bluuebunny/crossref_metadata_2025 huggingface dataset:
Quaternary Climate and Environment in the Lop Nur, Xinjiang
Authors: Mili WANG , Qingyu PU , Chenglin LIU , Yongzhi CHEN
Published: September 2010

Since the middle Early Pleistocene (1.20 Ma B.P.), the desert steppe climate and environment have predominated in the Lop Nur area, Xinjiang, characterized by warm humid epochs interrupted by dry cold intervals. The grain‐size and magnetic susceptibility curves record 30 climatic oscillations, each with a ca. 40 ka cycle, in the area since 1.2 Ma B.P., which reflects the controlling effects exerted by the astronomic factor on the environment. The Quaternary sedimentary environment in the Lop Nur gradually changed from a fresh lake through a brackish lake to a saline lake, showing a spiral evolution, and finally it evolved into a playa.
Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate
Authors: Jun CHEN , Yongjin WANG , Yang CHEN , Lianwen LIU , Junfeng JI , Huayu LU
Published: September 2010

Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain‐size fractions and chemical forms. Results show that Rb is quite rich in the fraction of less than 2 μm, and exits only in the residual phase, while Sr is distributed in sand and silt fractions, occurring in the residual and carbonate phases. Therefore, variations of the concentrations of Rb and Sr in loess and palaeosols are closely related not only to dustfall compositions depending on winter monsoon wind strength but also to summer monsoon‐induced pedogenic intensity. This indicates that variations of Rb/Sr ratio in Chinese loess sequences represent cyclic alternations of East Asian summer and winter monsoon climates on the orbital time‐scale. Variations in Sr concentrations along the sequence bear a high similarity to the oxygen isotope record of the deep sea sediments over the past 2.5 Ma, whereas variations in Rb concentrations are in good agreement with the record of magnetic susceptibility determined with the duplicated samples from the same profile. This suggests that (1) the high‐latitude ice volume is responsible for East Asian monsoon variations and (2) the signal of magnetic susceptibility depends dominantly on pedogenesis in Chinese loess sequences.
Pb Isotope Study of Some Nonferrous Metallic Deposits in China
Authors: Wenxin XU , Minyang CHEN , Chunyong PANG , Heng LI
Published: September 2010

Based on Pb‐Pb isochron data of more than 40 Precambrian polymetallic deposits, the authors consider that there are four mineralization periods for the Precambrian copper deposits in China, and the major copper deposits were formed at about 1800 Ma; there are three mineralization periods for gold deposits formed from Archaean to Proterozoic. By studying hundreds of lead isotope data from some Mesozoic continental subvolcanic Cu and Ag polymetallic deposits and fine‐disseminated gold deposits, the authors found that the calculation based on the lead single‐stage evolution model or two‐stage evolution model cannot give the true ore‐forming ages but can provide more information about mineralization and material sources of the deposits.
The Mechanism of Groundwater Salinization and Its Control in the Yaoba Oasis, Inner Mongolia
Authors: Bingchen WANG , Hanxue QIU , Qian XU , Xilai ZHENG , Guanqun LIU
Published: September 2010

The arid area is one of the most concerned areas among the water resources researchers and economists. Northwest China will be an important developing region of China in the 21st century. Yaoba is a well‐irrigation oasis within this arid area, which is located in the Alxa area west of the Helan Mountains and next to the Tengger desert in the east. It has contributed greatly to the local stock raising and agriculture since its development in 1970. However, the groundwater which the oasis depends on to survive has been getting salinized gradually and more serious in recent years.

A comprehensive study was carried out using the methods of groundwater environment isotope analysis, lithofacies and palaeogeography, calculations of water‐rock interaction and the existing form of chemical components in groundwater etc. It has been found that the salinization of groundwater is mainly caused by reinfiltration water solving the salt in soil which is deposited simultaneously with the sediments and accumulated in the vadose zone due to strong evaporation in the arid climate for the running of an irrigation scheme.

The saline groundwater in the Taosu Lake area southwest of the oasis is preliminarily regarded as the main source of groundwater salinization. However, it has been found that the groundwater has great differences in the D, 18O, H3and NO3 concentrations with that in the oasis, that is, the former plays only a limited role in the salinization of groundwater in the oasis.

