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  1. Article ; Online: Linking the Wrangellia flood basalts to the Galápagos hotspot

    J. Gregory Shellnutt / Jaroslav Dostal / Tung-Yi Lee

    Scientific Reports, Vol 11, Iss 1, Pp 1-

    2021  Volume 14

    Abstract: Abstract The Triassic volcanic rocks of Wrangellia erupted at an equatorial to tropical latitude that was within 3000 km of western North America. The mafic and ultramafic volcanic rocks are compositionally and isotopically similar to those of oceanic ... ...

    Abstract Abstract The Triassic volcanic rocks of Wrangellia erupted at an equatorial to tropical latitude that was within 3000 km of western North America. The mafic and ultramafic volcanic rocks are compositionally and isotopically similar to those of oceanic plateaux that were generated from a Pacific mantle plume-type source. The thermal conditions, estimated from the primitive rocks, indicate that it was a high temperature regime (TP > 1550 °C) consistent with elevated temperatures expected for a mantle plume. The only active hotspot currently located near the equator of the eastern Pacific Ocean that was active during the Mesozoic and produced ultramafic volcanic rocks is the Galápagos hotspot. The calculated mantle potential temperatures, trace elemental ratios, and Sr–Nd–Pb isotopes of the Wrangellia volcanic rocks are within the range of those from the Caribbean Plateau and Galápagos Islands, and collectively have similar internal variability as the Hawaii-Emperor island chain. The paleogeographic constraints, thermal estimates, and geochemistry suggests that it is possible that the Galápagos hotspot generated the volcanic rocks of Wrangellia and the Caribbean plateau or, more broadly, that the eastern Pacific (Panthalassa) Ocean was a unique region where anomalously high thermal conditions either periodically or continually existed from ~ 230 Ma to the present day.
    Keywords Medicine ; R ; Science ; Q
    Subject code 550
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Extrusion tectonism of Indochina reassessed

    Thi-Hue Dinh / Meng-Wan Yeh / Tung-Yi Lee / Michael J. Kunk / Robert P. Wintsch / Ryan McAleer

    Frontiers in Earth Science, Vol

    constraints from 40Ar/39Ar geochronology from the Day Nui Con Voi metamorphic massif, Vietnam

    2023  Volume 11

    Abstract: The extrusion tectonic model for the southeastern margin of the Himalayan orogeny links the crustal shear activity along the Red River Shear Zone (RRSZ) to the opening of the South China Sea (SCS). The Day Nui Con Voi (DNCV) metamorphic massif in ... ...

    Abstract The extrusion tectonic model for the southeastern margin of the Himalayan orogeny links the crustal shear activity along the Red River Shear Zone (RRSZ) to the opening of the South China Sea (SCS). The Day Nui Con Voi (DNCV) metamorphic massif in northern Vietnam strikes NW-SE, is bounded by the RRSZ to the south and continues along the strike where it meets the SCS. The DNCV is thus a critical area to document thermotectonic history in order to advance our understanding of the tectonic evolution of Indochina extrusion and its relationship to the opening of the SCS. Our new 40Ar/39Ar data combined with microstructural and petrological analyses constrained the timing of the left-lateral shearing of the RRSZ and revealed the thermal evolution of the DNCV metamorphic massif. Three ductile deformation events were observed. D1 formed NNW-SSE striking upright folds under granulite to upper amphibolite facies conditions. D2 was a horizontal to sub-horizontal folding event that occurred at amphibolite facies conditions. D3 was a doming event that formed NW-SE striking up-right folds bounded by left-lateral shearing mylonite belts along the two limbs. The S/C fabrics were defined by muscovite fish, quartz + albite + K-feldspar aggregates, and muscovite folia. The D3 doming event exhumed the DNCV metamorphic massif from amphibolite facies conditions to the lower greenschist facies conditions. The 40Ar/39Ar ages obtained from amphibole (∼26 Ma), phlogopite (∼25 Ma), muscovites (∼24-23 Ma), biotite (∼25-23 Ma), and K-feldspars (∼25-22 Ma) from different structural domains of the DNCV metamorphic massif indicated a rapid exhumation ∼26–22 Ma. We interpreted this as the time period for the D3 event, with the onset of left-lateral shearing occurring around 24 Ma based on ages obtained from syn-kinematic muscovites. This age was much younger than the initiation of sea-floor spreading of the SCS (since 32 Ma) but coincided with the age for the ridge jump event in the SCS. Based on these new data, we proposed that extrusion ...
    Keywords Red River Shear Zone (RRSZ) ; Day Nui Con Voi (DNCV) ; South China Sea (SCS) ; 40Ar/39Ar geochronology ; tectonic evolution ; Science ; Q
    Subject code 550
    Language English
    Publishing date 2023-07-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Zircon U-Pb geochronology of the Lan Sang gneisses and its tectonic implications for the Mae Ping shear zone, NW Thailand

