Alkaline Rocks and Carbonatites of the World

Funded by HiTech AlkCarb - New geomodels to explore deeper for Hi-Tech critical raw materials in Alkaline rocks and Carbonatites

Piedade

stripes

Occurrence number: 
025-00-097
Country: 
Brazil
Region: 
Sao Paulo
Location: 
Longitude: -47.4, Latitude: -23.7

This is a small dyke of porphyritic shonkinite with phenocrysts of biotite, aegirine-augite, apatite and orthoclase, in a groundmass of the same minerals plus nepheline. Weathered syenitic rocks also outcrop.

Age: 
121.8 Ma by K-Ar on biotite (Amaral et al. 1967).
References: 
KNECHT, T. 1960. Notas preliminares sobre novas ocorrencias de rochas alcalinas no estado de S. Paulo. Boletim da Sociedade Brasileira de Geologia, 9(1): 71-6. Melcher, quoted in AMARAL, G., BUSHEE, J., CORDANI, U.G., KAWASHITA, K. and REYNOLDS, J.H. 1967. Geochimica et Cosmochimica Acta, 31: 117-42
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith