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 The information contained herein must not be published without reference to the Director, Institute of Geological Sciences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 at Alva. 1 mines, many of which were little more than trial In general it would appear that mining in the adits into steep valley and hill sides. This is particu- Alva area was restricted by awkward terrain and larly true of many small baryte veins in the area lack of capital as well as by the small size of the I where trial workings probably represent unsuccess- deposits. ful prospects for copper or silver. By far the most successful workings were in the Silver Glen, a little 1 to the north-east of Alva, where mineralisation was first discovered in 1711. These workings SCOPE OF THE PRESENT INVESTIGATION provided most of the silver produced from the area in the early part of the eighteenth century. A small programme of shallow drilling was carried D Records suggest that this amounted to at least 45 out in 1978 to investigate the sub-surface tonnes of ore assaying 85% Ag. Furthermore, a characteristics of three of the more significant substantial amount of cobalt ore was produced occurrences of mineralisation in the Ochil Volcanic I from the Alva Silver Glen workings and earlier spoil Formation near Alva. Prior geophysical surveys D 1 . . . .
. . . NN. ’ , - . -00
E CARBONIFEROUS
a UPPER DEVONIAN
LOWER DEVONIAN I3 SEDIMENTS LOWER DEVONIAN -I- DUNFERMLINE jg VOLCAN ICS DALRAD IAN h9 - - MAJOR FAULTS Fig. 1 Generalised geology of central Scotland
2 were attempted but because of the high level of The oldest rocks cropping out in this area cultural noise meaningful results were unobtainable comprise the Lower Devonian Ochil Volcanic (see Appendix N). As geochemical soil sampling Formation. The regional dip is to the north-west at was also inhibited by artifacts and the nature of about 15” and near Tillicoultry they are c. 2400 m the topography, the selection of drilling sites was thick. No base is seen but c.900 m of older rocks based entirely on the available geological and occur further east bringing the total thickness to a mining information. The criteria for selection of minimum of 3300 m (Francis and others, 1970). the three borehole sites are presented in the detail- The volcanics are succeeded by over 4000 m of ed accounts of the Burnside, Balquharn and Lower Devonian sediments, of which the lowest Blairlogie districts given later in the report. The . 1000 m are largely derived from the volcanic rocks. plans of each borehole site given in Figures 4a, 5 These sediments occupy a broad tract of land to and 6 are based on theodolite surveys. the north of the Ochil Hills but are absent in the Locational and other information concerning east where the Upper Devonian lies unconformably the three boreholes are summarised in Table 1. on the volcanic rocks. Core recovery exceeded 95% overall but significant The Upper Devonian and Lower Carboniferous losses occurred over small sections in the drilling rocks do not crop out in this area but are almost of all three boreholes. These losses are most certainly present at depth on the south side of the probably attributable to intersections with fracture Ochil Fault. Various groups of the Upper Carbon- zones, some of which may carry mineralisation. iferous abut against the Ochil Fault and there is Unfortunately, sludge sampling proved impossible evidence that at least the highest divisions thin because of the loss of drilling returns over the towards the fault (Francis, 1956). same sections. Boulder clay covers the lower part of the Ochil Following the detailed logging of the borehole Fault scarp and extends southwards where it is in cores (Appendix I), the mineralised intersections turn covered by post-Glacial Carse Clays. All the and the typical rock types were subsampled for south-draining streams have developed alluvial geochemical analysis (Appendix II) and for petro- cones at the base of the scarp and spread out over graphical and mineralogical studies (Appendix III the Cat-se Clays. Screes and hillwash have also and Appendix N-V respectively). A suite of developed in places along the fault scarp. channel samples was also taken for analysis from the old mine workings in Alva Silver Glen (Table N, Appendix II). OCHIL VOLCANIC FORMATION Geochemical sampling of tributary alluvium The Ochil Volcanic Formation consists of a thick from the entire area of the Ochil Hills has been sequence of lavas with interdigitating coarse tuffs carried out in recent years and the analytical and agglomerates cut by frequent minor intrusions. results are being prepared in map form for future The lavas are mainly andesites and basal& publication. many of which have a chemical composition near the andesite-basalt boundary (Francis and others, 1970). Several varieties of andesite, notably pyroxene-andesite with feldspar GEOLOGY phenocrysts, pyroxene-andesite and homblend- andesite occur together with subordinate SUCCESSION trachyandesite and rhyodacite. Many of the The general succession of geological formations in lavas have fissures filled with sandstone and this area is summarised below: siltstone indicating contemparary deposition of Superficial deposits exotic sediments. Thus, though the lavas provided Recent and Pleistocene considerable detritus, subsidence was also taking Scree place in some areas. Most of the lavas show altera- Freshwater Alluvium (as alluvial cones) tion with replacement by carbonate and chlorite Marine and estuarine alluvium (post-Glacial) and albitisation is particularly prevalent. Recent Boulder clay work (French and others, 1977) suggests that potassic metasomatism took place at a late stage Solid formations in the volcanic history of the western Ochil Hills. Carboniferous Thickness, m The coarse tuffs, lapilli tuffs and agglomerates Upper Carboniferous (including show considerable lateral variation in thickness Coal Measures) 1350 but are coarsest and thickest along the southern Lower Carboniferous unknown margin of the Ochil Hills suggesting that this area Devonian was proximal to the source. They include rocks Upper Devonian (Old Red Sandstone) 325 which appear to be partially of sedimentary Lower Devonian (Old Red Sandstone) origin and may also include autobrecciated lavas Various formations of conglomerate which have a very similar appearance. The sandstone and mudstone 4200 composition of the fragmental material in the Ochil Volcanic Formation 3300
3 I Tabie 1 Summary characteristics of boreholes
Borehole No. I. 2 3 I Borehole name Bmrnside Balquharn Blairlogie NGR (NS) 8915 9757 8674 9742 8293 9690 Collar elevation (m) 93.4 50 (approx.) 17.5 u Inclination/azimuth (magnetic) a At surface 451053 45/060 451076 b Tropari surveys at 49/054 ( 80.0 m) 43/061 (150.0 m) 45/073 (100.0 m) I various depths 431049 (140.0 m) 41/047 (186.0 m) I Depth (m) 215.15 160.74 115.23 Map references I:50 000 39E (Alloa) I 1:lO 560 NS 89 NE NS 89 NE NS 89 NW
pyroclastics is largely comparable with that of the son with other well exposed areas of rocks of u lavas but also includes some fragments of a felsitic similar age to the north and east suggests that it is nature which cannot be matched locally. factual rather than apparent. Two main trends of fracturing occur, one roughly north-west and the other roughly north-east. These are considered to I LOWER DE VONIAN INTRUSIONS be of Lower Devonian age because of their close The volcanics are cut by many intrusions, the most association with the Lower Devonian dykes. A important of which are the diorite stocks near third, less common trend occurs, roughly east-west, I Tillicoultry. The stocks are cut off by the Ochil which is thought to be of Permo-Carboniferous Fault but geophysical evidence (McQuillin, in age by anology with neighbouring structures in the Francis and others, 1970) suggests that they Midland Valley. 8 extend, at depth, under the younger sediments All these trends have been mineralised to some to the south side of the fault. There is a meta- extent.. morphic aureole round the stocks with the devel- opment of feldspar porphyroblasts and aplitic I veins which, at the present level of erosion, OCHIL FA UL T extends outwards for c. 400 m. There are also The Ochil Fault is the dominant structure in this frequent dykes cutting the volcanic rocks, area and trends roughly east-west. It is a major 1 mostly albitised porphyrites, porphyries and fault with maximum downthrow near Alva which plagiophyres. Textural and petrological evidence decreases both to east and west. In this area, there suggest a genetic relationship between the diorites are about 650 m of volcanic rocks below Lower u and the dykes (Francis and others, 1970). The Devonian sediments in the scarp to the north of latter display a crude radial relationship to the the fault. To the south of the fault there is diorite stocks and also a marked concentration estimated to be 1000 to 1500 m of Upper Carbon- parallel to the main fault trends. This suggests if erous sediments, and probably also Lower 8 that the structural grain was already established Carboniferous, Upper Devonian and possibly before the intrusions were emplaced and possibly Lower Devonian sediments overlying the volcanic explains the fact that these trends can seldom be rocks exposed to the north of the fault. Thus the I traced in the overlying sediments. minimum displacement is 2000 m and possibly considerably greater. Limited field evidence indicates the southerly hade of a normai fault PERMO-CARBONIFEROUS INTRUSIONS but this is at variance with geophysical evidence I Discontinuous intrusions of quartz-dolerite cut the which suggests a northerly hade (Davison, 1924). volcanic rocks along the line of the Ochil Fault. Alternatively, the geophysical evidence may These are assumed to be of Permo-Carboniferous indicate a second subsurface structure hading 8 age by comparison with neighbouring areas. north, parallel to and north of the Ochil Fault. Recent comparatively shallow seismic activity also appears to have been centred north of the fault I FA UL TING (Davison, 1924; Burton and Neilson, 1979) and A number of faults affect the Ochil Volcanic along the fault (Dollar, 195 1). Formation and are most frequent along the The evidence of structure, vulcanicity, sedi- southern margin (Figure 2). This concentration mentation and the geophysicaI data all suggest 8 may be partly due to good exposure, but compari- that a zone along the Ochil Fault has had a long II 4 0 2km I --- Fault
Fig.2 Map showing fault pattern along southern margin of Ochil Hills and borehole sites
A
B
A) Baryte copper B) Calcite iron (oxide) C) Calcite iron (sulphide)
I I I I I I 1 6 4 2 0 2 4 6
Fig 3. Orientation of mineralised structures
