bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sedimentary Record of the Planation Surface in the Hoh Xil Region of the Northern Tibet Plateau
Authors: Haisheng YI , Chengshan WANG , Shun LIU , Zhifei LIU , Shifeng WANG 
Published: September 2010

AbstractMiocene marl is the most widespread Tertiary stratigraphic record in the northern Tibet Plateau, termed the Wudaoliang Group in the Hoh Xil region and the correlative Suonahu Formation in the Qiangtang region. The uniform marl overlies red beds of the Eocene‐Oligocene Fenghuoshan Group. The Wudaoliang Group is generally 100–400 m thick, but the thickest strata are 700–1300 m, located in the Haidinghu (Haiding Lake) and Tuotuohe (Tuotuo River) regions respectively. Based on observations from eight measured sections and outcrops, the thin‐bedded marl, which varies in colour from grey‐white to light brown‐grey, is explained as a large‐scale or serial lacustrine deposit stretching throughout northern Tibet.The Wudaoliang Group commonly crops out on geographic lowland at an average elevation of 4600 m above sea level within the mountain chains, showing concordant summit levels, e.g. the Fenghuoshan and Bairizhajia Mountains. These mountains with a flat ridge are considered to be remains of the palaeo‐planation surface. However, the spatial distribution of the Wudaoliang Group is not confined by the current mountain‐basin landform configuration. We have observed the Miocene Wudaoliang Group marl exposed on a 5233 m‐high mountain peak. The largest difference in height between the current lake level and the mesa crest is 600 m; the maximum dip angle is 25°, but usually below 10°, which is obviously different from the Fenghuoshan Group red beds with moderate to strong structural deformation. The horizon of the Wudaoliang Group thin‐bedded marl and its widespread occurrence throughout the northern Tibetan Plateau can only be reasonably inferred to a sedimentary record relevant to the palaeo‐planation. Its deposition occurred on primary land floor by erosion at 20 Ma and its bed surface is a typical sign of geomorphic rise and collapse after the erosion.
Changes of Atmospheric Circulation since the Last Interstadial as Indicated by the Lake‐status Record in China
Authors: Bin XUE , Ge YU 
Published: September 2010

AbstractThe effective precipitation and the frame of atmospheric circulation in the past three key periods, i.e. 30 ka BP, 18 ka BP and 6 ka BP, have been analyzed on the basis of the palaeolake status record produced by the Chinese Lake Status Data Base. The results show that the west‐central part of China was characterized by high lake‐levels at 30 ka BP, resulting from strengthened southwest monsoons; whereas the high lake stand, occurring in the west‐central part of China at 18 ka BP, was caused by the southward shift and the strengthening of westerlies although the high‐stand distribution was reduced. Meanwhile, the east‐central part of China was under the control of strong winter monsoons at 18 ka BP. The high lake‐levels, which occurred in the east‐central part of China at 6 ka BP, are related to the enhanced East‐Asian summer monsoons; while the lowering of the lake‐level in the west‐central part of China at 6 ka BP was due to the northward shift and corresponding shrink of the westerlies.A comparison between the lake status and the palaeoclimate models has shown that there do exist discrepancies between the geological evidence and the model simulations. The agreement between them provides a possible mechanical explanation on the geological phenomena, but the discrepancy shows that the model needs to be revised to a great extent.
Petrogenesis of Cenozoic Potassic Volcanic Rocks in the Nangqên Basin
Authors: Hongjuan SUN , Wanming DENG , Yuquan ZHANG 
Published: September 2010

AbstractThe Nangqên basin is one of the Tertiary pull‐apart basins situated in the east of the Qiangtang block. Similar to the adjacent Dengqên basin and Baxoi basin, there occurred a series of potassic volcanic and sub‐volcanic rocks, ranging from basic, intermediate to intermediate‐acid in lithology.Based on the study of petrology, mineralogy and geochemistry, including REEs, trace elements, isotopic elements and chronology, the authors concluded that the Cenozoic potassic volcanic rocks in the Nangqên basin were formed in the post‐collisional intraplate tectonic settings. The relations between the basic, intermediate and intermediate‐acid rocks are neither differentiation nor evolution, but instead the geochemical variability is mainly attributable to the different partial melting degrees of the mantle sources formed at depths of 50–80 km.The sources of the potassic rocks are enriched metasomatic mantle that has experienced multiple mixing of components mainly derived from the crust. The recycling model can be described as follows: after they had subducted to the mantle wedge, the crust‐derived rocks were metasomatized with the mantle materials. In view of the fact that the ratio of crust‐derived rocks increases by the age of volcanism, it can be concluded that the sources of the potassic rocks moved upwards progressively with time.The underplating of small scattered magmas upwelling from the asthenosphere may have induced partial melting of the sources of the volcanic rocks in some pull‐apart basins in the Hengduanshan area and the intense tectonic movements of large‐scale strike‐slip belts provided conduits for the ascending melts.
Oxidation Experiment of Natural Megacrystal Clinopyroxene: Implications for Assignment of Mössbauer Spectra
Authors: Xiachen ZHI , Peng CHEN , Chengzhong LIN , Shuqing CHEN , Guilan ZHANG , Yuzhi LI , Lei LIN 
Published: September 2010

