Contrary to the southern Appalachians, where Alleghanian magmatism is widespread and well documented, the expressions of magmatism in the Canadian Appalachians are limited. In this study, a suite of leucocratic dykes from the Cape Spencer area in southern New Brunswick, Canada, were investigated to determine the nature, timing and source of these magmas using zircon and monazite U-Pb geochronology, whole-rock geochemistry and Nd-Hf isotopes. An LA-ICP-MS U-Pb monazite Alleghanian age of 273.7 ± 1.3 Ma obtained for these dykes constitutes a new example of magmatism in the northern segment of the orogen, where significant strike-slip movement and reheating have been the primary markers of the Alleghanian Orogeny. These metaluminous leucocratic dykes are enriched in light rare elements, U and Th; depleted in high-field strength elements (HFSE; Nb, P, Ti); and have slight negative Europium anomalies [(Eu/Eu*)N = 0.72–0.95]. All the dykes samples have negative εNd(t) values (−9.76 to −5.7), negative εHf(t) values (−1.8 to −1.0) and Mesoproterozoic Nd depleted-model ages (TDM = 1371–1618 Ma). The geochemical and isotopic characteristics suggest that the dykes were formed by the partial melting of lower crust that assimilated Meguma metasedimentary rocks and/or Avalonian sedimentary rocks, following terminal subduction of the Rheic Ocean and thermal re-equilibration during the Alleghanian orogeny. The effects of the closure of the Rheic Ocean in the oblique collision between composite Laurentia and Gondwana were, to a certain extent, accommodated along the Minas Fault Zone, where magmatism and regional fluid flow were concentrated.

Garnet is a widespread minor accessory mineral in the Late Proterozoic Elat-Quarry granite of southern Israel and is more abundant in the associated pegmatite and aplite. All garnets are dominated by almandine and spessartine end-members. Granite-hosted garnets are zoned with relative enrichment of Mn in the core and Fe in the rim. The chemistry of the garnet in the pegmatite and aplite are comparable to the rim compositions of garnets in the granite, but with a slight Fe-depletion at the rims. Geochemical parameters for the granite indicate fractional crystallization largely of an S-type source magma to a peraluminous composition.

In the highly evolved granite magma, Fe is relatively diminished, and only small amounts of biotite can crystallize. Manganese becomes a compatible element forming Mn-rich garnet (cores), and reducing the Mn content in the magma, subsequently leading to Fe-enriched rims. The greater abundance of garnet in the pegmatite and aplite (and its larger crystal-size in the former) relate to the enhanced presence of a hydrous fluid within the magma. The tendency for garnet crystals to concentrate in bands is much more developed in the pegmatite than in the granite, and is associated with the effects of hydrofracturing (fracture-filling), and the crystallization of coarse-grained alkaline feldspars.

The ammonium content of pegmatites, aplites and granites from Alijó-Sanfins, northern Portugal, averages 162, 109 and 159 ppm respectively. There is no systematic difference in the NH4/K ratio between these rocks, and the variation in their ammonium content is mainly due to variations in the amount of potassium minerals they contain. The K-feldspars have higher NH4+ contents than the muscovites, but lower NH4/K ratios. The preference of NH4+ for micas rather than feldspars is not as great as that shown by rubidium. The ammonium content of pegmatites in general is highly variable, and is largely determined by the nature of the granites with which they are associated.

Cordierite is a characteristic mineral of many peraluminous felsic igneous rocks. A combination of T-P-X parameters, which overlap the stability conditions for felsic magmas, control its formation. Critical among these parameters are relatively low T, low P, and typically high (Mg+Fe2+), Mg/Fe2+, A/CNK, aAl2O3, and fO2. Spatial and textural information indicate that cordierite may originate in one of three principal ways in felsic igneous rocks: Type 1 Metamorphic: (a) xenocrystic (generally anhedral, many inclusions, spatial proximity to country rocks and pelitic xenoliths); (b) restitic (generally anhedral, high-grade metamorphic inclusions); Type 2 Magmatic: (a,b) peritectic (subhedral to euhedral, associated with leucosomes in migmatites or as reaction rims on garnet); (c) cotectic (euhedral, grain size compatibility with host rock, few inclusions); (d) pegmatitic (large subhedral to euhedral grains, associated with aplite-pegmatite contacts or pegmatitic portion alone); and Type 3 Metasomatic (spatially related to structural discontinuities in host, replacement of feldspar and/or biotite, intergrowths with quartz). Of these, Type 2a (peritectic) and Type 2c (cotectic) predominate in granitic and rhyolitic rocks derived from fluid-undersaturated peraluminous magmas, and Type 2d (pegmatitic) may be the most common type in fluid-saturated systems.

The Silbergrube Aplite (SA) in the Hagendorf-Pleystein Pegmatite District, near Waidhaus, Germany, is a mildly peraluminous NW-SE directed leucogranite dyke. It occurs in association with quartz dykes and aplitic metamorphic mobilizates in the NE Bavarian crystalline basement. The SA differs from other aplitic mobilizates in the region in having a less well developed strain-related mineral orientation and in containing only minor amounts of garnet and tourmaline. The aplitic metamorphic mobilizates and the SA are chemically and mmeralogically almost identical and yield the same age of formation of ∼302 Ma (stage I). The age of formation of the Hagendorf pegmatites seemingly post-dates the emplacement of the SA. The SA was emplaced at the boundary between fine-grained biotite granites and metamorphic country rocks within a zone of structural weakness, favouring the formation of disseminated late magmatic to hydrothermal mineralization of Li-bearing Fe-Mn phosphates (stages II and III). Brittle deformation along this zone was conducive to the faultbound Fe-Mn-Ca phosphates. Mineral telescoping is evident from the presence of Fe2+, Fe3+ and Mn2+ phosphates in fissures and vugs in a texturally highly variable host-rock environment (stage IV). This intimate intergrowth of phosphate minerals reflects contrasting physical and chemical conditions prevailing in a near-surface/ shallow epithermal S-deficient phosphate system (stage IV), similar to what is known from Cu-Au epithermal systems. The most recent mineral assemblages that formed under predominantly oxidizing conditions are correlated with the subtropical weathering during the Neogene which resulted in the formation of a peneplain truncating the SA and its country rocks (stage V). The SA is the root zone of the felsic aplitic-pegmatitic mobilizates in this region and is overprinted by an epithermal phosphate system.

At Alijó-Sanfins there are many granitic aplite and pegmatite veins crosscutting different petrographic facies of the Hercynian granite batholith and also mica-schists. They are tin-bearing granitic rocks. Thirty-four samples of K-feldspar and 34 of albite from these veins and host granites were analysed to establish the distribution of elements and their fractionation trends in the sequence of feldspar crystallization. Rubidium and Cs increase, and Ba, Sr, Ba/K, Sr/K and K/Rb decrease in K-feldspar, whereas Na increases and Sr and Ca decrease in albite, from granites to aplites and pegmatites. In a few aplite-pegmatite veins Rb, Rb/Ba and Rb/Sr increase and Ba, Sr, K/Rb and Ba/Sr decrease in K-feldspar, and Rb increases and Sr decreases in albite from aplite to coexisting pegmatite. Equilibrium was not attained for trace elements between coexisting feldspars.