马里亚纳“沟−盆”深水沉积环境稀土元素特征与物源约束     

肖春晖  王永红  林间  田纪伟 《海洋地质与第四纪地质》2021,(1):102-114

通过对西太平洋帕里西维拉海盆东南部的C-P19柱状样和马里亚纳海沟南坡的L3柱状样进行粒度和稀土元素地球化学分析,探讨了二者物源的异同。结果表明:研究区沉积物的稀土元素含量基本不受沉积物粒度控制,主要受控于物源变化。物源判别结果指示二者的物源具有同源性,其中西马里亚纳海脊剥蚀下来的火山物质对研究区的物质来源贡献最大。火山物质中的重矿物可以影响到稀土元素的含量,例如锆石的含量和稀土元素总量(ΣREY)的相关系数可达0.86。来自中国内陆黄土的陆源风尘物质对两个研究区的物源供给也有一定贡献,但其贡献程度较小。由于马里亚纳海沟南坡更加远离大陆且纬度更低,其接受的亚洲风尘也比帕里西维拉海盆和挑战者深渊更少。此外,南极底层水流经研究区,对海盆和海沟的沉积物都造成一定影响,而且在马里亚纳海沟南坡更加活跃,因而帕里西维拉海盆东南部的沉积物比马里亚纳海沟南坡更易于保存。  相似文献   

千岛—鄂霍次克海地区的地震分布、震源机制及应力状态   总被引：10，自引：0，他引：10       下载免费PDF全文

吴忠良  臧绍先 《地震地质》1989,11(2):85-95

利用1971年1月至1982年12月的地震资料,研究了千岛岛弧地区的地震分布及震源机制解,进而讨论了贝尼奥夫带的形态及应力状态。地震分布于沿海沟展布的NE向的弧形带上,除地壳内地震外,形成明显的贝尼奥夫带,贝尼奥夫带最深达619公里,两侧较浅,少于200公里,倾向近于NW55°,倾角为45°。地壳内的压应力轴位于NW方向,且接近于水平,反映了太平洋板块的挤压;俯冲带上应力轴随深度变化:114公里以上的T轴沿俯冲方向,114公里至175公里震源机制解分为两组,T轴沿俯冲方向和P轴沿俯冲方向;320公里至440公里范围内P轴有接近俯冲方向的趋势,但较为分散;515公里以下P轴相当集中,且沿俯冲方向。本文对这种应力分布的成因进行了讨论  相似文献   

Morphology and magnetic survey of the Rivera-Cocos plate boundary of Colima,Mexico     

Juan Ramón Peláez Gaviria  Carlos A. Mortera Gutiérrez  William L. Bandy  François Michaud 《Geofísica Internacional》2013,52(1):73-85

The propagation of the Pacific-Cocos Segment of the East Pacific Rise (EPR-PCS) has significantly altered the plate configuration at the north end of the Middle America Trench. This ridge propagation, the collision of the EPR-PCS with the Middle America Trench, the separation of the Rivera and Cocos plates and the formation of the Rivera Transform have produced a complex arrangement of morphotectonic elements in the area of Rivera-Cocos plate boundary, atypical of an oceanic transform boundary. Existing marine magnetic and bathymetric data has proved inadequate to unravel this complexity, thus, a dense grid of total field magnetic data were collected during campaigns MARTIC-04 and MARTIC-05 of the B/O EL PUMA in 2004 and 2006. These data have greatly clarified the magnetic lineation pattern adjacent to the Middle America trench, and have revealed an interesting en echelon, NE-SW oriented magnetic high offshore of the Manzanillo Graben. We interpret these new data to indicate that the EPR-PCS ridge segment reached the latitude (~18.3°N) of the present day Rivera Transform at about Chron 2A₃ (~3.5Ma) and propagated further northward, intersecting the Middle America Trench at about 1.7 Ma (Chron 2). At 1.5 Ma spreading ceased along the EPR north of 18.3°N and the EPR-PCS has since retreated southward in association with a southward propagation of the Moctezuma Spreading Segment. North of 18.3°N the seafloor near the trench has been broken into small, uplifted blocks, perhaps due to the subduction of the young lithosphere generated by the EPR-PCS.  相似文献   

