The discovery of magnesioferrite from Au (Fe, Cu) magnesian skarn depositsand study of the magnesioferrite-magnesiomagnetite series

Magnesioferrite, a rare metasomatic mineral, was discovered for the first t ime in China from the Qinlou Au (Fe, Cu) magnesian skarn deposit, Sanpu, Hu aibei, Auhui Province, and the Mulonggou Fe (Mo, Cu) magnesian skarn deposi t, Luonan County, Shaanxi Province. In this paper, the geological setting, mineral associations, chemical composition, some physical properties, X-ray powder diffraction data and infrared spectroscopy of magnesioferrite and m agnesiomagnetite are discussed. Magnesioferrite contains 17.66%-13.48% of M gO. Its main associated minerals are clinohumite, chondrodite, serpentine, calcite and magnesiomagnetite. The density of magnesioferrite is 4.537-4.72 0, reflectances in percent are: 17.8-18.1, hardness is 838-900 kg/mm(2), an d the cell parameter a(o)=8.371-8.379 Angstrom. A systematic study of the m agnesioferrite-magnesiomagnetite-magnetite series suggests that along with the increase of magnesioferrite molecules in the mineral, the density, refl ectances and cell parameters decrease correspondingly, the hardness heighte ns, and the infrared absorption spectral band becomes wider. The authors co nsider that magnesioferrite is a product of contact metasomatism between hy pabyssal intermediate-acid intrusions and dolomitic marble. It was formed i n shallow exocontact zones under relatively oxidized conditions.