Mineral Reconnaissance Programme Report
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Natural Environment Research Council Institute of Geological Sciences Mineral Reconnaissance Programme Report -4 A report prepared for the Department of Industry This report relates to work carried out by the institute of Geological Sciences on behalf of the Department of Industry. The information contained herein must not be published without reference to the Director, Institute of Geological Sciences D. Ostle Programme Manager Institute of Geological Sciences Keyworth, Nottingham NG12 5GG No. 53 Investigation of polymetallic mineralisation in Lower Devonian volcanics near Alva, central Scotland INSTITUTE OF GEOLOGICAL SCIENCES Natural Environment Research Council Mineral Reconnaissance Programme I Report No. 53 Investigation of polymetallic mineralisation in Lower Devonian volcanics near Alva, central Scotland Geology I. H. S. Hall, BSc I Drilling and Geochemistry M. J. Gallagher, PhD, MIMM 1 * Petrography B. R. H. Skilton, BSc 1 Geophysics C. E. Johnson, MSc I 0 Crown copyright 1982 London 1982 A report prepared for the Department of industry Mineral Reconnaissance Programme Reports 38 Geophysical evidence for a concealed eastern extension of the Tanygrisiau microgranite and its 10 Geophysical surveys around Talnotry mine, possible relationship to mineralisation Kirkcudbrightshire, Scotland 39 Copper-bearing intrusive rocks at Cairngarroch Bay, 11 A study of the space form of the Cornubian granite south-west Scotland batholith and its application to detailed gravity 40 Stratabound barium-zinc mineralisation in Dalradian surveys in Cornwall schist near Aberfeldy, Scotland: Final report 12 Mineral investigations in the Teign Valley, Devon. 41 Metalliferous mineralisation near Lutton, Ivybridge, Part 1 -6arytes Devon 13 Investigation of stratiform sulphide mineralisation at 42 Mineral exploration in the area around Culvennan McPhun’s Cairn, Argyllshire Fell, Kirkcowan, south-western Scotland 14 Mineral investigations at Woodhall and Longlands in 43 Disseminated copper-molybdenum mineralisation north Cumbria near Ballachulish, Highland Region 15 Investigation of stratiform sulphide mineralisation at 44 Reconnaissance geochemical maps of parts of south Meall Mor, South Knapdale, Argyll Devon and Cornwall 16 Report on geophysical and geological surveys at 45 Mineral investigatons near Bodmin, Cornwall. Part Blackmount, Argyllshire 2 New uranium, tin and copper occurrence in the 17 Lead, zinc and copper mineralisation in basal Tremayne area of St Columb Major Carboniferous rocks at Westwater, south Scotland 46 Gold mineralisation at the southern margin of the 18 A mineral reconnaissance survey of the Loch Doon granitoid complex, south-west Scotland Doon-Glenkens area, south-west Scotland 47 An airborne geophysical survey of the Whin Sill 19 A reconnaissance geochemical drainage survey of between Haltwhistle and Scats’ Gap, south the Criffel-Dalbeattie granodiorite complex and its Northumberland environs 48 Mineral investigations near Bodmin, Cornwall. Part 20 Geophysical field techniques for mineral exploration 3 The Mulberry and Wheal Prosper area 21 A geochemical drainage survey of the Fleet granitic 49 Seismic and gravity surveys over the concealed complex and its environs granite ridge at Bosworgy, Cornwall 22 Geochemical and geophysical investigations north- 50 Geochemical drainage survey of central Argyll, west of Llanrwst, North Wales Scotland 23 Disseminated sulphide mineralisation at Garbh 51 A reconnaissance geochemical survey of Anglesey Achadh, Argyllshire, Scotland 52 Miscellaneous investigations on mineralisation in 24 Geophysical investigations along parts of the Dent sedimentary rocks and Augill Faults 53 Investigation of polymetallic mineralisation in Lower 25 Mineral investigations near Bodmin, Cornwall. Part Devonian volcanics near Alva, central Scotland l-Airborne and ground geophysical surveys 26 Stratabound barium-zinc mineralisation in Dalradian schist near Aberfeldy, Scotland: Preliminary report 27 Airborne geophysical survey of part of Anglesey, North Wales 28 A mineral reconnaissance survey of the Abington-Biggar-Moffat area, south-central Scotland 29 Mineral exploration in the Harlech Dome, North Wales 30 Porphyry style copper mineralisation at Black Stockarton Moorsouth-west Scotland 31 Geophysical investigations in the Closehouse-Lunedale area The Institute of Geological Sciences was formed by the incorporation of the Geological Survey of Great Britain and 32 Investigations at Polyphant, near Launceston, the Geological Museum with Overseas Geological Surveys Cornwall and is a constituent body of the Natural Environment 33 Mineral investigations at Carrock Fell, Cumbria. Part Research Council 1 -Geophysical survey 34 Results of a gravity survey of the south-west margin Bibliographical reference of Dartmoor, Devon Hall, I. H. S., Gallagher, M. J. and others.’ 