ROLE OF PHYLLOSILICATES ON RHEOLOGICAL WEAKENING OF DETACHMENT SHEAR ZONES (RAFT RIVER MOUNTAINS, UT)

Structural studies of the Saint-Salvy zinc deposit and other Hercynian, veinhosted ore deposits in the French Massif Central and Pyrénées reveal a fourstage evolution of mineralized structures under rheological control: (i) localization of potential mineralized areas, guided by the presence of first-order lithological or structural heterogeneities that caused stress and strain perturbations; (ii) creation of second-order heterogeneities, corresponding to indurated shear zones that acted as rheological discontinuities; (iii) tectonic activation of these second-order heterogeneities, opening voids that allowed circulation of hydrothermal fluids and periodic trapping of ore minerals; (iv) reworking and partial destruction of the mineralized structures, caused by the reactivation of anisotropic surfaces acting as zones of weakness. The interaction between preexisting, first-order heterogeneities and regional shear strain caused instability, which in turn produced second-order and then lower-order heterogeneities. Such progressively smaller heterogeneities induced an increasingly focused, centripetal localization of structural disturbances that enabled hydrothermal fluid channelling. This is the reason that lower-order and late structures preferentially bear economic mineralization.

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The key role of µH2O gradients in deciphering microstructures and mineral assemblages of mylonites: examples from the Calabria polymetamorphic terrane

Mineralogy and Petrology ◽

10.1007/s00710-021-00766-8 ◽

2021 ◽

Author(s):

Fabrizio Tursi

Keyword(s):

Chemical Potential ◽

Shear Zones ◽

Chemical Potentials ◽

Ductile Shear Zones ◽

Mineral Assemblages ◽

Potential Gradients ◽

Ductile Shear ◽

Chemical Potential Gradients

AbstractA careful petrologic analysis of mylonites’ mineral assemblages is crucial for a thorough comprehension of the rheologic behaviour of ductile shear zones active during an orogenesis. In this view, understanding the way new minerals form in rocks sheared in a ductile manner and why relict porphyroblasts are preserved in zones where mineral reactions are generally supposed to be deformation-assisted, is essential. To this goal, the role of chemical potential gradients, particularly that of H2O (µH2O), was examined here through phase equilibrium modelling of syn-kinematic mineral assemblages developed in three distinct mylonites from the Calabria polymetamorphic terrane. Results revealed that gradients in chemical potentials have effects on the mineral assemblages of the studied mylonites, and that new syn-kinematic minerals formed in higher-µH2O conditions than the surroundings. In each case study, the banded fabric of the mylonites is related to the fluid availability in the system, with the fluid that was internally generated by the breakdown of OH-bearing minerals. The gradients in µH2O favoured the origin of bands enriched in hydrated minerals alternated with bands where anhydrous minerals were preserved even during exhumation. Thermodynamic modelling highlights that during the prograde stage of metamorphism, high-µH2O was necessary to form new minerals while relict, anhydrous porphyroblasts remained stable in condition of low-µH2O even during exhumation. Hence, the approach used in this contribution is an in-depth investigation of the fluid-present/-deficient conditions that affected mylonites during their activity, and provides a more robust interpretation of their microstructures, finally helping to explain the rheologic behaviour of ductile shear zones.

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CSR and ICT

Advances in Business Information Systems and Analytics - Corporate Social Responsibility for Valorization of Cultural Organizations ◽

10.4018/978-1-5225-3551-5.ch002 ◽

2018 ◽

pp. 24-53

Author(s):

Chiara Meret ◽

Michela Iannotta ◽

Mauro Gatti

Keyword(s):

Information And Communication Technologies ◽

Communication Technologies ◽

Shear Zones ◽

Demographic Development ◽

Bottom Line ◽

Systematic Analysis ◽

Csr Strategies ◽

Information And Communication ◽

Corporate Social

In line with the recent tendencies of limited natural resources, demographic development, dematerialization, and digitalization, this chapter underlines the necessity of deepening the role information and communication technologies (ICTs) play for corporate social responsibility (CSR) challenges. In fact, due to the diffuse integration of ICT into most of people's and firms' daily activities, companies cannot neglect the role of ICT in shaping CSR strategies. Hence, ICT has the potential to support the three main aspects of sustainable development—people, profit, and planet—which can be found in the so-called triple bottom line approach (TBL). However, the role of ICTs in supporting the shear zones between the abovementioned lines still counts a lack of contribution. Through a systematic analysis of the literature, the chapter affords insights for a further advance compared to the extant literature as the content analysis provides a description of how ICT support the sub-dimensions included in the three shear zones.

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Central Hoggar groundwaters and the role of shear zones: 87Sr/86Sr, δ18O, δ2H and 14C isotopes, geochemistry and water-rock interactions

Applied Geochemistry ◽

10.1016/j.apgeochem.2021.105179 ◽

2021 ◽

pp. 105179

Author(s):

M.E.H. Cherchali ◽

J.P. Liégeois ◽

M. Mesbah ◽

N. Daas ◽

K. Amrous ◽

...

