检索结果-南通市图书馆

Features of the Early Palaeozoic Mantle beneath Langao County and Its Formation Mechanism

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 1999年第3期73卷 356-365,371页

作者： XU Xueyi HUANG Yuehua xia linqi xia Zuchun Xi'an Institute of Geology and Mineral Resources Chinese Academy of Geological Sciences 166 Youyi Road Xi'an 710054

Phlogopite-amphibole pyroxenite xenoliths contained in an Early Palaeozoic alkali subvolcanic lamprophyre complex in Langao County, Shaanxi Province, are metasomatized mantle xenoliths, composed mainly of clinopyroxene, amphibole, phlogopite, apatite, pervoskite, ilmenite and sphene with well-developed subsolidus metamorphism-deformation textures, such as “triple points” and “cataclastic boundaries”. Minerological studies indicate that clinopyroxene is rich in SiO2 and MgO and poor in TiO2 and Al2O3, which is notably different from magmatogenic deep-seated megacrysts and phenocrysts formed in the range of mantle pressure. Amphibole and phlogopite have the compositional feature of mantle-derived amphibole and phlogopite. Sm-Nd isotope studies suggest that the metasomatized mantle beneath Langao County is the product of metasomatism of primitive mantle by melt (fluid) derived from the mantle plume, and the mantle metasomatism occurred 650 Ma ago. The process of mantle metasomatism changed from mantle metasomatism induced by CO2-, H2O- and CH4-rich fluid in the early stage to that induced by melt and P-, Ti-, Ca- and Fe-rich fluid in the late stage.

关键词： metasomatized mantle xenoliths mantle plume mantle metasomatism Langao County

Reassessment of petrogenesis of Carboniferous—Early Permian rift-related volcanic rocks in the Chinese Tianshan and its neighboring areas

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2012年第4期3卷 445-471页

作者： linqi xia Xueyi Xu xiangmin Li Zhongping Ma Zuchun xia Xi＇an Institute of Geology and Mineral Resources China Geological Survey Xi＇an Shaanxi 710054 China

The Carboniferous-Early Permian rift-related volcanic successions, covering large areas in the Chinese Tianshan and its adjacent areas, make up a newly recognized important Phanerozoic large igneous province in the world, which can be further divided into two sub-provinces： Tianshan and Tarim. The regional unconformity of Lower Carboniferous upon basement or pre-Carboniferous rocks, the ages （360--351 Ma） of the youngest ophiolite and the peak of subduction metamorphism of high pressure-low temperature metamorphic belt and the occurrence of Ni-Cu-bearing mafic-ultramafic intrusion with age of ~352 Ma and A-type granite with age of ~358 Ma reveal that the final closure of the Paleo-Asian Ocean might take place in the Early Mississippian. Our summation shows that at least four criteria, being normally used to identify ancient asthenosphere upwelling （or mantle plumes）, are met for this large igneous province：（1） surface uplift prior to magmatism; （2） being associated with continental rifting and breakup events; （3） chemical characteristics of asthenosphere （or plume） derived basalts; （4） close links to large-scale mineralization and the uncontaminated basalts, being analogous to those of many ＂ore-bearing＂ large igneous provinces, display Sr-Nd isotopic variations between plume and EMI geochemical signatures, These suggest that a Carboniferous asthenosphere upwelling and an Early Permian plume played the central role in the generation of the Tianshan--Tarim （central Asia） large igneous province.

关键词： Carboniferous-Early Permian rift-related volcanism Tianshan-Tarim (central Asia) large igneous province Asthenosphere Mantle plume Lithosphere contamination

Mid—Late Neoproterozoic rift-related volcanic rocks in China:Geological records of rifting and break-up of Rodinia

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2012年第4期3卷 375-399页

作者： linqi xia Zuchun xia Xueyi Xu xiangmin Li Zhongping Ma Xi＇an Institute of Geology and Mineral Resources China Geological Survey Xi＇an Shaanxi 710054 China

Early Cambrian and Mid--Late Neoproterozoic volcanic rocks in China are widespread on several Precambrian continental blocks, which had aggregated to form part of the Rodinia supercon- tinent by ca. 900 Ma. On the basis of petrogeochemical data, the basic lavas can be classified into two major magma types： HT （Ti/Y 〉 500） and LT （Ti/Y 〈 500） that can be further divided into HT1 （Nb/La 〉 0.85） and HT2 （Nb/La ≤ 0.85）, and LT1 （Nb/La 〉 0.85） and LT2 （Nb/La ≤ 0.85） subtypes, respectively. The geochemical variation of the HT2 and LT2 lavas can be accounted for by lithospheric contamination of asthenosphere- （or plume-） derived magmas, whereas the parental magmas of the HT1 and LT1 lavas did not undergo, during their ascent, pronounced lithospheric contamination. These volcanics exhibit at least three characteristics：（1） most have a compositional bimodality; （2） they were formed in an intracontinental rift setting; and （3） they are genetically linked with mantle plumes or a mantle surperplume. This rift-related volcanism at end of the Mid-- Neoproterozoic and Early Cambrian coincided temporally with the separation between Australia-- East Antarctica, South China and Laurentia and between Australia and Tarim, respectively.

