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    Application of Niched Pareto Genetic Algorithm to Multi-Objective Optimal Design of Groundwater System
    PENG Wei, WU Jian-feng, WU Ji-chun
    Abstract1960)      PDF (943KB)(184621)       Save
    Mostly, conflicting subjects are handled as single subject by several methods in groundwater system management problem. However, these techniques are only capable of finding one solution, which may sometimes contravene decision makers’willingness. On the contrary, multi-objective optimization approaches could provide the decision makers with a set of alternate solutions, being selected for a given site. In this paper, a program named NPGA-GW is developed for groundwater system multiobjective management, based on the niched Pareto genetic algorithm, which is coupled with the groundwater flow simulator MODFLOW and the contaminant transport simulator MT3DMS. NPGA-GW is applied to design pump-and-treat system that solves the multi-objective optimization model for a two-dimensional hypothetical test problem. The results show that a set of Pareto optimal solutions could be found in short term, which spanned trade-off curves wide enough for decision makers. To sum up,NPGA-GW has broad prospects in groundwater system management.
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    Cited: Baidu(9)
    Magmatism and Evolution of the Tibetan Plateau
    MO Xuan-Xue
    J4    2011, 17 (3): 351-.  
    Abstract3058)      PDF (15256KB)(7715)       Save

    The Tibetan Plateau  is one of  the regions  in China where  igneous rocks are very widely developed. Various  types of
    volcanic and plutonic rocks are distributed over 300,000 km2 in area and take 10% area of the entire Plateau. These igneous rocks
    and carried deep-seated nodules play  important  roles  in understanding geodynamic evolution of  the Tibetan Plateau, as either
    lithoprobes/windows or  tectonic  records, and are closely  related  to mineralization as well. This paper discusses some  important
    scientific  topics via studying  igneous  rocks.  (1) The  timing of  Indo-Asia collision: This  is a very  important scientific problem.
    There  is, however, a wide  range of discrepancy about  the  timing of  initiation of  the collision  (from earlier  than 70 Ma,  to even
    later than 34 Ma). According to multiple lines of evidences from the 1500 km-extending main collision zone in southern Tibet, we
    deduced a conclusion that Indo-Asia collision likely started from 65/70 Ma and completed in c. 40 Ma (syn-collisional stage), and
    then transformed into post-collisional stage after 40 Ma. (2) Underplating and magma mixing, an event of mantle-crust interaction
    during  syn-collisional  stage: There are abundant evidences  for underplating and magma mixing  in  southern Gangdese. An

    important process of continental growth and evolution took place in the Tibetan Plateau. (3) The origin of formation of extremely
    thick crust of  the Tibetan Plateau: A deduction of “Two  types of crust and  two  types of mechanism”  is suggested based on  the
    studies of collisional and post-collisional  igneous  rocks. There are  two  types of crust,  juvenile crust and  recycled crust,  in  the
    Plateau. Crustal  thickening of  the Plateau was caused by  two  types of mechanism,  i.e., both structural compression and  input of
    mantle materials via magmatism. (4) The composition, structure and evolution of the lithosphere of the Tibetan Plateau: There are
    three geochemical reservoirs in the lithospheric mantle, and three types of lithospheric structure underneath the Tibetan Plateau.
    Nodules and outcrops of mantle/lower crust-seated rocks are found in several locations of the Plateau. (5) Possible lateral flow of
    lower crust and upper mantle: Migration of collisional and post-collisional volcanism with time shows a highly distinctive pattern,
    which can be interpreted to reflect lateral flow of the lower crust and asthenospheric mantle induced by the approach and ensuing
    collision of relatively thick (India and Eurasia) continental plates.

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    PerformanceandMechanismsfortheRemovalofCopperIonsfrom AqueousSolutionsbyClayeyDolomite
    QIU Gao, XIE Qiaoqin, CHEN Tianhu*, LIU Haibo, XIE Jingjing, LI Hongwei, TIAN Yi
    J4    2015, 21 (4): 616-.  
    Abstract1626)      PDF (626KB)(6136)       Save

     In comparison to common dolomite and palygorskite clay, the effects of parameters such as pH, contact time, initial concentrationofcopperonremovalofcopperionsusingclayeydolomiteinpalygorskiteclaydepositwasinvestigatedusingstatic adsorptionexperiments.Thekineticsofcopperremovalwasdiscussedbythepseudo-first-order,thepseudo-second-orderandthe Elovichmodel,andthesorptionisothermwasanalyzedbyLangmuirandFreundlichisothermequations.Theresultsshowthatthe effectofpHontheremovalofcopper(II)ionbyclayeydolomitewaslessthantheothertwo.Morethan85%ofcopper(II)ionswere removedinthepHrangeof3to5andtheoptimumpHis5.Thekineticdataoftheremovalofcopperbyclayeydolomitefittedthe pseudo-second-orderkineticmodelverywell.Theremovalrateaswellastheefficiencywasthehighest.Theisothermdatacanbe described by the Freundlich model and the removal capacity was 186.2×10-3. The removal mechanisms were mainly surface precipitationinducedbythemineral-waterinteractionsandelectrostaticattractionbetweenpalygorskiteandthenewlyformedcolloid [Cu2CO3(OH)2].Thepresentstudyconcludesthatclayeydolomiteismoreeffectivebecauseoftheintergrowthofnanoscalepalygorskite andsub-micronporousdolomite,leadingtothehigh-efficientremovalofcopperionsthanthecommondolomiteandpalygorskiteclay, anditpossessesthepotentialfortreatingcopperwastewater.

