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991.
The composition of quartz inclusions and trace elements in ore indicate that gold-bearing fluid in the Xiadian gold deposit,Shandong Province,stemmed from both mantle and magma,belonging to a composite origin.Based on theoretical analysis and high temperature and high pressure experimental studies,gold-bearing fluid initiative localization mechanism and the forming environment of ore-host rocks are discussed in the present paper.The composite fluid extracted gold from rocks because of its expanding and injecting forces and injecting forces and flew through ore-conducive structures,leading to the breakup of rocks.The generation of ore-host faults and the precipitation of gold-bearing fluid occurred almost simultaneously.This study provides fur-ther information about the relationships between gold ore veins and basic-ultrabasic vein rocks and intermediate vein rocks,the spatial distribution of gold ore veins and the rules governing the migration of ore fluids. 相似文献
992.
SK setV4.0是中国地质科学院岩溶地质研究所GIS中心2001年4月开发成功的、具有自主板权的专业GIS平台软件。它集成了现今较为先进的组件、控件重用,面向对象编程等技术,并以美国Inprise公司的BorladnC^ Builder编译软件为开发平台,提供了全中文菜单环境,不仅具有基本信息和多图层查询、相关分析动态监测、多因子分析、图斑编辑、自动演示、系统维护等功能,而且还具有快速响应的工具条、友好的对话框和较强的纠错机制,很适合缺乏专业GIS人才的县市级政府管理部门使用。文中还以贵州省沿河县资源遥感信息系统为例,对SK setV4.0的功能和使用方法进行了具体的介绍。 相似文献
993.
Rob Westaway 《Tectonophysics》2002,348(4)
The Gulf of Corinth in central Greece is an active normal fault zone with particularly clear evidence of isostatic footwall uplift, constrained by Quaternary marine terraces, and hanging-wall subsidence and sedimentation. It is bounded to the south by a Pliocene to Early Pleistocene sedimentary basin, which is now eroding into the Gulf. Previous work has suggested that the relief across this region has increased dramatically since the Early Pleistocene, due to the isostatic response to increased rates of footwall erosion and hanging-wall sedimentation. It is indeed assumed here that incision accompanying the draw-down of global sea-level at 0.9 Ma, during the first major Pleistocene glaciation, initiated the erosion of the basin south of the Gulf of Corinth and so abruptly increased the sedimentation rate in the Gulf. The resulting transient thermal and isostatic response to these changes is modelled, with the subsiding depocentre and eroding sediment source coupled by flow in the lower continental crust. The subsequent enhancement of relief, involving an increase in bathymetry from near zero to 900 m and 500 m of uplift of the eroding land surface in the sediment source, is shown to be a direct consequence of this change. The model is sensitive to the effective viscosity of the lower crust, and can thus resolve this parameter by matching observations. A value of 6×1019 Pa s is indicated, suggesting a viscosity at the Moho no greater than 1018 Pa s. Similar transient topographic effects caused by increased rates of sedimentation and erosion are likely to be widespread within the geological record, suggesting that this coupling process involving flow in the weak lower crust may be of major geological and geomorphological importance. 相似文献
994.
Stability of earthquake moment tensor inversions: effect of the double-couple constraint 总被引:1,自引:0,他引:1
We show that spurious large non-double-couple components can be obtained in inversions for the full deviatoric moment tensor for shallow crustal earthquakes due to inaccurate Earth models. The traditional “best double-couple” solution does not in general provide an optimal estimate of a double-couple mechanism, and is only reliable when the non-double-couple component of the full deviatoric solution is small. The inverse problem for the moment tensors of the 1998 Antarctic Plate and 2000 Wharton Basin strike-slip earthquakes is shown in each case to have two well-fitting minima in the misfit function of pure double-couple solutions. Such pairs of solutions are most likely to exist for earthquakes which are close either to vertical strike-slip or to dip-slip on a fault plane dipping at 45°. It is shown theoretically that these pairs of solutions arise from the combination of the pure double-couple constraint and the instability of two elements of the moment tensor. No significant non-double-couple component is found for the shallow thrusting 1996 Biak, Indonesia earthquake. 相似文献
995.
