排序方式: 共有3条查询结果,搜索用时 15 毫秒
1
1.
Isotope and trace element evidence for depleted lithosphere in the source of enriched Ko’olau basalts 总被引:1,自引:0,他引:1
Vincent J. M. Salters Janne Blichert-Toft Zuzana Fekiacova Afi Sachi-Kocher Michael Bizimis 《Contributions to Mineralogy and Petrology》2006,151(3):297-312
We have measured the Hf and Nd isotopic compositions of 38 basalts from the Ko’olau drill hole, Hawai’i. The basalts show
limited variations in both 176Hf/177Hf and 143Nd/144Nd (ε
Nd varies from +4.2 to +7.3 and ε
Hf from +8.0 to +12.3). Their correlated variation has an R
2 of 0.86. The data form an array with a slope of 1.2 on an ε
Hf–ε
Nd isotope correlation diagram, while the slope of all Hawai’ian basalt data is 0.98. Both slopes are significantly shallower
than that of the mantle array of 1.4 defined by ocean island basalts. Previous studies have shown that a shallow slope in
Hf–Nd isotope space can be related to ancient pelagic sediments in the mantle source (Blichert-Toft et al. 1999; Salters and White 1998). However, the combined variations in Ko’olau basalts of Hf–Nd–Pb–Os isotopic compositions and trace element ratios, such
as La/Nb, Th/La and Sr/Nd, are not consistent with the simple addition of a sediment component to the mantle. We instead propose
that the shallow slope on the Hf–Nd isotope correlation diagram for Ko’olau shield stage basalts can be better explained if
the enriched endmember contains either an ancient oceanic lithosphere component or the high-176Hf/177Hf component observed in the Salt Lake Crater (SLC) peridotite xenoliths (which also have a depleted lithosphere origin).
Since Ko’olau basalts have high 187Os/188Os (0.135–0.160) and the SLC xenoliths have 187Os/188Os up to 0.13 (Lassiter et al. 2000) Os-isotopes are consistent with the latter being a component in the enriched Ko’olau source.
相似文献
Vincent J. M. SaltersEmail: |
2.
Françoise Andrieux-Loyer Afi Azandegbé Florian Caradec Xavier Philippon Roger Kérouel Agnès Youenou Jean-Louis Nicolas 《Aquatic Geochemistry》2014,20(6):573-611
This study aims to compare the impact of oyster cultures on diagenetic processes and the phosphorus cycle in the sediments of the Aber Benoît and the Rivière d’Auray, estuary of Brittany, France. Our results showed clear evidence of the seasonal impact of oyster cultures on sediment characteristics (grain size and organic matter parameters) and the phosphorus cycle, especially in the Aber Benoît. At this site, seasonal variations in sulfide and Fe concentrations in pore waters, as well as Fe–P concentrations in the solid phase, highlighted a shift from a system governed by iron reduction (Reference) to a system governed by sulfate reduction (beneath oyster). This could be partly explained by the increase in labile organic matter (i.e., biodeposits) beneath oysters, whose mineralization by sulfate led to high sulfide concentrations in pore waters (up to 4,475 µmol l?1). In turn, sulfide caused an enhanced release of phosphate in the summer, as adsorption sites for phosphate decreased through the formation of iron–sulfide compounds (FeS and FeS2). In the Aber Benoît, dissolved Fe/PO4 ratios could be used as an indicator of phosphate release into oxic water. Low Fe/PO4 ratios in the summer indicated higher effluxes of phosphate toward the water column (up to 47 µmol m?2 h?1). At other periods, Fe/PO4 ratios higher than 2 mol/mol indicated very low phosphate fluxes. In contrast, in the Rivière d’Auray, the occurrence of macroalgae, stranding regularly all over the site, clearly masked the impact of oyster cultures on sediment properties and the phosphorus cycle and made the use of Fe/PO4 ratios more difficult in terms of indicators of phosphate release. 相似文献
3.
Wahyudi A’an J. Rahmawati Susi Irawan Andri Hadiyanto Hadiyanto Prayudha Bayu Hafizt Muhammad Afdal Afdal Adi Novi S. Rustam Agustin Hernawan Udhi. E. Rahayu Yusmiana P. Iswari Marindah Y. Supriyadi Indarto H. Solihudin Tubagus Ati Restu Nur Afi Kepel Terry L. Kusumaningtyas Mariska A. Daulat August Salim Hadiwijaya L. Sudirman Nasir Suryono Devi D. Kiswara Wawan 《Ocean Science Journal》2020,55(1):85-97
Ocean Science Journal - Seagrass meadows provide critical ecosystem services for coastal areas, e.g., as nursery habitats for various fish species, help with water filtration of suspended sediment,... 相似文献
1