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    Cited: Baidu(1)
    The Metalliferous Mineralization Associatied with Adakitic Rocks
    WANG Qiang, TANG Gong-jian, JIA Xiao-hui, ZI Feng, JIANG Zi-qi, XU Ji-feng, ZHAO Zhen-hua
    Abstract1980)      PDF (1260KB)(5409)       Save
    Adakitic rocks have important implications for the metalliferous mineralization. This paper introduces the nomenclature of“ adakitic rocks”, the distribution and tectonic settings of the adakitic rocks associated with metalliferous mineralization. The factors that the adakitic rocks are favorable for the metalliferous mineralization are discussed in detail at last. Similar to a subducted oceanic crust-derived adakite, the“adakitic rocks”are characterized by the following geochemical characteristics: SiO2≥56wt%, Al2O3≥15 wt%, depleted Y (≤18×10-6 ) and heavy rare earth element contents ( Yb≤1.9×10-6 ), high Sr (rarely<400×10-6 ), negligibly positive Eu and Sr anomalies, and depleted high field strength element contents. They can be generated in different tectonic settings and by different mechanisms. The favorable tectonic settings for the metalliferous mineralization include arc, within-continent extension, and active collisional orogenic belt between different continents. Many large and giant are closely associated with adakitic rocks, indicating that they have a huge metalliferous potential. In the arc and within-continent extension settings, the interaction between subducted basaltic oceanic crust, or sediments, or delaminated continental crust-derived melts, or released super critical fluids with mantle causes contamination of melts by mantle peridotites on the one side, and metasomatism of mantle peridotites by the melts or fluids with high Fe2O3 on the other side. Thus, the raised oxygen fugacity in the mantle causes metal sulfides to be decomposed, which is favorable for the Cu-Au mineralization.
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    Cited: Baidu(47)
    Spatial-Temporal Distribution of Mesozoic Ore Deposits in South China and Their Metallogenic Settings
    MAO Jing-wen1, XIE Gui-qing1, GUO Chun-li1, YUAN Shun-da1, CHENG Yan-bo2, CHEN Yu-chuan1
    Abstract3418)      PDF (5028KB)(5323)       Save
    Based on extensive field investigation and precise geochronological data we proposed Mesozoic metallic mineralization in South China can be grouped into three pulses, i.e. Late Triassic (230~210 Ma), Mid-Late Jurassic (170~150 Ma), and Early-Middle Cretaceous (134~80Ma). The mineralization elements in these three pulses are different. The Triassic mineralization is Peraluminous granite-related W-Sn-Nb-Ta. The Mid-late Jurassic mineralization can be further divided into 170~160 Ma porphyry and skarn Cu and I-type granite-related Pb-Zn-Ag, and 160~150 Ma paraluminous granite-related polymetallic W-Sn. Although the Cretaceous mineralization lasted about 54 Ma, its peak ranged from 100 Ma to 90 Ma. The major types of the mineralization are epithermal Au-Ag-Cu and granite-related polymetallic tin (tungsten). The Triassic peraluminous granite-related W-Sn-Nb-Ta is a response to the post-collisional process of the South China plate with the North China plate. The Izanagi plate started to subduct beneath the Eurasian continent at ca. 180 Ma and then the porphyry copper deposits and vein type Pb-Zn-Ag deposits and their related I-type granitoids or aidakitic rocks formed when the subducted plate was teared up in several locations at 170~160 Ma.After then a big window occurred in the Nanling area, triggering the asthenospheric substance got into the upper crust so that developed large-scale high fractionation paraluminous granite and related polymetallic W-Sn mineralization. It was a relatively quiet period of 150~135 Ma in South China except for the Middle-Lower Yangtze River Valley area located in the northeastern margin of the South China plate. Because starting to change motion-direction to northeast the subucted plate was teared up along the Middle-Lower Yangtze River Valley which used to be a foreland basin of the Triassic Dabie-Sulu orogenic belt. A group of skarn-porphyry Cu-Mo-Au-Fe ore system and related I-type or aidakitic granites developed along the cross of the Middle-Lower Yangtze River Valley with the NE-trending faults at an age range of 145~135 Ma. From 135 Ma the subducted plate moved along several groups of regional-scale NE-striking fault zones comprising the Tan-Lu fault zone, which trigged the Eurasian continent to extensive extension. At the setting developed a lot of linear NE-trending Cretaceous faulting basins and metamorphic cores accompanied with volcanic rock eruption as well as epithermal Cu-Au-Ag ore system, granite-related polymetallic Sn (W) deposits and hydrothermal uranium deposits at age of 120~80 Ma with a peak of 100~90 Ma.
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    Overview of the Application and Prospect of Common Chemical Weathering Indices
    LI Xulong, ZHANG Xia, LIN Chunming, HUANG Shuya, LI Xin
    Geological Journal of China Universities    2022, 28 (1): 51-63.   DOI: 10.16108/j.issn1006-7493.2020118
    Abstract4665)      PDF (1109KB)(4652)       Save
    Common chemical weathering indices such as the Weathering Index of Parker (WIP), the Chemical Index of Alteration (CIA), the Index of Compositional Variability (ICV), CIX index and αAlE are often used to evaluate the chemical weathering intensity of source areas. But the factors which controlling the above chemical weathering indices should be considered, otherwise the results of the weathering evaluation will be distorted. This paper argues that the geological survey of source area should be known when chemical weathering indices are used to study the chemical weathering process. The selection of fine sediments or suspended matter can weaken the influence of grain size on chemical weathering indices. The impurities in the sediments are removed by acid treatment. Then, the Sc/Th-CIA diagram was used to reflect the material source information, Th/SC-Zr/Sc diagram was used to further distinguish the control effect of sedimentary differentiation and sedimentary recirculation, and then the samples with ICV value less than 1 were selected to eliminate the interference of recirculation. The A-CN-K diagram or the formula proposed by Panahi (2000) were used to correct the potassium metasomatism, and the strength of chemical weathering of source rocks was evaluated by CIA eventually. To ensure that the calculation of chemical weathering indices can accurately reflect the weathering situation of the source area, SPSS software can be used to analyze the proportion of some factors which affecting the CIA to construct characteristic weathering index of the study area.
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    Neotectonic Evolution of the Peripheral Zones of the Ordos Basin and Geodynamic Setting
    ZHANG Yue-qiao1, LIAO Chang-zhen2, SHI Wei3, HU Bo1
    Abstract2453)      PDF (2747KB)(4567)       Save
    based on satellite imagery interpretation, field structural measurements and morpho-tectonic analysis, this paper makes a brief synthesis on Cenozoic extensional history of the graben systems around the Ordos basin and delimits the lower bound of the initial age, 8 -9 Ma, of Neotectonic era in the peripheral zones of Ordos. Neotectonic evolution has been divided into 3 stages with distinct morpho-tectonic features. An early stage during the Latest Miocene to Early Pliocene was characterized by development of the Red clay basin and by initiation of the Shanxi graben system. The peripheral zones of the Ordos was dominated by transtension. A middle stage during the Late Pliocene and middle Pleistocene experienced multi tectonic events that were characterized by episodic compressive deformation along the SW margin, continued subsidence of the graben system along NW and SE margins, uplift of the Ordos basin and development of erosional valley and river terraces along the Jin-Shan deep incised valley of the Yellow River. The most recent neotectonic stage since the middle to Late Pleistocene was dominated by deformation of transpression and transtension in the peripheral zones of Ordos, with intensification of differential vertical motion and river incision. Fault activities during the neotectonic era include different combination of normal, sinistral and dextral strike-slip and reverse faulting. The Ordos block itself rotates around vertical axis, which was accommodated by normal faulting and crustal extension along the graben system. The episodic evolution of neotectonics in the Ordos regions has been dynamically related to fast northward growth and episodic eastward extrusion of Tibetan Plateau during the Late Cenozoic time
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    Cited: Baidu(63)
    Predevonian Tectonic Evolution of South China: from Cathaysian Block to Caledonian Period Folded Orogenic Belt
    SHU Liang-shu
    Abstract2181)      PDF (501KB)(4438)       Save
    The interpretation of Predevonian tectonics of South China is controversial long time both on its age and distribution. Based on the middle-high grade metamorphic rocks, ductile slipping rheologic structures exposed in the the Zhejiang- Fujian-Jiangxi-Guangdong domain and high quality dating data published recently, the author believes that an ancient continental block existed certainly in South China, which is composed of Proterozoic schist, gneiss and migmatite with an oldest age of 2 Ga, their protolites are clastic rocks, volcanic rocks and plutons. This old land is temporarily called as Cathaysian Continental Block which is limited in the domain between Shaoxing-Jiangshan-Pingxiang fault and Zhenghe-Dapu fault, and its scope is less than that defined by Grabau. During 800-900 Ma, following the closure of paleo-South China ocean, Cathaysian block collided with Yangzi block and then became a part of Rodinia supercontinent. Not long time after converging, by affection of breakup of Rodinia supercontinent, proto-Cathaysian continental block was split into three sub-blocks, namely the southeastern Zhejiang-northwestern Fujian, the central-southern Jiangxi and the Yunkaidashan, and several rifts or sea channels occurred among them. From Early Sinian to Late Ordovician, these sea channels were expanded and were filled by 10000-20000 m thick clastic rocks (containing limestone) and turbidites. However coeval ophiolite and volcanic rocks are absent, implying extended fault did not reach to upper mantle. New geochronological results indicate that the ophiolite and volcanic rocks in the study areas, which were described as Early Paleozoic by previous researchers, yielded pre-Sinian ages, concentrating mainly between 800 Ma and 900 Ma. Thus, the previous Early Paleozoic tectonic framework needs to be re-constructed. In Silurian, a strong tectono-thermal event took place in South China, causing closure of Sinian-Early Paleozoic sea channels and folding-uplifting of mega-thick sediments. The South China Caledonian fold and orogenic belt was formed on the Proterozoic metamorphic basement. In the study area, folding deformation and ductile slipping rheology are very common, including thrust and strike-slip deformation, the peak period of deformation is 420-400 Ma. At the same time, a violent granitic magmatism was started, forming numerous strongly peraluminous S-type granites with A/CNK (molar Al2O3/[CaO + Na2O + K2O]) > 1.1, and I-type granitoids is rare. Peak period of granitic magmatism took place in the 430-400 Ma. Then, the whole South China Caledonian folded geological bodies were overlain unconformably by Late Devonian conglomerate and coarse sandstone, indicating termination of folding and orogeny. From Late Devonian, a united paleo-geographic and sedimentary environment occurred really in the study domain and its neighboring areas.
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    Progress in Research on geochemistry of Tungsten
    MA Dong-sheng
    Abstract2611)      PDF (789KB)(4195)       Save
    China's tungsten reserves, production, consumption and volume of export all rank first in the world. China has been producing more than 80% of the total production in the world since 2000, and has preponderant influence in the nonferrous metal market of the world. Tungsten as an important strategic resource has found a wide utilization in modern life, industry, oil exploration, military equipments etc. The present paper reviews the progress in research on geochemistry of tungsten in last 20 years, including tungsten distributions in the solar system, in the earth and in the principal units and products from both endogenesis and supergenesis. The geochemical behavior of tungsten in magmas, hydrothermal fluids, supergenesis, and related effects on bionts, environment and health are also discussed. It is pointed out that the geochemistry of tungsten in its effects on environment and health is still a research gap in our country now. Special attention should be paid to this aspect of research.
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    Organic matrix-mineral interaction during cell wall  silicification in diatoms
    SHI Jia-yuan, YAO Qi-zhi, ZHOU Gen-tao
    J4    2011, 17 (1): 76-85.  
    Abstract2294)      PDF (791KB)(4191)       Save

