Internal Structure and Petrography of the Mineralized Faults in the Radomiro Tomic Deposit
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Counterclockwise Rotation of Late Eocene – Oligocene Forearc Deposits in Southern Peru and Its Significance for Oroclinal Bend
Counterclockwise rotation of Late Eocene – Oligocene forearc deposits in southern Peru and its significance for oroclinal bending in the Central Andes Pierrick Roperch, Thierry Sempere, Orlando Macedo, César Arriagada, Michel Fornari, Claudio Tapia, Marcelo Garcia, Carlo Laj To cite this version: Pierrick Roperch, Thierry Sempere, Orlando Macedo, César Arriagada, Michel Fornari, et al.. Coun- terclockwise rotation of Late Eocene – Oligocene forearc deposits in southern Peru and its significance for oroclinal bending in the Central Andes. Tectonics, American Geophysical Union (AGU), 2006, 25 (3), pp.TC3010. 10.1029/2005TC001882. insu-00261209 HAL Id: insu-00261209 https://hal-insu.archives-ouvertes.fr/insu-00261209 Submitted on 29 Jun 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. TECTONICS, VOL. 25, TC3010, doi:10.1029/2005TC001882, 2006 Counterclockwise rotation of late Eocene–Oligocene fore-arc deposits in southern Peru and its significance for oroclinal bending in the central Andes Pierrick Roperch,1,2 Thierry Sempere,3 Orlando Macedo,4 Ce´sar Arriagada,2 Michel Fornari,5 Claudio Tapia,2 Marcelo Garcı´a,6 and Carlo Laj7 Received 6 July 2005; revised 20 February 2006; accepted 14 March 2006; published 1 June 2006. -
Fault Rocks and Fault Mechanisms
Fault rocks and fault mechanisms R. H. SIBSON SUMMARY Physical factors likely to affect the genesis of the with the production of mylonite series rocks various fault rocks--frictional properties, tem- possessing strong tectonite fabrics. In some cases, perature, effective stress normal to the fault and fault rocks developed by transient seismic fault- differential stress--are examined in relation to ing can be distinguished from those generated the energy budget of fault zones, the main by slow aseismic shear. Random-fabric fault velocity modes of faulting and the type of fault- rocks may form as a result of seismic faulting ing, whether thrust, wrench, or normal. In a within the ductile shear zones from time to conceptual model of a major fault zone cutting time, but tend to be obliterated by continued crystalline quartzo-feldspathic crust, a zone of shearing. Resistance to shear within the fault elastico-frictional (EF) behaviour generating zone reaches a peak value (greatest for thrusts random-fabric fault rocks (gouge--breccia-- and least for normal faults) around the EF/OP cataclasite series--pseudotachylyte) overlies a transition level, which for normal geothermal region where quasi-plastic (QP) processes of gradients and an adequate supply of water, rock deformation operate in ductile shear zones occurs at depths of lO-15 km. SINCE LAPWORTH'$ (I885) description of the type mylonite from the Moine Thrust in NW Scotland, there have been many petrographic descriptions and classifications of the texturally distinctive rocks found associated with fault zones (e.g. Waters & Campbell 1935, Hsu 1955, Christie 196o , 1963, Reed 1964, Spry I969, Higgins 1971 ). -
Lithology and Internal Structure of the San Andreas Fault at Depth Based
1 1 Lithology and Internal Structure of the San Andreas Fault at depth based on 2 characterization of Phase 3 whole-rock core in the San Andreas Fault Observatory at 3 Depth (SAFOD) Borehole 4 By Kelly K. Bradbury1, James P. Evans1, Judith S. Chester2, Frederick M. Chester2, and David L. Kirschner3 5 1Geology Department, Utah State University, Logan, UT 84321-4505 6 2Center for Tectonophysics and Department of Geology and Geophysics, Texas A&M University, College Station, 7 Texas 77843 8 3Department of Earth and Atmospheric Sciences, St. Louis University, St. Louis, Missouri 63108 9 10 Abstract 11 We characterize the lithology and structure of the spot core obtained in 2007 during 12 Phase 3 drilling of the San Andreas Fault Observatory at Depth (SAFOD) in order to determine 13 the composition, structure, and deformation processes of the fault zone at 