    Yu-Ling Lin / Tung-Yi Lee / Hao-Yang Lee / Yoshiyuki Iizuka / Long Xiang Quek / Punya Charusiri

    Frontiers in Earth Science, Vol

    2023  Volume 11

    Abstract: The Mae Ping shear zone (MPSZ), a major shear zone trending NW-SE in Thailand, is responsible for the left-lateral displacement of the N-S Triassic-Jurassic granitoid and gneiss belt. This displacement is postulated to have contributed to Cenozoic ... ...

    Abstract The Mae Ping shear zone (MPSZ), a major shear zone trending NW-SE in Thailand, is responsible for the left-lateral displacement of the N-S Triassic-Jurassic granitoid and gneiss belt. This displacement is postulated to have contributed to Cenozoic extrusion tectonics. Within the Lan Sang National Park, the MPSZ exposes several intensely deformed lithologies, collectively known as the Lan Sang gneisses. These gneisses have attracted considerable attention for their potential to substantiate the extrusion model. However, the timing of the emplacement of the orthogneiss protolith is still debated. Moreover, the origin and distribution of the Eocene syn-shearing granodiorite within this shear zone are not well understood. To shed light on the magmatic history of the MPSZ, this study utilized zircon U-Pb geochronology to systematically investigate the Lan Sang gneisses. Our findings demonstrate that these gneisses can be categorized into paragneiss and orthogneiss groups. Paragneiss samples feature zircons displaying rounded detrital cores ranging from 3,078 to 450 Ma, with metamorphic rim overgrowth of ca. 200 Ma (most Th/U <0.01). This indicates that their Paleozoic sedimentary protoliths experienced high-grade metamorphism during the Triassic-Jurassic Indosinian orogeny. On the other hand, zircon from orthogneiss samples shows that their magmatic protoliths were predominantly emplaced either around ∼200 Ma or within 45-32 Ma. The Eocene-Oligocene magmatism likely coincided with the proposed Eocene metamorphism. Since these samples were deformed by left-lateral shearing, the left-lateral motion of the MPSZ probably ended after 32 Ma. Eocene-Oligocene magmatic events have also been identified in granite, mylonite, and gneiss samples from other regions along the Sibumasu terrane, including the Three Pagodas, Klaeng, Ranong, Khlong Marui shear zones, and the Doi Inthanon area. The Eocene-Oligocene magmatism was likely linked with the movement of the shear zones and may be responsible for the regional cooling ...
    Keywords Lan Sang gneisses ; Mae Ping shear zone ; zircon U-Pb geochronology ; Sibumasu ; Thailand ; syn-shearing intrusion ; Science ; Q
    Subject code 550
    Language English
    Publishing date 2023-09-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Temporal and structural evolution of the Early Palæogene rocks of the Seychelles microcontinent

    J. Gregory Shellnutt / Meng-Wan Yeh / Kenshi Suga / Tung-Yi Lee / Hao-Yang Lee / Te-Hsien Lin

    Scientific Reports, Vol 7, Iss 1, Pp 1-

    2017  Volume 7

    Abstract: Abstract The Early Palæogene Silhouette/North Island volcano-plutonic complex was emplaced during the rifting of the Seychelles microcontinent from western India. The complex is thought to have been emplaced during magnetochron C28n. However, the ... ...

