Andean Metallogenesis: A Synoptical Review and Interpretation (*)
(*) In: CORDANI, U.G. / MILANI, E.J. / THOMAS FILHO, A. / CAMPOS, D.A. TECTONIC EVOLUTION OF SOUTH AMERICA, P. 725-753 / RIO DE JANEIRO, 2000
Abstract- The paper presents an introductory view of the Andean belt and their mineral deposits, followed by a general description of each of the principal Andean metallic provinces: the iron, copper, gold-silver, pollymetallic and tin belts. Finally, the segmentation, zoning and metallogenetic evolution of the Andean belt is described and discussed.
Although a major part of the Andean ore deposits are related to magmatic activity, and calc-alkaline magmas are dominant, at least the larger deposits of the belt are related to short-lived disruptions in the normal tectonic regime and in the mechanisms of magma generation and emplacement. Both changes in rate and angle of convergence of the tectonic plates are key factors for explaining such disruptions though the deep structure of the continental lithospheric plate seems also important.
Most of the larger ore deposits of the Andean belt
have a Tertiary age and are in the central part of the
Resumen- La presente contribución entrega una visión introductoria de la cadena andina y sus yacimientos minerales, seguida por una descripción general de cada una de sus principales provincias metálicas: las fajas ferríferas, cupríferas, de metales preciosos, polimetálica y estañífera. Finalmente, se describen y discuten la segmentación, la zonificación metálica transversal y la evolución metalogenética de la cadena andina.
Aunque una parte principal de los yacimientos metalíferos andinos se relaciona directa o indirectamente a la actividad magmática y el magmatismo calcoalcalino ha sido dominante, al menos los principales yacimientos del orógeno se relacionan con trastornos del régimen tectónico y de los mecanismos de generación y emplazamiento de magmas. Tales trastornos han sido producidos por rápidos cambios en la velocidad de convergencia de las placas tectónicas oceánica y continental, así como por modificaciones del ángulo de convergencia, aunque probablemente también la geometría de la corteza continental profunda ha tenido un rol significativo.
La mayoría de los grandes yacimientos metalíferos andinos tiene edad terciaria y se encuentra en la parte central del orógeno (10º S a 35º S) donde su corteza continental es más profunda. Ello se interpreta en términos del mayor grado de evolución orogénica de ese segmento andino durante el lapso Mesozoico-Cenozoico. La relación antes señalada tiene un paralelo en la evolución magmática-metalogénica de los arcos de islas, donde tanto la producción de yacimientos de distinta tipología como la magnitud que ellos alcanzan crecen junto con el desarrollo de una corteza diorítico-tonalítica. Una posible explicación de esta analogía radica en las mayores oportunidades de interacción entre magmas, materiales sólidos y fluidos (desde la astenósfera hasta los niveles sedimentarios corticales) que ofrece la creciente complejidad del orógeno.
Introduction: The Andean Belt and its Mineral Deposits
In geological terms, the Andean belt has a particular
importance as a model for the evolution of magmatic arcs developed over close
to the continental crust, on an active, plate consuming, convergence border.
Although the magnetic anomalies of the oceanic floor permit to follow the
convergence history of the margin only as far back as the Cretaceous, there are
geological evidence of plate tectonic activity in the Andean domain during
Paleozoic times. In consequence, the geological evolution of the
The Andean belt is a complex orogenic system, that has
its maximum wide (near 800 km) around 18º S and comprehends several
cordilleras, sierras, plateaux, basins and valleys. Three well defined
different cordilleras and one sierra are distinguished in
The present Andean cordilleras lift up over the
western and north-western border of the South American tectonic plate and face
four other tectonic plates, three of them of oceanic type: The Nazca, Cocos and
The continental crust has different thickness along
the belt, attaining a maximum of 70 km under the Principal Cordillera, between
14º S and 22º S, a figure close to that of the continental crust under the
The presence of major longitudinal and transversal
faults is an important trait of the Andean geology. The first ones have
controled the vertical displacement of the longitudinal tectonic blocks, as
well as the magmatic emplacement and the distribution of ore deposits. Several
of these faults, as those of Romeral (
The Andean belt presents hundreds of strato volcanoes and many of them are important heights of the Belt. They are distributed in three main active segments: 5º N - 2º S (andesitic-basaltic), 16º S - 28º S (andesitic) and 37º S - 46º S (andesitic-basaltic). Only five strato-volcanoes are known in a more southern position (48º S - 56º S), and their composition are andesitic. The principal volcanic segment: 16º S - 28º S, also presents around 150.000 Km2 of Miocene-Pliocene rhyo-dacitic ignimbrites; some of the flows being linked to very large calderas (up to 30 km in diameter, Francis and Baker, 1978). Some of the Andean volcanoes have supplied important clues for understanding the genesis of the ore deposits, as in the cases of San Fernando, Ecuador (Goossens, 1972a), and El Laco, Chile (Park, 1961).
Although some authors, as Aubouin et al. (1973) and Zeil (1979), sustain the existence of fundamental differences between the Paleozoic and post Paleozoic geologic development of the Andean belt, these differences depend on the Andean segment and the period considered. Neither the episodes of marginal basin development nor the stages of strong horizontal compressive tectonics are exclusive traits of the Paleozoic evolution. On the other hand, important sedimentary Paleozoic basins are characterized by vertical tectonics. Also, calc-alkaline magmatism, so typical of the Mesozoic-Cenozoic Andean belts, is equally abundant during the Paleozoic, and attains a peak during the Permian. Thus, the Parmian-Triassic transition occurs in geological continuity. Finally, Paleozoic and post-Paleozoic tectonic directions are similar and the Paleozoic metallogenesis includes the same metals deposited in Mesozoic and Cenozoic times, although the areal distribution of the metallic belts is different. Porphyry copper deposits, a main trait of the Cenozoic Andean metallogenesis, were formed in the Andean domain at least since the Carboniferous (Sillitoe, 1977).
Nevertheless, some of the characteristics traits of
the Andean belt, e.g., the generation of large amounts of calc-alkaline
magmatism, became heightened in Mesozoic and Cenozoic times, whereas other,
like the accretion of oceanic prisms, lessened their relative importance. The
separation of South America from
Ensialic basin development was also important during
the Mesozoic and during the Cenozoic Andean evolution. However, some of these
Mesozoic basins (e.g., the Neocomian basin in central
The Andean belt exhibits the imprints of several important compressive episodes. However, their intensity was different along the belt. Besides, strong folding was attained only on the miogeosynclinal facies between the western volcanics and the eastern continental terrains.
Mesozoic Andean magmatism includes tholeiitic,
calc-alkaline and alkaline series. Tholeiitic series are characteristic of the
accreted oceanic prisms of the
Regarding the older ore deposits in the Andean domain, the only ones that have a possible Precambrian age are some Ni and Cr ores in ultrabasic rocks of the Eastern Cordillera of Perú, as well as some Ni-Cr deposits in ultrabasic rocks, Cu-Fe deposits in amphibolites and W deposits in granulites of the Pampean Ranges of Argentina, which have minor economic importance (Di Marco and Mutti, 1996; Stoll, 1975).
Though Paleozoic and post-Paleozoic Andean ore deposits
contain basically the same metals, there are some differences regarding the
type of deposits (e.g., there are not post-Paleozoic BIF’s). However, the main
difference concerns the huge amounts of ores formed after the Paleozoic,
specially in the Central and
The post-Paleozoic metallic provinces appear as 50 to
300 km wide belts, elongated parallel to the
The present exposition will now describe the different
metallic provinces of the
The iron belt
The iron ore deposits of the Andean domain (Fig. 1) may be grouped in four types: BIF type deposits of
the Nahuelbuta belt (
The BIF-type iron ores of Nahuelbuta are emplaced in high-pressure metamorphic rocks (pelitic schists, cherts and greenschists) that have a Lower Carboniferous metamorphic age and belong to an accreted terrain (Aguirre et al., 1972). The oceanic volcano-sedimentary prisms contains, in addition to the magnetite ores, some chromite podiform deposits and also some pyritic Cu-Zn massive sulfide bodies. The principal iron mineralization, that is interbeded with micaschists, crops out in three main areas, situated between 38º05’ S and 38º30 ‘ S, close to 73º15’ W. Ore reserves are about 100 M.t., containing 30% Fe (Oyarzun et al., 1984).
The oolithic iron deposits are found in northwest
The oolithic iron deposits of
The Kiruna-type iron deposits of north
Hydrothermal alteration is widespread and complex. However, actinolite, partly altered to chlorite, is dominant, followed by silicification and rock bleaching. Isotopic (K-Ar) dating of the iron deposits are between 128 Ma (Boquerón Chañar, Zentilli, 1974) and 110 Ma (Los Colorados, Pichón, 1981, and El Romeral, Munizaga et al., 1985). Several age determinations at El Algarrobo (Montecinos, 1983) are also in the 128-111 Ma span, which is coincident with the climax of the mafic magmatism, but also with the passage from the "Mariana" to the "Chilean" style of oceanic plate subduction (Sillitoe, 1991).
