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1.
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
2.
The link between metallogeny and craton destruction in the North China Craton (NCC) remains poorly understood, particularly the mechanisms within the interior of the craton. In this overview, we summarize the major stages in the history of formation and evolution of the NCC, the spatio-temporal distribution and types of major ore species, as well as mantle contribution to the metallogeny, in an attempt to evaluate the geodynamic settings of metallogeny and the mechanisms of formation of the ore deposits. The early Precambrian history of the NCC witnessed the amalgamation of micro-blocks and construction of the fundamental tectonic architecture of the craton by 2.5 Ga. The boundaries of these micro-blocks and the margins of the NCC remained as weak zones and were the principal locales along which inhomogeneous destruction of the craton occurred during later tectonothermal events. These zones record the formation of orogeny related gold, copper, iron and titanium during the early to middle Paleoproterozoic with ages ranging from 2.5 to 1.8 Ma. The Early Ordovician kimberlite and diamond mineralization at ca. 480 Ma, the Late Carboniferous and Early to middle Permian calc-alkaline, I-type granitoids and gold deposits of 324–300 Ma, and the Triassic alkaline rocks and gold–silver-polymetallic deposits occurring along these zones and the margins of the blocks correlate with rising mantle plume, southward subduction of the Siberian plate and northward subduction of the Yangtze plate, respectively. The voluminous Jurassic granitoids and Cretaceous intrusives carrying gold, molybdenum, copper, lead and zinc deposits are also localized along the weak zones and block margins. The concentration of most of these deposits in the eastern part of the NCC invokes correlation with lithosphere thinning associated with the westward subduction of the Pacific plate. Although magmatism and mineralization have been recorded along the margins and few places within the interior of the NCC in the Jurassic, their peak occurred in the Cretaceous in the eastern part of the NCC, marking large scale destruction of the craton at this time. The junctions of the boundaries between the micro-continental blocks are characterized by extensive inhomogeneous thinning. We propose that these junctions are probably for future mineral exploration targeting in the NCC. 相似文献
3.
The North China Craton (NCC) provides one of the classic examples of craton destruction, although the mechanisms and processes of its decratonization are yet to be fully understood. Here we integrate petrological, geochemical, geochronological and geophysical information from the NCC and conclude that the destruction of the craton involved multiple events of circum-craton subduction, which provided the driving force that destabilized mantle convection and tectonically eroded the lithospheric mantle beneath the craton. Furthermore, subducted-slab-derived fluids/melts weakened the subcontinental lithospheric mantle and facilitated thermo-mechanical and chemical erosion of the lithosphere. The more intense destruction beneath the eastern part of the NCC reflects the crucial contribution of Pacific plate subduction from the east that overprinted the mantle lithosphere modified during the early subduction processes. Our study further establishes the close relationship between lithospheric modification via peridotite–melt reactions induced by oceanic plate subduction and cratonic destruction. 相似文献
4.
The North China Craton (NCC) hosts some of the world-class gold deposits on the globe, which can be classified into distinct types as the “Jiaodong type”, explosive breccia type and skarn type. The “Jiaodong type” gold deposits were formed at ca. 120–130 Ma both in the margins and interior of the NCC. Two explosive breccia gold deposits formed at ac. 180 Ma and 120 Ma and are located in the southern margin and the interior of the NCC. Important skarn gold deposits of ca. 128 Ma formed within the interior of the NCC. Although the formation and distribution of these gold deposits are temporally and spatially heterogeneous, they are commonly related with the lithospheric destruction of the NCC. The interplay of several factors such as basement architecture, inhomogeneous decratonization, crust-mantle interaction, mantle dynamics, magmatic characteristics, high heat flow and massive flux of deep-derived ore-forming fluids operated in generating the gold endowment. All the three types of gold systems are closely related with granitoid plutons and different types of dykes, the magmas for which were sourced from the lower crust near the Moho discontinuity and involved the mixing and mingling of felsic and mafic magmas. The ore forming fluids display prominent magmatic signature and were largely derived from deep domains, with probable input from the asthenosphere mantle. The heterogeneous distribution of the giant gold systems in the NCC was geodynamically controlled by the destruction of the craton. The regions at the confluence of two or three Precambrian micro-continental-blocks are generally characterized by thinned lithosphere and high heat flow, constituting the potential sites of giant gold deposits. The mantle beneath these regions shows EM2 characteristics implying the involvement of subducted oceanic components. The magmatic intrusions associated with the gold systems crystallized under high oxygen fugacity conditions and were rich in volatiles. 相似文献
5.
