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Mineral Reconnaissance Programme (MRP) reports 51–60

51 A reconnaissance geochemical survey of Anglesey [9.63 Mb]

D C Cooper, M J C Nutt and D J Morgan (1982)

A reconnaissance field survey identified three groups of mineral occurrences, (a) copper, (b) copper (lead, zinc) and (c) baryte (lead), of which (b) is the most important. Drainage samples were collected from 440 sites, and soil samples were collected from three areas of poor drainage and thin drift cover. Cu, Pb, Zn, Ba, Fe, Mn, Co, Ni and Mo were determined in sediment samples and Cu, Pb, Zn, Ba, Fe, Mn, Ti, Ni, Sn, Sb and Ca in panned concentrates. Cu, Pb and Zn were determined in soil and water samples. The geochemical drainage survey encountered major difficulties from the lack of surface drainage, contamination, subdued topography, variable background geology and extensive drift deposits. The comparison of statistical analyses and mineralogical observations indicated that all high Sn and Sb levels were related to contamination and that factor analysis was an effective means of discrimination between anomalies caused by contamination and those due to mineralisation. Eighteen anomalous areas related to sulphide or baryte mineralisation were delineated. Six of these––at Carmel Head, Llandyfrydog, City Dulas, Llanbadrig, Cerrigceinwen and Lligwy—were the subject of further study.

52 Geochemical reconnaissance in the Cheshire Basin (pages 1–13) [2.66 Mb]

J H Bateson (1982)

Geochemical maps are presented to show the distribution of anomalous values of Cu, Pb and Co in soil samples from five areas on the outcrop of the Triassic Helsby Sandstone and Tarporley Siltstone formations. In each area the soil geochemistry identified the known area of mineralisation. Several other small areas with anomalously high soil values are presumed to reflect local, hitherto unknown mineralisation, but none of them appears to have the areal extent necessary for economic deposits. Suitable porous host rocks and fault structures appear to be common factors in the final location of the mineralisation.

52 Titanium dioxide in the Ayrshire Bauxitic Clay (pages 14–18) [2.66 Mb]

I B Cameron (1982)

TiO2 contents range from 1.2% to 14.17%, with a mean of 4.68%. The TiO2 is thought to come from the Carboniferous Passage Group lavas from which the clay is derived, the process of residual concentration being responsible for upgrading it. Extraction of Ti from bauxite has not yet proved possible, even at much higher grades.

52 The Marl Slate (Kupferschiefer) in the Southern North Sea Basin (pages 19–26) [2.66 Mb]

H W Haslam (1982)

Samples of the Permian Marl Slate from borehole cores in the Southern North Sea Basin were analysed for Cu, Pb, Zn, Ag, V, Ni, Co, Sb, As, Cr, Mo, Sn and Mn. The geochemical characteristics are similar to those described in Germany and north–east England. Maximum values of 7000 ppm Cu, 1.3% Zn and 340 ppm Pb were recorded.

53 Investigation of polymetallic mineralisation in Lower Devonian volcanics near Alva, central Scotland [4.35 Mb]

I H S Hall, M J Gallagher, B R H Skilton and C E Johnson (1982)

Boreholes drilled on three known occurrences of fracture–controlled mineralisation in the Lower Devonian Ochil Volcanic Formation intersected mineralised structures which contain only minor amounts of baryte and geochemical enrichments of Cu, As and U. Earlier Ag–Co mineralisation appears to have been followed by Cu–Ba mineralisation. Differential fracturing within the volcanic sequence and increased brecciation at fault intersections are the principal controls.

