Alkaline Rocks and Carbonatites of the World

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

Mato Preto


Occurrence number: 
Longitude: -49.2, Latitude: -24.75

The Mata Preto complex is intruded into the Precambrian metasediments of the Acungui Group and Tres Corregos granites but shows little topographical expression. The intrusion has been investigated in detail only in a small area in the southwest and a rather larger area in the northwest of the complex. The earliest rocks are ijolites and nepheline syenites which were followed by the intrusion of tuffs and breccias with a matrix of carbonate and silica and containing xenoliths of alkaline rocks, fenite and granite. Carbonatites were then emplaced, followed by various types of phonolite. The carbonatite of the southwest of the complex consists of an earlier feldspathic carbonatite breccia and a ferruginous carbonatite with local enrichment in REE, Th and P. A much more extensive area of carbonatite in the northwest of the complex consists essentially of sovites containing abundant fluorite and pyrite.

Concentrations of fluorite, baryte, galena and REE minerals occur (Rodrigues and Lima, 1984).
K-Ar on phonolite gave 65.6 and 67.0 Ma (Cordani and Hasui, 1968).
CORDANI, U.G. and HASUI, Y. 1968. Idades K-Ar de rochas alcalinas do primeiro planalto do estado do Parana. Anais Congresso Brasileiro de Geologia, 22: 149-53. LAPIDO LOUREIRO, F.E. and TAVARES, J.R. 1983. Duas novas ocorrencias de carbonatitos: Mato Preto e Barra do Rio Itapirapua. Revista Brasileira de Geociencias, 13: 7-11. RODRIGUES, C. de S. and LIMA, P.R.A. dos S. 1984. Carbonatitic complexes in Brazil. Companhia Brasileira de Metalurgia e Mineracao, 1-17
Fig. 1_220 Mato Preto (after Lapido Loureiro and Tavares, 1983, Fig. 4).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith