APPLICATION OF SELECTIVE EXTRACTION TECHNIQUES IN METAL-BEARING PHASES IDENTIFICATION - A SOUTH EUROPEAN CASE STUDY

The study described herein concerns the application of selective extra ction techniques on metal-bearing phases identified in gossan samples. Specifically, the study is directed towards the detection of Zn- and Pb-bearing phases in Balsa-Portel area (southern Portugal). In order t o identify the metal-bearing phases, samples were submitted to sequent ial extraction procedures using the following reagents: NH, acetate; h ydroxylamine hydrochloride; oxalate in darkness; H2O2; oxalate under U V irradiation; and finally, mixed acids (HCl-HNO3-HF). In the Balsa-Po rtel area, the Zn- and Ph-hearing phases generally occurring in the go ssan samples are lepidocrocite, Mn-oxides, cerussite and smithsonite, dissolved by oxalate under UV irradiation (lepidocrocite), hydroxylami ne hydrochloride (Mn-oxides) and ammonium acetate (cerussite and smith sonite). (C) 1998 Elsevier Science B.V. All rights reserved.