Work

Illite 40 Ar / 39 Ar low‐temperature mini‐plateaux: Enlightenment on hydrocarbon accumulation

Year: 2026

Type: article

Abstract: ABSTRACT Authigenic illite samples from the Baiyun Sag of the Pearl River Mouth Basin, South China Sea, were analysed by 40 Ar/ 39 Ar laser stepwise heating. Novel techniques were applied to distinguish authigenic illite signal from detrital contamination: (1) a fine‐step heating technique was elaborately applied to gently release argon from authigenic illite at low laser power steps and avoid the argon from coarse‐grained detrital minerals and (2) a powerful purification system including a temperature‐controlled cryotrap was employed to remove most organic matter. In this study, sample BY39 yielded a well‐defined low‐temperature mini‐plateau with a mini‐plateau age of 15.0 ± 0.7 Ma (2σ, 12 consecutive steps). Sample BY53 exhibited a low‐temperature segment with a weighted mean age of 16.5 ± 0.3 Ma (2σ, 8 consecutive steps), which, despite a subtle ascending trend, aligns with the age limit of BY39. These results represent the first reported instance of authigenic illite mini‐plateaux obtained from complex mineral mixtures. The robust nature of the BY39 mini‐plateau suggests that the youngest illite generation is not a trace component but represents a significant volumetric pulse of mineral growth, providing a sufficient argon budget to sustain multiple concordant steps. This rapid illitisation might be triggered by transient fluid pulses laden with CO 2 and organic acids derived from kerogen and oil cracking. The brief acceleration instead of an immediate cessation of illite formation during hydrocarbon accumulation provides a solid foundation for dating petroleum accumulation by the authigenic illite 40 Ar/ 39 Ar fine‐step heating technique. Additionally, high‐temperature heating steps yielded detrital ages (76 to 217 Ma) that reflect the provenance contribution of Mesozoic granites from South China to the Baiyun Sag.

Source: Sedimentology

DOI: 10.1111/sed.70102

Authors: Yang Wu, Li‐Yan He, He‐Sheng Shi, Hua‐Ning Qiu

Institutions: China University of Geosciences, Vrije Universiteit Amsterdam, China National Offshore Oil Corporation (China), East China University of Technology

Language: English

Topic: Hydrocarbon exploration and reservoir analysis

Subfield: Mechanics of Materials

Field: Engineering

Domain: Physical Sciences

Open Access status: green

Funders: National Natural Science Foundation of China, China Scholarship Council, National Science and Technology Major Project, Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China

Awards: 南海海山(链)岩浆活动的时间和成因及其对南海形成演化的制约, G2088104783, G2978328928, 地时-中国Ar-Ar定年关键技术：绵阳研究堆辐照方法, G4796259056