Geochemistry of Atlantis Massif crust

The Atlantis Massif (Mid-Atlantic Ridge, 30°N) is an oceanic core complex marked by distinct variations in crustal architecture, deformation and metamorphism over distances of at least 5 km. We report Sr and Nd isotope data and Rare Earth Element (REE) concentrations of gabbroic and ultramafic rocks drilled at the central dome (IODP Hole 1309D) and recovered by submersible from the southern ridge of the massif that underlie the peridotite-hosted Lost City Hydrothermal Field. Systematic variations between the two areas document variations in seawater penetration and degree of fluid-rock interaction during uplift and emplacement of the massif and hydrothermal activity associated with the formation of Lost City. Homogeneous Sr and Nd isotope compositions of the gabbroic rocks from the two areas (87Sr/86Sr: 0.70261-0.70429 and epsilon-Nd: +9.1 to +12.1) indicate an origin from a depleted mantle. At the central dome, serpentinized peridotites are rare and show elevated seawater-like Sr isotope compositions related to serpentinization at shallow crustal levels, whereas unaltered mantle isotopic compositions preserved in the gabbroic rocks attest to limited seawater interaction at depth. This portion of the massif remained relatively unaffected by Lost City hydrothermal activity. In contrast, pervasive alteration and seawater-like Sr and Nd isotope compositions of serpentinites at the southern wall (87Sr/86Sr: 0.70885-0.70918; epsilon-Nd: -4.7 to +11.3) indicate very high fluid-rock ratios (~20 and up to 10**6) and enhanced fluid fluxes during hydrothermal circulation. Our studies show that Nd isotopes are most sensitive to high fluid fluxes and are thus an important geochemical tracer for quantification of water-rock ratios in hydrothermal systems. Our results suggest that high fluxes and long-lived serpentinization processes may be critical to the formation of Lost City-type systems and that normal faulting and mass wasting in the south facilitate seawater penetration necessary to sustain hydrothermal activity.

Sulphur mineralogy and geochemistry of serpentinites and gabbros from the Atlantis Massif

In-situ uplifted portions of oceanic crust at the central dome of the Atlantis Massif (Mid-Atlantic Ridge, 30°N) were drilled during Expeditions 304 and 305 of the Integrated Ocean Drilling Program (IODP) and a 1.4 km section of predominantly gabbroic rocks with minor intercalated ultramafic rocks were recovered. Here we characterize variations in sulfur mineralogy and geochemistry of selected samples of serpentinized peridotites, olivine-rich troctolites and diverse gabbroic rocks recovered from Hole 1309D. These data are used to constrain alteration processes and redox conditions and are compared with the basement rocks of the southern wall of the Atlantis Massif, which hosts the Lost City Hydrothermal Field, 5 km to the south. The oceanic crust at the central dome is characterized by Ni-rich sulfides reflecting reducing conditions and limited seawater circulation. During uplift and exhumation, seawater interaction in gabbroic-dominated domains was limited, as indicated by homogeneous mantle-like sulfur contents and isotope compositions of gabbroic rocks and olivine-rich troctolites. Local variations from mantle compositions are related to magmatic variability or to interaction with seawater-derived fluids channeled along fault zones. The concomitant occurrence of mackinawite in olivine-rich troctolites and an anhydrite vein in a gabbro provide temperature constraints of 150-200 °C for late circulating fluids along local brittle faults below 700 m depth. In contrast, the ultramafic lithologies at the central dome represent domains with higher seawater fluxes and higher degrees of alteration and show distinct changes in sulfur geochemistry. The serpentinites in the upper part of the hole are characterized by high total sulfide contents, high d34Ssulfide values and low d34Ssulfate values, which reflect a multistage history primarily controlled by seawater-gabbro interaction and subsequent serpentinization. The basement rocks at the central dome record lower oxygen fugacities and more limited fluid fluxes compared with the serpentinites and gabbros of the Lost City hydrothermal system. Our studies are consistent with previous results and indicate that sulfur speciation and sulfur isotope compositions of altered oceanic mantle sequences commonly evolve over time. Heterogeneities in sulfur geochemistry reflect the fact that serpentinites are highly sensitive to local variations in fluid fluxes, temperature, oxygen and sulfur fugacities, and microbial activity.

