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Diastrophism
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
The mechanisms proposed for continental drift included lunar attraction, the earth’s rotational forces, gravity sliding of continental blocks and the drag applied by thermally driven convection currents in the quasi-solid mantle (sima) beneath the continental crust (sial). Before the later 1950s, the overriding majority of earth scientists rejected the concept of continental drift partly because they found the geological evidence ambiguous, but mainly because the mechanisms proposed for it seemed completely inadequate (Hallam, 1973).
Magmatism and Magmatic Rocks
Published in Aurèle Parriaux, Geology, 2018
But Wegener’s idea resurfaced in the middle of the 20th century when research on oceanic plates revealed the process of lithosphere generation, particularly as a result of the study of paleomagnetism (see § 4.3.4). The theory of continental drift became the theory of continental plate movement. The plates no longer moved along the boundary of SiAl and SiMa, but much deeper in the asthenosphere due to its viscosity. Convection currents became a much more realistic engine. Wegener’s successors advanced several arguments, notably that of large crustal structures. In 1960, Hess presented a process of oceanic expansion based on the presence of convection currents in the mantle below continents. He identified two types of primordial structures that emphasize the dynamic nature of ocean floor formation and support Wegener’s theory. Mid-oceanic ridges. This is where oceanic crust is produced. The process occurs symmetrically on both sides of the ridge, spreading the two lithospheric plates farther apart toward subduction zones. The oceanic ridges are true submarine mountain chains that extend tens of thousands of kilometers. They rise to an elevation of about 1500 m above the abyssal plains and have an average width of 1000 km. There is a gash at the center of the ridge that extends in the length of the rift. The rift has sharp walls, about 20 to 50 km apart, and the walls can be as deep as 1000 meters. Oceanographic exploration shows magmatic and hydrothermal activity at these ridges. The Mid-Atlantic Ridge emerges onto land in Iceland, making it possible to observe its topography directly (Fig. 6.3).Oceanic trenches: These are places where plates are consumed. Moving away from the oceanic ridge, the lithosphere progressively cools and thickens as a result of underplating of mantle material. When the plate reaches another less dense plate (such as a continental plate), it sinks into the asthenosphere, disappears, and is thus recycled. The trenches are several thousand meters deep (11,502 m for the Marianas Trench) and several hundreds of kilometers long. The largest are located in the Pacific and occur near island chains (Japan, Philippines, etc.) or near mountain chains (Andes) when they occur on the margin of continents.
Magmatism and Magmatic Rocks
Published in Aurèle Parriaux, Geology, 2018
But Wegener’s idea resurfaced in the middle of the 20th century when research on oceanic plates revealed the process of lithosphere generation, particularly as a result of the study of paleomagnetism (see § 4.3.4). The theory of continental drift became the theory of continental plate movement. The plates no longer moved along the boundary of SiAl and SiMa, but much deeper in the asthenosphere due to its viscosity. Convection currents became a much more realistic engine. Wegener’s successors advanced several arguments, notably that of large crustal structures. In 1960, Hess presented a process of oceanic expansion based on the presence of convection currents in the mantle below continents. He identified two types of primordial structures that emphasize the dynamic nature of ocean floor formation and support Wegener’s theory. Mid-oceanic ridges. This is where oceanic crust is produced. The process occurs symmetrically on both sides of the ridge, spreading the two lithospheric plates farther apart toward subduction zones. The oceanic ridges are true submarine mountain chains that extend tens of thousands of kilometers. They rise to an elevation of about 1500 m above the abyssal plains and have an average width of 1000 km. There is a gash at the center of the ridge that extends in the length of the rift. The rift has sharp walls, about 20 to 50 km apart, and the walls can be as deep as 1000 meters. Oceanographic exploration shows magmatic and hydrothermal activity at these ridges. The Mid-Atlantic Ridge emerges onto land in Iceland, making it possible to observe its topography directly (Fig. 6.3).Oceanic trenches: These are places where plates are consumed. Moving away from the oceanic ridge, the lithosphere progressively cools and thickens as a result of underplating of mantle material. When the plate reaches another less dense plate (such as a continental plate), it sinks into the asthenosphere, disappears, and is thus recycled. The trenches are several thousand meters deep (11,502 m for the Marianas Trench) and several hundreds of kilometers long. The largest are located in the Pacific and occur near island chains (Japan, Philippines, etc.) or near mountain chains (Andes) when they occur on the margin of continents.
Application of inverse gas chromatography to bench scale flotation of sulphide ore
Published in Canadian Metallurgical Quarterly, 2023
Shiva Mohammadi-Jam, Gilberto Rodrigues da Silva, Kristian E. Waters
The sulphide ores are an important source of various valuable base metals as sulphides, such as copper (chalcopyrite, CuFeS2), lead (galena, PbS) zinc (sphalerite, ZnS), nickel (pentlandite (Fe, Ni)9S8) [1, 2], and molybdenum (molybdenite, MoS2) [3]. Chalcopyrite can be found in most sulphide ore deposits, and although its copper content is not as much as other copper-bearing minerals such as cuprite (Cu2O) and chalcocite (Cu2S), it has been the principal source of copper for thousands of years due to its wide distribution in large quantities [3]. Non-valuable sulphide minerals such as pyrite (FeS2) and pyrrhotite (Fe(1-x)S where 0 < x ≤ 0.125) are considered gangue. The ore deposits can also be associated with non-sulphide gangue, such as feldspar ((K, Na, Ca)(SiAl)4O8 with a Si/Al ratio 1–3), quartz (SiO2), magnetite (Fe3O4), albite (NaAlSi3O8), anorthite (CaAl2Si2O8), cordierite ((Mg, Fe)2Al3(Si5AlO18)), dolomite (Ca, Mg(CO3)2), rhodonite ((Mn, Ca, Fe, Mg)SiO3), calcite (CaCO3), talc (Mg3Si4O10(OH)2), and chromite ((Fe, Mg, Al)Cr2O4) [4–9]. The most common method of sulphide ore beneficiation is froth flotation.