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Journal articles on the topic "Thrust faults (Geology) Australia, Central"
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Cape, C. D., R. M. O'Connor, J. M. Ravens, and D. J. Woodward. "Seismic expression of shallow structures in active tectonic settings in New Zealand." Exploration Geophysics 20, no. 2 (1989): 287. http://dx.doi.org/10.1071/eg989287.
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Late Cenozoic deformation along the Australian/Pacific plate boundary is seen in onshore New Zealand as zones characterised by extension- or transcurrent- or contraction-related structures. High-resolution multichannel seismic reflection data were acquired in several of these tectonic zones and successfully reveal the shallow structures within them. Thirty kilometres of dynamite reflection data in the Rangitaiki Plains, eastern Bay of Plenty, define a series of NE-trending normal faults within this extensional back-arc volcanic region. The data cross surface ruptures activated during the 1987 Edgecumbe earthquake. In the southern North Island, a 20 km Mini-Sosie? seismic profile details the Quaternary sedimentation history and reveals the structure of the active strike-slip and thrust fault systems that form the western and eastern edges of the Wairarapa basin, respectively. This basin is considered to sit astride the boundary between a zone of distributed strike-slip faults and an active accretionary prism. In the Nelson area, northwestern South Island, previously unrecognised low-angle thrust faults of Neogene or Quaternary age are seen from Mini-Sosie data to occur at very shallow depths. Crustal shortening here was previously thought to arise from movement on high-angle reverse faults, and the identification of these low-angle faults has prompted a reassessment of that model. A grid of 18 km of Mini-Sosie seismic data from the central eastern South Island delineates Neogene or Quaternary thrust faults in Cenozoic sediments. The thrusts are interpreted as reactivated Early Eocene normal faults, and the thrust fault geometry is dominated by these older structures.
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Wex, Sebastian, Neil S. Mancktelow, Friedrich Hawemann, Alfredo Camacho, and Giorgio Pennacchioni. "Inverted distribution of ductile deformation in the relatively “dry” middle crust across the Woodroffe Thrust, central Australia." Solid Earth 9, no. 4 (July 11, 2018): 859–78. http://dx.doi.org/10.5194/se-9-859-2018.
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Abstract. Thrust fault systems typically distribute shear strain preferentially into the hanging wall rather than the footwall. The Woodroffe Thrust in the Musgrave Block of central Australia is a regional-scale example that does not fit this model. It developed due to intracontinental shortening during the Petermann Orogeny (ca. 560–520 Ma) and is interpreted to be at least 600 km long in its E–W strike direction, with an approximate top-to-north minimum displacement of 60–100 km. The associated mylonite zone is most broadly developed in the footwall. The immediate hanging wall was only marginally involved in the mylonitization process, as can be demonstrated from the contrasting thorium signatures of mylonites derived from the upper amphibolite facies footwall and the granulite facies hanging wall protoliths. Thermal weakening cannot account for such an inverse deformation gradient, as syn-deformational P–T estimates for the Petermann Orogeny in the hanging wall and footwall from the same locality are very similar. The distribution of pseudotachylytes, which acted as preferred nucleation sites for shear deformation, also cannot provide an explanation, since these fault rocks are especially prevalent in the immediate hanging wall. The most likely reason for the inverted deformation gradient across the Woodroffe Thrust is water-assisted weakening due to the increased, but still limited, presence of aqueous fluids in the footwall. We also establish a qualitative increase in the abundance of fluids in the footwall along an approx. 60 km long section in the direction of thrusting, together with a slight decrease in the temperature of mylonitization (ca. 100 °C). These changes in ambient conditions are accompanied by a 6-fold decrease in thickness (from ca. 600 to 100 m) of the Woodroffe Thrust mylonitic zone.
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Pettinga, Jarg R., Mark D. Yetton, Russ J. Van Dissen, and Gaye Downes. "Earthquake source identification and characterisation for the Canterbury region, South Island, New Zealand." Bulletin of the New Zealand Society for Earthquake Engineering 34, no. 4 (December 31, 2001): 282–317. http://dx.doi.org/10.5459/bnzsee.34.4.282-317.
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The Canterbury region of the South Island of New Zealand straddles a wide zone of active earth deformation associated with the oblique continent-continent collision between the Australian and Pacific tectonic plates east of the Alpine fault. The associated ongoing crustal strain is documented by the shallow earthquake activity (at depths of <40 km) and surface deformation expressed by active faulting, folding and ongoing geodetic strain. The level of earth deformation activity (and consequent earthquake hazard) decreases from the northwest to the southeast across the region. Deeper-level subduction related earthquake events are confined to the northernmost parts of the region, beneath Marlborough.
