The Cnoc Rhaonastil minor dolerite intrusion on Islay, NW Scotland represents a single body of alkali olivine basalt magma which differentiated in situ, from leucodolerite, through teschenite to minor nepheline syenite. The syenites occur as isolated nests and pegmatitic schlieren within the leucodolerite, and schlieren of gabbroic pegmatite also occur at the margin of the teschenite. The differentiated rocks contain pyroxene, amphibole and biotite of variable compositions which reflect both primary fractionation processes and late-stage deuteric alteration and reaction.Mafic phases within the gabbroic pegmatite, teschenite and syenite are typically rimmed and speckled with biotite, the composition of which is controlled by the local environment of crystallization. The nepheline syenites contain primary ferro-kaersutite which, where in contact with interstitial patches, has been altered to arfvedsonite, which occasionally contains up to 1.2 wt.% ZrO2. The occurrence of Zr-arfvedsonite (and of Zr-aegirine) in interstitial patches suggests that variably trace element-enriched domains existed within the residual melts on very small scales.

Fluorcaphite [SrCaCa3(PO4)3F] is a rare strontium-calcium member of the apatite supergroup which was previously known only from the Khibiny and Lovozero alkaline complexes. This paper presents evidence of a third fluorcaphite occurrence. It was found in hydrothermally altered Lower Cretaceous teschenite, which forms an intrusive body (probably a sill) in the Lower Cretaceous siliciclastic flysch sediments at Tichá near Frenštát pod Radhoštěm, Silesian Unit, Outer Western Carpathians (Czech Republic). Fluorcaphite occurs as an accessory mineral in hydrothermal veins and in an adjacent alteration zone within the host teschenite. Vein-hosted fluorcaphite forms euhedral crystals and skeletal crusts enclosed in analcime while the teschenite-hosted fluorcaphite forms small overgrowths on older phenocrysts of magmatic apatite. Fluorcaphite from Tichá contains 0.50–1.97 Sr apfu, 2.96–4.49 Ca apfu, 0.59–1.09 F apfu and significantly lower Na (0.01–0.05 apfu) and LREE contents (up to 0.07 apfu). Fluorcaphite formed under hydrothermal conditions after solidification of the host teschenite during post-magmatic hydrothermal activity at temperatures probably between ∼150 and 300°C. The initial 87Sr/86Sr ratio of vein-hosted analcime +fluorcaphite (0.7063) is significantly higher than those of the host teschenite (0.7041). We therefore suggest a mix of strontium sources in the vein analcime+fluorcaphite: (1) from the host teschenite plus (2) from external source(s) including the Lower Cretaceous seawater and/or surrounding sedimentary rocks of the Silesian Unit. These data indicate an open-system fluid regime and the participation of various fluid sources during the alteration event giving rise to fluorcaphite.

A 49 m complete section through the 288 Ma Lugar Sill obtained from drill cores can be subdivided into nine units. The uppermost four units are teschenitic and are mirror images of the bottom four. A 35 m thick central unit consists of theralite passing down into kaersutite theralite and then picrite. Marginal chilling 'of the units indicates multiple intrusion from the outside inwards. Olivine in the central unit (Fo88–90) encloses Cr-rich spinels and increases in amount inwards to over 50%. Clinopyroxene, kaersutite and biotite show symmetrically increasing Fe/Mg from the centre of the sill outwards. Most major and trace elements vary symmetrically throughout the sill with those in the central unit reflecting mainly olivine distribution but incompatible elements exhibit upward enrichment. Remarkably, the most-evolved rocks in the sill are at its margins. The sill was formed by multiple injections of successively less-evolved teschenitic magmas followed by a larger pulse of theralitic liquid carrying abundant olivine phenocrysts. The amount of olivine in this final pulse increased during emplacement. Subsequent in-situ differentiation in the central unit, with upward enrichment in residual liquid and volatiles, gave rise to lugarites. The various magmas were produced in a lower-level magma chamber by differentiation of a mantle-derived, alkali-rich picritic magma.