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1.
A set of troilite-silicate-metal (TSM) inclusions and chondrule rims in the Bishunpur (LL3.1) chondrite provide information regarding impact brecciation of small bodies in the early solar system. The TSM inclusions and chondrule rims consist of numerous angular to subrounded silicate grains that are individually enclosed by fine networks of troilite. FeNi metal also occurs in the troilite matrix. The silicates include olivine (Fo55-98), low-Ca pyroxene (En78-98), and high-Ca pyroxene (En48-68Wo11-32). Al- and Si-rich glass coexists with the silicates. Relatively coarse silicate grains are apparently fragments of chondrules typical of petrologic type-3 chondrites. Troilite fills all available cracks and pores in the silicate grains. Some of the TSM inclusions and rims are themselves surrounded by fine-grained silicate-rich rims (FGR).The TSM inclusions and rims texturally resemble the troilite-rich regions in the Smyer H-chondrite breccia. They probably formed by shock-induced mobilization of troilite during an impact event on a primitive asteroidal body. Because silicates in the TSM inclusions and rims have highly unequilibrated compositions, their precursor was presumably type-3 chondritic material like Bishunpur itself. The TSM inclusions and the chondrules with the TSM rims were fragmented and dispersed after the impact-induced compaction, then reaccreted onto the Bishunpur parent body. FGR probably formed around the TSM inclusions and rims, as well as around some chondrules, during the reaccumulation process. Components of most type-2 and 3 chondrites probably experienced similar processing, i.e., dispersal of unconsolidated materials and subsequent reaccumulation. 相似文献
2.
第三纪是四川盆地大范围陆相沉积历史的最后阶段, 同时又是四川盆地重要的构造定形期.探究该时期原型盆地沉积充填规律与构造演化特征, 是揭示四川盆地形成演化过程, 还原其古地理、古气候演变的关键.在综合利用古地磁、地震、野外露头等资料的基础之上, 从盆-山结合的角度出发, 以地质历史时间为主要线索, 对第三纪原型盆地分阶段、分区域地进行了动态化分析研究.重建了各沉积时期原型盆地构造-古地理格局, 分析了盆地沉积充填规律并复原了不同阶段沉积相带的空间展布特征.主要受周缘山系逆冲推覆作用产生的构造负载和盆地基底构造的影响, 第三纪时期四川盆地沉积范围局限于西南部、南部地区, 以河、湖沉积环境为主, 处于持续地挤压、充填过程而具有萎缩消亡的趋势.现今残余第三系地层由老到新, 主要由名山组、芦山组、大邑砾岩组等地层组成(先后经历了: 受造山带挤压推覆作用和温暖干旱气候等因素影响, 发育湖盆边缘冲积扇和沙漠沉积环境, 处于快速沉降阶段的名山组沉积时期; 以及构造活动相对稳定, 湖盆面积不断减小, 以沙泥质沉积互层为特征的芦山组沉积时期; 和沿山前带由南向北迁移, 以发育大型冲积扇为特征的大邑砾岩组沉积时期).纵观整个第三纪构造演化历史, 反映出四川盆地西南部地区在第三纪时期表现为典型的陆内坳陷沉积盆地性质.同期的大地构造活动和气候变化等因素对原型盆地的形成与演化起到了重要的控制作用, 同时也对该时期盆地古地理格局和沉积充填规律产生了重要影响. 相似文献
3.
为精确识别黄土高原丘陵沟壑区典型小流域泥沙来源,分析了流域内“源-汇”地区土壤的理化性质及生物标志物(正构烷烃)作为潜在指纹识别因子,并建立了复合指纹模型。结果显示:单独的土壤理化指纹及正构烷烃均不能有效识别泥沙来源;土壤理化指纹和正构烷烃分别在林地、农地及沟道的辨别上显示出其局限性。多元化的复合指纹(碳优势指数CPI、Ca、TP、C20、C29、Fe)则能辨别90.5%的泥沙来源。模型结果显示沟道是该流域泥沙的主要来源,占60.8%,其次为农地占20.7%,林地占11.3%,草地占7.2%。研究表明,结合生物标志物的复合指纹法能更精确地反映泥沙来源,适用于各泥沙源头的地质条件差异较小的流域,对黄土高原小流域水土流失治理具有指导意义。 相似文献
4.