The iron belt also include smaller iron vein-type deposits as well as a few iron skarns, like Bandurrias, and some chalcopyrite-magnetite skarn ores, like San Cristobal, that have been mined for their copper content.
Concerning the origin of the main iron ore deposits of the belt, pneumatolytic-hidrothermal fluids were considered as a satisfactory depositional mechanism by Ruiz et al. (1965), Bookstrom (1977), Oyarzún and Frutos (1984) and other authors, although there are differences concerning the source of the fluids. However, Nystrom and Henríquez (1994) and Travisany et al. (1995), have recently proposed that these deposits were formed at a magmatic stage and later overprinted by hydrothermal fluids.
The iron deposits of the coastalt belt of Perú (Soler
et al, 1986; Cardozo and Cedillo, 1990) are similar in mineralogy to the
Cretaceous deposits of north
The iron-copper skarns deposits of the
Andahuaylas-Yauri zone in Perú are located along a WNW trending belt between
13º30’ S - 14º30’ S and 71º39’ W - 73º39’ W. The deposits are associated to
quartz monzonite stocks dated at 34-33 Ma, that intrude carbonatic sediments
dated as Albian-Turonian (Noble et al, 1984; Soler et al, 1986). The ores
include magnetite with some native gold as early minerals, and chalcopyrite as
a later sulfide phase. According to Bellido and
The El Laco Kiruna-type iron ore deposits, are made up
of several flow-like and subvolcanic intrusive magnetite bodies with the same
mineralogy, that also includes minor apatite. These bodies crop out across a
surface of 1,8 km2 around a Pliocene volcanic center of north
The copper province
Copper deposits are present from the northern to the
southern ends of the Andean belt, and their ages cover the Upper Paleozoic to
Pleistocene span. The deposits belong to a variety of types, among them
porphyry copper, enargitic vein and replacement, skarn, breccia pipe,
manto-type, massive sulfide, exotic etc. In those deposits, copper is
associated to a number of metals, like Mo, Fe, Au, Ag, Zn and Pb. In the
following paragraphs, the principals traits for each deposit type in the
Porphyry copper deposits are also present along the
whole andean belt (Fig. 9), where
they attain world’s marks, both in tonnage and grade. Besides, some of them, as
Sillitoe (1988), considers six epochs of porphyry
copper mineralization in the Chilean-Argentinean sector of the
Most porphyry copper deposits in the
Porphyry copper deposits present both spacial and
chrological clusters in the Andean belt. Thus, the
As pointed out before, many important porphyry copper
deposits in the
The Andean porphyry copper deposits have Mo contents that range between 0.01% and 0.1% and this metal follows copper in economic importance. Given the large tonnages of porphyries like Chuquicamata and El Teniente, they also rank among the major Mo deposits of the world (Ambrus, 1978). In exchange, gold content are rather low, with the important exception of the Farallon Negro district in Argentina, where Bajo de la Alumbrera attains 780 M.t. ore, containing 0.52% Cu and 0.67 g/t Au (Sasso and Clark, 1998).
Although the enargitic vein and replacement Cu +/- Au,
Ag, Zn, Pb deposits are better represented in Perú, they are also common in
other zones of the Tertiary volcanic belts of the
The Peruvian territory is also richely endowed in Cu
+/- Fe, Au, Zn deposits related to calcic skarns, partly as a consequence of
the broad distribution of Mesozoic back-arc carbonatic rocks, that host
Tertiary monzonitic granitoids (Fig. 7). As
mentioned before, some skarns deposits of the Andahuylas-Yauri zone are also
important for their magnetite content. Among the major skarn deposits in Perú,
stand out Antamina, Cobriza, Ferrobamba and Tintaya (Petersen and Vidal, 1996).
A second type of skarn, the amphibolitic Cu +/- Fe skarns deposits (Vidal et
al, 1990) is represented in Perú by Raul-Condestable and in
Breccia pipe ore deposits are widespread in the
Manto-type copper deposits are typically found in
volcano-sedimentary formations of Mesozoic age in north and central
Massive sulfide deposits are not abundant in the
Andean belt, although the accreted oceanic prisms of the
Favorable climatic and tectonic conditions for the
formation of exotic Cu deposits, existed in the Andes of south Perú and north
Chile between 12º S and 27º S (Munchmayer, 1996). In
Copper vein deposits are widespread, in the Andean belt
and it is difficult to present a synthesis of this subject. However, it is
important to state that Cu mining in the
Gold and silver metallic belts
Gold and silver were main lures for the Spanish conquerors in the Andean countries, and their hidden deposits, together with those of copper, are today the first target for the mining exploration companies.
In the northern Andes,
Gold mining began in Colonial times in
A general view of gold deposits in Perú was presented by Noble and Vidal (1994). This country has a long and important history as a gold and silver producer, that began in pre-Hispanic times. Noble and Vidal (1994), classify the Peruvian gold deposits (Fig. 5) in the following groups: 1- Quartz veins of Paleozoic and Mesozoic age: a) Pataz-Buldibuyo belt (Pataz, Parcoy, etc.); b) Santo Domingo-Ananea region (Ananea, Santo Domingo, etc.); c) Nazca-Ocoña belt (Calpa, Ishihuinca). 2- Gold bearing systems of Cenozoic age: a)Au-bearing porphyry and skarn deposits (Michiquillay, Tintaya, etc.); b) Sedimentary rock-hosted gold (Yauricocha, Utupara, etc.); Polymetallic and precious metal deposits, subdivided in: -Polymetallic systems (Quiruvila, Sayapullo, etc). -Epithermal deposits of the adularia-sericite type Ag-Au vein systems (Cailloma, Arcata, etc.) and of high-level, acid-sulfate systems (Yanacona, Ccarhuaraso, etc.). At julcani, the acid-sulfate stage was developed between two stages of adularia-sericite alteration. 3- Bulk mineable ores (Yanacocha, Hualgayoc). 4- Quaternary placer deposits.
Although Perú ranks third in present gold production among the Andean countries (after Chile and Colombia), this situation should soon be changed, due to a number of important mining projects, such as the Pierina mine by Barrick, near Ancash, programmed for a production of 22 t Au/year (equivalent to total gold production of Perú in 1993).
Silver is also an abundant metal in many hydrothermal deposits in the volcanic rocks of the Western Cordillera of Perú, appearing in independent primary (argentite, proustite, etc.) or secondary (native Ag, acantite, etc.) minerals, as well as in inclusions of silver minerals or soild solutions in galena and Cu sulfominerals (tetrahedrite, etc.). In exchange, Ag is commonly found only in solid solutions or inclusions in galena and sulfominerals in the deposits hosted by sedimentery rocks in the western and eastern cordilleras (Bellido and Montreuil, 1972). Among the principal Ag-rich deposits are Quiruvilca (polymetallic; Ag/Au = 100) and the ephithermal deposits of San Juan de Lucanas: Ag/Au = 160; María Luz-Huachacolpa district: Ag/Au = 450 and Julcani: Ag/Au = 65 (Noble and Vidal, 1994).
The Miocene sub-volcanic deposits of the central and
southern part of the Cordillera Real, west from the Altiplano region of
Although there are important Au-Ag deposits in
Gold production in
Chilean hydrothermal gold deposits are Jurassic to
Upper Miocene in age and their mineralizations are in hydrothermal breccias,
veins, stockworks and disseminations (Sillitoe, 1991). Although most of the Au
+/- Cu deposits correspond to Mesozoic pluton-related veins, only two
districts: Los Mantos de Punitaqui and El Bronce (Fig. 5) had Au content over 10 t. The rest of the deposits
over 10 t Au were classified by Sillitoe (1991) in four types: 1-High sulfidation, epithermal (Choquelimpie, Guanaco, El Hueso,
Of those deposits containing more than 10 t Au listed
before, only six deposits have Ag/Au ratios over 10 (Choquelimpie, Faride,
A review of precious and base metal deposits in
Argentina by Gemuts et al. (1996) mentions the Paramillos, (Mendoza) silver
deposit and the Gualilán gold deposit as the older mines in Argentina (Gualilán
dates from the 17th century). Modern exploration pre-1960 was
centered in high-grade precious and base metal deposits such as Mina Angela
(Ag-Pb-Zn-Au vein), Farallón Negro (Mn-Ag-Au vein) and El Aguilar, a sedex
massive sulfide deposit in the
The polymetallic province
The polymetallic province (Fig. 11) is present along all the Andean belt, although their
principal deposits are located in the Peruvian segment, wich also present thick
and widespread carbonatic sedimentary strata. Besides, though Paleozoic deposits
are known, some of them important like the Zn-Pb-Cu deposit of Los Bailadores,
El Aguilar (23º13’ S / 65º42’ W), a Pb-Zn-Ag sedex
deposit in Ordovician quartzites, represents the largest Paleozoic Pb-Zn
concentration in South America (Sureda and Martin, 1990), with some 30 M.t. ore
(12% Pb+Zn; 100 g/t Ag). The fact that a Cretaceus plutonic intrusion thermally
modified the original deposit and some skarn-type ore bodies were formed,
obscured the genesis of the deposit, now well established as a sedex
mineralization. Other Pb-Zn-Ba ores in Ordovician clastics sediments are those
of Pumahuasi (22º17’ S / 65º33’ W). They are part of a belt that continues for
some 500 km north, to the
Although Mesozoic and Cenozoic polymetallic deposits
are present in the Northern Andes (
During the Upper Triassic, the sea advanced from the north, and reached 13º S (Audebaud et al., 1973), covering the Pucará basin domain, a NW trending band between 76º W-77º W at 9º S and 72º W-74º W at 14º S, where clastic and carbonatic sediments were deposited. Westward, the basin also received andesitic lavas. The marine sedimentation continued during the Lias, when the basin was divided in two sectors (north and south). These sectors were united in the Dogger and separated again during the Malm by a major NW trending positive block. During the Malm and the Lower Cretaceous, marine sedimentation continued -in association to andesitic volcanics- only in the southwestern basin. However, a new marine transgression during the Albian -the sea coming this time from the south- covered the zone of the present western and Eastern cordilleras of Perú, and the sea remained there until the Upper Cretaceous (Senonian). Thus, paleogeographic conditions were favorable for the deposit of carbonatic rocks on the Peruvian territory. In exchange, contemporary basins on the Bolivian territory received only clastics sediments, except for some carbonates of Campanian-Maastrichtian age (Pareja et al., 1978).
