Gravity Flow on Slope and Abyssal Systems in the Qiongdongnan Basin,Northern South China Sea

The study of new seismic data permits the identification of sediment gravity flows in terms of internal architecture and the distribution on shelf and abyssal setting in the Qiongdongnan Basin （QDNB）. Six gravity flow types are recognized： （1） turbidite channels with a truncational basal and concordant overburden relationship along the shelf edge and slope, comprising laterally-shifting and vertically-aggrading channel complexes; （2） slides with a spoon-shaped morphology slip steps on the shelf-break and generated from the deformation of poorly-consolidated and high water content sediments; （3） slumps are limited on the shelf slope, triggered either by an anomalous slope gradient or by fault activity; （4） turbidite sheet complexes （TSC） were ascribed to the basin-floor fan and slope fan origin, occasionally feeding the deep marine deposits by turbidity currents; （5） sediment waves occurring in the lower slope-basin floor, and covering an area of approximately 400 km2, were generated beneath currents flowing across the sea bed; and （6） the central canyon in the deep water area represents an exceptive type of gravity flow composed of an association of debris flow, turbidite channels, and TSC. It presents planar multisegment and vertical multiphase characteristics. Turbidite associated with good petrophysical property in the canyon could be treated as a potential exploration target in the QDNB.

Mantle melting beneath the Southwest Indian Ridge: signals from clinopyroxene in abyssal peridotites

The mineral chemistry and texture of clinopyroxenes in peridotite from the Kingkong tectonic zone of the Southwest Indian Ridge segment in an effort to constrain mantle melting beneath this slow-spreading ridge are reported. There are three types of clinopyroxenes in the abyssal peridotites： coarse-grained, intergranu- lar and exsolved. The compositional variations among these three types suggest that the coarse-grained clinopyroxene is a mantle-derived source. The A1, Na and Ti contents and the Na/Ti ratio of the coarse- grained clinopyroxene may be used to monitor the degree of partial melting, combined with the contradis- tinction with Spinel Cr#, which is calculated to be between 7.9% and 14.9%, and may represent low degrees of melting in the global ocean ridge system. The along-axis compositional variations in the coarse-grained clinopyroxene suggest that the degree of partial melting is primarily controlled by the transform faults on both sides of the ridge. Nonetheless, the northwestern side of the ridge may be affected by a hypothesised detachment fault as documented by the calculated P-T conditions. Simultaneously high Na and low Ti con- tents in the coarse-grained clinoovroxene points to mantle heterogeneities along the ridge axis.

Observation of the abyssal western boundary current in the Philippine Sea

Mooring observations were conducted from July 16, 2011 to March 30, 2012 east of Mindanao, Philippines （127°2.8＇E, 8°0.3＇N） to observe the abyssal current at about 5 600 m deep and 500 m above the ocean bottom. Several features were revealed： 1） the observed abyssal current was highly variable with standard deviations of 57.3 mrn/s and 34.0 ram/s, larger than the mean values of-31.9 and 16.6 mm/s for the zonal and meridional components, respectively; 2） low-frequency current longer than 6 days exhibited strong seasonal variation, flowing southeastward （mean flow direction of 119.0° clockwise from north） before about October 1, 2011 and northwestward （mean flow direction of 60.5° counter-clockwise from north） thereafter; 3） the high-frequency flow bands were dominated by tidal currents O1, K1, M2, and S2, and near-inertial currents, whose frequencies were higher than the local inertial frequency. The two diurnal tidal constituents were much stronger than the two semidiumal ones. This study provides for the first time an observational insight into the abyssal western boundary current east of Mindanao based on long-term observations at one site. It is meaningful for further research into the deep and abyssal circulation over the whole Philippine Sea and the 3D structure of the westem boundary current system in this region. More observational and high-resolution model studies are needed to examine the spatial structure and temporal variation of the abyssal current over a much larger space and longer period, their relation to the upper-layer circulation, and the underlying dynamics.