To describe the geological setting and seismological activity in the region we have sub-divided the Canterbury region into eight domains that are defined on the basis of structural styles of deformation. These eight domains provide an appropriate geological and seismological context on which seismic hazard assessment can be based. A further, ninth source domain is defined to include the Alpine fault, but lies outside the region.
About 90 major active earthquake source faults within and surrounding the Canterbury region are characterised in terms of their type (sense of slip), geometry (fault dimensions and attitude) and activity (slip rates, single event displacements, recurrence intervals, and timing of last rupture). In the more active, northern part of the region strike-slip and oblique strike-slip faults predominate, and recurrence intervals range from 81 to >5,000 years. In the central and southern parts of the region oblique-reverse and reverse/thrust faults predominate, and recurrence intervals typically range from -2,500 to >20,000 years.
In this study we also review information on significant historical earthquakes that have impacted on the region (e,g. Christchurch earthquakes 1869 and 1870; North Canterbury 1888; Cheviot 1902; Motunau 1922; Buller 1929; Arthurs Pass 1929 and 1994; and others), and the record of instrumental seismicity. In addition, data from available paleoseismic studies within the region are included; and we also evaluate large potential earthquake sources outside the Canterbury region that are likely to produce significant shaking within the region. The most important of these is the Alpine fault, which we include as a separate source domain in this study.
The integrated geological and seismological data base presented in this paper provide the foundation for the probabilistic seismic hazard assessment for the Canterbury region, and this is presented in a following companion paper in this Bulletin (Stirling et al. this volume).
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Wigginton, Sarah S., Elizabeth S. Petrie, and James P. Evans. "The mechanics of initiation and development of thrust faults and thrust ramps." Mountain Geologist 59, no. 2 (April 28, 2022): 47–75. http://dx.doi.org/10.31582/rmag.mg.59.2.47.
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This study integrates the results of numerical modeling analyses based on outcrop studies and structural kinematic restorations to evaluate the mechanics of thrust fault initiation and development in mechanically layered sedimentary rocks. A field-based reconstruction of a mesoscopic thrust fault at Ketobe Knob in central Utah provides evidence of thrust ramp nucleation in competent units, and fault propagation upward and downward into weaker units at both fault tips. We investigate the effects of mechanical stratigraphy on stress heterogeneity, rupture direction, fold formation, and fault geometry motivated by the geometry of the Ketobe Knob thrust fault in central Utah; the finite element modeling examines how mechanical stratigraphy, load conditions, and fault configurations influence temporal and spatial variation in stress and strain. Our modeling focuses on the predicted deformation and stress distributions in four model domains: (1) an intact, mechanically stratified rock sequence, (2) a mechanically stratified section with a range of interlayer frictional strengths, and two faulted models, (3) one with a stress loading condition, and (4) one with a displacement loading condition. The models show that early stress increase in competent rock layers are accompanied by low stresses in the weaker rocks. The frictional models reveal that the heterogeneous stress variations increase contact frictional strength. Faulted models with a 20° dipping fault in the most competent unit result in stress increases above and below fault tips, with extremely high stresses predicted in a ‘back thrust’ location at the lower fault tip. These findings support the hypothesis that thrust faults and associated folds at the Ketobe Knob developed in accordance with a ramp-first kinematic model and development of structures was significantly influenced by the nature of the mechanical stratigraphy.
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SOTIROPOULOS, SPILIOS, EVANGELOS KAMBERIS, MARIA V. TRIANTAPHYLLOU, and THEODOR DOUTSOS. "Thrust sequences in the central part of the External Hellenides." Geological Magazine 140, no. 6 (November 2003): 661–68. http://dx.doi.org/10.1017/s0016756803008367.
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The model of a foreland propagating sequence already presented for the External Hellenides is significantly modified in this paper. New data are used, including structural maps, cross-sections, stratigraphic determinations and seismic profiles. In general, thrusts formed a foreland propagating sequence but they acted simultaneously for a long period of time. Thus, during the Middle Eocene the Pindos thrust resulted in the formation of the Ionian–Gavrovo foreland and acted in tandem with the newly formed Gavrovo thrust within the basin until the Late Oligocene. The Gavrovo thrust consists of segments, showing that out-of-sequence thrusting was important. Thrust nucleation and propagation history is strongly influenced by normal faults formed in the forebulge region of the Ionian–Gavrovo foreland basin. Shortening rates within the Gavrovo–Ionian foreland are low, about 1 mm/year. Although thrust load played an important role in the formation of this basin, the additional load of 3500 m thick clastics in the basin enhanced subsidence and underthrusting.
