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《International Geology Review》2012,54(4):468-481
The Neogene–Quaternary Siderno Basin is located in the southern Calabrian Arc, along an E–W transect including the Ionian side and part of the Tyrrhenian margin. The orogenic belt was generated by ongoing northward subduction of Ionian oceanic lithosphere beginning in the Early Cretaceous. Since the Oligocene, the area has experienced complex tectonics, including NW–SE-oriented pull-apart basins. The forearc region contains >2000 m of Oligocene-to-Quaternary strata that cover pre-Tertiary rocks. The succession forms an E-dipping monocline, with tectonic growth structures increasing upward. Erosional truncations and thickness variations suggest a different evolution for the Siderno Basin, which in comparison with northern and southern parts of the Ionian accretionary wedge, evolved differently during the Serravallian–Tortonian stages. NW–SE and NE–SW fault systems are dominant, the first exhibiting strike–slip and normal kinematics in the Nicotera–Gioiosa and Molochio–Antonimina fault zones. These structures were active during infilling of the Neogene basin, and represent a complex transfer zone. The NE–SW system shows two types of tectonic kinematics: (1) a compressive stage, with NW–SE-orientated shortening, responsible for inversion tectonics documented by east-verging folds, thrusts, and back-thrusts, and (2) emplacement of the variegated clay during the Langhian, which is related to back-thrust propagation. The strike–slip accommodated stress generated in the accretionary prism in response to subduction of Ionian lithosphere and progradation of the accretionary front of the Calabrian forearc. 相似文献
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《International Geology Review》2012,54(3):263-286
The ENE-trending, ca. 306–287 Ma, Totoltepec pluton is part of a Carboniferous–Permian continental magmatic arc on the western Pangaean margin. The 15 km?×?5 km pluton is bounded by two N–S Permian dextral faults, an E–W thrust to the south, and an E–W normal fault to the north. Thermobarometric data indicate that the main, ca. 289–287 Ma, part of the pluton was emplaced at ≤20 km depth and ≥700°C and was exhumed to 11 km and 400°C in 4 ± 2 million years. We have documented the following intrusive sequence: (1) the 306 Ma northern marginal mafic phase; (2) the 287 Ma main trondhjemitic phase; and (3) ca. 289–283 Ma sub-vertical dikes that vary from (a) N39E, undeformed with crystal growth perpendicular to the margins, through (b) ca. N50–73E, foliated and folded with sinistral shear indicators, to (c) N73–140E and boudinaged. The obliquity of the boundary between the folded and stretched dikes relative to the N–S dextral faults suggests sequential emplacement in a transtensional regime (with 20% E–W extension), followed by different degrees of clockwise rotation passing through a shortening field accompanied by sinistral shear into an extensional field. The ca. 289–287 Ma intrusion also contains a steep ENE-striking foliation and hornblende lineations varying from sub-horizontal to steeply plunging, probably the result of emplacement in a triclinic strain regime. We infer that magmatism ceased when some of the dextral motion was transferred from the western to the eastern bounding fault, causing thrusting to take place along the southern boundary of the pluton. This mechanism is also invoked for the rapid uplift and exhumation of the pluton between ca. 287 Ma and 283 Ma. The distinctive characteristics of the Totoltepec pluton should prove useful in identifying similar tectonic settings within continental arcs. 相似文献
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Geng Quanru Pan Guitang Jin Zhenmin Wang Liquan Liao Zhongli 《中国地质大学学报(英文版)》2005,16(4):283-296
