Institutional Repository of South China Sea Institute of Oceanology, CAS
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Mesozoic Deformation and Its Geological Significance in the Southern Margin of the South China Sea
No full textThe pre-Eocene history of the region around the present South China Sea is not well known. New multi-channel seismic profiles provide valuable insights into the probable Mesozoic history of this region. Detailed structural and stratigraphic interpretations of the multi-channel seismic profiles, calibrated with relevant drilling and dredging data, show major Mesozoic structural features. A structural restoration was done to remove the Cenozoic tectonic influence and calculate the Mesozoic tectonic compression ratios. The results indicate that two groups of compressive stress with diametrically opposite orientations, S(S)E-N(N)W and N(N)W-S(S)E, were active during the Mesozoic. The compression ratio values gradually decrease from north to south and from west to east in each stress orientation. The phenomena may be related to the opening of the proto-South China Sea (then located in south of the Nansha block) and the rate at which the Nansha block drifted northward in the late Jurassic to late Cretaceous. The Nansha block drifted northward until it collided and sutured with the southern China margin. The opening of the present South China Sea may be related to this suture zone, which was a tectonic zone of weakness
Ar-40/Ar-39 dating of oceanic plagiogranite: Constraints on the initiation of seafloor spreading in the South China Sea
No full textThe Cenozoic opening of the South China Sea was one of the most significant tectonic events in SE Asia, coinciding with complex regional rifting, subduction, terrane collision, and large-scale continental strike-slip faulting. The timing of the initiation of seafloor spreading in the South China Sea remains controversial due to a scarcity of incontrovertible age data. This work provides the first report of an oceanic plagiogranite from the Penglai Sea-mount, located on the 17 degrees N fossil spreading center of the East Sub-basin of the South China Sea, near the Manila Trench. Pyroxene and whole-rock Ar-40/Ar-39 dating yields ages of 32.3 +/- 0.5 Ma and 28.9 +/- 1.9 Ma, respectively. The plagiogranite show trace element and isotopic composition similar to those of mid-oceanic ridge basalts (MORB), with Sr-87/Sr-86(t) = 0.70394; epsilon(Nd)(t) = 8.21; (206)pb/(204)pb = 17.9930, (207)pb/(204)pb = 15.4839, Pb-208/Pb-204 = 37.8852; epsilon(Hf)(t) = 20.95; and gamma(Os)(t) = 15.89. It suggested that the rock formed due to differential cooling between adjacent layers of oceanic crust and asthenospheric shearing at the oceanic spreading ridge, resulting in the development of detachment faults. This triggered the subsequent ingress of seawater along the faults, which transformed into a hydrothermal fluid under the influence of shear and geothermal heating, altering the parent gabbro, and leading to the generation of the daughter plagiogranite by anatexis during the early Oligocene. This new geochronology also demonstrates that the initial opening of the South China Sea occurred before 32 Ma, thereby constraining the Cenozoic tectonic evolution of Southeast Asia. (C) 2018 Elsevier B.V. All rights reserved
Timing of the late Jehol Biota: New geochronometric constraints from the Jixi Basin, NE China
