Fig 4 - uploaded by Steven Micklethwaite
Content may be subject to copyright.
Structural maps of different fault and shear zone systems associated with mineralisation. The systems all display typical features such as segmentation, development of stepovers and branching at fault tips. (a) Cracow epithermal goldfield, Australia (modified from Micklethwaite, 2009). This is an example of a localised-type epithermal fault system where strain is coalesced into one to two large structures. The larger structures appear to comprise multiple segments and step-overs (labelled). (b) North Carlin trend goldfield, U.S.A. (compiled from Nevada Bureau of Mines and Geology Bulletin 111, 2002). The Post-Genesis fault system is two segments, separated by an underlapping stepover zone. Majority of mineralisation is close to and distributed laterally away from the stepover. (c) Lisheen Pb-Zn base metal deposit, Ireland (modified from Hitzman et al., 2002; Carboni et al., 2003). The Rathdowney and Barnalishee faults are interpreted as large single segments at depth (inset), forming multiple en echelon segments at shallower levels. Mineralisation is spatially associated with two different scales of stepover; the Lisheen relay between the two faults, and smaller second-order relays developed along the Rathdowney fault. (d, e) Mesothermal gold deposits, West Australia (modified from Micklethwaite and Cox, 2006). Mineralisation is spatially associated with and distributed laterally away from step-overs. In contrast, mineralisation at Cracow has no spatial relationship with a single fault location type but occurs at step-overs, fault segments and tip zones.
Source publication
Mineralisation associated with fault, vein and shear zone systems can be related to processes that operated when those systems were active. Despite the complexity of processes that operate in faults, veins and shear zones, there are typically systematic patterns in geometry (e.g. segmentation and step-overs) and scaling, which are the cumulative re...
Contexts in source publication
Context 1
... patterns exist in the geometry (e.g. step-overs and segmentation) and scaling properties of structural systems, which are also common to structures associated with mineral deposits (Fig. ...
Context 2
... the excellent study by Kim et al., 2003). Faults and veins typically comprise multiple segments that interact with or link adjacent segments, across step-overs (e.g. see annotations in Fig. 4a). The step-overs represent zones of more distributed strain, typically containing second-order structures such as branch faults, fracture networks or folding ( Pachell and Evans, 2002). Minima in fault displacement or vein thickness values occur at step-overs (e.g. Fig. 4d inset) when these quantities are traced along a structure ( ...
Context 3
... with or link adjacent segments, across step-overs (e.g. see annotations in Fig. 4a). The step-overs represent zones of more distributed strain, typically containing second-order structures such as branch faults, fracture networks or folding ( Pachell and Evans, 2002). Minima in fault displacement or vein thickness values occur at step-overs (e.g. Fig. 4d inset) when these quantities are traced along a structure ( Ellis and Dunlap, 1988;Peacock, 1991;Peacock and Sanderson, 1991;Pachell and Evans, 2002), although minima tend to disappear when bedding rotation or displacements on the full fracture network are accounted for at step-overs ( Walsh et al., 2003). Segmentation can also be ...
Context 4
... 1991;Peacock and Sanderson, 1991;Pachell and Evans, 2002), although minima tend to disappear when bedding rotation or displacements on the full fracture network are accounted for at step-overs ( Walsh et al., 2003). Segmentation can also be observed at multiple scales. Second- order variations in the displacement profile of the Black Flag fault (Fig. 4d inset) suggest the two large segments of the Black Flag fault are themselves composed of smaller segments. There are three important attributes of step-overs describing the nature of their linkage, geometry and strain field (Fig. 6). (1) Segments are hard-linked across step-overs by branch fault or fracture networks. Alternatively they are ...
Context 5
... has been proposed to explain the spacing of mineral deposit clusters along structural systems (Micklethwaite, 2007), such as is observed with mesothermal gold deposits (Robert and Poulsen, 1997;Weinberg et al., 2004;Robert et al., 2005). Fig. 4 shows fault and shear zone controlled mineral deposits correlated with segments and step-overs. Carlin-type gold, greenstone-hosted mesothermal gold and Pb-Zn mineralisation are associated with step-overs on large-scale faults (Fig. 4b-e). The step-overs are both contractional and extensional steps. Mesothermal mineralisation ...
