Mixed sand–mud bedforms produced by transient turbulent flows in the fringe of submarine fans: Indicators of flow transformation     

Megan L. Baker  Jaco H. Baas 《Sedimentology》2020,67(5):2645-2671

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川藏铁路交通廊道地质调查工程主要进展与成果     

郭长宝  王保弟  刘建康  涂杰楠  张永双  马剑飞  铁永波  韩冰  马鑫  刘峰  李雪  孟文  钟宁  杨志华  吴瑞安 《中国地质调查》2020,7(6):1-12

川藏铁路是我国正在规划建设的重点工程,由于其位于地形地貌和地质构造都极为复杂的青藏高原东部,在铁路规划建设中面临一系列迫切需要解决的关键地质问题: 区域性活动断裂与断错影响、地质灾害、高地应力及其引起的岩爆和大变形、高温热害、断裂带高压水与涌水突泥、高陡边坡稳定性等。为满足技术支撑川藏铁路规划建设、精准服务国家重大战略实施的需要,中国地质调查局部署了“川藏铁路交通廊道地质调查工程”,聚焦制约川藏铁路规划建设的关键问题,充分发挥地质调查工作对国家重大工程规划建设的支撑作用。2019年主要完成铁路沿线1:5万区域地质调查1 350 km²、1:5万地质灾害调查5 000 km²,建设6口大地热流地质参数井、8个地温监测站,完成地应力测量20孔,编制完成11份地质调查专报,提出的大渡河大桥段、理塘车站段、毛垭坝盆地段等线路优化建议/防灾建议被采纳; 首次将1:5 000大比例尺航空物探技术引入复杂山地铁路工程勘察,创新形成千米级超长水平钻孔定向取心钻进技术,实现500 m深的水平孔地应力测量突破等。该工程通过2019年调查研究,全力提升了铁路沿线地质调查程度与精度,并创新了复杂艰险山区重大工程地质问题与探测技术、地质灾害风险防控理论与减灾关键技术,有效支撑服务了川藏铁路规划建设。  相似文献   

提高地浸钻孔出水量的有效技术措施          下载免费PDF全文

胥虹 《探矿工程》2020,47(1):48-52

地浸钻孔是一种以采矿为目的的钻孔,提高钻孔出水量就是提高钻孔的采矿量。通过对多年地浸钻孔施工经验和理论进行分析,发现影响钻孔出水量的主要因素为钻井泥浆的成分和性能以及人工过滤层的渗透性差异,提出在地浸钻孔施工方案中采用植物胶净化泥浆钻进和扩孔、投砾罐射吸式填砾、物理化学组合洗井3种技术措施,对比前后施工钻孔的出水量大小,证明了该技术措施对提高地浸钻孔出水量具有良好的效果。  相似文献   

Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin-bearing (Homo naledi) Rising Star Cave system,South Africa     

Jelle P. Wiersma  Eric M. Roberts  Paul H. G. M. Dirks 《Sedimentology》2020,67(2):897-919

Unconsolidated mud clast breccia facies in the hominin-bearing (Homo naledi) Rising Star Cave, Cradle of Humankind, South Africa, are interpreted to have formed through a process termed sedimentary autobrecciation in this study. This process, by which most of the angular mud clast breccia deposits are thought to have formed autochthonously to para-autochthonously via a combination of erosion, desiccation, diagenesis and microbial alteration of laminated mud deposits, is thought to have taken place under relatively dry (i.e. non-flooded) conditions inside the cave. Subsequently, gravitational slumping and collapse was the dominant mechanism that produced the mud clast breccia deposits, which commonly accumulate into debris aprons. The mud clast breccia is typically associated with (micro) mammal fossils and is a common facies throughout the cave system, occurring in lithified and unlithified form. This facies has not been described from other cave localities in the Cradle of Humankind. Additionally, sedimentary autobrecciation took place during the deposition of some of the fossils within the Rising Star Cave, including the abundant Homo naledi skeletal remains found in the Dinaledi Subsystem. Reworking of the mud clast breccia deposits occurs in some chambers as they slump towards floor drains, resulting in the repositioning of fossils embedded in the breccias as evidenced by cross-cutting manganese staining lines on some Homo naledi fossil remains. The formation of the unlithified mud clast breccia deposits is a slow process, with first order formation rates estimated to be ca 8 × 10⁻⁴ mm year⁻¹. The slow formation of the unlithified mud clast breccia facies sediments and lack of laminated mud facies within these deposits, indicates that conditions in the Dinaledi Chamber were probably stable and dry for at least the last ca 300 ka, meaning that this study excludes Homo naledi being actively transported by fluvial mechanisms during the time their remains entered the cave.  相似文献   

