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1.
粘土矿物对有机质生烃的催化作用   总被引：4，自引：1，他引：3  
烃源岩的有机质主要以有机粘土复合体的形式存在。有机质生烃是一种有机粘土化学反应。反应过程中,有机质与粘土之间存在质子和电子迁移,粘土通过对水分子的吸附和离解为有机质加氢裂解提供H+,而有机质生成的有机酸激活了粘土的催化活性,也为蒙皂石伊利石化反应创造了条件。烃源岩不同粘土矿物的选择性催化特征是影响油气组成的最重要因素。粘土的催化活性大小和发育时间是决定烃源岩生烃潜力大小的因素。由于烃源岩在蒙皂石伊利石化阶段具有最大的催化活性,而且与有机质生烃反应同步,因此富含伊$蒙混合层的烃源岩是世界含油气盆地的最有利烃源岩。不同地质时期的烃类地质储量与烃源岩膨胀性粘土的丰度有密切关系。  相似文献   

2.
Alumina :sodium, potassium :sodium, and (001):(002) ratios, as in hydromicas, increase progressively in the clay fraction of weathered crust, depending on the degree of weathering, regardless of petrographic type of the original rock. Chemical and structural changes caused by weathering are expressed also in mineralogical composition of the clay fraction. The latter relationship is obscured in clays from coastal sediments and is disturbed in marine clays, although the alumina-sodium and the other two ratios are still suited as criteria of “maturity” of the clay substance, in either case. In the case of terrigenic-chemogenic or chemogenic rocks from high-salinity sedimentation basins, neither of the foregoing criteria or relations are found to be valid, because of the masking effect of allothigenic clays. —V.P. Sokoloff.  相似文献   

3.
Abstract Cordierite-anthophyllite rocks and related cordierite-rich, talc-rich and chlorite-rich rocks occur in the Rosebud Syncline, north-west Queensland, Australia, as part of a Proterozoic metasedimentary sequence. Field relations and rock compositions attest the sedimentary origin of these rather unusual metamorphic rocks. Their chemical composition is comparable to that of unmetamorphosed, alkali- and Ca-poor pelites, which are associated with some evaporite deposits. Other occurrences of cordierite-anthophyllite rocks have commonly been interpreted as metamorphosed chloritic alteration products derived from mafic or felsic volcanics. A comparative chemical study, using analyses of cordierite-anthophyllite rocks from such alteration zones and analyses of unmetamorphosed magnesian pelites, demonstrates the general chemical similarity between these two rock groups of entirely different origin. However, distinct differences in major element relations help to distinguish these two genetic groups. Particularly useful are Al2O3–FeO–MgO plots, in which evaporitic pelites occupy the Fe-poor side. The highly magnesian metamorphic rocks from the Rosebud Syncline fall entirely into the compositional field of evaporitic clays and shales. Furthermore, analyses of relatively immobile trace elements give supporting evidence for the sedimentary origin of these cordierite-anthophyllite rocks. The correlation with trace element ranges of clays and shales is very good. However, the correlation with trace element ranges of mafic and felsic volcanics is poor, and major discrepancies occur with Cr, Ni, Co, Nb, Sc, Th and Ti. Thus, the magnesian metamorphics of the Rosebud Syncline appear to be derived from evaporitic clays rich in magnesian clay minerals, such as palygorskite, sepiolite, chlorite or corrensite. The complete metamorphic rock assemblage of interlayered calcareous, aluminous and magnesian rocks is interpreted as a metamorphosed carbonate-evaporite-pelite sequence.  相似文献   