5 and complex history. is attributable to veining. On this basis, it can be in- ferred that the rocks of the Ochil Volcanic Forma- tion represent suitable source-rocks for most of the MINERALISATION metals now found in the vein structures. The All the known mineralisation in the Ochil Hills is exceptions are Cu and Co, for which the values along fault planes and fracture zones which in given in Table 2 are only about one-half of those some cases are also the sites of minor intrusions. of the average basalt, and possibly also Ba which The three main trends of faulting (Figure 3) have is present at only normal levels in the lavas and all been mineralised to some extent but are fragmental volcanic rocks. characterised by different associations of minerals The brecciated and veined volcanic rocks are (Francis and Dawson, in Francis and others, 1970). characterised not only by high Ca and Ba values A plot of the recorded mineral veins shows the due to carbonate and baryte veining but also by NW-SE trend (A in Figure 3) to be the most slightly enhanced values of As, Ag and Sb common. This trend has a dominantly baryte- compared with the other groups in Table 2. In copper association with iron and lead occurring BH 2 (Balquharn) a 4.74 m intersection in in small quantities and calcite and quartz as less brecciated rocks averages 2.3% Ba (Appendix II, common gangue minerals. Most of the iron occurs Table II). The rather high uranium content of the as pyrite. material recovered from the radioactive inter- The NE-SW trend (B in Figure 3) has a section in BH 1 (Burnside) is also of note (CXD dominantly calcite-iron association with the iron 119, Appendix II, Table I). occurring as an oxide. Silver with minor cobalt, The most significant values for economic copper and lead occur, and baryte and quartz are metals were those of Cu, Ag and Co obtained from less common gangue minerals. channel samples taken in the workings at Alva The E-W trend (C in Figure 3) is the least Silver Glen (Appendix II, Table IV). Up to 1.46% common and least well defined in direction. This Cu with 27 ppm Ag is present over 0.9 m (CXD trend also has a dominantly calcite-iron association 202) and 0.085% Co with 0.07% Cu over 2.5 m but in this case the iron occurs mostly as pyrite. (CXD 209). Silver and copper, with subordinate lead, arsenic and cobalt also occur, with quartz and minor baryte as gangue minerals. The Ochil Fault also follows this trend but there is no mineralisation GEOLOGY OF THE BURNSIDE DISTRICT visible or recorded at the few localities where it is exposed. GENERAL It has been suggested (op. cit.) that the NE- This district is one of complex geology where inter- SW and E-W trending faults (i.e. the calcite- bedded andesitic lavas and agglomerates have been iron associations) were mineralised during the affected by faults, intrusions and hydrothermal Permo-Carboniferous and the NW-SE trend was veins. Apart from a thin cover of hillwash and talus mineralised in Tertiary times. K-Ar ages on illite- in places, the area is largely drift-free, but natural rich concentrates from the mineralised rocks of exposure has been modified by spoil from the old the Alva area are late Carboniferous to early mine workings and opencast trenches dug along Permian (260-300 Ma) (Ineson and Mitchell, mineralised structures. 1974). Along the southern margin of the district quartz-dolerite has been intruded along the line of the Ochil Fault (Figure 4a). This intrusion has a LITHOGEOCHEMISTR Y pod-shaped outcrop which is about 80 m wide in Analyses of 31 selected core samples and 12 Silver Glen and the agglomerate which it cuts is channel samples for selected minor and major bleached, brecciated and contains a little elements are given in Appendix II. On the basis disseminated pyrite near the contact. To the north of the core analyses, average metal values have of the intrusion the succession comprises alterna- been calculated for the three main volcanic rock tions of thin andesitic lavas and agglomerates types in Table 2. A fourth category of brecciated which are overlain by a thick sequence of andesitic and veined core samples is also represented. lavas seen in the northern part of the district. Despite the small sample populations, composi- The lowest part of the sequence, seen only in the tional variability between samples of the same borehole (Figure 4b), comprises a minimum of lithological class, and the effects of calcite and 30 m of fragmental volcanic rock which includes baryte veining, several elements are -appreciably tuffs and agglomerates. enriched in the volcanics when compared against crustal abundance values for basaltic rocks (Turekian and Wedepohl, 1961; Taylor, 1964) FORMER MINE WORKINGS notably As: Rb, Zr, MO, Ag, Sb, Pb, Th and U. The main mineralisation occurs in the central part These metals most probably respresent inherent en- of the district, between the ENE-WSW fault (K in richments whereas the high Ba content of the tuffs Figure 4a) and the NW-SE fault H. No mineralisa-
6 .. b b b b b b b b b b b b b b b t b I 140- s45w N45t I I I I I I I I I I I I 1
I Geological boundary, Solid Fault, crossmark on .- downthrow side I Mineralized structure
Underground workings I Referred to in text I I Fig.&, Section of Burnside, Borehole 1
8 I Table 2 Average compositions of rock types from t le Ochil Volcanic Formation
Lavas Fragmental Tuffs Breccia ted and I volcanic rocks veined rocks
No. of I samples 11 5 7 5 % Ca 3.0 4.1 11.4 I Ti 0.73 0.64 0.36 Mn 0.079 0.083 0.20 Fe 5.8 5.5 4.0 I PPm co 26 23 26 26 Ni 55 35 44 36 cu 36 53 31 22 I Zn 97 62 62 45 As 22 11 12 34 Rb 63 66 26 I Sr 370 260 250 Y 26 24 20 Zr 270 250 160 Nb 14 9.6 6.8 I MO 2.6 3.0 3.0 Ag 1.1 1.0 1.4 1.8 Sn 1.8 2.0 0.8 1 Sb 2.8 2.4 3.6 Ba 470 370 1650 1150 de 57 46 28 I Pb 12 11 20 12 Th 9.2 8.8 6.8 I.J 3.6 3.6 3.6 2.8
I The values given in italics are regarded as high-anomalous
Individual rock analyses are given in Appendix II
tion is seen along fault K but the parallel fault F, been driven along the extensions of these some 30 m to the north, is one of the most structures from the chamber. From the south-east important mineralised structures in the district. corner a level has been driven for about 30 m Adit A into the east bank of Silver Burn and adit trending 164’ where the structure dips 78’W and B driven into the west bank follow this structure, a drivage has been made on the continuation driven which has been offset by north-south fault J. from the north-east corner of the chamber for I A narrow trench which has been cut on the east c. 5 m trending 350°. From the eastern side of the bank due east of B is believed to have been a chamber a level has been driven for c. 10 m along barren trial dug in an attempt to follow F on the the extension of the main structure (F) trending I east side of the stream. The mineralisation is in a 064” and dipping 78”s. An irregular, subvertical breccia c. 0.6 m wide and comprises calcite, quartz, structure, which appears to be the remnant of the pyrite, chalcopyrite, malachite, arsenopyrite, silver lode, is intersected in the north-east corner I argentite, galena, erythrite, ferruginous gouge and of the chamber and also in the shaft which has botryoids of hydrocarbon. Adit A, on the offset been sunk in the south-west corner of the chamber. continuation of F, is the entrance to a chamber This mineralised breccia appears to be developed 6 by 4 m which was the site of the rich silver lode at the intersection of the two main structures and now known as the ‘Silver Chamber’. The mineral- has a pipe-like form with a variable diameter ised fault and an associated altered thin basic dyke depending on the host rock (Figure 8). It is are seen in the chamber where they are offset by thought that the silver lode may have been a node I another roughly north-south fault (I) which has on this pipe and that the cobalt ore, reputedly also been mineralised. Structure I is more variable mined from the lower level, constituted another in thickness (maximum 0.4 m) and carries baryte, node with the intervening section being formed I quartz, chalcopyrite and malachite. Levels have largely of gangue minerals. Where seen the pipe is I 9 1 m wide and contains baryte, pyrite, chalcopyrite, with some calcite and traces of copper. The drivage malachite, ferruginous gouge and botryoids of to the south is blocked near the entrance but some hydrocarbon. Calcite, quartz, arsenopyrite, argen- baryte veins are seen on its projection in the drivage tite, galena and erythrite have also been recorded between adit B and shaft C. Some surface trench- previously (Francis and others, 1970). The shaft ing to the north of shaft C follows a similar trend. in the chamber is about 2.5 m square and descends Channel samples (Appendix II, Table IV, CXD for about 12 m. A small trial has been driven to the 210-211) collected from both branches of the south about 2 m below the floor of the chamber drivage to the north show high copper values. The and another level has been driven to the east at sample collected from the drivage to the south about 10 m down. A 20 m winze led down from shows high cobalt and nickel values and this intermediate level to a lower level which in moderately high copper values. turn had access to the surface by an unlocated adit (Wilson and Flett , 1921) in Silver Glen some 60 m to the south of the northern margin of the BOREHOLE DATA quartz-dolerite. There is also access to the shaft The Burnside borehole (Table 1) was sited at the from a winze in the north-east corner of the point of nearest reasonable access to the Silver chamber and above this is another shaft from Chamber (A) and aligned so that the mineralised ground level into the chamber. structures seen in the chamber would be Channel samples were collected from the encountered at depth (Figure 4). The sequence mineralised structures in the Silver Chamber and encountered in the borehole was essentially lavas analysed, Appendix II, Table IV. The east and (Appendix III, PTS 50006-10) with thin beds of south drivages gave anomalously high copper and agglomerate in the top 50 m*, overlying a thick silver and higher than normal cobalt values; the development of fragmental volcanic rock. The lavas north drivage gave anomalously high copper but are thin altered andesites, mostly feldsparphyric, neither adit A, the trial from the shaft, nor the but occasionally contain pyroxene phenocrysts. intersection gave any high values. They are typically vesicular with infillings of ,4dit B was driven west along structure F, to chlorite and calcite. The fra 11 occasional pyrite. Veining between 120 and 149 m, BOREHOLE DATA comprising sporadic calcite and dolomite This borehole was aligned to intersect structures B, (Appendix V, XE 279), forms a rather disperse C, D and E at depth (Figure 6). Difficult terrain zone (‘E’) which between 127 and 135 m occasion- and proximity of dwellings precluded intersection ally contains pyrite. Between 149.54 and 155.96 m of the major fault A. The sequence encountered (Appendix III, PTS 5022) carbonate and baryte was composed mainly of altered andesitic lavas veins up to 7 cm thick constitute mineralised zone with two thin bands of fragmental volcanic rock ‘D’. Pyrite and hematite occur in the main veins interbedded near base. Purplish feldsparphyric lava and a little chalcopyrite is associated with cross- (Appendix III, PTS 5023) and microphyric lavas cutting veinlets. Analyses (Appendix II, Table II) occur which are very vesicular, particularly near yielded low metal values except for a small inter- the tops of flows, but often throughout, and show section of baryte-bearing breccia (see ‘Lithogeo- well developed flow structures particularly near the chemistry’). bases of flows. The vesicles are normally filled by Correlation between structures seen at the chlorite and calcite but some of the larger surface and those seen in the