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Trexler, Charles C., Eric Cowgill, Nathan A. Niemi, Dylan A. Vasey, and Tea Godoladze. "Tectonostratigraphy and major structures of the Georgian Greater Caucasus: Implications for structural architecture, along-strike continuity, and orogen evolution." Geosphere 18, no. 1 (January 6, 2022): 211–40. http://dx.doi.org/10.1130/ges02385.1.
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Abstract Although the Greater Caucasus Mountains have played a central role in absorbing late Cenozoic convergence between the Arabian and Eurasian plates, the orogenic architecture and the ways in which it accommodates modern shortening remain debated. Here, we addressed this problem using geologic mapping along two transects across the southern half of the western Greater Caucasus to reveal a suite of regionally coherent stratigraphic packages that are juxtaposed across a series of thrust faults, which we call the North Georgia fault system. From south to north within this system, stratigraphically repeated ~5–10-km-thick thrust sheets show systematically increasing bedding dip angles (<30° in the south to subvertical in the core of the range). Likewise, exhumation depth increases toward the core of the range, based on low-temperature thermochronologic data and metamorphic grade of exposed rocks. In contrast, active shortening in the modern system is accommodated, at least in part, by thrust faults along the southern margin of the orogen. Facilitated by the North Georgia fault system, the western Greater Caucasus Mountains broadly behave as an in-sequence, southward-propagating imbricate thrust fan, with older faults within the range progressively abandoned and new structures forming to accommodate shortening as the thrust propagates southward. We suggest that the single-fault-centric “Main Caucasus thrust” paradigm is no longer appropriate, as it is a system of faults, the North Georgia fault system, that dominates the architecture of the western Greater Caucasus Mountains.
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FUENTES, FACUNDO, BRIAN K. HORTON, DANIEL STARCK, and ANDRÉS BOLL. "Structure and tectonic evolution of hybrid thick- and thin-skinned systems in the Malargüe fold–thrust belt, Neuquén basin, Argentina." Geological Magazine 153, no. 5-6 (July 25, 2016): 1066–84. http://dx.doi.org/10.1017/s0016756816000583.
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AbstractAndean Cenozoic shortening within the Malargüe fold–thrust belt of west-central Argentina has been dominated by basement faults largely influenced by pre-existing Mesozoic rift structures of the Neuquén basin system. The basement contractional structures, however, diverge from many classic inversion geometries in that they formed large hanging-wall anticlines with steeply dipping frontal forelimbs and structural relief in the order of several kilometres. During Cenozoic E–W shortening, the reactivated basement faults propagated into cover strata, feeding slip to shallow thrust systems that were later carried in piggyback fashion above newly formed basement structures, yielding complex thick- and thin-skinned structural relationships. In the adjacent foreland, Cenozoic clastic strata recorded the broad kinematic evolution of the fold–thrust belt. We present a set of structural cross-sections supported by regional surface maps and industry seismic and well data, along with new stratigraphic information for associated Neogene synorogenic foreland basin fill. Collectively, these results provide important constraints on the temporal and geometric linkages between the deeper basement faults (including both reactivated and newly formed structures) and shallow thin-skinned thrust systems, which, in turn, offer insights for the understanding of hydrocarbon systems in the actively explored Neuquén region of the Andean orogenic belt.
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Cheng, Feng, Andrew V. Zuza, Peter J. Haproff, Chen Wu, Christina Neudorf, Hong Chang, Xiangzhong Li, and Bing Li. "Accommodation of India–Asia convergence via strike-slip faulting and block rotation in the Qilian Shan fold–thrust belt, northern margin of the Tibetan Plateau." Journal of the Geological Society 178, no. 3 (January 29, 2021): jgs2020–207. http://dx.doi.org/10.1144/jgs2020-207.