Nicklinson v Ministry of Justice [2012] 304 (QB) : further UK developments regarding a person's right to choose when and how to die : assisted termination of life

UK High Court decision - application for declarations legitimising third party assistance in voluntary termination of life - facts - moral, social and ethical issues - analysis.

A Curious Harpour in Helle : An Edition of the Commentary on the Orpheus Metre of De consolatione philosophiae in MS Thott 304,2

Tutkielmani on tekstieditio keskiaikaisesta kommentaarista, joka löytyy Kööpenhaminan Kuninkaallisen kirjaston käsikirjoituksesta Thott 304,2. Käsikirjoitus voidaan ajoittaa 1400-luvun ensimmäiselle neljännekselle ja se on kirjoitettu keskienglanniksi. Se sisältää John Waltonin runomuotoisen käännöksen Boethiuksen 500-luvun alussa latinaksi kirjoittamasta teoksesta De consolatione philosophiae (Filosofian lohdutus) sekä teosta kommentoivan proosamuotoisen kommentaarin. Käsikirjoitus on vaillinainen, mutta sen säilyneet foliot ovat enimmäkseen erittäin hyväkuntoisia. Itse käsikirjoitusta on tutkittu vain muutamissa artikkeleissa ja yhdessä tutkielmassa; kommentaarista ei ole toistaiseksi tehty kattavaa tutkimusta. Tavoitteeni onkin tuoda kommentaari keskiaikaisen filosofian, keskienglannin ja käsikirjoitusten tutkijoiden käytettäviin. Käsikirjoitus Thott 304,2 on esimerkki epätyypillisestä myöhäiskeskiaikaisesta maallikkomesenaattiudesta Englannissa. Tavanmukaisesti maallikkomesenaatit tukivat uskonnollisten tekstien tuottamista ja kääntämistä, kun taas Thott 304,2 sisältää käännöksen filosofisesta tekstistä. Sen lisäksi mesenaatti oli nainen, aatelistoon kuuluva Elizabeth Berkeley. Varsin harvinaiseksi käsikirjoituksen tekee sen painaminen kirjaksi 1500-luvun alussa. Kirjanpainajan käsikirjoituksen sivuille tekemistä merkinnöistä saadaan korvaamatonta tietoa varhaisesta painotekniikasta, sillä kirjanpainajien käyttämiä käsikirjoituskopioita ei ole säilynyt kovin runsaasti. Waltonin käännös on säilynyt yli kahdessakymmenessä käsikirjoituskopiossa, joista vain Thott 304,2 sisältää laajan kommentaarin. 1500-luvun painoksesta on jäljellä kolme kopiota, ja ne sisältävät saman kommentaarin kuin Thott 304,2. Valitsin editoitavaksi niin kutsuttua Orfeus-runoa kommentoivan osan kommentaarista, sillä se muodostaa ehjän kokonaisuuden ja sopii pituutensa puolesta Pro gradu -tutkielmaan. Orfeus-runo on myös yksi käsikirjoituksen kattavimmin kommentoiduista runoista. Editio on niin sanottu diplomaattinen transkriptio, jossa käsikirjoituksen piirteet on pyritty säilyttämään mahdollisimman tarkasti edition luettavuuden siitä kuitenkaan kärsimättä. Perinteisistä editioista poiketen tutkielmani sisältää myös kommentaarin ja Orfeus-runon transkriptiot, joissa rivijako, lyhenteet ja erikoismerkit on säilytetty. Näiden transkriptioiden toivon auttavan erityisesti käsikirjoituksessa esiintyvien lyhenteiden, erikoismerkkien ja kirjanpainajan merkintöjen tulkinnassa ja tutkimisessa. Editiota ja transkriptioita täydentävät nykyenglanniksi kirjoitettu lyhennelmä kommentaarista ja kuvat käsikirjoituksen sivuista, joilla editoimani kommentaari on. Tutkielmaan sisältyy alkuperäisen tekstin, käännöksen, kommentaarin ja käsikirjoituksen taustaa valottava osuus. Esittelen myös kaikki löytämäni lähteet, joissa käsikirjoitus on mainittu tai joissa sitä on tutkittu. Liitteeksi olen laatinut sanaston helpottamaan kommentaarin tulkitsemista.

