Petrography and physicomechanical properties of alkali granites, alkali quartz syenite, and nepheline syenite from Ambela, NW Pakistan, have been investigated. Whereas the alkali quartz syenite and most of the alkali granites are megaporphyritic, the nepheline syenite and some of the alkali granites are microporphyritic. Their phenocryst shape and size and abundance of groundmass are also diffe...

The Monte Santo Alkaline Intrusive Suite (MSAIS) is an association syenite foid, nepheline syenite and syenite. The MSAIS rocks are intruded in metapelites of the Rio do Coco meta-volcanic-sedimentary Sequence and are abundant pegmathoid veins cutting all of them. The mineral paragenesis is represented by aegirina, arfvedsonite, albite and nepheline, crystallized during the initial phase of cry...

Feldspathic materials are used in the glass and ceramic industries as a source of alkalis, alumina and silica. These elements affect the rate and temperature of melting. fluidity of the melt and physical properties of the finished product. Silica, sodium, potassium and alumina ratios in the feldspar product vary for each industrial user, however, iron must be limited to less than 0. I per cent ...

Rare earth abundances were determined by neutron activation in twenty Hawaiian lavas and one diabase of known chemical and mineralogical compositions. These results demonstrate a systematic relationship between the absolute or relative rare earth abundances and the petroehemistry of these rocks. Three distinct lava groups are recognized. These correspond to: (1) tholeiites, (2) alkali series, (...

Using a recent compilation of African alkaline igneous rocks and carbonatites, we show that nearly 90% (28 of 32 occurrences) of nepheline syenite gneisses and deformed carbonatites are concentrated within known or inferred Proterozoic suture zones. Given the wellestablished intracontinental rift setting for these rocks and the likely continental collisional setting for their subsequent deforma...

The Beemerville alkaline complex, New Jersey, occurs at the western end of the CortlandtBeemerville magmatic belt. The eastern end of the belt is defined by the Cortlandt complex, New York, which largely consists of ultramafic and mafic rocks. Between these two intrusive centers is a linear almost east-west trending zone of lamprophyre and felsic dikes. The Beemerville complex consists of two l...