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Magma underplating and Hannuoba present crust-mantle transitional zone composition: Xenolith petrological and geochemical evidence

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Science China Earth Sciences 2005年第8期48卷 1089-1105页

作者： FAN Qicheng1.2. ZHANG Hongfu1. SUI Jianli1. ZHAI Mingguo1. SUN Qian2.& LI Ni2.1. institute of {1. and {2., Chinese Academy of Sciences, beijing 1.002., China 2. institute of {1., China Seismological Bureau, beijing 1.002., China 1. institute of {1. and {2. Chinese Academy of Sciences 100029 Beijing China 2. {1. of {1. China Seismological Bureau 100029 Beijing China

On the basis of mineral assemblage, mineralogy, petrology, and major, trace ele-mental and isotopic geochemistry of the underplated granulite- and eclogite-facies accumulate, peridotite and pyroxenite xenoliths entrained in Hannuoba Cenozoic basalts, this work con-strained the petrological constituents for the crust-mantle transitional zone, which is supported by the results of high-temperature and pressure velocity experiments on rocks and geophysics deep survey. Present lower part of lower crust is mainly composed of granulite-facies mafic accumu-lates (dominantly plagioclase websterite) and crust-mantle transitional zone dominantly com-posed of eclogite-facies pyroxenites with or without garnet and spinel lherzolites; Archaean ter-rain granulite is only nominally early lower crust. Magma underplating in the crust-mantle boundary led to the crustal vertical accretion and the formation of the crust-mantle transitional zone, which is a significant mechanism for the chemical adjustment of the crust-mantle boundary since the Phanerozoic.

关键词： magma underplating, xenolith petrology, geochemistry, cust-mantle boundary constituent, Hannuoba.

Si-and alkali-rich melt inclusions in minerals of mantle peridotites from eastern China:Implication for lithospheric evolution

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Science China Earth Sciences 2006年第1期49卷 43-49页

作者： FAN Qicheng1. SUI Jianli2. XU Ping2. LI Ni1. SUN Qian1.& WANG Tuanhua1.1. institute of {1., China Seismological Bureau,{2., China 2. institute of geology and geophysics, Chinese Academy of Sciences,{2., China 1. institute of {1. China Seismological Bureau Beijing 100029 China 2. institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China

Minerals of spinel- and garnet-facies mantle xenoliths entrained in Cenozoicbasalts from eastern China (North China, Northeastern China and Southeastern China coastal area)contains lots of melt inclusions. Studies on these melt inclusions show that the glass inclusionsare rich in SiO_2.(60%—68%) and alkalis (K_2.+Na_2. = 5%—1.%, especially for K_2.) as well asvolatiles such as H_2. and CO_2.(2.—7%), which belong to dacites and andesites of the high-K calcicalkali series rocks with few shoshonites. High Al and Ca diopside in melt inclusion is the productof melt crystallization at high temperature and pressure, rather than the product ofdevitrification. Results show that these K-rich (in general K_2. > 3%) intermediate-acidic silicatemelt inclusions have characteristics of continent without a genetical link to host basalts and theirphenocrystic minerals. Thus, these trapped melt inclusions represent melts of Mesozoic lithosphericmantle-crust interaction and imply that the continental lithospheric mantle beneath eastern Chinahad undergone fragmentation and recreation processes during the Mesozoic and Cenozoic periods. Thisresult undoubtly provides important implication for the evolution of sub-continental lithospherebeneath eastern China. We propose that these Si- and alkalis-rich melts should be responsible forthe mantle chemical heterogeneity underneath eastern China.

关键词： Si- and alkali-rich melt inclusion, mantle peridotite, lithospheric evolution, eastern China.

^(40)Ar/^(39)Ar dating of shear deformation of the Xianshuihe fault zone in west Sichuan and its tectonic significance

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Science China Earth Sciences 2004年第9期47卷 794-803页

作者： ZHANG Yueqiao1, CHEN Wen2. 3 & YANG Nong1 1. institute of Geomechanics, Chinese Academy of Geological Sciences, {1. 100081, China 2. institute of geology, Chinese Academy of Geological Sciences, {1. 100037, China 3. institute of geology and geophysics, Chinese Academy of Sciences, beijing 1.002., China institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China institute of {1. Chinese Academy of Geological Sciences Beijing 100037 China institute of {1. and {2. Chinese Academy of Sciences Beijing 100029 China

Based on field geological survey, structural measurements and classical Ar/Ar dating of mica, biotite and K-feldspar, we obtain cooling ages for Miocene left-lateral shear along the Xianshuihe fault zone. The results document two thermal events during the sinistral shear. The early event (1.0}1. Ma) corresponds to rapid cooling of the Zheduoshan granitic massif from above 700℃ to below 350℃. The late event (5-3.5 Ma) corresponds to cooling of granites intruded along the eastern side of the fault zone. These dating results provide important thermochronological constraint on the timing of late Cenozoic eastward extrusion of the Chuan-Dian Block in the SE Tibetan margin.

