413 results on '"Orogenesis"'
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52. Caracterización de las fases minerales y los fluidos hidrotermales presentes en el Distrito Casposo, Cordillera Frontal, San Juan, Argentina
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Diego Sebastián Palma, Guido, Diego Martín, and Jovic, Sebastián Miguel
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Minerales ,Vulcanismo ,Ciencias Naturales ,Geología ,Orogénesis - Abstract
El distrito Casposo se ubica en el borde oriental de la Cordillera Frontal, departamento de Calingasta, en el oeste de la provincia de San Juan, Argentina. El mismo se conforma de un extenso sistema de vetas epitermales de baja sulfuración, dentro del cual se desarrolla una mina en explotación (actualmente inactiva). Desde el inicio de sus actividades en el año 2011 y hasta el 2015, esta mina produjo un total de 283.200 oz de Au y 9,5 Moz de Ag. La geología del yacimiento está caracterizada por afloramientos de una secuencia marina (Formación La Puerta), depositada entre el Carbonífero y el Pérmico temprano, que fue intensamente deformado durante la fase orogénica San Rafael (Pérmico inferior). Sobre esta secuencia, y mediante una importante discordancia angular (Superficie San Rafael), tuvo lugar un importante magmatismo representado por el Grupo Choiyoi, de naturaleza subalcalina que evolucionó desde términos calcoalcalinos hacia composiciones shoshoníticas. Entre los 269,7 Ma y los 256,7 Ma (Pérmico medio a superior) este magmatismo presentó su mayor intensidad y volumen, resultando en una potente secuencia piroclástica con presencia de discordancias intraformacionales (Sección inferior y superior), que es intruída por cuerpos subvolcánicos (denominados Dacita Casposo y Andesita Cerro Pelado). Este vulcanismo evolucionó de manera sincrónica a la intrusión de importantes cuerpos plutónicos de grandes dimensiones como la Granodiorita Casposo, que potencialmente podrían representar las partes más profundas del mismo sistema magmático, aunque una importante falla N-S separa ambos ambientes. Durante las etapas terminales de este periodo, entre los 263,6 Ma y los 256,7 Ma, se habría instalado el sistema hidrotermal responsable de la formación del yacimiento, en cercana asociación con un conjunto de cuerpos subvolcánicos denominados Dique Félsico e Intrusivo Félsico. Luego del emplazamiento de la mineralización, y mediante un período de actividad magmática nula de ~ 12 Ma, ocurrió una reactivación del magmatismo a partir de los 249,7±2 Ma (Triásico Medio) que resultó en la intrusión de una sucesión de familias de diques de composiciones intermedias a ácidas (denominados Diques Básicos, Diques Riolíticos Porfíricos y Diques de Aplitas). El yacimiento abarca un área de aproximadamente 100 km2 formado por vetas que exhiben una marcada zonación composicional: las puramente silíceas concentradas en la zona de operaciones de mina (Mercado, Aztec, B Vein, Inca), vetas cuarzo-carbonáticos (Cerro Norte, Lucía), y las puramente carbonáticas con pulsos silíceos (Oveja Negra, Aurora, Casposo Norte, Leñador y Julieta). Las texturas predominantes son las de relleno de espacios abiertos, como los bandeados coloformes con desarrollo de ginguros, crustiformes, cocardas, masivas y brechas con cemento de sulfuros. Del detallado análisis estructural realizado sobre las secciones transversales y plantas de la zona de mina, se determinó un vector de máxima apertura NE-SO actuando en simultáneo a la formación de la mineralización (control sin-mineral), que luego habría sido afectada por al menos dos eventos posteriores de fallamiento (control post-mineral). A partir del análisis de detallado de la mineralogía y textura de la veta Inca, se discriminaron 9 pulsos que fueron agrupados en 6 episodios principales, siendo 5 de ellos de naturaleza hidrotermal y 1 de del tipo tectónico-hidrotermal. Los pulsos P1 y P2 son estériles. En el pulso P3 precipitan cuarzo-calcedonia con textura bandeada coloforme, y adularia subrómbica a pseudoacicular, con minerales de mena alojadas en bandas oscuras tipo ginguro. La mena se compone de electrum (10% Au – 90% Ag) y plata nativa, sulfosales como tetraedrita (rica en Ag), pirargirita y polibasita, teluros y seleniuros (naumanita y hessita) y sulfuros de metales base (esfalerita, galena y calcopirita). En el P4 precipitan sulfuros finos a gruesos junto a un cuarzo macizo, los minerales de mena se corresponden con sulfosales como la tetraedrita, y sulfuros de metales base. La evolución de los pulsos continúa hacia una composición donde predominan las arcillas verdes y las texturas brechosas en el P5. Continuo, aparece otro pulso silíceo y estéril (P6), con grandes cristales de adularia subrómbica. La secuencia sigue con un cuarzo microcristalino negro, masivo, de grano fino que posee la particularidad de exhibir molibdenita mostrando una extraña textura dendrítica (P7). En el pulso P8 actúan en simultáneo una componente hidráulica y otra tectónica, que generaron una brecha de matriz negra donde el cemento es masivo y posee anomalías de Mo; en ocasiones presenta pátinas azuladas que tiñen los clastos de los pulsos previos. Por último, se reconoce un evento menor que forma finas vetillas de carbonatos (P9). La mineralización se habría originado a partir del ascenso de soluciones cloruradas reducidas, con pH neutro a levemente alcalino, con salinidades del 7% NaCl eq. y con evidencias de ebullición; en tanto que los datos de isótopos estables establecen un origen producto de mezcla entre aguas meteóricas y magmáticas. La presencia de calcita de hábito hojoso, texturas de reemplazo de cuarzo y adularia pseudoacicular, bandeados coloformes y brechas, sumado a la coexistencia entre inclusiones fluidas ricas en fase vapor y líquido, evidencian a la ebullición como el factor responsable para la depositación metalífera. Por último, por las características observadas se puede clasificar ala Veta Inca como un sistema epitermal clásico de baja sulfuración, aunque ciertos atributos como las salinidades moderadas, la elevada relación Ag/Au, la presencia de sulfosales como tetraedrita, pirargirita y polibasita, y la presencia de esfalerita pobre en Fe, evidencian un estado de sulfuración intermedia., The Casposo district is located on the eastern edge of the Cordillera Frontal, Calingasta department, in the west of the San Juan province, Argentina. It consists of a larguest system of low sulfidation epithermal veins, within which there is an operating mine (currently inactive). Since the beginning of its activities in the year 2011 and until 2015, this mine produced a total of 283.200 oz of Au and 9,5 Moz of Ag. The geology of the deposit is characterized by outcrops of a marine sequence (La Puerta Formation), deposited between the Carboniferous and Early Permian, which was intensely deformed during the San Rafael orogenic phase (Lower Permian). Over this sequence, and through an important angular unconformity (San Rafael Surface), an important magmatism took place, represented by the Choiyoi Group, of subalkaline nature that evolved from calcalkaline to shoshonitic compositions. Between 269,7 Ma and 256,7 Ma (middle to upper Permian) this magmatism reached its highest intensity and volume, resulting in a thick pyroclastic sequence with the presence of intraformational unconformities (lower and upper section), which is intruded by subvolcanic bodies (Dacite Casposo and Andesita Cerro Pelado). This volcanism evolved synchronously with the intrusion of important large plutonic bodies such as the Casposo Granodiorite, which could potentially represent the deepest parts of the same magmatic system, although a major N-S fault separates both environments. During the