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Characteristics and Natural Gas Origin of Middle-Late Triassic Marine Source Rocks of the western Sichuan Depression, SW China

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Acta Geologica Sinica(English Edition) 2020年第2期94卷 376-398页

作者： SUN Tengjiao LUO Xiaoping QING Hairuo KOU Xueling SHENG Zhongming XU Guosheng ZUO Yinhui College of Energy Resource Chengdu University of TechnologyChengdu 610059China State Key Laboratory of Oil and Gas Geology and Exploitation.Chengdu 610059 China Department of Geology University of ReginaReginaSaskatchewanS4S0A2.Canada South Exploration Company SINOPECChengdu 610041China

A scientific exploration well(CK1) was drilled to expand the oil/gas production in the western Sichuan depression, SW, China. Seventy-three core samples and four natural gas samples from the Middle–Late Triassic strata were analyzed to determine the paleo-depositional setting and the abundance of organic matter(OM) and to evaluate the hydrocarbon-generation process and potential. This information was then used to identify the origin of the natural gas. The OM is characterized by medium n-alkanes(n C15–n C19), low pristane/phytane and terrigenous aquatic ratios(TAR), a carbon preference index(CPI) of ~1, regular steranes with C29 > C27 > C28, gammacerane/C30 hopane ratios of 0.15–0.32, and δDorg of-132‰ to-58‰, suggesting a marine algal/phytoplankton source with terrestrial input deposited in a reducing–transitional saline/marine sedimentary environment. Based on the TOC, HI index, and chloroform bitumen "A" the algalrich dolomites of the Leikoupo Formation are fair–good source rocks;the grey limestones of the Maantang Formation are fair source rocks;and the shales of the Xiaotangzi Formation are moderately good source rocks. In addition, maceral and carbon isotopes indicate that the kerogen of the Leikoupo and Maantang formations is type Ⅱ and that of the Xiaotangzi Formation is type Ⅱ–Ⅲ. The maturity parameters and the hopane and sterane isomerization suggest that the OM was advanced mature and produced wet–dry gases. One-dimensional modeling of the thermal-burial history suggests that hydrocarbon-generation occurred at 220–60 Ma. The gas components and C–H–He–Ar–Ne isotopes indicate that the oilassociated gases were generated in the Leikoupo and Maantang formations, and then, they mixed with gases from the Xiaotangzi Formation, which were probably contributed by the underlying Permian marine source rocks. Therefore, the deeply-buried Middle–Late Triassic marine source rocks in the western Sichuan depression and in similar basins have a great significant hydrocarbon potential.

关键词： Middle to Late Triassic source rock characteristics hydrocarbon generation and potential origin of naturalgas western Sichuan depression

A preliminary study on an upper ocean heat and salt content of the western Pacific warm pool region

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Acta Oceanologica Sinica 2019年第3期38卷 60-71页

作者： Xiaoxin Yang Xiaofen Wu Zenghong Liu Chunxin Yuan State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography Ministry of Natural Resources Dalian Naval Academy People's Libration Army College of Oceanic and Atmospheric Sciences Ocean University of China

On the basis of Argo profile data of the temperature and salinity from January 2001 to July 2014, the spatial distributions of an upper ocean heat content(OHC) and ocean salt content(OSC) of the western Pacific warm pool(WPWP) region and their seasonal and interannual variations are studied by a cyclostationary empirical orthogonal function(CSEOF) decomposition, a maximum entropy spectral analysis, and a correlation analysis.Probable reasons for variations are discussed. The results show the following.(1) The OHC variations in the subsurface layer of the WPWP are much greater than those in the surface layer. On the contrary, the OSC variations are mainly in the surface layer, while the subsurface layer varies little.(2) Compared with the OSC, the OHC of the WPWP region is more affected by El Ni?o-Southern Oscillation(ENSO) events. The CSEOF analysis shows that the OHC pattern in mode 1 has strong interannual oscillation, with eastern and western parts opposite in phase. The distribution of the OSC has a positive-negative-positive tripole pattern. Time series analysis shows that the OHC has three phase adjustments with the occurrence of ENSO events after 2007, while the OSC only had one such adjustment during the same period. Further analysis indicates that the OHC variations are mainly caused by ENSO events, local winds, and zonal currents, whereas the OSC variations are caused by much more complex reasons. Two of these, the zonal current and a freshwater flux, have a positive feedback on the OSC change in the WPWP region.

