Seismic signature of subduction termination from teleseismic P- and S-wave arrival-time tomography : the case of northern Borneo

Acknowledgments S.P. acknowledges support from the Natural Environmental Research Council (NERC) Grant NE/R013500/1 and from the European Union's Horizon 2020 Research and Innovation Program under Marie Skłodowska-Curie Grant Agreement 790203. We thank the TanDEM-X Science Communication Team (German Aerospace Center (DLR) e.V.) for providing TanDEM topographic data. We thank the NERC Geophysical Equipment Facility for loan 1038 and seismometers loaned by the University of Cambridge and Aberdeen. We would like to thank Zhong-Hai Li and an anonymous reviewer for their constructive feedback during the review process.Peer reviewedPostprin

Mineral exploration in the Lower Palaeozoic rocks of south-west Cumbria. Part 1, regional surveys

The results of geochemical, geological and geophysical surveys over Lower Palaeozoic rocks in the south-western part of Cumbria are given in two reports. This report (Part 1) describes the results of a geochemical drainage survey and an examination of mineralised sites, and relates them to information from new geological mapping and an assessment of regional geophysical data. Part 2 contains details of follow-up surveys in the Black Combe inlier. The geochemical drainage survey, involving the collection and analysis of heavy mineral concentrates and stream sediment samples from 119 sites, found substantial antimony, arsenic, barium, bismuth, copper, iron, lead, tin, tungsten and zinc anomalies. Gold was reported for the first time from this part of the Lake District: small amounts were noted in panned concentrates from five sites. Other minerals identified in panned concentrates included arsenopyrite, baryte, bismutite, bismuthinite, cassiterite, chalcopyrite, cerussite, pyrite, pyromorphite, scheelite, sphalerite, stolzite and wolfram&e. The examination of old workings and outcrops revealed many undocumented occurrences of quartzsulphide vein-style mineralisation. The chemical analysis of samples taken from old workings and other occurrences confirmed field observations that locally, particularly in the Black Combe area, this mineralisation is polymetallic with variable amounts of arsenic, gold, bismuth, copper, lead, zinc and in a few cases antimony, barium, cobalt, nickel, tungsten and tin. Iron mineralisation occurs both as oxide (hematite) and sulphide deposits. Mercury was present in appreciable amounts in samples from the High Brow pyrite mine. The distribution of panned concentrate anomalies suggests that the vein-style mineralisation is polyphase and that individual phases may be zoned. Highest zinc anomalies occur near Torver and the highest lead on the west side of Black Combe. Tin and tungsten are restricted largely to the central part of Black Combe, and the most prominent arsenic and bismuth anomalies are found in the same area. Copper anomalies are widespread over the Skiddaw Group and the Borrowdale Volcanic Group. Barium anomalies indicate that baryte mineralisation is weak and localised, occurring principally within the Black Combe area and close to the Windermere Supergroup basal unconformity. Iron oxides from host rocks and hematite mineralisation are responsible for local enrichments of iron, antimony, arsenic and molybdenum in panned concentrates

