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Crustal delamination induced by eclogitization of orogenic roots, in addition to plate subduction, is an important process that transfers crustal materials back into the mantle. Many previous studies have demonstrated a causal link between crustal delamination and eclogitization, but actual magmatic records of the process are rarely documented. Here we present detailed studies on two distinct late Paleozoic adakite suites in the Awulale Mountains (Chinese Western Tianshan), that is, the suites with high (HN) and low (LN) Nb/Ta ratios, to constrain the regional crustal delamination. Both igneous suites have adakitic affinity and formed by partial melting of the juvenile thickened lower crust with different residual mineral assemblages in their source regions. The late Carboniferous HN adakite has superchondritic Nb/Ta (21.4–23.3) and high Dy/Yb (2.66–2.88) ratios and may have formed via rutile‐bearing, eclogite‐controlled melting of the lower crust, implying crustal thickening and eclogitization. In contrast, the Permian LN adakites have varying and lower ranges of Nb/Ta (12.9–20.0) and Dy/Yb ratios (1.35–2.53), which were probably derived from mixing of garnet‐bearing amphibolite with minor rutile‐bearing, eclogite‐controlled melts, implying crustal thinning and the end of eclogitization. The succession of these two adakite suites suggests that during the late Carboniferous to early Permian, eclogitization of the orogenic root, accompanying successive crustal delaminations, occurred in this region. Accordingly, our results imply that adakites with different geochemical features are potential tracers for the mineralogy of orogenic roots and, importantly, provide convincing evidence for eclogitization‐induced crustal delamination in orogenic belts. Key Points: Two distinct adakite groups (with super/subchondritic Nb/Ta ratios) are present in the Awulale Mountains (Chinese Western Tianshan)Adakite geochemical features are controlled by the residual mineral assemblages in the magma sourcesAdakites in orogenic belts could be used to trace eclogitization‐induced crustal delamination events [ABSTRACT FROM AUTHOR]

Abstract: Melting and dehydration of subducted oceanic slabs dominate element recycling within the subduction factory, but the role of recycled oceanic crust in the source of intraplate magmas is poorly understood. In situ zircon O‐Hf isotope data from two Early Cretaceous alkaline A‐type granites that are genetically related to large‐scale extension of eastern China in the Late Mesozoic (circa 125 Ma) yield low δ18O (1.8 ± 0.3‰ to 5.1 ± 0.3‰, 2σ) and positive εHf(t) (1.5 ± 1.2 to 17 ± 1.2, 2σ). This suggests the contribution of altered oceanic crust and an enriched mantle component in the source region. Elevated initial 87Sr/86Sr and 206Pb/204Pb ratios, and εHf(t) whole rock values with relatively constant εNd(t) values beyond the normal mantle array, require a component that underwent seawater interaction in the source of protolith. The geochemical data require a complex source region for the alkaline A‐type granites in NE China involving more than 40% recycled oceanic crust. This altered oceanic crust beneath the Late Mesozoic lithospheric mantle likely represents remnants of multiple subduction and collision events between microblocks from the Late Paleozoic to Early Mesozoic in northeastern China. Recycling of subducted oceanic crust represents a novel exotic source for the origin of alkaline A‐type granites in intraplate extensional settings. [ABSTRACT FROM AUTHOR]