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A New Understanding on the emplacement of Ophiolitic Mélanges and Its Tectonic Significance: Insights from the Structural Analysis of the Remnant Oceanic Basin-Type Ophiolitic Mélanges

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Acta Geologica Sinica(English Edition) 2020年第S1期94卷 60-62页

作者： WANG Guocan ZHANG Pan Center for Global Tectonics School of Earth SciencesChina University of GeosciencesWuhan 430074China Geological Survey China University of GeosciencesWuhan 430074China

Ophiolites represent on-land fragments of paleooceanic crust and have been recognized as one of the key markers of suture zones.Here,we provide new insights into the emplacement of ophiolitic mélanges based on detailed geological mapping and structural analysis in the West Junggar and Songpan-Ganzi-Bayan Har orogens(Fig.1 and Fig.2).The results show that some ophiolitic mélange belts cannot be regarded as suture zones.The distribution of these ophiolitic mélange belts are usually associated with the structural processes during the closure of remnant oceanic basins.After the remnant-oceanic basin is filled with thick clastic deposit,the oceanic lithosphere material as the base of the remnant basin can be injected into the overlying sedimentary strata through various faultings under the regional compressive stress,forming the remnant oceanic basintype ophiolitic mélange system with dispersive distribution characteristics.Combining with previous researches,the emplacement mechanism of ophiolitic mélanges can be divided into four categories:subduction type which oceanic lithosphere subducted beneath active continental margin,obduction type which oceanic lithosphere obducted over passive continental margin,collision type between two continental lithospheres,and closure type of remnant-oceanic basin(Fig.3).These different types of ophiolitic mélange belts will be superimposed and even re-emplacement by the tectonic processes of post-plate convergence,complicating their distribution.Therefore,identifying the emplacement mechanism type of ophiolitic mélange belts formed in different tectonic processes and backgrounds is of importance for understanding the process of ocean-continental transition and the evolution of orogenic belts.

关键词： ophiolitic mélanges emplacement remnant-oceanic basin orogen tectonics

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emplacement and Evolution History of Pegmatites and Hydrothermal Deposits, Matale District, Sri Lanka

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International Journal of Geosciences 2011年第3期2卷 348-362页

作者： G.W.A.R Fernando A Pitawala T.H.N.G Amaraweera 不详

Excellent outcrops in Matale Sri Lanka provide unique insight into the emplacement and evolution history of hydrothermal and pegmatitic rocks in the central highlands of Sri Lanka. Field, structural, petrological, thermo-barometric studies in the metamorphic basement rocks in the central highlands and related hydrothermal deposits are presented in this study. Detailed petrographic and mineralogical data reveal peak metamorphic conditions for the crustal unit in the study area as 854 ± 44oC at 10.83 ± 0.86 kbar. Hydrothermal veins consisting of quartz and mica are closely related to cross-cutting pegmatites, which significantly post-date the peak metamorphic conditions of the crustal unit. Field relations indicate that the veins originated as ductile-brittle fractures have subsequently sealed by pegmatites and hydrothermal crystallization. Geological, textural and mineralogical data suggest that most enriched hydrothermal veins have evolved from a fractionated granitic melt progressively enriched in H2O, F, etc. Quartz, K-feldspar, mica, tourmaline, fluorite and topaz bear evidence of multistage crystallization that alternated with episodes of resorption. It was suggested that the level of emplacement of pegmatites of the Matale District was middle crust, near the crustal scale brittle-ductile transition zone at a temperature of about 600oC. For this crustal level and temperature range, it is considered very unlikely that intruding pegmatitic melts followed pre-existing cracks. As such the emplacement temperatures of the pegmatites could be well below the peak metamorphic estimates in the mafic granulites. The metamorphic P-T strategy and position of formation of hydrothermal deposits and pegmatites is summarized in the modified P-T-t-D diagrams.

