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Helmut Echtler - One of the best experts on this subject based on the ideXlab platform.
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Thermal basin modelling of the Arauco forearc basin, south central Chile - Heat flow and Active Margin tectonics
Tectonophysics, 2010Co-Authors: Philipp P. Kuhn, Helmut Echtler, Ralf Littke, Guillermo AlfaroAbstract:The Arauco basin is part of the coastal forearc domain in South-Central Chile. During its evolution since the Late Cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments. These different environments were established in alternating accretional and erosive subduction tectonic settings along the South Andean Active Margin. Whereas the general development is well understood, inconsistencies arise regarding the origin of the high thermal maturity of Eocene coals and the estimates of vertical movements of the whole area during the Cenozoic. Thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion. Results are based on the analysis of coal samples from surface outcrops, mines and drill cores of ten onshore wells from ENAP/Sipetrol. Newly derived vitrinite reflectance (VR r ) measurements indicated a temperature in the range of 135-150 °C for the oldest sediment unit of the Arauco basin, which was reached in post Eocene times. Furthermore, 1D basin modelling techniques indicate scenarios that could explain the coalification values in the basin's sediments. The models were calibrated against VR r data from drill core samples supplied by ENAP/Sipetrol. A Miocene and an Oligocene subsidence/inversion scenario were considered, while neither could be securely discarded based on the modelling results. Furthermore, it can be shown that the current thermal maturity was not reached by an increased heat flow (HF) or a deep subsidence only. Consequently, a structural inversion accompanied by the erosion of ~3.0±0.4 km depending on the locality in combination with a high HF of ~64±4 mW/m 2 is the best explanation of the available data. The HF, which is high for a forearc setting, can be attributed to the increased temperature of the relatively young subducted Nazca Plate and an additional influence of ascending hot fluids from the subduction zone. The maximum temperature gradient inferred is
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Thermal basin modelling of the Arauco forearc basin, south central Chile — Heat flow and Active Margin tectonics
Tectonophysics, 2009Co-Authors: Philipp P. Kuhn, Helmut Echtler, Ralf Littke, Guillermo AlfaroAbstract:Abstract The Arauco basin is part of the coastal forearc domain in South-Central Chile. During its evolution since the Late Cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments. These different environments were established in alternating accretional and erosive subduction tectonic settings along the South Andean Active Margin. Whereas the general development is well understood, inconsistencies arise regarding the origin of the high thermal maturity of Eocene coals and the estimates of vertical movements of the whole area during the Cenozoic. Thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion. Results are based on the analysis of coal samples from surface outcrops, mines and drill cores of ten onshore wells from ENAP/Sipetrol. Newly derived vitrinite reflectance (VR r ) measurements indicated a temperature in the range of 135–150 °C for the oldest sediment unit of the Arauco basin, which was reached in post Eocene times. Furthermore, 1D basin modelling techniques indicate scenarios that could explain the coalification values in the basin's sediments. The models were calibrated against VR r data from drill core samples supplied by ENAP/Sipetrol. A Miocene and an Oligocene subsidence/inversion scenario were considered, while neither could be securely discarded based on the modelling results. Furthermore, it can be shown that the current thermal maturity was not reached by an increased heat flow (HF) or a deep subsidence only. Consequently, a structural inversion accompanied by the erosion of ~ 3.0 ± 0.4 km depending on the locality in combination with a high HF of ~ 64 ± 4 mW/m 2 is the best explanation of the available data. The HF, which is high for a forearc setting, can be attributed to the increased temperature of the relatively young subducted Nazca Plate and an additional influence of ascending hot fluids from the subduction zone. The maximum temperature gradient inferred is
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turbiditic trench deposits at the south chilean Active Margin a pleistocene holocene record of climate and tectonics
Earth and Planetary Science Letters, 2008Co-Authors: Susanne Blumberg, Helmut Echtler, Frank Lamy, Helge W Arz, Michael Wiedicke, Gerald H. Haug, Onno OnckenAbstract:The Active plate Margin of South America is characterized by a frequent occurrence of large and devastating subduction earthquakes. Here we focus on marine sedimentary records off Southern Chile that are archiving the regional paleoseismic history over the Holocene and Late Pleistocene. The investigated records – Ocean Drilling Program (ODP) Site 1232 and SONNE core 50SL – are located at ~40°S and ~38°S, within the Peru–Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. On the basis of the sedimentological characteristics and the association with the Active Margin of Southern Chile, we assume that the turbidites are mainly seismically triggered, and may be considered as paleo-megaearthquake indicators. However, the long-term changes in turbidite recurrence times appear to be strongly influenced by climate and sea level changes as well. During sea level highstands in the Holocene and Marine Isotope Stage (MIS) 5, recurrence times of turbiditic layers are substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability. In addition, segmented tectonic uplift changes and related drainage inversions likely influenced the postglacial decrease in turbidite frequencies. Glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), on the other hand, are within the same order of magnitude as earthquake recurrence times derived from the historical record and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were high enough to enable recording of the complete sequence of large earthquakes in Southern Chile. Our data thus suggest that earthquake recurrence times on the order of 100 to 200 years are a persistent feature at least during the last glacial period. © 2008 Elsevier B.V. All rights reserved.