borehole is straight- examples containn quartz, dolomite and a little forward in the sense. that structure C, which is the baryte. Throughout the sequence irregular patches projected line of a fault with a throw of c.80 m, of greyish-green tuffaceous sandstone occur both was the only structure anticipated in the borehole, between and within the lava flows. The fragmental and only one good breccia zone (‘C’) was encount- volcanic rocks seen near the base of the hole ered. Mineralised zone ‘D’ in the core may include agglomerate (Appendix III, PTS 5024) and correlate with the continuation of vein B across lapilli tuff. Occasional fragments of pre-existing fault C, but the other zones are not visible at the tuff can be seen in the agglomerate, which in places surface. has a finely comminuted crystal matrix. Veins of quartz and calcite up to 2 cm thick (‘B’) are seen between 8.25 and 8.50 m*. Broken core at 50.60-51.50 m and 53.10-54.10 m, with some loss of recovery, probably represents a GEOLOGY OF THE BLAIRLOGIE DISTRICT structure (‘C’) though the only mineralisation seen GENERAL is some hematite staining on broken surfaces. The Blairlogie district is characterised by thick Broken and jointed core (‘D’), with thin calcite beds of coarse fragmental volcanic rock alternating veinlets, occurs between 70.25 and 71.75 m. with sequences of andesitic lavas (Figures 2 and 6). Structure ‘E’ is also seen as broken core with Within the lava groups there are thin agglomerates brown weathered areas and thin calcite veins and and thin lavas also occur within the fragmental veinlets between 102.25 and 103.36 m. Below this volcanic rock. The lavas are mostly altered a 0.5 cm calcite-baryte vein is developed at 107 m. feldsparphyric andesites though pyroxene-andesites Though none of the core from structures ‘B’, ‘C’, occur in the higher groups. They show typically ‘D’ or ‘E’ contains any significant mineralisation, rubbly vesicular tops and bases and are auto- the structures probably correlate with the project- brecciated in places with some tuffaceous sands- ed positions of surface structures B, C, D and E. stone infillings. The fragmental volcanic rocks are The lack of mineralisation at depth and the largely agglomerate and lapilli tuff. The occurrence of calcite and quartz rather than the agglomerate contains many 0.5-1.5 m blocks and baryte seen at the surface is enigmatic but may be some larger ones, suggesting that this is an area due to the fact that the lavas are less accommodat- proximal to a vent. The area is traversed by several ing as host rocks than the fragmental volcanic NW-SE faults which are well exposed on the rocks higher in the sequence. higher ground to the north of the present site. Mineral veins occur along all the faults, and adits and trials have been made along most of them. The most extensive workings are on fault A (Figure CONCLUSIONS 6) along which adits and winzes have been made at several levels and an adit driven for 18 m in an All three boreholes are considered to be successful easterly direction along a crosscutting vein (Dickie in that they intersected the target structures at or and Forster, 1976). Traces of copper minerals are near their projected positions. Though the amount present in a gangue of baryte with patches of silica of mineralisation encountered in the cores was and fragments of country rock. Native copper, disappointing, the information they provide, tetrahedrite, chrysocolla, chalcocite and malacite together with related surface studies, suggests have been recorded from this area (Francis and certain controls on mineralisation. others, 1970). The overall structural control and relationship with intrusions has already been described (Francis *Depths are not corrected for borehole inclination 13 r I \ -I \ I I * I \ / / ! / ,‘ I I r_ .\ I / !’ *, \ , v I / / / . s 68 w N 68 E 60 Alluvial cone Raised Beach Deposits, Post-Glacial 40 Fragmental Volcanic Rock Lava i Borehole site and alignment _I__- Drift boundary ---_ Geological boundary;solid A.- Fault, crossmark on downthrow side Mineral ized structure Rock outcrop shown by stipple * .:::.... ;., Y-c; :g lSP Spring Wall, house or road . ..a()... Contour, metres -60 0A Referred to in text 0 20 40 metres 14 Fig.6. Geological plan and section of Blairlogie Borehole, 3 FAULT To surface t I AAhAAhAAAA AAAA A ********** AAAAA - A A A A A-A P A A A ****** ********** AAAAAA AAAAAAAAAA ****** A A A A P CA A A A AAAPAA APAhAAAAAA A&&&** AAAhAAAA AAhAAh AA*AAhA hP*hAhAAP**P*AAuAAA A&AA&A AA~AAAAAPPAAAPAAA& AOAAAA AAAAAAAAPAAAA.AA~AAA AAAAPA AAAAAAAAAAAAAAAAAA6A 060, Ad A hAAAA.AAAAAAPAAAAAAA ~AAAAAA AAA~AAAAAAAAAAAAAAAAA “, z Fragmental volcanic rock A Slowdown with potential deposition cl 0 due todispersion of channels 6 Slowdown with potential depositior & FI ow structures in lava 0 due to fewer channels being available 4 Flow of hydrothermal fluids Fig. 7 Diagrammatic representation of differential flow in alternating lavas and fragmental volcanic rocks 15 1 I I t I I 1 1 I I I I 1 1 I Fig 8 Schematic diagram of silver lode formerly worked at Silver Glen, Alva I: t I 1 I 16 and others, 1970). The present work suggests that, Our colleagues E. G. Poole and J. Dawson provided within that framework, concentration may be valuable advice, K. I. G. Lawrie assisted in the field controlled by two main factors. Firstly, because and laboratory and the chemical analyses were of the very uneven texture of the fragmental carried out by T. K. Smith. volcanic rocks, fracturing is more diffuse and irregular than in the more homogeneous lavas (Figure 7). This gives a wider zone of weakness in REFERENCES the former to act as host rock and also a mechanism for differential rates of flow of the Burton, P. W. and Neilson, G. 1979. Earthquake swarms rising fluids. Thus concentrations may be expected in Scotland - A current example. Inst. Geol. Sci., to occur in the tops of thick fra,gmental volcanic Global Seismology Unit, Rep. No. 113, 30 pp. Davison, C. 1924. A history of British earthquakes. rock units (B in Figure 7) by blockage in the over- Cambridge. 416 pp. lying lavas where there are fewer fractures. A Dickie, D. M. and Forster, C. W. (Editors). 1976. &lines reduced rate of flow, with potential deposition, and minerals of the Ochils. Research Group will also occur in the tops of thick lavas and at the Clackmannanshire Field Studies Society. 43 pp. base of overlying units of fragmental volcanic rock Dollar, A. T. J. 1951. Catalogue of Scottish earthquakes, (A in Figure 7) where there is dispersal into a 1916-1949. Trans. Geol. Sot. Glasgow, Vol. 21, pp. 283-361. larger number of narrower and less continuous Dunham, Sir K. and others. 1978. United Kingdom. channels. This may account for the apparently In Bowie, S. H. U., Kvalheim, A. and Haslam, H. W. anomalous distribution of mineralisation at (editors), Jlineral Deposits of Europe, Vol. 1 Blairlogie. The other factor which appears to affect Northwest Europe (London: IMM and Miner. Sot.), concentration is the increase in brecciation on the pp. 263-317. Francis, E. H. 1956. The economic geology of the Stirling line of intersection of two structures. This would and Clackmannan Coalfield, Scotland: Area north of accentuate the difference in fracturing between the the River Forth, Coalfield Pap. Geol. SW-V., No. 1, different rock types giving a nodal distribution 53 PP. where there is interbedding. This is the model - Forsyth, I. H., Reid, W. A. and Armstrong, M. 1970. postulated for the silver-cobalt concentration at The geology of the Stirling district. Mem. Geol. Suru. G. B., Sheet 39,357 pp. Burnside (Figure 8). French, W. J., Hassan, M. D. and Westcott, J. E. 1977. At Burnside the main mineralisation is A celadonite-vermiculite series from the volcanic rocks associated with very altered minor intrusions of the Ochils, Stirlingshire. Mineral. Mag., Vol. 41, which appear to be integral parts of the complex pp. 481-485. Ineson, P. R. and Mitchell, J. G. 1974. K-Ar isotope age hydrothermal veins. The presence of quartzdolerite determinations from some Scottish mineral localities. at Burnside may be significant, but, since silver was Trans. Instn Min. Metall. (Sect. B: Appl. earth sci.), also mined at Airthrey [NS 815 9721 at a Vol. 83, p. B 13-18. ’ considerable distance from any known quartz- Taylor, S. R. 1964. Abundance of chemical elements in dolerite, its role here is more likely to be secondary the continental crust: a new table. Geochim. et Cosmochim. Acta, Vol. 28, p. 1273-1285. remobilisation than genetic. Turekian, K. K. and Wedepohl, K. H. 1961. Distribution The suggested principal controls of polymetallic of the elements in some major units of the earth’s mineralisation in the Western OchiIs may be crust. Bull. Geol. Sot. Am., Vol. 72, pp. 175-191. summarised as: Wilson, G. V. and Flett, J. S. 1921. The lead, zinc, 1 Deposition of Lower Devonian volcanic rocks copper and nickel ores of Scotland. Spec. Rep. Miner. Resour. G. B., Vol. 17, 159 pp. containing traces of copper, barium, silver and cobalt and therefore favourable as source rocks. 2 Emplacement of calcite-pyrite mineralisation with associated silver and cobalt along east-west structures, probably part of the Ochil Fault system; development of penecontemporary north- south structures with concentration of mineralisa- tion at the intersections of these and the east-west structures. 3 Later copper-barium mineralisation associated with NW-SE and NE-SW faulting of Upper Palaeozoic or younger age. ACKNOWLEDGEMENTS The co-operation of landowners and residents in the Alva, Balquharn and Blairlogie districts during the drilling operations is gratefully acknowledged. 17 c APPENDXX I BOREHOLE LOGS Detailed logs of the three Alva boreholes are given here. Reference should be made to Appendices II-III for supple- mentary geochemical and petrographical information. I I 18 - AWWDIX I TASLS I soFmioLE 1 Inclined Inter- depth section LithOlOgy Mineralisation m m 0.00 5.40 5.40 Superficial deposits Regmentd volcanic rock (agglomerate) .withfrsgments of feldsp-rphync Ramifying veinlets of calcite. Traces of lava. Some dark green, microph;rricwith c.hlonte-filled vesicies. pyrite. Some pale pink microphyre with chlorite-filled vesicles. iittle rock 7.90 2.50 matrix (cored in small pieces - recovery 28h) Lava (basaltic sndesite) pale grey with smell feldspar phenocrysts. Celcite veinlets up to 1 !Jm with traces Possibly a block at base of agglomerate. Jointing at 60° and 65o*, of pyrite d-15 0.25 broken near base with displaced veins Lava (pyroxene andesite) grey, vesicular with ohlorite end celcite Calcite veinlets up to 2 avnat 70' infilling. TOP erround away. Jointing 60-650. Fsrrmamesian Vein with gslena at 65' phenocrysts below-8.50 m. -Calcite vei& shou cut-off and‘dxplacment Joints at 70° with traces of pyrite. along minor 500 faults. Broken at 9.21 m. Jointing at ?Oo and 55O below 9.0 m. Core broken along joints 9.50-9.90 m with pyrite films. Base irregular with vein of calcite. Dip of base 20-25' Lava, grey with small, altered feldspar phenocrysts. Calcite and Calcite strsaks chlorite-filled vesicles in places. Joint8 75' and 60'. Pcssibly 11.28 0.44 a lava block. Dip, possibly faulted, at 5 Ra@entsl volcanic rock. Lava blocks, jointed. Vesicular, streaked Pyrite on 25' joint at 11.43 m out with calcite and chlorite infills. Irregular, brovnish-risked calcite and chlorite on 50° joints. Thin, 15.00 3.72 patches of lava with feldspar phenocryets. Joints SO', 6o" end 20°. broken calcite veins, cored as pieces 14.48-14.80 m Ra@nentel volcanic rock. Apperent bedding at 150. Joints at 45' Calcite stringers near base 22.42 7.42 broken at base Lava (pyroxene andesite) with smell, fermmsgnesian phenocrysts. Calcite and dolomite veins 22.47-22.60 m Redominent jointing at 40-50°. Joints at 60' end 85' from 18.20 to 19.0 m. Racturing 21.20-21.93 m. Strong jointing at 64O and 800 below 22.80 m to 23.10 m. Broken near base. No alteration. 