Lu–Hf and Sm–Nd isotope systematics of Korean spinel peridotites: A case for metasomatically induced Nd–Hf decoupling

摘要: Abstract We determined the Lu–Hf and Sm–Nd isotope compositions of spinel peridotite xenoliths in alkali basalts from Baengnyeong Jeju islands, South Korea, to constrain timing melt-depletion events stabilization lithospheric mantle beneath region. Equilibration temperatures estimated by two-pyroxene thermometry range 780 950 °C, 960 1010 °C for peridotites, respectively. The clinopyroxenes are characterized extremely radiogenic Hf association with isotopically less extreme Nd, resulting strong Nd–Hf decoupling referenced array. This is stark contrast well-correlated isotopic Nd clinopyroxenes, which plot along abundances were affected relatively recent secondary enrichments that overprinted light rare earth element isotopes, causing isotopes. peridotites appear have been re-equilibrated, probably as a result efficient diffusion at higher peridotites. tie lines clinopyroxene orthopyroxene four Korean negative slopes on isochron diagram, yielding ages. interpreted indicate exchange reaction metasomatic agents having low 176Hf/177Hf components. Secondary overprinting was facilitated considerably lower concentrations than co-located clinopyroxene. lherzolite yield errorchron age 1.9 ± 0.1 Ga, independently supported model Os (based Re depletion or TRD) 1.8 Ga refractory peridotite. interpret this mark time section area major melt extraction. Proterozoic removal coincided widespread ca. 2.1 tectonothermal documented throughout Peninsula. These observations system can be used date melting recorded xenoliths.