湖北京山中元古界打鼓石群沉积特征及其构造古地理意义   总被引：1，自引：0，他引：1  

熊兴斌  陈忆元 《地球科学》1991,16(5):489-495

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1989年大同—阳高地震的地质环境与地震构造   总被引：6，自引：1，他引：6  

苏宗正  程新原 《山西地震》1992,(1):19-30,36

1989年10月18日的大同—阳高地震发生于大同盆地的册田凹陷。册田凹陷走向北东东,其南缘的六棱山断裂为凹陷的主干断裂,是这次地震的控震断裂。该凹陷内发育北东向和北西向两组断裂,其中大王村断裂和团堡断裂规模最大。这两条断裂大部份隐伏于新生代沉积层之下。电法勘探、钻探、泉的分布及地貌现象均显示其展布位置。在北东东向区域压应力场的作用下,这两条断裂成为此次地震的发震断层。震源机制解结果和烈度分布特点支持上述结论。  相似文献   

Back-arc rifting in the Izu-Bonin Island Arc: Structural evolution of Hachijo and Aoga Shima Rifts   总被引：1，自引：0，他引：1  

Adam  Klaus Brian  Taylor Gregory F.  Moore Fumitoshi  Murakami Yukinobu  Okamura 《Island Arc》1992,1(1):16-31

Abstract Multi- and single-channel seismic profiles are used to investigate the structural evolution of back-arc rifting in the intra-oceanic Izu-Bonin Arc. Hachijo and Aoga Shima Rifts, located west of the Izu-Bonin frontal arc, are bounded along-strike by structural and volcanic highs west of Kurose Hole, North Aoga Shima Caldera and Myojin Sho arc volcanoes. Zig-zag and curvilinear faults subdivide the rifts longitudinally into an arc margin (AM), inner rift, outer rift and proto-remnant arc margin (PRA). Hachijo Rift is 65 km long and 20–40 km wide. Aoga Shima Rift is 70 km long and up to 45 km wide. Large-offset border fault zones, with convex and concave dip slopes and uplifted rift flanks, occur along the east (AM) side of the Hachijo Rift and along the west (PRA) side of the Aoga Shima Rift. No cross-rift structures are observed at the transfer zone between these two regions; differential strain may be accommodated by interdigitating rift-parallel faults rather than by strike- or oblique-slip faults. In the Aoga Shima Rift, a 12 km long flank uplift, facing the flank uplift of the PRA, extends northeast from beneath the Myojin Knoll Caldera. Fore-arc sedimentary sequences onlap this uplift creating an unconformity that constrains rift onset to ～1-2Ma. Estimates of extension (～3km) and inferred age suggest that these rifts are in the early syn-rift stage of back-arc formation. A two-stage evolution of early back-arc structural evolution is proposed: initially, half-graben form with synthetically faulted, structural rollovers (ramping side of the half-graben) dipping towards zig-zagging large-offset border fault zones. The half-graben asymmetry alternates sides along-strike. The present ‘full-graben’ stage is dominated by rift-parallel hanging wall collapse and by antithetic faulting that concentrates subsidence in an inner rift. Structurally controlled back-arc magmatism occurs within the rift and PRA during both stages. Significant complications to this simple model occur in the Aoga Shima Rift where the east-dipping half-graben dips away from the flank uplift along the PRA. A linear zone of weakness caused by the greater temperatures and crustal thickness along the arc volcanic line controls the initial locus of rifting. Rifts are better developed between the arc edifices; intrusions may be accommodating extensional strain adjacent to the arc volcanoes. Pre-existing structures have little influence on rift evolution; the rifts cut across large structural and volcanic highs west of the North Aoga Shima Caldera and Aoga Shima. Large, rift-elongate volcanic ridges, usually extruded within the most extended inner rift between arc volcanoes, may be the precursors of sea floor spreading. As extension continues, the fissure ridges may become spreading cells and propagate toward the ends of the rifts (adjacent to the arc volcanoes), eventually coalescing with those in adjacent rift basins to form a continuous spreading centre. Analysis of the rift fault patterns suggests an extension direction of N80°E ± 10° that is orthogonal to the trend of the active volcanic arc (N10°W). The zig-zag pattern of border faults may indicate orthorhombic fault formation in response to this extension. Elongation of arc volcanic constructs may also be developed along one set of the possible orthorhombic orientations. Border fault formation may modify the regional stress field locally within the rift basin resulting in the formation of rift-parallel faults and emplacement of rift-parallel volcanic ridges. The border faults dip 45–55° near the surface and the majority of the basin subsidence is accommodated by only a few of these faults. Distinct border fault reflections decreases dips to only 30° at 2.5 km below the sea floor (possibly flattening to near horizontal at 2.8 km although the overlying rollover geometry shows a deeper detachment) suggesting that these rifting structures may be detached at extremely shallow crustal levels.  相似文献   

