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1.
ＱｕａｎｔｉｔａｔｉｖｅＡｓｓｅｓｓｍｅｎｔａｎｄＺｏｎａｔｉｏｎｏｆＲｅｇｉｏｎａｌＣｒｕｓｔａｌＳｔａｂｉｌｉｔｙｉｎＣｈｉｎａＳｕｎＹｅ；ＴａｎＣｈｅｎｇｘｕａｎ（ＵｒｂａｎａｎｄＥｎｇｉｎｅｅｒｉｎｇＳｉｔｅＳｔａｂｉｌｉｔｙＲｅｓｅａｒｃｈ... 相似文献
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金沙江流域区域地壳稳定性分区与定量评价 总被引：13，自引：3，他引：10
金沙江中、下游横穿横断山南北构造带, 新构造运动强烈, 地震活动频繁, 各种内动力地质灾害比较严重, 该区区域地壳稳定性相对较差。为服务于金沙江水电工程规划建设和减灾防灾的需要, 本文对金沙江流域沿江地区进行了地壳稳定性的评价与分区。文中依据地壳稳定性定量评价的原则和方法, 建立地质构造背景、地壳结构、地震以及地球物理等指标, 并将地壳稳定性划分为四个等级:稳定、基本稳定、次稳定和不稳定。然后按照上述系统进行地壳稳定性分区。最后, 综合各项研究资料来确定各区的定量评价指标, 并采用模糊数学方法对各区地壳稳定性进行综合评价。 相似文献
3.
中国区域地壳稳定性定量化评价与分区 总被引：13，自引：1，他引：12
中国地处环太平洋构造带与地中海构造带交接部位,地质构造复杂,活动性较为强烈,各种内动力地质灾害比较严重,总体看来中国区域地壳稳定性相对较差。为了使区域地壳稳定性评价与分区获得定量化认识,更好地服务于经济建设和减灾防灾,本文在分析中国现今活动的主要构造体系与内动力地质灾害的分布规律的基础上,首先进行区域地壳稳定性定量化评价待评区的划分;其次进行定量化评价指标的选定、取值、权重分配及评价标准的确定;最后运用模糊数学进行中国区域地壳稳定性定量化评价与分区。 相似文献
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“5.12”汶川MS8.0大地震后关于我国区域地壳稳定性评价的思考 总被引：10，自引：9，他引：1
汶川大地震引起我们对区域地壳稳定性调查评价新的思考。本文简要介绍了我国区域地壳稳定性评价的理论基础（‘安全岛’理论、地质结构控制论、区域稳定工程地质学理论、‘场’论以及其他理论和观点）和初步形成的系统化、层次化、定量化、智能化区域地壳稳定性评价方法技术,指出区域地壳稳定性评价应向小区划和四维发展,为工程建设服务。最终编写、出版中华人民共和国国家标准一区域地壳稳定性评价规范,建立区域地壳稳定性评价体系;编制、发布、实施中华人民共和国国家标准-区域地壳稳定性评价区划图（1：400万）,形成区域地壳稳定性评价国家平台,作为国土规划和工程安全建设的法制性依据和标准。 相似文献
7.
O. P. Pandey K. Chandrakala P. R. Reddy G. Koti Reddy 《Journal of the Geological Society of India》2009,73(4):457-468
Recent surge in intraplate seismicity has led to detailed geological and geophysical investigations, covering different continental
segments of India including seismogenic region of Latur. A synthesis of such data sets to understand the prevailing tectonic
and thermal state of the Lithosphere beneath Latur region, that witnessed a large scale human loss due to 1993 seismic activity,
has revealed shallow surfacing of denser deeper crustal segments which may have resulted due to ongoing active subsurface
tectonic activity like uplift and erosion since geological past. Below this region, Moho temperature exceeds 500°C, heat flow
input from the mantle is quite high (29–35 mW/m2) and the asthenosphere is shallow (∼100±10 km). It is suggested that stress generated by ongoing upliftment and related subcrustal
thermal anomaly is concentrating in this denser and stronger mafic crust within which earthquakes tend to nucleate. In all
likelihood, the seismic activity witnessed in the region may stem from the deep crustal/lithospheric dynamics rather than
the role of fluids at the hypocentral depth. 相似文献
8.
