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1.
Yanbin Yao Dameng Liu Yao Che Dazhen Tang Shuheng Tang Wenhui Huang 《International Journal of Coal Geology》2009,80(2):113-123
This paper demonstrates capabilities of microfocus X-ray computed tomography (µCT) in characterizing the development of coal porosity and fractures. For the investigated coals, the CT number of minerals, pores and coal matrix are approximately 3000, < 600 and 1000–1600 Hounsfield unit (HU), respectively. The total CT number of analyzed coals mainly relate to the density, coal maceral composition, and proportion of minerals and pores. Although the estimated porosities by segmentation method show some uncertainty, the results correlate well with the analyzed porosities by helium gas method and water-saturated method. The aperture, spacing and spatial distribution of fractures, and mineral morphology are semi-quantitatively evaluated by µCT using a computer-aided design. The slicing analyses of coals demonstrated that distributions of porosity in coals are highly anisotropic. The spatial disposition of pores, fractures and minerals is the most important factor that influences coal porosity and permeability. In spite of the limitation of low spatial resolution (70 μm) and some ring artifacts of X-ray, µCT has major advantages in non-destructive detection and 3D visualized characterization of pores, fractures and minerals compared to traditional methods. 相似文献
2.
海拉尔盆地乌尔逊凹陷南屯组与松辽盆地孤店CO2气田泉头组发育大量含片钠铝石砂岩。通过偏光显微镜、扫描电镜、茜素红-S染色、X射线衍射、电子探针与INCA能谱分析等,对含片钠铝石砂岩的骨架碎屑组分、胶结物与自生矿物、成岩共生序列等岩石学特征进行了系统研究。研究表明,含片钠铝石砂岩的岩石类型为长石砂岩和岩屑长石砂岩,粒度以细粒、细-中粒为主,分选差-中等。砂岩中胶结物主要为次生加大石英、自生石英、片钠铝石、铁白云石和粘土矿物。其中,片钠铝石最高可达砂岩总体积的22％在砂岩中或以放射状、束状、菊花状、杂乱毛发状、毛球状、板状等集合体充填孔隙,或呈束状和板状交代长石和岩屑。电子探针与INCA能谱综合分析表明,片钠铝石主要由Na、Al、O、C等组成。在含片钠铝石砂岩中,成岩共生序列依次为粘土矿物包壳-次生加大石英、自生石英、自生高岭石-油气充注-CO2充注-片钠铝石-铁白云石。其中,CO2注入前形成的自生矿物组合主要为次生加大石英、自生石英和自生高岭石,CO2注入后形成的自生矿物组合主要为片钠铝石和铁白云石。 相似文献
3.
We use a reactive diffusion model to investigate what happens to CO2 injected into a subsurface sandstone reservoir capped by a chlorite- and illite-containing shale seal. The calculations simulate reaction and transport of supercritical (SC) CO2 at 348.15 K and 30 MPa up to 20,000 a. Given the low shale porosity (5%), chemical reactions mostly occurred in the sandstone for the first 2000 a with some precipitation at the ss/sh interface. From 2000 to 4000 a, ankerite, dolomite and illite began replacing Mg–Fe chlorite at the sandstone/shale interface. Transformation of chlorite to ankerite is the dominant reaction occluding the shale porosity in most simulations: from 4000 to 7500 a, this carbonation seals the reservoir and terminates reaction. Overall, the carbonates (calcite, ankerite, dolomite), chlorite and goethite all remain close to local chemical equilibrium with brine. Quartz is almost inert from the point of its dissolution/precipitation. However, the rate of quartz reaction controls the long-term decline in aqueous silica activity and its evolution toward equilibrium. The reactions of feldspars and clays depend strongly on their reaction rate constants (microcline is closer to local equilibrium than albite). The timing of porosity occlusion mostly therefore depends on the kinetic constants of kaolinite and illite. For example, an increase in the kaolinite kinetic constant by 0.25 logarithmic units hastened porosity closure by 4300 a. The earliest simulated closure of porosity occurred at approximately 108 a for simulations designed as sensitivity tests for the rate constants.These simulations also emphasize that the rate of CO2 immobilization as aqueous bicarbonate (solubility trapping) or as carbonate minerals (mineral trapping) in sandstone reservoirs depends upon reaction kinetics – but the relative fraction of each trapped CO2 species only depends upon the initial chemical composition of the host sandstone. For example, at the point of porosity occlusion the fraction of bicarbonate remaining in solution depends upon the initial Na and K content in the host rock but the fraction of carbonate mineralization depends only on the Ca, Mg, Fe content. Since ankerite is the dominant mineral that occludes porosity, the dissolved concentration of ferrous iron is also an important parameter. Future efforts should focus on cross-comparisons and ground-truthing of simulations made for standard case studies as well as laboratory measurements of the reactivities of clay minerals. 相似文献
4.
