A granodiorite stock intrudes complexly folded and thrust-faulted Paleozoic sedimentary rocks in the Osgood Mountains of eastern Humboldt County, Nevada. Within the metamorphic aureole surrounding the pluton, the sedimentary rocks are converted to cordierite hornfels and marble; tungsten-bearing tactites developed along the contacts of the granodiorite. Cutting the granodiorite and sedimentary rocks is the Getchell fault, along which the disseminated gold ore bodies of the Getchell mine are localized. K-Ar ages of the granodiorite, andesite porphyry, tungsten-bearing tactites, and altered granodiorite from the Getchell mine indicate that emplacement, alteration, and mineralization are all part of a magmatic-thermal episode which took place approximately 90 m.y. ago.

Newly-recognised porphyry-style mineralisation within the Ertsberg intrusion displays significant differences from porphyry mineralisation at the Grasberg porphyry Cu-Au deposit. Stockwork mineralisation in the Ertsberg occurs near the giant East Ertsberg Skarn System, close to the northern margin of the intrusion. Stockwork mineralisation in the diorite is spatially associated with 5-15 m wide, E-striking, dykes of porphyritic hornblende monzonite that cut equigranular Ertsberg diorite. The porphyry dykes strike parallel to major district structures and occur where those structures project into the Ertsberg intrusion. Hornblende abundance greater than biotite, the much greater content of sphene, a paucity of broken phenocrysts, and the aplitic groundmass distinguish the porphyry dykes in the Ertsberg Stockwork Zone from the finer-grained groundmass Kali dykes of the Grasberg deposit.

Ordovician volcanic, volcaniclastic and intrusive rocks of calc-alkaline affinity in the Eastern Subprovince of the Lachlan Orogen were formed in the intraoceanic Macquarie Volcanic Arc. The Macquarie Arc was developed in response to west-dipping subduction along part of the boundary between eastern Gondwana and the proto-Pacific Plate and was situated on the Gondwana Plate, some 1000 km east of Precambrian continental crust. The intervening area was occupied by a back arc basin that developed on oceanic crust as the proto-PacificPlate rolled back eastwards after the Middle Cambrian Delamerian Orogeny. Subsequent extension, strike-slip translation and thin-skinned tectonics have structurally dissected the single arc into four north to NNE trending structural belts of Ordovician calc-alkaline rocks that are separated largely by younger rift basins and in part by coeval craton-derived turbidites.

The Wernecke and Southern Ogilvie Mountains in Yukon are part of an almost east-west trending range in the northern Canadian Cordillera in which several areas of the Palaeo-Mesoproterozoic basement are exposed, enveloped by a Phanerozoic miogeoclinal sequence. The oldest division, the -1.8-1.4 Ga Wernecke Supergroup, is interpreted as a "clastic rift'". It is an up to 15 km thick pile, the bulk of which is a monotonous, well-bedded siltite-quartz rich litharenite-argillite, topped by carbonate-pelite units. Less than 1% of the area consists of small gabbro to diorite intrusions of several, mostly Palaeoproterozoic and Mesoproterozoic, generations. The predominantly brittle deformation regime produced extensive tracts of disrupted and dismembered units grading to tectonic (not subduction !) melange. These have been overprinted by large scale Na, Ca, Mg, Fe, C02 and lesser Si, K metasomatism to produce widespread albitisation, chloritisation, carbonatisation, hematitisation and less extensive sericitisation (with local biotite) of the fractured sedimentary » magmatic rocks as well as tectonic fragmentites. The "Wernecke Breccia" is a metasomatised disaggregated breccia series and it is associated with hundreds of small scattered showings of specular hematite, magnetite and chalcopyrite, several occurrences of U and Co minerals, and anomalous gold. Not even a marginally economic orebody has so far been discovered despite intermittent exploration going back to the 1960s. It appears that we are dealing with a moderately deep (closely above the ductile-brittle interface) level of regional release and displacement of metals from source rocks (Fe, Cu and Co from gabbros; U perhaps from carbonaceous argillites) by metasomatic destruction of the carrier minerals. However, the system lacked sufficient plumbing and the channelling required to produce better metal accumulations at higher levels.

Эпигенетическое месторождение Серра Пелада Au-PGE, залегающее в отложениях, и его потенциальная генетическая связь с железооксидно-медно-золотой минерализацией в минеральной провинции Карахас, Амазонский кратон, Бразилия

The Serra Pelada Au-PGE deposit is located within the Carajas Mineral Province of the southeastern Amazon Craton, Brazil. Gold-PGE ores are epigenetic and display a strong structural control, being hosted in sub-greenschist facies carbonaceous and calcareous meta-siltstone, within the hinge zone of a reclined, tight, regional-scale F2 synform. Although the entire orebody has undergone deep tropical weathering, some evidence of the original hydrothermal alteration is preserved. Gold-PGE mineralisation is associated with the formation of magnetite- and hematite-rich hydrothermal breccias, massive zones of hematite metasomatism, intense sericite (white mica)-kaolin metasomatism, siderite veining and a jasperoid envelope of amorphous silica alteration hosting rare disseminated pyrite. All other Au-PGE ore-related mineral assemblages have undergone intense weathering to hydrated Fe-oxides and secondary clay minerals, preventing further description of primary ore and alteration features. The geochemistry of the primary Au-PGE ores at Serra Pelada displays many similarities to that of Fe-oxide Cu-Au deposits within the Carajas Mineral Province, and indeed world-wide, in terms of metal association (eg. Co, Ni, Cu, U), LREE enrichment and accompanying Fe-metasomatism. The Au-Pd-Pt association also suggests ore metal transport in acid, oxidising, chloride-rich fluids, similar to those for Fe-oxide Cu-Au deposits. In combination with these similarities, and the location of the Serra Pelada Au-Pd-Pt deposit, it is suggested that the latter represents a distal equivalent to the Fe-oxide Cu-Au deposits and, as such, a target that may have been overlooked during exploration programs around such terrains globally.

Within Peru, Fe oxide-Cu-Au deposits are found mainly in the Western Andes range and on the coast, associated with the Jurassic-Cretaceous alkaline to calc-alkaline volcanism of the aborted ensialic Canete-Huarmey Marginal Basin. They also exist in the calc-alkaline plutons of the Coastal Batholith and theTholeiite Patap Super-unit, associated with continental margin processes. The exception is Cobriza (100 million tonnes' @ 1.5% Cu, Fe oxide-Cu-Au type; Cu calcic distal skarn) existing in the eastern range associated with Permian Tardihercynian distensive tectonics and alkaline granites.

Porphyry-style Cu-Au/Mo deposits are among the most sought after targets for both base and precious metal exploration in the world today. Of particular interest are the "super porphyry" copper and or gold deposits, because of their size, grade and ability to support large scale, long life, profitable operations.

The term "super porphyry" is interpreted loosely in this publication, relating in general to the largest deposits in any established porphyry province. For a discussion of the accepted terminology and size classification of large porphyry-style deposits, see the introduction section of Richards, (2005) in this publication.