化学刺激法提高花岗岩类岩石裂隙渗透性的实验研究     

郭清海  何曈  庄亚芹  骆进  张灿海 《地学前缘》2020,27(1):159-169

增强型地热系统(EGS)用于通过人工形成地热储层的方法从深部低渗透性岩体中开采地热能;国际上常采用水力压裂辅以化学刺激的方法改造EGS 储层以提高其渗透率。本文以采自青海共和盆地的花岗闪长岩样品为对象,选用3种不同化学刺激剂(氢氧化钠、盐酸和土酸),在3组不同注入流速条件下开展了系统化学刺激实验。结果表明:注入盐酸和土酸后样品渗透率均有提高,且采用土酸时渗透率提高幅度明显大于盐酸;但注入氢氧化钠后,样品渗透率反而降低。在3类化学刺激剂中,土酸对长石类矿物的溶蚀能力最强,而氢氧化钠溶液对石英的溶蚀能力最强,但氢氧化钠溶液在溶解岩石样品裂隙表面矿物后极易形成非定形态二氧化硅或非定形态铝硅酸盐蚀变矿物并阻塞裂隙,反而对化学刺激效果造成负面影响。总体来看,土酸是青海共和盆地干热岩体的最佳化学刺激剂。在中等注入速度(3 mL·min^-1)条件下,土酸对岩石样品的溶蚀程度就可达到最高;在此基础上进一步降低流速,则可能使溶解组分更易从液相中沉淀而充填于样品裂隙,导致样品渗透率有所下降。  相似文献   

西昌盆地上三叠统白果湾组富有机质泥页岩沉积岩相古地理与孔隙特征          下载免费PDF全文

客昆  秦建华  牟必鑫  魏洪刚  何伟  雷玉雪  陈杨  刘治成 《沉积与特提斯地质》2020,40(3):140-150

海陆过渡相富有机质泥页岩是页岩气勘查开发的重要领域。本文以西昌盆地上三叠统白果湾组富有机质泥页岩为研究对象,对研究区内富有机质泥页岩的沉积岩相古地理特征、微观孔隙类型、孔隙结构特征进行研究。白果湾组富有机质泥页岩段沉积相主要为湖泊相、三角洲相、河流相。发育不同类型的微孔隙,孔隙主要以小孔为主,微孔次之,平均孔径分布在5.56~56.89nm之间,比表面积平均为9.44m²/g,总孔体积平均为0.0187cm³/g。页岩气主要形成于滨浅湖亚相及半深湖亚相中,并主要吸附于富有机质泥页岩的小孔、微孔内;西昌盆地白果湾组富有机质泥页岩储集空间较好,具有良好的勘探潜力。  相似文献   

Morphological and sedimentary features of sandy-muddy transitional beaches in estuaries and bays along mesotidal to macrotidal coasts     

Shaohua Zhao  Hongshuai Qi  Feng Cai  Jun Zhu  Xiang Zhou  Gang Lei 《地球表面变化过程与地形》2020,45(7):1660-1676

Sandy-muddy transitional beaches (SMT-Beaches), representing the transition from sandy beaches to tidal mudflats, should theoretically develop very different morphological and sedimentological characteristics in river estuaries and in semi-enclosed bays due to their contrasting dynamic sedimentary environments. Evidence, however, is rare in the scientific literature. To reveal these morphological and sedimentary differences, the sand–mud transition (SMT) boundary distribution, beach profiles, and surface and downcore sediment grain-size compositions of 27 SMT-Beaches located along mesotidal to macrotidal coasts of the western Taiwan Strait, southeastern China, were investigated. The results show that typical estuarine SMT-Beaches are mainly characterized by an ambiguous SMT, a long distance between the SMT and the coastline (31–302 m), lower SMT and inflection point altitudes (average –0.76 m and –0.04 m), and lower upper beach gradients (~0.068) with fine sand. Estuarine SMT-Beach sediments display clear interbedded mud and sand layers, implying potential SMT migrations over various timescales. By contrast, typical bay SMT-Beaches are characterized by distinct SMT, a short distance between the SMT and the coastline (11–52 m), higher SMT and inflection point altitudes (~0.24 m and ~0.35 m), and narrower upper beaches with higher gradients (~0.095) and coarse sand. Bay SMT-Beaches present relatively stable sedimentary sequences and a narrow gravel belt surrounding the inflection point and/or SMT. These morphological and sedimentary differences between the two SMT-Beach types are initially constrained by sediment supply and transport and are further affected by tide conditions and wave climate. Sediment supply and transport predominately control the sediment structures, while the tidal range strongly influences spatial variations in SMT distances. Wave climate normally drives SMT altitude variations. This study highlights the morphological and sedimentary differences in SMT-Beaches in estuaries and bays, providing important knowledge for further revealing their morphodynamic processes and potential future nourishment. © 2020 John Wiley & Sons, Ltd.  相似文献   

