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Marte, Lobo
Main commodities: Au

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Marte and Lobo are porphyry gold deposits at that are 7 km apart at an altitude of 4200 m asl in the Maricunga district of Chile (#Location: 27° 10' 31" S, 69° 1' 37" W).

The Lobo and Marte deposits were discovered during the 1981-1982 field season by an exploration program led by Anglo American plc. Lobo was the result of a regional geochemical survey, whilst Marte was subsequently found after a program of regional soil sampling, geophysical surveys and geological mapping. The Marte deposit was mined by a joint venture between Anglo American and Cominco from 1988 to 1992 when the mine was placed on care and maintenance. A total of 3.78 Mt of ore @ 1.51 g/t Au, and 0.3 Mt of low-grade mineralisation were mined, along with 4.7 Mt of waste. Cominco's share passed to Teck Cominco and then Teck after the amalgamation of Teck and Cominco and a subsequent reorganisation. Kinross Gold acquired the Anglo American 40% interest in 2008 and Tecks 60% share in 2009 to gain 100% ownership through its Chilean subsidiary Compania Minera Maricunga. Kinross has completed further drilling and a Pre-Feasibility Study with the aim of beginning construction in 2025, and expected first production in 2027 at both mines that will be connected by rope conveyors to use a shared processing facility (Kinross Gold Corporation Annual SEC Information Form to 31 December 2020).

Both Marte and Lobo are related to small multiphase 14 to 13 Ma diorite porphyry stocks intruded into Late Miocene, partially eroded, stratovolcanoes. These intrusives are part of a linear, calc-alkaline volcanoplutonic arc emplaced during the Mid- to Late-Miocene as eastward directed subduction was shallowing. The basement below the deposits is has undergone cmpresssion with the development of a series of high angle reverse faults. The host horblende-biotite stock at Marte is subdivided into three phases, two mineralised porphyries and a weakly porphyritic, late mineralisation micro-diorite. Much of the latter comprises the matrix of an intrusion breccia which is locally cut by a closely related hydrothermal breccia.

Gold is found in quartz veinlet stockworks that may have been emplaced with K-silicate alteration (as evidenced by remnants of biotite and alkali feldspars) but are now associated with overprinted intermediate argillic sericite-clay assemblages rich in chlorite.   Pyrite is the principal sulphide with traces of chalcopyrite, bornite and molybdenite, while magnetite and hematite are important components. The ore zone contains around 10% each of pyrite and iron oxides. Hematite exceeds magnetite in abundance; both are hypogene in origin. Gypsum after anhydrite commonly exceeds 5% with traces of calcite and tourmaline. The mineralisation and alteration most affected the late stage microdiorite and its breccias. Erosional remnants of the andesitic roof volcanics are replaced by chalcedony and alunite rich advanced argillic alteration assemblages.

The initial pre-mining resource reported at Marte was 46 Mt @ 1.43 g/t Au and at Lobo 80 Mt @ 1.6 g/t Au. About 20% of these resources underwent supergene oxidation.

Teck Cominco reported the following as of December, 2007 for the Marte-Lobo project:
    indicated mineral resources - 97.68 Mt @ 1.72 g/t Au and
    inferred mineral resources - 9.25 Mt @ 1.56 g/t gold

Ore Reserve and Mineral Resource estimates for the Lobo-Marte project, as at 31 October 2021 (Kinross Release, 10 November, 2021) were:
    Probable Reserve - 160.702 Mt @ 1.30 g/t Au
    Indicated Resources - 99.44 Mt @ 0.74 g/t Au
    Inferred Resources - 18.474 Mt @ 0.75 g/t Au Kinross quotes Mineral Resources exclusive of Ore Reserves.

For more detail see the reference listed below.

The most recent source geological information used to prepare this decription was dated: 1995.    
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
   Selected References:
Sillitoe R H  1995 - Marte and Lobo, Chile: in Sillitoe R H,  Exploration and Discovery of Base- and Precious-Metal Deposits in the Circum-Pacific Region During the Last 25 Years Metal Mining Agency of Japan    pp 24-25
Sillitoe, R.H.,  1991 - Gold metallogeny of Chile - an introduction: in      Econ. Geol.   v.86, pp. 1187-1205.
Vila T, Sillitoe R H, Betzhold J, Viteri E  1991 - The porphyry gold deposit at Marte, northern Chile: in    Econ. Geol.   v86 pp 1271-1286

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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