Richard H Sillitoe

Porphyry Cu deposits in the Chilean and Argentinian central Andes occur in a series of orogen-parallel magmatic arcs, which migrated episodically eastward since the Early Cretaceous. The three Cenozoic belts, corresponding to Paleocene-early Eocene, middle Eocene-early Oligocene, and Miocene-early Pliocene epochs, cut obliquely across a composite b...

The following personalised narrative aims to document the highlights of my involvement in some of the ground breaking developments in Economic Geology and their direct application to mineral exploration and discovery over the past half century. The story begins with my introduction to geology at secondary school and university, followed by doctoral...

Hypogene porphyry Cu deposits, unaffected by supergene enrichment, are generally perceived as relatively low-grade orebodies, in keeping with a current average production grade of 0.53% Cu. Nonetheless, all or large parts of some deposits exceed 1% Cu, and smaller deposit components can be much higher in grade, locally >6% Cu. In view of the major...

Filo del Sol is a composite porphyry-epithermal deposit, straddling the frontier between Argentina and Chile at latitude 28°29′ S, that has attracted a great deal of recent attention because of several drill intersections in excess of 1 km long with unusually high Cu, Au, and Ag grades. The deposit is part of the 8.5-km-long, N- to NE-trending Filo...

In contrast to base- and precious-metal deposits associated with igneous activity, surface manifestations of ore formation at depth in continental sedimentary basins have not been recognized. Herein, the surface expressions of fluids capable of forming deeper red-bed copper deposits—a sediment-hosted stratiform copper deposit subtype—are documented...

Vein, stockwork, skarn, and carbonate-replacement Sn deposits commonly contain little or no Cu, but examples rich in Cu are also well known in many Sn belts worldwide. The origin of Sn-Cu deposits in association with fractionated and reduced, ilmenite-series granites of mostly metasedimentary crustal parentage is enigmatic because Cu, in contrast t...

Carlin-type gold deposits in northern Nevada are inferred to overlie concealed late Eocene plutons, which are increasingly thought to have provided magmatic input to the meteoric water-dominated fluids from which the gold was precipitated. The Larderello, Monte Amiata, and Latera geothermal systems in the Northern Apennines of southern Tuscany and...

The Jogran copper prospect in southern Ontario, Canada, is located on the northeastern shoulder of the North American Midcontinent rift system where it is centered on two small, closely spaced quartz monzonite porphyry intrusions emplaced into Neoarchean mafic metavolcanic rocks. Notwithstanding an atypical alteration zoning pattern, the distinctiv...

For the past 30 years, many investigators have distinguished two sorts of sedimentary rock-hosted, disseminated gold deposits: Carlin-type and distal-disseminated/ Carlin-like. The Carlin-type deposits commonly contain intermediate to silicic dikes and sills or no coeval intrusions at all as well as generally lacking an observed association with ot...

The Daero Paulos porphyry copper prospect, in the Asmara region of the central Eritrean highlands, is part of the Nakfa tectono-stratigraphic terrane, which, along with four other major and several minor terranes that constitute the Neoproterozoic Arabian-Nubian Shield, is characterized by juvenile, intra-oceanic island-arc crust. Alteration and mi...

The Rosen copper veins in southeastern Bulgaria are recognized for the first time as an iron oxide-copper-gold (IOCG) district. The veins are located in the East Srednogorie segment of the Carpathian-Balkan calc-alkaline volcano-plutonic arc and were formed during an end-stage interval of extreme slab rollback and intra-arc rifting, which gave rise...

Gold is either the only economically important metal or a major by-product in 11 well-characterized deposit types—paleoplacer, orogenic, porphyry, epithermal, Carlin, placer, reduced intrusion related, volcanogenic massive sulfide (VMS), skarn, carbonate replacement, and iron oxide-copper-gold (IOCG), arguably more than for those of any other metal...

Fruta del Norte is a completely concealed and extremely well-preserved, Late Jurassic epithermal gold-silver deposit of both low- and intermediate-sulfidation type, which is located in the remote Subandean mountain ranges of southeastern Ecuador. Currently defined indicated resources are 23.8 million metric tons (Mt) averaging 9.61 g/t Au and the t...

Radiometric ages for supergene alunite and jarosite effectively date the oxidation of former concentrations of pyrite and any associated sulfide minerals. These K-bearing sulfate minerals, formed under low-pH conditions, are uncommon supergene products in low-sulfidation epithermal deposits because of the general paucity of pyrite for acid generati...

This analysis concludes that there is little realistic likelihood of discovering large, high-grade porphyry Cu deposits in Japan and South Korea because of an unusual combination of geological factors. First, weak inter-plate coupling, trench retreat, and extension – a tectonic regime unfavorable for porphyry Cu formation – appears to have characte...

