Zircon geochronology and geochemistry of the Kızılağaç A-type metagranite in Bitlis Massif, SE Türkiye: a response of Early Cambrian mid-ocean ridge and trench collision?

We report an Early Palaeozoic granitic body intruding into the Bitlis Massif and present new zircon U-Pb geochronology, in situ zircon Hf isotopes and trace element data, whole-rock geochemistry, and Nd isotope compositions to better constrain the origin and tectonic setting of K & imath;z & imath;la & gbreve;a & ccedil; metagranite near Mu & scedil; area, Southeastern T & uuml;rkiye. Zircon U-Pb dating reveals emplacement ages ranging from 543 +/- 11 Ma to 525.4 +/- 17 Ma, indicating that the granitic body intruded the Precambrian basement units during Early Cambrian. K & imath;z & imath;la & gbreve;a & ccedil; metagranite, comprising monzogranite and granodiorite in modal composition, is characterized by high silica (SiO2 = 76.95-80.68 wt. %) and high total alkali content (K2O + Na2O = 6.39-8.93 wt. %). Geochemically, the rocks are peraluminous (A/CNK = 1.02-1.11) and exhibit a high-K calc-alkaline affinity. They display low Sr concentrations (5.59-65.86 ppm), pronounced negative Eu anomalies, and elevated Ga/Al ratios, all consistent with an A-type granite affinity. The samples show negative epsilon Nd(t) values ranging from -2.90 to -1.97 and zircon epsilon Hf(t) values between -5.07 and +6.64, with low Mg# values (14-45). Combined with petrographic observations, these geochemical characteristics suggest that the parental magma of the K & imath;z & imath;la & gbreve;a & ccedil; metagranite was derived from partial melting of both juvenile and older lower continental crust, followed by extensive feldspar-dominated fractional crystallization during magma ascent. Prolonged magmatic evolution likely led to the extraction of highly fractionated, silicic melt from the magma chamber, resulting in the formation of the peraluminous, high-silica A-type K & imath;z & imath;la & gbreve;a & ccedil; metagranite. We propose that Cambrian magmatism in the Bitlis Massif is related to crustal thinning associated with the waning stages of the Cadomian orogeny along the northern margin of Gondwana. The transition from a convergent margin to an extensional regime was possibly triggered by slab break-off of the Proto-Tethys oceanic lithosphere following a ridge-trench collision during the Early Cambrian.