terminal stages of this period, between 263,6 Ma and 256,7 Ma, the hydrothermal system responsible for the formation of the deposit would have been installed, in close association with a set of subvolcanic bodies called Felsic Dike and Felsic Intrusive. After the emplacement of the mineralization, and through a period of null magmatic activity of ~ 12 Ma, a reactivation of magmatism occurred from 249,7±2 Ma (Middle Triassic) that resulted in the intrusion of a succession of families of dykes of intermediate to acid compositions (Basic Dykes, Porphyritic Rhyolitic Dykes and Aplite Dykes). The deposit covers an area of approximately 100 km2 formed by veins that shows a marked compositional zoning: purely siliceous veins concentrated in the area of mine operations (Mercado, Aztec, B Vein, Inca), quartz-carbonate veins (Cerro Norte, Lucía), and purely carbonate veins with siliceous pulses (Oveja Negra, Aurora, Casposo Norte, Leñador and Julieta). The predominant textures are those of open space filling, such as colloform banding with the development of ginguros, crustiforms, cocards, massive and breccias with sulfide cement. From the detailed structural analysis carried out on the cross-sections and plans of the mine area, a vector of maximum NE-SW opening was determined, acting simultaneously with the formation of mineralization (syn-mineral control), which would have been affected by at least two subsequent faulting events (post-mineral control). From the detailed analysis of the mineralogy and texture of the Inca vein, 9 pulses were discriminated and grouped into 6 main episodes, being 5 of them of hydrothermal nature and 1 of tectonic-hydrothermal type. Pulses P1 and P2 are barren. Pulse P3 precipitates quartz-chalcedony with colloform banded texture, and subrhombic to pseudo-acicular adularia, with ore minerals hosted in dark gingurobands. The ore consists of electrum (10% Au - 90% Ag) and native silver, sulfosalts such as tetrahedrite (Ag-rich), pyrargyrite and polybasite, tellurides and selenides (naumanite and hessite) and base metal sulfides (sphalerite, galena and chalcopyrite). In P4, fine to coarse sulfides precipitate along with massive quartz, the ore minerals correspond to sulfosalts such as tetrahedrite, and base metal sulfides. The evolution of the pulses continues towards a composition dominated by green clays and brecciated textures in P5. Continuously, another siliceous and barren pulse appears (P6), with large crystals of subrhombic adularia. The sequence continues with a black, massive, fine-grained microcrystalline quartz that has the particularity of exhibiting molybdenite showing a strange dendritic texture (P7). In the P8 pulse, a hydraulic and a tectonic component act simultaneously, generating a black matrix breccia where the cement is massive and has Mo anomalies; sometimes it shows bluish patinas that stain the clasts of the previous pulses. Finally, a minor event that forms fine carbonate veins (P9) is recognized. The mineralization would have originated from the ascent of reduced chloride solutions, with neutral to slightly alkaline pH, with salinities of 7% NaCl eq. and with evidence of boiling, while the stable isotope data establish an origin product of mixing between meteoric and magmatic waters. The presence of platycalcite, quartz replacement textures and pseudoacicular adularia, colloform banding and breccias, along with the coexistence between vapor and liquid phase rich fluid inclusions, evidence boiling as the responsible factor for the ore deposition. Finally, due to the characteristics observed, the Inca Vein can be classified as a classic low sulfidation epithermal system, although certain attributes such as moderate salinities, high Ag/Au ratio, the presence of sulfosalts such as tetrahedrite, pyrargyrite and polybasite, and the presence of Fe-poor sphalerite, evidence an intermediate sulfidation state., Facultad de Ciencias Naturales y Museo
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- 2021
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53. Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias Mountains, Alaska.
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Gulick, Sean P. S., Jaeger, John M., Mix, Alan C., Asahi, Hirofumi, Bahlburg, Heinrich, Belanger, Christina L., Berbel, Glaucia B. B., Childress, Laurel, Cowan, Ellen, Drab, Laureen, Forwick, Matthias, Fukumura, Akemi, Ge, Shulan, Gupta, Shyam, Kioka, Arata, Konno, Susumu, LeVay, Leah J., März, Christian, Matsuzaki, Kenji M., and McClymont, Erin L.
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PLEISTOCENE paleoclimatology , *SEDIMENTS , *EROSION , *PLATE tectonics , *CLIMATE change , *MASS (Physics) , *GLACIERS , *HISTORY - Abstract
The article discusses the impact that climatic changes during the mid-Pleistocene period had on the loss of net mass from the St. Elias Mountains in Alaska, including its impact on plate tectonics and erosion. An overview of the role that climate changes played in the erosion of sediments of St. Elias Mountains is provided. The relationship between the expansion of glaciers and erosion is discussed.
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- 2015
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54. Intraplate orogenesis within accreted and scarred lithosphere: Example of the Eurekan Orogeny, Ellesmere Island.
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Heron, Philip J., Pysklywec, Russell N., and Stephenson, Randell
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OROGENY , *LITHOSPHERE , *TOPOGRAPHY , *GEODYNAMICS , *PALEOZOIC stratigraphic geology - Abstract
The Eurekan Orogeny, which created much of the high topography of Ellesmere Island and adjacent Greenland, exhibits a crustal architecture linked to intraplate orogenesis in the Cenozoic. It is generally considered that the rotation of Greenland in the Eocene (related to sedimentary basin formation in Baffin Bay) produced compressional intraplate tectonics. Deformation in the region is notably localized to the Central Ellesmere Domain and the Northern Ellesmere Domain. However, an important tectonic feature of Ellesmere Island is the Hazen Stable Block, which shows horizontal Paleogene Eureka Sound group strata overlying Palaeozoic-age steeply dipping beds. The intense deformation in the Hazen Stable Block is related to continental orogenesis in the Late Silurian–Devonian. Therefore, the Hazen Stable Block is thought to have undergone only minor Eurekan-age (55–35 Ma) deformation, while surrounding (highly deformed) units may have re-activated faults from Paleocene continental amalgamation. Here, high-resolution thermal–mechanical numerical experiments are implemented to explore lithospheric deformation (related to continental shortening) for a range of tectonic scenarios, namely, the presence of inherent deformational “scars” and rheologically strengthened crust/mantle lithosphere (both due to ancient continental accretion). This study marks the first geodynamic excursion to this high Arctic region, and we present some of the first interpretations of the development of Eurekan-age lithospheric evolution. Our results show that a rheologically strong Hazen Stable Block crust produces tectonics similar to the Eurekan Orogeny. Furthermore, lithospheric scars can generate more localized deformation and topography than rheological changes to the lithosphere and may offer a new interpretation on enigmatic intraplate tectonics. [ABSTRACT FROM AUTHOR]
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- 2015
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55. Seismically-induced mass movements and volumetric fluxes resulting from the 2010 Mw = 7.2 earthquake in the Sierra Cucapah, Mexico.
