马里亚纳弧前区锥形海山岩石学及成因

锥形海山是马里亚纳弧前区非火山成因的海山。它是由俯冲的太平洋板块对仰冲板块的上推作用,地壳下的上地幔物质底辟侵入的结果。海山顶部的岩石是由蛇纹石化超镁铁质方辉橄榄岩组成。其主要矿物成分为斜方辉石、橄榄石、尖晶石、磁铁矿、蛇纹石和碳酸盐。手标本呈显晶质块状构造,薄片中呈粒状、残留状、筛网状及斑状变晶结构。岩石化学特征表现为:低Si和Al,高M/F值,含水,亏损了所有过渡金属。岩石的成因属超基性岩浆直接结晶,后经海水的参入,在热液作用下普遍发生蛇纹石化和碳酸盐化。     

伊比利亚西部洋-陆过渡带钻探成果

ODP 149航次的科学家在伊比利亚西部洋-陆过渡带意外发现了广泛的上地幔露头．经钻孔确定了伊比利亚深海平原700m厚的沉积层下方橄榄岩海岭的位置，发现橄榄岩露头约19km宽．     

俯冲带水圈-岩石圈相互作用研究进展与启示

俯冲带系统是研究地球水圈-岩石圈相互作用的天然实验室。俯冲板片所携带的水进入俯冲带系统,显著影响俯冲板片上地幔蛇纹石化程度、岛弧岩浆活动以及俯冲带地震机制等构造动力学过程。沿着环太平洋俯冲带,由主动源地震探测得到的板片含水量结果可以很好地解释区域相关地震观测,同时由被动源地震探测到的上地幔低速异常区域都与俯冲板片断层发育区相一致。多道反射地震探测与数值模拟都揭示了俯冲板块正断层广泛存在,可穿透莫霍面,深度可达海底下至少20 km。俯冲板块正断层为流体进入地壳与上地幔提供了重要通道,导致上地幔蛇纹石化程度达到1.4%,甚至更高。在洋壳俯冲过程中,随着温压增加,在不同深度脱水形成不同性质流体与地幔反应。通过俯冲带流体包裹体和交代成因矿物等的研究发现水岩相互作用广泛存在。本文旨在回顾俯冲板片含水量探测及水岩相互作用研究,简述近年来取得的重要进展以及对将来相关研究的启示。     

大洋钻探第 176 航次

钻探表明 ,洋壳是一个由上而下的简单序列 ,即沉积岩、枕状玄武岩 (和辉绿岩 )以及位于上地幔岩石之上的巨厚辉长岩 ,其边界接近莫霍面的概念与事物的真实情况相距甚远。原来 ,洋壳的结构和厚度与洋中脊岩浆房中熔化的岩浆容积和扩张速度有关。对北大西洋科恩转换断层区的钻探工作查明 ,在扩张速度低的海脊中 ,洋壳下部辉长岩层的结构与岩浆和动力 (构造 )过程有关。拖网在该区发现的大量蛇纹石化橄榄岩碎片表明 ,洋壳第三层 (辉长岩 )的大部分是由蛇纹石组成的。尽管数个航次已成功地钻至这个岩层 ,但至今仍未获得完整的剖面。有了完整的剖…     

烃类聚集与板块转换边界的关系

海底热液中的主要挥发性成分之一是氢和甲烷,它们是由于洋壳构造遭受连续性破坏地区上的地幔岩石蛇纹石化而形成的。一般来说,上地幔岩石中橄榄石的蛇纹石化可用下列公式来表示:q[Mg2SiO4]×3[Fe2SiO4] 14H2O=6Mg3[Si2O5](OH)4 2[Fe2O3×FeO] 4H 通过实验表明,蛇纹石化过程是在     

