Abstract
This paper presents the mineralogical and geochemical compositions of coal benches and non-coal (carbonaceous rock benches, parting, roof and floor) samples from the No. 1 Coal in the Longtan Formation of the Permian-Lopingian epoch from the Shugentian Coalfield, eastern Yunnan Province, southwestern China. The coal is rich in Nb, Ta, Zr, and Hf, which were derived from the Kangdian Upland with the dominant compositions of the Emeishan basalt. The minerals identified in the samples include mixed-layer illite-smectite, kaolinite, quartz, siderite, and minor calcite, pyrite, anatase and ankerite. Albite and chamosite occur in the roof and floor samples. The parting sample (SGT1-2p) is characterized by abundant siderite (64.9%) and calcite (20.1%), and one carbonaceous rock sample SGT1-11 contained a large amount of pyrite (26.1%). Four factors were responsible for the geochemical and mineralogical compositions in the samples; namely, the terrigenous detrital materials transported from the Kangdian Upland, direct volcanic ash inputs, multi-stage inputs of hydrothermal fluids, and marine influences. The co-existence of siderite and pyrite was attributed to a continental-marine transitional environment.
Highlights
The mineralogical and geochemical compositions of coal seams are influenced by many factors and geological processes that may have taken place over several periods [1,2,3,4,5,6,7]
A number of studies have investigated the mineralogical and geochemical compositions of Lopingian coals and coal-bearing strata in southwestern China [12,13,14,15,16,17,18,19,20], which are dominantly controlled by Emeishan Large Igneous Province (ELIP) [21], as well as associated intense and frequent active volcanism [22,23,24,25] and related hydrothermal processes [10,26,27,28,29,30,31,32]
The total sulfur content of the coal benches was below 1%, and the coal could be classified as a low-sulfur coal [64].The carbonaceous rock benches had ash yields ranging from 54.9% to 72.0% (64.5% on average, on air dry basis), volatile matter from 30.3% to 67.50% (44.4% on average, on air dry basis), and total sulfur content from 0.42%
Summary
The mineralogical and geochemical compositions of coal seams are influenced by many factors and geological processes that may have taken place over several periods [1,2,3,4,5,6,7]. A number of studies have investigated the mineralogical and geochemical compositions of Lopingian coals and coal-bearing strata in southwestern China [12,13,14,15,16,17,18,19,20], which are dominantly controlled by Emeishan Large Igneous Province (ELIP) [21], as well as associated intense and frequent active volcanism [22,23,24,25] and related hydrothermal processes [10,26,27,28,29,30,31,32]. After the uplift of the Emeishan mantle plume, a large-scale basalt erupted and overflowed, and formed the Kangdian Upland in the middle of ELIP [42], which is the dominant sediment-source region for the Lopingian coal-bearing strata in eastern Yunnan, western Guizhou, and southern Sichuan provinces (Figure 1) [21,23,47,48,49]
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