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Geochemical characteristics of major and trace elements in the Okinawa Trough basaltic glass
Kun GUO, Shikui ZHAI, Zenghui YU, Zhigang ZENG, Xiaoyuan WANG, Xuebo YIN
2018, 37(2): 14-24. doi: 10.1007/s13131-017-1075-2
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The Okinawa Trough (OT) is a back-arc basin at an initial spreading stage that is under the influence of subduction of the Philippine Sea Plate. In this study, we analyzed the geochemical compositions of basaltic glass in the OT and discussed the effects of different magmatic sources, evolution, and subducted components in basalts. Our results showed that the middle and southern regions of the OT exhibit characteristics consistent with an iron-rich tholeiite series. Trace element proportions conform to the typical spider diagram pattern characteristic of back-arc basin basalts, rich in large ion lithophile elements (LILEs) including Rb, Ba, Pb, U, and Th, while depleted in high field-strength elements (HFSEs) including Nb, Ta, Zr, Hf, and Ti. The distribution of rare earth elements (REEs) is also consistent with enrichment by right-leaning light rare earth elements (LREEs). The addition of enriched mantle type I (EMI) materials as well as mantle heterogeneity may have led to variable degrees of enrichment in different regions. The magma source of the middle trough has undergone crystallization towards pyroxene, while development of plagioclase was restricted partly, and the crystallization of spinel and olivine ceased altogether. At the same time, crystallization of the southern OT magma source was dominated by olivine and including the formation of plagioclase, pyroxene, and magnetite (or titanomagnetite). Finally, the results of this study showed that 90% Th, 95% Ba in the southern basalt, 50%–70% Th and 70%–90% Ba in the middle basalt originated from subducted component. Different subducted component influence may be due to different subduction zone structural feature.
Diagenetic fluids evolution of Oligocene Huagang Formation sandstone reservoir in the south of Xihu Sag, the East China Sea Shelf Basin: constraints from petrology, mineralogy, and isotope geochemistry
Lewei HAO, Qi WANG, Ruiliang GUO, Chengrong TUO, Dongxu MA, Weiwei MOU, Bing TIAN
2018, 37(2): 25-34. doi: 10.1007/s13131-017-1126-8
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The Oligocene Huagang Formation is the main sandstone reservoir in the Xihu Sag, situated in the east of the East China Sea Shelf Basin. With an integrated approach of thin-section petrography, ultra-violet fluorescence microscopy, scanning electron microscopy, and isotope geochemistry, the different diagenetic features were identified, the typical diagenetic parasequences were established, and the diagenetic fluids evolution history were reconstructed for the Oligocene Huagang Formation sandstone reservoir in the south of Xihu Sag. The Huagang Formation sandstone reservoir is now in Period B of the mesodiagenesis, which has undergone significant diagenetic alterations such as mechanical compaction, Pore-lining chlorite cement, feldspar dissolution, quartz cementation and dissolution, and carbonate cementation. Three types of carbonate cements (early siderite, medium ferrocalcite and late ankerite) were identified in the Huagang Formation sandstone reservoir. The carbon and oxygen isotopic compositions of carbonate cements show that the early calcite precipitate from alkaline lacustrine environment whereas the late carbonate cements were closely related to the organic acids. To the Huagang Formation sandstone reservoir, it has experienced two main episodes of dissolution during diagenesis. The early dissolution is that unstable components such as feldspar, lithic fragments, and carbonate cement were dissolved by acidic water. The second dissolution is that quartz and other silicate minerals were dissolved under the alkaline condition. Two main phases of hydrocarbon charging occurred in this study area. The first hydrocarbon emplacement was prior to the medium carbonate cementation but posterior to feldspar dissolution and the onset of quartz cementation at the end of the Miocene. The second hydrocarbon charging occurred in the Quaternary period after the late carbonate precipitation.