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Existing models of intracontinental deformation have focused on plate-like rigid body motion v. viscous-flow-like distributed deformation. To elucidate how plate convergence is accommodated by intracontinental strike-slip faulting and block rotation within a fold–thrust belt, we examine the Cenozoic structural framework of the central Qilian Shan of northeastern Tibet, where the NW-striking, right-slip Elashan and Riyueshan faults terminate at the WNW-striking, left-slip Haiyuan and Kunlun faults. Field- and satellite-based observations of discrete right-slip fault segments, releasing bends, horsetail termination splays and off-fault normal faulting suggest that the right-slip faults accommodate block rotation and distributed west–east crustal stretching between the Haiyuan and Kunlun faults. Luminescence dating of offset terrace risers along the Riyueshan fault yields a Quaternary slip rate of c. 1.1 mm a−1, which is similar to previous estimates. By integrating our results with regional deformation constraints, we propose that the pattern of Cenozoic deformation in northeastern Tibet is compatible with west–east crustal stretching/lateral displacement, non-rigid off-fault deformation and broad clockwise rotation and bookshelf faulting, which together accommodate NE–SW India–Asia convergence. In this model, the faults represent strain localization that approximates continuum deformation during regional clockwise lithospheric flow against the rigid Eurasian continent.Supplementary material: Luminescence dating procedures and protocols is available at https://doi.org/10.17605/OSF.IO/CR9MNThematic collection: This article is part of the Fold-and-thrust belts and associated basins collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts
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Scherrenberg, Arne F., and Gideon Rosenbaum. "Photograph of the Month: Thrust duplex, low-angle normal faults and domino-style faults in laminated shale, Mt Isa, Australia." Journal of Structural Geology 31, no. 5 (May 2009): 475. http://dx.doi.org/10.1016/j.jsg.2008.10.015.
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Yaseen, Muhammad, Muhammad Shahab, Zeeshan Ahmad, Rehman Khan, Syed Farhan Ali Shah, and Abbas Ali Naseem. "Insights into the structure and surface geology of balanced and retrodeformed geological cross sections from the Nizampur basin, Khyber Pakhtunkhwa, Pakistan." Journal of Petroleum Exploration and Production Technology 11, no. 6 (May 9, 2021): 2561–71. http://dx.doi.org/10.1007/s13202-021-01180-8.
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AbstractThe current research work is an attempt to apply the basic geological procedures, methods of geological mapping, surface and subsurface interpretation and restoration of balanced and retrodeformed cross sections from the Nizampur basin, Khyber Pakhtunkhwa, Pakistan. The work also includes the documentation of several surface structural features, i.e., anticlines, synclines and different types of folds and faults exposed in the vicinity of study area. Four central thrust faults were recognized named as Kahi Thrusts along the cross sections. These thrust faults carried the older sequences of rocks over the younger sequences in different portion along the measured cross section. The folded and faulted rocks in the area show that stratigraphic framework comprises of Eocene, Paleocene, Cretaceous and Jurassic succession of rocks. There are Eocene rocks existing in the extreme South of the mapped area with addition of older Cretaceous and Jurassic succession and contains simple and large-scale folds, faults and back thrust. Two structural transect were mapped which encounter different folds and faults, i.e., X-sections AB oriented NS and CD oriented NE-SW. Restoration of the structural transects was calculated and assumed that at the formation of Main Boundary Thrust, the study area was exposed to the tectonic forces which prognosticated 19.5% shortening in rock sequences from Jurassic to Eocene succession along the measured cross section A_B.
Dissertations / Theses on the topic "Thrust faults (Geology) Australia, Central"
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Hansen, Ashley D. "Reservoir characterization and outcrop analogs to the Navajo sandstone in the Central Utah thrust belt exploration play /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1919.pdf.
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Krauss, Jason B. "High-pressure (HP), granulite-facies thrusting in a thick-skinned thrust system in the eastern Grenville Province, central Labrador /." Internet access available to MUN users only, 2002. http://collections.mun.ca/u?/theses,42716.
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Camanni, Giovanni. "The structure of the south‐central Taiwan thrust belt." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/284852.
