Lithospheric Mantle beneath the Korean Peninsula: Implications from Peridotite Xenoliths in Alkali Basalts

Abstract

Peridotite xenoliths hosted by alkali basalts from South Korea occur in Baengnyeong Island, Jeju Island, Boeun, Asan, Pyeongtaek and Ganseong areas. K-Ar whole-rock ages of the basaltic rocks range from 0.1 to 18.9 Ma. The peridotites are dominantly lherzolites and magnesian harzburgites, and the constituent minerals are Fo-rich olivine (Fo 88.4-92.0 ), En-rich orthopyroxene, Di-rich clinopyroxene, and Crrich spinel (Cr# = 7.8-53.6). Hydrous minerals, such as pargasite and phlogopite, or garnet have not been reported yet. The Korean peridotites are residues after variable degree of partial melting (up to 26%) and melt extraction from fertile MORB mantle. However, some samples (usually refractory harzburgites) exhibit metasomatic enrichment of the highly incompatible elements, such as LREE. Equilibration temperatures estimated using two-pyroxene geothermometry range from ca. 850 to 1050 o C. Sr and Nd isotopic compositions in clinopyroxene separates from the Korean peridotites show trends between depleted MORB-like mantle (DMM) and bulk silicate earth (BSE), which can be explained by secondary metasomatic overprinting of a precursor time-integrated depleted mantle. The Korean peridotite clinopyroxenes define mixing trends between DMM and EM2 end members on Sr-Pb and Nd-Pb isotopic correlation diagrams, without any corresponding changes in the basement. This is contrary to what we

Mineral ages and zircon Hf isotopic composition of the Andong ultramafic complex: implications for the evolution of Mesozoic subduction system and subcontinental lithospheric mantle beneath SE Korea

“…Our interpretation is not compatible with a recent tectonic model suggested by the detrital zircon ages of modern river sediments (Choi, Lee & Orihashi, 2012), in which continuous subduction angle increase and resultant slab rollback were the driving forces of apparent Triassic south-eastward arc migration in southern Korea (249–202 Ma). Note, however, that Triassic granitic magmatism in central and SE Korea occurred under different tectonic environments, that is, post-collisional stabilization of tectonically overthickened crust in the former region (Cho, Lee & Armstrong, 2008; Williams, Cho & Kim, 2009; Kim et al .…”

“…Geochemical and mineralogical studies have examined mantle xenoliths hosted by Cenozoic alkali basalts that ubiquitously occur in the Korean peninsula (Choi, 2012), but information about the pre-Cenozoic mantle lithosphere is quite restricted because of the lack of Mesozoic or Palaeozoic mantle xenoliths on the peninsula. These Cenozoic xenoliths are unexceptional spinel peridotites without hydrous minerals or garnet, which is indicative of a relatively thin (25–90 km; Park, 2010) subcontinental lithospheric mantle (SCLM) beneath the peninsula.…”

Petrochemical Characteristics of the Duibaejae Volcanic Rocks from Goseong, Gangwon-do, Korea

“…오봉리 화산체군을 중심 으로 북서쪽으로는 고성산 화산체와 남쪽으로는 운봉 산 화산체가 분포한다. 고성 지역의 현무암은 여러 연구자에 의해 연구된 바 있다 (Lee et al, 1993;Lee, 1995;Park and Park, 1996;Cho et al, 1998;Koh and Yun, 2005;Kil et al, 2007;Kim et al, 2010;Song et al, 2011;Choi, 2012;Kim et al, 2012). Park and Park(1996) (Fig.…”