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p.47–75 Submitted by Ana Valéria de Jesus Moura (anavaleria_131@hotmail.com) on 2012-01-25T12:38:56Z No. of bitstreams: 1 S0301926800000814-main.pdf: 2921220 bytes, checksum: 0e8fcaccfe604dd99b8008aabeeed8f8 (MD5) Made available in DSpace on 2012-01-25T12:38:56Z (GMT). No. of bitstreams: 1 S0301926800000814-main.pdf: 2921220 bytes, checksum: 0e8fcaccfe604dd99b8008aabeeed8f8 (MD5) Previous issue date: 2000 During the Transamazonian cycle (2.090.2 Ga), two silica-saturated alkaline granite suites were intruded along the border of the Sa˜o Francisco craton, northeastern Brazil. The Couro de Onça intrusive suite (COIS) is late tectonic relative to major deformational events, and the Serra do Meio suite (SMS) postdates this event, being interpreted as anorogenic type, deformed during the Brasiliano cycle (0.65–0.52 Ga). The COIS encompasses alkali-feldspar granites, syenogranites, monzogranites, with dykes of similar composition and age (2.15795 Ma). They are metaluminous rocks of alkaline affinity, whose evolution was probably controlled by mineral fractionation processes involving mainly plagioclase, amphibole, and Fe–Ti oxide. The SMS, whose probable age is 2.01 Ga, is composed of metaluminous and peralkaline granites, with associated quartz syenites, with Ti-aegirine transformed during the Brasiliano deformation to riebeckite titanite aenigmatite. The temperatures of two stages of metamorphic transformation, overprinted during the Brasiliano event, are estimated at about 550 and 400–450°C. Both magmatic suites are derived from enriched mantle sources. The metaluminous and peralkaline trends observed in the SMS, characterized by high concentrations of HFS and RE elements controlled mainly by F-activity, reflect the evolution of different primary magmas produced by successive melting of the same mantle sources, in an anorogenic setting.

Texto completo. Acesso restrito. p. 661–683 Submitted by Santiago Fabio (fabio.ssantiago@hotmail.com) on 2013-07-23T17:13:54Z No. of bitstreams: 1 33333333333.pdf: 964163 bytes, checksum: 09f72cd24bc736e4c284b4d2b3d1ee0b (MD5) Approved for entry into archive by Rodrigo Meirelles (rodrigomei@ufba.br) on 2013-11-01T11:53:44Z (GMT) No. of bitstreams: 1 33333333333.pdf: 964163 bytes, checksum: 09f72cd24bc736e4c284b4d2b3d1ee0b (MD5) Made available in DSpace on 2013-11-01T11:53:44Z (GMT). No. of bitstreams: 1 33333333333.pdf: 964163 bytes, checksum: 09f72cd24bc736e4c284b4d2b3d1ee0b (MD5) Previous issue date: 2000 The Neoproterozoic of northeastern Brazil was marked by the development of collisional fold belts, mainly surrounding the Sa˜o Francisco Craton, and an associated widespread granitic magmatism. The Casa Nova 555 ^ 10 Ma; Sri 0:7068 and Engrac¸adinha syenites and granites, intrusive in the Riacho do Pontal Fold Belt, are related to the late stages of this collisional event. Melanocratic syenites, probably generated by magmatic-flow cumulate processes, and mesocratic and leucocratic syenites, representing magmatic liquids, are associated with granites, pegmatites, and syenite–granite dykes. Homogeneous or perthitic alkali feldspar, quartz, aegirine–augite, diopside, titanite, apatite, magnesian biotite, winchite–richterite, and magnetite are the dominant mineral phases. It is suggested that these magmas belong to an ultrapotassic silica-saturated alkaline series, defined on the basis of its alkaline, silica-saturated character and by a K2O/Na2O ratio of .3.0 — that is, intermediate. Major- and trace-element evolution is consistent with mineral fractionation processes, controlled by magmatic flow, and dominated by apatite–titanite–pyroxene in the less differentiated terms and by alkali feldspar in the more evolved. The source of primary magmas is a previously subduction-metasomatised mantle, probably with anomalous enrichment in LREE and LILE elements. Barite– ilmenite mineralisations are related to the more differentiated Engrac¸adinha granites. Salvador