4.
微生物对碳酸盐岩的风化作用   总被引：7，自引：0，他引：7  
微生物-矿物相互作用可以促进许多表生生物地球化学反应过程,是表生地球化学研究的重要内容。通过综合岩石表面的微生物类群及其地质作用,分析碳酸盐岩微生物风化的各种现象,特别是微观尺度上的各种形态,阐述碳酸盐岩的微生物风化机制与风化产物,笔者提出微生物对碳酸盐岩风化的4种途径:(1)通过微生物在岩石表面和缝隙中生长,导致岩石表层发生生物溶蚀、生物磨蚀和生物钻孔作用,加速岩石风化进程;(2)微生物群体形成的钻孔网络可以增强岩石化学溶蚀的有效表面积并导致其表面强度减弱而促进机械侵蚀作用,微生物对周围岩石颗粒胶结结构的破坏、疏松作用也会导致岩石矿物颗粒的分解;(3)微生物的持水作用,微生物分泌的有机酸以及微生物呼吸所释放的CO2对岩表水分的酸化过程亦加速岩石矿物的分解;(4)微生物生长过程中从岩石内摄取营养元素和产生复杂的有机配体,能促进矿物元素的释放。文中提出在开展微生物对碳酸盐岩风化过程和机理研究的基础上,有必要引入微生物生物技术来综合开发本地低品位含钾磷矿产资源,加速岩溶地区山地土壤的形成与演化。  相似文献   

5.
This paper presents an overview of the modification of clay minerals by propping apart the clay layers with an inorganic complex. This expanded material is converted into a permanent two-dimensional structure, known as pillared clay or shortly PILC, by thermal treatment. The resulting material exhibits a two-dimensional porous structure with acidic properties comparable to that of zeolites. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal pillared clays. Biofuels form an interesting renewable energy source, where these porous, catalytically active materials can play an important role in the conversion of vegetable oils, such as canola oil, into biodiesel. Transesterification of vegetable oil is currently the method of choice for conversion to biofuel. The second part of this review focuses on the catalysts and cracking reaction conditions used for the production of biofuel. A distinction has been made in three different vegetable oils as starting materials: canola oil, palm oil and sunflower oil.  相似文献   

6.
Rocky desertification, a process of land degradation characterized by soil erosion and bedrock exposure, is one of the most serious land degradation problems in karst areas, and is regarded as an obstacle to local sustainable development. It is well known that human activities can accelerate rocky desertification; however, the effects of climate change on rocky desertification in karst areas are still unclear. This study focused on the effects of temperature and precipitation changes and human activities on rocky desertification in karst areas to determine the impacts of climate change and human disturbances on rocky desertification. Areas of different level of rocky desertification were obtained from Landsat TM (1987) and Landsat ETM+ (2000) images. The results show that, although the total desertification area increased by only 1.27% between 1987 and 2000, 17.73% of the slightly desertified land had degraded to a moderate or intense level, 2.01 and 15.71%, respectively. Meanwhile, between 1987 and 2000, the air temperature increased by 0.7°C, and precipitation increased by 170 mm. Statistical results indicate that the increase in precipitation was caused by heavy rainfall. In addition, under the interactive influences of heavy rainfall and temperature, the average karst dissolution rate was about 87 m3 km−2 a−1 during the 14 years in the study area. Further analysis indicated that rocky desertification was positively related with the increase in temperature and precipitation and especially with the heavy rainfall events. Climate change accelerated rocky desertification in the karst areas. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

7.
青藏高原东部金沙江流域盆地陆地风化特征   总被引：2，自引：0，他引：2       下载免费PDF全文
青藏高原东部金沙江流域是研究高原隆升与陆地风化的理想地区。本文通过对金沙江河流系统的取样,从河流溶质载荷主要离子和悬浮载荷粘土矿物等方面揭示青藏高原东部金沙江流域盆地陆地风化特征。研究表明,金沙江流域盆地陆地岩石风化主要是碳酸盐岩、蒸发盐岩和硅酸盐岩。利用S i、S i/TZ+*、S i/Na*+K和S i/K以及(Na*+K)/TZ+等5个指标结合流域区域岩石分布和土壤特征揭示出流域硅酸盐岩为浅表性初级风化,风化产物主要是富含阳离子的次生粘土矿物。  相似文献   

