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1.
XU Wang ZHENG Guodong MA Xiangxian Danielle FORTIN David R. HILTON LIANG Shouyun CHEN Zhi HU Guoyi 《《地质学报》英文版》2018,92(6):2201-2213
Organic-inorganic interactions occurring in petroleum-related mud volcanoes can help predict the chemical processes that are responsible for methane emissions to the atmosphere. Seven samples of mud breccia directly ejected from one crater were collected in the Dushanzi mud volcano, along with one argillite sample of the original reddish host rocks distal from the crater, for comparison purposes. The mineral and chemical compositions as well as iron species of all samples were determined using XRD, XRF and M?ssbauer spectroscopy, respectively. The results indicate that a series of marked reactions occurred in the mud volcano systems, more specifically in the mud breccia when compared to the original rocks. Changes mainly included: (1) some conversion of clay minerals from smectite into chlorite and illite, and the precipitation of secondary carbonate minerals such as calcite and siderite; (2) silicon depletion and significant elemental enrichment of iron, manganese, magnesium, calcium and phosphorus; and (3) transformation of iron from ferric species in hematite and smectite into ferrous species in siderite, chlorite and illite. These geochemical reactions likely induced the color changes of the original reddish Neogene argillite to the gray or black mud breccia, as a result of reduction of elements and/or alteration of minerals associated with the oxidation of hydrocarbons. Our results also suggest that greenhouse gases emitted from the mud volcanoes are lowered through a series of methane oxidation reactions and carbon fixation (i.e., through carbonate precipitation). 相似文献
2.
Seepage from hydrocarbon reservoirs can cause a number of chemical and/or mineralogical changes in overlying rocks and soils. These surface changes can be detected by remote sensing imaging systems. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imaging system in the visible and near infrared (VNIR) to shortwave infrared (SWIR) region. Band ratios of ASTER VNIR and SWIR data to detect red bed bleaching and secondary carbonate formation induced by hydrocarbon seepage are proposed through analysis of the spectral properties of rock samples. Results show that ASTER band ratios of 2/1 and 4/8 can discriminate bleached red beds and secondary carbonate minerals due to hydrocarbon seepage in the northern Tian Shan. They are in good agreement with mineral identification using X‐ray diffraction. The ratio technique derived from ASTER data may provide a potential approach for hydrocarbon exploration in areas with sparse vegetation cover. 相似文献
3.
Iron redistribution during postore stage at uranium deposits of the Khiagda ore field,Vitim district
B. T. Kochkin N. N. Tarasov V. I. Velichkin M. V. Nesterova A. A. Novgorodtsev L. S. Shulik 《Geology of Ore Deposits》2014,56(2):113-127
The localization conditions of mineralization at uranium deposits of the Khiagda ore field related to the economic sandstone type in paleovalleys are considered in this paper. These conditions allow different genetic treatments. Uncertainty in genetic estimates is caused by localization of orebodies in both gray sedimentary rocks at the boundary with bleached rocks and in the bleached rocks themselves. The results of mineralogical and geochemical studies have shown that bleaching is related to iron redistribution at the postore stage. Obvious evidence in favor of this conclusion has been obtained from statistical processing of quantitative soluble iron determinations in various geochemical types of host rocks. The postore bleaching is superposed on earlier oxidized and ore-bearing gray rocks, obliterating the coloration inherent to redox ore-controlling zoning. 相似文献
4.
Leaking hydrocarbon and associated fluids produce a reduced environment which initiates diagenetic reactions in the rocks and soils overlying hydrocarbon reservoirs. This article introduces mineralogical and geochemical alterations induced by hydrocarbon seepages in the Gachsaran evaporite Formation, Masjed Soleiman, Zagros Folded Belt, SW Iran, using various geochemical methods. X-ray diffraction (XRD) analysis revealed two dominant groups of mineralogical changes in the anomalous zone including: (1) spotty occurrences of jarosite, natroalunite, and sulfur; (2) simultaneous decrease of sulfate and increase of carbonate. The δ13C values of carbonate phases vary between −8.9‰ and −32.3‰ which support a partial contribution of hydrocarbon in these phases. pH measurements of rock samples indicated that hydrocarbon seepage causes decrease of pH, though not very significantly. However, pH in areas that show ongoing sour hydrocarbon seepage among rarely pure gypsum beds decrease to −0.09 which produces acid sulfate soil. Trace element concentrations indicated that Cr, Co, Ni, V, Cd, U, Cu, and Zn increase in various patterns around the hydrocarbon seepages excepting the areas with very low pH. 相似文献
5.
