Zircon U–Pb Geochronology of Baiyingaolao Formation from the Hadayingzi Region in the southern Great Xing’an Range, Northeast China     

MI Kuifeng  YAN Tingjie  Lü Zhicheng 《《地质学报》英文版》2019,93(Z2):39-40

Blueschists in the Yilan area, Heilongjiang Province, are known as important parts of the Heilongjiang Complex. However, their metamorphic evolution history is still unclear. Petrographical, and mineral chemical investigations on the blueschists from the Yilan area are carried out in this study. P‐T pseudosections are calculated in the system Na₂O‐CaO‐K₂O‐MnO‐FeO‐MgO‐Al₂O₃‐SiO₂‐H₂O‐TiO₂‐O (Fe₂O₃) (NCKMnFMASHTO) with the PERPLE_X software for three blueschist samples. Peak metamorphic conditions are estimated to be 500‐525°C, 1.14‐1.2 GPa for garnet‐barroisite schist (g‐brs‐wnc‐act‐phn‐chl‐ep‐ab‐stlp); 480°C, 1.4 GPa for chlorite‐epidote glaucophane schist (gl‐brs‐wnc‐act‐chl‐ep‐stlp) and 450‐500°C, 0.95‐1.2 GPa for phengite‐glaucophane schist (gl‐wnc‐phn‐ab‐ep‐chl‐sph), which indicate that they all underwent peak metamorphism in the limit epidote‐blueschist facies conditions. Combined with the previously reported geochemical and geochronological data, the clockwise P‐T paths of the blueschists are constructed. The formation of blueschists in the study area marks the young oceanic crust subduction, and represents the final closure of the Paleo‐Asian Ocean and the beginning of the Paleo‐Pacific tectonic system. The P‐T pseudosection recorded the P‐T increasing process before the metamorphic peak and that the maximum temperature was coincident with the maximum pressure in the process, which indicates that the epidote‐blueschist facies conditions implemented in the process of subduction, rather than exhumation. The retrograde trajectory nearly coincidently retraced the prograde trajectory, which represents the similar geothermal gradient (11‐14°C/km) in the subduction and the relatively slow exhumation process.  相似文献   

Fluid–rock interactions during continuous diagenesis of sandstone reservoirs and their effects on reservoir porosity          下载免费PDF全文

Leilei Yang  Tianfu Xu  Keyu Liu  Bo Peng  Zhichao Yu  Xiaomeng Xu 《Sedimentology》2017,64(5):1303-1321

The Cretaceous sandstone reservoir in the Kuche Depression, Tarim Basin, western China, was investigated with reference to its reservoir property evolution during diagenesis. Six general diagenetic stages were recognized through petrographic, mineralogical and geochemical analyses. Fluid–rock interaction experiments were conducted under these six continuous diagenetic conditions, that is with a simulation sequence of compaction → early diagenesis → organic acid incursion I → elevated temperature/pressure → organic acid incursion II → late diagenesis. Corresponding to these six experimental stages, a total of six models were constructed. Finally, an extended model of fluid–rock interaction during diagenesis at a geological timescale (from 30 Ma to present) was constructed after various parameters had been validated. Results demonstrate that the diagenetic stages from both the experimental and numerical simulations generally matched findings obtained from the petrographic and geochemical analyses: (i) With compaction becoming weakened, cementation by various minerals was gradually increased. (ii) Quartz overgrowth occurred because the contemporaneous sedimentary water was alkaline. (iii) Most minerals (for example, calcite and feldspar minerals) displayed dissolution owing to the first organic acid incursion, resulting in the visual porosity increasing to 29·26%. (iv) Increases in temperature and pressure caused a minor fluctuation of the porosity change. (v) The cement that formed during earlier stages largely dissolved with the second organic acid incursion. (vi) During the last stage, the reservoir fluid was diluted by sedimentary alkaline water and most minerals precipitated under an alkalic environment. The present porosity simulated is about 11·4%, comparable with the actually measured data. This study demonstrates that the combination of petrographic observations, laboratory experiments and numerical simulations can not only reconstruct the diagenetic process, but also provide a quantitative evaluation and prediction of reservoir petrophysical properties.  相似文献   

The episodic geomorphological-sedimentary evolution of different basins in the Fenwei Graben and its tectonic implication     

Xiaomeng Hu  Tianhang Zhou  Shun Cai 《地理学报(英文版)》2017,27(11):1359-1375

There are a series of basins in the Fenwei Graben. Field survey found that there took place several paleolake regressions or intensive stream down-incisions in all basins during the Mid-Late Quaternary. The lowest and oldest paleosol/loess units overlying three of the lacustrine terraces or alluvial ones and some paleomagenetism data from the lacustrine sediment indicate that the onset times of three paleolake regressions or intensive stream down-incisions are synchronous with the formation of L₉, L₆ and L₂ respectively in the Weihe Basin, S₈, S₅ and S₁ respectively in the Linfen-Taiyuan-Xingding Basins, and L₈, L₅ and L₁ respectively in the Datong Basin. The difference in the onset time of each lake regressions or intensive stream down-incision in different basins reveals that the farther the basin is from the Tibetan Plateau, the later it took place. Taking these field facts and the former research results in terms of the regional tectonic movement into account, it is inferred that the tectonic movement of the Tibetan Plateau most probably controlled such geomorphologicalsedimentary evolution in the graben.  相似文献   

