Cunliang Zhao

Evidence of widespread wildfires in a coal seam from the middle Permian of the North China Basin

The North China Basin is the largest coal-bearing basin in China, and has an areal extent of 800,000 km 2 . We analyzed 138 coal samples and in situ pillar coal samples of the middle Permian from this basin by macropetrography, microscope, scanning electron microscope, gas chromatography, and gas chromatography–mass spectrometer in order to study wildfires. High contents of inertinite (charcoal) and natural coke particles observed in coal samples indicate that vegetation in precursor mires and peats of the middle Permian coal from north China was exposed to far-ranging wildfires. In addition, high-molecular-weight polycyclic aromatic hydrocarbons were detected in the coal samples. These aromatic compounds were formed under high temperatures and provide further evidence of wildfire. These wildfires would have discharged significant CO and CO 2 gases into the atmosphere and affected the paleoclimate and paleoecosystem.

Long-Term, Low-Temperature Simulation of Early Diagenesis of Organic Matter from Algae: Significance for Immature Oil

Algae are good sources of immature oil. A long-term (more than 5 years), low-temperature (80°C) simulation of early diagenesis of organic matter from algae was carried out. In the very early stage of the simulation, different quantities of immature oil were generated after 26 to 56 days. After one year, algae showed obvious fluorescence, and the intensity was maintained during the remainder of the simulation. From the earlier stages of the simulation to the later stages, the asphaltene fractions of the soluble extracts decreased and the polar fractions increased. Asphaltene and polar compounds play important roles in the formation of immature oil, especially under briny environments. Finally, the changes in hydrocarbons during the simulation are discussed and the algae-originated phytenes and C20 bicyclic terpanes are suggested as biomarkers for immature oil.

Occurrence of rubidium and cesium in Iqe coal, Qinghai-Tibet Plateau: Evidence from sequential chemical extraction experiment

The occurrence of Rb and Cs in coal samples from Iqe coalfield was analyzed by a sequential chemical extraction experiment. Five types of Rb and Cs were determined in the coal: water soluble, ion exchangeable, organic bonded, carbonate, and silicate. The results indicated that the occurrence of Cs is similar with Rb in coal, and nearly all Rb and Cs are distributed in silicate. The occurrence of Rb and Cs is most likely associated with silicate minerals in coal. With the high correlation between Rb, Cs, and K, and the high content of kaolinite and illite in these coal samples, it can be inferred that illite probably is the main carrier of Rb and Cs. Minor amounts of Rb and Cs may also be adsorbed by kaolinite in Iqe coal, and Cs may exist in other states, such as an exchangeable ion.