AbstractThe Mössbauer spectra of natural megacrystal clinopyroxene are usually fitted by 4 sets of symmetric doublets, A‐A', B‐B', C‐C' and D‐D', respectively, in terms of increasing Qs value in literature. But the assignments of those doublets are quite different, except the D‐D' doublet assigned to Fe3+at the lattice site M***1 in previous papers. Particularly, the assignment and interpretation of the C‐C' doublet are diverse.The oxidation experiments of natural megacrystal clinopyroxene collected from the Hannuoba basalt, North China, were performed under controlled conditions of temperature at 1000°C and oxygen fugacity of FMQ buffer in 1, 2, ***3 and 5 days respectively. The oxidized samples were then measured by X‐ray diffraction spectrometry and Mössbauer spectrometry. The oxidation of clinopyroxene is characterized by Fe2+ → Fe3+at M1 under the subsolidus conditions, which is consistent with the increase of the area of the D‐D' doublet when the heating time increases. Accordingly, the area of the A‐A' and B‐B' doublets decreases with the increasing heating time. However, the area of C‐C' keeps almost constant.Therefore, the 4 sets of doublets can be assigned correctly as follows: A‐A' doublet to Fe+2at M1, B‐B' Fe2+at M1, C‐C' Fe2+at M2, and D‐D' Fe3+at M1. The M1 site splitting is due to the NNN (Next Nearest Neighbour) effect of the M2 site. The amount of Fe3+at the tetrohedral site of megacrystal clinopyroxene is negligible according to this study.
Liquid Immiscibility of Boninite in Xiangcheng, Southwestern China, and Its implication to Genetic Relationship between Boninite and Komatiitic Basalt
Authors: Zengqian HOU , Xiaoming QU , Urabe Tetusro , Takagi  , Naito  
Published: September 2010

AbstractBoninitic rocks and associated high‐magnesian basalt and high‐iron tholeiite in the Xiangcheng area constitute the basal horizon of the arc volcanic sequence in the Triassic Yidun Island‐Arc, southwestern China. The boninite occurs as pillow, massive and ocellar lavas; the last one possesses well‐developed globular structure and alternates with the former two. The boninite is characterized by the absence of phenocrysts of olivine and low‐Ca pyroxenes and by low CaO/Al2O3 ratios (<0.67) and high Cr (>1000 ppm) and Ni (>250 ppm). The normalized abundance patterns (NAP) of trace elements to primitive mantle are similar to the NAP of low‐Ca modern boninites and SHMB in the Archaean and Proterozoic.As a mechanism of ocellar texture, liquid immiscibility in boninite is supported by the following lines of evidence: (a) sharp contact between ocelli and matrix, (b) constant volumetric ratios of ocelli/matrix and common coalescence of ocelli in ocellar rocks, (c) identical micro‐spinifex textures and mineral assemblages with different modal mineral contents in ocelli‐matrix pairs, (d) bubbles and acicular clinopyroxene crystal strand over the boundary between ocelli and matrix, and (e) chemical compositions of ocelli and matrix corresponding to high‐Mg andesite and komatiitic basalt, respectively. The close association and geochemical similarities between ocellar boninites and pillow boninite/massive boninite suggest that these are comagmatic rocks. The primary features of the ocellar boninite indicated by high Mg/(Mg+Fe2+) ratio and high Cr and Ni abundance show that liquid immiscibility took place in the early evolution stage of the boninitic magma. The miscibility gap in boninite which is smaller than that in tholeiite is likely to be due to the low FeO*/MgO+FeO*ratio and high MgO content of the boninitic magma.The association of komatiite‐komatiitic basalt‐boninite (or SHMB) and the immiscibility phenomenon in high‐Mg lavas in some Archaean greenstone belts and ophiolites is also reexamined. It is considered that liquid immiscibility in parental boninitic magma probably produced komatiitic basalt, which often occurs in close association with boninite (or high‐Mg andesite).
Early Carboniferous Radiolarian Fauna from Heiyingshan South of the Tianshan Mountains and Its Geotectonic Significance
Authors: Yu LIU 
Published: September 2010

