The Geochemistry Of The Coals At P/T Boundary In Xuanwei, Yunnan And Its Paleoenvironmental Significance

The maceral composition, minerals and element geochemistry characteristics ofLate Permian C1coal in the Yantang mine of Xuanwei lung cancer area, Yunnan arestudied employing sedimentology, coal petrology, mineralogy, geochemistry of isotopeand element. The C1coal forming period were determined by SHRIMP U-Pb dating forpartings and negative excursion of δ13Corgin the C1coal. The results indicate that the C1coal formed close to the Permian-Triassic (P/T) Boundary with the ages of252.0±2.3Ma and252.3±2.1Ma. Furthmore, negative excursion of δ13Corgupward insub-coal seam B1affirmed that the C1coal formed close to the PTB. The inertinitecomponent of the coal increases upwards, coinciding with a globally recognized trendof increasing inertinite during the Carboniferous and Permian periods. Both abundant ofquartz and enriched trace elements signature show that the C1coal from the YantangMine has a unique geochemistry different from other coals in the same or differentsedimentary environment or different horizons. Two layers of parting in C1coal areidentified as tonsteins by typical minerals and enriched elements near the P/T boundary.The C1coal have been influenced by volcanic activity across Permian-Triassic transition,according to the above mentioned geochemistry analysis. Abundant quartz and enrichedtrace elements in the C1coals may be associated with PTB events.