Reply to comment by I. Pineda‐Velasco, T. T. Nguyen, H. Kitagawa, and E. Nakamura on “Diverse magmatic effects of subducting a hot slab in SW Japan: Results from forward modeling”

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The generation, transport, and accumulation of tropospheric dust have changed with the paleoclimatic changes of the Quaternary period. Such dust has accumulated in Japan ∼3000 km leeward of the source deserts in China. We analyzed the fractions of windblown fine quartz and bulk major and trace elements, and Sr‐Nd‐Pb isotopic compositions of loess in SW Japan deposited over the past 210 kyr. The results indicated extensive accumulation of tropospheric dust mixed with tephra fragments derived from the nearby Daisen volcano. The accumulation rate of fine quartz and selected elemental/isotopic compositions can be used as climatic proxies that reflect greater accumulation of dust in times of colder climate. Chemical indices for weathering show enhanced effects of weathering during times of warmer climate. The trace element compositions of the loess deposits are surprisingly similar to those of the Chinese loess, hemipelagic sediments in the Sea of Japan and the western Pacific Ocean, and the distal Chinese dust found in Canada. This similarity indicates that the loess dust shares major fractions of these fine‐grained sediments and that geochemical fractionation during the transport was limited. The Sr‐Nd‐Pb isotope compositions of the SW Japan loess indicate an origin predominantly in the Gobi Desert. The high‐latitude Pacific sediments and high‐latitude dust in Canada also show the same signature. However, isotopic compositions of samples from the southern Chinese loess plateau and mid to low‐latitude Pacific sediments are largely derived from the Taklimakan desert, which indicates different delivery pathways of the tropospheric dusts.

Section: Methodsmentioning

confidence: 99%

“…Multiple collector (MC)‐ICP‐MS (Elemental Plasma 54, Thermo Scientific, Waltham, MA, USA) was used for Pb isotope analysis. A Tl spike was used for mass fractionation correction [ Kimura et al ., ].…”

Section: Methodsmentioning

confidence: 99%

Geochemical records from loess deposits in Japan over the last 210 kyr: Lithogenic source changes and paleoclimatic indications

Miyazaki

Kimura

Katakuse³

2016

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“…NE Japan and SW Japan represent, respectively, a modern cold and a hot end‐member subduction zone [ Peacock and Wang , ; Syracuse et al ., ]. The details of ABS4 models for these subduction zones have been previously published [ Kimura and Nakajima , ; Kimura et al ., ; Kimura et al ., ]. We next briefly summarize the results of these models.…”

Section: Element Mass Balance In Subduction Zones and Formation Of Thmentioning

confidence: 99%

“…The rear‐arc high‐K calc‐alkaline basalts represent melts that are formed deeper (2–2.5 GPa) and at lower F (0.1–0.2) (Figure c) [ Kimura and Nakajima , ]. The high‐Nb basalts, high‐Mg andesites, and adakites in SW Japan are also mantle‐derived, but the ABS4 modeling shows that they reflect slab temperatures ∼200°C hotter than in NE Japan, along with higher mass fraction of slab melt in the mantle wedge, and more SED in the slab melts (Figure d) [ Kimura et al ., ].…”

Section: Element Mass Balance In Subduction Zones and Formation Of Thmentioning

confidence: 99%

See 1 more Smart Citation

Origin of geochemical mantle components: Role of subduction filter

Kimura

Gill

Skora

et al. 2016

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We quantitatively explore element redistribution at subduction zones using numerical mass balance models to evaluate the roles of the subduction zone filter in the Earth's geochemical cycle. Our models of slab residues after arc magma genesis differ from previous ones by being internally consistent with geodynamic models of modern arcs that successfully explain arc magma genesis and include element fluxes from the dehydration/melting of each underlying slab component. We assume that the mantle potential temperature

Tuffaceous Mud is a Volumetrically Important Volcaniclastic Facies of Submarine Arc Volcanism and Record of Climate Change

Gill

Bongiolo

Miyazaki

et al. 2018

The inorganic portion of tuffaceous mud and mudstone in an oceanic island arc can be mostly volcanic in origin. Consequently, a large volume of submarine volcaniclastic material is as extremely fine‐grained as products of subaerial eruptions (<100 µm). Using results of IODP Expedition 350 in the Izu rear arc, we show that such material can accumulate at high rates (12–20 cm/k.y.) within 13 km of the nearest seamount summit and scores of km behind the volcanic front. The geochemistry of bulk, acid‐leached mud, and its discrete vitriclasts, shows that >75% of the mud is volcanic, and that most of it was derived from proximal rear arc volcanic sources. It faithfully preserves integrated igneous geochemical information about arc evolution in much the same way that terrigenous shales track the evolution of continental crust. In addition, their high sedimentation rate enables high resolution study of climate cycles, including the effects of Pleistocene glaciation on the behavior of the Kuroshio Current in the Shikoku Basin south of Japan.