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1.
Dwijesh RAY Sridhar D. IYER Ranadip BANERJEE Saumitra MISRA M. WIDDOWSON 《《地质学报》英文版》2007,81(1):99-112
1 Introduction The Northern Central Indian Ridge (NCIR) between 3° and 11°S latitudes is joined to the north with the slow spreading Carlsberg Ridge (CR; ~24–26 mm/a, full spreading rate) and to the south with the intermediate spreading Southern Central Indian Ridge (SCIR; ~50 mm/ a) (Fig. 1). Earlier petrological investigations of the Central Indian Ridge were concentrated either on or along the CR to the north and at the southern end of the CIR up to the Rodriguez Triple Junc… 相似文献
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新疆东准噶尔克拉麦里蛇绿岩地球化学：洋脊俯冲的产物 总被引：5，自引：5，他引：5
新疆东准噶尔克拉麦里蛇绿岩中的镁铁质岩兼具有洋中脊玄武岩(MORB)和岛弧拉斑玄武岩(IAB)的特征,岩石地球化学特征表现为轻稀土(LREE)亏损、平坦或略微富集,不同程度地亏损高场强元素(HFSE)而富集大离子亲石元素(LILE),成分上非常相似于受洋脊俯冲影响的 Chile Ridge 和 Cocos Ridge 玄武岩。可以认为其可能形成于受洋脊俯冲影响的岛弧或弧前扩张环境。相对较高的ε_(Nd)(t)(7.2～9.8)、低 Nb/Zr、Ta/Yb 比值,说明在洋脊俯冲的影响下,其源区可能存在有至少三种组分:弧下地幔、来自消减板片流体和俯冲沉积物、MORB 地幔。 相似文献
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<正>The Southwest Indian Ridge is an ultraslow spreading ridge(~14-mm/yr)that formed~150 Ma with the breakup of Gondwana.It extends 7700 km from the Bouvet to the Rodriguez Triple Junction,crossing over the flank of the large southern Geoid high centered over Marion and Crozet islands and the Conrad Rise.There is a 相似文献
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HUANG Chi-Yue 《地球学报》2009,30(Z1):18-18
Marine surveys show that the submarine Huatung Ridge extends northward to the Lichi Mélange in the southwestern Coastal Range, suggesting that formation of the Lichi Mélange is related to the arcward thrusting of the forearc strata in the western part of the North Luzon Trough during the active arc-continent collision off southern Taiwan. New seismic survey along 21oN transact across over the North Luzon Trough in the in-cipient arc-continent collision zone further reveals that the deformation of the Huatung Ridge occurs soon after the sedimentation in the western forearc basin, while the sedimentation is continuous in the eastern part of the remnant North Luzon Trough until the complete closure of the forearc basin approaching to SE Taiwan. This suggests that the sequence in the Huatung Ridge can just be coeval to the lower sequence of the remnant forearc basin strata. Multiple lines of new evidence, including micropaleontology, clay mineralogy and fis-sion track analyses along the Mukeng River and its tributary key sections, are used to test this thrusting forearc origin hypothesis of the Lichi Mélange. 相似文献
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20060457 Chen Ronghua (Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, SOA, Hangzhou 310012, China ); Zhao Qingying Late Quaternary Carbonate Records in the West Flank of Juan De Fuca Ridge, Northeastern Pacific O- cean (Marine Geology & Quaternary Geolo- gy, ISSN0256-1492, CN37-1117/P, 25(1), 2005, p. 41 —46, 1 illus. , 4 tables, 15 refs. , with English abstract) Key words: Quaternary, carbonate, East Pacific Ocean 20060458 Feng Weimin (Nanjing In… 相似文献
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Tian-yu Zhang Pan-feng Li Lu-ning Shang Jing-yi Cong Xia Li Yong-jian Yao Yong Zhang 《China Geology》2022,5(1):96-109
The Philippine Sea Plate is located at the convergence zone of the Eurasian Plate,the Pacific Plate,and the Indo-Australian Plate.This paper divides the Philippine Sea Plate into two second-order tectonic units and eight third-order tectonic units by summarizing the marine geological,geophysical,and submarine geomorphological data of the Philippine Sea Plate collected for years and referring to the seafloor spreading theory and the trench-arc-basin system.The two second-order tectonic units are the West Philippine Sea block and the Izu-Bonin-Mariana arc-basin system.The former includes the West Philippine Basin,the Huatung Basin,the Daito Basin,and the Palau Basin,while the latter consists of the Kyushu-Palau Ridge,the Shikoku-Parece Vela Basin,the Izu-Bonin Arc,and the Mariana Arc.Furthermore,this study concludes that the Philippine Sea Plate has undergone three stages of tectonic evolution,namely the early stage of the evolution of marginal basins with Cretaceous basement(Early Cretaceous),the middle stage of the spreading of the West Philippine Basin(Eocene),and the late stage of the subduction of the Izu-Bonin-Mariana arc-basin system(Oligocene-present).The Kyushu-Palau Ridge is a window to discover the tectonic evolution of the Philippine Sea Plate due to its unique geographical location. 相似文献
