渝东南下古生界页岩构造裂缝形成及分布控制因素          下载免费PDF全文

岳锋  程礼军  焦伟伟  王飞 《地质科学》2016,(4):1090-1100

天然裂缝对页岩气储集和渗流有重要影响,但目前对页岩构造裂缝研究不够深入。本文通过露头、岩心裂缝观察和分析,探讨了渝东南下古生界页岩构造裂缝类型、形成机理及分布控制因素。基于裂缝特征及力学成因,将剪切裂缝分为高角度剪切裂缝、倾斜滑脱裂缝和水平滑脱裂缝。倾斜滑脱裂缝是在上覆岩层重力和水平构造应力共同作用下沿应力集中的软弱面发生剪切滑动形成,水平滑脱裂缝是在构造挤压应力作用条件下主要沿页理面方向的剪切或层间滑动形成;页理发育程度及岩层曲率是控制水平滑脱裂缝形成的关键因素,岩石矿物组成、构造作用及岩层厚度是控制其它类型构造裂缝形成和分布的主要因素,页岩岩石力学层的划分需要根据裂缝特征、岩性变化特征、岩石力学参数及沉积界面等综合确定,岩层厚度与层间构造裂缝密度呈负相关关系。  相似文献   

利用尺度空间及多角度地形断面提取山谷山脊线     

林铁  张翰超  金姣 《测绘通报》2016,(2):97-99

从数字高程模型中自动提取山脊线和山谷线,在测绘领域有着重要的意义。地形断面高程极值法是其中一种常用的方法,但此方法在提取过程中容易产生遗漏。针对此缺点,本文提出了基于尺度空间及多角度判断的地形断面高程极值法,主要步骤是构建影像金字塔,然后从上到下逐级提取并加密。试验验证了该方法的有效性,提取得到的山谷线或山脊线较为完整,并与实际地形相符合。  相似文献   

云南建水腊里河超基性岩地质特征及其构造意义          下载免费PDF全文

刘娇  周洋  郭宏杰  熊昕  李德威 《贵州地质》2016,33(3):178-186

川滇黔等地在二叠世晚期发生峨眉山玄武岩短期内大规模溢流喷发。滇西地区发育的镁铁—超镁铁质岩均被认为是峨眉山大火成岩省的产物,但在滇东地区却一直缺少该类岩石组合的报道。本文在滇东建水地区首次发现了腊里河超基性岩体,通过LA-ICP-MS锆石UPb定年分析表明该超基性岩先期形成年龄为(246±5.2)Ma,为晚二叠-早三叠世的产物,后期中侏罗世晚期(169.6±2.0)Ma(MSWD=3.5)发生岩浆活化。该超基性岩Mg#值平均为78.73,稀土元素表现出略微右倾的平坦型特征,Rb、Sr、Ba、Pb等大离子亲石元素相对富集,高场强元素Zr、Hf相对亏损,Ta异常富集。其地化特征表现出富集型地幔源区特征,与峨眉山玄武岩成因关系密切。晚二叠世建水地区由于地幔柱活动形成地表溢流玄武岩,在深部岩浆房由玄武质岩浆结晶分异作用形成超基性侵入岩,到中侏罗世晚期,伴随着华南地区发生多期次构造运动,先前存在于岩浆房中的超镁铁质岩经过后期热液改造活化,沿着断层裂隙侵入地表。  相似文献   

云南建水煌斑岩年代学和地球化学及其构造意义          下载免费PDF全文

刘娇  周洋  谢德根  纪星星  李德威 《中国地质》2016,(6):1977-1991

华南大陆内部燕山期的岩浆事件可分为2期:燕山早期180~150 Ma,燕山晚期140~80 Ma。而处于扬子板块西南缘的滇黔贵等地,仅见有第二期晚白垩世中酸性侵入岩与相关成矿作用,缺乏第一期岩浆活动的时间记录。本文在滇东建水地区首次发现了麦地村煌斑岩,对其进行高精度LA-ICP-MS锆石U-Pb定年和主微量元素测试分析。结果显示煌斑岩的锆石U-Pb年龄为(158.4±2.4)Ma(MSWD=4.2),为晚侏罗世的产物,补充了该区较为空白的第一期岩浆热事件。麦地村煌斑岩不相容元素明显高于原始地幔,表现出不同程度的富集,大离子亲石元素Rb、Ba、Ce等富集程度不明显,高场强元素中U、Ta、Pb等表现出一定程度富集,LREE相对富集,HREE相对亏损,不具有Nb-Ta-Ti负异常的俯冲型配分曲线特征,具有明显的OIB型洋岛玄武岩稀土元素配分特征,为板内伸展环境下的产物。滇东地区发育中生代时期的NNE构造,早期NNE向褶皱叠加有后期同方向正断层。早期褶皱表现为SEE-NWW挤压应力作用下的构造特征,后期断层表现出同方向张应力作用下的特征。煌斑岩正是由于该区发生挤压之后伴随着一期应力松弛调整,伸展减压作用诱发地幔物质部分融熔,来自于深处的软流圈地幔流体与岩石圈地幔发生交代作用,形成富集型地幔,交代富集的岩石圈地幔局部受热、部分熔融,发生上升侵位。煌斑岩的侵位时间即是滇东地区中生代从挤压向伸展转换的起始时间。  相似文献   