1982. 35 Geophysical investigation of chromite-bearing Investigation of polymetallic mineralisation in ultrabasic rocks in the Baltasound-Hagdale area, Lower Devonian volcanics near Alva, central Scotland. Unst, Shetland Islands Mineral Reconnaissance Programme Rep. Inst. Geol. Sci., No. 53 36 An appraisal of the VLF ground resistivity technique as an aid to mineral exploration 37 Compilation of stratabound mineralisation in the Printed in England for the Institute of Geological Sciences Scottish Caledonides by Rank Xerox CONTENTS flow in alternating lavas and fragmental volcanic rocks I5 Summary 1 8 Schematic diagram of silver lode formerly worked at Silver Glen, Alva 16 Introduction 1 Location 1 Mining history 1 TABLES Scope of the present investigation 1 1 Summary characteristics of boreholes 4 2 Average compositions of rock types from GeoIogy 3 the Ochil Volcanic Formation 9 Succession 3 Ochil Volcanic Formation 3 Lower Devonian intrusions 4 Permo-Carboniferous intrusions 4 Faulting 4 Ochil Fault 4 Mineralisation 6 Lithogeochemistry 6 Geology of the Burnside district 6 General 6 Former mine workings 6 Borehole data 10 GeoIogy of the Balquharn district 11 General 11 Borehole data 11 Geology of the Blairlogie district 13 General 13 Borehole data 13 Conclusions 13 Acknowledgements 17 References I7 Appendix I Borehole logs 18 Appendix II Geochemical data for core and chip samples 25 Appendix III Petrographical descriptions of selected core specimens 27 Appendix IV X-ray diffraction scans on Alva core samples 30 Appendix V X-ray determinations of minerals from Alva core samples 31 Appendix VI Geophysical surveys 32 FIGURES - 1 Generalised geology of the eastern part of central Scotland 2 2 Map showing fault pattern along southern margin of Ochil Hills and borehole sites 5 3 Orientation of mineralised structures 5 4a Geological plan of Bumside, borehole 1 7 4b Section of Bumside, borehole 1 8 5 Geological plan and section of Balquham, borehole 2 12 6 Geological plan and section of Blairlogie, borehole 3 14 7 Diagrammatic representation of differential a I 8 SUMMARY heaps for use in the pottery industry, following I its first recognition in 1759. The subsurface characteristics of three known A detailed modern account of the mineralisa- occurrences of fracture-controlled mineralisation tion in the Alva area is already available (Francis 8 in the Lower Devonian Ochil Volcanic Formation and others, 1970), based partly on earlier near Alva, central Scotland, were tested by shallow published records (Wilson and Flett, 1921) so that boreholes. Target structures were intersected by only brief reference to the main localities is needed each borehole, but they contain only minor here. However, it is of interest to note that I amounts of baryte and geochemical enrichments of anomalous radioactivity was identified for the copper, arsenic and uranium. Differential fractur- first time at several localities in the relatively ing within the variegated volcanic sequence and recent examination of the area (Francis and I enhanced brecciation at fault intersections are Dawson, in Francis and others, 1970). A brief principal controls. Earlier silver-cobalt mineralisa- reference to the Alva area is made in the tion appears to have been followed by copper- ‘Mineral Deposits of Europe’ volume dealing with 4 barium mineralisation. The andesitic rocks of the north-west Europe (Dunham and others, 1978). volcanic pile represent a suitable source for the Two main groups of workings can be metals. recognised, depending on whether (a) silver was produced or (b) other metals such as copper, iron 8 or lead were exploited, as follows: Mine locality National Grid INTRODUCTION Reference (NS) D LOCATION The three sites on which this investigation is based a. Silver producers lie along the southern margin of the Ochil Hills, 1 Airthrey 815 972 I some 45 km to the north-west of Edinburgh 2 Alva 892 976 (Figure 1). They are situated either at the base of 3 Carnaughton 878 975 the steep south-facing scar-p of the Ochils 4 Tillicoultry 912 978 I (Blairlogie, Balquharn) or at a short distance above the sharp break of slope as in Alva Silver b. Producers of other metals Glen (Burnside). At all three sites, however, 5 Airthrey Hill 795 978 access for heavy equipment is so severely restricted 6 Allan Water 787 983 I that optimum drilling positions were unobtainable. 7 Alva 892 976 8 Jerah 832 995 9 Tillicoultry (Daiglen) 911983 I MINING HISTORY Metalliferous mineralisation was exploited in the It can be seen that copper, as well as silver and Alva area intermittently from the seventeenth cobalt, were produced from the Silver Glen work- to the nineteenth centuries at numerous small ings