Formation mechanism of framboidal pyrite and its theory inversion of paleo-redox conditions

This paper is the result of mineral exploration engineering.

Objective Framboidal pyrite are widespread in modern sediments and sedimentary rocks, widely considered organic or inorganic genesis. Although both formation mechanisms have theoretical and experimental support, a formation mechanism with general significance has not yet been established well.

Methods This paper systematically and comprehensively studies the formation mechanism of framboidal pyrite, the application of redox conditions, and the influence of later environmental changes.

Results The size and texture of pyrite framboids and the sulfur isotopes between framboids have fluctuated with the oxygen level. Therefore, framboidal pyrite is used as a reconstruct paleoenvironment proxy commonly. Although the microcrystallines of framboidal pyrite are correlated to the particle size positively, their (Morphological evolution sequence), growth patterns, (aggregation factors), as well as the relationship with paleo-redox are still poorly understood. The redox condition inverse from particle sizes of pyrite framboids and chromium reduction-determined sulfur isotope has certain limitations. Therefore, a comprehensive analysis of redox indicators is expected, which requiring further studies on links between in-situ sulfur isotope and particle sizes of framboidal pyrite. Although the framboidal surface chemistry can be modified as changes in late oxidation conditions, the size distribution of framboidal pyrite is still meaningful as a redox indicator.

Conclusions In brief, experimental simulations, theoretical systems, and interdisciplinary studies on framboidal pyrite are still challenging and require further research.