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1.
麦哲伦海山链主要由十多座相对独立的平顶海山组成,呈北西向展布于太平洋海山密集区。结合前人对麦哲伦海山链形成和漂移的认识,从板块运动和几何学角度出发采用backtracking和hot-spotting海山追踪方法对该区海山的起源与形成进行了研究,结果表明,麦哲伦海山链是多热点成因的板内火山和板块构造运动共同作用的产物,最初于白垩纪期间由法属玻利尼西亚热点群西侧呈北北西向排列的热点活动产生,继而受到板块运动与区内近南北向和北北东向两组断裂及其热活化等的改造作用,最后形成了现今看到的平顶海山。 相似文献
2.
在利用地磁模拟方法的基础上，计算出麦哲伦海山群中的两个海山的古地磁数据。根据计算数据分析，对这些海山的年龄进行推测，据估算，这些海山的年龄相当于是白垩世，同时，还计算受力的太平洋板块运动的北分量为３．５ｃｍ／ａ所获结果与较早对海山年龄的估算及太平洋向北运动的速度非常吻合，这足以说明，复地磁模拟方法解决类似任务的有效程度。 相似文献
3.
《海洋地质与第四纪地质》2001,21(4):18-18
夏威夷—皇帝海山链的弯曲是固定热点基准结构中记录了板块运动变化的最好例证。换句话说 ,弯曲首先记录了夏威夷热点相对于太平洋岩石圈的运动差异。 4种研究支持近来的观点 :(1 )从相对板块运动数据预测的全球板块运动 ;(2 )源于北太平洋海盆的板块扩张速率数据 ;(3 )利用地球和地震层析成像技术的地幔流模拟 ;(4 )来自皇帝海岭的新的古地磁数据。虽然受以前钻探的限制要获得板块运动速率的数据仍相当困难 ,但是最实用的古地磁数据表明太平洋热点已经迁移 ,其运动速率可与晚白垩世至早第三纪 (81～43 Ma)的岩石圈板块相比。如果这个数据… 相似文献
4.
海坛岛频临太平洋边缘活动带，晚三叠纪以来太平洋板块向欧亚大陆板块的俯冲奠定了其地貌发育的基础。以差异性断块升降运动为特征的新构造运动和以流水、风以及海洋动力为主的外力的相互作用，塑了海坛岛的现代于貌景观。第四纪以来气候一海面的频繁变动对其地貌的发育也有着深刻的影响。海坛岛的地貌可划分为流水、风成和海成地貌三大类共１０种地貌基本类型。 相似文献
5.
图瓦卢是个位于太平洋玻利尼西亚群岛西部一岛国。介于东径176°～179°5′之间和南纬5°～10°5′之间。它是由9个大体上按西北—东南方向排列的珊瑚环礁组成,象链条一样绵延579公里散布在130万平方公里的海面上。图瓦卢(Tuvalu)是由9个环礁组成,即富纳富提、纳努芒阿、纳诺梅阿、纽陶、努伊、纽拉基塔、努库费陶、努库莱莱和瓦伊图普。其 相似文献
6.
按照“热点”理论,从该区升起的岩浆“柱”“穿透了”在其上缓慢移动的岩石图板块。在这种情况下产生了火山链。夏威夷岛向东南35km的太平洋底可作为观察这些过程的合适地点。洛依希活火山位于该区水下,它是由来自巨大的地下熔岩“柱”的岩浆补给的。喷出的熔岩在海底形成了高达3500m的海山,并继续生长。由海底火山产生了海岛@朱佛宏 相似文献
7.