蓬莱新生代玄武岩中的单斜辉石巨晶及深源包体的矿物化学

利用电子探针分析蓬莱新生代玄武岩中的单斜辉石巨晶及尖晶石二辉橄榄岩包体中的主要造岩矿物(单斜辉石、斜方辉石、橄榄石和尖晶石)的化学组成。利用单斜辉石地质温压计和二辉石地质温度计计算了尖晶石二辉橄榄岩包体的平衡温度和压力,计算表明它们来自于上地幔的不同深度,同时推测本区上地幔内存在化学组成的分带性。     

西太平洋俯冲板块正断层系统与动力学特征

俯冲带是地球上最大地震的发源地。俯冲板块正断层为海水进入上地幔,引起蛇纹石化提供通道,其地震可能引发大海啸。研究其动力学机制,对推动俯冲带动力学过程研究及保护人类生命安全都具有重要意义。本文综述了西太平洋汤加海沟、马里亚纳海沟、伊豆-小笠原海沟和日本海沟俯冲板块外缘隆起带到海沟附近的正断层分布与变形特征,定量化阐明了地球动力学模拟方法揭示的西太平洋俯冲板块正断层形成过程。研究发现汤加海沟和马里亚纳海沟的正断层平均断距最大;俯冲板片有效弹性厚度变化直接影响正断层形成区域,而有效弹性厚度与板块年龄相关性较大。本文系统性回顾了西太平洋俯冲动力学研究并且提出了对未来相关研究的启示。     

马里亚纳南部弧内坡橄榄岩的岩石学及地球化学特征:对弧前地幔流体交代作用的指示

马里亚纳俯冲带弧内坡由于俯冲的太平洋板片的侵蚀而出露了相当于弧下地幔成分的橄榄岩,这些橄榄岩是研究岛弧岩浆作用及弧下地幔流体交代作用难得的样品。报道了马里亚纳南部关岛以南的弧内坡橄榄岩的矿物组成、主量元素以及微量元素地球化学特征。这些岩石具有非常难熔的矿物组成:橄榄石具有很高的Mg,斜方辉石中的Al2O3含量极低,尖晶石具有很高的Cr。滑石、蛇纹石和角闪石(透闪石为主,有少量镁角闪石和浅闪石)则指示了流体在中低温度下对橄榄岩的交代作用,并表明流体可能含有较高的SiO2、Al2O3和Na2O。全岩的主量元素中,CaO和Al2O3的质量百分比含量很低,而MgO的含量较高(干体系下多在43%左右),显示岩石经历了高度熔融。微量元素中,U和Sr的含量较高,相对富集,可能是来源较浅的板片流体化学特点的反映。     

云南马关新生代地幔包体中橄榄石的显微构造及其反映的上地幔物理状态特征

利用氧化缀饰法研究了云南马关新生代地幔尖晶石二辉橄榄岩包体中橄榄石的位错构造。其位错构造种类多样、形态各异,主要包括(100)和(001)位错壁、亚颗粒构造、位错网格、{100}滑动条带构造等,表明该区上地幔岩具高温高应变和低温高应变特征。包体形成的温度T为1016—1098℃,压力P为18.3×108—20.6×108Pa。马关上地幔温压状态具有大洋地幔地温特征,热流值达85mW·m-2。上地幔的流动应力σ为27.9—59.7MPa,流动速率ε为1.37×10-18—2.17×10-16s-1,等效粘滞度η为9.18×1022—6.92×1024Pa·s。该区上地幔的高流动应力、高热状态和裂谷带型的流动速率、等效粘滞度特征,可能与16MaB.P.以来区域性东西向伸展作用有关。     

IODP367和368航次——南海张裂陆缘

正IODP 367和368航次将解决大陆解体期间岩石圈的减薄过程。据深反射地震数据揭示,南海北部(SCS)岩浆匮乏的张裂陆缘是一处优良的钻探地点。南海北部陆缘与伊比利亚纽芬兰岛裂谷陆缘相似,可能包括洋陆过渡带(COT)内已剥露及蛇纹石化的地幔。然而,最近的模拟研究表明,板弱化机制与其他的次大陆存在的岩石圈地幔的蛇纹石化不同。板块破裂的两个模式(在很热的软流圈地幔的情况下)可以有所     

Distribution and Sources of Methane in the Water Layers of the Antarctic Straits: Bransfield Strait and Antarctic Sound

Oceanology - Methane concentrations were measured in the water layers on two transects crossing the central part of Bransfield Strait and along the Antarctic Sound. In the abyssal sea of the...     

