Timing of magmatism of the Ditrău Alkaline Massif, Romania – A review based on new U–Pb and K/Ar data

Elemér Pál-Molnár,Réka Lukács,Luca Kiri,Máté Szemerédi,Edina Sogrik,Anikó Batki,Szabolcs Harangi,Enikő Eszter Almási,István Dunkl

doi:10.1556/24.2021.00001

Abstract

AbstractThe timing of Triassic magmatism of the Ditrău Alkaline Massif (Eastern Carpathians, Romania) is important for constraining the tectonic framework and emplacement context of this igneous suite during the closure of Paleotethys and coeval continental rifting, as well as formation of back-arc basins.Our latest geochronological data refine the previously reported ages ranging between 237.4 ± 9.1 and 81.3 ± 3.1 Ma. New K/Ar and U–Pb age data combined with all recently (post-1990) published ages indicate a relatively short magmatic span (between 238.6 ± 8.9 Ma and 225.3 ± 2.7 Ma; adding that the most relevant U–Pb ages scatter around ∼230 Ma) of the Ditrău Alkaline Massif. The age data complemented by corresponding palinspastic reconstructions shed light on the paleogeographic environment wherein the investigated igneous suite was formed.The magmatism of the Ditrău Alkaline Massif could be associated with an intra-plate, rift-related extensional tectonic setting at the southwestern margin of the East European Craton during the Middle–Late Triassic (Ladinian–Norian) period.

Highlights

YThe first two authors have contributed to this work.The Ditrau Alkaline Massif (DAM), located in the Eastern Carpathians (Romania), is an igneous suite characterized by complex structure and lithology
New K/Ar and U–Pb age data combined with all recently published ages indicate a relatively short magmatic span of the Ditrau Alkaline Massif
Detailed petrogenetic interpretation of this unit can be found in Pal-Molnar et al (2015b) and Heincz et al (2018); (b) the gradual transition between diorite, monzodiorite, monzonite and syenite is difficult to trace in the field; (c) transition between syenite, quartz syenite and granite can be continuous; (d) different-sized metamorphic xenoliths occur in syenite and granite; (e) rocks of the Tarnita Complex, diorite-syenite and syenitegranite transition zones are cross-cut by nepheline syenite; (f) syenite intruded into the Tarnita Complex; (g) nepheline syenite and rocks of (a)–(f) are cross-cut by tinguaite dykes; (h) lamprophyre dykes intersect all other rock types of the massif

Summary

Introduction

YThe first two authors have contributed to this work. The Ditrau Alkaline Massif (DAM), located in the Eastern Carpathians (Romania), is an igneous suite characterized by complex structure and lithology. Since its first mention by Lilienbach (1833) the DAM has been studied, including its petrotectonic environment, petrogenetic relations and the timing of magmatism Several analyses have been conducted with various dating methods (e.g., K/Ar, 40Ar/39Ar and U–Pb age determinations) on different rock types and mineral phases of the Ditrau. The interpretation of the results led to contradictory hypotheses on the genesis of the igneous complex and its rock associations. In order to better understand the evolution and magmatic processes of the massif, these data needed to be reconsidered and supplemented by additional, up-to-date age determination

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Conclusion