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Barlow, John, Barisin, Ivana, Rosser, Nick, Petley, David, Densmore, Alexander, and Wright, Tim
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EARTHQUAKES , *SEISMIC response , *MASS-wasting (Geology) , *SEDIMENTS , *FLUX (Energy) , *MOUNTAINS - Abstract
The observation that sediment flux from mountain ranges struck by high magnitude earthquakes can be strongly influenced by coseismic mass movements brings into question the nature of coseismic deformation as a net contributor to mountain building. To better constrain the role of high-magnitude earthquakes in orogenesis, high-resolution data of earthquake induced mass wasting is required for areas of differing tectonic, morphological, and climatic settings. Here we compare the erosional flux to the tectonic flux associated with the 2010 M w = 7.2 Sierra El Mayor earthquake in Mexico and examine the landslide patterning of coseismic mass movements associated with this event. The ruptured fault system has a significant strike-slip component with subsidence along the eastern flank and uplift on the western flank of the range. Peak ground acceleration was highest along the steepest sections of the range such that the frequency of landslide occurrence was strongly correlated to slope gradient. Both vertical and horizontal coseismic displacement demonstrated a strong control over landslide initiation. This result suggests that strike-slip systems experience very different landslide patterning to thrust faults during earthquakes. Based on interferometric analysis of synthetic aperture radar images, the earthquake resulted in a total uplifted volume of 41.6 × 10 6 m 3 and a loss of 95.2 × 10 6 m 3 due to subsidence. This suggests a net tectonic volumetric flux of − 53.6 × 10 6 m 3 . Sediment mobilisation by coseismic landslides is estimated at − 2.7 × 10 6 m 3 derived from a manually mapped inventory using SPOT 5 multispectral imagery. Thus, the net volume loss through coseismic subsidence of the mountain range generated a strongly negative mass flux, which was only marginally enhanced by mass wasting. [ABSTRACT FROM AUTHOR]
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- 2015
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56. Provenance Evolution of Age-Calibrated Strata Reveals When and How South China Block Collided With Gondwana
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Yang, C., Li, X.H., Li, Zheng-Xiang, Zhu, M., Lu, K., Yang, C., Li, X.H., Li, Zheng-Xiang, Zhu, M., and Lu, K.
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The South China Block (SCB) has been regarded by many as an integral part of Gondwana, but proposed timing and processes for its accretion to Gondwana vary and remain contentious, largely owing to the lack of reliable Pan-African age paleomagnetic data and tectono-magmatic records from the SCB. Integrated in situ U-Pb ages and Hf-O isotope analyses of detrital zircons from geochronologically well-calibrated Ediacaran-Cambrian sedimentary rocks of western SCB reveal age populations of 2.51, 1.85, 1.20, 0.80, and 0.52 Ga. Detrital zircon age spectra indicate a major tectonic transition for the SCB during 0.56–0.54 Ga, interpreted to reflect the beginning of the collision between SCB-Indochina and NW India blocks. The collisional event lasted until early Ordovician, leading to the suturing of the SCB-Indochina to the northern margin of East Gondwana.
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- 2020
57. ИЗУЧЕНИЕ ГЕОДИНАМИЧЕСКИХ АСПЕКТОВ ГЕОЛОГИЧЕСКОГО РАЗВИТИЯ ТЕРСКО-КАСПИЙСКОГО ПРОГИБА В СВЯЗИ С НЕФТЕГАЗОНОСНОСТЬЮ
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ороген ,субдукция ,плита ,нефтеносность ,plate ,rift ,Терско-Каспийский прогиб ,ocean ,orogenesis ,рифт ,океан ,Terek-Caspian trough ,oil-bearing capacity ,subduction - Abstract
Терско-Каспийский прогиб – крупная структурно-тектоническая единица, расположенная на стыке двух разновозрастных и различных по составу элементов земной коры, которые из-за общей геодинами-ческой обстановки приобрели статус единого мегапрогиба с характерными литолого-стратиграфическими, термобарическими, геохимическими и нефтегенерационными характеристиками, что подтверждается гео-лого-геофизическими исследованиями и промышленными скоплениями в пределах пространства изуче-ния., The Terek-Caspian trough is a large structural-tectonic unit located at the junction of two elements of the Earth's crust of different ages and different composition, which, due to the general geodynamic condition, acquired the status of a united mega-trough with characteristic lithological and stratigraphic, thermo-baric, geochemical and oil-generating characteristics, which is confirmed by geological and geophysical studies and industrial accumula-tions within the study area.
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- 2021
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58. Decoding low-temperature thermochronology signals in mountain belts: modelling the role of rift thermal imprint into continental collision
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Anthony Jourdon, Sébastien Ternois, Frédéric Mouthereau, Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Géodynamique - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre scientifique et Technique Jean Feger (CSTJF), TOTAL FINA ELF, OROGEN research project (Total-BRGM, CNRS-INSU), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)
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010504 meteorology & atmospheric sciences ,Continental collision ,alpine-type orogens ,Inversion (geology) ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences ,010502 geochemistry & geophysics ,01 natural sciences ,rifting ,Mantle (geology) ,Paleontology ,low-temperature thermochronology ,thermal inheritance ,0105 earth and related environmental sciences ,QE1-996.5 ,Rift ,numerical modelling ,Geology ,15. Life on land ,orogenesis ,Thermochronology ,Tectonics ,Mountain formation ,[SDU]Sciences of the Universe [physics] ,13. Climate action ,Accretion (geology) - Abstract
International audience; Resolving the timing of initiation and propagation of continental accretion associated with increasing topography and exhumation is a genuinely challenging task using low-temperature thermochronology. We present an integrated thermo-mechanical and low-temperature thermochronology modelling study of tectonically-inverted hyperextended rift systems. Model low-temperature thermochronology data sets for apatite (U-Th)/He, apatite fission-track, zircon (U-Th)/He and zircon fission-track systems, which are four widely used thermochronometric systems in orogenic settings, are generated from fourteen locations across a model collisional, doubly-vergent orogen. Our approach allows prediction of specific, distinct low-temperature thermochronology signatures for each domain (proximal, necking, hyperextended, exhumed mantle) of the two rifted margins that, in turn, enable deciphering which parts of the margins are involved in orogenic wedge development. Our results show that a combination of zircon (U-Th)/He and apatite fission-track data allows diagnostic investigation of model orogen tectonics and offers the