3 km depth where 14 creep and microseismicity occur. A total of approximately 41 m of spot core was taken from 15 three separate sections of the borehole; the core samples consist of fractured arkosic sandstones 16 and shale west of the SAF zone (Pacific Plate) and sheared fine-grained sedimentary rocks, 17 ultrafine black fault-related rocks, and phyllosilicate-rich fault gouge within the fault zone 18 (North American Plate). The fault zone at SAFOD consists of a broad zone of variably damaged 19 rock containing localized zones of highly concentrated shear that often juxtapose distinct 20 protoliths. Two zones of serpentinite-bearing clay gouge, each meters-thick, occur at the two 21 locations of aseismic creep identified in the borehole on the basis of casing deformation. -
Late Mesozoic to Paleogene Stratigraphy of the Salar De Atacama Basin, Antofagasta, Northern Chile: Implications for the Tectonic Evolution of the Central Andes
Late Mesozoic to Paleogene stratigraphy of the Salar de Atacama Basin, Antofagasta, Northern Chile: Implications for the tectonic evolution of the Central Andes Constantino Mpodozisa,T,Ce´sar Arriagadab, Matilde Bassoc, Pierrick Roperchd, Peter Cobbolde, Martin Reichf aServicio Nacional de Geologı´a y Minerı´a, now at Sipetrol. SA, Santiago, Chile bDepartamento de Geologı´a, Universidad de Chile, Santiago, Chile cServicio Nacional de Geologı´a y Minerı´a, Santiago, Chile dIRD/Dep. de Geologı´a, Universidad de Chile, Santiago, Chile eGe´osciences-Rennes (UMR6118 du CNRS), France fDepartment of Geological Sciences University of Michigan, United States Abstract The Salar de Atacama basin, the largest bpre-AndeanQ basin in Northern Chile, was formed in the early Late Cretaceous as a consequence of the tectonic closure and inversion of the Jurassic–Early Cretaceous Tarapaca´ back arc basin. Inversion led to uplift of the Cordillera de Domeyko (CD), a thick-skinned basement range bounded by a system of reverse faults and blind thrusts with alternating vergence along strike. The almost 6000-m-thick, upper Cretaceous to lower Paleocene sequences (Purilactis Group) infilling the Salar de Atacama basin reflects rapid local subsidence to the east of the CD. Its oldest outcropping unit (Tonel Formation) comprises more than 1000 m of continental red sandstones and evaporites, which began to accumulate as syntectonic growth strata during the initial stages of CD uplift. Tonel strata are capped by almost 3000 m of sandstones and conglomerates of western provenance, representing the sedimentary response to renewed pulses of tectonic shortening, which were deposited in alluvial fan, fluvial and eolian settings together with minor lacustrine mudstone (Purilactis Formation). -
Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs
Pure Appl. Geophys. Ó 2014 Springer Basel DOI 10.1007/s00024-014-0896-6 Pure and Applied Geophysics Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions 1 1 1 1 1 KELLY K. BRADBURY, COLTER R. DAVIS, JOHN W. SHERVAIS, SUSANNE U. JANECKE, and JAMES P. EVANS Abstract—We examine the fine-scale variations in mineralogi- 1. Introduction cal composition, geochemical alteration, and texture of the fault- related rocks from the Phase 3 whole-rock core sampled between 3,187.4 and 3,301.4 m measured depth within the San Andreas Fault Well-constrained geological, geochemical, and Observatory at Depth (SAFOD) borehole near Parkfield, California. geophysical models of active fault zones are needed if This work provides insight into the physical and chemical properties, we are to understand fault zone behavior and earth- structural architecture, and fluid-rock interactions associated with the actively deforming traces of the San Andreas Fault zone at depth. quake deformation, constraining the factors that affect Exhumed outcrops within the SAF system comprised of serpentinite- the distribution of earthquakes, and the nature of slip bearing protolith are examined for comparison at San Simeon, Goat in the shallow crust by developing realistic models of Rock State Park, and Nelson Creek, California. In the Phase 3 SAFOD drillcore samples, the fault-related rocks consist of multiple subsurface fault zone structure and ground motion juxtaposed lenses of sheared, foliated siltstone and shale with block- predictions. Earthquakes nucleate in rocks at depth in-matrix fabric, black cataclasite to ultracataclasite, and sheared (e.g., FAGERENG and TOY 2011;SIBSON 1977; 2003), serpentinite-bearing, finely foliated fault gouge. -
