Sedimentary environment of organic-rich shale in the Upper Permian Longtan Formation in Qinglong area, western Guizhou, China

Chen, Rong; Yuan, Kun; Zhang, Zi-ya; Xu, Qiufeng

doi:10.31035/cg2018086

“…Samples with low B/Ga and S/TOC ratios occur in a lithologic change interval from mud‐dominant to more sandy character and were deposited in an overall estuary‐to‐delta transitional environment (Figure 2). A comparable lithological change has also been revealed for the fluvial dominated late Permian successions in western South China (D. Chen, 1997). It would require an enhancement in fluvial transportation and sediment supply.…”

Section: A Rainfall Driven Reduction In Coastal Paleosalinity Of West...supporting

confidence: 64%

Enhanced Denudation of the Emeishan Large Igneous Province and Precipitation Forcing in the Late Permian

Yang,

Cawood,

Yuan

et al. 2023

JGR Solid Earth

0

View full text Add to dashboard Cite

Hydroclimate is an important factor controlling landscape evolution. But establishing the impact of hydroclimate is complicated by the influences of other processes and is especially hard to prove for those in deep time from geological record. During the late Permian, voluminous basaltic sediments were derived from the erosion of the Emeishan large igneous province in western South China. They provide a unique record critical in understanding the responses of tropical basaltic erosion to hydroclimate change without impacts of orogenic uplift, lithologic variation, vegetational difference and glacial‐interglacial change. Sampled successions define a negative carbon isotope excursion capable of making regional and global stratigraphic correlations in the middle Wuchiapingian interval corresponding to the final phase of the late Paleozoic ice age. This interval is associated with a petrofacies shift and a decreasing source weathering intensity, a downward shift of erosion loci, and a reduced coastal water paleosalinity. Applying present‐day temperature dependence pattern of basaltic weathering and using land surface temperatures approximated from nearby paleo‐seawaters, denudation rates were calculated for the Emeishan basaltic province and shows an increase from ∼71 to ∼107 m/Ma. This erosional acceleration is temporally correlated with a decrease in paleosalinity and likely linked to enhanced freshwater discharge in the middle Wuchiapingian. Scaling and landscape erosion modeling suggest ∼80%–130% increase in catchment precipitation could have driven this acceleration in denudation. Our work provides a positive test for the hydroclimate forcing on landscape erosion in deep time and underlines the mechanistic linkage of sediments with erosion and climate change.

show abstract

“… 37 The Longtan Formation is the major coal-bearing stratum in the Wenjiaba Mine, even in SW China, with a thickness of 300 m and 30 coal seams ( Figure 1 b). It was deposited in an alternate marine–continental environment, 38 and the lithologic associations are sandstone, silt, mudstone, and coal. Coal seams were numbered from top to bottom of the Longtan Formation, and coal seams C6, C7, C16, C23, C27, and C30 are the main minable coal seams in the Wenjiaba Mine; however, C6 coal is the main working bed at present, with a thickness of 2.5 m.…”

Section: Geological Settingsmentioning

confidence: 99%

Geochemical and Mineralogical Characteristics of the Li–Sr-Enriched Coal in the Wenjiaba Mine, Guizhou, SW China

Du

¹

,

Ning

²

,

Qiao

³

et al. 2021

View full text Add to dashboard Cite

This paper reports the mineralogical and geochemical compositions of C6 coal in the Late Permian Longtan Formation of the Wenjiaba Mine, Northern Guizhou in southwest (SW) China. The geochemical and mineralogical studies are the basis for the potential recovery of critical metals. The Longtan Formation, which is one of the major coal-bearing strata in SW China, contains dozens of coal seams. C6 coal is the main mineable coal seam in the Wenjiaba Mine and the whole coalfield. Proximate and ultimate analyses, inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF) spectrometry on trace and major element concentrations, and X-ray diffraction and SEM-EDS analyses were carried out. Results suggest that this anthracite coal is characterized by low ash yield and medium sulfur content. The minerals are mainly composed of clay minerals (kaolinite, chlorite, illite, and mixed-layer illite/smectite), pyrite, and carbonates. Lithium is significantly enriched in C6 coal, with an average of 124 μg/g, and it has a higher concentration in the lower portion of the coal seam than that in the upper one. Strontium is significantly enriched in samples WJB-05 and WJB-06, with concentrations of 3030 and 4580 μg/g, respectively, but it is normal or just slightly enriched in other benches of C6 coal. Additionally, Cu, Nb, and Ta are slightly enriched in the coal. Lithium, dominantly hosted by kaolinite in C6 coals, has a recovery potential. Celestine is one of the major Sr-bearing minerals in C6 coal.

