SCIENTIFIC COMMUNICATIONS FLUID INCLUSION STUDIES IN COGENETIC HEMATITE, HAUSMANNITE, AND GANGUE MINERALS

Fluid inclusions in hematite and hausmannite from high-grade Wessels-type ore from the Kalahari manganese field were studied using infrared microscopy. The data obtained suggest that both minerals were deposited co-genetically, along with gangue minerals uch as calcite and datolite, from high-salinity fluids. The minerals con-stituting the high-grade manganese ore were deposited attemperatures below 200øC, well below the tempera-ture range of 200 ø to 400øC that was estimated on the basis of the thermodynamic stability of common mineral assemblages. The observed melting behavior suggests that the enclosed fluids are rich in Ca and/or Mg salts. It is concluded that an important part of the salt load of the hydrothermal fluid can be attributed to metasomatic interaction with the Ca-Mn-Mg carbonate-rich sedimentary protore to the Wessels-type ore