Rnic~Ess T~Ese
GEOPHYSICAL RESEARCH LETTERS, VOL. 18, NO.5, PAGES 979-982, MAY 1991 HYDROGEOLOGY OF THRUST FAULTS AND CRYSTALLINE THRUST SHEETS: RESULTS OF COMBINED FIELD AND MODELING STUDIES Craig B. Forster Department of Geology & Geophysics, University of Utah James P. Evans Department of Geology, Utah State University Abstract. Field,. laboratory, and.modeling studies of faulted obtained for systems that span a wide range of spatial scales, rock yield insight 1Oto the hydraulic character of thrust faults. aid in establishing appropriate scales of observation. Although Late-stage fau lts comprise foliated and su?par~lel faults, ~ith our numerical models cannot provide a unique answer that clay-rich gouge and fracture zones, that YIeld mterpenetratmg applies directly to a given field situation, the numerical results layers of low-permeability gou~e and higher-permeab~l~ty do provide insight into this class of groundwater flow system. damage zones. Laboratory testmg suggests a permeabIlity contrast of two orders of magnitude between gouge and damage zones. Layers of differing permeability lead to overall Fault Zone Hydrogeology permeability anisotropy with maximum permeability within the plane of the fault and minimum permeability perpendicular to the fault plane. Numerical modeling of regional-scale fluid Precambrian granites and gneisses found in our field area flow and heat transport illustrates the impact of fault zone (northwest Wyoming) were thrusted over adjacent sedimentary hydrogeology on fluid flux, fluid pore pressure, and rocks along moderately-dipping thrust faults. About 150 m of temperature in the vicinity of a crystalline thrust sheet. exposed fault were examined through large-scale field mapping and detailed sampling both across and along strike. -
Crustal Faults in the Chilean Andes: Geological Constraints and Seismic Potential
Andean Geology 46 (1): 32-65. January, 2019 Andean Geology doi: 10.5027/andgeoV46n1-3067 www.andeangeology.cl Crustal faults in the Chilean Andes: geological constraints and seismic potential *Isabel Santibáñez1, José Cembrano2, Tiaren García-Pérez1, Carlos Costa3, Gonzalo Yáñez2, Carlos Marquardt4, Gloria Arancibia2, Gabriel González5 1 Programa de Doctorado en Ciencias de la Ingeniería, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Macul, Santiago, Chile. [email protected]; [email protected] 2 Departamento de Ingeniería Estructural y Geotécnica, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Macul, Santiago, Chile. [email protected]; [email protected]; [email protected] 3 Departamento de Geología, Universidad de San Luis, Ejercito de Los Andes 950, D5700HHW San Luis, Argentina. [email protected] 4 Departamento de Ingeniería Estructural y Geotécnica y Departamento de Ingeniería de Minería, Pontificia Universidad Católica de Chile. Avda. Vicuña Mackenna 4860, Macul, Santiago, Chile. [email protected] 5 Departamento de Ciencias Geológicas, Universidad Católica del Norte, Angamos 0610, Antofagasta, Chile. [email protected] * Corresponding author: [email protected] ABSTRACT. The Chilean Andes, as a characteristic tectonic and geomorphological region, is a perfect location to unravel the geologic nature of seismic hazards. The Chilean segment of the Nazca-South American subduction zone has experienced mega-earthquakes with Moment Magnitudes (Mw) >8.5 (e.g., Mw 9.5 Valdivia, 1960; Mw 8.8 Maule, 2010) and many large earthquakes with Mw >7.5, both with recurrence times of tens to hundreds of years. By contrast, crustal faults within the overriding South American plate commonly have longer recurrence times (thousands of years) and are known to produce earthquakes with maximum Mw of 7.0 to 7.5. -
Strength of Chrysotile-Serpentinite Gouge Under Hydrothermal Conditions: Can It Explain a Weak San Andreas Fault?
