I know hydroylisis effects the weathering of Granite but what temperaures do you need to make it occur.
Granite is made up of the following minerals: Quartz, Feldspar, (Potassium feldspar and Plagioclase Feldspar), Biotite Mica and other minor constituents.
Potassium Feldspar a.k.a. K-spar, microcline, orthoclase, potash-feldspar (K,Na)AlSi3O8 a potassium aluminum silicate
In granites, potassium feldspar comes in two slightly different forms, Orthoclase Feldspar and Microcline Feldspar. K-spar is typically pink to red or white. K-spar color is generally the principal influence on the color of granite. Plagioclase Feldspar CaAl2Si2O8 to NaAlSi3O8 In granites, plagioclase feldspar is typically white to light gray. However, it can be dark gray (especially in the center of a grain) or light green.
Biotite Mica K(Fe,Mg)3 AlSi3O10 (OH)2 a hydrous potassium iron magnesium aluminum silicate In granites, the dark (mafic) mineral is typically one or more of the following; biotite, hornblende, or pyroxene. In the granite image at which you were looking, biotite appears to be the dark mineral present. Biotite in granites is typically black or brown, and has a flakey texture that is distincitve. Quartz SiO2 crystalline form of silicon dioxide Quartz is the crystalline form of SiO2 that is prevalent at the earth's surface. In granites, quartz can be clear, or white, or yellowish, or light gray, or in some special instances, light blue (generally only 1 color per granite). Quartz typically has a greasy luster that makes it easy to identify. Chemical Weathering of Granite:
Some minerals weather really slowly (like quartz ). This is a function of the mineral's chemical stability. The mineral in Granite that is the most soluble is K-feldspar. So the rate of K-feldspar solubility will determine the rate of solubility for granite. The rate of solubility is related to the ability of the solvent ( water ) to attract the Cations in the rock. Water has some free Hydrogen atoms so it will attract cations in granite, and the solubility will be related to the most prominent reaction, and that is the solution of Feldspar to form Kaolinite. The rate will be higher in more acidic water since it has a greater number of free positively charged Hydrogen atoms, and the reaction will be faster.
Feldspar +Carbonic Acid +Water Kaolinite +Silica +Potassium + Bicarbonate 2 KAlSI3O8 +2 H2CO3+H2O=Al2Si2O5[OH]4+4 SiO2+2 K++ 2 HCO3- Solution Chemical Weathering of Marble: The Process involves Dissolving of Marble by weak acids over a long period of time Stronger acids obviously dissolve rocks faster Don't usually occur in nature Organic acids Generally weak but very common in nature Carbonic acid most common H2O + CO2 --> H2CO3 CO2 is produced by the decay of organic material Combines with groundwater to make carbonic acid And directly from the atmosphere Combines with rain water ALL RAIN WATER is actually acid rain!!! Carbonic acid may be weak but it is real hard on calcium carbonate Limestone, dolomite, marble CaCO3 + H2CO3 --> Ca+2 + 2HCO3-1 Ions are removed by percolating solutions Can completely dissolve large amounts of limestone and Marble. Stronger acids can be produced by the byproducts of burning fossil fuels: Sulfuric acid (H2O + SO2 --> H2SO4).
Source: http://www.graniteandmarbleinfo.com