Reca Project


Amapá is a state in northern Brazil located between the mouth of the Amazon river and the Oyapoque River which forms the border with French Guiana. A one week sampling campaign for the RECA and Source to Sink (BRGM/Total) projects was organized to Amapá in October and November 2019.

Tucano mine, Amapá, Brazil

The Tucano mine, located in Central Amapa close to the villages of Pedra Branca do Amaparí and Serra do Navio, is an active gold mine operated by Great Panther mining limited. The mine is hosted by the Paleoproterozoic Vila Nova Greenstone Belt and belongs to the sub-category of the Iron formation hosted Gold Deposits. The main ore mineralizations follow a N-S stretching shear zone which is hydrothermally altered.
Credit: B. Heller
During the field campaign in 2019 we were able to take samples in one of the open pits of the Tucano mine where deeply weathered shists and banded iron formations (BIF) are exposed. The formations have a near vertical dip and are locally crosscut by granitic dykes and sills. Samples were taken from the iron crusts that developed near the former land surface (ca. 260m a.s.l) on top of the shists and the BIFs as well as from one vertical profile of ca. 120m composed mainly of saprolites (weathered shists and dykes).

The samples are used for geochronological dating by (U-Th)/He method (iron crusts) and EPR method (kaolinite bearing iron crusts and samples from the vertical profile) coupled to standard mineralogical and geochemical analyses.
Credit: B. Heller
For more information on the mine see Interactive map with 3D views and aerial views of the mine

Western Amapá, Brazil

3 sites were sampled in area of Laranjal do Jarí in Western Amapá and on the other side of the Jarí River in Eastern Pará. The samples are lateritic iron and iron-aluminium duricrusts which developed on top of different geological units. At two sites with ca. 120m and 230m elevation, iron crusts developed on top of the Paleozoic sediments of the Amazon basin. At the third site, an abandoned small pit, a lateritic bauxitic crust developed probably on top of the Cretaceous-Paleocene Alter do Chão formation. The duricrust samples from Western Amapá are dated by (U-Th)/He dating in order to obtain a larger scale view of the weathering episodes in the Amazon basin.