Author:

Keywords:

Science & Technology, Physical Sciences, Mineralogy, 0403 Geology, 0602 Ecology, 0603 Evolutionary Biology, Geochemistry & Geophysics, 3705 Geology

Abstract:

Analyses of seven basalt dykes and three felsic dykes from the Kerala region are given with major elements and 22 trace elements. The chondrite-normalized REE patterns of the basalt dykes show pronounced differences in their shapes. Six are comparable with those of continental basalts; one is more similar to that of many ocean-floor basalts. In the Hf-Th-Ta discriminant diagram the dykes show wide scatter: only three plot in the field of tholeiitic within-plate basalts, the others in the fields of destructive plate margin rocks. Sr isotopes have been determined for three of the basic dykes and dated by the K/Ar method. The REE patterns of the felsic dykes are strongly enriched in LREE and depleted in HREE; one shows a distinct Eu anomaly. These patterns and high Th/U and Th/Ta ratios of the felsic dykes can be explained by an enrichment of REE by Cl-bearing fluids, and variable loss of CO2-bearing fluids and associated HREE, U and perhaps Ta- and Nb-complexes. The formation of the basaltic dykes is discussed in terms of contamination vs mantle fractionation processes.-I.Kb.