Context 6
... is observed with mesothermal gold deposits (Robert and Poulsen, 1997;Weinberg et al., 2004;Robert et al., 2005). Fig. 4 shows fault and shear zone controlled mineral deposits correlated with segments and step-overs. Carlin-type gold, greenstone-hosted mesothermal gold and Pb-Zn mineralisation are associated with step-overs on large-scale faults (Fig. 4b-e). The step-overs are both contractional and extensional steps. Mesothermal mineralisation specifically is hosted in, or associated with, small-displacement structures, some of which link across the step-overs (Fig. 4d,e). Pb- Zn mineralization at Lisheen (Fig. 4c and inset) has an association with soft-linkage between en echelon fault ...
Context 7
... gold, greenstone-hosted mesothermal gold and Pb-Zn mineralisation are associated with step-overs on large-scale faults (Fig. 4b-e). The step-overs are both contractional and extensional steps. Mesothermal mineralisation specifically is hosted in, or associated with, small-displacement structures, some of which link across the step-overs (Fig. 4d,e). Pb- Zn mineralization at Lisheen (Fig. 4c and inset) has an association with soft-linkage between en echelon fault ...
Context 8
... gold and Pb-Zn mineralisation are associated with step-overs on large-scale faults (Fig. 4b-e). The step-overs are both contractional and extensional steps. Mesothermal mineralisation specifically is hosted in, or associated with, small-displacement structures, some of which link across the step-overs (Fig. 4d,e). Pb- Zn mineralization at Lisheen (Fig. 4c and inset) has an association with soft-linkage between en echelon fault ...
Context 9
... influence of segmentation and step-overs on mineralisation does not appear to be limited by depth. For instance, the Carlin- type Au deposits associated with a stepover in Fig. 4b formed at >2 km depth ( Cline et al., 2005), whereas the mesothermal Au deposits of Fig. 4d,e typically form at mid-crustal depths (McCuaig and Kerrich, 1998) adjacent to regional-scale shear zones. Critically, mineralisation is distributed beyond the step-overs shown in Fig. 4, occupying significant surface areas of 4-15 km 2 . Thus ...
Context 10
... influence of segmentation and step-overs on mineralisation does not appear to be limited by depth. For instance, the Carlin- type Au deposits associated with a stepover in Fig. 4b formed at >2 km depth ( Cline et al., 2005), whereas the mesothermal Au deposits of Fig. 4d,e typically form at mid-crustal depths (McCuaig and Kerrich, 1998) adjacent to regional-scale shear zones. Critically, mineralisation is distributed beyond the step-overs shown in Fig. 4, occupying significant surface areas of 4-15 km 2 . Thus step-overs are a locus for, but not a limit to ...
Context 11
... instance, the Carlin- type Au deposits associated with a stepover in Fig. 4b formed at >2 km depth ( Cline et al., 2005), whereas the mesothermal Au deposits of Fig. 4d,e typically form at mid-crustal depths (McCuaig and Kerrich, 1998) adjacent to regional-scale shear zones. Critically, mineralisation is distributed beyond the step-overs shown in Fig. 4, occupying significant surface areas of 4-15 km 2 . Thus step-overs are a locus for, but not a limit to ...
Context 12
... observation that high b-values (>1.0) are encountered in stepover regions, when slip events jump or arrest at those step-overs, is important for stepover related mineral deposits (e.g. Fig. 4). High b-values indicate there is a high density of aftershocks and a high degree of connectivity generated in such regions, per earthquake sequence. In this regard accurate relocations of after- shocks give an indication of the density and connectivity that occurs per sequence. A good example is the 1986 M L 5.7 Mount Lewis earthquake ...
Citations
... This allows for the formation of potential economic ore deposits. In many conceptual models of the formation of ore deposits, fault zones are important structural features acting as collecting points of fluids and related metals, (Micklethwaite, S., 2010). ...
To recognize and delineate anomalies that may be related to structure and their relationship to metallurgy visualizing the structure
... Many global studies on ore deposits have shown that their behavior is controlled by specific structural contexts [1][2][3][4][5][6][7][8][9][10]. The most common structural evolution constraints on mineralization include: (1) faults and fractures in rocks [11][12][13], (2) extension and reduction around faults and shear zones [5,6,14,15], (3) the intersection of two syn-mineralization structures [16], (4) the junction point of faults and shear zones and highly resistant and/or chemical-responsive rocks, (5) lithological connections between competent and less competent rocks, faults, and shear zones (e.g., [17,18]), (6) regions that drop perpendicular to a stretch lineation, and (7) folding hinge zones, limbs, and slump folds (e.g., [19,20]). ...
