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Prospect for gold and other precious metals in meta-igneous rocks of Sri Lanka: implications from geochemistry

Authors:

Sanjeewa P.K. Malaviarachchi ,

University of Peradeniya, Peradeniya, LK
About Sanjeewa
Department of Geology, Faculty of Science and Postgraduate Institute of Science
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P.I. Dharmapriya,

University of Peradeniya, Peradeniya, LK
About P.I.
Department of Geology, Faculty of Science and Postgraduate Institute of Science
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H.M.D.A.H. Bandara,

University of Peradeniya, Peradeniya, LK
About H.M.D.A.H.
Postgraduate Institute of Science and National Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka
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M.H. Kodikara Arachchi,

National Building Research Organization, Jawatte Road, Colombo 7, LK
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N.D. Subasinghe

National Institute of Fundamental Studies, Hantana Road, Kandy, LK
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Abstract

This study presents some major, trace and precious metal geochemistry of some representative meta-igneous rocks from the Highland and Vijayan Complexes and Kataragama Kilippe (HC, VC, KK, respectively) of Sri Lanka. Our data show different geochemical trends in chemical-discrimination diagrams, indicating each lithological unit has distinct genetical environments. Most of the mafic samples of the HC and the KK fall geochemically in the tholiietic field. In contrast, the garnetiferrous charnockitic samples of the HC and majority of the VC samples plot in the calc-alkaline field. Rocks of the VC and KK and mafic rocks of HC, deviate from typical magmatic differentiation patterns probably due to a later interaction with secondary melts or fluids. There is a clear distinction of Pt/Pd and Au/Pt vs. MgO, in which all the samples except for the garnetiferrous charnockites of the HC show a negative correlation implying a sequestration of chalcophile melts from protolith magmas. Therefore, our data indicate that possibility of occurrence of gold (Au) and other precious metals (e.g. Pt and Pd) within the meta-igneous rock units of the HC, VC and KK is reasonable except for the garnetiferrous charnockitic rocks of the HC. The garnetiferrous charnockites of the HC do not account for any geochemical evidence sensitive to precious metal enrichments in protoliths. Our estimates show that the highest (in average) Au, Pt and Pd contents are found in the rocks of VC (8 mg/ton), KK (7 mg/ton) and HC (7 mg/ton), respectively. Although these precious metal abundances in the above prospective rock units are not as high as those present in global ore-grade rocks, yet ‘hard rock mining’ technique could be feasible to utilize as a small-scale industry to extract these metals, especially using rock-aggregates/rock powders dumped as wastes from rock quarries in Sri Lanka.
How to Cite: Malaviarachchi, S.P.K., Dharmapriya, P.I., Bandara, H.M.D.A.H., Arachchi, M.H.K. and Subasinghe, N.D., 2019. Prospect for gold and other precious metals in meta-igneous rocks of Sri Lanka: implications from geochemistry. Journal of the Geological Society of Sri Lanka, 20(1), pp.17–32. DOI: http://doi.org/10.4038/jgssl.v20i1.26
Published on 28 Feb 2019.
Peer Reviewed

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