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Mineral Reconnaissance Programme (MRP) reports 11-20

11 A study of the space form of the Cornubian granite batholith and its application to detailed gravity surveys in Cornwall (2.31 Mb)

J M C Tombs (1977)

A three–dimensional computer model of the Cornubian granite batholith, defined by polygonal contours, was created so that its calculated gravity field matched the observed Bouguer anomaly field both onshore and offshore. The model was used to define a background ('regional') field in three areas where detailed gravity surveys had been undertaken in the search for shallow granite. Maps of depth to granite were produced from the residual field by an iterative technique. Geological interpretations of the batholith model and of the depth maps are included in the report.

12 Mineral investigations in the Teign Valley, Devon. Part 1—Barytes (1.68 Mb)

K E Beer and T K Ball (1977)

Geochemical studies in the Teign Valley, carried out on stream sediment and soil samples, have indicated extensions of baryte mineralisation some 2.5km north and 1.2km south of the formerly mined strike length in Upper Palaeozoic sediments. Ba–Pb–Zn mineralisation is now known to extend over a total length of 12.3km and over a width rarely less than 0.5km, though ore bodies large enough to be worked occur only intermittently within this belt. Part of the southern extension was investigated by deeper sampling, a percussive drill being used to obtain powdered rock samples for assay. To the south of Hennock village a baryte–rich zone has been defined, some 1.2km long and 260m wide.

13 Investigation of stratiform sulphide mineralisation at McPhun's Cairn, Argyllshire (5.84 Mb)

C G Smith and others (1977)

A small stratiform occurrence of massive sulphide, apparently over 2m thick, occurs in the Dalradian schists at McPhun's Cairn beside Loch Fyne. At outcrop it contains 3.5% Zn, 3.0% Pb, 6 ppm Ag and 0.75 ppm Au. Geological, geophysical (IP, magnetic, resistivity) and geochemical (soil, stream sediment, panned concentrate) surveys and shallow drilling indicate the presence of only sporadic weak mineralisation. Regional structural analysis and examination of the mineralisation suggest that local concentration of sulphides occurred at the nose of a steeply plunging small fold system. A borehole to investigate the outcrop occurrence proved the extension of mineralisation down the fold axis.

14 Mineral investigations at Woodhall and Longlands in north Cumbria (4.05 Mb)

A J Wadge, J D Appleton and A D Evans (1977)

Geological mapping, soil and stream sediment sampling and IP and EM traverses over Lower Carboniferous limestones identified several geochemical and geophysical anomalies. Auger sampling of the former showed them to be due to surface redistribution of metals from disused Pb–Zn–Cu–baryte mines, whereas the weak geophysical anomalies in themselves do not constitute viable drilling targets.

15 Investigation of stratiform sulphide mineralisation at Meall Mor, South Knapdale, Argyll
(11.8 Mb)

C G Smith and others (1978)

A geochemical/geophysical/geological investigation of Cu mineralisation in the Meall Mor area was followed by the drilling of six shallow holes. The mineralisation occurs in a zone of weak stratiform sulphide mineralisation (the pyrite zone) with a strike length of 10km in the Upper Erins Quartzite of the Middle Dalradian. A geochemical drainage survey showed the existence of a strongly anomalous distribution of Cu and Sb in the Abhainn Srathain, which drains south from Meall Mor. Detailed soil and basal till sampling over the pyrite zone outlined a broad area enriched in Cu, and a coincident IP anomaly was found that stretched from Meall Mor south to the old mine workings on Abhainn Srathain and had probably been caused by a local enrichment of pyrite and chalcopyrite within the pyrite zone. Cu values range up to 0.24% Cu over 4.27m in the first two holes and up to 1.06% Cu over 2.67 m in the third. This enrichment may be related to a later remobilisation of the disseminated chalcopyrite.Graphic log of Borehole 1, Meall Mor (Report No. 15).