关键词： ocean heat content salt content the western Pacific warm pool Argo data

Springtime Convective Quasi-Biweekly Oscillation and Interannual Variation of Its Intensity over the South China Sea and western North Pacific

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Journal of Meteorological Research 2019年第2期33卷 323-335页

作者： Zhiqing XU Ke FAN Huijun WANG Nansen–Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Climate Change Research Center Chinese Academy of Sciences University of the Chinese Academy of Sciences Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science &Technology

This study investigates characteristics of the convective quasi-biweekly oscillation(QBWO) over the South China Sea(SCS) and western North Pacific(WNP) in spring, and the interannual variation of its intensity. Convective QBWO over the WNP and SCS shows both similarities and differences. Convective QBWO over the WNP originates mainly from southeast of the Philippine Sea and propagates northwestward. In contrast, convective QBWO over the SCS can be traced mainly to east of the Philippines and features a westward propagation. Such a westward or northwestward propagation is probably related to n = 1 equatorial Rossby waves. During the evolution of convective QBWO over the WNP and SCS, the vertical motion and specific humidity exhibit a barotropic structure and the vertical relative vorticity shows a baroclinic structure in the troposphere. The dominant mode of interannual variation of convective QBWO intensity over the SCS–WNP region in spring is homogeneous. Its positive phase indicates enhanced convective QBWO intensity accompanied by local enhanced QBWO intensity of vertical motion throughout the troposphere as well as local enhanced(weakened) QBWO intensity of kinetic energy, vertical relative vorticity,and wind in the lower(upper) troposphere. The positive phase usually results from local increases of the background moisture and anomalous vertical shear of easterlies. The latter contributes to the relationship between the dominant mode and QBWO intensities of kinetic energy, vertical relative vorticity, and wind. Finally, a connection between the dominant mode and the sea surface temperature anomalies in the tropical Pacific Ocean is demonstrated.

关键词： convective quasi-biweekly oscillation interannual variation South China Sea western North Pacific spring

Aoyitake plagiogranite in western Tarim Block, NW China: Age, geochemistry, petrogenesis and its tectonic implications

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Science China Earth Sciences 2006年第11期49卷 1121-1134页

作者： ZHANG Chuanlin1,2, YU Haifeng3, YE Haimin2, ZHAO Yu2 & ZHANG Dongsheng4 1. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China 2. Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, China 3. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China 4. The 2nd Regional Geological Investigation Party, Xinjiang Bureau of Geology and Mineral Resources, Changji 831100, China Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Nanjing Institute of Geology and Mineral Resources Nanjing China Tianjin Institute of Geology and Mineral Resources Tianjin China The 2nd Regional Geological Investigation Party Xinjiang Bureau of Geology and Mineral Resources Changji China

SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block, NW China. The plagiogranite intruded the Middle Pro- terozoic and Lower Carboniferous with an exposure area of ca. 60 km2 and crystallized at 330.7±4.8 Ma. Rock types mainly include tonalite, trondhjemite and minor amounts of diorite and quartz-diorite. Feldspars in the rocks are dominated by oligoclase-andesine, and minor perthite observed locally. The granites are sodic with Na/K ratios (molar) between 4 and 87. Total REE (50-220 ppm) show a clear positive correlation with SiO2. There is no LRRE/HREE fractionation (LaN/YbN=0.5-1.5), me- dium negative Eu anomalies (δ Eu=0.3-0.6), high Y content and low Sr/Y ratio (~1.0). These granites exhibit relatively juvenile Nd T2DM model ages of 470 to 580 Ma and positive εNd(331 Ma) values of 6.23 to 7.65. The aforementioned characteristics are similar to those of ocean island or ocean ridge plagiogranites. However, the regional geology, especially its scale, precludes that the plagiogranite pluton was derived directly from fractionational crystallization of mantle-derived basaltic magma. We interpreted that the primary magma of the pluton might be tonalitic in composition generated by ca. 50% partial melting of the juvenile basaltic crust. The primary magma experienced intensive frac- tionational crystallization, and intruded into the middle to upper crusts to form the granite pluton. In combination with the previous regional geological data, it is concluded that the plagiogranite pluton was emplaced within the Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenic belt.

