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Search Results: 1 - 10 of 3308 matches for " MO XuanXue "
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Two kinds of silicalites in Mount Ailao belt, Yunnan Province
Shangyue Shen,Qirong Wei,Huilan Cheng,Xuanxue Mo,Qinglai Feng
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02886325
Abstract: Two kinds of radiolarian silicalites at the bottom and top of the ophiolite in the Mount (Mt.) Ailao belt, Yunnan Province, are dealt with in this work in terms of geology, micro-paleontology, isotope and REE. The first kind of silicalite was defined as the turbidite formation. In this category, the radiolarian species lived in the Late Devonian (D3). The corresponding ecologic assemblage, composed of δ30Si (0.4‰–0.5‰, average 0.03‰), δCe (0.77–0.97, average 0.85) and LaN/YbN (0.77–1.06, average 0.96) of silicalite, shows that it occurred in the abyssal environment. The second kind of silicalite was defined as the mud-siliceous formation. Contacting conformably with the basalt of the ophiolite suit, the radiolarian silicalite at the top of ophiolite was in the category of the component units of the ophiolite in the Mt. Ailao belt. In this category, the radiolarian species lived in the Early Carboniferous (C1). The corresponding ecologic assemblage, composed of δ30Si (0.2‰–1.3‰, averaging 0.7‰), δCe (0.88–0.92, averaging 0.90) and LaN/YbN (0.77–1.45, averaging 1.22), of silicalites indicate that it occurred in the bathyal environment. All these facts domonstrate that the Mt. Ailao must have been a small ocean basin at that time.
Metamorphic peridotite and rock series of ophiolite belt in Mt. Ailao, Yunnan Province
Shen Shangyue,Wei Qirong,Cheng Huilan,Mo Xuanxue
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02884622
Abstract: The metamophic peridotite of ophiolite belt in Mt. Ailao is mmposed of lhenolite and harzburgite. The former shows the charateristics of primary pyrolite and the latter shows those of deleted (relict)pyrolite. By partial melting of Ihedite, two primary magmas: tholeiitic magma and picrite-basalt magma are formed. The former evoluted into gabbmdiabase-pyroxenic besalt rock series and show the characteristics of MORB; while the latter evoluted into gabbro-diorite-albite basalt-picrite basalt one, and show the characteristics of para-MORB.
40Ar-39Ar geochronology of Cenozoic Linzizong volcanic rocks from Linzhou Basin, Tibet, China, and their geological implications
Su Zhou,Xuanxue Mo,Guochen Dong,Zhidan Zhao,Ruizhao Qiu,Tieying Guo,Liangliang Wang
Chinese Science Bulletin , 2004, DOI: 10.1007/BF03184291
Abstract: Whole-rock and mineral separate Ar-Ar dating was carried out for the Linzizong volcanic rocks at Linzhou Basin in Tibet to constrain the time span of volcanism and the corresponding stratigraphic sequence. Sampling was based on detailed geologic mapping and stratigraphic sequence of Dianzhong, Nianbo, Pana Formations, systematically from the bottom to near the top. The results indicate that the Linzizong volcanic rocks erupted from Paleocene to middle of Eocene (64.43· 43.93 Ma). Among them, the Pana Formation formed from ca. 48.73 to 43.9 Ma, the Nianbo Formation around 54 Ma and the Dianzhong Formation from 64.4 to 60.6 Ma. In combination with evidence from the geochemical characteristics of the volcanic rocks, and from stratigraphy in southern Tibet, it is postulated that the age of the lowest member in the Dianzhong Formation of the Linzizong volcanic rock, which overlies unconformably the Late Cretaceous Shexing Formation, likely corresponds to the inception of the collision between Indian and Asian continents in southern Tibet.
