On the Origin of Bastnaesite-(La,Nd,Y) in the Nissi (Patitira) Bauxite Laterite Deposit, Lokris, Greece

Sofia Kalatha,Maria Economou-Eliopoulos,Ioannis Mitsis,Maria Perraki

doi:10.3390/min7030045

Abstract

A detailed geochemical study and a thorough mineralogical description of the rare-earth elements (REE)-minerals and associated minerals were carried out in two vertical profiles of approximately 4 m length, from the Nissi (Patitira) bauxite laterite deposit, Lokris, Greece, characterized by the presence of goethite in small sizes resembling bacterial cell coated by goethite and a significant REE enrichment. The enrichment of the REE concentrated in bastnaesite-group minerals, the intergrowths between REE-minerals and Al–Ni–silicates with significant sulfur contents and their association with goethite microtextures interpreted as bacteriomorphic, indicate REE remobilization along with iron bio-leaching and re-precipitation on karstified limestone. In addition to the previous-reported hydroxylbastnaesites, a (La,Nd,Y)(CO3)F member of the bastnaesite-group associated with Al–Ni–silicates were identified, the stability of which may reflect the dependence on the source rocks and the local variations of pH-Eh. Interaction between downward percolating water and carbonate rocks seems to be a very effective mechanism for REE fluorocarbonates deposition under alkaline and reducing conditions.

Highlights

The Fe–Ni laterite deposits in Greece are a major source of nickel, a metal of strategic significance.Greece’s Fe–Ni ore reserves are currently estimated to be in the range of 200 Mt at 0.9%–1.4% Ni ([1] and references therein)
The Nissi area deposits are comprised of a series of lenses, that may occur either as isolated typical Fe–Ni–laterite or bauxite laterite ores or as an association of Fe–Ni ore at the lowest part of the deposit, followed by bauxite laterite towards its upper part ([3] and references therein)—such as the Patitira deposit (Figure 1)
The mineralogy of the weathered rocks and the physico/chemical conditions are among major controlling factors of the composition of the aqueous phase, which in turn can control the degree to which rare-earth elements (REE) are released to the downward moving fluids in contrast to iron that is quite reactive [3,4,5,6,7,8,9,10,11,12,13,14,15,16,24,25,26]

Summary

Introduction

Greece’s Fe–Ni ore reserves are currently estimated to be in the range of 200 Mt at 0.9%–1.4% Ni ([1] and references therein). Aghios Ioannis mining area includes Nissi area deposits (located SSW of the Aghios Ioannis deposit) (Figure 1; [2]). The laterite ores at Aghios Ioannis and Nissi area deposits have been eroded, transported, and deposited onto karstified Triassic–Jurassic limestones and are conformably overlain by Upper Cretaceous limestones (Figure 1). The Nissi area deposits are comprised of a series of lenses, that may occur either as isolated typical Fe–Ni–laterite or bauxite laterite ores or as an association of Fe–Ni ore at the lowest part of the deposit, followed by bauxite laterite towards its upper part ([3] and references therein)—such as the Patitira deposit (located at the eastern part of the Nissi area) (Figure 1).

Methods

Discussion

Conclusion