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新疆天山石炭—二叠纪大规模岩浆成矿事件与形成机制探讨 总被引：1，自引：0，他引：1
天山地质构造演化复杂,多阶段演化中岩浆活动与成矿作用规模并不均衡。而石炭-二叠纪却是天山成矿带大规模岩浆活动和金属成矿作用的"爆发"期。本研究紧紧围绕岩浆铜镍矿床、斑岩型铜(钼)矿床及火山岩型磁铁矿矿床,从含矿岩体的岩浆起源、岩浆演化及成矿特点,系统研究地球深部相应岩浆活动的地质过程。通过典型矿床的深入剖析,建立相应矿床类型的成矿模式,破解制约找矿突破的控制因素,系统阐述了板块构造与地幔柱体制叠加并存的地质特征与成矿表现。联系塔里木地幔柱的活动特点和成矿表现,将其与天山造山带三类主要矿床类型建立关联,对比岩石学、年代学及地球化学研究,发现天山成矿带成矿类型与塔里木地幔柱及板块构造存有密切关系,可能是两种构造体制叠加并存的结果。塔里木克拉通深部熔融的地幔物质,围绕刚性塔里木克拉通边缘不断上涌,并与表壳物质发生交换,随着板块俯冲的持续和减弱,深部上涌的地幔物质不断加强,先后形成因深部地幔物质多寡而金属聚集的不同矿床类型。该地幔柱形成时深部过程与成矿作用认识模型的建立,极大地推进了板块构造、地幔柱与岩浆成矿作用的研究,同时可为天山及邻区找矿突破提供借鉴和指导。 相似文献
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峨眉山大火成岩省Cu-Ni-PGE成矿作用——几个典型矿床岩石地球化学特征的分析 总被引：2，自引：0，他引：2
峨眉山大火成岩省岩浆型Cu-Ni-PGE矿化岩体广泛分布,构成峨眉山地幔柱成矿系统中一个非常重要的成矿系列。本文剖析了峨眉山大火成岩省该类矿床的分布及部分典型矿床的地质地球化学特征和矿化特征,揭示了成矿岩体统一的地幔柱成因,阐述了Cu-Ni-PGE成矿作用与峨眉山地幔柱岩浆活动体系的关系,探讨了由于岩浆演化过程及硫化物熔离富集过程的差异所导致的矿化类型变异。指出Cu-Ni-PGE矿床成矿岩体原始岩浆为地幔柱高程度熔融的高镁玄武岩浆,成矿岩体与峨眉山低钛玄武岩同源,矿化岩体主要产于峨眉山地幔柱活动模型的内带低钛玄武岩分布区;金宝山、朱布、力马河、杨柳坪矿床分别代表峨眉山地幔柱Cu-Ni-PGE成矿作用不同成矿机制的端员类型。 相似文献
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地幔柱及其成矿系统研究是当前地学领域的热点之一,在我国已取得了较大进展,发表了大量论著。但对环太平洋极性超级地幔柱成矿系统的研究,目前还处于起步阶段。文章在前人研究成果的基础上,从以下几方面作了简要论述:1)地幔柱研究历史的回顾;2)地幔柱类型划分与成矿场;3)常规地幔柱判别标志;4)环太平洋极性超级地幔柱的厘定;5)环太平洋极性超级地幔柱成矿效应;6)华南亚地幔柱与成矿;7)环太平洋极性超级地幔柱的动力学讨论。笔者认为,中-新生代濒太平洋洲际性成矿域及其成矿大爆发,导源于太平洋超级地幔柱对成矿的响应。 相似文献
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地幔柱构造与地幔动力学--兼论其在中国大陆地质历史中的表现 总被引：5，自引：0，他引：5
肖龙 《矿物岩石地球化学通报》2004,23(3):239-245
地幔柱构造是基于全地慢对流模式、主要依据热点火山活动提出的新的全球构造理论。它的主要表现形式和产物是地幔柱头上部地壳抬升、岩浆活动形成大火成岩省、大型放射状岩墙群，并导致大陆裂解、板块运动和大规模成矿，是生物灭绝、磁极倒转的诱因。中国大陆的地质演化历史中保存了多期地幔柱活动印记，它们主要是华南新元古代Rodinia地幔柱、古生代古特提斯和峨眉山地幔柱和中一新生代中国东部地慢柱构造事件。上述地幔柱活动产生了地壳抬升、强烈岩浆活动、大陆伸展与裂解、岩石圈剧烈减薄和大规模成矿等重要地质事件。 相似文献
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中国东南部地幔柱及其与中生代大规模成矿关系初探 总被引：21，自引：4，他引：21
中国东南部是我国的钨锡铜金多金属矿床集中区，燕山期发生大规模成矿作用，研究大规模成矿的地球动力学背景显得尤为重要。本文结合前人的研究资料，初步讨论中国东南部地幔柱及其与中生代大规模成矿关系。通过对中国东南部地幔柱的地质和地球物理方面特征综合分析后，初步探讨了地幔柱构造的岩浆作用和成矿制约。本文认为中国东南部地幔柱不仅可能造成中生代火山─岩浆大爆发，而且可能与中生代大规模成矿有关。 相似文献
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试论华南中新生代地幔柱构造、铀成矿作用及其找矿方向 总被引：27，自引：6，他引：21
本文扼要地阐述了地幔柱构造的研究历史和现状,指出地幔柱构造作用是地质构造作用、火山岩浆活动、沉积变质作用、成矿作用体系的原动力;论述了华南中、新生代地幔柱构造的存在、作用特点及其与华南铀矿化的关系。华南４大类型的铀矿化应是在统一的地幔柱构造作用和影响下的产物。地幔柱构造不仅为铀的活化、迁移和富集提供热动力,而且还可能提供成矿物质来源,对进一步深入认识我国华南铀矿区域成矿规律,扩大老矿区,探索寻找成矿新区和新类型铀矿化具有积极的意义。 相似文献
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地球化学急变带与地幔柱资源系统 总被引：7，自引：2，他引：7
地幔柱产生大面积软流圈上涌，沿深断裂形成岩浆房，导致大规模溢流玄武岩裂隙式喷发。良好的地幔柱成矿系统常出现在岩石圈不连续界面和三叉拼接裂谷，表现为地球化学急变带。地幔柱资源系统包括以下几方面：(1)地幔柱岩浆分异成矿系统，从封闭到开放环境的岩浆分异形成了富钛、富镁和低钛三个岩浆端员，构成了Cu—Ni(PGE)硫化物、Fe—Ti—V氧化物和Cu—Ag自然金属三个成矿体系；(2)地幔柱同生火山热液成矿系统，包括赤铁矿—阳起石—硅化氧化铜，沥青化—绿泥石—浊沸石化自然铜和碳酸盐化硫化物三个成矿体系；(3)地幔柱同构造盆地油气系统，巨量岩浆的快速成溢流导致地壳的快速沉降，形成同构造热盆地，具有油气前景；(4)地幔柱火山岩、硅质岩和富有机质砂页岩组合为优势生态体系提供了地质环境。 相似文献