《Chemie der Erde / Geochemistry》2021,81(2):125736
The Lower Triassic Buntsandstein in Central Germany comprises one of the major clastic, lithified hydrocarbon reservoirs, it is a major groundwater aquifer and it is considered as a potential underground gas storage lithology. Thus, sandstones of the Buntsandstein from Thuringia and NE Hesse were used to analyse their geochemical composition combined with mineralogical data in order to investigate the origin of several bleaching phenomena in primary red beds, since these give a hint for mineral alteration, mineral formation and mineral reactivity in the course of fluid-rock-interactions. This is relevant for e.g. recent Carbon Capture and Storage (CCS) efforts. The origin of the observed bleaching phenomena is diverse and it is linked to certain stages of diagenesis and different episodes of fluid flow: (1) eodiagenetic bleaching coupled with palaeosoil formation and iron mobilisation, (2) mesodiagenetic bleaching as a result of hydrocarbon migration, (3) Tertiary bleaching due to CO2 degassing from Miocene volcanism, (4) Tertiary telodiagenetic bleaching due to weathering under humid climate conditions, and (5) weathering processes related to recent telodiagenesis/pedogenesis. This study emphasizes the multiple nature of fluids, which can induce iron mobilisation and bleaching of red beds. 相似文献
6.
鄂尔多斯盆地东胜砂岩型铀矿的显著特点,首先是矿床存在明显的绿色蚀变控矿带以及漂白现象,其次是含矿层较广泛地分布有不连续透镜状碳酸盐化钙质胶结砂岩。经粘土矿物X射线衍射分析、扫描电镜鉴定、包裹体化学成分等项测试,认为绿色蚀变和漂白现象是在大范围还原性环境下形成的,而其中的还原性流体主要与油气逸散作用有关;经对含矿层罐顶气和碳酸盐碳同位素以及部分有机地球化学参数分析后认为,上述蚀变现象主要与上古生界来源的含CH4、H2S、CO、CO2等成分的煤成气向北东方向的逸散蚀变作用有关。故可认为,顺油气逸散方向的盆地边缘且位于绿色蚀变带前锋线的区域是铀矿成矿及找矿的有利地区。 相似文献
7.
内蒙古巴音戈壁盆地因格井坳陷下白垩统巴音戈壁组上段是中国高放废物黏土岩处置库重点预选区段。通过对该段沉积岩开展岩石学、矿物学和地球化学等研究,发现该热水沉积岩岩相呈深灰色、灰色,具有纹层/条带状、网脉状、同生变形、“斑状”、块状共5种典型构造,主要矿物组分为白云石、铁白云石、方沸石、伊利石、钠长石和黄铁矿。依据主要矿物组分,将热水沉积岩分为混积岩、泥质白云岩、泥质沸石岩及含白云石沸石泥岩4类。地球化学测试结果表明: 热水沉积岩中主量元素铁、锰富集;深源气液型微量元素Mo、Sb、Zn、As、Sr、Ba丰度相对较高;稀土元素总量变化范围大,平均值为119.85μg/g,轻稀土明显富集,重稀土亏损,δCe未见明显亏损(平均值0.99),δEu中等偏强的负异常(平均值0.62);δ18O值以负偏为主。根据氧同位素值计算出的热水沉积物形成温度介于40.41~64.87℃之间,Fe-Mn-(Cu+Co+Ni)三角图解中热水沉积物均落入喷流沉积区。结合区域构造背景,认为该套热水沉积岩是在干旱的气候条件下,偏还原的半咸湖—咸湖湖水与深部岩浆热液相互作用形成的低温“白烟型”热水沉积岩,其中阿尔金断裂带在100—120Ma的活动是热水沉积岩形成的主控因素,其为白云化流体提供了运移通道。对巴音戈壁盆地下白垩统巴音戈壁组热水沉积岩的研究,有助于确定高放废物黏土岩地质处置库重点目标层位。 相似文献
8.
9.
The alkaline intrusive complexes of Tenerife and La Gomera (Canary Archipelago, Spain) are formed by nepheline syenites and
alkali gabbroids, and represent part of the oldest magmatic episodes in both islands. This work presents new studies of the
petrographic and geochemical features of these rocks, and offers the first data about their respective ore minerals (iron
oxides and sulphides). Mineralization is represented in both complexes by iron-rich patches and veins displaying a simple
paragenesis of magnetite, ilmenite, pyrite and pyrrhotite, in association with widespread chloritic alteration of the intrusive
host rocks. The comparative study of the mineralogical, textural and chemical characteristics of the ore minerals allows a
metallogenetic model to be proposed which comprises two stages (magmatic and hydrothermal) in La Gomera and only one (magmatic)
in Tenerife. The migration of the sulphide-bearing hydrothermal fluids far from the intrusive complex in Tenerife, and/or
possible re-melting process could explain the apparent absence of the later hydrothermal stage in Tenerife.
