吐鲁番坳陷中——上侏罗统碎屑岩中的自生粘土矿物特征及其成岩意义   总被引：14，自引：1，他引：13  

刘林玉  柳益群 《岩石学报》1998,14(2):258-268

利用岩石薄片和扫描电镜观察以及Ｘ－衍射资料研究了吐鲁番坳陷中上侏罗统碎屑岩中的自生粘土矿物特征,发现碎屑岩中的自生粘土矿物主要有五种类型,即蒙脱石、伊利石－蒙脱石混层、伊利石、绿泥石和高岭石。自生粘土矿物的形成和转化取决于碎屑岩原始矿物组分及其成岩环境。蒙脱石的迅速转化和高岭石的大量析出与碎屑岩的大规模溶解有着密切的关系。根据自生粘土矿物的组合特征,可以有效地确定碎屑岩的成岩阶段及其孔隙发育特征。  相似文献   

Experimental studies on the possible influences of composition changes of pore water on the stability conditions of methane hydrate in marine sediments   总被引：4，自引：1，他引：4  

Hailong Lu  Ryo Matsumoto 《Marine Chemistry》2005,93(2-4):149-157

Experiments with a set of electrolyte solutions have been carried out to investigate the effects of pore water composition changes on the stability conditions of methane hydrate in marine sediments. The results reveal that (1) SO₄²⁻ and Cl⁻ concentration changes can affect hydrate stability slightly, (2) the changes in both the type and the concentration of cations, which occur in normal diagenetic processes, do not exert a significant influence on the methane hydrate stability conditions, and (3) the shift of hydrate stability in pore water can be expressed as a function of the Cl⁻ concentration only. Based on the results above, an empirical equation ΔT (K)=0.00206 Cl⁻ (mmol/dm³) has been obtained for estimating the shift in the equilibrium temperature of methane hydrate in pore water at a given pressure.  相似文献   

Diagenetic effects on the well yield of dolomite aquifers in Slovenia     

Timotej Verbovšek 《Environmental Geology》2008,53(6):1173-1182

Diagenetic effects upon the hydraulic parameters of dolomite aquifers were examined. Results indicate that dolomites affected only by late (burial) diagenesis are economically more interesting to exploit than those formed first by early and then also affected by late diagenesis, as the values of most studied hydraulic parameters (transmissivity, specific capacity, linearized specific capacity and maximum yields) are higher in the former group. Data were collected from the hydrogeological reports of 298 wells in dolomites from Permian to Cretaceous age in Slovenia, classified in a relational hydrogeological database and analyzed by statistical methods. The studied parameters are hydraulic conductivity K, transmissivity T, specific capacity q (=Q/s), linearized specific capacity Ql (=q/d) and maximum yields Q _max. Values of the studied parameters are distributed log-normally according to most normality tests and span several orders of magnitude. Statistical tests show significant differences between the “late” and “early + late” groups for parameters q, Ql and T, and non-significant differences for K and Q _max.  相似文献   

The ammonite fauna and genesis of a mid-Cretaceous siliceous oolite from the Alagoas Basin, Brazil     

Peter Bengtson  Ulf Nordlund 《Cretaceous Research》1987,8(4)

Acanthoceratid ammonites from near Maceió, in the State of Alagoas, provide evidence of a mid-Cretaceous marine incursion into the present onshore part of the Alagoas Basin. The ammonites Pseudocalycoceras sp. cf. P. harpax (Stoliczka, 1864) and Kamerunoceras sp. are assigned a late Cenomanian age. The rock is a siliceous oolite that occurs as derived nodules and fragments in late Cenozoic continental sediments. It is interpreted as an originally calcareous oolite formed in a near-shore, high-energy environment. Absence of primary cement suggests that silicification took place early in diagenesis. The silicified, and therefore more resistant material from the original Cenomanian sequence was reworked and redeposited with the Cenozoic sediments. The age, indicated by the ammonites, suggests that the original deposition was related to the global late Cenomanian—early Turonian sea-level rise.  相似文献   