The HST3D model (a computer code for the simulation of heat and solute transport in a three‐dimensional groundwater system) was used to simulate the TDS movement in the oasis. A good simulation result has been obtained with the mean simulation error of 4.7% and the simulation trend is reasonable. It is proved that there is 3.0–4.0times105m3/a of reinfiltrated irrigation water in 3 main spots in the oasis. The oasis irrigation manner, winter irrigation to wash salt, the increase of wheat planting area, and no amount limit to water users (the farmers) are the main factors for causing the increase of water consumption as well as the groundwater salinization. The control measures on the groundwater salinization should include the establishement of reasonable irrigation regulations, water use limitation measures, flood utilization project, saltwater discharge, sealing of the upper layers to prevent the saline water to enter the pumping wells.
A Study of Near‐ and Super‐Critical Fluids Using Diamond Anvil Cell and in‐Situ FT‐IR Spectroscopy
Authors: Shumin HU , Ronghua ZHANG , Xuetong ZHANG
Published: September 2010

The phase relation and solution structure of water and NaCl aqueous solution have been observed and examined by using the hydrothermal diamond anvil cell (HDAC) at elevated temperatures and pressures and the in situ FT‐IR spectroscopy. The temperature of observations ranges from 25 to 850°C and the pressure up to 10 or 30 kb. At first, we observed the phase transition process from halite+liquid+vapour (H+L+V) to L+H, then to L (or supercritical fluid, SCF), and another path: H+L+V→L+V→L (or SCF) in heating process. By means of the visual microscope, the authors found that in the L+V immiscibility field L+V exhibits an ordered structure, i.e. a large visual cluster of solvent around ions. The liquid phase is manifested by vapour bubbles. When phase transitions are observed, the authors examined their infrared spectra by using the FT‐IR microscopy simultaneously. In the case of the phase transition from liquid (L) to liquid + vapor (L+V) immisciblity field of NaCl solutions, a sudden change (strong frequency shift) of infrared spectra of the aqueous solution is observed near the critical temperature of water as the temperature is raised from 25 to 650°C. The frequency of the maximum intensity of OH symmetric and asymmetric vibration varies with respect to temperature. The sharp peak of the OH stretching vibration of the maximum intensity appears in an interval from 300 to 400°C. It is indicated that the hydrogen bonding network is weakened and broken at last near the critical point of water, which causes the aqueous solution to become more associated. Besides, a pressure indicator (a mineral or compound) was introduced to the HDAC.
A Study of Devonian Reefs from Southern China
Authors: Tianqiu HONG , Ming HUANG , FLAJS G.
Published: September 2010

Three Devonian reefs (bioherms) from Yunnan and Guangxi, southern China, are studied in detail. Six microfacies types are differentiated. Colonial rugose corals (Columnaria, Disphyllum and Hexagonaria) at Qujing, tabulate corals (Alveolites) with massive stromatoporoids (Actinostroma and Stromatoporella) and sponges at Panxi, and massive stromatoporoids (Actinostroma, Trupetostroma and Stromatoporella) at Yangshuo belong to the most important reef builders. All the three reefs studied clearly reveal a successive evolution history. They developed on the carbonate banks, shallow carbonate platforms and platform margins in the Late Givetian and terminated in the Frasnian due to sea‐level falls related to local uplifts of platforms. This coincides with a eustatic fall of relative sea level at the Frasnian/Famennian transition.
Sedimentary Environments of the Cangfanggou Group in Junggar Basin, Xinjiang, in Response to Climate and Tectonic Regime
Authors: Zhanghua LOU , Rong ZHU , Zhonghua TANG , Zhigang LIU , Xiafei ZHAO , Zhongcai CHEN
Published: September 2010