The sediment-hosted stratiform Cu ± Co deposits and prospects of the Central African Copperbelt are characterized by two intimately associated mineralization styles: disseminated sulfides and sulfide-bearing quartz-carbonate veins and veinlets. It has been widely accepted that the disseminated mineralization was introduced during sediment diagenesi...

Mr. President, ladies, and gentlemen: My sincere thanks, Jeff, for your career review and accompanying kind words today. A surprising number of previous Penrose medalists have said that they felt humbled by the honor but, in my case, thrilled would perhaps better describe my initial reaction to receiving the news from SEG President Francois Robert....

History of the discovery of a 1M oz gold deposit in Turkey

The Udokan Cu–Ag deposit in Transbaikalian Russia is one of the largest individual examples of the sediment-hosted stratiform type. Mineralization is hosted by the Udokan Complex, a ~ 12,000-m-thick metasedimentary sequence deposited between ~ 2.2 and 2.06 Ga in a large intra- to peri-cratonic basin constructed over Archean basement of the Siberian...

Fruta del Norte is a completely concealed and extraordinarily well preserved epithermal gold-silver deposit located in the remote Cordillera del Cóndor mountain ranges of southeastern Ecuador. Currently defined resources in a single, steep, relatively small body, displaying exceptional grade continuity, contain 9.81 million ounces (Moz) of gold and...

Exploration for porphyry copper deposits beneath barren or poorly mineralized, advanced argillic lithocaps is becoming common­place; however, there have been few discoveries except in cases where the copper ± gold ± molybdenum mineralization has been partly exposed, typically as a result of partial lithocap erosion. At Valeriano, in the high Andes...

Approximately 10% of copper resources in the Central African Copperbelt, the world's largest, sedimenthosted stratiform copper province, occur in the Domes region of northwestern Zambia. The copper deposits and prospects are commonly hosted by amphibolite-facies metamorphic rocks and lie within or adjacent to several basement inliers. Minor molybde...

Many active volcanic-hydrothermal and geothermal systems are characterized by distinctive surface and near-surface landforms and products, which are generated during discharge of a spectrum of fluid types under varied conditions. Remnants of most of these products are preserved in some of their less-eroded, extinct equivalents: epithermal deposits...

Re-Os dating of two molybdenite samples from the Squaw Peak porphyry copper-molybdenum prospect in central Arizona returned essentially identical ages of 1,729 ± 7 and 1,738 ± 7 Ma. Therefore the prospect is not a component of the Laramide (Late Cretaceous-early Tertiary) porphyry copper province of southwestern North America as previously presumed...

The Caspiche porphyry gold-copper deposit, part of the Maricunga gold-silver-copper belt of northern Chile, was discovered in 2007 beneath postmineral cover by the third company to explore the property over a 21-year period. This company, Exeter Resource Corporation, has announced a proven and probable mineral reserve of 1,091 million tonnes (Mt) a...

The Central African Copperbelt of Zambia and Democratic Republic of Congo, along with its broad time equivalents in Botswana and Namibia (the Kalahari Copperbelt), is the world's largest sediment-hosted, stratiform copper province. The economically dominant stratiform copper ± cobalt or silver mineralization, accepted by many as at least partly ear...

Metal introduction at the late Paleocene to early Eocene Quellaveco porphyry copper-molybdenum deposit in southern Peru spans several phases of quartz monzonite porphyry emplacement and is bracketed by a precursor granodiorite pluton and a late-mineral porphyry body that postdates essentially all copper introduction. Together, the U-Pb ages of zirc...

Gold deposits are arguably more widely distributed through geological time, and present in more geological environments, than the economic concentrations of any other metal. Hence, gold occurs in both a majority of countries worldwide and a spectrum of deposit types. Nevertheless, current production is dominated by mines in just four countries: Chi...

Porphyry Cu systems host some of the most widely distributed mineralization types at convergent plate boundaries, including porphyry deposits centered on intrusions; skarn, carbonate-replacement, and sedimenthosted Au deposits in increasingly peripheral locations; and superjacent high- and intermediate-sulfidation epithermal deposits. The systems c...

A compilation of economically viable gold concentrations containing >= 10 Moz in the North and South American Cordillera reveals the existence of 22 discrete belts in addition to five major isolated deposits, more formed over the last 150 m.y. The gold concentrations are attributed to eight widely recognised deposit types, of which porphyry, sedime...

The high-grade Chañarcillo vein silver deposit in northern Chile has been repeatedly cited as an exemplar for supergene silver sulfide enrichment beneath a rich oxidized zone. By analogy with the supergene upgrading of copper deposits, it is claimed that silver released during oxidative weathering migrated progressively downward in acidic solutions...

Field observations in the Pueblo Viejo district, Dominican Republic, show that an extensive advanced argillic lithocap and the contained giant high-sulfidation epithermal gold-silver deposit were emplaced beneath a thick limestone cover. Massive silicification and associated magnetite and hematite, containing the same anomalous multielement suite a...

