印度洋Carlsberg洋脊玄武岩岩石地球化学特征及其地质意义   总被引：2，自引：0，他引：2  

淳明浩  于增慧  翟世奎 《海洋学报》2015,37(8):47-62

本文对采自印度洋Carlsberg脊14个站位的新鲜玄武岩样品进行了常量和微量元素组成分析,旨在研究岩浆源区地幔的性质以及岩浆作用过程。研究结果表明:该区玄武岩为典型的源于亏损型地幔的大洋中脊玄武岩,不同样品经历了不同程度的结晶分异作用,演化过程主要受控于橄榄石的结晶分异作用,部分样品中有单斜辉石结晶分异作用的影响,斜长石的结晶分异作用不显著;玄武岩岩浆来源于亏损型尖晶石二辉橄榄岩地幔的熔融,主微量元素组成中尚未见到富集型组分混入的证据;源区地幔不同比例的熔融作用及其后岩浆演化过程的差异是造成不同样品间地球化学性质差异的主要原因,彼此独立的局部岩浆作用过程是岩浆作用差异的主控制因素。Carlsberg脊玄武岩整体与全球标准大洋中脊玄武岩(N-MORB)平均组分相近,不同脊段间岩浆源区地幔的组成、熔融程度(比例)和熔融深度等无明显差异,这种特征向南直到CIR的北段。  相似文献   

Crustal structure and variation along the southern part of the Kyushu-Palau Ridge     

Xiaodong Wei  Weiwei Ding  Aiguo Ruan  Jie Zhang  Xiongwei Niu  Jiabiao Li  Yong Tang 《海洋学报(英文版)》2022,41(1):50-57

As an interoceanic arc, the Kyushu-Palau Ridge（KPR） is an exceptional place to study the subduction process and related magmatism through its interior velocity structure. However, the crustal structure and its nature of the KPR,especially the southern part with limited seismic data, are still in mystery. In order to unveil the crustal structure of the southern part of the KPR, this study uses deep reflection/refraction seismic data recorded by 24 ocean bottom seismometers to reconstruct a detail...  相似文献   

The terrace like feature in the mid-continental slope region off Trivandrum and a plausible model for India–Madagascar juxtaposition in immediate pre-drift scenario   总被引：1，自引：1，他引：0  

V. Yatheesh  G.C. Bhattacharya  K. Mahender 《Gondwana Research》2006,10(1-2):179

Bathymetry of the southwestern continental margin of India reveals the presence of an anomalous terrace like feature in the mid-continental slope region off Trivandrum. The genesis of this terrace of large areal extent ( 9000 sq. km.) is yet to be established. Based on exercises with several existing paleogeographic reconstruction models and updated compilation of identified offshore tectonic elements, this study attempts to identify a plausible model of India–Madagascar juxtaposition in immediate pre-drift scenario, which provides idea about genesis of this terrace. It is inferred that the terrace off Trivandrum and an anomalous bathymetric notch located in the northern Madagascar Ridge are conjugate features related to India–Madagascar separation and the rifted and sheared segments of the pre-drift plate boundary have shaped their outlines. The drifting of India from Madagascar is suggested to have commenced at about 86.5 Ma.  相似文献   

Depositional Age of a Fossil Whale Bone from São Paulo Ridge,South Atlantic Ocean,Based on Os Isotope Stratigraphy of a Ferromanganese Crust          下载免费PDF全文

Tatsuo Nozaki  Yutaro Takaya  Takashi Toyofuku  Ayaka Tokumaru  Kosuke T. Goto  Qing Chang  Jun‐ichi Kimura  Yasuhiro Kato  Katsuhiko Suzuki  Adolpho Herbert Augustin  Hiroshi Kitazato 《Resource Geology》2017,67(4):442-450

Whale carcasses (whale falls) deposited on the deep seafloor are associated with a distinctive biotic community. A fossil whale bone recovered from São Paulo Ridge, South Atlantic Ocean, during cruise YK13–04 Leg 1 of R/V Yokosuka was covered by a ferromanganese (Fe–Mn) crust approximately 9 mm thick. Here, we report an age constraint for this fossil bone on the basis of Os isotopic stratigraphy (¹⁸⁷Os/¹⁸⁸Os ratio) of the Fe–Mn crust. Major‐ and trace‐element compositions of the crust are similar to those of Fe–Mn crusts of predominantly hydrogenous origin. Rare earth element concentrations in samples of the crust, normalized with respect to Post‐Archean average Australian Shale, exhibit flat patterns with positive Ce and negative Y anomalies. These results indicate that the Fe–Mn crust consists predominantly of hydrogenous components and that it preserves the Os isotope composition of seawater at the time of its deposition. ¹⁸⁷Os/¹⁸⁸Os ratios of three Fe–Mn crust samples increased from 0.904 to 1.068 in ascending stratigraphic order. The value of 1.068 from the surface slice (0–3 mm depth in the crust) was identical to that of present‐day seawater within error (~1.06). The value of 0.904 from the basal slice (6–9 mm) equaled seawater values from ca. 4–5 Ma. Because it is unknown how long the bone lay on the seafloor before the Fe–Mn crust was deposited, the Os stratigraphic age of ca. 5 Ma is a minimum age of the fossil. This is the first application, to our knowledge, of marine Os isotope stratigraphy for determining the age of a fossil whale bone. Such data may offer valuable insights into the evolution of the whale‐fall biotic community.  相似文献   

