Abstract
Clastic successions found in the carbonate platform of continental margin during the Ordovician–Silurian Transition (OST) period are archives for interpreting paleo-depositional systems. ...Here, we report in-situ δ
18
O
quartz
and
87
Sr/
86
Sr
carbonate
isotope chemo-stratigraphy for an unconformable clastic unit from the Cathaysia terrane that rifted off the Gondwana Supercontinent in the Early Paleozoic Era. Our results suggest a depositional proxy and model for geological events attributed to rapid changes in the sedimentary environment during the OST period. Importantly, these results present crucial clues that infer the influence of Paleo-Tethys Sea opening, global eustatic regression, and rapid sedimentary provenance change. Our study provides insight into paleo-tracer that could be a key method for interpreting depositional system of carbonate platform based on in-situ mineral isotope chemo-stratigraphy that preserves the original value of provenance and geochemical condition.
The Permo-Triassic adakitic magmatism in the southern Korean Peninsula preserves important tectonomagmatic records along the East Asian continental margin. In this study, we present ...SHRIMP/LA–MC–ICPMS U-Pb zircon ages and Hf isotope signature with whole-rock geochemical compositions of the Middle Permian to Middle Triassic granitoid gneiss-granitoid suites and the Middle to Late Triassic plutonic rocks in the southeastern Korean Peninsula. The former yields three age groups of ca. 272–263 Ma, ca. 258–251 Ma and ca. 243–240 Ma, respectively. The latter group yields ca. 237–216 Ma ages, indicating a long term magmatism that lasted from the Middle Permian to late Triassic. The granitoid gneiss-granitoid suites have chemical compositions similar to high silica adakitic rocks, showing high SiO2 (59.55–73.97 wt.%), Na2O (3.55–5.30 wt.%), Sr/Y (30–401), and La/YbN (11–173), and low MgO (0.18–1.82 wt.%), Y (2–14 ppm) and YbN (2–7). These rocks are peraluminous with high Ba and Sr, and show relatively high K2O contents and K2O/Na2O ratios (> 0.7), with positive correlation between La/YbN vs. Sr/Y ratios and high initial Sr ratios. These features reflect different contribution of the slab-derived adakite melts that interacted with peridotitic mantle in the metasomatized mantle wedge and the Middle Paleoproterozoic lower crustal basement of the Yeongnam Massif. On the contrary, the Triassic alkaline magmatism in the Yeongnam Massif is alternatively interpreted either by a tectonic switch to the extension-dominated arc system or by a delamination of an overthickened arc. The results from this study offer important evidence for a common subduction-accretion system existed between the North and South China Cratons and microcontinents between them along margins of the East Asian continental blocks, with different plate interaction in different locations generating distinct magmatic suites.
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•The Permo-Triassic magmatic m rocks in southern Korea are adakitic rocks, having similar geochemical characteristics to adakites.•Tectonomagmatic records preserved in them might be linked to the magmatic responses to the Permo-Triassic tectonic events in East Asia.•The controversial tectonic nature of Late Triassic magmatism remains for further research in the Korean Peninsula.
