多宝山古生代海盆闭合的岩石学证据   总被引：2，自引：0，他引：2  
综合研究黑龙江多宝山地区古生代沉积地层、生物化石,通过分析侵入岩岩石地球化学及其锆石U--Pb 同位素测年资料,表明该地区早奥陶世至晚泥盆世早期为海相沉积地层,晚泥盆世晚期为海陆交互相沉积地层,早石炭世为陆相河湖沉积地层。多宝山海盆东南侧出露一套年龄为( 300 ± 3 ～ 357 ± 4) Ma 的花岗岩,其中正长、二长花岗质糜棱岩为后造山花岗岩,碱长花岗岩为造山后A 型花岗岩。表明多宝山海盆于晚泥盆世开始闭合,至早石炭世为陆相河湖沉积,晚石炭世-早二叠世为抬升剥蚀阶段。表现为多宝山地区于早石炭世开始造山,晚石炭世晚期或延至早二叠世发生造山后伸展作用。  相似文献   

20.
通过对甘新交界地区 3条石炭系和二叠系代表剖面的观察 ,结合多年调查东疆地层的资料积累 ,认为 :1)因绿条山组岩性组合及所含生物群与东疆的东古鲁巴斯套组相同 ,甘新交界地区绿条山组分布区是北塔山地层小区石炭系的南延部分 ,应从黑鹰山地层小区分出 ,甘新交界地区的中南部普遍缺失杜内期沉积 ;　 2 )阿齐山—康古尔—雅满苏火山岛弧带与博格达—哈尔里克火山岛弧带的构造造山历程不同 ,彼此的兴衰转换存在一定的时间差 ;　 3)甘肃北山石炭纪生物群与天山一级地层区的生物群相似 ,具有特提斯区系和西伯利亚—北美区系相互交会、混生的过渡性质 ;　 4 )来自兴蒙海槽的早二叠世海侵 ,未波及北疆地区 ,而是经由北山、红柳河谷地 ,终止于库姆塔格沙垄以东的狭小区域 ,根据雅满苏西大沟阿瑟尔期类化石的发现 ,推断至今从未发现早二叠世类化石的北山 ,主要原因是调查程度较低 ;　 5 )在金窝子金矿、2 10金矿及 2 30矿脉附近找到许多早二叠世生物化石 ,对仅根据一个同位素年龄数据 ( 36 1.1Ma)建立的“金窝子组”提出质疑 ,否定区内存在泥盆纪地层 ,认为金窝子金矿围岩地层的时代是早二叠世 ,不是晚泥盆世。  相似文献   

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