蒲阳河流域地下水水化学及同位素特征   总被引：3，自引：2，他引：1       下载免费PDF全文

沈萌萌  郭华明  李晓萌  修伟  倪萍  张迪 《水文地质工程地质》2017,(2):8-14

保定西部山前地区位于太行山及华北平原交界带,为缓解极端气候灾害对生产生活的影响,维持地下水资源的可持续开发利用,开展相关的地下水水化学及同位素特征研究。研究区地下水化学类型以HCO3—Ca·Mg、HCO3·SO4—Ca·Mg及SO4·HCO3—Ca·Mg为主,区内地下水主要来源于大气降水,流域内地表水补给地下水;地下水中化学成分为Ca2＋、Mg2＋、HCO-3、SO2-4,主要来源于岩石风化作用,同时受到人类活动的影响,地下水中硝酸盐含量明显升高;由于受到褶皱构造的控制,流域的上游及平原区均出现年龄大于60年的地下水,多数岩溶水年龄较复杂,从现代水到大于60年的水均有分布。研究成果为流域内水资源的合理开发利用提供建议,区内岩溶地下水的开发将在一定程度上缓解极端天气的影响。  相似文献   

沉积物不同提取态有机物特征及水文地球化学意义——以河套盆地典型研究区为例          下载免费PDF全文

李晓萌  郭华明  曹永生  张迪  修伟 《水文地质工程地质》2017,(2):40-47

地下水系统中有机物（OM）特征和活性对于地下水化学特征的形成和演化起着十分重要的作用。将内蒙古河套盆地表层湖相沉积物按10 cm间隔采集,并对沉积有机质的性质及来源进行重点分析。测量了不同深度上不同岩性沉积物的色度、水溶性有机物（WEOM）和盐溶性有机物（SEOM）含量及其光谱学特性。结果显示,沉积物的色度（R530-520）与TOC含量呈现相反的变化趋势:色度值较大时,TOC含量反而较小。相对于细砂层,黏土层的色度值较低,但TOC含量较高。相同的沉积物中,SEOM含量高于WEOM,但WEOM更易迁移至地下水中。有机物的光谱指数表明,WEOM以微生物来源为主,而SEOM以陆源为主。通过三维荧光光谱分析发现,荧光强度和沉积物有机碳（SOC）含量呈正相关;黏土层沉积有机物荧光强度更高;WEOM和SEOM均含类腐殖质成分和类蛋白成分,但SEOM中腐殖质成分较高;类腐殖质是所研究的沉积物中OM最主要的存在形式。  相似文献   

北京地区降水极值时空演变特征   总被引：4，自引：0，他引：4       下载免费PDF全文

宋晓猛  张建云  孔凡哲  王国庆  贺瑞敏  朱奎 《水科学进展》2017,28(2):161-173

为了科学评估变化环境下城市地区降水结构变化和深入认识特大型城市降水极值演变特征,以北京市为例,采用《北京市暴雨图集》中6种历时（10 min、30 min、1 h、6 h、24 h和72 h）的年最大暴雨统计数据和北京地区45个雨量站点1960-2012年汛期（6-9月）逐日降水观测资料,分别选择年最大值法和百分位阈值法,基于暴雨图集中的6种历时暴雨的统计特征值和两种百分位阈值下（95%和99%）的3种极端降水指标（发生次数、降水量和降水贡献率）分析北京地区降水极值的时空变化特征。研究结果表明:① 北京地区降水极值的空间分布受地形特征和城市化发展等因素影响而呈现出从东向西递减的趋势,且形成了局部区域高值中心;② 近50年来北京地区极端降水发生频次、极端降水量和极端降水的贡献率均表现出显著的下降趋势,在95%（99%）阈值条件下极端降水发生次数、极端降水量和极端降水贡献率的下降速率分别为0.13次/10 a（0.04次/10 a）、11.59 mm/10a（5.28 mm/a）和2%/10 a（1%/10 a）;③ 两个阶段（1960-1985年和1986-2012年）的城区与近郊的极端降水指标差异表现不同,1960-1985年在极端降水频次方面郊区占优,而极端降水量和贡献率则是城区较高,1986-2012年3个指标均表现为城区较高。  相似文献   