马尼拉俯冲带缺失中深源地震成因初探   总被引：1，自引：0，他引：1  

陈爱华  许鹤华  马辉  刘唐伟 《华南地震》2011,31(4):98-107

马尼拉俯冲带是整个南海地震活动多发区,地震成因与南海的形成和构造演化关系密切.对马尼拉俯冲带地震数据和层析成像结果进行了深入分析.结果表明:马尼拉俯冲带的地震活动主要为密集的浅源地震,缺失中深源地震.进一步分析揭示:①脱水和榴辉岩的形成在南海洋壳到达软流圈前就基本停止.马尼拉俯冲带南部在较浅的深度就转变为塑性变形,并停...  相似文献   

Free descent and on bottom ADCM measurements in the Puerto Rico Trench, 19.77°N, 67.40°W     

Wilford E. Schmidt  Eric Siegel 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(9):970-977

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西太平洋板块向我国东北地区深部俯冲的数值模拟   总被引：6，自引：3，他引：3       下载免费PDF全文

朱桂芝  石耀霖  陈石  张怀 《地球物理学报》2009,52(4):950-957

本文采用依赖温度的黏度结构以及考虑海洋板块和大陆板块厚度差异等特征,以太平洋板块向欧亚板块会聚速率作为板块速度的主要约束,通过变化海沟后撤速度模型,数值模拟西太平洋板块向中国东北的俯冲过程.结果表明,要产生类似于中国东北之下低角度的板片俯冲,海沟后撤是重要条件;而上下地幔黏度的较大差异是决定俯冲板片不穿透660 km相变面的决定因素;西太平洋板块向欧亚板块的俯冲应早于70 Ma B.P.,海沟后撤速度可能小于一些地质学家估计的45 mm/a, 而且可能是分阶段变化的;速度场表明运动学模型的反过程：大陆岩石圈之下物质的不断水平向东的流动和推挤可能成为海沟后撤的力源之一,地幔物质的这种东向流动可能与印度板块挤压碰撞欧亚板块有关,沿欧亚板块东缘的扩张构造可能是太平洋-欧亚板块运动和印度-欧亚板块运动的综合效应.  相似文献   

Determining the circulation depth of thermal springs in the southern Rocky Mountain Trench, south-eastern British Columbia, Canada using geothermometry and borehole temperature logs   总被引：1，自引：1，他引：0  

D. M. Allen  S. E. Grasby  D. A. Voormeij 《Hydrogeology Journal》2006,14(1-2):159-172

Geochemical data for thermal spring waters along the southern Rocky Mountain Trench in British Columbia, Canada were examined. The range of equilibration temperatures for the thermal springs is between 24 and 59°C, assuming that there is minimal mixing with colder shallow waters that might lead to a lowering of the calculated equilibration temperature. The chalcedony geothermometer is found to be the most appropriate given the carbonate host rocks. Temperature logs from 11 boreholes in the vicinity were used to calculate representative geothermal gradients, which range from 23.8 to 55.7°C/km with an average of 24.8±8.0°C/km. Using the average gradient and the range of equilibration temperatures calculated for each spring, the minimum range for the depth of origin of the thermal waters is 0.9–2.2 km. Heat flow values range from 90.3 to 155 mW/m², with an average of 109.1±21.0 mW/m². The moderate to high heat flow and heat generation result in generally higher temperatures at shallow depths, thus offering an explanation for the occurrence of thermal springs. The alignment of the thermal springs likely relates to the preferred northwest–southeast orientation for major thrust faults along the Rocky Mountain Trench, and with waters routed from depth along deep faults.

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Resumen Se examinan datos geoquímicos de aguas de fuentes termales a lo largo de la Trinchera sur de las Montañas Rocosas en Columbia Británica, Canadá. El rango de temperaturas de equilibrio para las fuentes termales se encuentra entre 24 y 59°C, asumiendo que existe mezcla mínima con aguas someras más frías que podrían conducir a un descenso de la temperatura de equilibrio calculada. El geotermómetro de calcedonia se ha encontrado que es el más apropiado debido a las rocas encajonantes carbonatadas. Se utilizaron los registros de temperatura de 11 pozos de la zona para calcular gradientes geotermales representativos, los cuales varían de 23.8 a 55.7°C/km con un promedio de 24.8±8.0°C/km. Utilizando el gradiente promedio y el rango de temperaturas de equilibrio calculadas para cada manantial, se estimó que el rango mínimo para la profundidad de origen de las aguas termales varía de 0.9 a 2.2 km. Los valores de flujo de calor varían de 90.3 a 155 mW/m², con un promedio de 109.1±21.0 mW/m². El flujo de calor moderado a alto y la generación de calor resultan en temperaturas generalmente más altas a profundidades someras ofreciendo de este modo una explicación para la ocurrencia de fuentes termales. El alineamiento de fuentes termales posiblemente se relaciona con la orientación preferida noroeste-sureste de fallas inversas principales a lo largo de la Trinchera de las Montañas Rocosas, y con aguas ascendentes profundas que se mueven a lo largo de fallas profundas.