8.
《International Geology Review》2012,54(12):1829-1838
Arguments are presented here to the effect that the parent rocks of the red kaolinitic weathered crust on the Adzharian shore of the Black Sea are not the Middle and Upper Eocene volcanogenic hard rocks, but montmorillonitic clays over dense lavas, of hydrothermal origin and with relict structures of hyaloclastites, tuffs, and porous lavas of basaltic or trachytic composition. The erosion of clayey metasomatites and the development of their eluvium and soils begins in Middle Pleistocene, it appears (together with the post-Bakunian orogenic phase), and is continuing even now. -- Author  相似文献   

9.
This paper reports the results of our recent studies and generalizes previously known data on the geology, mineralogy, geochemistry, and genesis of the Russia’s largest Latnenskoe refractory clay deposit. It is shown that conditions of its localization were defined by regional and local factors. The regional factors controlled the distribution of the clay raw material in the region, while the local factors were responsible for the genesis and composition of refractory clays of the Latnenskoe deposit. Our studies showed that the formation of refractory clays is not only related to terrigenous but also to authigenic processes of sedimentation. The terrigenous component of clays was formed by the erosion of kaolin weathering crusts of the Voronezh anteclise crystalline basement and Paleozoic sedimentary hydromica–kaolinite rocks. Authigenic processes were significantly contributed by organic matter, which determined the environmental pH and Eh parameters. It is established that the mineral matter of clays of the deposit is represented by three morphological modifications (crystalline, amorphous, and biomorphic), which were formed subsequently and (or) simultaneously and could be transformed into each other. Application of a complex of modern precision methods allowed us to reveal a previously unknown biomorphic modification of kaolinite, the major rock-forming mineral, as well as mixed-layer kaolinite-smectite in the clays. It is shown that the distribution of major and trace elements and the sulfur isotope composition in different technological types of clay depend mainly on the facies conditions of their formation. Technological properties of clay raw material are considered.  相似文献   

10.
西雅尔岗地区位于羌塘高原腹地，地理范围为东经88°00′至89°00′，北纬32°40′至33°40′.大地构造位置从属于羌塘地块的玛依岗日一阿木冈基底隆断带.在晚白坚一第三纪时期，受青藏高原整沐抬升的影响，沉积了一套巨厚的红色陆屑建造，其基本特征为沉积厚度大、粗粒沉积所占比例高、沉积类型复杂、横向及纵向上相变快、岩石的颜色多为红色及紫色.沉积相类型主要为冲积扇、扇三角洲及湖泊.化石类型卖要为植物〔柏型枝)，孢粉和鸟足印化石.反映了在干操气候条件下，快速堆积的沉积特征. 根据对该区岩石学的研究，发现岩石的矿物组合和结构类型皆因成岩作用的影响而发生了很大的变化.矿物组合的变化是由于沉积后附加的陆源机械渗人粘土，在地表条件下不稳定矿物及岩屑的溶解作用以及在成岩过程中自生矿物的形成作用所造成的.导致结构类型改变的原因是(1)机械渗人的碎屑粘土及自生的粘土矿物形成孔隙间的粘土质“成岩杂基”.而这些孔隙在最初沉积时则没有杂基存在;(2)松散沉积物在成岩过程中，结构颖粒的溶解作用;(3)由于压实及压溶作用而形成粉砂级及其它细小的颗粒;(4)交代作用及重结晶作用.这些成岩过程明显地反映了整个区域岩石的演化历史. 显微镜、扫描电镜的观察以及红外光谱的侧定结果表明该区红层的形成是由于在成岩过程中赤铁矿的沉淀而造成的.在扫描电镜下可清楚地识别出赤铁矿的自生晶形.由此可以断定赤铁矿在其形成过程中显然是起了染色剂的作用.它的形成主要受孔隙水的氧化还原条件所控制，似乎于气候的关系不大，尽管它是产于干旱条件的沉积物中. 基于对该区岩石的成岩作用及成岩历史演化序列的研究，建立了该区沉积后的成岩环境模式，亦即(l)早期的表生成岩浅埋藏环境，该环境明显受到沉积环境、沉积作用控制以及气候因素的影响;(2)晚期的成岩深埋藏环境，该环境则主要受地温梯度、压力、温度和孔隙水的地球化学条件的控制.  相似文献   

