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The Geosphere and Geochemistry
Published in Stanley Manahan, Environmental Chemistry, 2017
A key relationship in structural geology is that between the force or stress placed on a geological formation or object and the deformation resulting therefrom, called the strain. An important aspect of structural geology, therefore, is rheology, which deals with the deformation and flow of solids and semisolids. Whereas rocks tend to be strong, rigid, and brittle under the conditions at earth’s surface, their rheology changes such that they may become weak and pliable under the extreme conditions of temperature and pressure at significant depths below earth’s surface.
The Geosphere and Geochemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Earth's surface is constantly being reshaped by geological processes. The movement of rock masses during processes such as the formation of mountains results in substantial deformation of rock. At the opposite extreme of the size scale are defects in crystals at a microscopic level. Structural geology addresses the geometric forms of geologic structures over a wide range of size, the nature of structures formed by geological processes, and the formation of folds, faults, and other geological structures.
Formation of Cu–Au porphyry deposits: hydraulic quartz veins, magmatic processes and constraints from chlorine
Published in Australian Journal of Earth Sciences, 2023
G. N. Phillips, J. R. Vearncombe, J. D. Clemens, A. Day, A. F. M. Kisters, B. P. Von der Heyden
We address these questions in what represents a significant departure from the traditional magmatic model for these deposits, and we suggest that partitioning of the metals involving a silicate magma is not necessary. We can begin to answer some of these questions by introducing information from outside economic geology, especially from structural geology and hard rock (igneous and metamorphic) petrology. This study has selectively focused on the roles of rheology, rock mechanics, vein control, metal-enrichment processes and the sources of Cl. It has also proved beneficial to draw information and ideas learned from the study of other gold deposit types (e.g. gold-only deposits), which, although having some stark contrasts, inform on the general behaviour of the element gold in Earth’s crust. There is no attempt to discuss the many other anomalous elements such as Mo at this stage, as any viable model needs to adequately explain the origins of Cu and Au regardless of any other elements.
Small step, great rewards: rethinking mining sustainability from old perspectives to new frames
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Bing Wang, Xiang-Qian Pei, Yong-Jin Zhang, Yun-Bing Hou, Guo-Ping Hu
The rock and geological conditions mainly include reservoir depth, the type and structural geology of the coal seam, coal structure, and mechanical properties of rock, hydrogeological conditions, and the degree of coal metamorphism. Other indicators are coal field exposure, the thickness and quality of coal seam rock, internal structure of the coal seam, rock mass condition, groundwater level, bottom layer permeability and porosity, and underground roadway condition. The geological conditions determine the airtightness of the mine and the stability of the support rock stratum. The reservoir utilization mode has higher requirements for the airtightness of the mine, and the stability of the support rock stratum serves as the basis for most utilization modes.
The use of structural geology in the mineral exploration industry
Published in Australian Journal of Earth Sciences, 2023
This paper emphasises that the major control on many deposits is structure, and that structural geology is an essential tool for finding, assessing and mining almost all deposits. The paper provides tools for young company geologists to manage upwards. Structural geology has been instrumental in brownfields exploration in Australia and has dramatically increased early-mine reserves. Several essential points are made. First, one should not rely on or attempt to fit some preconceived genetic model for the deposit but document precisely the lithological/structural detail (particularly lineations) of the rocks under consideration; this is the fundamental basis for discovery of new deposits and the extension of existing deposits. Second, one should work to test hypotheses based on data, not to confirm existing models. Third, images are the primary deliverable to management and Directors; these images should involve detailed structural and lithological relations pertinent to defining the shape and extent of mineralisation along with volumes of mineralised waste and of waste. Again, they should not be cartoons of popular genetic models. Two areas stand out to be emphasised. The use of oriented drill core should be enhanced, since commonly these are the only data available. The paper discusses methods for gathering data from oriented drill core in some detail. Also, Resource grade estimation is still something of an art with many structurally unrealistic assumptions made. Structural data should be used to better constrain the interpolation of known mineralisation so that structurally realistic ore body models can be constructed. Importantly, anisotropy is both scale- and grade-dependent. The role of the structural geologist is to communicate a structural synthesis of the mineralisation so that value-added decisions can be made regarding exploration, Resource grade estimation and mine development.