The Hongseong area in the south-western Gyeonggi Block of the Korean Peninsula consists of several Precambrian complexes that were regionally metamorphosed during the Triassic collision between the ...North and South China Blocks. Paleoproterozoic and Neoproterozoic magmatism and Triassic regional metamorphism in the Hongseong area suggest a possible tectonic link with the Yangtze Craton in the South China Block. The early magmatism in the western Hongseong area was Neoproterozoic, while that in the eastern Hongseong area was Paleoproterozoic. Sensitive high-resolution ion microprobe (SHRIMP) U–Pb dating of zircon indicates that the Neoproterozoic igneous activity occurred at ca. 850–830
Ma. U–Pb ages of zircon cores and first metamorphic overgrowths in the Paleoproterozoic gneisses are indistinguishable (1.88–1.86
Ga), indicating that the igneous activity and early metamorphism occurred in relatively rapid succession. The geochemical signatures indicate an arc tectonic setting for both the Paleoproterozoic and Neoproterozoic rocks. The age and geochemical signatures of the Neoproterozoic magmatism can be matched with the Neoproterozoic magmatism at the margin of the Yangtze Craton before amalgamation of the Rodinian supercontitnent. The Paleoproterozoic igneous and metamorphic events may be related to the assembly of the Columbian supercontinent. Both the Neoproterozoic igneous rocks and the Paleoproterozoic orthogneisses in the Hongseong area were regionally metamorphosed in the Triassic, at ca. 235
Ma. This regional metamorphism is well correlated with metamorphism at the northern margin of the Yangtze Craton where the Qinling-Dabie-Sulu UHP metamorphic belt formed due to the Triassic collision between the Yangtze Craton and North China Blocks. Similarities in the overall age distribution and the geographic resemblance between the Hongseong area and the northern margin of the Yangtze Craton show that the Hongseong area in the south-western Gyeonggi Block was tectonically linked with the Yangtze Craton, at least since the time of Rodinia.
Bile acids (BAs) are recently recognized signalling molecules that profoundly affect metabolism. Because of detergent-like toxicity, BA levels must be tightly regulated. An orphan nuclear receptor, ...Small Heterodimer Partner (SHP), plays a key role in this regulation, but how SHP senses the BA signal for feedback transcriptional responses is not clearly understood. We show an unexpected function of a nucleoporin, RanBP2, in maintaining BA homoeostasis through SUMOylation of SHP. Upon BA signalling, RanBP2 co-localizes with SHP at the nuclear envelope region and mediates SUMO2 modification at K68, which facilitates nuclear transport of SHP and its interaction with repressive histone modifiers to inhibit BA synthetic genes. Mice expressing a SUMO-defective K68R SHP mutant have increased liver BA levels, and upon BA- or drug-induced biliary insults, these mice exhibit exacerbated cholestatic pathologies. These results demonstrate a function of RanBP2-mediated SUMOylation of SHP in maintaining BA homoeostasis and protecting from the BA hepatotoxicity.
Ophiolites, the remnants of ancient oceanic lithosphere, have been described from collisional sutures of various ages with only few examples from Archean terranes. Here we report the discovery of a ...Neoarchean ophiolite suite from the southern margin of the Dharwar Craton in India, tectonically intercalated within a Neoproterozoic suture zone. The metamorphosed and variably dismembered ophiolite suite, exposed around Devanur, comprises altered ultramafic units, websterite, gabbros, mafic dykes, amphibolites, trondhjemites and pegmatites associated with ferruginous metachert. Structural and petrographic studies indicate that the rocks represent a highly sheared and metamorphosed suite emplaced as a thrust sheet. The major and trace element geochemistry of the mafic dykes indicate derivation from basaltic–andesitic magmas with tholeiitic to calc-alkaline characteristics. The rocks display negative Nb anomalies with enrichment of LILE (K, Rb, Ba, Th) and depletion in HFSE (Ti, Nb, Hf, Tb). The tectonic discrimination of these rocks based on various geochemical plots suggests that they were generated in a suprasubduction zone setting. We present new SHRIMP zircon U–Pb data for two trondhjemite samples from this complex, which yield
238U–
206Pb ages of 2528
±
61 and 2545
±
56
Ma. The Neoarchean age from the trondhjemites obtained in our study is closely comparable to similar ages obtained in recent studies from magmatic zircons in charnockites and orthogneisses in the area. The suprasubduction zone assemblages and arc magmas suggest a Neoarchean ocean closure along the southern margin of the Dharwar Craton.
Display omitted
► Discovery of a Neoarchean suprasubduction ophiolite from southern India. ► U–Pb dating of zircons from trondhjemites yield ~
2.5
Ga. ► Neoarchean ocean closure along the southern margin of the Dharwar Craton.