    Biosilica, more specifically hydrated amorphous silica, often referred to as opal, is the second most abundant mineral
    type  formed by organisms, with only  the carbonate minerals exceeding  it  in abundance and distribution. As  the predominant
    contributor  to biosilica  in  the oceans, diatoms are known  for  the  intricate geometries and spectacular patterns of  their silica-
    based cell walls. Biochemical studies demonstrate that diatom biosilica is a composite material containing several general organic
    components in addition to inorganic silica, such as polysaccharides, long-chain polyamines and zwitterionic proteins. Functional
    studies on these organic components indicate that they play a crucial role in guiding silica precipitation as well as in the formation
    of species-specific nanopatterns. This article gives an overview of current knowledge on the function of above-mentioned organic
    and biological molecules  in biosilicification. Moreover, some studies of biomimetic mineralization using model organic additives
    and in vitro experiments using molecules extracted from organisms are also involved. An insight into the silicification mechanisms
    in diatoms will link the global cycles for Si and C mechanistically, whereas identification and classification of the components in
    diatoms may assist us in deeper understanding of material sources of petroleum and the evolutionary development of diatoms.

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    A Review on Mixed Rocks of Terrigenous Clastics and Carbonates and Their Petroleum-Gas Geological Significance
    FENG Jin-Lai, HU Kai, CAO Jian, CHEN Yan, WANG Long-Gang, ZHANG Ying, WANG Mu, ZHAO Jian
    J4    2011, 17 (2): 297-307.  
    Abstract3122)      PDF (3126KB)(4043)       Save

    The present progress in research on mixed rock of terrigenous clastics and carbonates is reviewed in this paper, mainly
    including classification,  terminology, depositional environment, depositional modes and petroleum-gas geological significance.
    It  is proposed by a comprehensive analysis  that  the depositional  facies  favorable  for  the mixed deposition mainly cover coastal
    and shallow-lake  faicies,  following by shallow-sea shelf, shore-shallow  lacustrine and delta  facies. The study on  the depositional
    environment  implies  that  the  factors controlling  the development of coastal mixed-rocks  include  tidal effect,  relatively strong
    hydrodynamic condition and a shallow sea environment favorable for the living of lower organisms. In contrast, with respect to the
    shore-shallow  lacustrine  rocks,  the  factors are  frequent  lake-level and climate changes. Consequently, a deep discussion on  the
    depositional micro-facies and associated environmental  factors may be an effective way  to  improve and better  the classification
    and  terminology of  the mixed  rocks. Furthermore, a synthetic depositional model  for  the marine and  lacustrine environment  is
    suggested based on above-mentioned analyses, combined with case studies in Paleogene and Neogene middle-deep mixed rocks in
    the northwestern Qaidam Basin. In addition, the shore-shallow sea and lake areas of mixed deposition can form high-quality targets of

    reservoir and source rocks, based on factual research data on source and reservoir sequences associated with mixed rocks.

