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The source and transport regions of fluidized (transported) breccias outcrop in the Cloncurry Fe-oxide-Cu-Au district. Discordant dykes and pipes with rounded clasts of metasedimentary calc-silicate rocks and minor felsic and mafic intrusions extend several kilometres upwards and outwards from the contact aureole of the 1530 Ma Williams Batholith into overlying schists and amphibolites. We used analytical equations for particle transport to estimate clast velocities ( ‡20 m sec )1 ), approaching volcanic ejecta rates. An abrupt release of overpressured magmatic-hydrothermal fluid is suggested by the localization of the base of the breccias in intensely veined contact aureoles (at around 10 km, constrained by mineral equilibria), incorporation of juvenile magmatic clasts, the scale and discordancy of the bodies, and the wide range of pressure variation (up to 150 MPa) inferred from CO 2 fluid inclusion densities and related decrepitation textures. The abundance of clasts derived from depth, rather than from the adjacent wallrocks, suggests that the pressure in the pipes was sufficient to restrict the inwards spalling of fragments from breccia walls; that is, the breccias were explosive rather than implosive, and some may have vented to the surface. At these depths, such extreme behaviour may have been achieved by release of dissolved fluids from crystallizing magma, in combination with a strongly fractured and fluid-laden carapace, sitting under a strong, low permeability barrier. The relationship of these breccias to the Ernest Henry iron-oxide-Cu-Au deposit suggests they may have been sources of fluids or mechanical energy for ore genesis, or alternately provided permeable pathways for later ore fluids.

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The Konos Hill prospect in NE Greece represents a telescoped Mo–Cu–Re–Au porphyry occurrence overprinted by deep-level high-sulfidation mineralization. Porphyry-style mineralization is exposed in the deeper parts of the system and comprises quartz stockwork veins hosted in subvolcanic intrusions of granodioritic composition. Ore minerals include pyrite, molybdenite, chalcopyrite, and rheniite. In the upper part of the system, intense hydrothermal alteration resulted in the formation of a silicified zone and the development of various advanced argillic alteration assemblages, which are spatially related to N–S, NNW–SSE, and E–W trending faults. More distal and downwards, advanced argillic alteration gradually evolves into phyllic assemblages dominated by quartz and sericite. Zunyite, along with various amounts of quartz, alunite, aluminum phosphate–sulfate minerals (APS), diaspore, kaolinite, and minor pyrophyllite, are the main minerals in the advanced argillic alteration. Mineral-chemical analyses reveal significant variance in the SiO2, F, and Cl content of zunyite. Alunite supergroup minerals display a wide compositional range corresponding to members of the alunite, beudantite, and plumbogummite subgroups. Diaspore displays an almost stoichiometric composition. Mineralization in the lithocap consists of pyrite, enargite, tetrahedrite/tennantite, and colusite. Bulk ore analyses of mineralized samples show a relative enrichment in elements such as Se, Mo, and Bi, which supports a genetic link between the studied lithocap and the underlying Konos Hill porphyry-style mineralization. The occurrence of advanced argillic alteration assemblages along the N–S, NNW–SSE, and E–W trending faults suggests that highly acidic hydrothermal fluids were ascending into the lithocap environment. Zunyite, along with diaspore, pyrophyllite, and Sr- and Rare Earth Elements-bearing APS minerals, mark the proximity of the hypogene advanced argillic alteration zone to the porphyry environment.

A B S T R A C TThe Skouries deposit is a platinum-group element (PGE) enriched Cu-Au porphyry system located in the Chalkidiki peninsula, Greece, with associated Ag, Bi and Te enrichment. The deposit is hosted by multiple porphyritic monzonite and syenite intrusions, which originated from a magma chamber at depth. An initial quartz monzonite porphyritic intrusion contains a quartz-magnetite ± chalcopyrite-pyrite vein stockwork with intense potassic alteration. The quartz monzonite intrusion is cross cut by a set of syenite and mafic porphyry dykes and quartz-chalcopyrite-bornite ± magnetite veins which host the majority of the Cu and Au mineralisation. Late stage quartz-pyrite veins, with associated phyllic alteration crosscut all previous vein generations. Electron microprobe and scanning electron microscopy shows that the PGE are hosted by platinum-group minerals (PGM) in the quartz-chalcopyrite-bornite ± magnetite veins and within potassic alteration assemblages. The PGE mineralisation in Skouries is therefore part of the main high temperature hypogene mineralisation event. [PdBi]. The most common platinum-group mineral is sopcheite. The PGM in Skouries are small, 52 µm 2 on average, and occur as spherical grains on the boundaries between sulphides and silicates, and as inclusions within hydrothermal quartz and sulphides. These observations support a "semi-metal collector model" whereby an immiscible Bi-Te melt acts as a collector for PGE and other precious metals in high temperature hydrothermal fluids. This mechanism would allow the formation of PGM in porphyries without Pt and Pd fluid saturation.