Page 17 - Geochemical Remote Sensing of The Sub-Surface

XVI Contents

Chapter 3. Spontaneous potentials and electrochemical cells ........................................................ 81
S.M. Hamilton
Introduction ................................................................................................................. 81
Geochemical transport mechanisms ............................................................................ 82
Diffusion ................................................................................................................. 82
Advective groundwater transport ............................................................................ 82
Gaseous transport .................................................................................................... 83
Electrochemical transport ....................................................................................... 85
Voltaic Cells ................................................................................................................ 86
Spontaneous potential in Earth materials .................................................................... 91
Measurement of spontaneous potential ................................................................... 92
Sources of spontaneous potential ............................................................................ 95
Redox stratification in the Earth ............................................................................. 98
Spontaneous potential cells ....................................................................................... 1 O0
Ohm's law in the development of cells ................................................................ 100
Cells associated with electronic conductors in bedrock ........................................ 101
Cells in the absence of electronic conductors ....................................................... 107
Field evidence for the presence of cells ............................................................... 112
Geochemical response to spontaneous potential cells ............................................... 113
lon mobility .......................................................................................................... 113
Geochemical anomalies ........................................................................................ 115
Conclusions ............................................................................................................... 118

PART If. REMOTE DISPERSION PATTERNS OF CO-GENETIC PROVENANCE
Chapter 4. Carbon dioxide dispersion halos around mineral deposits ......................................... 123
M. Zhang
Introduction ............................................................................................................... 123
Method ...................................................................................................................... 123
Case histories ............................................................................................................ 124
Discussion ................................................................................................................. 127
Speciation of carbon dioxide ................................................................................. 127
Formation of carbon dioxide dispersion patterns ................................................. 130
Factors affecting carbon dioxide anomalies ......................................................... 131
Conclusions ............................................................................................................... 131

Chapter 5. Light hydrocarbons for petroleum and gas prospecting ............................................. 133
V.T. Jones, M.D. Matthews and D.M. Richers
Introduction ............................................................................................................... 133
Origin of light hydrocarbon gases ............................................................................. 134
Origin of petroleum .............................................................................................. 134
Origin of light hydrocarbon gases in the near-surface .......................................... 137
Laboratory and field evidence of biogenic C2-C4 hydrocarbons ........................... 137
Distinguishing petrogenic and biogenic hydrocarbons ......................................... 140
History ....................................................................................................................... 140
Basic concepts ...................................................................................................... 141
Methods of geochemical prospecting .................................................................... 141