Mineral exploration in the Cockermouth area, Cumbria. Part 2: follow-up surveys

This report describes the results of geochemical, geological and geophysical surveys across three small areas of Carboniferous and Lower Palaeozoic rocks along the northern margin of the English Lake District. The areas were chosen from the appraisal of regional-scale survey data described by Cooper et al. (1991). In two of the areas, Ruthwaite and Tallentire, the objective was to provide more information on the extent and magnitude of fracture-controlled epigenetic baryte and base metal mineralisation. In the third area, at Whitrigg, brief surveys were carried out to aid the interpretation of unexplained geochemical and geophysical anomalies found during two projects carried out under the Mineral Exploration and Investment Grants Act (MEIGA). At Ruthwaite, where a mine formerly worked baryte from a fault separating Lower Palaeozoic and Carboniferous rocks, surface indications of further baryte mineralisation were found. Soil analyses indicated that mineralisation may be present along the continuation of the faultline worked at Ruthwaite and in the Eycott Volcanic Group rocks to the south of it. In this area relatively small, but in some circumstances perhaps economically attractive, deposits of baryte may be present under drift cover. In the Tallentire Hill area, geological mapping followed by traverse-based soil sampling showed that fracture-controlled mineralisation is widespread in the Carboniferous (Dinantian and Namurian) rocks. The fracture fillings consist dominantly of baryte, often accompanied by carbonate, with traces of copper and mercury. Where seen at surface the fracture fillings are too small, patchy and low-grade to be of any economic importance. Baryte mineralisation also occurs locally as patchy impregnations in sandstones. These are considered to be epigenetic deposits related to the fracture-controlled mineralisation. Trial geophysical surveys suggested that electrical methods may be useful in determining the extent of the mineralised sandstone. There is a possibility that more extensive baryte deposits may be present in the limestone succession underlying the mineralised sandstones. In the Whitrigg area, Carboniferous rocks are separated from Lower Palaeozoic rocks of the Eycott Volcanic Group by the easterly-trending Boundary Fault and north-westerly-trending Bothel Fault. Evidence from an old mineral working and the results of a soil survey indicate that patchy, epigenetic, fracture-controlled baryte and base metal mineralisation occurs along the Bothel Fault and, locally, in the adjacent rocks. A feature of this mineralisation is the presence of mercury, which is most abundant in a sample of brecciated and altered rock from the Eycott Volcanic Group. Prominent base metal in soil anomalies discovered by MEIGA-funded projects near Stangerhill are not associated with barium anomalies. It was concluded that these soil anomalies are most likely to be caused by secondary concentration in overburden, and that the source of metals may be a sub-cropping metalliferous horizon within the Carboniferous succession or, more probably, fracture-controlled mineralisation. Trial geophysical surveys carried out in all three areas indicated that in ground free of artificial sources the VLF(EM) and conductivity mapping methods could be useful for tracing faults beneath drift and providing information on drift thickness. Closely-spaced soil sampling proved effective for detecting mineralisation in areas where the drift cover is thin, and a trial soil-gas survey showed that this technique could also be useful for tracing faults beneath drift

Data challenges of time domain astronomy

Astronomy has been at the forefront of the development of the techniques and methodologies of data intensive science for over a decade with large sky surveys and distributed efforts such as the Virtual Observatory. However, it faces a new data deluge with the next generation of synoptic sky surveys which are opening up the time domain for discovery and exploration. This brings both new scientific opportunities and fresh challenges, in terms of data rates from robotic telescopes and exponential complexity in linked data, but also for data mining algorithms used in classification and decision making. In this paper, we describe how an informatics-based approach-part of the so-called "fourth paradigm" of scientific discovery-is emerging to deal with these. We review our experiences with the Palomar-Quest and Catalina Real-Time Transient Sky Surveys; in particular, addressing the issue of the heterogeneity of data associated with transient astronomical events (and other sensor networks) and how to manage and analyze it.Comment: 15 pages, 3 figures, to appear in special issue of Distributed and Parallel Databases on Data Intensive eScienc

Insights into the structure and dynamics of the upper mantle beneath Bass Strait, southeast Australia, using shear wave splitting

We investigate the structure of the upper mantle using teleseismic shear wave splitting measurements obtained at 32 broadband seismic stations located in Bass Strait and the surrounding region of southeast Australia. Our dataset includes ∼366 individual splitting measurements from SKS and SKKS phases. The pattern of seismic anisotropy from shear wave splitting analysis beneath the study area is complex and does not always correlate with magnetic lineaments or current N-S absolute plate motion. In the eastern Lachlan Fold Belt, fast shear waves are polarized parallel to the structural trend (∼N25E). Further south, fast shear wave polarization directions trend on average N25–75E from the Western Tasmania Terrane through Bass Strait to southern Victoria, which is consistent with the presence of an exotic Precambrian microcontinent in this region as previously postulated. Stations located on and around the Neogene-Quaternary Newer Volcanics Province in southern Victoria display sizeable delay times (∼2.7 s). These values are among the largest in the world and hence require either an unusually large intrinsic anisotropy frozen within the lithosphere, or a contribution from both the lithospheric and asthenospheric mantle. In the Eastern Tasmania Terrane, nearly all observed fast directions are approximately NW-SE. Although part of our data set strongly favours anisotropy originating from “fabric” frozen in the lithospheric mantle, a contribution from the asthenospheric flow related to the present day plate motion is also required to explain the observed splitting parameters. We suggest that deviation of asthenospheric mantle flow around lithospheric roots could be occurring, and so variations in anisotropy related to mantle flow may be expected. Alternatively, the pattern of fast polarisation orientations observed around Bass Strait may be consistent with radial mantle flow associated with a plume linked to the recently discovered Cosgrove volcanic track. However, it is difficult to characterise the relative contributions to the observed splitting from the lithospheric vs. asthenospheric upper mantle due to poor backazimuthal coverage of the data