Detrital zircon geochronology and Hf isotope analysis can be used for inferring provenance characteristics, and to evaluate the tectonic evolution of sedimentary basins and their link with regional ...orogenesis. The Paleozoic sequences of the Okcheon Belt consist of the Lower Paleozoic Joseon and the Upper Paleozoic Pyeongan supergroups with Middle Paleozoic hiatus locally on top of the Neoproterozoic bimodal volcanic rocks, reflecting an intracontinental rift setting between the two basements (viz. Gyeonggi and Yeongnam massifs) at southern part of the Korean Peninsula. Our detrital zircon U-Pb ages and Lu-Hf isotope results show that all these Paleozoic strata commonly have Paleoproterozoic and Paleozoic zircon ages with rare Meso- to Neoproterozoic ages. The individual zircon populations display following features, allowing estimation of their sedimentary provenances: (i) The Paleoproterozoic zircons (ca. 1.85 Ga and 2.50 Ga) with similar ranges of εHf(t) values are most common in the basement rocks of the Korean Peninsula, and were sourced from both the Gyeonggi and Yeongnam massifs. (ii) The Meso- to Neoproterozoic zircons, preserved only in the Middle to Late Cambrian clastic sedimentary rocks within the carbonate sequences probably reflect proximal provenance. (iii) The youngest Paleozoic zircons of each formation, almost coincident with their deposition ages, suggest presence of syndepositional magmatism, indicating proximal magmatic sources during their deposition. (iv) The Cambrian–Ordovician zircons, from the Lower Paleozoic sequences, but rare in the successive Upper Paleozoic sequences, suggest a provenance change after the hiatus between the two sedimentary successions. (v) The Permian zircons showing different εHf(t) values indicate that detrital sources were varied at that time. The integrated results in our study suggest provenance variability linked to diverse tectonic environments, reflecting prolonged subduction-related crustal evolution of the proto-Korean Peninsula during the Paleozoic.
Sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb ages and whole-rock chemical compositions of Early to Middle Jurassic plutons from the central to southern Korean Peninsula are reported ...to investigate the effect of paleo-Pacific plate subduction preserved along the continental margin. Twenty-one plutonic rocks from the Yeongnam massif (i.e., Sunchang and Namwon plutons), the Okcheon belt (Jeongup, Boeun, and Mungyeong plutons), the northeast (Gangreung pluton), and the Gyeonggi massif (Gonam, Anheung, and Ganghwa plutons) have age ranges from ca. 189–186Ma to 177Ma, 177–166Ma, and 177–173Ma, respectively. Most plutonic rocks have chemical compositions similar to adakites, showing high SiO2 (45.62–74.96wt.%), low MgO (0.01–2.84wt.%), high Na2O (2.65–4.83wt.%), high Sr/Y and La/Yb, low Y and Yb, as well as low HFSEs (Nb and Ta), but initial Sr ratios (0.7048–0.7262), K2O (0.50–5.88wt.%), and K2O/Na2O (0.34–2.1) were unlikely to have been formed by melting of either a thickened and/or delaminated lower continental crust, or an altered oceanic crust. These suggest that the “adakitic” plutonic rocks in this region resulted from partial melting of an enriched mantle source metasomatized by dewatering from a delaminated flat-slab. The spatial distributions of this continental adakitic plutonic belt, based on the present study, together with previously reported geochronological results, indicate that magmatic pulses gradually migrated toward the continent across the Korean Peninsula as a result of slab shallowing caused by periodic slab buckling. The similar geochronological and geochemical characteristics, petrogenesis and tectonic setting of the plutonic belt spanning the Korean Peninsula, Japan, eastern China, and eastern Russia indicate a possible link to an active subduction system that existed during the Early to Middle Jurassic, although the products of the plate subduction might differ in different locations along the East Asian continental margin.
