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1.
贵州兴义喀斯特景观特征 总被引：8，自引：2，他引：6
贵州省兴义市是典型的喀斯特地区,区内广泛分布着雄伟壮丽的喀斯特地貌景观,以高原、峡谷、峰丛、峰林、石林以及发育其间的瀑布群、泉群等组合为特征。其中,马岭河峡谷长74. 8km,谷底宽30～ 50m,切割深度300～ 700m,被誉为“高原峡谷一线天” ;两岸地表支流、泉水坠入河谷形成常年瀑布多达70余处,瀑高50～ 200m,构成云贵高原一大喀斯特水文地貌奇观;斜坡台原之上峰丛峰林密集相连,层层叠置,景象甚为雄伟壮观;其中峰体坡度较缓的锥状喀斯特先是在古地理的外动力环境影响下发育形成,后又经受高原抬升的影响,在发育持续时间、环境及其形态特征上与桂林峰林均有所不同,因而成为全球锥状喀斯特发育演化过程最为完整的范例之一。独特的兴义喀斯特景观,是在特定的岩性结构条件下,经长期构造运动抬升切割和风化剥蚀作用形成的,具有很大的科学意义和观赏价值。 相似文献
2.
V. A. Petrov M. Lespinasse V. V. Poluektov S. A. Ustinov V. A. Minaev 《Doklady Earth Sciences》2017,472(2):130-133
The interrelation between geometric parameters (density and length) of the fault systems of four scale levels (kilometers, meters, centimeters, and millimeters) was established for the first time by detailed structural study of the rocks of the Urtui granite massif located in the western framework of the Strel’tsovskii uranium caldera in the Southeastern Transbaikalia. The further use of these geostructural data for conceptual and numerical modeling of the fluid filtration processes and transport of radionuclides in a three-dimensional crack and pore space in the variably deformed and metasomatically altered crystalline rocks was substantiated. 相似文献
3.
The Cabo de Gata volcanic field of southeastern Spain contains several recently-recognized calderas. Some of the calderas are mineralized with epithermal gold, alunite, and base metal deposits, and others are barren, and yet they formed under generally similar conditions. Comparison of the magmatic, geochemical, and physical evolution of the Los Frailes, Rodalquilar, and Lomilla calderas provides insight into the processes of caldera evolution that led to precious-metal mineralization. The Los Frailes caldera formed at 14.4 Ma and is the oldest caldera. It formed in response to multiple eruptions of hornblende dacite magma. Following each eruption, the area collapsed and the caldera was invaded by the sea. Dacite domes fill the lower part of the caldera. Pyroxene andesites were erupted through the solidified core of the caldera and were probably initially responsible for magma generation. The Los Frailes caldera did not evolve to rhyolites nor was it subjected to the amount of structural development that the younger, mineralized Rodalquilar and Lomilla calderas were. 相似文献
4.
In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lava-flows related to the beginning of the volcanic system; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the system; and, finally 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage.The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique rift, with its principal extensional strain in an NNE–SSW direction (∼N10°).The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189 ± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188–178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism. 相似文献
5.
Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits 总被引：1，自引：0，他引：1
J. J. Rytuba A. Arribas Jr. C. G. Cunningham E. H. McKee M. H. Podwysocki J. G. Smith W. C. Kelly A. Arribas 《Mineralium Deposita》1990,25(1):S29-S35
The Rodalquilar caldera complex is located in the western part of the Cabo de Gata volcanic field in southeastern Spain and is the first documented example of epithermal gold-alunite mineralization within a caldera in Europe. The Rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 Ma from eruption of the Cinto ash-flow tuff. The oval Lomilla caldera, with a diameter of 2 km, is nested within the central resurgent dome of the older Rodalquilar caldera. The Lomilla caldera resulted from the eruption of the Lazaras ash-flow tuff which was ponded within the moat of the Rodalquilar caldera. The last phase of volcanic activity in the caldera complex was the emplacement of hornblende andesite flows and intrusions. This magmatic event resulted in structural doming of the caldera, opening of fractures and faults, and provided the heat source for the large hydrothermal systems which deposited quartz-alunite type gold deposits and base metal vein systems. The gold-alunite deposits are enclosed in areas of intense acid sulfate alteration and localized in ring and radial faults and fractures present in the east wall of the Lomilla caldera. Like other acid-sulfate type deposits, the Rodalquilar gold-alunite deposits are closely related in time and space to porphyritic, intermediate composition magma emplaced along caldera structures but unrelated to the caldera forming magmatic system. 相似文献
6.
