Mineralogy and geochemical characteristics of the Ibaga copper ore deposit in Singida-Tanzania: Implication for source of copper mineralization and ore quality

Abstract

The Ibaga copper deposit in the Nzega-Sekenke terrane is hosted in meta-sedimentary rocks and it has been rudimentarily mined by small scale miners for more than a decade. To study mineralogy and geochemical characteristics of the deposit, samples from outcrops and mining pit were collected for XRD, XRF and ICP-MS analysis. Results show that the ore is composed of chalcopyrite, covellite, cuprite, malachite and azurite as ore minerals; whereas augite, chlorite, actinolite, greenalite, birnessite, quartz, magnetite, berlinite, cristobalite, hematite, calcite and parisite are gangue minerals. The deposit is characterized by Cu (3.2–31.3 wt %), Fe (2.1–25.1 wt %), Ag (0.6–16.6 wt %) and lower concentration of penalized impurities Sb, Bi, As, Cd and (Al₂O₃ + MgO) than threshold limit set by copper smelters and refineries. The ore shows significant variation of Y/Ho = 21.75–40.00, Zr/Hf = 23.33–58.61 and Nb/Ta = 4.20–27.17. Presence of higher REE values of up to 2000 ppm in sample BG04 due to REE minerals known as parisite indicates that the deposit is potential prospect for REE. Consistent with the granites, the ore has Sm/Nd < 0.24 and enriched in LREE relative to HREE where ∑LREE/∑HREE = 4.7–9.0 and La/Lu = 32–769.3. The scatter plot of δCe versus δEu for ore and rock samples suggests closer genetic relationship between the ore, granite and quartz-sericite-schist. These results imply that the granitic intrusion triggered mineralization by skarnification into meta-sedimentary rocks and subsequently the ore underwent supergene enrichment.