The Early Jurassic bimodal volcanic rocks in the Yeba Formation, situated between Lhasa, Dagzê and Maizhokunggar, composed of metabasalt, basaltic ignimbrite, dacite, silicic tuff and volcanic breccia, are an important volcanic suite for the study of the tectonic evolution of the Gangdise magmatic arc and the Mesozoic Tethys. Based on systematic field investigations, we carried out geochemical studies on representative rock samples. Major and trace element compositions were analyzed for these rock samples by XRF and ICP-MS respectively, and an isotope analysis of Rb-Sr and Sm-Nd was carried out by a MAT 262 mass spectrograph. The results show that the SiO2 contents in lava rocks are 41 %-50.4 % and 64 %-69 %, belonging to calc-alkaline basalt and dacite. One notable feature of the basalt is its low TiO2 content, 0.66 %-1.01 %, much lower than those of continental tholeiite. The ΣREE contents of basalt and dacite are 60.3-135 μg/g and 126.4-167.9 μg/g respectively. Both rocks have similar REE and other trace element characteristics, with enriched LREE and LILE relative to HREE and HFS, similar REE patterns without Eu anomaly. The basalts have depleted Ti, Ta and Nb and slightly negative Nb and Ta anomalies, with Nb*＝0.54-1.17 averaging 0.84. The dacites have depleted P and Ti and also slightly negative Nb and Ta anomalies, with Nb*＝0.74-1.06 averaging 0.86. Major and trace elemental and isotopic studies suggest that both basalt and dacite originated from the partial melting of the mantle wedge at different degrees above the subduction zone. The spinal lherzolite in the upper mantle is likely to be their source rocks, which might have been affected by the selective metasomatism of fluids with crustal geochemistry. The LILE contents of both rocks were affected by metamorphism at later stages. The Yeba bimodal volcanic rocks formed in a temporal extensional situation in a mature island arc resulting from the Indosinian Gangdise magmatic arc. 相似文献
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Geotectonics - The Qazan granitoid pluton (South of Kashan, Iran) is situated in the central part of the Urumieh–Dokhtar Magmatic Arc. The plutonic body includes in its composition... 相似文献
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基于Arc／INFO的地学信息系统的设计与开发 总被引：1，自引：0，他引：1
论文主要研究了基于GIS技术和数据融合技术的地学信息系统的开发问题。采用国际先进的硬件、软件作为开发平台，建立了一个比较完善的湖南省国土资源地学信息系统。系统功能除常规空间信息查询外，还包括缓冲区分析、叠置分析、地质成图等各种复杂的分析功能。它为湖南省国土资源地学信息管理提供了一个重要手段，为区域地质找矿提供了一种新的研究思路。 相似文献
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GIS是获取、检索、分析、处理空间数据的数据库管理系统，是研究空间对象的有力工具，本文利用GIS软件Arc/Info为基本工具，以遥感数据作为获取，更新数据库数据的重要信息源，结合前人的地学资料，建立了湖北省区域稳定性评价空间数据库，阐述了该空间数据库的内容，功能，应用和意义。 相似文献
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MAO Qigui WANG Jinbing XIAO Wenjiao FANG Tonghui YU Mingjie AO Songjian ZHANG Ji’en 《《地质学报》英文版》2014,88(Z2):885-886
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Milos Island contains several epithermal deposits (e.g., Profitis Ilias–Chondro Vouno Pb–Zn–Ag–Au–Te–Cu, Triades–Galana–Agathia–Kondaros Pb–Zn–Ag–Bi–W–Mo ± Cu–Au, and Katsimoutis–Kondaros–Vani Pb–Zn–Ag–Mn) of Late Pliocene to Early Pleistocene age. These deposits are hosted in calc-alkaline volcanic rocks emplaced as a result of three successive magma pulses in an emergent volcanic edifice: submarine rhyolitic to rhyodacitic cryptodomes at ca. 2.7. Ma (Profitis Ilias–Chondro Vouno), submarine to subaerial andesite to dacite domes at ca. 2.2 to 1.5 Ma (Triades–Galana–Kondaros–Katsimouti–Vani). Hydrothermal alteration of the volcanic rocks includes advanced argillic- (both hypogene and steam-heated), argillic, phyllic, adularia-sericite and propylitic types. In the northern sector (Triades–Galana–Agathia–Kondaros), initial magma degassing derived from andesitic–dacitic intrusives along NE–SW to E–W trending faults resulted in the development of pre-ore hypogene advanced argillic alteration (dickite, alunite, ± diaspore, pyrophyllite, halite, and pyrite) in a submarine environment. Mineralogical data indicate common features among the Profitis Ilias–Chondro Vouno, Kondaros–Katsimoutis–Vani and Triades–Galana mineralized centers, all of which are characterized by the presence of galena, Fe-poor sphalerite, and chalcopyrite as well as abundant barite, adularia, sericite and, to a lesser extent, calcite, which are typical of intermediate-sulfidation epithermal type deposits. Locally, at Triades–Galana and Kondaros–Agathia, high-sulfidation conditions prevailed as suggested by the presence of coexisting enargite and covellite. The high silver and gold content of the western Milos deposits is derived from Ag-bearing sulfosalts (polybasite, pearceite, pyrargyrite, freibergite) and tellurides. Gold at Profitis Ilias, both as native gold and silver-gold tellurides, is present in base-metal precipitates within multicomponent blebs, which recrystallized to form hessite, petzite, altaite, coloradoite, and native gold. Mineralogical evidence (e.g. microchimney structures, copper sulfides, widespread occurrence