SHRIMP U-Pb zircon dating for the dacite of the Sangxiu Formation in the central segment of Tethyan Himalaya and its implications
Dicheng Zhu,Guitang Pan,Xuanxue Mo,Liquan Wang,Zhongli Liao,Xinsheng Jiang,Quanru Geng
Chinese Science Bulletin , 2005, DOI: 10.1007/BF02897481
Abstract: Petrology and SHRIMP U-Pb zircon chronology are reported for the dacite of the Sangxiu Formation in the central segment of Tethyan Himalaya to the southeast of Yangzuoyong Co. Twenty-one measured zircon grains from a dacite sample of the Sangxiu Formation can be divided into two groups, which include long columnar magmatic zircons of 133±3.0 Ma, representing the age of volcanism in the Sangxiu Formation, and inherited zircons consisting of core and overgrowth rim, in which ages of the three cores are 2244±16, 1153±33 and 492±25 Ma respectively; and the age of one overgrowth rim is 132.7±5.2 Ma. These ages are considered to represent the remelting of accretionary crust at different periods resulting from the volcanism of Sangxiu Formation. These volcanic rocks in the Sangxiu Formation, for which age is close to that of Bunbury basalt in southwestern margin of Australia, and older than that of Rajmahal basalt in northeastern India, maybe considered as the products of early activity of the hotspot represented by the Rajmahal basalt.
Geochronology and Nd and Pb isotope characteristics of gabbro dikes in the Luobusha ophiolite, Tibet
Su Zhou,Xuanxue Mo,J. J. Mahoney,Shuangquan Zhang,Tieyjing Guo,Zhidan Zhao
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9033
Abstract: We report a combined internal and whole-rock Sm-Nd isochron age, and Nd and Pb isotopic data for gabbro dikes of the Luobusha ophiolite in Tibet. The Sm-Nd isochron of data for two whole rocks and plagioclase and clinopyroxene separates from one of the rocks yields a Middle Jurassic age of (177±31) Ma (with an initial εNd(t) = +8), which provides a significant bound on the time of formation of the Luobusha ophiolite. The Nd and Pb isotopic characteristics of the dike indicate an Indian-Ocean-type isotopic affinity, and we conclude that the Luobusha ophiolite formed in an oceanic setting during the Middle Jurassic.
Experimental study on electrical conductivity of dunite at high temperature and pressure
Wang Duojun,Li Heping,Liu Congqiang,Zhao Zhidan,Mo Xuanxue,Guo Tieying,Su Gengli,Ding Dongye
Chinese Science Bulletin , 2001, DOI: 10.1007/BF02901139
Abstract: The electrical conductivities of the dunite from the Qinghai-Xizang (Tibetan) Plateau were measured with the impedance spectra method at 1.0–4.0 GPa and 6431093 K. The experimental results indicated that activation enthalpies of the dunite are smaller than 0.9 eV, the conduction mechanism in dunite may be attributed to the mixed electrical conduction involving grain interiors and boundaries. On the basis of the results of this experiment, we can deduce that there exists cold mantle in the area of Gaize-Lugu in the Qinghai-Xizang (Tibetan) Plateau by reverse methods from the magnetotelluric sounding data (conductivity-depths profile) available for western Tibet. The result provides the present cold mantle viewpoint with strong proof on the basis of high temperature and pressure experiments.