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The Taiwan thrust belt is generally thought to develop above a shallow, through-going basal detachment confined to within the sedimentary cover of the Eurasian continental margin. A number of data sets, however, such as surface geology, earthquake hypocentre, and seismic tomography data among others, suggest that crustal levels below the interpreted location of the detachment are also currently being involved in the deformation. In this thesis, new surface geology data were combined with several available geophysical data sets to find a model for the structure of the south-central part of the thrust belt that takes into account deformation taking place at depth. Results of this thesis indicate that beneath the internal Hsuehshan and Central ranges the structural development of the south-central Taiwan thrust belt is controlled by steeply dipping and deep-penetrating faults that are currently inverting pre-existing basement faults inherited from the Eurasian continental margin. Basement rocks are uplifted along these faults to form a basement culmination in the interior of the thrust belt. Beneath the more external Coastal Plain and Western Foothills, however, most of the deformation appears to be taking place near the basement-cover interface, which is acting as an extensive level of detachment and still preserves the extensional geometry inherited from the Eurasian margin.La estructura de la cordillera de Taiwán se considera constituida por un sistema de cabalgamientos y pliegues desarrollados sobre un despegue basal con suave inclinación, situado en la cobertera sedimentara de la margen continental Euroasiática. Una cantidad creciente de datos de sismicidad y de geología de superficie, sin embargo, indican la existencia de actividad generalizada de fracturas en la corteza media e inferior y sugieren que los niveles de la corteza por debajo de la ubicación del despegue basal también están actualmente involucrados en la deformación. En esta tesis, nuevos datos de geología de superficie se combinaron con varios conjuntos de datos geofísicos disponibles para encontrar un modelo para la estructura de la parte sur-central de la cordillera de Taiwán. Los resultados de este trabajo indican que debajo de la parte interna de la área de estudio el desarrollo estructural de la cordillera de Taiwán esta controlado por fallas mayores con alta inclinación, que penetran hasta partes profundas de la corteza, y que están reactivando fallas preexistentes heredadas de la margen continental Euroasiática. Rocas de basamento están elevadas a lo largo de estas fallas y forman una culminación por debajo de las partes internas de la cordillera. Por debajo de el Coastal Plain y de las Western Foothills en la parte externa de la área de estudio, sin embargo, la mayor parte de la deformación parece estar teniendo lugar cerca de la interfaz basamento-cobertera, que está actuando como un amplio nivel de despegue basal y aún conserva la geometría extensional heredada de la margen continental Euroasiática.
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Merguerian, Charles. "Stratigraphy, structural geology, and tectonic implications of the Shoo Fly Complex and the Calaveras-Shoo Fly thrust, Central Sierra Nevada, California." Thesis, 1985. https://doi.org/10.7916/d8-mdta-w378.
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Mylonitic rocks of the Shoo Fly Complex form a region of epidote-amphibolite grade quartzose and granitoid gneiss, subordinate schist and calcareous rocks, and rare amphibolite in the foothills of the Sierra Nevada range in central California. The Shoo Fly has endured a complicated Phanerozoic structural development involving seven superposed deformations at variable crustal depths. The first four of these (D1-D4) involved tight to isoclinal folding and shearing under medium grade metamorphic conditions. The last three (D5-D7) are marked by open folding and retrograde metamorphism of older fabric elements.
The Shoo Fly is in ductile fault contact with east-dipping argillite, chert, and marble of the Calaveras Complex. The Calaveras-Shoo Fly thrust formed during D3 and is a 1-2 km wide syn-metamorphic ductile shear zone. Recognition of D3 overprinting of older Dl+D2 fabrics along the thrust zone indicates that upper plate Shoo Fly rocks record an earlier and more complex structural history than the lower plate Calaveras rocks.
Paleozoic gneissic granitoids, an important lithologic component of the Shoo Fly, were intruded as a series of plutons ranging from calc-alkaline gabbro to granitoid (predominate) to syenite. They truncated the early S1 foliation in the Shoo Fly and were folded during regional D2 and D3 events when they were penetratively deformed into augen gneiss, blastomylonite, and ultramylonite.
The Sonora dike swarm occurs as an areally extensive (> 1500 km2) subvertical consanguineous suite of andesite, lamprophyre, and basalt dikes that trend east-west across the Calaveras and Shoo Fly Complexes. The metamorphic complexes form the basement to a middle Jurassic calc-alkaline plutonic arc (Jawbone granitoid sequence). A middle Jurassic K-Ar age on the dikes (157-159 m.y.) together with the data of this report indicate that they are petrogenetically related to the Jawbone granitoid sequence and that the dikes probably formed during subduction beneath a continental arc.
The dikes provide an important structural marker in the Shoo Fly and Calaveras Complexes. Intrusion of the dike swarm was sensitive to a structural anisotropy in the basement complexes. Since they intruded east-west along a spaced regional schistosity developed during folding of the Calaveras-Shoo Fly thrust, thrusting and subsequent folding were clearly pre-middle Jurassic events.