Juliane Ramelow Ulrich Riller Rolf L. Romer Onno Oncken 《International Journal of Earth Sciences》2006,95(3):529-541
A combined geochronological and structural analysis of the Miocene Negra Muerta Caldera was designed to better understand caldera formation associated with prominent faults on the central Andean plateau. Rb–Sr ages of the caldera outflow facies indicate that caldera formation occurred in two volcano-tectonic episodes. The first episode commenced with explosive eruption of the 9.0±0.1 Ma andesitic Acay Ignimbrite followed by a period of volcanic quiescence and moderate tectonic activity. Dominant volcanic and tectonic activity occurred during the second episode, which is bracketed by eruption of the 7.6±0.1 Ma rhyolitic Toba 1 Ignimbrite and effusive discharge of the 7.3±0.1 Ma rhyodacitic to andesitic lava flows. Structural relationships between rocks of the Negra Muerta Volcanic Complex and collapse-induced normal faults, notably NE-striking normal faults, agree with simultaneous volcanic activity and floor subsidence of the caldera during the second episode. Floor subsidence was achieved by tilting on an outward dipping reverse fault to the northwest of the caldera floor around a hinge zone located south of the caldera floor. This induced horizontal extension of the caldera floor and was accomplished by fragmentation of, and intrusion of dikes into, the floor. Collapse-induced and post-collapse fault populations of the caldera do not differ significantly in the directions of their axes of maximum extension and are in this respect kinematically compatible with left-lateral slip on the nearby Olacapato-El Toro Fault Zone. This furnishes evidence for a kinematic control by prominent faults on the formation of collapse calderas in the central Andes. The structural analysis of the Negra Muerta Caldera shows that collapse calderas can serve as deformation markers that contribute in elucidating the regional kinematic regime and the time of activity of prominent dislocations genetically related to collapse calderas. 相似文献
7.
Cecilia Pavón Pivetta Daniel Gregori Leonardo Benedini Mirta Garrido Leonardo Strazzere Mauro Geraldes 《International Geology Review》2020,62(15):1904-1930
ABSTRACT The northern zone of the Chon Aike Igneous Province, located in the North Patagonian Massif, exhibits extensive outcrops of Jurassic volcanic rocks of the Marifil Formation. In the Arroyo Verde area, the initial volcanic stage of the Marifil Formation, that we denominate V0 (192.6 ± 2.5 Ma), includes coulées, megabreccias and lapilli tuffs assigned to plinian-type volcanism. This magmatism was generated by cold-wet-oxidized magmas that resemble those produced in active continental margins and volcanic arcs. The second stage, located unconformably over the first, includes welded lava-like ignimbrites, massive lapilli tuff and rhyolitic lava flow that resemble the Snake River-type volcanism. The magma that produces this volcanic stage exhibit the characteristics of hot-dry-reduced magmas emplaced in intraplate continental environments associated with continental rifting. This stage coincides with the V1 volcanic episode early recorded in the Marifil Formation. 相似文献
8.
9.
相山铀矿田与斯特列利措夫铀矿田特征对比 总被引：1，自引：0，他引：1
相山铀矿田和斯特列利措夫铀矿田均产于破火山口中,相山火山盆地的基底为震旦系变质岩,斯特列利措夫盆地的基底为多期活化的片麻状花岗岩。两盆地的破火山口盖层均为陆相火山岩系,相山破火山口火山岩系为酸性和中酸性岩,斯特列利措夫破火山口火山岩系则为酸性和基性火山岩呈互层产出。破火山口内的构造和蚀变作用发育程度存在明显差异,这是两个铀矿田成矿远景不同的主要原因。 相似文献
10.