Detailed studies of petrology, palaeocurrent direction, palaeogeomorphology and palaeohydrodynamics have been conducted for the Permian‐Triassic Cangfanggou Group in the foredeep of the Bogda Mountains in the southeastern Junggar Basin, Xinjiang. Sedimentary environments and facies of alluvial fans and pebbly braided rivers, sandy braided rivers, meandering rivers, low‐sinuosity rivers, swamps and fresh‐water lakes are recognized in the group. Climate and tectonics of source areas strongly controlled the evolution of the sedimentary environments and facies in the foredeep. The block faulting in the Bogda Mountains increased the ground slope, which led to a drastic increase in the grain size of the sediments. Humid climate, being beneficial to plant growth, would provide protection of channel banks and at the same time weaken chemical weathering in the source area, thus large amounts of clay materials are available for the formation of clay plugs. As a result, stable banks and meandering river belts are formed. Conversely, increasing aridity would strengthen mechanical weathering and reduce the number of clay plugs. Besides, plants would diminish gradually and channels would become more mobile. In this case the decrease of transported clay materials would reduce the stability of the bank and result in a wider and shallower channel. Therefore, humid climate is beneficial to the formation of meandering rivers even if there is strong block faulting in the source areas and the ground slope is very large. As aridity further increases, plants would diminish and vanish at last, the meandering rivers prevalent under humid climate conditions would be transformed to low‐sinuosity rivers even if the ground is gentle and the land is tectonically stable. And as the climate became more arid and the source area uplifted intensively to provide more sedimentary materials, low‐sinuosity rivers would be transformed to braided ones quickly, and wedge‐like sedimentary bodies of the braided rivers would then advance towards the lower reaches. The increasingly arid climate led to prevailing mechanical and diminishing plant protection to the banks. Both active tectonic regime and humid climate resulted in very shallow and mobile channels, i.e. a braided river system.

The climate plays an important role in the evolution of rivers and lakes. The sinuosity and braiding parameters of channels are a result of complex interaction between climate (clay material supply, plant protection of the banks, flood events and so on) and tectonic regime (lithology of the source area, slopes and so on). Both factors can be estimated by sedimentological studies in the foothill belt.
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

Miocene 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

The 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.
Basic Lithofacies‐Succession Model for the Wumishan Cyclothems: Their Markov Chain Analysis and Regularly Vertical Stacking Patterns in the Third‐Order Sequences
Authors: Mingxiang MEI , Yongsheng MA , Qingyin GUO , Zhenbi Fei
Published: September 2010

Abstract  The Mesoproterozoic Wumishan Formation in the Jixian section of Tianjin is a succession of 3300‐m‐thick carbonate strata formed in a period of about 100 Ma (1310 ± 20 Ma‐1207 ± 10 Ma). In this succession of strata, the carbonate metre‐scale cyclic sequences belonging to peritidal type with an approximately symmetrical lithofacies‐succession are best developed. The wide development of 1:4 stacking patterns shows that these metre‐scale cyclic sequences are genetically related to the short‐eccentricity cycles, which are called the Wumishan cyclothems that could truly represent sedimentary cycles. Generally, massive and thick‐bedded calcareous dolomites and dolomitic limestones of stromatolite biostromes and thrombolite bioherms constitute the central part of the Wumishan cyclothems. The lower and upper parts consist of tidal flat dolostones, sandy‐muddy dolostone and the top part is composed of lagoonal facies dolomitic shales with a paleosol cap. Therefore, an approximately symmetrical lithofacies‐succession is formed. Many features such as the clear deepening and shoaling vectors of cyclothems, and all kinds of marks of fresh‐water diagenesis indicate that the Wumishan cyclothems are the product of autocyclic sedimentation governed by allocyclic high‐frequency sea‐level changes. The results of a Markov chain analysis reaffirm the existence of the lithofacies‐succession model of the Wumishan cyclothems. The boundaries of the Wumishan cyclothems are marked by the instantaneous exposed punctuated surface, which leads to the discrepancy between the cyclothems and the parasequences of the sequence stratigraphy terminology system. It is difficult to form a judgment that the time span of the Milankovitch cycles in the Precambrian is certainly equal to that of the Phanerozoic, but the regularly vertical stacking patterns of the seventh‐order rhythms, sixth‐order cyclothems and fifth‐order parasequence sets still indicate their consistency with the duration of the Milankovitch cycles in the Phanerozoic.
New Data of Daomanite and Hongshiite
Authors: Zuxiang YU
Published: September 2010

Abstract  In 1974 the author preliminarily reported two new platinum group minerals—daomanite and hongshiite. The two minerals were accepted by the Commission on New Minerals and Minerals Names of the International Mineralogical Association in 1976 and 1982 respectively. Because of the conditions at that time, the work was preliminary, for example, there were only reflectance values of four wave bands. Recently the author again made measurements of reflectances, corrected cell parameters by the four‐circle diffractometer and electron diffraction and supplemented their new occurrences and nomenclature.
Petrogenesis of Cenozoic Potassic Volcanic Rocks in the Nangqên Basin
Authors: Hongjuan SUN , Wanming DENG , Yuquan ZHANG
Published: September 2010

