25 results on '"Norton, G.E."'
Search Results
2. Anatomy of a lava dome collapse: the 20 March 2000 event at Soufrière Hills Volcano, Montserrat
- Author
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Carn, S.A, Watts, R.B, Thompson, G, and Norton, G.E
- Published
- 2004
- Full Text
- View/download PDF
3. Physicochemical properties of alkali carbonatite lavas: data from the 1988 eruption of Oldoinyo Lengai, Tanzania
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Dawson, J.B., Pinkerton, H., Norton, G.E., and Pyle, D.M.
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Lava -- Composition ,Carbonatites -- Analysis ,Earth sciences - Published
- 1990
4. Locating pyroclastic flows on Soufriere Hills Volcano, Montserrat, West Indies, using amplitude signals from high dynamic range instruments
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Jolly, A.D, Thompson, G, and Norton, G.E
- Published
- 2002
- Full Text
- View/download PDF
5. Dome collapse and vulcanian explosive activity, September to October 1997. MVO Special Report 5
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Young, S.R., Cole, P.D., Calder, E.S., Baptie, B.J., Bonadonna, Costanza, Francis, P.W., Herd, R.A., Jackson, P., Loughlin, S.C., Luckett, R., Norton, G.E., Rowley, K., Sparks, R.S.J., and Watts, R.
- Subjects
ddc:550 - Published
- 1999
6. Summary of information on coal for land-use planning purposes
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Chapman, G.R., Highley, D.E., Cameron, D.G., Norton, G.E., Taylor, L.E., Lusty, P.A.J., Chapman, G.R., Highley, D.E., Cameron, D.G., Norton, G.E., Taylor, L.E., and Lusty, P.A.J.
- Abstract
The UK has had a long history of coal production and coal was the UK’s most important primary fuel until 1971, when it was overtaken by petroleum. Although the importance of coal as an energy source has declined, it continues to provide around 17 per cent of the nation’s primary energy consumption and about one third of its electricity. In 2003 the UK became a net importer of coal and in 2005, of a total demand for coal of about 63 Mt, only 20 Mt was produced domestically. In the same year production of coal by surface mining exceeded deep-mine production for the first time. There will be a continuing market for coal in the medium term as part of a balanced and varied UK energy supply. The operators of almost 75 per cent of UK coal-fired electricity generating capacity have opted to fit flue gas desulphurisation equipment to enable their power stations to operate to at least 2015 in compliance with the EU Revised Large Combustion Plants Directive. In addition, several operators have announced their interest in building new and more efficient coal-fired plant. However, the extent that indigenous coal will continue to contribute to UK supply will depend on the competitiveness of deep-mined coal relative to imported coal and the extent that new deep mine and opencast reserves can be accessed. The recent significant decline in opencast coal production in England reflects the fact that new permissions have failed to replenish the reserves being worked. The report brings together data on coal production, trade, consumption and uses, and provides information on licensing and reserves. It also summarises information on opencast coal sites granted and refused planning permissions and recommends that a system of safeguarding shallow coal resources be put in place. Coal exploitation by methods other than conventional deep and shallow mining are also summarised.
- Published
- 2006
7. Devon (comprising Devon, Plymouth, Torbay, Dartmoor National Park and part of Exmoor National Park) : mineral resource information in support of national, regional and local planning
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Bloodworth, A.J, Norton, G.E., Mitchell, C.J., Scrivener, R.C., Cameron, D.G., Hobbs, S.F., Evans, D.J., Lott, G.K., Highley, D.E., Bloodworth, A.J, Norton, G.E., Mitchell, C.J., Scrivener, R.C., Cameron, D.G., Hobbs, S.F., Evans, D.J., Lott, G.K., and Highley, D.E.
- Published
- 2006
8. Cheshire (comprising Cheshire, Boroughs of Halton and Warrington) mineral resources : mineral resource information in support of national, regional and local planning
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Norton, G.E., Bloodworth, A.J., Cameron, D.G., Evans, D.J., Lott, G.K., Hobbs, S.F., Highley, D.E., Norton, G.E., Bloodworth, A.J., Cameron, D.G., Evans, D.J., Lott, G.K., Hobbs, S.F., and Highley, D.E.