长江三峡水电工程坝址区断裂新活动年龄分为两类:(1)>220×104a BP.和(2)(131-54)×104aBP.。坝区15公里范围内不存在近代活动断裂。地震基本烈度为Ⅵ度。地壳稳定性等级属稳定区。 相似文献
9.
Rebecca M. Flowers Samuel A. Bowring Kevin H. Mahan Michael L. Williams Ian S. Williams 《Contributions to Mineralogy and Petrology》2008,156(4):529-549
New U–Pb geochronology for an extensive exposure of high-pressure granulites in the East Lake Athabasca region of the western
Canadian shield is consistent with a history characterized by 2.55 Ga stabilization of cratonic lithosphere, 650 million years
of lower crustal residence and cratonic stability, and 1.9 Ga reactivation of the craton during lithospheric attenuation and
asthenospheric upwelling. High precision single-grain and fragment zircon data define distinctive discordia arrays between
2.55 and 1.9 Ga. U–Pb ion microprobe spot analyses yield a similar range of U–Pb dates with no obvious correlation between
date and cathodoluminescence zonation. We attribute the complex U–Pb zircon systematics to growth of the primary populations
during a 2.55 Ga high-pressure granulite facies event (~1.3 GPa, 850°C) recorded by the dominant mineral assemblage of the
mafic granulite gneisses, with subsequent zircon recrystallization and minor secondary zircon growth during a second high-pressure
granulite facies event (1.0 GPa, ~800°C) at 1.9 Ga. The occurrence of two discrete granulite facies metamorphic events in
the lower crust, separated by an interval of 650 million years that included isobaric cooling for at least some of this time,
suggests that the rocks resided at lower crustal depths until 1.9 Ga. We infer that this phase of lower crustal residence
and little tectonic activity is coincident with an extended period of cratonic stability. Detailed structural and thermochronological
datasets indicate that multistage unroofing of the lower crustal rocks occurred in the following 200 million years. Extended
lower crustal residence would logically be the history inferred for lower crust in most cratonic regions, but the unusual
aspect of the history in the East Lake Athabasca region is the subsequent lithospheric reactivation that initiated transport
of the lower crust to the surface. We suggest that a weakened strength profile related to the 1.9 Ga heating left the lithosphere
susceptible to far-field tectonic stresses from bounding orogens that drove the lower crustal exhumation. An ultimate return
to cratonic stability is responsible for the preservation of this extensive lower crustal exposure since 1.7 Ga. 相似文献
10.
冀西北姚家庄存在一套晚三叠世的超镁铁岩-正长岩杂岩体,岩体内发育具有环带特征的单斜辉石。辉石的环带有两种:简单环带和复杂环带。简单环带一般为正环带,辉石核部的MgO和Cr2O3含量高,Si O2、Fe O和Na2O含量低;边部的主要氧化物含量与核部刚好相反。简单正环带可以分为两类,其中核边接触带平滑、由核到边化学成分具有渐变特征的正环带辉石可能是岩浆在分离结晶或地壳混染过程中形成。而核边接触带有熔蚀结构、由核到边化学成分突变的正环带辉石可能是早期结晶的辉石颗粒受到晚期低镁岩浆的溶蚀改造而成的。复杂环带具有核-幔-边结构,其中,核部低镁高铁、幔部高镁低铁、边部与核部相似,但其Mg#更低,这些特征暗示了岩浆混合作用的存在,形成辉石核部的母岩浆可能来自富集的岩石圈地幔,幔部高Mg#的特征指示了软流圈地幔物质的贡献,其边部低Mg#的特征则指示了地壳物质的加入。具有韵律环带的复杂辉石是在岩浆多期侵入的过程中形成的。辉石环带的组成特征表明,姚家庄杂岩体是由岩浆多期侵位形成的,后期侵入的岩浆与前期就位的岩浆不断反应,形成了具有多种不同环带特征的辉石,并最终形成了空间上由外到内依次为辉石岩、辉石正长岩和正长岩的环状杂岩体。结合前人的研究成果,推测形成姚家庄岩体的岩浆主要来源于富集的岩石圈地幔,并由少量地壳组分和软流圈物质的贡献。 相似文献
11.
