Two magma fractionation paths for continental crust growth: Insights from the adakite-like and normal-arc granites in the Ailaoshan fold belt (SW Yunnan, China)

Abstract Geochemical similarities between the continental crust and arc magmas have led to inference that subduction zones may be primary sites of crustal growth. Thus, it is necessary unravel petrogenetic mechanism(s) granitoid generation in subduction-related settings understand growth through magmatic differentiation processes. In this study, we focused on oceanic-continental zones. We analyzed whole-rock geochemistry Sr-Nd isotopes, together with zircon U-Pb-Hf-O newly identified Middle Triassic granitoids Ailaoshan high-grade metamorphic complex (Yunnan, SW China). All studied granite samples were characterized by large ion lithophile element (e.g., Rb, Sr, Ba) enrichments high field strength Nb, Ta, Ti) depletions, similar arc-type rocks. They also showed a range Sr-Nd, (87Sr/86Sr)i = 0.7020–0.7048, ?Nd(t) +0.6 +4.2, Hf-O, ?Hf(t) +10.3 +18.1, ?18Ozircon 5.09‰–6.65‰, isotope compositions, which overlap those previously reported coeval (ca. 237–235 Ma) hornblende diorite granodiorite, formation was interpreted originated from mantle wedge metasomatized sediment-derived melt. Furthermore, fractionation trends some granitic diorite-granodiorite suite overlap. can divided into two geochemical groups: Group 1 has intermediate SiO2 (66.9–73.8 wt%) K2O (3.40–5.42 low MgO (0.19–1.09 contents shows depletion heavy rare earth elements (HREEs; e.g., Yb Y), resulting adakite-like Sr/Y (61–183) La/Yb (47–90) ratios. positive versus correlations negative HREE Y correlations, implying garnet-bearing assemblage. The Nb/La reveal assimilation trend. 2 relatively (72.6–76.5 (1.93–3.82 (0.05–0.83 middle REEs (MREEs; Gd Dy) (1–10) (4–11) granites show Gd/Yb correlation, indicates significant an amphibole-bearing Our results suggest both group formed setting common mantle-derived parental dioritic magma, but they experienced distinct While likely high-pressure (lower-crustal) garnet-dominated fractionation, generated low-pressure (middle-/upper-crustal) amphibole-/plagioclase-dominated fractionation. these are critical development more fractionated (felsic) upper crust.