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    Study on Infrared Spectra and Infrared Radiation Characteristics of Tourmaline
    LI Wen-wen1, WU Rui-hua1, DONG-Ying2
    Abstract2261)      PDF (570KB)(3994)       Save
    This paper studies the infrared spectra (IS) characteristics of different tourmaline species, and the infrared radiation (IR) characteristics after heat treatment on tourmaline species at different temperatures. The results show that the high IR ratio of tourmaline is due to the infrared activity of vibration in its crystal structure. The IR ratio of Fe tourmaline is close to that of Mg tourmaline, and both are higher than that of Li tourmaline. The IR ratio of tourmaline has some relationship with heat treatment temperature: with increasing heat treatment temperature, the IR ratio decreases. When heated to 800℃, the IR ratio reaches a maximum; while heated to higher than 900℃, tourmaline begins to decompose and its infrared radiation ratio drops down. At the room temperature, the largest monochromatic radiation wavelength of tourmaline is between 9μm and 10μm, which matches the wavelength (9.72μm) of the absolute blackbody very well. It demonstrates that tourmaline is a good material for infrared absorption and radiation.
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    Cited: Baidu(21)
    Igneous Petrotectonic Assemblages and Tectonic Settings: A Discussion
    DENG Jin-fu1, 2,XIAO Qing-hui 1, 2,SU Shang-guo1, 2,LIU Cui1,ZHAO Guo-chun1,WU Zong-xu1,LIU Yong1,2
    Abstract3918)      PDF (962KB)(3816)       Save
    This paper discusses igneous petrotectonic assemblages of various tectonic settings: 1. mid–ocean ridge spreading; 2. oceanic island; 3. island arc; 4. MORS–type and SSZ–type ophiolites; 5. active coutineutal marginal arc; 6.compositional polarity of subduction–related magmatic arcs; 7. continental collision; 8. continental rift; 9. stable craton or platform, etc. It is emphasized that the tholeiitic ( TH ), calc–alkaline ( CA ) and alkaline ( A ) series defined from various parameters by different authors have different scientific meanings. In this paper it is indicated that the same written terms of TH, CA and A but with various meanings could easily result in abuse of these terms, especially for the recognition of the tectonic settings. The difference between MORS – and SSZ –type ophiolites in terms of igneous petrotectonic assemblages is discussed. The lowest MgOwt% of the HMA is suggested ( Table 2 ), based on the data of petrological experiments. The terms of magnesian andesite–dacite and adakite are discussed, and in turn, the Kay's magnesian andesite–dacite of higher Sr/Y, lower FeO/MgO, and higher MgOwt% as well as higher Ni, Cr contents, are comprehensively used, which can be more satisfactory to define the slab–melt, rather than the single parameter of high Sr/Y. The various schemes of classification for the continental collision are indicated, and it is necessary to be careful for using these schemes. The post–orogenic and the continental rifting A type granites are suggested to be associated with or without the CA/r, respectively, and the meaning of A and CA, here, is determined by the Peacock's alkali–lime index.
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    Cited: Baidu(89)
    Advances in Characterization of Pore System of Gas Shales
    JIAO Kun, YAO Suping, WU Hao, LI Miaochun, TANG Zhongyi
    J4    2014, 20 (1): 151-.  
    Abstract1211)      PDF (1956KB)(3803)       Save
    Shale gas is the free, adsorbed and dissolved gas accumulated in dark shale beds. The nature of pores is a key factor to decide gas storing of shale gas reservoir. The structure of gas shales pores is complex, and the pore diameters are mainly in nano-scale. The methods used in conventional gas system study cannot explain high production of shale gas systems in USA. The characterization of nanopores in gas shales plays a key role in shale gas system evaluation. The studies of nanopores in gas shales are reviewed and compared with each other. There are three kinds of shale gas system characterization: (1) Image analysis is based on a stereological analysis, using various types of microscopes such as scanning electron microscopes (SEM), transmission electron microscopes (TEM), scanning tunneling microscope (STM) and atomic force microscopes (AFM); (2) Intrusive methods are based on gas adsorption, mercury porosimetry, and calorimetric methods; (3) Nonintrusive methods are based on radiation scattering, wave propagation, positron lifetime spectroscopy, etc. Image analysis can obtain the morphologic information directly, rapidly and conveniently. Intrusive methods have advantages in characterization of fractal features of pore system. Because of in-situ, non- invasive analysis and high penetrability of neutron and X-ray, nonintrusive methods can simulate the pore system evolution under multi-geological settings. As each method has its own advantages, multi-scale detection using multi-technology is recommended in shale gas pore system characterization.
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    Cited: Baidu(33)
    W-Sn-Nb-Ta-Bearing Granites in the Nanling Range and Their Relationship to Metallogengesis
    CHEN Jun, LU Jian-Jun, CHEN Wei-Feng, WANG Ru-Cheng, MA Dong-Sheng,ZHU Jin-chu, ZHANG Wen-lan and JI Jun-Feng
    Abstract3025)      PDF (3275KB)(3798)       Save
    The large-scale mineralizations of W, Sn, Nb and Ta related to granites took place in the Late Jurassic period in Nanling Range, South China. According to the petrological and geochemical features of ore-bearing granites and their relationship to mineralizations, they can be grouped into the following three major types: W-bearing granites, Sn-W-bearing granites and Ta-Nb-bearing granites. The W-bearing granites show low TiO2 and Ba+Sr contents and LREE/HREE ratios,intensive Eu depletion, high Rb and Y abundances and Rb/Sr ratios, and oversaturation in Al. They commonly underwent intensive differentiation and evolution. The Sn-W-bearing granites are characterized by enrichment of TiO2, total REE, HFSEs,Ba+Sr and Rb, higher CaO/(K2O+Na2O) and LREE/HREE ratios, metaluminous-weakly peraluminous feature and lower Rb/Sr ratios, and weaker differentiation and evolation. The Ta-Nb-bearing granites have very low TiO2, Ba+Sr, total REE and HFSEs contents and CaO/(K2O+Na2O) ratios, higher Al2O3/TiO2 and Rb/Sr ratios, higher Rb and Nb contents, and ACNK values. They are highly evolved. Good discrimination can be obtained between these three types of W-Sn-Nb-Ta-bearing granites on plots employing Nb-Y-Ce, (Ba+Sr)-Rb-(Zr+Nb+Ce+Y), LREE/HREE-Rb/Sr and LREE/HREE-(Zr+Nb+Ce+Y) diagrams. These three types of ore-bearing granites have obviously different evolutional trends. Metallogenesis is intimately related to the evolution of the ore-bearing granites. Mineralizations of Sn, W or W-Sn and Nb-Ta or Sn-W-Nb-Ta are closely related to biotite granites, twomica granites or muscovite granites and albite granites respectively. The important deposit types of W, Sn, Nb and Ta and their major features in the Nanling Range are summarized in the paper. The chloritized granite type tin deposit is proposed. This paper indicates that an attention to searching for both the chloritzed granite type tin deposits and greisen-quartz vein type W-Sn deposits in W-Sn-bearing granites in the Nanling Range should be especially paid.
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    Cited: Baidu(96)
    Characteristics of mineralized focuses in several breast diseases
    WANG Chang-qiu,ZHAO Wen-wen,LU An-huai,XIONG Cui-e,MEI Fang,LIU Jian-ying
    J4    2011, 17 (1): 29-38.  
    Abstract1974)      PDF (12309KB)(3718)       Save

