picrite

Symbols for picrite basalts as in Fig. 2.

Granitic rocks were also used and the famous Towie example may be serpentinised picrite.

At high degrees of partial melting of the mantle, komatiite and picrite are produced.

The rocks are picrite, alkaline basalt and trachyandesite.

Rock types include picrite, peridotite, dunite, pyroxenite, gabbro and granophyre.

Also dykes of augite syenite, picrite and tholeiite dolerite were intruded.

Inchmickery and Inchgarvie are of igneous origin and the latter is partly made up of picrite.

The basaltic occurrence of phlogopite is in association with picrite basalts and high-alumina basalts.

Nitroguanidine (Picrite)

(examples picrite, komatiite and peridotite)

Embedded in the diorite are a couple of large gabbro inclusions, as well as a picrite on the east of Braye Bay.

Some of the beaches there are of a greenish colour, because of the olivine sand resulting from picrite basalt lavas.

Most of the dykes are quartz-dolerites in terms of chemistry, with less common olivine gabbro, norite and bronzite picrite.

Chemical classifications are preferred to classify volcanic rocks, with phenocryst species used as a prefix, e.g. "olivine-bearing picrite" or "orthoclase-phyric rhyolite".

Volcanic rocks rich in magnesium may be produced by accumulation of olivine phenocrysts in basalt melts of normal chemistry: an example is picrite.

FIG. 1 Plot of Nd against γ Os, showing correlation for the Karoo picrite basalts.

This was followed later in the Neoproterozoic on the eastern side of the island with beds of diamictite, dolomite, mudstone, tholeiite, and picrite interleaved with conglomerate.

Because the picrite basalts show only a shallow correlation between Nd and Os isotope variation, the data neither require nor rule out the hyperbolic mixing curves (Fig. 3).

Pillow lavas are commonly of basaltic composition, although pillows formed of komatiite, picrite, boninite, basaltic andesite, andesite or even dacite are known.

The highest initial 187 Os/ 188 Os recorded in the picrite basalts are within the range recorded for OIB, and therefore consistent with a sub-lithospheric, plume-related, origin.

The picrite basalts show a broad positive correlation between γ Os and Nd which improves if the three samples from the Gomakwe area are considered separately, and may even represent two discrete correlations.

To test these assertions, we determined Os isotope compositions and Re and Os concentrations for eight of the Karoo picrite basalts whose elemental and isotopic parameters have previously been well characterized.

Dependent upon various regional locations, the NAIP is made up of MORB (Mid Ocean Ridge Basalt), alkali basalt, tholeiitic basalt, and picrite basalt.

Rhenium concentrations for the low- γ Os picrite basalts are significantly below those typical of asthenospheric melts including MORB, and this suggests that a Re-depleted component, such as SCLM, is involved.

To the low- 187 Os/ 188 Os end of the arrays, the picrite basalts have γ Os values that overlap those of MORB and approach the characteristic negative γ Os of lithospheric mantle xenoliths.