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Los Pijiguaos |
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Venezuela |
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Al
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Super Porphyry Cu and Au
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The Los Pijiguaos bauxite mine is located in the western part of the State of Bolivar in Venezuela.
Mining commenced in 1987, with a total crude bauxite production to the end of 2001 of more than 43 Mt. The annual production in 2002 was close to 5 Mt of bauxite. Proven and probable reserves at the same time were around 570 Mt at an economic cut-off grade of about 44 wt.% alumina (Al2O3) and a total silica (SiO2) content of less than 20 wt.%. The surrounding region is believed to contain as much as 6 GT of probable bauxite resources.
The Los Pijiguaos deposit was formed on a flat topped plateau from weathering of the underlying Mesoproterozoic Rapakivi-type Parguaza granite. The complete laterite profile is characterised by a vertical zonation, comprising: i). A concretionary zone (the bauxite horizon) which attains an average thickness of 7.6 m, with the best ore grades and greatest thickness within the mine corresponding to topographic highs; ii). mottled zone (the saprolite horizon); and iii). the granitic bed rock.
The distribution of grade follows distinct WNW-SSE trends, but is also influenced by the westerly inclination of the planation surface and the major NW-striking fault systems in the region. In addition, the orebody has an irregular geometry, dismembered and dissected by strong and prolonged fluvial erosion during and after uplift of the region. The resultant isolated mineable blocks are located on plateau remnants separated by deep valleys rendering only half of the entire lease area accessible to mining.
Gibbsite is the most abundant mineral in the economic-grade bauxite horizon, with minor associated nordstrandite. Kaolinite is absent from the bauxite zone, although in the underlying saprolite zone it can comprise more than 5 wt.%. There is an inverse correlation between gibbsite and quartz, with the abundance ratios for the two minerals decreasing from around 45 in the bauxite horizon to around 2 in the underlying saprolite zone. While hematite is commonly more abundant than goethite, in the bauxite horizon the goethite:hematite ratio is greater than 1. Anatase occurs as an accessory phase, mainly in the bauxite horizon.
Mass balance calculations indicate that bauxitisation resulted in progressive desilicification, hydration, and Al2O3 and Fe2O3 concentration in the residual weathering blanket. Silica as well as alkali and alkaline earth metals were almost completely leached, with mass and volume losses being of the order of 61% and 77%, respectively.
The Los Pijiguaos bauxite is a high-quality almost pure gibbsitic ore that allows processing to alumina by the low-temperature Bayer process at around 140°C.
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.
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Selected References:
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Meyer F M, Happel U, Hausberg J and Wiechowski A 2002 - The geometry and anatomy of the Los Pijiguaos bauxite deposit, Venezuela: in Ore Geology Reviews v20 pp 27-54
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Tosiani T, Melendez W and Vivas F, 2006 - Modeling humic acids transport in a bauxite profile: Los Pijiguaos, Venezuela: in J. of Geochemical Exploration v88 pp 246-248
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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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