Why should we use organic geochemistry in studying mineral deposits ?

Rock-Eval pyrolysis is a fundamental and popular organic geochemical method commonly employed by petroleum geologists to determine the quality, kerogen type (i.e. oilor gasprone) and thermal maturity of a potential source rock for hydrocarbons. The process can be simply described as the thermal decomposition of organic matter by heating in the absence of oxygen. A sample (usually up to 150 mg, depending on the organic matter content) is put into an oven and heated to 300°C in an inert atmosphere. Detectors collect hydrocarbons and carbon dioxide, which are recorded as peaks on a graph. The first peak, S1, records the volume of free hydrocarbons present in the sample before the analysis. The sample is then gradually heated to 550°C at 25°C/min, which leads to thermal decomposition (cracking) of the kerogen and produces hydrocarbons recorded as the S2 peak. CO2 generated from cracking of the kerogen is recorded as the S3 peak and is only trapped and collected at temperatures of up to 400°C, due to the potential for CO2 generation from the burning of any carbonate present within the sample at higher temperatures. Residual organic carbon is also measured by combusting the sample in the presence of oxygen and recording generated CO2 as the S4 peak. The measured peaks are used to estimate TOC (Total Organic Carbon, unit weight %), HI (“Hydrogen Index” S2∙100 TOC , unit mg hydrocarbons per gram TOC), OI