    Mineralization  characteristics  of mineralized  focuses  in malignant breast  tumor, benign breast  tumor, breast
    hyperplasia and mastitis frequently accompanied by calcification were investigated using optical microscope, environmental scan
    electron microscope  (ESEM) and micro-FTIR  (Fourier  transform  infrared spectroscopy). The results  indicate  that morphology of
    mineralization in different types of breast diseases are quite different. Collagen fibers and epithelial cells are closely related to the
    mineralization. The calcification is incident to breast invasive carcinoma and breast carcinoma in situ on the old necroses in ducts.
    Many calcified nano-bodies resembling psammoma body are formed on the collagen fibers in breast fibroadnoma. The mineralized
    focuses with fibrous texture and sheaf structure occur between the collagen fibers in breast hyperplasia, on which many calcified
    nano-balls are deposited. EDAX (energy dispersive X-ray analysis) results show that there may exist other calcium mineral (such
    as calcium oxalate) deposition than calcium phosphates in breast hyperplasia. The calcified focuses with thick fibrous texture have
    no special occurring positions in tissue of fat necrosis.

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    Characteristics of Granitic Pegmatite with High-Purity Quartz in Spruce Pine   Region, USA and Altay Region of Xinjiang, China
    ZHANG Ye , CHEN Pei-rong
    J4    2010, 16 (4): 426-435.  
    Abstract2936)      PDF (2093KB)(3686)       Save

    The alaskites/pegmatites from the Spruce Pine region of USA and the muscovite granites/pegmatites from the Altay region of Xinjiang, China, were comparatively studied. The pegmatites from both regions might be melt-vapor differentiation products of the peraluminous granitic magmas. The pegmatites from the Spruce Pine region with high-purity quartz were developed on the schist or gneiss background, whose major rock-forming minerals are rich in plagioclase, showing high Na/K ratios, high large-ion lithophile elements Sr and Ba contents, low high-field strength and rare earth elements contents, positive Eu anomalies,and low impurity elements contents in quartz. All these characteristics can be used as the discrimination criteria of high-purity quartz pegmatities. The Altay region of Xinjiang is abundant of pegmatites, and some samples studied showed the features which evidenced that the Altay pegmatite region has a perspective to find the gualified pegmatites with high-purity quartz.

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    Granitoids and Crustal Growth in the East-Kunlun Orogenic Belt
    MO Xuan-xue1, LUO Zhao-hua1, DENG Jin-fu1, YU Xue-hui1, LIU Cheng-dong2,CHEN Hong-wei1, YUAN Wan-ming1, LIU Yun-hua3
    Abstract2376)      PDF (978KB)(3631)       Save
    The East-Kunlun orogenic belt (abbrev. EKOB) is one of major tectono-magmatic belts in the Tibetan plateau. Four stages of granitoid plutonism took place in Precambrian (the Proterozoic), early Paleozoic (∈-D3), late Paleozoic-early Mesozoic (D3-T3), and late Mesozoic-Cenozoic (after early Jurassic), respectively. Among them, the late Paleozoic-early Mesozoic, especially Triassic granitoids are predominant. The basement of EKOB formed in late Paleo-Proterozoic. The early Paleozoic tectono-magmatic event sequence is comparable to that in the North-Qilian orogenic belt, and became a part of the Qilian-East-Kunlun Caledonian orogenic system. However, EKOB was involved in the Paleo-Tethyan tectonic regime during late Paleozoic-early Mesozoic period, and yielded an integrated Variscian-Indosinian orogenic cycle, similar to the Sanjiang Paleo-Tethyan orogeny. The south-Kunlun suture zone during that time was the main boundary between the north and the south China continents. Subsequently, EKOB was involved in the Tibetan collisional orogenic system in the Cenozoic since Indo-Eurasia collision. While the continental crust of EKOB mainly formed in late Paleo-Proterozoic, juvenile crust was also generated in the Phanerozoic time, similar to the Xing,anling-Mongolia, the Gangdese and the Andes orogenic belts. There are abundant conclusive evidences of underplating and magma mixing in the East-Kunlun granitoid belt. Initial values of 87Sr/86Sr of the East-Kunlun granitoids are mostly less than 0.710 and εNd (t) values of them range from-9.2 to + 3.6. These features imply that inputting of mantle materials and mixing between mantle- and crust- derived materials played an important role in crustal generation and evolution in EKOB during the Phanerozoic time. According to SHRIMP U-Pb dating of zircons from granitoid host rocks, mafic microgranular enclaves (MMEs) and associated gabbros, two major events of underplating and magma mixing took place in EKOB in the early-middle Devonian (394-403 Ma) and the middle Triassic (239-242 Ma), corresponding to the stage from the ending of subduction to the initiation of collision during the Caledonian and Variscian-Indosinian orogeny, respectively.
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    Review and Advancements of Studies on Silicate Weathering
    and the Global Carbon Cycle
    WU Weihua, ZHENG Hongbo, YANG Jiedong, LUO Chao
    J4    2012, 18 (2): 215-.  
    Abstract2022)      PDF (436KB)(3625)       Save

    Silicate weathering is a major sink of the atmospheric CO2, which directly affects the global carbon cycle and the
    climate. Since the pioneering work of Walker et al. (1981), studies on“ silicate weathering, carbon cycle and climate changes”
    have sprung up in recent years. Many advancements have been obtained from computer models to river water geochemistry andfrom large rivers with a drainage area exceeding to 106 km2 to monolithologic small watershed with tens/hundreds km2 drainagearea,. In the global scale, atmospheric CO2 consumption from silicate weathering is about 0.138-0.169 Gt per year. Compared tothe current atmospheric carbon content of 800 Gt, at first glance, this CO2 consumption rate seems so slow that silicate weatheringwould play only a negligible role in the global carbon cycle. However, atmospheric CO2 removed from silicate weathering istransported by rivers and thereafter precipitated in the ocean as carbonate minerals, and the residence time of carbon in carbonaterocks is in excess of millions of years. Therefore, silicate weathering is an important mechanism that modulates the long-termcarbon cycle. Moreover, researches show that the small watersheds draining basalts/ophiolites in the tropical zones have thehighest silicate weathering and CO2 consumption rates. It is estimated that CO2 consumption from volcanic rocks in the tropicalzones represents about 10% of the global export of carbon by silicate weathering, while the tropical volcanic arcs correspond toonly~1% of the exorheic drainage area worldwide.