Influence of cast versus wrought microstructure on the processing map for hot working of stainless steel type AISI 304

Processing maps for hot working of as-cast and wrought stainless steels of type AISI 304 have been developed in the temperature range 600 to 1250°C and strain rate range 0.001 to 100 s−1. The domain of dynamic recrystallization (DRX) in as-cast material occurs at higher temperatures (1250°C) and lower strain rates (0.001 s−1) than in the wrought steel (1100°C and 0.01 s−1). The effect is explained in terms of enhanced nucleation rate of DRX due to the carbide, ferrite particles, stable oxides/nitrides and second-phase intermetallics in the as-cast microstructure. The DRX domain is wider in the wrought material although the peak efficiency is less (32%) than in the as-cast case (40%). The flow instability regime is not significantly affected by the initial microstructure

Influence of strain rate and state-of-stress on the formation of ferrite in stainless steel type AISI 304 during hot working

The influence of strain rate and state-of-stress on the formation of ferrite in stainless steel type AISI 304L, 304 and 304 as-cast, during hot working has been studied. Compression and torsion tests were conducted in the temperature range 1100 to 1250 degrees C and strain rate range 0.001 to 100 s(-1) on these materials, Ferrite formation occurs during deformation at temperatures above 1150 degrees C and strain rates above 10 s(-1), in stainless steel type AISI 304L and 304. The tendency for the formation of ferrite is more in as-cast 304 than in wrought 304, In as-cast 304 the ferrite forms at lower temperatures and strain rates, The tendency for the ferrite formation is more in torsion than in compression.

Optimization of cold and warm workability in 304 stainless steel using instability maps

The deformation characteristics of stainless steel type AISI 3O4 under compression in the temperature range 20 degrees C to 600 degrees C and strain-rate range 0.001 to 100 s(-1) have been studied with a view to characterizing the flow instabilities occurring in the microstructure. At strain rates less than 5 s(-1), 304 stainless steel exhibits flow localization, whereas dynamic strain aging occurs at intermediate temperatures and below 0.5 s(-1). At room temperatures and strain rates less than 10 s(-1), martensite formation is observed. To avoid the preceding microstructural instabilities, cold and warm working should be carried out at strain rates greater than 5 s(-1). The continuum criterion, developed on the basis of the principles of maximum rate of entropy production and separability of the dissipation function, predicts accurately all the preceding instability features.

Influence of carbide particles on the dynamic recrystallization of as-cast 304 stainless steel: a study using secondary ion mass spectrometric (SIMS) analysis

The domain of dynamic recrystallization (DRX) in as-cast 304 stainless steel material occurs at higher temperatures (1250 degrees C) and lower strain rates (0.001 s(-1)) than in wrought 304 stainless steel (1100 degrees C and 0.01 s(-1)). The above result has been explained earlier on the basis of a simple theoretical DRX model involving the rate of nucleation versus rate of grain boundary migration. The present investigation is aimed at examining experimentally the influence of carbide particles on the DRX of ascast 304 using secondary ion mass spectrometric (SIMS) analysis. Isothermal compression tests at a constant true strain rate have been performed on wrought 304 and as-cast 304 materials in the temperature and strain rate ranges of 1000 to 1250 degrees C and 0.001 to 1 s(-1) respectively. The SIMS analysis carried out on the deformed samples revealed that the large carbides present in the as-cast 304 material strongly influence the DRX process. In as-cast 304 material, the presence of large carbide particles in the microstructure shifts the DRX domain to higher temperature and lower strain rate in comparison with wrought 304 material.