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R. W. Botz V. Georgiev P. Stoffers Kh. Khrischev V. Kostadinov 《International Journal of Earth Sciences》1993,82(4):663-666
The Precipitation of carbonate cements in the Pobitite Kamani area (Lower Eocene) began during early diagenesis of sediments. There is evidence, however, that calcite is still forming today.The negative 13C values to –29.2 suggest that the carbonate formed during degradation of 12C-enriched organic matter (perhaps partly from oxidation of methane). The 18O values of –0.9 to –1.6 reflect the marine origin of the early diagenetic carbonate cements. Most of the carbonates, however, formed during late diagenesis (at approximately 1300 m burial depth) and/or recently (after uplift) from percolating groundwaters. These carbonates have an isotopic composition characteristic of carbonates which precipitated from meteoric waters under normal sedimentary temperatures in isotopic equilibrium with 12C-enriched soil carbon dioxide. 相似文献
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XI Kelai CAO Yingchang LIN Miruo LIU Keyu WU Songtao YUAN Guanghui YANG Tian 《《地质学报》英文版》2019,93(1):213-226
This article reviews the applications of light stable isotope, including carbon, oxygen and hydrogen, in thestudies on origin and formation temperature of authigenic carbonate, quartz and clay minerals. Theoretical knowledge andanalytical methods for major light stable isotopes are introduced in detail. Negative and positive δ13C values indicatesignificant differences on the origin of carbonate cements. The δ18O value is an effective palaeotemperature scale forauthigenic minerals formation. Various fractionation equations between δ18O and temperature are proposed for carbonatecements, quartz cements and clay minerals, whose merit and demerit, applicable conditions are clarified clearly. Clumpedisotope analysis can reconstruct the temperature of carbonate precipitation with no requirement on the δ18O of initial waters,which makes temperature calculation of carbonate cements formation more convenient and accurate. Hydrogen and oxygenisotopes mainly reflect the origin of diagenetic fluid for clay mineral formation, providing reliable evidence for diageneticenvironment analysis. This work aims at helping researchers for better understanding the applications of light stable isotopein sandstone diagenesis. 相似文献
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《Chemie der Erde / Geochemistry》2017,77(2):257-266
