鄂尔多斯盆地子长地区长2沉积特征

根据岩石类型及特征、颗粒磨圆度和接触方式、沉积构造等对鄂尔多斯盆地子长地区长2油层的沉积相进行了系统研究.研究显示:子长地区长2构造结构与陕北斜坡一致,发育近东西向的宽缓鼻状构造;储层岩性主要为细粒长石砂岩和岩屑长石砂岩;属于三角洲沉积体系,发育三角洲平原亚相,其微相类型主要有水上分流河道、陆上天然堤、沼泽微相,其中砂...     

汤原断陷古近系宝泉岭组沉积特征及其对铀成矿作用的制约

本文以汤原断陷古近系宝泉岭组为主要研究目标层位,开展了沉积岩石学特征、古沉积环境特征、沉积体系特征及层间氧化带发育特征等方面的研究,探讨了宝泉岭组发育特征及其对铀成矿作用的制约。研究认为：(1)宝泉岭组砂岩类型主要为长石岩屑杂砂岩和岩屑砂岩,岩石具典型的低成分成熟度、低结构成熟度特征,具有近物源搬运的特征;(2)古近系宝泉岭组沉积时期为陆相淡水环境,古气候表现为温湿—干热气候,地球化学环境表现为还原环境,具较高的还原容量,有利于铀元素的还原沉淀;(3)宝泉岭组发育扇三角洲相,主要砂体表现为分流河道和水下分流河道两类,其中分流河道砂体应作为研究区下一步砂岩型铀矿找矿的主攻砂体类型。     

陕北延安丹霞地貌类型特征及演化模式分析

陕北延安地处黄土高原腹地,属典型的大陆性季风气候,区内大面积黄土覆盖,中西部地区沿河谷、沟谷出露丹霞地貌造景岩层——白垩系洛河组巨厚-块状红色砂岩,因而形成了延安地区特有的沟谷型丹霞地貌,依据沟谷形态、规模等特征,将其进一步划分为天井式、狭缝式、巷道式、宽谷式丹霞地貌4个类别,并通过对沟谷型丹霞地貌影响因素的分析,初步建立沟谷型丹霞地貌演化模式。     

红层岩石微观特性与抗压强度关系试验研究

岩石的微观特性对其宏观力学性质具有重要影响,目前关于红层岩石微观结构与抗压强度的定量关系尚缺乏系统的研究。本文对四川屏山县红层岩石取样进行了单轴压缩试验,利用偏光显微镜和扫描电镜对其微观特性进行了观察。通过对红层砂岩、粉砂岩、泥岩的单轴抗压强度和微观特性的试验分析与对比,得出了红层岩石单轴抗压强度与矿物成分、矿物含量、胶结物类型等微观特性之间的一些函数关系。试验结果表明:石英和粘土矿物的含量对红层岩石的单轴抗压强度影响最大。石英含量与红层岩石单轴抗压强度呈现正相关,粘土矿物含量与红层岩石单轴抗压强度呈负相关。当矿物含量基本相同时,岩石内颗粒分布均匀的岩石单轴抗压强度明显高于颗粒分布不均匀的岩石。     

武汉地区志留系坟头组砂岩特性研究

志留系坟头组地层在武汉地区分布广泛,区内以泥质粉砂岩、粉砂岩及粉砂质泥岩为主。在显微镜薄片鉴定、岩样描述和单轴抗压强度试验的基础上,分析了武汉地区坟头组地层中石英细砂岩及含岩屑石英砂岩的矿物组成及其工程性质,结果显示矿物组成中石英和长石含量高,饱和单轴抗压强度大,这些特征明显有别于坟头组泥岩。但它们外表相似,是定名中容易误判的原因,应将其判定为细砂岩而非泥岩。石英细砂岩及含岩屑石英砂岩的揭露,丰富了武汉地区坟头组地层的岩石种类及层序关系。根据坟头组下岩层中化石的种类及特征,武汉地区坟头组地层时代应为早志留系。     