2004年12月26日苏门答腊-安达曼大地震构造特征及地震海啸灾害 总被引：16，自引：0，他引：16
2004年12月26日在印度尼西亚苏门答腊岛西侧海域发生的地震是自1964 年阿拉斯加大地震以来最大的地震,震级达到9级或9级以上。它是由印度洋板块向缅甸微板块底下俯冲过程中的逆断层作用造成的。印度洋板块以每年6~7 cm的速率向北北东方向运动,与南亚板块发生斜向聚敛俯冲,此运动在该地区解耦为印度洋板块沿巽他海沟的正向俯冲及缅甸微板块东侧的右旋走向平移运动。主震破裂模型研究的结果表明,破裂是由南向北传播的,地震破裂带长达1 200余km,宽度约100 km,最大位移约为20 m,地震断层向上穿透海沟底面,估计约有10 m左右的错距。这次大地震的同震效应导致地球自转轴摆动、地球自转加速,日长缩短。据目前统计,地震引发的大海啸造成305 276人死亡,被此次海啸夺走生命的人数超过了有史以来历次大海啸灾难中死亡人数的总和。 相似文献
11.
The in-depth investigation of fractured reservoirs is mainly limited to geophysical data that is in 3D and mostly on the scale of hundred meters to several kilometers or boreholes data that is in 1D and at meter to lower scale. The study of outcropping analogues of buried reservoirs is therefore a key tool for the characterization of the fault and fracture network at the reservoir scale. Tamariu granite has been the subject of this study with the aim to analyse faults and fractures from seismic to borehole scale. With the combination of satellite picture at different resolution and field study, we perform a statistical analysis focused of the length and orientation from infra centimeter crack to hundred kilometer length fault. On the whole range of scale studied, i.e. on 7 orders of magnitude, we have defined a length distribution following a power-law with an exponent a = −2. On the contrary to the length that can be modelled with a unique law, the orientation data shows a variation depending on the scale of observation: as the fault and fracture sets are suitable from the regional faults to the centimeter crack, the proportion of the sets varies at each scale of observation. 相似文献
12.
Kroly Nmeth Shane J. Cronin Robert B. Stewart Douglas Charley 《Sedimentary Geology》2009,220(3-4):256
Ambrym is one of the most voluminous active volcanoes in the Melanesian arc. It consists of a 35 by 50 km island elongated east–west, parallel with an active fissure zone. The central part of Ambrym, about 800 m above sea level, contains a 12 kilometre-wide caldera, with two active intra-caldera cone-complexes, Marum and Benbow. These frequently erupting complexes provide large volumes of tephra (lapilli and ash) to fill the surrounding caldera and create an exceptionally large devegetated plateau “ash plain”, as well as sediment-choked fluvial systems leading outward from the summit caldera. Deposits from fall, subordinate base surge and small-volume pyroclastic (scoria) flows dominate the volcaniclastic sequences in near vent regions. Frequent and high-intensity rainfall results in rapid erosion of freshly deposited tephra, forming small-scale debris flow- and modified grain flow-dominated deposits. Box-shaped channel systems are initially deep and narrow on the upper flanks of the composite cones and are filled bank-to-bank with lapilli-dominated debris flow deposits. These units spill out into larger channel systems forming debris aprons of thousands of overlapping and anastomosing long, narrow lobes of poorly sorted lapilli-dominated deposits. These deposits are typically remobilised by hyperconcentrated flows, debris-rich stream flows and rare debris flows that pass down increasingly shallower and broader box-shaped valleys. Lenses and lags of fines and primary fall deposits occur interbedded between the dominantly tabular hyperconcentrated flow deposits of these reaches. Aeolian sedimentation forms elongated sand dunes flanking the western rim of the ash-plain. Outside the caldera, initially steep-sided immature box-canyons are formed again, conveying dominantly hyperconcentrated flow deposits. These gradually pass into broad channels on lesser gradients in coastal areas and terminate at the coast in the form of prograding fans of ash-dominated deposits. The extra-caldera deposits are typically better sorted and contain other bedding features characteristic of more dilute fluvial flows and transitional hyperconcentrated flows. These outer flank volcaniclastics fill valleys to modify restricted portions of the dominantly constructional landscape (lava flows, and satellite cones) of Ambrym. Apparent maturity of the volcanic system has resulted in the subsidence of the present summit caldera at a similar rate to its infill by volcaniclastic deposits. 相似文献
13.