most valuable source of thermochronological information for the reconstruction of the crustal architecture of the model inverted rifted margins. The two thermochronometric systems have actually very close and wide closure windows, allowing to study orogenic processes over a larger temperature range, and therefore over a longer period of time. Comparison of model data for inverted rifted margins with model data for non-inverted, purely thermally-relaxed rifted margins enables assessing the actual contribution of tectonic inversion with respect to thermal relaxation. We apply this approach to one of the best-documented natural examples of inverted rift systems, the Pyrenees. Similarities between our thermochronometric modelling results and published low-temperature thermochronology data from the Pyrenees provide new insights into the evolution of the range from rifting to collision. In particular, they suggest that the core of the Pyrenean orogen, the Axial Zone, consists of the inverted lower plate necking and hyperextended domains while the Pyrenean retrowedge fold-and-thrust belt, the North Pyrenean Zone, represents the inverted upper plate distal rifted margin (exhumed mantle, hyperextended and necking domains). This is in good agreement with previous, independent reconstructions from literature, showing the power that our integrated study offers in identifying processes involved in orogenesis, especially early inversion, as well as in predicting which domains of rifted margins are accreted during mountain building.; Identifier au moyen de la thermochronologie basse température le moment à partir duquel l’accrétion continentale s’amorce et se propage est une tâche difficile. Dans cette étude, nous couplons modélisation thermomécanique de systèmes hyper-amincis inversés et thermochronologie basse température pour prédire la signature thermochronologique de quatre systèmes basse température communément utilisés en domaine orogénique ((U-Th)/He sur apatite, traces de fission sur apatite, (U-Th)/He sur zircon et traces de fission sur zircon). Notre approche de modélisation permet de prédire les signatures thermochronologiques basse température propres à chaque domaine de marge du système extensif (domaine proximal, zone de neck, domaine hyper-aminci et domaine de manteau exhumé). Ces signatures permettent en retour d’identifier les domaines de marge impliqués dans l’accrétion continentale qui suit l’extension. Nos résultats montrent que la combinaison des signatures thermochronologiques des systèmes (U-Th)/He sur zircon et traces de fission sur apatite renseigne sur les processus mis en jeu lors de la formation d’un orogène collisionnel à double vergence, ainsi que sur l’architecture des marges inversées durant l’orogénèse. Les deux systèmes thermochronométriques possèdent en effet des gammes de température de fermeture voisines et relativement larges, permettant d’étudier les processus orogéniques sur un intervalle de températures plus grand, et donc sur une période de temps plus longue. La comparaison des signatures thermochronologiques prédites dans un modèle thermomécanique d’inversion avec celles prédites dans un modèle de relaxation thermique, sans convergence postérieure à l’extension, permet d’apprécier la nécessaire contribution des processus tectoniques d’inversion par rapport au processus de relaxation thermique postrift. Nous appliquons notre approche à l’un des exemples naturels les mieux documentés de systèmes de rift inversé, les Pyrénées. Les similitudes qui existent entre nos prédictions thermochronométriques et les données de thermochronologie basse température publiées pour les Pyrénées fournissent de nouvelles informations sur la formation et l’évolution de l’orogène pyrénéen. En particulier, ces similitudes suggèrent que la zone interne de déformation pyrénéenne, la Zone Axial, est constituée des domaines de neck et hyper-aminci de la plaque inférieure, inversés durant l’accrétion, tandis que le prisme orogénique qui se développe sur la plaque européenne, la Zone Nord-pyrénéenne, représente la marge distale inversée de la plaque supérieure. Ce résultat est en accord avec les précédentes reconstructions publiées de la dynamique pyrénéenne, démontrant ainsi le potentiel de notre approche dans l’identification des processus impliqués dans l’orogenèse, notamment l’inversion précoce, ainsi que dans la prédiction du type de domaine de marge accrété lors de la formation des chaînes de montagnes.
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- 2021
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59. orogenesis
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Herrmann, Helmut and Bucksch, Herbert
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- 2014
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60. Herpetological phylogeographic analyses support a Miocene focal point of Himalayan uplift and biological diversification
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Wenjie Dong, Jie-Qiong Jin, Chen-Qi Lu, Fang Yan, Jing Che, Ke Jiang, David M. Hillis, Ting-Ting Fu, Wei Gao, Hong-Man Chen, Wei Xu, Yun-He Wu, and Ya-Ping Zhang
- Subjects
0106 biological sciences ,0301 basic medicine ,AcademicSubjects/SCI00010 ,EARTH SCIENCES ,Diversification (finance) ,Biodiversity ,Monsoon ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,Paleontology ,biology.animal ,Endemism ,in situ diversification ,biotic assembly ,Multidisciplinary ,biology ,Vertebrate ,Orogeny ,orogenesis ,amphibians and reptiles ,Phylogeography ,030104 developmental biology ,Geography ,Biological dispersal ,monsoon system ,AcademicSubjects/MED00010 ,Research Article - Abstract
The Himalaya are among the youngest and highest mountains in the world, but the exact timing of their uplift and origins of their biodiversity are still in debate. The Himalayan region is a relatively small area but with exceptional diversity and endemism. One common hypothesis to explain the rich montane diversity is uplift-driven diversification—that orogeny creates conditions favoring rapid in situ speciation of resident lineages. We test this hypothesis in the Himalayan region using amphibians and reptiles, two environmentally sensitive vertebrate groups. In addition, analysis of diversification of the herpetofauna provides an independent source of information to test competing geological hypotheses of Himalayan orogenesis. We conclude that the origins of the Himalayan herpetofauna date to the early Paleocene, but that diversification of most groups was concentrated in the Miocene. There was an increase in both rates and modes of diversification during the early to middle Miocene, together with regional interchange (dispersal) between the Himalaya and adjacent regions. Our analyses support a recently proposed stepwise geological model of Himalayan uplift beginning in the Paleocene, with a subsequent rapid increase of uplifting during the Miocene, finally giving rise to the intensification of the modern South Asian Monsoon.
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- 2020
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61. Survival Conditions of Folding in Different Depth During Orogenesis-Deformation in Texas Creek and Chester Dome, USA.