Rich stratiform polymetallic deposits, with very high
Zn grades, are found in the sedimentary rocks of the Triassic--Liassic platform
of the Pucará basin (Amstutz and Fontboté, 1987; Cardozo and Cedillo, 1990).
They are, in part, of the Mississippi Valley type, such as San Vicente, located
in the eastern facies of the basin, and Shalipayko, in the western part, which
also includes some deposits that present volcanic influence, e.g., Carahuacra,
San Vicente, that has been the larger Zn producer of Perú is in sedimentary
rocks of tidal flats, lagoon and carbonatic reef facies. The Cercapuquio Pb-Zn
stratiform deposit in central Perú (Cedillo, 1990), hosted by lagoonal
sediments of Upper Jurassic age, also exhibits strong semilarities to
About 80 stratabound Zn-Pb (Ag-Cu) ore deposits and prospects are known in the Valanginian to Aptian Santa Formation, deposited in an ephemeral basin (Cardozo and Cedillo, 1990). Among the principal deposits are Huanzala (Fig. 7) and El Extraño (9º09’ S / 78º05’ W). Several traits of these ore deposits indicate a syn-diagenetic origin, e.g., the presence of rhytmites involving the ore minerals (Samaniego, 1980). However, there are also evidences of hydrothermal activity and contact metamorphism affected the deposits.
The stratabound ore deposits of the Casma Formation (Middle Albian) are rich in sphalerite and barite and have minor Cu, Pb and Ag contents. The principal deposits of this group, Leonila Graciela (Vidal, 1987), in 11º51’ S / 76º37’ W, is hosted by altered volcano-sedimentary rocks.
Lead-zinc (silver) stratabound deposits are hosted by
Upper Cretaceous carbonate rocks in Hualgayoc (Fig. 7), Western Cordillera of northern Perú (Cardoso and
Cedillo, 1990). Many of the deposits are in the Chulec Formation (e.g.
The major enargitic stratabound Cu-Pb-Zn-Ag deposit of
Colquijirca (Fig. 7) some
Most of the hydrothermal polymetallic deposits in Perú
(Soler et al., 1986; Cardozo and Cedillo, 1990) are associated to subvolcanic
intrusive of Miocene age in the northern and central part of the country.
Although it is possible that some of the deposits considered as Miocene, such
as Uchucchacua are Late Eocene-Early Oligocene in age (Soler and Bonhomme,
1988, cited by Cardozo and Cedillo, 1990), the Miocene remains as a principal
metallogenical period for this and other types of ore deposits. Cardozo and
Cedillo (1990) classify the hydrothermal polymetallic deposits of Miocene age
in five groups: 1- Complex deposits, including
both replacement and veins. They are normally zoned and rich in
Cu-As sulfosalts. Cerro de Pasco, Huarón, Morococha etc, are included in this
group. 2- Skarn bodies, some of them
associated with veins, like
The Miocene belt of polymetallic ore deposits in
A further southward extension of the Miocene
polymetallic belt is represented by Pb-Zn-Ag (Cu, Bi) veins in northwest
In the Patagonian Cordillera of Argentina and
At least in the case of the Chilean polymetallic deposits of the Patagonian Cordillera, it is possible that they belong to different ages of mineralization although these ages remain uncertain. Thus, Pb-Zn-Ag-(Cu) deposits occur between 46º00’ S and 47º20’ S, hosted by Paleozoic metamorphic rocks (phyllites and marbles of marin origin) intruded by post-Paleozoic granitoids (Ruiz and Peebles, 1988; Schneider and Toloza, 1990). The main deposit, Mina Silva (46º33’ S / 72º24’ W) is made up of high grade Pb-Zn (Ag) ores, with minor copper contents, that form lenticular bodies hosted by metamorphic limestone. Although Ruiz and Peebles (1988) interpreted the deposit as a Paleozoic singenetic mineralization. Schneider and Toloza (1990) argue that all ore deposits of the district (wich also include stratabound and not-stratabound deposits in Jurassic rocks) are related to calc-alkaline magmatism developed in a Mesozoic back-arc setting.
The other important district of this belt is El Toqui,
at 45º00’ S / 71º58’ W, described by Wellmer et al. (1983) and Wellmer and
Reeve (1990). The district, which covers some 25 km2, contains
several bodies in an Early Cretaceous formation made up of silicic volcanic
rocks and clastic and carbonatic marine sediments, intruded by quartz-bearing
porphyries. The basal volcanic unit is cross-cut by Zn-Pb-Ag veins and is
overlaid by andesitic-rhyolitic flows and clastic-carbonatic sediments, that
host the statiform sulfide ore bodies. They are localizad in three
stratigraphic levels, at the interfingered zones of carbonatic rocks with black
shales or pyroclastic horizons, and contain Zn-Pb-Cu or just Zn as principal
economic metals, while Ag is recovered as a sub-product. The larger ore body,
The tin province
Of the different Andean metallic provinces, the tin
belt presents the higher degree of definition and specification. Thus, all the
major deposits are in the Bolivian territory, along a NW to NS belt, up to
Although the principal deposits of the tin metallic province have a Tertiary or Lower Mesozoic age and are located in the Cordillera Real of Bolivia, tin deposits of Paleozoic ages are known in the Argentinean territory. Also, it is possible that some minor tin deposits in the Caraballa Cordillera of Perú, close to the Bolivian border, be related to Permian granitoids (Clark et al., 1983).
The Argentinean Paleozoic tin deposits occur in two areas of the Pampean Ranges (Fig. 12). Those of the northern area are vein or greisen type; their age is Cambrian to Silurian and their ores include cassiterite, wolframite and sulfide minerals. The deposits of the southern area are pegmatitic and have a Cambrian to Ordovician age (Malvicine, 1975). Their interest is more scientific than strictly economic.
The tin belt of
The host rocks for both the igneous bodies and the tin
deposits of the whole belt are Paleozoic clastic metasedimentary rocks, that
are the products of a detritic sedimentation that began as early as the
Cambrian, in a shallow but persistent intercratonic marine basin (Zeil, 1979)
and continued till the Middle Devonian, when conditions changed from marine to
continental, but the subsidence of the basin -and the sedimentation- persisted
up to the Mesozoic. The outcrops of these monotonous series of shales and sandstones
-10 to 20 km thick- make up a major part of the present
Two types of tin deposits of Upper Triassic-Lower Jurassic age are known. The more abundant correspond to Sn-W veins associated to greisen-type alteration, within small batholiths (e.g., Yani, Sorata) or in the contact metamorphic zone imprinted by the batholiths in the Paleozoic sedimentary host rocks. The age of the batholiths emplacement is in the 257 to 150 M.a. span (Grant et al., 1980). Among the principal districts are those of Sayaquira, Caracoles and Araca. None of them attains the magnitude of the Tertiary Sn-Ag deposits.
The other type of Upper Triassic-Lower Jurassic tin deposits, which is found along a NW band, north of 19º S, present stratabound control of the ores. Although this type of tin deposit is not economical under present tin price conditions, its origin (syngenetic or epigenetic deposit of the ores) poses an interesting problem (Schneider and Lehmann, 1977). As stated by Lehmann (1985, 1990), the host rocks for the stratabound tin deposits are Lower Paleozoic metasedimentary rocks, wich are intruded by granites and granodiorites.