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地幔柱及其成矿作用综述 总被引：1，自引：0，他引：1
地幔柱理论在成矿学中的应用使对矿质来源的研究与地球的演化联系起来,而不再是简单地识别地壳来源或地幔来源.文章系统介绍了地幔柱特征、地幔柱成矿机制、地幔柱的演化对成矿的控制及地幔柱成矿系统. 相似文献
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板块俯冲起始与大陆地壳演化 总被引：1，自引：0，他引：1
组成大陆地壳的物质主要来自两个地质过程:地幔柱活动和板块俯冲。目前大多数研究认为板块俯冲起始于30多亿年前。在板块俯冲起始之前,基性的初始地壳物质受热重熔是大陆地壳生长的主要方式,其中,地幔柱活动是关键。地幔柱不仅向地壳输送玄武质岩浆,同时导致已有玄武质岩石和沉积岩通过部分熔融向中酸性岩石转化。当原始岩石圈强度足够大时,地幔柱会导致岩石圈倾斜、破裂,产生下滑力,诱发板块俯冲。板块俯冲引发岩浆活动,产生大量的岩浆岩,如岛弧安山岩、弧后盆玄武岩等。这些岩浆岩通过喷发、侵位,再经由块体拼贴、增生等过程加入到大陆地壳,是大陆地壳生长的主要途径。同时,板内岩浆活动乃至地幔柱活动等也与板块俯冲有直接或者间接的联系。俯冲再循环物质促进地幔柱发育,也为大陆地壳的生长提供物源和热能。与此同时,大陆地壳不断风化剥蚀,其中一部分沉积物随俯冲板块再循环到地幔,而板块俯冲过程也通过俯冲剥蚀等过程,将仰冲盘岩石圈物质刮削带入地幔。这些是大陆地壳消减的主要途径。目前大陆地壳增生和消减基本处于动态平衡。 相似文献
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地幔柱的概念、分类、演化与大规模成矿——对中国西南部的探讨 总被引：33，自引：2，他引：33
自核幔边界上升的物质 ,当其汇聚成圆柱状的结合体 ,并因其相对于周围地幔环境来说具有温度更高、活动性更强、粘度更低等特点而能够上升到壳幔边界时 ,一般可以演化成为具有宽厚的冠状构造和细长的尾部构造的地幔柱。地幔柱进一步与地壳发生作用 ,可以在地表记录下一系列的热点或形成巨大的火成岩省。根据地幔柱最后出露的位置 ,可以将其分为洋壳和陆壳环境下产出的两种基本类型 ,也可以根据其演化历史分出不同的阶段 ,如初始阶段、上升阶段、成熟阶段和衰退阶段。中国西南部地区可能经历了两次以上的地幔柱冲击 ,二叠纪的峨眉山玄武岩是一个古生代晚期演化比较彻底的地幔柱留下的记录 ,而新生代以来的地幔柱活动可能正在发育 ,深部物质的大规模上隆可能是青藏高原隆升的一个原因 ,大量的散布的幔源岩浆活动和流体作用可能是中国西南部大规模成矿作用的重要原因。 相似文献
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《International Geology Review》2012,54(8):879-893
Plate subduction and mantle plumes are two of the most important material transport processes of the silicate Earth. Currently, a debate exists over whether the subducted oceanic crust is recycled back to the Earth's surface through mantle plumes, and can explain their derivation and major characteristics. It is also puzzling as to why plume heads have huge melting capacities and differ dramatically from plume tails both in size and chemical composition. We present data showing that both ocean island basalt and mid-ocean ridge basalt have identical supra-primitive mantle mean Nb/U values of ～46.7, significantly larger than that of the primitive mantle value. From a mass balance calculation based on Nb/U?we have determined that nearly the whole mantle has evolved by plate subduction-induced crustal recycling during formation of the continental crust. This mixing back of subducted oceanic crust, however, is not straightforward, because it generally would be denser than the surrounding mantle, both in solid and liquid states. A mineral segregation model is proposed here to reconcile different lines of observation. First of all, subducted oceanic crustal sections are denser than the surrounding mantle, such that they can stay in the lower mantle, for billions of years as implied by isotopic data. Parts of subducted oceanic crust may eventually lose a large proportion of their heavy minerals, magnesian-silicate-perovskite and calcium-silicate-perovskite, through density segregation