西太平洋若干沟-弧-盆体系及板内岩浆成因研究进展 总被引：1，自引：0，他引：1
板块俯冲和板内岩浆作用都是导致地表和地球内部物质大规模循环的重要地质过程。但是,两个地质过程的岩浆成因机制,以及成因上的内在联系都存在很大争议。西太平洋是全球沟-弧-盆体系最发育的地区,也是全球板内火山作用(海山和洋底高原)分布最集中的场所。为阐明西太平洋海盆的上地幔软流圈性质、岛弧岩浆形成的控制机制、以及板块内部火山作用(碱性火山岩)的成因机制,在中国科学院战略性先导科技专项(A类)"热带西太平洋海洋系统物质能量交换及其影响"项目的资助下,本文对西太平洋马里亚纳-雅浦俯冲系统、汤加-科玛迪克俯冲带及其俯冲前缘海盆的成因机制、南中国海扩张期海盆玄武岩和板内火山作用、西太平洋海盆上地幔的Dupal异常分布和成因机制等展开了系统的岩石学和地球化学研究,并取得了新的科学认识和成果。主要认识包括:(1)雅浦岛弧主要由变质岩-角闪岩组成,其形成于3—6Kbar温压条件下,代表岛弧下部来自帕里西维拉海盆的变质基底;(2)加洛林洋脊主要由玄武岩组成,其不是一个岛弧,而可能是一个地幔柱形成的洋底高原;(3)汤加-科玛迪克岛弧岩浆组成体现了西南太平洋俯冲板片俯冲速率的直接影响;(4)厘定了汤加-科玛迪克俯冲前缘板块的年龄(103.7Ma),并认识到其代表古太平洋扩张中心并消耗了Ontong Java超级地幔柱的组分;(5)首次在南海发现了碳酸盐化的硅酸岩岩浆向碱性玄武岩转化的现象,提出了板内碱性玄武岩成因的新链条;(6)西太平洋海盆的地幔广泛存在Dupal异常,该异常从西太平洋岛弧俯冲带一直延伸至南海海盆,其中南海海盆的Dupal异常主要受到大陆裂解和海南地幔柱作用的双重影响。通过以上认识,进一步揭示了西太平洋沟-弧-盆体系和板内岩浆体系作用机制,以及俯冲板片物质与板内火山活动之间的成因关联,这对于深刻理解板块构造导致的地球内外物质循环规律有一定的推动作用。 相似文献
8.
对广东三水盆地上白垩统三水组、大 山组、古新统莘庄组及始新统 心组、宝月组的系统的古地磁研究结果表明：（１）旋转运动是该区构造运动的主要形式，顺时针旋转盆地拉张发育，这时针旋转盆地挤压衰亡，发育的程度与旋转角度有关；（２）始新世该区旋转方向由顺时针旋转变为道时针旋转，对应于太平洋－库拉板块对欧亚板块作用方向的改变，说明三水盆地的形成发育与太平洋－库拉板块对欧亚板块的作用密切相关；（３）三水盆地所在的华南地块从晚白垩世至始新世在纬向上不存在明显的运动，一直停留在略低于现今纬度的位置上。 相似文献
9.
10.
南海海盆形成演化模式初探 总被引：12，自引：2，他引：12
为了解南海大陆架及邻近海域的基础地质环境，我们于１９９１－１９９５年编制了《南海大陆架及邻近海域基础环境图集》。编图过程中，针对南海的地质地球物理特征，在研究了南海周围地区地质构造及前人研究成果的基础上，提出了南海海盆地受印澳板块与欧亚板块及太平洋板块与欧亚板的双重影响，它们之间的相互作用引发南海地区地幔单向流动及流动方向的改变，造成地壳拉张陷形成南海海盆的模式。 相似文献
11.
A. P. Sedov G. I. Kazakevich V. V. Matveenkov L. P. Volokitina S. V. Luk’yanov V. A. Rashidov 《Oceanology》2008,48(4):578-587
A possible mechanism of the formation of chains of intraplate seamounts and islands alternative to the “hot spot” hypothesis is considered. It is related to the appearance of additional stresses in the lithospheric plate when it ascends over a mantle inhomogeneity and descends from it. The magnitude of these stresses (～600 bar) is sufficient for formation of deep fracture zones. In the paper, schemes of formation of volcanic chains are described. The formation of the “faults-volcanoes-volcanic chains” sequence may follow two different ways. The first is controlled by the fracture zones formed along the direction of the plate movement. In this case, feeding channels are localized along the boundary of the rise. If the chain is gradually formed simultaneously with the plate motion, the age of the volcanoes along the chain may change in a more or less regular way. The second type is formed by fractures orthogonal to the movement direction. They may be formed when the plate ascends over a mantle inhomogeneity and/or descends from it. In this case, adjacent volcanoes may have similar ages. A combination of these two variants may also be encountered. The mechanism posed allowed us to explain selected facts referring to the volcanic chains of French Polynesia and may be applied to other regions of the Pacific Ocean. 相似文献
12.
