Nature of Late Mesoproterozoic to Early Neoproterozoic magmatism in the western Gyeonggi massif, Korean Peninsula and its tectonic significance

Park, Seung-Ik,Kim, Sung Won,Kwon, Sanghoon,Santosh, M.,Ko, Kyoungtae,Kee, Weon-Seo INTERNATIONAL ASSOCIATION FOR GONDWANA RESEARCH 2017 GONDWANA RESEARCH Vol.47 No.-

<P><B>Abstract</B></P> <P>The western margin of the Gyeonggi massif, southern Korean Peninsula, has preserved N–S trending Neoproterozoic and sporadic Late Mesoproterozoic metaigneous rocks. Here we present the results from systematic field mapping, sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb dating, and whole-rock geochemical analyses of the Mesoproterozoic and Early Neoproterozoic metaplutonic rocks in the Hongseong area, together with previously published data from the western Gyeonggi massif. The SHRIMP ages of these rocks are categorized into three groups: (1) Late Mesoproterozoic (ca. 1.25–1.15Ga), (2) Early Neoproterozoic (ca. 900–770Ma), and (3) late Early Neoproterozoic (ca. 762–730Ma). The geochronological and geochemical features of the Late Mesoproterozoic rocks suggest that they were possibly formed in association with convergent plate motion. The Early and late Early Neoproterozoic rocks are interpreted to arc-related orogenic and rift-related post-orogenic environments, respectively. These age results and the tectonic signatures provide insight into the convergence process along the margins of the Rodinia supercontinent.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Late Mesoproterozoic to Middle Neoproterozoic arc magmatism in the western Gyeonggi massif, Korean Peninsula </LI> <LI> Late Mesoproterozoic to Middle Neoproterozoic metaplutons display the evolution of the Rodinia supercontinent </LI> <LI> Late Mesoproterozoic to Middle Neoproterozoic metaplutons provide the convergence process along the margins of the supercontinent </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Early to Middle Paleozoic tectonometamorphic evolution of the Hongseong area, central western Korean Peninsula: Tectonic implications

Kim, Sung Won,Kwon, Sanghoon,Park, Seung-Ik,Yi, Keewook,Santosh, M.,Kim, Hyeong Soo INTERNATIONAL ASSOCIATION FOR GONDWANA RESEARCH 2017 GONDWANA RESEARCH Vol.47 No.-

<P><B>Abstract</B></P> <P>The migmatized gneiss (viz. Gwangcheon gneiss) of the southern Hongseong area, central–western Korean Peninsula underwent intermediate to high granulite-facies metamorphism (ca. 9.2–12.0kbar and 770–870°C) during Early Silurian to Early Devonian in age. Field and petrographic evidences from the Gwangcheon migmatite provide a clear indication of partial melting. Particularly the migmatized paragneiss is juxtaposed with arc-related doleritic metagabbro, which might be related to the heat source of the migmatization. The migmatized paragneiss has similar arc-related geochemical characteristics, such as depletions in Ta–Nb, Sr, P, and Ti and enrichments in large ion lithophile elements (LILE) caused by the partial melting effect related to the doleritic metagabbro. Sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb dating of the migmatized paragneiss yielded ages of 432±6Ma, 431±10Ma, 421±3Ma, and 403±3Ma. The U–Pb ages of inherited zircons from the migmatized paragneiss yielded an age spectra from Neoarchean to Early Paleozoic, with a dominant age population at Neoproterozoic. In contrast, new-growth and recrystallized equant zircons showed dominant concordant Early Silurian to Early Devonian ages that provide critical evidence on the timing of migmatization. These age results and the tectonic signatures are similar to those reported from the Central China Orogenic Belt in China, indicating their tectonic linkage at the northeastern margin of eastern Gondwana during Early to Middle Paleozoic in age.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Early to Middle Paleozoic arc-related migmatization in the Korean Peninsula </LI> <LI> Intermediate to high granulite-facies metamorphism during Early Silurian to Early Devonian </LI> <LI> Similar Early to Middle Paleozoic arc tectonic setting related to Central China Orogenic Belt in China </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Evolution of the Late Cretaceous Dadaepo Basin, SE Korea, in response to oblique subduction of the proto-Pacific (Izanagi/Kula) or Pacific plate

