Wagner Amaral
Felipe Holanda dos Santos
Wagner da Silva Amaral
Douglas Teixeira Martins
Ana Clara Braga de Souza

The Borborema Province hosts several Mn-rich metasedimentary sequences, containing up to 40 wt% MnO(total). These sequences are composed of Mn oxide and Mn silicate lenses that alternate with spessartite quartzite layers. They are also spatially associated with graphite-bearing gneissic and granitic rocks. Here, we use the Lagoa do Riacho manganese deposit, a Mn-rich sequence of the northern Borborema Province (within the Canindé do Ceará Complex), to constrain the time of deposition of the Mn-rich sedimentary protolith, discuss its tectonic setting, and draw correlations between African and Brazilian manganese deposits. The age of the youngest detrital zircon population from a meter-sized spessartite quartzite bed, interlayered with oxidized Mn ore, was close to 2130 Ma. Similarly, a gneiss hosting the Mn mineralization yielded a maximum depositional age close to 2156 Ma. U–Pb dating of zircon metamorphic overgrowths from the Mn-bearing sequences and host rocks coupled to a zircon U–Pb crystallization age of an intrusive leucocratic granite provided a minimum age interval for the Mn-rich succession (ca. 2106–2023 Ma). These constraints point to a Rhyacian depositional age (ca. 2200–2100 Ma) for the Mn-rich precursors, which were most likely deposited as syn-orogenic sediments. The results also allow us to conclude that the age range of 2200–2100 Ma is coeval with the timing of deposition of other world-class manganese deposits, such as those from the Francevillian and Birimian groups in Gabon and Ghana, respectively, besides those from the South American Platform (e.g., Serra do Navio, Carajás, and Minas Gerais).

Keywords: Borborema province; Manganese; U–Pb dating; Detrital zircon; Paleoproterozoic; Rhyacian

Wagner da Silva Amaral