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Effect of Overpressure on Rock Frame and Its Implications for Overpressure Evolution

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Journal of China University of Geosciences 2007年第3期18卷 232-241页

作者：石万忠徐辉龙何生陈红汉 Faculty of Earth Resources China University of Geosciences cas key laboratory of marginal sea geology South China Sea Institute of Oceanology

Overpressure is a hot topic in the study of sedimentary basins. It is important in generation, maturation migration, and accumulation of hydrocarbon, but the effects of overpressure on rock frame have not been investigated. In this study, experiments were carried out to study the effects of overpressure on rock frame structures using five core samples from the Junggar basin, Northwest China. The deformations and velocities for the samples were measured at different effective pressures related to non-equilibrium compaction and fluid expansion overpressure mechanisms. The results show that the effect of overpressure on rock frames gradually increases when the effective pressure drops down to a certain value （called critical pressure）. Moreover, non-equilibrium compaction mechanism has more effects on rock frames than fluid expansion mechanism under the same effective pressure. Furthermore to study rock frame structural changes, we use Kuster and Toksoz＇s expressions to simulate the effective aspect ratios of inclusions a （penny shapes） for different effective pressures. The results show that the a decreases dramatically when the effective pressure decreases from the critical pressure. Changes of a can be interpreted as responses to the rock frame changes when grains conform one another by rotating and self-adjusting. However, different mechanisms of overpressure have different effects on rock frames. The rock frame can be affected more easily by overpressure in shallow regions generated by non-equilibrium compaction mechanism. Once this kind of rock frames are preserved after overpressure releases to a normal hydrostatic pressure, they can be identified by their specific rock frame characters. This method provides a new way to study overpressure release and fluid migration and accumulation.

关键词： overpressure rock frame grain structure experimental measurement overpressure evolution

Detection and indication of 1,3,4-C27-29 triol in the sediment of northern South China sea

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Science China Earth Sciences 2016年第6期59卷 1187-1194页

作者： ZHU XiaoWei MAO ShengYi WU NengYou JIA GuoDong SUN YongGe GUAN HongXiang WU DaiDai key laboratory of marginal sea geology South China Sea Institute of OceanologyCASGuangzhou 510301China key laboratory of marginal sea geology Guangzhou Institute of GeochemistryCASGuangzhou 510640China key laboratory of Gas Hydrate Guangzhou Institute of Energy ConversionCASGuangzhou 510640China Department ofGeosciences Zhejiang UniversityHangzhou 310037China Guangzhou Center for Gas Hydrate Research CASGuangzhou 510640China

After the detection of the 1,20,21-C29 long-chain triol in some sediments and freshwater pteridophytes, in this study a new homologous long-chain triol, 1,3,4-C27-29, is detected for the first time in the Site4B core sediment in the northern South China sea. The hydroxyl location and length of the carbon chain of this newly discovered triol differ from those of 1,20,21-C29 triol. The test results of its molecular distribution and individual carbon isotope reveal that 1,3,4-C29triol has a good correlation with n-C26-30 even carbon-numbered long-chain fatty alcohols, with R2 （n=68） values of 0.905, 0.929 and 0.903, respectively, and its carbon isotope composition, at -32.3%o_1.9%o, is similar to that of rt-C26.30, at -29.13%o^0.87%o, -32.98%o^1.28%o, and -32.98%o^1.28%o. 1,3,4-C29 triol from the Site4B core sediment and terrigenous long-chain fatty alcohol （n-C26.34） show highly consistent distribution trends in the entire section; thus, the former could serve as a proxy indicator of the terrigenous input. Considering that the 1,20,21-C29 triol in previous research belongs to Azolla, which are fresh water pteridophytes, the 1,3,4-C27-29 triol identified in this study might have similar biogenetic derivation. Thus, determination of its biogenic area and growing environment could provide potential organic geochemical evidence supporting the terrigenous input and source in the northern South China sea.

关键词： Long-chain triol Northern South China sea Terrigenous input

Assessment of coral bleaching using symbiotic zooxanthellae density and satellite remote sensing data in the Nansha Islands,South China sea

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Chinese Science Bulletin 2011年第10期56卷 1031-1037页

作者： LI Shu,YU KeFu,CHEN TianRan,SHI Qi & ZHANG HuiLing cas key laboratory of marginal sea geology,South China sea Institute of Oceanology,Chinese Academy of Sciences Guangzhou 510301,China cas key laboratory of marginal sea geology South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou China

Coral bleaching,characterized by a significant loss of symbiotic zooxanthellae,is the primary cause of mass coral mortality and reef degradation throughout the *** characteristics,processes,and resistance of corals to bleaching varies significantly and is dependent on environmental *** documented a mass coral bleaching event in June 2007 at the Meiji and Zhubi Reefs,Nansha Islands (NS),South China sea using ecological surveys and measurement of coral zooxanthellae density and sea surface temperatures (SST).More than 35 species of corals (between 0-20 m in depth) were *** bleached corals accounted for 15.6% of total corals in the investigated *** branching corals Pocillopora and Acropora were the most vulnerable species whereas the massive corals Porites and Favia were more tolerant of the high ***,we found no evidence of bleaching in Agariciidae corals suggesting that this family is resistant to thermal *** bleached corals had lost 72%-90% of their symbiotic ***,corals that had no visual signs of bleaching had also lost 31%-53% of their zooxanthellae suggesting that most corals were experiencing the early stage of *** monthly mean SST during June 2007 was 30.8°C,the highest since *** on measurements of SST and the Hotspots and DHW data (NOAA),we conclude that it the extremely high SSTs triggered this coral bleaching *** results suggest that the previously accepted temperature thresholds used to predict coral bleaching based on satellite data are likely to underestimate the extent and intensity of coral bleaching,at least in the NS.

