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Productora

Chile

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The extensive Productora iron oxide copper-gold mineralised system is located 15 km SSW of the town of Vallenar, and 170 km NNE of La Serena, and 625 km north of Santiago, in the Third Region of north-central Chile.

The district lies within the "Chilean Iron Belt" which is associated with the long-lived, north-trending Atacama Fault Zone. This brittle-ductile structure has been active since the Early Cretaceous and has involved recurrent sinistral strike-slip displacements. The deposit is geographically centred around the Productora Valley which comprises several talus-filled basins. These basins are surrounded by, and lie along strike from, a north-trending zone of hydrothermal alteration (Fe oxide-albite- K feldspar-biotite-tourmaline-sericite-silica) that can be discontinuously traced over an 8 km length, reaching 3 km in outcrop width. It contains five small, shallow former mines (Productora, Santa Innes, Monseratt, Remolina and Fortuna) worked for Cu oxides and Au, as well as eight magnetite mines and more than eighty pits and occurrences with iron oxides±Cu±Au±U±REE±apatite mineralisation.

The geology of the region comprises a poorly exposed basement of Paleozoic rocks overlain by Mesozoic and Cenozoic volcanic and sedimentary sequences. Jurassic and younger deposition was mainly composed of calc-alkaline andesitic lavas and flow breccias with some continental clastic sediments (Aguirre et al., 1974; Clarke et al., 1976), laid down in a continental margin, back-arc environment (Coira et al., 1982). The Andean Orogeny commenced during the early Jurassic (Clark et al., 1976), and the subsequent volcanism and plutonism moved progressively eastwards with time. Jurassic plutons occur along the coast, while Cretaceous and younger plutons outcrop further east.

The immediate mineralised system developed within early to mid-Cretaceous andesites, rhyolitic tuffs, ignimbrites, arenites and quartzites that were intruded by upper Cretaceous to lower Tertiary calc-alkaline granodiorites, dacites, monzonites, and aplites, with the bulk of the volcanic rocks exposed along the main mineralised trend being siliceous and of rhyolitic composition. Dacites and andesites are also interlayered with the rhyolitic volcanics.

The Productora project area is associated with a NNE-trending fault zone, interpreted to be a splay from the NNW-SSE Atacama fault zone (AFZ) which is located 5 kms to the west. The associated widespread and intense metasomatic and hydrothermal alteration appears to be related to late Cretaceous to early Tertiary movement on the AFZ.

The sequence hosting the Productora mineralisation is composed of a rhyolitic breccia, while metasomatised middle-Cretaceous to early-Tertiary granitoid intrusions (Fortin, 1990) outcrop to the south and east of the mineralised zone. The host sequence is cross-cut by andesitic to latitic dykes which tend to be far less altered than the host sequence suggesting they were emplaced relatively late in the geological history.

Two zones of intense copper, gold, molybdenum, cobalt and uranium associated metasomatic surface alteration have been recognised along the main NNE-trending mineralised trend: one at Productora (central area) and the other at Carmen (northern area). Geochemical work has recognised a distinct metal association comprising copper, gold, molybdenum, cobalt, uranium, silver, vanadium, bismuth and phosphorus.

Alteration comprises silicification with pyrite and chalcopyrite, accompanied by potassic alteration (K feldspar), argillisation, tourmalinisation, iron-oxide alteration and sericitisation. There is an obvious zonation of alteration mineralogy from K feldspar-tourmaline in the south to chlorite-K feldspar-carbonate in the north, probably reflecting a temperature gradient, suggesting a cooling of the system northwards and a gentle northerly plunge to the hydrothermal system.

Discrete clockwise jogs along the Productora fault zone mark locally changes in its strike from N-S to NNE orientations. These jogs represent areas as they are likely to be associated with wider zones of fracturing promoting increased secondary permeability suitable for focusing hydrothermal fluids. The Productora fault trends NNE in the area between the Productora and Santa Innes mines, indicating these two mineralised zones are located broadly proximal to either end of a NNE-trending fault jog.

Another, sub-parallel but slightly convergent, fault has been mapped to the west of Productora, also associated with magnetite and copper mineralisation. This fault trends more uniformly NNE and joins the Productora fault approximately 2 km north of the old Productora mine. It is interpreted to be a splay off the Productora fault (referred to as the Western Splay fault) and has numerous abandoned copper workings distributed along its trace, many of which are weakly to moderately radioactive. Numerous cross-cutting NW-trending faults have been mapped, many of which are associated with copper mineralisation and variably elevated levels of radioactivity. In addition, numerous examples of E-W and NE-trending faults are evident, commonly associated with copper mineralisation. These observations suggest a close association between faulting and mineralisation.

Primary mineralisation appears to rely upon the interplay of favourable lithological units (with primary permeability), regional faults and cross faults (both providing secondary permeability). Locations where favourable lithological units coincide with cross-faults and with regional fault jogs (and fracture zones) represent favourable sites for mineralisation. In addition, areas where regional fault splays bifurcate from the master fault (e.g., 2km north of the old Productora mine), appear to be associated with relatively large fracture zones containing many mineralised veins. The abundance of old copper shafts in the fracture zone between the Western Splay fault and the Productora fault is also relatively well mineralised.

Productura is the subject of a paper in the monograph: "Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective" volume 2, published by PGC Publishing, Adelaide, Australia. The full abstract summarising the deposit, and the reference list from the paper can be displayed by selecting options offered below.

This summary is based on information from Ray and Dick (2002), and the Hot Chili Limited website (2012)

JORC compliant mineral resource estimates (Hot Chili Ltd website, 2013) at a 0.3% Cu cut-off are:
      indicated resource - 70.6 Mt @ 0.6% Cu, 0.1 g/t Au, 0.014% Mo, 0.8% Cueq.;
      inferred resource - 94.6 Mt @ 0.6% Cu, 0.1 g/t Au, 0.0126% Mo, 0.7% Cueq.;
      TOTAL resource - 165.2 Mt @ 0.6% Cu, 0.1 g/t Au, 0.0132% Mo, 0.7% Cueq..

The most recent source geological information used to prepare this summary was dated: 2012.     Record last updated: 4/9/2012
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
 References to this deposit in the PGC Literature Collection:
Ray G E and Dick L A,  2002 - The Productora Prospect in North-Central Chile: An Example of an Intrusion-Related, Candelaria Type Fe-Cu-Au Hydrothermal System: in Porter T M (Ed.), 2002 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, PGC Publishing, Adelaide   v.2 pp. 131-151

 References to this deposit in PGC Publications: Want any of our books ? Pricelist
Ray G E, Dick L A, 2002 - The Productora prospect in north-central Chile: An example of an intrusion-related, Candelaria type Fe-Cu-Au hydrothermal system,   in  Porter T M, (Ed.),  Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective,  v2  pp 131-151
Buy   Abstract


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