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The El Laco magnetite-apatite ore deposits in the Andean Cordillera of northern Chile occur as massive, tabular bodies, as stratified, pyroclastic ores, and as crosscutting dykes and vein complexes. The ore deposits and surrounding volcanic rocks, mainly andesites, are Plio-Pleistocene in age and preserve many of their original volcanic textures and structures. All the field and laboratory data are consistent with an origin by eruption and shallow intrusion of a high-temperature, volatile-rich, iron-oxide magma. A number of other iron-oxide-apatite deposits of Cenozoic age in the Andean Cordillera, and a belt of Cretaceous iron deposits in the Coastal Cordillera of Chile also have features that suggest a magmatic origin. Associated with these magmatic ore deposits are economic and sub-economic concentrations of Cu, Au, U, and REE.
At Benfontein, near Kimberley, South Africa, three sills of kimberlite intrude Dwyka shales and overlying Karroo dolerite. Each sill results from numerous injections of kimberlitethat have consolidated to give the sill a layered appearance. Many layers - show magmatic sedimentation features and cumulus textures, and, although some show in situdifferentiation, other layers result from pre-injection differentiations The transporting, intercumulus liquid was carbonate-rich and some layers have differentiated to form a carbonate rock composed of the intercumulus calcite; this, on trace element and isotopic data, shows strong affinities with carbonatite. In one of the sills 'one calcite layer has migrated diapirically into overlying layers in.the sill. These sedimentation features, combined with thermal metamorphism of country-rock shales and the presence of quench calcite and apatite, are interpreted as evidence that the kimberlite was injected as a highly mobile fluid, comprising megacrysts of olivine, garnet, pyroxene, mica and picroilmenite in a hot carbonatitic liquid from which olivine, magnetic spinel, perov-skite, apatite, calcite, dolomite, ankerite and quartz crystallised. The evidence that the transportation medium was a warm carbonatitic liquid is directly opposed to earlier hypotheses proposing that kimberlite is intruded as a cold or plastic paste, and also supports proposals of a genetic link between kimberlite and carbonatite.
Magmatic Nickel-Copper-Platinum-group element sulfide deposits form as the result of the segregation and concentration of droplets of liquid sulfide from mafic or ultramafic magma, and the partitioning of chalcophile elements into these from the silicate magma.
The size of the deposits, their grades and ratios of economic metals are very variable. This is illustrated in Table 1.1, which summarizes data on tonnes ofresources + production, grades ofNi, Cu, Co and PGE, tonnes of contained metal, and value of the ore and of the individual metals. It is also illustrated in Fig. 1.1, which shows the percentages that Ni+Co, Cu and the PGE contribute to the value of many magmatic sulfide deposits/camps. <...>
The association between fithospheric extension, continental break-up, mantle plumes and massive bursts of igneous activity is well recognized, but their causal relationship remains controversial. According to active mantle hypotheses, rifting is initiated by doming above a mantle plume. Alternative hypotheses consider magmatism as a passive response to lithospheric stretching and rifting with the chance unroofing of a plume only enhancing lithospheric failure and producing abnormally large volumes of basaltic magmatism. Some models combine aspects of both active and passive hypotheses and it is the arrival of a new plume beneath lithosphere already under tension that causes it to split and form a new ocean. The active and passive hypotheses highlight important differences in the relative timing of rifting, magmatism and uplift. Consequently, this debate should be resolved and the main aim of this volume is to integrate relevant tectonic, geochemical and geophysical data which will lead to a better understanding of the causal relationships between magmatism and continental break-up.
Программа MagModel версии 1.4. предназначена для решения прямой задачи магниторазведки для двухмерного тела произвольной формы. Программа написана на языке Visual Basic NET 2010 Express, с использованием платформы Framework NET 4.0. Программа предназначена для использования на операционной системе семейства Windows (XP/Vista/7) Автор программы – Новиков К.В. (novikovkv@gmail.com).Программа является бесплатной и распространяется по принципу freeware (см. Лицензионное Соглашение). Внимание, перед началом работы убедитесь, что на компьютере установлен пакет Microsoft Framework NET 4.02, необходимы для работы программы.
Fifty years have now passed since Graham (1954) published his seminal paper advocating the use of anisotropy of magnetic susceptibility (AMS) as a rapid and sensitive petrofabric tool. During these five decades, Graham's 'underexploited' method has become standard, and AMS and related techniques are now routinely applied to characterizing fabrics in a wide variety of geological materials (e.g. the GEOREF database lists over 500 journal publications with 'magnetic anisotropy' as keywords).
Magnetic polarity stratigraphy, the stratigraphic record of polarity reversals in rocks and sediments, is now thoroughly integrated into biostratigraphy and chemostratigraphy. For Late Mesozoic to Quaternary times, the geomagnetic polarity record is central to the construction of geologic time scales, linking biostratigraphies, isotope stratigraphies, and absolute ages.
1 Corresponding Main Metallogenic Epochs to Key Geological Events in the North China Craton: An Example for Secular Changes in the Evolving Earth Mingguo Zhai and Xiyan Zhu Part I Archean Crustal Growth and Metallogeny 2 Archean Continental Crust in the Southern North China Craton
Chunrong Diwu, Chengli Zhang, and Yong Sun 3 Structural Architecture and Spatial-Temporal Distribution of the Archean Domains in the Eastern North China Craton Peng Peng
Some engineering fields change dramatically from year to year, with radical breakthroughs in technology happening often. These fields may have hundreds or more papers and texts published each year on the latest best practices. Maintenance engineering is a field which, for the most part, hasn’t fundamentally changed much over the years. And there aren’t many sources for the latest information or best practices. But in recent years, maintenance engineering has, more and more, put an emphasis on true reliability. A business which is asset-intensive, such as manufacturing, relies on a reliability-centered field of engineering to be successful. In my opinion, reliability engineering itself has become a technology used for the purpose of improving manufacturing capacity, without capital investment. The Maintenance Engineering Handbook has long been regarded as the premier source for expertise on maintenance theory and practices for any industry. This text has been considered invaluable and now, this latest edition defines those practices that are critical to developing an effective reliability engineering function within your business. This text is no longer just about mechanical, electrical, and civil maintenance engineering. Instead, the seventh edition also focuses on recognized and proven best practices in maintenance, repair, and overhaul (MRO) inventory management, root-cause analysis, and performance management. Keith Mobley, the editor in chief of this text, has more than 35 years of direct experience in corporate management, process and equipment design, and reliability-centered maintenance methodologies. For the past 16 years, he has helped hundreds of clients across the globe achieve and sustain world-class performance through the implementation of maintenance and reliability engineering principles. You may spend your career worrying about excessive downtime and high maintenance costs as a result of repetitive failures. As a fellow veteran maintenance and reliability engineer, I encourage you to recognize that this field is changing and improvements are being made that empower today’s business leaders. This text can help you reap the benefits of those changes so that your hard work produces the best possible results.
Throughout the history of the study of the Earth, geologists have attempted to understand the factors and forces which shape the surface of our globe. In this book, we shall attempt to summarise the current theories of how the gross surface layer of the Earth evolves tectonically.
