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71.
72.
Lithoprobe and industry seismic profiles have furnished evidence of major zones of easterly dipping Grenville deformed crust extending southwest from exposed Grenville rocks north of Lake Ontario. Additional constraints on subsurface structure limited to the postulated Clarendon–Linden fault system south of Lake Ontario are provided by five east–west reflection lines recorded in 1976. Spatial correlations between seismic structure and magnetic anomalies are described from both Lake Ontario and the newly reprocessed New York lines.In the Paleozoic to Precambrian upper crust, the New York seismic sections show: (1) An easterly thickening wedge of subhorizontal Paleozoic strata unconformably overlying a Precambrian basement whose surface has an apparent regional easterly dip of 1–2°. Minor apparent normal offsets, possibly on the order of tens of meters, occur within the Paleozoic section. The generally poorly reflective unconformity may be locally characterized by topographic relief on the order of 100 m; (2) Apparent local displacement on the order of 90 m at the level of the Black River Group diminishes upward to little or no apparent offset of Queenston Shale; (3) Within the limited seismic sections, there appears to be no evidence that the complete upper crustal section is vertically or subvertically offset; (4) Dipping structure in the Paleozoic strata (15° to 35°) resembles some underlying Precambrian basement elements; (5) The surface continuity of inferred faults constituting the Clarendon–Linden system is not strongly supported by the seismic data.Beneath the Paleozoic strata, the seismic sections show both linear and arcuate reflector geometry with easterly apparent dips of 15° to 35° similar to the deep structures imaged on seismic lines from nearby Lake Ontario and on Lithoprobe lines to the north. The similarity supports an extension of easterly dipping Central Metasedimentary Belt structures of the Grenville orogen from southern Ontario to beneath western New York State.From a comparison of the magnetic and gravity fields with the New York seismic sections, we suggest: (1) The largely nonmagnetic Paleozoic strata appear to contribute negligibly to magnetic anomalies. Seismically imaged fractures in the New York Paleozoic strata appear to lie mainly west of a positive gravity anomaly. The relationship between magnetic and gravity anomalies and the changes in the geometry of interpreted Precambrian structures remains enigmatic; (2) North to northeast trending curvilinear magnetic and gravity anomalies parallel, but are not restricted to the principal trend of the postulated Clarendon–Linden fault system. Paleozoic fractures of the Clarendon–Linden system may partly overlie a southward extension of the Composite Arc Belt boundary zone. 相似文献
73.
《Journal of Geochemical Exploration》2002,76(3)
Many studies have shown systematic correlations between the composition of plutons worldwide and the metal content of associated skarns. This is the first report of similar correlations between the composition of Çelebi granitoid and skarns of the Çelebi district in Central Anatolia, Turkey. The Çelebi district is well known for its polymetallic Fe–W and Cu vein ores. These are hosted by calcic skarn zones. Both exoskarns (pyroxene–garnet) and endoskarns (epidote–pyroxene) occur in the district formed mainly along the granitoid contacts and along the fractures within the marble. Based on mineralogy, petrology and geochemistry, two different igneous rocks were recognized in the Çelebi granitoid, referred to as leucocratic (felsic) and mesocratic (intermediate) Çelebi granitoid. The leucocratic Çelebi occurs as dominant rock type, and is classified as granite. The mesocratic Çelebi is not widespread and is classified as adamellite, tonalite, quartz monzonite and quartz monzodiorite. The mesocratic Çelebi has I-type characteristics, and have subalkaline, calc-alkaline and metaluminous characteristics like most worldwide skarn granitoids.A post-collisional tectonic setting is proposed on the basis of field evidence, the relative timing of intrusions with respect to metamorphic and obducted ophiolitic rocks and trace element geochemistry. The high abundance of La and Ce and the enrichment of V in mafic components suggest that Çelebi granitoids are formed by partial melting of mantle rocks, but have been contaminated by interaction with continental crust involving possible magma mixing processes (i.e. mixing of coexisting felsic and mafic magmas). In the district, the mesocratic type and mafic microgranular enclaves (MME) mainly within leucocratic type represent a mafic underplating magma that was mixed with and/or injected into felsic magma of the leucocratic type.The present study shows that Fe mineralization is associated with mesocratic Çelebi type, whereas W mineralization is associated with leucocratic type. Mesocratic Çelebi granitoid is significantly different from the worldwide average of plutons associated with Fe skarns. In particular, MgO vs. SiO2, FeOt+CaO+Na2O/K2O vs. SiO2, Fe2O3/Fe2O3+FeO vs. SiO2 and V vs. Ni vary from typical values (are lower than values typical for plutons associated with Fe skarns) for plutons associated with Fe skarns. Instead, it resembles the geochemical characteristics of plutons associated with worldwide Cu and possibly Au skarns. This suggests new exploration possibilities for copper and gold in the Çelebi district. 相似文献
74.