of barite, aragonite) suggests that precious metal mineralization in western Milos mineralization formed in a submarine setting.We present information on the surface distribution of Au, Ag, Cu, Pb, Zn, As, Sb, Hg, Mo, Bi, W and Cd at western Milos. Gold is enriched at Profitis Ilias–Chondro Vouno deposits and to a lesser extent at Triades–Galana. Arsenic is absent from the southern sector but shows elevated concentrations together with molybdenum, bismuth and tungsten at the northern sector (Triades–Galana, Vani deposits). The differences in precious and base metal abundances may be related to the depths at which the deposits are exposed, and/or different sources of magma. The metal signatures of the Triades–Galana and Agathia–Kondaros–Katsimouti–Vani (Mo–Bi–W–As–Hg–Ag–Au) occurrences compared to Profitis Ilias (Te–Au–Ag) reflect different sources of magma (dacite–rhyodacite for Profitis Ilias, andesite–dacite for Triades–Galana, and dacite for Kondaros–Katsimoutis). The enrichment of Te, Mo, W, and Bi in the deposits is a strong indication of a direct magmatic contribution of these metals.At western Milos, precious and base-metal vein mineralization was deposited during episodic injection of magmatic volatiles and dilution of the hydrothermal fluids by seawater. The mineralization represents seafloor/sub-seafloor precipitation of sulfides that formed in stockwork zones. Base and precious metal mineralization formed from intermediate- to high-sulfidation state fluids and mostly under boiling conditions as indicated by the widespread occurrence of adularia associated with metallic mineralization. We speculate that the widespread occurrence of boiling and the shallow depth of the precious- and base-metal emplacement prevented the formation of seafloor massive sulfides. 相似文献
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The Yidun Arc was formed in response to the westward subduction of Garze–Litang Ocean (a branch of Paleotethys) in the Late Triassic, where abundant porphyry Cu–Mo deposits (221–213 Ma) developed along the regional NW–SE sinistral faults and emplaced in the southern portion of the arc. The ore-related porphyries are mostly metaluminous or slightly peraluminous, belonging to shoshonitic high-potassium calc-alkaline I-type granites, with εHf(t) values of −6.64 to +4.12. The ore-bearing magmas were probably derived from the partial melting of subduction-metasomatic-enriched mantle, with the contamination of underplated mafic materials. The Late Cretaceous (88–80 Ma) highly fractionated I-type granite belt and related porphyry Cu–Mo deposits and magmatic-hydrothermal Cu–Mo–W deposits occur along approximately N–S-trending faults in the Yidun Arc. This belt extended across the Yidun Arc and Garze–Litang suture zone to the north and across the Yangtze Craton to the south, intruding the Late Triassic porphyry belt. The ore-related porphyries are characterized by high silica and high total alkalis, with enrichment in large ion lithophile elements (LILEs; Rb, U and K) and depletion in high field strength elements (HFSE; Nb, Ta, P and Ti) and Ba. They have lower εHf(t) values varying from −9.55 to −2.75, and significant negative Eu anomalies, indicating that the ore-bearing porphyritic magmas originated from ancient middle-upper crust. Two-stage magmatism and mineralization were superimposed in the Xiangcheng-Shangri-La district. Some ore deposits comprise two episodes of magmatism and associated mineralization such as both 207 ± 3.0 Ma granodiorite and 82.1 ± 1.2 Ma monzogranite intruded in the Xiuwacu deposit, causing Cu–Mo–W polymetallic mineralization. To date, 11 Late Triassic porphyry Cu deposits (e.g. the Pulang giant deposit with 5.1 Mt Cu), and five Late Cretaceous porphyry Cu–Mo (W) deposits (e.g. Tongchanggou Mo deposit with 0.59 Mt Mo) have been evaluated in the Xiangcheng-Shangri-La district. The continuity and inheritance of multiphase magmatism and the new understanding of superimposed mineralization will help to guide future exploration. 相似文献
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Spiridonov E. M. Filimonov S. V. Semikolennykh E. S. Korotaeva N. N. Krivitskaya N. N. 《Geology of Ore Deposits》2020,62(7):638-651
Geology of Ore Deposits - Chevkinite-(Се) and perrierite-(Се), which are characteristic minerals of alkaline igneous rocks and high-temperature alkaline alterations, are... 相似文献