Geochemical characteristics of Oligocene-Miocene sediments from the deepwater area of the northern South China Sea and their provenance implications
Shuhui CHEN, Peijun QIAO, Houhe ZHANG, Xiaojun XIE, Yuchi CUI, Lei SHAO
2018, 37(2): 35-43. doi: 10.1007/s13131-017-1127-7
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Geochemical and detrital zircon U-Pb dating data for drilled sediments from the Baiyun deepwater area of the northern South China Sea demonstrate a change of sedimentary sources from the Oligocene to the Miocene. Zircon ages of the pre-rift Eocene sequences are dominated by Yanshanian ages with various peak values (110–115 Ma for U1435 and L21; 150 Ma for H1), indicating local sediment supply from the pre-existing Mesozoic magmatic belt. For the Oligocene sediments in the northern part of the basin, the rare earth elements show different distribution characteristics, indicating sediment supply from the paleo-Zhujiang River (Pearl River), as also confirmed by the multimodal zircon age spectra of the Lower Oligocene strata in Well X28. By contrast, a positive Eu anomaly characterizes sediments from the western and southern parts of the basin, indicating potential provenances from intermediate to basic volcanic rock materials. The Baiyun Movement at the end of the Oligocene contributed to a large-scale subsidence in the deepwater area and also a northward retreat of continental shelf break, leading to deepening depositional environment in the basin. As a result, all the detrital zircon ages of the Upper Oligocene strata from Wells X28, L13, and L21 share a similar distribution, implying the possible control of a common source like the Zhujiang River. During the Miocene, whereas sediments in the northern area were mainly sourced from the Zhujiang River Delta, and those in the southern deepwater area continued to be affected by basic volcanic activities, the Dongsha Uplift could have contributed as the main source to the eastern area.
Geochemistry of borehole cutting shale and natural gas accumulation in the deepwater area of the Zhujiang River Mouth-Qiongdongnan Basin in the northern South China Sea
Gang GAO, Gongcheng ZHANG, Guo CHEN, Wenzhe GANG, Huailei SHEN, Ke ZHAO
2018, 37(2): 44-53. doi: 10.1007/s13131-018-1151-2
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The Qiongdongnan Basin and Zhujiang River (Pearl River) Mouth Basin, important petroliferous basins in the northern South China Sea, contain abundant oil and gas resource. In this study, on basis of discussing impact of oil-base mud on TOC content and Rock-Eval parameters of cutting shale samples, the authors did comprehensive analysis of source rock quality, thermal evolution and control effect of source rock in gas accumulation of the Qiongdongnan and the Zhujiang River Mouth Basins. The contrast analysis of TOC contents and Rock-Eval parameters before and after extraction for cutting shale samples indicates that except for a weaker impact on Rock-Eval parameter S2, oil-base mud has certain impact on Rock-Eval S1, Tmax and TOC contents. When concerning oil-base mud influence on source rock geochemistry parameters, the shales in the Yacheng/Enping, Lingshui/Zhuhai and Sanya/Zhuhai Formations have mainly Type II and III organic matter with better gas potential and oil potential. The thermal evolution analysis suggests that the depth interval of the oil window is between 3 000 m and 5 000 m. Source rocks in the deepwater area have generated abundant gas mainly due to the late stage of the oil window and the high-supper mature stage. Gas reservoir formation condition analysis made clear that the source rock is the primary factor and fault is a necessary condition for gas accumulation. Spatial coupling of source, fault and reservoir is essential for gas accumulation and the inside of hydrocarbon-generating sag is future potential gas exploration area.