日本的活动断层和火山——访日考察报告     

丁原章  黄日恒  郭钦华  王高盛 《华南地震》1990,(3)

本文简述日本的地质构造、火山、地震活动的轮廓和特点;重点报导作者在日本现场考察活动断层和火山的结果;对日本在地学领域研究的特点、经验及趋向进行了概括相评述。  相似文献   

Magnetics in geoexploration     

William J. Hinze  Ralph R. B. Von Frese 《Journal of Earth System Science》1990,99(4):515-547

The magnetic method is the oldest and one of the most widely used geophysical techniques for exploring the earth’s subsurface. It is a relatively easy and inexpensive tool to employ, being applicable to a wide variety of subsurface exploration problems involving horizontal magnetic property variations occurring from near the base of the crust to within the uppermost meter of soil. Successful applications of the magnetic method require an in-depth understanding of its basic principles and careful field work, data reduction, and interpretation. Commonly, interpretations are limited to qualitative approaches which simply map the spatial location of anomalous subsurface conditions, but under favourable circumstances the technological status of the method will permit more quantitative interpretations involving specification of the nature of the anomalous sources. No other geophysical method provides critical input to such a wide variety of problems. However, seldom does the magnetic method provide the complete answer to an investigation problem. As a result, it is generally used in concert with other geophysical and geological data to limit its interpretational ambiguities.  相似文献   

华南陆块液体钾、锂资源的区域成矿背景与成矿作用初探   总被引：7，自引：1，他引：6  

刘成林  余小灿  赵艳军  王九一  王立成  徐海明  李坚  王春连 《矿床地质》2016,35(6):1119-1143

中国华南陆块江汉盆地的江陵凹陷和潜江凹陷以及江西吉泰盆地等裂谷盆地,在白垩纪—古近纪时期,发育了大量的蒸发岩,并形成了富含钾、锂、铷、铯、溴、碘、硼元素的卤水,这些高价值元素的含量多达到工业利用品位或综合利用品位,资源潜力巨大。这些资源的富集区域分布于华南陆块与新华夏裂谷构造的交汇处,同时也是华南花岗岩省与新华夏裂谷玄武岩的分布区。通过对该区域大地构造、火成岩、古气候、古地理特征与全球海侵事件等综合分析,同时结合盆地卤水化学成分的研究,作者提出华南陆块(地区)的中生代—新生代盆地(群)可能是液体钾、锂、铷、铯、溴、碘、硼资源的成矿区;成矿物质受到白垩纪—古近纪火山活动带来的深部物质及海侵事件带来的海水等多源补给,前者主要带来锂、钾、铷、铯等,后者带来钾及溴、碘等。华南盆地卤水中钾、锂等元素的富集是内生与外生地质动力作用的结果,即构造-火成岩-海侵-干旱气候耦合作用的结果,成矿作用过程可以归结为裂谷沉积成矿,主要形成富钾、锂卤水;埋藏阶段这些卤水通常转移到孔隙发育的碎屑岩、玄武岩及断裂带内保存,形成盆地深层卤水矿床。  相似文献   

Climate‐modulated sequence development in a tropical rift basin during the Late Palaeocene to Early Eocene super greenhouse Earth          下载免费PDF全文

Arpita Samanta  Melinda K. Bera  Anindya Sarkar 《Sedimentology》2016,63(4):917-939

