Geochemical evidence in the northeast Lau Basin for subduction of the Cook-Austral volcanic chain in the Tonga Trench

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 17 (2016): 1694–1724, doi:10.1002/2015GC006237.Lau Basin basalts host an array of geochemical signatures that suggest incorporation of enriched mantle source material often associated with intraplate hotspots, but the origin of these signatures remain uncertain. Geochemical signatures associated with mantle material entrained from the nearby Samoan hotspot are present in northwest Lau Basin lavas, and subducted seamounts from the Louisville hotspot track may contribute geochemical signatures to the Tonga Arc. However, lavas in the northeast Lau Basin (NELB) have unique enriched geochemical signatures that cannot be related to these hotspots, but can be attributed to the subduction of seamounts associated with the Cook-Austral volcanic lineament. Here we present geochemical data on a new suite of NELB lavas—ranging in 40Ar/39Ar age from 1.3 Ma to 0.365 ka—that have extreme signatures of geochemical enrichment, including lavas with the highest 206Pb/204Pb (19.580) and among the lowest 143Nd/144Nd (0.512697) encountered in the Lau Basin to date. These signatures are linked to the canonical EM1 (enriched mantle 1) and HIMU (high-μ = 238U/204Pb) mantle end-members, respectively. Using a plate reconstruction model, we show that older portions of the traces of two of the Cook-Austral hotspots that contributed volcanism to the Cook-Austral volcanic lineament—the Rarotonga and Rurutu hotspots—were potentially subducted in the Tonga Trench beneath the NELB. The geochemical signatures of the Rarotonga, Rurutu, and Samoan hotspots provide a compelling match to the extreme geochemical components observed in the new NELB lavas.NSF. Grant Number OCE-1153894, EAR-1347377, EAR-1145202, and EAR-1348082; French Agence Nationale de la Recherche Grant Number: ANR-10-BLANC-0603; NSF Grant Numbers: OCE-1154070, OCE-1232985, OCE-1153959 and OCE-14330972016-11-1

Geochemical evidence in the northeast Lau Basin for subduction of the Cook-Austral volcanic chain in the Tonga Trench

Lau Basin basalts host an array of geochemical signatures that suggest incorporation of enriched mantle source material often associated with intraplate hotspots, but the origin of these signatures remain uncertain. Geochemical signatures associated with mantle material entrained from the nearby Samoan hotspot are present in northwest Lau Basin lavas, and subducted seamounts from the Louisville hotspot track may contribute geochemical signatures to the Tonga Arc. However, lavas in the northeast Lau Basin (NELB) have unique enriched geochemical signatures that cannot be related to these hotspots, but can be attributed to the subduction of seamounts associated with the Cook-Austral volcanic lineament. Here we present geochemical data on a new suite of NELB lavas—ranging in ⁴⁰Ar/³⁹Ar age from 1.3 Ma to 0.365 ka—that have extreme signatures of geochemical enrichment, including lavas with the highest ²⁰⁶Pb/²⁰⁴Pb (19.580) and among the lowest ¹⁴³Nd/¹⁴⁴Nd (0.512697) encountered in the Lau Basin to date. These signatures are linked to the canonical EM1 (enriched mantle 1) and HIMU (high-μ = ²³⁸U/²⁰⁴Pb) mantle end-members, respectively. Using a plate reconstruction model, we show that older portions of the traces of two of the Cook-Austral hotspots that contributed volcanism to the Cook-Austral volcanic lineament—the Rarotonga and Rurutu hotspots—were potentially subducted in the Tonga Trench beneath the NELB. The geochemical signatures of the Rarotonga, Rurutu, and Samoan hotspots provide a compelling match to the extreme geochemical components observed in the new NELB lavas.Keywords: subduction, Cook-Australs, Lau Basin, geochemistry, Samo

Waste handling and packaging plant project description

ORNL currently has about 300 m{sup 3} of remote handled transuranic (RHTRU) solid waste retrievably stored in trenches and a bunker. This material will be processed through the Waste Handling and Packaging Plant (WHDP) for shipment to the Waste Isolation Pilot Plant (WIPP). Details of siting, construction, and conceptual flow of RHTRU waste through the plant are provided. ORNL also has liquid waste and sludge stored in the Melton Valley Storage Tanks (MVST). The sludge also contains TRU waste, and the WHPP will process an expected volume of 500,000 gallons of a suernatant/sludge slurry for shipment to the WIPP. Specific systems which require more development include the cask transfer system, the linear accelerator-based nondestructive assay and nondestructive evaluation equipment. (MHB

Kinetic and crystallographic studies of a redesigned manganese-binding site in cytochrome c peroxidase

Manganese peroxidase (MnP) from the white rot fungus Phanerochaete chrysosporium contains a manganese-binding site that plays a critical role in its function. Previously, a MnII-binding site was designed into cytochrome c peroxidase (CcP) based on sequence homology (Yeung et al. in Chem. Biol. 4:215-222, 1997; Gengenbach et al. in Biochemistry 38:11425-11432, 1999). Here, we report a redesign of this site based on X-ray structural comparison of MnP and CcP. The variant, CcP(D37E, V45E, H181E), displays 2.5-fold higher catalytic efficiency (kcat/KM) than the variant in the original design, mostly due to a stronger KM of 1.9 mM (vs. 4.1 mM). High-resolution X-ray crystal structures of a metal-free form and a form with CoII at the designed MnII site were also obtained. The metal ion in the engineered metal-binding site overlays well with Mn II bound in MnP, suggesting that this variant is the closest structural model of the MnII-binding site in MnP for which a crystal structure exists. A major difference arises in the distances of the ligands to the metal; the metal-ligand interactions in the CcP variant are much weaker than the corresponding interactions in MnP, probably owing to partial occupancy of metal ion at the designed site, difference in the identity of metal ions (CoII rather than MnII) and other interactions in the second coordination sphere. These results indicate that the metal ion, the ligands, and the environment around the metal-binding site play important roles in tuning the structure and function of metalloenzymes. © 2006 SBIC

Disability sports coaching: towards a critical understanding

This paper is Closed Access.The growing work that addresses coaching disabled athletes has thus far failed to engage with the field of disability studies, and as a result misses a crucial opportunity to develop a critical understanding of coach learning and practice in disability sport. Therefore, the aim of this paper is to bridge the gap between coaching and disability studies and to review critically the current literature in coaching, in order to problematise some of the assumptions that underpin disability coaching research. Disability studies, and in particular the models of disability, are an important first step in a critical understanding in disability sport coaching. The models of disability provide a lens through which researchers, coach educators and coaches can question how they learn to coach disabled athletes, interrogate knowledge about impairment and disability, and critically evaluate coaching practice. In connecting with disability studies, we hope to help coaches and researchers make sense of how they position disability, and appreciate how coaching knowledge and practice are produced in context. In turn, we feel that such critical understandings have the potential to develop nuanced and sophisticated ways of thinking about, and developing, disability sports coaching