... Many global studies on ore deposits have shown that their behavior is controlled by specific structural contexts [1][2][3][4][5][6][7][8][9][10]. The most common structural evolution constraints on mineralization include: (1) faults and fractures in rocks [11][12][13], (2) extension and reduction around faults and shear zones [5,6,14,15], (3) the intersection of two syn-mineralization structures [16], (4) the junction point of faults and shear zones and highly resistant and/or chemical-responsive rocks, (5) lithological connections between competent and less competent rocks, faults, and shear zones (e.g., [17,18]), (6) regions that drop perpendicular to a stretch lineation, and (7) folding hinge zones, limbs, and slump folds (e.g., [19,20]). The latter remains one of the most popular. ...
... Many global studies on ore deposits have shown that their behavior is controlled by specific structural contexts [1][2][3][4][5][6][7][8][9][10]. The most common structural evolution constraints on mineralization include: (1) faults and fractures in rocks [11][12][13], (2) extension and reduction around faults and shear zones [5,6,14,15], (3) the intersection of two syn-mineralization structures [16], (4) the junction point of faults and shear zones and highly resistant and/or chemical-responsive rocks, (5) lithological connections between competent and less competent rocks, faults, and shear zones (e.g., [17,18]), (6) regions that drop perpendicular to a stretch lineation, and (7) folding hinge zones, limbs, and slump folds (e.g., [19,20]). The latter remains one of the most popular. ...
The Toko-Nlonkeng area is situated in the Nyong Complex of the northwestern Congo craton. In this study, airborne geophysical data (radiometric and magnetic) and structural data (outcrops and core samples) were used to investigate the relationship between structural evolution, iron formation (IFs)-hosted iron ore deposits, and gold mineralization in the Paleoproterozoic Nyong complex greenstone belt in southwestern Cameroon. Magnetic and radiometric trends, combined with field data, show general NE-SW, NW-SE, and E-W directions that correlate with the main gold-bearing structures. The study area has undergone four (04) deformation phases relating to polycyclic metamorphic and magmatic events. The D1 and D2 phases are the result of progressive ductile and transpressional deformation; D3 is a brittle-ductile deformation; and D4 is essentially brittle with various types of fracture networks late to post-orogenic. The D3 deformation phase is characterized by constrictive deformation with C3 shears and meso‑ to mega-P3-folds, and the main stress axes show φσ2 > φσ1> φσ3, reflecting a shearing tectonic regime with a maximum E-W shortening. This polyphase deformation is derived from the Eburnean/Trans-Amazonian deformation related to the collision between the Congo and São Francisco cratons. The main strain in the structural style of the Nyong Complex appears to be transpressive tectonics. This study reveals that iron ore and gold mineralization were mostly found on the hinges of folds and confirms that folding shear zones controlled the iron ore and gold target in the Nyong Complex and Northeast Brazil. The study proposes an approach to optimize future exploration activity based on the integration of the data.
... Notably, many quartz vein gold-silver deposits have been reported around the Chungnam Basin, and some of them were actively mined for several decades in the past century (Yoo et al., 2003(Yoo et al., , 2006(Yoo et al., , 2010Choi et al., 2006). These ore deposits and quartz vein systems are a tracer of extensive migration of ancient crustal fluids during seismic events (Loucks and Mavrogenes, 1999;Townend and Zoback, 2000;Micklethwaite et al., 2010Micklethwaite et al., , 2015, likely linked to the structural evolution of This study focuses on the northeastern Chungnam Basin close to the Samgwang deposit-one of the largest gold deposits in the southern Korean Peninsula (Yoo et al., 2010;Lee et al., 2019;Fig. 1). ...
... The permeability increases from approximately Table 2 Relative abundances of illite polytypes determined using the full-pattern-fitting method and the K-Ar age dating results for different size fractions of the fault clays. 10 − 20 -10 − 16 m 2 to 10 − 13 -10 − 11 m 2 when the fault slip occurs in the coseismic phase (Micklethwaite et al., 2010). During the postseismic phase, the fault-fill vein is precipitated from the circulating fluid, sealing the fault plane. ...
... 10,11 and 15) are typical of the result of a coseismic faulting, pressurized hydrothermal fluid migration, and a postseismic mineral precipitation. In the postseismic-interseismic phase, quartz precipitation, pressure solution, recrystallization, and grain boundary bulging likely decreased the permeability of the fault plane gradually (Fig. 15c-d;Boullier and Robert, 1992;Micklethwaite et al., 2010). The near-vertical stylolites inside the fault-fill veins and the buckled extension veins are interpreted to be developed by sustained shortening during the postseismic-interseismic phase owing to renewed shear stress increase along the fault (Figs. ...
