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塔里木盆地库车坳陷东部阳霞煤矿一带出露绿泥绢云母石英片岩,原被划分为古元古界地层,该片岩中的碎屑锆石呈自形形态,锆石的环带丰富,具有典型的岩浆锆石特点。对锆石进行的ICP MS U Pb同位素地质年代学研究表明,锆石的年龄介于1179~794 Ma之间,峰期年龄集中于810~794 Ma,说明该片岩之原岩的沉积上限年龄不早于794 Ma。结合区域资料分析认为,该基底地层应该属于新元古界,形成时代相对较新,因此导致库车坳陷具有较高的地温梯度和较强的构造活动性。此外,在810~794 Ma时塔里木地块东北部发生过岩浆事件,该事件应该与塔里木地块的裂解有关。 相似文献
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B.E. Leveridge R.K. Shail 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(4):540-567
Exposed marine Devonian rocks of Great Britain are in South-West England where successions together span most of the Devonian Period. The Geological Conservation Review (GCR) sites of the volume are located in Cornwall and Devon, the latter providing the historic stratotype of the Devonian System. Site stratigraphies are linked to basins of three sub-provinces. Those represent different, albeit largely penecontemporaneous, tectonosedimentary regimes of the differing settings of the Rhenohercynian Zone. The sites and their selection criteria based on their international and national importance in understanding Devonian geological history are listed. A History of Research section provides a detailed review of work on the Devonian rocks of the province from 1839, when Sedgwick and Murchison proposed establishment of the system, to the present and the recent recognition of the relationships between its numerous successions and their dependence upon, extensional and contractional tectonic structures and processes. Other sections detail the Stratigraphical Framework of Devonian strata; Devonian Chronostratigraphy, tracing development and refinement of the Series’ and Stages of the system; and Biostratigraphy, in relation to the faunal groups of the province and their relevance to biozone establishment and environmental discrimination. The chapter concludes with an explanation of current understanding of the evolution of the plate settings of the province that determined the nature of the marine Devonian and its stratigraphy in South-West England. 相似文献
998.
The Anqing Fe–Cu skarn deposit, with an age of 134 to 142 Ma and resources of 62.4 Mt at 0.906% Cu and 32.2% Fe, is one of the most important deposits in the Yangtze River Metallogenic Belt, East China. To better understand the localization of orebodies and thus facilitate predictive exploration of deep orebodies, computational modeling is used to simulate the coupled geodynamic processes during the syn-tectonic cooling of the ore-related intrusion, based on geological and geophysical investigations in the Anqing orefield.The occurrences of the ore veins and veinlets in diorite and skarn, as well as the sharp zigzag boundary of the orebody, indicate that the Cu ores were deposited after the solidification of the diorite and skarn formation, and were located in some tensional structural spaces that are unevenly distributed along the contact zone between the felsic intrusion and sedimentary carbonates. The locations of orebodies are closely associated with the contact zone shape. The computational results of two models with two typical contact-shapes show that pore fluid flow was focused into the dilation zones from different sources. All the significant dilation zones, in which the existing orebodies were located, are distributed in some specific places of the south contact zone of the intrusion. In addition, these dilation zones are closely related to the contact zone shape of the intrusion and can control the location of orebodies through the coupled mechano-thermo-hydrological processes during cooling of the intrusion in the extension setting. The skarns are not critical for controlling the localization of orebodies. This means that exploration for deep ore should target deep dilation zones close to the contact boundary of the intrusion. Such recognition may provide a useful guide in selecting exploration targets in the Anqing orefield. As a direct result of computational modeling, an orebody has been discovered in the deep dilation zone in this orefield. It demonstrates that computational modeling is a promising tool for understanding the metallogenic processes and for facilitating the deep exploration of hidden orebodies that are related to intrusions. 相似文献
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高分辨湖泊沉积和孢粉记录对气候、水文变化的响应 总被引:4,自引:2,他引:2
通过对长江中游网湖钻孔高精度分层样品(1.5年/样品)的沉积学和孢粉学研究,试图揭示过去百年网湖在由开放到封闭体系变化中,沉积孢粉与气候、水文动力变化的过程及其相互关系.相关分析和低频滤波分析,反映出沉积物和孢粉的变化对流域降水和长江流量的敏感响应.在过去130年中的多雨洪水年份,湖泊受长江倒灌影响,沉积物以黏土细颗粒... 相似文献