El Soldado is the largest (>200 Mt @ 1.4% Cu) of the known Cu manto-type deposits in central Chile. It is strata-bound within a submarine, bimodal calc-alkaline basalt - rhyodacite unit of the Lower Cretaceous Lo Prado Formation., which also contains marine carbonaceous shales and volcaniclastic sandstones. Although stratigraphically restricted, the clustered orebodies are mostly vein-like and discordant, controlled by a system of N-S to NNW faults fonned within a transtensional zone (cymoid loop) of a sinistral, strike-slip brittle shear system. Individual orebodies are zoned, with an external and deeper zone of barren pyrite, followed inward by concentric zones with chalcopyrite-pyrite, chalcopyrite bornite, bornite-chalcocite, and a central zone of chalcocite (± digenite ± covellite) and abundant hematite. The deposit was formed in two main phases: l)a low-temperature, diagenetic phase during which framboidal pyrite developed in association with migrated petroleum, at ca. 130 to 120 Ma; 2) a high-temperature (>300°C from fluid inclusions) hydrothennal phase at ca. 103 Ma, (coinciding with batholith emplacement), that deposited early hematite (± magnetite), followed by chalcopyrite, bornite and chalcocite, mostly replacing pre-existing pyrite, with the excess Fe forming hematite. Gangue minerals are calcite, albite, k-feldspar and chlorite. The hydrothermal Cu mineralization is associated with an increase in Na and depletion in K in host rocks, although there are localised zones of K increase in bornite-chalcocite assemblages near structures. Isotopic studies indicate that: a) the sulphur in diagenetic pyrite provided the bulk of the sulphur for Cu sulphides; b) petroleum was the source of carbon in bitumen and part of the carbonate; c) osmium in diagenetic pyrite was derived from the black shales; d) strontium in calcites was inherited from the Cretaceous arc lavas; e) oxygen isotopes in carbonates, and K-feldspar and atmospheric argon in K-feldspar plus the high salinity of fluid inclusions (21-26% NaCl equivalent) suggest a basinal connate-metamorphic brine was responsible for Cu transport, yet a (distal) magmatic component to the fluids cannot be ruled out.

The Arizaro and Lindero prospects are possibly the youngest recognised examples of the hydrothermal iron oxide-copper-gold class of deposits in the world. These two prospects, and numerous other iron-oxide manifestations, form a newly discovered district within northwest Argentina. The Arizaro and Lindero prospects are hosted within mid-Miocene, calc-alkaline, dominantly andesitic, volcanic complexes that formed within a convergent plate margin tectonic setting. This descriptive paper presents observations from surface geology and petrographic studies.

The Productora prospect is situated 15 km SSW of the town of Vallenar in the Third Region, north-central Chile. It lies within the "Chilean Iron Belt" close to the north-trending Atacama Fault system. The belt contains a variety of Fe oxide ±Cu ±Au-bearing deposits including Candelaria (366 million tonnes averaging 1.08 % Cu, 0.26 g/t Au) which is situated in the Punta del Cobre region approximately 150 km north of Productora. The age, structural setting, alteration assemblages and styles of mineralisation in the Productora area resemble those present at Candelaria, but Productora differs in its spatial association with intrusive rocks and its lack of skarn assemblages.

Located approximately 400 km south of Lima, Peru, the Marcona and Pampa de Pongo deposits are the largest iron accumulations with associated copper and gold along the western coast of South America. Approximate resources include more than 1400 Mt of iron ore at Marcona and 1000 Mt of magnetite mineralisation at Pampa de Pongo. Both deposits contain some copper and gold and exhibit numerous features that allow their inclusion in the "Iron Oxide-Copper-Gold" clan of deposits, alongside such examples asCandelaria and Mantos Blancos in Chile. The two deposits form part of a cluster of similar occurrences that together define the "Marcona Fe-Cu District".

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.

The Selwyn Line is the name adopted for an open arcuate zone of iron-copper-gold mineralisation, located ~150 km southeast of Mount Isa, in the Mount Isa Proterozoic inlier, northwest Queensland, Australia. Since the discovery of gold mineralisation in the Selwyn Hills in the 1970's, 5 small mines have been operated. These exploited high grade ironstone hosted gold-copper mineralisation, located within a zone of poly-aged shearing and complex alteration. The mines are located within the Starra Shear which has a history of ductile-brittle, brittle-ductile and brittle deformation. The structure is altered over widths of between 100 m and 500 m, and for over 10 km along strike. The alteration involved early albite +quartz +calcite +scapolite +actinolite replacement of the host sheared meta-sediments of the Staveley Formation. This was followed by a magnetite/hematite+biotite+quartz(+pyrite) overprint, and finally post tectonic oxidation of the magnetite, and chlorite-calcite alteration with associated chalcopyrite and gold mineralisation, and limited pyrite fonnation (Rotherham 1997). The high grade zones exhibit indications of strong structural controls. They typically plunge steeply to the north along magnetite bearing extensional duplex structures and shear planes which include portions of the hanging wall bounding shears and link structures to the footwall bounding shears. The dimensions of the mined and mineable resource (<8 mt) have always been regarded as small for typical Fe-Cu-Au systems. However resource work done on lower cut-off grades indicates that the system is more typical of the large systems of this sort found elsewhere in the district, with a pre-mining global resource of at least 29 mt at 2.5g/t Au and 1.4% Cu (at a 1.5% Cu Equivalent cutoff using a factor of- 0.8 depending on where the ore is from), 49 mt at 1.76 g/t Au and 1.05% Cu using a 1.0% cut off, or 95mt at 1. lg/t Au and 0.74%Cu at a 0.5% cutoff. These are embraced within a larger mineralised system with a global resource of 253 mt @ 0.48g/t Au and 0.34% Cu at measured, indicated and inferred categories, to a depth of ~300m below surface (using a 0.2% Cu Equivalent cut off).