黄骅坳陷三马地区中-深部储层成岩作用及主控因素分析 总被引：12，自引：2，他引：12
黄骅坳陷三马地区储集岩样品的显微特征及成岩矿物的组合关系分析结果表明，三马地区下第三系中深层储层主要处于晚成岩A期，成岩现象包括石英、长石的次生加大、碳酸盐矿物胶结作用、矿物交代作用、溶解作用和粘土矿物转化作用等。其中石英次生加大于2700m左右开始出现，随埋深增大，石英增生加强；长石次生加大现象不十分普遍；碳酸盐胶结作用包括早期自生泥晶方解石胶结作用、连晶方解石和晚期白云石(或铁方解石)的胶结作用。在扫描电镜下可见到方解石与含铁方解石集合体充填在粒间孔隙中或与石英、钠长石及粘土矿物共生，白云岩多呈菱形粒状分布于粒间；常见的交代现象主要有方解石交代长石、石英及粘土矿物，粘土矿物交代长石、石英等；溶解作用主要有长石的溶解、碳酸盐颗粒的溶解和方解石胶结物的溶解等，粘土矿物的转化主要为蒙脱石、高岭石向伊利石(或绿泥石)转化。还讨论了储层岩相、岩性特征、孔隙水中有机酸含量、早期方解石的充填、烃类早期注入等因素对储层成岩演化的控制作用。 相似文献
5.
页岩气储集空间与储层矿物特征关系密切,以四川盆地东缘龙马溪组页岩为研究对象,利用矿物组成、微量元素、地球化学等测试结果,结合低温氮气吸附法和高分辨率成像技术,采用多元统计分析方法,建立了页岩孔容预测方程,并分析孔隙分布特征和影响因素。结果表明,龙马溪组中部和底部页岩组分含量差异较大,生物成因的自生石英发育是龙马溪组底部石英含量高的主要原因;页岩纳米级孔隙以2~5 nm为主,对孔容贡献率介于64.2%~70.1%;建立的页岩组分含量与孔容的预测模型高度显著。脆性矿物孔、黏土矿物片间孔及其粒内孔是富黏土矿物页岩的主要孔隙类型,孔隙呈微缝状,小于2 nm孔隙不发育;有机质含量是富有机质页岩孔容大小的主控因素,有机质孔的面孔率介于8.8%~12.5%;有机质含量及成熟度是小于2 nm微孔发育的主控因素,大于50 nm孔隙的发育则受控于黏土矿物、石英及长石含量。 相似文献
6.
Mineralogy and geochemistry of a Late Permian coal in the Dafang Coalfield, Guizhou, China: influence from siliceous and iron-rich calcic hydrothermal fluids 总被引：16，自引：2，他引：16
Shifeng Dai Chen-Lin Chou Mei Yue Kunli Luo Deyi Ren 《International Journal of Coal Geology》2005,61(3-4):241-258
This paper describes the influence of siliceous and iron-rich calcic low-temperature hydrothermal fluids (LTHF) on the mineralogy and geochemistry of the Late Permian No. 11 Coal (anthracitic, Rr=2.85%) in the Dafang Coalfield in northwestern Guizhou Province, China. The No. 11 Coal has high contents of vein ankerite (10.2 vol.%) and vein quartz (11.4 vol.%), with formation temperatures of 85 and 180 °C, respectively, indicating that vein ankerite and vein quartz were derived from low-temperature calcic and siliceous hydrothermal fluids in two epigenetic episodes. The vein quartz appears to have formed earlier than vein ankerite did, and at least three distinct stages of ankerite formation with different Ca/Sr and Fe/Mn ratios were observed.The two types of mineral veins are sources of different suites of major and trace metals. Scanning electron microscope and sequential extraction studies show that, in addition to Fe, Mg, and Ca, vein ankerite is the dominant source of Mn, Cu, Ni, Pb, and Zn in the coal, and the contents of these five elements are as high as 0.09% and 74.0, 33.6, 185, and 289 μg/g, respectively. In contrast, vein quartz is the main carrier mineral for platinum-group elements (PGEs) Pd, Pt, and Ir in the coal, and the contents of Pd, Pt, and Ir are 1.57, 0.15, and 0.007 μg/g, respectively. Sequential extraction showed a high PGE content in the silicate fraction, up to 10.4 μg/g Pd, 1.23 μg/g Pt, and 0.05 μg/g Ir, respectively. It is concluded that the formation of ankerite and quartz and the anomalous enrichment of trace elements in the No. 11 Coal in the Dafang Coalfield, Guizhou, result from the influx of calcic and siliceous low-temperature hydrothermal fluids. 相似文献
7.