AbstractAbundant and well‐preserved fossil radiolarians found from the Artencasher Formation, Heiyingshan of Baicheng County, Xinjiang Uygur Autonomous Region, are identified, including 15 species and 2 unnamed species in 9 genera. The fauna is dominated by the Family Entactiniidae of Spumellaria. According to the faunal characteristics, the radiolarians may be divided into five assemblages, namely, the Triaenosphaera sicarius, Entatinosphaera palimbola, Entactinia vulgaris, Belowea cf. variabilis and Archocyrtium sp assemblages. The fauna may be correlated with that from the Early Carboniferous of Frankenwald and Rein in Germany. Thus, ophiolite was formed in the Carboniferous, while the age of collision between the ***Ili plate and the Tarim plate is Early Carboniferous.
Collision Tectonics between the Tarim Block (Basin) and the Northwestern Tibet Plateau: New Observations from a Multidisciplinary Geoscientific Investigation in the Western Kunlun Mountains
Authors: Xuchang XIAO , Xun LIU , Rui GAO , KAO Houn , Zhaohua LUO 
Published: September 2010

AbstractNew results from deep seismic reflection profiling, wide‐angle reflection‐refraction profiling and broadband seismic experiments reveal that a series of south‐dipping reflectors occur on the southern margin of the Tarim block (basin). However, it is these south‐dipping structures that are intercepted by another series of north‐dipping reflectors at depths from 30 to about 150 km beneath the foreland of the W Kunlun Mountains. No evidence from the above geophysical data as well as geochemical and surface geological data indicate the southward subduction of the Tarim block beneath the W Kunlun Mountains (NW Tibet plateau), forming the so‐called “two‐sided subduction” model for the Tibet plateau as proposed by previous studies. So the authors infer that the tectonic interaction between the Tarim block and the W Kunlun block was chiefly affected by a “horizontal compression in opposite directions”, which brought about “face‐to‐face contact” between these two lithospheric blocks and led to the thickening, shortening and densifying of the lithosphere. Hence a “delamination” was formed due to the gravitational instability created by the thickening and densifying; then alkaline basic volcanic rocks (mainly shoshonite series) was erupted along the northern margin of the Tibet plateau owing to the delamination. This inference for the formation of the alkaline basic volcanics has been confirmed by recent geochemical and petrological studies in Tibet, indicating that different contacts control different magmatic activities: the alkali basalts are always developed in the “horizontal shortening boundary (contact)” on the northern margin of the Tibet plateau, while the muscovite granite and two‐mica granite (leucogranite) in the “subductional contact” on the southern margin of the Tibet plateau.
Research on Diageneses of Cambrian Shoal Facies Carbonate Rocks in the Xiadong Area, Hubei Province
Authors: Xiulian ZHANG , Lingzhi JIANG 
Published: September 2010

AbstractWith continuous outcrops, developed shoal facies rocks, complete types of diagenesis and changeable diagenetic environments, Cambrian strata are well developed in the Xiadong area, Yichang, Hubei Province. Under the combined influence of numerous diageneses, secondary pores can be formed, which result in better reservoir properties of the rock strata.The Cambrian rocks in this area consist of mainly carbonate rocks and secondarily detrital rocks. The carbonate rocks are dominated by grainstones including wormkalk, calcirudite‐calcarenite, oolitic limestone and oncolitic limestone. Graded bedding and cross bedding are well developed in the strata, which indicates that the formation environment is of a high‐energy shoal facies.In this area, there has developed a sequence of stable Cambrian platform carbonate deposition. The evolution trend is as follows: open sea shelf faciesŕintertidal low‐energy restricted sea faciesŕintertidal high‐energy shoal faciesŕcoastal shoal faciesŕevaporite tidal‐flat facies.The diageneses that the strata have experienced mainly include dolomitization, dedolomitization and dissolution, which are constructive diageneses for the formation of secondary pores, such as intercrystal pores, intercrystal solution pores, gypsum mold pores and caverns of dolomite.The diagenetic facies intervals can be divided into the unitary and the compound ones, totalling 22 in the area.In the early atmospheric fresh‐water diagenetic environment and the late epidiagenetic environment, Cambrian rocks, especially dolomite of the Middle and Upper Cambrian, experienced extensive and profound fresh water corrosion, forming pore intervals with a porosity ranging from 5% to 15%.
Organic Composition of Sulphide Ores in the Okinawa Trough and Its Implications
Authors: Qiling ZHANG , Zengqian HOU , Shaohua TANG 
Published: September 2010