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The Kuh-e Dom Pluton is located along the central northeastern margin of the Urumieh–Dokhtar Magmatic Arc, spanning a wide range of compositions from felsic rocks, including granite, granodiorite, and quartz monzonite, through to intermediate-mafic rocks comprising monzonite, monzodiorite, diorite, monzogabbro, and gabbro. The Urumieh–Dokhtar Magmatic Arc forms a distinct linear magmatic complex that is aligned parallel with the orogenic suture of the Zagros fold-thrust belt. Most samples display characteristics of metaluminous, high-K calc-alkaline, I-type granitoids. The initial isotopic signatures range from εNd (47 Ma) = −4.77 to −5.89 and 87Sr/86Sr(i) = 0.7069 to 0.7074 for felsic rocks and εNd (47 Ma) = −3.04 to −4.06 and 87Sr/86Sr(i) = 0.7063 to 0.7067 for intermediate to mafic rocks. This geochemical and isotopic evidence support a mixed origin for the Kuh-e Dom hybrid granitoid with a range of contributions of both the crust and mantle, most probably by the interaction between lower crust- and mantle-derived magmas. It is seem, the felsic rocks incorporate about 56–74% lower crust-derived magma and about 26–44% of the enriched mantle-derived mafic magma. In contrast, 66–84% of the enriched mantle-derived mafic magma incorporates 16–34% of lower crust-derived magma to generate the intermediate-mafic rocks. According to the differences in chemical composition, the felsic rocks contain a higher proportion of crustal material than the intermediate to mafic ones. Enrichment in LILEs and depletion in HFSEs with marked negative Nb, Ba, and Ti anomalies are consistent with subduction-related magmatism in an active continental margin arc environment. This suggestion is consistent with the interpretation of the Urumieh–Dokhtar Magmatic Arc as an active continental margin during subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent. 相似文献
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Geology and Genesis of Peraluminous Granites in East Tianshan Upper Paleozoic Island Arc Belt 总被引：6，自引：1，他引：6
A peraluminous granite belt occurs along the connecting zone between the Turpan-Hami Precambrian block and the Upper Paleozoic island arc belt. Muscovite granite and twomica granite are the essential lithological components of that belt. All the potassium feldspars in these granites are microcline. Heavy minerals are dominated by magnetite. SiO2 contents of these granites are greater than 73% with most of the A/NKC values greater than 1.1, normative corundum values greater than 1. Plots of CIPW norms in the (Al-K-Na)-Ca-(Fe2++ Mg) diagram are mostly situated in the plagioclase-cordierite-muscovite region. The rocks are characterized by very low contents of minor elements and ΣREE with strong Eu depletion, δ18O values between 6.6‰ and 7.0‰, Rb-Sr isochron age of 260.2 ± 6.2 Ma and an initial87Sr/86 Sr ratio of 0.7052. These granites might have been produced by partial melting of moderately acidic volcanites and low-maturity sediments in the basement sequences and could be genetically connected with the southward A-type subduction of the Turpan-Hami block following the closure of the Middle Carboniferous back-arc basin. 相似文献
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《International Geology Review》2012,54(8):1039-1050
Basic volcanic rocks from Tafresh, west Kashan, and west Nain volcanic successions in the central part of Urumieh-Dokhtar Magmatic Assemblage (UDMA) of Iran yield K–Ar ages ranging from 26.8 to 18.2 Ma. These ages indicate significant Late Oligocene–Early Miocene basic volcanism in the UDMA. These ages, combined with K–Ar ages of 26.0 and 14.1 Ma, respectively, for associated low-silica and high-silica adakites, help constrain reconstructions of the UDMA geodynamic evolution. Late Oligocene–Early Miocene slab roll-back associated with an asthenospheric mantle influx are suggested as the major processes responsible for concurrent volcanism showing Nb–Ta-depleted, Nb–Ta-enriched and low-silica adakite signatures. Slab roll-back, the likely consequence of a decrease in subduction velocity, led to partial melting of the subducted slab and produced Early–Middle Miocene high-silica (dacitic) adakites. Oligocene to Miocene volcanic rocks do not conform to the Oligocene continental collisional model for the UDMA, rather they suggest a decrease in the subduction rate that prompted the asthenospheric mantle influx. 相似文献