Numerical modeling of the influence of exchange through the Bosporus and Dardanelles Straits on the hydrophysical fields of the Marmara Sea

A long-term (18 years) prognostic experiment on the formation of the Marmara Sea hydrodynamic structure driven by the exchange through straits with zero atmospheric forcing is carried out using a numerical nonlinear circulation model. The seasonal variability is taken into account by specifying the water temperature in the Bosporus. It is shown that the mutual adaptation of hydrophysical fields and their adjustment to the physical and geographical conditions of the sea are caused by rapid (tens of days) and slow (several tens of years) adjustment mechanisms. An S-shaped jet current directed from the Bosporus Strait to the Dardanelles is formed in the upper 20-m layer. A cyclonic eddy is periodically formed near the northern boundary of the Marmara Sea. An anticyclonic pattern is well defined in the central part of the sea. In deeper layers there is an abyssal jet current formed by the inflow of the high-density Aegean water to the Marmara Sea. These features of the Marmara Sea circulation are confirmed by observational data.     

Relation Matrix of Water Exchange for Sea Bays and Its Application

1 .IntroductionWater exchange of sea bays is a basic issue for marine environment study. Water exchange be-tween a coastal area andthe outside area dueto advection and diffusionis animportant waytoimprovethe water qualityinthe coastal area . Withthe rapid…     

Q structure of the oceanic crust

Compressional wave attenuations and velocities have been measured as a function of confining pressure in ophiolite samples representing a cross-section of the oceanic crust and uppermost mantle. Data are presented for basalts, diabase dikes, gabbros and a suite of serpentinites and peridotites showing a range of serpentization. An ultrasonic pulse-echo spectral ratio technique was used to determine the attenuations to confining pressures of 500 MPa. From this data a Q profile for the oceanic crust and upper mantle is presented. Q is found to moderately increase with depth through the pillow basalts of the upper oceanic crust. The sheeted dike rocks of Layer 2C show an increase in Q with depth due to progressive metamorphism (from greenschist to amphibolite facies). Q drops abruptly from Layer 2C to Layer 3, though it is not clear why the gabbros have such low Q's. The crust-mantle boundary is a Q discontinuity; however, the Q contrast between Layer 3 and the upper mantle could be altered by upper mantle serpentinization, interlayered gabbros and peridotites at the boundary, or serpentinized peridotite diapirs intruding the gabbroic section. Q varies significantly with the percentage of serpentinization in the ultramafic samples, with the largest changes in Q being at the extremes of zero and full serpentinization. Q is sensitive to the overburden pressure for all of the samples.     

深渊生物资源取样装备技术体系研究

针对深渊生物资源研究的需求，自主研发了用于全海深深度的深渊沉积物、水体和宏生物的保压取样装置，深渊沉积物保压转移装置，深渊微生物原位过滤及保存装置和高压培养高压酶学测定装置。在深海模拟环境验证了取样装置在万米深度下的工作性能。相关装置在“探索一号”科考船的TS15、TS21-1和TS21-2大洋科考航次中，搭载“奋斗者”号载人潜器、“2号”深渊着陆器、“原位实验”号着陆器于西菲律宾盆区和马里亚纳海沟进行了海上试验，成功获取了万米深度沉积物、水体和宏生物保压样品以及微生物原位过滤滤膜；成功进行了沉积物保压样品的保压转移试验。初步形成了深渊海域生物资源取样的装备技术体系，为深渊海底生物和基因资源开发，深渊生命过程等科学研究提供技术手段。     

