Comparative study on geochemical characterization of the Carboniferousaluminous argillites from the Huainan Coal Basin, China

Aluminous argillites were widely deposited in the Taiyuan Formation at the Huainan Coalfield at the southeast margin of the North China Plate. However, knowledge about their formation conditions and geochemical characterizations is not presently known. We recovered underground aluminous argillites at depths of 485-610 m from a borehole in the Zhangji Coal Mine and characterized their geochemical parameters, including major and trace elements, by X-ray fluorescence, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry. The provenance, climatic conditions during the weathering process of parent rocks, weathering extent, and depositional environments of Huainan aluminous argillites were investigated. Results show that Huainan aluminous argillites are depleted in alkalis and alkaline earth elements and enriched in Al, Fe, and Ti. The ratios of immobile trace elements such as Nb/Ta and Zr/Hf are similar in all the argillite samples. The NASC-normalized rare earth element (REE) patterns of the argillites show an enrichment of heavy REEs and depletion of light REEs, with positive Ce and negative Eu anomalies. The provenance analysis indicates that the studied aluminous argillites probably derived from the common parent rocks composed of felsic to intermediate igneous rocks. These argillites were presumably deposited under anoxic environments.</p

Influence of magmatic intrusions on organic nitrogen in coal: A case studyfrom the Zhuji mine, the Huainan coalfield, China

Although the influence of magmatic intrusions on coal has been studied extensively at many locations, data on changes of organic nitrogen forms in coal in response to this kind of geological instantaneous heating is still scarce. To fill this information gap, a total of five coal samples, including four coal samples collected along a coal transect approaching a magmatic intrusion and one unaltered coal sample, were collected from the No. 3 coal seam of the Zhuji mine in the Huainan coalfield, China and were analyzed for organic nitrogen forms using X-ray photoelectron spectroscopy (XPS), together with the determination of coal quality parameters and elemental composition. Due to the effect of magmatic intrusion, ash yield and carbon content of the coals increase, whereas moisture, volatile matter, oxygen, nitrogen and total sulfur decrease. The N-5 peak is dominant in unaltered and moderately altered coals, but disappears entirely in the coals adjacent to the magmatic intrusion due to the strong thermal influence. The N-Q peak mainly represents &ldquo;protonated&rdquo; quaternary nitrogen in unaltered and moderately altered coals. The N-Q peak can be transformed to the N-6 peak through the deprotonation of &ldquo;protonated&rdquo; quaternary nitrogen resulting from the loss of oxygen groups under the thermal influence of the magmatic intrusion. Closer to the magmatic intrusion, the N-Q peak is assigned to &ldquo;graphitic&rdquo; quaternary nitrogen, which increases sharply and becomes the predominant form eventually. Magmatic intrusion is responsible for the conversion of less stable nitrogen forms to more stable forms in coal