High-precision zircon geochronology and geochemistry of evolved magmatic centres in the Paraná-Etendeka LIP: Temporal placement and tectono-magmatic origin of the Damaraland complexes, Namibia

In the African section of the Paraná-Etendeka Large Igneous Province (LIP), several early Cretaceous intrusive complexes with highly variable bulk rock compositions ranging from subalkaline to alkaline‑carbonatitic are strikingly aligned on a SW-NE trend and are clearly related to the large igneous province that straddles Africa and South America based on their 40Ar/39Ar and RbSr ages. We use high-precision zircon UPb geochronology, zircon Hf isotope compositions, and bulk-rock and zircon geochemistry of these intrusions to decipher the spatial pattern of magmatism and the mechanisms of magma formation and evolution. High-precision CA-ID-TIMS zircon ages show that the plutons were emplaced without clear spatial systematics over at least 1.4 Myr from 133.2 to 131.8 Ma and likely postdate the peak of volcanic activity in the southern Etendeka (Namibia) and the Paraná (Brazil), estimated to be between 135 and 133 Ma. The youngest Damaraland zircon ages overlap with previously reported baddeleyite ages for mafic dykes and sills in the southern Paraná, confirming that magmatism in the whole LIP continued beyond 132 Ma. In the whole Damaraland province, intrusive rocks follow two distinct evolution paths towards both the granite/rhyolite and the syenite/phonolite minima. The near-synchronous emplacement of silicic to highly alkaline bodies with no clear spatial or temporal pattern is best explained by lithospheric extension driven by mantle upwelling along reactivated lineaments accommodating active N-S rifting of the South Atlantic. Negative zircon εHf(t) values in silicic complexes (−5 to −12) likely stem from crustal contamination during ascent of primitive mafic melts via "path contamination" and/or from a heterogenous mantle source already contaminated by recycled crustal material ("source contamination"). Similarly variable, but on average less negative zircon εHf(t) in alkaline and carbonatitic intrusions (0 to −6) reflect source contamination and preferential low degree melting of fertile portions in a heterogenous mantle source. These mantle heterogeneities likely originate from recycling of ancient lithosphere during subduction in the Neoproterozoic, or from fertile material brought up by the Tristan-Gough mantle plume via intrusion and/or exposed by lithospheric erosion, fertilizing the lithospheric mantle under the Damaraland prior to and during the main flood basalt event.