关键词： Hydrothermal veins Pegmatites emplacement history brittle deformation Sri Lanka

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emplacement MECHANISM OF THE SUPER-LARGE JINGSHAN GOLD DEPOSIT IN JIANGXI,CHINA

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Journal of Central South University 1996年第1期8卷 72-74页

作者： Li Peizheng Wu Yangzhi Zhou Juecheng(Department of Geology, Central South University ofTechnology, Changsha 410083, China)

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ＥＭＰＬＡＣＥＭＥＮＴＭＥＣＨＡＮＩＳＭＯＦＴＨＥＳＵＰＥＲ－ＬＡＲＧＥＪＩＮＧＳＨＡＮＧＯＬＤＤＥＰＯＳＩＴＩＮＪＩＡＮＧＸＩ，ＣＨＩＮＡＬｉＰｅｉｚｈｅｎｇＷｕＹａｎｇｚｈｉＺｈｏｕＪｕｅｃｈｅｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｌｏｇｙ，Ｃｅ...

关键词： superlarge gold deposit emplacement of deposit ductile shear zone Jiangxi

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Magma chamber growth models in the upper crust: A review of the hydraulic and inertial constraints

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Geoscience Frontiers 2019年第3期10卷 1211-1218页

作者： Eugenio Aragón Fernando J.D'Eramo Lucio P.Pinotti Manuel Demartis José María Tubía Roberto F.Weinberg Jorge E.Coniglio Centro de Investigaciones Geologicas (CONICET-Universidad Nacional de La Plata).Diagonal 113 N° 275 Universidad Nacional de Río Cuarto CONICET Departamento de Geología (Ruta Nac.N° 36 Km 601) Departamento de Geodinámica Universidad del País Vasco (UPV/EHU) School of Earth Atmosphere and Environment Monash University

Finite volumes of magma moving in confinement, store hydraulic potential energy for the generation,control and transmission of power. The Pascal's principle in a hydraulic jack arrangement is used to model the vertical and lateral growth of sills. The small input piston of the hydraulic jack is equivalent to the feeder dike, the upper large expansible piston equivalent to the magmatic chamber and the inertial force of the magma in the dike is the input force. This arrangement is particularly relevant to the case of sills expanding with blunt tips, for which rapid fracture propagation is inhibited. Hydraulic models concur with experimental data that show that lateral expansion of magma into a sill is promoted when the vertical ascent of magma through a feeder dike reaches the bottom contact with an overlying, flat rigid-layer. At this point, the magma is forced to decelerate, triggering a pressure wave through the conduit caused by the continued ascent of magma further down(fluid-hammer effect). This pressure wave can provide overpressure enough to trigger the initial hydraulic lateral expansion of magma into an incipient sill, and still have enough input inertial force left to continue feeding the hydraulic system. The lateral expansion underneath the strong impeding layer, causes an area increase and thus, further hydraulic amplification of the input inertial force on the sides and roof of the incipient sill, triggering further expansion in a self-reinforcing process. Initially, the lateral pressure increase is larger than that in the roof allowing the sill to expand. However, expansion eventually increases the total integrated force on the roof allowing its uplift into either a laccolith, if the roof preserves continuity, or into a piston bounded by a circular set of fractures. Hydraulic models for shallow magmatic chambers, also suggest that laccolith-like intrusions require the existence of a self-supported chamber roof. In contrast, if the roof of magmatic chambers loses the self-supporting capacity, lopolit

关键词： Pascal’s principle Geologic hydraulic jack emplacement Sills growth Fluid hammer

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The significance of U-Pb zircon ages in zoned plutons:the case of the Flamenco pluton, Coastal Range batholith, northern Chile

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Geoscience Frontiers 2019年第3期10卷 1073-1099页

作者： Natalia Rodríguez Juan Díaz-Alvarado Carlos Fernández Paulina Fuentes Christoph Breitkreuz Colombo Celso Gaeta Tassinari Departamento de Geología Universidad de Atacama Departamento de Ciencias de la Tierra Universidad de Huelva Institut für Geologie TU Bergakademie Freiberg High Resolution Geochronological Laboratory University of S?o Paulo

Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geochemical differentiation and the magma replenishment rates are revealed by geochemistry and field relations, together with the increasingly accurate U-Pb geochronology, which has promoted the knowledge about the pluton incremental assembly theories.The Flamenco pluton, located in the Coastal Range of northern Chile, is part of the Upper Triassic to Early Cretaceous Andean intrusives formed in the western active margin of South America, and present a normal zoned structure with mafic magmatic facies(mostly gabbros and Qtz-diorites) close to the contacts with the host metasediments, and tonalites, granodiorites and granites in the inner areas. A combined study of the field relations, geochemistry and zircon geochronology of the magmatic facies was applied to determine the emplacement sequence of the Flamenco pluton, revealing three distinguishable domains separated by metasedimentary septa. The SW area is constituted by mostly homogeneous leucocratic granodiorites that yielded an age of 213 Ma as the best estimation for their emplacement age. Distinctive geochemical characteristics, such as the absence of an Eu anomaly, the depletion in HREE, or the highest Sr, Sr/Y and Ce/Yb values among the granodioritic facies of the pluton,involve lower T and/or higher P conditions at the magmatic source according to experimental studies.These conditions were established during an early stage of the Andean magmatic arc building that is firstly defined here as Upper Triassic. The NW and E domains of the pluton were sequentially emplaced between 194 Ma and 186 Ma and both the field relations and the detailed geochronological results suggest that the mafic facies intruded latter in the emplacement sequence. To the NW, Qtz-dioritic and gabbroic externally emplaced pulses gave a younger crystallization age of 186.3 ± 1.8

关键词： Zircon U-Pb geochronology Zoned plutons Andean magmatic arc Sequential emplacement Individual and statistical zircon ages

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Mechanisms of abnormal overpressure generation in Kuqa foreland thrust belt and their impacts on oil and gas reservoir formation

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Chinese Science Bulletin 2002年第S1期47卷 85-93页

作者： PI Xuejun XIE Huiwen ZHANG Cun TIAN Zuoji Chengdu Science&Technology University Chengdu 610059China Tarim Oil Field Company Korla 841000China RIPED Beijing 100083China

Based on overview for mechanism of abnormaloverpressure generation in sedimentary basins, an insightdiscussion is made by the authors for the distribution, fea-tures and generation mechanisms of abnormal overpressurein the Kuqa foreland thrust belt. The abnormal overpressurein the Kelasu structure zone west to the Kuqa forelandthrust belt was primarily distributed in Eogene to lowerCretaceous formations; structural compression and struc-tural emplacement as well as the containment of Eogenegyps-salt formation constituted the main mechanisms for thegeneration of abnormal overpressure. The abnormal over-pressure zone in the eastern Yiqikelike structure zone wasdistributed primarily in lower Jurassic Ahe Group, resultingfrom hydrocarbon generation as well as structural stressother than from under-compaction. Various distributionsand generating mechanisms have different impacts upon theformation of oil and gas reservoirs. K-E reservoir in the Ke-lasu zone is an allochthonous abnormal overpressure system.One of the conditions for reservoir accumulation is the mi-gration of hydrocarbon (T-J hydrocarbon source rock) alongthe fault up to K-E reservoir and accumulated into reservoir.And this migration process was controlled by the abnormaloverpressure system in K-E reservoir. The confined abnor-mal overpressure system in the Yiqikelike structure zoneconstituted the main cause for the poor developing of dis-solved porosity in T-J reservoir, resulting in poor physicalproperty of reservoir. The poor physical property of T-J res-ervoir of Yinan 2 structure was the main cause for the ab-sence of oil accumulation, but the presence of natural gasreservoir in the structure.

关键词： abnormal overpressure structural emplacement hydrocarbon generation formation of oil and gas reservoir Kuqa foreland thrust belt.

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四川盆地油气构造遥感专题研讨会在崇庆县召开

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四川地质学报 1994年第2期14卷 160-160页

作者：张树铭四川省地矿局

四川盆地油气构造遥感专题研讨会在崇庆县召开四川省地质学会遥感地质、石油地质、煤田地质专业委员会与四川省石油学会油气开发专业委员会联合召开的《四川盆地油气构造遥感专题研讨会》，于１９９４年４月２５至２７日在崇庆县政府招... 详细信息

四川盆地油气构造遥感专题研讨会在崇庆县召开四川省地质学会遥感地质、石油地质、煤田地质专业委员会与四川省石油学会油气开发专业委员会联合召开的《四川盆地油气构造遥感专题研讨会》，于１９９４年４月２５至２７日在崇庆县政府招待所举行。共１８个单位的代表出席了...

关键词： tectonic dynamic remobilization of element migration power of ore fluid release of tectonic energy emplacement mechaniasm

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