A proposed GSSP for the base of the Middle Ordovician Series： the Huanghuachang section,Yichang, China

The Huanghuachang section near Yichang, southern China meets the requirements of Global Stratotype Section and Point (GSSP) for the base of the Middle Ordovician Series and the yet-to-be-named third stage of the Ordovician System (or lower stage of Middle Ordovician Series). The conodont succession at the section is complete across the Lower to Middle Ordovician series boundary and several excellent phylogenetic lineages of Baltoniodus, Trapezognathus, Periodon, and Microzarkodina are represented. The definition of the base of the Middle Ordovician is proposed to be the first appearance datum (FAD) of Baltoniodus? triangularis in the section. It is followed closely by the FAD of Microzarkodina flabellum, which is taken as a reasonable proxy for the boundary. This level approximates the boundary between the lower and upper intervals of the Azygograptus suecicus graptolite Biozone, and nearly coincides with the base of the Belonechitina henryi chitinozoan Biozone.The proposed GSSP for the base of the international Middle Ordovician Series is located in a roadside exposure at the base of Bed (SHod) 16, 10.57 m above the base of the Dawan Formation in the measured Huanghuachang section near Yichang City, southern China. The same faunal succession is also recorded from the Chenjiahe (formerly Daping) section, 5 km to the north of the Huanghuachang section. The proposed boundary horizon can be recognized and correlated globally with high precision in both relatively shallow-water carbonate facies as well as in deep-water graptolite facies.     

Se-hyperaccumulator found for the first time in Enshi, Hubei, China

The Enshi area, Hubei Province in China, is a typical seleniferous environment, where seleniferous carbonaceous shale and carbonaceous siliceous rocks of Permian widely occur. In the 1960＇s, the first selenosis case in the human population in the world had even brought out at Yutangba Village, Shuanghe community, which resulted in move-off all local residenters The Enshi area possesses the advantageous natural conditions to develop Se-hyperaccnmulator. The selenosis case of human population may be related to having eaten the wild vegetable hyperaccumulating selenium. Mao Dajun （1997） found that the most seleniferous plant was cabbage in the Enshi area which contains Se 224.30 mg/kg. In order to find out Se-hyperaccnmulator in China as soon as possible, the present research made a lot of work on many numbers of wild plants which grow in Enshi, Hubei Province, China. Finally, we found Thlaspi arvenst L., the first Se-hyperaccumulator of China at Yutangba Village. In this plant, Thlaspi arvenst L., the contents of selenium （DW） are 802-870 mg/kg （the average 843 mg/kg） for the whole plant, 1121 mg/kg for root, 511 mg/kg for stem and 1427 mg/kg for leaf, respectively. The newly found Thlaspi arvenst L. by us is the most seleniferous plant which has been found in China up to now, whose Se in its leaf is higher than the international criterion of 1000 mg/kg for Se-hyperaccnmulator.     

Ore-Forming Mechanism for the Hongshan Deposit in Yunnan Province, China

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Hydrocarbon migration in the Zagros Basin,offshore Iran,for understanding the fluid flow in the Oligocene–Miocene carbonate reservoirs

Kuh-e Mond Field is a conventional heavy oil resource in the Zagros foreland Basin, Iran, produced from the fractured carbonates partially filled by dolomite, calcite, and anhydrite cement. Vitrinite reflectance data from carbonate reservoir suggest low-maturation levels corresponding to paleotemperatures as low as 50 °C. The observed maturation level (< 0.5% Rmax) does not exceed values for simple burial maturation based on the estimated burial history. Oil inclusions within fracture-filled calcite and dolomite cement indicate the key role of these fractures in oil migration.The fluid inclusion temperature profiles constructed from the available data revealed the occurrence of petroleum in dolomite, calcite, and anhydrite and characterize the distinct variations in the homogenization temperatures (T_h). Fluid inclusions in syntectonic calcite veins homogenize between 22 °C and 90 °C, showing a salinity decrease from 22 to 18 eq. wt.% NaCl. Fluid inclusions in anhydrite homogenize at < 50 °C, showing that the pore fluids became warmer and more saline during burial. The T_h range in the calcite-dolomite cement depicts a change in water composition; therefore, we infer these cements precipitated from petroleum-derived fluids. The microthermometry data on the petroleum fluid inclusions suggest that the reservoir was filled with heavy black oils and high-salinity waters and indicate that undersaturated oil was present in a hydrostatically pressured reservoir.The T_h data do not support vertical migration of hot fluids througout the section, but extensive lateral fluid migration, most likely, drove tectonically dewatering in the south or west of the pool.     