关键词： Xianshuihe fault zone, Zheduoshan granitic massif, sinistral shear deformation, 40Ar/39Ar dating, late Cenozoic.

Carbon isotope composition and its implications of Lower Cretaceous Aptian-Albian shallow water carbonates in the Cuoqin Basin, North Tibet

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Science China Earth Sciences 2004年第3期47卷 247-254页

作者： ZHU Jingquan1. LI Yongtie2. JIANG Maosheng1.& CHEN Daizhao1.1. {1. of {1. and {2., Chinese Academy of Sciences, beijing 1.002., China 2. Research {1. of Petroleum Exploration and Development, CNPC, beijing 1.0083, China Chinese Acad Sci Inst Geol & Geophys Beijing 100029 Peoples R China CNPC Res Inst Petr Explorat & Dev Beijing 100083 Peoples R China

The d 13. values of Lower Cretaceous Aptian-Albian platform-type carbonates in the Cuoqin Basin, North Tibet vary between {1.48 and 5.46. The mean value is 3.93. The values are not only provided with positive excursion, but also 1.1. higher than those of con-temporaneous pelagic carbonates which possess pretty high d 13. values. The origin is ap-proached. During the oceanic anoxic events, a great number of organisms were rapidly buried, causing the increase of the d 13. value of oceanic total dissolved carbon (TDC) and generally promoting the values of marine carbonates. After that, owing to the organisms undergoing dif-ferent isotopic fractionation in the paleo-ocean with stratified structure, d 13. values of shallow sea carbonate were obviously higher than those of pelagic carbonates.

关键词： shallow water carbonate, stable carbon isotope, paleooceanography, Aptian-Albian stage, Cuoqin Basin.

Mineralogy and crystal structure determination of Mg-fillowite

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Science China Earth Sciences 2005年第5期48卷 635-646页

作者： MA Zhesheng 1., SHI Nicheng 1.& YE Danian 2.1. China University of Geosciences, {1. 1.0083, China 2. {1. of {2., Chinese Academy of Sciences, beijing 1.002., China 1. China University of Geosciences 100083 Beijing China 2. {1. of {1. Chinese Academy of Sciences 100029 Beijing China

Accurate crystal structure determination of complex phosphate Mg-fillowite ? Na2.a(Mn4Mg2.e)7[PO4]6 has been finished. Mg-fillowite occurs in muscovite-pegmatite in the Altay area, Xinjiang, China. It is of the trigonal lattice, with space group R-3, unit cell a=1.51.3(3) nm, c=4.31.1.2. nm, V=8.5736 nm3, Z = 1.. The R-factor of the determination accuracy is R (I > 2. ( I )) = 0.0776. The cationic polyhedra consist of two kinds of structural units: compound col- umn and screw column. In three-dimensional space, they are linked with each other through corner sharing or edge sharing to build the entire structure. There are 45 atoms in an asymmetric unit and 72. atoms in a unit cell. In terms of types and connection manners of the coordination polyhedra, the degree of complicity is rarely seen in all mineral crystal structures. Study of such a structure is significant for the classification of phosphate and the building rule of coordination polyhedra in a complex crystal structure.

关键词： Mg-fillowite, complex phosphate, crystal structure, coordination polyhedron.

Geological analysis and physical modeling of structural pumping in high effective formation of Kela 2.gas field

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Science China Earth Sciences 2006年第10期49卷 1070-1078页

作者： ZHAO Wenzhi1. WANG Hongjun1. SHAN Jiazeng2. WANG Zecheng1.& XU Dafeng1.1. Research {1. of Petroleum Exploration and Development, Petrochina, {1. 1.0083, China {2., Chinese Academy of Sciences, beijing 1.002., China 1. Research institute of Petroleum Exploration and Development Petrochina Beijing 100083 China 2. institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China

In a 3-D closed geological body, in case “structural expanding” inside is induced by stress, it can produce the pressure difference between the expanding cell and surrounding rock, then generate a pumping force directed toward the cell and accelerate the directional flow of fluid in the strata. The structural style and conditions of gas reservoir-formation in the Kuqa depression are favorable to the structural pumping. According to similarity principle, a physical modeling of structure formation and gas filling process of the Kela 2.gas field has justified the occurrence of structural pumping and its important role in gas-reservoir formation with high efficiency under the compressive and well-sealed circumstance. Therefore, authors propose that structural pumping is an important mechanism of gas reservoir-formation with high efficiency in the Kuqa depression.

