Observations of the relationship between linear or planar features on either side of dykes usually form the basis of a field determination of their mode of emplacement, although it is known that sections oblique to planar features may lead to conflicting results. In Eastern Tasmania only rarely are examples encountered where dyke wall-rock units are of use. However, dyke wall irregularities are...

[1] Lava dome eruptions are commonly characterized by large fluctuations in discharge rate with cyclic behaviour on time-scales ranging from hours to decades. Examples include Bezymianny volcano (Russia), Merapi (Java), Santiaguito (Guatemala), Mt St Helens (USA), Mt Unzen (Japan), and Soufrière Hills volcano (Montserrat). Previous models have assumed simple cylindrical conduits for magma trans...

The rift-related magmas of the Proterozoic Gardar Igneous Province were emplaced across the contact between the South Greenland Archaean craton and the Palaeoproterozoic Ketilidian mobile belt. It has been suggested that the geochemistry of Gardar intrusive rocks in the two areas varies across the craton margin and that this reflects a lithospheric control. However, comparison of the geochemica...

Microdiamonds from the Akluilâk minette dykes (Nunavut, Canada) are similar to diamonds formed in subducted metamorphic rocks. High concentrations of unaggregated nitrogen and positive delta(15)N suggest that the microdiamonds formed within rocks subducted to ultrahigh pressures before being sampled by the minette magma 1.8 billion years ago. This ultrahigh pressure metamorphism in North Americ...

Ilmenites from alkaline basic dykes in the Gardar province, south Greenland have Zr contents up to 3850ppm and Nb contents up to 1030ppm. These elements substitute for Ti in the octahedral site. These are amongst the highest recorded Zr and Nb contents for ilmenites, giving distribution coefficients (Kd ilmeniteJmatrix) for Zr up to 11.6 and Nb up to 70.3. Fractionation of ilmenite may thus hav...