Water characteristics of abyssal and hadal zones in the southern Yap Trench observed with the submersible Jiaolong

Using observations in an applied cruise of the submersible Jiaolong,water characteristics,geostrophic transport,and turbulent mixing in abyssal and hadal zones of the southern Yap Trench were studied.The spatial structures of deep water show that the abyssal water is cold,saline,and oxygen rich.The hadal water has very small changes in potential temperature and potential density,and a little decrease in salinity and obvious decrease in oxygen.The isotherm,isopycnal,and isohaline are depressed in abyss over the central trench.The turbulent mixing is enhanced in the near-bottom zone and the hadal water on the trench slope,especially at the steep slope,the dissipation rate and diffusivity is strong,which weakens the stratification.The geostrophic flows move southward in the western region of the trench and northward in the eastern region,indicating cyclonic circulation.In the central region of the trench,the water transport is^1.74 Sv southward.In the hadal zone,the northward and southward transports are balanced.Our analysis suggests that the abyssal water in the southern Yap Trench is from Lower Circumpolar Water(LCPW)and the hadal water seems to be of the isolated local water rather than LCPW.

Tephra records from abyssal sediments off western Sumatra in recent 135 ka: evidence from Core IR-GC1

Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with theδ18O-based age, it is suggested that ash Layer A is cor-related to the youngest Toba tuff （YTT）, Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic erup-tion event.

Intra-seasonal variability of the abyssal currents in COMRA's contract area in the Clarion-Clipperton Zone

In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific,is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products.Mooring observations were conducted from September 13,2017 to August 15,2018 in the COMRA contact area(10°N,154°W).The results were as follows:(1)At depths below 200 m,the kinetic energy of intra-seasonal variability(20-100 d)accounts for more than 40%of the overall low-frequency variability,while the ratio reaches more than 50%below 2000 m.(2)At depths below 200 m,currents show a synchronous oscillation with a characteristic time scale of 30 d,lasting from October to the following January;the energy of the 30-d oscillation increases with depth until the layer of approximately 4616 m,and the maximum velocity is approximately 10 cm/s.(3)The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.

Glacial bedforms in the Northwind Abyssal Plain,Chukchi Borderland

A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedition(CHINARE-Arc9)in 2018 and previously published data.The new data reveal scours that developed at water depths of 850–1030 m with an orientation of about 75°/255°.The maximum water depth occurs in the southernmost scour and is deeper than that from previous investigations,which showed a maximum scouring depth of about 900 m on the seamount.The topographic and geomorphological characteristics suggest that these scours resulted from erosion by the ice shelf extending from the Chukchi margin and/or Laurentide Ice Sheet that grounded on the crest of the seamount and moved in a NE–SW direction.Other possibilities of their genesis include armadas of large icebergs/multi-keel icebergs calved from the Chukchi Shelf or the Laurentide Ice Sheet.The new data provide new constraints for assessing the extent and volume of the ice sheet in the Chukchi area during glacial maxima.

Rediscovery of the abyssal species Peniagone leander Pawson and Foell,1986(Holothuroidea:Elasipodida:Elpidiidae):the first record from the Mariana Trench area

The elpidiid holothurian Peniagone leander Pawson and Foell,1986 is recorded for the first time from the Mariana Trench area at a depth of 5571 m.The type description of this species was based on only in-situ photographs.P.leander is re-described and illustrated based on a preserved material and in-situ photographs taken on the seabed.The 16S rRNA was also obtained from the specimen and submitted to GenBank.This is the fourth discovery of this species,extending its bathymetric range in the western Pacific Ocean.

A STUDY ON THE BAROCLINIC STRUCTURE OF THE ABYSSAL CIRCULATION

In this paper, the linear continuously stratified model of the abyssal circulation proposed by Pedlosky (1992) was extended to include the second order term -(γθ zzz ) in the vertical turbulent mixing parameterization of - (w′θ′) z=k υθ zz -γθ zzz , in which k υ is a vertical diffusion coefficient, and γ is the second order coefficient of turbulent mixing (or simply called γ term and γ<0 is only allowed). The influence of the γ term on the baroclinic structure of the abyssal circulation driven by upwelling out of the abyss was investigated. It was found that the γ term has a noticeable influence on the baroclinic structure of the upwelling driven abyssal circulation. For uniform upwelling, it favors the baroclinic layering of the abyssal circulation in the eastern part of the basin, but prevents the layering in the west. In addition, this parameter was found to decrease the vertically averaging meridional velocity of the abyssal circulation from the west to the east on the southern boundary. For upwelling localized near the eastern boundary, the γ-term favors baroclinic layering of the abyssal circulation in the whole basin. Especially, on the southern boundary the γ-term could strengthen the vertically averaging meridional velocity in the west, but greatly weaken it in the east. The model presented here might be considered as an extension of the Pedlosky baroclinic model of the abyssal circulation.