Available geochronologic data sets middle Ordovician to late Devonian intrusive ages for the gneissic granitoids, establishing a pre-late Devonian depositional age for the Shoo Fly. D1 and intrusion of the orthogneiss protoliths may have been precursors of the Late Devonian to Early Mississippian Antler orogeny or, alternatively, may have occurred significantly earlier than the Antler orogeny. Based on cross-cutting relations, D2 formed during the Antler orogeny, D3 and possibly D4 during the Sonoma orogeny, and D5 and D6 during the Nevadan orogeny.
Books on the topic "Thrust faults (Geology) Australia, Central"
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Witkind, Irving Jerome. Implications of deformation along the east flank of the Charleston-Nebo thrust plate, central Utah. Washington: U.S. G.P.O., 1987.
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Baker, Dan M. Balanced structural cross-sections of the central Salt Range and Potwar Plateau of Pakistan: Shortening and overthrust deformation. 1987.
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M, Guthrie Gregory, Osborne W. Edward, and Geological Society of America. Southeastern Section, eds. Contrasts in structural styles and mechanisms in a foreland-hinterland transition zone, central Alabama Appalachians: A guidebook for Field Trip II, 39th Annual Meeting, Southeastern Section, Geological Society of America, Tuscaloosa, Alabama, April 3-4, 1990. [Tuscaloosa]: Geological Survey of Alabama, 1990.
Find full textBook chapters on the topic "Thrust faults (Geology) Australia, Central"
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Glikson, A. Y., C. G. Ballhaus, B. R. Goleby, and R. D. Shaw. "Major Thrust Faults and the Vertical Zonation of the Middle to Upper Proterozoic Crust in Central Australia." In Exposed Cross-Sections of the Continental Crust, 285–304. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0675-4_11.
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Hooper, Robert J., and Robert D. Hatcher. "Day 1: The geology of the east end of the Pine Mountain window and adjacent Piedmont, central Georgia." In Southern Appalachian Windows: Comparison of Styles, Scales, Geometry and Detachment Levels of Thrust Faults in the Foreland and Internides of a Thrust-Dominated Orogen: Atlanta, Georgia to Winston-Salem, North Carolina June 28–July 8, 1989, 11–20. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft167p0011.
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Wilson, Alan J., Nick Lisowiec, Cameron Switzer, Anthony C. Harris, Robert A. Creaser, and C. Mark Fanning. "Chapter 11: The Telfer Gold-Copper Deposit, Paterson Province, Western Australia." In Geology of the World’s Major Gold Deposits and Provinces, 227–49. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.11.
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Abstract The giant (>20 Moz) Telfer Au-Cu deposit is located in the Paterson Province of Western Australia and is hosted by complexly deformed marine Neoproterozoic metasedimentary siltstones and quartz arenites. The Telfer district also contains magnetite- and ilmenite-series granitoids dated between ca. 645 and 600 Ma and a world-class W skarn deposit associated with the reduced, ~604 Ma O’Callaghans granite. Based on monazite and xenotime U-Pb geochronology, Telfer is estimated to be older than O’Callaghans, forming between 645 and 620 Ma. Au-Cu mineralization at Telfer is hosted in multistage, bedding-parallel quartz-dolomite-pyrite-chalcopyrite reefs and related discordant veins and stockworks of similar composition that were emplaced into two NW-striking doubly plunging anticlines or domes. Mineralization is late orogenic in timing, with hot (≤460°C), saline (<50 wt % NaCl equiv) ore fluids channeled into preexisting domes along a series of shallow, ENE-verging thrust faults and associated fault-propagated fold corridors. A combination of fault-propagated fold corridors acting as fluid conduits below the apex of the Telfer domes and the rheology and chemical contrast between interbedded siltstone and quartz arenite units within the dome are considered key parameters in the formation of the Telfer deposit. Based on the presence of the reduced Au-Cu-W-Bi-Te-Sn-Co-As assemblage, saline and carbonic, high-temperature hydrothermal fluids in Telfer ore, and widespread ilmenite-series granites locally associated with W skarn mineralization, Telfer is considered to be a distal, intrusion-related gold deposit, the high copper content of which may be explained by the predominance of highly saline, magmatic fluids in gangue assemblages cogenetic with ore.
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Malone, David, John Craddock, Alexandra Wallenberg, Betrand Gaschot, and John A. Luczaj. "Geology of Chief Joseph Pass, Wyoming: Crest of Rattlesnake Mountain anticline and escape path of the Eocene Heart Mountain slide." In Tectonic Evolution of the Sevier-Laramide Hinterland, Thrust Belt, and Foreland, and Postorogenic Slab Rollback (180–20 Ma). Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2555(12).