16 Report on geophysical and geological surveys at Blackmount, Argyllshire (1.3 Mb)

C G Smith and G R Marsden (1977)

The underlying Precambrian Moine psammite at Blackmount, on the southern fringe of Rannoch Moor, contains granitic veins that probably stem from the adjacent Moor of Rannoch granite. These veins are generally pyritiferous and, at one locality, carry small amounts of molybdenite. Blackmount is also traversed by the Ericht–Laidon Fault, which, in theory and by analogy with the Tyndrum Fault, could be a site of significant sulphide mineralisation. Magnetic, VLF–EM, Slingram EM and induced polarisation measurements which were carried out in the area of the veins suggest that the mineralisation has little or no lateral or depth continuation. Similar surveys were successful in locating the Ericht–Laidon Fault beneath drift, but suggest that to the greatest depth that was investigated no associated mineralisation is present.

17 Lead, zinc and copper mineralisation in basal Carboniferous rocks at Westwater, south Scotland (11.4 Mb)

M J Gallagher and others (1977)

A zone of Pb, Zn and Cu mineralisation is developed over a minimum of 4km of strike of basal Carboniferous cementstone group sediments and immediately underlying Birrenswark Lavas at Westwater, near Langholm. Grades in sparse rock exposures and shallow boreholes are usually 0.1–0.3% of combined metals over 1–2m of thickness, but a fissure vein of higher grade and a relatively thick zone of disseminated sulphides were also located. Galena, sphalerite, chalcopyrite and baryte occur mainly in thin dolomite veins, but disseminations of galena are also present in sandstone units. The mineralisation is of low–temperature type and was emplaced along northeasterly–trending normal faults and cross faults regarded as late Carboniferous in age. Mineralisation was controlled by faulting, regional facies variation and local lithological variation, as well as by stratigraphic position. The heavy mineral fraction of stream sediment is the optimum sampling type in reconnaissance exploration of areas of calcareous rocks, such as the Lower Carboniferous of south Scotland, and basal till sampling is the most effective method of follow–up exploration in those areas where glacial deposits are widespread and often thick.

18 A mineral reconnaissance survey of the Doon–Glenkens area, south–west Scotland (10 Mb)

J Dawson and others (1977)

Geological, geophysical and geochemical surveys were carried out over the Loch Doon and Carsphairn granites and the surrounding Lower Palaeozoic sediments. Geochemical drainage surveys led to the discovery of several occurrences of Cu, Pb, Zn, Mo, W and Au. Airborne electromagnetic and magnetic surveys showed prominent anomalies associated with belts of black shales.

19 A reconnaissance geochemical drainage survey of the Criffel–Dalbeattie granodiorite complex and its environs (9.65 Mb)

R C Leake, M J Brown, A R Date and T K Smith (1978)

Regional geochemical maps, compiled from multi–element analysis of stream sediments (Li, Be, B, MgO, K2O, CaO, TiO2, V, Cr, Mn, Fe2O3, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Sn, Ba, Pb, U) and panned concentrates (Ca, Ti, Mn, Fe, Ni, Cu, Zn, Y, Zr, Nb, Sn, Sb, Ba, Ce, Pb, Th, U) show patterns of element distribution related to geology and mineralisation of the region. Broad–scale patterns in the distribution of some elements reflect compositional variations in both the Lower Palaeozoic turbidite sequence and the Criffel–Dalbeattie granodiorite complex, both of which may be sub–divided into specific units on the basis of the geochemical data. The follow–up of Cu anomalies in drainage samples from the Black Stockarton Moor area led to the discovery of porphyry–style Cu mineralisation (Report No. 30) and related disseminated Cu mineralisation at Screel Burn. The area to the west of the Criffel–Dalbeattie plutonic complex is also characterised by relatively high B levels in stream sediments, which reflect the widespread occurrence of tourmaline both in association with and peripheral to the Cu mineralisation. Vein mineralisation, usually containing baryte in addition to base metals, is identifiable from the drainage survey at the eastern margin of the Criffel–Dalbeattie granodiorite, in association with the Lower Carboniferous rocks along the Solway coast, and within the Lower Palaeozoic turbidites in the west of the area.

20 Geophysical field techniques for mineral exploration (3.55 Mb)

A J Burley, J D Cornwell and J M C Tombs (1978)

Details are given of the geophysical equipment and methods used in airborne and ground surveys for the Mineral Reconnaissance Programme. Airborne surveys employ magnetic, electromagnetic and radiometric equipment. Ground surveys use electromagnetic (Slingram, Turam and VLF), resistivity and induced polarisation, magnetic and gravity methods. Borehole logging methods are also described and six case histories are given.