Introduction - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 10

ion should therefore, be present in K-feldspar and different types of micas (e.g.
phengite, biotite etc.) and clay minerals in the sediments.
Some peralkaline minettes are characterised by high NH 4 + content (Hall 1999),
this might suggest that parent magmas for lamproites and other K-rich rocks were
generated by partial melting of secondary protoliths, subducted into the mantle
during crustal recycling. Some studies conducted by Jia et al. (2002) on nitrogen
content of ultrapotassic rocks should therefore be of importance in this regard.
Some interesting questions arise in case of potassic volcanism in the regions
related to continental rifting, which are associated with a mantle plume or sets of
plumes? In that case what are the tectonic processes involved? What kind of
metasomatic reactions take place in the subcontinental lithospheric mantle bound-
ary layer? These are the questions that have been addressed in this volume.