in ultra-low-velocity zones as well as in very-low-velocity provinces at the core-mantle boundary due to low viscosity. The remaining minerals would thus become lighter than the surrounding mantle, and could rise, trapping mantle materials, and forming mantle plumes. Mineral segregation progressively increases the SiO2 content of the ascending oceanic crust, which enhances flux melting, and results in giant Si-enriched plume heads followed by dramatically abridged plume tails. Therefore, ancient mineral-segregated subducted oceanic crust is likely to be a major trigger and driving force for the formation of mantle plumes. 相似文献
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俯冲工厂和大陆物质的俯冲再循环研究 总被引：3，自引：3，他引：3
板块的俯冲系统可以比拟为一个工厂。再循环研究强调对俯冲物质各种组分的行为、去向的追踪和定量分析。沉积物俯冲和俯冲侵蚀作用导致陆壳物质返回地幔,初步估算表明,大陆物质返回地幔的速率与岩浆活动导致陆壳生长的速率在数量上大体相当,晚近时期陆壳的净增长速率可能近于零。大洋岛玄武岩地化特征上的多样性提示,沉入下地幔的板片可能从深部卷入地幔柱的源区。俯冲再循环过程对地壳、地幔的动力学和演化产生深刻影响。 相似文献
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《International Geology Review》2012,54(9):1051-1071
Asia is the world’s largest but youngest continent, in which Pacific-type (P-type) and collision-type (C-type) orogenic belts coexist with numerous amalgamated continental blocks. P-type orogens represent major sites of continental growth through tonalite-trondhjemite-granodiorite type (TTG-type) juvenile granitoid magmatism and accretion of oceanic crust and intra-oceanic arcs. The Asian continent includes several P-type orogenic belts, of which the largest are the Central Asian and Western Pacific. The Central Asian Orogenic Belt is dominated by P-type fossil orogens arranged with a regular northward subduction polarity. The Western Pacific is characterized by ongoing P-type orogeny related to the westward subduction of the Pacific plate. Asia has a multi-cratonic structure and its post-Palaeozoic history has witnessed amalgamation of the Laurasia composite continent and Pangaea supercontinent. Nowadays, Asia is surrounded by double-sided subduction zones, which generate new TTG-type crust and supply oceanic crust and microcontinents to its active margins. The TTG-crust can be tectonically eroded and subducted down to the mantle transition zone to form a ‘second’ continent, which may generate mantle upwelling, plumes, and extensive intra-plate volcanism. Moreover, recent plate movements around Asia are dominated by northward directions, which resulted in the India–Eurasia and Arabia–Eurasia collisions beginning at 50–45 and 23–20 Ma, respectively, and will result in Africa–Eurasia collision in the near future. Therefore, Asia is the best candidate to serve as the nucleus for a future supercontinent ‘Amasia’, likely to form 200–250 Ma in the future. In this paper we unravel a puzzle of continental growth in Asia through P-type orogeny by discussing its tectonic history and geological structure, subduction polarity in P-type orogens, tectonic erosion of TTG-type crust and arc subduction at convergent margins, generation of mantle plumes, and prospects of Asia growth and overgrowth. 相似文献