海原-六盘山断裂是青藏高原东北缘的大型边界断裂带,是中国大陆典型的地震危险区。地壳构造加载特征的定量研究有助于分析区域孕震环境,参考青藏高原东北缘GPS形变和岩石圈精细结构等资料,本文建立海原-六盘山断裂带周缘的三维岩石圈分层模型,分析现今构造加载作用下区域地壳形变和应力演化特征。数值计算结果显示:青藏高原东北缘现今处于以北东-南西向的水平挤压为主导和北西-南东向的水平引张的变形特征。青藏高原东北缘中-下地壳流变性质影响上覆脆性地壳应力环境,中地壳较低粘滞系数对应的模型地壳应力计算值与研究区实际地壳应力场相近。海原断裂中-西段构造加载作用显著,具有相对较高的库仑应力积累和最大剪应力分布;而六盘山断裂周缘地壳应力和最大剪应力小于海原断裂带。构造应力积累的空间分布差异说明六盘山断裂具有较弱的构造孕震环境,而研究区走滑型断裂的孕震加载作用显著。尽管六盘山处于较低的应力状态,但仍不能轻易忽视其长期存在的强震空区所暗示的发震潜力。 相似文献
12.
区域地壳稳定性研究的后顾与前瞻 总被引：2，自引：0，他引：2
文章回顾了中国区域地壳稳定性研究的历史,划分了其发展阶段,阐述了不同学派的基本观点,分析了该领域面临的新挑战并指出了其未来的发展方向。明确提出,在活动地区选出并评价相对稳定地块(安全岛)作为重大工程场址将是未来的主流。 相似文献
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Andrea Brogi 《International Journal of Earth Sciences》2008,97(4):677-703
The tectonic evolution of the Mt Amiata volcano-geothermal area is under discussion. Some authors state that this region,
as well as the hinterland of the Northern Apennines, were affected by compression from the Cretaceous to the Quaternary. In
contrast, most authors believe that extension drove the tectonic evolution of the Northern Apennines from the Early Miocene
to the Quaternary. Field data, seismic analyses and borehole logs have been integrated in order to better define the structural
features of the continental crust in the Mt Amiata geothermal area. In this paper I propose the hypothesis that the structure
of the crust in the Mt Amiata volcano-geothermal area derives from two main geological processes: (1) contractional tectonics
related to the stacking of the Northern Apennines (Cretaceous–Early Miocene), (2) subsequent extensional collapse of the hinterland
of the mountain chain, and related opening of the Northern Tyrrhenian Sea (Early Miocene–Quaternary). Compressional and extensional
structures characterise the Mt Amiata region, although extensional structures dominate its geological framework. In particular
the extension produced: (a) Middle-Late Miocene boudinage of the previously stacked tectonic units; (b) Pliocene–Quaternary
normal faulting which favoured the emplacement of a magmatic body in the middle-upper crust; and (c) the eruption of the Mt
Amiata volcano, which gave rise to an acid and intermediate volcanic complex (0.3–0.19 Ma). The extension produced the space
necessary to accommodate the Middle-Late Miocene marine and continental sediments. Pliocene and Quaternary normal and transtensional
faults dissected the previous structures and influenced the Early Middle Pliocene marine sedimentation within the structural
depressions neighbouring the Mt Amiata volcano. The magmatic body was emplaced at depth (about 6–7 km) during the Pliocene
extension, and produced the eruption of the Mt Amiata volcano during the Late Pleistocene. This gave rise to local uplift,
presently reaching about 3,000 m, as well as a negative Bouguer anomaly (−16 mgal), both centred on the Mt Amiata area. The
crustal dome shows a good correspondence with the convex shape of the regional seismic marker known as the K-horizon, which
