Geochemistry of the black rock series of lower Cambrian Qiongzhusi Formation, SW Yangtze Block, China: Reconstruction of sedimentary and tectonic environments

Abstract

The black rock series in the Qiongzhusi Formation contains important geochemical information about the early Cambrian tectonic and ecological environment of the southwestern Yangtze Block. In this paper, major, trace, and rare earth element data are presented in an attempt to reveal the sediment source during the deposition of the early Cambrian Qiongzhusi Formation and to reconstruct the sedimentary tectonic environment and weathering intensity during that time. The basin primarily received continental clastic material with neutral-acidic igneous rocks from a stable source and with a moderate level of maturity during the depositional period of the Qiongzhusi Formation. Furthermore, the strata were weakly influenced by submarine hydrothermal fluids during diagenesis. The reconstruction of the sedimentary environment and weathering intensity shows that P2O5 enrichment and water body stratification occurred due to the effects of upwelling ocean currents during the depositional period of the Qiongzhusi Formation. The combination of upwelling and bottom-water hydrothermal fluids led to environmental changes in the study area, from dry and hot to moist and warm. Last, the reconstruction of the tectonic environment of the Qiongzhusi Formation indicates that deposition occurred in continental slope and marginal marine environments associated with a continental arc tectonic system. These findings provide an essential basis for the comprehensive reconstruction of the early Cambrian sedimentary environment of the Yangtze Block.

Influence of magma intrusion on coal geochemical characteristics: a case study of Tiefa Daxing coal mine

“…Four coal samples were selected in the position that was completely unaffected by magma and the magma intrusion area, which were recorded as S 5 709 normal coal (# 1), S 5 709 metamorphic coal (# 2), S 2 905 normal coal (# 3), and S 2 905 metamorphic coal (# 4). The weight of each coal sample is 2 kg 15,20 . After the coal sample is mined, it is sealed in a sealed bag and transported to the laboratory.…”

Effect of magma intrusion on pore structure and trace element migration of anthracite

“…A total of ve coal samples of different levels were collected, among which samples M01-M04 were thermally affected coals and M05 was normal coal. After collection, these samples were sealed immediately to prevent deviation from the experimental results due to contamination and oxidation 17 . In addition, we also selected four coal samples from the S 5 709 and S 2 905 mining faces in Bi's paper (# 1 and # 3 are normal coal samples; # 2 and # 4 are thermally affected coal samples) to compare and analyse the mineral composition of normal coal and thermally affected coal in uenced by magma intrusion into the coal seams 12 .…”

Geochemistry of marine black shale of the Cambrian Qiongzhusi Formation, Yangtze Plate, SW China: implications for provenance and paleoweathering

“…The chemical weathering of source rocks can be assessed using the chemical index of alteration proposed by Nesbitt and Young [16], the chemical index of weathering which removes K 2 O to eliminate the influence of potassium metasomatism [47], and the plagioclase index of alteration which adjusts the K 2 O and Al 2 O 3 contribution from potassium feldspar and monitors the degree of plagioclase weathering that has been successfully used for the reconstruction of paleoweathering [48][49][50][51][52][53][54][55][56][57][58].…”