Paleomagnetic and Geochemical Constraints on the Timing and Duration of the CAMP Activity in Northeastern Brazil

Marcia Emesto l, Giuliano Bellieni 2, Enzo M. Piccirillo 3, Leila S. Marques 4, Angelo de Min 5,
Igor G. Pacca l, Gutemberg Martins 4 and José W.P. Macedo 5

1 Departamento de Geofisica, Instituto Astronomico e Geofisico, University of Sao Paulo, Rua do Matao, 1226, Cidade Universitaria, 05508-900 Sao Paulo, SP - Brasil  Tel.:55-11-3818 4755; Fax:55-11- 3818 5034  e-mail: marcia@iag.usp.br
2 Dipartimento di Mineralogia e Petrologia, University of Padova, Italy
3 Dipartimento di Scienze della Terra, University of Trieste, Italy
4 Departamento de Geologia, Federal University of Ceara Brazil
5 Departamento de Fisica, Federal University of Rio Grande do Norte, Brazil

ABSTRACT

 The northeastern border of the Maranhao basin (NE Brazil) is dominated by low-Ti tholeiites which display the same magnetic remanence as the Mosquito Formation.  Two low-Ti tholeiitic flows (Early Jurassic) from Lavras basin, and the low-Ti dikes outcropping in the Ceara State also show strong geochemical affinity with the Mosquito tholeiites.  Analogue compositional similarity exists between the Early Cretaceous high-Ti rocks of Ceara, those from Ceara and the Sardinha intrusives (MaranhAo basin).  On paleomagnetic basis, three age groups were identified in the Ceara-Mirim dike swarm: Early Cretaceous (subswarms I, III, V), Early Jurassic (subswarm IV), and Late Triassic (subswarm II).  Corresponding paleomagnetic poles were calculated by combining these data with those from the Maranhao basin, and Ceara dikes.  The Early Jurassic pole fits well other CAMP poles from South America, the Late Triassic age might represent a magmatic manifestation preceding of about 20-30 My the CAMP activity in NE Brazil.