This sample is a holocrystalline
, greyish pink, medium-grained, equigranular granite dominated by quartz; perthitic potassium feldspar grains, which are moderately altered to sericite; plagioclase grains, which are altered to sericite in their central parts (Fig.
The host rocks and their enclaves are usually equigranular and holocrystalline
, but porphyritic texture also exists in the enclaves.
Olivine almost disappears in the holocrystalline
inner parts of the lamproitic main body, but is locally common in the glassy lavas where there is a porphyric texture with glassy to microcrystalline groundmass.
The main constituent rocks are holocrystalline
aegirine phonolite, so-called tinguaite, nepheline syenite, and vent-filling intrusive pyroclastic rocks.
Petrographically gabbroic rocks are melanocratic, holocrystalline
, medium to coarse grained and subpoilikitic in texture.
The intrusive analogues (theralites, essexitic gabbros, ijolites and essexites) show a holocrystalline
inequigranular texture, with diopsidic pyroxene ([Wo.sub.44-51][Fs.sub.8-17]), olivine ([Fo.sub.75-82] to [Fo.sub.44-66]), mica (Ti-phlogopite to Ti-biotite), Timagnetite, alkali feldspar, and nepheline ([Ne.sub.64-80][Ks.sub.20-36]) [+ or -] leucite [+ or -] amphibole.
Tholeiitic basalts have a fine grained holocrystalline
groundmass, indicating a lava flow with a fairly rapid crystallization process.
Dredging from bathymetric highs recovered pillow lavas, pillow fragments, and holocrystalline
rocks, all basaltic in composition.