关键词： Neoproterozoic Bimodal volcanism Continental rift Mantle plume Rodinia supercontinent China

Relationships between Basic and Silicic Magmatism in Continental Rift Settings:A Petrogeochemical Study of Carboniferous Post-collisional Rift Silicic Volcanics in Tianshan,NW China

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2005年第5期79卷 633-653页

作者： xia linqi xia Zuchun XU Xueyi LI xiangmin MA Zhongping WANG Lishe Xi＇ an Institute of Geology and Mineral Resources China Geological Survey Xi＇ an Shaanxi 710054

Petrogeochemical data are reported for silicic volcanic rocks from the Tianshan Carboniferous rift, with the aim of discussing the petrogenesis of silicic magmas. Incompatible element vs. incompatible element diagrams display smooth positive trends for the Tianshan Carboniferous rift-related volcanic rocks; the isotope ratios of the silicic lavas [^87Sr/^86S（t）=0.699880.70532; eNd（t）=4.76-8.00; ^206pb/^204pb（t）=17.435-18.017; ^207Pb/^204Pb（t）=15.438-15.509; ^208Pb/^204Pb（t） = 37.075-37.723] encompass those of the basic lavas. These data suggest a genetic link between rhyolites and basalts, but are not definitive in establishing whether silicic rocks are related to basalts through fractional crystallization or partial melting. Geochemical modeling of incompatible vs. compatible elements excludes the possibility that silicic melts are generated by the melting of basaltic rocks, and indicates a derivation by fractional crystallization plus moderate assimilation of wall rocks （AFC） starting from intermediate rocks to silicic rocks. Continuous AFC from basalt to rhyolite, with small rates of crustal assimilation, best explains the geochemical data. The presence or absence of bimodal volcanism （the ＂Daly Gap＂） might be related to cooling rates of magma chambers. In central and eastern Tianshan, the crust was thinner and the cooling rates of the magma chamber within the crust were greater. These conditions resulted in a rapid fall in temperature within the magma reservoir and caused a narrow temperature interval over which intermediate melts formed, effectively reducing the volume of the intermediate melts.

关键词： Carboniferous rift-related silicic volcanic rocks geochemistry bimodal volcanism Tianshan NW China.

On the Relationship between Mantle Metasomatism and Partial Melting—Evidence from Mantlederived Lherzolite Xenoliths from Nshan,China

在线全文

学校读者我要写书评

暂无评论

Chinese Journal Of Geochemistry 1993年第4期12卷 289-307页

作者： xia linqi xia Zuchun Zhang Cheng Xu Xueyi Xi'an Research Institute of Geology and Mineral Resources Ministry of Geology and Mineral ResourcesXi'an710054

Studies of the mantle-derived iherzolites from Nushan show that in addition to CO2,there were present H2O and small amounts of CO, CH4, SO2,Cl and F in the initial mantlc fluids derived fron the asthenospheric mantlc plumc .The imitial fluids accumulated in some regions of the mantle, resulting in lowering of the mantle solidus (and liquidus) and partial melting of the upper mantle. Melts formed from low-degree of fluid-involved partial melting of the upper mantle would be highly enriched in incompatible *** and melts are allthe metasomatic agents for mantle metasomatism, and the interaction between them and the depleted mantle could result in the substan-tial local enrichment of LREE and incompatible elements in the *** case that the concentration of H2O in the fluids (and melts) is lower ,only cryptic metasomatism would occur, in case that the concentration of H2O is higher,the degree of partial melting would be higher and hydrous metasomatic phases(e.g. amphiboles )would nucleate. Under such circumstances, there would occur model metasomatism.

关键词： mantle metasomafism partial melting Ihetzolite xenolilh Nushan

Geology and geochemistry of the Bingdaban ophiolitic mélange in the boundary fault zone on the northern Central Tianshan Belt,and its tectonic implications

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2007年第1期50卷 17-24页

作者： DONG YunPeng ZHANG GuoWei ZHOU DingWu LUO JinHai ZHANG ChengLi xia linqi XU XueYi LI xiangMin The Key Laboratory of Continental Dynamics Ministry of EducationDepartment of GeologyNorthwest UniversityXi’an 710069China Shandong University of Science and Technology Qingdao 266510China Xi’an Institute of Geology and Mineral Resources China Geological SurveyXi’an 710054China