Measurements are presented of volume changes in granite during room-temperature compression to 100, 200 and 300 MPa confining pressure followed by temperature increase to 900°C. Comparison with thermal expansion and compressibility data for the constituent minerals allows changes in porosity to be estimated. Under confining pressure, porosity is found to decrease with heating to 200°C through expansion of the minerals into cracks which are thought to be related to the geological cooling history of the rock. Between 200°C and 840°C porosity increases as a result of differential thermal expansion of the constituent minerals, but crack opening is increasingly suppressed at higher confining pressures. Extrapolation of the results indicates that differential thermal expansion can no longer cause crack opening in dry granite at confining pressures in excess of 450 MPa. The quartz α-β transition temperature in granite is marked by a kink in the thermal expansion curve of the rock, and it is found to increase by 60°C–70°C per 100 MPa confining pressure, as opposed to the published value of 26°C per 100 MPa for single crystals of quartz. Equations are presented which allow calculation of the effects of confining pressure and temperature on the stresses and displacements in and around a spherical inclusion embedded in a matrix of different elasticity and thermal expansion. The theory, together with a simple self-consistent model for granite, accounts semiquantitatively for the observations of thermal expansion and the effect of confining pressure thereon, and for the observed α-β transition temperatures for quartz in granite. 相似文献
8.
Christophe Tournassat Catherine Lerouge Philippe Blanc Jocelyne Brendlé Jean-Marc Greneche Stéphane Touzelet Eric C. Gaucher 《Applied Geochemistry》2008
Iron and Sr bearing phases were thoroughly investigated by means of spectrometric and microscopic techniques in Callovian–Oxfordian (COX) samples originating from the ANDRA Underground Research Laboratory (URL) in Bure (France). Strontium was found to be essentially associated with celestite, whereas Fe was found to be distributed over a wide range of mineral phases. Iron was mainly present as Fe(II) in the studied samples (∼93% from Mössbauer results). Most of the Fe(II) was found to be in pyrite, sideroplesite/ankerite and clay minerals. Iron(III), if present, was associated with clay minerals (probably illite, illite-smectite mixed layer minerals and chlorite). No Fe(III) oxy(hydro)xide could be detected in the samples. Strontianite was not observed either. Based on these observations, it is likely that the COX porewater is in equilibrium with the following carbonate minerals, calcite, dolomite and ankerite/sideroplesite, but not with strontianite. It is shown that this equilibrium information can be combined with clay cation exchange composition information in order to give direct estimates or constraints on the solubility products of the carbonate minerals dolomite, siderite and strontianite. As a consequence, an experimental method was developed to retrieve the cation exchanged Fe(II) in very well preserved COX samples. 相似文献
9.
鄂尔多斯盆地临兴地区上古生界致密砂岩储集层中矿物组成多样、孔隙结构复杂且黏土矿物含量高,直接影响储层改造和开发效果。文章基于X 衍射、铸体薄片、气测孔渗、压汞和敏感性实验,系统研究了储层敏感性及其影响因素。结果表明研究区砂岩中石英和岩屑含量高,长石含量较低,以岩屑砂岩、岩屑石英砂岩、长石岩屑砂岩和石英砂岩为主。黏土矿物主要为伊利石、高岭石、绿泥石以及伊/蒙混层;储层普遍低孔低渗,孔隙结构较差。速敏以太原组最强,山西组最弱,与伊利石+绿泥石含量正相关,高岭石含量负相关。水敏下石盒子组最强,太原组最弱,与伊/蒙混层含量正相关。盐敏与水敏有类似特点,与伊/蒙混层含量表现出正相关。酸敏山西组最强,下石盒子组最弱,与绿泥石和铁白云石矿物含量正相关。碱敏性山西组最强,太原组最弱,受长石、石英和高岭石含量影响。相关认识有助于指导研究区钻井、压裂等施工工艺选择和排采控制。 相似文献
10.
