New, Single Zircon (Pb-Evaporation) Ages from Vendian Intrusions in the Basement beneath the Pechora Basin, Northeastern Baltica

Abstract

Thc Prceambrian basement beneath the Peehora Basin of northern Russia is known from deep (up to approx. 4.5 km) drill holes to be largely composed of Neoproterozoie sueeessions, variously deforrned and metamorphosed and intruded by magmatie suites of Vendian age. Presented here are new single-zircon, Pb-evaporation (Kober method) ages from eight intrusions aeross the Izhrna, Peehora and Bolshezernelskaya Zones, all from below the Lower Ordovieian (loeally Middle Cambrian) uneonformity. The majority ofthe intrusions (six) yield remarkably similar ages of 550-560 Ma, apparently dating a widespread pulse of lateto post-tectonic magmatism. An early Vendian granite (618 Ma) has been identified in the northeasternmost region (Bolshezernelskaya zone) and a Dcvonian granodiorite (380 Ma) in the Peehora Zone, where mid to late Palaeozoie magmatism has bcen prcviously reported. Evidenee of inheritanee in the zireon populations suggests the presenee of Mesoproterozoie erust beneath the Neoproterozoie eomplexcs.