corresponds to the 450°C isotherm, and the areas with greatest heat flow. This is probably a consequence of the above-cited
magmatic body presently in the process of solidification. A Late Pleistocene eruption occurred along a crustal fissure striking
N50° (Mt Amiata Fault), which crosscuts the crustal dome. Hydrothermal circulation, proven by the occurrence of thermal springs
and gas vents (mainly CO2 and H2S), mainly occurs along the Mt Amiata Fault both in the northeastern ans southwestern sides of the volcano. 相似文献
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西藏南部南迦巴瓦地区中新世-上新世地壳深熔作用 总被引：1，自引：0，他引：1
位于喜马拉雅东构造结的南迦巴瓦地块经历了复杂的构造变形、强烈的变质和深熔作用,是研究碰撞造山过程中地壳深熔作用的重要对象。完整地厘定新生代晚期岩浆作用期次对于揭示南迦巴瓦地区的构造演化历史和深部过程具有重要意义。南迦巴瓦地块3件淡色花岗岩样品的锆石U-Pb定年结果显示该地块经历了11.30±0.16Ma和2.59±0.04Ma两期地壳深熔作用,可能与南迦巴瓦地块晚新生代快速隆升和剥蚀相关。南迦巴瓦地块保存了大量的~11Ma变质作用和地壳深熔作用记录指示该时间段为构造活动剧烈期。上新世晚期的淡色花岗岩表明,穹窿的隆升和剥蚀所导致的岩浆作用至少持续到了~2.59Ma,代表了南迦巴瓦地区一次年轻的构造岩浆事件。 相似文献
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A three-dimensional gravity modelling of the Carpatho-Pannonian region was carried out to get a better image of the Moho boundary
and the most prominent intra-crustal density heterogeneities. At first, only the major density boundaries were considered:
the bottom of the Tertiary basin fill, the Moho discontinuity and the lithosphere to asthenosphere boundary. Density contrasts
were represented by relative densities. The improved density model shows a transitional unit of high density at the base of
the crust along the Teisseyre-Tornquist Zone. In the Western Carpathians, an extensive, relatively low-density unit was inferred
in mid-crustal levels. The border zone between the Southern Carpathians and the Transylvanian basin is characterized by a
sharp, step-like contact of the two crustal units. The Moho configuration reveals important information on the tectonic evolution
of the region. Zones of continental collision are represented by thick Moho roots (Eastern Alps, Eastern Carpathians). Transpressional
orogenic segments, however, are different: in the Western Carpathians, the Moho is a flat surface; in the Dinarides, a medium
Moho root is observed; the Southern Carpathians are characterized by a thick crustal root. The differences are explained with
the presence or absence of “subductible” oceanic crust along the Carpathians during the extrusion of Pannonian blocks. 相似文献
18.
Magmatic processes that generated the rhyolite of Glass Mountain, Medicine Lake volcano, N. California 总被引：13，自引：1，他引：13
Timothy L. Grove Julie M. Donnelly-Nolan Todd Housh 《Contributions to Mineralogy and Petrology》1997,127(3):205-223
Glass Mountain consists of a 1 km3, compositionally zoned rhyolite to dacite glass flow containing magmatic inclusions and xenoliths of underlying shallow crust.
Mixing of magmas produced by fractional crystallization of andesite and crustal melting generated the rhyolite of Glass Mountain.