Strength of chrysotile-serpentinite gouge under hydrothermal conditions: Can it explain a weak San Andreas fault? D. E. Moore D. A. Lockner U.S. Geological Survey, Menlo Park, California 94025 R. Summers Ma Shengli Institute of Geology, State Seismological Bureau, Beijing, China J. D. Byerlee U.S. Geological Survey, Menlo Park, California 94025 ABSTRACT more, it has been suggested that at higher temperatures (Reinen et Chrysotile-bearing serpentinite is a constituent of the San An- al., 1993) and/or lower strain rates (Reinen and Tullis, 1995) the dreas fault zone in central and northern California. At room tem- frictional strength of chrysotile may be reduced to Յ 0.1. As a test perature, chrysotile gouge has a very low coefficient of friction ( of this hypothesis, we report here on the strength of a pure chrysotile Ϸ 0.2), raising the possibility that under hydrothermal conditions gouge at elevated temperatures and a wide range of velocities, in- might be reduced sufficiently (to <0.1) to explain the apparent tended to more closely represent conditions at depth in the fault. weakness of the fault. To test this hypothesis, we measured the Our results suggest that chrysotile alone is not a likely explanation frictional strength of a pure chrysotile gouge at temperatures to for a weak San Andreas fault. ؇C and axial-shortening velocities as low as 0.001 m/s. As 290 temperature increases to Ϸ100 ؇C, the strength of the chrysotile EXPERIMENTAL PROCEDURES gouge decreases slightly at low velocities, but at temperatures The chrysotile gouge used in this study was prepared from a ؇C, it is substantially stronger and essentially independent of soft, layered, light to medium grayish-green rock from the New Idria 200< velocity at the lowest velocities tested. -
Physical Properties of Surface Outcrop Cataclastic Fault Rocks, Alpine Fault, New Zealand
Article Volume 13, Number 1 28 January 2012 Q01018, doi:10.1029/2011GC003872 ISSN: 1525-2027 Physical properties of surface outcrop cataclastic fault rocks, Alpine Fault, New Zealand C. Boulton Department of Geological Sciences, University of Canterbury, PB 4800, Christchurch 8042, New Zealand ([email protected]) B. M. Carpenter Department of Geosciences, Pennsylvania State University, 522 Deike Building, University Park, Pennsylvania 16802, USA V. Toy Department of Geology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand C. Marone Department of Geosciences, Pennsylvania State University, 522 Deike Building, University Park, Pennsylvania 16802, USA [1] We present a unified analysis of physical properties of cataclastic fault rocks collected from surface exposures of the central Alpine Fault at Gaunt Creek and Waikukupa River, New Zealand. Friction experi- ments on fault gouge and intact samples of cataclasite were conducted at 30–33 MPa effective normal stress (sn′) using a double-direct shear configuration and controlled pore fluid pressure in a true triaxial pressure vessel. Samples from a scarp outcrop on the southwest bank of Gaunt Creek display (1) an increase in fault normal permeability (k=7.45 Â 10À20 m2 to k = 1.15 Â 10À16 m2), (2) a transition from frictionally weak (m = 0.44) fault gouge to frictionally strong (m = 0.50–0.55) cataclasite, (3) a change in friction rate depen- dence (a-b) from solely velocity strengthening, to velocity strengthening and weakening, and (4) an increase in the rate of frictional healing with increasing distance from the footwall fluvioglacial gravels contact. At Gaunt Creek, alteration of the primary clay minerals chlorite and illite/muscovite to smectite, kaolinite, and goethite accompanies an increase in friction coefficient (m = 0.31 to m = 0.44) and fault- perpendicular permeability (k=3.10 Â 10À20 m2 to k = 7.45 Â 10À20 m2). -
Generation of Sintered Fault Rock and Its Implications for Earthquake
ARTICLE https://doi.org/10.1038/s43247-020-0004-z OPEN Generation of sintered fault rock and its implications for earthquake energetics and fault healing ✉ Tetsuro Hirono 1 , Shunya Kaneki 2, Tsuyoshi Ishikawa 3, Jun Kameda4, Naoya Tonoike1,7, Akihiro Ito5 & Yuji Miyazaki6 1234567890():,; After an earthquake, faults can recover strength through fault healing, but the mechanisms responsible are not well understood. Seismic slip may induce sintering, a bonding process between solid particles in contact under high temperatures without melting, which could produce a fault rock with elevated strength and chemical stability. Here we present results from electron microscope analyses that show a typical sintered structure in a black disk- shaped rock from the Chelungpu fault, Taiwan. This structure is experimentally reproducible in simulated fault material, prepared from the local host-rock, by heating at 800–900 °C. Through thermal and kinetic analyses of experimental materials, we show that sintering is an exothermic process which can generate energy to enhance post-slip thermochemical reac- tions in the fault. We propose that sintering substantially contributes to earthquake ener- getics and fault healing and that its occurrence can be a useful indicator of past seismic slip. 1 Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. 