库车前陆冲断带超深层储层是当前天然气勘探开发的重要领域, 具有特低孔、特低渗-低渗, 裂缝-孔隙型, 测试高产储集特征。 为揭示储层中粘土矿物的特征及其对储层演化、储层性质的控制作用, 本文以大量微观实验分析（X 衍射、扫描电镜、激光共聚焦扫描、 铸体薄片、高压压汞）为依据, 研究表明：主要的粘土矿物含量为 5%～12%, 矿物类型以伊利石、伊蒙混层为主, 其次为绿泥石, 成因以成岩早期沉积水体继承性沉淀及成岩中晚期长石质次生溶蚀产物为主;砂岩中早期沉积型粘土矿物主要富集于三角洲前缘水下河道砂体的侧缘、水道砂体的顶底面附近, 其形成粘土薄膜可有效抑制超深层储层早中成岩期硅质、长石质次生加大, 保存基质孔隙, 不同期粘土杂基也可提供大量矿物晶间微孔隙, 微孔隙度可达 1%～4%, 是天然气的主要储集空间之一;粘土矿物是降低储层渗透率的主控因素, 6%～ 9%的粘土矿物含量（尤其是伊利石及伊蒙混层）可降低超深层储层渗透率 10～100 倍, 使渗透率总体为 0.01×10 -3 μm 2 ～0.1×10 -3 μm 2 。 粘土矿物含量及赋存特征：早期长期（130～23 Ma）浅 埋（< 3 000 m）期储集性能保存良好, 晚期（23 Ma 左右）深埋（> 3 000 m）期基质渗透性急剧降低, 总体致密化（< 0.1×10 -3 μm 2 ）, 这是研究区的关键因素。 粘土矿物的特征及其分布对评价砂岩储集性质, 预测超深层天然气有利储层的分布具有重要地质意义。 相似文献
11.
以沾化凹陷渤南洼陷罗63井和义21井沙一段取心段为例,依据研究样品的热解、全岩与黏土矿物X射线衍射、有机岩石学、孔隙度、氩离子抛光+扫描电镜以及微孔隙结构等分析结果,开展了沙一段湖相富有机质烃源岩岩石学与孔隙结构特征研究,结果表明：罗63井和义21井沙一段取心段富有机质烃源岩主要由碳酸盐矿物、黏土矿物和石英组成,另含少量长石、黄铁矿和石膏,其中黏土矿物主要由伊/蒙混层、伊利石组成,由取心段顶部至底部,碳酸盐矿物质量分数明显增高,而黏土矿物和石英则显著降低,呈现由钙质或灰质泥岩至演变为泥质灰岩的特征,岩石构造类型包括层状、纹层状和块状3类;罗63井和义21井沙一段取心段富有机质烃源岩平均孔隙度分别为2.09%和4.43%,具纹层状构造的烃源岩具有相对高的孔隙度;主要发育矿物基质孔隙（即粒间孔隙和粒内孔隙）和裂缝型孔隙两大类,而有机质孔隙不发育,孔隙半径从十几微米至几纳米的孔隙均有分布,以发育孔径50 nm以上的宏孔为主。 相似文献
12.
Colin R. Ward John C. Taylor C. E. Matulis L. S. Dale 《International Journal of Coal Geology》2001,46(2-4)
The mineral matter in the eight reference North American coal samples of the Argonne Premium Coal series has been investigated on a quantitative basis using X-ray diffraction (XRD) techniques. X-ray diffraction data obtained from electronic low-temperature (oxygen–plasma) ash (LTA) residues, from ashes produced by heating the coals in air at 370°C, and also from the raw coals themselves, were evaluated using an interactive data processing system (
™) based on Rietveld interpretation methods. The results from the three types of material (LTA, 370°C ash and raw coal) were compared for each sample. This allowed the components present in the raw coals in crystalline form to be recognised separately from mineral artifacts produced, particularly in the low-rank coals, from interaction of organically associated elements (Ca, S, etc.) during the two ashing processes.After the allowance for the production of any artifacts, the quantitative mineral assemblages identified from XRD of the raw coals were found to be consistent, even for coals having a relatively low ash percentage (around 5%), with the results obtained from the respective mineral concentrates prepared by the ashing methods. The effects of heating the coal to 370°C could also be distinguished, relative to the raw coal or the LTA, through changes in components such as pyrite and the clay minerals.Although some areas of uncertainty exist, particularly with magnesium in the low-rank coals, the calculated chemical compositions of the coal ash derived from the mineral mixtures identified for each coal were also found to be consistent with the results of direct chemical analysis of the respective coal ash materials. 相似文献
13.
