Heavy mineral as a tool to refine the stratigraphy of kaolin deposits in the Rio Capim Area, Northern Brazil

Abstract

Studies of heavy minerals in kaolin deposits from the Ipixuna Formation in the Rio Capim area (Northern Brazil) showed a mature to super mature assemblage dominated by zircon and tourmaline, and subordinately rutile, kyanite and staurolite. These minerals do not change much throughout the whole section; however, each kaolin unit displays a particular signature, defined by differences in the proportions of the whole assemblage of heavy minerals, as well as of their textural characteristics. This work revealed that the lower and upper kaolin units can be definitely considered as distinct depositional sequences. A higher proportion of opaque minerals and higher zircon values characterize the lower unit. The higher volumes of anhedric, rounded to sub-rounded grains of zircon and tourmaline in the upper unit suggests that this includes grains that were undergone to a higher degree of reworking. The increased volume of unaltered staurolite and kyanite in the upper unit leads to conclude that, even considering sediment reworking, a distinct source must be invoked. The results also show that the characteristics of the heavy mineral assemblage from the intermediate unit are comparable with those from the upper unit, which suggests they might record a same stratigraphic sequence.

The contribution of lateritization processes to the formation of the kaolin deposits from eastern Amazon

“…Sousa et al (2007a) using geochronological data from several zircon grains extracted from both soft and flint kaolin found two distinct source areas for the kaolin-bearing sediments, which confirmed the lateritic origin of kaolin. This agrees with earlier contributions and yet is in disagreement with Góes et al (2007), who used the data of heavy minerals to discredit lateritic weathering for the kaolin deposits.…”

“…Santos et al (2007) conducted d 18 O and d D analyzes on kaolinites originating from soft and hard (semi-flint) kaolin from Rio Capim deposits and concluded that kaolinites were not in equilibrium with modern weathering processes. These authors concluded that kaolinites must have been formed during different phases of paleoweathering (Santos et al, 2007), which is in contradiction to Santos and Rossetti (2003), Rossetti and Santos (2006) for flint kaolin and Góes et al (2007), who have all supported the argument of sedimentary deposition. Recently, Sousa et al (2007b) offered new insights regarding the chemical, mineralogical and micromorphological characteristics and origins of kaolin deposits.…”

“…2b) kaolin at the base, soft kaolin at the intermediary portion and flint kaolin at the top (Sousa et al, 1999a;Sousa, 2000;Rossetti and Santos 2006;Wilson et al, 2006;Sousa et al, 2007b). Bedding and crossed bedding are frequent and support the general sedimentary nature of the unit (Santos and Rossetti, 2003;Rossetti and Santos, 2006;Góes et al, 2007). Iron oxihydroxides expressed by concretions, mottlings, and diffusion aureoles and columnar structures, although subtle, suggest that the lower unit was affected by deep tropical weathering -represented by the lateritization process.…”

“…The kaolin mining at PCKBD began in 1996 with the following companies: Sumitomo Some authors consider that the Capim kaolin is typically of sedimentary origin (Krebs and Arantes, 1973;Monteiro, 1977;Coura et al, 1986;Santos and Rossetti, 2003;Rossetti and Santos, 2006;Wilson et al, 2006;Murray et al, 2007;Góes et al, 2007), while others point to weathering originating from Miocene Barreiras sediments (Hurst and Bosio, 1975;Murray and Partridge, 1981), or from cretaceous sediments of Itapecuru or Ipixuna formations (Costa, 1991;Costa and Moraes, 1992;Moraes, 1994;Moraes et al, 1994;Costa, 1997;Kotschoubey et al, 1996;Costa and Moraes, 1998;Sousa et al, 1999a,b;Kotschoubey et al, 1999;Sousa, 2000;Sousa et al, 2007b). Santos et al (2007) conducted d 18 O and d D analyzes on kaolinites originating from soft and hard (semi-flint) kaolin from Rio Capim deposits and concluded that kaolinites were not in equilibrium with modern weathering processes.…”

Mineral Contaminants of the Sedimentary Kaolin Ore From Ipixuna Mine, Brazil

“…Deposits from Rio Capim and their chemical analysis indicated intense lateritic processes, characterized by ferruginization and deferruginization, that created the several facies (Souza et al, 2006). Studies involving heavy minerals from the Rio Capim area indicated that the age of the kaolin deposits from Ipixuna Formation is Late Cretaceous (Góes et al, 2007). Rio Jari and Rio Capim are areas where sedimentary kaolin deposits are mined and their ages are, respectively, Pliocene and Tertiary (Murray et al, 1982;Murray et al, 2007).…”