|
Arizaro, Lindero |
|
|
Salta, Argentina |
| Main commodities:
Cu Au
|
|
 |
|
|
 |
Super Porphyry Cu and Au
|
IOCG Deposits - 70 papers
|
All papers now Open Access.
Available as Full Text for direct download or on request. |
|
|
The Arizaro and Lindero prospects in the Puna Belt of North-west Argentina are geologically significant iron oxide copper-gold (IOCG) occurrences. They are located in the state of Salta, approximately 220 km west of the city of Salta, close to the Chile border, and approximately 350 km NE of the Chilean city of Copiapo.
The Arizaro and Lindero prospects are possibly the youngest (at 15 Ma) recognized examples of the hydrothermal iron oxide-copper-gold class of deposits in the world. These two prospects, and numerous other iron-oxide manifestations, form a newly discovered district within northwest Argentina.
Both prospects are hosted within mid-Miocene, calc-alkaline, dominantly andesitic, volcanic complexes that formed within a convergent plate margin tectonic setting.
Arizaro and Lindero are located at the southern limit of the Salar de Arizaro, one of the largest salars in South America. The salar occupies the western third of a large 100 x 100 km intra-arc basin, which is referred to as the Arizaro Basin, unconformably overlying a basement of Early to Middle Ordovician granitic plutons and Proterozoic to Palaeozoic volcanic and sedimentary sequences. The Arizaro Basin is bounded by major normal, strike-slip and reverse/thrust fault systems, and is interpreted to contain ~4000 m of sedimentary fill. In the Arizaro and Lindero district, Cretaceous to late Oligocene red arkosic sandstones are unconformably overlain by mid-Miocene volcanic flows and volcaniclastic sediments and are cross-cut by intrusive rocks which comprise the Arizaro volcanic complex, covering an area of ~6 x 4 km.
The Arizaro volcanic complex consists of three zones containing abundant calc-alkaline intrusive rocks which are each surrounded by lava flows and volcaniclastic rocks, representing a series of partially dissected volcanic edifices. These extrusive rocks are cut by calc-alkaline dykes which extend radially away from each of the intrusive centres.
The Arizaro prospect is located within an intrusive centre of the Arizaro volcanic complex. The intrusive core is surrounded by volcaniclastic breccias which are cut by radial dykes.
Alteration at the Arizaro prospect is zoned from distal calcite-epidote-chlorite alteration (propylitic) inwards to actinolite-potassium feldspar-magnetite-biotite±diopside-albite alteration (calcic-potassic) and finally to a central core of intense potassium feldspar-magnetite-biotite alteration (potassic). Weak hydrolytic alteration (quartz-sericite-clay) occurs on the periphery of the system and overprints other alteration types.
Exposed mineralisation at Arizaro is dominated by supergene, copper oxide minerals which replace chalcopyrite and minor bornite. Chalcopyrite is generally fine-grained (<0.5 mm), is commonly associated with bornite and intergrown with magnetite. Micron-sized gold (±Pd) grains occur with chalcopyrite-copper oxide accumulations, although chalcopyrite-gold intergrowths have not yet been identified. The highest copper and gold grades are contained almost exclusively within the strong to intense potassic alteration zone. Sulphides are primarily disseminated but also occur within magnetite veins.
The Lindero prospect forms a semi-circular mineralised halo around a steep hill containing an intrusive core.
Alteration at Lindero forms near-complete, concentric rings that are zoned from a central chlorite-calcite core, outwards into potassic alteration (potassium feldspar-magnetite-biotite), into hydrolytic alteration (quartz-sericite-clay-limonite), and finally to an outer propylitic alteration zone (epidote-calcite). Both prospects contain magnetite-rich, pyrite-absent assemblages with Cu-Au and elevated Pd and REE concentrations (La-Ce-Nd). Sulphides are largely restricted to zones of strong to intense potassic alteration and consists of disseminated chalcopyrite and minor bornite.
High copper and gold values at Lindero are restricted to the potassic alteration zone. Mineralisation is strongest along a northeast-trending zone in the southeast
part of the prospect. Mineralisation at Lindero is dominated by copper oxides, with chalcopyrite rarely observed. The highest copper concentrations occur within potassium feldspar-magnetite-biotite breccia zones.
The interplay between extensional tectonics, magmatism, and thermal convection of saline basinal brines is probably critical for the development of the Arizaro-Lindero alteration systems.
Reserves have not been published, although at Lindero, a 900 m long, >70 m wide zone has an average grade of 0.66 g/t Au and 0.13 % Cu, with higher grade intersections that include: 134 m @ 1.65 g/t Au, 0.126% Cu; 110 m @ 1.08 g/t Au, 0.106% Cu; and 74 m @ 1.47 g/t Au, 0.121% Cu.
These deposits are 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 most recent source geological information used to prepare this decription was dated: 2002.
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.
|
|
|
|
Dow R J and Hitzman M W, 2002 - Geology of the Arizaro and Lindero Prospects, Salta Province, Northwest Argentina: Mid-Miocene Hydrothermal Fe-Ox Copper-Gold Mineralisation: in Porter T M (Ed.), 2002 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, PGC Publishing, Adelaide v.2 pp. 153-161
|
|
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.
|
Top | Search Again | PGC Home | Terms & Conditions
|
|