54 Copper mineralisation near Middleton Tyas, North Yorkshire [3.28 Mb]

A J Wadge and others (1982)

Geochemical soil sampling outlined an area of 6 km2 of anomalous Cu values to the south of the mined area at Middleton Tyas. The drift in this area is thick, and the cause of the anomalies is not known. Examination of the known mineralisation in the area, which occurs in Lower Carboniferous limestones, suggest that it originated from metalliferous brines migrating from the Stainmore Trough or a similar Lower Carboniferous sedimentary basin to the east. The possibility that the mineralisation is syngenetic is now discounted, and shallow holes into the Permian succession showed that no Kupferschiefer facies is present, which eliminates the Permian as a source for the Cu. The primary Cu sulphides were enhanced in grade by supergene enrichment under arid conditions in early Permian times.

55 Mineral exploration in the area of the Fore Burn igneous complex, south–western Scotland [4.13 Mb]

P M Allen and others (1982)

The Fore Burn igneous complex consists mainly of quartz microdiorite, tonalite and feldspar porphyry forming semi–concordant or concordant bodies in early Devonian volcanic and sedimentary rocks, just north of the Southern Upland Fault, 24 km east of Girvan. Several small bodies of intrusion breccia occur within the complex and the country rock and there is a zone of monolithological breccias along a fault followed by the Fore Burn itself. Alteration to sericite, carbonate and chlorite is widespread, and tourmaline is also widely distributed. The most intensely altered rocks occur in the breccia zone along the Fore Burn. There the breccias contain locally abundant disseminated sulphides and are cut by veins rich in sulphides. Drainage and rock geochemistry and detailed mineralogical study showed that arsenopyrite, pyrite and chalcopyrite occur in the breccia zone, with smaller quantities of tennantite, tetrahedrite and cobaltite. Cu, As, Mo, Au, Sb, Bi, Co, Ni, Pb, and Zn were all enriched in mineralised rock. Native gold was identified in a quartz–tourmaline vein, with chalcopyrite and other sulphides. Geophysical surveys located three small areas of low resistivity, one of which is in the breccia zone. The induced polarisation chargeability levels do not indicate any widespread, significant, near–surface disseminated sulphide mineralisation.

56 Geophysical and geochemical investigations over the Long Rake, Haddon Fields, Derbyshire [4.79 Mb]

M J Brown and R D Ogilvy (1982)

Geophysical and geochemical investigations were undertaken over the Long Rake, a major mineralised vein in Dinantian limestones, to establish which methods show the best response to the mineralisation. The mineralised structure carries high concentrations of fluorite with associated lead and zinc minerals and the gangue minerals barite and calcite. Gravity and magnetic anomalies such as those obtained over the Long Rake could have limited applications for the indirect location of veins whose approximate position is known. Induced polarisation, resistivity and electromagnetic measurements failed to produce anomalies that could be directly attributed to the mineralisation or its host structure. However, reconnaissance mapping with very low frequency electromagnetic and Radiohm methods showed that, over a large section of the survey area, the fluorspar vein could be mapped by its association with the sub–drift shale–limestone contact. The determination of a wide range of elements in soils and tills showed that the more mobile elements, such as F and Zn, are particularly useful in detecting mineralisation over broad areas. Less mobile elements tend to exhibit localised dispersion patterns, which have applications for the precise location of an orebody. Pb, Ba, Sr, Ca, Zn, Rb and Th are enriched in soils above the Long Rake in areas of thin overburden, but only Ba, Sr and Pb maintain significant contrast in thickening cover towards the west. The use of basal till samples was found to have no advantage over subsurface soil samples, as geochemical contrast was not improved.

57 Mineral exploration in the Ravenstonedale area, Cumbria [2.40 Mb]

J H Bateson and A D Evans (1982)

Following stream–sediment and soil sampling, four areas of anomalous Cu, Pb and Zn in soils were recognised in an area of Lower Carboniferous rocks close to the Silurian unconformity: at Stennerskeugh Clouds, Birkett Common, Crosby Garrett Fell and Windy Hill. VLF–EM and IP surveys at Stennerskeugh Clouds and Crosby Garrett Fell showed anomalies attributed to the presence of shale bands in the Carboniferous succession. Previous geophysical surveys at Birkett Common had suggested the presence of small mineralised structures, but the present geochemical and geophysical results do not indicate the presence of mineralisation of economic significance in the area.