The North China Craton (NCC), which is composed of the eastern NCC and the western NCC sutured by the Palaeoproterozoic Trans‐North China Orogen, is one of the oldest continental nuclei in the world and the largest cratonic block in China. The eastern NCC is widely known for its significant lithospheric thinning and destruction during the Late Mesozoic. Models on the destruction of the eastern NCC can be principally grouped into two: (1) thermal/mechanical and/or chemical erosion, and (2) lower crustal and (or) lithospheric delamination. The erosion model suggests that the NCC lithospheric thinning resulted from chemical and/or mechanical interactions of lithospheric mantle with melts or hydrous fluids derived from the asthenosphere, whereas the delamination model proposes lithospheric destruction through foundering of eclogitic lower crust together with lithospheric mantle into the underlying convecting mantle. However, those models lack seismic evidence to explain the destruction process. Here, we analyse the crustal structure and upper mantle discontinuity by employing the H–k stacking technique of receiver function as well as the depth domain receiver function. Our results indicate deep mantle upwelling and lower crustal delamination beneath the eastern NCC, and suggest that either or both of these processes contributed to the unique lithospheric thinning and destruction of the eastern NCC. © 2013 The Authors. Geological Journal published by John Wiley & Sons, Ltd. 相似文献
6.
Based on the Zimbabwe craton, it is suggested that, during the Archaean, full decoupling between a strong upper crust and a strong upper mantle across a weak detachment zone at the Moho allowed the independent development of crustal and mantle geometries in response to lithospheric shortening. This is an effective way to explain the field observations made in the Zimbabwe craton, which suggest a late-Archaean interplay between lateral accretionary processes through low angle thrust stacking and underplating and deep seated lineament zones with a possible mantle origin. The lineament zones play an important role in the localisation of mineral deposits such as base metals, gold, and possibly diamonds. Thickening of the mantle lithosphere occurred independently from the crust, through early Archaean melt segregation and/or lithospheric underplating. 相似文献
7.
A review of the geodynamic setting of large-scale Late Mesozoic gold mineralization in the North China Craton: an association with lithospheric thinning 总被引：22，自引：0，他引：22
Abundant gold deposits are distributed along the margins of the North China Craton (NCC). Occurring throughout the Precambrian basement and located in or proximal to Mesozoic granitoids, these deposits show a consistent spatial–temporal association with Late Jurassic–Early Cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock. Their ages are mainly Early Cretaceous (130–110 Ma) and constrain a very short period of metallogenesis. Sr–Nd–Pb isotopic tracers of ores, minerals and associated rocks indicate that gold and associated metals mainly were derived from multi-sources, i.e., the wall rocks (Precambrian basement and Mesozoic granites) and associated mafic rocks.Previous studies, including high surface heat flow, uplift and later basin development, slow seismic wave speeds in the upper mantle, and a change in the character of mantle xenoliths sampled by Paleozoic to Cenozoic magmas, have been used to suggest that ancient, cratonic mantle lithosphere was removed from the base of the NCC some time after the Ordovician, and replaced by younger, less refractory lithospheric mantle. The geochemistry and isotopic compositions of the mafic rocks associated with gold mineralization (130–110 Ma) indicate that they were derived from an ancient enriched lithospheric mantle source; whereas, the mafic dikes and volcanic rocks younger than 110 Ma were derived from a relatively depleted mantle source, i.e., asthenospheric mantle. According to their age and sources, relation to magmatism and geodynamic framework, the gold deposits were formed during lithospheric thinning. The removal of lithospheric mantle and the upwelling of new asthenospheric mantle induced partial melting and dehydration of the lithospheric mantle and lower crust due to an increase of temperature. The fluids derived from the lower crust were mixed with magmatic and meteoric waters, and resulted in the deposition of gold and associated metals. 相似文献
8.