Kellhuani, one of the three principal stratabound-type
tin deposits (Lehmann, 1985; 1990) is located some 15 km north of
The Tertiary tin deposits (Sillitoe et al., 1975; Grant
et al., 1976, 1980; Francis et al., 1981) are related to sub-volcanic intrusive
bodies, partly brecciated, at a high emplacement level, that cross-cut the
Paleozoic clastic formations. Grant et al. (1979), distinguished two
chronological groups. The first is formed by 26 to
The first group include such important deposits as Llallagua, Cerro Rico and Chorolque. Although their principal economic mineralization is vein-type, they also contain, as a whole, some 80 M.t. of disseminated ore grading 0,3% Sn, wich is still far from attaining economic interest, but represents an important reserve for the future. Five principal geological-mineralogical traits are common to the deposits of this groups: 1-The mineralization is centered on small (1-2 km2) porphyric stocks, emplaced under or whitin volcanic pipes. 2- Several pulses of intrusion and breccification are observed. Some stocks are converted to breccia pipes. 3- The stocks and their host rocks have suffered and intense and penetrative feldspar-destructive hydrothermal alteration, in which sericite and tourmaline predominate. 4- The mineralization is very complex. The main sulfides that accompany the cassiterite are pyrite, stannite, chalcopyrite, sphalerite and arsenopyrite. 5- The disseminated mineralization is earlier than the high-grade vein-type one. The radiometric dating by Sr isotopy have yielded Miocene ages like 20 Ma at Llallagua, 15-14 Ma at Cerro Rico and 17-12 Ma at Chorolque (Grant et al., 1980).
The magmas related to tin mineralization usually have a much differentiated petrological evolution (Lehmann, 1990). Although some magmas related to the Bolivian tin porphyries are evolved, like at Karikari, Potosí, where peraluminous, high initial Sr isotopic ratios (0.707-0.716) magmas, evolved from andesite to toscanite (Grant et al., 1980), in general, tin porphyries are associated with only moderately fractioned subvolcanic rocks of rhyodacitic composition. However, the recent paper by Dietrich et al. (1999) provided analytical evidence (melt inclusions data) for the origin of the Bolivian tin porphyry magmas by mixing of high evolved silicic melts -containing quartz phenocryts- with andesitic to basaltic melt fractions, in an upper crustal reservoir. We will back again to this section on Andean magmas.
In the group of "non-porphyric" deposits are
included vein-type Sn mineralizations, hosted in Paleozoic clastic rocks that
are not related to outcroping intrusive bodies (except dykes). Among them are
the Colquiri (fluorite-sphalerite-cassiterite); Huanuni,
Tin-silver veins in northwest
Andean magmas and ore deposits
Magmatic rocks are dominant in the Andean belt and most ore deposits are directly or indirectly associated to magmatic activity. A major part of the extrusive and intrusive rocks of Paleozoic to Cenozoic age belong to the calc-alkaline series, although tholeiitic rocks are present in the accreted oceanic prisms of the northern Andes, and both shoshonitic and alkaline rocks are associated to the calc-alkaline series. Except for the tholeiitic rocks, the chemical and isotopic composition of Andean igneous rocks suggest that their magmas originated from common though variable sources and mechanisms. This point is illustrated by the strong similarities in chemical and isotopic composition of rocks from such differents setting and age as the Paleozoic granitoids of the Cordillera Frontal in Argentina (87Sr/86Sr (i) = 0.7053 - 0.7070; Caminos et al., 1979) and the Plio-Quaternary andesites of the Central Andes (87Sr/86Sr (i) = 0.7051 - 0.7077; Pichler and Zeil, 1972; Mc Nutt et al., 1975). The general model (López-Escobar et al., 1977, 1979, 1995; Thorpe and Francis, 1979) considers that the Andean magmas originate in the Upper Mantle zone between the subducted oceanic plate and the continental crust. The model also considers the participation of melts and fluids from the upper layers of the subducting plate, as a trigger mechanism for partial melting in the mantle, a contibution that has been sustained by Be-10 isotopy (Morris et al, 1985). The final composition of Andean magmas are then explained in term of different contribution from the oceanic plate, variable degrees of partial melting of mantle materials, different fractional crystallization processes during the rise of magmas and possible contamination in their passage through the continental crust. An alternative source proposed for Andean magmas generated in zones with a thick continental crust, are the lower crustal levels (e.g., Pichler and Zeil, 1972; Mc Kee et al., 1994). The participation of mantle melts interacting with crust derived melts in deep reservoir, has also been considered and sustained by Sr isotopy (e.g., Deruelle and Moorbath, 1993, for lavas from the south-central Andes).
The incorporation of crustal -igneous and sedimentary-
materials to the magmas during its passage through the crust is well
established as a mechanism for emplacement of the Coastal Batholith of Perú
(described in the important book by Pitcher et al., eds., 1985, and considered
as a model for batholith emplacement in the
However, it is possible that crustal materials contribute to the magma enrichment in LIL-type (e.g., K, Rb, Ba) and incompatible (e.g., Cu, Mo, Pb) elements, by partial assimilation of crustal materials. Thus, normal high-K and shoshonitic, intermediate to mafic, Mesozoic volcanics rocks in central-north Chile, differ only by their K, Rb and Ba content, non LIL-elements remaining almost constant (Oyarzún et al., 1993).
In consequence, several sources are possible to contribute metals and metaloids to the Andean ore deposits related to magmatic processes, and the isotopic data are relevant to assess their relative importance.
Two elements are most relevant in terms of their
isotopic ratios to evaluate possible ore sources. They are the Pb isotopic
ratios for the metals and the S isotopic ratios for the metaloids. However, Pb
has a strong tendency to accumulate in the crust and the interpretation of their
isotopic ratios in term of sources for the ores do not necessarily apply to
other metals like Cu, Zn or
There are numerous studies on Pb isotopic ratios in
Andean igneous rocks and ore deposits. In general, they conclude that different
sources participate in variable degrees according to the tectonic settings of
the rocks and the ore deposits. Thus, Puig (1988, 1990) points out to the
relatively narrow range of Pb isotopic ratios in Andean ore deposits,
interpreted by this author in terms of reservoir mixing processes during the
Andean evolution. However, he also established some relationship between the Pb
isotopic ratios and the tectonic setting of the deposits. Thus, polymetallic
ores in volcano-sedimentary rocks of the tectonically extensional Lower
Cretaceous basin in
Regarding to 32S/34S isotopy,
the different studies are coincident in terms of the magmatic origin of sulphur
in most of the sulfide metallic deposits of the Andean belt. In the case of
porphyry copper systems, d34S in sulfide minerals is very close to
the meteoritic standard (e.g.; -3 o/oo at
Though the close relationship between magmas and Andean ore deposits is well established, many aspects of this relation remain poorly understood or are just begining to clarify. In the following paragraphs, some of this aspects will be briefly considered.
Porphyry copper deposits are the best studied deposits
in the Andean belt and possibly in the world. They have low 87Sr/86Sr
(i) ratios, very low d34S indexes and, at least those of the
Eocene-Oligocene span in northern
Several studies (e.g., Baldwin and Pearce, 1982;
López-Escobar and Vergara, 1982) have intended to find some significant
relation between the chemical composition of low altered intrusive rocks
associated to porphyry copper deposits and their "productivity" in
terms of porphyric mineralization. However, no significant difference was found
regarding "non-productive" contemporary intrusive rocks. The only
exception was some smaller content of Y and Mn observed by Baldwin and Pearce
(1982) in the "productive" porphyries of the
However, the possibility that porphyry copper systems were not related to normal calc-alkaline batholiths but rather to magnetite-rich, mafic bodies of batholithic magnitude, was recently rise by Behn and Camus (1997). These authors considered the presence of large ENE and NWN magnetic anomalies that exhibit spacial coincidence with Eocene-Oligocene porphyry copper deposits between 18º S and 27º S, in terms of mafic magmatic reservoirs from which porphyry copper systems were possibly derived.
Although calc-alkaline magmatism has been assumed as
the source for porphyry copper systems, it is well known that the principal
mineralization is closely associated to potassium metasomatism. Skewes and
Arévalo (1997) have proposed a daring alternative interpretation to their
relationship for the case of El Teniente, where the Cu (Mo) ore is in K-rich
biotitic andesites, that host quartz dioritic and dacitic porphyties. Instead
of the traditional interpretation (that is, the andesites were hydtothermally
altered by the porphyries), they consider that the andesites represent an ore rich,
high-K, intrusive magma. Considering the chemical analysis published by Camus
(1975), these andesites, if interpreted as primary rocks, should be classified
as absarokites (shoshonitic basalt) according to the Peccerillo and
Besides, the model by Skewes and Arévalo (1997) is
close to the ore-magma concept, which has been applied in
The fact that the Tertiary igneous rocks related to
Sn-Ag mineralization in south
Finally, although most of the Andean ore deposits are associated to magmatic activity, wich has been almost permanent in the belt, the matallogenetic activity seem rather discontinuos and related to significant tectonic disruptions that abruptly desplaced the magmatic belts. Therefore, favorable conditions for mixing of different types of magmas may have occurred during these disruptive episodes, that will be discussed in the next section.