Received: 29 January 1998 / Accepted: 1 April 1998 相似文献
10.
Dieter Pudlo Viktor Reitenbach Daniel Albrecht Leonhard Ganzer Ulrich Gernert Joachim Wienand Bernd Kohlhepp Reinhard Gaupp 《Environmental Earth Sciences》2012,67(2):369-384
In the framework of the German R&D joint project CLEAN (CO2 large-scale enhanced gas recovery in the Altmark natural gas field), Rotliegend reservoir sandstones of the Altensalzwedel block in the Altmark area (Saxony-Anhalt, central Germany) have been studied to characterise litho- and diagenetic facies, mineral content, geochemical composition, and petrophysical properties. These sands have been deposited in a playa environment dominated by aeolian dunes, dry to wet sand flats and fluvial channel fills. The sediments exhibit distinct mineralogical, geochemical, and petrophysical features related to litho- and diagenetic facies types. In sandstones of the damp to wet sandflats, their pristine red colours are preserved and porosity and permeability are only low. Rocks of the aeolian environment and most of the channel fill deposits are preferentially bleached and exhibit moderate to high porosity and permeability. Although geochemical element whole rock content in these rocks is very similar, element correlations are different. Variations in porosity and permeability are mainly due to calcite and anhydrite dissolution and differences in clay coatings with Fe-bearing illitic-chloritic composition exposed to the pore space. Moreover, mineral dissolution patterns as well as compositions (of clays and carbonate) and morphotypes of authigenic minerals (chlorite, illite) are different in red and bleached rocks. Comparison of the geochemical composition and mineralogical features of diagenetically altered sandstones and samples exposed to CO2-bearing fluids in laboratory batch experiments exhibit similar character. Experiments prove an increase in wettability and water binding capacity during CO2 impact. 相似文献
11.
基于沉积相的研究认为鄂尔多斯盆地西北部罗汉洞期在缓倾斜坡带发育河流相一辫状河三角洲相一湖泊相沉积。依据酸解烃特征参数C1／∑C,C1／C2＋及酸解烃判别分析（z值法、Φ值法及判别因子法）论证了赋存于罗汉洞组地层中的烃气源于三叠系上统湖相生油岩系中的油型气。通过综合剖析赋存于罗汉洞组中油气的地球化学特征、油气还原蚀变特征和铀矿化关系,论证了罗汉洞组的褪色蚀变（漂白）是渗逸到该层位中的酸解烃类气体对岩石发生诱发蚀变的结果,论述了沉积成岩作用期间在辫状河三角洲相中发生铀初步富集,提出沉积相组合与油气还原蚀变带的空间配置是后期铀矿化空间定位的制约因素。 相似文献
12.
We investigated the weathering-pedogenesis of carbonate rocks and its environmental effects in subtropical regions of China. The investigation demonstrated that the weathering- pedogenesis of carbonate rocks is the process of a joint action of corrosion and illuviation and metasomatism in subtropical region. It is characterized by multi-stage, multi-path and multi-style. With the persisting development of weathering-pedogenesis of carbonate rocks, metasomatic pedogenesis progressively became the main process of the weathering-pedogenesis and the dominant style of formation of minerals. And it proceeds through the whole process of evolution of the weathering-pedogenesis of carbonate rocks. The stage evolution of weathering-pedogenesis of carbonate rocks and the fractionation evolution of newly produced minerals are characterized by obvious vertically zoning structures and the rules of gradation of elements geochemical characteristics in the carbonate rocks weathering profiles. The geochemical process of weathering-pedogenesis of carbonate rocks can be divided into three geochemical evolution stages, i.e., the Ca, Mg-depletion and Si, Al-enrichment stage; the Fe, Mn enrichment stage and the Si-depletion and Al-enrichment stage in the subtropical regions. Consistent with the three geochemical evolution stages, the sequence of formation and evolution of minerals can be divided into the clay mineral stage; the Fe, Mn oxide and the gibbsite stage. The influence of weathering-pedogenesis of carbonate rocks on the chemical forms of heavy elements is mainly affected via newly produced components and minerals in the process of weathering-pedogenesis, e.g., iron oxide minerals and organic matters. The important mechanism for the mobilization, transport and pollution of F and As is affected the selective adsorption and desorption of F and As on the surface of iron oxide minerals in the subtropical karst zones, i.e., the selective adsorption and desorption on mineral surfaces of newly produced minerals in the process of weath 相似文献
13.