Sugar cane bagasse ash from SOSUCAM company in Cameroon was used to synthesize sodium waterglass as a new alternative hardener. The new hardener was used to prepare metakaolin-based geopolymer cements. The compressive strength of the resulting geopolymer cement cured at room temperature for 28 days was 32.9 MPa. Samples soaked for 28 days in water in parallel experiments revealed a strength of 31.4 MPa. This shows that exposure of water does not lead to any weakening. The value of water absorption was 7.1% in the water-soaked cements, indicating the presence of fewer pores and voids than in the dry cements. However, in SEM micrographs, the microstructure of geopolymer cement appears rather homogeneous and compact without any change by water soaking. It can thus be concluded that sodium waterglass from sugar cane bagasse ash can be used as an alternative hardener or reactive ingredient for producing geopolymer cement with a high degree of cross-linking geopolymer framework. The use of this low-value silica-rich waste for producing sodium waterglass results in environmental benefits including a significant reduction of CO2 emission and energy consumption compared to the production of commercial sodium waterglass. 相似文献
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The Upper Triassic Yanchang Formation in the southern Ordos Basin is a tight sandstone but productive hydrocarbon exploration target. A variety of analyses, including thin-sections, cathodoluminescence (CL), scanning electron microscope (SEM), X-ray diffraction (XRD), fluorescence, isotope and fluid inclusion, have been used to analyse the reservoir petrology and diagenesis to understand the evolution of reservoir porosity. The sandstones are mostly feldspathic litharenites and lithic arkoses with low porosities (7.6% on average) and extremely low permeabilities (0.49 mD on average). A complex diagenetic alteration history of the reservoir caused different kinds of reduction in reservoir porosity. The carbonate cements are sourced from adjacent organic-rich mudstone and precipitated with a higher content near the edges of sandstone units and a lower content at the centres of sandstone units, resulting in two different diagenetic evolution paths. The analysis of porosity evolution history and hydrocarbon emplacement produced the following conclusions: (1) during the eodiagenesis period, mechanical compaction reduced the primary porosity dramatically from 40 to 19%; and (2) during the mesodiagenesis period, the first-phase oil charged the reservoir (porosity ranging from 14 to 19%) as bitumen along detrital grains forming a preferential pathway for subsequent oil emplacements. In the second-phase of oil charge, the reservoir porosity ranged from 9 to 14% limiting water–rock reactions. During the third-phase of oil charge, porosity of the reservoir remained at 9%. In general, the densification period (with a porosity close to 10%) of the reservoir occurs at the same time as the major oil emplacement and may be an explanation for the low oil saturation of the Chang 8 tight sandstone. 相似文献
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Haiqiang Bai Xiaojun Xie Gongcheng Zhang Ying Chen Ziyu Liu Lianqiao Xiong Jianrong Hao Xin Li 《海洋学报(英文版)》2023,42(3):65-75