- Published
- 2006
9. Mineral resource information in support of national, regional and local planning : Cheshire (comprising Cheshire, Boroughs of Halton and Warrington)
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Norton, G.E., Bloodworth, A.J., Cameron, D.G., Evans, D.J., Lott, G.K., Hobbs, S.F., Spencer, N.A., Highley, D.E., Norton, G.E., Bloodworth, A.J., Cameron, D.G., Evans, D.J., Lott, G.K., Hobbs, S.F., Spencer, N.A., and Highley, D.E.
- Abstract
This report is one of a series prepared by the British Geological Survey for various administrative areas in England for the Office of the Deputy Prime Minister’s research project Mineral Resource Information in Support of National, Regional and Local Planning. The accompanying map relates to the county of Cheshire (comprising Cheshire, Boroughs of Halton and Warrington), and delineates the mineral resources of current, or potential, economic interest in the area and the sites where minerals are or have been worked. It also relates these to national planning designations, which may represent constraints on the extraction of minerals. Three major elements of information are presented: • the geological distribution and importance of mineral resources; • the extent of mineral planning permissions and the location of current mineral workings; and • the extent of selected, nationally-designated planning constraints. This wide range of information, much of which is scattered and not always available in a consistent and convenient form, is presented on a digitally-generated summary map on the scale of 1:100 000. This scale is convenient for the overall display of the data and allows for a legible topographic base on which to depict the information. However, all the data are held digitally at larger scales using a Geographical Information System (GIS), which allows easy revision, updating and customisation of the information together with its possible integration with other datasets. The information will form part of a Summary of the Mineral Resources of the North West Region. The purpose of the work is to assist all interested parties involved in the preparation and review of development plans, both in relation to the extraction of minerals and the protection of mineral resources from sterilisation. It provides a knowledge base, in a consistent format, on the nature and extent of mineral resources and the environmental constraints, which may affect their extraction. An imp
- Published
- 2005
10. A guide to the construction of the DGSM Nottingham Melton Lithoframe 250K model
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Jones, N.S., Norton, G.E., Royles, C.P., Jones, N.S., Norton, G.E., and Royles, C.P.
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This report describes the rationale behind the construction of the Nottingham Melton Lithoframe 250K GOCAD model. This work was carried out between April 2001-March 2005, as part of the Nottingham Melton DGSM-UK project (E1362S96 Task 06). This model comprises the area of the combined Nottingham and Melton 50K geological map sheets.
- Published
- 2005
11. Mineral resource information in support of national, regional and local planning : Devon (comprising Devon, Plymouth, Torbay, Dartmoor National Park and part of Exmoor National Park)
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Bloodworth, A.J., Norton, G.E., Mitchell, C.J., Scrivener, R.C., Cameron, D.G., Hobbs, S.F., Evans, D.J., Lott, G.K., Highley, D.E., Bloodworth, A.J., Norton, G.E., Mitchell, C.J., Scrivener, R.C., Cameron, D.G., Hobbs, S.F., Evans, D.J., Lott, G.K., and Highley, D.E.
- Abstract
This report is one of a series prepared by the British Geological Survey for various administrative areas in England for the Office of the Deputy Prime Minister’s research project Mineral Resource Information in Support of National, Regional and Local Planning. The accompanying maps relate to the county of Devon and delineates the mineral resources of current, or potential, economic interest in the area and the sites where minerals are or have been worked. It also relates these to national planning designations, which may represent constraints on the extraction of minerals. Three major elements of information are presented: • the geological distribution and importance of mineral resources; • the extent of mineral planning permissions and the location of current mineral workings; and • the extent of selected, nationally-designated planning constraints. This wide range of information, much of which is scattered and not always available in a consistent and convenient form, is presented on two digitally-generated summary map on the scale of 1:100 000. This scale is convenient for the overall display of the data and allows for a legible topographic base on which to depict the information. However, all the data are held digitally at larger scales using a Geographical Information System (GIS), which allows easy revision, updating and customisation of the information together with its possible integration with other datasets. The information will form part of a Summary of the Mineral Resources of the South West Region. The purpose of the work is to assist all interested parties involved in the preparation and review of development plans, both in relation to the extraction of minerals and the protection of mineral resources from sterilisation. It provides a knowledge base, in a consistent format, on the nature and extent of mineral resources and the environmental constraints, which may affect their extraction. An important objective is to provide baseline data for the long t
- Published
- 2005
12. Mineral resource information in support of national, regional and local planning : Wiltshire (comprising Wiltshire and the Borough of Swindon)
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Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Wilkinson, I.J., Burke, H.F., Spencer, N.A., Highley, D.E., Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Wilkinson, I.J., Burke, H.F., Spencer, N.A., and Highley, D.E.