塔里木盆地古生界岩石轻烃的地球化学特征 总被引：2，自引：0，他引：2
基于塔里木盆地古生界岩石酸解轻烃相对低的庚烷值、石蜡指数值、轻质芳烃含量、δ13C1‰值、正构 异构烷烃、环戊烷 己烷与区域内海相油气截然相反的分布形式,确认酸解轻烃的主体应属于存在于矿物晶格中的早期烃类,后期储层再成熟作用不明显,并可进一步推论区域内构造上的高成熟海相油气主要源自盆地深处的相关烃源岩、经历较远距离的运移。同时也发现岩石酸解轻烃具有较高K值的样品,其绝对值稍小于原油的高K值,但两者在区域分布上一致,前者的高K值与高丰度的2 ,3二甲戊烷有关。 相似文献
14.
高陡边坡滑坡体黄土的强度特性研究 总被引：6，自引：0，他引：6
黄土台塬是黄土地区典型的地貌特征,塬边多为高陡边坡,极易发生崩塌和滑坡地质灾害。位于陕西境内泾河以南的黄土塬－泾阳南塬为典型的高陡黄土边坡,其崩塌、滑坡地质灾害频繁发生,自东南向西北的大小滑坡形成了延绵约30 km的滑坡群。对泾阳南塬滑坡群进行分析,以其中一规模较大的近年滑坡--东风滑坡为例进行了实地考察、现场测量,对滑坡体后缘和前缘的黄土进行了一系列的室内物理和力学性质试验。分析了高陡黄土边坡滑坡的发生过程和破坏机制,由颗粒分析和湿陷性试验得出滑坡体前后缘土体的湿陷液化特征。分析了不同含水率对强度参数的影响,并对比分析了原状黄土和重塑黄土的强度参数和结构性,验证了重塑饱和黄土的应力-应变关系和体应变-轴应变关系与邓肯-张模型符合较好,为高陡黄土边坡稳定性分析强度参数的合理选取提供了参考 相似文献
15.
Contemporaneous Trachyandesitic and Calc-alkaline Volcanism of the Huerto Andesite, San Juan Volcanic Field, Colorado, USA 总被引：2，自引：0，他引：2
Locally, voluminous andesitic volcanism both preceded and followedlarge eruptions of silicic ash-flow tuff from many calderasin the San Juan volcanic field. The most voluminous post-collapselava suite of the central San Juan caldera cluster is the 28Ma Huerto Andesite, a diverse assemblage erupted from at least5–6 volcanic centres that were active around the southernmargins of the La Garita caldera shortly after eruption of theFish Canyon Tuff. These andesitic centres are inferred, in part,to represent eruptions of magma that ponded and differentiatedwithin the crust below the La Garita caldera, thereby providingthe thermal energy necessary for rejuvenation and remobilizationof the Fish Canyon magma body. The multiple Huerto eruptivecentres produced two magmatic series that differ in phenocrystmineralogy (hydrous vs anhydrous assemblages), whole-rock majorand trace element chemistry and isotopic compositions. Hornblende-bearinglavas from three volcanic centres located close to the southeasternmargin of the La Garita caldera (Eagle Mountain–FourmileCreek, West Fork of the San Juan River, Table Mountain) definea high-K calc-alkaline series (57–65 wt % SiO2) that isoxidized, hydrous and sulphur rich. Trachyandesitic lavas fromwidely separated centres at Baldy Mountain–Red Lake (westernmargin), Sugarloaf Mountain (southern margin) and Ribbon Mesa(20 km east of the La Garita caldera) are mutually indistinguishable(55–61 wt % SiO2); they are characterized by higher andmore variable concentrations of alkalis and many incompatibletrace elements (e.g. Zr, Nb, heavy rare earth elements), andthey contain anhydrous phenocryst assemblages (including olivine).These mildly alkaline magmas were less water rich and oxidizedthan the hornblende-bearing calc-alkaline suite. The same distinctionscharacterize the voluminous precaldera andesitic lavas of theConejos Formation, indicating that these contrasting suitesare long-term manifestations of San Juan volcanism. The favouredmodel for their origin involves contrasting ascent paths anddifferentiation histories through crustal columns with differentthermal and density gradients. Magmas ascending into the mainfocus of the La Garita caldera were impeded, and they evolvedat greater depths, retaining more of their primary volatileload. This model is supported by systematic differences in isotopiccompositions suggestive of crust–magma interactions withcontrasting lithologies. KEY WORDS: alkaline; calc-alkaline; petrogenesis; episodic magmatism; Fish Canyon system 相似文献
16.