Mixing events between the crust- and mantle-derived magmas in eastern kunlun: Evidence from zircon SHRIMP II chronology
Chengdong Liu,Xuanxue Mo,Zhaohua Luo,Xuehui Yu,Hongwei Chen,Shuwei Li,Xin Zhao
Chinese Science Bulletin , 2004, DOI: 10.1007/BF02889756
Abstract: Various shaped mafic microgranular enclaves (MMEs) together with several mafic massifs are developed within the Yuegelu granitoid pluton in the eastern part of the Eastern Kunlun. On the basis of detailed field geological surveying and of the results of the petrological and geochemical studies it is suggested that there must be some genetic relationship among the granodiorite host, the MMEs and the hornblende (Hb)-gabbro massifs. Magmatic zircon grains are extracted from samples of granodiorite host rock, Hb-gabbro and the MMEs for U-Pb dating. The U-Pb ages are determined by using SHRIMP II technique, which yields the ages of 242 ± 6 Ma, 239 ± 6 Ma and 241 ± 5 Ma, respectively. The overall correspondence in the U-Pb dating results of them excludes the possibility that the MMEs in the granitoids are solid refractory relics from the source region or that they are xenoliths from the wall rocks. It can also rule out the possibility of a later emplacement of basic magma after the solidification of the granitoids. This dating result indicates that they are the products of magma mixing in early-mid Triassic epoch. Among them the granitoid host is chemically akin to the acidic end member during the magma mixing process, the Hb-gabbro is akin to the basic ones while the MMEs are the incompletely mixed basic magma clots trapped in the acidic magma. Combined with the results from other researches on this pluton it is reasonable to consider that in the mid-Triassic the Eastern Kunlun granitoid belt had undergone a process of magma mixing between the mantle-derived basic magma and the crustal acidic magma which indicates that the injection of mantle materials and energy into the crust and the reactions between them played an important role in the formation of the granitoid rocks.
40Ar/39Ar dating for Cenozoic kamafugite from western Qinling in Gansu Province
Xuehui Yu,Zhidan Zhao,Su Zhou,Xuanxue Mo,Deqing Zhu,Yonglei Wang
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2010-7
Abstract: 40Ar/39Ar ages were determined for 6 phlogopite samples from a kamafugite pipe occurring in western Qinling, yielding a time span of 22 to 23 Ma for kamafugite eruption. Together with known geochronological data for the Qinghai-Tibet Plateau (QTP) and its peripheral regions, it is concluded that these Cenozoic potassic-ultrapotassic volcanic rocks are products of post-collisional volcanism. The age of the Cenozoic volcanic rocks in western Qinling partly overlaps that of potassic volcanics from the Gandise belt, reflecting the northward migration of the post-collisional volcanism in QTP. The age data not only confirm the temporal and spatial migration of post-collisional volcanism in QTP, but also provide geochronological constraints on the geodynamic setting at depth and the regimes of the tectonic evolution since Neogene in western Qinling regions.
Dynamic Analysis of Immiscible Differentiation Process of Magma
岩浆不混溶分异过程动力学分析

Tan Jin,Mo Xuanxue,Zhao Shanrong,Deng Jinfu,
谭劲

岩石学报 , 1998,
Abstract: This article, based on dynamics of immiscible differentiation process of magma, analyzes the development stages of immiscible spherical phases. In the early stage when the tiny spherical phases are smaller than micron scale, they collide and merge violently, therefore,they develop rapidly and are difficult to be preserved. Meanwhile they will be reformed or destroyed by crystallization.Under the other extreme condition, the big spherical phases above meter scale are also difficult to be preserved as spheres because of fast gravitional separating, but they provide conditions for forming large scale geological body. Only millimeter to centimeter scale spherical phases, which develop relatively slowly, can be easily preserved. Micron scale spheres may be preserved in quenched volcanic matrix. According to dynamics,the differentiation process of immiscible in magma would be one of effective magmatic evolution differentiation mechanisms.
Precambrian granitic rocks,continental crustal evolution and craton formation of the North China Platform.
华北地台前寒武花岗岩类、陆壳演化与克拉通形成

Deng Jinfu,Wu Zongxu,Zhao Guochun,Zhao Hailing,Luo Zhaohua,Mo Xuanxue,

岩石学报 , 1999,
Abstract: Based on study of Precambrian granitic rocks, this paper suggests that T 1T 2, T 1T 2G 1G 2 and G 1G 2 associations represent inmature,semi mature and mature continental crustal composition, respectively. Continental root and its nature are discussed. Ten Archean continental nucleuses have been recognized. Formation of Mezoarchean initial continental nucleus, Archean continental nucleus in Neoarchean, two micro continental scale continental nucleus in the latest Archean, and formation of the North China craton by tectonic assemblage of the two mature continental nucleuses in Paleoproterozoic are disussed.
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