Andean tectonics and ore deposits
Although magmatic activity provide the direct source and mechanisms for the generation of ore deposits in the Andean belt, tectonics controls not only the production and emplacement of magmas, but also the channels for the ore bearing fluids. Besides, although the association between plutonic and coeval volcanics rocks is a normal trait of the Andean magmatism, the ratios between the volumes of intrusive and extrusives magmas has been much variable, the volcanism being favored during the stretching stages and the plutonism increasing with the compressive tectonic pulses.
Both the geological and the metallogenetical evolution of the Andean belt during the Mesozoic-Cenozoic span, can be consistenly explained in terms of the interactions of the continental and oceanic lithospheric plates. Among the main consequences of this interaction are the continuos production of calc-alkaline magmas, the accretion to the continent of oceanic prisms, the development of back-arc basins, the occurance of several orogenetic episodes, the formation of mega-fault zones and the generation of ore deposits.
Post-Paleozoic accretion of oceanic prisms occured
during Tertiary times in the Northern Andes (
Two subduction styles have been recognized for the
tectonic evolution of the central and south central
As pointed out by Sillitoe (1988, 1991), the eastward shifting of magmatism in the Chilean-Argentinian Andes from the Jurassic to Miocene times, have produced several N-S ore deposits belts, coincident with the position of the contemporaneous magmatic belt. They include porphyry copper deposits since the Albian. Although the eastward shifting has been interpreted in terms of a flatter angle of the subducting slab, due to an acceleration to the convergence rate of the tectonic plates, the machanism is not completely understood. Thus, as stated by Sasso and Clark (1998) for the Middle Miocene stage: "The arc therefore dis not merely shift eastward (Davidson and Mpodozis, 1991) but, within the limits of error of the 40Ar/39Ar dating technique, instantaneously broadened in the Middle Miocene". Other example of sudden horizontal eastward magmatic and metallogenetic displacement, is that of the Andahuaylas-Yauri Cu-Fe skarns belt, linked by Noble et al. (1984) to a change in the subduction geometry due to the Incaica orogeny.
As explained by Scheuber and Reutter (1992), the stress component normal to the plate boundary produces structures of crustal shortening or extension, while the component parallel to the plate boundary (in case of oblique convergence) causes longitudinal wrenching.
Two important fault zones in the north Chilean Andes are interpreted in terms of oblique subduction. They are the Atacama and the Domeyko fault zones, to which many high tonnage ore deposits are associated (Fig. 10). The Atacama Foult Zone (AFZ) represent an older weakness zone of the crust that was reactivated in the Early Cretaceous, as a consequence of a N20ºE plate convergence, the oceanic Aluk plate coming from the NNW (Pardo-Casas and Molnar, 1987). The oblique plate convergence generated regional shearing traduced in dominant sinistral strike-slip movements, up to several tenths of km (Bonson et al, 1997). During the Lower Cretaceous, magmas and their derivative fluids, responsible for Kiruna-type Fe and Cu-Fe deposits like Manto Verde, were focused into dilational sites and fault intersections at the AFZ (Thiele and Pincheira, 1987; Bonson et al., 1997).
The Domeyko Fault Zone is also interpreted in terms of
an oblique convergence , this time the oceanic plate (Farallón) coming from the
SW with a convergence rate of 12 cm/year. This fault zone is also considered as
an early structure, along which a deep readjustment of the crust occured
An important wrench fault in Perú is the Huara Fault
System (Petersen and Vidal, 1996) that has a N to EN direction and occurs in
the brittle environment of the Coastal Batholith, along a Lima-Cerro de Pasco
course. Several volcanogenic massive sulfide deposits as well as important
polymetallic districts (e.g., Casapalca,
As pointed out by Maksaev and Zentilli (1988), mega fault zones have complex relationships with both magmas and ore deposits. They probably represent major weakness zones within the crust, that have some control on the paths of the rising magmas. However, those magmas also contribute to the weakness of the zone, affecting the rheological properties of the rocks. In consequence, the wrenching process due to the parallel stress component (Scheuber and Reutter, 1992) is enhanced. On the other hand, although most of the stockwork-type porphyry copper deposits of the Andes (e.g., Chaucha in Ecuador, Goosens and Hollister, 1973) are related to important faults, other major deposits, like those of the "Arequipa lineament" (Hollister, 1974) or El Teniente (Camus, 1975), do not present evident structural controls (although their alignement points to deep seated controls).
Thus, the genesis the major Andean deposits, although controled by the position of the magmatic arc and favored by structures like the wrenching faul zones, should be related to deep seated disturbances, affecting the geometrical and physico-chemical relationships between the subducting oceanic plate, the asthenosphere and the mantle-crust boundary. This concept, illustrated e.g., by the Sasso and Clark (1998) model for the Middle Miocene broading of the magmatic arc and the genesis of porphyry Cu (Au) deposits in Argentina, may explain why the larger Andean deposits were formed during such short "pulsative" span as those established for Kiruna-type deposits in north Chile (Oyarzún and Frutos, 1984) and for porphyry copper deposits along the whole Andean belt (Sillitoe, 1988).
The metallogenic zoning and evolution of the Andean belt
Three main subjects will be discussed in this section:
the tectonic segmentation of the
As with many central subjects of Andean
metallogenesis, the implications of the tectonic segmentations of the Andes in
terms of magmatism and ore deposits were first rise by Sillitoe (1974), who
proposed 16 tectonic boundaries between Oº (Carnegie Ridge) and 44º S (Chile
Ridge). Some of these boundaries, which were proposed on the basis of main
structures, seismic and volcanic activity, main morphological units, old
terrain outcrops and the intersections with oceanic ridges, are coincident with
the longitudinal limits of the metallic belts. Thus, the tin belt is restricted
to three segments, enclosed by boundaries 5 (northern limits of the belt of
The Andean tectonic segmentation is the result of a
number of heterogeneities along the belt, which is made up of old and young
terrains and tectonic blocks. Among the formers is the Precambrian Arequipa
Massif, in SW Perú (Petford and Atherton, 1995), while the Western Cordillera
of Colombia is made up of a Cretaceous oceanic prism accreted to the continent
during Tertiary times. If one considers the heterogeneittes of the continental
crust, the geometry of the continent, the complexities in the oceanic plates
(e.g., the ridges) and the variation in speed and angle of convergence between
the plates (and their consequences in the subduction zone), longitudinal
segmentation is a natural consequence. However, the relationships between
tectonic boundaries and metallic belts is rather uncertain in terms of
cause-effect. Thus, the tin povince may be, in part, a consequence of the
thicker continental crust between boundaries 5 and 8, that could have favored
the magma mixing process proposed by Dietrich et al. (1999). In exchange, the
pause of the iron belt north of boundary 9 may be interpreted in terms of the
higher erosion degree that affect the Lower Cretaceous series, resulting in the
unroofing of the batholithic levels. In general, erosion levels have been
considered an important factor for explaining metallic belts distribution in
Besides erosion levels, several other factors have
been considered to explain the longitudinal discontinuities of Andean metallic
provinces (Oyarzún, 1985, 1990). Thus, Mesozoic paleogeographical conditions in
central Perú were favorable to the abundant deposition of carbonatic sediments,
a factor considering favorable for the rich development of the polymetallic
province in this country. In exchange, this province is less developed in
The presence of "metallic domains" (Routhier, 1980), defined as volumes of the continental crust that are endowed with a special metalliferous potential during long geological times, is neither a good explanation for the longitudinal Andean metallic segmentation. In fact, although Paleozoic and post-Paleozoic Andean metallic provinces are similar in nature, their different geographical distribution is not consistent with the concept of metallic domains. Thus, even the Sn-W belts, that have a coherent "continental" position in all the three geological eras, present, however, different latitudinal situations.
It is likely that the elusive answer be a combination of factors, involving plate tectonics, magma mixing, the nature of host rocks, regional erosion levels etc. For instance, the fact that the Andean segments between 26º30’ S and 30º30’ S seem anomalously rich in gold, is interpreted by Sasso and Clark (1998) in terms of an upwelling asthenosphere, a transverse rupture in the subducting slab and a minimum contamination by shallow crustal lithologies. Thus, both Cu and Au are considered as directly contributed by the asthenosphere to the partial melting zone in the overlying lithospheric wedge.
Concerning the transversal zoning of the Andean belt, the fact that modern volcanic and subvolcanic igneous rocks also present such a zoning (with alkaline and K-rich magmas at greater distance from the present oceanic trench, Palacios and Oyarzun, 1975). Although the same factors proposed to explain the longitudinal segmentation have been considered for the transversal zoning, plate tectonic has received a major atention. Thus, Sillitoe (1972) proposed a "geostill" model based on metallic elements provided by the subducting plate to the melting zone of the lithospheric slab, and Oyarzún and Frutos (1974) a similar model, but based on the "anionic" elements, like sulphur and halogens.