Sequence developments in rift basins are considered to be influenced largely by tectonics and to a lesser extent by eustatic sea‐level and climate. Studies indicate that in passive margin basins, climate can mask the effects of tectonics and eustasy by modulating the sediment supply. It is, however, less understood how the sedimentary sequence in rift basins might respond to strong climatic fluctuations where tectonic pulses generate rapid accommodation space. Here a case study has been provided to assess the effect of climate vis à vis sea‐level and tectonics on sequence development in the Cambay rift basin, western India, during the Early Palaeogene (Late Palaeocene to Early Eocene) super greenhouse globe. Facies analysis of this shale–lignite sequence suggests deposition in a lagoon/bay, developed over the Deccan Trap basement. Detailed sequence stratigraphic analysis using basin‐wide representative composite sections, marker lignite seam, event bed and high‐resolution carbon isotope (δ¹³C) chemostratigraphy suggest an overall transgressive motif. Among the three prominent Early Eocene eustatic highstands, only the one at ca 53·7 Ma is expressed by the thickest coal accumulation throughout the basin. Expression of the other sequence stratigraphic surfaces is subdued and can be due to the overall finer grain size of the sediment or local variation in the subsidence rate at different fault‐controlled mini‐basins. Enigmatic presence of a maximum flooding surface coinciding with the 53·7 Ma climate event (Eocene Thermal Maximum 2), manifested by negative carbon isotope excursion, indicates possible influence of climate over and above tectonics in developing the rift sequence. Qualitative rainfall variation assessed using the magnitude of the carbon isotope excursion and pollen abundance show that a relatively dry/low precipitation climatic phase during the Eocene Thermal Maximum 2 hindered the siliclastic supply to the basin. Thus, it has been inferred that climate‐induced high siliciclastic supply possibly enhanced the autocyclic reorganization and hindered the development of the key sequence stratigraphic surfaces across the basin during climate extremes.  相似文献   

辽东裂谷白云金矿载金黄铁矿Re-Os定年及其地质意义   总被引：2，自引：0，他引：2  

张朋  李斌  李杰  柴鹏  王希今  沙德铭  时建民 《大地构造与成矿学》2016,(4):731-738

白云金矿是辽东裂谷区内重要的大型金矿之一,长期以来缺少直接的年代学数据。本次对白云金矿不同矿石类型中的8件载金黄铁矿进行了Re-Os同位素定年,获得其等时线年龄为225.3±7.0 Ma(MSWD=5.8),187Os/188Os初始值为2.1±2.8。结合前人的研究成果及本次年代学研究得出:白云金矿形成于印支期,其成矿物质主要为壳源,白云金矿是与印支期岩浆活动有关的热液矿床;其形成构造背景可能为受蒙古–鄂霍次克大洋向南北两侧俯冲之后的陆内后碰撞造山环境。本次研究也为今后在辽东裂谷区寻找与印支期岩浆活动有关的矿床提供了依据。  相似文献   

东昆仑中段万宝沟群玄武岩的形成时代和构造意义     

许鑫  宋述光  苏犁 《岩石矿物学杂志》2016,35(6):965-980

万宝沟群位于柴达木地块南缘、东昆仑造山带中段,主要由溢流相玄武岩、火山和陆源碎屑岩以及灰岩组成。万宝沟玄武岩可以分为两类:高Ti碱性玄武岩和低Ti拉斑玄武岩,前者具有高的Ti/Y(502~660)、Nb/Y(0.8~1.6)值和Ti O2含量(2.76%~4.97%),与OIB类似;后者具有相对低的Ti/Y(383~439)、Nb/Y(0.3~0.4)值和Ti O2含量(1.80%~2.49%),与E-MORB类似。SIMS锆石年代学结果表明万宝沟玄武岩形成于新元古代(762±2 Ma)。野外地层和地球化学特征显示万宝沟玄武岩可能形成于大陆裂谷或者初始洋盆环境,代表Rodinia超大陆裂解的峰期阶段。  相似文献   

Tectonics of an incipient oceanic rift     

P. Choukroune  J. Francheteau  B. Auvray  J. M. Auzende  J. P. Brun  B. Sichler  F. Arthaud  J. C. Lepine 《Marine Geophysical Researches》1988,9(2):147-163

The results of 26 dives with the diving saucer Cyana in the Gulf of Tadjoura and Ghoubbet al Kharab (Republic of Djibouti) are presented. One can demonstrate that the sites of recent volcanism, tectonics and hydrothermal activity within the axial part of the Gulf of Tadjoura coincide with topographic highs trending at a high angle (azimuth 135°) with respect to the average trend of the axial trough of the Gulf (azimuth 080°). The highs owe their relief to both volcanism and normal faulting along a trend of 130–140°. Recent faulting on the bounding walls of the axial trough is also found along a trend of 130–140° where the faults interfere with another set of apparently older faults trending 070° parallel to the axial trough. Spacing between the active zones of the Gulf is regular and about 30 km. No evidence for transform faulting has been found, in contradiction to all previous kinematic models of the Gulf of Tadjoura. There is evidence that the presently active phase of opening associated with 130–140° faults is less than 0.7 my old and that there was an older phase associated with 070°–080° faults creating the main trough of the Gulf. The basaltic lavas created during the two phases have evolved from transitional to tholeiitic.  相似文献