Original paper

Bi-Ag-bearing tetrahedrite-tennantite in the Kapsalina copper mineralisation, Thasos island, Northern Greece

Vavelidis, M.; Melfos, V.

Abstract

The mineralogy, chemistry and fluid inclusions of the Bi–Ag-copper mineralisation of the Kapsalina area, at the southwestern part of the Thasos island, is studied for the first time. The ore mineralisation is hosted in quartz veins and consists mainly of chalcopyrite and pyrite, as well as bismuthinite, Bi–Ag-bearing tetrahedrite-tennatite and gersdorffite. The ore bodies contain up to 740 ppm Ag. Tetrahedrite contains Bi up to 2.98 wt % and Ag up to 2.05 wt %, while tennantite is poorer in Bi (up to 1.18 wt %) and Ag (up to 1.24 wt %). Calculation of the cell sizes of fahlores show that they increase with the increasing of the Bi and Ag contents. The microthermometric study shows that the mineralisation was formed at temperatures varying mainly from 120 to 280 °C, with a peak at 200 °C. The pressures of the hydrothermal fluids are estimated between 10 and 90 bars and indicate that the mineralisation was formed in a shallow depth. A mixing between ascending hydrothermal fluids and downward migrating dilute meteoric water is probably the main process which caused the mineralisation deposition.

Keywords

tetrahedritetennantitechemical compositionbismuthcell sizefluid inclusionsgersdorffitethasos islandgreece