2 Disaster Prevention Research Institute, Kyoto University, Uji, Kyoto 611-0011, Japan. 3 Kochi Institute for Core Sample Research, Japan Agency for Marine-Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan. 4 Department of Natural History Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan. -
Plate Tectonic Setting of the Andean Cordillera
183 by Victor A. Ramos Plate tectonic setting of the Andean Cordillera Laboratorio de Tectónica Andina, Universidad de Buenos Aires, Argentina. E-mail: [email protected] The Andes are a natural laboratory for the study of the acterize the different segments are widely variable. The present interaction between subduction of the oceanic plate and overview will focus on the major geological differences among these segments, based on today’s plate-tectonic knowledge of this moun- active geological processes. Inter- and intraplate seis- tain chain. micity, volcanic activity, thick- and thin-skinned fold and thrust belts, and foreland basin subsidence, in con- junction with space geodetic observations, contribute to Major geological provinces characterize the present plate tectonic setting of discrete The Andes north of the Golfo de Guayaquil are unique, as estab- segments of the Andes. The inherited geological history, lished by Gansser (1973). The Northern Andes record an important as well as the present tectonic setting, is responsible for accretion of oceanic crust during Jurassic, late Cretaceous, and Pale- the unique geology of the Northern, Central, and South- ogene times. As a result, the Western Cordillera of Colombia and Ecuador is mainly constituted of an oceanic basement that during ern Andes. The Northern Andes are the result of Meso- accretion was related to ophiolite obduction, important penetrative zoic and Cenozoic collisions of oceanic terranes, prior deformation and metamorphism, in cases up to blue schist facies. to the present Andean-type setting. The Central Andes Further north, the emplacement of the Caribbean nappes was related to the collision of an island arc system, the Bonaire block, during have a long history of subduction and volcanic arc Paleogene times (Bosch and Rodríguez, 1992, Kellogg and Bonini, activity, while the Southern Andes record the closing of 1982). -
Scientific Drilling Into the San Andreas Fault Zone —An Overview of SAFOD’S First Five Years
Science Reports Scientific Drilling Into the San Andreas Fault Zone —An Overview of SAFOD’s First Five Years by Mark Zoback, Stephen Hickman, William Ellsworth, and the SAFOD Science Team doi:10.2204/iodp.sd.11.02.2011 Abstract Detailed planning of a research experiment focused on drilling, sampling, and downhole measurements directly The San Andreas Fault Observatory at Depth (SAFOD) within the San Andreas Fault Zone began with an interna- was drilled to study the physical and chemical processes tional workshop held in Asilomar, California in December controlling faulting and earthquake generation along an 1992. This workshop highlighted the importance of active, plate-bounding fault at depth. SAFOD is located near deploying a permanent geophysical observatory within the Parkfield, California and penetrates a section of the fault that fault zone at seismogenic depth for near-field monitoring of is moving due to a combination of repeating microearth- earthquake nucleation. Hence, from the outset, the SAFOD quakes and fault creep. Geophysical logs define the San project has been designed to achieve two parallel suites of Andreas Fault Zone to be relatively broad (~200 m), contain- objectives. The first is to carry out a series of experiments in ing several discrete zones only 2–3 m wide that exhibit very and near the San Andreas Fault that address long-standing low P- and S-wave velocities and low resistivity. Two of these questions about the physical and chemical processes that zones have progressively deformed the cemented casing at control deformation and earthquake generation within active measured depths of 3192 m and 3302 m.