11.
浅析北方红粘土对碳酸盐岩溶蚀作用的影响   总被引：1，自引：0，他引：1  
北方碳酸盐岩发育的红色风化壳大都是第Ⅰ、Ⅱ间冰期湿热气候条件下溶蚀与风化作用的结果,形成硅铝—铁型风化壳。风化壳中红粘土化学成分R_2O_3(Al_2O_3+Fe_2O_3)含量达20—30％。当降水或地表水的垂直下渗、红粘土的氢离子浓度加大,溶蚀性增强,沿红粘土和碳酸盐岩接触面产生溶蚀作用,形成石芽、溶沟、溶槽、溶痕等岩溶地形,并在它们的表面保留有红粘土痕迹。  相似文献   

12.
喀斯特石漠化--中国西南最严重的生态地质环境问题   总被引：99，自引：1，他引：98  
作为最严重的环境地质问题,日益扩展的土地石漠化,正在吞噬着中国西南喀斯特地区民众的生存空间,已经构成灾害和贫困之源。喀斯特石漠化是土地荒漠化的主要类型之一,是人类不合理经济活动叠加于脆弱生态地质环境背景上的综合作用结果。它以脆弱的生态地质环境为基础,以强烈的人类活动为驱动力,以土地生产力退化为本质,以出现类似荒漠景观为标志。中国西南脆弱的喀斯特生态环境是经过漫长的地质历史演化而形成的,它对喀斯特石漠化具有明显的控制作用。构造运动塑造了陡峻而破碎的喀斯特地貌格局,古环境演化奠定了石漠化的物质基础。喀斯特地区的人口压力及不合理的人类活动,导致土地资源的严重退化、植被覆盖度锐减、水土流失加剧和生态环境严重恶化,超载的社会经济压力是导致喀斯特土地石漠化最重要的驱动力。尽管喀斯特石漠化综合治理非常艰巨,但仍具备恢复或重建生态环境的可能性。  相似文献   

13.
谭元松 《福建地质》2010,29(2):101-106
永泰无岩坑钼矿体贮存于成矿母岩燕山晚期中粗粒含黑云母花岗岩边缘相细晶质花岗岩硅化褪色蚀变带中,储矿构造主要为花岗岩岩体顶部的内接触带即岩凸构造,以及区域性北西向断裂的次级裂隙。矿床成因属岩浆期后热液充填型。  相似文献   

14.
Crustose lichens are distributed extensively in karst areas in Southern China. They can be found on the surface of carbonate rocks. Through biophysical and biochemical processes, crustose lichens reform the subsurface of carbonate rocks and in the meanwhile change their physical and chemical properties: (1) the mechanical strength decreases by 17.04° on average (up to 33.2° ); (2) the chemical solution surface area increases from 28.26% to 75.36% (lichen microholes considered only); and (3) the water-holding capacity is greatly improved. Comparative field experiments between biokarst samples underneath crustose lichens and fresh rock samples with the same composition and texture show that the corrosional rate of carbonate rocks of the former is 1.264-1.643 times higher than that of the latter. Crustose lichens are considered as an activator of the surface corrosion of carbonate rocks.  相似文献   