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    A Preliminary Discussion on Large Igneous Provinces and Associated Ore Deposits
    XIAO Long1, PIRAJNO Franco2, HE Qi1
    Abstract2051)      PDF (773KB)(3563)       Save
    Large igneous provinces (LIPs) are grouped into mafic (MLIPs) and silicic (SLIPs), based on their dominant components, mafic or silicic volcanic and intrusive rocks, respectively. The formation of these LIPs requires extremely high heat flow from mantle, which results in extensive melting of mantle, subcontinental lithospheric mantle and lower crust. The typically massive magmatism of LIPs also results in extensive energy and materials exchange thereby causing the formation of a range of important ore systems. MLIPs and SLIPs have different magma sources, compositions, temperatures, pressures, fluids and oxygen fugacities, and experience distinct magmatic evolutionary histories. MLIPs tend to form magmatic Cr-Cu-Ni-PGE sulfide and V-Ti-Fe oxide deposits, some hydrothermal Cu-Pb-Zn-Au-Ag deposits and distal epithermal systems. SLIPs, on the other hand, tend to form metasomatic and/or hydrothermal Cu-Pb-Zn-Au-Ag, W-Sn, U-Th-REE, As-Sb and low-sulfidation epithermal ore systems. Detailed studies of LIPs and associated ore deposits will enable better constrain the metallogenic and ore genesis models, which in turn will help in the discovery of giant ore deposits.
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    Cited: Baidu(23)
    Hainan Mantle Plume and the Formation and Evolution of the South China Sea
    YAN Quan-shu1,2 and SHI Xue-fa1
    Abstract2526)      PDF (771KB)(3557)       Save
    Seismic tomographic images obtained from the mantle under the southeast Asia region indicate there may exist a mantle plume beneath and around the Hainan island. A sub-vertical low-velocity column is imaged beneath the Hainan and the South China Sea, and extends from shallow depths to 660-km seismic discontinuity (i.e., the interface between upper mantle and lower mantle), and continuously to a depht of 1900 km. There is a large quantity of Cenozoic alkali basalts distributed in the South China Sea and its adjacent areas which include Leiqiong Peninsula, Hainan Island, Beibuwan Basin, Weizhou Island in Guangxi province and Indochina block. The geochemical data for these basalts show the characteristics of OIB-type basalt and DUPAL-like isotopic anomaly, and imply its deepseated origin. In addition, the average value of Tp (mantle potential temperature) for the South China Sea inferred from olivine-fluid equilibrium, is 1661℃, which is higher than that of MORB and lies between the corresponding values of Hawaii hotspot and Iceland hotspot. Based on evidences mentioned above, combined with numerical model experimental data, it shows that there does exist a mantle plume beneath the Hainan Island and adjacent areas. Until recently, scholars have developed many models about the formation and evolution of the South China Sea, and the debating issue is the geodynamic source. We suggest that the Hainan plume may be a significant geodynamical source for the formation and evolution of the South China Sea. Here the Hainan plume is introduced into our preliminary model about the formation and evolution of the South China Sea. The model is as follows: (1) 50-32 Ma, Integrated effects of collision between thd Indian Ocean plate and Euro-Asian plate resulted in retrogression of Pacific plate, created a extensional tectonic setting, and provided a channel for ascent of the mantle plume; (2) 32-21 Ma. When the head of mantle plume arrived at asthenosphere, it immediately interacted with the spreading center of the South China Sea by lateral material flow, which enhanced spreading spead. During 26-24 Ma, there took place a ridge jump, which adjusted the spreading center from nearby 18。N (i.e., present-day center of NW sub-basin) to nearby 15.5。N (i.e., present-day center of East sub-basin); (3) 21-15.5 Ma. With the mantle plume effect gradually enhancing, the hotspot-spreading center interaction became more and more intensive, and at about 21 Ma, there took place a ridge jump again, and induced the opening of SW sub-basin; (4) 15.5-0 Ma. Due to collision between the Indo-Australian plate and the Sunda continent, the spreading stopped. Subsequently, the earlier formed oceanic crust subducted along Nansha trench and Manila trench. However, the mantle plume still existed up to now. An actual evidence is: since the Pliocene a large amount of alkali basalt erupted in the South China Sea and its adjacent areas.
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    Cited: Baidu(63)
    History of Volcanic Activity, Magma Evolution and Eruptive Mechanisms of the Changbai Volcanic Province
    FAN Qi-cheng1, SUI Jian-li2, WANG Tuan-hua1, LI Ni1, SUN Qian1
    Abstract2449)      PDF (1004KB)(3556)       Save
    Volcanic rocks cover large area of the Changbai Mountain Range, Northeast China. As the largest Quaternary volcanic province in China, the Changbaishan volcanic province can be divided into four parts, including the Tianchi volcanic province (TVP), the Wangtian,e volcanic province (WVP), the Longang volcanic provicne (LVP) and the Tumen River volcanic province (TRVP). Volcanic activity in TRVP and WVP began in Pliocene, dominated in Pliocene-Mid-Pleistocene (5.5 ~0.19 Ma) and Pliocene-Early-Pleistocene (4.77 ~2.12 Ma), respectively. TVP and LVP activated in Quaternary, from Early-Pleistocene to Holocene. The volcanic activities and products in these four volcanic provinces are different. In TRPV, it is tholeiite from flood eruption; while in TVP, WVP and LVP, the volcanic eruptions formed lava shields of potassic trachybasalt in the early stage, and then different magma evolution paths occurred. In TVP and WVP, potassic trachyebasalt emplaced into the crustal chamber, stored and experienced strong fractional crystallization. The evolved magma was mainly alkaline rhyolitic and pantelleritic, highly enriched in silicon, alkalies and volatiles. Its eruptions formed two huge stratovolcanoes. Activity of the potassic trachybasalt beneath the TVP controlled two kinds of eruptions: the millennium eruption of Tiachi Volcano, which was triggered by refluxing of the mantle trachybasalt magma to the crustal chamber and subsequent magma mixing; and the centric eruption of the potassic trachybasalt, which formed the big cone of Tianchi Volcano and many other small cones in the vicinity. In the LVP, on the lava shield occurred over 160 volcanic cones, The rock type of these eruptions was unique potassic trachybasalt. Geochemical data of trace elements and Sr-Nd-Pb isotopes indicate that the mantle sources were mixtures of asthenosphere and enriched lithospheric mantle. As to the LVP, the volcanics were dominated by depleted mantle of asthenosphere, and with less entertainment of enriched lithosphere. After the late Pliocene, geodynamics of the Changbai Mountain Range was controlled by the subduction of the western Pacific Plate and the extension of the Northeastern Asian back arc. In this special active continental margin, large scale of potassic trachybasalt activity occurred again.
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    Cited: Baidu(64)
    On Granitic Tectono-Magmatic Assemblages
    WANG De-zi,SHU Liang-shu
    Abstract1947)      PDF (3934KB)(3536)       Save
    Granitic tectono-magmatic assemblages mainly reflect the genetic connections between the magma types of granites and tectonic environments. Viewing from the global scope, particularly looking at the situation in China,the granitic tectono-magmatic assemblages could be divided into five major types: (1) oceanic crust subduction type, such as continental margins on both sides of the Pacific Ocean; (2) continent continent collision type, e.g., the Himalaya-Gangdise collisional belt; (3) extensional continental margin type, such as the Southeast China extensional margin and the Basin and Range Province, USA; (4) inland faulted depression type, such as the Lower Yangtze faulted depression and the Qiantan-Xinjiang faulted depression; (5) rift type, such as the Eastern African Rift and the Panxi Rift of China. By calculating the calc-alkali index (CA) and alumina saturation index (ASI), the magma types of the granites can be roughly determined. The temporal and spatial evolution of orogenic granitic belt shows certain kind of regularities: subduction type granites → collision type granites → extensional type granites. Or, it may be described as: precollision granites → syncollision granites → postcollision granites. However, instead of giving general assumptions, we should carefully examine and analyze actual cases and conditions before reaching a conclusion.
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    Intraplate Extensional Magmatism of North China Craton and Break-up of Three Supercontinents and Their Deep Dynamics
    YAN Guo-han1, CAI Jian-hui1,2, REN Kang-xu1,3, HE Guo-qi1, MU Bao-lei1,Xu Bao-liang1, LI Feng-tang1, Yang Bin1
    Abstract2177)      PDF (830KB)(3473)       Save
    Based on authers' twenty years research on isotope geochronology and spatial distribution of intraplate extensional magmatic rocks (such as alkaline intrusives etc. ) in North China Craton, as well as the existing references, this paper suggests that intraplate extensional magmatisms of North China Craton were concentrated in three stages: the latest Paleoproterozoic-early Mesoproterozoic era(1 850~1 600 Ma), the middle-late Neoproterozoic era(900~600 Ma)and the latest Palaeozoic-Cenozoic era(250 Ma~now), respectively, as named the first, the second and the third extensional stage. The appearance frequency and the spatial distribution of the three stages extensional magmatisms are distinctly different from each other. The third stage has the highest appearance frequency and widest distribution, and the first stage takes second place. It must be especially emphasized that the isochron ages of the three stages magmatic rocks are basically coincident with the break-up timings of Columbia, Rodinia and Pangaea supercontinents,respectively, showing different degrees of response of North China Craton to the break-up of related supercontinents. The activities of super mantle hot plumes are popularly considered as the deep geodynamics of dispersal of supercontinents. So it is speculated that the distance from North China Craton to the center of super mantle hot plume activities in the third extensional stage was the nearest, and that in the second stage was the farthest.
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    Substitute Indices of Summer Monsoon in Eolian Sediment and Its Paleoclimatic Significance
    SUN Yu-bing, CHEN Tian-hu, XIE Qiao-qin
    Abstract2005)      PDF (1195KB)(3446)       Save
    This paper systemically measured the proxy indices of the summer monsoon from the loess-paleosol sequences in the red clay sequences of the Xifeng profile, Gansu Province, including the values of magnetic susceptibility (MS) and frequency dependent magnetic susceptibility, and the contents of carbonate, organic matter and free iron oxides. We reconstructed the change characteristics of the paleoclimate by the carbonate contents and the values of magnetic susceptibility. The results showed that the frequency dependent magnetic susceptibility and the contents of organic matter and free iron oxides are positively correlated with the magnetic susceptibility, while the carbonate contents are negatively correlated with it. All these features can be regarded as the proxy indices of the summer monsoon. The paleoclimatic change of the whole Quaternary by the mathematic model could be divided into three periods: 0~1.1 Ma BP, 1.1~1.9 Ma BP and 1.9~2.6 Ma BP. The annual mean precipitation and annual mean temperature decreased obviously since 0.1Ma BP, which indicates that the climate will be more and more dry and cold in the future.
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    Cited: Baidu(4)
    Zircon U-Pb Dating and Hf Isotopic Compositions of Porphyrites from
    the Ningwu Basin and Their Geological Implications
    HU Jin-ping, JIANG Shao-yong
    J4    2010, 16 (3): 294-308.  
    Abstract4101)      PDF (4325KB)(3430)       Save

