J. Phys. IV France
Volume 104, March 2003
Page(s) 399 - 402

J. Phys. IV France
104 (2003) 399
DOI: 10.1051/jp4:20030108

Phosphatization of basaltic rocks from Sal Island, Cape Verde Archipelago: A microtopochemical approach using synchrotron radiation X-ray fluorescence

M.O. Figueiredo1, 2, T. Pereira da Silva1, 2, J.P. Veiga1, 2 and P. Chevallier3

1  Cryst. & Miner. Centre, IICT, AI. D. Afonso Henriques 41-4°, 1000-123 Lisboa, Portugal
2  CENIMAT, Fac. Sci., New Univ. Lisbon, Quinta da Torre, 2829-516 Caparica, Portugal
3  LURE, Centre Universitaire Paris-Sud, bâtiment 209C, 91405 Orsay, France

The geochemical processes involved in phosphorous enrichment of volcanic rocks under shallow seawater are not yet fully understood. As a contribution to this problematic, a detailed chemical characterization of phosphatized basaltic hyaloclastites assigned at Sal Island, Cape Verde archipelago, was undertaken using synchrotron radiation X-ray fluorescence. The mineralogical constitution of the samples was characterized by combining X-ray diffraction and electron microprobe data. Micromappings of metallogenetically significant components and other mobile chemical species were obtained. A positive correlation between Br plus Sr, on one side, and As plus Cr and Zn, on the other, is pointed out and brief comments are presented on the selective up-take of chemical elements in close dependence from the mineral assemblage formed by phosphatization.

© EDP Sciences 2003