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.
In the ridge N of Wadgrai, there is a 350 m long and a few to some meters thick composite dyke comprising up to 2 m thick reddish pink granite sheets flanking a dark doleritic
rock on both sides.
Recent baddeleyite datings of the Breven-Hallefors doleritic
dyke swarm in south-central Sweden opposite NW Lithuania at ca 1.
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.
A renewed period of magmatism affected Madagascar during the Cretaceous period with the emplacement of doleritic
dikes and the eruption of basaltic flows along the east coast and in the sedimentary basins of Mahajanga, Morondava and Toliara.
All over the massif, the peridotites are crosscut by numerous doleritic
dykes with chilled margins.
In the area of San Pablo (FIGURE 3) a swarm of doleritic
and albititic dykes cut the San Pablo Complex (Radelli, 1995).