Distributions of selenium and related elements in high pyrite and Se-enriched rocks from Ziyang, Central China

Tian, Huan, Xie, Shuyun, Carranza, Emmanuel John M, Bao, Zhengyu, Zhang, Hai, Wu, Shitou, Wei, Changhua, and Ma, Zhenzhen (2020) Distributions of selenium and related elements in high pyrite and Se-enriched rocks from Ziyang, Central China. Journal of Geochemical Exploration, 212. 106506.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website: https://doi.org/10.1016/j.gexplo.2020.10...


Pyrite-bearing volcanic tuff and carbonaceous slates of the Lower Cambrian Lujiaping Formation have been considered the source of selenium (Se) in high-Se soils in the area of the Naore Village of the Ziyang County, China, where acute Se toxicity occurred in the 1980s. For geochemical exploration, the accumulation and distribution of Se and trace elements within the pyrite grains are of great indicative significance for understanding the possible origin and forming mechanism of the Se enrichment. In this work, 7 rock samples and 89 pyrite grains were collected and analysed to investigate the element micro-distribution within the pyrite grains using EPMA and LA-ICP-MS. The whole-rock analysis shows that the pyrite-bearing Lower Cambrian rocks in Ziyang are commonly enriched in Se, As, Mo, Cd, Cr, Ni, Sb, Cu and Ba. In situ microanalysis indicates that Se (30-1880 mu g/g) and As (160-2960 mu g/g) concentrations within the pyrite grains are 1-2 orders of magnitude higher than those in the host rocks (Se: 0.56-73.1 mu g/g, As: 2.56-195 mu g/g) and that the Se contents are negatively correlated with pyrite mineral sizes. Grain-scale element mappings of fresh Se-enriched pyrites reveal two types of Se and As distribution patterns (type-I: high-Se 120-1870 mu g/g and low-As < 150-1580 mu g/g cores, type-II: low-Se 60-680 mu g/g and low-As < 150-1310 mu g/g cores) with alternating Se or As contents during the growth of zoned pyrite. The texture of pyrite element zoning reflects multi-stage hydrothermal pulses with changing trace element concentrations. Type-II pyrite formed later than type-I pyrite. Genetic analysis confirms that Se-enriched strata were strongly affected by hydrothermal submarine deposition and that Se in pyrite was mainly derived from hydrothermal fluids. Secondary hydrothermal erosion led to the formation of high-Se "fractures" (Se content 19.3 wt%). In summary, utilizing pyrite as an indicator for the Lower Cambrian Lujiaping Formation Se-bearing strata extends our understanding of selenium geochemical processes and highlights the mechanistic aspects of Se.

Item ID: 62901
Item Type: Article (Research - C1)
ISSN: 0375-6742
Keywords: Se-enriched pyrite, Element zoning, Hydrothermal fluid, Lower Cambrian
Copyright Information: © 2020 Elsevier B.V. All rights reserved.
Funders: National Key Research and Development Program of China (NKRDP), Natural Science Foundation of Hubei Province (NSF), Fundamental Research Funds for the Central Universities (FRFCU), China University of Geosciences (CUG), China Geological Survey Program (CGSP), Science and Technology Agency of Shaanxi Province (STASP), China Geological Sciences Institute of Geophysical Geochemical Exploration (IGGE)
Projects and Grants: NKRDP Grant 2016YFC0600501, NSF Hubei Province 2019CFB235, CUG Grant G1323519320, CUG Grant CUG170104, CGSP Grant 12120113087100, CGSP Grant DD20160095-13, STASP Grant 2016FP3-11, STASP Grant 2017TSCXL-NY-02-01, IGGE No.WHS201302
Date Deposited: 22 Apr 2020 07:34
FoR Codes: 37 EARTH SCIENCES > 3703 Geochemistry > 370301 Exploration geochemistry @ 100%
Downloads: Total: 1
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page