《Gondwana Research》2014,25(3-4):849-864
We have imaged the lithospheric structure beneath the central and western North China Craton (NCC) with Rayleigh wave tomography. The Rayleigh waveforms of 100 teleseismic events recorded by 208 broadband stations are used to yield high-resolution phase velocity maps at 13 periods from 20 s to 143 s. A 3-D S-wave velocity model is constructed based on the phase velocity maps. Our S-wave velocity model is broadly consistent with the results of previous tomography studies, but shows more detailed variations within the lithosphere. The Trans-North China Orogen (TNCO) is generally characterized by low-velocity anomalies but exhibits great heterogeneities. Two major low-velocity zones (LVZs) are observed in the north and south, respectively. The northern LVZ laterally coincides with sites of Cenozoic magmatism and extends to depths greater than 200 km. We propose that a small-scale mantle upwelling is present, confined to the north of the TNCO. A high-velocity patch in the uppermost mantle is also observed between the two LVZs adjacent to the narrow transtensional zone of the Cenozoic Shanxi–Shaanxi Rift (SSR). We interpret this as the remnant of a cratonic mantle root. The Ordos Block in the western NCC is associated with high-velocity anomalies, similarly reflecting the existence of cratonic mantle root, but a discernible low-velocity layer is observed at depths of 100–150 km in this location. We interpret that this mid-lithospheric structure was probably formed by metasomatic processes during the early formation of the NCC. Based on the observations from our S-wave velocity model, we conclude that the current highly heterogeneous lithospheric structure beneath the TNCO is the result of multiphase reworking of pre-existing mechanically weak zones since the amalgamation of the craton. The latest Cenozoic lithospheric reworking is dominated by the far-field effects of both Pacific plate subduction and the India–Eurasia collision. 相似文献
9.
The abundances and isotopic compositions of Helium and Argon have been analyzed in a suite of fresh spinel peridotite xenoliths in Cenozoic basalts from the eastern North China Craton (NCC) by step-wise heating experiments, to investigate the nature of noble gas reservoirs in the subcontinental lithospheric mantle beneath this region. The xenoliths include one harzburgite collected from Hebi in the interior of the NCC, two lherzolites from Hannuoba at the northern margin of the craton, and three lherzolites from Shanwang and Nushan on the eastern margin. 3He/4He ratios in most of the xenoliths are similar to those of mid-ocean ridge basalts (MORB) or slightly lower (2–10.5 Ra, where Ra is the 3He/4He ratio of the atmosphere), suggesting mixing of MORB-like and radiogenic components. One olivine separate from Nushan has a helium value of 25.3 Ra, probably suggesting cosmogenic 3He addition. The 40Ar/36Ar ratios vary from atmospheric value (296) to 1625, significantly lower than the MORB value. Available data of the peridotite xenoliths indicate the He and Ar isotopic systematics of the mantle reservoirs beneath the NCC can be interpreted as mixtures of at least three end-members including MORB-like, radiogenic and atmospheric components. We suggest that the MORB-like noble gases were derived from the underlying asthenosphere during mantle upwelling, whereas the radiogenic and recycled components probably were incorporated into the lithospheric mantle during circum-craton subduction of oceanic crust. Available data suggest that the MORB-like fluids are better preserved in the interior of the NCC, whereas the radiogenic ones are more prevalent at the margins. The Paleo-Asian ocean subduction system probably was responsible for the enriched and recycled noble gas signatures on the northern margin of the craton, while the Pacific subduction system could account for the observed He–Ar isotopic signatures beneath the eastern part. Therefore, integration of helium and argon isotopes reflects heterogeneous metasomatism in the lithospheric mantle and demonstrates the critical importance of lithospheric mantle modification related to both circum-craton subduction of oceanic crust and asthenospheric upwelling beneath the eastern NCC. 相似文献
10.