ABYSS以惊险为主题的解谜游戏

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Characteristics of pCO_(2) in surface water of the Bering Abyssal Plain and their effects on carbon cycle in the western Arctic Ocean

Characteristics of the pCO2 distribution in surface water of the Bering Abyssal Plain and their relationships with the ambient hydrological conditions were discussed using variations of the partial pressure of CO2 in surface water of the Bering Abyssal Plain and the Chukchi Sea. Data in this study are from a field investigation during the First Chinese National Arctic Research Expedition in 1999. Compared to the high productivity in the Bering Continental Shelf, much lower levels of chlorophyll a were observed in the Bering Abyssal Plain. The effect of hydrological factors on the pCO2 distribution in surface seawater of the Plain in summer has become a major driving force and dominated over biological factors. The Plain also presents a High Nutrient Low Chlorophyll (HNLC). In addition, the pCO2 distribution in the Bering Abyssal Plain has also been found to be influenced from the Bering Slope Current which would transform to the Anadyr Cur- rent when it inflows northwestward over the Plain. The Anadyr Current would bring a high nutrient water to the western Arctic Ocean where local nutrients are almost depleted in the surface water during the summer time. Resupplying nutrients would stimulate the growth of phytoplankton and enhance capacity of absorbing atmospheric CO2 in the surface water. Otherwise, in the Bering Sea the dissolved inorganic carbon brought from freshwater are not deposited down to the deep sea water but most of them would be transported into the western Arctic Ocean by the Alaska Coastal Current to form a carbon sink there. Therefore, the two carbon sinks in the western Arctic Ocean, one carried by the Anadyr Current and another by the Alaska Costal Current, will impli- cate the western Arctic Ocean in global change.

Altered Spinel as a Petrotectonic Indicator in Abyssal Peridotite from the Easternmost Part of Southwest Indian Ridge

The easternmost part of Southwest Indian Ridge（SWIR） has special crustal structure, magmatic and tectonic processes. Abyssal peridotite from the easternmost part of Southwest Indian Ridge（63.5oE/28oS） is serpentinized spinel lherzolite. The accessory spinel has zoned texture, which was studied by petrography, electron probe micro-analysis（EPMA）, and backscattered electron（BSE） imaging to reconstruct the petrotectonic and hydrothermal metamorphic history of the host abyssal peridotite. The fresh core is magmatic Al-spinel with low Cr~#. The average extent of melting of the abyssal peridotite is about 5.9%. The composition of fresh magmatic spinel core indicates the studied area to be an anomalously thin crust with a melt-poor system. Hydrothermal reaction modifies the chemical composition of magmatic spinel. Ferritchromit is the first product forming the inner rim during pre-serpentinization. The abyssal ferritchromit crystalized as micro- to nano-sized particle with no triple grain boundary, indicating they crystalized in a rapid cooling process during hydrothermal alteration. Chemical compositions of ferritchromit indicate a hydrothermal metamorphism in amphibolite facies. Magnetite in the outer rim was formed by replacement of ferritchromit during syn- or post-serpentinization. Authigenic chlorites crystallized in two events：（1） after formation of ferritchromit crystallized as vein in fracture-zone near the core of spinel and （2） after formation of magnetite crystallized at outermost rim. They are different in compositions, indicating their formation temperature was about 289 oC and declined to 214 oC. These results show that the abyssal peridotite had undergone amphibolite to lower-greenschist facies hydrothermal events during pre- to syn-serpentinization or post-serpentinization.