AbstractA preliminary organic geochemical study shows that the sulphide ores from the hydrothermal deposit of the Okinawa Trough are generally low in the total organic carbon and extremely low in the soluble organic matter. In the aliphatic hydrocarbon fraction, the n‐alkanes range from C15 to C35, with usual maxima in the middle n‐C20 region and strong odd‐carbon number predominance when n > C25 (CPI = 1.2). The dominant analog in the aromatic fraction is phenanthrene, a polynuclear aromatic hydrocarbon, which provides evidence for hydrothermal activity. The organic matter derived mainly from marine planktonic and terrigenous vascular plants is entrapped in a high‐temperature regime such as an active chimney and cooled quickly in the sulphide ores on the seafloor. Organic matter and sulphides are definitely products of a high‐temperature alteration. The biomarker compounds indicate that the ores are formed under low Eh and pH conditions—a reducing to anoxic environment, which is favourable for sulphates to be reduced into sulphides by biogenic (bacterial) or abiogenic activity.
Hydrogeological Characteristics of a Karst Mountainous Catchment in the Northwest of Vietnam
Authors: TAM V. T. , VU T.M.N. , BATELAAN O. 
Published: September 2010

AbstractThis paper presents a preliminary assessment of the hydrogeological characteristics of a karst mountainous catchment, the Suoi Muoi River catchment, in the northwest of Vietnam. The catchment is located at 600–700 m a.s.l. and covers an area of 284 km. Exposed limestone occupies 32% of the total catchment area. Various types of assessments have been carried out, including geological and hydrogeological field surveys, cave surveys, dye‐tracer tests, meteorological and surface water monitoring. Geological studies and cave surveys have identified the most important active cave/conduit systems within the catchment. Although these data are essential, they are insufficient to make a comprehensive appraisal of the hydrologic nature of the catchment under interest. An attempt was made to calculate a global water balance of the catchment, based on short‐term (15 months) meteorological and streamflow records. The results show that, despite the existence of a number of substantial cavern conduit systems, the groundwater system of the catchment is governed by the fracture/fissure matrix. The cavern conduit systems only collect groundwater from the adjacent fracture matrix and/or connect topographically isolated surface watercourses. The groundwater storage of the cavern conduit systems appears to be regionally insignificant in comparison with the governed fracture matrix groundwater system.
Baiyun Cave in Naigu Shilin, Yunnan Karst, China
Authors: ŜEBELA S. , SLABE T. , KOGOVŜEK J. , Hong LIU , PRUNER P. 
Published: September 2010

AbstractThe Baiyun cave is a 380 m long karst cave in the Naigu Shilin, situated 70 km southeast of Kunming, Yunnan Province, China. The prevailing orientations of the cave passages are N110°–120°E and N0°‐10°W and those of the fissures in the cave are N30°–40°W and N20°–30°W. The cave is developed in the thick‐bedded Lower Permian Qixia Formation. The cave has an active water flow and is currently at the near water‐table stage. There are large amounts of different infills of cave sediments. The cave shows different stages of paragenesis. The palaeomagnetic analysis of cave sediments shows that their ages are younger than 780 ka B.P. (the Brunhes Chron). The upper part of the sampled profile belongs to the reverse Blake event (112.3–117.9 ka B.P.). The formation of the Baiyun cave is directly connected with the development of the Naigu Shilin. The formation of karst underground and surface features depends on the regional tectonic deformation and the Cenozoic extension of the study area.
Characteristics of Oil Contamination and Numerical Modelling of Its Transport in Fracture‐Karst Water in Zibo City, China
Authors: Xueyu ZHU , Xiaoxing QIAN , Jianli LIU 
Published: September 2010

AbstractIn this paper, the hydraulic characteristics of the fracture‐karst aquifer and the distribution patterns of petrochemical contaminants are studied. Then, a numerical model using the mixed Eulerian‐Lagrangian approach is constructed to predict the distribution and transport of petrochemical compounds in groundwater. The results of numerical modelling and sensitivity analysis show that it may be a workable way for aquifer remediation to combine contamination sources control and capture zone establishment.
Eclogites of the Dabie Region: Retrograde Metamorphism and Fluid Evolution
Authors: Lianxing GU , Jianguo DU , Jianping ZHAI , Chenghao ZHAO , Jianguo FAN , Wenlan ZHANG 
Published: September 2010

