TITLE:
Mixed-Source Post-Collisional Magmatism in the Rhodope Metamorphic Complex: New Geochemical and Isotopic Insights from the Elatia Pluton (N. Greece)
AUTHORS:
Kyriaki Pipera
KEYWORDS:
Magmatic Enclaves, Elatia Pluton, Rhodope Metamorphic Complex, Eocene Magmatism
JOURNAL NAME:
Open Journal of Geology,
Vol.15 No.8,
August
22,
2025
ABSTRACT: Tertiary to Early Miocene post-collision granitoids intrude the whole Rhodope Metamorphic Complex (RMC; northern Greece and southern Bulgaria) during the extensional event that followed the collapse of the orogen. The Barutin-Buynovo-Elatia-Skaloti-Paranesti batholith in northern Greece and southern Bulgaria is the largest plutonic body of the Rhodope Metamorphic Complex (RMC) and is rather significant among these numerous post-collision plutons. A new field survey, combined with new whole-rock major, trace, REE, and Sr-Nd isotope analyses, focuses on the Elatia granodiorite in northern Greece and its mafic enclaves and diorite for the first time by representing members that record the earliest stages of magma evolution. All rocks display typical subduction-related characteristics with enrichment in LILE and LREE and depletion in HFSE but with enrichment in MREE. Major and compatible trace elements decrease smoothly with increasing SiO2 from the enclaves to the most evolved granodiorite, consistent with fractional crystallization of hornblende, biotite, plagioclase, titanite, and apatite. The alkaline enclaves and diorite, together with the “adakitic” character of the granodiorite, suggest high degrees of melting of a volumetrically minor mantle component. The diorite has a very low 87Sr/86Sr ratio (0.70425) and high 143Nd/144Nd (0.51269), the lowest and highest values respectively among the Eocene plutons so far in RMC, pointing to an origin from a depleted mantle melt. Isotope ratios for the granodiorite and enclaves lie between the depleted mantle and the RMC crust, implying intense magma mixing. Probability-based discrimination diagrams place the pluton in the post-collision field. All data indicate an early post-collisional origin at ~56 Ma, rather than pre-collision. Mafic-felsic mixing members with concurrent FC (fractional crystallization) provide the best explanation for the spread of the geochemical indicators. These results realign the Elatia pluton with other early Eocene, post-collisional granites of the RMC, providing a framework for future research.