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ABSTRACT Rattlesnake Mountain is a Laramide uplift cored by Archean gneiss that formed by offset along two reverse faults with opposing dips, the result being an asymmetric anticline with a drape fold of Cambrian–Cretaceous sediments. Rattlesnake Mountain was uplifted ca. 57 Ma and was a structural buttress that impeded motion of upper-plate blocks of the catastrophic Heart Mountain slide (49.19 Ma). North of Pat O’Hara Mountain anticline, Rattlesnake Mountain anticline has a central graben that formed ca. 52 Ma (U-Pb age on vein calcite in normal faults) into which O- and C-depleted fluids propagated upward with hydrocarbons. The graben is defined by down-dropped Triassic Chugwater shales atop the anticline that facilitated motion of Heart Mountain slide blocks of Paleozoic limestones dolomite (i.e., the Ordovician Bighorn Dolomite and Mississippian Madison Limestone) onto, and over, Rattlesnake Mountain into the Bighorn Basin. Heart Mountain fault gouge was also injected downward into the bounding Rattlesnake Mountain graben normal faults (U-Pb age ca. 48.8 ± 5 Ma), based on O and C isotopes; there is no anisotropy of magnetic susceptibility fabric present. Calcite veins parallel to graben normal faults precipitated from meteoric waters (recorded by O and C isotopes) heated by the uplifting Rattlesnake Mountain anticline and crystallized at 57 °C (fluid inclusions) in the presence of oil. Calcite twinning strain results from graben injectites and calcite veins are different; we also documented a random layer-parallel shortening strain pattern for the Heart Mountain slide blocks in the ramp region (n = 4; west) and on the land surface (n = 5; atop Rattlesnake Mountain). We observed an absence of any twinning strain overprint (low negative expected values) in the allochthonous upper-plate blocks and in autochthonous carbonates directly below the Heart Mountain slide surface, again indicating rapid motion including horizontal rotation about vertical axes of the upper-plate Heart Mountain slide blocks during the Eocene.
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Ogawa, Yujiro, and Shin’ichi Mori. "Gravitational sliding or tectonic thrusting?: Examples and field recognition in the Miura-Boso subduction zone prism." In Plate Tectonics, Ophiolites, and Societal Significance of Geology: A Celebration of the Career of Eldridge Moores. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2552(10).
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ABSTRACT Discrimination between gravity slides and tectonic fold-and-thrust belts in the geologic record has long been a challenge, as both have similar layer shortening structures resulting from single bed duplication by thrust faults of outcrop to map scales. Outcrops on uplifted benches within the Miocene to Pliocene Misaki accretionary unit of Miura-Boso accretionary prism, Miura Peninsula, central Japan, preserve good examples of various types of bedding duplication and duplex structures with multiple styles of folds. These provide a foundation for discussion of the processes, mechanisms, and tectonic implications of structure formation in shallow parts of accretionary prisms. Careful observation of 2-D or 3-D and time dimensions of attitudes allows discrimination between formative processes. The structures of gravitational slide origin develop under semi-lithified conditions existing before the sediments are incorporated into the prism at the shallow surfaces of the outward, or on the inward slopes of the trench. They are constrained within the intraformational horizons above bedding-parallel detachment faults and are unconformably covered with the superjacent beds, or are intruded by diapiric, sedimentary sill or dike intrusions associated with liquefaction or fluidization under ductile conditions. The directions of vergence are variable. On the other hand, layer shortening structure formed by tectonic deformation within the accretionary prism are characterized by more constant styles and attitudes, and by strong shear features with cataclastic textures. In these structures, the fault surfaces are oblique to the bedding, and the beds are systematically duplicated (i.e., lacking random styles of slump folds), and they are commonly associated with fault-propagation folds. Gravitational slide bodies may be further deformed at deeper levels in the prism by tectonism. Such deformed rocks with both processes constitute the whole accretionary prism at depth, and later may be deformed, exhumed to shallow levels, and exposed at the surface of the trench slope, where they may experience further deformation. These observations are not only applicable in time and space to large-scale thrust-and-fold belts of accretionary prism orogens, but to small-scale examples. If we know the total 3-D geometry of geologic bodies, including the time and scale of deformational stages, we can discriminate between gravitational slide and tectonic formation of each fold-and-thrust belt at the various scales of occurrence.