No full textThe Jehol Biota is a world-famous Early Cretaceous terrestrial ecosystem in East Asia and has revealed exceptionally well preserved fossils which provide significant insights into the origin and evolution of birds and feathers, and the early diversifications of mammals and angiosperms. After the long-lived controversies over the timing of the biota varying from Late Jurassic to Early Cretaceous in last century, the lifespan of the early-middle Jehol Biota has been precisely dated from Barremian to early Aptian (ca. 131-120 Ma) by a series of recent radiometric analyses. However, few well constrained ages are available for the late Jehol Biota, hindering our complete understanding of the evolutionary history of the terrestrial ecosystem. Alternating marine and non marine deposits of the Chengzihe Formation in eastern Heilongjiang have yielded a non-marine bivalve assemblage of the Jehol Biota, basal angiosperms, and Cretaceous marine index bivalves, which collectively offer crucial and indisputable clues against the prevailing Jurassic time of the biota since 1990s. Here we present the first discovery of tephra layers from the Chengzihe Formation, dated by zircon U-Pb geochronology as ca. 116-111 Ma, providing the first quantitative age calibration for the early angiosperms and the Jehol bivalve assemblage. Therefore, we demonstrate that the duration of the Jehol Biota extends to late Aptian-early Albian, approximately 4-9 Myr younger than the currently accepted age limits
Chemical compositions and precipitation timing of basement calcium carbonate veins from the South China Sea
No full textSixteen calcium carbonate veins (CCVs) within the igneous basement recovered from both East and Southwest Sub-basin, close to the fossil spreading ridge of the South China Sea during the Integrated Ocean Drilling Program (IODP) Expedition 349 were investigated. The CCVs are composed primarily of either calcite or aragonite, and some of mixed aragonite and calcite. The delta O-18 values of CCVs range from 25.5 to 31.8%o VSMOW, indicating these are typical low temperature basement carbonates precipitated at temperatures of 12-40 degrees C. The Sr-87/Sr-86 ratios of CCVs from Site U1431 show a strong negative correlation with delta O-18-calculated temperatures, regardless of carbonate phases calcite or aragonite, indicating CCVs with lower Sr-87/Sr-86 ratios have precipitated from moderately warmer and more geochemically evolved hydrothermal fluids, and reflecting that precipitation of CCVs might have occurred any time between 14.5 and 0 Ma at Site U1431. The formation timing of CCVs at Site U1431 is consistent with the ongoing hydrothermal flow and circulation led by recharging seawater into the volcanic basement through the nearby outcropped seamount. The oldest ages of CCVs from Site U1433 at the Southwestern sub-basin of SCS were determined to be similar to 18-11 Ma, based on basement age of 18.5 Ma and the well-established seawater Sr-87/Sr-86 ratio curve. It indicates that the hydrothermal circulation at Site U1433 which is more distal to a recharging/discharging site was only active until similar to 11 Ma. In consequence, the CCVs within basalts from Sites U1431 and U1433 provide more insights into the past hydrologic conditions and hydrothermal circulation along the fossil ridge flank in the SCS
深海来源微生物乙酰酯酶的酶学性质鉴定及拆分制备D-乳酸甲酯