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初论幔柱构造成矿体系 总被引：12，自引：0，他引：12
从板块构造与板块边界矿床、超大陆旋回与大陆边界矿床、地幔热点与大陆内部矿床的角度 ,阐述了幔柱构造成矿体系的基本思想、分类、成矿特征及旋回性 ,提出了热幔柱和冷幔柱两个成矿体系和地幔热柱 -热点、地幔热柱 -大陆裂谷、地幔热柱 -大洋扩张、冷幔柱 -前寒武纪硅铝壳造山、冷幔柱 -显生宙硅铝壳 /洋壳造山等五个成矿系统 ,并初步划分了矿床成矿系列 ,例举了某些典型矿床。 相似文献
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<正>Greenstone belts of the eastern Dharwar Craton,India are reinterpreted as composite tectonostratigraphic terranes of accreted plume-derived and convergent margin-derived magmatic sequences based on new high-precision elemental data.The former are dominated by a komatiile plus Mg-tholeiitic basalt volcanic association,with deep water siliciclastic and banded iron formation(BIF) sedimentary rocks.Plumes melted at90 km under thin rifted continental lithosphere to preserve inlraoceanic and continental margin aspects.Associated alkaline basalts record subduction-recycling of Mesoarchean oceanic crust,incubated in the asthenosphere.and erupted coevally with Mg basalts from a heterogeneous mantle plume.Together.komaliites-Mg basalts-alkaline basalts plot along the Phanerozoic mantle array in Th/Yb versus Nb/Yb coordinate space,representing zoned plumes,establishing that these reservoirs were present in the Neoarchean mantle. Convergent margin magmatic associations are dominated by tholeiitic to calc-alkaline basalts eompositionally similar to recent intraoceanic arcs.As well,boninitic flows sourced in extremely depleted mantle are present,and the association of arc basalts with Mg-andesites-Nb enriched basalts-adakites documented from Cenozoic arcs characterized by subduction of young(20 Ma),hot,oceanic lithosphere. Consequently.Cenozoic style "hot" subduction was operating in the Neoarchean.These diverse volcanic associations were assembled to give composite terranes in a subduction-accretion orogen at～2.1 Ga,coevally with a global accretionary orogen at ~2.7 Ga,and associated orogenic gold mineralization. Archean lithospheric mantle,distinctive in being thick,refractory,and buoyant,formed complementary to the accreted plume and convergent margin terranes.as migrating arcs captured thick plumeplateaus. and the refractory,low density.residue of plume melting coupled with accreted imbricated plume-arc crust. 相似文献
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《地学前缘(英文版)》2020,11(4):1133-1144
