末次冰消期（1.9万年）以来冲绳海槽中部黏土矿物来源及其环境响应          下载免费PDF全文

田旭  胡邦琦  王飞飞  黄威  丁雪  宋维宇  徐方建 《中国地质》2020,47(5):1501-1511

基于采自冲绳海槽中部的CS2站柱状沉积物黏土矿物和AMS¹⁴C年代分析，探讨了末次冰消期以来冲绳海槽中部黏土矿物的物质来源及其环境指示意义。结果显示，CS2站黏土矿物以伊利石为主，其次为绿泥石，高岭石和蒙脱石含量较少。根据黏土矿物分布趋势变化，CS2站柱状沉积物可划分为3个阶段：阶段（I 19~12 ka BP）和阶段Ⅱ （12~8 ka BP）期间沉积物主要来源于长江，台湾和黄河物质也有一定影响，其物质来源主要受海平面升降的控制；阶段Ⅲ（8~0 ka BP）主要来源于长江和台湾，黄河贡献有限，主要受黑潮演化的影响。CS2站（蒙脱石+高岭石） （/伊利石+绿泥石）比值可以作为东亚季风演化的矿物学指标，指标变化显示出东亚冬季风强度相对夏季风的强度在16.4~14.8 ka BP和12.8~11.6 ka BP期间有两次显著的加强，指示当时气候相对寒冷干燥，结果可以与格陵兰冰心δ¹⁸O和三宝洞δ¹⁸O记录等很好对比。  相似文献   

Provenance and tectonic settings of the Late Paleozoic sandstones in central Inner Mongolia,NE China: Constraints on the evolution of the southeastern Central Asian Orogenic Belt     

《Gondwana Research》2020

Late Paleozoic sedimentary strata outcrop extensively in central Inner Mongolia, and are a key to understanding the tectonic evolution of the southeastern Central Orogenic Belt. A combined analysis of petrography, whole-rock major and trace element, and Nd isotope is carried out on representative sandstones from the Late Paleozoic sedimentary strata (420–270 Ma). The sandstones are mainly wackes and litharenites in lithology, with low SiO₂/Al₂O₃ of 2.85–9.47 (averagely 5.22) and poor textural and compositional maturities, implying short sediment transportation between the depositional basins and provenances. The trace element compositions are generally comparable to that of the average upper continent crust (UCC), with negatively-sloping chondrite-normalized rare earth element distribution patterns ((La/Yb)_N = 3.43–11; averagely 6.94) and flat UCC-normalized trace element distribution patterns. The Nd isotopic compositions show great variation (Ԑ_Nd(t) = −5.01 to 5.35) with depositional time of the sandstones, and coincide well with the arc magmatic phases in central Inner Mongolia. The geochemical signatures of the sandstones indicate that the dominant provenances are intermediate to felsic arc magmatic rocks that have ages approximating the deposition, although old, recycled sediments may have made a minor contribution. An active continental arc setting during the Late Paleozoic in central Inner Mongolia, controlled by the northward subduction of the Paleo-Asian oceanic slab, was the most likely depositional tectonic setting of the sandstones. This active continental arc setting continued to at least 270 Ma, implying that the final closure of the Paleo-Asian Ocean along the Solonker suture zone most likely occurred sometime during the Late Permian to Early Triassic. The northward subduction of the Paleo-Asian Ocean is likely of West Pacific-style, in which the present-day Baolidao arc has a close genetic link with the South Mongolian microcontinent and, likely, the former originally formed as the arc margin of the latter.  相似文献   

An improved analytical approach for simulating the lateral kinematic distress of deepwater offshore pipelines     

《Applied Ocean Research》2019

Offshore pipelines are critical infrastructures and any possible damage may have devastating financial and environmental consequences. Earthquake-related geohazards (such as strong ground motion, active seismic faults, submarine landslides and debris flows) consist crucial threats that an offshore pipeline has to overcome. The main aim of the current study is to examine analytically a seabed-laid offshore pipeline subjected to a lateral kinematic distress due to a submarine landslide or a debris flow. Extra emphasis is given on the impact of pipe-soil interaction on the pipe response, by the realistic representation of the soil resistance via a tri-linear model. Firstly, the proposed analytical model is validated with a numerical model utilizing the finite-element method. Subsequently, various combinations of soil parameters and loading conditions that affect the examined problem are investigated with realistic input data taken from the offshore section of the high-pressure natural-gas pipeline TAP (Trans Adriatic Pipeline) in the Adriatic Sea. Finally, useful conclusions are drawn regarding the applicability and the efficiency of the proposed approach.  相似文献   

