Thermal modelling of the Cheshire Basin using BasinModTM

The Cheshire Basin is a half-graben formed as one of a series of sedimentary basins during Permo-Triassic rifting. The Permo-Triassic infill of this basin may have been up to four or five kilometres thick prior to geologically recent erosion. The basin is flanked to the East and West by Carboniferous and older rocks. The succession in this region displays widespread uplift and erosion resulting from northward encroachment of the Variscan Front at the end of the Carboniferous. This report details the development of 1-D thermal models and integration to a 2-D model of the Cheshire Basin. BasinModTM (Platte River Software) has been used to model compaction and temperature through burial over geological time using a variety of datasets. The report considers the Cheshire Basin area through the Carboniferous to the present day, concentrating on the late Carboniferous Coal Measures where maturity data are available. Heat flow in this region was assumed to be generally high during the latest Carboniferous to early Permian. Modelled isotherms and maturity plots imply that the greatest temperatures attained in the productive Coal Measures occurred during Permian to Cretaceous burial in the basin centre, and during late Carboniferous to Permian time outside of the basin. The 1-D models imply that some Carboniferous Coal Measures reached the oil generation window. Minor oil stains and shows were found in some Cheshire Basin boreholes. However there does not appear to be a suitable trap to create a commercially viable reservoir. The BasinMod model results and this best practice report with accompanying checklist and guidelines are stored electronically for the DGSM

The calcified seaweed (maerl) deposits of the Falkland Islands

Scattered across many foreshore areas around the Falkland Islands (Fig. 1) are fragments of white, limy material derived from carbonate-fixing, marine red algae. Locally, the limy detritus is sufficiently abundant to have built-up substantial beach deposits. In their report accompanying publication of the 1:250 000 scale geological maps of the islands, Aldiss and Edwards (1998) drew attention to the potential importance of these deposits as a source of agricultural lime, particularly in the absence of any other indigenous source of limestone. Very similar material has been exploited elsewhere in the world for both agricultural and horticultural use; for example, sub-tidal banks were extensively dredged in the English Channel off Cornwall and Brittanny. There, the limy, algal debris is referred to generically as Lithothamion, and commercially as maerl. The equivalent material in the Falkland Islands is known locally as calcified seaweed

Dioctahedral mixed K-Na-micas and paragonite in diagenetic to low-temperature metamorphic terrains: bulk rock chemical, thermodynamic and textural constraints

Abstract Metamorphic mineral assemblages in low-temperature metaclastic rocks often contain paragonite and/or its precursor metastable phase (mixed K-Na-white mica). Relationships between the bulk rock major element chemistries and the formation of paragonite at seven localities from Central and SE-Europe were studied, comparing the bulk chemical characteristics with mineral assemblage, mineral chemical and metamorphic petrological data. Considerable overlaps between the projection fields of bulk chemistries of the Pg-free and Pg-bearing metaclastic rocks indicate significant differences between the actual (as analyzed) and effective bulk chemical compositions. Where inherited, clastic, inert phases/constituents were excluded, it was found that a decrease in Na/(Na+Al*) and in K/(K+Al*) ratios of rocks favors the formation and occurrence of Pg and its precursor phases (Al* denotes here the atomic quantity of aluminum in feldspars, white micas and “pure” hydrous or anhydrous aluminosilicates). In contrast to earlier suggestions, enrichment in Na and/or an increase in Na/K ratio by themselves do not lead to formation of paragonite. Bulk rock chemistries favorable to formation of paragonite and its precursor phases are characterized by enrichment in Al and depletion in Na, K, Ca (and also, Mg and Fe2+). Such bulk rock chemistries are characteristic of chemically “mature” (strongly weathered) source rocks of the pelites and may also be formed by synand post-sedimentary magmatism-related hydrothermal (leaching) activity. What part of the whole rock is active in determining the effective bulk chemistry was investigated by textural examination of diagenetic and anchizone-grade samples. It is hypothesized that although solid phases act as local sources and sinks, transport of elements such as Na through the grain boundaries have much larger communication distances. Sodium-rich white micas nucleate heterogeneously using existing phyllosilicates as templates and are distributed widely on the thin section scale. The results of modeling by THERMOCALC suggest that paragonite preferably forms at higher pressures in low-T metapelites. The stability fields of Pg-bearing assemblages increase, the Pg-in reaction line is shifted towards lower pressures, while the stability field of the Chl-Ms-Ab-Qtz assemblage decreases and is shifted towards higher temperatures with increasing Al* content and decreasing Na/(Na+Al*) and K/(K+Al*) ratios

