Lead Isotope Evidence For The Detrital Origin Of Witwatersrand Pyrites And Its Bearing On The Provenance Of The Witwatersrand Gold

Geochemical Studies is a collection of papers dealing with ore petrology, particularly on the genesis of ores found in sediments. One paper describes the minor elements in metal deposits in sedimentary rocks, focusing on geochemical work on certain classes of ores in sediments and on the theories of origin of the deposits. With better techniques of microprobe analysis of trace elements, the paper notes that ore deposits in sedimentary rocks can be characterized by their minor element suites. One paper points out that large ore deposits cannot possibly be formed by a migration of substances (known as "negative" diffusion). The paper estimates that the quantities of material that can be accumulated in a sediment horizon with a great affinity for these materials, say in a period of one billion years, will still not be sufficient to produce a large ore deposit. The paper estimates the necessary diffusion coefficients that occur in deep structures, where increased mobilities of various substances occur. Geologists, geochemists, and engineers working with fossil fuels will find the collection highly significant.

The papers in this volume are dedicated to Professor Dr. Dr. h.c. G. Christian Amstutz by his colleagues, friends, and students on the occasion of his 60th anniversary. The authors of this book - the theme was restricted to syngenesis and epigenesis in the formation of mineral deposits - wish to honour with their articles a scientist who has contributed to, and substantially promoted the understanding of the genesis of mineral deposits in the last decades. The majority of the articles deal with strata-bound depos its, thus reflecting one of his main scientific interests. In the tradition of his professors, Paul Niggli and Paul Ramdohr, G.C. Amstutz has maintained an open and active interest in many fields of earth science. His numerous papers have triggered a remarkable number of new ideas and investigations in a variety of fields, and the "happy marriage" of economic geology with sedimentology is cer tainly one of his main successes, starting with the first Symposium on Sedimentology and Ore Genesis at the Sixth International Sedimentological Congress at Delft in 1963.

Mineral deposits have supplied useful or valuable material for human consumption long before they became objects of scientific curiosity or commercial exploitation. In fact, the earliest human interest in rocks was probably because of the easily accessible, useful (e. g. , red pigment in the form of earthy hematite) or valuable (e. g. , native gold and gemstones) materials they contained at places. In modem times, the study of mineral deposits has evolved into an applied science employing detailed field observations, sophisticated laboratory techniques for additional information, and computer modeling to build complex hypotheses. Understanding concepts that would someday help geologists to find new mineral deposits or exploit the known ones more efficiently have always been, and will continue to be, at the core of any course on mineral deposits, but it is a fascinating subject in its own right, even for students who do not intend to be professional economic geologists. I believe that a course on mineral deposits should be designed as a "capstone course" that illustrates a comprehensive application of concepts from many other disciplines in geology (mineralogy, stratigraphy and sedimentation, structure and tectonics, petrology, geochemistry, paleontology, geomorphology, etc. ). This book is intended as a text for such an introductory course in economic geology, primarily for senior undergraduate and graduate students in colleges and universities. It should also serve as a useful information resource for professional economic geologists.

Annotated Bibliographies of Mineral Deposits in Africa, Asia (Exclusive of the USSR) and Australasia brings together annotated bibliographies of mineral deposits in Africa, Asia (with the exception of the USSR), and Australasia. Each bibliography is followed by notes to show the deposit's location; geological framework; age and type; structural and stratigraphic relations; conditions of formation; and position in the modified Lindgren classification. Comprised of 25 chapters, this volume begins with an introduction to the more important sources of references in the bibliographies, set down in alphabetical order with the number of references provided by each source. The distribution of deposits by continent and country follows. The deposits include molybdenum, nickel, copper, lead, and tin. Eruptive rocks, the metamorphic cycle, and the mineralization process are addressed, along with liquid immiscibility between silicate magmas and sulfide melts; the geology, mineralogy, and petrology of ore deposits in various mines; and the significance of mineralized breccia pipes. This book will be of value to mineralogists, geologists, and earth and mineral scientists as well as students interested in ore deposits.