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CAO, Hui and XU, Cuiping
- Subjects
- *
OROGENY , *GRAVITATIONAL collapse , *SEDIMENTARY rocks , *METAMORPHISM (Geology) , *MIGMATITE - Abstract
A succession of 5 FIA trends (foliation intersection or inflection axes in porphyroblasts) preserved in high temperature-low pressure regime PreCambrian rocks in the Texas Creek, Arkansas River region reflected by the fold axial plane traces and schistosity data in this region. Similar fold axial plane trace data measured in Palaeozoic rocks in Chester Dome, Vermont, which is high temperature to medium pressure regime, only preserve the effects of the youngest FIAs of the all 5 FIA sets that obtained in this region. The other three FIA sets have no equivalent fold axial planes. This difference from shallow to deeper orogenic regimes reflects decreasing competency at greater pressure with collapse and unfolding of earlier formed folds. The greater overlying load of rocks has tended to flatten all but the very largest early-formed structures, preserving only those folds that were more recently developed. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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62. Tectonic setting of Cretaceous porphyry copper deposits of northern Chile (28°-30° S) and its relations with magmatic evolution and metallogeny
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Christian Creixell, Javier Fuentes, Esteban Salazar, and Hessel Bierma
- Subjects
Stratigraphy ,Geochemistry ,Central Andes ,010502 geochemistry & geophysics ,01 natural sciences ,Unconformity ,Transpression ,Porphyry copper deposit ,Cretaceous ,Metallogeny ,Metallogenesis ,Geochemistry and Petrology ,0105 earth and related environmental sciences ,Orogenesis ,First episode ,geography ,geography.geographical_feature_category ,010401 analytical chemistry ,Paleontology ,Geology ,0104 chemical sciences ,Volcanic rock ,Porphyry copper ,Back-arc basin - Abstract
Cretaceous porphyry copper deposits of northern Chile (28º-29º30’ S) are genetically related with dacitic to dioritic porphyries and they represent a still poorly-explored target for Cu resources. The porphyries correspond to stocks distributed into two separated discontinuous NS trending belts of different age. The location of these porphyries is generally adjacent to orogen-parallel major fault systems that extend along the studied segment and also have a marked temporal relationship with deformation events registered along these structures. A first episode of Cu-bearing porphyry emplacement took place between 116 and 104 Ma (Mina Unión or Frontera, Cachiyuyo, Punta Colorada, Dos Amigos, Tricolor porphyries). These Early Cretaceous dacite to diorite porphyries are spatially associated with the eastern segments of the Atacama Fault System, which records sinistral transpression that started at 121 Ma producing ground uplift, consequent denudation and exhumation of the Early Cretaceous magmatic arc. This resulted in a change from marine to continental deposition with an angular unconformity in the site of the back-arc basin after of eastward migration of the deformation around 112-110 Ma. At the scale of the continental margin, this deformation is correlated with early stage of the Mochica Orogenic event described in Perú. A second episode of Cu-bearing porphyry emplacement occurred between 92 and 87 Ma (Elisa, Johana, Las Campanas and La Verde deposits), which are spatially and temporally associated with the regional-scale Las Cañas-El Torito reverse fault, active between 89 and 84 Ma, during the Peruvian Orogenic Phase. This fault up thrust to the west part of the Chañarcillo Group rocks (Lower Cretaceous) over the younger upper levels of the Cerrillos Formation (Upper Cretaceous). The integrated geological mapping and geochemical data of the Early to Late Cretaceous volcanic rocks indicates that both Early Cretaceous sinistral transpression and Late Cretaceous east-west compression were not significant in promote changes in magma genesis, except for slight changes in trace element ratios (increase in Th/Ta, Nb/Ta and La/Yb) suggesting that the Late Cretaceous deformation event produced only slightly increase in crustal thickness (>40 km), but far from being comparable to major Cenozoic orogenic phases, at least along the magmatic arc to back-arc domains in the study area. Finally, our study give insights about regional geological parameters that can be used as a first order guide for exploration of Cu resources along Cretaceous magmatic belts of northern Chile, where both Early and Late Cretaceous Cu-bearing porphyry intrusions are restricted to a large structural block bounded to the west and east by Cretaceous fault systems.
- Published
- 2020
63. Signature of Cenozoic orogenic movements in combustion metamorphic rocks: mineralogy and geochronology (example of the Salair-Kuznetsk Basin transition)
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Novikova, S [RAS, Novosibirsk (Russian Federation)]
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- 2008
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64. Early jointing in coal and black shale: Evidence for an Appalachian-wide stress field as a prelude to the Alleghanian orogeny
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Whitaker, A [Penn State University, University Park, PA (United States). Dept. of Geoscience]
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- 2006
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65. The tectonic context of hafnium isotopes in zircon.
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Sundell, K.E. and Macdonald, F.A.
- Subjects
- *
HAFNIUM isotopes , *ZIRCON , *SUTURE zones (Structural geology) , *CRUST of the earth , *PALEOGEOGRAPHY , *GEOCHEMICAL cycles , *DIGITAL preservation , *OROGENIC belts ,GONDWANA (Continent) - Abstract
The assembly and dispersion of continental crust are first-order controls on paleogeography and geochemical cycles. The associated reworking of Earth's crust can be tracked with zircon initial hafnium (ε Hf T) through space and time. Here we apply a new method of quantitative analysis using ε Hf T density estimates based on a compilation of 155,329 ε Hf T values. Investigation of the global database reveals significant geographic and temporal bias in the ε Hf T record associated with sampling and regional tectonic events. Recent research has attempted to address global ε Hf T bias using resampling methods to augment gaps of low ε Hf T data density, which in turn obfuscates tectonic signals and artificially weights outliers. Instead, we evaluate ε Hf T density patterns for both igneous and detrital zircon on eight continental zones demarcated by Paleozoic sutures: Africa, Antarctica, Asia, Australia, Baltica, North America, Peri-Gondwana, and South America. Pairwise two-dimensional quantitative comparison highlights similarity in timing and ε Hf T values between zones, all of which can be linked to documented shared regional tectonism. Integration of all pairwise comparisons reveals that peak similarity corresponds to the timing of supercontinent amalgamation, and that the associated ε Hf T differs depending on the style of supercontinent amalgamation, particularly internal versus external orogenesis. The three most recent supercontinents produced distinctive ε Hf T signals, shared by the constituent continental zones. The supercontinents Rodinia and Pangea were constructed through collisions of marginal arc terranes, peripheral to ancient crust, and did not produce highly enriched ε Hf T values. In contrast, Ediacaran to Cambrian formation of the Gondwana supercontinent was largely the product of internal Pan-African orogens that formed directly after Neoproterozoic Rodinia rifting and arc accretion forming the Arabian Shield. The final assembly of Gondwana was dominated by continent-continent collisions of old radiogenic crust without establishment and accretion of extensive intervening depleted arc terranes, resulting in a more enriched distribution of ε Hf T values compared to prior and subsequent supercontinent formation. The secular ε Hf T record is the product of spatiotemporally biased sampling and preservation of specific orogenic belts with predictable ε Hf T data arrays, modulated by the amalgamation, tenure, and breakup of supercontinents through time. • Zircon Hf is predictable based on tectonic context. • Global Hf records are geographically and temporally biased. • All major Hf excursions can be linked to regional orogenic events. • Zircon Hf is modulated by the amalgamation, tenure, and breakup of supercontinents. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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66. Middle proterozoic tectonic activity in west Texas and eastern New Mexico and analysis of gravity and magnetic anomalies
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Keller, G [Univ. of Texas, El Paso (United States)]
- Published
- 1994
67. Character of the Alleghanian orogeny in the hinterland of the southern Appalachians: Kinematics and tectonic models
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Maher, Jr, H [Univ. of Nebraska, Omaha, NE (United States). Dept. of Geography and Geology]
- Published
- 1994
68. Tectonic geomorphology of the south-central Appalachians: The influence of Triassic extension
- Author
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Henika, W [Virginia Dept. of Mines, Minerals and Energy, Blacksburg, VA (United States). Division of Mineral Resources]
- Published
- 1994
69. Middle Cambrian to Late Ordovician evolution of the Appalachian margin: Foundering of a passive margin to form a subduction zone and volcanic arc
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Washington, P [Washington (Paul A.), Southern Pines, NC (United States)]
- Published
- 1994
70. The internal versus external dynamics in building the Andes (46°30′–47°30′ S) at the Patagonia slab window, with special references to the lower Miocene morphotectonic frontline: a review
- Author
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Jacques Bourgois, Jose Frutos, Maria Eugenia Cisternas, Institut des Sciences de la Terre de Paris (iSTeP), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), and Instituto de Geologia Economica Aplicada
- Subjects
Slab window ,geography ,geography.geographical_feature_category ,Rift ,010504 meteorology & atmospheric sciences ,Subduction ,Andean frontline ,15. Life on land ,Fault (geology) ,Morphotectonic ,010502 geochemistry & geophysics ,01 natural sciences ,Paleontology ,Tectonics ,Basement (geology) ,Uplift dynamics ,[SDU]Sciences of the Universe [physics] ,Patagonia ,South American Plate ,General Earth and Planetary Sciences ,Foreland basin ,Geology ,Orogenesis ,0105 earth and related environmental sciences - Abstract
International audience; New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46°30’ and 47°30′S. The right lateral transtensional Marques–Zeballos Pass fault system (MZPRS) controlled the 800–1200 m uplift of the Andes at 16.1–18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10–15° westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148–178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif.The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge −1 segment (SCR −1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47°S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E–W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N–S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological “twin” of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in–depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3–4 Myr.
