@article{Castrillón Peña_Cramer_Guerrero_2022, title={Hydrothermal organic aggregates associated with the high-Ni grades of the Cerro Matoso laterite deposit, Montelíbano, Colombia.}, volume={47}, url={https://ofioliti.it/index.php/ofioliti/article/view/687}, DOI={10.4454/ofioliti.v47i2.555}, abstractNote={<p>Mineralogical and geochemical analyses (EDS, ICP-MS, XRD) of black mudstones locally overlying the peridotites of Cerro Matoso at Pit-1 link these<br />sediments with deep-sea hydrothermal systems. In this unit, rounded particles were identified that would correspond with organic aggregates commonly found<br />in reducing environments related to hydrothermal vent systems. These aggregates are formed by methane-producing microorganism (methanogens) metabolism<br />that sustains such extreme environments mediated by anaerobic methane-consuming cell consortia. The organic aggregates register Ni content up to 8<br />wt%. For this fossilized methanogen-AOM (Anaerobic Oxidation of Methane) consortium we propose an ultramafic contribution, followed by a hydrothermal<br />enrichment of Black/White-Smoker type and a supplementary contribution of bio-mineralized Ni of the organics within the sediments during the formation<br />of the Ni-bearing deposit. The sediments configured an atypical lateritic profile at the Pit-1 where Ni-concentrations reached up to 8 wt%, in contrast to the<br />southern Pit-2 where the peridotites developed a typical lateritic profile with nickel concentrations not exceeding 4 wt%. During the Cretaceous and Cenozoic, the ultramafic rocks and associated deep-sea hydrothermal-related sediments were accreted to the South American continent. They were recently exhumed allowing supergene Ni-enrichment forming the laterite deposit known today with its locally extraordinary high Ni contents. Together with the organics, authigenic phyllosilicates and Fe-(oxy) hydroxides are the main ‘‘ore minerals” that contributed to add the lateritic Ni-enrichment after supergene leaching processes due to weathering of the Cerro Matoso peridotites.</p>}, number={2}, journal={Ofioliti}, author={Castrillón Peña, Andrés and Cramer, Thomas Heinrich and Guerrero, Javier}, year={2022}, month={Jul.} }