Petrology of potassic alkaline ultramafic and carbonatitic rocks from Planalto da Serra (Mato Grosso State), Brazil

Autor(es)

Comin-Chiaramonti, Piero ^[1] ; Gomes, Celso B. ^[2] ; De Min, Angelo ^[1] ; Ruberti, Excelso ^[2] ; Girardi, Vicente A. V. ^[2] ; Slejko, Francesca ^[1] ; Neder, Renato D. ^[3] ; Pinho, Francisco E. C. ^[3]

Afiliação do(s) autor(es)

^[1] Univ Trieste, Dept Math & Geosci, I-34127 Trieste - Italy

^[2] Univ Sao Paulo, Inst Geosci, BR-05508080 Sao Paulo - Brazil

^[3] Univ Fed Mato Grosso, Inst Geosci, BR-78060900 Cuiaba - Brazil

• Tipo de documento: Artigo Científico
• Fonte: CENTRAL EUROPEAN JOURNAL OF GEOSCIENCES; v. 6, n. 4, p. 565-587, DEC 2014.
• Citações Web of Science: 2

Resumo

The Planalto da Serra igneous rocks form plugs, necks and dykes of carbonate-rich ultramafic lamprophyres (aillikites and glimmerites with kamafugitic affinity) and carbonatites (alvikites and beforsites). Phlogopite and/or tetraphlogopite, diopside and melanitic garnet are restricted to aillikitic rock-types, whereas pyroclore occurs only in carbonatites. Aillikites and carbonatites are altered to hydrotermalites, having chlorite and serpentine as dominant minerals. Planalto da Serra igneous rock association has kamafugitic affinity (i.e. effusive, ultrapotassic. High LREE/HREE fractionation, incompatible elements data and Sr-Nd isotopes, suggest that the K-ultramafic alkaline and carbonatite rocks originated from a variably metasomatized mantle source enriched in radiogenic Sr. Crustal contamination is negligible or absent. Age values of 600 Ma rule out the geochronological relationship between the investigated intrusions and the Mesozoic alkaline bodies from the Azimuth 125A degrees lineament. The TDM model ages allow to conclude that Planalto da Serra magma is derived from the partial melting of a mantle source metasomatised by K-rich carbonatated melt during the Early to Late Neoproterozoic. On the basis of alkaline magmatism repetitions at 600 Ma and 90-80 Ma we question the subsistence of a stationary mantle plume for so long time. (AU)

• Processo FAPESP: 10/50887-3 - Investigacao petrologica e geoquimica de rochas alcalinas da plataforma brasileira.
• Beneficiário: Celso de Barros Gomes
• Modalidade de apoio: Auxílio à Pesquisa - Regular