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在基于成像测井、岩心及薄片资料对玉北地区构造裂缝进行识别并总结其发育规律的基础上,根据裂缝切割关系、充填方解石阴极发光及包裹体特征划分裂缝发育期次,并应用有限元法数值模拟不同裂缝发育期古构造应力场特征,结合裂缝发育力学机制,分析不同时期断层-褶皱控制下的裂缝成因模式。研究结果表明,玉北地区奥陶系构造裂缝主要沿高陡带发育,其发育程度、产状受断层、褶皱共同控制,共发育4期裂缝,其中加里东中期Ⅰ、Ⅲ幕裂缝受断层主控、加里东晚期至海西早期裂缝受断层与褶皱共同控制、海西晚期裂缝主要受褶皱控制;与断裂走向较一致的高角度裂缝对储层发育贡献最大,加里东晚期—海西早期及海西晚期两期裂缝发育区,更有利于油气聚集。  相似文献
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塔里木盆地被沙漠区覆盖,基底岩心样品对前寒武纪构造演化的研究具有重要意义.在前人研究基础上,结合盆地内钻井、地震资料,通过基底岩心样品的锆石U-Pb年代学和地球化学分析,为塔里木盆地北缘新元古代构造演化格架提供约束.LA-ICP-MS法给出片麻岩基底样品的加权平均年龄为822±7 Ma(置信度95%,MSWD=2.4),SHRIMP法在上覆震旦系砂岩中获得~2.5 Ga和2.1~1.8 Ga的两组锆石年龄.岩相学和元素地球化学特征显示二云斜长片麻岩样品的原岩为花岗闪长岩类,与相邻钻井揭示的青白口系基性岩墙都属于钙碱性–高钾钙碱性岩浆系列,具有相似的REE配分型式,以强烈亏损Nb、Ta、P等HFSE为特征.构造环境判别图解和Sr-Nd同位素比值显示塔里木盆地北缘新元古代早期的岩浆活动可能形成于陆缘弧的构造环境.  相似文献
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Western Yunnan is composed of several extruded continental microblocks that were generated by the oblique collision between the Indian and Asian continents during the Cenozoic. In this study, the magmatic and tectonic frameworks of western Yunnan in the Cenozoic were analyzed based on geochemistry, Sr–Nd–Pb isotopes, and apatite/zircon fission track dating. Magmatism during the Cenozoic in western Yunnan was then divided into three distinctive episodes: alkali granite rocks produced from 55 to 46 Ma were derived from the anatexis of crustal materials; bimodal igneous rocks formed between 37 and 24 Ma were possibly derived from an EMII mantle with a contribution from continental materials; and intermediate–basic volcanic rocks produced in the Tengchong microblocks since ~16 Ma are considered to be generated by the partial melting of the upper mantle that was induced by the pulling apart of the dextral Gaoligong strike–slip fault system. Moreover, fission track analysis of apatite and zircon indicates that the regional crustal uplift in western Yunnan possibly began at ~34 Ma, with accelerated annealing occurring at ~24 Ma, ~13 Ma, and ~4 Ma. During the past 24 Ma, the average denudation rate was ~0.32 mm/yr for the faulted block controlled by the Chongshan–Lancang River fault. However, crustal uplift has been relatively gentle in places lacking influence from strike–slip shear zones, with an average denudation rate of ~0.2 mm/yr. Combined with strike–slip shear and block rotation in the Cenozoic, the tectonic evolution of western Yunnan since ~45 Ma can thus be divided into four stages occurring at 45–37 Ma, 37–24 Ma, 24–13 Ma, and 13–0 Ma.  相似文献
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