Conventionally, geochemical exploration for gold is based on the assumptions that (1) gold is chemically inert in surficial environments; (2) gold occurs mainly in discrete grains; and (3) gold is transferred by mechanical means to form clastic dispersion halos and dispersion trains. Consequently, the commonly adopted methodology has been (1) to determine gold in heavy mineral concentrates; (2) to use large samples in order to improve the reproducibility of gold analyses; (3) to use high detection limits and thresholds; and (4) to determine total gold contents and pathfinder elements in the samples. However, these methods are not always successful in locating gold deposits, and they have limited application in the search for buried or blind deposits.

In China, studies of the distribution and migration of particulate and ultrafine gold indicated that (1) gold is active and mobile in surficial environments; (2) gold occurs not only as discrete grains, but also as ultrafine particles and other complex forms; and (3) regional low-concentration gold anomalies as well as local anomalies over buried gold deposits originate from ultrafine gold and other complex forms of gold. The methodology developed in China for regional and local geochemical gold exploration is based on this experience. Results of investigations around two gold deposits in China are presented.

Petrography (from the Greek petra meaning rock and graphus meaning writing or a record) originated over 150 years ago as a technique employed primarily by geologists, who used microscopes to examine rock samples to identify their mineralogical and chemical characteristics. Petrographic techniques have since been applied to a wide range of materials used in construction including building stone, aggregate, soil, cement, concrete, mortar, brick, and bituminous mixtures. The polarising microscope has been used for the examination of cementitious materials since 1887. Almost one hundred years ago a series of six articles'1' in Concrete and Concrete Construction, the forerunner of today's CONCRETE, described the possibilities of using a microscope for examining concrete. In the last 40 years, petrography has become widely used for both research and commercial investigation of concrete structures. Petrographic examination is a laboratory procedure that is unique in that it relies highly on visual inspection of the samples. It requires specialist sample preparation and microscopical equipment and operators with appropriate qualifications and experience. Using the microscope the petrographer can determine the composition of concrete, assess its quality, and investigate the causes and extent of any deterioration. Photographs taken through the microscope (photomicrographs) record petrographic features of concrete samples. <...>

Resource evaluation drilling is usually on a regular pattern; the pattern spacing should be optimised to maximise profit from mining, accounting for the cost of drilling and the value of additional information from increased density of drilling, and also to reduce risk in mined ore tonnes and grades to an acceptable level. Conditional simulation methods for determining optimum drilling spacing are more powerful than traditional methods, and simulation methods can take into account local variability in grade. Mining profit functions can consider profit and density of evaluation drilling so that profit can be maximised.

The papers in this volume consider the general themes of flow confinement and topographic control on processes and sedimentary architecture in deep water clastic systems.
This publication grew out of an international workshop on Confined Turbidite Systems, held in Nice (France) in September 2001. Many of the papers presented at that meeting related to case studies of the Ores d'Annot turbidites, which are so spectacularly exposed in the region north of Nice. Hence we have also produced a companion volume in the same series (Geological Society Special Publication 221) specifically focusing on the Ores d'Annot.