Factors Controlling the Surficial Dispersion of Arsenic, Antimony, Bismuth and Selenium from Mineral Deposits in the British Isles by Charles J. Moon A Thesis Submitted for the Degree of Doctor of Philosophy in the University of London Applied Geochemistry Research Group Geology Department Imperial College London April 1983 ii ABSTRACT This research investigates the cost effective uses of arsenic, antimony, bismuth and selenium as pathfinder elements in geochemical exploration by establishing the controls on their secondary dispersion in soils and drainage sediments. Sensitive and precise determination of these elements in geochemical samples (rapidly and routinely) is made possible by advances in analytical methodology, whereby their volatile hydrides are generated and flushed into an inductively coupled plasma emission spectrometer. A background study of stream sediments from south- west England confirms that the distribution of arsenic, bismuth and selenium is correlatable with bedrock geology but scavenging, of arsenic by ferric oxides and selenium by organic matter, is locally important. All the elements are relatively enriched in fine grained (reducing) clastic sediments although bismuth is most abundant in granitic intrusives. Detailed studies of lA mineral deposits in the British Isles indicate the exploration effectiveness of these pathfinders. Selenium (with arsenic and antimony) is useful in the location of nickel deposits at Arthrath, Scotland. Bismuth and arsenic pick out the tungsten deposits at Ballinglen, Ireland and polymetallic uraniferous veins at Dalbeattie, Scotland. The Kuroko-type deposit at Avoca, Ireland shows distinct zonation from base to top of bismuth, arsenic and antimony with bismuth associated with the copper zone and antimony with the lead-zinc rich zone. Antimony is a good pathfinder for two Irish style base metal deposits (Keel and Mallow, Ireland) and arsenic for vein gold deposits (Clontibret, Ireland). In the surficial environment, arsenic and selenium are potentially mobile while bismuth shows limited mobility and antimony is almost immobile. The mobilities of arsenic and selenium are inhibited by accumulation at geochemical barriers: both by ferric oxides; and for selenium by organic matter. Arsenic can be recommended for regional and detailed geochemical surveys in temperate terrains but care must be taken to note areas of iron scavenging. Antimony and bismuth are best applied in detailed prospecting with deep sampling much more effective for antimony in areas of moderate to thick overburden. Selenium has very restricted utility in temperate terrains as a result of its affinity for organic matter. All four pathfinders are effective in lateritised areas, where transition metals are particularly prone to leaching. Acknowledgements This research was undertaken while the author was a research assistant at Imperial College. Financial support was provided by the National Environment Research Council and the Raw Materials Commission of the European Economic Community. I gratefully thank Martin Hale who initiated and supervised the project and this thesis. Thanks go to other members of the team associated with the project: Michael Wheatley; great assistance through two long years of analysis and computing Dianne Wraith: help with analysis and literature in the project's early stages Flavio Tavora: valuable discussions and rock sampling of Scottish areas Many other members of the Applied Geochemistry Research Group have contributed ideas and expertise, notably: Eva Banerjee and Barry Coles: assistance with ICP analyses Barrie Oakes: much help in the field and with organic carbon determinations Annette Johnson and Anne Metcalfe: loan of water sampling equipment and advice on its use Behrooz Pahlavanpour: initial advice on hydride methods The following members of the mining industry and government surveys freely gave of their time and knowledge, and are warmly thanked: Messrs P. McArdle and A. Thomas: Avoca Messrs A. Bowden, J. Clifford and Dr. R. Steiger: XV Ballinglen (especially for arranging tungsten determinations) Dr. J. Morris and Mr. D. Wilbur: Clontibret Dr. M. Gallagher: Glendinning Messrs V. Byrne, D. Cliff and D. Smith: Keel Dr. J. Carter and Mr. D. Wilbur: Mallow Completion of this thesis was greatly expidited by the skills of: Ella Ng Cheing Hin and Tony Brown: Drafting Grace Lau: Photography Beryl Oakes: Typing and they are thanked for their contribution. Source of Data for Figures After = Figure modified or redrafted from the source From = Figure reproduced directly from the source vi Table of Contents Page Abstract ii Acknowledgements i v Table of Contents vi List of Tables xv List of Figures xvdi Part I-Introduction and Review of Primary Concentrations Chapter 1 Introduction » 1 . 