Zircon petrochronology in large igneous provinces reveals upper crustal contamination processes: new U–Pb ages, Hf and O isotopes, and trace elements from the Central Atlantic magmatic province (CAMP)

Abstract Zircon occasionally crystallizes in evolved melt pockets mafic large igneous province (LIP) magmas, and these cases, it is used to provide high-precision age constraints on LIP events. The precision accuracy of ages from LIPs are crucially important, because they may be implicated mass extinctions. However, why zircon magmas not clearly understood, since their compositions should limit saturation. Here, we investigate the occurrence (and baddeleyite) intrusive extrusive rocks Central Atlantic Magmatic Province (CAMP) using petrography, trace-element analysis, Ti temperatures, Hf oxygen isotopes, U–Pb geochronology, along with petrological thermal modeling. We new for CAMP sills that intruded into Paleozoic sediments Brazil, indicating high low magmatism this area occurred synchronously over 264 ± 57 ka. show upper crustal assimilation, especially shales, during emplacement likely led Assimilation also supported by ? 18 O values some rare negative ?Hf crystals. only sample analyzed was North Mountain basalt Nova Scotia, Canada. This contains a variation its crystals (up 4 Ma), older have slightly more suggesting presence small (micron scale) xenocrystic cores associated very late-stage sediment assimilation. dataset as whole suggests rare. Assuming no cores, considering undersaturated nature melts, oldest clusters population record magma (or time when assimilation occurred), younger reflect Pb loss, given U concentrations zircon. Our identification heterogeneous isotopic elemental indicates saturate isolated minute just before system cools below solidus.