Geothermometry applications for the Balıkesir thermal waters,Turkey

In this study, reservoir temperatures of Balıkesir geothermal waters in northwestern Turkey are estimated with various geochemical models. The geothermal fluids in the region are represented by Na–SO₄, Na–HCO₃ and Ca–HCO₃ type waters with discharge temperatures up to 98°C. It was determined that the solubility of silica in most of the waters is controlled by the chalcedony phase. Equilibrium states of the Balıkesir thermal waters studied by means of Na–K–Mg–Ca diagram, mineral saturation calculations and activity diagrams in the system composed of Na₂O–CaO–K₂O–Al₂O₃–SiO₂–H₂O phases approximate a reservoir temperature of about 120°C. Most of the waters are found to be equilibrated with calcite, chalcedony ± quartz and muscovite at predicted temperature ranges, similar to those calculated from the chemical geothermometers.     

Application Research for Geogas Prospecting in the Xinqu Gold Deposit, Gansu, China

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Tracing to the Source of Ore-forming Fluids for the Huanxiangwa Gold Deposit, Western Henan

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Isotopic Geochronological Evidence for the Caledonian Xiongdian Eclogite in the Northwestern Dabie Mountains,China

A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern Dabie Mountains, has been geochronologically studied using the single-zircon U-Pb, 40Ar-39Ar and Sm-Nd methods. Prismatic zircons occurring as inclusions within garnets define a minimum crystallization age of 399.5±1.6 Ma. 40Ar-39Ar dating on amphibole gives a plateau age.of 399.2 ± 4 Ma, which is interpreted as a retrogression age of amphibolite facies. This integrated study enables us to conclude that the age of high-pressure metamorphism is older than 399.5 ± 1.6 Ma, suggesting Caledonian collision between the North China and Yangtze plates. Round zircon within the aggregate of quartz and muscovite gives a concordant age of 301± 2 Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399.2 Ma shortly after eclogitization and later retrogressive metamorphism at 301 Ma. Sm-Nd mineral isochron of garnet+omphacite gives     

Petrology,geochemistry, and geochronology of the Zhonggang ocean island,northern Tibet: implications for the evolution of the Banggongco–Nujiang oceanic arm of the Neo-Tethys

This study presents new data relating to the tectonic evolution of the Zhonggang ocean island, within the Mesozoic Banggongco–Nujiang suture zone of northern Tibet, and discusses the implications of these data for the evolution of this region. Thirteen basalt and ten gabbro samples were collected from a sampling transect through this area; these samples have light rare earth element (LREE)-enriched chondrite-normalized REE patterns, and are enriched in highly incompatible elements, yielding primitive-mantle-normalized trace-element variation patterns that are similar to ocean island basalts (OIB). A gabbro dike intruded into basalt of the Zhonggang ocean island and was overlain by basaltic conglomerate, suggesting that this dike was formed after the basalt, but before the basaltic conglomerate. The gabbro dike yields an LA–ICP–MS zircon U–Pb age of 116.2 ± 4.1 Ma, indicating the timing of formation of the Zhonggang ocean island, and suggesting in turn that the Banggongco–Nujiang Neo-Tethys Ocean remained open at this time. These data, combined with the geological history of the region, indicates that the Banggongco–Nujiang Neo-Tethys Ocean opened between the late Permian and the Early Triassic, expanded rapidly between Late Triassic and Middle Jurassic time, and finally closed between the late Early and early Late Cretaceous.     