This study explores the coupled processes of structural inversion and fluid migration around the northeastern part of the Mesozoic Chungnam Basin in the southwestern Korean Peninsula, focusing on quartz vein systems genetically linked to an orogenic gold deposit. Our results show that the inversion structures reflect the coexistence of strike-slip simple shear and pure shear components caused by NW–SE crustal shortening, leading to a transpressional deformation model. The quartz veins, filling the high-angle faults with a reverse slip component and adjacent hydrofractured wall rocks, represent transient fluid flow related to seismic faulting and fault valving during the inversion. New K–Ar ages of illite polytypes in fault gouges, determined using the Illite-age-analysis (IAA) method, indicate Late Jurassic–Early Cretaceous fault reactivations. Notably, ca. 160 Ma 2M1 illite age from a fault zone filled with an orogenic gold–bearing quartz vein indicates that the inversion and auriferous hydrothermal fluid flow started with a magmatic quiescence in the southern Korean Peninsula likely owing to the flat subduction of the Paleo-Pacific Plate. Our findings suggest that the orogenic gold–bearing vein system was likely sourced from the subcrustal metamorphic fluid in the flat subduction zone of the Mesozoic East Asian Continental margin.
... Investigating gradients downdip in the main reactivated shear zones recorded by mineralogy and fluid inclusions could be one way to test the hypothesis that brittle faults marking a significant offset of the unconformity could be rooted at depth and have a ductile equivalent enabling metamorphic fluids to be generated. In such a scheme, the role of active faulting and shearing processes would be a trigger of the initiation of a self-organized hydrothermal system (Micklethwaite et al. 2010, Hronsky 2011) and the brittle-ductile transition could be considered as a threshold barrier. Chi et al. (2018) have compiled a large number of U-Pb ages of uraninite and some Ar-Ar ages of illite alteration related to U mineralization obtained from U deposits in the Athabasca Basin, ranging from ca. 1590 to 60 Ma. ...
... The D 1BR -related shear zone structures and main fault-fill vein may have acting as a primary plumbing system and fluid pathways to bring gold in the system with gold deposition. Reconcentration occurring in lower order structures (Cox and Ruming, 2004;Micklethwaite et al., 2010;Hronsky et al., 2012) such as adjacent fractures to the shear zone where tension-vein arrays are developing, zones of intersection between the fault-fill vein and the subvertical tension-veins arrays (at the Manse target for example) and sites of folding (late episode of the D 1BR deformation stage, Fig. 14A). ...
... Paleo-stress interpretation of these NNW-striking structures shows a shortening direction, oriented NW-SE to WNW-ESE, and a predicted dilational ore shoot orientation nearly vertical (σ2) that corresponds to the favorable sites with a restricted continuation along strikes. These interaction zones that can be referred as damage zones following the definition of Kim et al. (2000) and Peacock et al. (2017) are sites of high damage intensity, important dilation/fracturing, and consequently high fluid flux sites (Cox et al., 2001;Bierlein et al., 2006;Micklethwaite et al., 2010) with a higher density of gold-bearing D 2BR -related veins. ...
... Therefore, although fluid channeling is pervasive throughout the shear zone, only segments of mean-stress variations constitute sites for intense fluid focusing (Ridley, 1993). These places are typically irregular segments within shear zones where there is a shear component (Ridley, 1993;Micklethwaite et al., 2010). In the ISZ, these sites occur along the segment with a dominant simple shear component. ...
... De esta manera, la evolución de un sistema epitermal puede estudiarse a través de los cambios en las texturas del cuarzo para los sucesivos episodios de relleno dentro de las estructuras vetiformes (e.g., Buchanan, 1981;Morrison et al., 1990;Corbett y Leach, 1997 1 ). Para que pueda ocurrir una sucesión de episodios hidrotermales, se precisa disponibilidad de espacio y buena permeabilidad, factores que se dan con la ocurrencia de múltiples eventos tectónicos dentro de la estructura (Micklethwaite et al., 2010). ...
