Iron quartzites of the Simandou mountain (Republic of Guinea)

In this article, we for the first time fully describe geology and petrography of iron quartzite formation, localized in Southeast Guinea Simandou mountain range. region, a meridional distribution belt banded magnetite quartzites (itabirite) Lower Proterozoic metamorphic series has been mapped. The rocks form an extended (210 km) narrow (0.4-7 complex synclinal structure background Archean granite-gneiss basement. includes lower sequence metaterrigenous up to 400-500 m thick (metasandstone, quartzite, phyllite, mica schist) upper itabiritic 220-450 thick. metamorphism increases from north south greenschist epidoteamphibolite facies. Members two varieties are distinguished stratum - itabirite amphibole itabirite. composition is (wt %): 51-55, quartz 48-36, rest cummingtonite mica. 39-47, 31- 30, (cummingtonite) 24-15, hedenbergite, calcite. Rich martite hematitegoethite ores (60-66% Fe) formed lateritic weathering crust after itabirite, forming manto deposits with depth 9 350 m.