Geochemistry and origin of migmatites of Al-Zurbi metamorphic belt, SW Taiz, republic of Yemen

Abstract EN

The metamorphic belt of Al-Zurbi area is situated in a tecton- ically active region and was subjected to at least three regional deforma- tional phases.

The belt is of amphibolite facies and comprises migmatites and non-mig- matitic rocks.

The migmatites are dominantly granitic in composition and comprise migmatite leucosomes and migmatite palaeosomes fractions.

The chemistry and mineralogy of the migmatite palaeosomes are similar to those of the gneisses.

The migmatite leucosomes show stromatic and ptyg- matic structures.

The average composition of the migmatite leucosomes ac¬cords reasonably well with that of the low-Ca granites.

The migmatite palaeosomes have higher total iron, Ti02, CaO, MgO, Sr, Ni, Zr, and Co arid lower SiO,, K,0, Rb, Nb, Cu, and Y contents relative to the high-Ca granitic rocks.

The migmatite leucosomes are believed to have been formed by partial melting of metasediments with different proportions of alkalis and calcium, at relatively low temperatures and low water activity.

The melts were crystallized together with the unmelted solids (restites).