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Turbiditic trench deposits at the South-Chilean Active Margin: A Pleistocene–Holocene record of climate and tectonics
Earth and Planetary Science Letters, 2008Co-Authors: Susanne Blumberg, Helmut Echtler, Frank Lamy, Helge W Arz, Michael Wiedicke, Gerald H. Haug, Onno OnckenAbstract:The Active plate Margin of South America is characterized by a frequent occurrence of large and devastating subduction earthquakes. Here we focus on marine sedimentary records off Southern Chile that are archiving the regional paleoseismic history over the Holocene and Late Pleistocene. The investigated records – Ocean Drilling Program (ODP) Site 1232 and SONNE core 50SL – are located at ~40°S and ~38°S, within the Peru–Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. On the basis of the sedimentological characteristics and the association with the Active Margin of Southern Chile, we assume that the turbidites are mainly seismically triggered, and may be considered as paleo-megaearthquake indicators. However, the long-term changes in turbidite recurrence times appear to be strongly influenced by climate and sea level changes as well. During sea level highstands in the Holocene and Marine Isotope Stage (MIS) 5, recurrence times of turbiditic layers are substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability. In addition, segmented tectonic uplift changes and related drainage inversions likely influenced the postglacial decrease in turbidite frequencies. Glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), on the other hand, are within the same order of magnitude as earthquake recurrence times derived from the historical record and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were high enough to enable recording of the complete sequence of large earthquakes in Southern Chile. Our data thus suggest that earthquake recurrence times on the order of 100 to 200 years are a persistent feature at least during the last glacial period. © 2008 Elsevier B.V. All rights reserved.
Onno Oncken - One of the best experts on this subject based on the ideXlab platform.
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turbiditic trench deposits at the south chilean Active Margin a pleistocene holocene record of climate and tectonics
Earth and Planetary Science Letters, 2008Co-Authors: Susanne Blumberg, Helmut Echtler, Frank Lamy, Helge W Arz, Michael Wiedicke, Gerald H. Haug, Onno OnckenAbstract:The Active plate Margin of South America is characterized by a frequent occurrence of large and devastating subduction earthquakes. Here we focus on marine sedimentary records off Southern Chile that are archiving the regional paleoseismic history over the Holocene and Late Pleistocene. The investigated records – Ocean Drilling Program (ODP) Site 1232 and SONNE core 50SL – are located at ~40°S and ~38°S, within the Peru–Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. On the basis of the sedimentological characteristics and the association with the Active Margin of Southern Chile, we assume that the turbidites are mainly seismically triggered, and may be considered as paleo-megaearthquake indicators. However, the long-term changes in turbidite recurrence times appear to be strongly influenced by climate and sea level changes as well. During sea level highstands in the Holocene and Marine Isotope Stage (MIS) 5, recurrence times of turbiditic layers are substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability. In addition, segmented tectonic uplift changes and related drainage inversions likely influenced the postglacial decrease in turbidite frequencies. Glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), on the other hand, are within the same order of magnitude as earthquake recurrence times derived from the historical record and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were high enough to enable recording of the complete sequence of large earthquakes in Southern Chile. Our data thus suggest that earthquake recurrence times on the order of 100 to 200 years are a persistent feature at least during the last glacial period. © 2008 Elsevier B.V. All rights reserved.
