0000000000548439
AUTHOR
Andrea Somogyi
Distribution, redox state and (bio)geochemical implications of arsenic in present day microbialites of Laguna Brava, Salar de Atacama
Understanding how microorganisms adapted to the high arsenic concentration present on early Earth requires understanding of the processes involved in the arsenic biogeochemical cycle operating in living microbial mats. To this end, we investigated a living microbial mat from Laguna Brava (Salar de Atacama, Chile), a hypersaline lake with high arsenic concentration, using an array of conventional geochemical techniques, such as X-ray diffraction, SEM-EDX and Confocal Laser Scanning Microscopy (CLSM), combined with state-of-the-art high resolution scanning imaging techniques, including X-ray micro-fluorescence (μXRF) and X-ray Absorption Near Edge Structure (XANES) mapping. This experimental …
Detection of a Ca-rich lithology in the Earth's deep (>300 km) convecting mantle
Earth's deep convecting upper mantle is believed to represent a rather homogenous geochemical reservoir of spinel or garnet lherzolite with primitive major element and moderately depleted trace element composition. Only where subduction occurs is this homogeneity disrupted by a suite of rocks ranging from eclogites/garnet pyroxenites (former oceanic crust) to residual harzburgites. In addition to these well documented peridotitic and metabasaltic rocks we have now discovered the presence of a chemically distinct reservoir in the deep convecting upper mantle. In situ structural analyses (micro X-ray diffraction and micro Raman spectroscopy) and three-dimensional trace element mapping (confoc…
Geochemical evidence for arsenic cycling in living microbialites of a High Altitude Andean Lake (Laguna Diamante, Argentina)
Arsenic is best known as an environmental toxin, but this element could also serve as a metabolic energy source to certain microorganisms. Moreover, As cycling may have driven microbial life on early Earth prior to oxygenation of the atmosphere. Still, little is known about the arsenic cycling processes occurring in the presence of microorganisms and the possible traces that could be preserved in the rock record. To advance our understanding of this we studied the geochemical proxies of microbial As metabolism in living microbialites from Laguna Diamante, a likely Precambrian ecosystem analogue (Catamarca, Argentina). In this study, we show that the coexistence of As(III) and As(V) strongly…