Topic
Petrography
About: Petrography is a research topic. Over the lifetime, 7449 publications have been published within this topic receiving 102018 citations.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this article, the degradation of concrete pavements is attributed to the development of the alkali-silica reaction (ASR), involving the strained quartz, and the aggregate deleterious constituents are mainly glassy vulcanites and volcanic glass, generally altered to argillaceous minerals, with undulatory extinction.
43 citations
••
TL;DR: Petrographic studies of subsurface cores of the Fountain Formation (Pennsylvanian) in the Denver region, Colorado, show that detrital grains of potassium feldspar have been pervasively and complexly albitized during burial diagenesis as discussed by the authors.
Abstract: Petrographic studies of subsurface cores of the Fountain Formation (Pennsylvanian) in the Denver region, Colorado, show that detrital grains of potassium feldspar have been pervasively and complexly albitized during burial diagenesis. In some strata, all detrital grains of potassium feldspar have been convened to albite. In some instances, the conversion has taken place directly; in others it has involved prior replacement of the potassium feldspar by other minerals, particularly anhydrite, calcite, and dolomite, which in turn are replaced by albite. The albitized grains display fabrics such as perthitic intergrowths and chessboard twinning that are strikingly similar to replacement fabrics produced in feldspars by igneous and metamorphic processes. If successive stages of the convers on to albite were not preserved, the diagenetically albitized grains might easily be interpreted erroneously as detrital grains of plagioclase, perthite, or antiperthite derived from igneous or metamorphic source rocks. The sodium required for the albitization is presumed to have been derived from intraformational sources, particularly from diagenetically altered detrital grains of sodium-rich plagioclase, which have been extensively replaced by sodium-free clay minerals. Ions released in the course of the albitization have provided important intrastratal sources of potassium, aluminum, and silicon, which have been reprecipitated locally in authigenic minerals, particularly albite, illitic clays, and adularia.
43 citations
••
TL;DR: In this paper, mineralogical, petrographic and geochemical analyses were performed to investigate the sandstone composition and texture, pore system, and diagenetic minerals of Upper Triassic sandstones in the Central Sichuan Basin, Southwest China.
Abstract: Mineralogical, petrographic, and geochemical analyses were performed to investigate the sandstone composition and texture, pore system, and diagenetic minerals of Upper Triassic sandstones in the Central Sichuan Basin, Southwest China The results show that authigenic quartz, clay minerals, and carbonates are the main pore-filling constituents The pore systems consist of intergranular porosity, secondary porosity, microporosity, and microfractures Loss of depositional porosity is greater due to compaction than to cementation Eodiagenesis includes mechanical compaction, precipitation of early calcite cements, kaolinite, and smectite, and leaching of feldspars by meteoric water Mesodiagenesis consists of compaction, framework grain dissolution, and subsequent precipitation of illite, quartz, and late carbonate cements Six lithofacies were identified on the basis of petrographic analyses, namely, (a) argillaceous sandstones; (b) poorly sorted sandstones; (c) quartz-cemented sandstones; (d) carbonate-cemented sandstones; (e) clay-mineral-cemented sandstones, and (f) clean sandstones with abundant secondary porosity The best reservoir-quality rocks have high percentages of detrital quartz but low percentages of matrix, quartz, and carbonate cement Differences in textural and compositional attributes of various lithofacies significantly affect porosity-depth trends The diagenetic evolution pathways and reservoir-quality prediction models of various lithofacies are reconstructed by integrated petrographic data This work provides insights into describing the different lithofacies by petrographic analysis and helps to investigate how detrital composition and texture influence the diagenesis and reservoir quality evolution in tight gas sandstones
43 citations
••
TL;DR: Scanning electron microscopy reveals that carbonate grains in sublittoral sediments in the North Sea have surfaces with a microscopic etch relief, caused by dissolution of calcium carbonate, taking place at the shallow sea floor.
Abstract: Scanning electron microscopy reveals that carbonate grains in sublittoral sediments in the North Sea have surfaces with a microscopic etch relief. In structurally complex skeletal grains, the relief grades into marginal corrosion zones. The etch patterns are caused by dissolution of calcium carbonate, taking place at the shallow sea floor. Carbonate phases affected are calcite, aragonite, and a spectrum of magnesian calcites.
43 citations
••
TL;DR: The early Proterozoic Chelmsford Formation, a coarse-grained turbidite unit in the Sudbury Basin, was deposited near the margin of the Superior Province craton at about the time of Penokean orogenesis as discussed by the authors.
Abstract: The early Proterozoic Chelmsford Formation, a coarse-grained turbidite unit in the Sudbury Basin, was deposited near the margin of the Superior Province craton at about the time of Penokean orogenesis. Petrography, geochemistry, and Nd and Pb isotopes are consistent with derivation of the Chelmsford Formation from late Archean Superior Province rocks. The framework mineralogy of medium sandstones is dominated by quartz, plagioclase, and minor K-feldspar, consistent with derivation from plutonic rocks. The abundance of matrix (up to 40%), however, allows additional sources. The behavior of Al2O3 relative to Na2O, CaO, and K2O constrains the source to have had, on average, a minor weathering history. Slightly elevated SiO2 and low Z , relative to average plutonic rocks, suggest that there was no more than a minor recycled sedimentary component in the source. High abundances and sympathetic variations in ferromagnesians indicate a mafic component. REE and whole-rock Nd and Pb isotopes constrain the Chelmsford Formation to have been derived from late Archean, LREE,-enriched rocks without significant Eu anomalies, and allow neither a significant component of Penokean mantle-derived material nor early Archean crust. Pb isotopes in feldspar populations require a Superior Province source. Although the age, location, and facies of the Chelmsford Formation are consistent with deposition in response to early Proterozoic active margin processes, the integrated provenance data require the sediment source to have been dominated by relatively fresh Superior Province rocks associated with basement uplift.
43 citations