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Tolagnaro - Mandena, Petriky, Sainte Luce |
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Madagascar |
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Ti Zr
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Mandena, Petriky and Sainte Luce heavy mineral sand ilmenite - zircon deposits are centred some 8, 13 and 32 km respectively north along the coast from the city of Tolagnaro in the Fort-Dauphin region on the south-eastern tip of Madagascar.
These deposits occur along the south-eastern shoreline as palaeo-strandlines separated from the Indian Ocean by barrier islands, lagoons and sand dunes. The deposits occur to a depth of 15 m below the current surface and are close to the prevailing water table. The principal heavy minerals are ilmenite, zircon and lesser monazite.
The hinterland from which the heavy minerals have been derived is the Paleoproterozoic Bekily Block which occupies the south western third of the island. This block was subjected to strong Pan African migmatisation and is cut by a series of late Neoproterozoic, generally north-south shears which in part subdivide it into smaller domains. The Bekily Block is composed of the following units from east to west:
Androyen Series - which occupies the eastern three quarters of the block and is in turn subdivided, from east to west into the:
- Fort Dauphin Group - in which the dominant facies are leptynites composed of quartz, perthitic orthoclase, garnet, cordierite and sillimanite, with interlayers of alumino-silicate gneiss with garnet and rare biotite.
- Tranomara Group - which is characterised by calcic to magnesian paragneisses (with plagioclase, garnet, diopside, pyroxenes and wernerite) with associated leptynites and gneisses containing garnet, cordierite and sillimanite, lesser bands of red granite and intervals of leuco-leptynites and charnockites. Although some older Archaean dates are recorded, these rocks generally date at 2292±96 Ma to 2066±153 Ma, cut by pegmatites of 1140 Ma age.
- Ampandrandava Group - comprising leptynites with garnet, sillimanite and cordierite gneisses and intercalated, locally important graphite gneiss, crystalline carbonates, quartzite and pyroxenite with phlogopite. Age dates range from 2083±75 Ma to 1227±28 Ma.
Ampanihy Series - which is dominated by garnet, biotite, sillimanite leptynites with common graphite and interlayers of quartzitic, amphibolitic calc-silicates (also containing pyroxene and wernerite) and manganiferous gondites. The series is interpreted to represent platformal sediments with associated felsic volcanics and manganiferous carbonatic formations.
Vohibory Series - characterised by an abundance of amphibolites, amphibole-pyroxene gneiss, pyritic leptynites and calc-silicates, possibly representing a metamorphosed mafic-felsic volcano-sedimentary pile.
The total resources prior to mining in the three deposits spread over a 65 km interval along the coast comprised around 650 Mt @ 4.3% ilmenite, 0.2% zircon within heavy mineral sands which total approximately 5% of the ore containing around 86% ilmenite and 4% zircon. The average grade of contained TiO2 is approximately 60%.
Proved + Probable reserves, at the end of 2007 (Rio Tinto 2008) - 12.4 Mt of TiO2
Measured + Indicated + Inferres resources, at the end of 2007 (Rio Tinto 2008) - 38.8 Mt of TiO2
The most recent source geological information used to prepare this decription was dated: 2007.
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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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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