夏日哈木超大型Ni-Co矿床不同矿石结构的成因意义探讨OA

The Xiarihamu Ni-Co deposit in the East Kunlun Orogenic Belt is the largest magmatic sulfide deposit dis-covered in an orogenic setting,with mineralization hosted mainly in orthopyroxenite and harzburgite.However,the sulfide-silicate textures developed in these two lithologies are markedly different.In this study,we use micro-beam XRF mapping and 3D X-ray computed tomography of drill core samples to quantify the geometry of sul-fide in contrasting ore textures and to investigate sulfide transport and deposition mechanism within magma plumbing systems.Our results show that in harzburgite,sulfide melt is able to percolate downward through the pores of olivine.Sulfide percolation displaces intercumulus silicate melt and produces net textures.When sulfide percolation confines silicate melt into progressively smaller,enclosed pockets,capillary resistance increases geo-metrically and further percolation is arrested,producing the observed patchy net-texture.By contrast,weak wet-ting of orthopyroxene by sulfide inhibit displacement of intercumulus silicate melt in orthopyroxenite,leading to disseminated ore textures.Moreover,orthopyroxenite contains several semi-massive sulfide horizons that are poorly connected to one another.The presence of sulfide matrix with silicate inclusions cannot be simply attribut-ed to post accumulation percolative aggregation of sulfide droplets;rather,we infer that sulfide melt were re-en-trained in conduit flow,underwent only partial fragmentation during transport,and were deposited as the ob-served massive bodies.Consequently,orthopyroxenite commonly contains both disseminated sulfide droplets and sulfide matrix,and overall sulfide connectivity within orthopyroxenite is low.The Xiarihamu deposit formed in a dynamic conduit system.Multiple injections of ultramafic magma propagated from West to East along a long-lived conduit system.Dense sulfide melt ponded in hydraulic traps along channel floors,producing massive sul-fide accumulations.Subsequent magma pulses re-entrained the sulfide accumulations and transported them short distances;in widened,low velocity conduit segments sulfide liquid and silicate melt co-deposited as semi-mas-sive bodies in the central part of the intrusion.These observations demonstrate that gravity driven percolation and the wetting relationships between cumulus phases and sulfide melt exert dominant control on ore texture develop-ment,and they provide new constraints on the mechanisms of sulfide enrichment and on exploration models for magmatic conduit deposits.