1 Aims 1 1.2 "Why Use Pathfinder Geochemistry?" 1 1.3 Approach of this Study 3 1.4 Arrangement of this Thesis 3 1 .5 Field and Laboratory Methods 4 1.5-1 Sampling Methods 4 1.5-2 Analytical Techniques 7 1.5.3 Quality Control of Analytical Data 8 1 .6 Data Handling 9 Chapter 2 Primary Dispersion and Concentration : A Review 10 2.1 Primary Distribution : Ba ckground^ . chem cal Cycles 10 2.1.1 Background Geochemical Cycles 10 2.1.2 Background Distribution in Igneous Rocks 12 vii 2.1.3 Background Distribution in Sedimentary Rocks 13 2.2 Primary Concentration and Ore Deposition 13 2.2.1 Selenium and the Problem of S „ , . , x Se Ratios 13 a Sulphur ^^Ratios 17 g 2.2.2 Arsenic-A Universal Pathfinder? 18 2.2.3 Antimony 22 2.2.4 Bismuth - A Pathfinder for Tungsten? 24 2.3 Lithogeochemical Applications of the Pathfinders 27 Part II-Detailed Studies Chapter 3 South Vest England Background Study 32 3.1 Introduction 32 3.1.1 Sample Selection 32 3.1.2 Elements Determined 33 3.1.3 Data Processing 33 3.2 Results 36 3.2.1 Element Associations 36 3-2.2 Arsenic Distribution 45 3.2.3 Bismuth Distribution 61 3.2.4 Selenium Distribution 68 3.3 Discussion and Conclusions 74 viii Chapter 4 Vein Hosted Deposits 77 4.1 Dalbeattie 77 4.1.1 Geology 77 a Surficial Geology 79 4.1.2 Programme 79 a Lithogeochemical Traverse DB01 80 b Soil Traverse DB02 81 8 c Soil Traverse DB03 9 4.1.3 Discussion 89 4.2 Ballinglen 94 4.2.1 Geology 94 a Solid Geology 94 b Surficial Geology 96 4.2.2 Programme 96 a Lithogeochemistry 98 b Soil Traverse BG01 98 c Soil Traverse BG02 106 d Soil Traverse BG04 109 e Overburden Traverse BG05 1°9 f Stream Sediments BG03 111 g Stream Waters BG03 115 4.2.3 Discussion 123 4.2 Clontibret 130 4.3.1 Geology 130 4.3.2 Programme 130 ix a Soil Traverse CT03 133 b Bryanlitter Soil Traverse CT02 133 c Ballyg reany Soil Traverse CT01 140 d Stream Sediments CT04 140 4.3-3 Discussion 145 Chapter 5 Deposits Hosted By Igneous Rocks In Glaciated Areas 148 5.1 Arthrath 148 5.1.1 Geo logy 148 a Solid Geology 149 b Surfi cial Geology 149 c Rock Geochemistry 152 5-1.2 Programme 152 a Soil Traverse AR01 154 b Soil Traverse AR02 160 c Stream Sediments AR03 1 67 5.1.3 Discussion 168 5.2 Kilmelford 173 5.2.1 Geology 173 a Solid Geology 173 b Surficial Geology 176 c Rock Geochemistry 176 5.2.2 Programme 176 a Rock Geochemistry KD02 179 b Soil Traverses KD03 and KD04 179 c Stream Sediments KD01 193 XV 5.2.1 Discussion 200 Chapter 6 Stratabound Deposits Hosted By Clastic Sediments 205 6 . 1 Av o ca 206 6.1.1 Geology 206 6.1.2 Programme 208 a Sampling 208 b Lithogeochemistry 210 c Surficial Dispersion...v . .., . Till profil e 021c6 i Trench Geochemistry 216 ii Basal Till Cobra Samples 219 iii Dispersion Through The Till 219 d Regional Traverse 223 6.1.3 Discussion 228 a Primary Concentration Lithogeochemistry 228 b Secondary Dispersion 232 6.2 Meal1 Mor 233 6.2.1 Geology 233 a Solid Geology 233 b Surficial Geology 235 6.2.2 Programme 235 a Lithogeochemistry 237 b Soil traverses MM02 and MM03 237 c Stream Sediments and Waters 248 6.2.3 Discussion 250 6.3 Glendinning 256 xi 6.3.1 Geology 256 a Surficial Geology 258 6.3.2 Programme 258 a Soil Traverses GD02 and GD03 258 b Stream Sediments GD01 266 c Detailed Investigation of Glenshanna Burn 266 6.3.3 Discussion 274 Chapter 7 Carbonate Hosted Deposits In Glaciated Terrain 277 7.1 Keel 277 7.1.1 Geology 277 a Solid Geology 277 b Lithogeochemistry 279 c Surficial Geology 280 7.1.2 Programme 280 a Regional Traverse KL01 282 b Till Profile KL01 289 c Soil Traverse KL02 292 d Soil Traverse KL03 292 e Stream Sediments and Waters KL04 292 7.1.3 Discussion 296 7.2 Mallow 300 7.2.1 Geology and Regional Geochemistry 300 a Solid Geology 300 b Surficial Geology 301 c Regional Geochemistry 301 xii 7.2.2 Programme 304 a Soil Traverse MW01 304 b Soil Traverse MW02 309 7-2.3 Discussion 313 Part III Comparison of Detailed Studies with Literature Descriptions of Pathfinder Surficial Dispersion; Exploration Implications and Conclusions Chapter 8 Behaviour of the Pathfinders in the Surficial Environment and Applicability in Prospecting 315 8.1 Surficial Dispersion: Theory and Evidence-A Review 315 8.1.1 Arsenic 315 8.1.2 Antimony 316 8.1.3 Bismuth 326 8.1.4 Selenium 327 8.2 Comparison of Pathfinder Dispersion from Detailed and Published Studies 330 8.2.1 Arsenic 330 a Soils and Overburden 330 b Stream waters and Sediments 331 8.2.2 Antimony 336 a Soils and Overburden 338 b Stream Waters and Sediments 339 8.2.3 Bismuth 338 a Soils and Overburden 339 xiii b Stream Waters and sediments 339 8.2.4 Selenium 340 a Soils and Overburden 340 b Stream Waters and Sediments 341 8.3 Exploration Implications of the Studies: Comparison of Detailed Studies with Published Accounts 342 8.3.1 Arseni c 342 8.3.2 Antimony