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Turbiditic trench deposits at the South-Chilean Active Margin: A Pleistocene–Holocene record of climate and tectonics
Earth and Planetary Science Letters, 2008Co-Authors: Susanne Blumberg, Helmut Echtler, Frank Lamy, Helge W Arz, Michael Wiedicke, Gerald H. Haug, Onno OnckenAbstract:The Active plate Margin of South America is characterized by a frequent occurrence of large and devastating subduction earthquakes. Here we focus on marine sedimentary records off Southern Chile that are archiving the regional paleoseismic history over the Holocene and Late Pleistocene. The investigated records – Ocean Drilling Program (ODP) Site 1232 and SONNE core 50SL – are located at ~40°S and ~38°S, within the Peru–Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. On the basis of the sedimentological characteristics and the association with the Active Margin of Southern Chile, we assume that the turbidites are mainly seismically triggered, and may be considered as paleo-megaearthquake indicators. However, the long-term changes in turbidite recurrence times appear to be strongly influenced by climate and sea level changes as well. During sea level highstands in the Holocene and Marine Isotope Stage (MIS) 5, recurrence times of turbiditic layers are substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability. In addition, segmented tectonic uplift changes and related drainage inversions likely influenced the postglacial decrease in turbidite frequencies. Glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), on the other hand, are within the same order of magnitude as earthquake recurrence times derived from the historical record and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were high enough to enable recording of the complete sequence of large earthquakes in Southern Chile. Our data thus suggest that earthquake recurrence times on the order of 100 to 200 years are a persistent feature at least during the last glacial period. © 2008 Elsevier B.V. All rights reserved.
Guillermo Alfaro - One of the best experts on this subject based on the ideXlab platform.
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Thermal basin modelling of the Arauco forearc basin, south central Chile - Heat flow and Active Margin tectonics
Tectonophysics, 2010Co-Authors: Philipp P. Kuhn, Helmut Echtler, Ralf Littke, Guillermo AlfaroAbstract:The Arauco basin is part of the coastal forearc domain in South-Central Chile. During its evolution since the Late Cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments. These different environments were established in alternating accretional and erosive subduction tectonic settings along the South Andean Active Margin. Whereas the general development is well understood, inconsistencies arise regarding the origin of the high thermal maturity of Eocene coals and the estimates of vertical movements of the whole area during the Cenozoic. Thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion. Results are based on the analysis of coal samples from surface outcrops, mines and drill cores of ten onshore wells from ENAP/Sipetrol. Newly derived vitrinite reflectance (VR r ) measurements indicated a temperature in the range of 135-150 °C for the oldest sediment unit of the Arauco basin, which was reached in post Eocene times. Furthermore, 1D basin modelling techniques indicate scenarios that could explain the coalification values in the basin's sediments. The models were calibrated against VR r data from drill core samples supplied by ENAP/Sipetrol. A Miocene and an Oligocene subsidence/inversion scenario were considered, while neither could be securely discarded based on the modelling results. Furthermore, it can be shown that the current thermal maturity was not reached by an increased heat flow (HF) or a deep subsidence only. Consequently, a structural inversion accompanied by the erosion of ~3.0±0.4 km depending on the locality in combination with a high HF of ~64±4 mW/m 2 is the best explanation of the available data. The HF, which is high for a forearc setting, can be attributed to the increased temperature of the relatively young subducted Nazca Plate and an additional influence of ascending hot fluids from the subduction zone. The maximum temperature gradient inferred is
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Thermal basin modelling of the Arauco forearc basin, south central Chile — Heat flow and Active Margin tectonics
