Metallogeny And Petrogenesis Of Lamprophyres In The Mid European Variscides

Presents a model important for the exploration for Sn, W, Mo, Ag, Cu, Zn, Pb, In, and U mineralization in the Bohemian Massif and comparable ore deposit provinces worldwide.

Lithium-cesium-tantalum (LCT) pegmatites are important resources for rare metals. For Cs, only the LCT pegmatites with the zeolite group mineral pollucite at Bikita (Zimbabwe Craton) and Tanco (Superior Province Craton) are of commercial importance. Common characteristics of world-class LCT pegmatite deposits include their Meso- to Neoarchean age and geological setting within greenstone belt lithologies on Archean Cratons. This study presents the first coherent and comparative scientific investigation of five major LCT pegmatite systems from the Yilgarn, Pilbara and Zimbabwe Craton. For the evaluation of their Cs potential and of the genetic concepts of pollucite formation, the pegmatites from Wodgina, Londonderry, Mount Deans and Cattlin Creek were compared to the Bikita pollucite mineralization. The integration of the new data (e.g., geochronological and radiogenic isotope data) into the complex geological framework: 1) enhances our knowledge of the formation of LCT pegmatite systems, and 2) will contribute to the further exploration of additional world-class LCT pegmatite deposits, which 3) may host massive pollucite mineralisations.

This vivid introduction to economic geology not only describes the most important deposit types, but also the processes involved in their formation. Magmatic, hydrothermal and sedimentary processes as well as weathering and alteration are explained in the framework of plate tectonics and the history of the Earth. The chapter about fossil fuels includes unconventional deposits and the much-debated fracking. Other topics covered are exploration, mining and economic aspects like commodity prices.

This book will broaden readers’ understanding of pegmatites in a special geodynamic setting, dealing with the emplacement of the Hagendorf-Pleystein Pegmatite Province (HPPP) in the Central European Variscides. This treatise illustrates the complex processes leading to the formation and partial destruction of the pegmatites, documenting the geochronological, chemical, mineralogical, geological and geomorphological / sedimentological data set. The book starts with a detailed account of the economic geology of the various pegmatites, explaining why these deposits are a major resource of ceramic raw materials. In its concluding section, a model of the pegmatite evolution in an ensialic orogen provides meaningful insights into the genetic aspects of pegmatite generation. The Late Paleozoic rare-element pegmatites of the HPPP, Oberpfalz-SE, Germany, rank among the largest concentrations in Europe. The biggest pegmatite of this mining district totals 4.4 million tons of ore (Hagendorf-South). The mining history of the HPPP is restricted to the 20th century, when local entrepreneurs started mining operations in search of ceramic raw materials, feldspar and quartz. Today the “Silbergrube Aplite” is still worked for feldspar. The traditional mining of pegmatitic and aplitic rocks in Central Europe, such as the Bohemian Massif, which is shared by Germany, the Czech Republic, Poland and Austria, has been focused on these industrial minerals. In addition to these major commodities, lithium was mined for a period of time. But even today many of these pegmatites of calc-alkaline affiliation have not lost their appeal to mineralogists and mineral enthusiasts for their wealth of minerals that contain P, Nb, Ta, Li, Be, B, U, Th, Sc, Ti and Sn. The most favorable crustal section to bring about pegmatitic rocks of this type, encompassing pegmatoids, metapegmatites, reactivated pseudopegmatites and pegmatites sensu stricto is the ensialic orogen, exemplified by the Variscan (Hercynian) Orogen, which geodynamically connects the Paleozoic pegmatite provinces in North America and Europe. The geological history of the HPPP, however, goes much further than the Carboniferous-Permian magmatic activity, when the last structural disturbances of the Variscan orogeny affected the NE-Bavarian Basement between 450 and 330 Ma. During this time mafic magmatic rocks together with calcareous and arenaceous sediments were converted into paragneisses, calcsilicate rocks, and amphibolites. It is the period of time when tectonic shortening led to over thrusting and when the emplacement of nappes and the architectural elements of the ensialic orogen began taking shape. During the Late Permian, the Mesozoic and the Cenozoic, the HPPP did not lie idle in geological terms; hypogene and supergene alteration continued and found its most recent expression in alluvial-fluvial “nigrine” placer deposits, which resulted from the unroofing of the pegmatites and aplites in the HPPP and can be used even outside HPPP as an ore guide to pegmatites.

Paleoproterozoic to Cenozoic lamprophyres, lamproites and related rock types (e.g., orangeites, kimberlites) are volatile-rich mafic magmatic rocks with a unique potential for the investigation of processes affecting mantle reservoirs. They originated from primary mantle-derived melts that intruded both cratons and off-craton regions, which were parts of former supercontinents – Columbia, Rodinia and Gondwana–Pangea. Well-known for hosting economic minerals and elements such as diamonds, base metals, gold and platinum-group elements, they are also significant for our understanding of deep-mantle processes, such as mantle metasomatism and mantle plume–lithosphere interactions, as well as large-scale geodynamic processes, such as subduction-related tectonics, and supercontinent amalgamation and break-up. This book aims to provide a timely overview of the state-of-the-art and recent advances as achieved by various research groups around the world. Mineralogical, geochemical, geochronological and isotope analyses are used to decipher the complex petrogenesis and metallogenesis of these extraordinary rocks, and unravel a complete history of tectonic events related to individual supercontinent cycles.

In recent years, there has been increasing interest from geoscientists in potassic ig neous rocks. Academic geoscientists have been interested in their petrogenesis and their potential value in defining the tectonic setting of the terranes into which they were intruded, and exploration geoscientists have become increasingly interested in the association of these rocks with major epithermal gold and porphyry gold-copper deposits. Despite this current interest, there is no comprehensive textbook that deals with these aspects of potassic igneous rocks. This book redresses this situation by elucidating the characteristic features of potassic (high-K) igneous rocks, erecting a hierarchical scheme that allows interpre tation of their tectonic setting using whole-rock geochemistry, and investigating their associations with a variety of gold and copper-gold deposits, worldwide. About two thirds of the book is based on a PhD thesis by Dr Daniel Muller which was produced at the Key Centre for Strategic Mineral Deposits within the Department of Geology and Geophysics at The University of Western Australia under the supervision of Professor David Groves, the late Dr Nick Rock, Professor Eugen Stumpf!, Dr Wayne Taylor, and Dr Brendon Griffin. The remainder of the book has been compiled from the literature using the collective experience of the two authors. The book is dedi cated to the memory of Dr Rock who initiated the research project but died before its completion.