Raúl Merinero Palomares

A Mathematical Algorithm to Simulate the Growth and Transformation of Framboidal Pyrite: Characterization of the Biogenic Influence in Their Size Distributions

We developed and implemented a mathematical algorithm to model the growth of sedimentary framboidal pyrite simulating diverse natural mechanisms. The algorithm starts with growth in open system, based in the Proportional Effect Law, and finishes with growth in closed system at constant volume, following processes of dissolution, interstitial spaces infilling and framboidal and prismatic overgrowth. The algorithm was implemented varying more than 30 variables including: (1) an initial framboid diameter to simulate aggregation over pre-existing spherical surfaces and then the likely induction of the spherical morphology by microorganisms, (2) the decrease of microcrystal size from core to rim simulating the fall of supersaturation when growth advances, (3) packing coefficient to reproduce the inclusion of organic matter and other small substances inside framboids. Results obtained show that: (1) the microcrystal aggregation over spherical surfaces influences significantly the shape of the framboidal size distribution generating narrow populations in the sense of small size variation; (2) this effect can be masked by the decrease of the microcrystal size when supersaturation falls and by the decrease of the packing coefficient by particles trapped in framboidal structure. The main conclusion of this study is that mathematical computer simulation of the growth of framboidal pyrite allows the easy generation of large framboid populations with size distribution similar to that observed in nature, simulating the biogenic influence in the acquisition of the spherical morphology, the main question remained in the theory of framboidal pyrite formation.