Multi-stage formation of the Feragen ophiolite,Norway:Implication from petrology and geochemistry of peridotites and chromitites and its potential for prospecting

The ultramafic massif of Feragen,which belongs to the eastern ophiolitic belt of Norway,has abundant amounts of chromite ores.Recent studies have revealed a complex melt evolution in a supra-subduction zone(SSZ)environment.This study presents new whole-rock major element,trace element,and platinum-group element chemistry to evaluate their petrogenesis and tectonic evolution.Harzburgites have high CaO,Al_(2)O_(3),TiO_(2),MgO,and REE contents corresponding to abyssal peridotites,whereas dunites have low CaO,Al_(2)O_(3),TiO_(2),MgO,and REE contents corresponding to SSZ peridotites.The Cr^(#)and TiO_(2) of chromian spinels in the harzburgites suggest as much as about 15%–20%melting and the dunites are more depleted with>40%melting.The harzburgites and the dunites and high-Cr chromitites represent,respectively,the products of low-degree partial melting in a back-arc setting,and the products of melt-rock interaction in a SSZ environment.The calculated fO_(2) values for dunites and high-Cr chromitites(-0.17–+0.23 and+2.78–+5.65,respectively and generally above the FMQ buffer)are also consistent with the interaction between back-arc ophiolites with oxidized boninitic melts in a SSZ setting.

不同构造环境下蛇纹岩化作用的对比——以西南天山和北祁连造山带为例

蛇纹石含水量约为13%,是地球上重要的含水矿物,广泛分布于洋底、俯冲带、弧前等环境。同时,海水、俯冲带衍生流体中的活动性元素(B、Li、As、Sb、Pb、Cs、U、Sr、Ba)也可随蛇纹石化作用而富集在蛇纹石中。因此,蛇纹石可以作为流体和流体活动性元素的载体参与不同的地质过程。然而,不同的构造环境有不同的温度压力、水岩比值、流体性质、氧化还原条件。不同环境下的蛇纹石化作用,不仅会形成不同种类的蛇纹石(例如利蛇纹石,叶蛇纹石),也有可能会导致蛇纹石的元素富集特征不同,这就需要进一步研究流体活动性元素的地球化学行为和元素富集特征。基于对世界范围内不同环境蛇纹岩数据资料的整理分析,结合西南天山和祁连山两个典型造山带的蛇纹岩样品,我们发现深海蛇纹岩与俯冲带蛇纹岩,B、Ba、Cs表现出不同的富集特征:①深海蛇纹岩具有明显更高的B元素含量,可能反映了B在低温下更容易进入到蛇纹岩中;②俯冲带以及弧前环境下形成的蛇纹岩由于可能有沉积物的输入,Ba、Cs的含量相对较高。这一结论有助于以后通过蛇纹岩的元素地球化学特征反演其相对的构造环境。

深海橄榄岩蛇纹石化温度条件的氧同位素约束

深海橄榄岩在海底洋中脊、俯冲带和大陆边缘等构造环境中广泛分布,并普遍经历后期蚀变,其中蛇纹石化作用是最主要的蚀变类型。蛇纹石化是指橄榄岩中富镁铁矿物,如橄榄石和辉石,被蛇纹石、磁铁矿、水镁石等一系列次生矿物所取代的化学过程。蛇纹石化反应条件与热液循环、成矿物质迁移等具有密切的联系,对指示热液成矿作用具有重要意义。传统的岩石矿物学、地球化学方法在反映蛇纹石化条件时具有多解性和不确定性,不同矿物或不同化学指标可能指示不同的结果。氧同位素在自然界普遍存在,氧同位素示踪法具有适用范围广、容易比对、支持原位微区分析等优点,可以清晰地反映矿物或岩石-流体体系的反应条件和过程。该文主要综述了氧同位素测温法的原理、深海橄榄岩蛇纹石化过程、氧同位素测温法在深海橄榄岩蛇纹石化过程中的应用案例、蛇纹石氧同位素组成变化的影响因素以及氧同位素测温法的优势和局限性等问题,为后续更深入地了解深海橄榄岩蛇纹石化过程提供参考。

