GEOLOGY
SEDIMENTOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Calcite crystals much larger than the sediment grain size
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Quartz crystals that go into extinction with the grains they surround
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Dolomite crystals that increase in size from the edge to the centre of pore spaces
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Iron oxide crystals that form rims of uniform thickness around grains
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Detailed explanation-1: -Calcite cement is one of the most abundant and widespread authigenic phases in sandstones, especially in shallow-marine sandstones. Calcite cement consolidates sand into rock but occludes previous pore space that would have served as a reservoir for water and hydrocarbons.
Detailed explanation-2: -Common cementing minerals are calcite (CaCO3), silica (SiO2), iron oxides and clay minerals.
Detailed explanation-3: -Sandstones with Carbonate Cement 64X Most sandstones contain some kind of mineral material in the pore spaces that binds the grains together. This is called a mineral cement. Sandstones occasionally have carbonate mineral cements that cause the rock to react to HCl.
Detailed explanation-4: -Early formed calcite cement was sourced from the dissolution of biogenic marine carbonates in the modified seawaters evidenced by bulk geochemical data. • The maturation of organic matters played a significant role in the porosity improvement.