Spatial and temporal evolution of magmatism in the Aegean and its relationship to the development of post-subduction porphyry copper mineralisation: a geochemical and isotope study.

<p dir="ltr">Porphyry copper deposits (PCDs) supply critical metals for clean electricity technologies, including ~75% of the world’s Cu, half the Mo, and one-fifth of the Au. PCDs are typically associated with subduction zones. Post-subduction PCDs are enriched in economically and technologically important metals such as Au and Te.</p><p dir="ltr">Hypotheses for post-subduction magma formation include remelting of subduction-metasomatised subcontinental lithospheric mantle (SCLM), or lower-crustal hydrous cumulates. Remelting can be triggered by delamination of SCLM, collisional lithospheric thickening, or post-subduction extension causing asthenospheric upwelling.</p><p dir="ltr">This study applies x-ray and mass-spectrometry techniques to whole rock and zircons from intrusive and extrusive volcanic rocks across five magmatic centres in the Aegean of Greece: Skouries, Samothraki, Limnos, Lesvos, and Milos. Elemental and isotope data, integrated with literature data from Tinos and the Maronia Magmatic Corridor, are used to investigate magma genesis, sources, and PCD formation.</p><p dir="ltr">U-Pb geochronology reveals that post-subduction magmatism was active between 19.94 ± 0.41 Ma and 17.43 ± 0.14 Ma, with earlier activity (to ~33 Ma) recorded in literature. Individual magmatic centres were active for 1-2 My.</p><p dir="ltr">Least squares residual modelling shows post-subduction Aegean magmas fractionated a typical arc magma assemblage, suggesting no plagioclase suppression. Amphibole presence further implies these magmas were moderately hydrous.</p><p dir="ltr">Isotope data show these magmas are derived from an asthenospheric source, variably mixed with crustal material derived from the subducted Vardar Ocean. Some Tinos magmas also interacted with upper crustal material. 87Sr/86Sr range from 0.7077 to 0.7103, and 143Nd/144Nd range from 0.5122 to 0.5124, with Milos demonstrating more mantle-like values, and Tinos displaying more crustal values.</p><p dir="ltr">These findings suggest a multi-million year lead-up to subduction-related PCDs is not required for post-subduction PCDs, with related magmas lacking distinct fertility indicators. A mineralisation peak at ~18 Ma including Skouries, Limnos, and Lesvos may reflect enhanced asthenospheric input.</p>