关键词：珊瑚礁南沙群岛中国南海卫星遥感数据漂白黄藻密度共生

Propagating subduction initiation of the Caroline Plate at the Mussau Trench

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Science China Earth Sciences 2025年第1期 253-269页

作者： Chun-Feng LI Yongkang DENG Tao WU Dongdong DONG Guoliang ZHANG Jiazheng ZHANG Yutao LIU Yaqing LI Fugui TANG Lulu ZHANG Department of Marine Sciences Zhejiang University laboratory of Marine Mineral Resources Laoshan Laboratory key Lab of Marine geology and Environment Institute of Oceanology Chinese Academy of Sciences key Lab of Ocean and marginal sea geology South China Sea Institute of Oceanology Chinese Academy of Sciences Science & Technology on Integrated Information System Lab Institute of Software Chinese Academy of Sciences

New seismic imaging from the Mussau Trench confirms that, under horizontal compression on an oceanic plate boundary, it is within the young and weak oceanic plate that a trench will develop, and it is the young plate, not so long after its birth, that starts to subduct toward the old plate. The Mesozoic Pacific Plate cannot easily bend, under the joint horizontal compression and vertical gravity pull, even with a pre-existing weak zone in place and with a large age offset across the plate boundary. The bending of the Caroline Plate near the northern end of the Mussau Trench started only after a long-time span of trench migration, and/or after a prolonged transition from initial compression to trench development. Highly contrasting trench deformation and sedimentary accretion between two parallel seismic sections support an evident migration of underthrusting or significant longitudinal heterogeneity along the trench. The swift transition from underthrusting to non-thrusting can be explained by a counter-clockwise rotation of the Caroline Plate. That miniature accretionary wedges develop even before the subduction initiates imply strong compression and uplifting before the underthrusting can kick-start. Rotation of the Caroline Plate have been halted as the Mussau Trench is seismically rather quiet and the Lyra Trough to the east shows relaxational extension.

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Organic Matters and Lipid Biomarkers in Surface Sediments from the Northern South China sea:Origins and Transport

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Journal of Earth Science 2014年第1期25卷 189-196页

作者： Weihai Xu Wen Yan Zhong Chen Han Chen Weixia Huang Tian Lin cas key laboratory of marginal sea geology South China Sea Institute of OceanologyChinese Academy of Sciences Institute of Geochemistry Chinese Academy of Sciences

In this study, content and distribution of organic matters （OM） and lipid biomarkers in surface sediments from northern South China sea （SCS） were identified to reveal the sources and transport of fine-grained sediments. Organic matters and lipid biomarkers exhibited distinct spatial variation in northern SCS. Terrestrial discharge from the Pearl River and some mountainous rivers in southwestern Taiwan may contribute to the relatively high organic matters in the corresponding sea areas. The detection of unsaturated fatty acid homologues suggested the algal and/or bacterial OM contribution to surface sediments. The composites and distribution of lipid biomarkers indicate their mixed sources from terrestrial plants, marine algae and bacterial. Together with the proof of clay min- eral composites in the sediments, the results suggested that the currents, including the Guangdong Coastal Current and Kuroshio Current, control the transport and distribution of terrestrial sediment and the sedimentary environment in the northern SCS.

关键词： surface sediment lipid biomarker South China sea sedimentation transport.

Structural Geochemical Study of the Yuxi Fold-Thrust Belt in the Southern North China Plate

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Journal of China University of Geosciences 2006年第2期17卷 95-102页

作者：李文勇夏斌李东旭 School of Earth Sciences and Resources China University of Geosciences cas key laboratory of marginal sea geology Guangzhou Institute of Geochemistry

The Yuxi （豫西） fold-thrust fracture belt is part of the gigantic fold-thrust fracture belt that extends NW in the southern North China plate. The contents of major elements of tectonites were analyzed by ICP-AES. The analysis of chemical compositions and new stress minerals indicates： extending from the surrounding country rocks to the center of the fracture belt, the Fe2O3 content gradually increases while the FeO content gradually decreases; regular increase, decrease or peak changes are shown for chemical compositions like SiO2, Al2O3, Fe2O3, MgO, CaO, FeO, loss on ignition, TIO：, K2O, Na2 O, etc.. New stress minerals are developed for the south branch and few for the north branch. The characteristics of chemical compositions and new stress minerals of the thrust fracture demonstrate that the fracture belt has undergone a process from a closed reducing environmental system to a relatively open. oxidizing environmental system, andcompressive fractures have resulted from compression in the late stages of evolution, and the dynamothermal metamorphism and thrusting intensities are different between the south and north branches of the belt, which is strong for the south branch but relatively weak for the north branch.