Alain Blot 《Comptes Rendus Geoscience》2004,336(16):1473-1480
The main discrimination criteria between the gossans and ferruginous laterites are the iron secondary minerals, well known as direct crystallization after weathering of the main sulphide minerals. The characteristics of these iron oxihydroxides and their association in supergene rocks affect all the physical, mineralogical, geochemical, and crystal-chemical aspects: morphology, facies, microfacies, mineralogical constitution, geochemical composition and iron oxide/hydroxide crystal chemistry give thus distinction criteria. In West Africa, where lateritic iron crusts are abundant, the research of the above characteristics could be an alternative method to the classical blind-soil and alluvial-sediment geochemical prospecting. To cite this article: A. Blot, C. R. Geoscience 336 (2004). 相似文献
14.
陕南凤凰岭南缘变质镁铁质—超镁铁质侵入岩为富含Fe、Ti等有用元素的含矿岩体。利用岩石地球化学方法、偏光显微镜和电子探针技术对该区镁铁质—超镁铁质侵入岩的岩石学、地球化学和矿物学特征进行了研究,并对Fe-Ti氧化物的形成、富集进行了初步探讨,对成岩、成矿作用具有一定的参考意义。结果表明,成矿镁铁质—超镁铁质侵入岩与非成矿镁铁质—超镁铁质侵入岩为不同岩浆源区、同期岩浆作用的产物,镁铁质—超镁铁质侵入岩类的Fe-Ti矿化作用与初始岩浆的源岩之间具有密切关系。Fe-Ti氧化物主要以钛铁矿和榍石的形式存在,局部见少量金红石。化学成分上,钛铁矿具富锰贫镁特征,本区Fe-Ti氧化物的形成和富集过程经历了岩浆结晶分异阶段和热液蚀变阶段。 相似文献
15.
Ibrahim A. Salem Mohamed E. Ibrahim Mohamed Abd El Monsef 《Arabian Journal of Geosciences》2012,5(3):385-406
The present work deals with the geology, mineralogy, geochemistry, and origin of the metagabbroic-hosted manganese deposits at Wadi Maliek in the southern Eastern Desert of Egypt. The manganese veins are found in the shear zones and channel ways of the fault planes within the metagabbroic rocks pointing to those hydrothermal solutions carrying manganese and iron load penetrating along these fractures. These faults are striking N 80° E?CS 80° W with dipping 65°. These veins vary in thickness from 15?cm up to 125?cm wide; each vein may show difference in thickness from bottom to top. Microscopic examinations, X-ray diffraction, infrared spectral, differential thermal (DTA), thermogravimetric (TGA), and ESEM-EDAX analyses revealed that the manganese minerals consist mainly of pyrolusite, psilomelane, and ramsdellite. Goethite and hematite are the common iron minerals. Petrographically, the manganese deposits can be classified into three ore types based on the predominance of manganese and iron minerals: manganese, manganese?Ciron, and iron ore types. The geochemistry of Maliek deposits indicated that the total averages of some major oxides in manganese, manganese?Ciron, and iron ore types are respectively as follows: SiO2 (15.64%, 11.52%, and 20.58%), MnO (39.9%, 17.81%, and 0.77%), FeO* (7.13%, 33.31%, and 37.08%), CaO (5.89%, 5.82%, and 5.32%), and Na2O (1.04%, 1.61%, and 1.53%). With regard to trace elements, the Maliek manganese deposits are rich in Zn, Ba, Pb, Sr, and V. Based on the geological, mineralogical, and geochemical results, the studied manganese deposits are considered to be precipitated from hydrothermal solution. 相似文献
16.
17.
