The groundmass in these rocks comprises plagioclase (calcic and esinetosodic labradorite), clinopyroxene
or brown primary amphibole, biotite, ilmenite, olivine relics in some pyroxene-bearing dykes, rare pyrite in the amphibole-bearing types, and minor quantities of a range of secondary minerals as in the altered rocks.
We have determined in situ concentrations of 28 trace elements (REE, Ba, Rb, Sr, Th, U, Nb, Ta, Pb, Zr, Hf, Y, Sc, V, Co and Cr) in olivine, plagioclase, orthopyroxene, clinopyroxene
, amphibole and phlogopite on two polished thick sections (130 [micro]m) by laser ablation ICP-MS at the Natural History Museum of London, using a New Wave UP193FX gas laser source operating at 193 nm coupled to an Agilent 7500CS ICP-MS.
Diabase dikes have been extensive but scattered and have green to brown colors that have plagioclase, clinopyroxene
and opaque mineral.
Lavas from SER contain variable abundances of plagioclase, clinopyroxene
and olivine phenocrysts, commonly in glomeroporphyritic clusters.
Mafic minerals (biotite and hastingsitic hornblende with rare clinopyroxene
inclusions) account for up to 10 vol% of the rock.
Strongly opacitized salite to sodic fassaite grains of matrix, rounded in shape and pale green in colour distinctly differ in their composition from clinopyroxene
Petrographically, the Lower Angeles corresponds with a vesicular andesitic-basaltic lava, with a hypocristalline porphyritic to glomeroporphyritic texture, with phenocrystals of plagioclase, clinopyroxene
, orthopiroxene, olivine and opaque crystals.
The mafic rocks are porphyritic to aphyric and consist of calcic plagioclase, clinopyroxene
+- olivine or hornblendic amphibole, ilmenite, titanite, and a range of secondary minerals.
The phenocrysts of plagioclase or clinopyroxene
are larger than 4 mm of long, while the groundmass is fine-grained and less than 0.
Petrogenetic significance of orthopyroxene-free garnet + clinopyroxene
+ plagioclase [+ or -] quartz-bearing metabasites with respect to the amphibolite and granulite facies, Journal of Metamorphic Geology.
Phenocrysts consist mostly of plagioclase and rarely, clinopyroxene
2) Ijolite refers to a series of plutonic rocks containing nepheline and 30-60% mafic minerals, generally clinopyroxene
, and including titanite, apatite and sometimes andradite (Jackson, 1997).