太平洋卫星测高重力场与地球动力学特征

通过多卫星测高数据的综合处理，获得西太平洋卫星测高重力场，进行不同尺度、深度构造动力信息的分离，探讨诸边缘海盆的地球动力学问题。测高大地水准面反映了研究区板块相互作用的特点，其高频成分可以刻画各海盆的构造特征。测高空间重力异常也可刻画陆架构造及盆地分布，由其推算出的海底地形含有大量的海底构造信息。各边缘海盆的莫霍面埋深具有往南变浅的趋势，与菲律宾海各海盆的莫霍面埋深大致相当，说明岛弧两侧的构造动力强度基本相似。大尺度地幔流应力场总体上反映了欧亚板块向东南蠕散和太平洋板块向北西扩张的特点；日本海北侧和南海巽他陆架的中尺度上地幔对流与地幔柱之间有着密切关系，西菲律宾海的上地幔对流强化了日本-琉球-台湾-菲律宾岛弧的活动强度；小尺度地幔流主要限于软流圈层内部，在各海盆分散，而在冲绳海槽和马里亚纳海槽则会聚，可与均衡重力异常类比。还讨论了大、中、小地幔流体系的特点及相互之间的关系，籍以阐明海盆及海槽演化的地球动力学过程。     

唐山国际旅游岛内海水环境改善措施试验研究

文章基于潮流物理模型,研究分析了唐山国际旅游岛内海水动力和水体交换能力特性。研究结果表明,东侧排水河河宽度现有宽度较窄,内海东侧水流动力较弱,水体交换能力相对较差。拓宽排水河宽度,能有效增强内海东侧水动力,提高水体交换能力。适当拓宽排水河宽度,能改善唐山国际旅游岛内海水环境。     

Hydrographic structure in association with deep boundary current in the north of the Shikoku Basin

High quality CTD data were collected in the north of the Shikoku Basin where an abyssal boundary current has been observed through direct current measurements. Analyses of hydrographic data showed:

1. Colder and saltier water (heavier water) compared to surrounding waters is found above the continental shelf-toe and the eastern flank of the Kyushu-Palau Ridge where the existence of the abyssal boundary current has been expected. The heavier water has a horizontal extent of about 50 km.
2. The heavier water has the vertical scale of 2000 m from the sea bottom, and is associated with a thermal wind shear which enhances a component of the flow toward a direction looking the Nankai Trough (a trough located along the northern end of the Shikoku Basin) to the left in the abyss. The assumed “level of no motion” at about 2500 m depth gives the geostrophically estimated current in a good agreement with the directly measured current.

A volume transport associated with the colder and higher salinity water is estimated to be about 2 Sv off Cape Shiono-misaki which may include a recirculation above the Nankai Trough. This is about twice of the transport estimated in the interior of the Shikoku Basin through a vorticity balance between the stretching term and latitudinal variation of the planetary vorticity.     

Edwardsia sojabio sp. n. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae), a new abyssal sea anemone from the Sea ofJapan

The paper describes new deep-water edwardsiid sea anemone Edwardsia sojabio sp. n. which is very common on soft muddy bottoms at lower bathyal and upper abyssal depths in the Sea of Japan. It was recorded in high quantity in depths between 2545 and 3550 m and is the second abyssal species of the genus Edwardsia.     

海湾水交换对取排水工程的响应

建立三门湾附近海域的水动力和水质模型,研究核电站取排水工程对海湾水交换的影响。计算得到取排水工程建立后三门湾海域40 d的海水交换率由51.60%变为51.06%,降低了0.54%。将三门湾海域分区分析,结果发现靠近排水工程的汊道水交换率降低最多,降低了5.36%,其余区域水交换率也都有所降低,但是降低幅度不大。结果表明:取排水工程的建立使得湾内水流状况发生变化,不同区域的水交换率变化相差较大;排水工程切断了附近汊道水流与外海的交换,导致排水口附近海域水交换率降低最多。