琼东南盆地北礁地区梅山组丘形反射特征     

李俞锋  蒲仁海  胡宝清  樊笑微  李斌  邓东  王飞  郭瑞川 《海洋学报》2017,39(12):53-62

目前琼东南盆地北礁凹陷中中新统梅山组顶部丘形反射引起广泛关注,但对其成因有不同认识。本文通过高精度二维、三维地震、钻井资料,研究丘形反射的特征。研究表明北礁地区梅山组顶部发育近东西向展布的长条形丘体,丘间为水道,丘内为中-弱振幅的地震反射,与西南部强振幅水道砂岩形成鲜明的对比,波阻抗反演揭示丘内为低波阻抗,属泥岩范畴。梅山组塑性丘内地层发生重力扩展,在其上覆的脆性地层（强振幅砂岩和弱振幅泥岩）发育多边形断层,反推出梅山组形成于深水环境,丘为泥丘,沉积环境分析也认为北礁凹陷中中新世为半深海沉积,梅山组的丘-谷分别对应上覆地层的谷-丘,认为是底流剥蚀/沉积成因。本文的研究对南海北部丘形反射的认识有重要意义,并可降低油气探勘风险。  相似文献   

天山乌苏段火山泥元素组成及含量分析     

尹兆明  姜莹芳  张亚刚  张学敏  张乐涛  王彩云  曹嘉洌  王瑶  方静涵  黄楠楠 《干旱区地理》2017,40(5):1047-1053

采用能量色散型X射线荧光光谱分析（EDXRF）对新疆乌苏天山泥火山土壤样品的元素含量进行了测定。采用单指标评价指数法和内梅罗综合指数法,对新疆天山乌苏段火山泥中的重金属的种类和含量进行了研究,结果显示：Cd、As、Cu元素的含量达到土壤环境质量评价的二级标准,Hg、Pb、Cr、Zn、Ni元素的含量达到土壤环境质量评价的一级标准,乌苏天山火山泥综合评价达到二级标准。将火山泥的元素含量与新疆地区不同土质的土壤元素含量进行比较,与干旱区不同省份的土壤元素含量进行比较,分析了火山泥元素组成及含量的成因。  相似文献   

origin of the mud volcano in northern tianshan constrained by geochemical investigation     

GAO Xiao-qi  LIANG Hui  WANG Hai-tao  ZHENG Li-ming  LI Jie  ZHAO Chun-qing  XIANG Yang  ZHANG Tao 《地震地质》2015,37(4):1215-1224

Mud volcano is a kind of structural geological phenomena under certain hydrogeological environment and can bring plenty of valuable information to the ground when it erupts, therefore, many researchers call it as "Heaven granted well" whose depth can be up to 12km. Mud volcanoes in Xinjiang are distributed in the central-west region of North Tianshan, and five of them are representative, namely, Horgus, Dushanzi, Wenquan, Poplar valley, and Sailetike. We tested the gas, fluid and solid components of these mud volcanoes through investigations and studies of topography and geomorphology, geological and hydrogeological conditions, and mud debris characteristics, and preliminary obtained the origin of these mud volcanoes based on geochemical features. Finally, the paper describes briefly that the continuous enchancement of regional crustal tectonic stress can not only give rise to the seismogenesis and earthquake occurrence, but also break the original cycle of mud volcano to bring about significant activity, therefore, the two have a certain homology relationship.  相似文献