Exploration prospects of oil and gas in the Northwestern part of the Offshore Indus Basin,Pakistan     

《China Geology》2020,3(4):633-642

Oil and gas resources are short in Pakistan and no commercially viable oil and gas sources have been yet discovered in its offshore areas up to now. In this study, the onshore-offshore stratigraphic correlation and seismic data interpretation were conducted to determine the oil and gas resource potential in the Offshore Indus Basin, Pakistan. Based on the comprehensive analysis of the results and previous data, it is considered that the Cretaceous may widely exist and three sets of source rocks may be developed in the Offshore Indus Basin. The presence of Miocene mudstones has been proven by drilling to be high-quality source rocks, while the Cretaceous and Paleocene–Eocene mudstones are potential source rocks. Tectonic-lithologic traps are developed in the northwestern part of the basin affected by the strike-slip faults along Murray Ridge. Furthermore, the Cretaceous and Paleocene–Eocene source rocks are thick and are slightly affected by volcanic activities. Therefore, it can be inferred that the northwestern part of Offshore Indus Basin enjoys good prospects of oil and gas resources.  相似文献   

Gakkel洋中脊基底隆起的非对称地壳结构          下载免费PDF全文

凌子龙  高金耀  赵俐红  杨春国  管清胜  张涛 《地球物理学报》2019,62(5):1755-1771

超慢速扩张的北冰洋Gakkel洋中脊具有六个沿扩张方向的线性基底隆起(本文编号为A—F).这些线性基底隆起在中轴两侧的地球物理场和地壳结构呈现不同程度的非对称性.本文利用Gakkel洋中脊的地形、空间重力异常(FAA)和航空磁力数据,计算了它的扩张速率、剩余地幔布格重力异常(RMBA)、地壳厚度和非均衡地形.根据中轴两侧地形和地壳厚度的对称关系,我们将六个基底隆起分为对称型和非对称型两种类型.整体上,B、D和F区基底隆起在中轴两侧的地形和地壳厚度的非对称幅值(两侧差值的绝对值)较小,其中地形的非对称幅值分别为～157m、～125m、～208m,地壳厚度的非对称幅值分别为～1km、～0.06km、～0.3km;而A、C和E区的非对称幅值较大,其中地形的非对称幅值分别为～510m、～410m、～673m,地壳厚度的非对称幅值分别为～2km、～2.5km、～1.1km.我们因此推断B、D和F区具有相对对称的地壳结构,而A、C和E区具有非对称的地壳结构.根据A、C和E区中轴两侧非均衡地形的对称关系和非对称地形的补偿状态,推测A区的非对称性可能是由岩浆分配不均所导致;而C区和E区的非对称性可能是由构造断层作用使断层下盘向上抬升变薄所导致.我们进一步推测洋中脊走向的改变可能使得构造作用更易集中于基底隆起的一侧.  相似文献   

由下扬子区海陆对比分析南黄海盆地下志留统烃源岩特征及其主控因素     

蔡来星  肖国林  郭兴伟  王蛟  吴志强  李宝刚 《吉林大学学报(地球科学版)》2019,49(1):39-52

针对南黄海盆地海相油气勘探的重大需求，在收集、整理下扬子苏、浙、皖地区地质和地化资料的基础上，依托科学钻探CSDP-2井岩心，系统对比了南黄海盆地与下扬子陆区早志留世古地理背景和沉积充填特征，进而利用一系列地化测试数据总结了南黄海盆地下志留统烃源岩特征并探讨其主控因素。研究结果表明：南黄海盆地大陆架科学钻探CSDP-2井目前已钻遇了坟头组和高家边组上部两套丰度很低的厚层、暗色（粉砂质）泥岩，其有机质类型主要为Ⅱ₂型，热演化程度已整体进入过成熟阶段；受控于全球海侵事件和扬子板块构造活动的发展阶段，早志留世初期深水陆棚环境逐渐向后期的浅水陆棚环境演变，加之早期较高的初级生产力和良好的保存条件，使得下扬子区高家边组下部烃源岩的品质明显高于上部，并以底部黑色笔石页岩段有机质丰度最高。因此，南黄海盆地高家边组底部理应存在一套优质烃源岩层，可作为下一步页岩气勘探的重点层位。  相似文献   