河南舞阳铁矿田铁山庙组矿层下盘地质体成因

舞阳铁矿是一超大型矿床,共提交资源量超过11亿t。采用对岩性和副矿物特征、地质状态、岩相学标志分析以及岩石测试的方法,得出了铁山庙组铁矿层的下盘地质体原岩为石英砂岩或长石石英砂岩、经变质作用而形成白粒岩的沉积变质成因。研究区铁矿分布面积高达50多平方千米,由于受深度和地质演化的影响,已进行过勘查的区域仅占约20%,在其深部仍有较大的找矿空间。     

扬子地块北缘镇巴穿心店地区南华系碎屑锆石U-Pb年龄及其物源示踪

扬子地块北缘镇巴穿心店地区发育有完整的南华系—震旦系沉积地层,记录了研究区及邻区南华纪沉积特征,对于研究扬子地块北缘新元古代晚期构造演化历史和Rodinia超大陆演化过程具有重要的地质意义。研究区南华系由下至上可划分为4套岩石地层单位,分别为长安组、古城组、大塘坡组和南沱组。南华系砂岩地球化学特征表明,研究区南华系化学风化作用较弱,经历了较低程度的沉积物再旋回作用。砂岩的CIA、CIW、PIA、Rb/Sr等古气候指标显示,研究区南华系具有由寒冷干燥—有波动的寒冷干燥—趋于稳定的温暖湿润—寒冷干燥的古气候演化趋势。在Dickinson三角图解中清晰地反映了南华系各组砂岩具有再旋回造山带和切割岩浆弧物源的特征,同时砂岩岩石地球化学特征也指示南华系的物源区主体应由中酸性岩浆岩组成。南华系长安组、古城组和南沱组3件碎屑锆石U-Pb年龄样品的年龄分布特征类似,主要年龄区间为新元古代晚期（约780~约641 Ma）,并显示出约 750~约 740 Ma的显著峰值。结合区域地质资料,研究区南华系沉积时代应为约 720~约 635 Ma,物源应主要来自位于现今研究区西侧的扬子地块北缘汉南—米仓山微地块的新元古代岩浆岩,其沉积事件对应于新元古代中晚期扬子地块北缘伸展-裂解阶段,为Rodinia超大陆裂解过程的沉积响应。     

酸性环境中钙质胶结砂岩的化学损伤模型

针对大部分工程中常见的砂岩最可能、最不利的化学环境---酸性环境中的力学性质的衰变、弱化问题,对钙质胶结长石砂岩进行了室内不同pH值溶液的模拟试验,对所得到的抗压强度试验及CT扫描试验结果进行了分析与总结,发现砂岩中主要胶结物CaCO3的溶解是岩石强度和变形衰减的主要原因,在此基础上利用化学动力学理论和损伤力学理论提出了可应用于酸性溶液的岩石化学损伤强度模型,并用室内实验结果对所提模型进行了检验与验证。     

丹霞地层砂岩及花岗岩矿物表面金属氧化物膜的光电响应

地球表面出露各种各样的矿物,由于表生地球化学作用,矿物的表面常被一层金属氧化物膜所覆盖,该氧化物膜受到太阳光的照射能否产生光电效应是当前的研究前缘。对来自江西龙虎山丹霞地层的含砾砂岩和江西赣州燕山期稀土矿化的半风化花岗岩进行矿物的光电测试表明:(1)龙虎山丹霞红层的主要矿物成分为长石、石英、粘土等,岩性为红色中粗粒砂岩,局部地区的砂岩中含有砾石,砂岩磨圆度一般,泥质胶结结构,压实程度一般。江西赣州燕山期半风化花岗岩采集自离子吸附型稀土矿区,具有典型的中粗粒花岗结构,由于风化作用,岩石相对较为松散,主要的矿物为长石、石英,并含少量的黑云母。(2)光电测试显示丹霞地层中红色砂岩的光电效应不明显,原因可能与沟道的制作过宽、探头接触等因素导致光电流低于检出限有关;对半风化花岗岩的石英颗粒进行挑选,然后直接将石英的表面制作成电极器件,光照结果显示微弱的光电响应。     