《Applied Geochemistry》2000,15(9):1265-1290
Massive sulphide deposits of the northern Iberian Pyrite Belt (IPB) are mainly hosted by felsic volcanic rocks of rhyolitic to dacitic composition. Beneath most of the massive ores of this area (e.g., Concepción, San Miguel, Aguas Teñidas Este or San Telmo deposits) there is usually a wide hydrothermal alteration halo associated with stockwork-type mineralization. Within these alteration envelopes there are two principal rock types: (1) chlorite-rich rocks, linked to the inner and more intensely altered zones and dominantly comprising chlorite+pyrite+quartz+sericite (+carbonate+rutile+zircon+chalcopyrite), and (2) sericite-rich rocks, more common in the peripheral zones and showing a dominant paragenesis of sericite+quartz+pyrite+chlorite (+carbonate+rutile+zircon+sphalerite). Mass-balance calculations comparing altered and least-altered felsic volcanic rocks suggest that sericitization was accompanied by moderate enrichment in Mg, Fe and H2O, with depletion in Si, Na and K, and a slight net mass loss of about 3%. Chloritization shows an overall pattern which is similar to that of the sericitic alteration, but with large gains in Fe, Mg and H2O (and minor enrichment in Si, S and Mn), and a significant loss of Na and K and a minor loss of Ca and Rb. However, chloritization has involved a much larger net mass change (mass gain of about 28%). Only a few elements such as Nb, Y, Zr, Ti, P and LREE appear to have remained inert during hydrothermal alteration, whilst Ti and Al have undergone very minor mobilization. The results point to the severity of the physico-chemical conditions that prevailed during the waxing stage of the ore-forming hydrothermal systems. Further, mineralogical and geochemical studies of the altered footwall rocks in the studied deposits indicate that hydrothermal ore-bearing fluids reacted with host rocks in a multi-stage process which produced a succession of mineralogical and chemical changes as the temperature increased. 相似文献
18.
In orogens, shortening is mainly accommodated by thrusts, which constitute preferential zones for fluid–rock interactions. Fluid flow, mass transfer, and mineralogical reactions taking place along thrusts have been intensely investigated, especially in sedimentary basins for petroleum and uranium research. This study combines petrological investigations, mineralogical quantifications, and geochemical characterizations with a wide range of analytical tools with the aim of defining the fluid properties (nature, origin, temperature, and redox) and fluid–host rock interactions (mass transfers, recrystallization mechanisms, and newly formed synkinematic mineralization) in the Pic-de-Port-Vieux thrust fault zone (Pyrenees, Spain). We demonstrate that two geochemically contrasted rocks have been transformed by fluid flow under low-grade metamorphism conditions during thrusting. The hanging-wall Triassic red pelite was locally bleached, while the footwall Cretaceous dolomitic limestone was mylonitized. The results suggest that thrusting was accompanied by a dynamic calcite recrystallization in the dolomitic limestone as well as by leaching of iron via destabilization of iron oxides and phyllosilicate crystallization in the pelite. Geochemical and physical changes highlighted in this study have strong implications on the understanding of the thrust behavior (tectonic and hydraulic), and improve our knowledge of fluid–rock interactions in open fluid systems in the crust. 相似文献
19.
Liu Qingsheng Department of Geophysics China University of Geosciences Wuhan The State Key Laboratory of Oil/Gas Reservoir Geology Exploitation of China Institute of Chengdu Technology Chengdu Wu Qifan Li Haixia Department o 《中国地质大学学报(英文版)》2001,12(2)
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20.
The volcanogenic Woodlawn Cu‐Pb‐Zn sulphide mineralization occurs within a low‐grade metamorphosed sequence of Middle to Upper Silurian felsic volcanics and fine‐grained sedimentary rocks. Studies on a total of 234 rock samples from diamond drill holes have delineated zones of hydrothermally altered rocks extending more than ～500 m laterally from the main ore lens, at least ～100 m into the foot wall and up to ～200 m into the hanging wall. These altered rocks contain virtually no remnants of primary feldspars and ferromagnesian minerals, and they are variably chloritized, sericitized and silicified. Chlorite and disseminated sulphide minerals are most abundant in zone I, a restricted zone of intense alteration immediately around the main ore lens, whereas sericitic muscovite is most abundant in the relatively extensive zone II, further from the ore. Silicification is also a feature of volcanics well beyond the limits of observed phyllosilicate‐rich alteration zones. Chemical changes within the hydrothermally altered rocks include major enrichment of Fe, Mg, S, Si and H2O, more sporadic enrichment of Ag, Ba, Bi, Cd, Cu, Mn, Pb, Sn and Zn, and major depletion of Ca, Na and Sr. K is depleted in zone I and shows considerable variation, but no overall depletion or enrichment, in zone II. Lithological, mineralogical and geochemical features around the Woodlawn orebody are basically similar to those associated with the younger, unmetamorphosed Kuroko deposits. 相似文献