Ancient deep roots for Mesozoic world-class gold deposits in the north China craton:An integrated genetic perspective     

Cheng-Xue Yang  M.Santosh 《地学前缘(英文版)》2020,11(1):203-214

The North China Craton(NCC)hosts some of the world-class gold deposits that formed more than 2 billion years after the major orogenic cycles and cratonization.The diverse models for the genesis of these deposits remain equivocal,and mostly focused on the craton margin examples,although synchronous deposits formed in the interior domains.Here we adopt an integrated geological and geophysical perspective to evaluate the possible factors that contributed to the formation of the major gold deposits in the NCC.In the Archean tectonic framework of the NCC,the locations of the major gold deposits fall within or adjacent to greenstone belts or the margins of micro-continents.In the Paleoproterozoic framework,they are markedly aligned along two major collisional sutures-the Trans North China Orogen and the Jiao-Liao-Ji Belt.Since the Mesozoic intrusions hosting these deposits do not carry adequate signals for the source of gold,we explore the deep roots based on available geophysical data.We show that the gold deposits are preferentially distributed above zones of uplifted MOHO and shallow LAB corresponding to thinned crust and eroded sub-lithospheric mantle,and that the mineralization is located above regions of high heat flow representing mantle upwelling.The NCC was at the center of a multi-convergent regime during the Mesozoic which intensely churned the mantle and significantly en riched it.The geophysical data on Moho and LAB upwarp from the centre towards east of the craton is more consistent with paleo-Pacific slab subduction from the east exerting the dominant control on lithospheric thinning.Based on these results,and together with an evaluation of the geochemical and isotopic features of the Mesozoic magmatic intrusions hosting the gold mineralization,we propose a genetic model that invokes reworking of ancient Au archives preserved in the lower crust and metasomatised upper mantle and which were generated through multiple subduction,underplating and cumulation events associated with cratonization of the NCC as well as the subduction-collision of Yangtze Craton with the NCC.The heat and material input along zones of heterogeneously thinned lithosphere from a rising turbulent mantle triggered by Mesozoic convergent margins surrounding the craton aided in reworking the deep roots of the ancient Au reservoirs,leading to the major gold metallogeny along craton margins as well as in the interior of the NCC.  相似文献   

华北南缘中元古界高山河群碎屑锆石U-Pb年代学及其地质意义^*          下载免费PDF全文

王淼  周洪瑞  张恒 《古地理学报》2020,22(1):39-55

为了探讨华北板块南缘中元古代沉积地层的时代归属和物质来源、区域古地理格局和大地构造特征,对豫西灵宝福地地区的高山河群进行碎屑锆石U-Pb年代学和锆石微量元素特征研究。获得的高山河群年龄最小(年轻)的单颗碎屑锆石 ²⁰⁷Pb/²⁰⁶Pb 年龄值为1685±39 Ma,从而限制了高山河群最早沉积年龄不早于1700 Ma。结合上覆的龙家园组年代学标定(1594±12 Ma),将高山河群的形成年代限定为1700—1600 Ma,即中元古代长城纪的中晚期,属国际地质年表的“固结纪”。高山河群中碎屑锆石 ²⁰⁷Pb/²⁰⁶Pb 年龄范围为1685—2751 Ma,呈现1850 Ma、2150 Ma、2300 Ma和2500 Ma共4个年龄峰值,对应于华北克拉通古元古代重要的地质事件,并且高山河群以1850 Ma和2500 Ma峰值年龄段的地质体为主要的物源区。根据高山河群与云梦山组碎屑锆石年龄频率对比,推测在豫西地区西侧存在以往报道较少的年龄为2500 Ma的地质体。根据熊耳群火山岩及其对应锆石的地球化学特征和熊耳期盆地动力学性质,并结合高山河群沉积相特征和沉积盆地构造属性,认为熊耳群形成于与“岛弧”共生的拉张性质的弧后盆地地区,而其上覆的高山河群为弧后盆地靠近大陆一侧的具有被动大陆边缘性质的滨浅海沉积。  相似文献   