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Mid-Ocean Ridge Basalts (MORB) from the Northern Central Indian Ridge (NCIR) were recovered between latitudes 3° and 11°S and are olivine tholeiite with higher abundances of K and Rb.They are of typical transitional MORB (T-MORB) variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg# ＞ 0.68 are the product of partial melting at an estimated pressure of ～ 1 GPa. It is inferred that the magma was subsequently modified at a pressure ＞ 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure (between 1-0.5 GPa), the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2O5 and Na2O. There was,however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K2O. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cr. In addition, the ∑REE of the magma also increased with fractionation,without any change in (La/Yb)n value. 相似文献
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在奥林匹克坝cu-U-Au矿床、基鲁纳铁矿、佩阿里奇(Pea Ridge)铁矿床、以及加拿大育空地区的沃内克山中许多Cu-U-Au矿化角砾岩体的近期研究工作表明,这些矿床是一类与大陆裂谷作用有关的元古宙铁—稀土矿床。在澳大利亚的斯图亚特陆架,铁主要呈赤铁矿产在蚀变的碱性花岗岩内形成角砾岩—岩墙杂岩体的异类角砾岩中(奥林匹克坝),或呈赤铁矿或磁铁矿细网脉矿床产在火山岩中(阿克罗波里斯)。在育空地区的沃内克山中,80多个角砾岩墙和岩筒位于中元 相似文献
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洋岛和洋底高原玄武岩数据挖掘：地球化学特征及其与MORB的对比 总被引：6，自引：0，他引：6
本文集合了GEOROC和PetDB两个数据库的资料,对全球洋岛玄武岩(Ocean Island Basalt,OIB)和洋底高原玄武岩(Ocean Plateau Basalt,OPB)数据进行分析研究。OIB和OPB是板内岩浆活动的产物,其形成一般与地幔柱(热点)有关。OPB通常指示地幔柱的头部,温度相对较低;OIB代表地幔柱的尾部,温度较高。我们对OIB的数据研究表明,OIB中的不相容元素并非像先前认为的那么富集,在构造判别图中,OIB和洋中脊玄武岩(Mid Ocean Ridge Basalt,MORB)有很大一部分是重叠的,揭示OIB源区既有强烈富集不相容元素的,也有明显亏损的,甚至还有强烈亏损类似岛弧玄武岩(Island Arc Basalt,IAB)的。OPB是指发育在海洋和大陆边缘的来自地幔的巨量玄武岩,虽然与OIB同属于板内环境,但OPB的地球化学性质更接近富集型洋中脊玄武岩(Enrich Mid Ocean Ridge Basalt,E-MORB),可能具有OIB和MORB之间过渡的特征。研究表明,OIB和OPB的源区除了来自下地幔以外(地幔柱),部分可能来自上地幔,有些还可能与板块消减带物质的再循环作用有关。因此,OIB和OPB的成因不可能只用地幔柱一种模式予以解释,还应当考虑板块活动中其他因素(洋壳再循环、古老陆壳再循环、消减带物质以及水的加入,部分熔融程度、岩浆混合作用、不同地幔端元混合等)的影响。 相似文献
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The Siberian–Icelandic hotspot track is the only preserved continental hotspot track. Although the track and its associated age progression between 160 Ma and 60 Ma are not yet well understood, this section of the track is closely linked to the tectonic evolution of Amerasian Basin, the Alpha-Mendeleev Ridge and Baffin Bay. Using paleomagnetic data, volcanic structures and marine geophysical data, the paleogeography of Arctic plates (Eurasian plate, North American Plate, Greenland Plate and Alaska Microplate) was reconstructed and the Siberian–Icelandic hotspot track was interlinked between 160 Ma and 60 Ma. Our results suggested that the Alpha-Mendeleev Ridge could be a part of the hotspot track that formed between 160 Ma and 120 Ma. During this period, the hotspot controlled the tectonic evolution of Baffin Bay and the distribution of mafic rock in Greenland. Throughout the Mesozoic Era, the aforementioned Arctic plates experienced clockwise rotation and migrated northeast towards the North Pacific. The vertical influence from the ancient Icelandic mantle plume broke this balance, slowing down some plates and resulting in the opening of several ocean basins. This process controlled the tectonic evolution of the Arctic. 相似文献
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《吉林大学学报(地球科学版)》2015,(Z1)
<正>卡尔斯伯格洋中脊(Carlsberg Ridge;CR)位于印度洋北部,南端与中印度洋中脊相连,北端延伸进入红海。CR洋脊半扩张速率为11-16mm/yr(Ramana,et al.1993),为慢速扩张洋脊,具有类似于北大西洋中脊的地形地貌特征(Raju,et al.2008)。作为印度洋中脊的重要组成部分,CR洋脊是最年轻和最复杂的洋脊之一,也是研究程度最低的洋脊之一(Murton,et al.2005;Nauret,et al.2006;Ray,et al.2013)。印度 相似文献
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B. Gehrke K. S. Lackschewitz H. -J. Wallrabe-Adams 《International Journal of Earth Sciences》1996,85(3):525-535
Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to
identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses.
