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131.

五龙沟金矿田位于东昆仑造山带东段,金成矿与三叠纪岩浆作用、脆性和/或韧性变形显示密切时空联系。但是,金容矿地质体类型与控矿构造特征尚不清,金成矿受哪些关键要素控矿尚不明确。本文通过广泛深入的文献资料调研与详细的野外调查,详细阐明了五龙沟地区金矿床地质特征与成矿地质环境,系统梳理、总结与对比了不同地段金矿床的矿化类型、容矿地质体与控矿构造。研究表明,五龙沟金矿田发育微细脉型、蚀变岩型、石英脉型等3种矿化类型,容矿地质体主要以元古界—奥陶系变质岩系与侵入岩类为主。早期韧性剪切作用导致矿源层中金的活化与预富集,金矿化主要受控于晚期北西向脆性变形及相关断裂破碎带。大规模金成矿与古特提斯洋关闭及伴随的同/后碰撞构造过程有关。北西向构造—蚀变带、侵入岩类与古老变质基底是五龙沟金矿田的重要勘查标志。

  相似文献   
132.
南黄海盆地在大地构造位置上位于下扬子准地台的东部,是我国东部重要的中新生代陆相含油气盆地。关于南黄海盆地的成因机制,现在还存在较大的争论,故对南黄海盆地的成因机制进行了讨论和总结。南黄海盆地处在特提斯构造域、亚洲构造域和滨太平洋构造域的中心位置,其形成过程中受到多种因素的影响,不同时期起到主要作用的因素不同。  相似文献   
133.
In north-central Wopmay Orogen, syntectonic low-P(Buchan-type) suites of mineral isograds outline regional metamorphic temperature culminations that are associated, at the higher structural levels, with emplacement of early Proterozoic plutons in the west part of a deformed and eastward transported continental margin prism. The mapped isograds mark the first occurrence of biotite, staurolite, andalusite, sillimanite, sillimanite-K feldspar and K feldspar-plagioclase-quartz ± muscovite (granitic) pods in metapelites, with increasing proximity to the plutons.
Microprobe analyses and field observations have resulted in the formulation of reactions for the 'ideal'pelitic system K2O-Na2O-FeO-MgO-Al2O3-SiO2-H2O-Al2O3-SiO2-H2O, to account for the various mineral assemblages of each metamorphic zone. A P-T petrogenetic grid showing erosion surface P-T curves for the northern Wopmay Orogen pelites, compiled on the basis of the mapped isograds and the inferred reaction(s) for each metamorphic zone, documents a variation in exposed metamorphic pressure ranging between 2 and 4 kbar.
The configuration of a new bathograd, based on the invariant model reaction sillimanite + K feldspar + plagioclase + biotite + quartz + vapor ± muscovite + liquid and interpolated across three metamorphic suites, is consistent with a major regional structure culmination and with independently determined pressures obtained from anorthite-grossular-quartz-Al2SiO5 geobarometry. The positive correlation between the configuration of the bathograd and the structural and pressure culmination points to the pressure-dependence of anatectic-granitic-pod mineral associations.  相似文献   
134.
Understanding how the Australian continent came together requires an understanding of structure in all levels of the lithosphere. Deep seismic reflection profiles across several Proterozoic orogens have revealed entirely buried tectonic elements, termed seismic provinces. Although undoubtedly important, the nature of these seismic provinces is typically not well characterised. The Capricorn Orogen is one such region, where the upper crust is relatively well known from geological and geophysical studies, but much of the deep crust is buried beneath Proterozoic basins. Here we combine geophysical datasets, including active and passive source seismic data and gravity data, to image the density, seismic velocity and compositional structure of the deep crust of the Capricorn Orogen. Crustal structure interpreted from deep seismic reflection studies is re-scaled using velocity information from receiver function studies. This modified geometry is used to construct a density model that satisfies Bouguer gravity data. Finally, after correcting for temperature and pressure dependencies, the velocity and density information is used to generate a compositional model of the orogen. This model indicates a varied structure with at least four distinct blocks between the Yilgarn and Pilbara cratons, bounded by major shear zones. We suggest that this variation is linked to multiple accretion events during the amalgamation of the West Australian Craton.  相似文献   
135.
The southwestern Pacific region consists of segmented and translated continental fragments of the Gondwanan margin. Tectonic reconstructions of this region are challenged by the fact that many fragmented continental blocks are submerged and/or concealed under younger sedimentary cover. The Queensland Plateau (offshore northeastern Australia) is one such submerged continental block. We present detrital zircon geochronological and morphological data, complemented by petrographic observations, from samples obtained from the only two drill cores that penetrated the Paleozoic metasedimentary strata of the Queensland Plateau (Ocean Drilling Program leg 133, sites 824 and 825). Results provide maximum age constraints of 319.4 ± 3.5 and 298.9 ± 2.5 Ma for the time of deposition, which in conjunction with evidence for deformation, indicate that the metasedimentary successions are most likely upper Carboniferous to lower Permian. A comparison of our results with a larger dataset of detrital zircon ages from the Tasmanides suggests that the Paleozoic successions of the Queensland Plateau formed in a backarc basin that was part of the northern continuation of the New England Orogen and/or the East Australian Rift System. However, unlike most of the New England Orogen, a distinctive component of the detrital zircon age spectra of the Mossman Orogen is also recognised, suggesting the existence of a late Paleozoic drainage system that crossed the northern Tasmanides en route from the North Australian Craton. A distinctive shift from abraded zircon grains to grains with well-preserved morphology at ca 305 Ma reflects a direct drainage of first-cycle sediments, most likely from an outboard arc and/or backarc magmatism.  相似文献   
136.
《China Geology》2018,1(1):84-108
There are large volumes of the Phanerozoic granitoid rocks in China and neighboring areas. In recent years, numerous new and precise U-Pb zircon ages have been published for these granitoids, and define many important magmatic events, such as ca. 500 Ma granitoid events in the West Junggar, Altai orogens in the NW China, and Qinling orogen in the central China. These ages accurately constrain the time of important Early Paleozoic, Late Paleozoic, Early Mesozoic and Late Mesozoic magmatic events of the northern, central, western, southern and eastern orogenic Mountains in China. There occur various types of granitoids in China, such as calc-alkaline granite, alkali granite, highly-fractionated granite, leucogranite, adakite, and rapakivi granite. Rapakivi granites are not only typical Proterozoic as in the North China Craton, but were also emplaced during Paleozoic and Mesozoic in the Kunlun-Qinling orogen, a part of the China Central Orogenic Belt (CCOB). Nd-Hf isotopic tracing and mapping show that granitoids in the southern Central Asian Orogenic Belt (CAOB) in China (or the Northern China Orogenic Belt) are characterized predominantly by juvenile sources. The juvenile crust in this orogenic domain accounts for over 50% by area, distinguishing it from other orogenic belts in the world, and those in central (e.g., Qinling), southwestern and eastern China. Based on a large amount of new age data, a preliminary granitoid and granitoid-tectonic maps of China have been preliminarily compiled, and an evolutionary framework of Phanerozoic granitoids in China and neighboring areas has been established from the view of assembly and breakup of continental blocks. Research ideas on granitoid tectonics has also been proposed and discussed.  相似文献   
137.
“秦岭-大别-苏鲁”造山带中“古特提斯缝合带”的连接   总被引:7,自引:0,他引:7  
中国大陆西北部的"古特提斯缝合带"如何与东面的"秦岭-大别-苏鲁"造山带连接,是涉及中国大陆中部构造格架的关键问题之一。南秦岭造山带中的古特提斯蛇绿岩带和东秦岭-桐柏-大别-苏鲁造山带中三叠纪高压-超高压变质带的对比,以及一条位于两者之间的220~204 Ma的大型左行走滑剪切带的存在,提供了它们之间关系的新的视角,为此,我们提出南秦岭的勉略蛇绿岩带向东通过宁陕-湘河大型左行走滑剪切带,和大陆俯冲与深俯冲造成的"耀岭河-桐柏-大别-苏鲁"高压—超高压变质带北缘连接,构成"秦岭-大别-苏鲁"造山带中的古特提斯缝合带新模式。沿着这条边界,南秦岭构造单元可以分为南部的南秦岭被动陆缘单元和北部的南秦岭主动陆缘单元,后者向东的延伸由于南、北板块之间三叠纪的剪切碰撞而尖灭。  相似文献   
138.
