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Geostatistical appraisal of the Upper Precambrian gold deposits of the Cachoeiras de Minas region, Paraíba, Brazil
Published in Vladimír Strakoš, Vladimír Kebo, Radim Farana, Lubomír Smutný, Mine Planning and Equipment Selection 1997, 2020
A.G.F. Vieira, T.R. Gopinath, A. A. Lima
The Covico vein has an extension of 800 m and its average thickness varies from 0.2 m to 1.6 m. The vein tend to be discontinuous due to faulting and shearing, and also due to the thinning out of the vein (boudinage) which is frequent along the strike and along the dip direction. Strike of the vein is Ν60Έ parallel to the foliation of the country rocks and the dip varies from 70°SE to vertical. The quartz in which the gold is found is generally white to brown in color due to iron oxides and contains graphite in many parts like in Farias. Gold is confined to the ferruginous zones and associated with oxidized sulfides, graphite and few carbonates. The country rocks in which the quartz vein is found are graphitic meta-pelitic rocks which occur within the feisic rocks.
Deformation of a halite-anhydrite sequence under bulk constriction: Preliminary results from thermomechanical experiments
Published in Manfred Wallner, Karl-Heinz Lux, Wolfgang Minkley, H. Reginald Hardy, The Mechanical Behavior of Salt – Understanding of THMC Processes in Salt, 2017
G. Zulauf, J. Zulauf, O. Bornemann
Close-up views of XY = XZ sections show the layer to be affected by fracture boudinage consistent with brittle-ductile behaviour of anhydrite. Most of the fractures are aligned subperpendicular to the layer. In a few cases, however, there are fractures which are oriented oblique to the layer. The boudins are in a few cases asymmetric with respect to the X-axis suggesting local non-coaxial deformation. The necks between the boudins are in most cases entirely filled with halite. However, in a few cases halite was not able to fill the neck completely (Fig. 1). A further feature of XY = XZ sections is a striking fabric in the deformed halite matrix (Fig. 1).
Geological Structures
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
The structures to be considered here are fracture-cleavage, tension gashes, boudinage and slickensides. Slaty cleavage (or flow cleavage), which results from the growth of new, oriented minerals, has been discussed in Chapter 7 (q.v.).
Foliation boudinage structures in the Mount Isa Cu system
Published in Australian Journal of Earth Sciences, 2023
B. J. Williams, T. G. Blenkinsop, R. Lilly, M. P. Thompson, P. Ila’ava
Foliation boudinage structures are vein-like boudin structures that form in highly anisotropic and homogeneous rocks during layer parallel extension and layer normal shortening of fractures (Platt & Vissers, 1980). Foliation boudinage structures are found within well foliated or finely laminated rocks where they form most commonly under greenschist and amphibolite facies conditions (Arslan et al., 2008). Fracture dilation leads to an open central void that provides space for mineral precipitation. Aerden (1991) identified these structures to be a controlling feature of the Rosebery Pb–Zn deposit in Tasmania, where multiple foliation boudinage structures exist with dimensions of 100’s of metres.