Mineral exploration in the Cockermouth area, Cumbria. Part 1 : regional surveys

The results of geochemical, geological and geophysical surveys over Carboniferous rocks along the northern margin of the English Lake District are given in two reports. This report (Part 1) describes broadscale surveys across an area bounded by Caldbeck in the east and the coast at Maryport in the west, and confined roughly by the boundary of Carboniferous rocks to the north and south. Part 2 contains details of orientation and follow-up surveys in the Ruthwaite, Tallentire and Whitrigg areas. Revision geological mapping of the area discovered many new occurrences of baryte mineralisation, which is particularly common in the Dinantian and Namurian rocks of the Tallentire - Bothel area. The mineralisation usually comprises epigenetic fracture fillings of baryte, often accompanied by brown carbonate and minor chalcopyrite or malachite. Locally in the Tallentire area baryte also occurs in disseminated and veinlet form within the Hensingham Grit. Lead-zinc mineralisation is less common; it occurs as epigenetic fracture fillings and locally as syngenetic or diagenetic concentrations in mudstones and shales of the Coal Measures. A geochemical drainage survey involving the analysis of water, stream sediment and panned concentrate samples revealed the presence of numerous metal anomalies. These required careful interpretation due to the presence of extensive contamination and glacial deposits derived from metalliferous source rocks in the Lake District and southern Scotland. The mineralogical examination of panned concentrates was used successfully to discriminate between anomalies caused by natural and artificial sources. In many cases evidence for both sources was found in a single sample. The data confumed the widespread occurrence of baryte and suggested that hitherto undetected mineralisation may be present around Ruthwaite (Ba), Tallentire Hill (Ba, Cu), Broughton Moor (Ba, base-metals), near Binsey (polymetallic) and south of Stockdale (Zn, Pb). Gold and cinnabar were reported for the first time from this area. Gold was observed in 21 panned concentrates, most collected over Upper Carboniferous rocks in the west of the area. It may have a local bedrock source, but comes probably from glacial deposits derived from mineralised Lower Palaeozoic rocks in southern Scotland and the north-east Lake District. Cinnabar was identified in 22 concentrates and is believed to be locally derived. Samples of mineral veins and altered wallrocks contain appreciable (up to 40 ppm) Hg, indicating that it is associated with the epigenetic mineralisation. A re-appraisal of the existing regional magnetic and gravity data for the area suggested that a north-west-trending fracture, named the Bothel Fault, could be a more significant structure than was apparent from existing maps, and may have been active during the Carboniferous. The magnitude of the gravity anomaly over the Solway Basin suggests the presence of either a thickened Carboniferous sequence, perhaps across a concealed growth fault, or more low-density (acid volcanic) rocks in the Lower Palaeozoic basement than is indicated on existing maps. Satellite imagery proved useful for indicating the direction of ice movement from glacial features, as well as suggesting the possible location of major fractures along the southern edge of the Solway Basin. It was concluded that the baryte mineralisation may be present locally in sufficient quantities to be of economic interest, but that base-metal mineralisation was weak. The epigenetic mineralisation is considered to be Upper Carboniferous to Lower Permian in age and to be the product of fluid flow through open fractures at the margin of the Solway Basin. The deposits have several features in common with Irish and Pennine-style ore deposits but there are also some clear differences, notably the paucity of Pb-Zn mineralisation

Encoding multiple quantum coherences in non-commuting bases

Multiple quantum (MQ) coherences are characterized by their coherence number and the number of spins that make up the state, though only the coherence number is normally measured. We present a simple set of measurements that extend our knowledge of the MQ state by recording the coherences in two non-commuting bases-the x and the z bases (related by a similarity transformation). The measurement of coherences in a basis other than the usual z basis also permits the study of spin dynamics under Hamiltonians that conserve z basis coherence number.close212