Jj. Cocheme et al., ZEOLITIZATION PROCESSES IN BASIC LAVAS OF THE BAUCARIT FORMATION, NORTHWESTERN MEXICO, Revista geologica de Chile, 21(2), 1994, pp. 217-231
Basalts and basaltic andesites in terbedded with sandstones in the mol
assic Baucarit Formation of northwestern Mexico show contrasting zeoli
te and clay assemblages in amygdales and in veins cross-cutting the fl
ows. In amygdales, heulandite-clinoptilolite, chabazite, offretite/eri
onite and phillipsite are associated with a di-smectite clay. in veins
, mesolite, analcime and stilbite are associated with minor clay, quar
tz and calcite. The low temperature nature of the zeolites and clays s
uggests that the infiltrating fluid had a temperature below 100 degree
s C and probably ca. 60 degrees C, The absence of a pervasive alterati
on and a lack of correspondence between clay and host-rock chemistry s
uggest that this fluid was probably of a meteoric and fresh water char
acter, which subsequently evolved into a more alkaline nature followin
g interaction with glassy material in the interbedded mollassic sedime
nts.