Display omitted
•Mid-Paleozoic sequences of western South Korea were sourced from peripheral clastic provenance.•Metamorphic zircons from Mid-Paleozoic sequences are compared with that of the ...Cathaysia Block.•Zircon populations from Mid-Paleozoic sequences indicate the Early Paleozoic location during Gondwana assembly.
The Middle Paleozoic metasedimentary sequences of the western Gyeonggi Massif (Taean Formation and Wolhyeonri Complex), Imjingang Belt, and southwestern Okcheon Belt, provide clues to the successive tectonic events that occurred during the evolution of the Korean Peninsula. In this study, we present SHRIMP U–Pb ages of detrital zircon grains from the metasandstones of the Taean Formation and Yeoncheon Group of the Imjingang Belt and from quartzites in three Paleozoic formations of the southwestern Okcheon Belt. The zircon grains from all of the samples yielded similar U–Pb age spectra of Paleoarchean/Neoarchean to Middle Paleozoic, with a dominant age population within the Paleozoic. The maximum ages of deposition estimated from the youngest dominant concordant detrital zircons were 431–457Ma for the western Gyeonggi Massif and Imjingang Belt, and 380–355Ma for the southwestern Okcheon Belt. Permian metamorphic zircon overgrowths correlated with subduction prior to the Triassic collision were also found. Middle Paleozoic metamorphic zircon overgrowths that can be compared to those of the Yunkai–Wuishan Orogenic Belt of the Cathaysia Block were indentified in the Wolhyeonri Complex. The dominant zircon populations of this study and the available data for the Korean Peninsula compare well with those from the Yangtze Block, Cathaysia Block, and Qilian–Qinling Orogenic Belt, which were located at the northeastern margin of eastern Gondwana during the Early Paleozoic.
Arc magmas, metavolcanics and hydrated mantle peridotite from the Hongseong area in western Gyeonggi massif provide evidence for Paleozoic subduction tectonics in the Korean Peninsula. Zircons in a ...tonalitic orthogneiss from the Wolhyeonri complex dated in this study through SHRIMP U–Pb technique yield ages of ca. 437Ma and ca. 414Ma. In addition, SHRIMP U–Pb zircon dating of a garnet-bearing paragneiss in the Wolhyeonri complex records evidence for Middle Paleozoic (ca. 427Ma) thermal metamorphism. Petrological and geochemical data from the Paleozoic suite provide robust evidence for mid Paleozoic arc-related magmatism.
Petrological and geochemical data from the Paleozoic suite, including the composition of chromian spinel from the serpentinite bodies enclosing high-pressure mafic and felsic blocks also suggest rifted arc/forearc tectonic setting in a supra-subduction zone environment. The serpentinite bodies preserve the imprints of forearc magmas derived through significant mantle/melt interaction during the opening and subsequent evolution of the forearc. These results indicate that the Paleozoic Hongseong area might have been located in an arc–forearc tectonic environment coeval with the plutonism and volcanism preserved in the Wolhyeonri complex. The Hongseong area thus preserves important clues to the Paleozoic subduction prior to the subsequent Triassic “Alpine-type” collision, suggesting a common tectonic linkage among Paleozoic to Triassic East Asian continents before the final assembly of the Pangaea supercontinent.
Display omitted
•Paleozoic arc magmatism in the Hongseong area of the western Gyeonggi massif, Korea.•Paleozoic rifted arc/forearc environment from serpentinite bodies enclosing HP blocks.•Paleozoic Pacific-type subduction before the final assembly of the Triassic NE Asia.
Fluids play a major role in facilitating igneous/metamorphic processes in the Earth’s crust and mantle. In this study, we investigate the nature and composition of fluids in Earth’s interior by ...studying the lower crustal rocks. We compare accessory minerals (e.g., apatite, monazite, allanite, and titanite), their texture, mineral reactions and composition among regionally distributed metamorphosed mafic and felsic rocks representing the roots of Neoarchean arc magmatism from the Nilgiri Block of the Southern Granulite Terrane in India. Regional trends in accessory minerals show the formation of monazite, allanite, and titanite in the felsic rocks. Apatite is depleted in REEs in all the rock types, irrespective of the difference in their whole-rock chemistry. Textural features and mineral reactions show that these accessory minerals were affected by fluids present in the lower crustal conditions. By comparing our results with those from previous experimental results, we further show that acidic CO
2
-H
2
O-HCl-HF fluids stable in lower crustal conditions could have resulted in these chemical and textural features. Dielectric constant of water is high (10–35 compared to lower crustal conditions) in high-pressure and low-temperature conditions of subduction zones and the upper mantle. Such conditions would enhance dissociation of HCl (compared to lower crust) and result in acidic fluids during dehydration reactions in subduction zones and in the upper mantle. Our results have important implications in understanding the nature and composition of fluids in Earth’s interior and would be helpful to model the tectonic and deep geochemical processes in both early and modern conditions in planetary interiors.
