Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Ponta do Morro

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Occurrence number: 
025-00-130
Country: 
Brazil
Region: 
Mato Grosso
Location: 
Longitude: -55.71012, Latitude: -16.27129
Carbonatite: 
No

The Ponta do Morro alkaline complex is located in the state of Mato Grosso of west-central Brazil. It consists of a crescent-shaped, silica-saturated to over-saturated granite-syenite association covering an area of ~7 km2, intruding the metasediments of the Upper Precambrian Cuiabá Group. Granitic lithologies dominate, displaying graphic intergrowths of quartz and mesoperthite, with alkali amphiboles (barroisite to winchite) and subordinate Na-bearing clinopyroxene (aegirine-augite). Syenites are subordinate and exist in both one and two feldspar varieties, with notable minerals including aegirine/aegirine-augite pyroxenes and riebeckite-arfvedsonite amphiboles and accessory fayalite, aenigmatite and astrophyllite. The main body is intruded by 30-40 cm thick trachytic and rhyolitic dykes, concentrated along the eastern border. Geochemical data, including whole rock major and trace element, mineral chemical, and Rb-Sr isotopic can be found in Souza et al. (2005) and Souza (1997).

Age: 
97.3 ± 1.1 Ma Rb-Sr whole rock (Souza at al., 2005)
References: 
SOUSA, M.Z.A., 1997. Petrologia Geoquímica do Complexo Alcalino Ponta do Morro-MT. Doctoral thesis, Universidade de São Paulo. SOUSA, M.Z.A., RUBERTI, E., COMIN-CHIARAMONTI, P. & GOMES, C.B. 2005. In: Comin-Chiaramonti, P. & Gomes, C.B. (eds) Mesozoic to Cenozoic alkaline magmatism in the Brazilian Platform. Editora Universidade de São Paulo, São Paulo, 71-89. In: Comin-Chiaramonti, P. & Gomes, C.B. (eds) Mesozoic to Cenozoic alkaline magmatism in the Brazilian Platform. Editora Universidade de São Paulo, São Paulo, 241-260.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith