Poems

Poems include: Sometimes, I Like to Walk the Shore, by Michelle L. Haymon and Transitory, by Dick Pearso

Anisotropy in seafloor flange, slab, and crust samples from measurements of permeability and porosity : implications for fluid flow and deposit evolution

Author Posting. © American Geophysical Union, 2012. 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 13 (2012): Q03018, doi:10.1029/2011GC003840.Seafloor hydrothermal vents accommodate the convective transfer of fluids from subsurface environments to the oceans. In addition to black smoker chimneys, a variety of other deposit-types form. Flanges protrude from the sides of edifices as horizontal ledges, below which vent fluids pool. Slabs are hydrothermally silicified layered volcaniclastic deposits. Crusts are deposits composed of previously deposited material underlain by hot fluids. Permeability and porosity measurements were conducted on flanges from Guaymas Basin and the Main Endeavour Vent Field, slabs from the Lucky Strike Vent Field, and a crust sample from the Trans-Atlantic Geotraverse (TAG) active mound. Cores taken parallel to textural layers have high permeabilities (≈10−12 m2) and porosities (30–40%) that follow a power law relationship with exponent α ≈ 1 to 2. Cores taken perpendicular to layering have permeabilities from 10−16 to 10−12 m2 and porosities from 20 to 45%, with α ≈ 5 to 8. The two distinct trends result from the heterogeneity of textural layers within these deposits. Microstructural observations show large variations in grain packing and pore distributions between layers, consistent with flow perpendicular to layering being more susceptible to changes in permeability that result from mineral precipitation than flow parallel to layering. These results imply that the primary flow direction in these deposits is parallel to layering, whereas flow perpendicular to layering is more restricted. Quantification of anisotropic permeability provides important constraints for determination of fluid flux from these layered deposits, and temperatures, chemistry, and availability of nutrients to organisms living in and at exteriors of deposits.This work was supported by the National Science Foundation under grants EAR-0741339 and OCE-0648337. Partial support for JG and WZ from DOE # DEFG0207ER15916 is also acknowledged.2012-09-2

High-Resolution Surveys Along the Hot Spot–Affected Galapagos Spreading Center: 1. Distribution of Hydrothermal Activity

The spatial density of hydrothermal activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on hydrothermal activity using high-resolution mapping of plumes overlying the hot spot–affected Galapagos Spreading Center from 95o to 89o42\u27W (~560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid-ocean ridge with a similar magmatic budget. Plume distributions on the Galapagos Spreading Center were uncorrelated with abrupt variations in the depth of the along-axis melt lens, so these variations are apparently not controlled by hydrothermal cooling differences. We also found no statistical difference (for a significance level of 0.05) in plume incidence between where the seismically imaged melt lens is shallow (2 ± 0.56 km, ph = 0.108 ± 0.045) and where it is deep (3.4 ± 0.7 km, ph = 0.121 ± 0.015). The Galapagos Spreading Center thus joins mid-ocean ridges near the Iceland (Reykjanes Ridge), St. Paul-Amsterdam (South East Indian Ridge), and Ascension (Mid- Atlantic Ridge) hot spots as locations of anomalously scarce high-temperature venting. This scarcity implies that convective cooling along hot spot–affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid-ocean ridges

Submeter bathymetric mapping of volcanic and hydrothermal features on the East Pacific Rise crest at 9°50′N

Author Posting. © American Geophysical Union, 2007. 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 8 (2007): Q01006, doi:10.1029/2006GC001333.Recent advances in underwater vehicle navigation and sonar technology now permit detailed mapping of complex seafloor bathymetry found at mid-ocean ridge crests. Imagenex 881 (675 kHz) scanning sonar data collected during low-altitude (~5 m) surveys conducted with DSV Alvin were used to produce submeter resolution bathymetric maps of five hydrothermal vent areas at the East Pacific Rise (EPR) Ridge2000 Integrated Study Site (9°50′N, “bull's-eye”). Data were collected during 29 dives in 2004 and 2005 and were merged through a grid rectification technique to create high-resolution (0.5 m grid) composite maps. These are the first submeter bathymetric maps generated with a scanning sonar mounted on Alvin. The composite maps can be used to quantify the dimensions of meter-scale volcanic and hydrothermal features within the EPR axial summit trough (AST) including hydrothermal vent structures, lava pillars, collapse areas, the trough walls, and primary volcanic fissures. Existing Autonomous Benthic Explorer (ABE) bathymetry data (675 kHz scanning sonar) collected at this site provide the broader geologic context necessary to interpret the meter-scale features resolved in the composite maps. The grid rectification technique we employed can be used to optimize vehicle time by permitting the creation of high-resolution bathymetry maps from data collected during multiple, coordinated, short-duration surveys after primary dive objectives are met. This method can also be used to colocate future near-bottom sonar data sets within the high-resolution composite maps, enabling quantification of bathymetric changes associated with active volcanic, hydrothermal and tectonic processes.This work was supported by an NSF Ridge2000 fellowship to V.L.F. and a Woods Hole Oceanographic Institution fellowship supported by the W. Alan Clark Senior Scientist Chair (D.J.F.). Funding was also provided by the Censsis Engineering Research Center of the National Science Foundation under grant EEC-9986821. Support for field and laboratory studies was provided by the National Science Foundation under grants OCE-9819261 (D.J.F. and M.T.), OCE-0096468 (D.J.F. and T.S.), OCE-0328117 (SMC), OCE-0525863 (D.J.F. and S.A.S.), OCE-0112737 ATM-0427220 (L.L.W.), and OCE- 0327261 and OCE-0328117 (T.S.). Additional support was provided by The Edwin Link Foundation (J.C.K.)

Hydrothermal circulation at the Cleft-Vance overlapping spreading center : results of a magnetometric resistivity survey

We report on a magnetometric resistivity sounding carried out in the overlapping spreading center between the Cleft and Vance segments of the Juan de Fuca Ridge. The data collected reveal a strong three dimensionality in the crustal electrical resistivity structure on wavelengths of a few kilometers. Areas of reduced crustal electrical resistivities, with values approaching that of seawater, are seen beneath the neovolcanic zones of both active spreading centers. We interpret these reduced resistivities as evidence of active hydrothermal circulation within the uppermost 1 km of hot, young oceanic crust

Navigational infrastructure at the East Pacific Rise 9°50′N area following the 2005–2006 eruption : seafloor benchmarks and near-bottom multibeam surveys

Author Posting. © American Geophysical Union, 2008. 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 9 (2008):Q11T04, doi:10.1029/2008GC002070.Four seafloor benchmarks were deployed with ROV Jason2 at frequently visited areas along the northern East Pacific Rise (NEPR) ridge crest near 9°50′N, within the Ridge2000 EPR integrated study site (ISS) bull's eye. When used in concert with established deep-ocean acoustic positioning techniques, these benchmarks provide navigational infrastructure to facilitate the integration of near-bottom data at this site by allowing efficient and quantitative coregistration of data and observations collected on multiple dives and over multiple cruises. High-resolution, near-bottom multibeam bathymetric surveys also were conducted along and across the ridge crest to provide a morphological and geological context for the benchmark areas. We describe the navigation and data processing techniques used to constrain the benchmark positions and outline operational details to effectively use benchmarks at this and other deep-ocean sites where multidisciplinary time series studies are conducted. The well-constrained positions of the benchmarks provide a consistent geospatial framework that can be used to limit navigational uncertainties during seafloor sampling and mapping programs and enable accurate spatial coregistration and integration of observations. These data are important to test a range of multidisciplinary hypotheses that seek to link geological, chemical, and biological processes associated with crustal accretion and energy transfer from the mantle to the hydrosphere at mid-ocean ridges

Origin of high Mg and SO 4 fluids in sediments of the Terceira Rift, Azores – indications for caminite dissolution in a waning hydrothermal system

During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyper‐slow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2800 m water depth show an anomalous composition with Mg, SO4, and total alkalinity (TA) concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25Mg(OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite, and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection towards the seafloor

Biallelic variants in WARS1 cause a highly variable neurodevelopmental syndrome and implicate a critical exon for normal auditory function

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes for faithful assignment of amino acids to their cognate tRNA. Variants in ARS genes are frequently associated with clinically heterogeneous phenotypes in humans and follow both autosomal dominant or recessive inheritance patterns in many instances. Variants in tryptophanyl-tRNA synthetase 1 (WARS1) cause autosomal dominantly inherited distal hereditary motor neuropathy and Charcot-Marie-Tooth disease. Presently, only one family with biallelic WARS1 variants has been described. We present three affected individuals from two families with biallelic variants (p.Met1? and p.(Asp419Asn)) in WARS1, showing varying severities of developmental delay and intellectual disability. Hearing impairment and microcephaly, as well as abnormalities of the brain, skeletal system, movement/gait, and behavior were variable features. Phenotyping of knocked down wars-1 in a C. elegans model showed depletion is associated with defects in germ cell development. A wars1 knockout vertebrate model recapitulates the human clinical phenotypes, confirms variant pathogenicity and uncovers evidence implicating the p.Met1? variant as potentially impacting an exon critical for normal hearing. Together, our findings provide consolidating evidence for biallelic disruption of WARS1 as causal for an autosomal recessive neurodevelopmental syndrome and present a vertebrate model that recapitulates key phenotypes observed in patients. This article is protected by copyright. All rights reserved

Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis

Mineralogical and geochemical features of sulfide chimneys from the 49°39′E hydrothermal field on the Southwest Indian Ridge and their geological inferences

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chinese Science Bulletin 56 (2011): 2828-2838, doi:10.1007/s11434-011-4619-4.During January–May in 2007, the Chinese research cruise DY115-19 discovered an active hydrothermal field at 49°39′E/37°47′S on the ultraslow spreading Southwest Indian Ridge (SWIR). This was also the first active hydrothermal field found along an ultraslow-spreading ridge. We analyzed mineralogical, textural and geochemical compositions of the sulfide chimneys obtained from the 49°39′E field. Chimney samples show a concentric mineral zone around the fluid channel. The mineral assemblages of the interiors consist mainly of chalcopyrite, with pyrite and sphalerite as minor constitunets. In the intermediate portion, pyrite becomes the dominant mineral, with chalcopyrite and sphalerite as minor constitunets. For the outer wall, the majority of minerals are pyrite and sphalerite, with few chalcopyrite. Towards the outer margin of the chimney wall, the mineral grains become small and irregular in shape gradually, while minerals within interstices are abundant. These features are similar to those chimney edifices found on the East Pacific Rise and Mid-Atlantic Ridge. The average contents of Cu, Fe and Zn in our chimney samples were 2.83 wt%, 45.6 wt% and 3.28 wt%, respectively. The average Au and Ag contents were up to 2.0 ppm and 70.2 ppm respectively, higher than the massive sulfides from most hydrothermal fields along mid-ocean ridge. The rare earth elements geochemistry of the sulfide chimneys show a pattern distinctive from the sulfides recovered from typical hydrothermal fields along sediment-starved mid-ocean ridge, with the enrichment of light rare earth elements but the weak, mostly negative, Eu anomaly. This is attributed to the distinct mineralization environment or fluid compositions in this area.This work was supported by the China Ocean Mineral Resources Research and Development Association Program (DY115- 02-1-01) and the State Oceanic Administration Youth Science Fund (2010318)