This volume documents the techniques for geochemical remote sensing of the subsurface, to present case-history evidence of their successes and limitations, and to consider their further potential. The chapters in Part I focus on the mechanisms and models of dispersion that give rise to the patterns we attempt to detect. Part II deals with the detection of dispersion patterns that owe their origins to processes, such as leakage, that are allied to resource emplacement. Part III describes the detection of dispersion patterns that are generated by processes, such as radiodecay and oxidation, taking place in deposits after their emplacement.
Every chapter brings a fresh perspective. Radon has met with much success in uranium exploration, whilst thorough research studies on helium and mercury lead to conclusions that tend to discourage use of these gases in mineral exploration. The case for light hydrocarbons is one of compelling simplicity whilst elaborate mathematical and electrochemical models are advanced for metal migration.
Editors foreword v Preface vii List of contributors ix PART I. GENETIC MODELS OF REMOTE DISPERSION PATTERNS Genesis, behaviour and detection of gases in the crust 3(14) M. Hale Introduction 3(1) The geochemical background 4(2) The atmosphere 4(2) The soil air 6(1) Indicator and pathfinder gases for exploration 6(2) Gases contemporaneous with resource emplacement 7(1) Gases of post-mineralisation provenance 7(1) Mechanisms of gas migration 8(5) Diffusion 8(3) Mass flow 11(1) Gas streaming 12(1) Indicator and pathfinder gas data acquisition 13(1) Conclusions 14(3) Geoelectrochemistry and stream dispersion 17(64) O. F. Putikov B. Wen Introduction 17(1) Geoelectrochemical prospecting 17(36) Physico-chemical basis 17(19) Partial extraction of metals (CHIM) 36(10) Diffusion extraction of metals (MDE) 46(3) Organometallic (MPF) and thermomagnetic (TMGM) patterns 49(4) Geoelectrochemical exploration 53(25) Physico-chemical basis 53(7) Contact polarisation (CPC) 60(9) Contactless polarisation (CLPC) 69(4) Polarographic logging (PL) 73(5) Discussion and conclusions 78(3) Spontaneous potentials and electrochemical cells 81(42) S.M. Hamilton Introduction 81(1) Geochemical transport mechanisms 82(4) Diffusion 82(1) Advective groundwater transport 82(1) Gaseous transport 83(2) Electrochemical transport 85(1) Voltaic Cells 86(5) Spontaneous potential in Earth materials 91(9) Measurement of spontaneous potential 92(3) Sources of spontaneous potential 95(3) Redox stratification in the Earth 98(2) Spontaneous potential cells 100(13) Ohms law in the development of cells 100(1) Cells associated with electronic conductors in bedrock 101(6) Cells in the absence of electronic conductors 107(5) Field evidence for the presence of cells 112(1) Geochemical response to spontaneous potential cells 113(5) Ion mobility 113(2) Geochemical anomalies 115(3) Conclusions 118(5) PART II. REMOTE DISPERSION PATTERNS OF CO-GENETIC PROVENANCE Carbon dioxide dispersion halos around mineral deposits 123(10) M. Zhang Introduction 123(1) Method 123(1) Case histories 124(3) Discussion 127(4) Speciation of carbon dioxide 127(3) Formation of carbon dioxide dispersion patterns 130(1) Factors affecting carbon dioxide anomalies 131(1) Conclusions 131(2) Light hydrocarbons for petroleum and gas prospecting 133(80) V.T. Jones M.D. Matthews D.M. Richers Introduction 133(1) Origin of light hydrocarbon gases 134(6) Origin of petroleum 134(3) Origin of light hydrocarbon gases in the near-surface 137(1) Laboratory and field evidence of biogenic C2-C4 hydrocarbons 