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DGGV-E-Publikationen

Titel: Linking Laser-Ablation ICP-MS analysis and sulfide textures in identifying gold remobilization and enrichment processes in modern seafloor massive sulfides, Kolumbo arc volcano, Greece

Autoren:
Stephanos P. Kilias1, Evangelia Zygouri1, Nikolaos Zegkinoglou1, Manuel Keith2, Thomas Zack3, Daniel J. Smith4, Paraskevi Nomikou1, Paraskevi Polymenakou5

Institutionen:
1National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, 15784 Athens, Greece; 2University of Erlangen-Nuremberg, GeoZentrum Nordbayern, 91054 Erlangen, Germany; 3University of Gothenburg, Department of Earth Sciences, SE-405 30 Gothenburg, Sweden; 4University of Leicester, School of Geography, Geology and the Environment, University Road, Leicester LE1 7RH, UK; 5Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, 71003, Heraklion, Crete, Greece

Veranstaltung: GeoKarlsruhe 2021

Datum: 2021

DOI: 10.48380/dggv-dcqa-0067

Zusammenfassung:
Target settings to secure sustainable access to raw materials include seafloor massive sulphide (SMS) resources. Gold-rich SMS deposits, are often the result of complex interplay of multiple Au enrichment events. Recent studies have shown that high-grade Au ores result from Au remobilization from preexisting mineralization, driven by fluid-induced coupled dissolution-reprecipitation (CDR) reactions; however investigations into this process in modern Au-rich SMS, are lacking. To tackle this issue, Au-rich [AuBULK≤32ppm; Au/(Cu+Zn+Pb)=1.9], polymetallic (Sb, Tl, Hg, Ag, Mo, Te) diffuser chimney samples from the active Kolumbo shallow-water SMS system, Hellenic Volcanic Arc, were geochemically and texturally examined using combined SEM-EDS imaging, and LA-ICP-MS spot analysis and trace element mapping. Recrystallized subhedral auriferous arsenian pyrite2 (≤65 ppm Au, ≤13290 ppm As) records textures, being porosity growth concurrent with the presence of native gold and accessory pore-filling Pb-Sb sulfosalts, indicating that recrystallization proceeded via fluid-mediated CDR reactions. The latter caused replacement of earlier, colloform-banded, Au-rich arsenian pyrite1 (≤130 ppm Au, ≤9057 ppm As) by pyrite2, and liberated invisible Au (nanoparticles and/or lattice-bound) and associated elements (Pb, Sb). Furthermore, textural evidence indicates that porous orpiment with Pb-Sb sulfosalt inclusions, showing extreme Au enrichment (≤861 ppm Au) compared to other SMS deposits worldwide, was formed by replacement of Au- and As-rich Pb-Sb sulfosalts (≤132 ppm Au, ≤6550 ppm As) via CDR reactions. This study provides significant evidence that in arc-related Au-rich polymetallic SMS deposits, native and invisible Au are closely associated to various sulfides/sulfosalts, and CDR reactions may contribute to upgrading Au grades during hydrothermal reworking.



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