Abstract

The Dabie orogenic belt is characterized by the presence of large volumes of intrusive and volcanic rocks that formed in Late Mesozoic times. Most of the intrusive bodies are I-type granites but it is still unclear whether there are contemporary A-type granites. Here, we report the first unambiguous discovery of A-type granite from Baiyashan in the North Dabie tectonic belt. The crystallization age of the body has been fixed as 120.4 ± 1.2 Ma using U–Pb analysis of zircons by LA-ICPMS. The Baiyashan granite is enriched in Si, K, Na, Rb and REE, has elevated FeOtot/(FeOtot + MgO) and Ga/Al ratios, and is depleted in Mg, Ca, Mn, Ba, Sr, P and Ti. The REE composition shows highly fractionated patterns with (La/Yb)N = 6.95–16.68 and Eu*/Eu = 0.33–0.59. Its crystallization age, field relationships, petrographic and geochemical data show beyond doubt that the Baiyashan granite is an Early Cretaceous A-type granite. Sr–Nd isotope systematics are characterized by a high ISr of 0.708–0.714 and a low ɛNd of −7.5 to −19.4, with TDM2 = 1.5–2.5 Ga, and these data indicate that the magmas were dominantly sourced from partial melting of middle to lower crustal intermediate-felsic igneous rocks and mingling with mafic to intermediate magmas, during rift-related magmatism associated with subduction of the Palaeo-Pacific Plate beneath Eastern China in Early Cretaceous times.

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