《地学前缘(英文版)》2022,13(2):101339
The current margins of the North China and Yangtze Cratons provide arguably the best examples globally of anomalously high mineral endowment within a 100 km buffer zone, hosting 66 diverse world-class to giant ore systems that help explain China’s premier position as a producer of multiple metal and mineral commodities. After the cratonization of these crustal blocks during the Neoarchean-Paleoproterozoic, with incorporation of iron ores on assembled micro-block margins, the margins of the cratons experienced multiple convergence and rifting events leading to metasomatism and fertilization of their underlying sub-continental lithospheric mantle. The rifted margins with trans-lithosphere faults provided pathways for Cu-Au (Mo-W-Sn)-bearing felsic to Ni-Cu-bearing ultrabasic intrusions and REE-rich carbonatite magmas, and for the development of marginal sedimentary basins with both Cu-Pb-Zn-rich source units and reactive carbonate or carbonaceous host rocks. There was diachronous formation of hydrothermal orogenic gold, antimony, and bismuth systems in the narrow orogenic belts between the cratons. Complexity in the Mesozoic Paleo-Pacific subduction systems resulted in asthenosphere upwelling and lithosphere extension and thinning in the North China Craton, leading to anomalous heat flow and formation of orogenic gold deposits, including those of the giant Jiaodong gold province on its north-eastern margin. These gold deposits, many of which formed from fluids liberated by devolatilization of previously metasomatized sub-continental lithospheric mantle, helped propel China to be the premier gold producer globally. The thick sub-continental lithospheric mantle of the cold buoyant cratons helped the preservation of some of the world’s oldest porphyry-skarn and epithermal mineral systems. Although craton margins globally control the formation and preservation of a diverse range of mineral deposits, China represents the premier example in terms of metal endowment due to the anomalous length of its craton margins combined with their abnormally complex tectonic history. 相似文献
11.
The continental craton is generally considered to be stable, due to its low-density and high viscosity; however, the thinning and destruction of cratonic lithosphere have been observed at various parts of the globe, for example, the eastern North China Craton (NCC). Although a large number of geological and geophysical data have been collected to study the NCC, the mechanisms and dynamic processes are still widely debated. In this study, using 2-D high-resolution thermo-mechanical models, we systematically explore the key constraints on the destruction of cratonic lithosphere. The model results indicate that the craton destruction processes can be strongly influenced by the presence of the so-called mid-lithosphere discontinuity (MLD), and its interaction with subduction. The properties of the MLD layer and the density contrast between the lithospheric mantle and asthenosphere play significant roles in the destruction processes. Specifically, the presence of a deep and low-viscosity MLD layer within the cratonic lithosphere tends to enhance instability of the craton, making it easier for lithosphere destruction. In addition, a relatively thick oceanic crust, high convergence rate, and large initial subduction angles favor the craton destruction. Finally, we compare the model results with the observations of NCC, which indicate that the interaction between the Paleo-Pacific subduction and the MLD layer in the cratonic lithosphere has played an important role in the observed large-scale lithospheric removal of the eastern North China Craton. 相似文献
12.
非造山带型金矿--胶东型金矿的陆内成矿作用 总被引：42，自引：2，他引：40
综合了全球有关金矿床的资料 ,Goldfarb和Groves等发表了著名的造山带金矿的论述 ,提出了与造山带有关的金矿在全球范围和从中太古代到整个显生宙的地质时期有广泛的分布和周期性。该类金矿的特点是与变形和变质的中地壳岩块共生 ,特别是在空间上与相应的地壳构造一致。金矿出现在造山带的不同构造部位 ,与不同的金属共生或伴生成矿。胶东作为一个重要的金矿矿集区 ,以不到中国领土面积的 0 .2 % ,而金矿产量占全国的 1 /4。国内一些地质学家也将胶东型金矿划归为造山带型金矿。最近的研究表明 ,胶东矿集区的东界与华北克拉通的东界吻合 ,金矿以华北克拉通变质岩及其有关的侵入岩为控矿围岩。主成矿期成矿时代为 (1 2 0± 1 0 )Ma ,约在不到 1 0Ma的短时限内。成矿物质具有多元性 ,既来自于控矿围岩———花岗片麻岩和变质岩 ,又来自于幔源的岩浆岩 ,特别是与中基性脉岩、偏碱的钙碱性花岗岩的侵入关系密切。除胶东金矿集区之外 ,华北克拉通的边缘和内部普遍含有金矿 ,而且金矿的物质来源、成矿方式、矿产类型、成矿围岩和成矿年龄都是一致的。这种大规模、短时限、高强度的成矿 ,被中国地质学家所重视并称为中生代成矿大爆发或金属异常巨量堆积。深部结构和成分的研究表明 ,华北东部的岩石圈在中生代急 相似文献
13.