Keyword(s):

Shear Zones

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The Role of Nanograins in Ductile Shear Zones: An Example from Hainan Island, Northern Margin of South China Sea

Nanoscience and Nanotechnology Letters ◽

10.1166/nnl.2018.2690 ◽

2018 ◽

Vol 10 (4) ◽

pp. 512-519

Author(s):

Yin Wang ◽

Hailing Liu ◽

Xuefen Zhang ◽

Rongwei Zhu ◽

Yuhan Li

Keyword(s):

South China Sea ◽

South China ◽

Hainan Island ◽

Shear Zones ◽

Northern Margin ◽

China Sea ◽

Ductile Shear Zones ◽

Ductile Shear

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Fluid processes during the exhumation of high-P metamorphic belts

Mineralogical Magazine ◽

10.1180/0026461026610016 ◽

2002 ◽

Vol 66 (1) ◽

pp. 93-119 ◽

Cited By ~ 31

Author(s):

J. A. Miller ◽

I. S. Buick ◽

I. Cartwright ◽

A. Barnicoat

Keyword(s):

Fluid Flow ◽

Partial Melting ◽

Significant Role ◽

Large Scale ◽

Shear Zones ◽

Direct Role ◽

Detachment Faults ◽

Dehydration Reactions ◽

Exhumation History

AbstractFluids can play a direct role in exhumation by influencing exhumation mechanisms and the driving processes for these mechanisms. In addition, the process of exhumation leads to the development of fluid-related features that in themselves may not drive exhumation. Fluids involved in exhumation are generally derived from dehydration reactions occurring during decompression, but at shallower crustal levels may also involve the introduction of exotic fluids. The composition of fluids attending exhumation are generally saline – CO2 mixtures, but N2, CH4, H2O mixtures have also been recorded. Studies of fluid features related to exhumation have found that fluids may contribute to density changes and the initiation of partial melting during decompression, as well as the development of extensive vein systems. However, the preservation of geochemical signatures related to fluid processes occurring prior to high-P and ultrahigh-P metamorphism indicates that large-scale pervasive fluid flow systems, in general, do not operate at any stage during the exhumation history. Large-scale channelled fluid flow may have operated in detachment faults and shear zones related to exhumation, and this requires further study. The most significant role of fluids during exhumation appears to be their controlling influence on the preservation of high-P or ultrahigh-P rocks.

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The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extension

Geologica Carpathica ◽

10.2478/v10096-011-0026-7 ◽

2011 ◽

Vol 62 (4) ◽

pp. 345-359 ◽

Cited By ~ 13

Author(s):

Erman Özsayin ◽

Kadir Dirik

Keyword(s):

Fault Zone ◽

Structural Evolution ◽

Shear Zones ◽

Fault Zones ◽

Fault System ◽

Western Boundary ◽

Southeastern Part ◽

Anatolian Plateau ◽

Isparta Angle

The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extensionThe NW-SE striking extensional Inönü-Eskişehir Fault System is one of the most important active shear zones in Central Anatolia. This shear zone is comprised of semi-independent fault segments that constitute an integral array of crustal-scale faults that transverse the interior of the Anatolian plateau region. The WNW striking Eskişehir Fault Zone constitutes the western to central part of the system. Toward the southeast, this system splays into three fault zones. The NW striking Ilıca Fault Zone defines the northern branch of this splay. The middle and southern branches are the Yeniceoba and Cihanbeyli Fault Zones, which also constitute the western boundary of the tectonically active extensional Tuzgölü Basin. The Sultanhanı Fault Zone is the southeastern part of the system and also controls the southewestern margin of the Tuzgölü Basin. Structural observations and kinematic analysis of mesoscale faults in the Yeniceoba and Cihanbeyli Fault Zones clearly indicate a two-stage deformation history and kinematic changeover from contraction to extension. N-S compression was responsible for the development of the dextral Yeniceoba Fault Zone. Activity along this structure was superseded by normal faulting driven by NNE-SSW oriented tension that was accompanied by the reactivation of the Yeniceoba Fault Zone and the formation of the Cihanbeyli Fault Zone. The branching of the Inönü-Eskişehir Fault System into three fault zones (aligned with the apex of the Isparta Angle) and the formation of graben and halfgraben in the southeastern part of this system suggest ongoing asymmetric extension in the Anatolian Plateau. This extension is compatible with a clockwise rotation of the area, which may be associated with the eastern sector of the Isparta Angle, an oroclinal structure in the western central part of the plateau. As the initiation of extension in the central to southeastern part of the Inönü-Eskişehir Fault System has similarities with structures associated with the Isparta Angle, there may be a possible relationship between the active deformation and bending of the orocline and adjacent areas.

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