通过对中西太平洋海山形态剖面的山体高度、山顶直径、基底直径、山顶直径与基底直径之比、山体坡度、山体高度与基底直径比值六个参数多元统计分析,发现可以根据山体高度与基底直径的比值对海山形态类型进行分类:比值小于0.10的为平顶海山(Ⅰ类),大于0.10的为尖顶海山(Ⅱ类),对于等于0.10的海山需参考平坦度和山体坡度,平坦度大和山体坡度缓的为Ⅰ类,反之为Ⅱ类。西太平洋的麦哲伦海山区、马绍尔群岛基本以平顶海山为主,介于中西太平洋之间的威克—马尔库斯海山区和中太平洋海山区、莱恩群岛平顶海山与尖顶海山共同发育。对各种类型海山上钴结壳分布研究发现,无论是在尖顶海山还是在平顶海山,板状结壳均比较发育,但砾状结壳在平顶海山比在尖顶海山的发育。中太平洋尖顶海山的结壳比平顶海山的发育,但由于山顶面积小,钴结壳资源量不大。仅从平顶海山看,在麦哲伦海山区、威克—马尔库斯海山区板状结壳比中太平洋海山区、马绍尔群岛、莱恩群岛的板状结壳发育,前者的板状结壳平均厚度大于3 cm,后者的板状结壳平均厚度小于3 cm,总体上是西太平洋平顶海山钴结壳比中太平洋平顶海山的发育。两种类型海山各方向上的资源分布明显不同,在平顶海山的西部山坡的资源比东部山坡的丰富,尖顶海山的则刚好相反。 相似文献
13.
Moo Hee Kang Hyun-Chul Han Hyesu Yun Gee Soo Kong Kyong O. Kim Youn Soo Lee 《Marine Geophysical Researches》2007,28(3):257-269
A seamount chain with an approximately WNW trend is observed in the northeastern Ulleung Basin. It has been argued that these
seamounts, including two islands called Ulleung and Dok islands, were formed by a hotspot process or by ridge related volcanism.
Many geological and geophysical studies have been done for all the seamounts and islands in the chain except Anyongbok Seamount,
which is close to the proposed spreading ridge. We first report morphological characteristics, sediment distribution patterns,
and the crustal thickness of Anyongbok Seamount using multibeam bathymetry data, seismic reflection profiles, and 3D gravity
modeling. The morphology of Anyongbok Seamount shows a cone shaped feature and is characterized by the development of many
flank cones and flank rift zones. The estimated surface volume is about 60 km3, and implies that the seamount is smaller than the other seamounts in the chain. No sediments have been observed on the seamount
except the lower slope, which is covered by more than 1,000 m of strata. The crustal structure obtained from a 3D gravity
modeling (GFR = 3.11, SD 3.82 = mGal) suggests that the seamount was formed around the boundary of the Ulleung Plateau and
the Ulleung Basin, and the estimated crustal thickness is about 20 km, which is a little thicker than other nearby seamounts
distributed along the northeastern boundary of the Ulleung Basin. This significant crustal thickness also implies that Anyongbok
Seamount might not be related to ridge volcanism. 相似文献
14.
Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province(WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new ~(40)Ar/~(39) Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt(OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element(REE) patterns and a spider diagram of the samples in this study show OIB(Ocean Island Basalt) like behavior. The range of ~(87)Sr/~(86) Sr values is from 0.704 60 to 0.706 24, the range of ~(206)Pb/~(204) Pb values is from 18.241 to 18.599, and the range of ~(143)Nd/~(144) Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new ~(40)Ar/~(39) Ar age data show that these seamounts formed at ～97 and ～106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins. 相似文献
15.
Ye. V. Zhuleva 《Oceanology》2010,50(1):107-112
The volumes of formed volcanoes are an important indicator of the formation intensity of the ocean floor volcanogenic morphostructure
under different geodynamic conditions. The distribution of the volumes of volcanoes that formed within the oceanic lithosphere
of different geological ages is considered to analyze the spatial and time dynamics of the scopes of the seamount formation.
The greatest volumes of effused rocks concentrate in volcanoes of different heights on the different-age segments of the lithosphere.
The total volumes of volcanogenic substance growing with increasing age and thickness of the lithosphere is caused by the
increasing range of the heights of the formed volcanoes and the growing number of big seamounts. Despite that the volcanic
seamounts formed within the mid-oceanic ridges, on the divergent boundaries of the lithospheric plates and in the transform
faults most often, half of the volcanogenic material was emitted to the earth’s surface during the spreading of the intraplate
volcanism. A leading part in the formation of the volcanogenic morphostructure of the ocean floor belongs to the formation
of big seamounts with heights of 4–6 km and volumes from 1500 to 5100 km3, respectively, in the provinces with ages from 60 to 90 mln years. 相似文献
16.
