Geochemical Characterization, Tectonic Setting, and Metamorphic History of Metabasites from Jandaq Metamorphic Complex, Iran

Abstract

Metabasites within the Jandaq Metamorphic Complex (JMC), Iran, offer valuable insights into the region’s magmatic and metamorphic history. Whole-rock geochemical data (major, trace, and rare earth elements) coupled with Sm-Nd isotopes were used to decipher the protolith origin and tectonic setting of formation of these metabasites. Our results demonstrate a predominantly ortho-amphibolitic nature for the JMC metabasites, with igneous protoliths ranging from basalt to andesite based on geochemical discrimination diagrams (Zr versus MgO and Sm/Nd). They exhibit geochemical affinities closer to enriched mid-oceanic ridge basalts (E-MORB) rather than normal MORB, implying a nascent oceanic basin within an intracontinental extensional setting. Trace element signatures (LILE enrichment, HFSE depletion) suggest a metasomatized subcontinental lithospheric mantle (SCLM) or a metasomatized lithospheric mantle beneath the oceanic crust as the parental magma source. Sm-Nd isotopic data suggest a potential plume source for the protoliths. These rocks were metamorphosed further by at least three metamorphic events: M1 (regional metamorphism, Barrovian-type; 616–687°C, 8–11 kbar), M2 (a brittle deformation event), and a later retrograde metamorphism (M3). These findings provide a comprehensive understanding of the geochemical characteristics, tectonic setting, and metamorphic evolution of JMC metabasites, shedding light on the geological history of the Jandaq region as a Paleo-Tethyan remnant.