Carbonate cements are the most abundant authigenic mineral and impact on physical properties greatly in sandstone reservoir. In this paper, Pinghu Formation of Xihu Sag was taken as a target. Characteristics,distribution and formation of carbonate cements were investigated via optical microscopy, cathodoluminescence(CL), electron probe and in-situ carbon-oxygen isotope. The results showed that carbonate cements varied in types and shapes. Calcite/dolomite mainly present as poikilotopic cements, ... 相似文献
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以重点钻井的岩芯样品和薄片的观察为基础,结合扫描电镜、X衍射、储层物性和压汞等化验资料的分析,对柴达木盆地平台地区路乐河组砂岩储层的物性特征及其主控因素进行了研究。结果表明路乐河组砂岩储层的岩石类型以岩屑砂岩和长石质岩屑砂岩为主,颗粒分选和磨圆中等-较差,成分成熟度和结构成熟度中等-较低;储层物性表现为以中孔-中渗为主,低孔-低渗为辅的特征,且孔隙度和渗透率相关性好;原生粒间孔是最主要的孔隙类型,约占70%,其次是粒间溶孔和粒内溶孔。压实作用和胶结作用分别减少了路乐河组砂岩储层原始孔隙的31.8%和29.5%,是其物性条件变差的最主要因素。在成岩演化早期阶段,碳酸盐胶结物增强了储集岩的抗压实能力,有效抵御压实作用在成岩阶段早期对储集岩粒间孔隙的破坏;在成岩演化晚期阶段,碳酸盐胶结物又为溶蚀作用提供了空间和物质基础,形成部分次生溶蚀孔隙,对平台地区路乐河组储层的物性又有一定程度的改善。 相似文献
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方解石是东胜地区直罗组含铀砂岩中重要的胶结物类型,同时碳酸盐化与铀成矿作用关系密切。通过方解石胶结物岩石学、矿物学、碳氧同位素分析,研究了含铀砂岩中方解石碳氧同位素组成、沉淀机制及铀成矿意义。研究表明,东胜地区砂岩类型为长石岩屑砂岩、岩屑砂岩和石英砂岩,粘土矿物主要由蒙皂石、伊利石、高岭石和绿泥石组成,方解石类型以含铁矿方解石为主,其次为铁方解石。方解石δ~(13)C_(PDB)为-15.7‰~-1.6‰,平均-9.08‰,δ~(18)O_(PDB)为-15.6‰~-10‰,平均-12.4‰,显示其形成与有机酸脱羧作用有关,碳来源为有机碳。碳氧同位素分析数据计算表明,与方解石平衡的水相氧同位素组成变化范围较宽,为-7.66%-9.71‰,推测较轻的同位素组成具有封存大气降水的特征,而较重同位素组成则反映成岩成矿过程中深部富含油气低温热流体的加入。综合分析认为,东胜地区直罗组砂岩中方解石是地表水和深部油气共同作用的结果:早期有机酸促使长石类骨架颗粒溶蚀,形成石英颗粒次生加大边,并伴随着自生高岭石沉淀;后期随着大量烃类注入砂岩中,成岩成矿环境由酸性向碱性转变,还原性增强,介质水中的CO_2与Ca~(2+)圾Fe~(2+)结合形成含铁为特征的方解石,沉淀在原生粒间孔和各类次生溶蚀孔隙中。整个过程都伴随有铀元素运移和沉淀,暗示东胜铀矿床是地表水和深部油气混合作用形成的。 相似文献
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砂岩型铀矿赋矿地层方解石胶结物C、O同位素组成对研究成矿机制具有重要的理论和实践意义。前人在成矿流体来源定性判断方面做了大量的研究工作,但缺乏对成矿混合流体的组分特征及相关参数的定量认识。根据内蒙古东胜地区东南部皂火壕和西北部纳岭沟铀矿床赋矿地层直罗组方解石胶结物C、O同位素组成特征,建立了渗出热卤水和渗入地层水两种不同流体混合生成方解石胶结物C、O同位素组成定量成因模型,并研究了两种流体来源、溶解碳的浓度比、流体比例以及热液温度等综合因素。除少数样品方解石胶结物为地层沉积时形成外,大部分方解石胶结物是热卤水与地层水两种流体混合作用的结果,古生界有机酸脱羧作用导致热卤水中富含CO_2。东胜地区砂岩型铀矿成矿流体地层水与热卤水比例为0.5～0.9,地层水所占的比例较大;热卤水与地层水溶解碳浓度比主要范围为1.5～5.0,部分大于10.0,热卤水中溶解碳浓度较高,是富含CO_2的流体。混合流体温度分为两个主要范围55～80℃、90～140℃,结合古盐度和盐度指数反演,表明成矿流体为有机与无机混合成因的低温热液流体。用砂岩型铀矿赋矿地层方解石胶结物C、O同位素组成,可定量模拟两种流体溶解碳浓度比、流体比例和方解石形成时温度等流体成矿条件,解释碳酸盐胶结物成因,以便从成矿流体角度更好地理解成矿作用过程。 相似文献
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砂岩型铀矿赋矿地层方解石胶结物C、O同位素组成对研究成矿机制具有重要的理论和实践意义。前人在成矿流体来源定性判断方面做了大量的研究工作,但缺乏对成矿混合流体的组分特征及相关参数的定量认识。根据内蒙古东胜地区东南部皂火壕和西北部纳岭沟铀矿床赋矿地层直罗组方解石胶结物C、O同位素组成特征,建立了渗出热卤水和渗入地层水两种不同流体混合生成方解石胶结物C、O同位素组成定量成因模型,并研究了两种流体来源、溶解碳的浓度比、流体比例以及热液温度等综合因素。除少数样品方解石胶结物为地层沉积时形成外,大部分方解石胶结物是热卤水与地层水两种流体混合作用的结果,古生界有机酸脱羧作用导致热卤水中富含CO2。东胜地区砂岩型铀矿成矿流体地层水与热卤水比例为0.5~0.9,地层水所占的比例较大;热卤水与地层水溶解碳浓度比主要范围为1.5~5.0,部分大于10.0,热卤水中溶解碳浓度较高,是富含CO2的流体。混合流体温度分为两个主要范围55~80℃、90~140℃,结合古盐度和盐度指数反演,表明成矿流体为有机与无机混合成因的低温热液流体。用砂岩型铀矿赋矿地层方解石胶结物C、O同位素组成,可定量模拟两种流体溶解碳浓度比、流体比例和方解石形成时温度等流体成矿条件,解释碳酸盐胶结物成因,以便从成矿流体角度更好地理解成矿作用过程。 相似文献
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