2] in the groundmass
are semi-quantitatively estimated in selected mudstone sites by SEM-EDS.
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.
The 170-250 pm groundmass
plagioclase size fraction was obtained by repeated passes through a Frantz magnetic separator at increasing field strengths.
The andesites of Noorabad ophiolite in hand specimen and thin section have phenocrysts of plagioclase in a groundmass
of clinopyroxene and amphibole minerals.
surrounding the glass clasts and crystal fragments seem to be flushed with organic matter with different sizes and structures showing different degrees of biodegradation and alteration to amorphous organic matter (AOM).
34 Ma for the Taylor Creek sanidine Age in bold is preferred Sample Material K/Ca Total fusion N total Age (ka) + 2[sigma] Media Luna groundmass
Basalt###Occasional crystals of quartz, chert and plagioclase embedded in brownish to black fillings glassy groundmass
It consists of ophiolite grains which made up of fine sand-sized, well sorted, subangular to subrounded ophiolite, quartz, chert and micrite limestone grains scattered in groundmass
composed of partially dolomitized calcite or micritic matrix.
This is highly encouraging as NEV027 only just intersected the top of the intrusive complex with several large Chim Formation clasts (fragments) incorporated within the porphyry groundmass
Alteration of both phenocrysts and groundmass
is also evident in most sections, with olivine partly or totally altered to iddingsite, and plagioclase weathering to clay minerals.
The melanophyres of the Ilfeld Basin, which come from the earlier or earliest of the eruptive episodes, are brown to black, with a fine-grained groundmass
composed of oligoclase, augite, biotite, apatite and magnetite, with phenocrysts, most of which are tabular crystals of augite (Luedecke, 1896).
80]) and clinopyroxene phenocysts in a fine-grained groundmass
enclosing interstitial glass.
1985) 1 <30 Manic, only fabric units of one size group or <10 amorphorous material present Cefiiric, coarser units linked by finer material 2 30-50 Chitonie, coarser units are surrounded by a cover of 10-20 smaller units <30 3 >50 Chitonic 20-30 Enaulie, a skeleton of larger units with aggregates <30 of smaller units in the interstitial spaces 4 50-100 30-60 30-60 5 100 Enaulic >60 Porphyritic, larger units occur in a dense <30 groundmass
of smaller units Table 2.
In addition to these visual observations, a powder x-ray diffraction analysis was run on one coprolite specimen to determine the major composition of its groundmass
Still downwards, the rock consist of a feldspathic groundmass
with a texture close to nebulitic in which only very thin amphibolitic films occur, corresponding to (or transposed into) schistosity planes, and offoliated hololeucocratic granite.