Page 12 - Handbook of Gold Exploration and Evaluation

Preface

The intention of an earlier text Alluvial Mining ± The Geology, Technology and
Economics of Placers ± was to provide a basic understanding of the
fundamentals of alluvial mining theory and practice for placer engineers and
geologists to build upon. The beach sand minerals rutile, zircon, ilmenite and
middle density minerals cassiterite and tantalite took prominence over gold and
other noble metals of higher density and greater unit value. The overall response
was encouraging but the amount of fresh evidence emerging from ongoing
studies showed that a fresh book was needed based solely upon gold as a unique
metal in its own right. This book, the Handbook of Gold Exploration and
Evaluation is designed primarily for professional geologists and engineers
engaged in gold exploration-evaluation exercises, and as a text for under-
graduate and graduate students in higher schools of learning. Since much of the
treatment is empirical, it should also provide useful reference material for
prospectors and small-scale miners.
Presentation of the text commences with a brief description of the nature of
gold and of those properties that make it unique amongst all other minerals. The
history of gold is reviewed from the earliest times recorded by man until the
beginning of the 20th century when geologists were beginning to understand
how the Earth's surface was formed and what causes it to change over time.
New theories involving the metallogenic roles of orogenic-related volcanics and
sedimentation within intracratonic basins were being examined. Geophysicists
were investigating the structure of the Earth and its magnetic, electrical and
magnetic properties. Classical geology, which could once tell only what
happened in a past sequence of events but seldom how or why, was now finding
answers in the new and revolutionary approach to mineral exploration, the
global theory of plate tectonics. Resurgence of efforts seeking an understanding
of universal processes involved with the origin and general structure of the Earth
and its neighbours in space was stimulated by discoveries in planetary science.
Explanations based upon plate tectonic theory are offered for the evolution
and inter-relationship of oceanic and continental crust and the supercontinental
cycle in which continental masses continually join together, drift apart and