The Shatsky and Hess Rises,the Mid-Pacific Mountains and the Line Islands large igneous provinces(LIPs) present different challenges to conventional plume models.Resolving the genesis of these LIPs is important not only for a more complete understanding of mantle plumes and plume-generated magmatism,but also for establishing the role of subducted LIP conjugates in the evolution of the Laramide orogeny and other circum-Pacific orogenic events,which are related to the development of large porphyry systems.Given past difficulties in developing consistent geodynamic models for these LIPs,it is useful to consider whether viable alternative geodynamic scenarios may be provided by recent concepts such as melt channel networks and channel-associated lineaments,along with the "two mode"model of melt generation,where a deeply-sourced channel network is superimposed on the plume,evolving and adapting over millions of years.A plume may also interact with transform faults in close proximity to a mid ocean ridge,with the resultant bathymetric character strongly affected by the relative age difference of lithosphere across the fault.Our results suggest that the new two-mode melt models resolve key persistent issues associated with the Shatsky Rise and other LIPs and provide evidence for the existence of a conduit system within plumes that feed deeply-sourced material to the plume head,with flow maintained over considerable distances.The conduit system eventually breaks down during plume-ridge separation and may do so prior to the plume head being freed from the triple junction or spreading ridge.There is evidence for not only plume head capture by a triple junction but also for substantial deformation of the plume stem as the distance between the stem and anchored plume head increases.The evidence suggests that young transforms can serve as pathways for plume material migration,at least in certain plume head-transform configurations.A fortuitous similarity between the path of the Shatsky and Sio plumes,with respect to young spreading ridges and transforms,helps to clarify previously problematic bathymetric features that were not readily ascribed to fixed plumes alone.The Line Island Chain,which has been the subject of a vast number of models,is related mainly to several plumes that passed beneath the same region of oceanic crust,a relatively rare event that has resulted in LIP formation rather than a regular seamount track.Our findings have important implications for the timing and mechanism for the Laramide Orogeny in North America,demonstrating that the Hess Rise conjugate may be much smaller than traditionally thought.The Mid Pacific Mountains conjugate may not exist at all,given large parts of these LIPs were formed at an ‘off-ridge' site.This needs to be taken into account while considering the effects of conjugate collision on mineralization and orogenic events. 相似文献
19.