The 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

The 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

Boninitic 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

Abundant 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

New 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

With 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

A 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

This 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

The 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

In 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.
On the Karst Ecosystem
Authors: Daoxian Yuan
Published: September 2010

In this paper the author gives a definition of the karst ecosystem and discusses the characteristics of the karst environment and karst ecosystem and the relationship between life and the karst environment. Finally he clarifies the structure, driving force and functions of the karst system.
Metamorphism of the Basement of the Qilian Fold Belt in the Minhe‐Ledu Area, Qinghai Province, NW China
Authors: Chinglang TSAI , Kunghua WEI , Chenshu WANG
Published: September 2010

Abstract  The basement of the central Qilian fold belt exposed along the Minhe‐Ledu highway consists of psammitic schists, metabasitic rocks, and crystalline limestone. Migmatitic rocks occur sporadically among psammitic schist and metabasitic rocks. The mineral assemblage of psammitic schist is muscovite + biotite + feldspar + quartz ± tourmaline ± titanite ± sillimanite and that of metabasitic rocks is amphibole + plagioclase + biotite ± apatite ± magnetite ± pyroxene ± garnet ± quartz. The migmatitic rock consists of leucosome and restite of various volume proportions; the former consists of muscovite + alkaline feldspar + quartz ± garnet ± plagioclase while the latter is either fragments of psammitic schist or those of metabasitic rock. The crystalline limestone consists of calcite that has been partly replaced by olivine. The olivine was subsequently altered to serpentine. Weak deformations as indicated by cleavages and fractures were imposed prominently on the psammitic schists, occasionally on metabasitic rocks, but not on migmatitic rocks. The basement experienced metamorphism up to temperature 606–778°C and pressure 4.8–6.1 kbar (0.48–0.61 GPa), equivalent to amphibolite‐granulite facies. The peak of the metamorphism is marked by a migmatization which occurred at several localities along the studied route 587‐535 Ma ago. The basement also recorded a retrograde metamorphism of greenschist facies, during which biotite, garnet, amphibole, and pyroxene were partly altered to chlorite.
Major Characteristics of the Lajishan Orogenic Belt of the South Qilian Mountains and Its Geotectonic Attribute
Authors: Weiran YANG , Qinglu DENG , Xiuling WU
Published: September 2010

Abstract  The Lajishan orogenic belt is one of the E‐W‐trending Caledonian orogenic belts within the Qinling‐Qilian orogenic system. It was formed upon the Jiningian basement by intensive taphrogenesis. Its major characteristics comprise the prominent faulting along the north and south boundaries, the highly complicated petrological and petro‐geochemical features of the volcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonic analysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested that the Lajishan orogenic belt has undergone a complete “opening‐closing” cycle, which can be further divided into 3 second‐order “opening‐closing” cycles. The composite characteristics of the “opening‐closing” movement show that Laji Mountain is a typical fault orogenic belt. The fault orogenic belt is one of the most important types of intracontinental orogens. It is of critical theoretical and practical significance to summarize the characteristics and the diagnostic criteria of this kind of orogenic belts, and study the mechanism of their formation and build models of their evolution.
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.
Researches on Plants from the Lower Devonian Xujiachong Formation in the Qujing District, Eastern Yunnan
Authors: Deming WANG , Shougang HAO , Zhenfeng LIU
Published: September 2010

Abstract  Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang et Hao 2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation, the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in this district. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllum australianum) and their horizons, it is proved for the first time that the mid‐lower assemblage of the Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora of southeastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and the stratigraphic sequence, the mid‐lower part of the Xujiachong Formation is considered to be of (late) Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and the lithology, the upper part of the Xujiachong Formation is dated to be of early Emsian age. The Xujiachong flora belonged to the northeastern Gondwana palaeophytogeographic unit during the Early Devonian. The early Emsian assemblage of this flora inherited the characters of the Posongchong flora and also exhibited the endemic elements. Belonging to different phytogeographic units, the Xujiachong and Posongchong floras differ from the coeval flora of the Laurussian palaeocontinent. The Xujiachong flora is comparatively simple in composition, while the Posongchong flora has abundant and highly diversified endemics. The disparity between them has resulted from the different environments.
Structural and Chronological Evidence for the India‐Eurasia Collision of the Early Paleocene in the Eastern Himalayan Syntaxis, Namjagbarwa
Authors: Jinjiang ZHANG , Jianqing JI , Dalai ZHONG , Haiqing SANG , Shundong HE
Published: September 2010