15.
The Navachab gold deposit in the Damara belt of central Namibia is hosted by a near-vertical sequence of amphibolite facies shelf-type metasediments, including marble, calc-silicate rock, and biotite schist. Petrologic and geochemical data were collected in the ore, alteration halos, and the wall rock to evaluate transport of elements and interaction between the wall rock and the mineralizing fluid. The semi-massive sulfide lenses and quartz–sulfide veins are characterized by a complex polymetallic ore assemblage, comprising pyrrhotite, chalcopyrite, sphalerite, and arsenopyrite, native bismuth, gold, bismuthinite, and bismuth tellurides. Mass balance calculations indicate the addition of up to several orders of magnitude of Au, Bi, As, Ag, and Cu. The mineralized zones also record up to eightfold higher Mn and Fe concentrations. The semi-massive sulfide lenses are situated in the banded calc-silicate rock. Petrologic and textural data indicate that they represent hydraulic breccias that contain up to 50 vol.% ore minerals, and that are dominated by a high-temperature (T) alteration assemblage of garnet–clinopyroxene–K-feldspar–quartz. The quartz–sulfide veins crosscut all lithological units. Their thickness and mineralogy is strongly controlled by the composition and rheological behavior of the wall rocks. In the biotite schist and calc-silicate rock, they are up to several decimeters thick and quartz-rich, whereas in the marble, the same veins are only a few millimeters thick and dominated by sulfides. The associated alteration halos comprise (1) an actinolite–quartz alteration in the biotite schist, (2) a garnet–clinopyroxene–K-feldspar–quartz alteration in the marble and calc-silicate rock, and (3) a garnet–biotite alteration that is recorded in all rock types except the marble. The hydrothermal overprint was associated with large-scale carbonate dissolution and a dramatic increase in CO2 in the ore fluid. Decarbonation of wall rocks, as well as a low REE content of the ore fluid resulted in the mobilization of the REE, and the decoupling of the LREE from the HREE. The alteration halos not only parallel the mineralized zones, but may also follow up single layers away from the mineralization. Alteration is far more pronounced facing upward, indicating that the rocks were steep when veining occurred. The petrologic and geochemical data indicate that the actinolite–quartz– and garnet–clinopyroxene–K-feldspar–quartz alterations formed in equilibrium with a fluid (super-) saturated in Si, and were mainly controlled by the composition of the wall rocks. In contrast, the garnet–biotite alteration formed by interaction with a fluid undersaturated in Si, and was mainly controlled by the fluid composition. This points to major differences in fluid–rock ratios and changes in fluid composition during alteration. The alteration systematics and geometry of the hydrothermal vein system are consistent with cyclic fluctuations in fluid pressure during fault valve action. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

16.
The newly bared rocks created by the Wenchuan earthquake are undergoing continual intensive erosion in the form of detachment and movement of individual grains. Grain erosion is defined as the phenomenon of breaking down bare rocks under the action of insolation and temperature change, detachment of grains from the rockwalls by wind, flow down of grains on the slope under the action of gravity, and accumulation of grains at the toe of the mountain, forming a deposit fan. The Wenchuan earthquake, which occurred in Sichuan on May 12, 2008, caused thousands of avalanches and landslides and left scars on slopes and a huge area of bare rocks. Grain erosion causes flying stones, injured humans and resulted in numerous slope debris flows. The process of grain erosion and strategies to limit the erosion were studied by field investigations and field experiments. According to these field investigations and field studies, the most serious grain erosion occurs in spring and early summer when it is very dry. Rocks are broken down to grains under the action of insolation and temperature change. Then, wind blows the grains from the bare rock down slope. Experimental results showed that the amount of grains blown down by wind per area of rock surface per unit time is proportional to the fourth power of the wind speed. However, the size of the grains blown down by wind increases linearly with the wind speed. An experiment proved that grain erosion can be controlled with two moss species. Moss spores were mixed with clay suspension and splashed on bare rocks. The moss species germinated on the rock surface in one month and greened the bare rocks in two months. The moss layer protected the rocks from insolation and mitigated the effects of temperature change, thus effectively mitigated grain erosion.  相似文献   

