Super porphyry copper and gold deposits. Volume 1

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.

These two volumes have been designed to provide an overview of the distribution, tectonic, geologic and metallogenic setting, and the characteristics of the world's largest porphyry-style Cu-Au/Mo deposits and the 'provinces' or 'belts' in which they occur. Most of the larger deposits covered contain in excess of 5 Mt, up to more than 75 Mt of Cu (or more than 750 t of Au). The result is a collection of 25 new papers, occupying 550 pages, that include overview papers on the occurrence of large porphyry systems, as well as descriptions of individual porphyry orebodies, districts that contain clusters of porphyry deposits and porphyry 'belts' or 'provinces' that embrace strings of such deposits. This has involved detail of some deposits that many would not rate as "super porphyries", but which provide an insight into the setting of "super porphyries" and the evolution of the provinces that contain such deposits.

Up to the 1960's there was an acceptance by many that porphyry copper deposits were restricted to late Cretaceous to early Tertiary porphyritic textured "granitic" intrusive associations that were localised in the U.S. "South-west", and in northern Chile and southern Peru, and were Cu-Mo orebodies (Gilmour, et. al., 1995). Since then however, it has been realised that porphyry-style deposits were formed throughout the geologic record and on all continents. Substantial deposits are found in the Proterozoic e.g., Haib in Namibia, southern Africa; and the 'porphyry affinity' quartz-vein network at Malanjkand in India; through the Palaeozoic, e.g., the Ordovician Bozshakol deposit in Kazakhstan (see Seltmann and Porter, in this publication); the Ordovician Cadia deposits in Australia (see Porter and Glen, in this publication); the Devonian Oyu Tolgoi system in southern Mongolia (see Seltmann and Porter, in this publication); the Late Carboniferous Almalyk deposit in Uzbekistan (see Golovanov et al., in this publication);

through the Mesozoic, e.g., the Jurassic Dexing deposit in south-eastern China (see Rui et al, in this publication); during the Cretaceous and the Tertiary, e.g., many of the deposits in western North America in Mexico, the U.S. and Canada (see Phillips et al; McMillan; Cook and Porter; -all in this publication) and in Chile, Argentina and Peru in South America (see Camus; Stern and Skewes; Brown; Skewes et al; Porter; Faunes et al.; Masterman et al.; and Lipten and Smith; - all in this publication) to giant deposits in very young rocks, e.g., the Pliocene Grasberg system in Papua, Indonesia (see Paterson and Cloos, in this publication) and the similar aged Tampakan deposit in the Philippines (see Rohrlach and Loucks, also in this puiblication). This list emphasises the wide geographic and temporal spread of significant porphyry-style deposits.

The papers in these two volumes have all been invited, based on the editor's research and design, to provide the global perspective the title promises. They cover a comprehensive and representative selection of the most important deposits throughout the geologic time scale (except the Proterozoic) and the main porphyry belts of the world, and concentrate on descriptive detail. The authors were selected for their expertise and reputation pertinent to the subject of the paper they have been asked to prepare. The background and credentials of the principal authors to contribute, as well as 'corresponding author' contacts are listed in a 'Biography' section at the end of each volume. All papers have been carefully reviewed by the editor, an experienced geologist who has visited and studied most of the deposits included in the two volumes. Selected contributions were also submitted for external review, particularly those in which the editor is an author or co-author.

The papers have been grouped by volume and geographic region, namely those relating to South America (the Andean belt) and North America (the 'cordilleran' deposits) are in volume 1; while those within Australasia (deposits within and on the margins of the current Australian Plate) and Eurasia (the Southeast Asian Archipelago, the Tethyan Orogenic Belt and the deposits of central Eurasia) are in volume 2. A general grouping for non-geographic specific contributions, is included in volume 1. Within this framework, papers are arranged by progressive geographic location order along individual belts, while where more than one belt is found within the same region, papers from each belt are grouped consecutively. Specifically, within the Eurasia section, the first two chapters (Rohrlach and Loucks; and Rui et al.) relate to deposits on the westernmargin of the Pacific Plate, while the next three (Hou et al.; Zarisvandi et al.; and Armstrong et al.) cover three representative segments spanning the length of the Tethyan (or Alpine-Himalayan) Orogenic Belt in the Himalayas of Tibet, in Iran, and the Balkans of south-eastern Europe respectively. The focus of the final three papers is the vast belt of Palaeozoic to Mesozoic deposits that stretches across central Eurasia from the Urals to the Pacific coast (Seltmann and Porter; Golovanov etal.; and Gerel and Munkhtsengel).