Seismic analysis of early-mid Miocene carbonate platform in the southern Qiongdongnan Basin, South China Sea
Xiaochuan WU, Renhai PU, Ying CHEN, Hongjun QU, Huailei SHEN
2018, 37(2): 54-65. doi: 10.1007/s13131-017-1128-6
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The southern uplift of the Qiongdongnan Basin is a deepwater area in which no wells have beens drilled. The Miocene-Quaternary strata in the Xisha Islands, which are located 40–100 km to the south, are composed of carbonate reef formations. Paleotectonic and paleogeographic analyses of the basin suggest that the southern uplift experienced favorable geological conditions for the development of carbonate reefs during the Miocene. The high-impedance carbonates have high amplitudes and low frequencies on seismic profiles. The reefs are distributed on paleotectonic highs and are thicker than the contemporaneous formations. A forward model of the variation in carbonate thickness based on lithological and velocity information from wells in nearby regions can simulate the seismic response of carbonates with different thicknesses. We identified several important controlling points for determining the thickness of carbonates from seismic profiles, including the pinchout point, the λ/4 thickness point, and the λ/2 thickness point. We depict a carbonate thickness map in the deepwater area of the southern Qiongdongnan Basin based on this model. The carbonate thickness map, the paleotectonic and paleogeographic background, and the seismic response characteristics of reefs suggest that the carbonates that developed on the southern uplift of the Qiongdongnan Basin during the Miocene were mainly an isolated carbonate platform peninsula and ramp deposits. It consisted of gentle ramp platform, steep slope platform, platform depression, gravity flow, and reef bank facies.
Tectono-thermal evolution of the Liwan Sag, deepwater area in the Zhujiang River Mouth Basin, northern South China Sea
Xiaoyin TANG, Shaopeng HUANG, Shuchun YANG, Guangzheng JIANG, Mo JI, Shengbiao HU
2018, 37(2): 66-75. doi: 10.1007/s13131-017-1125-9
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The Liwan Sag, with an area of 4 000 km2, is one of the deepwater sags in the Zhujiang River (Pearl River) Mouth Basin, northern South China Sea. Inspired by the exploration success in oil and gas resources in the deepwater sags worldwide, we conducted the thermal modeling to investigate the tectono-thermal history of the Liwan Sag, which has been widely thought to be important to understand tectonic activities as well as hydrocarbon potential of a basin. Using the multi-stage finite stretching model, the tectonic subsidence history and the thermal history have been obtained for 12 artificial wells, which were constructed on basis of one seismic profile newly acquired in the study area. Two stages of rifting during the time periods of 49–33.9 Ma and 33.9–23 Ma can be recognized from the tectonic subsidence pattern, and there are two phases of heating processes corresponding to the rifting. The reconstructed average basal paleo-heat flow values at the end of the rifting events are ~70.5 and ~94.2 mW/m2 respectively. Following the heating periods, the study area has undergone a persistent thermal attenuation phase since 23 Ma and the basal heat flow cooled down to ~71.8–82.5 mW/m2 at present.
Cloning, expression profiling and promoter functional analysis of bone morphogenetic protein 2 in the tongue sole (Cynoglossus semilaevis)
Qian MA, Yanjun FAN, Zhimeng ZHUANG, Shufang LIU
2018, 37(2): 76-84. doi: 10.1007/s13131-018-1164-x
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BMP2 plays crucial roles in vertebrate developmental process and acts as a bone inducer during osteogenesis. We present here the molecular cloning of bmp2 cDNA from the marine flatfish Cynoglossus semilaevis, and the analysis of bmp2 expression profiling and promoter function. The full length of bmp2 cDNA sequence is 2 048 bp, which encodes a protein of 422 amino acids. Tissue expression distribution of bmp2 was examined in 14 tissues of mature individuals by quantitative real time PCR (qRT-PCR). The results revealed that bmp2 was expressed ubiquitously, and the highest expression level was detected in the spinal cord. Moreover, bmp2 expression levels were detected at 15 sampling time points of early developmental stages (egg, larva, juvenile and fingerling stages). The highest expression level of bmp2 was observed at the gastrula stage, which was about ten times higher than those at the other three embryo stages. Whole-mount in situ hybridization showed that the bmp2 signal was strongly detected at the location of the crown-like larval fin, heart and liver, and slightly expressed in the notochord at one day post hatch (dph); then the expression of bmp2 started to be concentrated in notochord at three dph. Subsequently, we characterized the 5′-flanking region of bmp2 by testing the promoter activity by Luciferase reporter assays. Positive regulatory region was detected at the location of –179 to +109. The predicted transcription factor binding sites (E-box binding factors, zinc finger transcription factor, etc.) in this region might participate in the transcriptional regulation of the bmp2 gene.
