Research paperGeneration and evolution of diamondoids in source rock

- Diamondoids in source rock are generated in maturity range of 0.8-1.7% EasyRo.
- Extract is the dominant contributor of diamondoids in source rock.
- Diamondoid indices can be used to evaluate the maturity of highly mature source rock.

Thermal maturation-related variations in the abundance and distribution of diamondoids in source rocks were investigated by thermal simulation experiments on extracts and kerogen obtained from a same marine shale, and by quantitative analysis of diamondoids within pyrolysates using highly sensitive and selective gas chromatography-triple quadrupole mass spectrometry (GC-MS-MS). The results indicate that diamondoids within the marine shale are generated mainly during 0.8%-1.7% EasyRo, generally deriving from extractable organic matter within source rocks, and are destroyed after 1.7% EasyRo to be entirely removed by ca. 3.0% EasyRo. Ternary plots of the relative distribution of diamondoids and bivariate diagrams for diamondoid parameters (e.g., DMA/MD vs. DMAI-1, and DMA/MD vs. TMAI-1) show systematic changes in diamondoids with increasing thermal maturity (expressed as EasyRo).