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Résumé Les données géothermiques de sources thermales le long de la partie sud du fossé des Montagnes Rocheuses en Colombie Britannique, Canada, sont étudiées. Léchelle des températures déquilibre des sources thermales se situe entre 24 et 59°C, en assumant quil y a un mélange minimum avec les eaux froides de surface, ce qui conduit à une sous-évaluation de la température déquilibre. La calcédoine apparaît être le géothermomètre le plus approprié vu les roches hôtes carbonatées. Les diagraphies de température provenant de 11 forages proches ont été utilisées pour calculer le gradient géothermique représentatif, gradient compris entre 23.8 et 55.7°/km avec une moyenne de 24.8°/km. En utilisant le gradient moyen et les valeurs de température déquilibre calculées pour chaque source, la profondeur minimum des eaux thermales se situerait entre 0.9 et 2.2 km. Les flux de chaleur sont évalués entre 90.3 et 155 mW/m, avec une moyenne de 109.1±21.0 mW/m. Le transfert moyen de chaleur et la génération de chaleur résulte en températures ordinairement plus élevées aux faibles profondeurs, qui ainsi offre une explication à loccurrence de sources thermales. Les alignements de sources thermales sont vraisemblablement en relation avec lorientation Nord-Sud des principales failles-vraies le long du fossé des Montagnes Rocheuses, et avec lécoulement des eaux des profondeurs le long des failles.

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Indenter-tectonics in the Philippines: Example from the Palawan Microcontinental Block - Philippine Mobile Belt Collision     

Graciano P. Yumul  Jr  Carla B. Dimalanta  Rodolfo A. Tamayo  Jr 《Resource Geology》2005,55(3):189-198

Abstract. The aseismic Palawan microcontinental block is an oceanic bathymetric high that has collided with the seismically-ac-tive Philippine Mobile Belt since the Early Miocene. Consequently, tectonic microblocks immediately north (Luzon) and south (Western Visayas Block) of the collision front rotated in opposite senses. The rotation led the microblocks to onramp adjacent strike-slip faults, and converted these to subduction zones, namely, the current Manila and Negros Trenches. In addition, the collision also initiated the southward propagation of a major left-lateral strike slip fault, the Philippine Fault Zone, and the Philippine Trench, which bounds the Philippine archipelago along its eastern boundary. Based on onshore and offshore data, the Philippine Fault Zone and the East Luzon Trough - Philippine Trench appears to also propagate northward. Furthermore, the opposite direction of propagation is also noted for the Manila and Negros Trenches from the locus of the collision in the Central Philippines to their northern and southern extensions, respectively. The ages of initiation of the Manila Trench (Early Miocene), Philippine Fault Zone (Middle Miocene) and Philippine Trench (Pliocene) as encountered along a west to east transect in the Central Philippines are consistent with the collision and subsequent indentation of Palawan with the rest of the Philippine Mobile Belt.  相似文献   

Earthquake mechanisms in the Hellenic Trench near Crete   总被引：1，自引：0，他引：1  

T. Taymaz  J. Jackson  R. Westaway 《Geophysical Journal International》1990,102(3):695-731

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华北地区与日本海沟地震的相关性分析   总被引：3，自引：1，他引：3  

李文英  王秀英 《地震》1996,16(3):219-224

据板块运动及构造动力的因果关系研究了我国华北地区６级以上与日本海沟地区７级以上地震活动的关系，结果表明，两个地区群体地震活动在时间轴上的不均匀分布及起伏具有一定的同步性，且华北地区的群体地震活动的开始时间晚于日本海沟地区。  相似文献