In the Lachlan Fold Belt of southeastern Australia, major orogenic gold and porphyry gold–copper deposits formed simultaneously
within distinct tectonic settings during a very short time interval at ca. 440 Ma. The driving mechanism that controlled the
temporal coincidence of these deposits remains largely unexplained. A review of contemporaneous metallogenic, tectonic, magmatic
and sedimentological events in central and eastern Australia reveals that a change in subduction dynamics along the Australian
sector of the Early Palaeozoic circum–Gondwana mega-subduction system could have influenced lithospheric stress conditions
far inboard of the subduction margin. The magnitude of ore formation and the spatial extent of related events are proposed
in this paper to have been controlled by the interplay of mantle processes and lithospheric changes that followed slab break-off
along a portion of the mega-subduction system surrounding Gondwana at that time. Slab break-off after subduction lock-up caused
mantle upwelling that, in turn, provided an instantaneous heat supply for magmatic and hydrothermal events. Coincident reorganisation
of lithospheric stress conditions far inboard of the proto-Pacific margin of Australia controlled reactivation of deep-lithospheric
fault structures. These fault systems provided a pathway for fluids and heat fuelled by mantle upwelling into the upper lithosphere
and caused the deposition of ~440 Ma gold deposits in the Lachlan Fold Belt, as well as a range of metallogenic, tectonic
and sedimentary changes elsewhere in central and eastern Australia. 相似文献
14.
华北克拉通北缘及邻区印支期岩浆活动与钼和金成矿作用 总被引：4，自引：0，他引：4
对华北克拉通北缘及邻区19处钼矿床和5处金矿床的产出环境、形成时代和成矿机理及其与印支期侵入岩的关系进行了讨论。尽管各个矿床所处的地理位置不同,但是它们大都在前寒武纪或早古生代地层中产出,并且与印支期侵入岩具有密切的时空分布关系。印支期钼矿床的形成作用可以从早三叠世一直持续到晚三叠世,大规模成矿作用高峰期为230~220 Ma。相比之下,金矿床的形成时间明显早于钼矿床,同位素年龄数据集中分布在245~239 Ma。研究结果表明,自早三叠世开始,华北克拉通北缘及邻区曾发生过多期大规模伸展构造作用,并且形成若干条近东西向展布的裂陷带。张裂构造作用所诱发的富碱性岩浆作用及相关流体活动为钼或金矿床的形成提供了动力和物质来源,因此,印支期侵入岩发育区是寻找隐伏钼或金矿床的有利地区。 相似文献
15.
华北克拉通东部早白垩世伸展盆地的发育过程及其对克拉通的破坏 总被引：1，自引：0，他引：1
在晚侏罗世华北克拉通东部破坏之初出现了区域性隆起,全区缺失上侏罗统沉积。在早白垩世早期,出现了区域性的伸展活动,断陷盆地形成,克拉通南、北缘伸展活动最强,北部燕山构造带以出现变质核杂岩为特征,南部出现宽裂谷型盆地。早白垩世中期华北克拉通东部普遍出现了火山活动与岩浆侵入。早白垩世晚期克拉通上以出现窄裂谷型盆地为特征,沿北北东走向的郯庐断裂带断陷活动最强。这些断陷盆地的演化过程揭示,经历地表抬升后,克拉通破坏之初的岩石圈热而弱,从而形成变质核杂岩或宽裂谷型盆地。这期间的破坏强度在空间上具有不均匀分布的特征,受控于早期岩石圈地幔的结构。经过早白垩世中期的大量岩浆活动之后,早白垩世晚期克拉通岩石圈温度降低、强度变大,从而利用早期大型断裂构造形成窄裂谷型盆地。这现象支持华北克拉通东部晚中生代的岩石圈减薄是以逐渐拆沉机制为主。 相似文献
16.