•Early to Middle Paleozoic arc magmatism in the Korean Peninsula.•Early to Middle Paleozoic magmatic pulse within Late Ordovician to Early Devonian.•Similar Early to Middle Paleozoic arc and ...subsequent collapsing tectonic setting related to Qinling orogenic belt in China.
The Hongseong area of the central southwestern Korean Peninsula has been tectonically correlated to the Qinling–Dabie–Sulu collisional belt of the central China Orogenic Belt. Here we have presented geochemical and sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon data on the metaigneous rocks from the Early to Middle Paleozoic Gwangcheon gneiss, located in the middle of the Hongseong area. Our data show U–Pb ages of ca. 450Ma for quartz-dioritic gneiss, 442Ma for metagabbro, 409, 407 and 402Ma for tonalitic gneiss, 440Ma for intermediate dyke, and 401Ma for mafic intrusive. The rocks display geochemical features suggesting magma generation within Late Ordovician (ca. 450Ma) to Early Devonian (ca. 401Ma) subduction-related volcanic arc and subsequent collapsing environment. The ages and geochemical characteristics presented in this study correlate well with those of the Early to Middle Paleozoic orogenic belts in the Qinling orogenic belt. Our study provides further insights into the tectonic linkage among Paleozoic to Triassic East Asian continents, with evidence for a Paleozoic Pacific-type subduction prior to the Triassic Alpine-type collision.
During subduction, continental margins experience shortening along with inversion of extensional sedimentary basins. Here we explore a tectonic scenario for the inversion of two-phase extensional ...basin systems, where the Early−Middle Jurassic intra-arc volcano-sedimentary Oseosan Volcanic Complex was developed on top of the Late Triassic−Early Jurassic post-collisional sequences, namely the Chungnam Basin. The basin shortening was accommodated mostly by contractional faults and related folds. In the basement, regional high-angle reverse faults as well as low-angle thrusts accommodate the overall shortening, and are compatible with those preserved in the cover. This suggests that their spatial and temporal development is strongly dependent on the initial basin geometry and inherited structures. Changes in transport direction observed along the basement-sedimentary cover interface is a characteristic structural feature, reflecting sequential kinematic evolution during basin inversion. Propagation of basement faults also enhanced shortening of the overlying sedimentary cover sequences. We constrain timing of the Late Jurassic−Early Cretaceous (ca. 158−110 Ma) inversion from altered K-feldspar 40Ar/39Ar ages in stacked thrust sheets and K-Ar illite ages of fault gouges, along with previously reported geochronological data from the area. This “non-magmatic phase” of the Daebo Orogeny is contemporaneous with the timing of magmatic quiescence across the Korean Peninsula. We propose the role of flat/low-angle subduction of the Paleo-Pacific Plate for the development of the “Laramide-style” basement-involved orogenic event along East Asian continental margin.
Display omitted
•Structural inversion of Early to Middle Mesozoic two-phase extensional systems during subduction of the Paleo-Pacific Plate.•Basement-involved contractional deformation in relation to the initial basin geometry and inherited structures.•Late Jurassic to Early Cretaceous magmatic quiescence reflecting flat/shallow subduction-related orogenic event.
Glacio-isostatic adjustment (GIA) and tectonic activity are important factors in the formation of marine terraces. Late Holocene wave-cut benches in the eastern part of the West Sea of Korea, also ...called the Yellow Sea, can be divided into two steps: 531 cm above sea level (ASL) for the upper bench (T2) and 464–481 cm ASL for the lower bench (T1). Sediments on the benches are classified into four units, and are interpreted to be beach deposits according to gravel shape, texture, and seaward inclination. The overlying sediment indicates that T2 was formed at approximately 530 cm ASL before 2900 yr BP, and T1 at approximately 460–480 cm ASL before 1520 yr BP. Late Holocene (4000–2000 yr BP) relative sea level (RSL) curves based on GIA models are inconsistent with the wave-cut bench elevations. Comparing T1 and T2 benches to the RSL curves of the West Sea, the upper and the lower benches were uplifted by approximately 5–8 m and 4–7 m, respectively. Although the area is several hundred kilometers away from plate boundaries, the high frequency of earthquakes in the West Sea may have induced the uplift of wave-cut benches during the last 2000 years. These indicate that the west coast of the Korean Peninsula (KP) should no longer be considered an area of subsidence, but be assigned to a regime of uplift during the late Holocene.
Display omitted
•Late Holocene wave-cut benches indicate that the the west coast of Korea should no longer be regarded area of subsidence but area of uplift.•The benches have been uplifted 5–8 m or 4–7 m based on the RSL curves.•High frequency, small-scale earthquakes play an important role in uplift of the benches.
PDF