24.28 1.86 ?fault or natural. Lava (basaltic an&site) with frequent feldspar phenocrysts end sane Chlorite and pyrite on various joints. olivine pseudomorphs in vesicular matrix. Broken at top. Dominant 26.06-26.41 m traces of pyrite along joints jointing 4S" and 80° with sliokensides on 80°. Bleached vesicular 27.65-27.90 m traces of dissemtnated p@te 28.90 3.62 pale brownish matrix in beaal 70 cm. Dip of base 550 Feldspars present but not obvious. Greenish mey. Pyrite (Pchalcopyrite) infill&g 3 m Oocasionel pyioreni or olivine pseudomorphs in lower p&t, Banding craoks at high sngles and also parallel at 55'. Psle, bleached "Incipient homfelsing" for 10 cm at base. to bending at5P. Thin calcite veins 31.10 2.20 Base in contact tith injection at 85O at similardip but oblique to thin feldsparphyric bands. Thin barytes, ceJ.cita-chlorite-pyritevein (2 mm). Galena at 30.25 m , Lava injection: cuts both nreceedinu end succeedFnn items. Bleached zone cont& strdngers end 3l.JO to feldspa;phyric; 10 cm zone at topand intmaive veFns of pyrite up to 1 om with chlorite 32.96 lower contact at 85-90' end b&es. 7-8 nssvein of chlorite- calcite-p@to (?some haematite) at base. Lava, pale end bleached at wsicliiar; feldspsrs present but Veined with cslcite to 32.62 m. Little 35.00 3.90 not obvious; jointed. pyrite along thin veins. 2 sxscalcite *to vein 33.40-33.75 m. Thin veins with spread of Pyrite and blebs up to 8 mm diameter to 34.93 m. Veins and veinlets in greenish matrix below. Lava: feldsparphyric; pinkish. Brecciated, veined with vugs. Pyrite along top margin up to 1.5 cm. 38.85 3.85 PFnL aphyric lava below 36.50 m Cut by cauplex hydrothermal breccia veM.ng from top to 38.75 m. Ragmentalvolosnic mckwithpale enddarker fra@uente. Jointing Calcite veins 2-3 ssswith pyrite edgee. 55O. More messive below with thin veins end stringers. Bedding Broken band at 39.70 m. Celcite-pyrite- 41.56 2.71 irregular, with broken pieces above base 45' galena stringers, top to 39.62 m. 40.20 m - breccia sane - calcite-mte- galenaandpurpliahquarts. calcitein bandsup to 5 cm Lava. Feldspar and small fermmagnesian phenocryata. Broken bend VeFns and stringers of calcite and pyrite. 41.02 5.46 at 43.02 m. Dip of base 48' Injection veins 43.30 to 43.80 m. Pyrite and calcite-pyrite veinlets and stringers below. Injection so*e with pale 10 cm bend at top with selvagee of chlorite- ce.lcit%-pyriteat 44.63 to 45.65 m. 90' atringers at 45.02 m, 45.2%45.30 m end 46.33-46.50 m of calcite-pyrite. Calcitcchloritbpyrite vein at bottom. Lava; abundant smell to medim feldspars and s- ferrcmagneeian Calcite and pyrite veinlets at 65'. 3 cm phenocrysts. Pale and sltered below 50.38 m. (Thh selvage of calcite-pyrite vein at 48.33 m. Requent So.68 3.66 altered rock at bese.) Dip of base 36O. chlorite-calcite-pyriteveinlets in altered Zone. Injection; fine, baked andpeletop margin. Pale reaction rim some pyrite films. at 0.5 cm basa& margin. (Thin selvage of altered rock at base.) 9.38 0.70 Dip of base 40 Rwentsl volcanic rock. Fine to medium grained at top; coarser Occasionsl films of pyrite and calcite. below vith fine, aphyric, grey fragments; some vesicular, coarser Thin 70° calcite-quartz veins from brown; scme red apbyric and some with microphenocryets (wide rsnge 55.50-55.72 m. Broken end jointedwith of types and weathering). Many of frwente vesicular and brownish calcite and clay tieral films and some below 56.00 m. Jointing sporadic - 750-80' end occasionally 20°. imn-staining between 56.10-56.58 m. 450 joint with Umonite stainbq end some slickensidee acmse planes Thin 2 cm veins of quarts-calcite with from 56.97-57.30 a. Larger, eub-rounded fre@nenta below 57 m. pele pen ?chlorite veins in places. Sporadic 45' and 80' joints, moetly with limonite staining below 80-85 at 57.33 to 58.35 m 58.35 m. core bmken 59 m to 59.83 m. Dissociated block of lava with small feldepars 58.45 to 58.60 m. Broken at base - possibly 59.83 8.45 small fault. RElguLmltalv01csni0 Rock; fwents of vesioulsr and non-vesicular Thiok calcite vetis and stringers aphyric lava in matrix of lava with small felrpar phenocrysts. 62 m Ra@ents often show reaction rim to matrix which in turn is more purplish with round frs@entr - othersmoreirregularon a small scale but still show reection rims to matrix. Sane reddish, ar fwents, others with very diffuse mangins, 200, 45O and 85e? joints at intervals. Core bmken 61.30-61.80 m. 20 cm 65.20 5.37 block of veeioular, aphyric lava at 62 m. 19 I APPZXDIX I TABE I CONTmmD Inclined Inter- bPf.h section LithOlOgy Kinsre.lisation m m Lava, injection with abundant feldspar phenocmsts. Brscciated Quarta4slcitcchlorite veins, often with near top. Phenoorysts obvious in places but difficult to see in flesh-coloured inner margins near top. others. Lowsraargia with veining, 2 cmirids: s0me sltsration Occssionsl blebs of pyrite, both in veins 71.75 6.55 on both sides. Oblique to cars length overj0 cm snd matrix, less frequent below 66.20 m Rssmeeal volcsnio rock. Vesicular *lava" matrix with vesicles Some irregular patches of calcite infilling and-small feldspar phenocrysts. Free&s of similsr material, gaps around some fr snts. 3 cm calcite slightly reddened: others verg vesicular; *ems with reaction vein at 76.9h m andT cm vein at 77.OL m rims: others vith0ut. Wide variety of fragsnts to 80.00 m - bra thin veinlsts of cslcits below 8o.OO m below wstly buf'f-grsyvssiculsr mck with small fsldsp~. but still with irregular infills. Matrirbscomss tuffsseonsdownwrds: compossdofsmsllfrsgssnts 1 cm cslcite vein, JO", to cars length, &aldlapilli. Most largs f-e&s, up to 25 cm. have well-defined at 102.U~ m with pyrite film on joint swgias sad chilled aelvsgus but IU)rsa0tion in the matrix. S0me surface cutting vein at 102.&S m lPrgrrrrrrrrrrrrrrrrrrrrrrtsviUlmolrPluldamargina&~v~.Pals bm=r 0.5 cm calcite vsin at lob.93 m coarse, vssinrlar frmnts predomimats below 90.00 m. Large Occasional thin calcite veins and infilliws block of pinkishbmun. ftielapilli tufftith wmll-dsfinsd top 118.20 ta 118.50 m. Broksn with thin snd bottcm,105.02 to 105.75 m. Hised frwsnts below with s_ oalcite veins 122.10 to 122.60 m. Calcite calcite infill. Finer with frsquent lapilli below 107.96 m to up to 1 a at 12&.20 to 12h.&6 m; 100.95 m. Lugs blockof pinkish tuff with stilbits in matrix ocossional thin veins below at 109.05 m. Well-defined lapilli bslow, sass reddened, others vlthrsa0timrims. Sow quartz gralas in matrix below 110.8G m 129.92 61r.72 to 113.10 n. Bmksnnsarbase. Bssaltvitb small to medium fsldspers nesr top,becw progressivsly smaller and ffner dorm. 5 cm bleached zons 133.06 3.a 20 cm from top. Peldspusmars frsqusnttowsrds bae. Raigmntal volomic rack with lapilli (l-2 uu). Irre@prand hw thin calcite veins in broken corn broken 1L3 to lwl.10 m. Lupr amd fewer frmts below lb3 to l&.10 m. Rather broksnbslov with 157.50 m Fr,fine-grsined matrix. Blsschsd to pale brown below irngular calciteveins ia places. 150A7 PL. Brecciated below 158.62 m to 159.30 m. mpu=d Network of thin calcite veins 157.50 m. red, sub-r0undsd sad sub-sngulu frmts bslow to 168.20 m. Brecoiated with calcits veins and occasional Corner below vith scattered, rsddened frmts to base films of chsloopyrits below 158.62 m to 171.19 38.13 159.30 n Tuff; fine. Imgulsrdiftie patches of oslcite in natrix. m.ia calcite a?ld cslcite-quartz-chlorite Bmksn sad coredin pieces. ?C0rs loss. veins sad soattersd Ilppll,csloits Mills 17b.72 3.53 in matrix. Silt; brown; very cslosreous. Scw~lindetslmi.aats Part4 fnzilled cavity. 175.63 0.91 fwts. G-Y and lightly40ns0lidatsd in plooer. Lmva, abundsntmsdha feldsprrplunoc=m** Bmvsryian~@pr Thin, imgular calcite and os0lite veins. 176.20 0.57 withbleachedsolu. Probably a dyke. Lava1 fins, pals brown with ohlorlte-osloite vesicles. Vey thin imgular vsinlsts Of calcite 176.65 O.b5 snd stilbits. Lavawith frequentfeldspar ph-zysts. Ve~bmken with s0mse of pale green slteratlon. Breociatsd 178.U t0 i78.9o m. 181.00 3.35 Veiaedmm&a at 10’. Rpbably m. mf: fine; reddmned in pla0es frm 181.p m. Coarssr below Veined with csloite snd gslw 183.60 m, beccdng paler snd blesshed below la&.10 I with orng Csloite smd s- mite veining 181.80 to Matrix more abundrmt at 182.00 m. Ocoamiondtun caloiteveins Bedded ia pls0es with at i+5O. Thim film oaloits 102 m to Matrix finsvitb small 187.20 m. OccamioMlfilma of oaloita feldspar13below 189.3&m enolosiag discrets, very irregular wlih-spsoksof pyrite. Bmksa 186.91 m frmts; s-rsddslled. ~mksm 193.70ta 193.06 m. %rs to 187.03 m dth filma of calcite and ocmrpastdth no visible olrts to 19l& n. Pew below to oocasioaalspoke of galmua 195.85 m, thsm Mattered t0 197 m. Sharp juactiom at 197.60 m with beloU. All oa a Uttle veryfine, purple ?lava sbovs arwthsr sh8q junction at 197.88 m: m.lasraliratiomto 19h m. Filmuithgslsma frmts in plures below,becc&n# 0~10 froqwnt do~nwud~. Pale, 2Ql.gom. Filmsof calcite with pyrite purple bsnd with very irrsgulpr top at 202.56 m smd sbup bm at and ruw cholwgyrits 2oth.25 and 2oL.70 m 203.20 m. Hsmy mmts below, N larger below 21h m. to 2o5 1. calcite vith @hna at 206.40 m Caloits with pyrite at 207.a m colcits dth chrlcopyrite at ma.75 m Ciloik with grlms at 212.91r m to 213.72 m? 215.15 %.lS Calcite dth galsma at 215.15 m 215.15 shd of B0mh0ls lAl1in01ill&i0ns srs givsmvith respectto corelsmgtb. 20 llppENDIX1 TABLH II BOREEOLE2 Inclined Inter- &Pa wction LltholO~ 0 m 0.00 owrburden of fr-tr and pieceaOf uoatbemd, fra&m~tal wlcanic mck. Rental ~loauicrock (agglomerate): Frequentfregnentr Calcitertriagen at bareat 70°. (j-5 cm) ofwidely rariablelava+qpea(dark, apbyric with emall faldepazw palewith large feldepatcl: puplo, aphyric; gz$en&hp.byric;someveryveeionlu; ecmepink, claetio Co-e matrix. R-e&e smallervith lome matrix 7.15 2.11 to baee. 'Sharp,ltratimc bane. Lapillituff; banded;rod brown and grsenteh purple. Cn~doly Thin caloitowiaa at loo and &so. a.&0 1.25 bedded(iaolinod at So)* ulth Mattered0.5 om -ta. Vtp1 ~oloaaiozvok (agglwrak). AboUdant~lfr~ta knaatamalrlgdolaIit8/calcitevein4 at top,mostly 2-3 cm but up to 10 as (frmte videlyvariable - 13.62 to 13.85 m. aa in overlyingunit).Fh@wnta mostly with rounded oornore. Coarse matrix. R&w finerbut& with exude bedding la plaooa 13.52 5.12 krclinodat TOO. StratQmphic base hdimd at 500. Lava (andeoite):Purple with mt am8llpbnoayats. Banda ofengulu~te,moetlyofe~lar~ butdth different weatheriagi aleoeaw exotice. Stratigraphicbaaoinolhed 19.5l 6.05 at 700 Ra@~talwloa.tcrock (ag&merate); banded.R-ta, 1-2 om Qlmik v&la with Calcite moatlyoverSQ* ofmioroperphyTiticlavaandeaeverp patoh@ 20.10 to 2O.LO m at XI0 to core veaiouhrlava. ?I.