Origin of the Late Jurassic to Early Cretaceous peraluminous granitoids in the northeastern Hunan province (middle Yangtze region), South China: Geodynamic implications for the Paleo-Pacific subduction

摘要: The Late Mesozoic granitic belt in the northeastern Hunan province (situated south of middle Yangtze region) represents western front large magmatic SE China. In order to determine their ages and petrogenesis, we carried out zircon U–Pb dating, Hf isotope whole-rock geochemical analyses for four plutons, namely Taohuashan, Dayunshan-Mufushan, Wangxiang Lianyunshan. Our SIMS ages, together with previously published data, reveal that activities this area can be roughly subdivided into three phases at 151–146 Ma, 132–127 Ma ca. 117 Dayunshan-Mufushan batholith therein is a composite pluton. These plutons are mainly composed weakly strongly peraluminous biotite or two-mica monzogranites, minor amount granodiorites. Their features similar S-type as well fractionated granites, enrichment LREEs negative Ba, Sr, Nb, P Ti anomalies. All samples show eHf(t) values ranging from −12.5 −3.6, corresponding crustal model (TDMC) 1.4–2.0 Ga. It inferred these granitoids were derived partial melting metasedimentary rocks analogous Neoproterozoic Lengjiaxi Group, predominantly psammitic component. Fractional crystallization probably played an important role magma evolution, while input mantle-derived was insignificant. Combined other geological evidence, our new data allow us propose Cretaceous (132–127 Ma) magmatism might response episodic slab rollback Paleo-Pacific plate, early-stage (151–146 overlapped epilogue Jurassic flare-up subsequent quiescence foreshadowed transformation foundering subducted flat-slab rollback. Alternatively, after SE-directed intracontinental subduction central SCB cannot ruled geodynamic interpretation