西湖凹陷砂岩储层异常高孔带分布及成因 总被引：1，自引：0，他引：1
依据大量岩石薄片、铸体薄片、碳酸盐碳氧同位素测试、流体包裹体分析、黏土矿物X衍射、激光共聚焦显微镜技术以及物性资料,结合区域构造沉积背景,研究了东海盆地西湖凹陷砂岩储层异常高孔带分布规律及成因。结果表明:储层2 500~3 100 m和3 400~4 400 m的深度段发育大量的次生孔隙,两段次生孔隙带成因不同。第一段次生孔隙是在酸性环境下主要由有机酸等酸性流体溶蚀长石类矿物导致,还有少部分是由TSR反应生成的H2S溶蚀造成。第二段次生孔隙带主要由残余的早期酸性溶蚀孔和碱性环境下高岭石的伊利石化导致,少部分则由碱性流体溶蚀石英颗粒形成,同时异常高压保护深层次生孔隙,而且形成了一定量的裂缝。异常高孔带成因机理有助于优质储层的预测。 相似文献
14.
Summary ¶Mineral grains unidentifiable by means of cathodoluminescence (CL) and/or polarizing microscopy (including non-luminescent or opaque minerals) can be readily identified with energy dispersive X-ray spectrometry, attached to the CL equipment. Chemical identification is possible of mineral grains (ten to a few tens of microns) that are even smaller than the electron beam area, by using index elements if the unknown mineral analyzed is surrounded by grains of simple or known chemical composition (e.g. minute areas of carbonate cement surrounded by quartz or clay minerals; clay cements surrounded by quartz or carbonate) and simultaneous with CL microscopy.Results are presented of Cambrian, Carboniferous and Jurassic sandstones from Sweden and Germany. Transparent and opaque minerals, i.a. feldspars, luminescent and non-luminescent carbonate minerals as well as luminescent and non-luminescent clay minerals were identified in thin sections. The analytical procedure described here is especially helpful when rapid petrographic analysis has to be carried out of samples with complex composition, of which the petrographer had no previous experience. 相似文献
15.
东营凹陷泥页岩矿物组成及脆度分析 总被引：5，自引：0，他引：5
对东营凹陷泥页岩矿物组成、脆度进行了系统研究,并与北美页岩进行了对比。研究表明:东营凹陷沙三下和沙四上亚段泥页岩主要由黏土矿物、陆源碎屑矿物（主要指石英和长石）和自生非黏土矿物（主要指碳酸盐和黄铁矿）三部分组成;泥页岩黏土矿物含量平均只有25％左右,远低于海相泥岩和传统观点;石英含量平均为29%,远低于海相页岩;长石含量平均约5％,高于海相泥岩;自生的碳酸盐矿物含量较高,平均约37％;分析认为,陆相盆地面积较小、距物源区近以及相变快是导致研究区泥页岩矿物组成特征的主要原因。鉴于此,提出了新的脆度计算方法并计算了东营凹陷泥页岩的石英脆度、碳酸盐脆度和总脆度。对比发现,碳酸矿物盐含量与泥页岩脆度相关性较好,是影响泥页岩脆度的主要因素。最后指出:研究区泥页岩脆性较好,易于形成天然裂缝或被压裂,是页岩气潜在的有利储层。 相似文献
16.
17.
A geological database for parameterization in numerical modeling of subsurface storage in northern Germany 总被引：1，自引：0，他引：1
Underground land use can play a significant role in future concepts of energy and gas storage and requires an improved understanding of the parameters of potential storage formations (saline aquifers), for instance of porosity and permeability, and also of mineralogical and gas compositions. This study aims at providing data examples and calculating vertical spatial variations through variogram analyses of important North German geological reservoirs from Dogger, Rhaetian, Middle Buntsandstein, and Rotliegend (Sub)Groups and Formations, focusing on the western part of the North German Basin. Vertical correlation lengths of porosity and permeability data range between 0 and 30 m, while most results are calculated at approximately 2–4 m and do not show relevant differences among the evaluated formations. In the majority of the regarded formations, the Kozeny–Carman relationship between porosity and permeability is supported as long as low porosity and permeability values are excluded from the evaluation. Mineral percentages varied significantly among the evaluated sediments. Besides quartz, ankerite is the main compound in the Dogger Group, while feldspars and clay minerals were more frequent in the Rhaetian, Middle Buntsandstein, and Rotliegend sediments. Methane was the main gas compound in the reservoirs, followed by nitrogen, ethane, and carbon dioxide. This study serves as preparatory work to allow for the parameterization of geological models and a subsequent simulation of fluid transport to evaluate (long-term) safety and impacts of geothermal and gas storage projects. 相似文献
18.
Sulphide and carbonate minerals from nine bituminous coal seams of a Paralic Series were investigated by means of polished-section microscopy, scanning electron microscopy and absorption spectral analyses. In addition to syngenetic accumulations of kaolinite, illite and quartz, diagenetic veinlets of subhedral pyrite and marcasite most often occur in vitrinite clast fissures and in post-tectonic fissures, nests and lenses with fusinite. Epigenetic anhedral and subhedral grains of ankerite, dolomite, siderite and calcite are also frequently found in post-tectonic veins. Pyrite replaced some of the marcasite grains and it dominates in older coal seams in the Flora Beds as compared with the Grodziec Beds. Occasionally there are anhedral and subhedral galena, sphalerite and chalcopyrite grains among coal macerals as well as cerussite among post-tectonic carbonate veins. They all represent the only minerals that are abundant in definite chalcophile elements (Cd, Co, Cu, Ni, Pb, Zn). In addition to the minerals just mentioned, the elements occurred in pyrite and ankerite grains, which contained inclusions of fusinite and other minerals (among others, clay and carbonate minerals in pyrite, pyrite in carbonates). Although there is a low content of minerals accumulating Cd, Co, Cu, Ni, Pb and Zn, the minerals significantly influence the average concentration of elements in the coal seams. In the Grodziec Beds, mineral matter, especially carbonates and sulphides, determines (>50%) the concentration of Cd, Cu, Pb and Zn in coal. The basic part of Cd, Co and Ni in the coal seams of the Grodziec Beds and of Co, Cu, Ni, Pb and Zn in coal seams of the Flora Beds originates from organic matter. These regularities can be important, from an ecological perspective, in stating whether the coals investigated are useful for combustion and in chemical processing. 相似文献
19.
孔隙结构是制约页岩气赋存与运移的重要因素。页岩致密、低渗,其孔隙度极低。酸液可溶蚀页岩中的部分矿物,使其孔隙增加,促进页岩内部的气体流动。论文利用稀盐酸、氢氟酸、混合酸分别对页岩试样进行了不同时间的酸化处理,应用扫描电镜(SEM)观测了酸化前后湖南牛蹄塘组页岩试样表面的孔隙。基于MATLAB对页岩酸化前后的电镜扫描结果进行了孔隙度分析,页岩试样孔隙度为10.68%,纯水、稀盐酸、氢氟酸、混合酸分别浸泡24 h后,试样孔隙度分别增加了1.21倍、1.3倍、2.61倍、2.99倍。利用扫描电镜能谱仪测试了酸化前后页岩的元素变化,分析了页岩试样与不同酸液反应的机理和反应程度。结果表明:1 h酸化后,氢氟酸作用后的页岩试样表面残有大量石英和黏土矿物;而混合酸作用后的页岩试样表面虽残有大量石英,但黏土矿物含量明显减小,混合酸液作用下黏土矿物更容易被溶蚀。混合酸溶液酸性最强,24 h酸化后,混合酸与石英和黏土矿物剧烈反应。混合酸作用后页岩的孔隙最为发育,促进了页岩渗透率的增加。 相似文献
20.
《矿物学报》2013,(Z1)
Linxia Basin is a late Cenozoic fault-block basin along the border between the Tibet plateau and the Loess plateau in Northwestern China. Its formation and sediments record may be directly affected by the structural dynamics and the uplift of the Tibet Plateau. For this reason, we studied the mineral characteristics of the Maogou formation of Miocene sediments using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results showed that quartz, chlorite, illite, calcite, plagioclase, orthoclase, kaolinite, and trace palygorskite are present throughout the sequence of the cross-section in Linxia basin. In contrast, gypsum and ankerite occur occasionally in the upper portion of the Miocene deposits. The content of calcite varied with layers in the profile and was relatively concentrated in mudstone. Chlorite and illite were observed transforming into palygorskite under SEM observation. Based on the mineral characteristics and the change of mineral composition, especially the clay minerals, it could be inferred that an arid environment prevailed in the region with warm and cold intervals during Miocene time. 相似文献