We have collected about 150 magnetotelluric (MT) soundings in northeastern Nevada in the region of the Ruby Mountains metamorphic core complex uplift and southern Carlin mineral trend, in an effort to illuminate controls on core complex evolution and deposition of world-class gold deposits. The region has experienced a broad range of tectonic events including several periods of compressional and extensional deformation, which have contributed to the total expression of electrical resistivity. Most of the soundings reside in three east–west profiles across increasing degrees of core uplift to the north (Bald Mountain, Harrison Pass, and Secret Pass latitudes). One short cross-line was also taken to assess an east–west structure to the north of the northern profile. Model resistivity cross-sections were derived from the MT data using a 2-D inversion algorithm, which damps departures of model parameters from an a priori structure. Geological interpretation of the resistivity combines previous seismic, potential field and isotope models, structural and petrological models for regional compression and extension, and detailed structural/stratigraphic interpretations incorporating drilling for petroleum and mineral exploration. To first order, the resistivity structure is one of a moderately conductive, Phanerozoic sedimentary section fundamentally disrupted by intrusion and uplift of resistive crystalline rocks. Late Devonian and early Mississippian shales of the Pilot and Chainman Formations together form an important conductive marker sequence in the stratigraphy and show pronounced increases in conductance (conductivity–thickness product) from east to west. These increases are attributed to graphitization caused by Elko–Sevier era compressional shear deformation and possibly by intrusive heating. The resistive crystalline central massifs adjoin the host stratigraphy across crustal-scale, steeply dipping fault zones. The zones provide pathways to the lower crust for heterogeneous, upper crustal induced, electric current flow. Resistive core complex crust appears steeply bounded under the middle of the neighboring grabens and not to deepen at a shallow angle to arbitrary distances to the west. The numerous crustal breaks imaged with MT may contribute to the low effective elastic thickness (Te) estimated regionally for the Great Basin and exemplify the mid-crustal, steeply dipping slip zones in which major earthquakes nucleate. An east–west oriented conductor in the crystalline upper crust spans the East Humboldt Range and northern Ruby Mountains. The conductor may be related to nearby graphitic metasediments, with possible alteration by middle Tertiary magmatism. Lower crustal resistivity everywhere under the profiles is low and appears quasi one-dimensional. It is consistent with a low rock porosity (<1 vol.%) containing hypersaline brines and possible water-undersaturated crustal melts, residual to the mostly Miocene regional extension. The resistivity expression of the southern Carlin Trend (CT) in the Pinon Range is not a simple lineament but rather a family of structures attributed to Eocene intrusion, stratal deformation, and alteration/graphitization. Substantial reactivation or overprinting by core complex uplift or Basin–Range extensional events seems likely. We concur with others that the Carlin Trend may result in part from overlap of the large Eocene Northeast Nevada Volcanic Field with Precambrian–Paleozoic deep-water clastic source rocks thickening abruptly to the west of the Pinon Range, and projecting to the north–northwest. 相似文献
996.
As a legacy of the centrally planned economy, the economies in transition of Central and Eastern Europe (CEE) have a unique
potential to reduce their greenhouse gas emissions through the improvement in their high energy intensities. Since much of
this `low-hanging fruit' in energy-efficiency improvements can be highly cost-effective, many developed countries facing difficulties
in meeting their greenhouse gas (GHG) emission targets domestically are eager to find such opportunities in the CEE region.
Therefore, studies analysing the potentials and costs of carbon dioxide reduction through technology improvement in the region
have come into the limelight. While there are a few excellent studies in the region aimed at analysing climate change abatement
potentials, they all embark on different assumptions, methodologies and boundary conditions. It is hence difficult, if not
impossible, to compare and analyse the results of these studies across different authors, countries or time horizons. Consequently,
the purpose of this paper is to place four leading studies on GHG mitigation through technology improvement from the CEE region
into an internationally comparable framework. Four studies were selected from three countries, Poland, Hungary and Estonia,
which are all the results of major national and international efforts to assess costs and potentials of GHG reduction. The
paper places their assumptions, methods and final results into a framework which enables policy-makers and project designers
to compare these across geographical and technological boundaries. Since other studies from around the globe have been analysed
in this framework in the literature, this paper provides a vehicle for the findings of these four studies to be compared to
others worldwide. In addition, the paper highlights a few areas where similar studies to be completed in the future in the
region may be enhanced by incorporating features used in GHG mitigation research in other parts of the world.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
997.
Traditional models of urban development are no longer adequate to describe current metropolitan transformations. These are
now at the centre of a debate concerning management and administration. In Italy, delays in resolving problems of urban and
metropolitan government, despite the legal framework provided by Law 142/90, have weighed heavily on the larger urban areas
of the country: Rome, Naples, Milan, which have not been able to tackle the issue of metropolitan government. Recent legislation,
while not providing a pre-defined institutional solution, allows separate administrative districts to collectively establish
metropolitan institutions of `variable geometry'. The Milan urban area is not one city, but a system of mutually-dependent
cities, linked to each other and the rest of the world by a transport network still requiring much investment. The vitality
of its economic structure (especially its small firms) is held back by seriously inadequate infrastructure and low external
economic efficiency. The provincial capital may boast `historic centrality' but the most interesting potential for development
is to be found on the periphery and in the administrative districts immediately surrounding it, in the recovery of derelict
industrial areas and dormitory towns established in the 1950s and 1960s, especially to the north. Recovery of derelict areas,
green areas, and better transport links within the urban area and with the outside world are the key elements in the reorganization
of `Greater Milan'. In this situation of rapid transformation the most appropriate political strategies involve negotiated
planning.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
998.
999.
近年来,在国土资源部的高度重视下,我区相继建立了一系列地学数据库。这些地学数据库的建立不仅为地矿行业提供了基础性数据,也加速了"数字国土工程"和国土资源信息化建设的步伐。随着信息技术的高速发展,利用地理信息系统(GIS)将各类地学数据有机地结合起来,形成地学数据应用与管理系统,最终通过网络服务于社会,必将是各类地学数据发展的必然趋势。 相似文献
1000.