Submitted by Edisangela Bastos (edisangela@ufpa.br) on 2017-05-15T11:33:49Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_IntemperismoQuimicoRochas.pdf: 11761461 bytes, checksum: 0e0f2cc1478ae6521b04e42a80ca2281 (MD5) / Approved for entry into archive by Edisangela Bastos (edisangela@ufpa.br) on 2017-05-15T16:45:44Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_IntemperismoQuimicoRochas.pdf: 11761461 bytes, checksum: 0e0f2cc1478ae6521b04e42a80ca2281 (MD5) / Made available in DSpace on 2017-05-15T16:45:44Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_IntemperismoQuimicoRochas.pdf: 11761461 bytes, checksum: 0e0f2cc1478ae6521b04e42a80ca2281 (MD5) Previous issue date: 1980-05-13 / FUFMT - Fundação Universidade Federal de Mato Grosso / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / FINEP - Financiadora de Estudos e Projetos / Visando caracterizar intemperismo químico de rochas graníticas ocorrentes na região Bragantina - NE do Pará - perfis de solos residuais derivados dessas rochas, sob condições de relevo suave, boa drenagem e clima tropical úmido com estações chuvosa e de estiagem bem definidas, foram estudados sob o ponto de vista mineralógico e geoquímico. Os solos da área objeto de estudo são constituídos essencialmente por quartzo, seguido de caolinita e pequenas quantidades de muscovita, óxidos secundários, feldspatos e minerais pesados, produtos da decomposição dos minerais das rochas originais que se degradaram na seguinte seqüência: biotita>feldspato>muscovita>quartzo e minerais pesados. Predominantemente são solos quartzo-arenosos, resultantes da decomposição de caolinita condicionada pela elevada pluviosidade da região. A grande resistência do quartzo, associada à intensa lixiviação dos perfis, permitiu o desenvolvimento de solos texturalmente homogêneos. / Profiles of residual soils derived from granitic rocks which occur in the Bragantina Region, Northeastern Pará, were studied chemically and mineralogically. These soils were developed in an ares of gentle topography and good drainage under tropical conditions with well defined "dry" and rainy seasons. The mineral composition of these soils consists essentially of quartz and with decreasing abundantes also appear kaolinite, muscovite, secondary oxides, feldspar and heavy minerals. This mineral assemblage resulted from the chemical weathering of the parent granitic rocks wh.ose original minerals were decomposed in the following sequence: biotite, feldspars, muscovite, quartz and heavy minerals. The soils are dominantly sandy from which significant amounts of kaolinite, produced during the earlier stages of weathering, were lost in consequente of the intense leaching that is favored by the high pluvial precipitation oves the region. The great stability of quartz under tropical conditions together with the intense leaching of the regolith has led to the development of texturally homogeneous soils in the Bragantina Region.