137(3) Distinguishing petrogenic and biogenic hydrocarbons 140(1) History 140(3) Basic concepts 141(1) Methods of geochemical prospecting 141(2) Physical basis for migration of hydrocarbons to the surface 143(5) Basic assumptions 143(1) Physical transportation by effusion 144(1) Physical transportation by diffusion 144(4) Hydrocarbon residence sites at surface 148(4) Free gas 149(1) Bound gas 150(1) Choice of free gas or bound gas 150(2) Factors influencing near - surface hydrocarbon flux 152(3) Microbial activity 152(1) Barometric pumping 152(1) Earthquakes 153(2) Sampling and measurement methods 155(25) Atmospheric techniques 155(4) Soil gas 159(11) Dissolved gas 170(2) Headspace gas 172(1) Disaggregation 173(3) Acid extraction 176(3) Fluorescence 179(1) Sampling strategy 180(2) Data interpretation 182(10) Preferential pathway model 182(5) Geochemical populations 187(5) Case histories 192(19) Neuquen Basin, Argentina 192(3) High Island area, Gulf of Mexico 195(2) Great Basin, Railroad Valley, Nevada 197(11) Overthrust Belt, Wyoming-Utah 208(3) Conclusions 211(2) Gas geochemistry surveys for petroleum 213(20) T. Ruan Q. Fei Introduction 213(1) Theoretical principles 214(4) Indicator gases 216(1) Gas migration 217(1) Surface expressions of hydrocarbon migration 218(1) Gas anomalies 218(1) Alteration 218(1) Modes of occurrence of gases in microseeps 219(3) Free molecules 220(1) Adsorbed molecules 220(1) Microbubbles 221(1) Mineral constituents 221(1) Practical methods 222(3) Soil air 222(1) Soil 223(2) Case histories 225(6) Ordos Basin 225(4) Lixian Depression 229(2) Conclusions 231(2) Aerospace detection of hydrocarbon-induced alteration 233(16) H. Yang F.D. Van der Meer J. Zhang Introduction 233(2) Hydrocarbon microseepage 233(1) Induces surface manifestations of microseepage 234(1) Remote detection of induced surface manifestations 235(9) Bleached red beds 236(2) Kaolinisation 238(1) Carbonate enrichment 238(2) Vegetation stress 240(4) Other anomalies 244(1) Problems and future trends 244(5) PART III. REMOTE DISPERSION PATTERN OF POST-GENETIC PROVENANCE Sulphur gases 249(42) M.E. Hinkle J.S. Lovell Introduction 249(1) Chemistry and geochemistry of sulphur gases 250(6) Experimental techniques 256(14) Sample collection 256(3) Analysis by gas chromatography 259(8) Other methods of analysis 267(1) Reference materials 267(2) Sample storage and preparation for analysis 269(1) Degassing soils and molecular sieve adsorbents 269(1) Injection of samples 270(1) Recording analytical results 270(1) Case histories 270(17) Johnson Camp, Arizona 271(12) North Silver Bell, Arizona 283(2) Cradon, Wisconsin 285(1) Kazakhstan 286(1) Ireland 286(1) Discussion 287(1) Conclusions 288(3) Sulphide anions and compounds 291(12) X. Sun Introduction 291(1) Experimental investigations 291(4) Soil adsorption of hydrogen sulphide 291(2) Hydrogen sulphide transport through soil 293(1) Redox conditions for hydrogen sulphide persistence 294(1) Conclusions of experimental investigations 295(1) Field investigations 295(6) Mineralisation beneath thick transported overburden 297(2) Mineralisation beneath thick lithic cover 299(1) Mineralisation beneath mixed eluvium and transported sediment 300(1) Discussion 301(1) Undetected mineralisation 301(1) False anomalies 302(1) Conclusions 302(1) Helium 303(50) C.R.M. Butt M.J. Gole W. Dyck Introduction 303(1) Occurrence 304(6) Discovery 304(1) Abundance and origin 304(1) Abundance in the Earth and atmosphere 305(1) Isotope ratios 306(1) Properties and migration 307(3) Sampling 310(3) Soil and overburden gases 310(1) Soils 