The relief of high limestone plateaus of the Transcaspian region (Ustyurt, Steppe Mangyshlak, and Krasnovodsk) is leveled and primarily tectonic: ridges and depressions (tens and hundreds of kilometers in length and tens, rarely a few hundred meters in amplitude) are composed of gentle (10–40) positive and negative deformations of the Neogene cover. The plateaus are bounded by ledges (chinoks). Against the background of the gentle hilly topography, one can observe smaller but sufficiently long (tens of kilometers) groups of arc-shaped parallel limestone ridges (2–8 m high) that crosscut large morphological irregularities. All topographic forms on the plateau resulted from a prolonged (many millions years) weathering and arid denudation. Therefore, insignificant differences of stability appeared in limestones armoring the plateau. Analysis of the composition and structure of limestones in linear arc-shaped ridges of ledges and the plateau surface showed that the limestones represent an extremely shallow-water facies of shelf sediments. The arc-shaped limestone ridges on the plateau are exposed, partially modified, accumulative, and biogenic-accumulative forms of bottom relief. Similar accumulative forms coupled with biogenic buildups are known in nontropic carbonate shelves of recent seas. The finding of coastal-marine forms on the limestone plateau surface suggests a shallow-water sedimentation regime in Neogene basins persisting over short time spans. Study of such forms is of interest for the refinement of water depths, wave–wind regime, and currents in Neogene basins, as well as for prospecting for oil–gas fields and placer accumulations. 相似文献
17.
The Chubut Group constitutes the most widespread sedimentary unit in NE Patagonia, characterized by variable-energy fluvial deposits. U–Pb analysis of detrital zircons from two sections of the Chubut Group constraint the age of the oldest sedimentary rocks in the northeast of the Somuncurá – Cañadón Asfalto Basin. In the Cañadón Williams area, at San Jorge section, 20 km NW of Telsen locality, dating of 56 detrital zircons from a medium to coarse sandstone indicated a maximum depositional age of 109 ± 1 Ma (n = 4). These sandstones were interpreted to represent shallow channels, associated with a lacustrine system. In the Telsen locality, a laser ablation analysis of 115 detrital zircons from a medium to coarse-grained sandstone, from fluvial channel facies, yielded a maximum depositional age of ca. 106 ± 1 Ma (n = 8). Both ages are consistent with volcanic events of the Barremian to Albian age in the central Patagonian Andes Region. Cathodoluminescence images of zircons from the San Jorge sample suggest an igneous origin, which is further supported by Th/U values above 0.5 in most of the grains. The distribution of the statistical modes of the main age populations of detrital zircons for the two samples [182, 185 and 189 Ma for Telsen sample (T2S) and 181 ± 1 Ma for San Jorge sample (SJS)] matches the age of the volcanic Marifil Formation. The rocks of the Marifil Formation of these ages are exposed NE to SE of the study area. The abundance of zircons of similar Jurassic ages (n = 52 for SJS and n = 105 for T2S) and the external morphology of the zircons in the sample SJS, implies a close proximity of the source area. Suggestion that the Marifil Formation was the main provenance source is also supported by northeast–southeasterly paleocurrents measured at the San Jorge and Telsen sections. 相似文献
18.
