588 research outputs found
Alteration and vein mineralisation within the Lizard complex, south Cornwall: Constraints on the timing of serpentinisation.
Two distinct episodes of serpentinisation have been identified within the peridotites of the Lizard complex. The first episode (primary serpentinisation) is represented by the complex and pervasive hydration of the Lizard peridotite. The second (later) episode is characterised by a pale to dark green, pseudo-fibrous mixture of lizardite and chrysotile that is restricted to fractures (vein serpentine). Mineralised north-north-west and east-north-east trending fault zones contain fragments of vein serpentine generated during this second episode. Faults with similar orientations and mineralogy within the gabbro unit contain adularia which have been previously elated by Ar-10-Ar-39 and K-Ar methods at 210-220 Ma (Triassic). Stable isotope ratios indicate that the mineralisation within the gabbro and peridotite is genetically similar. The primary and secondary serpentinisation episodes are therefore interpreted as pre-Triassic in age. A latest Carboniferous to early Permian age is proposed for the formation of vein serpentine and a late Devonian to Carboniferous age is proposed for the primary serpentinisation episode. This is envisaged to have taken place post-obduction but a pre-obduction initiation of serpentinisation cannot be discounted
Baseline geochemistry of Devonian low-grade metasedimentary rocks in Cornwall: preliminary data and environmental significance.
Geochemical baseline data provide information on the state of the environment before modification by mining and other
anthropogenic activities. A summary of the analyses of 41 elements on 100 samples from Devonian metasedimentary rocks away
from areas of mineralization and granite intrusions in Cornwall are presented. The data show a remarkable consistency. Differences
in major elements can be related largely to changes in mineral proportion expected from grain size variations within the sedimentary
rocks. The trace element data indicate that similar types of sediment accumulated in the Gramscatho, Looe and Trevone basins and
that subsequent metamorphism has not significantly re-distributed elements. Compared with an average UK Lower Palaeozoic shale
and the North American Shale Composite, the Devonian metasedimentary rocks of Cornwall appear to be marginally depleted in
many trace elements. Values for As, Ni and Cr frequently exceed published soil guideline values, especially in mudstones, which brings
into question the issue of the identification of land, which is considered to be polluted
A re-interpretation of the internal structure of the Lizard complex ophiolite, south Cornwall.
publication-status: PublishedPrevious models for the tectonic-stratigraphy of the Lizard complex ophiolite have proposed three thrust-bounded units. However, our studies indicate that post-obduction extensional faulting may have exerted a hitherto unrecognised effect on the present distribution of lithologies. Field and previously published geophysical evidence suggest that the uppermost tectonic unit (the Crousa Downs Unit) represents the downfaulted upper levels of the Goonhilly Downs Unit. Deformed lithologies previously thought to be part of the Goonhilly Downs Unit are reassigned to the underlying Basal Unit. A revised model for the tectonic-stratigraphy is presented. The Basal Nappe is underlain by the Basal Thrust and comprises the Traboe schists, the Landewednack schists and the Old Lizard Head Series. The Goonhilly Downs Nappe, underlain by the Goonhilly Downs Thrust, structurally overlies the Basal Nappe and comprises serpentinised peridotite, Trelan and Crousa Gabbro and the Porthoustock Sheeted Dyke Complex. This work highlights the importance of late- to post-Variscan extensional deformation in south Cornwall
The Geodiversity Profile Handbook
Mineral Industry Research Organisation: Aggregates Sustainability Levy Fun
Access and safety at geological sites: a manual for landowners, quarry operators and the geological visitor
Mineral Industry Research Organisation: Aggregates Sustainability Levy Fun
Two-dimensional Packing in Prolate Granular Materials
We investigate the two-dimensional packing of extremely prolate (aspect ratio
) granular materials, comparing experiments with Monte-Carlo
simulations. The average packing fraction of particles with aspect ratio
is . We quantify the orientational correlation of
particles and find a correlation length of two particle lengths. The functional
form of the decay of orientational correlation is the same in both experiments
and simulations spanning three orders of magnitude in aspect ratio. This
function decays over a distance of two particle lengths. It is possible to
identify voids in the pile with sizes ranging over two orders of magnitude. The
experimental void distribution function is a power law with exponent
. Void distributions in simulated piles do not decay as a
power law, but do show a broad tail. We extend the simulation to investigate
the scaling at very large aspect ratios. A geometric argument predicts the pile
number density to scale as . Simulations do indeed scale this way,
but particle alignment complicates the picture, and the actual number densities
are quite a bit larger than predicted.Comment: 6 pages + 10 ps/eps figure
Treatment regimens and outcomes in severe and moderate haemophilia A in the UK: The THUNDER study
Introduction: The THUNDER study provides an analysis of treatment patterns and outcomes in UK patients with severe or moderate haemophilia A (SHA/MHA) in 2015.
Methods: Patients with SHA or MHA registered with the UK National Haemophilia Database (NHD) were segregated by severity, inhibitor status and age. Haemophilia joint health score (HJHS) was derived from NHD records and treatment regimen and annualized bleed/jointâbleed rate (ABR/AJBR) from Haemtrack (HT) in HTâcompliant patients.
Results: We report 1810 patients with SHA and 864 with MHA. Prophylaxis was used in 94.9% (n = 130/137) of HTâcompliant children <12 years with SHA, falling to 74.1% (n = 123/166) aged â„40 years. Median ABR increased with age (1.0, IQR 0.0â5.0, <12 years; 3.0 IQR, 1.0â8.0, â„40 years). Inhibitors were present in 159 (8.8%) SHA and 34 (3.9%) MHA. Median ABR increased from 2.0 (<12 years) to 21.(â„40 years) in SHA inhibitor patients using prophylaxis. Prophylaxis was used by 68.8% of HTâcompliant MHA patients (n = 106) (median FVIII baseline 0.01 IU/mL) associated with a median (IQR) ABR of 3.0 (1.0â7.0). Median HJHS (n = 453) increased with age in SHA and MHA. Median (IQR) HJHS was higher in SHA inhibitor (17.0, 0.0â64.5) than nonâ or past inhibitor patients (7.0, 0.0â23.0).
Conclusions: Increasing ABR with age persists despite current prophylaxis regimens.SHA and MHA had similar ABR/AJBR and HJHS, leading to a suspicion that a subgroup of MHA may be relatively undertreated. More intensive prophylaxis may improve outcomes, but this requires further study
PREDICTING THE SUMMER TEMPERATURE OF SMALL STREAMS IN SOUTHWESTERN WISCONSIN 1
One of the biggest challenges in managing cold water streams in the Midwest is understanding how stream temperature is controlled by the complex interactions among meteorologic processes, channel geometry, and ground water inflow. Inflow of cold ground water, shade provided by riparian vegetation, and channel width are the most important factors controlling summer stream temperatures. A simple screening model was used to quantitatively evaluate the importance of these factors and guide management decisions. The model uses an analytical solution to the heat transport equation to predict steady-state temperature throughout a stream reach. The model matches field data from four streams in southwestern Wisconsin quite well (typically within 1°C) and helps explain the observed warming and cooling trends along each stream reach. The distribution of ground water inflow throughout a stream reach has an important influence on stream temperature, and springs are especially effective at providing thermal refuge for fish. Although simple, this model provides insight into the importance of ground water and the impact different management strategies, such as planting trees to increase shade, may have on summer stream temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74032/1/j.1752-1688.2005.tb03714.x.pd
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