陕西神木白垩纪恐龙足迹沉积环境与时代研究

2017年,陕西省地质调查中心在陕西神木市中鸡镇公格沟白垩系紫红色砒砂岩中发现多处恐龙足迹,这在鄂尔多斯盆地东北部尚属首次。含恐龙足迹地层岩石组合为一套典型沙漠相"红色砒砂岩"系:岩石组合以紫红色—暗紫红色厚—块状粉砂质泥岩、泥质粉砂岩与薄层中—粗粒长石石英砂岩、石英砂岩为主,构成典型的丹霞地貌景观。发现识别出恐龙足迹3处,小型四足动物足迹2处。根据足迹形态对比,推断恐龙为兽脚类实雷龙类、恐爪龙类足迹,小型四足足迹为哺乳动物足迹类,恐龙足迹分布在水深更浅的滨岸线附近。由于恐龙足迹产地地层研究程度较低,因此,恐龙足迹的研究在地层年代确定以及恢复岩相古环境方面具有重大意义。西部邻区鄂尔多斯盆地鄂托克旗查布地区中生代植物化石组合以银杏类为主,次为真蕨类,属有利于植物快速生长的温暖潮湿—干燥温带—亚热带气候,适合恐龙生活的有利地区。神木市栏杆堡镇邱井沟侏罗系曾经发现恐龙足迹,表明神木市恐龙足迹化石从早、中侏罗世到早白垩世均有分布。下白垩系洛河组沙漠相湖泊沉积中有少量的火山灰层,表明气候炎热干燥。早、中侏罗世与早白垩世恐龙足迹形成时代、岩相古地理、沉积环境明显不同。     

陕西靖边龙洲波浪式丹霞地貌景观特征及其成景环境分析

陕北靖边龙洲波浪式丹霞地貌发育在陕北黄土高原向沙漠高原的过渡地带,成景地层为白垩系洛河组,发育大型斜层理、交错层理的巨厚层-块状风成砂岩,主要受流水侵蚀和风力侵蚀改造作用形成,多沿正-负地貌过渡地段,如谷顶发育,呈带状分布,形态具有圆滑、流畅,犹如波浪的特征,其微观或单体形态还有"陀螺状""油塔状""丝带状""金钱状"等,其不同于中国南方丹霞地貌,国内罕见;在世界范围内,与美国亚利桑那州波浪谷在成景地层、时代尤其是景观发育部位、组合和特征方面存在明显差异,其对比研究价值巨大。龙洲丹霞地貌的成景环境受构造隆升、节理、裂隙、水流侵蚀、风力侵蚀改造、重力崩塌、冻融作用等多个内外因素耦合控制。     

Borehole breakouts and compaction bands in two high-porosity sandstones

We compare the shape and mechanism of failure around vertical boreholes drilled in blocks of two high-porosity sandstones subjected to unequal far-field principal stresses. Tablerock sandstone has a porosity of 28%, and is composed of 55% quartz and 37% weaker feldspar grains. Grain cementation is substantial through microcrystalline quartz. Critical far-field stresses induce failure around boreholes in the form of V-shaped (dog-eared) breakouts, the result of dilatant intra and trans-granular microcracking subparallel to both the maximum horizontal far-field stress and to the borehole wall. On the other hand, boreholes in Mansfield sandstone, which has similar porosity (26%), but contains mainly quartz grains (90%) held together primarily by spot-sutured contacts, fail by developing fracture-like breakouts. We show evidence suggesting that Mansfield sandstone breakouts are preceded by the development of a narrow (several grain diameters) localized compaction zone along the direction of the least horizontal stress, which is where the maximum compressive tangential stress concentration occurs. Failure mechanism here is simply the removal by the circulating drilling fluid of mainly intact grains loosened during the formation of the compaction band. The type of cementation, mineral homogeneity, grain strength, and sphericity appear to be major factors in the formation of compaction bands. Some breakout dimensions in both rocks are correlatable to the far-field principal stresses, and can be potentially used (in conjunction with other information) as indicators of their magnitudes.     