&mbritefra@Mntnoprtop. Couno*pinkish le-@. Thickcarbonate veia(calcite/b&e/ matrix. IYanyaptryrio audmioroptolic -ta below20&m. dolomite)23-a to 23.aa II pbout 150 to Ragmahe IWE* tier apdll0z1 tied beh 23.88 m. Bmn, core length. Oocaaional thin calcite weattu~ 26.90 to 27.35 P. Mootly mall fmgent* below etrindwa bolov. cm calcite-liwnite 31.33 11.76 28.70 n p-a* d0t8i ht0 hpilu ida b0i0v. tnin at 27.10 m, d to co- length. 4illl Wf: pinklrh with coarser frqge~ta. - 33.95 2.62 lobatem outlhoa: crudew at 650 Re@entalvoloaaicawok: abwuIantandvariedMt8mostly Thin calofte veiaparalleltocore to exceed.iwrScm; eomeflowb~~&d; aotauchmeirix;aLmad& 35.60 m. Con bzwken dth inqulsr 2 to 5 a-t8 0fml-yvuleddok tfpo8belowfl.sn, calcitemiru belowto 36.05 m. h@= iaoludingpale, buff and grey apbyrio rwke: wmo darker rocka, caloita vmin&g 36.54-36.59 DI. 1 cm calcit* ouu Mt of "aoid"lava. 1 a0 pale grey aaidioVyko” with vein 37.15-37.25 1. Ooccuiapil thin calcite CIuutzaelw 81.7W2.03 n. Lar#o bloeke of ffne, pale Wf, v&la belov. 0.5 au calcitevwin veeioolw lava lil-17.20 m; blookylava with mell feldepur w1.7w.h.85 m. Ooca8ioaal thin calciteveins3 and etring8a-ebelow 47 m. 1 a calcitePquatz Plnerbaad at b7 a with beddhg at 5o”. veinperpesu3ioula.r to core at U.GL(m. 10 cm -ta mall& tomdm bese. complexzone of veinletaof calcitesod ccqnnmdwhauithoalcita incentreand fleckeofpFit.cmdec-bmao mughe at So.65 m. 2cmirregolarveinof orlcite-hauatikat 51.10m. b om coarparmdveinuithcalcite,barJrk and thin pUkieh lava4ootionandO.S an baryte veinat Slh.55ID. T&I calcitevuiae at interPale below. 1 EIDirre@l&- oalcite v8i11at 58.53 1. SObttsmd thin C&cite 61.52 27.57 wiw at bane. h&llli tUff: glWy vfth on& bedding in plaoesinclinad at Thin calcite wine sndveinlek. Heav . Bandm of ooamer fkqp0nt.m of apbyric lava, - wry baryta mining at 700 botrwn 63.18 aud miculu. Pkue, pale, beaded MU bame. 63.70 II. I=-&=b.=M~W~~ 67.00 5.M m lmmatik near beae. Lava (aldewle)t purple,ry mioular. hay (Miolea ahow So&tered very irro&u See veninr (acme elangaticnrindbedatso0. Duk red b&w 72.33n. with heematite). Brokenwithbrrpkaad W. p8leinfill of tuffaoeaues&stone below 75.20 m. hamatlte veins up to 1 cm below 66.20 m. h~tobroociated in baaal QI. Poetic. Eauatite in vesiclesbelow 71.50 m. Brokan and rmifyin~ calcite wine 72.85-73.1s m. Large haesatite-infilled vwicle873.80 I. l?miQix@ buyk vmina 83.95 16.95 74.x-75.20 m. Lava(andmite): bromm,rubblytop. 10 cm of purplishbrobm Caloite.baryte. chlorite infi1U.t~ of vesioulorlaTa below with lnfillad veaiolo~. Baa& ofpeleglvy veeiole;. ir&ulubuytevei~;eaw wdstcw at intervaleto ab.70ID. Patoheeofgreygrwn tithcatral patoh*eof calciteup to1 cm. edtone below86.75 m. vary ordsuhr below95.80 1. soor Poworveinrrbelow a7.88r. Eoavily veined g7.12 13.17 iuolusiau of tuff at baw. wtlo. withbyto 95.37-95.80 m. s4Jme veining belov. -tJ. volceniorook: frmtm of aghyricla-881 a- Ooouionalirregular veialete ofbaryteaad reddened;acaevithmiCxqhalooryet8 Of foldaprr. R-b calcite. Barytevmiaa up to 0.5 cm ue J-lbQ at top but are dler downs&. COIV broken 1olr.90-105.10m. 105.82 a.70 102.10-lOlb.jo m. raulqulialdfra@mente below San iepr bm -W 108.15-108.25 & IWwork baryte4 aoaecalcite veining 112.11 6.29 109.56 n with minor bamatite below 111.20m. Breocia. Heavyveining by buyte-oubonate. Sme dieaeminated pyrite(?areeaopyrfte)end a llk.98 2.87 little-tit., meetlyin baaal12 a. 115.33 0.35 ~tslvolcenio rock: lav8wta Heavilyveined vith baryte md haematite. Brecoia. Heavybaryte-cwbonato. Watite 116.85 1.52 t&w&lout. Tuff: ml., cxqmot. Coueu MU hue. Pinenotworkofbuytevuining. I¶Ola frequent below 118.65m. Thinbrryte tninlete aadoocaaionalcalcite-baxyto at 122.05ID. S-o haamatitoat intorvalabelow. t4orerogularcalcitcbuyte veina at750 126.95 10.10 bolos125.50 m. 128.20 1.25 wtal wloanfc rock(lopilli tuff): fra@uat#about 7 cm Scattered,thin, irregular borpte Edna. Turf: fine, conpaot. Ooo~lonal irre&arbaryte veinaup to 1 cm vi& [email protected] apecks 131.65 3.lrs of pyritm. Wfr cdouwow Wf at buo. Rmtuy In basal Scatteredoalcita -d baryte v&u up to Zli . 0.5 cm wide. Requent caloiteveiniq 137.OL 5.39 ti 136-137.0& m. 21 1 APPaDIxI TABLZII BOREBOLF2 COlmNuED Inclined Inter- Lithologl Hinerslicrotion &Pa section m m R~ental volcanic rock: frwntr of eic green, red Tuff fraigrientrout by diffuse netvo* of and brom lava; soae with micropheaocrysts of feldspu: a fev calcite and calcite-bPryte wins up to B with microp@eaocryats of pyroxene; some ve.9icu.l~‘. some not: 0.5 cm vide. Saw haematitearound ooo~ional mentor of tuff cut by veine. R-ta mnaller llrY.19 1. Network of calcite and buyte at lkY.19 m. veiaing lh9.9~,-lh9.7k m. A few fibin winlets of oalcite at 149.90 m. Scattered wMrts and veins up to 1 cm tide of brryte and a little calcite to 152.36 o. B Scattmed wina of baayte up to 1 cm wide below. Calcite to l5h m. Veina BZY btsplsoed sad cut by other wins or veinleta Veinletr of calcite and 7 am oalotte-buyte vein at 155.Q m at Ir5O. F?equent baryte-calcite veining with tracer of pyrite ohaloopyrlte and hamnatite II apparently within veti; chsloopyz%te on filma traversing vein at right s&es,~SSJ.iL -155.96 m. &attend thin veina leer thsn 0.5 cm and wlnletn of baryte, often traversed or dlaplaoed by others. Thin calcite winn 160.7h 23.70 160.22-160.71, m. Bad of borehole *Al1 inolinations are given with reapeot to core lenstb. 22 APEBDIXI TAB= III BoRQmLE 3 Inclined Ictelc depth section Litholom Hineralisation m m O.d7 0.37 Overburden: piece8of weatheredlava Lava: purplib 5-Y: ha~~t~sll fel~armicmp~crysts; Sam. irregularhaematitic bandingto rcmeirregclarjoints at*. Scatteredcalcite and chlorite-fille 1.35m. weiclea frepent ia banal 5 an. Stratigraphicbaee irregular and 2.47 1.60 balledat 40 . Lava: 2 cm brown "bole"at top. Purplieh;abundsnt. amall, Occ~ionalthinveFar, and rtringereof lath-likephencoryata of feldspar. Veryveeicular with Mill* calcite. 2 cm aphyricband at 7.02m of calcite,chlorite and rem quartz. Irregularsaude~etiill withqurtz-hammatite Millin@. at 11.60-11.70m, may be baeeof flowunit. Reddenedbelov with @as&z-calcitewine at 8.25m (1 cm) and quartzand calcite-chloriteinfills to 11.90 III. Pale,bleached a.50m (2 cm) at 90°. Irregularquartz 15 cm zoneaaeociated with parallel infill of eandatoneat 13.65 m. and calcite-chlorltawina iaplacor. v;mabFen belov15.30 m. Grey-Sreen.3 cm m&and a& bendat 4 jointavith calcite filme below 15 m. . . Lavabelow hae f-r and eaallerfeldspars. Brown-grey wsicularflov unit (na above);darkervithlarger phenocryeta belovjoint at f7.12m. Bellingetructcree below 17.45 m with 17.30 15.33 ran&toneiafillm to 17.80PI. Reddenin&alOng!3Wgial. Lava: grey: purpliahbandatith greenish aeh infillfnball Chloritiand calcitein woiclea. et=cturasto la.33m. Abundantplatay feldaper phenocryhe and frequentamall chlorite and calciteweiclee. Feldsper distributionpatchy. Jointingapprcximakly parallel to cora lengthfrom 20.10 to b-e. Flovbaae&n&craluithgreorU~ 21.10 3.70 "sandetone"infill ia burl 25 cm. Lava: purplishwith "sandstone"infillingin top 12 cm. b-t Chloriteend calcitein waicles. -1 latha of feldepu. Veaiculptwith celcite, chlorite usi-. 800 jointingfrcm 21.90-22.25 m. Irre@u Wtadstene'~ infill* at 22.50-23.08 I. Elongatioll of waiclee),liaepri~ of inclwionasrrd lathe orientation mate a dip of .5C"at 24.00m. Elongate,1 cp green"lava" inclusion caueing a buff-coloured reactionrim in hostat 23.85m. Rmmded, quutz-Milled veeiclee fl-zm24.10-24.50 m. Veeioleeelongate below. Largecelcite and chlorife-filledweiclee on reddanodWxLe at 25.85m. Basal3Ocm consirtaof infilledbuff aad purplelava (aa above)vith "san&Me" Veeicularwith chlorite-ca~~ite. with gmenieh aahwdge at 26.15 IL 26.20 5.10 Broken at base Lsvaz bmtiahgrey; fTequentpiil plateyfeldepur. Veeiculrr Celcite.chlorite aad quart2in vesicles. withcalcite, chlorite and quartsInfill*. Palor in basal10 cm. 28.20 2.00 CrMniah,chloritic jlmction. Lava: purplish;mom red at top. Requent.saall,lath-ahnpod calcite and chlorite In wsiclee. feldepprpheaocryata. a mafica. V8eiWlPt; wetly chlorite alldcalcite. Verywaiculargremn-mdmottledzeae with flow bw (?baseof flow unit) at p.90-31.00 I. Lava (aa above) belowbanded unrt. wer Weandstone"5afille at 32.52-32.8sm 35.05 s.a.5 and 34.80-35.0sm. Lsvar purpliahneartop, ~bolw. Abuuda& 41, platay chlorite Ln wsiclee. feldsparsand a fw U, ecattered, irregular,chlorite-filled vesicles. Bandaof bmvlliah wathering. Broken in bae&l75 cm. 39.00 3.95 Menear bw. Iavu purplish;rod-purple atto%bmvPtah lnlover part. Calcfteawl chloritein wsiclee. Fmqumtmall latheof feldapet. Vesiculprwith imqulpc %auiat+me"infills. Row-top atnActurespre8ellt. Calcite and 42.05 3.05 chloritelafllle. "S~tone"infille at intervale tobaae. hvax brouniehat top,ebmbelow. Pev patcheeof Calcite,quartz and chloritain waicles. "mndatone". Abundmt41 plateyfeldspaaa. Sam veeiclea io2fll~dCcrlcf~,qupttZ~chlOdtoupto75~. Green tcffacwussaudatone 46.13-46.30 m with bedding at 70' tc core largth. Sand&me at 46.40-46.47m and 47.00-47.12m with so.38 a.33 reddeMdlavabetueQl. Palebroun flwbue. hvar red bxwn; ecattered,dl feldsparmxysts. Chlorita 8ud calcite in veeicles. 51.50 1.12 Ve8iculsrdthcalciteandchlorite. Brokenbelow9.60 m Lavu -browen; spbyric; capact. Calcite and Calciteand chloritain vreicles. chloritaweiolee. Ratherbmka with haematitestaining WtlteetafAag. Red zeolite-chlorite 54.04 2.54 53.9OG4.04m. voiningneubaae. Lava: Purplishat top,gral below. Requent feldqmu Caloito-chloritchaematitein wsicles. microphomcryst8.Soattemd 1~ vaeiclesmd frequent mallrr calciteand chloritcfilledwniclea. PhoIlocryata more-m dowWard to San, boccmi.ngmcmvesiculub.lav withfenrmicropbnnocxyete inplecea. Brcke~~below 62.90 m. m oalcitewaiclee near bau. Basalball- etructuma 63.gO 9.06 63.78-63.90m. Lava: abundautslprll feldspar mioruphenocryete. PUrplil#h Chloriteend celcitoin weiclea. at top, palobuffnearb-e. Scattered,largleh chlorite-calcite 66.56 2.66 filledveelclea. Dip atp to oorelength. L&a above): dark md at top. soattamd,irreguler calcite II%Wgulercalcite iaf111e. 67.17 0.61 . BleachA scne67.1ob7.17 m (hue of flow unit)at 45'. Lava: frequenteaallfeld8pareaudmicrophenocryats. Saattrred Chlorite and oalcitein voriclea. chloritaacd calcitewaiolea. Ala0diffuee calcfto patches in Calcitein diffuw patcheeaad u matrixaEli IaTelgllu veinn. Brokenbelow 70.25 a with jointing irreguluwiae. at 150 to corelez@l. Chlorite-filledweiclee more frequent 71.75 4.58 belov71&J m. Bleechedinbasal 10 om. Lava (M above)I v.ry v*bx2lar txhm&out with calciteand Celciteand chloriteFn veaicle6. chlorik Willa. I~gular,@wy-gmon earldntoae-WfinZillfng Occaeionelthin winlets of calcite 72.05-72.80 m, 82.85-83.23m, a4.20-a4.um 8nd 86.W-87.60m 75.w76.22 m. Calcitevainlets ti Slickeaeideaurfaceo aad floccbeaodructtws belov87.20 m. rtringenbelow. 89.68 17.93 More reddewd at baeeof flovuaLt. Lava (ae ebcve):purplish at top. Vesicularwith calcite Calciteand chloritein veaiclea. chloriteWilla. Grwnieh aall&toneinfill frcmtop to 91.15 1.47 89.90m. Pd. brounishbaml2C cmwith floubue 8tructurea. Rmtal VolcauicRock: irregularblocks of lav8.mclrtly Chloritein veaiclea. aphyric;ecWgreenieh, othare reddiehpuIgl0; roo,With 93.85 2.70 abuudultail1 chloriteveaiclos. _ 23 APPmDIXI TAN.2III BOEEBOLE3 CONTINUED Inclined Inter- Lithology Mineralisation depth section m m Lava: grey with frequent smsll feldapars. 