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Seltmann, Reimar, Richard J. Goldfarb, Bo Zu, Robert A. Creaser, Alla Dolgopolova, and Vitaly V. Shatov. "Chapter 24: Muruntau, Uzbekistan: The World’s Largest Epigenetic Gold Deposit." In Geology of the World’s Major Gold Deposits and Provinces, 497–521. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.24.
Full textAbstract:
Abstract Muruntau in the Central Kyzylkum desert of the South Tien Shan, western Uzbekistan, with past production of ~3,000 metric tons (t) Au since 1967, present annual production of ~60 t Au, and large remaining resources, is the world’s largest epigenetic Au deposit. The host rocks are the mainly Cambrian-Ordovician siliciclastic flysch of the Besapan sequence. The rocks were deformed into a broadly east-west fold-and-thrust belt prior to ca. 300 Ma during ocean closure along the South Tien Shan suture. A subsequent tectonic transition was characterized by left-lateral motion on regional splays from the suture and by a massive thermal event documented by widespread 300 to 275 Ma magmatism. The Besapan rocks were subjected to middle to upper greenschist-facies regional metamorphism, an overprinting more local thermal metamorphism to produce a large hornfels aureole, and then Au-related hydrothermal activity all during early parts of the thermal event. The giant Muruntau Au deposit formed in the low-strain hornfels rocks at ca. 288 Ma at the intersection of one of the east-west splays, the Sangruntau-Tamdytau shear zone, with a NE-trending regional fault zone, the Muruntau-Daugyztau fault, which likely formed as a cross fault during the onset of left-lateral translation on the regional splays. Interaction between the two faults opened a large dilational zone along a plunging anticlinorium fold nose that served as a major site for hydrothermal fluid focusing. The Au ores are dominantly present as a series of moderately to steeply dipping quartz ± K-feldspar stockwork systems surrounding uncommon central veins and with widespread lower Au-grade metasomatites (i.e., disseminated ores). Pervasive alteration is biotite-K-feldspar, although locally albitization is dominant. Sulfides are mainly arsenopyrite, pyrite, and lesser pyrrhotite, and scheelite may be present both in preore ductile veins and in the more brittle auriferous stockwork systems. The low-salinity, aqueous-carbonic ore-forming fluids probably deposited the bulk of the ore at 400° ± 50°C and 6-to 10-km paleodepth. The genesis of the deposit remains controversial with metamorphic, thermal aureole gold (TAG), and models related to mantle upwelling all having been suggested in recent years. More importantly, the question as to why there was such a focusing of so much Au and fluid into this one location, forming an ore system an order of magnitude larger than other giant Au deposits in metamorphic terranes, remains unresolved.
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Busby, C. J., T. L. Pavlis, S. M. Roeske, and B. Tikoff. "The North American Cordillera during the Mesozoic to Paleogene: Selected questions and controversies." In Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(31).
Full textAbstract:
ABSTRACT The North American Cordillera experienced significant and varied tectonism during the Triassic to Paleogene time interval. Herein, we highlight selected questions and controversies that remain at this time. First, we describe two tectonic processes that have hindered interpretations of the evolution of the orogen: (1) strike-slip systems with poorly resolved displacement; and (2) the closing of ocean basins of uncertain size, origin, and mechanism of closure. Next, we divide the orogen into southern, central, and northern segments to discuss selected controversies relevant to each area. Controversies/questions from the southern segment include: What is the origin of cryptic transform faults (Mojave-Sonora megashear vs. California Coahuila transform fault)? Is the Nazas an arc or a continental rift province? What is the Arperos basin (Guerrero terrane), and did its closure produce the Mexican fold-and-thrust belt? How may inherited basement control patterns of deformation during subduction? Controversies/questions from the central segment include: Can steeply dipping mantle anomalies be reconciled with geology? What caused high-flux events in the Sierra Nevada batholith? What is the origin of the North American Cordilleran anatectic belt? How does the Idaho segment of the orogen connect to the north and south? Controversies/questions from the northern segment include: How do we solve the Baja–British Columbia problem? How big and what kind of basin was the Early Cretaceous lost ocean basin? What connections can be found between Arctic geology and Cordilleran geology in Alaska? How do the Cretaceous tectonic events in the Arctic and northern Alaska connect with the Cordilleran Cretaceous events? What caused the Eocene tectonic transitions seen throughout the northern Cordillera? By addressing these questions along the length of the Cordillera, we hope to highlight common problems and facilitate productive discussion on the development of these features.