The North China Craton (NCC) preserves the history of crustal growth and craton formation during the early Precambrian followed by extensive lithospheric thinning and craton destruction in the Mesozoic. Here we present evidence for magma mixing and mingling associated with the Mesozoic tectonic processes from the Central NCC, along the Trans-North China Orogen, a paleo suture along which the Eastern and Western Blocks were amalgamated at end of Paleoproterozoic. Our investigations focus on two granitoids – the Chiwawu and the Mapeng plutons. Typical signatures for the interaction of mafic and felsic magmas are observed in these plutons such as: (1) the presence of diorite enclaves; (2) flow structures; (3) schlierens; (4) varying degrees of hybridization; and (5) macro-, and micro-textures. Porphyritic feldspar crystals show numerous mineral inclusions as well as rapakivi and anti-rapakivi textures. We present bulk chemistry, zircon U–Pb geochronology and REE data, and Lu–Hf isotopes on the granitoids, diorite enclaves, and surrounding basement rocks to constrain the timing of intraplate magmatism and processes of interaction between felsic and mafic magmas. Our LA-ICP-MS zircon U–Pb data show that the pophyritic granodiorite was emplaced at 129.7 ± 1.0 Ma. The diorite enclaves within this granodiorite show identical ages (128.2 ± 1.5 Ma). The basement TTG (tonalite–trondhjemite–granodiorite) gneisses formed at ca. 2.5 Ga coinciding with the major period of crustal accretion in the NCC. The 1.85 Ga age from zircons in the gabbro with positive Hf isotope signature may be related to mantle magmatism during post-collisional extension following the assembly of the Western and Eastern Blocks of the NCC along the Trans-North China Orogen. Our Hf isotope data indicate that the Neoarchean–Paleoproterozoic basement rocks were derived from complex sources of both juvenile magmas and reworked ancient crust, whereas the magma source for the Mesozoic units are dominantly reworked basement rocks. Our study provides a window to intraplate magmatism triggered by mantle upwelling beneath a paleosuture in the North China Craton. 相似文献
17.
胶东-朝鲜半岛中生代金成矿作用 总被引：8，自引：2，他引：6
华北克拉通东部与朝鲜半岛相接,是中朝克拉通的重要组成部分。在华北克拉通东部的胶东半岛和朝鲜半岛内皆产出有不同规模的金矿床,并具有显著的地域特色。胶东半岛已发现金矿床(点)近200处,其中三山岛、焦家、新城、玲珑等为世界级金矿,它们为石英脉型和受构造控制的蚀变岩型,成矿时间主要集中在~120Ma,说明金成矿作用是在相当短的时间内,在同一成矿背景下和同一构造-岩浆-流体成矿系统下完成的。成矿流体主要来自幔源岩浆以及幔源岩浆与地壳相互作用产生的地质流体,就位环境与地壳/岩石圈在早白垩世强烈伸展构造变形有关,为克拉通破坏型金矿;与我国辽东相邻的朝鲜半岛北部平安北道等地金矿储量较大,成矿类型与特征辽东五龙金矿类似,为石英脉型矿化,也可能为早白垩世与华北克拉通岩石圈减薄、破坏相关的金矿床;朝鲜半岛南部的韩国金(银)矿床分成侏罗纪中温热液型和白垩纪浅成低温热液型两类,其中侏罗纪热液脉状金矿成矿特征虽与胶东金矿类似,但成矿时代(峰期~160Ma)有显著差异。而白垩纪浅成低温热液型金-银矿化主要发生在100~70Ma,与太平洋板块俯冲作用相关,为典型的环太平洋斑岩-次火山活动有关的浅成低温贱金属成矿系列。胶东和朝鲜半岛金矿床类型、特征及成矿时间的异同,与区域中生代地质演化及地球动力学背景密切相关。 相似文献
18.
