Cobalt in the regolith upon Nui Nua ultramafic Massif

Abstract

Cobalt (Co) Metal plays an increasingly important role in the battery and engine manufacturing industry for electric cars. Previously most of Co was mined as by-product in copper ore deposits in Central Africa. Recently, the proportion of Co extracted from other sources such as weathering-derived mines on ultramafic rocks is increasing. In Vietnam, Cobalt has been discovered in Cu-Ni ore deposits in the Northeast and Northwest Regions. The literature shows that cobalt is found in small amounts in ultramafic rocks. During the weathering process of ultramafic rocks, Co ions will be priority adsorbed in the hydroxide colloids of Mn and Fe (goethite and asbolan). In the regolith upon Nui Nua Masif, Ni content increased dramatically (several times) from 0.19% in bedrocks up to 1% in some locations, while cobalt content just increased only slightly (from 0.02% in bedrock to 0.05 regolith, rarely up to 0.1%). The results of the previous analysis of weathered crust samples of ultramafic rocks of Nui Nua massif by several authors show that, unlike Ni which is presented in both silicate minerals and Fe-Mn oxide/hydroxide, cobalt ions tend to be concentrated in Fe-Mn oxides/hydroxides. Our SEM analyses combined with EDS show some remarkable results: the Co content in some specific minerals is quite high from 1.12÷4.67% (denominator). This is only a preliminary result and it is necessary to conduct more work to further detailed studies defining the Co potential in weathering products of ultramafic rocks of Nui Nua massif as well as in the areas where other ultramafic rocks are developed. Recently, research confirmed that there is a significant Co-Ni occurrence discovered in Mau Lam Valley (Southwest of Nui Nua Massif).