Lherzolite xenolith in Monchiquite, Streap.


Lherzolite. This rock is as far as can be ascertained, is representative of material that makes up the mantle. Very rarely seen at the earth’s surface, at least in unaltered form. This rock has been carried up from great depth very rapidly as xenoliths in a very violent eruption. Part of the dyke material is present in the slide, so the contact can be studied. Lherzolite consists mainly of olivine with orthopyroxene and chrome diopside, and minor chromite, some brown isotropic mineral which I believe is perovskite. The dyke material is reported in the geological literature to be Monchiquite, a member of the lamprophyre group. It consists mainly of pinkish augite (titanium rich?) with magnetite and small laths of kaersutite.
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