A variety of metals and deposit types define the metallogeny of the Andes from Colombia through Ecuador, Peru, and Bolivia to Argentina and Chile, although porphyry copper and epithermal gold deposits undoubtedly predominate and will continue to do so. Discoveries over the last 30 yrs or so, predominantly in the central Andes and especially Chile,...

A variety of metals and deposit types define the metallogeny of the Andes from Colombia through Ecuador, Peru, and Bolivia to Argentina and Chile, although porphyry copper and epithermal gold deposits undoubtedly predominate and will continue to do so. Discoveries over the last 30 yrs or so, predominantly in the central Andes and especially Chile,...

Global political and economic developments shape both the demand for minerals and primary metals and their supply. Overall, demand has moved broadly in step with economic activity over the past 30 years. Notwithstanding the collapse of the Soviet Union and Eastern Bloc countries, demand grew more rapidly in the second half of the period than the fi...

Iron oxide-copper-gold (IOCG) deposits, defined primarily by their elevated magnetite and/or hematite contents, constitute a broad, ill-defined clan related to a variety of tectono-magmatic settings. The youngest and, therefore, most readily understandable IOCG belt is located in the Coastal Cordillera of northern Chile and southern Peru, where it...

Epithermal Au and Ag deposits of both vein and bulk-tonnage styles may be broadly grouped into high-sulfidation (HS), intermediate-sulfidation (IS), and low-sulfidation (LS) types based on the sulfidation states of their hypogene sulfide assemblages. The HS and LS types may be subdivided using additional parameters, particularly related igneous roc...

The El Laco magnetite deposit has been interpreted as lava flows and feeder dikes formed from iron oxide magma, but more recently, as a product of metasomatic replacement. Open-pit exposure created at Laco Sur during the 1990s reveals that the massive magnetite contains magnetite-veined blocks and smaller fragments of altered andesitic volcanic roc...

Porphyry copper-gold, skarn copper-gold, sediment-hosted (Carlin-style) gold, breccia pipe, low-sulphidation epithermal gold, pluton-related (mesothermal or orogenic) gold vein and volcanogenic massive sulphide deposits associated with alkaline rocks are commonly broadly similar to those hosted by their calc-alkaline counterparts. In contrast, porp...

High-sulphidation (HS) gold, silver and/or copper deposits are generated in both the epithermal and the upper parts of the underlying porphyry environments over vertical intervals of up to 2 km. The HS deposits are generated in advanced argillic lithocaps, which are products of the absorption of acidic magmatic volatiles by voluminous groundwater s...

Chuquicamata is the world's largest porphyry copper deposit, notwithstanding the fact that a portion of the orebody has been faulted off by postmineralization movement along the West fault. In order to locate the missing portion of the orebody in the vertical dimension, a study was designed to estimate the sense and amount of vertical displacement...

Grassroots exploration has led to discovery of 10 porphyry copper prospects in the previously unexplored Jurassic arc of southeastern Ecuador. The prospects are located in steep, wet, jungle-covered terrain in the Pangui area, part of the Cordillera del Cóndor. The exploration program, initially mounted in search of gold in the Oriente foreland bas...

An under-recognized and economically important class of intrusion-related gold deposits, which occur within magmatic provinces best known for tungsten and/or tin mineralization, is described with reference to seven major deposits (Fort Knox, Mokrsko, Salave, Vasilkovskoe, Timbarra, Kidston and Kori Kollo). These gold deposits contain a metal suite...

A spectrum of intrusion-related vein gold deposits is recognized. Representative examples are described of the following geochemical associations: Au-Fe oxide–Cu, Au–Cu–Mo–Zn, Au–As–Pb–Zn–Cu, Au–Te–Pb–Zn–Cu and Au–As–Bi–Sb. The associated intrusions range from small outcropping stocks to complex batholiths. The different vein associations are belie...

Zones of advanced argillic alteration constituting lithocaps are commonplace in the shallow parts of porphyry copper systems. Similar lithocaps are also recognized in the shallowly eroded southern part of the Bolivian tin-silver belt, where mineralization typically is centred on felsic volcanic domes. A well-preserved lithocap at Potosí is dominate...

Eleven gold‐rich porphyry copper and 14 epithermal gold deposits around the Pacific rim contain > 200 t (‐7 million oz) of gold. These large porphyry‐type deposits conform to a single overall model, whereas the large epithermal gold deposits are varied in both genetic type and mineralisation style. Most regional and local characteristics of the lar...

Granitic rocks, spanning a broad range of compositions and silica contents, are related genetically to a spectrum of precious-, chalcophile-and lithophile-metal deposits. The metals present are dictated by the composition, degree of fractionation and redox states of the associated intrusions. The fertile intrusions and associated metal deposits occ...