The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary.
Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial
distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on
the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from
the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability
in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and
glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts
of illite, chlorite, and kaolinite characterize ice-rafted sediments of the “Heinrich layers”. In these sediments smectite
crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order,
similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained
sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic
surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations
and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating
a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase
in fine-grained quartz (<2μm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted
material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of
fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated
at around 10 ka, where a strong increase in smectite of low crystallographic order is detected. 相似文献
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《Scientia Geologica Sinica》1999,(1)
1.IntroductionStudyontheclimaticchangesontimescalesof10'-yearduringthelastdeglaciationperiodandtheirenvironmentaleffectsmaybeexpectedtoprovidevaluableknowledgeforpredictingpossibletrendofclimaticchangesinthefutUreglobalwarming.TheclimaticsignalsinrelationwiththeNorthAtlanticYoungerDryasEventhavebeenreportedinalargenumberofterrestrialrecordsinChina(e.g.Gasseetal.,1991,Anetal.,1993)andinthesurroundingoceans(Kudrassetal.,1991;Broekeretal.,1988,Wangetal.,1994).However,theclimaticbehaviourofth… 相似文献
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青藏高原南部谢通门地区出露-些中侏罗世的闪长岩,岩石具有类似于埃达克质岩的地球化学特征,如高的Si02(＞59％)、Sr (771 ～798μg/g)、低HREE和Y(＜12 μg/g)含量,高Sr/Y(＞64)、La/Yb(4.4＜ (La/Yb)N＜19.2)值,较高的MgO (3.02％ ～3.17％),具有一定Sr正异常和无明显Eu负异常.拉萨地块南部在中侏罗世时期不仅发育有基性和酸性的岩浆作用,而且还发育有斑岩型矿床——雄村斑岩Cu-Au矿床.另外,谢通门闪长岩具有与太平洋西北部Bowes Ridge地区中基性埃达克质岩十分相似的地球化学特征,而后者形成于中新世俯冲大洋板片断离的构造环境之中.因此研究区中侏罗世谢通门闪长岩很可能为北向俯冲的新特提斯洋板片断离并发生部分熔融的产物. 相似文献
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《地质科技情报》1989,(Z1)
泥盆系-密西西比系的Pilot页岩为Alligator Ridge浸染型金矿床的主岩。该矿床与美国西部大盆地中的另一些浸染型金矿床类似,人们研究过Pilot页岩中的有机质,试图确定有机质的来源及其成熟过程,找到一种比矿物蚀变模式能更精确地反映这种贵金属分布状态的蚀变参数。本研究采用石油勘探中的一般技术方法测定Pilot页岩中的有机质类型,丰度及成熟度。岩石标本和矿石标本中有机质的类型、丰度均十分相似。对于酪根采用透射光研究,结果表明大部分有机质主要由细小的非晶质(海藻来源的)集合体构成,并含有少量镜质体。它们与Tissot和Welte(1978)提出的来源于海洋的第Ⅰ类或第Ⅱ类有机质吻合。在Alligator Ridge矿床的大多数碳酸盐岩中有机碳总量最高可达1%~3%。没有发现任何证据说明有机质是热液输入及活化转移的。对有机质作畜热裂解分析、并测定其镜质体反射率,研究有机质的成熟程度,结果表明含矿标本中有机质的成熟度明显高于未受成矿作用影响的标本。合矿标本的氢指数值一般小于40(H/C原子比值约为0.5),与之相比,岩石标本则为230~315(H/C为1)。镜质体反射率的变化显示出相似的但不大明显的变化:含矿标本中镜质体反射率为1%~1.3%,而岩石标本镜质体反射率为0.4%~0.5%。除了靠近Pilot页岩下部的接触带以外,在远 相似文献
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1Introduction Seamountsarethewell knownfeaturesinthe world’soceans,beingmostcommoninthePacific (Smith,1988;Pringleetal.,1991;Hasse,1991). Recentvolcanicactivityoccursinthezonesondi vergentorconvergentplatemarginsorintheintraplate regimes.Seamountsexisteitherasisolatedvolcanic edifices(Gardneretal.,1984;MertzandRenne, 1995)or,sometimes,formlinearchainstogetherwith oceanislands.Anumberofgeochronologicalinvestiga tionsonoceanislands(DuncanandMcDougall,1974; Dymond,1975;McDougall,1979… 相似文献