'low baling with Occasional thin calcite veins. reductionof lava to buff rim and green inside. Associated 95.83 1.98 green siltstone fmm 95.05 m to base. Ragmental volcanic rock: lapilli awl fragments of different Oocaeional thin. irregular calcite veins lava types. Irregular, green tuff inclusions 101.35-101.95 m; up to 0.5 cm. Occasional calcite infill fine tuff below to 102.25 m, rather broken below with pale in matrix. 1 103.36 7.53 brow&h patches. Lava: @ey with f?zequentsmsll feldepus; purple patches below 0.5 cm calcite-baxytc vein 106.70-107.80 m. 115.23 11.87 113 m to base. 115.23 Ebd of borehole u *All Lnolinationa are given with reapeot to core length. I 24 APPENDIX II GEOCHEMICAL DATA FOR CORE AND CHIP SAMPLES Samples of core (31) from the three Alva boreholes were selected for analysis on the basis of the presence of visible mineralisation and in some instances as being representa- tive of particular rock types. A small group of chip samples (12) from the old mine workings in Silver Glen was also analysed. The sample material was crushed to 1-2 mm particle size, quartered and approximately 200 g ground in a tungsten carbide tema mill to less than 50 pm size. Most of the analyses were performed by X-ray fluorescence spectrometry using a Philips 1450/20 spectrometer (analyst T. K. Smith). The Cu, Zn, Ag and Pb analyses shown in parentheses in Tables I, II and III were obtained by atomic absorption spectrophotometry using a hot HNOa attack. Those U analyses reported in parentheses were determined by XRF, the remainder by delayed neutron activation analysis. The underlined values in Tables I-IV are regarded as high-anomalous. 25 APPENDIX II TABLEI BoREiOLSl Ssmple DePtk m Inter- So=arY ---- % ---- ~~~~~~~~~----~~~~*-~~~~~-~~~~~_~-~~~~__~_ No. From To section dercription Ca Ti RI Fe Co- -lu CU ZLl As Rbsr YZr NbHo &J Sn Sb Ba Ce Pb Th U CXD m Basaltic 110 26.39 27.78 1.39 sndesfte llvo 2.556 0.956 0.086 7.002 30 (30) 30 (65) 60 (90) al 13 57 552 41 430 16 4 (1) 2 4 1 614 75 (20) 15 12 5 111 28.90 29.65 0.75 hva 1.278 1.025 0.057 6.076 25 (35) 25 (wo)a (70) 55 E 90 416 46 480 16 4 (1) o 2 5 501 83 (30) 26 15 6 112 31.65 33.25 1.60 Lava 9.072 0.520 0.130 h.340 30 (60) 48 (75) 61 (370) 287 27 74 323 22 166 8 3 (2) 1 0 0 389 50 (SO) 32 6 2 118 35.00 36.20 1.20 Bmccia 1.754 0.957 0.063 6.199 25 (35) 26 (70) 62 (30) 13 x 71 152 3i3388 17 0 (1) 1 0 7 269 69(20) 914 5 113 36.50 38.37 1.ar Iveined lava 15.594 0.394 0.138 3.905 25 (50) 33 (38) 50 (120) 95 37 37 308 30 222 8 3 (3) 2 4 9 257 57 (60) 48 9 3 Fk4&meatsl 114 40.20 41.55 1.35 volcanicrock 5.884 0.51& 0.106 4.373 15 (35) 21 (22) 30 (60) 37 8 85 208 21 165 7 5 (1) 1 3 4 248 31 (80) 20 5 2 115 65.19 66.54 1.35 Lava 9.527 0.57& 0.131 3.437 20 (45) 39 (45) 38 (70) 64 5M 233 29 256 13 2 (2) 1 3 7 353 63 (20) 0 10 3 116 68.35 69.60 1.25 IFragmental 3.319 0.965 0.068 6.826 30 (40) 28 (61) 70 (l(X) lo5 5 70 372 39 433 18 4 (2) 2 6 5 551 73 (20) V 13 5 117 95.66 96.92 1.26 polcanic -* 1.528 0.705 0.057 6.227 30 (65) 60 (119)135 (70) 73 5 72 437 22 241 8 3 (1) 1 2 2 755 43 (20) 9 10 3 Brecclated and veinedfrqmental 119 158.62 159.30 0.68 mlcanic mck 3.406 0.356 0.077 3.766 35 45 opg) (40) 32 80 361 25 205 11 17 (2) 3 0 2 701 33 (20) 9% 126 190.6a 191.33 0.65 Tuff 25 45 (so) (50) 9 (0) 750 (15) (3) 127 196.84 197.20 0.36 Tuff 20 15 (15) (60) 8 (1) 716 (15) (5) 128 208.60 209.10 0.9 P 30 (85) (Bo) 14 (l) 719 (25) (4) 129A 212.70 213.20 30 45 (15) (50) 5 (2) l47 (22) (3) 13Q 214.55 215.15 0.60 35 70 (30) (80) 12 (1) 575 (20) (5) APPmeDIx II TABLEII xElEmLE2 101 20.55 23.24 2.69 Agglomerate 2.386 0.432 0.055 3.887 15 (25) 34 (5) 8 (40) 36 47 53 96 19 222 10 4 (1) 1 1 6 56 23 (10) 8 9 3 Carbonate--reined 102 23.24 23.88 0.64 agg1cmrd.e 12.284 0.178 u 3.454 20 (20) 17 (5) 0 (20) 14 15 11 283 9 84 5 2 (2) 1 0 0 m 0 (20) 0 4 1 103 kl.32 42.96 1.64 mmtd 4.833 0.467 0.085 5.080 20 (30) 24 (10) 13 (50) 5.5 21 51 158 18 192 7 2 (1) 1 0 0 149 40 (20) 6 8 3 lo4 44.98 47.17 2.19 volcmic rocks 4.716 0.526 0.098 4.818 20 (a) 42 (20) 19 (45) 42 16 54 126 21 195 8 1 (1) 0 0 1 129 43 (20) 4 8 3 105 79.77 81.10 1.33 Vesicularlava 5.084 0.54h 0.104 5.946 25 (40) 48 (20) 22 (50) 48 37 34 132 19 157 6 3 (1) 1 2 7 84 64 (20) 9 8 2 106 112.11 114.98 2.87 IBreccio 18.049 0.122 Q&& 2.957 30 (40) 31 (10) 0 (40) 31 5 9 143 11 49 3 3 (3) 2 0 0 m 12 (20) 1 2 1 vith baryte 707 114.98 116.85 1.87 Peiping 9.048 0.128 0.257 3.232 30 (50) 74 (15) 0 (80) 74 8 3 375 12 58 1 7 (2) 3 0 25.03 0 (20) 2 5 1 108 120.50 121.60 1.10 Tuff 7.487 0.273 0.183 3.421 20 (40) 70 (IO) 10 (75) 70 24 11 56 l5 98 5 0 (2) 2 0 16 79 24 (20) 7 4 I Lapillitufr vlth 109 135.95 137.04 1.09 calcite veins 16.807 0.264 0.161 2.610 20 (35) 31 (15) 8 (40) 31 10 26 214 13 98 5 0 (3) 2 0 2 m 4(20) 2 4 1 Fragmental 0010suicrock 12!3B155.44 155.96 0.52 with baryta vah 35 (30) (20) (70) 9 (1) (20) (1) APPmDIx II TABlJZIII BORFHOLE3 120 13.95 14.75 0.80 bva 1.001 0.828 0.065 6.863 25 (80) 71 (30) 19 (90) 87 l4 28 446 25 257 17 3 (1) 1 3 3 432 51 (m) 9 9 2 121 22.15 23.15 1.00 Lava 0.408 0.431 0.046 3.827 30 (55) 45 (15) 16 (70) 65 32 94 322 15 222 11 0 (1) 1 0 5 654 34 (10) 2 7 2 122 23.71 24.62 0.89 Lava 0.680 0.844 0.069 7.068 25 (75) 76 (20) 21 (90) 99 11 39 507 24 260 17 2 (1) 1 0 0 634 54 (10) 8 8 2 123 28.60 29.57 0.97 Lava 0.670 0.781 0.061 6.711 25 (75) 73 (20) 20 (70) 75 10 24 404 23 250 15 2 (1) 0 3 2 331 46 (20) 7 8 2 124 51.90 52.70 0.80 lava 0.829 0.757 0.056 6.566 25 (70) 73 (10) 6 (90) 97 5 82 274 21 260 17 2 (1) 1 0 0 496 57 (10) 11 10 2 125 58.25 59.26 1.01 Lava 1.562 0.753 0.059 6.335 30 (80) 75 (15) 5 (110) ll2 14 68 464 23 247 17 3 (1) 3 3 1 717 53 (20) 11 8 2 APPEXXX II TABLEIV Vein samplesSilver Glen 201I Uinze 1.00 8EE2 P 20 85 50 2 30 202 Esstdrive 0.9 70s OS4 50 35 J&g 40 7 40 203 South drive 0.12 78v 164 65 50 E 60 -16 30 A 20 204 NorthMve 0.40 7% 350 15 20 1165 20 205 I Lawr south drive 0.65 80~ 165 20 35 175 40 30 206Jhtrmce aiit 0.70 75s 240 40 40 230 50 3 60 20 209)South drive 2.5 8W 350 !z!zx! !zi 20 10 210-NorthMve (wst)0.80 &3S 020 15 3oz!2!x 20 2 k 10 211)Northdrive 0.45 75s 030 25 _?O lJ&J 30 10 212 6Om&mnentrance 1.50 75s 242 20 25 160 60 1 213 lOmf3nuentrance1.50 80s 065 25 40 a 60 P P 10 214) 20m &v~entrance 1.0 65s 252 20 35 '65 60 2 26 APPENDIX III Altered andesitic lava (PTS 5007) An overall greenish-grey coloured rock in hand specimen. PETROGRAPHICAL DESCRIPTIONS OF SELECTED The rock has suffered strong hydrothermal alteration, but CORE SPECIMENS in areas where alteration has been less intense, phenocrysts General of plagioclase set in a fine-g-rained matrix can be made out. Selected lengths of core were examined optically by In thin-section the euhedral feldspar crystals are seen to be polished thin sections in transmitted and reflected light broken down into microscopic aggregates of chlorite and following preliminary examination of hand-specimens with clay minerals with small patches of sericite. The fine- a stereoscopic microscope. Carbonate determinations were grained matrix appears turbid and this is probably due to accomplished by staining with Alizarin-Red solution. the presence of a clay mineral and fine hematitic dust. Bulk XRD scanning of crushed (-120 mesh) rock was Two generations of veining can be recognised; infilling carried out by D. J. Morgan (Appendix IV). Qualitative minerals are chlorite, quartz, calcite and a trace of XRF analysis of mineralised samples was carried out by epidote. Some tiny, quartz-rich veins postdate earlier, D. J. Bland to elucidate the association of base metals chlorite veins. Sulphide mineralisation is largely confined present and results are incorporated in descriptions. to a single fracture surface and consists of a superficial aggregate of pyrite with occasional blebs of chalcopyrite. Depth in m Section Description (PTS) Altered andesitic lava (PTS 5008) In hand specimen, a grey-coloured, minutely vesicular, Borehole 1, Bumside porphyritic rock with phenocrysts of plagioclase distributed 28.90 5006 Altered andesitic lava throughout a fine grained matrix. A vague flow structure is 28.90-29.00 5007 Altered andesitic lava present. In thin section, euhedral outlines of the original 35.60 5008 Altered andesitic lava feldspar crystals are preserved in microscopic aggregates of 36.60 5009 Altered diabase sericite and chlorite (penninite). The matrix is fine-grained 37.70 5010 Altered andesitic lava and appears to consist of chlorite and clay mineral. A 38.00-38.13 5011 Altered fault breccia narrow vein, containing calcite, quartz and hematite cuts 65.57 5012 Altered fault breccia the rock. Pyrite is contained within this vein and, in 66.00 . 5013 Altered andesitic lava addition, forms small, superficial, scaly masses on fracture 70.90 5014 Altered andesitic lava surfaces. 112.52 5015 Hyaloclastite Borehole 2, Balquharn Altered diabase (PTS 5009) 9.30 5016 Porphyritic lava/tuff/altered In hand specimen this is a fine-grained, brownish-coloured, andesite vesicular rock of dense, homogenous aspect suggesting that 91.85 5017 Agglomerate it is of hypabyssal intrusive type. There is a faint dark to 74.64 5018 Andesitic lava light colour change across the rock. In thin section, the 115.83 5019 Explosion breccia rock displays a relict ophitic fabric in which large sub- 148.62 5020 Glassy tuff idiomorphic crystals of pyroxene are moulded around and 155.10 5021 Glassy tuff completely envelope idiomorphic crystals of strongly 155.90 5022 Carbonate vein rock sericitised and chloritised plagioclase. The pyroxene (possibly augite) phenocrysts are strongly decomposed to Borehole 3, Biairlogie an aggregate of chlorite and clay minerals but their sub- 63.78 5023 Altered andesitic lava idiomorphic character is emphasised by an internal mesh- 101.54-101.73 5024 Agglomerate work of iron oxide rodlets. The matrix is too fine g-rained to be resolved by optical methods but appears to be highly chloritic. Some particularly conspicuous patches of green Altered andesitic lava (PTS 5006) chlorite may have replaced biotite. The many small vesicles In hand specimen, a greyish-green porphyritic rock. that disrupt the fabric of the rock are commonly infilled Although alteration has been marked, a remnant igneous with quartz, chalcedony, calcite and chlorite; in some texture may be discerned in the form of phenocrysts of instances pyrite totally replaces these minerals and two plagioclase set in a cryptocrystalline matrix. The feldspar pyrite growth stages can be recognised. phenocrysts display a distinct colour change; in areas where hydrothermal alteration has been intense, the phenocrysts Altered andesitic lava (PTS 5010) are yellowish in colour whilst in areas only mildly altered, In hand specimen, the rock is purple-green in colour and the feldspar retains its more usual creamish white colour. exhibits a porphyritic texture with large (up to 1 cm in In thin section, this observation reflects a difference in length) phenocrysts of altered plagioclase distributed mineralogy. The strongly altered plagioclase grains have throughout a fine-grained matrix. In areas where altera- been broken down into a microscopic aggregate of chlorite tion has been most intense the overall purplish colour of and clay minerals whilst those phenocrysts of ‘fresher’ the rock becomes green with total obliteration of the aspect are strongly sericitised. The form of the original original igneous texture. feldspar crystal is commonly preserved. In thin section, the plagioclase phenocrysts are present It is not possible to determine