- Abstract
This report is one of a series prepared by the British Geological Survey for various administrative areas in England for the Office of the Deputy Prime Minister’s research project Mineral Resource Information in Support of National, Regional and Local Planning. The accompanying map relates to the county of Wiltshire and delineates the mineral resources of current, or potential, economic interest in the area and the sites where minerals are or have been worked. It also relates these to national planning designations, which may represent constraints on the extraction of minerals. Three major elements of information are presented: • the geological distribution and important of mineral resources; • the extent of mineral planning permissions and the location of current mineral workings; and • the extent of selected, nationally-designated planning constraints. This wide range of information, much of which is scattered and not always available in a consistent and convenient form, is presented on a digitally-generated summary map on the scale of 1:100 000. This scale is convenient for the overall display of the data and allows for a legible topographic base on which to depict the information. However all the data are held digitally at larger scales using a Geographical Information System (GIS), which allows easy revision, updating and customisation of the information together with its possible integration with other datasets. The information will form part of a Summary of the Mineral Resources of the South West Region. The purpose of the work is to assist all interested parties involved in the preparation and review of development plans, both in relation to the extraction of minerals and the protection of mineral resources from sterilisation. It provides a knowledge base, in a consistent format, on the nature and extent of mineral resources and the environmental constraints, which may affect their extraction. An important objective is to provide baseline data for the long t
- Published
- 2004
13. Mineral resource information in support of national, regional and local planning : Oxfordshire
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Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Arbon, K.A., Spencer, N.A., Highley, D.E., Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Arbon, K.A., Spencer, N.A., and Highley, D.E.
- Abstract
This report is one of a series prepared by the British Geological Survey for various administrative areas in England for the Office of the Deputy Prime Minister’s research project Mineral Resource Information in Support of National, Regional and Local Planning. The accompanying map relates to the county of Oxfordshire and delineates the mineral resources of current, or potential, economic interest in the area and the sites where minerals are or have been worked. It also relates these to national planning designations, which may represent constraints on the extraction of minerals. Three major elements of information are presented: • the geological distribution and importance of mineral resources; • the extent of mineral planning permissions and the location of current mineral workings; and • the extent of selected, nationally-designated planning constraints. This wide range of information, much of which is scattered and not always available in a consistent and convenient form, is presented on a digitally-generated summary map on the scale of 1:100 000. This scale is convenient for the overall display of the data and allows for a legible topographic base on which to depict the information. However, all the data are held digitally at larger scales using a Geographical Information System (GIS), which allows easy revision, updating and customisation of the information together with its possible integration with other datasets. The information will be incorporated into a regional GIS which will provide a Summary of the Mineral Resources of the South East Region. The purpose of the work is to assist all interested parties involved in the preparation and review of development plans, both in relation to the extraction of minerals and the protection of mineral resources from sterilisation. It provides a knowledge base, in a consistent format, on the nature and extent of mineral resources and the environmental constraints which may affect their extraction. An important objecti
- Published
- 2004
14. Wiltshire (comprising Wiltshire and Swindon) mineral resources : mineral resource information in support of national, regional and local planning
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Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Wilkinson, I.J., Burke, H.F., Highley, D.E., Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Wilkinson, I.J., Burke, H.F., and Highley, D.E.