岩浆热场：它的基本特征及其与地热场的区别 总被引：6，自引：6，他引：0
"岩浆热场"指的是由岩浆引发的瞬间热场。热场的热主要来自未固结的岩浆,岩浆加热了围岩,使下地壳、中地壳和上地壳的下部在一个短暂的时间内保持一种高热状态。岩浆热场与地热场有许多不同:(1)热的来源不同。地热场的热主要来自地壳物质放射性生成的热;岩浆热场的热来自岩浆。(2)热的分布不同。地热场的等温面总体上呈水平分布,温度随深度增加而增加;岩浆热场的等温面则围绕岩体分布,靠近岩体温度高,远离岩体温度低,故岩浆热场的等温面是大体垂直于地热场等温面分布的。(3)热场的规模不同。地热场是全球性的,岩浆热场是局部性的,只在有岩浆的地方才出现。岩体小则规模小(热场宽度仅几米或几十米),岩体大则规模大(宽约几千米);如果存在大规模岩浆活动,岩浆热场的长宽均可达几百或上千千米,如在中国东部中生代大规模岩浆活动期间。(4)热持续的时间不同。地热场可以持续很长的时间(几十、几百或几千个百万年);岩浆热场是瞬间的突发性事件,持续的时间从几年到几个百万年。岩浆热场最重要的意义是,它是热液赖以上升的通道,它有利于来自下地壳底部和壳幔过渡带的流体(热液)的活动,使含矿热液得以顺利上升,并在热场范围内进行充分的活动、对流循环、萃取围岩中的成矿金属元素,并在地壳浅部岩浆热场之上合适的部位沉淀富集成矿。"岩浆热场"的概念依赖于对岩浆物理性质和过程的深入了解,由于我们这方面的知识相对贫乏,所以目前对岩浆热场的了解还是很肤浅的。 相似文献
19.
DEREK B. BOOTH 《Boreas: An International Journal of Quaternary Research》1986,15(3):247-263
Large embankments, typically several kilometers in lateral extent and many tens of meters high, choke the mouths of each alpine valley of the central Cascade Range, Washington State, U.S.A., at or near their junctions with the Puget Lowland. They comprise till and bedded gravel, sand, and silt, aggraded into ice-dammed lakes. The embankments lie within the late-Pleistocene Cordilleran ice-sheet limit and so do not mark the location of the ice-maximum terminus. Reconstruction of the subglacial hydraulic potential field indicates that these ice-dammed lakes would have drained subglacially via spillways located near the junction of each alpine valley and the Lowland. Physical processes tended to stabilize the grounding line for each ice tongue close to its respective spillway location. Because sedimentation rates are highest adjacent to the grounding line, subaqueous sedimentation formed a growing embankment there. In some valleys, subsequent subaerial lake drainage or decay of the active-ice dam resulted in late-stage deposition of deltas or valley trains. This analysis of ice-water behavior is based on physical principles that should be generally applicable to any environment where glaciers terminate against ice-dammed bodies of water. 相似文献
20.
兰州市辖3县5区,总面积1.3万km2。位于陇西黄土高原西部,海拔1 500~3 500m,地势总体上表现为西南部高、东北部低。广覆黄土的低山丘陵及其夹峙的河谷平原,构成了本区的基本地貌景观。平原区生态地质环境较好,特别是河谷平原内的一、二级阶地,具有地形平坦、地势开阔的优越条件,是人类生产与生活最佳地段、也是人口相对密集的区域,如兰州黄河河谷平原、永登庄浪河谷平原、榆中盆地、秦王川盆地等。本文剖析,评价其供水现状,提供可持续发展的对策,具有重要意义。 相似文献