show abstract

“…The regional structure is characterized by NNE-trending and NE-trending folds and faults. The study area is intersected by the Hezhang-Zunyi NE-trending fault to the north and surrounded by the Nayong fault to the southeast [19,20]. Since the formation of the continent in the Middle Permian, the crust has been exposed and eroded.…”

Section: Geological Conditions For Shale Developmentmentioning

confidence: 99%

“…The alternating sedimentary facies combinations, including lagoon facies, tidal-control delta facies, tidal-flat facies, and peat swamp facies, were developed during the Longtan Period [21]. The shale has a small single layer thickness but large cumulative thickness, containing multiple interlayers and coal seams [20,22]. The lithology is dominated by black carbon shale, silty mudstone, sandstone, siltstone, marlite, and coal (Figure 1).…”

Section: Geological Conditions For Shale Developmentmentioning

confidence: 99%

Fractal Characteristics of Pores in the Longtan Shales of Guizhou, Southwest China

Huang

¹

,

Zhang

²

,

Zhang

³

et al. 2020

View full text Add to dashboard Cite

The pore structure of marine-continental transitional shales from the Longtan Formation in Guizhou, China, was investigated using fractal dimensions calculated by the FHH (Frenkel-Halsey-Hill) model based on low-temperature N2 adsorption data. Results show that the overall D 1 (fractal dimension under low relative pressure, P / P 0 ≤ 0.5 ) and D 2 (fractal dimension under high relative pressure, P / P 0 > 0.5 ) values of Longtan shales were relatively large, with average values of 2.7426 and 2.7838, respectively, indicating a strong adsorption and storage capacity and complex pore structure. The correlation analysis of fractal dimensions with specific surface area, average pore size, and maximum gas absorption volume indicates that D 1 can comprehensively characterize the adsorption and storage capacity of shales, while D 2 can effectively characterize the pore structure complexity. Further correlation among pore fractal dimension, shale organic geochemical parameters, and mineral composition parameters shows that there is a significant positive correlation between fractal dimensions and organic matter abundance as well as a complex correlation between fractal dimension and organic matter maturity. Fractal dimensions increase with an increase in clay mineral content and pyrite content but decrease with an increase in quartz content. Considering the actual geological evaluation and shale gas exploitation characteristics, a lower limit for D 1 and upper limit for D 2 should be set as evaluation criteria for favorable reservoirs. Combined with the shale gas-bearing property test results of Longtan shales in Guizhou, the favorable reservoir evaluation criteria are set as D 1 ≥ 2.60 and D 2 ≤ 2.85 . When D 1 is less than 2.60, the storage capacity of the shales is insufficient. When D 2 is greater than 2.85, the shale pore structure is too complicated, resulting in poor permeability and difficult exploitation.

show abstract

Sedimentary environment of organic-rich shale in the Upper Permian Longtan Formation in Qinglong area, western Guizhou, China

Cited by 7 publications

References 0 publications

Enhanced Denudation of the Emeishan Large Igneous Province and Precipitation Forcing in the Late Permian

Enhanced Denudation of the Emeishan Large Igneous Province and Precipitation Forcing in the Late Permian

Geochemical and Mineralogical Characteristics of the Li–Sr-Enriched Coal in the Wenjiaba Mine, Guizhou, SW China

Fractal Characteristics of Pores in the Longtan Shales of Guizhou, Southwest China

Contact Info

Product

Resources

About