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•Early to Middle Jurassic continental adakitic arc magmatism in the Korean Peninsula•Migration of Jurassic magmatic pulses as a result of slab shallowing caused by periodic slab buckling•Similar Jurassic arc tectonic setting related to paleo-Pacific plate subduction in East Asia
The Jucheon-Pyeongchang area in the northwestern Taebaeksan Zone of the Okcheon fold-thrust belt preserved several thrust faults placing the Precambrian basement granite gneisses of the Gyeonggi ...Massif on top of the Early Paleozoic Joseon Supergroup and the age-unknown Bangrim Group. Especially, the thrust faults in the study area show the closed-loop patterns on the map view, showing older allochthonous strata surrounded by younger autochthonous or para-autochthonous strata. These basement-involved thrusts including Klippes will provide important information on the hinterland portion of the fold-thrust belt. For defining Klippe geometry in the thrust fault terrains of the Jucheon-Pyeongchang area by older on younger relationship, the stratigraphic position of the age-unknown Bangrim Group should be determined. The Middle Cambrian maximum depositional age by the detrital zircon SHRIMP U-Pb method from this study, together with field relations and previous research results suggest that the Bangrim Group overlies the Precambrian basement rocks by nonconformity and underlies the Cambrian Yangdeok Group (Jangsan and Myobong formations). The structural geometric interpretation of the Pyeongchang area based on newly defined stratigraphy indicates that the Wungyori and Barngrim thrusts are the same folded thrust, and can be interpreted as a Klippe, having Precambrian hanging wall granite gneisses surrounded by younger Cambrian strata of the Joseon Supergroup and the Bangrim Group. Further detailed structural studies on the Jucheon-Pyeongchang area can give crucial insights into the basement-involved deformation during the structural evolution of the Okcheon Belt. 한반도의 대표적인 습곡-단층대 중 하나인 옥천대의 주천-평창지역에는 경기육괴 기반암을 고생대 조선누층군 및 시대미상의 방림층군 상위로 충상시키는 다수의 트러스트 단층이 발달한다. 이 지역의 트러스트들은 상반의 암체가 하반의 암체로 완전히 둘러싸인 폐곡선 형태의 독특한 자취를 보이며, 이는 전형적인 클리페의 지질도 상 특징으로 해석될 수 있다. 특히, 연구 지역과 같이 트러스트 상반에 기반암을 포함하는 클리페의 경우에는 습곡-단층대 배후지의 구조 발달을 이해하는데 중요하다. 그러나 클리페 구조가 잘 정의되기 위해서는 층서적으로 오래된 암체가 트러스트를 경계로 상대적으로 젊은 암체의 상위에 구조적으로 완전히 고립된 형태를 보여야 하기 때문에, 연구지역에 넓게 분포하는 시대미상 방림층군의 지질연대가 매우 중요하다. 본 연구에서는 SHRIMP U-Pb 저어콘 연대측정을 통해 획득한 방림층군의 최대 퇴적시기와 야외조사 결과 및 기존 연구를 종합하여, 방림층군을 아래로는 선캄브리아시대 화강편마암과 위로는 전기 고생대 조선누층군 양덕층군(장산층, 묘봉층)의 지층 사이에 놓이는 고생대 캄브리아기 최하부 지층에 대비하였다. 이를 바탕으로 평창지역에 대한 구조기하 형태 연구를 수행한 결과, 운교리트러스트와 방림트러스트는 하나의 습곡된 트러스트이며 운교리트러스트 상반의 암체들이 하반 암체들에 의해 완전히 고립된 특징을 보이는 클리페 모델로 해석이 가능함을 확인하였다. 향후 주천-평창지역에 대한 구조지질학적 측면의 후속 연구들을 통해 클리페 모델에 대한 추가적인 테스트가 이루어진다면, 옥천대의 구조 진화에 있어서 기반암을 포함하는 변형 기작의 역할에 대해 중요한 정보를 획득할 수 있을 것이다.
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► Early Neoproterozoic arc magmatism from the western South Korea related to the assembly of Rodinia. ► Middle Neoproterozoic anorogenic alkali plutons in the same area related to the ...disruption of Rodinia. ► These Neoproterozoic plutons provide important constraints on a regional tectonic link associated with evolution of Rodinia in East Asia.
We report sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages, and whole-rock chemical and isotopic (Sr–Nd) compositions from tonalite–trondhjemite–granodiorite (TTG) and alkaline plutons in and around the “Hongseong-Imjingang suture” along the western margin of the Gyeonggi massif, South Korea. The Neoproterozoic TTG and the alkali plutons from the Hongseong area of the Gyeonggi massif yield zircon U–Pb ages of ca. 841–822 Ma and ca. 751–746 Ma, respectively. Based on the geochemical and Nd–Sr isotope data on these plutons, together with the previously reported SHRIMP age of ca. 900 Ma from a tonalite, TTG plutons of ca. 900–820 Ma are interpreted as the products of arc-related magmatism. Their geochemical signatures include enrichment in LREE, negative Nb, Ta and Ti anomalies and relatively low ɛNd(T) values between −0.5 and +5.0. The TTG plutons are coeval with those recently identified in and around the Yangtze block in China. In contrast, the alkali plutons from the Hongseong area, together with the previously reported ones around the Imjingang belt, represent anorogenic-type magmas that can be attributed to the disruption of Rodinia. They display significant negative Eu anomalies, and are strongly depleted in Sr, P and Ti. This transition from arc setting at ca. 900–820 Ma to continental rift setting at ca. 750–740 Ma suggests a regional tectonic link for the amalgamation and disruption of Rodinia in Northeast Asia.
