Apophyllite from the Upper Pliocene Grad volcaniclastics, NE Slovenia
AbstractIn some lava fragments from the Grad volcaniclastics, apophyllite occurs as a reaction product of quartzite accidentals and still molten alkali basaltic lava, and also, as a hydrothermal mineral in vesicles and veinlets. Apophyllite can be encountered only in the lava fragments, while in the host volcaniclastic only zeolites occur. During the rise of alkali basaltic magma to the surface, it assimilated some of the Tertiary sediments. Consequently, the residual and deuteric liquids probably became slightly enriched with silica and enabled crystallisation of apophyllite. Under zeolite facies conditions, apophyllite became unstable and got replaced by zeolites.
How to Cite
Kralj, P. (1999). Apophyllite from the Upper Pliocene Grad volcaniclastics, NE Slovenia . Geologija, 42(1), 151–157. https://doi.org/10.5474/geologija.1999.009