    Ningwu volcanic basin is one of the most important basins related to mineral deposits in middle-lower reaches of the
    Yangtze River belt. Four volcanic units occur in the basin, in an ascending order, the Longwangshan Formation, the Dawangshan
    Formation, the Gushan Foramtion and the Niangniangshan Formation, with some high-level sub-volcanic igneous rocks intruding
    them. Detailed zircon U-Pb dating and Hf  isotopic composition measurement were performed on  the host  rocks  (gabbro-diorite
    porphyrites) of  the Washan  iron deposit. The zircon U-Pb ages of  three samples are  (123±1) Ma,  (127±3) Ma and  (125±2)
    Ma, respectively.Together with previously published precise zircon U-Pb dating results for volcanic rocks (127 to 131Ma), these
    results have placed a better constraint on  the magmatic and mineralization activity duration of  the Ningwu volcanic basin. The
    zircons  from  the Ningwu porphyrites have εHf
    ( t ) values  from -6.3  to -8.6. Together with other available geochemical data,  the
    Hf  isotope data  indicate  that  the Ningwu porphyrites may have derived  from upwelling depleted asthenospheric mantle mixed
    with enriched mantle and crust, which was controlled by the extensive lithosphere extension at around 125 Ma. The lower εHf(t)
    values and slightly younger ages of  the gabbro-diorite porphyrites  than  their hosting volcanic  rocks may  indicate more crust
    material involvement in the porphyrite petrogenesis.

