Mineralogical and geochemical characteristics of tonsteins from the Middle Jurassic Yan'an Formation, Ordos Basin, North China

Reconstruction of provenance and tectonic setting of the Middle Jurrasic Yan'an Formation (Ordos Basin, North China) by analysis of major, trace and rare earth elements in the coals

“…The source area of clastic deposits of the Yan'an Formation in the northern and eastern parts of the Ordos Basin has thus been investigated, suggesting that the source rocks of the clastic deposits of the Yan'an Formation there were Archean and Early Proterozoic granites and granite-gneisses in the Yinshan Mountains, Lvliang Mountains, and in an area around Alxa in the north of the Ordos Basin (Huang E, F, and G: Bhatia andCrook (1986). et al, 2009;Lei et al, 2017;Zhang et al, 2022). This finding seems also applicable to the study area, as indicated by a comparison of the REE in the silty mudstones with the study by Huang et al (2009) (Fig.…”

“…On the other hand, distinctly negative Eu anomalies (Fig. 5A, C, E) may have been caused by interference with tonsteins derived from airborne pyroclastics from alkali rhyolites (Zhang et al, 2021(Zhang et al, , 2022, (Taylor and Mclennan, 1985). volcanogenic hydrothermal solutions, or felsic or felsic/intermediate continental material (Dai et al, 2016).…”

Geochronology, Mineralogy, and Geochemistry of the Tonsteins from the Permo–Carboniferous Benxi Formation, Ordos Basin, North China Craton

“…Many altered volcanic ashes (tonstein) have been observed in coal seams (Dai et al, 2017 and references therein;Zhang et al, 2022), occurring mainly as thin but laterally persistent layers (Bohor and Triplehorn, 1993;Dai et al, 2011Dai et al, , 2017Spears, 2012;Spears and Arbuzov, 2019). These tonsteins are significant for global chronostratigraphic calibration and correlation.…”

“…These tonsteins are significant for global chronostratigraphic calibration and correlation. As some primary minerals that survived weathering and postdepositional alteration in tonsteins (such as zircon, sanidine, and monazite) can be used for the determination of radiometric age to identify and correlate coal seams (Lyons et al, 2006;Guerra-Sommer et al, 2008a, b;Wainman et al, 2015;Zhang et al, 2022). The significance of geochemistry and mineralogy of tonsteins can provide useful information to infer regional volcanism events in geology history, the nature of source magmas, depositional conditions of peat accumulation, the subsequent diagenetic processes after coal formation, and regional tectonic evolution of coal-bearing sequences (Dai et al, 2017;Hower et al, 2018Hower et al, , 2022.…”

“…The leaching by groundwaters/ hydrothermal solutions elements from tonsteins into the peat. Thus the underlying or overlying coal benches may enrich some critical elements and then form ore deposits (Crowley et al, 1989;Hower et al, 1999Hower et al, , 2018Dai et al, 2003Dai et al, , 2017Zhang et al, 2022). In addition, tonsteins can affect the quality of mined coals by elevating the mineral matter content (Seredin and Finkelman, 2008;Dai et al, 2012aDai et al, , b, 2017Seredin and Dai, 2012;Hower et al, 2015).…”