Abstract  The eastern Himalayan syntaxis in Namjagbarwa is a high‐grade metamorphic terrain formed by the India‐Eurasia collision and northward indentation of the Indian continent into Asia. Right‐ and left‐lateral slip zones were formed by the indentation on the eastern and western boundaries of the syntaxis respectively. The Dongjug‐Mainling fault zone is the main shear zone on the western boundary. This fault zone is a left‐lateral slip belt with a large component of thrusting. The kinematics of the fault is consistent with the shortening within the syntaxis, and the slipping history along it represents the indenting process of the syntaxis. The Ar‐Ar chronological study shows that the age of the early deformation in the Dongjug‐Mainling fault zone ranges from 62 to 59 Ma. This evidences that the India‐Eurasia collision occurred in the early Paleocene in the eastern Himalayan syntaxis.
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

The 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

Optical, 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.
Constitution Water in Mantle‐derived Megacryst and Xenolith Pyroxene of an Ultrabasic Pipe in Anyuan, Jiangxi
Authors: Song YE , Baoming ZHANG , Jinru DI , Mei YANG , Delong YE
Published: September 2010

This paper studies the hydrous facies of mantle‐derived megacryst clinopyroxenes and pyroxenes of xenoliths of pyroxenolite and spinel peridotite as well as garnet pyroxenolite in a kimberlitic lamprophyre pipe in Anyuan, Jiangxi, by Fourier Transform Infrared (FTIR). It explores the relationship between the water content of pyroxene on the one hand and its composition and source depths on the other hand. All the samples contain constitution water. Spectra of the clinopyroxene are dominated by two groups of bands: 3607–3630 cm−1 and 3522–3542 cm−1. Spectra of the orthopyroxene are dominated by three groups of bands: 3410–3424 cm−1, 3510–3516 cm−1 and 3560–3595 cm−1. The water content of the clinopyroxenes has a positive correlation with their FeO and Al2O3 contents. The source depths of mantle‐derived clinopyroxene megacrysts, pyroxenolite, spinel peritotite and garnet pyroxenelite increase gradually in order. The Al2O3 and water contents of four pyroxenes have similar correlation with the source depths.
A New Platy‐armored Worm from the Early Cambrian Chengjiang Lagerstätte, South China
Authors: Jian HAN , Xingliang ZHANG , Zhifei ZHANG , Degan SHU
Published: September 2010

Abstract  The Lower Cambrian Chengjiang Lagerstätte provides a good window to explore the origin and radiation of early bilaterians. Here we describe a netted sclerite‐bearing worm Tabelliscolex hexagonus gen. et sp. nov., and tentatively assign it to palaeoscolecidans of priapulids. The cuticle of the animal is covered with two kinds of platy sclerites which are constructed by hexagonally arranged tubercles. Similar structures of the sclerites can be seen on some Cambrian palaeoscolecidans and lobopods, so, this new species is critical for understanding the relationships between lobopods and palaeoscolecidans.
Estimation of 2‐D and 3‐D Fracture Densities from 1‐D Data — Experimental and Field Results
Authors: Jiandong XU , JACOBI Robert D.
Published: September 2010

Abstract  2‐D and 3‐D densities of fractures are commonly used in mining safety design, natural gas and oil production in fractured reservoirs, and the characterization of subsurface flow and transportation systems in fractured rocks. However, many field data sets are collected in 1‐D frequency (f) (e.g., scanlines and borehole data). We have developed an ARC/INFO‐based technology to calculate fracture frequency and densities for a given fracture network. A series of numerical simulations are performed in order to determine the optimal orientation of a scanline, along which the maximum fracture frequency of a fracture network can be obtained. We calculated the frequency (f) and densities (both D1 and D2) of 36 natural fracture trace maps, and investigated the statistical relationship between fracture frequency and fracture density D1, i.e. D1=1.340f+ 0.034. We derived analytical solutions for converting dimensional density (D1) to non‐dimensional densities (D2 and D3) assuming that fracture length distribution follows an exponential or power law. A comparison between observed and calculated results based on the equations we developed shows that (1) there exists a linear relationship between fracture frequency and fracture density (D1), and this relationship can be used to estimate fracture density (D1) if the fracture frequency is determined from a scanline survey or from borehole data; (2) the analytical solutions we derived can accurately determine the non‐dimensional 2‐D fracture density (D2) in practice and 3‐D fracture density (D3) in theory if the fracture length distribution function is assumed.