西菲律宾海盆的构造沉积特征及对海盆演化的指示——来自地球物理大断面的证据     

董冬冬  张正一  张广旭  白永良  范建柯 《海洋与湖沼》2017,48(6):1415-1425

菲律宾海发育了全球最典型的沟弧盆体系,新老俯冲系统众多,是研究大洋板块扩张过程的理想场所。本文主要利用2015年中科院海洋所在西菲律宾海采集的1400km地球物理大断面,并结合最新的重力数据,对比、分析了西菲律宾海内部古扩张中心(中央海盆裂谷)和残留弧(九州-帕劳海脊)的沉积地貌和地壳结构特征。研究表明:(1)中央海盆裂谷内部发育远洋沉积为主的沉积物,沉积层序分布不均,局部盆地内沉积物厚度可达300m。九州-帕劳海脊附近发育与火山碎屑物源有关的厚层沉积物;(2)以129°30′E处的转换断层为界,裂谷东西部洋壳结构分别体现"慢速"和"快速"扩张特征,东部洋壳岩浆供应较少,厚度较小,断裂较为发育,其附近可能发生水岩作用;西部洋壳岩浆供应较多,厚度较大,结构相对均一;盆地西部的小规模地幔柱可能控制了裂谷东西部不同洋壳结构的发育;(3)九州-帕劳海脊内的角度不整合面代表岛弧裂解事件,张裂与挤压构造共同发育反映了裂解过程的复杂性。  相似文献   

Lipid biomarker composition in surface sediments from the Carlsberg Ridge near the Tianxiu Hydrothermal Field     

Shengyi Mao  Hongxiang Guan  Lihua Liu  Xiqiu Han  Xueping Chen  Juan Yu  Yongge Sun  Yejian Wang 《海洋学报(英文版)》2021,40(8):53-64

Hydrothermal venting has a profound effect on the chemical and biological properties of local and distal seawater and sediments. In this study, lipid biomarkers were analyzed to examine the potential influence of hydrothermal activity on the fate of organic matter(OM) in surface sediments around Tianxiu Hydrothermal Field in the Carlsberg Ridge(CR), Northwest Indian Ocean. By comparing the biomarker distributions of the samples with that of other typical hydrothermal sediments in the mid ocean ridge, it is shown that the location of the samples is not affected by the hydrothermal activity. The relatively low abundances of terrestrial n-alkyl lipids and riverine1,15-C32 diol suggested a minor contribution of terrigenous OM to the study area. The bacteria contributed predominantly to sedimentary marine OM; however, other marine source organisms, e.g., eukaryotes(i.e.,phytoplankton and fungi) could not be completely neglected. The marine-originated biomarkers showed significantly variable distributions between the two sediments, suggesting different dynamic physical and biogeochemical processes controlling the fate of marine OM. This study identified various diagnostic biomarkers(5,5-diethyl alkanes, diols and β-OH FAs), which may have significant environmental implications for future works in this region.  相似文献   

Palinspastic reconstruction of the Grenville terrane in the Blue Ridge Geologic Province,southern and central Appalachians,U.S.A     

M. J. Bartholomew 《Geological Journal》1983,18(3):241-253

Examinations of Grenville massifs in the Blue Ridge Geologic Province of Virginia and North Carolina indicate that the country rocks (∼ 1100–1450 Ma) are layered gneisses that were metamorphosed during Grenville orogenesis (∼ 1000–1100 Ma) to amphibolite to granulite facies and intruded by plutonic suites. Subsequently, the Grenville terrane was intruded by a suite of peralkaline granitic plutons (∼ 700 Ma) and progressively overlapped westward by Upper Precambrian to Cambrian sedimentary and volcanic rocks. Following deposition of Upper Precambrian and Palaeozoic rocks, the Blue Ridge Geologic Province was subjected to Taconic metamorphism (∼ 450–480 Ma) which generally increased in intensity southeastward from greenschist (chlorite grade) to upper amphibolite (sillimanite grade) facies. Large-scale late Devonian thrusting (∼ 350 Ma) along the Fries fault system and the Brevard zone-Yadkin fault system produced the present day distribution of juxtaposed Grenville massifs and Palaeozoic metamorphic zones in the Blue Ridge Geologic Province. Palinspastic restoration of the Taconic metamorphic zones to their pre-late Devonian relative positions yields an ∼ 50 km displacement on the Fries fault system near the Grandfather Mountain window and and an ∼ 80 km displacement on the Smith River allochthon farther east. Restoration of the Grenville massifs to this same palinspastic base shows that Grenville metamorphic grade decreased southeastward from the deeper granulite facies (opx + gar) to the shallower granulite facies (opx ± amp) to amphibolite facies.  相似文献   

地基微波遥感大气水汽总量的普适性回归反演   总被引：7，自引：2，他引：7       下载免费PDF全文

吕达仁  魏重  忻妙新 《大气科学》1993,17(6):721-731

本文利用不同季节、经纬度和海拔高度的历史探空资料为样本,用回归分析和岭回归分析相结合建立了适用于全球各地的双波长地基微波辐射计遥感晴空大气水汽总量的回归方程.多种数值检验表明,所提出的反演关系式的精度较高能提供实际应用.同时,将20.6和31.65GHz及22.2和35.0GHz两组频率对的结果作了比较.  相似文献