Immature lateritic profiles are very common in Amazonia, such as in southern region of the state of Pará. However, these profiles are poorly researched their potential for hosting important mineral deposits, such as Au, Pt, Ni, Mn and mineralizations associated the resistate minerals (Sn, Nb-Ta, Y). In the Paragominas-Rondon do Pará region, these formations sometimes dominate the local landscape, both as autochthonous and as allochthonous deposits. To understand the process of formation of these profiles to contribute to the understanding of the geological evolution during the Cenozoic in the regions of Abel Figueiredo and Rondon do Pará is the objective of this work. Two autochthonous profiles located in the Abel Figueiredo region, southeast of Pará, one of them at km 137 of BR-222 and the other at km 138 of the same highway were selected for a textural, mineralogical and geochemical studies, besides characterizeation of the content heavy minerals and anatase for discussions of the source rock and evolution processes. Fieldwork, X-ray diffraction, optical and scanning electron microscopy and multielementary chemical analyzes were carried out. The profiles generally are equivalent in terms of succession of horizons, comprising from bottom to top by: clayey horizon, which is present only in the profile of km 138, is reddish brown in color with white patches and massive aspect; the partially dismantled columnar iron-aluminous crust, of dark reddish brown coloration, columnar structure, parallelized by channels filled by silt clayey material; partially dismantled nodular iron-aluminous crust of dark reddish brown coloration, with ochre tones, nodular structure, microporous to cavernous appearance; subspherolithic horizon of the profile of km 138 is represented by reddish brown subespheroliths, surrounded by a yellowish-brown clayey matrix, while the equivalent of the profile of km 137 is called the spherolithic to nodular horizon represented by spheroliths and nodules surrounded by matrix of brown color; topsoil, is of earthy consistency and homogeneous, correlated to the latosols of Amazonia. This structuring from the crust ferroaluminosa columnar shows increasing degree of biochemical and physical disaggregation marked by the dismantling and crustal fragmentation, by the occurrence of columnar pattern and nodules, and the comminution of the nodular fragments at the top giving rise to the spherolites /subespherolites. This structural pattern expresses a typical granodecrescent process, culminating with the topsoil, predominantly silty-clayey; The mineralogy of the lateritic profiles and topsoils consist of hematite, goethite, kaolinite, quartz, and as accessory anatase and heavy minerals (zircon, rutile, tourmaline, kyanite and staurolite) that describe a classic lateritic succession. Hematite and goethite are the main iron-bearing minerals that capture highly mobile elements (V, Cr, As, Se, Mo, Ag, Sb, Hg and Bi) fixed on crusts and their degradation products (nodules, spheroliths and subespheroliths). Caulinite and al-goethite play less importance in the capture of elements, but they support that the lateritic profile was affected by tropical weathering. Zircon, a mineral of residual behavior as well as the anatase, shows affinity with Ta, Nb, Y and ETR and comes from a single source of granitic filiation. The mineralogy and geochemistry indicate a continuous evolution of the partially dismantled columnar iron-aluminous crust to partially dismantled nodular iron-aluminous crust and this to the subesferolithic horizon or spherolithic to nodular horizon and finally to the topsoil. The distribution of SiO2, Al2O3, Fe2O3 and TiO2 shows that the crusts, nodules and spheroliths are similar chemically. This similarity is also demonstrated by the same pattern of distribution curves of trace elements and REE. Hematite and ferric goethite decompose and form kaolinite, Al-goethite, with parallel residual quartz and residual anatase concentration, which is manifested by the increase of SiO2 and Al2O3 and TiO2 and the subsequent gradual loss of Fe2O3. The mineralogical and chemical similarity between the clay matrix and the topsoil testifies that this matrix generated by the degradation of crust is the likely source of the topsoil. The lateritic profile began its development from the Miocene, when it was exposed to intense tropical forest root activity that biochemically decomposed the preexisting crusts giving rise to the nodules and spheroliths / subespheroliths with generation of clay matrix and simultaneously forming kaolinite and Al-goethite. The topsoil was formed at the top of the hills of the lower surface under the warm and humid Amazon climate during the Pleistocene.
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