- Published
- 2021
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71. Crimean orogene: A nappe interpretation
- Author
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Smirnov, S [Ukrainian State Geological Research Institute, Lvov (Ukraine)]
- Published
- 1993
72. The Gibraltar arc: An orogenic float modified by late transpression
- Author
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Flinch, J [Rice Univ., Houston, TX (United States)]
- Published
- 1993
73. Structure and hydrocarbon habitats of the Polish Carpathian Province
- Author
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Strzetelski, W [Institute of Fossil Fuels, Krakow (Poland)]
- Published
- 1993
74. Tectonic evolution and paleogeography of Europe
- Author
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Leary, D [Exxon Exploration Company, Houston, TX (United States)]
- Published
- 1993
75. Relations between tectonic zones of the Albanides on the basis of results of geophysical studies
- Author
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Frasheri, A [Polytechnic Univ., Tirana (Albania)]
- Published
- 1993
76. Structure and prospects of Alpine basins and foredeep, Aquataine basin: Exploration in the foreland of an Alpine fold and thrust belt
- Author
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Villien, A [Elf Aquitaine Production, Boussens (France)]
- Published
- 1993
77. Paleotopographic control of basal Chesterian sedimentation in the black warrior basin of Alabama
- Author
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Rindsberg, A [Geological Survey of Alabama, Tuscaloosa, AL (United States)]
- Published
- 1993
78. Tectonic implications of REE, Th, and Sc analyses of metamorphosed mudstones, Boyden Cave roof pendant, Sierra Nevada, California
- Author
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Girty, G [San Diego State Univ., CA (United States). Dept. of Geological Sciences]
- Published
- 1993
79. Strength and survival of subducted lithosphere during the Laramide orogeny
- Author
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Spencer, J [Arizona Geological Survey, Tucson, AZ (United States)]
- Published
- 1993
80. The timing of Jurassic orogenesis in the continental arc terrane of the western US Cordillera: Jackston Mountains, northwestern Nevada
- Author
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Wright, J [Rice Univ., Houston, TX (United States). Dept. of Geology and Geophysics]
- Published
- 1993
81. Paleozoic stratigraphy and tectonics in northernmost Nevada: Implications for the nature of the Antler orogeny
- Author
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Wardlaw, B [Geological Survey, Reston, VA (United States)]
- Published
- 1993
82. Paleogeographic and paleotectonic setting of sedimentary basins in the Sevier thrust belt and hinterland, eastern Great Basin
- Author
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Suydam, J [Washington State Univ., Pullman, WA (United States). Dept. of Geology]
- Published
- 1993
83. New evidence for Early Paleozoic orogeny in the eastern Klamath terrane, northern California
- Author
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Masson, P
- Published
- 1993
84. Timing and heat sources for the Barrovian metamorphism, Scotland.
- Author
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Viete, Daniel R., Oliver, Grahame J.H., Fraser, Geoff L., Forster, Marnie A., and Lister, Gordon S.
- Subjects
- *
METAMORPHISM (Geology) , *ZIRCON , *MIGMATITE , *MUSCOVITE , *MAGMATISM , *SILLIMANITE - Abstract
Abstract: New SHRIMP U/Pb zircon ages of 472.2±5.8Ma and 471.2±5.9Ma are presented for the age of peak metamorphism of Barrovian migmatites. 40Ar/39Ar ages for white mica from the Barrovian metamorphic series are presented, and are recalculated using recently-proposed revisions to the 40K decay constants to allow more precise and accurate comparison with U/Pb ages. The 40Ar/39Ar ages are found to vary systematically with increasing metamorphic grade, between c. 465Ma for the biotite zone and c. 461Ma for the sillimanite zone. There is no evidence for any significant metamorphic heating during the first 15Myr of the Grampian Orogeny (before c. 473Ma) or the final 4Myr (after c. 465Ma). The Barrovian metamorphism occurred over a period of ~8Myr within the ~27-Myr Grampian Orogeny. The Barrovian metamorphism records punctuated heating, was temporally and spatially associated with large-scale bimodal magmatism, and developed within crust that was not overthickened. The temporally distinct nature of the Barrovian metamorphic episode within the Grampian Orogeny, and its heating pattern and tectonic context, are not consistent with significant heat contribution from thermal equilibration of overthickened crust. Rather, the Barrovian metamorphism records a transient phase of crustal thermal disequilibrium during the Grampian Orogeny. Temporal and spatial association with Grampian bimodal magmatism is consistent with production of the Barrovian metamorphic series within the middle crust as the result of advection of heat from the lower crust and/or mantle. The Barrovian metamorphic series – the classic example of ‘orogenic regional metamorphism’ – did not form in response to crustal thickening and thermal relaxation, but appears to record large-scale contact metamorphism. [Copyright &y& Elsevier]
- Published
- 2013
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85. The Tauern Window (Eastern Alps, Austria): a new tectonic map, with cross-sections and a tectonometamorphic synthesis.