Thickness and geothermal gradient of Neoarchean continental crust: Inference from the southeastern North China Craton     

《Gondwana Research》2019

The thickness and geothermal gradient of Archean continental crust are critical factors for understanding the geodynamic processes in Earth's early continental crust. Archean tonalite-trondhjemite-granodiorite (TTG) gneisses provide one of the potential indicators of paleo-crustal thickness and geothermal gradient because crust-derived TTG melts are generally thought to originate from partial melting of mafic rocks at the crustal root. In the Western Shandong Province (WSP) of the North China Craton (NCC), two episodes of Neoarchean TTG magmatism are recognized at ~2.70 Ga and ~2.55 Ga which were sourced from partial melting of juvenile crustal components. The ~2.70 Ga TTG gneisses show highly fractionated rare earth element (REE) patterns (average (La/Yb)_N = 39), whereas the ~2.55 Ga TTG gneisses have relatively less fractionated REE patterns (average (La/Yb)_N = 18). Petrogenetic evaluation suggest that the magmatic precursors of the TTG gneisses of both episodes originated from partial melting of juvenile crustal materials at different crustal depths with residual mineral phases of Grt, Cpx, Amp, Pl and Ilm. Together with the garnet proportion in the residue, the P–T pseudosections of equilibrium mineral assemblages, and the temperature calculated from Titanium-in-zircon thermometer, we estimate the Neoarchean crustal thicknesses as 44–51 km with geothermal gradients of 17 to 20 °C/km for the ~2.70 Ga TTG gneisses whereas the ~2.55 Ga TTG gneisses show lesser crustal thicknesses of 35–43 km with geothermal gradients of 19 to 26 °C/km, with an approximately 10 km difference in crustal thickness. Our estimates on the thicknesses and geothermal gradients of the Neoarchean crust are similar to those (~41 km, ~20 °C/km) of the modern average continental crust, indicating that a modern-style plate tectonic regime may have played an important role in the formation and evolution of the Neoarchean continental crust in the NCC.  相似文献   

Tectono-stratigraphic terranes in Archaean gneiss complexes as evidence for plate tectonics: The Nuuk region,southern West Greenland     

《Gondwana Research》2019

Prior to 1970 grey gneiss complexes were interpreted as partially-melted sedimentary sequences. Once it was recognised from the Nuuk region that they comprised calc-alkaline igneous complexes, it was understood that such complexes world-wide were dominated by TTG (trondhjemite-tonalite-granodiorite) initially found to have juvenile Sr, Nd and, subsequently, Hf isotopic signatures. Between 1970 and 1985 the Nuuk region gneiss complex was interpreted by the non-uniformitarian ‘super-event’ model of crust formation which proposed occasional but extensive crust formation, with craton-wide correlation of granulite facies metamorphism and deformational phases. The igneous rocks formed in a late- Meso- to early Neoarchaean super-event engulfed crust formed in an Eoarchaean super-event. Mapping and reinterpretation at Færingehavn showed there are three TTG gneiss domains, each with different early accretionary, metamorphic and tectonic histories, separated by folded meta-mylonites. This established the key feature of the tectono-stratigraphic terrane model; that each terrane has an early intra-terrane history of crust formation, deformation and metamorphism, upon which is superimposed a later deformation and metamorphic history common to several terranes after they were juxtaposed. Remapping and >250 U-Pb zircon age determinations have refined the geological evolution of the entire Nuuk region, and has confirmed at least four main crust formation events and two collisional orogenies with associated transient high pressure metamorphism within clockwise P-T-t loops. Via independent corroborative studies the tectono-stratigraphic terrane model has been accepted for the Nuuk region and, through the discovery of similar relations across other gneiss complexes, its mode of evolution is found to be applicable to Archaean high-grade gneiss complexes worldwide. The TTG and mafic components that dominate each terrane have geochemistry interpreted to indicate subduction-related magmatism at convergent plate boundaries. Each terrane is thus dominated by juvenile additions to the crust. Intra-terrane sedimentary rocks show near unimodal age distributions in contrast to those near the boundaries which are more diverse and complex. The combined geochronological, metamorphic and structural evidence of convergence of these terranes leading to collisional orogeny, this indicates that plate tectonic processes operated throughout the Archaean.  相似文献   