红层泥岩的剪切蠕变试验研究

红层是红色陆相沉积为主的碎屑沉积岩层,岩性以砂岩、泥岩、粉砂岩和页岩为主。红层中的泥岩抗压强度较低,并具有明显的流变特性,蠕变变形量较大,常造成工程边坡的失稳和破坏,在进行工程勘察设计时应充分考虑红层泥岩的蠕变特性,进行合理的参数取值。本文通过对滇中地区红层泥岩进行的室内剪切蠕变试验研究,分析了不同的法向正应力下天然状态与饱水状态红层泥岩的剪切蠕变特性,并通过对红层泥岩长期强度与短期强度试验资料的分析,提出了红层泥岩长期剪切强度的取值建议。     

Inconsistency of changes in uniaxial compressive strength and P-wave velocity of sandstone after temperature treatments

It is generally accepted that the uniaxial compressive strength(UCS)and P-wave velocity of rocks tend to decrease simultaneously with increasing temperature.However,based on a great number of statistical data and systematic analysis of the microstructure variation of rocks with temperature rising and corresponding propagation mechanism of elastic wave,the results show that(1)There are three different trends for the changes of UCS and P-wave velocity of sandstone when heated from room temperature(20
C or 25
C)to 800
C:(i)Both the UCS and P-wave velocity decrease simultaneously;(ii)The UCS increases initially and then decreases,while the P-wave velocity decreases continuously;and(iii)The UCS increases initially and then fluctuates,while the P-wave velocity continuously decreases.(2)The UCS changes at room temperaturee400
C,400
Ce600
C,and 600
Ce800
C are mainly attributed to the discrepancy of microstructure characteristics and quartz content,the transformation plasticity of clay minerals,and the balance between the thermal cementation and thermal damage,respectively.(3)The inconsistency in the trends of UCS and P-wave velocity changes is caused by the change of quartz content,phase transition of water and certain minerals.     

Experimental research on creep behaviors of sandstone under uniaxial compressive and tensile stresses

The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the self-developed direct tension device and creep testing machine RLW-2000M are used to conduct the creep tests on red sandstone under uniaxial compressive and tensile stresses. The short-term and long-term creep behaviors of rocks under compressive and tensile stresses are investigated, as well as the long-term strength of rocks. It is shown that, under low-stress levels, the creep curve of sandstone consists of decay and steady creep stages; while under high-stress levels, it presents the accelerated creep stage and creep fracture presents characteristics of brittle materials. The relationship between tensile stress and time under uniaxial tension is also put forward. Finally, a nonlinear viscoelastoplastic creep model is used to describe the creep behaviors of rocks under uniaxial compressive and tensile stresses.     

二连盆地额仁淖尔凹陷砂岩型铀矿元素地球化学特征

额仁淖尔凹陷近期发现的砂岩型铀矿床反映了该区具有砂岩型铀矿找矿潜力。本文通过该区不同岩性常量元素与稀土元素分布规律的研究,揭示了额仁淖尔凹陷砂岩型铀矿元素地球化学特征,探讨了该区元素地球化学与铀成矿的关系。额仁淖尔凹陷内铀成矿作用与FeO、CaO、MgO和烧失量关系密切;稀土元素具有分区分带性,由氧化砂岩中迁出,在含矿砂岩中局部沉淀富集,形成较大的含量差异;轻重稀土的分异程度与氧化作用有关。以上特征可作为该地区铀矿勘查地球化学标志。     

Experimental research on creep behaviors of sandstone under uniaxial compressive and tensile stresses

The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the self-developed direct tension device and creep testing machine RLW-2000M are used to conduct the creep tests on red sandstone under uniaxial compressive and tensile stresses. The short-term and long-term creep behaviors of rocks under compressive and tensile stresses are investigated, as well as the long-term strength of rocks. It is shown that, under low-stress levels, the creep curve of sandstone consists of decay and steady creep stages; while under high-stress levels, it presents the accelerated creep stage and creep fracture presents characteristics of brittle materials. The relationship between tensile stress and time under uniaxial tension is also put forward. Finally, a nonlinear viscoelastoplastic creep model is used to describe the creep behaviors of rocks under uniaxial compressive and tensile stresses.