Changes of visceral properties and digestive enzymes in the herbivorous marine teleost Siganus canaliculatus fed on different diets
Dizhi XIE, Shude XU, Qingyang WU, Fang CHEN, Shuqi WANG, Cuihong YOU, Yuanyou LI
2018, 37(2): 85-93. doi: 10.1007/s13131-018-1165-9
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The rabbitfish Siganus canaliculatus is one of the few cultured herbivorous marine teleosts. To better understand the digestive physiology of this fish and provide data for designing formulated feed using macroalgae as an ingredient, the changes of visceral properties and digestive enzyme activities were investigated after the juveniles were fed on different types of food including raw fish (RF), formulated diet (FD) or macroalgae Enteromorpha prolifra (EP) and Gracilaria lemaneiformis (GL) for eight weeks. The results showed that the hepatosomatic and viscerosomatic indices in the RF and FD groups, as well as the relative intestine length (RIL) in the EP and GL groups, were significantly higher than those in other groups. Additionally, differences in the histological structure of the liver and anterior intestine were also observed among different dietary groups. The hepatic nuclei were displaced to the periphery by lipid inclusions in fish fed RF. The highest levels of mucosal folds were found in the anterior intestines of fish fed macroalgae. Digestive enzyme activity profiles showed obvious fluctuations in the first three weeks, and then leveled off in the following weeks. The levels of protease, lipase and α-amylase in the alimentary tract showed changes related to the levels of dietary protein, lipid and carbohydrate, respectively. Although macroalgae significantly inhibited the activity of protease in the stomach, it increased RIL and the number of mucosal folds in the anterior intestine so as to compensate for the influences on protease activities in the stomach. This study suggests that the digestive tract of rabbitfish can well adapt to different diets, and needs about three weeks to physiologically acclimatize to the nutritional status, thus implying that rabbitfish are somewhat omnivorous.
A stock assessment for Illex argentinus in Southwest Atlantic using an environmentally dependent surplus production model
Jintao WANG, Xinjun CHEN, W. Staples Kevin, Yong CHEN
2018, 37(2): 94-101. doi: 10.1007/s13131-017-1131-y
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The southern Patagonian stock (SPS) of Argentinian shortfin squid, Illex argentinus, is an economically important squid fishery in the Southwest Atlantic. Environmental conditions in the region play an important role in regulating the population dynamics of the I. argentinus population. This study develops an environmentally dependent surplus production (EDSP) model to evaluate the stock abundance of I. argentines during the period of 2000 to 2010. The environmental factors (favorable spawning habitat areas with sea surface temperature of 16–18°C) were assumed to be closely associated with carrying capacity (K) in the EDSP model. Deviance Information Criterion (DIC) values suggest that the estimated EDSP model with environmental factors fits the data better than a Schaefer surplus model without environmental factors under uniform and normal scenarios. The EDSP model estimated a maximum sustainable yield (MSY) from 351 600 t to 685 100 t and a biomass from 1 322 400 t to 1 803 000 t. The fishing mortality coefficient of I. argentinus from 2000 to 2010 was smaller than the values of F0.1 and FMSY. Furthermore, the time series biomass plot of I. argentinus from 2000 to 2010 shows that the biomass of I. argentinus and this fishery were in a good state and not presently experiencing overfishing. This study suggests that the environmental conditions of the habitat should be considered within squid stock assessment and management.