文中通过多源数据融合、模型构建、数据试验、二维离散小波变换和功率谱分析等方法获取了大别造山带东段深、浅部场源布格异常及其场源似深度,并结合地壳结构、地质构造、岩石圈有效弹性厚度和地震活动等资料,讨论了地壳深、浅部的结构特征及地震活动构造背景。结果表明,低频布格异常显示大别造山带东段与华北地块间深部构造缝合带在东部应位于青山-晓天断裂前缘,在落儿岭-土地岭断裂和商城-麻城断裂之间向N偏移至梅山-龙河口断裂之下,造山带南侧与扬子地块间深部构造缝合带位于襄樊-广济断裂以北约20km,造山带东侧与扬子地块间的深部构造转换带位于郯庐断裂带之下,造山带东段腹地显著的低频布格异常低值表明对应部位的莫霍面存在明显下凹,造山带内部的布格异常高梯度带表明其深部结构不完整;高频布格异常揭示肥中断裂、六安-合肥断裂、肥西-韩摆渡断裂和郯庐断裂带等主要断裂对地壳中上部密度结构的影响明显,落儿岭-土地岭断裂对地壳中上部密度结构的影响范围向N延伸至肥西-韩摆渡断裂前缘。结合地震活动资料进一步分析认为,大别造山带东段与华北地块在青山-晓天断裂前缘附近接触和相互作用,且大别造山带东段地壳深、浅部结构均不完整,不利于应力积累,趋向于在断裂交错的脆弱部位频繁释放应力,是霍山地区小地震活动频繁的主要原因。  相似文献   
139.
Detailed subsurface structure of the eastern Junggar Basin is investigated using a large number of high-resolution two-dimensional reflection seismic profiles and well data. Our results reveal thrust faults, some of which are with strike-slip component, and fault-related folds dominating the subsurface structure of the study area. The thrust faults mainly show a divergent pattern towards the west and convergence towards the east. We divide these thrust faults and folds into three structural systems. The north thrust system, located in the north of the study area, is characterized by top-to-the southwest imbricate thrusts initiated from late Paleozoic. The central transpression system, dominating the central study area, mainly consists of thrust faults with visible strike-slip component, active from early Mesozoic until Cretaceous. The South thrust system includes top-to-the southeast thrusts in the southern part of the study area. The existence of these structural systems indicates that the eastern Junggar Basin underwent obvious intracontinental deformation in Mesozoic, probably due to the continuous convergence between the Altay and the Tianshan orogens after the main collision-accretion processes of the Central Asian Orogenic Belt.  相似文献   
140.
秦祁昆结合部广泛发育中三叠世岛弧钙碱性岩浆作用,已发现大量与其相关的斑岩型—夕卡岩型铜金、铜钼和银铅锌多金属矿床。瓦勒根金矿床是近年来在该区新发现的一个斑岩型金矿床,矿区内出露有众多的石英斑岩和花岗斑岩,且均发育有金矿化,其中石英斑岩与金矿化关系更为密切。LA-ICP-MS锆石U-Pb年龄表明,花岗斑岩形成于中三叠世(237Ma),其中包含有丰富的晚古生代及元古宙继承性锆石。这一特征与区域上的斑岩型铜金矿床含矿岩体具有相似性。进一步说明,古特提斯洋在秦祁昆结合部发生向北消减所形成的岩浆捕获了早于三叠纪的壳源和幔源物质,从而形成了岛弧钙碱性岩浆及相关的斑岩型—夕卡岩型矿床组合。  相似文献   
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