Tomoko Komada David J. Burdige Cédric Magen Huan-Lei Li Jeffrey Chanton 《Aquatic Geochemistry》2016,22(5-6):593-618
Geochemical and isotopic data for the uppermost 1.2 m of the sediments of the central Santa Monica Basin plain were examined to better understand organic matter deposition and recycling at this site. Isotopic signatures (Δ14C and δ13C) of methane (CH4) and dissolved inorganic carbon (DIC) indicate the occurrence of anaerobic oxidation of CH4 that is fueled by CH4 supplied from a relict reservoir that is decoupled from local organic carbon (Corg) degradation and methanogenesis. This finding was corroborated by a flux budget of pore-water solutes across the basal horizon of the profile. Together these results provide a plausible explanation for the anomalously low ratio between alkalinity production and sulfate consumption reported for these sediments over two decades ago. Shifts in Δ14C and δ13C signatures of Corg have previously been reported across the 20-cm depth horizon for this site and attributed to a transition from oxic to anoxic bottom water that occurred ~350 years BP. However, we show that this horizon also coincides with a boundary between the base of a hemipelagic mud section and the top of a turbidite interval, complicating the interpretation of organic geochemical data across this boundary. Radiocarbon signatures of DIC diffusing upward into surface sediments indicate that remineralization at depth is supported by relatively 14C-enriched Corg within the sedimentary matrix. While the exact nature of this Corg is unclear, possible sources are hemipelagic mud sections that were buried rapidly under thick turbidites, and 14C-rich moieties dispersed within Corg-poor turbidite sections. 相似文献
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Inspired by recent significant agricultural yield losses in the eastern China and a missing operational monitoring system, we developed a comprehensive drought monitoring model to better understand the impact of individual key factors contributing to this issue. The resulting model, the ‘Humidity calibrated Drought Condition Index’(HcDCI) was applied for the years 2001 to 2019 in form of a case study to Weihai County, Shandong Province in East China. Design and development are based on a linear ... 相似文献
8.
一、五台运动对构造格局的影响五台运动表现的地区,主要是在华北的五台山区、太行山区、冀东、鲁西、豫西地区以及东北的辽东地区,其绝对年龄时限大致为22—23亿年。现已证实,经历五台运动后,华北地区的克拉通化更加明显,被认为属于中国境内克拉通化最早与最完备的地区。在太古宙末期,华北古陆块与西部的塔里木古陆块可能相联的局面至早元古宙末期已逐渐解体;并且这 相似文献
9.
The long-lived nuclide 92Nb together with 91Nb and 94Nb were produced from Mo by neutron irradiation. The activities of the nuclides were determined by γ spectroscopy and the atomic abundances were determined by mass spectrometry. Intercomparison of 92Nb and 94Nb activities and abundances yielded a value for half-life yr based on a value for half-life yr. The same value was obtained within errors from absolute counting data and dilution analysis. 相似文献
10.
通过将卫星定位和计算机视觉定位组合,可以使智能手机在城市、峡谷等卫星定位结果跳变或中断的情况下,仍为用户提供连续、高精度的位置服务.因此,为改善手机端卫星信号不理想区域的定位精度,设计和实现了GNSS与单目相机组合导航的实验.通过数据平滑、旋转矩阵求解等过程完成系统间的轨迹转换,并分析了坐标转换误差.使用结合贝叶斯估计的卡尔曼滤波对两种轨迹进行融合处理.最终结果表明,在城市环境下,GNSS与单目相机组合后,定位误差小于3 m的概率由21.21%提升至48.15%,小于5 m的概率由48.82%提升至70.03%. 相似文献