磷块岩中的硅质组分和硅质岩   总被引：2，自引：0，他引：2  

刘魁梧  韩安平 《岩石学报》1990,6(1):46-55,T002

磷块岩中存在着大量硅质组分和硅质层。硅质矿物以自生石英、硅质条带、燧石结核、硅质胶结物和硅质交代物的形式产出。硅质胶结物有四种结构形式,在剖面和平面上与其它成分胶结物有一定的演变关系。硅化作用有众多的宏观和微观形态,硅化结果使P_2O_5含量大大下降。盆地型磷块岩硅化作用的硅源可能来自海底火山活动,台地型磷块岩硅化作用的硅源主要与陆源水的混合有关。  相似文献   

Diagenesis of Upper Carboniferous rocks in the Ouachita foreland shelf in mid-continent USA: an overview of widespread effects of a Variscan-equivalent orogeny     

A. W. Walton  K. M. Wojcik  R. H. Goldstein  C. E. Barker 《International Journal of Earth Sciences》1995,84(3):535-551

Diagenesis of Upper Carboniferous foreland shelf rocks in southeastern Kansas took place at temperatures as high as 100–150° C at a depth of less than 2 km. High temperatures are the result of the long distance (hundreds of kilometers) advection of groundwater related to collisional orogeny in the Ouachita tectonic belt to the south. Orogenic activity in the Ouachita area was broadly Late Carboniferous, equivalent to the Variscan activity of Europe. Mississippi Valley-type Pb-Zn deposits and oil and gas fields in the US midcontinent and elsewhere are commonly attributed to regional groundwater flow resulting from such collisional events. This paper describes the diagenesis and thermal effects in sandstone and limestone of Upper Carboniferous siliciclastic and limestone-shale cyclothems, the purported confining layer of a supposed regional aquifer. Diagenesis took place in early, intermediate, and late stages. Many intermediate and late stage events in the sandstones have equivalents in the limestones, suggesting that the causes were regional. The sandstone paragenesis includes siderite cement (early stage), quartz overgrowths (intermediate stage), dissolution of feldspar and carbonates, followed by minor Fe calcite, pore-filling kaolinite and sub-poikilotopic Ca ankerite (late stage). The limestone paragenesis includes calcite cement (early stage); megaquartz, chalcedony, and Fe calcite spar (intermediate stage); and dissolution, Ca-Fe dolomite and kaolinite (late stage). The R _m value of vitrinite shows a regional average of 0.6–0.7%; Rock-Eval T _maX suggests a comparable degree of organic maturity. The T _h of aqueous fluid inclusions in late stage Ca-Fe-Mg carbonates ranges from 90 to 160° and T _mice indicates very saline water (>200000 ppm NaCl equivalent); ¹⁸O suggests that the water is of basinal origin. Local warm spots have higher R _m, T _max, and T _h. The results constrain numerical models of regional fluid migration, which is widely viewed as an artesian flow from recharge areas in the Ouachita belt across the foreland basin onto the foreland shelf area. Such models must account for heating effects that extend at least 500 km from the orogenic front and affect both supposed aquifer beds and the overlying supposed confining layer. Warm spots indicate either more rapid or more prolonged flow locally. T _h and T _mice data show the highest temperatures coincided with high salinity fluids.  相似文献   

Hydrogeochemical characterization of oilfield waters from southeast Maracaibo Basin (Venezuela): Diagenetic effects on chemical and isotopic composition     

《Marine and Petroleum Geology》2016

  相似文献   

Controls on reservoir quality of Lower Cretaceous tight sandstones in the Laiyang Sag,Jiaolai Basin,Eastern China: Integrated sedimentologic,diagenetic and microfracturing data     