- Published
- 2004
15. Oxfordshire mineral resources : mineral resource information in support of national, regional and local planning
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Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Arbon, K.A., Highley, D.E., Norton, G.E., Cameron, D.G., Bloodworth, A.J., Evans, D.J., Lott, G.K., Arbon, K.A., and Highley, D.E.
- Published
- 2004
16. Mineral investigations in the Northumberland trough : part 5, The Kirkbean area, south-west Scotland
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Smith, R.T., Norton, G.E., Walker, A.S.D., Kimbell, G.S., Gibberd, A.J.G., McMillan, A.A., Smith, R.T., Norton, G.E., Walker, A.S.D., Kimbell, G.S., Gibberd, A.J.G., and McMillan, A.A.
- Abstract
Exploration for carbonate-hosted base-metal mineralisation on the North Solway coastal belt was undertaken in 1992-93 as part of a broader scale MRP investigation of a 70 km strike length of Lower Carboniferous rocks at the northern margin of the Solway-Northumberland Basin. The project area was selected partly on the basis of its similarities with the tectonosedimentary environment of the Lower Dinantian central Irish basin which hosts several major stratabound lead-zinc deposits, and the presence of geochemical base-metal anomalies coincident with basin margin structures. Two of the most important criteria for the formation of major SEDEX Irish-style deposits, the presence of major syn-depositional basin margin faults and a geothermal system over a zone of high heat flow in the crust (Andrew, 1993), are recognised in the north Solway area. The presence of mafic lavas and possible associated mineralising hydrothermal activity are considered to further increase the economic potential of the area.
- Published
- 1996
17. Exploration for volcanogenic mineralisation in south-west Wales
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Coleman, T.B., Norton, G.E., Chacksfield, B.C., Cooper, D.C., Cornwell, J.D., Coleman, T.B., Norton, G.E., Chacksfield, B.C., Cooper, D.C., and Cornwell, J.D.
- Abstract
South-west Wales has extensive and voluminous extrusive and intrusive volcanic rocks of Grdovician age interbedded with black shales and other sedimentary rocks, a sequence which has proved to contain economic base-metal deposits in other areas of the British Isles and elsewhere. No significant mineral deposits are known in the area apart from a small lead mine at Llanfymach which was abandoned in the last century. The Mineral Reconnaissance Programme has completed several projects in the area in the past 20 years and this report is a compilation of data collected during the programme but not previously published, together with data from additional new investigations in the Treffgame, Crosswell and Llangynog areas. Regional interpretations of the geophysics (gravity and aeromagnetics), lithogeochemistry and petrogenesis are presented in the report. These include the physical properties of many of the rock types and a study of the rare-earth-element (REE) contents of examples of the volcanic rocks to determine their origin and their potential for volcanogenic massive sulphide (VMS) and preciousmetal mineralisation. More detailed investigations were carried out in the Treffgame area, following on from earlier MRP work which included the drilling of three cored boreholes. The published summary report (Brown et al., 1987) contained little data as these were in a separate unpublished dataset which was later released on open file. The current report publishes some of the results of the earlier work, including details of the drilling. No sulphides other than pyrite were found during the earlier survey but up to 8.6% Ba (as baryte) was found in rhyolite lavas and tuf& in Borehole 1 on Dudwell Mountain. This prompted further investigations, described in this report, which included additional soil geochemistry coupled with geophysical techniques not used in the earlier survey. The aim was to investigate the possibility that volcanogenic mineralisation at depths of up to 100 m
- Published
- 1995
18. Exploration for carbonate-hosted base-metal mineralisation near Ashbourne, Derbyshire
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Cornwell, J.D., Busby, J.P., Coleman, T.B., Norton, G.E., Cornwell, J.D., Busby, J.P., Coleman, T.B., and Norton, G.E.
