Genetic relationship between hydrocarbon system evolution and Carlin-type gold mineralization: Insights from ReOs pyrobitumen and pyrite geochronology in the Nanpanjiang Basin, South China

Ge, Xiang; Selby, David; Liu, Junjie; Chen, Youzhi; Cheng, Guofan; Shen, Chuanbo

Abstract

The spatial association of hydrocarbons with metalliferous ore deposits is found worldwide and is particularly common to Carlin-type gold systems. Both liquid oil and pyrobitumen are found in Carlin-type gold deposits of North Nevada, USA and the Nanpanjiang Basin, South China. However, the temporal and genetic association of hydrocarbons and gold mineralization are still debated. To this end, using rhenium‑osmium (Resingle bondOs) geochronology of pyrobitumen and gold-bearing pyrite from the Laizishan and Banqi reservoirs and the Yata Carlin-type gold deposit in the Nanpanjiang Basin, we consider hydrocarbons played a critical role in the mineralization process. A Resingle bondOs age of 228 ± 16 Ma obtained for highly mature pyrobitumen suggests that liquid oil cracking occurred during the Late Triassic in the Laizishan and Banqi reservoirs. This age is in agreement with the modelled thermal history of the Nanpanjiang Basin. Additionally, a broadly identical gold-bearing pyrite Resingle bondOs age of 218 ± 25 Ma from Yata Carlin-type gold deposit which is in agreement with ages reported for other Carlin-type gold deposits in the Nanpanjiang Basin (e.g., in-situ SIMS Usingle bondPb rutile = 213.6 ± 5.4 Ma, Resingle bondOs arsenopyrite = 204 ± 19 Ma - 235 ± 33 Ma and Rbsingle bondSr illite = 212.8 ± 4.6 Ma) suggests the auriferous Carlin-type systems of the Nanpanjiang Basin also formed during the Late Triassic. Integrating our Resingle bondOs data, with recent liquid hydrocarbon experimental data and fluid inclusion data from both reservoirs and gold deposits within the Nanpanjiang Basin, a methane (CH4) dominated thermochemical sulfate reduction (TSR) process, which introduced hydrogen sulfide (H2S) into basinal fluid and ultimately led to the deposition of gold-bearing pyrite by sulfidation, is considered to be the genetic link between of pyrobitumen and gold-bearing pyrite mineralization of the Carlin-type systems of the Nanpanjiang Basin.

Citation

Ge, X., Selby, D., Liu, J., Chen, Y., Cheng, G., & Shen, C. (2021). Genetic relationship between hydrocarbon system evolution and Carlin-type gold mineralization: Insights from ReOs pyrobitumen and pyrite geochronology in the Nanpanjiang Basin, South China. Chemical Geology, 559, Article 119953. https://doi.org/10.1016/j.chemgeo.2020.119953

• Journal Article Type: Article
• Acceptance Date: Oct 21, 2020
• Online Publication Date: Oct 24, 2020
• Publication Date: 2021-01
• Deposit Date: Nov 5, 2020
• Publicly Available Date: Oct 24, 2021
• Journal: Chemical Geology
• Print ISSN: 0009-2541
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 559
• Article Number: 119953
• DOI: https://doi.org/10.1016/j.chemgeo.2020.119953