Supergene chalcocite enrichment during weathering is an economically vital natural process that may lead to severalfold increases in the copper content of sulfide deposits. A scanning electron microscope study of chalcocite (Cu2S) from major enriched copper deposits in northern Chile revealed myriad bacterioform bodies in original growth positions...

Twenty-five samples of supergene alunite collected from deeply developed supergene profiles in porphyry copper deposits and prospects between latitudes 20° and 27° S in northern Chile yield K/Ar ages ranging from about 34 to 14 Ma. Therefore supergene oxidation and enrichment processes were active from the early Oligocene to the middle Miocene, a m...

Telescoping is the process of juxtaposing or overprinting early, deep mineralization, commonly of porphyry type, and late, shallow, generally epithermal styles of precious- and base-metal mineralization. Telescoping is attributed to synhydrothermal degradation of volcanic paleosurfaces, as a result of either rapid erosion under pluvial conditions o...

High sulfidation precious metal ore is hosted by strata-bound bodies of pervasively silicified, welded ash-flow tuff. The ore-bearing tuff is bounded on all sides, both stratigraphically and structurally, by aquitards, mainly andesite flows. A lower andesite sequence, beneath the mineralized tuff horizons, is the host for a large zone of low-grade...

Indonesia possesses a spectrum of precious- and base-metal deposits typical of Cenozoic volcano-plutonic arcs. Porphyry Cu-Au, porphyry Mo, skarn Cu-Au, sediment-hosted Au, low-sulphidation epithermal Au, high-sulphidation epithermal Au and volcanogenic massive sulphide (VMS) Au are all represented, although the first, third and fifth of these are...

Three aspects of models for epithermal precious-metal deposits in volcanic settings are of particular concern to the explorationist: genetic type, geometrical controls and shallow features. A first-order division of epithermal deposits distinguishes high-sulphidation (HS) or acid-sulphate, and low-sulphidation (LS) or adularia-sericite types. The L...

Gold-rich porphyry copper deposits are emplaced in a variety of subduction-related settings, especially around the Pacific rim, and are underlain by both oceanic and cratonic crust in either extensional or compressional tectonic regimes. The deposits are asssociated with composite porphyry stocks of steep, cylindrical form that commonly intrude coe...

Fifty-six principal gold deposits in the western Pacific region were generated in multiple volcanoplutonic arcs during the last 25 million years. At least 75% of the contained gold was introduced in association with intrusive stocks, commonly porphyries. The gold-bearing magmatic arcs were all constructed in response to subduction of oceanic lithos...

The Maricunga belt is a linear metallogenic unit defined by at least 14 zones of gold and/or silver mineralization between latitudes 26° and 28°S in the Andean Cordillera of northern Chile. Previous metal mineralization is related to a belt of Miocene volcanic rocks, most of which constitute a series of large compound stratovolcanoes of calc-alkali...

The gold deposit is part of a linear, calc-alkaline volcanoplutonic arc constructed during the mid- to late Miocene as eastward-directed subduction was shallowing. Stock emplacement and gold mineralization took place within a coeval andesitic stratovolcano at 13 to 14 Ma. The hornblende-biotite diorite stock is subdivided into three phases: two min...

The principal deposits are mainly of epithermal and porphyry type, with one major pluton-related vein and one distal contact metasomatic deposit. High sulfidation deposits dominate the epithermal category and include a broad spectrum of mineralization styles. Porphyry-type deposits, including newly recognized gold-only examples at Marte and Lobo, a...

The nine principal mineralized centers in the belt, were dated radiometrically using the K-Ar method. Hypogene alunite from advanced argillic assemblages was dated from eight of the deposits. The 18 new radiometric ages permit subdivision of the Maricunga belt into two overlapping, longitudinal subbelts: the western of early Miocene (including late...

A broad spectrum of gold mineralization styles is found in the epizonal intrusive environment, and a number of these give rise to world-class gold deposits (Figure 6.1). Here the spectrum is subdivided into: (a) intrusion-hosted stock-work/disseminated deposits of both porphyry and non-porphyry types, the former possessing all the essential geologi...

The Nalesbitan lode Au deposit in the Bicol peninsula of southeastern Luzon, Philippines, is of the acid-sulphate type, and originally contained a minimum of about 15 tonnes of Au. Mineralization is hosted by Pliocene andesitic volcanic rocks transected by a northwest-striking, steeply west-dipping, sinistral strike-slip fault zone, which is consid...

Sediment-hosted or Carlin-type gold deposits are currently thought to have been generated at shallow levels in geothermal systems, the gold having been scavenged from host sedimentary sequences by meteoric hydrothermal fluids. In contrast, we propose that gold was contributed by magmatic hydrothermal fluids and was deposited on the peripheries of b...