关键词： Kela 2 gas field, structural pumping, gas-reservoir formation mechanism, high efficiency,physical modeling.

The features of gravity field and deep structure in western part of the South Yellow Sea

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Chinese Science Bulletin 2000年第8期45卷 759-764页

作者： WANG Qianshen1.& AN Yulin1. institute of {1., Chinese Academy of Sciences, {2. 1.01.1. China 2. Chinese University of geology, {2. 1.0083, China institute of {1. Chinesc Academy of Sciences Beijing China Chinese University of geology Beijing China

The gravity data from the sea region to the west of 1.0}° E of the South Yellow Sea have been processed and the feature of gravity fields analyzed. An experience relationship formula on the filter wavelength and corresponding depth has been put forward. Combined with the geological and seismic data, the deep tectonic framework and structural characters as well as possible favourable prospecting district for hydrocarbon in the South Yellow Sea have been discussed and analyzed.

关键词： western part of the South Yellow Sea gravity field deep structure.

Comparison of eastern paleo-Tethyan ophiolites and its geodynamic significance--Evidence from Dur'ngoi ophiolite

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Science China Earth Sciences 2004年第4期47卷 378-384页

作者： CHEN Liang1.2. SUN Yong1.2. PEI Xianzhi2. Feng Tao2.& Zhang Guowei2.1. Open Laboratory of Continental Dynamics, Ministry of Education, Northwest University, Xi抋n 71.069, China 2. institute of geology and geophysics, Chinese Academy of Sciences,{1., China Open Laboratory of Continental Dynamics Ministry of Education Northwest University Xi’an 710069 China institute of {1. and {2. Chinese Academy of Sciences Beijing 100029 China

Nd-Pb isotopic geochemistry of metabasalt from Dur抧goi ophiolite, Qinghai Prov-ince, NW China reveals the presence of DMM mixing with EMII components in its upper mantle source, which is comparable with present Indian MORB. Comparisons indicate that the geo-chemistry, chronology and source characteristics of Dur抧goi ophiolite coincide with Pa-leo-tethyan ophiolites from 揝anjiang?area. Together with evidences from regional geology in adjacent areas, this study proves that independent paleo-tethyan basins evolved contemporarily, the dynamics of which is attributed to the interaction of mantle plume with over-riding lithosphere.

关键词： ophiolite, Paleo-Tethys, DUPAL anomaly, Indosinian movement.

Characteristics and geological significance of olivine xenocrysts in Cenozoic volcanic rocks from western Qinling

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Progress in Natural Science:Materials International 2006年第12期16卷 1300-1306页

作者： SU Benxun~ 1.2.**, ZHANG Hongfu~1. XIAO Yan~ 1.2.and ZHAO Xinmiao~ 1.2.(1. State Key Laboratory of Lithospheric Evolution, institute of {1. and {2., Chinese Academy of Sciences, beijing 1.002., China 2. Graduate School of Chinese Academy of Sciences, beijing 1.0039, China) [a]State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China [b]Graduate School of Chinese Academy of Sciences Beijing China

Cenozoic volcanic rocks from the Haoti, Dangchang County of the western Qinling Mountains, contain a few clearly-zoned olivines. These olivines are relatively big in grain sizes and usually have cracks or broken features. Their cores have similar compositions （Mg#=90.4-91.0） to those for the peridotitic xenoliths entrained in host volcanic rocks and their rims are close to the compositions of olivine phenocrysts （Mg#=85.5-81.9）. The CaO contents in these zoned olivines are lower than 0.1.. These features demonstrate that the clearly-zoned olivines are xenocrysts and disaggregated from mantle peridotites. The zoned texture was the result of the interaction between the olivine and host magma. Available data show that the volcanic rocks would have been derived from the mantle source metasomatized by subducted hydrathermally-altered oceanic crust. The formation of these Cenozoic volcanic rocks was perhaps related to the rapid uplift of the Tibetan Plateau.

关键词： Western Qinling Dangchang Haoti Cenozoic volcanic rocks olivine xenocrysts zoned texture.