关键词： western Tarim, Aoyitake plagiogranite, age, geochemistry, tectonic implications.

Response of the western North Pacific subtropical ocean to the slow-moving super typhoon Nanmadol

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Journal of Oceanology and Limnology 2019年第3期37卷 938-956页

作者： YANG Bing HOU Yijun LI Min Institute of Oceanology Chinese Academy of SciencesQingdao 266071China Key Laboratory of Ocean Circulation and Waves Chinese Academy of SciencesQingdao 266071China Laboratory for Ocean and Climate Dynamics Qingdao National Laboratory for Marine Science and TechnologyQingdao 266237China Institute of Oceanographic Instrumentation Shandong Academy of SciencesQingdao 266001China

Based on in-situ observation,satellite and reanalysis data,responses of the western North Pacific subtropical ocean(WNPSO)to the slow-moving category 5 super typhoon Nanmadol in 2011 are analyzed.The dynamical response is dominated by near-inertial currents and Ekman currents with maximum amplitude of 0.39m/s and 0.15m/s,respectively.The near-inertial currents concentrated around 100m below the sea surface and had an e-folding timescale of 4 days.The near-inertial energy propagated both upward and downward,and the vertical phase speed and wavelength were estimated to be 5m/h and 175m,respectively.The frequency of the near-inertial currents was blue-shifted near the surface and redshifted in ocean interior which may relate to wave propagation and/or background vorticity.The resultant surface cooling reaches-4.35℃ and happens when translation speed of Nanmadol is smaller than 3.0m/s.When Nanmadol reaches super typhoon intensity,the cooling is less than 3.0℃ suggesting that the typhoon translation speed plays important roles as well as typhoon intensity in surface cooling.Upwelling induced by the slow-moving typhoon wind leads to typhoon track confined cooling area and the right-hand bias of cooling is slight.The mixed layer cooling and thermocline warming are induced by wind-generated upwelling and vertical entrainment.Vertical entrainment also led to mixed layer salinity increase and thermocline salinity decrease,however,mixed layer salinity decrease occurs at certain stations as well.Our results suggest that typhoon translation speed is a vital factor responsible for the oceanic thermohaline and dynamical responses,and the small Mach number(slow typhoon translation speed)facilitate development of Ekman current and upwelling.

关键词： oceanic response western North Pacific subtropical ocean South China Sea typhoon Nanmadol

Bacterial community in deep subseafloor sediments from the western Pacific "warm pool"

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Science China Earth Sciences 2008年第4期51卷 618-624页

作者： ZHAO Jing1 & ZENG RunYing2 1 College of Oceanography and Environmental Science, Xiamen University, Xiamen 361005, China 2 Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China College of Oceanography and Environmental Science Xiamen University Xiamen China Key Laboratory of Marine Biogenetic Resources Third Institute of Oceanography State Oceanic Administration Xiamen China