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    Recognizing the TTG Rock Types: Discussion and Suggestion
    FENG Yan-Fang, DENG Jin-Fu, XIAO Qing-Hui, XING Guang-Fu, SU Shang-Guo, CUI Xian-Yue, GONG Fan-Ying
    J4    2011, 17 (3): 406-.  
    Abstract3607)      PDF (667KB)(3370)       Save

            This paper briefly describes and compares  two  international classifications of  the  rock  types of TTG series:the Le Maitre’s QAP modal classification based on accurate mineral modes, and  the O’Connor's An-Ab-Or normative classification when the Q-norm is>10%. Both modal and normative classifications are generally consistent with each other. The field 5 of the QAP is called tonalite as the root name. It includes trondhjemite and plagiogranite (adopted by part of the USSR geologists). The latter may be called as    light-coloured  (M≤10)  tonalite. However,  the  tonalite and  trondhjemite can be directly determined by using  the An-Ab-Or normative classification. Based on  the comparison between  the Le Maitre’s QAP modal classification and some Chinese modified QAP modal classifications, and paying attention  to some examples  for  recognizing  the TTG  rock  types using O’Connor’s An-Ab-Or normative classification by  the authors, several suggestions are proposed here as  follows:  (1) The Le Maitre’s QAP modal classification may be used for recognition of the TTG rock types, when the accurate mineral modes are available, and then the procedure is necessary to be determined whether these rock types are tonalite or trondhjemite using the M indexes. When the chemical data are available but the accurate modes are lacking, the O’Connor’s normative classification may be used. When both the accurate mineral modes and the chemical data are available, both classifications may be used for a better recognition of  the TTG  rock  types;  (2)  In  terms of widespread utilization of  the O’Connor’s classification  for  the Archean grey gneiss and granite-greenstone belt, and for some Phanerozoic magmatic arcs, a suggestion of using the O’Connor’s classification for  the orogenic belts  in China may be helpful  for  recognizing  the TTG  rock  types;  (3) A unified classification  is needed  for regional  igneous petrological  investigations, particularly  in China, because of  large available chemical data rather  than accurate mineral modes, then the O’Connor’s normative classification may be suggested; (4) The O’Connor’s classification  is actually a chemical classification, which is good for a comparison between the intrusive and volcanic rocks, as well as between the igneous rocks and  the experimental melts. Finally, a  two-step  recognition procedure  is suggested: Firstly, use  the TAS classification by Middlemost to discriminate the felsic rocks; and second, use the O’Connor’s An-Ab-Or normative classification for recognition of TTG rock types.

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    Cited: Baidu(11)
    Trace elements in quartz lattice and their implications for petrogenesis and mineralization
    CHEN Jian-feng, ZHANG Hui
    J4    2011, 17 (1): 125-135.  
    Abstract2851)      PDF (649KB)(3334)       Save

    Quartz  is widely distributed  in  the  igneous, sedimental and metamorphic  rocks, and hydrothermal ore deposits. As
    its specific stability  in composition and  texture, quartz does carry   much more petrogenetic and metallogenic  information  than
    other rock-forming minerals. Quartz, originated from different stages of magmatic-hydrothermal system and/or different geological
    settings, shows great differences  in  its  lattice  texture and distribution of  trace elements, because of  its different behavior  in  the
    history of geological processes. To interprate the factors affecting trace elements entering  quartz lattice and find out high-sensitive
    elements  in particular geological environments,  the  trace element distribution and  textural characteristics of quartz  lattice are
    investigated by use of micro-area in situ technique and cathodeluminescence. Therefore, the provenance of quartz formation can
    be traced, and then useful geological-geochemical information about the petrogenesis and metallization can be deduced. Moreover,
    as shown in this paper that there is a linear relationship between Al, Ti contents and the formation temperature of quartz. It might
    be extensively used as a tentative geothermometer.

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    Discovery of Impact Ejecta from Taihu Lake Impact Crater
    WANG He-nian, XIE Zhi-dong*, QIAN Han-dong
    Abstract2820)      PDF (11020KB)(3320)       Save
    The hypothesis of impact origin of the Taihu Lake was proposed about twenty years ago, but never confirmed.Recently some weird-shaped concretions were found embedded in the mud layer in the vicinity of the Taihu Lake, which might be impact ejecta from the Taihu impact crater. These new samples comprise two categories. One is rich in iron with fine siderite as concretion matrix, including abundant small spheroid concretions, stick-shaped concretions, and irregular shaped concretions.The other one is poor in iron with calcite as concretion matrix, including twisted-shaped concretions. The fragments embedded in matrix mainly consist of angular-sharp-edged quartz grains, and minor fragments of clay and plagioclase minerals. The sizes of the ejected materials range from centimeters of massive rocks to millimeters even to micrometers of the spheroids. Most hand samples show abundant semi-plastic features, such as twisted shape and molten crust, which might be caused by their flying in the air in the molten or semi-molten status. All these features suggest that these new samples once experienced a series of the impact cratering processes, such as the shock-induced fragmentation, shock-induced melting, ejection into the air, flying in the air, and falling in and around the impact crater. The components of the ejected materials are consistent with the target rocks in the Taihu Lake area. The confirmation of impact ejecta is another important discovery after the discovery of the shock-induced microfeatures in deformed quartz in the sandstone of islands in the Taihu Lake. The discovery of the ejection materials, combining with other features, confirmed the impact origin of the Taihu Lake.
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    Cited: Baidu(8)
    Effects of Melt Refertilization on the Subcontinental Lithospheric Mantle
    Sun Jing, Liu Chuanzhou, Wu Fuyuan
    J4    2012, 18 (1): 52-61.  
    Abstract2403)      PDF (1386KB)(3270)       Save

    The lherzolites have been commonly regarded as mantle residues after low degrees of partial melting. However, melt
    refertilization, which refers to transform the refractory harzburgites to fertile lherzolites through adding asthenosphere-derived
    basaltic melts, provides a new explanation for the fertile lherzolites. Besides the enrichment in major elements, this process also transforms the enriched characteristics in trace elements and Sr-Nd isotopes of the harzburgites to the depleted characteristics of lherzolites. It is still highly debated as to whether melt refertilization can change the Os isotopic compositions of mantle peridotites, which depend on the ratios of the refertilizing melts, the sulfur saturation of the melt, and the time of refertilization, etc. The melt/rock ratios in the sub-continental lithospheric mantle are commonly low. Therefore, effects of melt refertilization on the Os isotopic compositions of the peridotites are probably limited. In addition to chemical compositions, addition of refertilizing melts changes the physical properties. Melt refertilization would destabilize the lithospheric mantle through increasing the permeability and decreasing the viscosity. Although it can change the chemical-physical properties of the lithospheric mantle, it is unclear whether the melt refertilization process is responsible for lithospheric thinning and craton destruction.

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    Cited: Baidu(4)