Добрый день, Коллеги. Важное сообщение, просьба принять участие. Музей Ферсмана ищет помощь для реставрационных работ в помещении. Подробности по ссылке
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.
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.
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.
Employing two recently studied crustal-scale shear zones as type examples, this paper summarizes the major Palaeoproterozoic (Svecokarelian) shear tectonics of the central Fennoscandian Shield and demonstrates that this part of the Shield was not as stable during the Svecokarelian Orogeny as commonly assumed.
The collision of the Svecofennian island arc with the Karelian Continent first created numerous NW-SE trending folds and thrusts of stages Di and D2, which were then modified by successive shearing during stages D3 and D4. Stage D3 built up a system of N-S trending shear zones, here named the Savolappi Shear System, the type example of which is the Hir-vaskoski Shear Zone. This is a dextral strike-slip shear zone at least 150 km long and 10-30 km wide, characterized by blastomylonitic fault rocks and various structures such as hook folds, Z-fo!ds and sheath folds associated with the principal displacement zone, synthetic Riedel shears, and pinnate shears. The traces of the axial planes of F3 en-echelon folds deviate 15е—30е anticlockwise from the plane of the principal displacement zone. Other members of the Savolappi Shear System are the Pajala Shear Zone in northern Sweden and the Russian North Karelia Shear Zone in the east.
Stage D4 created a conjugate shear system called the Finlandia Shear System, the type example of which is the Oulujarvi Shear Zone. This is a NE-SW trending sinistral strike-slip shear zone more than 250 km long and 20-30 km wide across its southwestern end. It is composed of a NE-SW trending principal displacement zone, synthetic Riedel shears, and pinnate shears with antithetic Riedel shears in a NW-SE direction. Typical fault rocks within these shears are S-C mylon-ites. The axial-plane traces of F+folds of all scales diverge by 20°-40° clockwise from the plane of the principal displacement zone. The Kuopio Shear Zone is a conjugate NW-SE trending counterpart of the Oulujarvi Shear Zone. As a whole, the Finlandia Shear System forms a conjugate network of NW-SE and NE-SW trending shear zones which occupies most of the northern and central Fennoscandian Shield.
Shelley's lines paint a picture of a lost world, a world resurrected from the antiquities of Greek mythology. But Shelley had more than ancient legends to go on; he was acutely aware of the discoveries of great extinct beasts from the writings of contemporary naturalists. It is known that Shelley attended lectures on mineralogy at Oxford and possessed a library of scientific works which included the writings of Newton, Laplace, Herschel, Davy and Erasmus Darwin. By 1812 he was familiar with James Parkinson's Organic remains published in three volumes between 1804 and 1811.