Abstract  Based upon fluid effects, retrograde metamorphism of eclogites in the Dabie region can be divided into the fluid‐poor, fluid‐bearing and fluid‐rich stages. The fluid‐poor stage is marked by polymorphic inversion, recrystallization and exsolution of solid solutions, and is thought to represent eclogite‐facies retrograde environments. The fluid‐bearing stage is likely to have occurred at the late stage of ecologite‐facies diaphthorosis and is represented by kyanite porphyroblasts, rutile, and sodic pyroxene in association with high‐pressure hydrous minerals such as phengite and zoisite (clinozoisite) without significant amount of hydrous minerals such as amphibole, epidote and biotite. The fluid‐rich stage might have commenced concomitantly with lower amphibolite‐facies diaphthoresis and persisted all the way towards the near‐surface environment. The product of this stage is characterized by plentiful hydrous and volatile‐bearing phases.The dissemination‐type rutile mineralizations in eclogites might have formed by preferential shearing‐induced pressure solution of gangue minerals at the fluid‐bearing stage. The accompanying vein rutile was precipitated from fluids of this stage after local transport and concentration, and may hence represent proximal mobilization of titanium from the eclogite. Therefore, rutile veins can be used as an exploration indicator for dissemination‐type rutile deposits.
Discovery of Borax‐bearing Mirabilite Beds in Dong Co, Northern Tibet, and Its Palaeoclimatic Significance
Authors: Lejun WEI , Mianping ZHENG , Xifang LIU , Keqin CAI , Zhen NIE 
Published: September 2010

AbstractThe authors investigated lacustrine chemical sediments on terrace‐I of Dong Co—a salt lake in the interior of the northern Tibetan Plateau and firstly discovered borax and a complete sedimentary section with five pure mirabilite beds. According to the sedimentary characteristics of rhythmic layering, palaeotemperatures for the formation of the cold‐phase mineral—mirabilite—at the profiles and 14C dating, the authors applied the theory and method of comparative salinology in the study of the history of the palaeoclimate and palaeoenvironment of Dong Co in the early and middle Holocene and drew the conclusion that the salt lake had experienced the following climatic evolution: the warm and moist stage (>8470 a BP and possibly to 10500 a BP)→ cold and dry stage (8470–8170 a BP)→ warm and moist stage (8170–7590 a BP)→stage of repeated climatic oscillations (7590–7400 a BP, alternation of three dry oscillations and three moist oscillations in a generally cold climatic background)→cold and dry stage (7400–6940 a BP)→warm and moist stage (6940–6620 a BP)→cold and dry stage (6620–6410 a BP)→warm and moist stage (after 6410 a BP).
Low‐Temperature Plasticity of Naturally Deformed Calcite Rocks
Authors: Junlai LIU , WEBER Klaus 
Published: September 2010

AbstractOptical, cathodoluminescence and transmission electron microscope (TEM) analyses were conducted on four groups of calcite fault rocks, a cataclastic limestone, cataclastic coarse‐grained marbles from two fault zones, and a fractured mylonite. These fault rocks show similar microstructural characteristics and give clues to similar processes of rock deformation. They are characterized by the structural contrast between macroscopic cataclastic (brittle) and microscopic mylonitic (ductile) microstructures. Intragranular deformation microstructures (i.e. deformation twins, kink bands and microfractures) are well preserved in the deformed grains in clasts or in primary rocks. The matrix materials are of extremely fine grains with diffusive features. Dislocation microstructures for co‐existing brittle deformation and crystalline plasticity were revealed using TEM. Tangled dislocations are often preserved at the cores of highly deformed clasts, while dislocation walls form in the transitions to the fine‐grained matrix materials and free dislocations, dislocation loops and dislocation dipoles are observed both in the deformed clasts and in the fine‐grained matrix materials. Dynamic recrystallization grains from subgrain rotation recrystallization and subsequent grain boundary migration constitute the major parts of the matrix materials. Statistical measurements of densities of free dislocations, grain sizes of subgrains and dynamically recrystallized grains suggest an unsteady state of the rock deformation. Microstructural and cathodoluminescence analyses prove that fluid activity is one of the major parts of faulting processes. Low‐temperature plasticity, and thereby induced co‐existence of macroscopic brittle and microscopic ductile microstructures are attributed to hydrolytic weakening due to the involvement of fluid phases in deformation and subsequent variation of rock rheology. During hydrolytic weakening, fluid phases, e.g. water, enhance the rate of dislocation slip and climb, and increase the rate of recovery of strain‐hardened rocks, which accommodates fracturing.