Regeneration and utilization of nutrients during collapse of a <Emphasis Type="Italic">Mesodinium rubrum</Emphasis> red tide and its influence on phytoplankton species composition     

Yafeng Zhang  Xiuxian Song  Paul J. Harrison  Sheng Liu  Zhiming Yu  Jinjun Kan  Peiyuan Qian  Hao Liu  Kedong Yin 《中国科学:地球科学(英文版)》2018,61(10):1384-1396

High-biomass red tides occur frequently in some semi-enclosed bays of Hong Kong where ambient nutrients are not high enough to support such a high phytoplankton biomass. These high-biomass red tides release massive inorganic nutrients into local waters during their collapse. We hypothesized that the massive inorganic nutrients released from the collapse of red tides would fuel growth of other phytoplankton species. This could influence phytoplankton species composition. We tested the hypothesis using a red tide event caused by Mesodinium rubrum (M. rubrum) in a semi-enclosed bay, Port Shelter. The red tide patch had a cell density as high as 5.0×10⁵ cells L^?1, and high chlorophyll a (63.71 μg L^?1). Ambient inorganic nutrients (nitrate: \(\rm{NO}_3^-\), ammonium: \(\rm{NH}_4^+\), phosphate: \(\rm{PO}_4^{3-}\), silicate: \(\rm{SiO}_4^{3-}\)) were low both in the red tide patch and the non-red-tide patch (clear waters outside the red tide patch). Nutrient addition experiments were conducted by adding all the inorganic nutrients to water samples from the two patches followed by incubation for 9 days. The results showed that the addition of inorganic nutrients did not sustain high M. rubrum cell density, which collapsed after day 1, and did not drive M. rubrum in the non-red-tide patch sample to the same high-cell density in the red tide patch sample. This confirmed that nutrients were not the driving factor for the formation of this red tide event, or for its collapse. The death of M. rubrum after day 1 released high concentrations of \(\rm{NO}_3^-\), \(\rm{PO}_4^{3-}\), \(\rm{SiO}_4^{3-}\), \(\rm{NH}_4^+\), and urea. Bacterial abundance and heterotrophic activity increased, reaching the highest on day 3 or 4, and decreased as cell density of M. rubrum declined. The released nutrients stimulated growth of diatoms, such as Chaetoceros affinis var. circinalis, Thalassiothrix frauenfeldii, and Nitzschia sp., particularly with additions of \(\rm{SiO}_4^{3-}\) treatments, and other species. These results demonstrated that initiation of M. rubrum red tides in the bay was not directly driven by nutrients. However, the massive inorganic nutrients released from the collapse of the red tide could induce a second bloom in low-ambient nutrient water, influencing phytoplankton species composition.  相似文献   

强光照和黑暗条件下刺参体壁的基因表达差异     

张立斌  冯其明  孙丽娜  房燕  徐冬雪  张涛  杨红生 《海洋学报(英文版)》2018,37(5):54-66

参对光照变化非常敏感，研究刺参对光照的分子响应非常重要。本研究应用RNA测序获取了刺参暴露于强光（“强光”）、正常光照（“对照”）和完全黑暗（“黑暗”）环境下体壁的基因表达谱情况，通过“对照”与“黑暗”，“对照”与“强光”和“黑暗”与“强光”的比较，在|log₂ ratio|≥1和FDR≤0.001的标准下分别发现了1161、113和1705个差异表达基因（DEGs）。基因本体分析表明，“cellular process”和“binding”在“生物过程”和“分子功能”类别中的DEGs富集最多，而“cell”和“cell part”在“细胞组分”类别中的DEGs富集最多。将DEGs与Kyoto Encyclopedia基因和基因组数据库上的于214、41和229条通路进行比对，发现了51、2和57条通路分别显著富集。本研究发现的光特异性DEGs可作为深入研究刺参对光照变化的生化适应机制的重要目标基因。  相似文献