- Abstract
Exploration has been carried out for lead-zinc-baryte mineralisation in Carboniferous (Dinantian) limestones to the south of the main mining district of the Peak District. Previous evidence from regional gravity surveys suggested the existence here of a ridge of limestones, the Snelston ridge, largely concealed beneath a thin cover of Permo-Triassic rocks. The structural setting suggests that the area could lie near the projected margin of the Staffordshire stable shelf area and at the northern margin of the Needwood Permo-Triassic Basin. Evidence provided by old mining activity in two small limestone inliers on the Snelston ridge encouraged the present exploration for concealed mineralisation either at the unconformity between these rocks and the overlying PermeTriassic or, more importantly, hosted by limestones. Interpretation of the improved regional gravity data sets and detailed traverses led to better definition of the location of the concealed limestone surface. Additional evidence on the concealed structure was provided by a commercial seismic reflection profile which became available during the project, and which clearly indicated the fault-controlled nature of the ridge. The gravity interpretation, supported by evidence from resistivity soundings, led to the siting of a borehole. This proved the existence of a shallow (60 m) Dinantian limestone ridge but found little mineralisation at the unconformity, apart from minor barium enhancement. At the Limestone Hill inlier, previous mining history and limited evidence from exposures pointed to the existence of sulphide and baryte mineralisation in the exposed Chadian knoll-reef limestone. High barium, lead and zinc values were obtained from soils over the exposed limestone and geophysical surveys improved the interpretation of the near-surface geology. A borehole proved extensive replacement galena-sphalerite-baryte mineralisation with up to 10% Pb over an intersection of about 10 m near the top of the knoll-ree
- Published
- 1995
19. Regional appraisal of the potential for stratabound base-metal mineralisation in the Solway basin
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Colman, T., Holloway, S., Smith, R.T., Norton, G.E., Kimbell, G.S., Walker, A.S.D., Tragheim, D.G., Colman, T., Holloway, S., Smith, R.T., Norton, G.E., Kimbell, G.S., Walker, A.S.D., and Tragheim, D.G.
- Abstract
The Carboniferous Solway-Northumberland extensional basin covers an area of 6500 km2 in northern England and southern Scotland (Figure 1.1). The basin, which is up to 7 km thick, developed due to N-S extension with major fault-controlled subsidence during the Courceyan-Holkerian (syn-extension phase), followed by more gradual post-extension regional subsidence during the later Carboniferous. It straddles the trace of the Iapetus Suture which marks the collision zone of the palaeo-North American and palaeo-European continents during Caledonian times. The major Irish lead-zinc deposits, including the world-class Navan deposit lie along the western extension of the Iapetus Suture. The basin is poorly exposed away from the margins and is covered by later Permo-Trias sediments. Much of the basin is also mantled with extensive drift deposits. Minor lead-zinc vein and replacement mineralisation occurs along the northern boundary of the basin, close to the contact with the underlying Lower Palaeozoic rocks of the Southern Uplands and vein style mineralisation carrying barite and minor base metals occurs along the southern margin at the contact with the Lower Palaeozoic rocks of the Lake District. More extensive syn-diagenetic mineralisation of Sedex style found in Ireland may occur adjacent to the major basin-controlling faults. Investigations of the regional geochemistry. geophysics and deep geology, together with Landsat imagery, show that the basin could be prospective for this style of mineralisation, but that the most likely rocks, in tenns of chronostratigraphy, are likely to be at considerable depth on the southern margin. However, suitable conditions for the emplacement of this mineralisation may be found in several areas close to the northern margin and in the Bewcastle Anticline.
- Published
- 1995
20. Mineralisation in the Middle Devonian volcanic belt and associated rocks of South Devon
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Leake, R.C., Norton, G.E., Leake, R.C., and Norton, G.E.