关键词： structural geochemistry thrust fracture belt Yuxi southern North China plate.

Clay mineral distribution in surface sediments of the South China sea and its significance for in sediment sources and transport

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Chinese Journal of Oceanology and Limnology 2010年第2期28卷 407-415页

作者：刘建国陈木宏陈忠颜文 key laboratory of marginal sea geology South China Sea Institute of Oceanology Chinese Academy of Sciences

Clay minerals of surface sediments in the South China sea （SCS） are analyzed with X-ray diffraction, and their transport is explored with a grain size trend analysis （GSTA） model. Results show that clay mineral types in various sedimentary environments have different sediment sources and transport routes. Sediments in the northern SCS （north of 20°N） between the southwest of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly from sediments on Taiwan Island and/or the Yangtze River. Sediments from the Pearl River are characterized by high kaolinite and low smectite content, and most are distributed in the area between the mouth of the Pearl River and northeast of Hainan Island and transported vertically from the continental shelf to the slope. Characterized by high illite content, sediments from Kalimantan Island are transported toward the Nansha Trough. Sediments from Luzon Island are related with volcanic materials, and are transported westwards according to smectite distribution. On the Sunda Shelf, sediments from the Mekong River are transported southeast in the north while sediments from the Indonesian islands are transported northward in the south. Ascertaining surface sediment sources and their transport routes will not only improve understanding of modem transportation and depositional processes, but also aid paleoenvironmental and paleoclimatic analysis of the SCS.

关键词： clay minerals surface sediments sediment sources South China sea sediment transport

Cold tolerance of subtropical Porites lutea from the northern South China sea

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Acta Oceanologica Sinica 2016年第12期35卷 58-64页

作者： CHEN Tianran LI Shu SHI Qi CHEN Tegu key laboratory of marginal sea geology South China Sea Institute of OceanologyChinese Academy of Sciences

marginal scleractinian corals growing at their latitudinal limits should be quite sensitive to variations in winter sea surface temperatures(SSTs). An extreme cold event occurring in early 2008 offered a unique opportunity to examine the effect of cold-water anomalies on Porites lutea corals and their physiological tolerance and acclimation in the subtropical northern South China sea(NSCS). Besides in-situ observation, a subsequent aquarium-based experiment was designed for reproducing the chilling process and a 50-year-long Sr/Ca ratio profile from two P. lutea skeletal slabs was analyzed for reconstructed the historical annual minimum SSTs which ceased Porites calcification. The 2008 low-temperature anomaly caused the minimum daily mean SSTs dropped below 13°C in the Daya Bay. The stress symptoms displayed by local P. lutea colonies included polyp retraction, reduced coloration and pale, but none showed tissue sloughing. The ability of P. lutea to survive implied its tolerance of extreme low temperatures. Here we suggest a model on the tolerance of high-latitude Porites under low-temperature stresses, which is when SSTs drop below 18°C, Porites corals contract their tentacles(losing heterotrophic capability), then cease calcification(reducing energy consumption), and meanwhile maintain relatively high levels of zooxanthellae density(sustaining host’s life via photosynthetic capacity of symbiotic zooxanthellae). This study revealed remarkable acclimatization of P. lutea corals to low temperature extremes. This acclimatization is beneficial for Porites corals in the NSCS to expand their living ranges towards the higher-latitude areas and have the potential to be the incipient reef former.

关键词： low-temperature stress cold tolerance subtropical coral Porites lutea northern South China sea

Crustal activities recorded incoral reefs in the northwestern South China sea

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Chinese Science Bulletin 2006年第B12期51卷 89-94页

作者： ZHAN Wenhuan YAO Yantao ZHANG Zhiqiang SUN Zongxun ZHAN Meizhen SUN Longtao LIU Zaifeng cas key laboratory of marginal sea geology South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China

Coral reefs in the northwest of South China sea have recorded the information from not only the environmental variation but also the crustal activities there during their development. The main crustal activities correlated with the coral reef development include fault, seismic, and volcano activities, etc. The high-resolution spark seismic profiles in the northwestern South China sea show that the fault activities in the coral reef region have been clearly recorded, and appear as neonatal faults incising reefs. Earthquakes in the coral reef region are rather intense, especially the two occurring on December, 31, 1994, and January, 10, 1995, around the southwest of Leizhou Peninsula, with the magnitude of 6.1 and 6.2, respectively. They have great influence on the growth of the local coral reefs. Quaternary volcanos are active in the northwestern South China sea, especially around the southwest of Leizhou Peninsula, and they have obvious control of the coral reef development. Some submarine volcanoes form the substrates of coral reef, while a few emerge above the sea surface and form coral islands.

关键词：南海西北部海域珊瑚礁外壳活动性环境变化