汾河地堑湖盆第四纪地貌—沉积特征的构造控制   总被引：4，自引：1，他引：3  

胡小猛  郭家秀  胡向阳 《地理学报》2010,65(1):73-81

野外对临汾、太原盆地第四纪中晚期所发育的湖积地貌-沉积特征调查发现,湖盆在对应于S8、S5和S1古土壤开始发育时期(时代分别为0.77Ma BP、0.55Ma BP和0.13Ma BP)曾发生了三次强烈湖退,这三次湖退都是构造原因所致的;而在L11-S8、L8-S5、L5-S1黄土古土壤堆积发育期间(时代分别对应于0.96～0.77Ma BP、0.74～0.55Ma BP和0.47～0.13Ma BP)、以及S1古土壤发育以后的时期(时代为0.07Ma BP之后)出现的却是缓慢湖侵或盆地下沉。根据这些发现并结合地球物理学前期已获得的有关盆地深部上地幔结构及活动规律,本文提出了盆地湖侵-湖退过程的构造控制模式。在上地幔强烈上拱→减弱或渐趋稳定→再次强烈上拱的构造循环中,地表湖盆会以大幅快速湖退→缓慢湖侵→再大幅快速湖退这样的表现与之对应。盆地地表的地貌-沉积发育与地下的上地幔活动应具有因果关系。  相似文献   

三种经典夜间陆地雾遥感反演方法的适用性对比分析          下载免费PDF全文

赵诗童  时晓曚  吴晓京  杨超  张苏平  衣立 《海洋气象学报》2021,41(1):45-57

相较于地面站点观测,卫星可以监测更大范围的夜间雾区分布,目前虽然已存在几种经典的夜间陆地雾遥感反演算法,然而其在我国大范围陆上的适用性尚不清楚。基于葵花8号(Himawari-8)静止气象卫星数据,分别利用双通道差值法、温度差值法及归一化大雾指数法反演了我国2016年1月—2018年12月的夜间陆地雾区,并用地面观测资料以鉴定成功评分、准确率、判识率和误判率为指标参数对雾区反演结果进行验证分析,讨论了三种反演方法的适用性。结果显示:1)三种夜间陆地雾反演方法在秋季和冬季反演效果最好,其中温度差值法的鉴定成功评分高、准确率高、误判率低,反演效果最好,双通道差值法的判识率高、误判率高,反演效果次之,归一化大雾指数法效果最差。2)三种方法对夜间陆地雾的反演在秋季和冬季的最佳适用区域略有不同,但都倾向于在平原和盆地达到最佳效果,如华北平原、长江中下游平原和四川盆地。3)两次雾过程的反演结果显示,温度差值法和双通道差值法对平原地区夜间雾的识别能力均较强,在具体雾过程反演中各有优势。  相似文献   

大同火山活动在区域沉积中的记录和阶段性历史研究     

胡小猛  周天航  蔡顺  陈硕  刘毓阳  陈美君 《地理学报》2017,72(9):1669-1679

大同火山活动的阶段性历史是一个尚未被揭示清楚的地学问题。野外实地考察及室内磁化率、化学成分、粒度和古地磁的测定结果显示：古湖滨处水平层理发育的火山碎屑层存在4个不同倾角的倾斜;古湖近岸处的湖相沉积层中含有4层火山碎屑层;古湖深处的湖相沉积层中出现4个磁化率显著正异常的层位,且这些层位粒度都较粗;古湖岸上的黄土沉积中出现3个磁化率为峰值、Rb/Sr比值为谷值的层位;古湖深处湖相沉积剖面中存在B/M和Jaramillo磁极性界限。据此进一步分析后认为：① 湖相沉积剖面中的磁化率显著正异常层位、黄土沉积中的高磁化率—低Rb/Sr比值层位可能是混入了大量火山灰物质;它们是区域火山活跃期的记录。② 系列沉积剖面特征指示区域火山活动曾经历4个活跃期,每个活跃期期间有多次密集的火山喷发。③ 4个活跃期的年代大约为早于0.90 Ma BP（第一活跃期）、~0.47 Ma BP（第二活跃期）、~0.31 Ma BP（第三活跃期）和~0.09 Ma BP（第四活跃期）;黄土沉积中还记录了区域北部有一个发生于~0.19 Ma BP的活跃期。此外,区域湖相沉积中所记录的4个火山活跃期都出现在湖退时期,平静期出现在湖侵时期。  相似文献   

青岛地区一次雾霾重污染天气过程特征分析     

王建林  时晓曚  赵文雪  夏子瑶 《气象科技》2018,46(6):1251-1257

利用青岛市环境监测中心站环境监测资料、青岛市气象常规观测资料、美国国家环境预报中心(NCEP)再分析资料,对青岛地区2016年12月18—21日的一次雾霾重污染天气过程进行分析。结果表明:污染期间,亚欧大陆中高纬度地区500hPa呈两槽一脊的环流形式,青岛处于弱槽系统控制下,空气质量好转时,高空锋区明显增强,西北风加大,地面冷锋快速东移;此次雾霾重污染天气过程空气中近地面相对湿度一直维持较高,重污染期间小于2.6m·s~(-1)的地面风速对污染物扩散没有明显作用;污染物的浓度增加、持续阶段与气象要素能见度、风速、混合层厚度呈负相关性,与相对湿度呈正相关性,与温度的相关性较低;污染过程中青岛市区24h的输入污染源主要来自半岛北部地区,主要污染物为PM_(2.5)颗粒。  相似文献