中亚造山带作为地球上规模宏伟的造山带之一,是显生宙以来陆壳增生和伸展作用强烈的地区。华北克拉通是世界上最古老的陆块之一,晚中生代以来经历了大规模的伸展作用。中亚造山带与华北克拉通南北相连,悠久的构造演化进程使这一地区成为研究大陆造山及造山后伸展作用的理想场所。本文对新近完成的横过中亚造山带南缘一华北克拉通北缘(洪格尔-怀来)的600 km大地电磁长剖面,进行了严格规范的数据处理、分析和反演,获得了深部电性结构模型,研究了中亚造山带南缘和华北克拉通北缘深部壳幔结构,进而为该区构造演化提供新的依据。沿剖面,上地壳高阻体与分布的花岗岩对应;中、下地壳向北倾斜的高导层与其下方高导体相连,指示出地幔物质上升的通道,该套高导层与高导体可能形成于板块碰撞后的伸展环境,反映出地幔物质的上升作用是碰撞后构造伸展的主要动力。 相似文献
19.
The North China Craton (NCC) provides a classic example for extensive destruction of the cratonic lithosphere. The Mesozoic magmatism which contributed to the decratonization of the NCC was also accompanied by the formation of a variety of mineral deposits. In order to gain further insights into the cratonic destruction process, typical iron and gold deposits are investigated here. Helium–argon isotopic data on pyrite, from typical skarn iron deposits of the Beiminghe and Fushan in the Han-Xing district of the central NCC, and the Linglong and Canzhuang gold deposits in the Jiaodong district in the eastern NCC, are presented in this paper. The 3He/4He, 40Ar/36Ar and 40Ar/4He ratios show generally uniform patterns within the individual deposits and reveal a complex evolutionary history of the ore-forming fluids with varying degree of crust–mantle interaction. The ore-forming fluids associated with the gold mineralization at the Jiaodong mine have higher content of fluids of mantle origin with mantle helium ranging from 1.24% to 18.02% (average 6.73%; N = 18). In contrast, the ore-forming fluids related to the iron ore deposits contain less mantle contribution with mantle helium ranging from 0.12% to 4.96% (average 1.29%; N = 10). Our results suggest complex and heterogeneous crust–mantle processes associated with the magmatism and metallogeny, where the lithosphere of the eastern NCC was subjected to more extensive thinning and destruction as compared with that in the western part, consistent with the observations from geophysical studies in the region. Our study demonstrates that fluids associated with the Mesozoic metallogenic processes in the NCC provide useful insights into the geodynamics of destruction and refertilization of the cratonic lithosphere. 相似文献
20.
华北克拉通绿岩带型金成矿系统初析 总被引：5，自引：0，他引：5
华北克拉通中绿岩带型金矿床是我国重要的矿床类型之一，也是我国黄金产量和储量的主要来源。从构造动力体制来看，华北克拉通在漫长的演化历史中曾经达过中晚元古代的离散型陆缘，早古生代到晚古生代的汇聚型陆缘和显生宙中生代克拉通活化多个构造阶段。金矿床主要形成于克拉通活化阶段，其总的构造背景可概括为由挤压，碰撞作用晚期或期后向伸展构造的转变时期。金成矿具有明显的区域地球化学背景。虽然华北克拉通绿岩带型金矿床形成时代不尽相同，但具有相似的地质地球化学特征，并与显生宙花岗岩类侵入体具晚于花岗岩，指示金矿化是构造－花岗岩浆演化晚期的产物。因此，这些金矿床基本上可归为一个成矿系统，即绿岩带中与花岗质岩浆作用于有关的热液成矿系统。 相似文献