The properties and tectonic significance of the fault bound zone on the northern margin of the Central Tianshan belt are key issues to understand the tectonic framework and evolutionary history of the Tianshan Orogenic Belt. Based on the geological and geochemical studies in the Tianshan orogenic belt, it is suggested that the ophiolitic slices found in the Bingdaban area represent the remaining oceanic crust of the Early Paleozoic ocean between the Hazakstan and Zhungaer blocks. Mainly com-posed of basalts, gabbros and diabases, the ophiolites were overthrust onto the boundary fault be-tween the Northern Tianshan and Central Tianshan belts. The major element geochemistry is charac-terized by high TiO2 (1.50%-2.25%) and MgO (6.64%-9.35%), low K2O (0.06%-0.41%) and P2O5 (0.1%-0.2%), and Na2O>K2O as well. Low ΣREE and depletion in LREE indicate that the original magma was derived from a depleted mantle source. Compared with a primitive mantle, the geochemistry of the basalts from the Bingdaban area is featureded by depletion in Th, U, Nb, La, Ce and Pr, and unfrac-tionated in HFS elements. The ratios of Zr/Nb, Nb/La, Hf/Ta, Th/Yb and Hf/Th are similar to those of the typical N-MORB. It can be interpreted that the basalts in the Bingdaban area were derived from a de-pleted mantle source, and formed in a matured mid-oceanic ridge setting during the matured evolu-tionary stage of the Northern Tianshan ocean. In comparison with the basalts, the diabases from the Bingdaban area show higher contents of Al2O3, ∑REE and HFS elements as well as unfractionated incompatible elements except Cs, Rb and Ba, and about 10 times the values of the primitive mantle. Thus, the diabases are thought to be derived from a primitive mantle and similar to the typical E-MORB. The diabases also have slight Nb depletion accompanying no apparent Th enrichment compared with N-MORB. From studies of the regional geology and all above evidence, it can be suggested that the diabases from the Bingdaban

关键词： geochemistry ophiolite suture zone Bingdaban Tianshan orogenic belt.

THESIS FOR GRADUATION:The Thermobarogeochemical Study of Silicate Melt lnclusins in Different Minerals of Lava

在线全文

学校读者我要写书评

暂无评论

THESIS FOR GRADUATION:The Thermobarogeochemical Study of Sil...

Carboniferous Post-collisional Rift Volcanism of the Tianshan Mountains, Northwestern China

作者： xia linqi

＜正＞This doctorate thesis studies in detail the evolution of silicate melt inclu- sions during trapping and after trapping,their classification,the kinetics of ho- mogenization process of silicate melt inclusion and the principal characteristics of silicate melt inclusions in cardinal minerals(olivine,pyroxene,plagioclase,

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2003年第3期77卷 338-360页

作者： xia linqi, XU Xueyi, xia Zuchun, LI xiangmin, MA Zhongping and WANG Lishe Xi’an Institute of Geology and Mineral Resources, China Geological Survey, Xi’an, Shaanxi 710054 E-mail: geologyx@***. Liu Shuchun and Liu Xinzhu xian Inst Geol & Mineral Resources China Geol Surv Xian 710054 Shaanxi Peoples R China

The Tianshan Carboniferous post-collisional rift volcanic rocks occur in northwestern China as a large igneous province. Based on petrogeochemical data, the Tianshan Carboniferous post-collisional rift basic lavas can be classified into two major magma types: (1) the low-Ti/Y type situated in the eastern-central Tianshan area, which exhibits low Ti/Y (500), Ce/Yb (>11) and SiO2 (49-55%), and relatively low Fe2O3T (5.8-7.8%). Elemental data suggest that chemical variations of the low-Ti/Y and high-Ti/Y lavas cannot be explained by fractional crystallization from a common parental magma. The Tianshan Carboniferous basic lavas originated most likely from an OIB-like asthenospheric mantle source (87Sr/86Sr(t) ≈ 0.703-0.705, eNd(0 = +4 to +7). The crustal contamination and continental lithospheric mantle have also contributed significantly to the formation of the basic lavas of the Tianshan Carboniferous post-collisional rift. The silicic lavas were probably generated by partial melting of the crust. The data of this study show that spatial petrogeochemical variations exist in the Carboniferous post-collisional rift volcanics province in the Tianshan region. Occurrence of the thickest volcanics dominated by tholeiitic lavas may imply that the center of the mantle-melting anomaly (mantle plume) was in the eastern Tianshan area at that time. The basic volcanic magmas in the eastern Tianshan area were generated by a relatively high degree of partial melting of the mantle source around the spinel-garnet transition zone, whereas the alkaline basaltic lavas are of the dominant magma type in the western Tianshan area, which were generated by a low degree of partial melting of the mantle source within the stable garnet region, thus the basic lavas of the western Tianshan area might have resulted from relatively thick li

关键词： Carboniferous post-collisional rift volcanics geochemistry petrogenesis asthenosphere lithosphere Tianshan Mountains NW China

Paleosubmarine Volcanism and Mineralization from North Qilian Mountains

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 1999年第1期18卷 38-41页

作者： xia linqi xia Zuchun Ren Youxiang Xu Xueyi Peng Ligui Institute of Geology and Mineral Resources, CAGS, Xi ’an 710054

This paper summarizes the history of tectono magmatic evolution, the types and backgrounds of mineralization prior to the orogenic period of North Qilian Mountains. It points out that: during the process of Paleozoic ocean basin opening and closing, the large scale marine volcanism and massive sulfide deposits controlled by sea floor hydrothermal circulation systems are the two sharpest features in the geological developing history of the orogenic belt, which are also the most two important aspects related to each other and should be given a special attention in the geological studies in the region.

关键词： paleosubmarine volcanism massive sulfide deposit North Qilian Mountains.