Andean Cu-Au-base metals province of the Andes and Caribbean Plate - Overview


Main commodities: Cu Au Mo Ag Zn Pb Sn W
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The Andean Orogen, extends along the entire west coast of the South America continent, from Tierra del Fuego on its southern tip, through the Isthmus of Panama, to southern Mexico in central America and the Caribbean Islands. It may be divided into four main, laterally contiguous segments, the economically most important of which is the Central Andes of central to northern Chile, northern Argentina and southern Peru. Only three of these four segments have to date been shown to host giant porphyry style deposits. In addition to porphyry Cu±Mo±Au deposits, the orogen also hosts porphyry/skarn Cu±Au±Mo±Zn, porphyry Sn±W, epithermal Au±Ag, 'Cordilleran' epithermal polymetallic replacement and vein deposits, VHMS base metal and carbonate hosted Pb-Zn mineralisation. Each segment has a differing tectonic, geologic and metallogenic character, with internal subdivisions.

This is intended as the top level, introductory record to the Andean Cu-Au-base metals province, with links to detailed descriptions of each of the four subdivisions. These descriptions include the tectonic, geological and metallogenic setting of each, which in turn, has links to descriptions of the significant ore deposits that are hosted therein. Each of the detailed descriptions includes geological maps showing the features mentioned below, and a list of references.

These subdivisions are as follows, from south to north:

Southern Andean or Patagonian Cordillera

The ‘Southern Andes’ and Patagonia represent a Jurassic to Recent orogen developed on the western margin of the Patagonia Terrane, above the Chile-Peru trench subduction zone. The Patagonia Terrane occupies most of Chile and Argentina south of ~39°S, and is a Lower to Late Palaeozoic allochthonous to peri-autochthonous terrane that collided with the south to southwestern margin of Gondwana in the Lower Permian. Collision appears to have been along an east-west to ESE-WNW line that extends from south of Concepcion in Chile to south of Bahia Blanca in Argentina. Basement to the Patagonian terrane is predominantly composed of crystalline metamorphic rocks and foliated granitoids, representing protoliths that are indicated to be no older than Late Cambrian to Lower Ordovician. Two metamorphic-magmatic belts overprint these rocks, the northern apparently related to the Permian collision with the Gondwana to the north, the second trending NNW-SSE, possibly connected with collision with an exotic Proterozoic terrane approaching from the west in the southwestern part of the terrane. All of these rocks are overlain by late Palaeozoic to Mesozoic sequences and an extensive continental volcanic sheet related the break-up of Gondwana, as well as thick Tertiary intracontinental rocks. The southern Andes lie in the climatic zone of the westerlies which bring high rainfall to the southern Chilean Andes (in contrast to the rains shadow, desert conditions of the Central Andes). This has resulted in much stronger erosion, commensurate uplift, and erosion of the magmatic arc to its batholithic roots, removing the vertical interval in which porphyry copper systems are developed. This may in part account for the absence of major porphyry-style mineralisation in the Southern Andes.

Central Andes

The Central Andes are markedly different. This region, between Concepcion and the Abancay Deflection in southern Peru, is characterised by a collage of north-south sliver-like exotic terranes of Palaeo- to Neoproterozoic rocks that were progressively accreted to the margins if the Rio de la Plata and Amazon cratons between ~1.1 Ga and the Early Devonian. This activity was accompanied by alternating periods of extension accompanied by predominantly clastic sedimentary successions and compression associated with magmatic arc development. This section of the orogen is also characterised by continuing periods of Mesozoic to Holocene magmatism, developed over a Proterozoic basement and intervening Palaeozoic rocks, initially in a dominantly extensional semi-marine regime and from the late Cretaceous in a continental setting with pulses of compression. It is also characterised by multiple pulses of significant porphyry Cu- Mo/Au, Au-Cu, Au and Sn-Ag deposits, including many of the world’s largest such deposits. These pulses produced eastward younging linear temporal zones of porphyry and some epithermal deposits, from the Jurassic, Mid- to Late Cretaceous, Paleocene to Early Eocene, Middle Eocene to Early Oligocene, Upper Oligocene to Mid Miocene and Upper Miocene to Lower Pliocene. In addition, being in the rain shadow of the SE prevailing weather pattern, conditions that protected the cordillera from rapid erosion, but were also conducive to the generation of thick supergene blankets.

Peruvian Andes

The Peruvian Andes are separated from the Central Andes by a long-lived ENE-WSW structural dislocation that partitioned tectonic activity along the margin of Gondwana since at least the accumulation Rodinia at the close of the Mesoproterozoic. North of this structure there were possibly only one or two remaining accreted exotic terranes. In addition magmatic activity is less well developed. During the late Palaeozoic to Late Cretaceous, unlike the Central Andes, the less structurally complex and more stable basement in Peru was covered by a broad foreland basin, the western sections of which were characterised by extensive carbonate bearing platformal rocks. While magmatism was still developed from the Late Cretaceous within this arc, and major porphyry mineralisation was developed, apart from the Late Oligocene La Arena deposit in northern Peru, all known significant deposits are of Miocene age. However, because of the widespread carbonates of the intruded country rocks, skarn alteration is common at most deposits. Porphyry to epithermal gold mineralisation is more common, and Cordilleran-style epithermal base metal deposits are important, both of which are zonally related to porphyry systems. This section of the Andes is more tropical to monsoonal, with higher rainfall and less well developed supergene sulphide mineralisation. There is a transition between the Central and Peruvian Andes near Cusco on the northern extremity of the former, where the Middle Eocene to Early Oligocene porphyry province overlaps the southern limit of the carbonate platform to produce extensive mineralised skarn alteration.

Northern Andes and Caribbean Plate

The Northern Andes in Ecuador and Northern Andes and Caribbean immediately to the north mark another major change in the Andean Orogen, marked by the Huancabamba Deflection. In this zone, a Jurassic arc was formed during a period of extension in what is now a well inland section of the Andean Orogen. However during the Lower Cretaceous, a thick oceanic plateau on the oceanic craton that was obliquely approaching the continent from the SW, impacted with the continental margin. It was too thick to subduct and continued to slide NW along the margin of Gondwana, leaving behind accreted slivers separated by major dextral shears. The result was a ~200 km wide collage of Mesozoic age oceanic terranes accreted to the NW margin of Ecuador and Bolivia. As the leading edge of is plateau progressed to the NE, it gradually filled the gap between the diverging North and South American plates to form the Caribbean Plate. By the Paleocene, subduction resumed to the west of the trailing edge of this terrane and continues to the present producing a Tertiary magmatic arc on the oceanic basement that extends along the west coast of Colombia, Panama and further north to Mexico. Gold rich porphyry deposits are developed chiefly, but not exclusively within zones of major faulting within the oceanic terranes, and are dominantly of Miocene age, with one major Eocene deposit and some Paleocene examples on the adjacent, mainly continental terranes. The Jurassic arc in the transition to the Peruvian Andes in Ecuador, and extending into southern Colombia, also contains significant porphyry Cu-Au and epithermal Au mineralisation.

The most recent source geological information used to prepare this summary was dated: 2018.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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