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南京蒋庙岩体的年代学、地球化学及其地质意义 总被引:1,自引:1,他引:0
南京蒋庙侵入岩体的主体为辉长岩-闪长岩,并伴有少量的二长岩。LA-ICP-MS锆石U-Pb定年表明,其形成于118±1.1Ma,为长江中下游地区中生代最晚的一次岩浆活动。岩石地球化学资料表明,在岩浆上升及结晶过程中无明显的地壳物质混染。蒋庙岩体的εNd(t)值为-0.49~-2.29,介于DMM及EMII之间。简单二单元混合计算表明,其源区中有较高比例的软流圈物质加入。综合其它年龄资料,长江中下游地区中生代岩浆活动可分为3期:早期为151~133Ma,中期为131~126Ma,晚期为125~118Ma。中生代时期该区总体处于板内伸展的构造环境,经历了岩石圈拉张、软流圈持续上涌的地幔过程。 相似文献
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We have used a 2-D microphysics model to study the effects of atmospheric motions on the albedo of Titan's thick haze layer. We compare our results to the observed variations of Titan's brightness with season and latitude. We use two wind fields; the first is a simple pole-to-pole Hadley cell that reverses twice a year. The second is based on the results of a preliminary Titan GCM. Seasonally varying wind fields, with horizontal velocities of about 1 cm sec-1 at optical depth unity, are capable of producing the observed change in geometric albedo of about 10% over the Titan year. Neither of the two wind fields can adequately reproduce the latitudinal distribution of reflectivity seen by Voyager. At visible wavelengths, where only haze opacity is important, upwelling produces darkening by increasing the particle size at optical depth unity. This is due to the suspension of larger particles as well as the lateral removal of smaller particles from the top of the atmosphere. At UV wavelengths and at 0.89 micrometers the albedo is determined by the competing effects of the gas the haze material. Gas is bright in the UV and dark at 0.89 micrometers. Haze transport at high altitudes controls the UV albedo and transport at low altitude controls the 0.89 micrometers albedo. Comparisons between the hemispheric contrast at UV, visible, and IR wavelengths can be diagnostic of the vertical structure of the wind field on Titan. 相似文献
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古地幔流体及其在大陆克拉通地幔演化中的意义——以华北地台为例 总被引:4,自引:0,他引:4
古生代含捕虏体的金伯利岩和新生代含捕虏体的玄武岩同出于华北地台,提供了研究自古生代以来岩石圈演化的深源探针。古生代含金伯利岩的侵位表明古生代时曾存在冷厚的岩石圈;而新生代含捕虏体玄武岩的喷发,表明新生代时存在热薄的岩石圈。岩石圈减薄与“大洋化”是层圈物质交换作用在一定历史阶段中的反映。地幔流体是地幔演化产物,反之又作用于地幔演化。富含地幔流体的幔内剪切带及交代矿物层作为幔内软薄弱带,存在热、流体、化学及机械的耦合,是岩石圈减薄拆沉作用的重要界面位置。 相似文献
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通过大量野外地质调查和深部物探(地震剖面、MT和重力)综合构造解释,在位于东起八盘水磨,西对乌鲁克恰特以西的南天山前陆冲断带中,确定了阿图什-八盘水磨反冲构造系统及其三角带构造;该反冲系统由小阿图什-八盘水磨和乌尔-喀拉套山反冲构造系统及小阿图什-乌鲁克恰特被变形的反冲构造系统组成;即在以往认为南天山向塔里木盆地大规模中推覆的地区,塔里木盆地美国层第四纪以来沿多组滑脱面向天山新生代造山带反冲推覆。塔里木盆地反冲构造系统发育的区域基底埋深往往大于10km,对应麦盖提基底构造下凹区,而相邻柯坪塔格薄皮推覆构造系统发育的区域基底埋深一般小于10km,对应巴楚基底构造上隆区;逆冲和反冲构造转换带基底埋深约10km,平衡剖面恢复表明弧形逆冲和反冲构造顶部分别为逆冲和反冲位移量最大位置。 相似文献
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