Ardennite in a high-P/T meta-conglomerate near Vitolište in the westernmost Vardar zone, Republic of Macedonia

Abstract

A new occurrence of ardennite near Vitoliste in the southernmost Republic of Macedonia (FYROM) is described. In the westernmost Vardar zone, a high- P / T metamorphic conglomerate contains reddish clasts (up to 20–30 vol% of the rock) that consist of quartz, hematite, ardennite, pyrophyllite, sudoite, cookeite, phengite rimmed by muscovite, epidote/piemontite, lawsonite, tourmaline, titanite, albite, apatite and ±rutile. Epidote may contain inclusions of pumpellyite–(Fe 2+ ) and is partially transformed to piemontite. Ardennite is generally poor in As and its composition essentially follows the T4 exchange vector (Si + Al + P) −1 V, whereby Al and P are relatively low. Three compositional types of ardennite can be distinguished: ardennite-(V), ‘ardennite-(V,Si)’ and ‘ardennite-(Si)’, the latter possibly representing lavoisierite inter- and overgrowths. Metamorphic conditions of 0.65–0.80 GPa and 340–370 °C are deduced. The reddish Fe–Mn–(V–As)-rich detritus may have originated from a hydrothermal Fe–Mn deposit or, more likely, from a nickel–laterite deposit developed from weathered ophiolites. Such laterites and bauxites resulted from re-deposition of ophiolite material in shallow seawater during the Lower Cretaceous.