groundmass

The Phenocrysts in the granite is feldspar and quartz however, the groundmass consists of Perthtized alkali feldspar, quartz, muscovite and biotite.

The fragments are commonly covered by thin coatings of clayey material, with a different composition than the groundmass, and some fragments show truncation of internal planar features.

The feldspar phenocrysts and feldspar in the groundmass are pervasively altered to buff white clay.

Its reason of anomaly is possibly from change of the plumb line due to the motion of the groundmass before earthquake (Zhang, 1981).

A detailed microanalytical geochemical and in situ Sr-isotope study performed on glassy groundmass of single ash clast showed unusually high [sup.87]Sr/[sup.86]Sr values (up to 0.70668) for Icelandic volcanism (0.7026-0.7037 [94]) (Figure 8(c)); these high isotopic values were also associated to atypical elemental compositions compared to most of the juvenile ash fragments of the eruption.

The dominating biogenic compounds are: (i) calcite as < 5 m[micro] micrite forming the groundmass mudstone, and both micrite of the matrix and > 5 m[micro] to 1 mm grains--skeletal particles (shells and their broken fragments) in wackestone, (ii) silica as < 5 m[micro] particles belonging to the groundmass of mudstone and wackestone matrix, (iii) organic matter (kerogen) in the mudstone and matrix of wackestone, (iv) phosphate skeletal fragments in certain interbeds of wackestone and very fine apatite in groundmass.

The mega-porphyritic andesites with large and white plagioclases set in a green to gray groundmass are also present in the Venarch area.

In order to better position the isolated occurrence of the Baltic dolerite sills in the geological evolution of the region, we used the obtained new [sup.40]Ar/[sup.39]Ar dating results of a whole-rock and a groundmass plagioclase sample in combination with whole-rock major and trace element data.

Boulis and Attia found that the anatase presents as very fine Ti-bearing grains disseminated throughout the kaolinite groundmass. (19) Calcination of KF pigment up to 900[degrees]C reduced LOI from 13.92 to 0.78 due to dehydration and dehydroxylation of kaolinite to produce metakaolinite, which is the most active form of kaolinite (Table 2.) The bleaching of metakaolinite (Cal K/d) reduced the iron oxide content from 0.24 to 0.12 (wt%).

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. Phlogopite and diopside are mainly present in holocrystalline rocks as subhedral and euhedral crystals (Fig.