Olivine phenocrysts (2%) appear opacitized and show kelyphitic rims composed of orthopyroxene
Like these granitoids, the Vlc-2 granodiorite is different from the Palaeoproterozoic charnockites of the Kursiai intrusion in Lithuania by lacking orthopyroxene
but being rich in amphibole and brown biotite, which indicates lower temperatures of crystallization and somewhat higher contents of [H.
Major element compositions of olivine, orthopyroxene
, clinopyroxene, plagioclase, amphibole and phlogopite has been analysed directly on polished thin and thick (130 [micro]m) sections at the Centro Nacional de Microscopia Electronica (Complutense University of Madrid) using a JEOL JXA-8900 M electron microprobe with four wavelength-dispersive spectrometers.
The minerals of these rocks consists of olivine, clinopyroxene, orthopyroxene
and chrome- spinel that have mesh and granular texture that altered to serpentine minerals and iron-oxid (Fig.
The dyke rock has a distinctive cross-columnar field appearance, and a subophitic to micro-porphyritic texture with abundant Ti-bearing augite, calcic plagioclase, scattered euhedral orthopyroxene
phenocrysts, and coarse-grained glomerophyric clumps of augite with plagioclase.
By studying thin slices of the gabbros under polarizing microscopes, the scientists identified substantial amounts of the mineral orthopyroxene
, a magnesium silicate that was thought to be absent from the lower crust.
These crystals (one shown), of a mineral called orthopyroxene
, grow in zoned "rims," each formed as fresh magma arrives from below and cools.
The main minerals are plagioclase, clinopyroxene, orthopyroxene
, and magnetite; the veins and vugs contain quartz, calcite, and zeolite.
, olivine and mangnetite were also detected in contaminated soils including allophane and quartz (Table 2).
The primary mineralogy of komatiites is simple: phenocrysts of olivine and spinel/chromite (+/pyroxene) are enclosed in a groundmass composed of glass, calcic clinopyroxene and minor orthopyroxene
They consist of idioblastic hornblende and subordinate plagioclase (labradorite) with, as accessory minerals, orthopyroxene
, magnetite, and ilmenite which can be locally abundant.
1:00 Shannon Heinle (UND) CLINOPYROXENE, ORTHOPYROXENE
, AND OLIVINE CHEMISTRIES IN ULTRAMAFIC TO MAFIC XENOLITHS