Hydrosweep mapping of crust in the Central Indian Ocean Basin reveals abundant volcanoes ocurring both as isolated seamounts and linear seamount chains parallel to flow lines. Their shapes, sizes and overall style of occurrence are indistinguishable from near-axis seamounts in the Pacific. Evidence from seamount morphology, distributions and petrography of dredged samples suggests that they were generated near the fast-spreading Southeast Indian Ridge at 50–60 Ma. If so, this style of near-axis seamount generation may be a result of fast-spreading rate rather than a peculiarity of the present Pacific spreading ridges. In fact, the results of several recent studies, taken together, suggest that the style of axis/near-axis seamount volcanism varies systematically as a function of spreading rate. 相似文献
17.
The breakup of western margin of Australia from Greater India started around 155 Ma and progressed southwards. After the separation, the interceding intraplate region experienced large volumes of submarine volcanism, extending over 100 Myrs. The Christmas Island Seamount Province (CHRISP, as it has been dubbed) lies south of the Java-Sunda Trench, and contains numerous submerged volcanic seamounts, and two sub-aerially exposed island groups—Cocos (Keeling) Islands, and Christmas Island. While recent geochronological investigations have shed light on the diverse eruption ages of the volcanics of this region, some islands/seamounts have demonstrated protracted volcanic histories, and it is not clear how the volcanic loading, tectonic subsidence, and subsequent emergence history of the islands relates to these discrete volcanic episodes. This study utilises a number of geophysical techniques to determine the crustal structure, loading and subsidence history, and last sub-aerial exposure age for the CHRISP. The study shows that flexural and subsidence modelling are reliable techniques in constraining the age of the seamounts when geochronological techniques are not possible. Utilising regional gravity signatures, we model the crustal structure underneath the Cocos (Keeling) Island, and constrain the thickness of the limestone cover between 900 and 2,100 m. Using age-depth subsidence curves for oceanic lithosphere the time since these seamounts were exposed above sea-level was determined, and a trend in exposure ages that youngs towards the west is observed. Two episodes of volcanism have been recorded at Christmas Island and they are of different origin. The younger phase in the Pliocene is a manifestation of flexure induced cracks produced in the lithosphere as it rides the subduction fore-bulge, whereas a low velocity seismic zone rising from the lower mantle, and tectonic reorganization, may be associated with the older Eocene volcanic phase, as well as much of the rest of the province. Our modelling also supports the existence of an older, undated volcanic core to Christmas Island, based on the loading ages from flexural modelling. 相似文献
18.
Origin of West Pacific seamounts and features of the cretaceous dynamics of the Pacific plate 总被引：1，自引：0，他引：1
A. A. Stepashko 《Oceanology》2006,46(3):411-417
A correlation between the age and position of 25 seamounts in the West Pacific Ocean formed, judging from the 40Ar/39Ar data, in the period from 120 to 65 My B.P. was recognized. The seamounts studied are joined into linear zones with extensions up to 5000 km; the age of the seamounts decreases in the southeastern direction. In the interval 93–83 My B.P., the seamount formation was extremely rapid; this interval coincides with the period of acceleration in the Pacific plate movements. In the middle of this interval, 87 My B.P., an intensification of the magmatic activity accompanying the seamount formation was observed simultaneously with the extinction of the Isanagi plate and the appearance of the Kula plate. The results of this study are in the best agreement with the hypothesis of diffuse tension of the Pacific plate at its displacement in the northwestern direction, which led to the formation of weak zones of decompressional melting. The complementary character of the system of tension zones in the western part of the ocean with respect to the system of major transform faults in its eastern part, which probably reflects the common general process of deformation of the Pacific lithosphere in the Cretaceous, is shown. 相似文献
19.
Spreading cycles in the Pacific Ocean 总被引：1，自引：0，他引：1
A. A. Stepashko 《Oceanology》2008,48(3):401-408
Changes in the spreading rates in the Pharallon-Pacific-Izanagi (Kula) triple junction during the Cretaceous and Cenozoic are revised using new data of the dynamics of the Pacific plate. The cyclic character of the spreading is recognized, and the stages of its acceleration and deceleration are distinguished. Approximately 130, 87, and 42 My B.P., at the culminations of the cycles, when maximal spreading rates were reached, the principal rearrangements in the tectonic evolution of the ocean occurred. The spreading rates were minimal about 140, 120, 65, and 15 My B.P. The latter periods are marked by pulses of basalt magmatism in the west, east, and northeast of the Pacific Ocean. The study recognized no signs of the intrusion of the Middle Cretaceous superplume, which was suggested by Larson. Both the cycling revealed and the pulsations of the intraplate volcanism are most probably related to the regularities of the deformations of the oceanic lithosphere and reflect the periodic alternations of regimes of compression and extension of the Pacific plate during the last 180 My. 相似文献