    Abstract Abstract The Early Palæogene Silhouette/North Island volcano-plutonic complex was emplaced during the rifting of the Seychelles microcontinent from western India. The complex is thought to have been emplaced during magnetochron C28n. However, the magnetic polarities of the rocks are almost entirely reversed and inconsistent with a normal polarity. In this study we present new in situ zircon U/Pb geochronology of the different intrusive facies of the Silhouette/North Island complex in order to address the timing of emplacement and the apparent magnetic polarity dichotomy. The rocks from Silhouette yielded weighted mean 206Pb/238U ages from 62.4 ± 0.9 Ma to 63.1 ± 0.9 Ma whereas the rocks from North Island yielded slightly younger mean ages between 60.6 ± 0.7 Ma to 61.0 ± 0.8 Ma. The secular latitudinal variation from Silhouette to North Island is consistent with the anticlockwise rotation of the Seychelles microcontinent and the measured polarities. The rocks from Silhouette were emplaced across a polarity cycle (C26r-C27n-C27r) and the rocks from North Island were emplaced entirely within a magnetic reversal (C26r). Moreover, the rocks from North Island and those from the conjugate margin of India are contemporaneous and together mark the culmination of rift-related magmatism.
    Keywords Medicine ; R ; Science ; Q
    Subject code 550
    Language English
    Publishing date 2017-03-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Structural inversion in the northern South China Sea continental margin and its tectonic implications

    Chin-Da Huang / Tung-Yi Lee / Ching-Hua Lo / Sun-Lin Chung / Jong-Chang Wu / Ching-Lung Tien / Meng-Wan Yeh / Shiu-Chi Chen / Yu-Lu Chan / Ching-Yi Hu

    Terrestrial, Atmospheric and Oceanic Sciences, Vol 28, Iss 6, Pp 891-

    2017  Volume 922

    Abstract: The northern South China Sea (SCS) continental margin was proposed to be an active margin during the Mesozoic. However, only a few papers discussed the Mesozoic structural evolution in this region. Here, we provide information based on the seismic ... ...

    Abstract The northern South China Sea (SCS) continental margin was proposed to be an active margin during the Mesozoic. However, only a few papers discussed the Mesozoic structural evolution in this region. Here, we provide information based on the seismic profile interpretations with age control from biostratigraphic studies and detrital zircon U-Pb dates of well MZ-1-1 in the western Dongsha-Penghu Uplift of the northern SCS continental margin. The industrial seismic profiles reveal evidence for structural inversion as represented by folds and high-angle reverse faults, formed by reactivation of pre-existing normal faults. The inversion event likely started after the Early Cretaceous, and developed in Late Cretaceous, but ceased before the Cenozoic. The areal extent of the structural inversion was restricted in the western Dongsha-Penghu Uplift and was approximately 100 km in width. Based on the paleogeographic reconstruction of SCS, the structural inversion was likely formed by a collision between the seamount (volcanic islands) swarm of the current North Palawan block (mainly the Calamian Islands) and the northern SCS continental margin around Late Cretaceous.
    Keywords Geography (General) ; G1-922 ; Geology ; QE1-996.5
    Subject code 550
    Language English
    Publishing date 2017-01-01T00:00:00Z
    Publisher Chinese Geoscience Union
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Core Slabbing and Nannofossil Analysis on the Chelungpu Fault Zone, Taichung, Taiwan

    Jong-Chang Wu / Shiuh-Tsann Huang / Ming-Huei Wang1 / Chin-Chun Tsai1 / Wen-Wei Mei1 / Jih-Hao Hung / Tung- Yi Lee / Kenn-Ming Yang / Kun-Fa Lee

    Terrestrial, Atmospheric and Oceanic Sciences, Vol 18, Iss 2, p

    2007  Volume 295

    Abstract: The results of this nannofossil analysis supply essential information for determining the formation boundaries in the upper Pliocene to Pleistocene. These results also verify the existence of a repetition fossil zone. ...

    Abstract The results of this nannofossil analysis supply essential information for determining the formation boundaries in the upper Pliocene to Pleistocene. These results also verify the existence of a repetition fossil zone.
    Keywords Nannofossil analysis ; Biostratigraphy ; Chelungpu fault ; Taichung area ; Geography (General) ; G1-922 ; Geology ; QE1-996.5
    Language English
    Publishing date 2007-01-01T00:00:00Z
    Publisher Chinese Geoscience Union
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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