Some of the rocks were low-silica basalts, high silica dacite, olivine basalts ultramafic ( picratic ) basalts, and quartz-bearning granitoid rocks.
22.
Locally this is known as " Dhu Stone " ( Welsh for Black Stone ); geologically it is an olivine basalt, sometimes coarse enough to be a dolerite.
23.
There have been three basalt lava types identified at Kone, aphyric basalt, olivine basalt and a third basalt which contains large phenocrysts of olivine, augite and plagioclase.
24.
Most of this detritus is erosional in nature, but pyroclastic rocks created by hot avalanches of extruded lava also contribute . thick olivine basalt found in the Jaz Murian depression may also come from Bazman.
25.
Rotuma is a shield volcano made of alkali-olivine basalt and hawaiite, with many small cones, and reaches 256 metres ( 840 ft ) above sea level at Mount Suelhof near the center of the island.
26.
The ancestral and modern stages differ primarily in the composition of the erupted lavas; ancestral lavas consisted of a characteristic mixture of dacite and andesite, while modern lava is very diverse ( ranging from olivine basalt to andesite and dacite ).
27.
At intermediate dephs high-alumina basalt magmas are formed ( Mount Fuji, Southern Yatsugatake Volcanic Group, Mount Ontake, for instance ) and at dephs greater than 250 km alkali olivine basalt ones ( Oki-DMgo, for instance ).