No full textD-乳酸及其酯是重要的手性药物中间体和手性化工产品。从南海深海芽孢杆菌Bacillus sp.SCSIO15029克隆到一个乙酰酯酶基因bae02030,表达并鉴定该酶Bae02030的酶学性质。该酯酶的最适p H和最适温度分别为8.5和35℃,其对多种有机溶剂和表面活性剂具有较好的耐受性。乙酰酯酶Bae02030能够通过水解拆分消旋乳酸甲酯来制备光学纯的D-乳酸甲酯。通过对拆分反应进行优化,添加体积分数为60%的正庚烷能够改善乙酰酯酶Bae02030的光学选择性,所制备的D-乳酸甲酯的对映体过量值(e.e.s)超过99%,转化率(c)为56%。深海微生物来源的乙酰酯酶Bae02030作为生物催化剂在工业上制备手性药物中间体具有较好的应用潜力
酶催化功能混杂性研究进展
No full text酶催化生物体内化学反应,是生命代谢形成运转的动力。与传统观点认为酶具有专一性催化功能相对,近年来生物信息与实验分析都证实了酶具有多种混杂催化功能是普遍存在的现象。在过去的几十亿年里,古老酶一直不断演化以适应变化的环境,形成现代功能多样的酶蛋白家族。基于独特底物结合模式和动态蛋白结构的催化功能混杂性是酶蛋白适应性演化的基础。酶的混杂活性有望被开发应用于药物酶法合成及环境修复领域。本文就酶催化功能混杂性的普遍性、分子机理、可进化性等方面的相关研究进展进行综述
南海4个花刺参地理群体的遗传多样性研究
No full text在我国南海涠洲岛、临高、琼海和三亚4个地区采集野生花刺参。利用线粒体cox1对这4个花刺参群体83个个体的遗传多样性进行分析,共检测到34个多态位点和23个单倍型。4个群体的核苷酸多样性为0.00128~0.01684,单倍型多样性为0.30719~0.96190。Tajima′s D检验的结果显示,涠洲岛、三亚和琼海群体符合中性进化模型。4个群体的邻接结果显示,涠洲岛先与临高群体聚集在一起,再与三亚聚集,最后与琼海聚集。临高群体和涠洲岛群体之间,三亚群体和琼海群体之间不存在遗传分化,其余群体间有不同程度的遗传分化。4个群体间均存在一定程度的基因流。群体间未形成完全隔阂的地理群体。分子方差分析显示,群体内个体间的遗传变异占87.20%,群体间的遗传变异占12.80%。从单倍型邻接树和单倍型网络关系图中未发现有地理谱系结构的单倍型
大亚湾夏季和冬季超微型浮游生物的时空分布及环境调控
No full text通过流式细胞法,于2015年夏季(7月)和冬季(12月)对大亚湾超微型浮游生物(聚球藻、超微型真核藻类和异养细菌)的时空变化及环境调控进行了比较研究。结果表明,夏季聚球藻、超微型真核藻类和异养细菌的丰度分别为(44.56±46.26)×10~3 cells·m L~(–1)、(3.00±4.50)×10~3 cells·m L~(–1)和(12.31±7.54)×10~5 cells·m L~(–1),冬季的丰度分别为(12.48±3.96)×10~3 cells·m L~(–1)、(0.78±0.71)×10~3 cells·m L~(–1)和(3.83±1.39)×10~5 cells·m L~(–1)。超微型浮游生物的丰度呈现为夏季高于冬季,受到温度、溶解无机氮组成和透明度的影响。夏季表层丰度明显高于底层,但冬季表底层无明显差异。在水平分布上,夏季湾内高营养盐基本对应高丰度,但石化区附近(S3站)营养盐高丰度却较低,范和港(S1站)低营养盐丰度却较高;湾口和湾外区主要受到外海水的影响,超微型浮游生物的3个类群丰度均较低。在沿岸流、海水垂直混合、外源营养盐输入等多个因素共同影响下,冬季湾中部和大鹏澳附近的聚球藻丰度较高,超微型真核藻类在湾口和范和港丰度较高,异养细菌在湾内和湾西部丰度较高。两个季节超微型真核藻类和异养细菌呈显著正相关
创伤弧菌TF3全基因组包含的CRISPR-Cas系统及MGIVvuTF3基因岛分析
No full text【目的】分析创伤弧菌(Vibrio vulnificus)全基因组框架序列,挖掘感兴趣的遗传位点,探索其是否具有CRISPR系统及其特征。【方法】在病虾体内分离获得了一株创伤弧菌TF3,通过Illumina Miseq测序得到基因组框架序列。经注释分析发现其基因组中存在一个CRISPR-Cas系统,命名为CRISPR-CasTF3,进一步分析发现CRISPR-CasTF3位于一个基因岛上,将该基因岛命名为MGIVvu TF3。对CRISPR-CasTF3及MGIVvu TF3的特征和来源进行了分析。【结果】CRISPR-CasTF3属于与大肠杆菌类似的Ι-E型CRISPR-Cas系统,CRISPR-CasTF3包括8个cas基因,其排列为cas3-cas8e-cse2-cas6-cas7-cas5-cas1-cas2;具有50个重复序列,每二个重复序列间为一个Spacer序列。MGIVvu TF3具有att L和att R序列,含有位点特异性整合、剪切、转移相关的基因。MGIVvu TF3与霍乱弧菌O395基因组中的一个基因岛MGIVch0395具较高相似性,二者最显著的差别在于Spacer序列完全不同,以及各有几个非保守的预测基因。【结论】MGIVvu TF3及CRISPR-CasTF3极有可能通过基因水平转移获得,并且CRISPR-CasTF3系统可以借助MGIVvu TF3实现水平转移
Utilization of deep-sea microbial esterase PHE21 to generate chiral sec-butyl acetate through kinetic resolutions
No full textWe previously identified and characterized 1 novel deep-sea microbial esterase PHE21 and used PHE21 as a green biocatalyst to generate chiral ethyl (S)-3-hydroxybutyrate, 1 key chiral chemical, with high enantiomeric excess and yield through kinetic resolution. Herein, we further explored the potential of esterase PHE21 in the enantioselective preparation of secondary butanol, which was hard to be resolved by lipases/esterases. Despite the fact that chiral secondary butanols and their ester derivatives were hard to prepare, esterase PHE21 was used as a green biocatalyst in the generation of (S)-sec-butyl acetate through hydrolytic reactions and the enantiomeric excess, and the conversion of (S)-sec-butyl acetate reached 98% and 52%, respectively, after process optimization. Esterase PHE21 was also used to generate (R)-sec-butyl acetate through asymmetric transesterification reactions, and the enantiomeric excess and conversion of (R)-sec-butyl acetate reached 64% and 43%, respectively, after process optimization. Deep-sea microbial esterase PHE21 was characterized to be a useful biocatalyst in the kinetic resolution of secondary butanol and other valuable chiral secondary alcohols