Mobilization of Metals in Oceanic core complex (MOMO): source to sink investigation of gabbroic-ultramafic hosted VMS deposits
Final Report Abstract
Seafloor massive sulfides (SMS) deposits associated with gabbroic and ultramafic rocks in slow to ultra-slow MOR settings often located on or near oceanic core complexes (OCC). They are referred to as gabbroic-hosted or ultramafic-hosted VMS deposits and are variably enriched in precious (Au) critical (Co) and base (Cu-Ni) metals which is uncommon for classical VMS deposits. Because of their unique nature and metal endowment, the UM-VMS deposits should be considered as a stand-alone sub-group of VMS deposits, which possibly represent untapped mineral resource with high future potential. The combination of ophiolites main geological features, detachment stratigraphy and geochemistry of volcanic rocks and chromite grains allows to characterize the three main tectonic environments in which UM-VMS deposit form: MOR, OCT and SSZ. The UM-VMS formation is associated with hydrothermal fluid circulation in ultramafic rocks forming the footwall of detachment faults. They overall show similar alteration pattern, structural control, ore morphology, mineralogy and metal endowment, which allow distinguishing them from magmatic Ni-Cu-PGE and mafic-type VMS deposits. In order to locate the source of the metals enriched in gabbroic-ultramafic hosted VMS deposits the ocean drilling program (ODP) Hole 735B located on the Atlantis Bank OCC and the Limassol Forest complex in Cyprus is studied. The ODP Hole 735B recovers gabbroic rocks down to 1508 meters below seafloor (mbsf) and shows evidence for high temperature alteration zones where possible metal mobilization occurred during high temperature hydrothermal fluid circulation. Mass balance calculations from the source zones of the Atlantis Bank detachment highlights that metal mobilization during hydrothermal alteration of gabbroic rocks along detachment faults can fully account for the formation of OCC-related SMS deposits at slow and ultraslow spreading ridges. The Troodos ophiolite shows evidences for relics of OCC with seafloor-related high temperature hydrothermal alteration and associated massive sulfide mineralizations. The Limassol Forest complex is characterized by Cu-Ni-Co-As-Au mineralizations which are mostly confined to the margins of the serpentines along the Dierna shear zone. The host rocks are highly sheared, brecciated and completely serpentinized harzburgite. The largest mineralizations occur at Lakxia tou Mavrou and Pevkos, which are characterized by massive lenticular veins and disseminated sulfides and arsenides. The results of this project are the basis for our recently funded project “UltraMAfic-hosted seafloor MassIve sulfide deposits: a mineral system approach (UMAMI)“. This project will provide further publications in the field.
Publications
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Mineralization associated with gabbroic-ultramafic hosted VMS deposits from the Troodos ophiolite and ODP Hole 735B – an investigation of oceanic core complex. GeoKarlsruhe (oral)
Patten, C.G.C., Junge, M. & Peillod, A.
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Ultramafichosted volcanogenic massive sulfide deposits: an overlooked sub-class of VMS deposits forming in complex tectonic environments? GeoKarlsruhe (oral)
Patten, C.G.C., Coltat, R., Junge, M. Peillod, A. Ulrich, M., Manatschal, G. & Kolb, J.
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Ultramafichosted volcanogenic massive sulfide deposits: an overlooked sub-class of VMS deposits forming in complex tectonic environments? Goldschmidt Lyon (oral)
Patten, C.G.C., Coltat, R., Junge, M. Peillod, A. Ulrich, M., Manatschal, G. & Kolb, J.
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Ancient to Modern Marine Mineral Deposits: Metal Fluxes and Mechanisms of Formation. Mineralization associated with gabbroic-hosted VMS deposits from ODP Hole 735B. Goldschmidt Hawaii (oral)
Peillod, A., Junge, M., Coltat, R. & Patten, C.
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Ultramafic-hosted volcanogenic massive sulfide deposits: an overlooked sub-class of VMS deposit forming in complex tectonic environments. Earth-Science Reviews, 224, 103891.
Patten, C.G.C.; Coltat, R.; Junge, M.; Peillod, A.; Ulrich, M.; Manatschal, G. & Kolb, J.
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Ultramafichosted volcanogenic massive sulfide deposits: an overlooked sub-class of VMS deposits forming in complex tectonic environments? 16th SGA biennial meeting, New Zealand (oral)
Patten, C.G.C., Coltat, R., Junge, M. Peillod, A. Ulrich, M., Manatschal, G. & Kolb, J.
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Ultramafichosted volcanogenic massive sulfide deposits: an overlooked sub-class of VMS deposits? International Platinum Symposium, Cardiff (poster)
Patten, C.G.C., Coltat, R., Junge, M. Peillod, A. Ulrich, M., Manatschal, G. & Kolb, J.