Within the Eastern Succession of the Australian Mount Isa Inlier, Monakoff is a 1 million tonne (mt) Mesoproterozoic, oxide Cu-Au deposit only 13 km from the large (167 mt) Ernest Henry mine. The two deposits share similar geochemical signatures (Ba-Cu-Au-U-Pb-Zn-As-Sb-Co-W-Mo-Mn-F-REE), suggesting commonality of origin. This signature is far more complex than those of most other Eastern Succession Cu-Au oxide systems, but it is extremely similar to the signatures of some recently discovered large Brazilian examples, such as Alemao. Monakoff ore has a barite-carbonate-fluorite-magnetite-chalcopyrite-dominated mineralogy, and contains economic quantities of Cu, Au, Co, U and Ag; the 1-2% levels of both Pb and Zn are unusually high for oxide Cu-Au deposits. However, it lacks the distinctive K-feldspar alteration halo of Ernest Henry. It occurs on the northern south-dipping limb of the Pumpkin Gully Syncline, considered to be a regional, EW-oriented, D2 fold, bounded to the north and west by Di thrust contacts. A splay of the northern thrust hosts the main Monakoff mineralisation. Naraku Batholith elements outcrop ~2 km north of Monakoff; and ore alteration records post-ore hornfels recrystallisation.

The Olympic Cu-Au province on the eastern margin of the Gawler Craton includes three major regions of hydrothermal alteration and mineralisation: Stuart Shelf basement (including the Olympic Dam Cu-U-Au deposit), Mount Woods lnlier and the Moonta-Wallaroo-Roopena region. Each of these regions contains high-, moderate- and low-temperature Fe-oxide rich alteration, Cu-Au+U mineralisation, and felsic to mafic Mesoproterozoic (-1590 Ma) intrusions of the Hiltaba Suite with or without coeval Gawler Range Volcanics. The three regions are interpreted to represent the 'footprints' of separate crustal-scale thermal anomalies. Three key hydrothermal alteration and ore mineral assemblages are recognised in the metallogenic province: (1) CAM: calcsilicate - alkali feldspar ± magnetite ± Fe-Cu sulphides (generally minor); (2) MB: magnetite-biotite + Fe-Cu sulphides; and (3) HSCC: hematite-sericite-chlorite-carbonate ± Fe-Cu sulphides ± U, REE minerals. Ore grade Cu-U-Au mineralisation is generally associated with the HSCC assemblage, which is paragenetically later than the CAM and MB assemblages in most deposits and prospects. The crustal level of exposure of the hydrothermal systems may vary significantly between and within the three mineralised regions. The CAM, MB and HSCC assemblages and associated Cu-Au mineralisation represent a possible spectrum of settings from deeper, higher temperature, shear-hosted environments to near-surface, low-temperature breccia and fault settings.

Геологическая структура, распределение и контроль железооксидно-медно-золотой минерализации в кратоне Гоулер, Южная Австралия: Часть I - Геологическая и тектоническая структура

The Archaean to Mesoproterozoic Gawler Craton hosts a range of economic mineral commodities, including Au (central Craton), Ag-Pb-Zn (eastern Eyre Peninsula) and iron ore of the Middleback Ranges. A major iron-oxide copper-gold province containing the world class Olympic Dam Cu-U-Au-Ag-REE deposits extends ~ 500 km along the eastern margin of the Craton, from the Mount Woods Inlier in the north to the Moonta-Wallaroo district in the south. This paper presents new advances in our understanding of the structure, deformation history and tectonic evolution of the Gawler Craton, which may lead to a better understanding of the distribution of these mineral systems. The Craton is subdivided into tectonic domains, each encompassing an area of crust containing similar lithological and structural associations. New tectonic events have been defined within the three major orogenic cycles of the Gawler Craton (the Sleaford, Kimban and Kararan Orogenies). The recent discovery that much of the craton comprises relatively juvenile Proterozoic crust has improved our understanding of cratonic evolution. We propose growth through accretion in magmatic arc settings along the eastern margin of an arcuate Archaean core at ~ 1850 Ma (Donington Suite), and along the southwestern margin at ~ 1680 Ma (Tunkillia Suite) and 1620 Ma (St Peters Suite). We suggest an alternative model to a largely anorogenic setting for emplacement of the Hiltaba Suite, an intracontinental, extensional back-arc, located behind a northeast dipping subduction zone, south of the Nuyts Domain, which produced the arc-related magmatism of the St Peters Suite.

The Hiltaba Suite magmatic event was widespread across the Gawler Craton, and is broadly associated, both temporally and in places spatially with a major mineralising event. At the Olympic Dam deposit, a close spatial and temporal association is recognised between its host rock, the Roxby Downs Granite, and iron-oxide copper-gold mineralisation. Other mineral prospects related to Hiltaba Suite magmatism include Tarcoola, Tunkillia, Myall, Sheoak, Barns, and possibly Weednana, and Menninnie Dam. The presence of Hiltaba Suite granites is an important factor for exploration companies in tenement selection.

This preface presents the background to this book, the second volume of the "Hydrothermal Iron Oxide Copper-Gold & Related Deposits - A Global Perspective" series, and briefly discusses the rationale for inviting the papers it contains, their format and what it is hoped the volume will achieve. It also offers some observations on the unifying characteristics of the iron oxide copper-gold family of deposits and what they may represent in a broader context.