- Abstract
This report describes the results of further exploration within the belt of Middle Devonian volcanic rocks between Plymouth and Totnes in south Devon. Soil sampling was carried out to augment the coverage of the volcanic belt described in Mineral Reconnaissance Programme Report No. 79 (Leake et al., 1985) and to extend it into adjacent sedimentary rocks. The 4815 overburden samples indicate that the area as a whole is highly enriched in antimony and, to a lesser extent, arsenic. No evidence was found of further stratiform exhalative mineralisation in addition to the massive pyrite and ferruginous carbonate at Higher Ludbrook and the baryte at Lower Burraton described in MRP Report No. 79. However, four main areas showing evidence of metal-enriched sedimentary rocks have been outlined. In three of the areas, enrichment in Mn in the soils derived from the sedimentary rocks is accompanied by low amplitude enrichment in Zn and Pb, reaching around 200 ppm Zn and 170 ppm Pb. The fourth area, adjacent to the separate belt of volcanic rocks northwest of Totnes, is more extensive and of higher amplitude (reaching over 700 ppm Zn and 600 ppm Pb). The soil and dAlIhole data indicate that extensive hydrothermal systems were associated with the alkali basaltic volcanism in the area and that submarine hydrothermal activity took place. The close similarity in geology between the area and the Rhenish basin in Germany, which hosts the Meggen SEDEX deposit, indicates that south Devon and east Cornwall remain prospective for submarine exhalative mineralisation. Overburden samples indicate that polymetallic mineralisation occurs within a zone about 3 km long in the west of the area. The zone is enriched in As, Pb, Zn, Mn and Cu and is similar to polymetallic mineralisation carrying gold which occurs further south in Devon, described in Mineral Reconnaissance Programme Report No 121 (Leake et al., 1992). Evidence for further polymetahic mineralisation is present in the northeast of the
- Published
- 1993
21. Evidence for gold mineralisation in the Lower Palaeozoic and Precambrian rocks of south-west Wales.
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Norton G.E., Cooper D.C., Cornwell J.D., Davies J.R., Norton G.E., Cooper D.C., Cornwell J.D., and Davies J.R.
- Abstract
Geochemical surveys were carried out across an area of 400 km3 to investigate reported alluvial gold occurrences. An orientation survey indicated that gold has different grain sizes in different catchments and that fine gold may be present locally. Grains are angular to well rounded and there are no clear pathfinder elements for gold. Follow-up sampling indicated that stream-sediment and panned concentrate variation could be related to gold, black shales, limestones, mafic chloritic rocks, contamination and nodular monazite. Prospective gold-bearing catchments included Afon Marlais, Deepford Brook, Fenton Brook and streams south of New Moat. Gold was recorded in three panned overburden samples and available geophysical data suggested an association between gold and shallow basement or faults controlling depth to basement. Analysis of all available data indicated three main sources of alluvial gold: palaeoplacers, porphyry-style Cu-Au and black shale/shear zone mineralisation., Geochemical surveys were carried out across an area of 400 km3 to investigate reported alluvial gold occurrences. An orientation survey indicated that gold has different grain sizes in different catchments and that fine gold may be present locally. Grains are angular to well rounded and there are no clear pathfinder elements for gold. Follow-up sampling indicated that stream-sediment and panned concentrate variation could be related to gold, black shales, limestones, mafic chloritic rocks, contamination and nodular monazite. Prospective gold-bearing catchments included Afon Marlais, Deepford Brook, Fenton Brook and streams south of New Moat. Gold was recorded in three panned overburden samples and available geophysical data suggested an association between gold and shallow basement or faults controlling depth to basement. Analysis of all available data indicated three main sources of alluvial gold: palaeoplacers, porphyry-style Cu-Au and black shale/shear zone mineralisation.
22. The MIDAS project (multiple data-set analysis for gold in Europe): evidence from the British Caledonides.
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Plant J.A., Gunn A.G., Morrissey C.J., Norton G.E., Rollin K.E., Simpson P.R., Stone P., Wiggans G.N., Plant J.A., Gunn A.G., Morrissey C.J., Norton G.E., Rollin K.E., Simpson P.R., Stone P., and Wiggans G.N.