- Author
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Schmid, Stefan, Scharf, Andreas, Handy, Mark, and Rosenberg, Claudio
- Subjects
- *
CROSS-sectional method , *OROGENIC belts , *LITERATURE databases , *EXTRUSION process , *MIOCENE Epoch - Abstract
We present a tectonic map of the Tauern Window and surrounding units (Eastern Alps, Austria), combined with a series of crustal-scale cross-sections parallel and perpendicular to the Alpine orogen. This compilation, largely based on literature data and completed by own investigations, reveals that the present-day structure of the Tauern Window is primarily characterized by a crustal-scale duplex, the Venediger Duplex (Venediger Nappe system), formed during the Oligocene, and overprinted by doming and lateral extrusion during the Miocene. This severe Miocene overprint was most probably triggered by the indentation of the Southalpine Units east of the Giudicarie Belt, initiating at 23-21 Ma and linked to a lithosphere-scale reorganization of the geometry of mantle slabs. A kinematic reconstruction shows that accretion of European lithosphere and oceanic domains to the Adriatic (Austroalpine) upper plate, accompanied by high-pressure overprint of some of the units of the Tauern Window, has a long history, starting in Turonian time (around 90 Ma) and culminating in Lutetian to Bartonian time (45-37 Ma). [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
86. Does subduction polarity changes below the Alps? Inferences from analogue modelling
- Author
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Luth, Stefan, Willingshofer, Ernst, Sokoutis, Dimitrios, and Cloetingh, Sierd
- Subjects
- *
SUBDUCTION , *POLARITY (Physics) , *CONTINENTS , *LITHOSPHERE , *STRUCTURAL geology , *GEOMETRIC tomography , *EARTH'S mantle , *EARTH (Planet) - Abstract
Abstract: The surface expression of a lateral polarity change of continental mantle lithosphere subduction has been studied by using lithosphere-scale physical models. Key parameters investigated were: the degree of lateral coupling between adjacent domains of opposing subduction polarity, the width of the zone separating the domains, and the lithosphere geometry and rheology. The model results illustrate an asymmetric lithospheric structure induced by deformation of the downgoing plates, which have been separated by a narrow transition zone. A wide and symmetric orogenic wedge overlying a region of thickened mantle lithosphere and hampered subduction characterizes this transition zone. In addition, interaction between the neighboring subduction domains caused downbending of the upper plates and resulted in the lateral termination of crustal structures and lowering of surface topography. The lateral extent of interaction between the domains strongly depends on the degree of coupling between the domains, the rheology of the mantle lithosphere and the amount of bulk shortening. The modelling results have major implications on the interpretation of seismic and tomographic data from the European Alps in terms of the crust and lithosphere geometries. It appears that an observed lateral change of subduction polarity at mantle depth can explain the variations of wedge build-up between the Western/Central and Eastern Alps. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
87. Neoproterozoic to Permian evolution of the Cape Fold Belt, South Africa: Constraints on sediment provenance and orogenesis from high-precision 40Ar/39Ar dating of detrital and metamorphic micas
- Author
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Blewett, Scarlett Caroline Joyce and Blewett, Scarlett Caroline Joyce
- Abstract
The Permian Cape Fold Belt extends 1300 km along the western and southern coastal margins of South Africa. It comprises complexly deformed rocks of the lower-Palaeozoic Cape Supergroup, and Mesozoic parts of the Karoo Supergroup. Large-scale thrusts expose portions of the underlying Saldania Belt; a low-grade metamorphic belt intruded by granites of the ca. 550-500 Ma Cape Granite Suite. Both the Cape Fold Belt and Saldania Belt are segments of ancient continent-scale orogenic systems. The former is thought to be a portion of the Permian Gondwanides Orogen that extended from the Sierra de la Ventana Fold Belt of Argentina, across southern Africa, and into the Falkland (Malvinas) Islands, and Ellsworth-Whitmore Mountains of Antarctica, whereas the latter is considered one of the many Neoproterozoic-Cambrian Pan-African/Brasilliano terranes developed during the amalgamation of west Gondwana. However, fragmentation of Gondwana and separation of the Cape Fold Belt from its neighbouring terranes during the Cretaceous has provided major challenges in understanding both the geodynamic evolution of the poorly exposed Saldania Belt and the mechanics by which the Cape Orogen formed within the Gondwana interior. Gondwanan tectonic models often rely on geochronological provenance studies to not only link sedimentary sources and sinks, but to also correlate sedimentary successions in separated terranes. Previous geochronological provenance studies on the Cape Fold Belt have utilised U-Pb dating of detrital zircons to suggest that sediments of the Saldania Belt and Cape Supergroup were largely sourced from Mesoproterozoic rocks of the Namaqua-Natal Metamorphic Belt to the immediate north and underlying the Cape Fold Belt, as well as undifferentiated Pan-African and/or Brasilliano terranes. However, as zircon is able to survive orogenic recycling and long-distance transport, U-Pb detrital zircon studies have been unable to identify the most recent and proximal sources of sediments
- Published
- 2019
88. Effects of fault-weakening processes on oblique intracontinental rifting and subsequent tectonic inversion
- Author
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Swiss National Science Foundation, Ruh, Jonas Bruno [0000-0001-7035-1453], Ruh, Jonas Bruno, Swiss National Science Foundation, Ruh, Jonas Bruno [0000-0001-7035-1453], and Ruh, Jonas Bruno
- Abstract
In many mountain belts, deformation concentrates along mechanically weak fault zones inherited from earlier tectonic events. This work investigates the effects of two modes of structural weakening on the orientation of rifting and later tectonic inversion with respect to the imposed divergence/convergence direction in a high-resolution 3D finite difference model with a viscous-frictional rheology. In the first set of experiments, weakening consists in a decrease in frictional strength with increasing shear strain. The generated normal faults strike orthogonal to the imposed divergence direction. These faults are reactivated during tectonic inversion and absorb 50 to 70 percent of accumulated strain. In the second set of experiments, frictional strength is a decreasing function of shear strain rate. The generated faults are oblique to the divergence direction, implying oblique fault slip. Fault reactivation depends on the obliquity of the inverted rift to convergence direction, where larger obliquity leads to more intense fault reactivation. These new numerical results are compared to previous analogue and numerical models on the one hand, and natural examples of intracontinental mountain ranges due to tectonic inversion on the other hand. These comparisons demonstrate that both modes of frictional weakening should be taken into account when seeking to understand large-scale rifting and inversion tectonics.
- Published
- 2019
89. Fracture history of the Divide Creek and Wolf Creek anticlines and its relation to Laramide basin-margin tectonism, southern Piceance basin, northwestern Colorado
- Author
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Verbeek, E
- Published
- 1992
90. The Cretaceous record in a northeast-trending transect, northern Utah to east-central Wyoming
- Author
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Merewether, E [U.S. Geological Survey, Denver, CO (United States)]
- Published
- 1991
91. Neogene-Quaternary eustasy and collision tectonism in western Taiwan
- Author
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Teng, L [National Taiwan Univ. (China)]
- Published
- 1991
92. Thermal and structural history of the San Emigdio Mountains, southern San Joaquin basin, California, based on fission-track analysis
- Author
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Corrigan, J [Univ. of Texas, Austin (United States)]
- Published
- 1991
93. Transition from convergence to escape: Field evidence from the West Carpathians
- Author
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Keith, Jr, J [Univ. of South Carolina, Columbia (United States)]
- Published
- 1991
94. Late Palezoic structure of the southern part of the Uinta Basin, Utah, from seismic reflection data
- Author
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Hainsworth, T
- Published
- 1991
95. Trench migration and upper plate strain over a convecting mantle
- Author
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Husson, Laurent
- Subjects
- *
PLATE tectonics , *SUBDUCTION zones , *DEFORMATIONS (Mechanics) , *INTERFACES (Physical sciences) , *DRAG (Aerodynamics) , *CONTROL theory (Engineering) , *EARTH'S mantle , *EARTH (Planet) - Abstract
Abstract: Trench motion and upper plate deformation ultimately respond to mantle flow. Herein I build upon the mantle flow model results of Conrad and Behn (2010) and compute the drag forces underneath all plates, and show that they control the dynamics of plates and plate boundaries. The small misfit angle between between the traction azimuths of mantle traction and absolute plate motion corroborates the idea that convective mantle drag is a prominent driver of plate tectonics. Less intuitive is the fact that the interplay between the drag forces from the upper and lower plates, that amounts to −5 to 8.5×1012 Nm−1 (per unit trench length), dictates both trench migration rates and upper plate deformation. At odds with the classic view that assigns the prime role to the idiosyncrasies of subduction zones (slab age, interplate friction, water content etc), I find that the intrinsic properties of subduction zones in fact only modulate this behavior. More specifically, the mean value of the integrated trenchward mantle drag force from the lower and upper plates (from −2 to 6.5×1012 Nm−1) controls upper plate deformation. Conversely, it is the difference between the lower and upper plates mantle drag forces (from −3 to 10×1012 Nm−1) that controls trench migration rates. In addition, I find that a minimum trenchward force of ∼2.5×1012 Nm−1 must be supplied by mantle drag before trenches can actually advance, and before upper plates undergo compression. This force results from the default tendency of slabs to rollback when solely excited by their own buoyancy, and is thus the effective tensional force that slab pull exerts on the plate interface. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
