Microstructural constraints on magma emplacement and sulfide transport mechanisms

摘要: The poorly constrained nature of the physical transfer sulfides along magmatic conduits has implications for genesis and localization mineral deposits as well understanding the large-scale mobility volatiles metals across different geochemical reservoirs. Our natural laboratory to address this topic is a sulfide-bearing ultramafic pipe emplaced in deep crust the Ivrea-Verbano Zone, northwest Italy. comprises volatile-rich peridotite, that contains disseminated, blebby semi-massive enriched nickel, copper platinum-group elements. integration electron backscatter diffraction orientation data 3D X-ray computed tomography analyses from study indicate 1) most olivine crystallized upon emplacement of magma; 2) shape texture intra-granular sulfide blebs principally hosted within central portions reflect early saturation 3) marginal areas 1recorded higher strain compare cores pipes. differences size distribution of the grains between areas are due magma emplacement dynamics. larger aggregates forming bulk Ni-Cu-PGE mineralization along margins interpreted form by coalescence large number smaller sulfide droplets. observed the Valmaggia dynamics emplacement, locally record role water- carbon dioxide-bearing entrainment dense sulfide liquids. These processes provide viable mechanism transport in chalcophile siderophile upper mantle into lower continental crust, where they may be available later remobilization ore systems subsequently the middle crust.