Qal’eh hasan ali maars, central Iran

A group of craters 120 km southeast of Kerman, the largest 1200 m across and 300 m deep, are typical maars, excavated depression with rims of bedded pyroclastic debris. Most of the crater rims are composed entirely of country rock clasts, but the largest crater yields tephrite, composed of phenocrysts of phlogopite, clinopyroxene, and olivine in a groundmass of anorthoclase, analcime, hauyne, clinopyroxene and magnetite, and a cumulate of phlogopite and clinopyroxene with highly potassic glass. The occurrence of hauyne as a ground mass mineral is a rare or unique feature. The maar field lies in the projection to the south of the Nayband fault and, with some flows near that fault, represents a province of Quaternary alkali basalt volcanism.