The bacterial community in deep subseafloor sediments at a depth of 230 cm from the western Pacific "warm pool" is studied by construction of 16S rDNA clone library and PCR-RFLP (Restriction Fragment Length Polymorphism) analysis. The results indicate that the bacterial community in these sediments is mainly composed of five groups: α-Proteobacteria, β-Proteobacteria, CFB group (Cytophaga / Flexi-bacteria / Bacteroides), Acidobacteria and gram positive bacteria, with a few genera detected in each group. The most abundant bacteria group is α-Proteobacteria, and the next is β-Proteobacteria. The dominant species in α-and β-Proteobacteria are Sphingomonas paucimobilis and Pseudomonas alca-ligenes respectively. The CFB group is simply composed of members belonging to Flavobacterium. The gram positive bacteria are rich, and mainly consists of the genus Geobacillus. The analysis of bacterial community indicates that organic matter is still abundant in the subseafloor sediments at the depth of 230 cm in the western Pacific "warm pool" . These bacteria in this deep biosphere may play an impor-tant role in the nitrogen cycle of deep sea sediments at "warm pool" .

关键词： western Pacific 'warm pool' deep subseafloor sediment bacterial community

Record of Early-Stage Rodingitization from the Purang Ophiolite Complex,western Tibet

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Journal of Earth Science 2019年第6期30卷 1108-1124页

作者： Songjie Wang Xu-Ping Li Wenyong Duan Fanmei Kong Zeli Wang Shandong Key Laboratory of Depositional Mineralization and Sedimentary Minerals Shandong University of Science and Technology

Rodingitization,commonly coupled with serpentinization of ultramafic rocks,bears significant information for fluid-rock interactions and element transfer from sea-floor to subduction zone environments.Numerous outcrops of rodingites are exposed along the Yarlung Zangbo suture zone(YZSZ)of southern Tibet,providing us an excellent opportunity to probe the petrogenetic processes,and unravel their implications for regional tectonic evolution.Several studies have been performed on rodingites from the eastern to central portions of the YZSZ,whereas limited work has ever been conducted on rodingitized rocks from the western segment of the YZSZ,precluding a comprehensive understanding of this lithological type.In this paper,we present detailed studies of petrology,mineral,whole-rock geochemistry and phase equilibrium modeling on a suite of newly recognized rodingites within the Purang ophiolite massif in the southwestern part of the YZSZ.The rodingites have a major metasomatic mineral association of chlorite,clinozoisite,amphibole and minor amounts of plagioclase,representing products of an early-stage rodingitization.They generally present compositions of low SiO2(48.89 wt.%–53.57 wt.%),Fe2O3^T(3.77 wt.%–5.56 wt.%),Na2O(1.31 wt.%–1.93 wt.%),Al2O3(4.78 wt.%–8.84 wt.%),moderate CaO(9.69 wt.%–11.23 wt.%),and high MgO(24.11 wt.%–26.08 wt.%)concentrations with extremely high Mg^# values[Mg^#=100×Mg/(Mg+Fe^2+)molar]of 89–92.Bulk-rock recalculation reveals that the rodingites have a protolith of mantle-derived olivine gabbro or gabbronorite.They have low rare earth element compositions(∑REE=2.4 ppm–6.5 ppm)and are characterized by flat LREE and slightly enriched HREE patterns with positive Eu anomalies;they also exhibit positive anomalies in Sr,U and Pb and negative anomalies in high-field strength elements,including Nb,P and Ti,suggesting for a subduction-zone imprinting.Phase equilibrium modeling shows that the rodingitization did take place at P<2 kbar and T=~350–400℃,consistent with low greenschist facies conditions.Taking

关键词： Purang ophiolite complex early-stage rodingitization geochemistry phase equilibrium modeling western Tibet

Influence of atmospheric heat sources over the Tibetan Plateau and the tropical western North Pacific on the inter-decadal variations of the stratosphere-troposphere exchange of water vapor

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Science China Earth Sciences 2008年第8期51卷 1179-1193页

作者： ZHAN RuiFen1,2&LI JianPing2 1Shanghai Typhoon Institute of China Meteorological Administration,Shanghai 200030,China 2State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China Shanghai Typhoon Institute of China Meteorological Administration Shanghai China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

