Asian continental nature of87Sr/86Sr ratios in north central Pacific sediments

Asahara, Yoshihiro; Tanaka, Tsuyoshi; Kamioka, Hikari; Nishimura, Akira

doi:10.1016/0012-821x(95)00048-h

Cited by 108 publications

(65 citation statements)

References 16 publications

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“…Several investigations of the size fractions of the sediments have indicated that as the grain size decreases, the 87 Sr/ 86 Sr ratios increase in the acid-insoluble residual fraction and yield the highest value in the clay fraction [54]. The upper portion of the CR Basin primarily runs mainly through the Qinghai-Tibet Plateau and has a number of major tributaries, where the exposed rocks are clastic sedimentary (including Jurassic red sandstone), igneous and metamorphic.…”

Section: Causes Of Seasonal Variations In Riverine Isotopic Compositionsmentioning

confidence: 99%

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

et al. 2011

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Section: Causes Of Seasonal Variations In Riverine Isotopic Compositionsmentioning

confidence: 99%

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

et al. 2011

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“…Weber et al (1996) proposed two terrigenous materials as the provenance of North Pacific sediments, fine (<4.2 mm) Asian loess (AL) and average of basalts in the Kurile-Kamchatka Islands. Because this estimation assumes that a small part of loess undergoes dissolution in the surface water (Nakai et al, 1993;Jones et al, 1994;Asahara et al, 1995;Weber et al, 1998) and that the elemental abundance of loess changes with the grain-size Weber et al, 1996), Chinese loess (n : Gao et al, 1998;Taylor and McLennan, 1985;Shaw et al, 1986;Wedepohl, 1995), and averaged KK volcanic materials (j : Bailey, 1993) Bailey (1993) and Weber et al (1996)…”

Section: Temporal and Vertical Change Of Elemental Composition In Setmentioning

confidence: 99%

“…, isotopic composition of neodymium and strontium (Nakai et al, 1993;Jones et al, 1994;Asahara et al, 1995) and elemental composition (Kyte et al, 1993;Nakai et al, 1993;Bailey, 1993). These studies revealed that terrigenous debris in sediment in the North Pacific consist of Asian loess and some volcanic detritus, however, detailed end-members of these materials could not be defined because of variations of the transport process (Rea and Hovan, 1995) and compositional change of particles in the water column (Shimizu et al, 1994;Graves et al, 1994).…”

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confidence: 99%

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

2004

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In order to understand the origins and transport processes of lithogenic aluminosilicate in the western North Pacific, time-series sediment traps were deployed at Stn. KNOT at 44∞N 155∞E (water depth: 5320 m). Annual mean content of aluminum (Al) which is a proxy of lithogenic material in settling particles was 0.38% at 1 km depth, 0.78% at 3 km depth and 1.14% at 5 km depth, respectively. Mass fluxes were corrected by 230 Th and 231 Pa activities in particles and seawater. Annual mean corrected Al fluxes at 1, 3 and 5 km depths were calculated to 0.45, 0.46 and 0.33 g/m 2 /year, respectively. Lanthanum/ytterbium (La/Yb) and thorium/scandium (Th/Sc) ratios were used as proxies for estimating the origin of lithogenic aluminosilicate in settling particles. Both La/Yb and Th/Sc ratios in settling particles increased with depth, and the seasonal variation was the smallest at 5 km depth. It was considered that variations of La/Yb and Th/Sc ratios in settling particles reflected the change of source material of lithogenic aluminosilicates. Origins of lithogenic materials in the settling particles were summarized using two end-members, loess from central Asian continent (AL) and basalts from the Kurile-Kamchatka Islands (KK). Contributions of end-members in settling particles were estimated from the La/Yb and Th/Sc ratios. The contribution of KK particles in lithogenic materials was calculated to be 84% at 1 km depth, and 61% at 3 and 5 km depths, respectively. Although the KK material was the dominant constituent of the terrigenous component in settling particles at Stn. KNOT, the KK flux decreased with depth. On the other hand, the AL flux increased with depth and the significant increase of the AL flux was presumably due to the lateral import of AL particles to the deep layer at Stn. KNOT. From these results we conclude that the distribution of lithogenic materials recorded in sediments in the western North Pacific are influenced by the northward transport of AL within the deep layer.

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“…Sr isotopic ratios of limestone samples have been determined according to the method in Asahara et al (1995). Each pulverized sample weighed 0.5 g was dissolved in HCl.…”

Section: Methodsmentioning

confidence: 99%

Rare earth element and strontium isotopic study of seamount-type limestones in Mesozoic accretionary complex of Southern Chichibu Terrane, central Japan: Implication for incorporation process of seawater REE into limestones.

et al. 2003

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Ishimaki and Tahara limestones occur as exotic blocks juxtaposed in the Mesozoic (Jurassic) accretionary complex of Southern Chichibu Terrane in eastern Aichi Prefecture, central Japan. They are supposed to be of the seamount-type limestone, since they have no terrigenous materials and are intimately associated with greenstones. REE (rare earth elements) and Sr isotopic studies for the limestones have been made in order to know their geochemical characteristics, ages and origins. Their 87 Sr/ 86 Sr ratios, when referred to the seawater 87 Sr/ 86 Sr curve and relevant geological data, suggest that Ishimaki and Tahara limestones are the late Permian and the Carboniferous to the Early Permian, respectively. Two greenstone fragments found inside the Ishimaki limestone block and one greenstone sample associated with Tahara limestone block, resemble the Hawaiian alkali basalt in their REE and Y patterns. This is supporting the idea that the limestone blocks may be parts of reef limestones on ancient volcanic seamounts. All the limestone samples, except three unusual Tahara ones, show seawater REE and Y signatures in their chondritenormalized patterns. Their REE/Ca ratios, however, are 10 2 -10 4 times as high as those ratios of modern biogenic carbonates like corals and the seawater. Accordingly, seawater REE and Y were incorporated into the limestones, when originally biogenic carbonates transformed into inorganic calcite and its secondary growths occurred in diagenesis in contact with sufficient seawater. This view is favored by the reported REE partition experiment between calcite overgrowths and seawater solution. The seawater Ce anomaly as a function of water depth in the modern ocean is a key to infer the water depth of the REE and Y incorporation. The Ce anomalies given by log(Ce/Ce*) for about a half of Ishimaki samples and most of Tahara ones are between -0.5 and -0.2, which are compatible with the shallow water origin. Another half of Ishimaki samples, however, have log(Ce/Ce*) values between -0.7 and -1.0, suggesting moderately deep waters (ca. 500-1000 m deep or more). This may reflect such a situation that water depths of REE incorporation into the seamount-type limestones are generally greater than the depositional water depths of original biogenic carbonates because of the fate of limestone-capped volcanic seamounts decided by the oceanic plate motion.

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Asian continental nature of87Sr/86Sr ratios in north central Pacific sediments

Cited by 108 publications

References 16 publications

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

Rare earth element and strontium isotopic study of seamount-type limestones in Mesozoic accretionary complex of Southern Chichibu Terrane, central Japan: Implication for incorporation process of seawater REE into limestones.

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