Spatiotemporal distribution of magmatism and crustal inheritance within an extensional–rotational environment: an updated geochronology of the Miocene and Quaternary magmatism of the South Apuseni Mountains

Abstract

Extension-related magmatism with arc-like features was active in the South Apuseni Mountains, Romania during the Neogene and Quaternary. The current chronological framework is primarily restricted to K–Ar dates. We present here new laser ablation inductively coupled plasma mass spectrometry U–Pb zircon age data for 20 subvolcanic and volcanic rocks from eight different Cenozoic volcanic–intrusive complexes and from Jurassic and Cretaceous lava flows. Our results support magmatic ages between c. 14 and c. 7 Ma, with Uroi, an alkaline intrusion, occurring significantly later at c. 1.5 Ma. Revising the timeline for the South Apuseni Mountains palaeomagnetic rotations shows that most of the clockwise vertical-axis rotation of these mountains (54.4° ± 10.7°) took place between c. 14 and 11 Ma, the age interval when the majority of the magmas were emplaced. Xenocrystic zircon dates show differences in the age populations between individual volcanic–intrusive complexes. A Permo-Triassic population is almost ubiquitous, indicating that basement Permo-Triassic igneous rocks are more widespread than previously thought, or that they were significantly involved in the generation of Neogene magmas. However, other observed age populations, such as Triassic or Paleogene, have no clear correspondence in the known geological record, indicating the presence of a cryptic component interacting with Neogene magmas. Supplementary material: Full analytical details and age calculations for the U–Pb age data collected during this study, rock samples and separated zircon fraction descriptions and the palaeomagnetic and age databases are available at https://doi.org/10.6084/m9.figshare.c.6951429