Chapter 15: Geology and Economics of the Giant Molo Graphite Deposit, Southern Madagascar
Published:January 01, 2018
Craig Scherba, Jean-Francois Montreuil, C. Tucker Barrie, 2018. "Geology and Economics of the Giant Molo Graphite Deposit, Southern Madagascar", Metals, Minerals, and Society, Antonio M. Arribas R., Jeffrey L. Mauk
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Flake graphite is a critical battery material due to its role as the primary anode component in lithium-ion batteries. With the shift to electrification of vehicles, it is forecast that in the next five years flake graphite’s number-one use will be in battery applications, overtaking its traditional industrial uses. The burgeoning demand for battery anode materials is anticipated to double the current natural flake graphite market of roughly 645,000 tonnes per annum by 2025, which will require new flake graphite sources like the Molo graphite deposit to come into production.
The Molo graphite deposit is world class due to its large size (NI 43–101 measured resource of 23.62 Mt at 6.32% C, indicated resource of 76.75 Mt at 6.25% C, and inferred resource of 40.91 Mt at 5.78% C), high proportion of large and jumbo flake (46.4%), and high average flake carbon purity (97.27% C). The deposit was discovered in 2011 as the result of a regional exploration program initiated by NextSource Materials Inc. following their delineation of a vanadium deposit called the Green Giant. Graphitic mineralization in the Molo is bimodally distributed, with low-grade and high-grade zones having carbon cutoff grades of 2 and 4% C, respectively. High-grade mineralization is associated with metamorphosed siltstones and mudstones, while low-grade mineralization is associated with rocks interpreted to represent metamorphosed sandstones, which are interpreted to be more favorable hosts for large- and jumbo-flake graphite.
The Molo graphite deposit appears to have resulted from many mineralizing events, which extended over a period of time that may range from ca. 900 to ca. 490 Ma. These include graphitization during the emplacement of anorthosite complexes, graphitization in a high-strain regime under high-pressure and high-temperature granulite facies metamorphism during the collision of the Androyen domain with the Vohibory domain, graphite refining and recrystallization believed to have taken place during East Gondwana and West Gondwana collision, and the formation of postcollisional hydrothermal vein graphite during orogenic collapse. The superimposition of the tectono-metamorphic history of southern Madagascar on a sedimentary sequence in which the protoliths were rich in organic carbon has resulted in world-class flake graphite mineralization with high carbon purities and large flake sizes.