Application of a catch-based method for stock assessment of three important fisheries in the East China Sea
Kui ZHANG, Jun ZHANG, Youwei XU, Mingshuai SUN, Zuozhi CHEN, Meng YUAN
2018, 37(2): 102-109. doi: 10.1007/s13131-018-1173-9
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Most fisheries in China do not have maximum sustainable yield (MSY) estimates due to limited and poor data. Therefore, finding a common method to estimate MSY or total allowable catch (TAC) for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model. Estimates for intrinsic rate of increase (r) and five levels of process error were considered. Results showed hairtail Trichiurus japonicas (Temminck and Schlegel) and small yellow croaker Larimichthys polyactis (Bleeker) fisheries experienced overfishing from the mid-1990s to the early 2000s, and the suggested TACs were 55.8×104 t and 9.06×104 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea (Richardson) caused the fishery’s collapse in the 1980s, and it has not recovered until today. The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.
Enhanced a novel β-agarase production in recombinant Escherichia coli BL21 (DE3) through induction mode optimization and glycerol feeding strategy
Zhuhua CHAN, Xinglin CHEN, Yanping HOU, Boliang GAO, Chungui ZHAO, Suping YANG, Runying ZENG
2018, 37(2): 110-118. doi: 10.1007/s13131-018-1172-x
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Agarases are hydrolytic enzymes that act on the hydrolysis of agar and have a broad range of applications in food, cosmetics and pharmaceutical industries. In this study, a glycerol feeding strategy based on induction mode optimization for high cell density and β-agarase production was established, which could effectively control acetate yield. First, exponential feeding strategy of glycerol with different overall specific growth rates (μ) was applied in the pre-induction phase. The results showed that the low μ (μ=0.2) was suggested to be the optimal for cell growth and β-agarase production. Second, the effects of induction temperature and the inducer concentration on cell growth and β-agarase production were investigated in the post-induction phase. When induced by isopropyl-β-d-thiogalactoside (IPTG), the strategy of 0.8 mmol/L IPTG induction at 20°C was found to be optimal for β-agarase production. When cultivation was induced by continuous lactose feeding strategy of 1.0 g/(L·h), the β-agarase activity reached 112.5 U/mL, which represented the highest β-agarase production to date. Furthermore, the β-agarase was capable of degrading G. lemaneiformis powder directly to produce neoagarooligosaccharide, and the hydrolysates were neoagarotetraose (NA4) and neoagarohexaose (NA6). The overall research may be useful for the industrial production and application of β-agarase.
Lipid accumulation and CO2 utilization of two marine oil-rich microalgal strains in response to CO2 aeration
Shuai WANG, Li ZHENG, Xiaotian HAN, Baijuan YANG, Jingxi LI, Chengjun SUN
2018, 37(2): 119-126. doi: 10.1007/s13131-018-1171-y
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Biological CO2 sequestration by microalgae is a promising and environmentally friendly technology applied to sequester CO2. The characteristics of neutral lipid accumulation by two marine oil-rich microalgal strains, namely, Isochrysis galbana and Nannochloropsis sp., through CO2 enrichment cultivation were investigated in this study. The optimum culture conditions of the two microalgal strains are 10% CO2 and f medium. The maximum biomass productivity, total lipid content, maximum lipid productivity, carbon content, and CO2 fixation ability of the two microalgal strains were obtained. The corresponding parameters of the two strains were as follows: ((142.42±4.58) g/(m2·d), (149.92±1.80) g/(m2·d)), ((39.95±0.77)%, (37.91±0.58)%), ((84.47±1.56) g/(m2·d), (89.90±1.98) g/(m2·d)), ((45.98±1.75)%, (46.88±2.01)%), and ((33.74±1.65) g/(m2·d), (34.08±1.32) g/(m2·d)). Results indicated that the two marine microalgal strains with high CO2 fixation ability are potential strains for marine biodiesel development coupled with CO2 emission reduction.