17.
Based on materials collected in 2003–2007, data on aquatic lichens of the genus Verrucaria from the rocky littoral zone of Lake Baikal are discussed. The maximum density of their occurrence was observed at a depth of 1.5 m; 95–100% of rock fragments recovered from depths of 1.5–2.2 m are encrusted by 24–43% with the thalli of Verrucaria spp. It was found that the lichens contribute actively to the physical and physicochemical weathering of their rock substrate and prefer to reside on the rocks of granitic composition. The chemical composition of aquatic verrucaria is dominated by the same elements that are most abundant in the rocks (Ca > K > Fe > Al > Mg > P > S > Na > Mn > Sr > Ba), and, in most cases, the characteristic element ratios of the rock compositions are preserved in the composition of the thalli of Verrucaria spp. Compared with the elemental composition of the near-bottom water layer, the lichens most extensively concentrate the elements that slowly migrate in water: Gd > Sm > Pr > Nd > Al > La > Dy > Tb > Y > Lu > Ce > Yb > Be > Tm > Co > Nb > Mn > Zn. Compared with the composition of rocks, the mineral composition of the thalli of Verrucaria spp. is enriched by a factor of 100–10 in Hg > As > P > Zn > Li > S > U > Mo > Se > Cd > Ca > Tl > Sr > Pb > Be.  相似文献   

18.
有机质丰度是传统评价烃源岩方法的重要指标,笔者认为有机粘土复合体是烃源岩有机质的主要赋存形式。有机质生烃反应是一种有机粘土化学反应,有机质脱羧基反应是有机粘土的氧化-还原反应,有机质的热解反应是一个加氢裂解过程,含有剩余C0是烃源岩的基本特征,它说明在烃源岩生烃反应中C0始终是有剩余的,不会因为C0的不足而影响烃源岩的生烃能力。笔者认为制约烃源岩生烃能力大小的不是烃源岩C0的丰度,而是氢的来源和丰度,烃源岩粘土通过吸附水分子为生烃反应提供H+能力(Br nsted酸性)的大小和时间是决定生烃潜力大小的关键。烃源岩粘土的不同催化特性是影响油气组成的重要因素,蒙皂石对甾烷的异构化有明显促进作用。  相似文献   

19.
用有机粘土化学研究生油理论   总被引：2，自引：1，他引：2  
有机粘土化学反应是自然界广泛存在的一种具有重要意义的反应。有机粘土化学因得到广泛应用和发展而被认为是２１世纪的科学。沉积物中的有机质绝大部分以粘土－有机质复合体形成存在。粘土吸附有机质是促使有机质富集和沉积的最重要因素。  相似文献   

20.
荥巩煤田大峪沟矿段深部铝土矿床是最近找矿突破发现的一个大型铝土矿床。该铝土矿床成矿时代为早二叠世,成矿物源主要为古陆铝硅酸岩风化物,少量为中奥陶统马家沟组碳酸盐岩风化产物,成矿环境为潮坪-沼泽环境,由长期的沉积间断、特定的岩相古地理环境、构造变形和表生风化作用共同控制着矿床的形成;上石炭统本溪组是铝土矿形成的含矿岩系;海湾泻湖相沉积环境是铝土矿床形成的有利条件;下古生界奥陶系、寒武系古岩溶侵蚀面是铝土矿形成的有利场所,古岩溶侵蚀面洼地及漏斗是铝土矿的定位空间。大峪沟矿段铝土矿床成因模式属于"古陆风化+碎屑和化学沉积";成矿机制为机械和化学分异。含矿岩系底部铁质风化壳/铁质黏土岩为碳酸盐岩风化形成,铝(黏)土矿来源于铝硅酸盐岩。大峪沟深部铝土矿床的发现为河南省寻找深部铝土矿床指明了方向。  相似文献   

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