深海阀门载荷与设计研究

随着陆地资源储量减少,海洋资源越来越受到各方的重视。深海阀门是深海资源开发的重要设备之一,也是目前深海勘探运输工程面临的难点。本文对深海阀门实际工作载荷进行分析,从功能性载荷、环境载荷和偶然载荷3种实际工况下的载荷类型进行概括和总结,并在其基础上展开对深海阀门关键技术研究的论述;从不同深海阀门载荷特点入手,讨论密封、深海静压力、地震、流体压力、海浪力等因素对深海阀门设计、运行的研究,对当前众多学者探索研究进行总结,从理论和实际应用探讨其优势并进行完善;最后对深海阀门载荷与设计研究进行展望。

四种常用高通量测序拼接软件的应用比较

新一代测序平台的诞生推动了对全基因组鸟枪法测序数据的拼接算法和软件的研究,自2005年以来多种用于高通量测序的序列拼接软件已经被开发出来,并且在不断地进行改进以提高拼接效果。本文利用目前广泛使用的高通量测序拼接软件Velvet、AbySS、SOAPdenovo和CLC Genomic Workbench分别对本试验室分离的一株噬菌体IME08的高通量测序结果进行拼接,介绍这几种拼接软件的安装使用及参数优化,并对不同软件的拼接结果进行比较,针对不同的拼接软件得到优化的拼接参数,可为其他研究人员使用上述软件提供参考借鉴。

海德格尔晚年对深渊哲学首次系统的公开表达——《思想的基本原则》中深渊问题的五个向度

《思想的基本原则》所包含的五个演讲,未明言地以离基-深渊为枢纽而建立起整体关联,也是海德格尔深渊哲学首次系统的公开表达。《思想的基本原则》揭示出了离基深渊的五个向度:离弃形而上学中存在者层次上的根据、向深渊的跳跃、作为本有的深渊、传统哲学的可论证性与逻辑学等方面的无基或深渊特征、作为语言之本质的离基-深渊。这在一定程度上也拓展了《哲学论稿》中深渊哲学的语言之维,并揭示出海德格尔思想从“存有的地方性”通向“存有的拓扑学”的路径。

“天人相应”视域中的汉藏医文化渊流关系阐释

汉医与藏医在“天人相应”思想的关照下,在独立传承、相互借鉴、相互勾连的过程中,在文化要素上呈现出诸多勾连,具体表现在“天人相应”思想在二者文化起源(生活与巫术)、思维方式(经验思维与意象思维)、诊疗方法、用药等方面的映现,并在病因病机、养生指导、医生医德等方面呈现出互通之处。从汉医和藏医文化交集的历史上足见汉医和藏医的渊流关系,中华各民族千百年的发展进程,是各民族大团结、大融合共同建设文明团结、和谐美丽生存环境的过程。从汉医和藏医文化交集的历史上,足见汉医和藏医皆为中华民族历史共同体地理空间内在交往交流交融的结果,并通过地方性知识生成了主体共性共在下的差异化医学知识谱系。

东非被动大陆边缘盆地构造—沉积特征及其对大气田富集的控制作用

东非海域近5年来发现了一系列大气田,主要分布于鲁武马盆地和坦桑尼亚盆地,可采储量达3.8×1012m3。通过区域构造演化、盆地构造—沉积特征研究,认为该区主要经历了3期构造—沉积演化阶段:1晚石炭世—早侏罗世卡鲁裂谷期,以河流相、湖相和三角洲相沉积为主;2中侏罗世—早白垩世马达加斯加裂谷期,以陆相和浅海相沉积为主,发育主力烃源岩;3晚白垩世—第四纪马达加斯加漂移期,以被动大陆边缘沉积为主,海底扇、斜坡扇和重力流水道等浊积砂岩构成主力储层,泥岩构成良好的区域性盖层。大气田主力成藏组合包括鲁武马盆地渐新统—上新统、古新统—始新统砂岩及坦桑尼亚盆地渐新统、上白垩统砂岩。鲁武马盆地大气田主要分布于深水区逆冲断层带及其前缘,重力滑塌和侏罗系盐底辟构造使鲁武马三角洲前缘广泛发育逆冲断层带,逆冲断层成为良好的油气运移通道,油气自深部烃源岩向上运移、聚集于逆冲断层带砂岩储层中;坦桑尼亚盆地大气田主要分布于斜坡重力流水道砂岩中,南北向正断层控制油气富集。