The distribution of the Cu and Sn metalliv provinces
at both sides of the
Although the importance of plate tectonics in terms of
Andean metallogenesis is well sustained , it is also certain that the tectonic
and magmatic evolution of some Andean segments include periods when the
subduction process was perturbed or exhibited little activity. This is the
case, e.g., of the Lower Cretaceous basin in Perú (Atherton and Webb, 1989) and
The comparison of the post-Paleozoic metallogenetical evolution of the Andean belt with that of the island arcs, e.g., the Fidji arc, reveals interesting similarities, specially in terms of increase in both the number of different types of ore deposits and the magnitude attained by the larger ones. For the case of the island arcs, this evolution is parallel to the development of a dioritic tonalitic crust. Thus, at Fidji (Colley and Greenbaum, 1980), this crust was developed during the Tertiary, following a stage of tholeiitic and andesitic volcanism and compressive episode. Not only the number and magnitude of sulfide deposiits greatly increased, but also the number of metals involved and the number of types of metallic deposits (from one: massif sulfides to four, including porphyry copper deposits).
Concerning the Andean belt is amazing the number of
important deposits of Tertiary age, as well as their distribution in or around
the central part of the Andes (10º S to 35º S), where the continental crust
attained its maximum thickness. That is the case for all the metallic
provinces, except for the iron belt (though the important Pliocene magnetite
deposit of El Laco is in the high
In metallogenic terms, an evolved crust implies a higher degree of structural complexity, better opportunities for magma mixing, contributions from sedimentary strata with different chemical compositions etc. Also, a number of geological levels, from the asthenosphere to the sedimentary strata may participate in the generation and differentiation of magmas and in the genesis of the ore deposits resulting of their emplacement and interactions with the host rocks and fluids in the upper levels of the crust.
Acknowledgments-The present contribution has a far background in a
doctoral thesis presented at
I also acknowledge the kind invitation from Dr. C. Schobbenhaus and from the editors Profs. T. Filho and J. Milani to participate in this important publication, and to the reviewers who labored to polish the ideas and the presentation of my manuscript. Finally, my thanks to Angélica for the drawings that illustrate this paper and to Ricardo, for his help to finish my manuscript under difficult logistic circumstances.
Aberg, G., Aguirre, L., Levi, B. and Nystrom, J. 1983.
Spreading subsidence and generation of ensialic marginal basins: an example
from the Early Cretaceous of central
Aguirre, L., Herve, F. and Godoy, E. 1972.
Distribution of metamorphic facies in
Ahlfeld, F. 1967. Metallogenetic epochs and provinces
Ambrus, J. 1988. Chilean molybdenum resources. In:
International molybdenum encyclopaedia. (Edited by Sutulov, A.) 1, pp87-93.
Amstutz, G.C. and Fontboté, L. 1987. Yacimientos estratoligados en el sector central del borde móvil andino. Elementos para una síntesis. In: Investigaciones alemanas recientes en Latinoamérica. Geología (Edited by Miller, H.) pp 123-136. Bonn.
Angelelli, V., Fernández, J.C., Herrera, A. and Aristarain, L. 1970. Descripción del Mapa Metalogénico de la República Argentina. Dirección Nacional de Geología y Minería, Buenos Aires, 172 p.
Angulo, R. 1978. Recursos minerales de Colombia. Instituto Nacional de Investigaciones Geológico-Mineras, Bogotá. 544 p.
Arenas, M.J. 1988. Geological, mineralogical and
chemical characteristics of epithermal precious-metal deposits in southern Perú
(Abstract). Revista Geológica de Chile.
Atherton, M.P. and Webb, S. 1989. Volcanic facies, structure, and geochemistry of the marginal basin rocks of central Perú. Journal of South American Earth Sciences, 2, 241-261.
Atkin, B.P., Injoque, J.L. and
Auboin, J., Borello, A.V., Cecioni, G., Charrier, R., Chotin, P., Frutos, J., Thiele, R. and Vicente, J.C. 1973. Esquisse paléogéographique et structurale des Andes Méridionales. Revue de Géographique Physique et de Géologie Dynamique 15, 11-72.
Audebaud, E., Capdevilla, R., Dalmayrac, B., Debelmas, J., Laubacher, G., Lefevre, C., Marocco, R., Martínez, C., Mattauer, M., Mégard, F., Paredes, J. and Tomasi, P. 1973. Les traits géologiques essentiels des Andes Centrales (Pérou-Bolivie). Revue de Géographie Physique et de Géologie Dynamique 15, 73-114.
Baldwin, J. A. and Pearce, J.A. 1982. Discrimination of productive and non productive porphyric intrusions in the Chilean Andes. 1982. Economic Geology 77, 664-674.
Barrero, D. 1976. Mapa metalogénico de Colombia (1:5.000.000). Instituto Nacional de Investigaciones Geológio-Mineras. INGEOMIN, Bogotá.
Behn, R. and Camus, F. 1997. Transanomalías magnéticas: imagen geofísica de metalotectos y clusters de pórfidos cupríferos andinos. Proceedings VIII Congreso Geológico Chileno (Antofagasta) 2, 852-856.
Bellido, E. and Montreuil, L. 1972. Aspectos generales de la metalogenia del Perú. Servicio de Geología y Minería, Lima, 149 p.
Bellido, E., Gerard, D. and Paredes, J. 1972. Mapa Metalogénico del Perú. 1:2.500.000. Servicio de Geología y Minería, Lima.
Bonson, C.G., Grocott, J. and Rankin, H. 1997. A
structural model for the development of Fe-Cu mineralization, Coastal
Bookstrom, A.A. 1977. The magnetite deposits of
Bossi, G.E. and Viramonte, J.G. 1975. Contribución al conocimiento de la petrología de los yacimientos ferríferos sedimentarios de Zapla y Unchimé (provincias de Jujuy y Salta, República Argentina). Proceedings II Congreso Iberoamericano de Geología Económica (Buenos Aires) 5, 181-202.
Burnham, C.E. and Ohmoto, H. 1980. Late stage processes of felsic magmatism. In: Granitic magmatism and related mineralization (Edited by Ishihara, S. and Takenouchi, S). Mining Geology (Tokio) Special Issue 8, 1-12.
Caminos, R., Cordani, U. and
Camus, F. 1975. Geology of El Teniente orebody with emphasis on wall-rock alternation. Economic Geology, 70, 1341-1372.
Camus, F. 1985. Los yacimientos estratoligados de Cu, Pb-Zn y Ag de Chile. In: Geología y recursos minerales de Chile (Edited by Frutos, J., Oyarzun, R. and Pincheira, M.). Editorial Universidad de Concepción, Concepción, 2, 547-635.
Camus, F., Sillitoe, R.H. and Petersen, R. (Editors). 1996. Andean copper deposits: new discoveries, mineralization styles and metallogeny. Society of Economic Geologists Special Publication 5, 198 p.
Canchaya, S. 1990. Stratabound ore deposits of
Hualgayoc, Catamarca, Perú. In: Stratabound ore deposits in the
Cardozo, M. and Cedillo, E. 1990.
Geologic-metallogenetic evolution of the Peruvian Andes. In: Stratabound ore
deposits in the
Carlson, G.C. 1977. Geology of the Bailadores,
Cedillo, E. 1990. Stratabound lead-zinc deposits in
the Jurassic Chaucha Formation,
Colley, H. and Greenbaum, D. 1980. The mineral deposits and metallogenesis of the Fidji platform. Economic Geology, 75, 807-829.
Coney, P.J. 1970. The geotectonic cycle and the new
global tectonics. Bulletin of the Geological Society of
Corvalán, J. 1981. Plate-tectonic map of the Circum-Pacific region-Southeast quadrant (1:10.000.000). Circum-Pacific Council for Energy and Mineral Resources and the American Association of Petroleum Geologists.
Cuadra, W.A. and Dunkerley, P.M. 1991. A history of
Davidson, J. and Mpodozis, C. 1991. Regional geologic
setting of epithermal gold deposits,
Deruelle, B. and Moorbath, S. 1993. A similar magma
source for ignimbrites and non-ignimbritic lavas from
Dietrich, A., Lehmann, B., Wallianos, A., Traxel, K.
and Palacios, C. 1999. Magma mixing in Bolivian tin porphyries. Naturwissenschaften
Di Marco, A. and Mutti, D. 1996. Los depósitos de Cu-Fe en anfibolitas de la Sierra de Cunuputo, Córdoba. Instituto de Recursos Minerales, Universidad Nacional de La Plata, Argentina. Publicación Nº 5, 311-316.
Echavarría, L.E. and Etcheverry, R.O. 1998. Características geoquímicas de la mineralización epitermal del area El Dorado-Monserrat, Provincia de Santa Cruz, Argentina. Revista Geológica de Chile, 25, 1, 69-83.
Ericksen, G.E. 1976. Metallogenic provinces of the southeastern Pacific region. American Association of Petroleoum Geologists. Memoir 25, 527-538.
Espinoza, S., Véliz, H., Esquivel, J., Arias, J. and
Field, C. W. and Gustafson, L.B. 1976. Sulfur isotopes
in the porphyry copper deposit at
Fontboté, L., Gunnesch, K.A. and Baumann, A. 1990.
