Small but mighty: microorganisms offer inspiration for mine remediation and waste stabilisation

Abstract

Understanding the natural microbiological mechanisms that promote iron cycling in iron ore mine environments may provide novel tools for the remediation of the fragile, iron-rich duricrust ecosystems associated with these environments as well as provide a solution for the stabilisation of hillslopes and tailings (waste) dams. A diverse array of microfossils is frequently identified throughout metrescale duricrusts (canga; >50 wt.% Fe) that cap iron ore deposits in Brazil, shedding light on the intimate role of microorganisms in the evolution of these crusts. Nanoscale secondary ion mass spectrometry revealed that carbon and nitrogen biosignatures are occasionally preserved, and typically associated with the cell envelope structures of microfossils. The microfossils are 1-5 mm in length, with filamentous and rod-shaped morphologies commonly preserved1,2. When examined using backscatter electron scanning electron microscopy, canga shows a complex microstructure from repeated dissolution and re-precipitation of iron oxide minerals. Geochronology3, geochemistry4 and microbiology5 provide insights into the past and present-day role of microorganisms in the evolution of canga. These dynamic biogeochemical processes in canga contribute to the continuous formation of new iron cements, preserving some of world's longest-lived continuously exposed surfaces. Harnessing and accelerating the biogeochemical cycling of iron may contribute to the development of novel technologies for mine remediation and waste stabilisation.