Late Cretaceous volcanic arc magmatism in southeast Anatolian Orogenic Belt: Constraints from whole‐rock, mineral chemistry, Sr–Nd isotopes and U–Pb zircon ages of the Baskil Intrusive Complex (Malatya, Turkey)

Abstract

The voluminous intrusive and extrusive magmatism was formed in the Elazığ‐Malatya region of the Southeast Anatolian Orogenic Belt (SAOB) as a consequence of the continental collision and/or convergent orogeny. The SAOB holds a great number of stratigraphic, metamorphic and tectonomagmatic units in the Elazığ‐Malatya region that are crucial for recognition of the geodynamic setting of southeast Anatolia during the Upper Cretaceous. The Baskil Intrusive Complex (BIC) is composed of mainly tonalitic/granodioritic and dioritic/gabbroic plutonic rocks, while its sub‐volcanic phase is represented by granophyre, aplite and microgabbro, which were intruded into the Upper Cretaceous supra‐subduction zone (SSZ)‐type İspendere ophiolites (SE Turkey). New U–Pb laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) zircon data provided crystallization ages ranging from 84.3 to 81.5 Ma for the BIC. Mafic and felsic rocks of the BIC have a low‐ to medium‐K calc‐alkaline, I‐type, metaluminous character, whereas extremely evolved felsic rocks of this complex show a peraluminous composition. The aluminium‐in‐hornblende barometery (~196 to 299 MPa) of magnesio‐hornblendes in the Baskil intrusive rocks indicates their emplacement in the shallow‐ to moderate crustal plutonic levels at a minimum of 7.3 km to a maximum of 11.1 km depth. The Baskil intrusive rocks present depletion in Ti, Nb, Ta, light REE with respect to primitive mantle, and relative enrichment in large‐ion lithophile element (Rb, Ba, Pb, Sr, Th), thus infer a pronounced subduction signature. Both mafic and felsic intrusives show low initial 87Sr/86Sr ratios (0.70357–0.70561) together with a high initial 143Nd/144Nd ratios (0.51279–0.51289), and high ƐNd(T) values (5.0–7.0) and relatively young Nd crustal residence model ages (TDM = 0.31–0.48 Ga). Based on our field, mineralogical and geochemical findings, we suggest that the BIC was originated from an amphibolitic source that interacted with subducted crust within SSZ and was changed by fluids during the early stages of the short‐lived volcanic arc magmatism that evolved at the fringe of the Tauride Platform.