Isotope Method for Confined Groundwater Recharge of the Lower Reaches of the Heihe River, Inner Mongolia, China

Environmental isotopes have been applied to analyze confined groundwater recharge in the lower reaches of the Heihe River,Inner Mongolia.CFC is regarded as a tracer that determines the date of groundwater,the date being less than 45 a.The confined groundwater within the Gurinai area and Ejin Basin other than the surface water of Heihe River might have originated from precipitation from Qilian Mountain or/and the Tibetan Plateau.The deep confined groundwater overflows into an upper aquifer and emerges into the ground,forming springs and lakes within the low-lying area.The recharge volume is estimated to be around 400 million-cubic meters.     

A Tentative Apparent Polar Wander Path for the Shan-Thai-Malay Block,SW Yunnan, China

1.IntroductionTheShan--Thai-MalayBlock(STMB)isadonorcontinentalfragmentintheSWborderregionofChinaandSoutheastAsia.IthaslongbeenrecognizedasablockdisplacedfromGondwanaintheLatePaleozoic(Mitchell,1981;Cao,1986).ThePaleozoicmarinesequenceandfossilassemblagesaremarkedlydifferentfromthoseofotherChineseblockssuchasYangtze,NorthChinaandTarim,aswellaseasternChineseblocks.Instead,specificsedimentaryfactessuchasEarlyPenmanglaciomarinedeposits,Carboniferouscool-coldwaterfaunaandPenmanGlossopt…     

Exotic crustal block accretion to the eastern Gondwanaland margin in the Late Cambrian–Tasmania,the Selwyn Block,and implications for the Cambrian–Silurian evolution of the Ross,Delamerian, and Lachlan orogens

Reconstructions of the Cambrian–Silurian tectonic evolution of eastern Gondwanaland, when the Australian Tasmanides and Antarctic Ross Orogen developed, rely on correlation between structural elements in SE Australia and Northern Victoria Land (NVL), Antarctica. A variety of published models exist but none completely solve the tectonic puzzle that is the Delamerian–Lachlan transition in the Tasmanides. This paper summarizes the understanding of Cambrian (Delamerian) to Silurian (Lachlan) geological evolution of the eastern Tasmanides, taking into account new deep seismic data that clarifies the geological connection between Victoria and Tasmania — the ‘Selwyn Block’ model. It evaluates previous attempts at correlation between NVL, Tasmania and Victoria, and presents a new scenario that encompasses the most robust correlations. Tasmania together with the Selwyn Block is reinterpreted as an exotic Proterozoic microcontinental block – ‘VanDieland’ – that collided into the east Gondwanaland margin south of western Victoria, and north of NVL in the Late Cambrian, perhaps terminating the Delamerian Orogeny in SE Australia. Subsequent north-east ‘tectonic escape’ of VanDieland in the Early Ordovician explains the present-day outboard position of Tasmania with respect to the rest of the Delamerian orogen, the origin of the hiatus that separates the Delamerian and Lachlan orogenic cycles in Australia, and how western Lachlan oceanic crust developed as a ‘trapped plate-segment’. The model establishes a new structural template for subsequent Lachlan Orogen development and Mesozoic Australia–Antarctica separation.     

New radiocarbon age constraints for the 120 km-long Toomba flow,north Queensland,Australia

The Toomba flow is the youngest flow of the Nulla volcanic province, located in north Queensland. This 120?km-long flow has yielded a published ⁴⁰Ar/³⁹Ar age of 21,000?±?3000 years. In contrast, seven published conventional radiocarbon (¹⁴C) analyses of carbon-bearing material beneath the flow yielded radiocarbon ages of 16,000 to <2500?BP. These radiocarbon ages are younger than the ⁴⁰Ar/³⁹Ar age, potentially due to contamination of the charcoal by younger carbon that was not removed by the acid–base pre-treatment. We have re-examined the radiocarbon age of Toomba flow using newly sampled charcoal buried beneath the Toomba flow in combination with hydrogen pyrolysis pre-treatment and accelerated mass spectrometer (AMS) measurements. We determined a calibrated radiocarbon age of 20,815–19,726?cal BP (2σ) for the material beneath the Toomba flow. Our radiocarbon age, therefore: (1) is older than previous radiocarbon ages for the Toomba flow, (2) provides the most precise age yet available for the Toomba flow, (3) is in agreement with the ⁴⁰Ar/³⁹Ar age, and (4) validates that hydrogen pyrolysis is a robust and effective pre-treatment method, for subtropical conditions where samples are susceptible to contamination by younger carbon. The Toomba flow erupted during the Last Glacial Maximum, but the preserved surface suggests that the rate of weathering and soil formation has been almost negligible in this region, despite being situated in a subtropical climate that experiences highly variable often intense rainfall.     

