ABSTRACT Airborne radiometric (gamma-ray) data provide estimates of the concentrations of potassium (K), thorium (Th), and uranium (U) in soil, regolith, and bedrock. Radiometric data constitute an important source of geochemical information, commonly used in mineral exploration and for geological mapping of Earth and other planets. Airborne radiometric data have rarely been applied to the exploration and analyses of impact structures, in contrast with other conventional geophysical tools (e.g., gravimetry, magnetism, and seismic reflection/refraction). This work represents the first systematic survey of the K, Th, and U radiometric signatures of Australian impact structures, based on the continent-wide airborne radiometric coverage of Australia. We first formulated several hypotheses regarding the possible causes of formation of circular radiometric patterns associated with impact structures. Then, the radiometric signatures of 17 exposed impact structures in Australia were documented. Our observations confirmed the supposition that impact structures are commonly associated with circular radiometric patterns. We then selected the five structures with the most prominent circular radiometric patterns (Gosses Bluff, Lawn Hill, Acraman, Spider, and Shoemaker), and we discuss the possible origin of these anomalies. Based on these five case studies, we argue that such patterns result from either crustal deformation induced by the impact event and/or from postimpact superficial processes controlled by the crater topography. This work also suggests that airborne radiometric data may be useful, in combination with other geophysical tools, in the search for new possible impact structures.

With the myriad of measurement techniques and definitions of clays, the first question generally asked is “how much clay is there” in a sample? This often refers to the magnitude of a clay attribute in the sample and the answer to this question may vary depending on the measurement method. Does the method measure the clay-mineral type, the size distribution or mean size, the surface area, cation exchange capacity (CEC), rheology, or plasticity? Clay mineral type, particle size, and surface area are commonly used in mining operations to optimize oil-sand ore blending. In bitumen extraction and tailings management, where slurry behavior contributes to the process performance, propertiess uch as rheology and plasticity are also used. The previous chapters in the volume have introduced the various properties of clay particles and clay minerals. The present chapter describes the common methods of measuring clays and clay minerals in oil sands.

The clay minerals present in the oil-sands ore are responsible for some of the most challenging (and intriguing) processing behavior experienced on a routine basis in oil-sands surface mining. In previous chapters, significant details have been provided on how specific clay properties can give rise to changes in slurry rheology and interface phenomena. Because the bitumen extraction process relies heavily on manipulation of interfacial effects to enhance separation, changes in clay content in the ore, not surprisingly, can have a dramatic impact on the ability to process the material. This chapter provides an overview of the extraction process, the influence of clay minerals on bitumen recovery, and the challenges in reacting to changes in the ore clay content in a typical operation. The chapters that follow focus on the larger issue of tailings treatment to create a reclaimed landscape at the end of mine life.