Occurrence and petrography of volcaniclastic rocks in the Tertiary Shimanto Supergroup along the east coast of the Hata Peninsula, southwestern Shikoku, Southwest Japan, and its significance

和雄, 君波; 照喜, 今岡

doi:10.5575/geosoc.112.107

Cited by 3 publications

(4 citation statements)

References 22 publications

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“…At the southernmost end of the Hata Peninsula, near Cape Ashizuri, Oligocene‐Early Miocene sediments are cropped out. They include blocks of Eocene limestone and Oligocene‐Early Miocene volcanic effusions [ Kimikami and Imaoka , ]. The petrochemical character of these rocks shows an alkaline affinity.…”

Section: Geology and Geophysics Of The Shimanto Belt On Shikoku Islandmentioning

confidence: 99%

Middle Miocene swift migration of the TTT triple junction and rapid crustal growth in southwest Japan: A review

et al. 2014

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We review recent progress in geological and geophysical investigation in SW Japan, Nankai Trough, and Philippine Sea Plate (PSP), and propose a hypothesis for the Miocene tectonics in SW Japan driven by middle Miocene swift migration of the TTT (trench-trench-trench) triple junction. The new hypothesis is based on the new interpretations as follows. Near-trench magmatism in the outer zone of SW Japan is ascribed to a collision of proto-Izu arc in addition to the previous model of an oceanic ridge of the Shikoku Basin and hot PSP subduction. The indentation structures at Capes Ashizuri, Muroto in Shikoku, and Shiono on the Kii Peninsula were previously explained by "kink folding" due to recent E-W compression. We alternatively suppose the collision of the active arc or topographic peaks such as seamounts inferred from geological and experimental observations. The main crustal component in SW Japan is suggested to be of igneous plutonic rocks rather than the previous interpretation of Cretaceous to Tertiary accretionary complexes. This is typically illustrated in the outer zone to the north of Capes Ashizuri, Muroto, and Shiono from geophysical observation of gravity anomalies, velocity and resistivity, together with geological estimations of caldera age and the size of its root pluton. Episodic crustal growth due to intrusion of igneous rock and subduction of the PSP may have stopped after approximately 12 Ma and restarted at approximately 6 Ma. Our emphasis for this gap is a cessation and resurgence of subduction rather than the previous interpretation, i.e., decreasing of subduction rate.

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Section: Geology and Geophysics Of The Shimanto Belt On Shikoku Islandmentioning

confidence: 99%

Middle Miocene swift migration of the TTT triple junction and rapid crustal growth in southwest Japan: A review

et al. 2014

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“…Whole‐rock geochemical compositions of the volcaniclastic fragments and blocks were analyzed by XRF spectrometry. Samples have undergone varying degrees of alteration, and samples with limited alteration were selected for analysis by Kiminami and Imaoka (2006). Of the samples, 79% (15 of 19 computable samples) are classified as OI.…”

Section: Example Applications: Evaluating the Geochemical Characteris...mentioning

confidence: 99%

“…Probabilities of membership, derived from the average of the total available samples, are OI 76.12%, CA 9.98%, CFB 6.70%, MOR 6.16%, OP 0.93%, BAB 0.08%, IA 0.03%, and IOA 0.00%. These volcanic fragments were inferred to have originated in OI settings, based on their geological occurrences and geochemical compositions (Kiminami & Imaoka, 2006). The geochemical database of Haraguchi et al (2018) was used to retrieve this data set.…”

Section: Example Applications: Evaluating the Geochemical Characteris...mentioning

confidence: 99%

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An Introduction to SGTPPR: Sparse Geochemical Tectono‐Magmatic Setting Probabilistic MembershiP DiscriminatoR

Ueki,

Hino,

Kuwatani

2024

Geochem Geophys Geosyst

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We present a new and easy‐to‐use geochemical tectono‐magmatic setting discriminator to calculate the probability of membership (the Sparse Geochemical Tectono‐magmatic setting Probabilistic membershiP discriminatoR, SGTPPR) that runs in Excel. It outputs the probability of membership for eight different tectono‐magmatic settings (mid‐ocean ridge, oceanic island, oceanic plateau, continental flood basalt province, intra‐oceanic arc, continental arc, island arc, and back‐arc basin) for a given volcanic rock sample based on major and selected trace element contents (SiO2, TiO2, Al2O3, Fe2O3, MgO, CaO, K2O, Na2O, Rb, Sr, Y, Zr, Nb, and Ba). We consider all possible ratios and multiplications of these contents, in addition to the contents themselves, which improves the discrimination accuracy. We use a statistical method called sparse multinomial logistic regression to construct a robust and predictive discrimination model. By imposing the sparsity, only a small number of essential variables are included in the model. The variables are objectively extracted from 287 possible geochemical variables, including all possible ratios and multiplications of the major and trace element contents. The constructed model exhibits a high classification ability, indicating that tectonic discrimination using major and selected trace elements yields a high classification ability when ratios and multiplications are considered. The system outputs the relative weights of the variables (i.e., contents, and ratios and multiplications of contents) of the input geochemical data to the calculated membership probabilities. This information can be used to evaluate and interpret the results. We apply the model to multiple samples of a geological unit, to determine the tectonic setting.

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The Ashizuri granite-alkaline gabbro complex in the forearc of a Paleogene accretionary complex, Shikoku, Japan: Constraints on evolution by zircon U-Pb age and trace element composition

et al. 2020

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Occurrence and petrography of volcaniclastic rocks in the Tertiary Shimanto Supergroup along the east coast of the Hata Peninsula, southwestern Shikoku, Southwest Japan, and its significance

Cited by 3 publications

References 22 publications

Middle Miocene swift migration of the TTT triple junction and rapid crustal growth in southwest Japan: A review

Middle Miocene swift migration of the TTT triple junction and rapid crustal growth in southwest Japan: A review

An Introduction to SGTPPR: Sparse Geochemical Tectono‐Magmatic Setting Probabilistic MembershiP DiscriminatoR

The Ashizuri granite-alkaline gabbro complex in the forearc of a Paleogene accretionary complex, Shikoku, Japan: Constraints on evolution by zircon U-Pb age and trace element composition

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