All units are metric, using standard international abbreviations. Mass is expressed in grams (g), kilograms (kg), tonnes (t), thousands of tonnes (Kt), millions of tonnes (Mt) and billions of tonnes (Gt). Similarly, length (width, depth or diameter) is expressed in microns (j^m), millimetres (mm), metres (m) and kilometres (km). Absolute ages are recorded as millions of years (Ma) or billions of years (Ga) before the present, while age ranges are in millions of years (M.y. or m.y.) or thousands of years (K.y.). Grades are in percent (%) or grams per tonne (g/t). Gold contents are in tonnes (t). For those accustomed to ounces, 1 Moz = 31.10348 tonnes.

Spelling has been standardised in all papers to 'Commonwealth English' as applied in Australia, where the volumes are published, and as used (with some variations) in the majority of English speaking countries. This usage includes 'metres', 'kilometres', 'sulphide', 'mineralisation', 'mineralised', 'colour', 'grey', Archaean, and 'Palaeozoic'.

Content

1. Cumulative Factors in the Generation of Giant Calc-Alkaline Porphyry Cu Deposits (Jeremy P. Richards)
2. Thermal History Analysis of Selected Chilean, Indonesian and Iranian Porphyry Cu-Mo-Au Deposits (Brent I.A. Mclnnes, Noreen J. Evans, Frank Q. Fu, Steve Garwin, Elena Belousova,  W.L. Griffin, Alfredo Bertens, Djadjang Sukarna, Sam Permanadewi, Ross L. Andrew and Katja Deckart)
3. The Andean Porphyry Systems (Francisco Camus)
4. Origin of Giant Miocene and Pliocene Cu-Mo Deposits in Central Chile: Role of Ridge Subduction, Decreased Subduction Angle, Subduction Erosion, Crustal Thickening, and Long-Lived, Batholith-Size, Open-System Magma Chambers (Charles R. Stern and M. Alexandra Skewes)
5. The El Teniente Megabreccia Deposit, the World's Largest Copper Deposit (M. Alexandra Skewes, Alejandro Arevalo, Ricardo Floody, Patricio H. Zuhiga and Charles R. Stern)
6. A Review of the Geology and Mineralisation of the Alumbrera Porphyry Copper-Gold Deposit, Northwestern Argentina. (Steve C. Brown)
7. The Escondida Porphyry Copper Deposit, Northern Chile: Discovery, Setting, Geology, Hypogene Mineralisation and Supergene Ore - A Review (T.Mike Porter)
8. Chuquicamata, Core of a Planetary Scale Cu-Mo Anomaly (Alejandro Faunes, Fernando Hintze, Armando Sina, Hector Veliz, Mario Vivanco and Geological Staff (of 2003))
9. Geology and Discovery of Porphyry Cu-Mo-Ag Deposits in the Collahuasi District, Northern Chile (Glenton J. Masterman, David R. Cooke and Richard L. Moore)
10. The Geology of the Antamina Copper-Zinc Deposit, Peru, South America (Eric J. Lipten and Scott W. Smith)
11. The Geologic History of Oxidation and Supergene Enrichment in the Porphyry Copper Deposits of Southwestern North America (Sterling S. Cook and T. Mike Porter)
12. Geology of the Bingham Mining District, Salt Lake County, Utah (Charles H. Phillips, Edward D. Harrison and Tracy W. Smith)
13. Porphyry Cu-Mo Deposits of the Highland Valley District, Guichon Creek Batholith, British Columbia, Canada (W.J. McMillan)