311(1) Waters 312(1) Analysis 313(4) Mass spectrometry 313(2) Gas chromatography 315(1) Portable helium analysers 316(1) Determination of helium isotope ratios 316(1) Analysis of waters 316(1) Variations of helium concentrations 317(3) Soil and overburden gases 317(2) Groundwaters 319(1) Biological activity and soil gas composition 319(1) Helium surveys in mineral exploration 320(18) Rationale 320(1) Helium in gases and soils 321(1) Soil and overburden gas surveys 321(5) Soil surveys 326(1) Discussion of soil-gas and soil survey techniques 327(1) Helium in waters 328(1) Groundwater surveys in uranium-mineralised areas 328(3) Groundwater surveys in non-mineralised areas 331(5) Surface water surveys 336(2) Discussion of water survey techniques 338(1) Helium surveys in petroleum exploration 338(5) Helium surveys in geothermal resource exploration 343(3) Helium in thermal waters and gases 343(1) Helium surveys for geothermal resources 344(2) Helium associated with faults 346(4) Faults as secondary sources of helium 346(1) Groundwater surveys 346(2) Soil gas surveys 348(1) Helium monitoring in earthquake prediction 349(1) Conclusions 350(3) Migration of helium in the near-surface environment 350(2) Application of helium surveys 352(1) Radon 353(42) W. Dyck I.R. Jonasson Introduction 353(1) Physical and chemical properties of radon 354(2) Definitions 356(1) Geochemistry of radon 357(25) Concentrations of radon and radium in natural environments 358(7) Disequilibrium in the uranium decay series 365(2) Emanation and mobility of radon 367(15) Analytical methods 382(7) Principles of methods 383(1) Instantaneous mode 384(2) Semi-integrating mode 386(2) Fully-integrated mode 388(1) Field methods 389(3) Determination of radon in natural waters 389(2) Determination of radon in soil emanations 391(1) Comparison studies and case histories 392(2) Future needs 394(1) Mercury 395(44) G.R. Carr J.R. Wilmshurst Introduction 395(1) Geochemistry of mercury 396(3) Behaviour of mercury in the primary environment 399(7) Low temperature epithermal base-metal deposits 399(1) Volcanogenic massive sulphide deposits 400(2) Sediment-hosted massive sulphide deposits 402(1) Gold deposits 403(1) The role of metamorphism 404(2) Behaviour of mercury in the secondary environment 406(21) Outcropping mineral deposits in dry climates 406(6) Outcropping mineral deposits in wet climates 412(5) Blind and buried mineral deposits in dry climates 417(5) Blind and buried mineral deposits in wet climates 422(5) Sampling media 427(8) Atmospheric air 427(3) Soil gas 430(1) Soil 431(2) Comparison of soil and soil gas 433(1) Rocks 434(1) Recommended analytical procedures 435(2) Conclusions 437(2) Discrimination of mercury anomalies 439(12) Z. Hu Introduction 439(1) Method 440(1) Case histories 440(7) Traverses over known mineral deposits 440(4) Regional traverse 444(1) Regional grid 445(2) Discussion 447(1) Conclusions 448(3) Oxygen and carbon dioxide in soil air 451(20) J.S. Lovell Introduction 451(1) Oxygen and carbon dioxide in the subsurface 452(5) Sampling and analytical methods 457(4) Oxygen and carbon dioxide analysers 457(2) Orstat gas analyser 459(1) Draeger tubes 459(1) Gas chromatography and mass spectrometry 460(1) Case histories 461(7) Russia 461(1) Azerbaijan 462(1) Kyrgyzstan 463(1) Namibia 463(1) Johnson Camp, Arizona 464(2) Colorado Plateau, Arizona 466(2) Discussion 468(1) Conclusions 469(2) References 471(42) Author index 513(16) Geographical index 529(4) Petroleum and mineral deposit index 533(4) Subject index 537
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