华北克拉通南缘石炭系本溪组铁-铝黏土矿物质来源: 以河南三门峡大安铝黏土矿床为例^*          下载免费PDF全文

刘学飞  王庆飞  马遥  李中明  赵利华  周智慧  刘百顺  马欣莉 《古地理学报》2020,22(5):965-976

华北克拉通在中奥陶世至晚石炭世期间一直出露地表,经历了长期的风化作用,形成大规模的铁-铝黏土矿,其成矿物源一直是研究的热点,尤其是本溪组底部铁矿和铁质黏土矿与上部铝黏土矿是否为同一来源尚未查清。本研究选取克拉通南缘大安铝黏土矿床作为研究对象,展开微区矿物及元素地球化学组成分析,进一步探讨铁-铝黏土矿物质来源。大安矿床内含矿岩系自下而上包括铁质黏土岩、铝土矿、铝质黏土矿;局部喀斯特高地缺失铝土矿,铝质黏土矿直接覆盖于铁质黏土岩之上。铁质黏土岩在洼地以菱铁矿、黄铁矿和伊利石为主,在隆起区以赤铁矿、伊利石和高岭石为主。铝土矿以硬水铝石、伊利石和锐钛矿为主;铝质黏土矿主要矿物为伊利石。矿物微区分析在黏土矿底部发现大量的碳化硅和少量自然硅、硅铁矿、铬铁矿;区域对比揭示北秦岭造山带内商丹缝合带和二郎坪群中的蛇绿岩为铝黏土矿形成提供了成矿物质。本溪组底部铁质黏土与上部铝黏土矿稳定元素比率(例如Zr/TiO₂、Hf/TiO₂、Nb/TiO₂、Ta/TiO₂)存在明显差异,揭示二者为不同来源: 底部铁质黏土岩和铁矿层为底板碳酸盐岩原地风化的产物;而上部铝黏土矿是异地搬运物,北秦岭造山带在晚石炭世的整体抬升为华北铝黏土矿形成提供了重要的成矿物质。  相似文献   

Using Mesoproterozoic sedimentary geochemistry to reconstruct basin tectonic geography and link organic carbon productivity to nutrient flux from a Northern Australian large igneous Province     

Bo Yang  Alan S. Collins  Grant M. Cox  Amber J. M. Jarrett  Steven Denyszyn  Morgan L. Blades  Juraj Farkaš  Stijn Glorie 《Basin Research》2020,32(6):1734-1750

The Beetaloo Sub-basin, northern Australia, is considered the main depocentre of the 1,000-km scale Mesoproterozoic Wilton package of the greater McArthur Basin – the host to one of the oldest hydrocarbon global resources. The ca. 1.40–1.31 Ga upper Roper Group and the latest Mesoproterozoic to early Neoproterozoic unnamed group of the Beetaloo Sub-basin, together, record ca. 500 million years of depositional history within the North Australia Craton. Whole-rock shale Sm–Nd and Pb isotope data from these sediments reveal sedimentary provenance and their evolution from ca. 1.35 to 0.85 Ga. Furthermore, these data, together with shale major/trace elements data from this study and pyrolysis data from previous publications, are used to develop a dynamic tectonic geography model that links the organic carbon production and burial to an enhanced weathering of nutrients from a large igneous province. The ca. 1.35–1.31 Ga Kyalla Formation of the upper Roper Group is composed of isotopically evolved sedimentary detritus that passes up, into more isotopically juvenile Pb values towards the top of the formation. The increase in juvenile compositions coincides with elevated total organic carbon (TOC) contents of these sediments. The coherently enriched juvenile compositions and TOC the upper portions of the Kyalla Formation are interpreted to reflect an increase in nutrient supply associated with the weathering of basaltic sources (e.g. phosphorous). Possible, relatively juvenile, basaltic sources include the Wankanki Supersuite in the western Musgraves and the Derim Derim–Galiwinku large igneous province (LIP). The transition into juvenile, basaltic sources directly before a supersequence-bounding unconformity is here interpreted to reflect uplift and erosion of the Derim Derim–Galiwinku LIP, rather than an influx of southern Musgrave sources. A new baddeleyite crystallisation age of 1,312.9 ± 0.7 Ma provides both a tight constraint on the age of this LIP, along with its associated magmatic uplift, as well as providing a minimum age constraint for Roper Group deposition. The unconformably overlying lower and upper Jamison sandstones are at least 300 million years younger than the Kyalla Formation and were sourced from the Musgrave Province. An up-section increase in isotopically juvenile compositions seen in these rocks is interpreted to document the progressive exhumation of the western Musgrave Province. The overlying Hayfield mudstone received detritus from both the Musgrave and Arunta regions, and its isotopic geochemistry reveals affinities with other early Neoproterozoic basins (e.g. Amadeus, Victoria and Officer basins), indicating the potential for inter-basin correlations.  相似文献   