Associations of autozygosity with a broad range of human phenotypes

In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (F-ROH) for >1.4 million individuals, we show that F-ROH is significantly associated (p <0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: F-ROH equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44-66%] in the odds of having children. Finally, the effects of F-ROH are confirmed within full-sibling pairs, where the variation in F-ROH is independent of all environmental confounding.Peer reviewe

The Majorana Demonstrator: Progress towards showing the feasibility of a tonne-scale 76Ge neutrinoless double-beta decay experiment

The Majorana Demonstrator will search for the neutrinoless double-beta decay (0vββ) of the 76Ge isotope with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate the neutrino is its own anti-particle, demonstrate that lepton number is not conserved, and provide information on the absolute mass-scale of the neutrino. The Demonstrator is being assembled at the 4850 foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be contained in a low-background environment and surrounded by passive and active shielding. The goals for the Demonstrator are: demonstrating a background rate less than 3 t-1 y-1 in the 4 keV region of interest (ROI) surrounding the 2039 keV 76Ge endpoint energy; establishing the technology required to build a tonne-scale germanium based double-beta decay experiment; testing the recent claim of observation of 0vββ [1]; and performing a direct search for light WIMPs (3-10 GeV/c2)

The MAJORANA experiment: An ultra-low background search for neutrinoless double-beta decay

The observation of neutrinoless double-beta decay would resolve the Majorana nature of the neutrino and could provide information on the absolute scale of the neutrino mass. The initial phase of the MAJORANA experiment, known as the DEMONSTRATOR, will house 40 kg of Ge in an ultra-low background shielded environment at the 4850' level of the Sanford Underground Laboratory in Lead, SD. The objective of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a narrow region of interest around the 76Ge neutrinoless double-beta decay peak

Characteristics of signals originating near the lithium-diffused N+ contact of high purity germanium p-type point contact detectors

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein

Search for Neutrinoless Double- β Decay in Ge 76 with the Majorana Demonstrator

The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in Ge76. The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in Ge76) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Qββ and a very low background with no observed candidate events in 9.95 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of 1.9×1025 yr (90% C.L.). This result constrains the effective Majorana neutrino mass to below 240-520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4.0-2.5+3.1 counts/(FWHM t yr)

Metamorphism of the Lower Palaeozoic rocks of the Leadhills district, southern Scotland, 1:50K sheets 15E & 23E

Systematic studies of metapelitic grade linked with the geological re-survey of the Southern Uplands have been used to generate a series of contoured metamorphic maps which currently cover nearly two-thirds of the Lower Palaeozoic terrane. These studies have used X-ray diffraction (XRD) measurements of clay mineral reaction progress, particularly white mica (illite) crystallinity, to delineate zones of diagenesis and low-grade metamorphism in the imbricated Ordovician and Silurian strata. Although the regional pattern revealed by metapelitic zonal sequences shows considerable variations in metamorphic trends, patterns of increasing grade from older into younger strata suggest that accretionary burial was the main cause of regional metamorphism (Merriman & Roberts, in press). These patterns also reflect the different levels of exhumation of the terrane, by both normal movement on reactivated thrust faults and differential block movement on north-north-west-trending faults

Metamorphism of the Palaeozoic rocks of the Torquay district, Devon, 1:50k sheet 350

The pattern of regional metamorphism indicated by illite crystallinity has been used to interpret the tectonic and thermal history of the Torquay district. The metamorphic pattern is primarily related to the fold-and-thrust geometry but has been modified by later NW-trending faults. Areas of lower grades are associated with limestone and volcanic rock formed on the Torquay and Brixham basin highs that were generated by listric fault block rotation during passive margin rifting. Anchizonal grade associated with these rocks indicates burial under an overburden thickness of at least 5 km. The source of the overburden was the frontal portion of a thrust stack that advanced northwards as the rift system contracted and inverted. The tectonically thickened rear of the stack is represented by epizonal rocks cropping out in the southwest of the district. These rocks formed at temperatures of 300-350ºC under a tectonic overburden of at least 7 km