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
75.
北秦岭中生代沙河湾岩体环斑结构特征及有关问题的讨论 总被引:12,自引:0,他引:12
该岩体的环斑结构主要发育于边部含巨斑状黑云角闪石英二长岩中 ,环斑长石粒径一般 2cm× 4cm。形态多呈自形、半自形 ,有些为卵形。环斑长石由核部钾长石和多层或单层斜长石外壳两部分构成。钾长石内核呈肉红色 ,一般是由单颗粒组成 ,具卡氏双晶 ,普遍发育规则的条纹结构 ;中心部分钾长石分子含量Or为 95 ,边部为 84。外壳斜长石牌号一般为An2 0± ,为奥长石。内核和外壳中均发育石英、斜长石、黑云母、角闪石等矿物的包裹体 ;包裹体在其边部较多 ,中部较少 ,钾长石斑晶中的石英包裹体呈不规则的凹面状和水滴状。岩石中主要矿物具有 2个世代。这些特征显示 ,沙河湾岩体中的环斑结构与典型的环斑结构是相同的。亦表明典型的环斑结构可以出现于不同的时代和构造环境。由于其形成时代和产出背景不同于典型环斑花岗岩 ,该岩体属典型环斑花岗岩还是一种新的似环斑花岗岩还有待于进一步研究。 相似文献
76.
77.
Ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers. Due to differential settlement, the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure. Here, we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks, which increasingly affect some middle- and large-sized cities in the world. For that purpose, the ground loss theory is applied to sediments overlying a sinusoidal-shaped graben. This analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear. It also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues. Finally, when a crack has completely developed, the tensile zone shifts towards the center of the graben, creating a new area for potential cracking and faulting. 相似文献
78.
79.
多种驱动力作用下东亚大陆形变及应力场演化 总被引:7,自引:0,他引:7
将印度板块持续地向北推进、下伏地幔小尺度对流对增厚大陆岩石层的搬离作用以及剥蚀作用视为形成现今东亚大陆形变和应力场格局的主驱动力。在一梯形区域内,利用数值模拟的方法,研究了东亚大陆在不同的边界条件、不同的剥蚀率系数及不同的岩石力学参数条件下的形变及应力场格局。与现代空间大地测量技术 CGPS)以及利用地震观测得到的结果进行了对比。结果表明,本文模型预测的结果与上述的观测结果有较好的吻合,其西部地区比东部吻合得更好。说明控制东亚大陆西部形变和应力场基本格局的主驱动力,来源于印度板块对欧亚板块的碰撞、挤压,而对东部地区还应当考虑其与太平洋板块和菲律宾板块的相互作用。与此同时,下伏地幔小尺度对流对增厚大陆岩石层的搬离作用以及风化剥蚀对应力场的演化过程也不可忽视。 相似文献
80.
Beyond world cities: Central America in a global space of flows 总被引:1,自引:0,他引:1
Central America is a region without a world city. Traditionally, the region's national projects have been based upon openness to the world economy: how do the region's contemporary transnational projects connect to the world economy under the new conditions of openness that is contemporary globalization? Focusing upon advanced producer services, three connections into the world city network are identified: global service firms operating directly in Central American cities, local service firms operating indirectly through extra-regional world cities and global service firms operating through Latin American regional offices. Miami is confirmed as the primary world city through which Central America connects into the world economy 相似文献