北黄海海底麻坑群形态的定量研究及控制因素   总被引：1，自引：0，他引：1  

刘晓瑜  冯秀丽  陈义兰  唐秋华  刘乐军  路波  焦鹏飞 《海洋学报》2018,40(3):36-49

本文基于高分辨率多波束水深数据和反向散射强度数据，对北黄海海底麻坑群的形态参数进行定量研究，结合水深、地形坡度和后向散射强度的变化准确界定了麻坑的轮廓，识别出圆形、椭圆形、拉长型麻坑共282个，并在ArcGIS软件中对其形态参数进行了分析计算，麻坑的平均长轴1.36 km，短轴0.78 km，直径0.94 km，面积0.88 km2，平均周长3.82 km，长宽比1.83，深度0.3~2.5 m，平均面积密集度13%，麻坑的剖面形态有麻坑边缘凹陷、中部有明显凸起（W1型），麻坑边缘凹陷、中部略凸起（W2型），麻坑中部单纯凹陷（V型），分别集中分布在麻坑群的北部、南部、西部。麻坑的平面规模大、深度小的原因与地层中形成麻坑的游离气体浓度较小有关，也可能受到了地震、海啸等外力的诱发。麻坑的长轴优势走向为ENE-WSW、NNE-SSW，底流对其形状的塑造起了较大作用，部分麻坑成串排列，形成串珠状的麻坑链，其排列方式受到海底古河道、古潟湖等沉积地层结构的控制。海底麻坑群发育区反向散射强度为-60~-71 dB，麻坑内部较麻坑外部平均高5 dB，可能为麻坑内部气体泄漏引起海底沉积物被剥蚀后残留下的粗颗粒物质或海底生物活动留下的遗迹导致的。  相似文献   

Postglacial variability in near‐bottom current speed on the continental shelf off south‐west Spitsbergen          下载免费PDF全文

BEATA STERNAL  WITOLD SZCZUCISKI  MATTHIAS FORWICK  MAREK ZAJĄCZKOWSKI  STANISŁAW LORENC  JOANNA PRZYTARSKA 《第四纪科学杂志》2014,29(8):767-777

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Zircon U–Pb ages and Hf isotope compositions of migmatites from the North Qinling terrane and their geological implications     

Q. Liu  Y.‐B. Wu  H. Wang  S. Gao  Z.‐W. Qin  X.‐C. Liu  S.‐H. Yang  H.‐J. Gong 《Journal of Metamorphic Geology》2014,32(2):177-193

Migmatites are predominant in the North Qinling (NQ) orogen, but their formation ages are poorly constrained. This paper presents a combined study of cathodoluminescence imaging, U–Pb age, trace element and Hf isotopes of zircon in migmatites from the NQ unit. In the migmatites, most zircon grains occur as new, homogeneous crystals, while some are present as overgrowth rims around inherited cores. Morphological and trace element features suggest that the zircon crystals are metamorphic and formed during partial melting. The inherited cores have oscillatory zoning and yield U–Pb ages of c. 900 Ma, representing their protolith ages. The early Neoproterozoic protoliths probably formed in an active continental margin, being a response to the assembly of the supercontinent Rodinia. The migmatite zircon yields Hf model ages of 1911 ± 20 to 990 ± 22 Ma, indicating that the protoliths were derived from reworking of Palaeoproterozoic to Neoproterozoic crustal materials. The anatexis zircon yields formation ages ranging from 455 ± 5 to 420 ± 4 Ma, with a peak at c. 435 Ma. Combined with previous results, we suggest that the migmatization of the NQ terrane occurred at c. 455–400 Ma. The migmatization was c. 50 Ma later than the c. 490 Ma ultra‐high‐P (UHP) metamorphism, indicating that they occurred in two independent tectonic events. By contrast, the migmatization was coeval with the granulite facies metamorphism and the granitic magmatism in the NQ unit, which collectively argue for their formation due to the northward subduction of the Shangdan Ocean. UHP rocks were distributed mainly along the northern margin and occasionally in the inner part of the NQ unit, indicating that they were exhumed along the northern edge and detached from the basement by the subsequent migmatization process.  相似文献   

Provenance of sediment in the Labrador Current: a record of hinterland glaciation over the past 125 ka          下载免费PDF全文

LONGJIANG MAO  DAVID J. W. PIPER  FRANCKY SAINT‐ANGE  JOHN T. ANDREWS  MARKUS KIENAST 《第四纪科学杂志》2014,29(7):650-660

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A Middle Palaeolithic site in the southern North Sea: investigating the archaeology and palaeogeography of Area 240          下载免费PDF全文

L. TIZZARD  A. R. BICKET  J. BENJAMIN  D. DE LOECKER 《第四纪科学杂志》2014,29(7):698-710

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华北板块南缘中段中上三叠统软沉积变形构造的发现及其地质意义     

全晓园  刘池洋  张龙  张东东  王建强  马奂奂  冯琦  翟光麾 《现代地质》2020,34(2):333-344

豫西地区中上三叠统主要出露在济源、义马、伊川和南召一带。印支期秦岭造山运动控制和影响着邻区中上三叠统盆地属性和沉积地层展布。通过观察研究区野外露头剖面,发现中上三叠统发育一系列典型的软沉积变形构造,包括液化底辟、枕状构造、液化柱、液化卷曲变形、负载、球-枕、火焰状构造、液化角砾岩。这些软沉积变形在垂向上表现出明显的复现性,在侧向上表现为沿地层连续展布,表明该时期研究区内地层受到频繁强烈的地震影响。通过对这些软沉积现象的识别和形成机制解释,判定其触发因素为秦岭造山过程中伴生的地震。区内地层中震积岩的存在即是对秦岭造山过程中构造活动的响应。  相似文献