Paratacamite from Gypsum Veins in Sandstones of the Kuqa Basin,Xinjiang, China: Implications for a New Epigenetic Cu Enrichment Mechanism          下载免费PDF全文

Yangtong Cao  Chenglin Liu  Pengcheng Jiao  Chunlian Wang 《Resource Geology》2016,66(2):114-126

The Kuqa Basin filled with Paleogene evaporite series is located in the northeast of the Tarim Basin, Xinjiang, China. It is famous for sandstone‐hosted Cu deposits formed by synsedimentary processes. However, our recent studies reveal that there has been another Cu mineralization mechanism in this basin. Field investigations show that there is a close relationship among faults, salt domes, and brine. Cu deposits are mainly located in two east–west‐trending anticlinal belts in the basin, adjacent to salt domes in the belts. Cu minerals in gypsum veins of the Jidike and Kangcun formations have been investigated by SEM, EDS, and X‐ray diffraction methods. The occurrence of paratacamite in gypsum veins has been reported to coexist with glauberite and halite in the joint planes of sandstones. In addition, it occurs accompanying residual crystal salt encrustation in limestone fractures, or in sandstones in dendritic form. These features indicate that the surface‐Cu enrichment in the Kuqa Basin might have originated from Cu‐bearing brine in the underlying evaporite units, which migrated upward along fractures. In addition, the presence of H₂S in the east–west fault belt in the Kuqa Basin, and the discovery of surface sulfur, calcium carbonate, and covellite, suggest thermochemical sulfate reduction near salt domes in the deeper parts of the rock units. This process resulted in the generation of reduced brine and provided a favorable environment for Cu enrichment. Therefore, the surface‐Cu mineralization near salt domes is interpreted to be the result of Cu‐bearing brine migrating upward to the surface along faults (or joints) following the intrusion of deep salt domes. The geological evidence indicates the presence of reducing brine and Cu‐bearing brine near the salt dome in the deeper rocks of the Kuqa Basin, thus making the intrusive contact zone of the salt dome a favorable site for the epigenetic enrichment of Cu. Our study demonstrates that Cu enrichment in the Kuqa Basin resulted not only from synsedimentary deposition but also through epigenetic enrichment associated with salt dome intrusion and brine‐rich fluids.  相似文献   

Analysis of the contribution of multiple factors to the recent decrease in discharge and sediment yield in the Yellow River Basin,China   总被引：5，自引：1，他引：4  

Wenyi Yao  Peiqing Xiao  Zhenzhou Shen  Jinhua Wang  Peng Jiao 《地理学报(英文版)》2016,26(9):1289-1304

The Yellow River basin is well known for its high sediment yield. However, this sediment yield has clearly decreased since the 1980s, especially after the year 2000. The annual average sediment yield was 1.2 billion tons before 2000, but has significantly decreased to 0.3 billion tons over the last 10 years. Changes in discharge and sediment yield for the Yellow River have attracted the attention of both the Central Government and local communities. This study aimed to identify the individual contributions of changes in precipitation and human activities (e.g. water conservancy projects, terracing, silt dams, socio-economic and needs, and soil and water conservation measures) to the decrease in discharge and sediment yield of the Yellow River. The study used both improved the hydrological method and the soil and water conservation method. The study focused on discharge analysis for the upper reaches and the investigation of sediments for the middle reaches of the river. The results showed that discharge and sediment yield have both presented significant decreasing trends over the past 50 years. Precipitation showed an insignificant decreasing trend over the same period. The annual average discharge decreased by 5.68 billion m³ above Lanzhou reach of the Yellow River from 2000 to 2012; human activities (e.g. socio-economic water use) contributed 43.4% of the total reduction, whereas natural factors (e.g. evaporation from lakes, wetlands and reservoirs) accounted for 56.6%. The decrease in annual discharge and sediment yield of the section between Hekouzhen station and Tongguan station were 12.4 billion m³ and 1.24 billion tons, respectively. Human activities contributed 76.5% and 72.2% of the total reduction in discharge and sediment yield, respectively, and were therefore the dominant factors in the changes in discharge and sediment yield of the Yellow River.  相似文献   