Melting experiments were carried out on basaltic andesite and andesite magmatic inclusions at 100, 150 and 200 MPa, H2O-saturated with oxygen fugacity controlled at the nickel-nickel oxide buffer to provide evidence of the role of fractional
crystallization in the origin of the rhyolite of Glass Mountain. Isotopic evidence indicates that the crustal component assimilated
at Glass Mountain constitutes at least 55 to 60% of the mass of erupted rhyolite. A large volume of mafic andesite (2 to 2.5
km3) periodically replenished the magma reservoir(s) beneath Glass Mountain, underwent extensive fractional crystallization and
provided the heat necessary to melt the crust. The crystalline residues of fractionation as well as residual liquids expelled
from the cumulate residues are preserved as magmatic inclusions and indicate that this fractionation process occurred at two
distinct depths. The presence and composition of amphibole in magmatic inclusions preserve evidence for crystallization of
the andesite at pressures of at least 200 MPa (6 km depth) under near H2O-saturated conditions. Mineralogical evidence preserved in olivine-plagioclase and olivine-plagioclase-high-Ca clinopyroxene-bearing
magmatic inclusions indicates that crystallization under near H2O-saturated conditions also occurred at pressures of 100 MPa (3 km depth) or less. Petrologic, isotopic and geochemical evidence
indicate that the andesite underwent fractional crystallization to form the differentiated melts but had no chemical interaction
with the melted crustal component. Heat released by the fractionation process was responsible for heating and melting the
crust.
Received: 26 March 1996 / Accepted: 14 November 1996 相似文献
19.
内蒙古化德县三胜钨钼矿床位于华北陆块北缘,为岩浆期后中高温热液型矿床。采用辉钼矿Re-Os同位素分析获得辉钼矿的模式年龄加权平均值为138±1Ma,等时线年龄为138.6±1.4Ma,推测三胜钨钼矿床的形成时代为燕山晚期,这与区域上华北陆块北缘主要金属矿床的形成年龄吻合。辉钼矿的Re含量平均值为0.5548×10~(-6),表明其主要为地壳来源特征。成矿发生在陆内构造环境,为燕山期大规模构造-岩浆作用的产物。 相似文献
20.
《地学前缘(英文版)》2022,13(2):101138
In paleogeographic reconstructions of the Columbia and Rodinia Supercontinents, the position of the Greater India landmass is ambiguous. This, coupled with a limited understanding of the tectonic evolution of the mobile belts along which the mosaic of crustal domains in India accreted, impedes precise correlation among the dispersed crustal fragments in supercontinent reconstructions. Using structural, metamorphic phase equilibria, chronological and geochemical investigations, this study aims to reconstruct the tectonic evolution of the Chottanagpur Gneiss Complex (CGC) as a distinct crustal block at the eastern end of the Greater Indian Proterozoic Fold Belt (GIPFOB) along which the North India Block (NIB) and the South India Block (SIB) accreted. The study focuses on two issues, e.g. dating the Early Neoproterozoic (0.92 Ga) accretion of the CGC with the NIB contemporaneous with the assembly of Rodinia, and documenting the widespread (>24,000 km2) plutonism of 1.5–1.4 Ga weakly peraluminous, calc-alkalic to alkali-calcic and ferroan A-type granitoids (± garnet) devoid of mafic microgrannular enclaves and coeval mafic emplacements in the crustal block. These dominantly within-plate granitoids arguably formed by asthenospheric upwelling induced partial melting of garnet-bearing anatectic quartzofeldspathic gneisses that dominate the Early Mesoproterozoic basement of the block. The major and trace element chemistry of the granitoids is similar to the 1.35–1.45 Ga A-type granitoids in Laurentia/Amazonia emplaced contemporaneous with the 1.5–1.3 Ga breakup of the Columbia Supercontinent.This study suggests the Chottanagpur Gneiss Complex occured as a fragmented crustal block following the breakup of the Columbia Supercontinent; the crustal block was subsequently integrated within India during the Early Neoproterozoic oblique accretion between the NIB and SIB contemporaneous with the Rodinia Supercontinent assembly. 相似文献