Calcite precipitation Sandstone

The mineral phases calcite, dolomite, halite, and gypsum for the Cretaceous limestone, as well as albite, quartz, anorthite, K-mica for the sandstone, and the gaseous phase C02 have to be defined. Furthermore it is assumed that dolomite, gypsum, and halite only dissolve, while calcite precipitates and C02 degasses. Under those conditions and with an uncertainty of 4%, two models are obtained (Table 47). 

Chemical evidence supports the petrographic observation that calcite in sandstones precipitates... 

Milliken K. L., McBride E. E., Cavazza W., Cibin U., Fontana D., Picard M. D., and Zuffa G. (1998) Geochemical history of calcite precipitation in Tertiary sandstones. Northern Apennines, Italy. In Carbonate Cementation in Sandstones. Distribution Patterns and Geochemical Evolution (ed. S. Morad). International Association of Sedimentologists, Oxford, vol. 26, pp. 213-240. 

There are at least three genetic types of calcite present in the studied sandstones, but not all of them are differentiated by texture or stable isotopic composition. The presence of deep-burial, late calcites precipitated from evolved pore waters is likely, but these cements are restricted to specific intervals. 

There seems to be no obvious systematic difference in the amount or type of calcite cementation in sandstones that have been buried to depths of 4-5 km and temperatures of more than 150°C versus otherwise unconsolidated sandstones that have not been deeper than 1.5 km and that have not been subjected to temperatures of more than around 70°C (Plate 9 Table 1). This suggests that most calcite cementation is probably complete at shallow to moderate burial depths and at relatively low temperatures, although examples of later calcite precipitation that postdates initial quartz cementation have been documented (e.g. Saigal Bjor-lykke, 1987 Walderhaug, 1990 Taylor Soule, 1993). The oxygen isotopic compositions of calcite... 

Few fluid inclusion data have been published for calcite cement in shallow marine sandstones, and homogenization temperatures in calcite may possibly be reset (Barker Goldstein, 1990). However, the measurements reported by Saigal Bjorlykke (1987) are in the range 56-68 C and thus compatible with calcite precipitation prior to deep burial. Finally, the high intergranular volumes found in many calcite-cemented sandstone samples (Table 1) also indicate relatively early calcite precipitation. 

Geochemical history of calcite precipitation in Tertiary sandstones, northern Apennines, Italy... 

Two hypotheses have been put forward to explain the origin of calcite concretions in the Namorado Sandstone (i) growth was essentially controlled by local sources of carbonate and early bacterial processes, with the initial calcite precipitating either at... 

Sedimentary rocks with the highest arsenic concentrations largely consist of materials that readily sorb or contain arsenic, such as organic matter, iron (oxy)(hydr)oxides, clay minerals, and sulfide compounds. Arsenian pyrite and arsenic-sorbing organic matter are especially common in coals and shales. Ironstones and iron formations are mainly composed of hematite and other iron (oxy)(hydr)oxides that readily sorb or coprecipitate arsenic. Iron compounds also occur as cements in some sandstones. Although almost any type of sedimentary rock could contain arsenic-rich minerals precipitated by subsurface fluids (Section 3.6.4), many sandstones and carbonates consist almost entirely of minerals that by themselves retain very little arsenic namely, quartz in sandstones and dolomite and calcite in limestones. 

Very simply, a sandstone has a grain composition of stone detritus (quartz, feldspar, detritic mica/clays) and a binder that may be clayey, quartzitic, or carbonatic (or mixtures thereof) [51, 55]. The mineral composition of limestone is mostly calcium carbonate, often derived fi om precipitated calcium carbonate and fossil shell remnants fi-om marine organisms and a calcitic binder matrix [51, 56, 57]. 

At shallow depths carbonate cements may cause sands to become brittle and hard. Carbonate which precipitates on the sea floor may also form hard grounds in dominantly clastic sequences. Sandstones may become calcite cemented due to dissolution of biogenic aragonite at relatively shallow depth (less than a few hundred meters). Calcareous sediments flushed by meteoric water at shallow depth or exposed during regression may become rapidly ce-... 

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