Tectonophysics, 2009Co-Authors: Philipp P. Kuhn, Helmut Echtler, Ralf Littke, Guillermo AlfaroAbstract:Abstract The Arauco basin is part of the coastal forearc domain in South-Central Chile. During its evolution since the Late Cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments. These different environments were established in alternating accretional and erosive subduction tectonic settings along the South Andean Active Margin. Whereas the general development is well understood, inconsistencies arise regarding the origin of the high thermal maturity of Eocene coals and the estimates of vertical movements of the whole area during the Cenozoic. Thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion. Results are based on the analysis of coal samples from surface outcrops, mines and drill cores of ten onshore wells from ENAP/Sipetrol. Newly derived vitrinite reflectance (VR r ) measurements indicated a temperature in the range of 135–150 °C for the oldest sediment unit of the Arauco basin, which was reached in post Eocene times. Furthermore, 1D basin modelling techniques indicate scenarios that could explain the coalification values in the basin's sediments. The models were calibrated against VR r data from drill core samples supplied by ENAP/Sipetrol. A Miocene and an Oligocene subsidence/inversion scenario were considered, while neither could be securely discarded based on the modelling results. Furthermore, it can be shown that the current thermal maturity was not reached by an increased heat flow (HF) or a deep subsidence only. Consequently, a structural inversion accompanied by the erosion of ~ 3.0 ± 0.4 km depending on the locality in combination with a high HF of ~ 64 ± 4 mW/m 2 is the best explanation of the available data. The HF, which is high for a forearc setting, can be attributed to the increased temperature of the relatively young subducted Nazca Plate and an additional influence of ascending hot fluids from the subduction zone. The maximum temperature gradient inferred is
Richard Alan Spikings - One of the best experts on this subject based on the ideXlab platform.
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A revised interpretation of the Chon Aike magmatic province: Active Margin origin and implications for the opening of the Weddell Sea
Lithos, 2021Co-Authors: Joaquin Bastias, Richard Alan Spikings, Teal R. Riley, Alexey Ulianov, A. M. Grunow, Massimo Chiaradia, Francisco HervéAbstract:Abstract Late Triassic – Jurassic igneous rocks of the Antarctic Peninsula and Patagonia provide evidence for the evolution of the Margin of southwestern Gondwana. We present new geochronological (LA-ICP-MS zircon U Pb dates) analyses of 12 intrusive and volcanic rocks, which are complemented by geochemical and zircon isotopic (Hf) as well as whole rock isotopic (Nd, Sr) data. These are combined with similar analyses of 73 other igneous rocks by previous studies, to constrain the magmatic evolution and Late Triassic – Jurassic tectonic setting. The distribution of crystallisation ages reveals four main magmatic pulses that collectively span ~225–145 Ma, all of which have compositions that are consistent with a continental arc setting. The first episode occurred between ~223–200 Ma, and records Active Margin magmatism within the Antarctic Peninsula and northern Patagonia, and reveals the presence of a flat-slab that gave rise to magmatism in eastern Patagonia. After a period of magmatic quiescence (~200–188 Ma), the second episode occurred between ~188 and 178 Ma, with a continuation of arc magmatism above a flattened slab. The third episode spanned ~173–160 Ma, and its geographic distribution suggests the slab was steepening, driving magmatism towards the south and west in Patagonia. Finally, the fourth period occurred between ~157 and ~ 145 Ma, during which time magmas were emplaced along the Antarctic Peninsula and western Patagonia, with no evidence for flat-slab subduction. The analysed rocks include the Chon Aike magmatic province, which has been considered to have been influenced by the break-up of Gondwana, via heating associated with the Karoo plume in southern Africa and the Active Margin in western Patagonia and the Antarctic Peninsula. Our new data and revised compilation now suggest that the Early - Middle Chon Aike Jurassic silicic magmatic province in Patagonia and the Antarctic Peninsula can be entirely accounted by Active Margin processes. We also show that the final stage of Jurassic magmatism (~157–145 Ma) was coincident with rifting that formed oceanic lithosphere of the Weddell Sea and back-arc extension of the Rocas Verdes Basin, potentially revealing the presence of a triple junction located between southern Patagonia and the northern Antarctic Peninsula that led to the disassembly of southern Gondwana.