96. Tectonic development of the North Patagonian Andes and their related Miocene foreland basin (41°30′-43°S).
- Author
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Orts, Darío Leandro, Folguera, Andrés, Encinas, Alfonso, Ramos, Miguel, Tobal, Jonathan, and Ramos, Víctor A.
- Abstract
The Northern Patagonian Andes have been constructed through multiple mechanisms that range from tectonic inversion of extensional structures of Early to Middle Jurassic age in the Main Andes to Oligocene in the Precordilleran region. These have acted during two distinctive orogenic stages, first in late Early Cretaceous and later in Miocene times Late Oligocene extension separates these two contractional periods and is recorded by half-grabens developed in the retroarc region. The last contractional stage coexists with an eastward foreland expansion of the late Miocene arc whose roots are presently exposed as minor granitic stocks and volcanic piles subordinately in the Main Andes, east of the present arc. As a consequence of this orogenic stage a foreland basin has developed, having progressed from 18 Ma in the main North Patagonian Andes, where the mountain front was flooded by a marine transgression corresponding to the base of the Ñirihuau Formation, to 11 Ma in the foreland area. Cannibalization of this foreland basin occurred initially in the hinterland and then progressed to the foreland zone. Blind structures formed a broken foreland at the frontal zone inferred from growth strata geometries. During Pliocene to Quaternary times most of the contractional deformation was dissipated in the orogenic wedge at the time when the arc front retracted to its present position. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
97. Size and exhumation rate of ultrahigh-pressure terranes linked to orogenic stage
- Author
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Kylander-Clark, Andrew R.C., Hacker, Bradley R., and Mattinson, Chris G.
- Subjects
- *
HIGH pressure (Technology) , *OROGENIC belts , *SUBDUCTION , *SLABS (Structural geology) , *LITHOSPHERE , *COMPARATIVE studies , *EARTH'S mantle , *EARTH (Planet) - Abstract
Abstract: A growing set of data indicates a stark contrast between the evolution of two types of ultrahigh-pressure (UHP) terranes: large terranes that evolved slowly (over 10–30Myr), and small terranes that formed and were exhumed on timescales of <10Myr. Here we compare the characteristics – area, thickness, formation rate, exhumation rate, age, and tectonic setting – of these two endmember types of UHP terrane worldwide. We suggest that the two UHP terrane types may form during different orogenic stages because of variations in the buoyancy and traction forces due to different proportions of subducting crust and mantle lithosphere or to different rates of subduction. The initial stages of continent collision involve the subduction of thin continental crust or microcontinents, and thus tectonic forces are dominated by the density of the oceanic slab; subduction rates are rapid and subduction angles are initially steep. However, as collision matures, thicker and larger pieces of continental material are subducted, and the positive buoyancy of the down-going slab becomes more prominent; subduction angles become gentle and convergence slows. Assessing the validity of this hypothesis is critical to understanding the physical and chemical evolution of Earth''s crust and mantle. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
98. Plate motions, Andean orogeny, and volcanism above the South Atlantic convection cell
- Author
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Husson, Laurent, Conrad, Clinton P., and Faccenna, Claudio
- Subjects
- *
PLATE tectonics , *OROGENY , *VOLCANISM , *OCEAN convection , *KINEMATICS , *GEOMETRIC analysis , *MATHEMATICAL models - Abstract
Abstract: The geometric and kinematic evolution of the Andes provides insight onto the nature of the force balance beneath the South American plate. While the Andean load is opposed on its western edge by the force induced by subduction of the Nazca plate, its more elusive eastern counterpart, which we explore herein, requires some contribution from the mantle beneath the South Atlantic. Using a mantle flow model, we show that the Andes owe their existence to basal drag beneath South America caused by a cylindrical convection cell under the South Atlantic. We find that the observed Andean uplift requires both westward push from active upwelling beneath Africa and westward drag toward the downgoing Nazca slab. These mutually-reinforcing downwellings and upwellings amount to 38% and 23% of the total driving force, respectively. Further decomposition reveals that the South Atlantic cell is most vigorous near its center, rendering the net drag force higher where the Andes also reach their highest elevation. Kinematic reconstructions suggest that the South Atlantic cell could have grown owing to the migration of the Nazca slab until ~50Ma. We propose that from 50Ma onwards, the cell may have ceased growing westward because (i) it had reached an optimal aspect ratio and (ii) the Nazca slab became anchored into the lower mantle. Continued westward motion of the plates, however, moved the surface expressions of spreading and convergence away from the upwelling and downwelling arms of this cell. Evidence for this scenario comes from the coeval tectonic, morphologic, and magmatic events in Africa and South America during the Tertiary. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
99. The 3d relief models and structure of the Earth's upper crust in the Amur region.
- Author
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Usikov, V.
- Subjects
- *
CRUST of the earth , *GEOGRAPHIC information systems , *MORPHOTECTONICS , *OROGENY , *GEOLOGY - Abstract
The analysis of 3D relief models of the lower Amur region and several adjacent areas suggested that the structure of the region is related to the horizontal tectonic layering of the upper part of the Amur plate. When it was dislocated to the northwest at the terminal Cretaceous, some fragments of the upper layers were displaced not strictly synchronously but with some lag relative to the whole plate. This scenario was responsible for the formation of the main morphostructural elements of the region: river valleys, mountain ranges, and graben series. These inferences are supported by field observations and some geological data. The proposed hypothesis can also be applied for several other regions. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
100. Los conos de deyección del valle de El General, Costa Rica.
- Author
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Bergoeing, Jean Pierre
- Subjects
- *
OROGENY , *GLACIAL Epoch , *ALLUVIAL fans , *PIEDMONTS (Geology) , *ALLUVIUM - Abstract
The Talamanca's orogenesis and the two last inter-glacial periods are the main factors that built the vast alluvial fans in the Talamanca's Pacific piedmont and where we discovered at least five correlative deposits. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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