Reef Cenomanian Carbonate Hosted Fluorite Ore Deposits at Jebel Mokta, Northeastern Tunisia

Abstract

The Cenomanian limestone-hosted Fluorite deposit of Jebel Mokta is located in the north east of Tunisia, 35 km SE the capital city Tunis. This deposit occurs in the form of open-space fillings and veins hosted in the upper Cenomanian reef limestone. In the present paper, field work, petrography and microthermometric studies of fluid inclusions were implemented to characterize the relevant fluid mineralization aspects. The relating data proved to indicate that primary fluid inclusions persistent in the fluorite appear to display homogenization temperatures ranging between 124 °C and 135 °C. The fluid inclusions salinities ranging from 15 wt% NaCl equiv to 18 wt% NaCl equiv. The homogenization temperatures of primary fluid inclusions in calcite turn out to range between 9 and 5% NaCl equiv and 13 wt% NaCl equiv. Such features could well stand as a microthermometric evidence for the mixing of two fluids with different temperatures and different salinities. Mineralization is spatially and, possibly, genetically related to the NE-SW and E–W-trending fractures, which acted as conducts and/or depositional sites for the circulating hydrothermal fluids. The fluorite deposit is considered to have be formed from basinal fluids, and has been compared to Mississippi Valley-type.