The dolerites are texturally basaltic, doleritic
and gabbroic and are altered compare to lamprophyres.
Two series of volcanic rocks, one andesitic the other doleritic
(which would now be termed basalts), were also noted.
The results of petrographic studies indicate that the rocks are mostly of doleritic
to dioritic compositions characterized by vein and cavity fillings of calcite.
The area is underlain by sedimentary rocks of the Tarkastad subgroup and Beaufort karoo supergroup with post-karoo doleritic
intrusions [18, 19].
(2003) record saponite as the main phyllosilicate in the contact between the marl-limestone rhythmite and doleritic
laccolith of Sierra de Priego (Cordoba), as a consequence of a late hydrothermal process after contact metamorphism produced by the intrusion of subvolcanic rocks.
These rocks have doleritic
, intergranular and poikilitic texture (Fig 4D).
Besides, the presence of ubiquitous intrusive bodies that are either doleritic
or gabbroic has been delineated in the Bornu Basin by Carter et al.
The moderate bulk densities can be attributed to a combination of relatively high organic matter content in the doleritic
soils, low use of machinery and slash retention and scattering on the harvested forest sites.
Basalt-hosted mineralisation is found within the basaltic and doleritic
rocks around the 1974 discovery area.
Samples of outcropping granite and dolerite and of granitic and doleritic
saprolite were collected from Jarrahdale railway cutting (30 km north of the Huntly mine).