《Marine and Petroleum Geology》2016

The Jiaolai Basin (Fig. 1) is an under-explored rift basin that has produced minor oil from Lower Cretaceous lacustrine deltaic sandstones. The reservoir quality is highly heterogeneous and is an important exploratory unknown in the basin. This study investigates how reservoir porosity and permeability vary with diagenetic minerals and burial history, particularly the effects of fracturing on the diagenesis and reservoir deliverability. The Laiyang sandstones are tight reservoirs with low porosity and permeability (Φ < 10% and K < 1 mD). Spatial variations in detrital supply and burial history significantly affected the diagenetic alterations during burial. In the western Laiyang Sag, the rocks are primarily feldspathic litharenites that underwent progressive burial, and thus, the primary porosity was partially to completely eliminated as a result of significant mechanical compaction of ductile grains. In contrast, in the eastern Laiyang Sag, the rocks are lithic arkoses that were uplifted to the surface and extensively eroded, which resulted in less porosity reduction by compaction. The tectonic uplift could promote leaching by meteoric water and the dissolution of remaining feldspars and calcite cement. Relatively high-quality reservoirs are preferentially developed in distributary channel and mouth-bar sandstones with chlorite rims on detrital quartz grains, which are also the locations of aqueous fluid flow that produced secondary porosity. The fold-related fractures are primarily developed in the silt–sandstones of Longwangzhuang and Shuinan members in the eastern Laiyang Sag. Quartz is the most prevalent fracture filling mineral in the Laiyang sandstones, and most of the small-aperture fractures are completely sealed, whereas the large-aperture fractures in a given set may be only partially sealed. The greatest fracture density is in the silt–sandstones containing more brittle minerals such as calcite and quartz cement. The wide apertures are crucial to preservation of the fracture porosity, and the great variation in the distribution of fracture-filling cements presents an opportunity for targeting fractures that contribute to fluid flow.  相似文献   

四川西部罗江构造须家河组四段储层特征与成岩作用     

罗锋 《华南地质与矿产》2006,(1):47-53

通过普通薄片、铸体薄片、压汞曲线以及孔隙度和渗透率资料的分析,对四川盆地西部罗江构造三叠系须家河组四段储层的岩石学特征、成岩作用类型等进行了研究.结果表明,孔隙的形成和演化受成岩作用的控制.主要的成岩作用有压实作用、胶结作用、压溶作用和溶解作用.压实作用、胶结作用不利于孔隙的演化,而溶解作用产生的次生孔隙,有利于天然气在储层中聚集成藏,形成较好的储层.  相似文献   

Tomographic study of Paleoproterozoic carbonates as key to understanding the formation of molar-tooth structure     

Darrel G.F. Long   《Gondwana Research》2007,12(4):566-570

X-ray computed tomographic studies of relatively pure Paleoproterozoic limestones from the George Formation, Muskwa Assemblage, northern British Columbia, Canada indicate that molar-tooth structures developed along linked fractures in gel-like semi-plastic carbonate mud, with a high organic content. Where pore fluid and/or gas pressures matched confining loads, MT blobs developed. Where pressure exceeded loads, cracks propagated into adjacent semi-elastic sediment and were rapidly filled by clusters of uniform, equant, microcrystalline carbonate. Where abundant carbonate was not precipitated, incipient cracks and sheets collapsed leaving residual trains of microcrystalline carbonate with similar density to the molar-tooth carbonate. Tomographic studies show that the density of calcite domains within petrographically uniform sheets of MT void-filling calcite is uneven, suggesting that precipitation was not instantaneous, but was propagated from discrete centres.

It is here suggested that carbonate production and sediment rheology were both strongly influenced by organic matter. During early sea-floor diagenesis microcrystalline carbonate precipitated within organic-rich sediment with high water content, possibly within decomposing mats of microbial extracellular polymeric substances (EPS). When pore pressures in the host sediment increased in response to cyclic loading by long-period waves, pore fluids containing EPS were injected into newly created fractures, allowing rapid precipitation of molar-tooth carbonate. Because tomographic studies allow detailed resolution of minor density differences, they provide a useful method of evaluating structures in relatively uniform carbonate rocks of any age.  相似文献