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Late Triassic-Jurassic Active Margin magmatism in southwestern Gondwana: implications for the tectonic evolution of the Antarctic Peninsula, Patagonia and the Weddell Sea
2020Co-Authors: Joaquin Bastias, Richard Alan Spikings, Teal R. Riley, Alexey Ulianov, A. M. Grunow, Massimo Chiaradia, Urs Schaltegger, Alex Burton-johnsonAbstract:<p>We present new geochemical, isotopic and geochronological analyses of Late Triassic-Jurassic volcanic and intrusive rocks of the Antarctic Peninsula and Patagonia. Whole-rock geochemical data suggest that all of these igneous units formed in an Active Margin setting. This conclusion challenges the current paradigm that Jurassic magmatism of the Chon Aike province formed by the migration of the Karoo mantle plume from Africa towards the Pacific Margin (Pankhurst et al., 2000). KDE analysis of 98 crystallisation ages reveals four main pulses of magmatism (V0: ~223-200 Ma; V1: ~188-178 Ma; V2: ~173-160 Ma; V3: ~157-145 Ma), which are approximately coincident with the episodic nature of the Chon Aike Magmatic Province reported by Pankhurst et al. (2000). Some magmatic units in eastern Patagonia are distal to the hypothetical paleo-trench relative to most Active Margin magmatism. These rocks have geochemical and geochronological characteristics that are indistinguishable from Active Margin-related rocks located ~200km from the palaeo-trench. Thus, we propose that a segment of the slab formed a flat-slab along southwestern Gondwana during the Late Triassic-Jurassic. This flat-slab is probably a temporal extension of the flat-slab episode suggested by Navarrete et al. (2019) for the Late Triassic (V0 episode) in eastern Patagonia. The progressive migration of the flat-slab magmatism to the southwestern Margin of Patagonia suggest an evolution of its architecture during the Jurassic. Further, we propose that the flat-slab magmatism present in eastern Patagonia was triggered by slab failure, where foundering of the slab drove upwelling of hot mantle, forming a broad arc in an inland position in eastern Patagonia. Flat-slab subduction finished during the V3 episode (~157-145 Ma), with a continuation of an Active Margin along the western Margin of the Antarctic Peninsula and Patagonia. Coeval extension in the South Atlantic and in western Patagonia lead to sea floor spreading, the formation of the Weddell Sea (~155-147 Ma; e.g. Konig & Jokat. 2006) and the Rocas Verdes Basin (~150 Ma; e.g. Calderon et al., 2007), respectively. The paleogeographic reconstructions juxtapose the northern Antarctic Peninsula and southern Patagonia during the Late Jurassic (e.g. Jokat et al., 2003), which suggest that the Rocas Verdes Basin and the Weddell Sea are oriented by a ~120&#176; angle and potentially meet in southern Patagonia. This junction of sea-floor spreadings corresponds to the limits of the southern Rocas Verdes Basin with the eastern Weddell Sea oceanic lithosphere. We suggest that these rifts formed part of a triple junction, while the third rift arm should be located with a sub north-south orientation in the Antarctic Peninsula. Vast regions of the Antarctic Peninsula remain unexplored beneath the ice-cap, although we speculate that the third arm may correspond to the Eastern Palmer Land Shear Zone, which currently has a lateral extension of ~1500km (Vaughan & Storey, 2000). This new triple junction would be a Ridge-Ridge-Transform Fault intersection.</p><p>Calderon et al. 2007. JGS,164: 1011-1022.</p><p>Jokat et al. 2003. JGR, 108: 2428.</p><p>Konig & Jokat. 2006, 111: B12102.</p><p>Pankhurst et al. 2000. JP, 41(5): 605-625.</p><p>Navarrete et al. 2019. ESR, 194: 125-159.</p><p>Vaughan & Storey. 2000. JGS, 157: 1243-1256.</p>
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multi proxy isotopic tracing of magmatic sources and crustal recycling in the palaeozoic to early jurassic Active Margin of north western gondwana
