The two summits of the hill defined by the Logrosan granite (the San Cristobal hill) are composed of a microporphyritic (two-texture) granite and an aplitic granite (Evolved Units) (Fig.
A total of 9 representative samples weighted between 3-5 kg were collected for whole-rock geochemistry (6 medium to coarse-grained granites from the Main Unit and 3 fine-grained or microporphyritic granites from the Evolved Units) (Table 1).
Thin sections of dyke contacts show microporphyritic
crystals of plagioclase, augite, and orthopyroxene scattered in a dark glassy matrix (Fig.
These include: alkali granite, granite and microporphyritic
The mineralization is associated with intense montmorillonite-quartz-carbonate-pyrite alteration developed in a microporphyritic
The rhyolite occurs as aphanitic to porphyritic flows and ignimbritic tuffs with flow banding and microporphyritic
to porphyritic textures (Fig.
The significance of flow structure in microporphyritic
ophitic basalts of Arthurs Seat.
Lavas are commonly amygdaloidal and/or microporphyritic
with phenocrysts of feldspar and, more rarely, pyroxene or quartz, set in a glassy to microcrystalline groundmass.