Page 20 - Geochemical Remote Sensing of The Sub-Surface

Contents XIX

Soil adsorption of hydrogen sulphide ................................................................... 291
Hydrogen sulphide transport through soil ............................................................. 293
Redox conditions for hydrogen sulphide persistence ............................................ 294
Conclusions of experimental investigations ......................................................... 295
Field investigations ................................................................................................... 295
Mineralisation beneath thick transported overburden ........................................... 297
Mineralisation beneath thick lithic cover .............................................................. 299
Mineralisation beneath mixed eluvium and transported sediment ........................ 300
Discussion ................................................................................................................. 301
Undetected mineralisation .................................................................................... 301
False anomalies .................................................................................................... 302
Conclusions ............................................................................................................... 302

Chapter 10. Helium ...................................................................................................................... 303
C.R.M. Butt, M.J. Gole and W. Dyck
Introduction ............................................................................................................... 303
Occurrence ................................................................................................................ 304
Discovery .............................................................................................................. 304
Abundance and origin ........................................................................................... 304
Abundance in the Earth and atmosphere ............................................................... 305
Isotope ratios ........................................................................................................ 306
Properties and migration ....................................................................................... 307
Sampling ................................................................................................................... 310
Soil and overburden gases .................................................................................... 310
Soils ...................................................................................................................... 311
Waters ................................................................................................................... 312
Analysis .................................................................................................................... 313
Mass spectrometry ................................................................................................ 313
Gas chromatography ............................................................................................. 315
Portable helium analysers ..................................................................................... 316
Determination of helium isotope ratios ................................................................. 316
Analysis of waters ................................................................................................ 316
Variations of helium concentrations ......................................................................... 317
Soil and overburden gases .................................................................................... 317
Groundwaters ....................................................................................................... 319
Biological activity and soil gas composition ........................................................ 319
Helium surveys in mineral exploration ..................................................................... 320
Rationale ............................................................................................................... 320
Helium in gases and soils ..................................................................................... 321
Soil and overburden gas surveys ...................................................................... 321
Soil surveys ...................................................................................................... 326
Discussion of soil-gas and soil survey techniques ............................................ 327
Helium in waters ................................................................................................... 328
Groundwater surveys in uranium-mineralised areas ......................................... 328
Groundwater surveys in non-mineralised areas ................................................ 331
Surface water surveys ....................................................................................... 336
Discussion of water survey techniques ............................................................. 338