Inherited or not inherited: Complexities in dating the atypical ‘cold’ Chopok granite (Nízke Tatry Mountains, Slovakia)

• Published in: Gondwana research Vol. 87; pp. 138 - 161
• Main Authors: Burda, Jolanta, Klötzli, Urs, Woskowicz-Ślęzak, Beata, Li, Qiu-Li, Liu, Yu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2020
• Subjects: Carpathians; Nízke Tatry; Phosphate dating; Zircon dating; ‘Cold’ granite; Phosphate dating; ‘Cold’ granite; Carpathians; Zircon dating; Nízke Tatry
• ISSN: 1342-937X; 1878-0571
• DOI: 10.1016/j.gr.2020.05.018

Zircon U-Pb SIMS dating combined with in-context (in thin section) monazite and xenotime U + Th-total Pb dating was used to clarify the Palaeozoic evolution of the ‘cold’ Chopok granite (Nízke Tatry Mountains, Slovakia). Four distinct zircon, monazite and xenotime age domains testify to a prolonged evolution from igneous formation to multi-stage metasomatism and hydrothermal overprinting. The geological interpretation of age patterns from ‘cold’ granites, expected to have low zircon saturation temperatures (<800 °C) and relatively high amounts of zircon inheritance, requires special care, especially for what concerns proper attribution of zircon inheritance and igneous growth ages. These issues can be resolved using zircon saturation temperatures (TZrn) as proxy for the amount of zircon inheritance in combination with the temperature differences between TZrn and the granite solidus. In this respect, the Chopok granite is an atypical ‘cold’ granite. Due to TZrn being substantially lower (ca. 80 °C ± 50 °C) than the granite solidus temperature, practically no zircon inheritance was found. The zircon age data indicates that the Chopok granite is a product of an Early Ordovician (475.8 ± 3.3 Ma) magmatic event, corresponding with the widespread Early Palaeozoic magmatism recorded throughout the European Variscan belt. This is further corroborated by phosphate mineral ages. The post-magmatic activity recorded in the U-Pb systematics of zircon and phosphates overgrowths can be related to the different phases of the evolution of the Variscan orogen: Early Carboniferous (ca. 352 Ma) metasomatism documents the main Variscan orogenic event, whereas the Permo-Triassic age (ca. 255 Ma) reflects thermo-tectonic activity associated with large-scale crustal extension, contemporaneous with the initial continental leading to the break-up of Pangea. [Display omitted] •‘Cold’ - ‘hot’ granite classification is not ubiquitously valid.•The Chopok granite is an atypical ‘cold’ granite in showing little inheritance.•The Chopok granite formation is Early Ordovician not Carboniferous.