- Abstract
Screening multiple geoscience data sets on a Geographical Information System allows exploration criteria to be identified. In the British Caledonian terrane, zones of gold concentration are characterised by their oceanic affinity. They include a former extensional orogenic basin (the Dalradian), a back-arc basin (the northern Southern Uplands) and an extensional to subduction-related continental margin (the Lake District). The gold belts typically comprise turbiditic greywacke-shale sequences, with or without contemporaneous tholeiitic volcanics. The most significant mineralisation is in rocks at or below amphibolite facies. No consistent association with any geophysical feature has been characterised, but there are elevated levels of As, Sb and other elements and gold is widespread in heavy-mineral concentrates. Mineralisation is localised by features such as post-tectonic granitoid intrusions, shear zones, fold closures and lithological contacts. The orebodies typically record multi-stage paragenesis., Screening multiple geoscience data sets on a Geographical Information System allows exploration criteria to be identified. In the British Caledonian terrane, zones of gold concentration are characterised by their oceanic affinity. They include a former extensional orogenic basin (the Dalradian), a back-arc basin (the northern Southern Uplands) and an extensional to subduction-related continental margin (the Lake District). The gold belts typically comprise turbiditic greywacke-shale sequences, with or without contemporaneous tholeiitic volcanics. The most significant mineralisation is in rocks at or below amphibolite facies. No consistent association with any geophysical feature has been characterised, but there are elevated levels of As, Sb and other elements and gold is widespread in heavy-mineral concentrates. Mineralisation is localised by features such as post-tectonic granitoid intrusions, shear zones, fold closures and lithological contacts. The orebodies typically record multi-stage paragenesis.
23. Exploration for carbonate-hosted base-metal mineralisation near Ashbourne, Derbyshire.
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Cornwell J.D., Busby J.P., Colman T.B., Norton G.E., Cornwell J.D., Busby J.P., Colman T.B., and Norton G.E.
- Abstract
Previous evidence from regional gravity surveys south of the main Peak District mining area suggested that a ridge of limestones, the Snelston ridge, lies beneath a thin cover of Permo-Triassic rocks. The history of old mining activity in two small inliers encouraged exploration for concealed mineralisation, either limestone-hosted or unconformity-related. The limestone surface was more clearly defined and additional evidence from a commercial seismic reflection profile indicated the fault-controlled nature of the ridge. A borehole proved the existence of the ridge at 60 m depth but found only minor barium enhancement at the unconformity. At the Limestone Hill inlier, previous mining and the few exposures suggested sulphide and barite mineralisation in the Chadian knoll-reef limestone. High Ba, Pb and Zn values were obtained from soils over the exposed limestone and geophysical surveys improved the near-surface interpretation. A borehole proved extensive galena, sphalerite and barite replacement-type mineralisation with up to 10% Pb over about 10 m near the top of the reef, where the rock is highly dolomitised and cavernous. There is no evidence of fluorite, but barite is common at the surface and occurs in the borehole core. Two further boreholes on the flanks of the knoll-reef showed that mineralisation does not extend laterally to any great distance. Further work to detect other, completely concealed reefs with more extensive replacement mineralisation is recommended., Previous evidence from regional gravity surveys south of the main Peak District mining area suggested that a ridge of limestones, the Snelston ridge, lies beneath a thin cover of Permo-Triassic rocks. The history of old mining activity in two small inliers encouraged exploration for concealed mineralisation, either limestone-hosted or unconformity-related. The limestone surface was more clearly defined and additional evidence from a commercial seismic reflection profile indicated the fault-controlled nature of the ridge. A borehole proved the existence of the ridge at 60 m depth but found only minor barium enhancement at the unconformity. At the Limestone Hill inlier, previous mining and the few exposures suggested sulphide and barite mineralisation in the Chadian knoll-reef limestone. High Ba, Pb and Zn values were obtained from soils over the exposed limestone and geophysical surveys improved the near-surface interpretation. A borehole proved extensive galena, sphalerite and barite replacement-type mineralisation with up to 10% Pb over about 10 m near the top of the reef, where the rock is highly dolomitised and cavernous. There is no evidence of fluorite, but barite is common at the surface and occurs in the borehole core. Two further boreholes on the flanks of the knoll-reef showed that mineralisation does not extend laterally to any great distance. Further work to detect other, completely concealed reefs with more extensive replacement mineralisation is recommended.