Metastasis is responsible for 90% of human cancer mortality, yet it remains a challenge to model human cancer metastasis in vivo. Here we describe mouse models of high-grade serous ovarian cancer, ...also known as high-grade serous carcinoma (HGSC), the most common and deadliest human ovarian cancer type. Mice genetically engineered to harbor Dicer1 and Pten inactivation and mutant p53 robustly replicate the peritoneal metastases of human HGSC with complete penetrance. Arising from the fallopian tube, tumors spread to the ovary and metastasize throughout the pelvic and peritoneal cavities, invariably inducing hemorrhagic ascites. Widespread and abundant peritoneal metastases ultimately cause mouse deaths (100%). Besides the phenotypic and histopathological similarities, mouse HGSCs also display marked chromosomal instability, impaired DNA repair, and chemosensitivity. Faithfully recapitulating the clinical metastases as well as molecular and genomic features of human HGSC, this murine model will be valuable for elucidating the mechanisms underlying the development and progression of metastatic ovarian cancer and also for evaluating potential therapies.
•The Taebaeksan zone in the NE of the Okcheon belt preserved architecture of a typical fold-thrust belt.•Highly connected thrust traces in the Yeongwol area are better explained by duplex model than ...folded imbricate fan model.•Evidence for polyphase tectonic events in the Taebaeksan zone following the Permo–Triassic Songrim (Indosinian) orogeny.
Structural interpretation of the distinct map pattern defined by highly connected thrust traces in the map view of the Taebaeksan Zone provides insight into the structural style of the northeastern Okcheon Belt. The map pattern can generally be explained by either a folded imbricate fan or a hinterland dipping duplex. The same geometry could also be formed by a complex combination of major imbricate thrusts and their connecting splays, having the structural architecture of a typical fold-thrust belt. However, a folded imbricate fan model is not adequate to explain the absence of late Paleozoic to early Mesozoic strata (i.e. the Pyeongan Supergroup) between two major thrusts (viz. the Pyeongchang and Machari thrusts) in this area. This result further suggests that the Yeongwol area, the western part of the Taebaeksan Zone, is a duplex that corresponds to a more internal and deeper hinterland part of the fold-thrust belt, while the imbricate thrusts with low connectivity in the Taebaek area, the eastern part of the Taebaeksan Zone, indicate a more external and shallower foreland portion of the belt. In addition, cross-cutting relations and newly obtained sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages from a cross-cutting dike and syntectonic sedimentary rocks suggest limited thrust reactivation after the early Jurassic and early Tertiary, respectively. In spite of this, the original geometry of the fold-thrust wedge in the Taebaeksan Zone remained well preserved.