the exact nature of the as euhedral crystals but are strongly sericitised and contain fine-grained matrix by optical means. Its cloudy character irregular patches of clay and amorphous iron oxide. The is probably due to the presence of a clay mineral although matrix is microscopically fine grained but probably no clay minerals were detected by bulk XRD examination contains chlorite and clay minerals and hematitic dust. of duplicate material. The rock is traversed by a series of The rock is cut by two large veins of identical mineralogy veins which contain calcite, ferroan dolomite, quartz, and of probable coeval age. The country rock in areas hematite, chlorite and a trace of epidote. The calcite immediately adjacent to these veins is noticeably bleached bearing veins postdate the sulphide phase of mineralisation. and highly chloritic. The infilling vein minerals are quartz, The rock is strongly mineralised with intergrowths of calcite, chlorite, goethite, a trace of epidote and pyrite. pyrite, marcasite and occasional flecks of chalcopyrite. The mineralisation is probably epigenetic in origin, belong- Altered fault breccia (PTS 5011) ing to veins produced during a possible episode of faulting. In hand specimen, an overall greenish-grey coloured rock consisting of sub-angular, calcite-rimmed, fine grained, green rock fragments set in a pale grey coloured crystalline matrix. In thin section, the rock fragments are highly 27 1 chloritised but occasionally show a fine-grained porphyritic areas of coarse calcite indicate that the vein developed by texture, suggesting altered lava. The matrix consists of successive minor stages. Disseminated chalcopyrite is coarse, platy calcite, a little chlorite and a trace, of present throughout the rock, and in the carbonate-rich muscovite. There is a sparse distribution of marcasite, vein it occurs inter-grown with bomite. . I pyrite and pyrrhotite throughout the rock. Tuff-breccia or hyaloclastite (PTS 5015) Altered fault breccia (PTS 5012) In hand specimen, creamish-brown rock consisting of sub- In hand specimen, an overall greenish-grey coloured rock angular fragments of chloritised, fine-grained igneous rock I consisting of calcite-rimmed lenticular masses and sub- set in a pale grey coloured crystalline matrix. angular, fine-grained, green rock fragments set in a pale In thin section, the rock fragments fall into two grey crystalline matrix. categories. The most common type is composed largely of In section, the rock fragments are highly chloritic and yellowish palagonite, sometimes altering - to fine green siliceous and do not display any particular textural chlorite and patches of dark brown unaltered glass. u characteristics. However, some tiny vesicles, rimmed with Fragments of the second type display the more regular quartz and infilled with calcite and chlorite are present, and fabric of a porphyritic lava, with phenocrysts of kaolinised as bulk XRD examination of duplicate material indicates feldspar set in a dark glassy matrix. The fragments are I an appreciable amount of feldspar, it is suggested that the distributed throughout a coarse, ferroan dolomite matrix rock fragments probably represent an altered acidic lava. which is largely replacive. The rock is barren of sulphide The matrix consists of finely crystalline calcite, a little mineralisation. quartz, chlorite, a trace of epidote and tiny diffuse patches I of a radial aggregate of brown carbonate. A large vein, Junction between extrusive rocks (PTS 5016) rimmed by chlorite and quartz, and containing coarse platy The rock is composed of three components: calcite, a trace of chlorite and specks of hematite, cuts the a. Altered andesitic lava. In hand specimen, this rock. In areas immediately adjacent to the vein, there is component is fine grained, vesicular and pale brown in II strong carbonate replacement. Sulphide mineralisation is colour. The texture is porphyritic with altered phenocrysts limited to disseminated pyrite and occasional flecks of of feldspar set in a (?) clay matrix. In thin secton, the feld- chalcopyrite. spars show strong sericitisation with alteration to kaolinite in many instances. The exact nature of the cryptocrystalline I Altered andesitic lava (PTS 5013) matrix is difficult to determine by optical means but it This is a mottled, brownish-green coloured rock with appears to be highly chloritic and cloudy due to a (?)clay phenocrysts of plagioclase (up to 0.5 cm in length) set in mineral (XRD examination of duplicate material indicates a fine-grained matrix. Strong hydrothermal alteration an appreciable amount of kaolinite) and a fine hematitic B probably accounts for the rock’s mottled appearance. dust. The rock is markedly amygdaoloidal with calcite, In section, the idiomorphic feldspar phenocrysts appear chalcedony and chlorite constiuting the infilling minerals. strongly sericitised, and where alteration is more pro- The lava is devoid of sulphide mineralisation. nounced small patches of chlorite and kaolinite occur. b. Glassy tuff: the contact between this component and I The matrix is fine grained and cloudy but seems to consist the underlying andesitic lava (a) is uneven. In hand of a fine meshwork of feldspar laths, chlorite, iron oxide specimen, the rock is of greenish-brown colour, with sub- and a (?) clay mineral. Some small irregular patches of angular fragments (up to 4 mm in length) set in a crypto- chlorite may be after hornblende. A large vein, which crystalline matrix. In section, the rock displays a brecciated contains quartz, chlorite, calcite and hematite cuts the texture with sub-angular fragments of chloritised extrusive u rock. A series of tiny veins, filled with chlorite, (?) rock (probably andesite), volcanic tuff and altered feldspar clinozoisite and calcite intersect the large vein and thus set in a largely devitrified, siliceous matrix. A few tiny postdate it. With the exception of a trace amount of vesicles are filled with chlorite. The rock contains minor disseminated pyrite, the rock is devoid of sulphide minerals. disseminated pyrite. Some large irregular-shaped cavities I in lava (a) are filled with material of this glassy tuff which Altered andesitic lava (PTS 5014) is, therefore, of younger age than the lava (a). In hand specimen, a greenish-grey coloured rock with large C. Porphyritic lava. A linear (?) erosion surface separates phenocrysts of altered plagioclase (up to 1.0 cm in length) component (b) from an overlying lava. In hand specimen u distributed throughout a fine-g-rained matrix. Where hydro- the lava is chocolate coloured with uniformly sized feld- thermal alteration has been marked, the rock has a bleached spar phenocrysts set in a sparse, fine-grained matrix. In appearance. thin section, the feldspar phenocrysts show some evidence In thin section, the plagioclase displays a wide of kaolinisation but are almost totally replaced by calcite. I spectrum of alteration. Some of the phenocrysts are The carbonate replacement has been selective, for the relatively fresh and are andesine (an average composition largely devitrified siliceous matrix is unaffected. The is Abs,AnGs). In areas of intense alteration, the feldspars texture is somewhat unusual for a lava in that the distri- retain their idiomorphic form but consist of sericite and/or bution of generally equant phenocrysts exceeds 80% of I (?) kaolinite. Some subidiomorphic crystals of (?) pyroxene the total rock. The rock is microscopically vesicular with are apparent, now completely replaced by chlorite with infillings of chalcedony and chlorite and the presence of tiny rodlets of iron oxide reflecting a ghost cleavage. The hematitic dust accounts for the overall brownish colour. matrix is fine grained and consists of a mesh-work of small Some tiny, discontinuous ‘hair’ veins contain chlorite I laths of plagioclase, chlorite, hematite and probable clay. and ferroan dolomite. There is no sulphide mineralisation. The rock is cut by a large vein which in one area attains Of the three eruptive rocks present, this lava (c) is of a width of 2.0 cm. The vein is infilled with fragments of youngest age, with glassy tuff (b) occupying an inter- volcanic glass which has been largely devitrified to mediate age between rocks (a) and (c). I spherulitic palagonite. The palagonite in some areas shows alteration to green chlorite. These devitrified fragments are Tuff-breccia (agglomerate) (PTS 5017) distributed throughout an often replacive matrix of fibrous In hand specimen a greenish-brown coloured rock with iron-rich calcite which has grown at right-angles to the large unsorted, angular to sub-angular fragments (up to I walls of the vein. It is suggested that the vein is of tectonic 5.0 cm in length) of fine-grained, porphyritic extrusive origin and possibly related to an episode of faulting. The rock. In section the large fragments consist of chloritised lack of correspondence between vein margins implies lateral lava, tuff, dark volcanic glass, devitrified glass shards and movement during formation of the vein. The complex sericitised feldspar set in a devitrified glassy matrix. The I pattern of elongated patches of fibrous calcite and irregular rock is traversed by a series of veins containing ferroan dolomite which has resulted in marked carbonate alteration. a 28 From vein cross-cutting relationships two distinct and a trace of quartz. The introduction of the carbonate generations of carbonate growth can be recognised. The vein has resulted in marked carbonate alteration of the host rock is barren of sulphide mineralisation. rock. From vein cross-cutting relationships, two episodes of carbonate mineralisation can be recognised. The rock Andesitic lava (PTS 5018) contains blebs of chalcopyrite in trace amount. In hand specimen, a dark grey to black porphyritic rock with phenocrysts of feldspar set in a fine-g-rained matrix. Carbonate vein rock (PTS 5022) In thin section the idiomorphic feldspar phenocrysts The hand specimen of this rock consists almost entirely show strong alteration to kaolinite and occasionally contain of pink coloured carbonate in which large, angular frag- wisps of green chlorite. Some of the larger feldspar pheno- ments of an altered, porphyritic, extrusive rock are trysts are almost totally replaced by ferroan dolomite. embedded. In thin section the fragments consist of dark The matrix consists of a mesh-work of kaolinised feldspar volcanic glass and chloritised lava which are set in a fine, laths, a dark volcanic glass and minor goethite. A few small devitrified, siliceous matrix. The carbonate phase consists vesicles contain quartz, chalcedony, chlorite and calcite. of ferroan dolomite with small patches of calcite, and With the exception of a trace of chalcopyrite, the rock is trace amounts of chlorite, quartz and hematite. The devoid of sulphide minerals. fragments of extrusive rock are extensively altered and Numerous veins cut the lava and two series can be replaced by the carbonate phase. There is an isolated deposit distinguished: of chalcopyrite and pyrite on a fracture surface. la discontinuous quartz-filled veins lb later veins which contain ferroan dolomite, chlorite Altered andesitic lava (PTS 5023) and a little epidote In hand specimen, a dark brown coloured, porphyritic, 2 a large vein (up to 3.0 cm wide) rimmed by quartz and vesicular