El distrito Casposo se encuentra ubicado en la cordillera Frontal, en el centro-oeste de la provincia de San Juan, Argentina. Se caracteriza por la presencia de un sistema de vetas epitermales de baja sulfuración hospedado en rocas volcánicas del Grupo Choiyoi, donde se destacan los sectores Mercado-Kamila y Julieta, los cuales concentran los mayores recursos del distrito. El sector Julieta es un sistema vetiforme auroargentífero de cuarzo-calcita, con texturas bandeadas coloformes, brechosas y reemplazos tipo lattice bladed. En este estudio, a partir del análisis detallado de la mineralogía y textura de las vetas del sector Julieta (denominadas en este trabajo simplemente como veta Julieta), se discriminaron 9 pulsos que fueron agrupados en 4 eventos principales, 3 de ellos de naturaleza hidrotermal y 1 del tipo tectónico-hidrotermal. Los pulsos P1, P2 y P3 son estériles y de naturaleza carbonática, mientras que P4 y P5A son de composición calcedónica y con textura bandeada coloforme. Este último posee bandas color crema con adularia y bandas negras tipo ginguro bands, a las cuales se asocian máximos valores de 5,5 g/t Au y 52 g/t Ag. El pulso P5B también es silíceo, aunque de textura brechosa, mientras que el pulso P6 es de naturaleza silíceo-carbonática. La evolución de los pulsos migra hacia composiciones carbonáticas, representada por los pulsos P7 y P8, ambos de textura brechosa. El último evento consiste en un pulso silíceo-ferruginoso del tipo tectónico-hidrotermal (P9). La veta Julieta posee un rumbo definido NOSE , con subestructuras menores de orientación E-O y N-S, y puede dividirse en 3 segmentos según su morfología: norte, central y sur. Tanto los mayores espesores, como las mayores inclinaciones y los altos valores de metales preciosos se asocian a inflexiones generadas entre los 3 segmentos. Respecto a la geometría de los clavos mineralizados, la veta posee un clavo principal subhorizontal, el que respondería a un control del tipo litológico, en tanto que clavos secundarios subverticales obedecerían a un control del tipo estructural. Por otro lado, diferencias en la reología de las unidades hospedantes de la mineralización estarían controlando la morfología de la veta, y conformarían, en este caso, un sigmoide en la vertical. Factores como la evolución composicional de los eventos mineralizantes, la morfología del cuerpo mineralizado y la distribución de los metales preciosos permitieron identificar en este trabajo la importancia del control litológico y estructural en la mineralización de la veta Julieta. Palabras clave: Control estructural, Mineralización, Baja sulfuración, 3D.
... From a metallogenic point of view, many studies have considered the faults as important high-permeability conduits for fluid circulation and ore concentrations (Faulkner and Armitage, 2013;Funedda et al., 2018;. Furthermore, permeability contrast and wall-rock competence are interpreted as important factors controlling the distribution and geometry of the ore deposit (Micklethwaite, 2010;Funedda et al., 2018;. The Paleozoic terrains of the eastern Anti-Atlas are mostly characterized by numerous vein-type mineral deposits including, the Oumejrane Cu-Ni district, Tadaout-Tizi N'rsas, Tijekhet and M'fis mining districts as well as the southern part of the Maider Basin district which constitutes the subject area of the present paper. ...
... Investigating gradients downdip in the main reactivated shear zones recorded by mineralogy and fluid inclusions could be one way to test the hypothesis that brittle faults marking a significant offset of the unconformity could be rooted at depth and have a ductile equivalent enabling metamorphic fluids to be generated. Thus, the role of active faulting and shearing processes would be a trigger of the initiation of a selforganized hydrothermal system (Micklethwaite et al. 2010, Hronsky 2011) and the brittle-ductile transition could be considered as a threshold barrier. ...
Understanding the structural framework of metallogenic provinces and identification of transient events during which fluid circulation and trapping of mineralization occur is a major challenge for exploration of mineral systems. Analogies between geothermal systems, orogenic gold and unconformity related deposits reveal the role of permeability enhancement during episodes marked by the coupling of tectonic activity and fluid flow. Thus, in the case of Unconformity-Related Uranium deposits of the Athabasca Basin (Saskatchewan, Canada), a new model can be proposed considering that the interplay between compressional fault reactivation and thermal convection is the main driver of this fluid flow system. Short-lived, deformation-driven fluid flow are recorded by the structural and mineralogical evolution of the reactivated basement-hosted fault system.
... A fundamental aim of structural analysis applied to mineralization is to identify how deformation influenced the enhancement or decrease of permeability in rocks [2]. Lineaments are closely connected to the formation of hydrothermal ore deposits, lineament characteristics can potentially be used to identify new exploration areas [3]. ...
In this study, we have investigated the status of faults in terms of precession and subsequence, and their relationship with vein mineralization in Kaybarkuh intrusive body in East of Iran. At least, three generations of faults are evidenced in Dasht-e-Bayaz (DB) fault terminal. During formation of faults, the stress orientation in the region has changed at least once probably due to DB fault evolution. Mineralization, especially gold and copper, is formed along the third-generation faults and sometimes on the fault surfaces. It can be predicted that mineralization also happened in the tensioned area of Kal-Shur covered by salt playa and Quaternary sediments, which requires subsurface and geophysics studies.
