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Hypogene mineralization and fluid flow in high-grade BIF hosted iron ore

Sao Francisco Craton, Minas Gerais, Brazil

This PhD project will investigate a variety of high-grade BIF-hosted iron ore deposit in the Quadrilátero Ferrífero (QF) which is located at the southern border of the Sao Francisco Craton, Minas Gerais, Brazil. Despite over 100 years of mining and exploration of iron ore in the QF, there is still a distinct dearth of information on the exact geological and geochemical environment in which the different hypogene iron ore types (e.g. massive magnetite, martite, granoblastic hematite, microplaty hematite, specularite) formed.  

Even though most of the iron ore deposits within the QF appear to be related to regional fold zones and different strain domains at a larger scale, it is still not known, which geological processes control of the location of high-grade iron ore bodies. Furthermore, the exact role of igneous intrusions in regards to the upgrade from BIF (~35 % Fe) to high-grade iron ore is still not well constrained. The main high-grade (> 63% Fe) iron ore deposits are hosted by the Caue-Formation, a Paleoproterozoic Banded Iron Formation of Lake-Superior Type. Besides basic petrographical and mineralogical studies, new analytical technology, such as Laser ICPMS for trace element mineral chemistry, in-situ SIMS for oxygen and iron isotope chemistry and infra-red geothermometry for fluid inclusion studies in iron oxides will be used to better constrain the paleohydrothermal fluid sources and iron ore forming processes. This work will lead to the refinement of the genetic model for iron bodies, which can be used to explore for deep extension of existing and/or new concealed high-grade iron ore.


Iron Research Bibliography

Hensler, A. S., S. G. Hagemann, et al. (2011). A mineralogical and textural comparison of different high-grade iron ore styles in the Iron Quadrangle, Minas Gerais, Brazil. 11th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, SGA, Antofagasta, Chile.

Hensler, A. S., M. E. N. Vieira Neri, et al. (2011). The BIF-hosted, high-grade Fe-ore deposit of Passa Tempo: evidence for “Fe-skarn”-type mineralization? 11th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, SGA, Antofagasta, Chile.