Topic
Petrography
About: Petrography is a research topic. Over the lifetime, 7449 publications have been published within this topic receiving 102018 citations.
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TL;DR: The diagenetic history of the Rotliegendes Sandstone reservoir in the Rough Gas Field was studied using thin-sections, XRD analyses and SEM in this article, showing that early, environmentally-related diagnesis (eogenesis) shows a marked variability with sedimentary facies.
Abstract: The diagenetic history of the Rotliegendes Sandstone reservoir in the Rough Gas Field was studied using thin-sections, XRD analyses and SEM. The Rotliegendes comprises a sequence of fine-grained fluvial sheet-flood sandstones and coarse, gravelly, low-sinuosity channel sandstones, with thin aeolian interbeds, overlain by a sequence of aeolian dune and interdune sandstones. Early, environmentally-related diagnesis (eogenesis) shows a marked variability with sedimentary facies. Within aeolian sandstones, poikilotopic anhydrite and fine, rhombic dolomite are preserved. Fluvially-derived sandstones typically contain infiltrated detrital clays and early authigenic mixed-layer clays, together with coarse, framework-displacive dolomite. Feldspars show varying degrees of alteration within all facies. These eogenetic features reflect patterns of groundwater movement during the Rotliegendes and early Zechstein. Mineral dissolution and precipitation were controlled by the chemistry of the groundwaters. Burial diagenetic (mesogenetic) features are superimposed on eogenetic cements. Authigenic clays have been converted to illitic clays. In addition, mesogenetic chlorite has formed and quartz and strongly ferroan dolomite cements are recognized. These minerals may be related to clay diagenesis within the underlying Carboniferous Coal Measures. Early, framework-supporting anyhdrite, and both phases of dolomite, have been partially dissolved, creating secondary porosity. This is attributed to the action of acidic porewaters, generated by the maturation of organic material within the Carboniferous. Post-dissolution kaolinite, gypsum and minor pyrite infill secondary pores. Gas emplacement from the Late Cretaceous onwards effectively halted further diagenetic reactions.
32 citations
01 Apr 1974
TL;DR: In this article, Hsü et al. investigated the formation and deposition of the Red Sea evaporites and found that they are of the same age as the evaporites found by deep sea drilling in the Mediterranean Sea.
Abstract: The top of the evaporite sequence correlates with a strong reflector (Reflector S) which has been mapped over much of the Red Sea (Ross et al., 1969, Phillips and Ross, 1970). This indicates that the Red Sea appears to be underlain by late Miocene evaporites throughout most of its extent. Miocene sediments, including evaporites, are known from a few outcrops along the coastal plains of the Gulf of Suez to lat 14°N (Sadek, 1959, cited in Friedman, 1972; Heybroek, 1965; Friedman, 1972). Along the length of the Red Sea, the presence of Miocene salt is indicated by seismic reflection studies (Lowell and Genik, 1972) and confirmed by drilling. The recently published data from deep exploratory wells (Ahmed, 1972) demonstrate the great thickness of elastics and evaporites which were deposited in the Red Sea depression during Miocene time. The Red Sea evaporites are of the same age as the evaporites found by deep sea drilling (DSDP Leg 13) in the Mediterranean Sea. Therefore, Reflector S in the Red Sea is comparable to Reflector M in the Mediterranean. It is assumed that during Miocene time a connection between these two basins was established (Coleman, this volume) resulting in a similar origin for the evaporites deposited in the Red Sea and in the Mediterranean Sea. The origin of the Mediterranean evaporites has been discussed in great detail (Hsü et al., 1973; Nesteroff, 1973; Friedman, 1973). The formation of evaporites may be interpreted by three different hypotheses. 1) Evaporation of a shallow restricted shelf sea or lagoon which receives inflows from the open ocean. 2) Evaporation of a deep-water basin which is separated from the open ocean by a shallow sill (Schmalz, 1969). 3) Evaporation of playas or salt lakes which are situated in desiccated deep basins isolated from the open ocean (Hsü et al., 1973). The purpose of this study is to show whether one of these models might apply to the formation and deposition of the Red Sea evaporites. Therefore, a detailed petrographic and geochemical investigation was carried out.
32 citations
TL;DR: In particular, the chemical composition of silicate-melt inclusions indicate the fractional crystallization of clinopyroxene+plagioclase±FeTi oxides as discussed by the authors.
32 citations
TL;DR: Petrographic methods have been widely applied in the coking industry especially in predicting coke strength and coke reactivity and to a lesser extent in predicting coking pressure and volume change.
32 citations
TL;DR: The Bruderheim meteorite has been examined both petrographically and chemically as mentioned in this paper, showing that it is texturally related to pyroxene, troilite, and metallic iron-nickel.
Abstract: The Bruderheim meteorite, a hypersthene chondrite, has been examined both petrographically and chemically. The minerals of the meteorite are olivine (Fo_(78)), hypersthene (En_(78)), plagioclase (Ab_(95)), apatite, merrillite, chromite, troilite, and metallic iron-nickel. Comparison of petrographic and chemical analyses shows that (1) pyroxene, troilite, and metallic iron-nickel are texturally related; (2) there is substantial CaO contained in the hypersthene; (3) there are important variations in samples the size of a thin section, and it is likely that there are also sampling errors on quantities of the size used for chemical analysis. The texture of the meteorite, including the principal chondrule types, is described.
32 citations