Metal sources in stratabound ore deposits in the
Francis, P.W. and Baker, M.C.W. 1978. Sources of two
large ignimbrites in the central
Francis, P.W., Baker, M.C.W. and Halls, C.1981. The
Frutos, J. 1975. Porphyry copper-type mineralization and geosynclinal tectonic evolution in the Chilean Andes. Annales de la Societé Géologique de Belgique 98, 5-15.
Frutos, J. and Oyarzún, J. 1975. Tectonic and
geochemical evidence concerning the genesis of El Laco magnetite lava flows
Frutos, J., Fontboté, L., and Amstutz, G.C. 1990. Map
of stratabound ore deposits of the
Frutos, J., Oyarzún, J., Shiga, Y. and Alfaro, G.
1990. The El Laco magnetite lava flow deposits, northern
Giacosa, R., Márquez, M. and Pezzuchi, H. 1988. Actualización metalogénica de la región patagónica al sur del paralelo 42º S, República Argentina. Proceedings Tercer Congreso Nacional de Geología Económica (San Juan), 3, A1-A20.
Goosens, P.J. 1969. Mapa índice mineralógico. República del Ecuador (1:1.000.000). Servicio Nacional de Geología y Minería, Quito.
Goossens, P. 1972a. An exhalative volcanic iron
sulfide stratabound deposit near
Goossens, P. 1972b. Metallogeny in Ecuadorian
Goossens, P. and Hollister, V.F. 1973. Structural
control and hydrothermal alteration pattern at Chaucha porphyry copper,
Gorzawski, H., Fontboté, L., Field, C.W. and Tejada,
R. 1990. Sulfur isotope studies in the zinc-lead mine San Vicente, central
Perú. In: Stratabound ore deposits in the
Grant, J.N., Halls, C.,
Grant, J.N., Halls, C.,
Grant, J.N., Halls, C., Sheppard, S.M.F. and
Grez, E., Aguilar, A., Henríquez, F. and Nystrom, J.O.
1991. Magnetita Pedernales: A new magmatic iron deposit in
Gustafson, L.B. and Hunt, J.P. 1975. The porphyry
copper deposit at
Hollister, V.F. 1974. Regional characteristics of
porphyry copper deposits of
Ishihara, S. 1977. The magnetite-series and
ilmenite-series granitic rocks. Mining Geology (
Ishihara, S. 1978. Metallogenesis in the Japanese
island-arc system. Journal of the Geological Society,
Ishihara, S. 1981. The granitoids series and mineralization. In: Economic Geology 75 Anniversary volume (Edited by Skinner, B.J.), 458-484.
Ishihara, S. and Ulriksen, C. 1980. The
magnetite-series and ilmenite-series granitoids in
James, D.E. 1971. Plate tectonic model for the
evolution of the
Larson, A. and Oreskes, N. 1994. The magnetite
Lehmann, B. 1985. Formation of the strata-bound
Kellhuani tin deposits,
Lehmann, B. 1990. The stratabound Kellhuani tin
Lehmann, B. 1990. Metallogeny of tin. Springer
Lehne, R.W. 1990. The polymetallic ore deposits of
Colquijirca, central Perú. In: Stratabound ore deposits in the
Levi, B. and Aguirre, L. 1981. Ensialic
spreading-subsidence in the Mesozoic and Paleogene Andes of central
Levi, B., Nystrom, J.O., Thiele, R. and Aberg, G.
1988. Geochemical trends in Mesozoic-Tertiary volcanic rocks from the Andes in
Long, K., Ludington, S., du Bray, E., Ramos, O. and Mc
Kee, E.H. 1992. Geology and mineral deposits of La Joya district,
López-Escobar, L. and Vergara, M. 1982. Geoquímica y petrogénesis de rocas granodioríticas asociadas con el yacimiento cuprífero de Río Blanco-Los Bronces. Revista Geológica de Chile (Santiago). 15, 59-70.
López-Escobar, L., Frey, F.A. and Vergara, M. 1977. Andesites
and high-alumina basalts from the central-south
López-Escobar, L., Frey, F.A. and Oyarzún, J. 1979. Geochemical
characteristics of central
López-Escobar, L., Cembrano, J. and
Maksaev, V. and Zentilli, M. 1988. Marco metalogénico regional de los megadepósitos de tipo pórfido cuprífero del Norte Grande de Chile. Proceedings V Congreso Geológico Chileno (Santiago) 1, B181-B212.
Malvicini, L. 1975. La continuación del cinturón occidental de estaño y wolframio de América del Sur en Argentina. Proceedings V Congreso Latinoamericano de Geología (Buenos Aires), 2, 384-404.
Malvicini, L. and Llambías, E. 1982. El magmatismo Mioceno y las manifestaciones metalíferas asociadas en Argentina. Proceedings V Congreso Latinoamericano de Geología (Buenos Aires), 3, 547-566.
Márquez, M.J. 1988. Mineralización polimetálica asociada al magmatismo mioceno en la Cordillera Patagónica austral, provincia de Santa Cruz, Argentina. Proceedings V Congreso Geológico Chileno (Santiago) 1, B237-B256.
Márquez, A., Oyarzun, R., Doblas, M. and Verma, S.P. 1999. Alkalic (ocean-island basalt type) and calc-alkalic volcanism in the Mexican volcanic belt: A case for plume-related magmatism and propagating rifting at an active margin?. Geology, 27, 1, 51-54.
Macfarlane, A.W., Marcet, P., Le Huray, A.P. and
Petersen, U. 1990. Lead isotope provinces of the
Mc Kee, E.H., Robinson, A.C., Rybuta, J.J., Cutiño, L.
and Moscoso, R.D. 1994. Age and Sr isotopic composition of volcanic rocks in
the Maricunga belt,
Mc Kinstry, H.E. 1936. Geology of the silver deposit at Colquijirca, Perú. Economic Geology, 31, p 618-635.
Montecinos, P. 1983. Pétrologie des roches intrusives associées au gisement de fer El Algarrobo (Chile). Dr-Ing. Thesis, Université de Paris-Sud, 191 p.
Morris, J., Tera, F., Hammond, R., López-Escobar, L.,
Klein, J. and Middleton, R. 1985. Be-10 in lavas from the Andean Southern
Volcanic Zone (35º40’ S): Evidence for sediment subduction. Comunicaciones (
Munchmayer, C. 1996. Exotic deposits-products of lateral migration of supergene solutions from porphyry copper deposits. In: Andean copper deposits: new discoveries, mineralization styles and metallogeny (Edited by Camus, F., Sillitoe, R.H. and Petersen, R.). Society of Economic Geologists Special Publication 5, 43-58.
Munizaga, F., Huete, C. and Hervé, F. 1985. Geocronología K-Ar y razones iniciales 87Sr/86Sr de la "Faja Pacífica de Desarrollos Hidrotermales". Proceedings IV Congreso Geológico Chileno (Antofagasta) 3, 4/357-4/479.
Munizaga, F., Holmgren, C., Huete, C. and Kawashita, K.
1988. Geocronología de los yacimientos de cobre El Soldado y Lo Aguirre, Chile
central. Proceedings V Congreso Geológico Chileno (
Noble, D.C. and Vidal, C.E. 1994. Gold in Perú. SEG Newsletter, 17, p1 and 7-17.
Noble, D.C., Mc Kee, E.H., Eyzaguirre, R. and Marocco, R. 1984. Age and regional tectonic and metallogenetic implications of igneous activity and mineralization in the Andahuaylas-Yauri belt of southern Perú. Economic Geology, 79, 172-176.
Nystrom, J. O. and Henríquez, F. 1994. Magmatic
features of iron ores of the Kiruna-type in
Ortiz, F. 1990. Massive sulfides in
Oyarzún, J. 1985. La métallogenie andine: cadre géologique, petrologique et géochemique, et essai d’interpretation. Sc.D. Thesis, Université de Paris-Sud. 864 p.
Oyarzún, J. 1990. El desarrollo geológico y metalogénico de
la cadena andina. In: Yacimientos Minerales (Edited by Lunar, R. and
Oyarzun, R.). Editorial R.
Oyarzún, J. and Frutos, J. 1974. Porphyry copper and tin-bearing porphyries. A discussion of genetic models. Physics of the Earth and Planetary Interiors 9, 259-263.
Oyarzún, J. and Frutos, J. 1980. Metallogenesis and
porphyry deposits of the
Oyarzún, J. and Frutos, J. 1984. Tectonic and
petrological frame of the Cretaceous iron deposits of northern
Oyarzún, J., Levi, B. and Nystrom, J.O. 1993. A
within-plate geochemical signature and continental margin setting for the
Mesozoic-Cenozoic lavas of central
Oyarzun, R., Clemmey, H. and Collao, S. 1984. Chemical
characteristics of the Nahuelbuta mountains banded iron formations, southern
Oyarzun, R., Ortega, L., Sierra, J., Lunar, R. and
Oyarzún, J. 1996. The manto-type gold deposits of Andacollo (
Palacios, C. and Oyarzun, R. 1975. Relationships
between depth to Benioff zone and K and Sr concentrations in volcanic rocks of
Pareja, J., Vargas, C., Suarez, R., Ballon, A., Carrasco, R. and Villarroel, A. 1978. Mapa geológico de Bolivia. Memoria explicativa. Y.P.F.B. and Servicio Geológico de Bolivia (La Paz) 27 p.