This study investigates the Stratosphere-Troposphere Exchange(STE) of water vapor,emphasizes its interdecadal variations over Asia in boreal summer,and discusses the influences of atmospheric heat sources over the Tibetan Plateau and the tropical western North Pacific(WNP) on them by using the Wei method with reanalysis data from the European Centre for Medium-Range Weather Forecasts(ECMWF) for the years of 1958-2001.The climatology shows that the upward transport of water vapor across the tropopause in boreal summer is the most robust over the joining area of the South Asian Peninsula and Indian-Pacific Oceans(defined as AIPO).The upward transport over there can persistently convey the abundant water vapor into the stratosphere and then influence the distribution and variation of the stratospheric water vapor.The analysis shows that interdecadal variations of the water vapor exchange over the AIPO are significant,and its abrupt change occurred in the mid-1970s and the early 1990s.In these three periods,as important channels of the water vapor exchange,the effect of Bay of Bengal-East Asia as well as South China Sea was gradually weakening,while the role of the WNP becomes more and more important.Further studies show that atmospheric heat sources over the Tibetan Plateau and the WNP are two main factors in determining the interdecadal variations of water vapor exchange.The thermal influences over the Tibetan Plateau and the WNP have been greatly adjusted over the pass 44 years.Their synthesis influences the interdecadal variations of the water vapor exchange by changing the Asian summer monsoon,but their roles vary with time and regions.Especially after 1992,the influence of heat source over the Tibetan Plateau remarkably weakens,while the heat source over the WNP dominates the across-tropopause water vapor exchange.Results have important implications for understanding the transport of other components in the atmosphere and estimating the impact of human activities(emission) on global climate.

关键词： Tibetan Plateau tropical western North Pacific atmospheric heat source STE inter-decadal variations

Redox evolution of western Tianshan subduction zone and its effect on deep carbon cycle

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Geoscience Frontiers 2020年第3期11卷 915-924页

作者： Renbiao Tao Lijuan Zhang Lifei Zhang The MOE Key Laboratory of Orogenic Belt and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China Univ Lyon Ens de LyonUniversite Lyon 1CNRSUMR 5276 LGL-TPEF-69622VilleurbanneFrance

Knowing the phase relations of carbon-bearing phases at high-pressure(HP) and high-temperature(HT) condition is essential for understanding the deep carbon cycle in the subduction zones.In particular,the phase relation of carbon-bearing phases is also strongly influenced by redox condition of subduction zones,which is poorly explored.Here we summarized the phase relations of carbon-bearing phases(calcite,aragonite,dolomite,magnesite,graphite,hydrocarbon) in HP metamorphic rocks(marble,metapelite,eclogite) from the western Tianshan subduction zone and high-pressure experiments.During prograde progress of subduction,carbonates in altered oceanic crust change from Ca-carbonate(calcite) to Ca,Mg-carbonate(dolomite),then finally to Mgcarbonate(magnesite) via Mg-Ca cation exchange reaction between silicate and carbonate,while calcite in sedimentary calcareous ooze on oceanic crust directly transfers to high-pressure aragonite in marble or amorphous CaCO3 in subduction zones.Redox evolution also plays a significant effect on the carbon speciation in the western Tianshan subduction zone.The prograde oxygen fugacity of the western Tianshan subduction zone was constrained by mineral assemblage of garnet-omphacite from FMQ-1.9 to FMQ-2.5 at its metamorphic peak(maximum P-T) conditions.In comparison with redox conditions of other subduction zones,western Tianshan has the lowest oxygen fugacity.Graphite and light hydrocarbon inclusions were ubiqutously identified in western Tianshan HP metamorphic rocks and speculated to be formed from reduction of Fe-carbonate at low redox condition,which is also confirmed by high-pressure experimental simulation.Based on petrological observation and high-pressure simulation,a polarized redox model of reducing slab but oxidizing mantle wedge in subduction zone is proposed,and its effect on deep carbon cycle in subduction zones is further discussed.

关键词： Oxygen fugacity western Tianshan Subduction zone Deep carbon cycle Polarized redox model