58 Investigations of small intrusions in southern Scotland [3.48 Mb]

D C Cooper, M E Parker and P M Allen (1982)

Sixteen small Caledonian intrusions, ranging from granite to diorite, were examined for indications of disseminated mineralisation. Stream–sediment and panned concentrate samples were collected from streams crossing some of the intrusions, and reconnaissance geophysical surveys were conducted over Priestlaw, Cockburn Law and Lamberton Moor. Rock samples from some of the intrusions were analysed for major and trace elements. Hydrothermal alteration—in places with associated pyrite—was recorded at Mains of Dhuloch, Mochrum, Priesthope, Lamberton Moor, Broad Law, Glenluce, Priestlaw, Cockburn Law and Mull of Galloway. Cu enrichments were recorded locally, but it was concluded that in no case is there a likelihood of appreciable porphyry copper mineralisation at or near the surface.

59 Stratabound arsenic and vein antimony mineralisation in Silurian greywackes at Glendinning, south Scotland [7.59 Mb]

M J Gallagher and others (1983)

Stratiform and disseminated pyrite–arsenopyrite concentrations are overprinted by fracture–controlled polymetallic mineralisation, including stibnite, in Silurian sediments at Glendinning, near Langholm. Three shallow boreholes were drilled on an anomaly defined by VLF–EM and IP surveys and by Sb values >20 ppm in thin, B–C horizon soils. A parallel conductive zone with an accompanying soil anomaly but lacking an IP response was investigated by a fourth hole. The stratabound sulphides form disseminations and bands parallel to the bedding and are particularly concentrated in intraformational breccia units regarded as debris flows, which, together with the presence of small–scale slump folds in the greywackes, testify to the existence of an unstable slope during sedimentation. The thickest such unit has a true thickness of 4m and, together with 8m of adjoining greywackes, grades 0.7% As and 0.07 ppm Au. Phases of fracture–controlled Fe–As–Sb–Pb–Zn–Cu–(?)Hg mineralisation associated with widespread dolomite and quartz veinlets and narrow breccia veins are superimposed on the strata–bound mineralisation. Their spatial association with the strata–bound mineralisation and the presence of up to 0.33% Sb in the stratiform arsenopyrite and as much as 5% As in the stratiform pyrite favour a common source for the As and Sb. This source was probably a synsedimentary metal accumulation in a mid or lower fan environment in which euxinic conditions developed periodically. (After publication of this report most of the drill cores were analysed for Au by BP Minerals International Ltd: maximum values were 0.4 ppm Au over 3.7 m true thickness of breccia vein and fractured siltstone.)

60 Mineral investigations at Carrock Fell, Cumbria. Part 2—Geochemical investigations [4.28 Mb]

M J Brown (1983)

Soil samples were collected from an area of 5 km2 around the tungsten veins at Carrock. New areas of mineral potential to the northeast of the mine were identified from the coincidence of geochemical anomalies with strong linear VLF features. High levels of W, Cu, Zn, As, Rb and Pb and low levels of Sr are evident in the soils above the worked veins. These elements, with the exception of As, constitute a broad zone of anomalously high values to the north and east of the vein system, accompanied by low Sr values extending up to 1km east of the worked veins over a distance of 1.2km north–south. A broad As halo is apparent for some 800m west of the main vein system. The distribution patterns of some elements unrelated to mineralisation reflect bedrock lithological variation. Gamma spectrometry demonstrates a distinct increase in the K/Th ratios over the main veins and delineates a potential area of mineralisation to the west of the mine, coincident with a strong VLF anomaly. Qualitative, contoured maps of the count rate for the U and K channels delineate the sub–outcrop of the granite. The geochemical results and previously reported geophysical results (Report No. 33) enabled three areas to be recommended for further, detailed exploration.