Spatio-temporal distribution of magmatism and crustal inheritance within an extensional-rotational environment: An updated geochronology of the Miocene & Quaternary magmatism of the South Apuseni Mountains

Abstract

Magmatism with arc-like features, formed in extensional settings, was active in the South Apuseni Mountains, Romania, during the Neogene and Quaternary periods. To date the chronological framework is primarily restricted to K-Ar dates. We present newly determined LA-ICP-MS U-Pb zircon age data for subvolcanic and volcanic rocks (N=20) from 8 different Cenozoic volcanic-intrusive complexes and from Jurassic and Cretaceous lava flows. Our results support magmatic ages between c. 14 to c. 7 Ma, with Uroi, an alkaline intrusion, occurring significantly later at c. 1.5 Ma. Revising the timeline for the South Apuseni Mountains paleomagnetic rotations shows that most of the vertical-axis clockwise rotation of the Apuseni Mountains (54.4° ± 10.7°) took place between approximately 14 and 11 Ma, the age interval when the majority of magmas were emplaced. Xenocrystic zircon dates exhibit differences in 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: https://doi.org/10.6084/m9.figshare.c.6951429