lava with phenocrysts of altered feldspar distribut- containing banded ferroan dolomite, the growth ed throughout a glassy matrix. history of which is visible from the distribution of In section, the phenocrysts of feldspar appear some- hematite. This vein also contains tiny lenses of fine, what chloritised and compositionally fall within the oligo- crystalline quartz and an occasional fragment of the clase range (an average value is Absz Ant 8). Some idio- country rock. Its age relationships relative to_ veins__.. morphic crystals composed entirely of a blue chlorite la and lb are uncertain. - (penninite) and which- occasionally -show a relict ophitic texture involving small laths of piagioclase, are probably Explosion breccia (PTS 5019) pseudomorphs after a ferromagnesian mineral. Smaller In hand specimen, a pale brownish-green coloured rock patches of- green chlorite are probably replacing biotite. consisting of angular to sub-angular fragments (up to The matrix consists of a fine mesh of tiny feldspar laths 2.8 cm in length) of lava and tuff set in a cryptocrystalline and devitrified volcanic glass. The lava is m&kedlyvesicular matrix. In thin section the lava and tuff fragments show with vesicle diameters -&nging in size from 1.0 mm to marked devitrification and are highly chloritic. Some 2.5 cm. The smallest vesicles-are frequently filled with phenocrysts of feldspar show alteration to kaolinite but the chlorite and calcite, but those of large dimensions are majority are totally chloritised. Hematite is present in rimmed by hematite and quartz, and contain carbonate accessory amount. The rock is strongly silicified but an (both calcite and ferroan dolomite), fragments of country episode of carbonate (ferroan dolomite) veining with rock, chlorite and baryte. The baryte is in the form of marked carbonate alteration postdates the silicification. long slender crystals and its growth is confined to the The rock is devoid of sulphide mineralisation. centres of the vesicles. The edges of the baryte crystals are rimmed by hematite and the mineral is many instances Glassy tuff(PTS 5020) is replaced by the carbonate phase. The rock is devoid of In hand specimen, a brownish-green coloured rock consist- sulphide mineralisation. ing of fragments of altered fine-grained extrusive rock set in a cryptocrystalline matrix. In thin section, the Agglomerate (PTS 5024) angular fragments consist of chloritised lava and tuff, This rock is. greenish coloured with large, angular, clasts fragments of dark volcanic glass and kaolinised feldspar. of an altered extrusive rock set in a fine chlorite-rich matrix. The glassy matrix shows strong devitrification with In section, the clasts consist of strongly chloritised(?) marked replacement by chlorite and contains abundant andesitic lava and a glassy tuff. In the lavaclasts, the phenol hematite and a patchy distribution of chalcedony. A trysts of plagioclase display marked alteration to sericite large vein cuts the rock, composed of ferroan dolomite, and not infre&ently to kaolinite. The phenocrysts are also quartz, small angular fragments of country rock, hematite heavily fractured but as they retain euhedral crystal out- and chlorite. The introduction of this vein has resulted in lines their deformation was probably a post-consolidation strong carbonate replacement of the host rock. Along the phenomenon. The matrix of the lava consists of a fine mesh marginal areas of the carbonate vein and the host rock, of altered plagioclase laths and devitrified volcanic glass. baryte occurs in slender, elongated crystals. The baryte Other clasts have a more tuffaceous character and contain is totally confined to a narrow zone and has clearly formed fragments of quartz, volcanic glass, plagioclase and potassic prior to the carbonate phase which largely replaces it. feldspar, all of which are set in a devitrified glassy matrix. The rock is devoid of sulphide mineralisation. The agglomerate matrix consists of finely comminuted mineral fragments of which quartz is the major constituent, Glassy tuff (PTS 5021) accompanied by fragments of devitrified volcanic glass, In hand specimen, a brownish-green coloured rock, contain- plagioclase, muscovite and chlorite. The rock contains a ing angular fragments of altered extrusive rock, set in a minor amount of hematite but is devoid of sulphide cryptociystalline matrix. In thin section, the fragments mineralisation. consist of chloritised lava and tuff, fragments of dark volcanic glass and kaolinised feldspar. Some of the individual fragments contain amygdales which are common- ly filled with chalcedony. The glassy matrix shows signs of strong devitrification with chlorite replacement and contains an appreciable amount of skeletal hematite. The rock has been invaded by a series of large carbonate veins. The veins are composed of ferroan dolomite, the growth history of which is frequently highlighted by zones of iron oxide staining, small fragments of chloritised country rock 29 APPENDIX IV X-RA Y DIFFRACTION SCANS ON AL VA CORE SAMPLES (Analyst: D. J. Morgan) Depth in m Major p30%) Moderate (1 O-3 0%) Minor ( Borehole 1, Burnside 28.90 feldspar calcite, quartz, chlorite 28.90-29.00 quartz feldspar, chlorite ?mica 38.00-38.13 calcite chlorite, ?mica 65.57 calcite, quartz feldspar, chlorite 66.00 quartz feldspar chlorite, mica 112.52 kaolinite, dolomite quartz Borehole 2, Balquharn 9.30 calcite quartz, dolomite, feldspar kaolinite 115.83 dolomite, quartz kaolinite 30 APPENDIX V X-RA Y DETERMINATIONS OF MINERALS FROM AL VA CORE SAMPLES (Analyst: R. I. Lawson) Sample Depth in m Description X-Ray Film Determination Borehole 1, Burnside _ CXD 21 8.45 Bright silvery flake XE 227 galena Red brown mineral XE 228 sphalerite CXD 11 45 .oo Circular radiating mineral XE 336 pyrite CXD 132 206.40 Black mineral in calcite XE 282 galena CXD 131 212.94 Metallic fragments XE 337,343, iron, possibly drill casing embedded in fracture 344 surface Borehole 2, Balquham CXD 39 120.90 Brown vein mineral XE 279 dolomite 31 APPENDIX VI ground value from the south to north, and much greater irregularity over the lavas north of the fault. GEOPHYSICAL SURVEYS Introduction Balquharn (BH 2). Geophysical surveys were carried out to In November 1977 geophysical surveys using VLF and determine whether any mineralisation associated with the magnetic methods were carried out around each of the intersection of the Ochil fault and a northwesterly trending three proposed borehole sites. The aims of these surveys subsidiary fault could be detected. VLF profiles were were (1) to establish the geophysical response to known inconclusive owing to topographic effects and distortion geological structures, (2) to give further structural informa- by the road and fences. Magnetic profiles changed from tion at ground surface and at depth, and (3) to detect smooth to irregular across the Ochil fault from south to possible mineralisation associated with the structures and north, with little change in background level. thereby specify optimum positions for the boreholes. Subsequently in July and November 1978 the three bore- BlairEogie (BH 3). Geophysical surveys were carried out to holes were logged geophysically by BPB with caliper, determine whether the Blairlogie copper-baryte veins could resistivity, formation density, gamma ray, neutron-neutron, be detected geophysically and if there was evidence for sonic, S P and temperature measurements. The principal significant mineralisation in the veins at depth. The extent result derived from the geophysical logs is the identification of the survey lines was limited in the west by roads and of a thin unit enriched in uranium on the gamma ray log of buildings, and in the east by steep crags and thick Burnside BH 1 between 158.60 and 159.30 m. This vegetation. All profiles showed strong responses to fences anomaly was confirmed by chemical analysis of the small and a water pipe. VLF in-phase profiles showed extreme amount of bleached breccia core recovered (CXD 119, topographic correlation. No significant anomalies could be Appendix II, Table I). Copies of the borehole logs are correlated with mapped veins due either to limited depth available on request from the Head of the Applied Geo- extent or to insufficient conductivity and magnetic physics Unit, Institute of Geological Sciences, Keyworth, susceptibility contrast. Nottingham, NG12 5GG. Regional geophysical coverage in the area includes the Conclusions aeromagnetic survey (Institute of Geological Sciences, 1962), No geophysical evidence was obtained of the location of regional gravity surveys completed in 1976 by AGU, and mineralised structures in the three districts proposed for a seismic reflection test carried out, over the Devonian lavas drilling. It was possible to locate the exact position of the of the Ochil Hills (Andrew, 1978). Ochil fault by magnetic surveys, but VLF surveys were inconclusive owing to greater distortion of profiles by Regional surveys fences, roads and pipes, and extreme topographic effects. The aeromagnetic map shows a gradient of about 50 gammas/km associated with the Ochil Fault between References Stirling and Alva. South of and parallel to the fault is an Andrew, E. M. 1978. Geothermal exploration in the elongated ‘low’ which may be due to the buried river valley Midland Valley of Scotland. Inst. Geol. Sci., Applied within the Carboniferous sediments. North of the fault Geophysics Unit, Rep. No. 64. positive irregular anomalies are associated with the Institute of Geological Sciences. 1962. Aeromagnetic Devonian lavas. map one inch Sheet 18. The regional gravity field is dominated by a broad negative anomaly which occurs on the southern side of the Ochil Fault, associated with a great thickness of low density Carboniferous sediments in the Clackmannan Syncline. The area of interest lies on the western flanks of this anomaly. The seismic test line was located approximately 10 km north-east of the Alva survey area, within the Devonian lavas of the Ochil Hills. Low velocity layer refraction tests showed a weathered layer of approximately 16 m thickness, but reflections were too weak to be interpreted. Natural seismic activity near the Ochil fault implies that at depth the fault may be inclined to the north. Detailed surveys At each site, VLF and total magnetic field measurements were taken at 10 m intervals along parallel traverses 50 m apart, and up to 850 m in length. The traverses were orientated approximately north-south at Bumside and Balquham, and east-west at Blairlogie, or approximately at right-angles to the structures under investigation. Burnside (BH 2). The surveys were carried out to determine whether any westward strike extension of the polymetallic mineralisation in Silver Glen could be detected, and for information about the position, structure, and possible associated mineralisation of the Ochil fault and the quartzdolerite intrusion on the fault. No significant geophysical anomalies were found on strike from the old silver deposit. South of this the VLF profiles were inconclusive owing to topographic effects and distortion due to fences and a large water pipe running more or less along the line of the Ochil fault. Magnetic profiles were similarly distorted but indicated clearly the position of the OchiI fault by a sharp increase in back- 32