Structural and Chronological Evidence for the India-Eurasia Collision of the Early Paleocene in the Eastern Himalayan Syntaxis, Namjagbarwa

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.     

Sedimentation model for the quaternary intramontane Bhimtal–Naukuchiatal Lake deposits,Nainital, India

The Bhimtal–Naukuchiatal Lake was created due to blocking of the valley by a huge debris flow along a narrow outlet at about 40 ka BP. The lake basin was filled intermittently due to fluvio-lacustrine and colluvial processes that deposited a thick sequence of interbedded mud and gravel. In the basin fill sequence five major lithofacies, most of them divisible into subfacies, have been identified and assigned to specific depositional environments. The coarsening upward (CU) mud-silt cycles represent sedimentation in a lake setting. The clasts-and mud-supported gravels consists of fining upward (FU) and CU sequences, respectively, indicating deposition by channel processes and debris flows. Having basin wide extent, the pedogenic mottled, clayey silt unit represents an important tectonic event when the lake was temporarily drained and sediments were sub-aerially exposed. Fluctuating arid–semiarid to humid climatic conditions and repeated tectonic activity may have governed the mode of sedimentation and ultimately the basin fill history.     

Evidence for strong paleoearthquakes along the Talas-Fergana Fault near the Kök-Bel Pass,Kyrgyzstan

Paleoseismological study along the Talas-Fergana Fault near the Kök-Bel Pass in the central Western Tien Shan allows us to estimate the rate of late Holocene horizontal offset at 13–14 mm/yr, as well as the radiocarbon age of the strong earthquakes that occurred here about 300, 2400, and 5000 yr ago.     

A dynamic stability analysis for the Olinalá landslide,northeastern Mexico

Natural Hazards - We have evaluated slope stability conditions considering different triggering conditions for the Olinalá landslide, a paleo-landslide located in the northern front of the...     

Kinematic vorticity analysis along the Karakoram Shear Zone,Pangong Mountains,Karakoram: Implications for the India–Asia tectonics

The Karakoram Shear Zone (KSZ) is a northwest-southeast trending dextral ductile shear zone that has mylonitized the Tangste and Darbuk granitoids of the southern margin of the Asian plate. Kinematic vorticity (W_k) has been estimated in 6 mylonitized Tangste granite samples, using Porphyroclast Hyperbolic Distribution (PHD) and Shear Band (SB) Analyses methods on well-developed quartz and feldspar porphyroclasts, and synthetic and antithetic shear bands respectively to visualize the overall deformation of the KSZ. The PHD and SB analyses yield W_k values ranging from W_k=0.29 to 0.43 and 0.45 to 0.93, respectively, thus indicating distinct pure and simple shear dominant regimes during different stages of the evolution of the KSZ. Strain has essentially been pure shear when southern edge of the Asian plate was initially juxtaposed against the Indian plate around 70 Ma, and changed to simple shear, possibly during the reactivation of this shear zone during 21-13 Ma to produce the shear bands.     

The Global Boundary Stratotype Section and Point （GSSP） for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France

Following the unanimous recommendation of the International Commission on Stratigraphy, the Global boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage is defined at a level 36 metres below the top of the Marnes Bleues Formation, a level that corresponds to the the first appearance of the planktonic foraminiferan Rotalipora globotruncanoides Sigal, 1948, on the south side of Mont Risou, east of Rosans, Haute-Alpes, France, where it can be placed in the context of a series of secondary marker levels based on nannofossils, planktonic foraminifera, ammonites,and an ornate δ^13C curve.