Seismic images under 60 hotspots: Search for mantle plumes 总被引：10，自引：0，他引：10
The mantle plume hypothesis is now widely known to explain hotspot volcanoes, but direct evidence for actual plumes is weak, and seismic images are available for only a few hotspots. In this work, we present whole-mantle tomographic images under 60 major hotspots on Earth. The lateral resolution of the tomographic images is about 300 km under the continental hotspots and 400–600 under the oceanic hotspots. Twelve plume-like, continuous low-velocity (low-V) anomalies in both the upper and lower mantle are visible under Hawaii, Tahiti, Louisville, Iceland, Cape Verde, Reunion, Kerguelen, Amsterdam, Afar, Eifel, Hainan, and Cobb hotspots, suggesting that they may be 12 whole-mantle plumes originating from the core–mantle boundary (CMB). Clear upper-mantle low-V anomalies are visible under Easter, Azores, Vema, East Australia, and Erebus hotspots, which may be 5 upper-mantle plumes. A mid-mantle plume may exist under the San Felix hotspot. The active intra-plate volcanoes in Northeast Asia (e.g., Changbai, Wudalianchi, etc.) are related to the stagnant Pacific slab in the mantle transition zone. The Tengchong volcano in Southwest China is related to the subduction of the Burma microplate under the Eurasian plate. Although low-V anomalies are generally visible in some depth range in the mantle under other hotspots, their plume features are not clear, and their origins are still unknown. The 12 whole-mantle plumes show tilted images, suggesting that plumes are not fixed in the mantle but can be deflected by the mantle flow. In most cases, the seismic images under the hotspots are complex, particularly around the mantle transition zone. A thin low-V layer is visible right beneath the 660-km discontinuity under some hotspots, while under a few other hotspots, low-V anomalies spread laterally just above the 660-km discontinuity. These may reflect ponding of plume materials in the top part of the lower mantle or the bottom of the upper mantle. The variety of behaviors of the low-V anomalies under hotspots reflects strong lateral variations in temperature and viscosity of the mantle, which control the generation and ascending of mantle plumes as well as the flow pattern of mantle convection. 相似文献
20.
Were the Deccan Flood Basalts Derived in Part from Ancient Oceanic Crust Within the Indian Continental Lithosphere? 总被引：5，自引：1，他引：5
Deep mantle plumes supposedly incorporate deeply subducted eclogitized oceanic crust, and continental flood basalts (CFBs) are now thought by some to be derived from such eclogite-bearing peridotite plumes. Eclogite-peridotite mixtures have much lower solidi (and produce much greater melt fractions for a given temperature) than peridotite. Fe-rich (eclogite- or pyroxenite-bearing) sources have been inferred for many CFBs. However, plumes with considerable amounts of eclogite should have difficulty in upwelling owing to the high density of eclogite. Besides, CFBs are always located along pre-existing lithospheric structures (suture zones, edges of thick cratons) and commonly associated with lithospheric rifting and continental breakup. India's major late Mesozoic CFB, the Deccan Traps, erupted through rift zones and a new continental margin that had developed along ancient suture zones traversing the subcontinent. Many Deccan basalts are too Fe-rich to have been in equilibrium with a peridotite mantle source, and have commonly been considered to be significantly fractionated derivatives of picritic liquids. However, it is possible to view them as relatively less evolved liquids derived from a source with extra fertility (i.e., an Fe-rich source). A new non-plume, plate tectonic model for Icelandic hotspot volcanism involves melting of a shallowly recycled slab of eclogitized Iapetus oceanic crust formerly trapped along the Caledonian suture. The model explains the geochemical-petrological characteristics of Icelandic basalts, and is consistent with passive upper mantle upwelling under Iceland inferred from recent seismic tomography. Based on the petrological and geochemical features of the Deccan flood basalts of the type section, in the Western Ghats, I propose that old, eclogitized oceanic crust trapped in the ancient Indian suture zones could have produced voluminous basaltic melts during the Deccan event. 相似文献