Spatiotemporal dynamics of the climatic impacts on greenup date in the Tibetan Plateau     

Qing Chang  Jiahua Zhang  Wenzhe Jiao  Fengmei Yao  Siyuan Wang 《Environmental Earth Sciences》2016,75(20):1343

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Tracing submarine groundwater discharge flux in Tolo Harbor,Hong Kong (China)     

Yi Liu  Jiu Jimmy Jiao  Ho Kwan Cheng 《Hydrogeology Journal》2018,26(6):1857-1873

Submarine groundwater discharge (SGD) is an important pathway for groundwater and associated chemicals to discharge to the sea. Groundwater levels monitored along a transect perpendicular to the shoreline are used to calculate SGD flux from the nearshore aquifer to Tolo Harbor, Hong Kong (China). The calculated SGD flux—recharge/discharge measured with Darcy’s Law methods—agrees well with estimates based on geo-tracer techniques and seepage meter in Tolo Harbor during previous studies. The estimated freshwater SGD is 1.69–2.0 m²/d at the study site and 0.3?±?0.04 cm/d for the whole of Tolo Harbor, which is comparable to the river discharge (0.25?±?0.07 cm/d) and precipitation (0.45?±?0.15 cm/d). The tide-driven SGD in the intertidal zone is 13.98–17.59 m²/d at the study site and 2.42?±?0.56 cm/d for the whole of Tolo Harbor. The SGD occurring in the subtidal zone and the bottom of Tolo Harbor is 3.12?±?4.63 cm/d. Fresh SGD accounts for ~5% of the total SGD, while the rest (~95%) is contributed by saline SGD driven by various forces. About 96% of the tide-driven SGD in the intertidal zone occurs in the ebbing tide period because the head difference between the groundwater level and sea level is great during this period. Tide-driven SGD in the spring tide is ~1.2 times that during neap tide. The tidal fluctuation amplitude and tide-driven SGD in the intertidal zone are positively correlated to each other; thus, a spring neap variation of the tide-driven SGD is observed.  相似文献   

A comparative analysis of the NDVIg and NDVI3g in monitoring vegetation phenology changes in the Northern Hemisphere     

Qing Chang  Wenzhe Jiao  Fengmei Yao 《国际地球制图》2018,33(1):1-20

Phenology is a sensitive and critical feature of vegetation and is a good indicator for climate change studies. The global inventory modelling and mapping studies (GIMMS) normalized difference vegetation index (NDVI) has been the most widely used data source for monitoring of the vegetation dynamics over large geographical areas in the past two decades. With the release of the third version of the NDVI (GIMMS NDVI3g) recently, it is important to compare the NDVI3g data with those of the previous version (NDVIg) to link existing studies with future applications of the NDVI3g in monitoring vegetation phenology. In this study, the three most popular satellite start of vegetation growing season (SOS) extraction methods were used, and the differences between SOSg and SOS3g arising from the methods were explored. The amplitude and the peak values of the NDVI3g are higher than those of the NDVIg curve, which indicated that the SOS derived from the NDVIg (SOSg) was significantly later than that derived from the NDVI3g (SOS3g) based on all the methods, for the whole northern hemisphere. In addition, SOSg and SOS3g both showed an advancing trend during 1982–2006, but that trend was more significant with SOSg than with SOS3g in the results from all three methods. In summary, the difference between SOSg and SOS3g (in the multi-year mean SOS, SOS change slope and the turning point in the time series) varied among the methods and was partly related to latitude. For the multi-year mean SOS, the difference increased with latitude intervals in the low latitudes (0–30°N) and decreased in the mid- and high-latitude intervals. The GIMMS NDVI3g data-sets seemed more sensitive than the GIMMS NDVIg in detecting information about the ground, and the SOS3g data were better correlated both with the in situ observations and the SOS derived from the Moderate Resolution Imaging Spectroradiometer NDVI. For the northern hemisphere, previous satellite measures (SOS derived from GIMMS NDVIg) may have overestimated the advancing trend of the SOS by an average of 0.032 d yr^–1.  相似文献   

如何用ArcGIS 9.3制作1∶10000地形图     

石礁 《测绘与空间地理信息》2018,(2):176-177

随着1∶10 000数据的更新,制图文件已不再是附属产品,并逐步成为1∶10 000地形图制作过程中的重要环节。本文简要介绍了用ArcGIS 9.3制图的过程和注意事项。  相似文献