Pardo-Casas, F. and Molnar, P. 1987. Relative motion of the Nazca (Farallón) and South American plates since Late Cretaceous time. Tectonics, 6, 233-248.
Park, C.F. 1961. A magnetite "flow" in
Peccerillo, A. and Taylor, S.R. 1976. Geochemistry of
Eocene calc-alkaline volcanic rocks from the Kastamonu area, northern
Petersen, U. 1970. Metallogenetic provinces in
Petersen, U. 1977. Introduction to "An issue devoted to mineral deposits in the South American Cordillera". Economic Geology, 72, 887-892.
Petersen, U. and Vidal, C. 1996. Magmatic and tectonic controls on the nature and distribution of copper deposits in Perú. In: Andean copper deposits: new discoveries, mineralization styles and metallogeny (Edited by Camus, F., Sillitoe, R.H. and Petersen, R.) Society of Economic Geologists special publication 5, p1-18.
Petersen, U., Macfarlane, A.W. and Danielson, A. 1993.
Lead isotopic provinces in
Petford, N. and Atherton, M.P. 1995. Crustal segmentation and isotopic significance of the Abancay Deflection: Northern Central Andes (9-20º S). Revista Geológica de Chile (Santiago) 22, 2, 235-243.
Pichler, H. and Zeil, W. 1972. The Cenozoic rhyolite-andesite association of the Chilean Andes. Bulletin Volcanologique, 35, 424-452.
Pitcher, W.S., Atherton, M.P., Cobbing, E.J. and Beckinsale, R.D (Editors). 1985. Magmatism at a plate edge: the Peruvian Andes. Blackie (Glasgow), 328 p.
Puig, A. 1988. Geologic and metallogenetic significance of the isotopic composition of lead in galenas of the Chilean Andes. Economic Geology. 83, 843-858.
Puig, A. 1990. Lead isotopes in the Chilean ores. In:
Stratabound ore deposits in the
Reyes, M. 1991. The Andacollo strata-bound gold
Routhier, P. 1980. Oú sont les métaux por l’avenir?-Les provinces métalliques. Essai de metallogénie globale. Memoire du BRGM Nº 105 (Orleans), 410 p.
Ruiz, C. and Peebles, F. 1988. Geología y yacimientos metalíferos de Chile. Editorial Universitaria, Santiago, 334 p.
Ruiz, C., Aguirre, L., Corvalán, J., Klohn, C., Klohn, E. and Levi, B. 1965. Geología y yacimientos metalíferos de Chile. Instituto de Investigaciones Geológicas, Santiago, 305 p and maps.
Samaniego, A. 1980. Strata-bound Pb-Zn
(Ag-Cu) ore occurences in Early Cretaceous sediments of north and central
Perú-a contribution to their metallogenesis. Doctoral thesis,
Sasaki, A., Ulriksen, C., Sato, K. and Ishihara, S.
1984. Sulfur isotope reconnaissance of porphyry copper and manto-type deposits
Sasso, A.M. and Clak, A.H. 1988. The Farallón Negro
Scheuber, E. and Reutter, K.J. 1992. Magmatic arc
tectonics in the central
Schneider, A. 1987. Eruptive processes, mineralization
and isotopic evolution of the Los Frailes-Karikari region,
Schneider, H.J. and Lehmann, B. 1977. Contribution to
a new genetical concept on the Bolivian tin province. In: Time and
strata-bound ore deposits (Edited by Klemm, D.D. and Schneider, H.J.).
Springer Verlag (
Schneider, A. and Toloza, R. 1990. The minig district
of the General Carrera lake and the Rosillo manto deposit, Aysen province,
Skewes, A. and Arévalo, A. 1997. Andesitas de la mina El
Teniente. Proceedings VIII Congreso Geológico Chileno,
Sillitoe, R. H. 1972. Relation of metal provinces in
Sillitoe, R.H. 1973. The tops and bottoms of prophyry copper deposits. Economic Geology, 68, 799-815.
Sillitoe, R.H. 1974. Tectonic segmentation of the
Sillitoe, R.H. 1976. Metallic mineralization affiliated to sub-aereal volcanism: a review. Procedings Annual Meeting of the Geological Society, London-Institution of Mining and Metallurgy. 99-116.
Sillitoe, R.H. 1977. Permo-Carboniferous, Upper Cretaceous and Miocene porphyry copper type mineralizations in the Argentinean Andes. Economic Geology 72, 99-103.
Sillitoe, R.H. 1983. Enargite-bearing massive sulfide deposits high in porphyry copper systems. Economic Geology 78, 348-352.
Sillitoe, R.H. 1988. Epochs of intrusion-related
copper mineralization in the
Sillitoe, R.H. 1991. Gold metallogeny of
Sillitoe, R.H. 1992. Gold and copper metallogeny in the Central Andes-past, present and future exploration objectives. SEG Distinguished Lecture. In: Economic Geology, 87, 2205-2216.
Sillitoe, R.H. and Sawkins. 1971. Geologic,
mineralogic and fluid inclusion studies relating to the origin of
copper-bearing tourmaline breccia pipes,
Sillitoe, R.H., Halls, C. and Grant, J.N. 1975. Porphyry
tin deposits in
Sillitoe, R.H., Jaramillo, L., Damon, P., Shafiqullah,
M. and Escovar, R. 1982. Setting, characteristics and age of the Andean
porphyry copper belt in
Sillitoe, R.H., Marquardt, J.C., Ramírez, F., Becerra,
H. and Gómez, M. 1996. Geology of the concealed MM porphyry copper deposit,
Chuquicamata District, northern
Soler, P. and Bonhomme, M.G. 1988. New K-Ar age
determinations of intrusive rocks from the
Soler, P., Grandin, G. and Fornari, M. 1986. Essai de synthese sur la métallogenie du Pérou. Géodynamique, 1, 1, 33-68.
Spiro, B. and Puig, A. 1988. The source of sulphur in polymetallic deposits in the Cretaceous magmatic arc, Chilean Andes. Journal of South American Earth Sciences, 1, 3, 261-266.
Stoll, W.C. 1975. Yacimientos stratabound de scheelita
en el basamento cristalino de
Sureda, R.J. and Martin, J.L. 1990. El Aguilar mine:
an Ordovician sediment-hosted stratabound lead-zinc deposit in the
Sureda, R., Galliski, M., Argañaraz, P. and Daroca, J. 1986. Aspectos metalogénicos del noroeste argentino (provincias de Salta y Jujuy). Capricornio (Salta), 1, 39-96
R. and Pincheira, M. 1987. Tectónica transpresiva y movimiento de desgarre en el
segmento sur de
Thorpe, R.S. and Francis, P.W. 1979. Petrogenetic
relationships of volcanic and intrusive rocks of the
Turneaure, F.S. 1960. A comparative study of major ore
deposits of central
Turneaure, F.S. 1971. The Bolivian tin-silver province. Economic Geology 66, 215-225.
Travisany, V., Henríquez, F. and Nystrom, J.O. 1995. Magnetite lava flows in the Pleito-Melón district of the Chilean iron belt. Economic Geology, 90, 438-444.
Uyeda, S. and Kanamori, H. 1979. Back-arc opening and mode of subduction. Journal of Geophysic Research, 84, 1049-1061.
Vidal, C. 1987. Kuroko-type deposits in the Middle
Vidal, C., Injoque-Espinoza, J., Sedder, G.B. and
Mukasa, S.B. 1990. Amphibollitic Cu-Fe skarn deposits in the central coast of
W. and Henríquez, F. 1998. Génesis común de los depósitos estratoligados y
vetiformes de cobre del Jurásico Medio a Superior en
Vivallo, W., Henríquez, F. and Espinoza, S. 1994. Oxygen
and sulfur isotopes in hydrothermally altered rocks and gypsum deposits at El
Laco mining district, nothern
Wellmer, F.W. and Reeve, E.J. 1990.The Toqui
Wellmer, F.W., Reeve, E.J., Wentzlau, E. and
Westenberger, H. 1983. Geology and ore deposits of El Toqui district,
Zeil, W. 1979. The
Zentilli, M. 1974. Geological evolution and
matallogenetic relationships in the Andes of northern
Zentilli, M., Doe, B.R., Hedge, C.E., Alvarez, O., Tidy, E. and Daroca, J.A. 1988. Isótopos de plomo en yacimientos de tipo pórfido cuprífero comparados con otros depósitos metalíferos en los Andes de Chile y Argentina. Proceedings V Congreso Geológico Chileno (Santiago), 1, B331-B369.