24. Exploration for volcanogenic mineralisation in south-west Wales.
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Colman T.B., Chacksfield B.C., Cooper D.C., Cornwell J.D., Norton G.E., Colman T.B., Chacksfield B.C., Cooper D.C., Cornwell J.D., and Norton G.E.
- Abstract
The area has extensive and voluminous volcanic rocks of Ordovician age interbedded with black shales and other sedimentary rocks, a sequence which contains economic base metals in other areas of the British Isles and elsewhere. No significant deposits are known apart from a small abandoned lead mine at Llanfyrnach. Regional geophysics, lithogeochemistry and petrogenesis are interpreted, including a study of the REE contents of volcanic samples to determine their potential for volcanogenic massive sulphides and precious metals. More detailed investigations in the Treffgarne area included three cored boreholes; up to 8% Ba as barite was found in rhyolite lavas and tuffs on Dudwell Mountain. Further investigations included additional soil sampling and geophysical exploration (gravity, electromagnetic and self-potential) to identify possible volcanogenic mineralisation at depths of up to 100 m between the widely spaced lines of the initial survey. Massive barite and disseminated pyrite were found in a metre-wide zone of hydrothermal alteration in Rock Farm Quarry at the western end of the Roch Rhyolite Group. In the Crosswell area anomalous Ba levels (over 2 000 ppm) in the soil was coincident with strike-parallel EM conductors associated with black shales overlying volcanic rocks of the Fishguard Group. A regional lithogeochemical survey showed that the Sealyham Volcanic Group had similar alteration to that at Treffgarne., The area has extensive and voluminous volcanic rocks of Ordovician age interbedded with black shales and other sedimentary rocks, a sequence which contains economic base metals in other areas of the British Isles and elsewhere. No significant deposits are known apart from a small abandoned lead mine at Llanfyrnach. Regional geophysics, lithogeochemistry and petrogenesis are interpreted, including a study of the REE contents of volcanic samples to determine their potential for volcanogenic massive sulphides and precious metals. More detailed investigations in the Treffgarne area included three cored boreholes; up to 8% Ba as barite was found in rhyolite lavas and tuffs on Dudwell Mountain. Further investigations included additional soil sampling and geophysical exploration (gravity, electromagnetic and self-potential) to identify possible volcanogenic mineralisation at depths of up to 100 m between the widely spaced lines of the initial survey. Massive barite and disseminated pyrite were found in a metre-wide zone of hydrothermal alteration in Rock Farm Quarry at the western end of the Roch Rhyolite Group. In the Crosswell area anomalous Ba levels (over 2 000 ppm) in the soil was coincident with strike-parallel EM conductors associated with black shales overlying volcanic rocks of the Fishguard Group. A regional lithogeochemical survey showed that the Sealyham Volcanic Group had similar alteration to that at Treffgarne.
25. Mineralisation in the Middle Devonian volcanic belt and associated rocks of south Devon.
- Author
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Leake R.C., Norton G.E., Leake R.C., and Norton G.E.
- Abstract
The results are described of exploration within the belt of Middle Devonian volcanic rocks between Plymouth and Totnes in south Devon. Overburden geochemical data and borehole data indicated that extensive hydrothermal systems were associated with the volcanic activity. There was also evidence of metal-enriched sedimentary rocks which suggested that submarine hydrothermal activity took place during at least some of the Devonian. The close similarity between the area and the Rhenish basin in Germany, which hosts the Meggen SEDEX deposit, indicated that south Devon and east Cornwall remain prospective for submarine exhalative mineralisation., The results are described of exploration within the belt of Middle Devonian volcanic rocks between Plymouth and Totnes in south Devon. Overburden geochemical data and borehole data indicated that extensive hydrothermal systems were associated with the volcanic activity. There was also evidence of metal-enriched sedimentary rocks which suggested that submarine hydrothermal activity took place during at least some of the Devonian. The close similarity between the area and the Rhenish basin in Germany, which hosts the Meggen SEDEX deposit, indicated that south Devon and east Cornwall remain prospective for submarine exhalative mineralisation.
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