The Nagercoil block is the southernmost crustal segment of the Southern Granulite Terrane (SGT) in India and is mainly composed of charnockitic rocks and felsic gneisses (charnockite suite). In this ...study, we present petrologic, geochemical, zircon U–Pb, REE, and Hf isotopic studies on the charnockites and leucogneiss from the Nagercoil block. Based on field investigations and petrologic studies, the charnockites can be divided into garnet-bearing and garnet-absent anhydrous granulite facies rocks with orthopyroxene. The charnockites and leucogneiss show transition from adakites to non-adakitic magmatic rocks, with enrichment in LREEs (light rare earth elements) and LILEs (large ion lithophile elements), and depletion in HREEs (heavy rare earth elements) and HFSEs (high field strength elements). Some of the charnockites and the leucogneiss show typical HSA (high silica adakite) characters, (high SiO2, Al2O3, Ba–Sr, La/Yb, and Sr/Y). The HSA is considered to have formed from the interaction of slab derived melts and peridotitic mantle wedge. The high Ba–Sr features were possibly inherited from subducted oceanic crust melting under high thermal gradient during Precambrian. The magmas were underplated and subjected to fractional crystallization. Zircon grains from the charnockite and leucogneiss show zoned magmatic cores surrounded by structureless metamorphic rims. Magmatic zircon grains from the charnockites show ages ranging from 1983 ± 8.8 Ma to 2046 ± 14 Ma, and the metamorphic domains show an age range of 502 ± 14 Ma to 547 ± 8.7 Ma. Zircon from the leucogneiss yielded magmatic and metamorphic ages of 1860 ± 20 Ma and 575.6 ± 8.8 Ma. Both charnockites and leucogneiss show two prominent age peaks at 1987 Ma and 568 Ma. The REE data of the zircon grains show LREE depletion and HREE enrichment, with the metamorphic grains showing more depletion in HREE. Zircon Hf isotopic data of the magmatic cores of zircon grains from the charnockite yielded εHf(t) values from −1.17 to 0.46 with TDM and TDMC and age peaks at 2392 Ma and 2638 Ma, suggesting Neoarchean to Paleoproterozoic juvenile sources. We suggest that the high Ba–Sr adakitic charnockite suite from the Nagercoil block formed in a Paleoproterozoic magmatic arc setting during the assembly of the Columbia supercontinent, and underwent high-grade metamorphism associated with the amalgamation of the Gondwana supercontinent during the late Neoproterozoic–Cambrian. Our study provides new insights into the vestiges of Columbia fragments within the Gondwana assembly with two distinct cycles of crustal evolution.
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•Nagercoil charnockites show high Ba-Sr and high silica adakitic features.•Magmatic protoliths formed during ca. 2046 to 1983 Ma and metamorphism at 594–502 Ma.•Magma source involved juvenile Neoarchean-Paleoproterozoic sources.•Paleoproterozoic arc magmatism associated with Columbia supercontinent assembly.•Late Neoproterozoic-Cambrian metamorphism related to Gondwana assembly.
The signature of a prolonged subduction–accretion history from Paleozoic to Early Mesozoic is preserved within the dismembered serpentinite mélanges within the Hongseong suture. Here we present major ...and trace element data from the mafic fragments/blocks within the Baekdong serpentinite mélange revealing their arc-like tholeiite affinity within a suprasubduction zone tectonic setting. Chromian spinel compositions from the Baekdong hydrated mantle peridotite (serpentinite) are characterized by high Cr# (0.53–0.67) and Fe
2+/Fe
3+ ratio, medium Mg# (0.42–0.55), and Al
2O
3 contents (17–25
wt.%) indicating a forearc tectonic environment for the hydrated mantle peridotite. The estimated melting degree (>
17.6%) and FeO/MgO of the parental melt (0.9–1.3) are consistent with that of forearc magmas. SHRIMP zircon U–Pb ages from a high-grade mafic rock and an anorthosite from the study area give protolith ages of ~
310
Ma and ~
228
Ma, respectively. Zircons from an associated orthogneiss block within the mélange yield a Neoproterozoic crystallization age of ~
748
Ma. These results, together with the recent SHRIMP zircon ages from other dismembered serpentinite mélanges within the Wolhyeonri complex, suggest that Paleozoic to Early Mesozoic subduction and subsequent collision events led to the exhumation of the hydrated forearc mantle peridotites from a metasomatized mantle wedge. The Hongseong region preserves important clues to a long-lived subduction system related to global events associated with the final amalgamation of the Pangaea supercontinent.
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► Exotic blocks of arc tholeiite basalt/gabbro and anorthosite within the serpentinite mélange. ► Forearc tectonic environment for the hydrated mantle peridotite. ► Paleozoic to Early Mesozoic subduction and subsequent collision led to the exhumation of the hydrated forearc mantle peridotites from a metasomatized mantle wedge.
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