Cho, H.,Son, M.,Cheon, Y.,Sohn, Y.K.,Kim, J.S.,Kang, H.C. International Association for Gondwana Research 2016 GONDWANA RESEARCH Vol.39 No.-

The Dadaepo Basin is a small Late Cretaceous sedimentary basin in SE Korea, located on the eastern margin of Asia. The basin is an isolated extensional basin situated between the NNE-striking Yangsan and Dongnae faults. The basin-fill sediments, named the Dadaepo Formation, consist of channelized conglomerates and sandstones intercalated with dominantly purple mudstones in the lower part. The upper part is dominated by fine- to coarse-grained tuffaceous sandstones and olive to dark gray mudstones with abundant volcanic interbeds. The formation unconformably overlies dacitic rocks dated at ca. 94Ma and is overlain by basaltic andesite dated at ca. 69Ma (Ar-Ar ages). The overall configuration of the strata of the Dadaepo Formation indicates syndepositional tilting of the basin floor to the north-northeast. A number of outcrop-scale faults are observed in the basin-fill sediments, of which the majority are NW-striking normal faults, including syndepositional growth faults. The orientations of mafic (magmatic) and clastic dikes, interpreted as being approximately contemporaneous with the deposition of the Dadaepo Formation, are also nearly parallel to the strikes of outcrop-scale normal faults. All these extensional structures consistently indicate NE-SW extension of the basin and obliquely intersect the basin-bounding Yangsan and Dongnae faults at angles of 40<SUP>o</SUP>-60<SUP>o</SUP>. It is thus concluded that the Dadaepo Formation was deposited in a pull-apart basin that subsided as a result of NNE-striking sinistral strike-slip faulting in the southeastern part of the Korean Peninsula during the Campanian (Late Cretaceous). This strike-slip faulting was related to north-northwestward oblique subduction of the proto-Pacific (Izanagi/Kula) or Pacific plate under the eastern margin of the Eurasian plate.

Three-dimensional time-evolving plume-slab interaction for the generation of the Abukuma adakite, Northeast Japan

Lee, C.,Lim, C. International Association for Gondwana Research 2016 GONDWANA RESEARCH Vol.38 No.-

The pulse-like eruption of the Abukuma adakite in Northeast Japan at ~16Ma has previously been explained by localized and short-term (pulse-like) plume-slab interaction, where the plume ascended through a slab neck that developed in the subducted Pacific plate. However, because previous research was based on a two-dimensional (2D) model, considering the three-dimensional (3D) aspects of the plume blob that was injected into the corner of the mantle wedge was impossible, and its effects on the plume-slab interaction remained unknown. In this study, we conducted a series of 3D kinematic-dynamic numerical subduction models to evaluate the effects of the 3D plume blob on the partial melting of the subducted oceanic crust by varying the duration and size of the plume blob. Our 3D model shows two major outcomes in contrast to 2D model. First, a 3D plume blob with a duration of 5Myr, a thickness of 60km, and a wide range of widths from 80 to 200km is correlated with the pulse-like eruption of the Abukuma adakite, compared to the longer and much thicker 2D plume blob, which has a duration of 10Myr and a thickness of 70km. This result indicates that the 2D model overestimated the duration and thickness of the plume blob compared to those from the 3D model. Second, a 'trough' of lower slab surface temperatures developed by 3D plume-slab interaction, which intensified the temperature contrasts between the plume-slab contacting zone and the adjacent slab surface. The vigorous injection of the low viscosity plume blob into the corner of the mantle wedge generated lateral (trench-parallel) and returning mantle flow, which impeded the incoming corner flow from reaching the slab surface and produced the troughs of lower slab surface temperatures near the plume-slab contacting zone. The 3D plume-slab interaction thus has an important implication for the Quaternary arc volcanism and the 3D mantle flow in Northeast Japan.