Gondwana Research, 2019Co-Authors: Roelant Van Der Lelij, Richard Alan Spikings, Massimo Chiaradia, Axel Gerdes, Torsten Vennemann, Andres MoraAbstract:Abstract We trace source variations of Active Margin granitoids which crystallised intermittently over ~300 Ma in varying kinematic regimes, by combining zircon Lu-Hf isotopic data from Early Palaeozoic to Early Jurassic igneous and metaigneous rocks in the Merida Andes, Venezuela and the Santander Massif, Colombia, with new whole rock Rb/Sr and Sm-Nd isotopic data, and quartz O isotopic data. These new data are unique in South America because they were obtained from discrete magmatic and metamorphic zircon populations, providing a high temporal resolution dataset, and compare several isotopic systems on the same samples. Collectively, these data provide valuable insight into the evolution of the isotopic structure of the continental crust in long-lived Active Margins. Phanerozoic Active Margin-related granitoids in the Merida Andes and the Santander Massif yield zircon Lu-Hf model ages ranging between 0.77 Ga and 1.57 Ga which clearly define temporal trends that can be correlated with changes in tectonic regimes. The oldest Lu-Hf model ages of >1.3 Ga are restricted to granitoids which formed during Barrovian metamorphism and crustal thickening between ~499 Ma and ~473 Ma. These granitoids yield high initial 87Sr/86Sr ratios, suggesting that evolved, Rb-rich middle to upper crust was the major source of melt. Granitoids and rhyolites which crystallised during subsequent extension between ~472 Ma and ~452 Ma yield younger Lu-Hf model ages of 0.80 Ga–1.3 Ga and low initial 87Sr/86Sr ratios, suggesting that they were derived from much more juvenile, Rb-poor sources such as mafic lower crust and mantle-derived melts. The rapid change in magmatic sources at ~472 Ma can be attributed either to reduced crustal assimilation during extension, or a short pulse of crustal growth by addition of juvenile material to the continental crust. Between ~472 Ma and ~196 Ma Lu-Hf model ages remain mostly constant between ~1.0 and ~1.2 Ga. The large scatter and the absence of definite trends in initial 87Sr/86Sr ratios suggest that both mafic, Rb-poor, and evolved Rb-rich sources were important precursors of Active Margin magmas in Colombia and Venezuela throughout the Palaeozoic to the Early Jurassic. Previous studies have shown that the genesis of arc magmas may be stimulated by heat advection to the crust during the underplating of mantle derived melt, but the absence of permanent younging trends in Lu-Hf model ages from ~472 Ma to ~196 Ma suggests that very little new crust was generated during this period in the studied region. An overwhelming majority of the analysed igneous rocks yield zircon Lu-Hf model ages of >1 Ga which may be accounted for by documented local crustal end members of 1 Ga–1.6 Ga, and do not require contributions from the depleted mantle. Therefore, recycling of ~1 Ga and older crust was a dominant process in the north-western corner of Gondwana between ~472 Ma and ~196 Ma. This study shows that whole rock Sm-Nd and zircon Lu-Hf data can be interpreted similarly regarding the age of the source regions, whereas Rb-Sr and O isotope data from the same rocks yield valuable information regarding the geochemical nature of the source.
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High temperature (>350 °C) thermal histories of the long lived (>500 Ma) Active Margin of Ecuador and Colombia: Apatite, titanite and rutile U-Pb thermochronology
Geochimica et Cosmochimica Acta, 2018Co-Authors: Andre Navin Paul, Richard Alan Spikings, Alexey Ulianov, Maria OvtcharovaAbstract:Abstract Quantitative reconstruction of thermal histories can be a powerful tool to study numerous natural processes such as tectonic plate interaction, cratonic stability and extra-terrestrial phenomena such as asteroid ejection. A majority of thermochronological studies have focused on temperatures lower than 300 °C. Few previous studies have demonstrated that U-Pb data from apatite and other accessory phases can be used to recover thermal history information at T > 350 °C. We present U-Pb data from apatite, to constrain the thermal histories of Triassic peralluminous anatectites from the Northern Andes between the temperatures of ∼350–550 °C. The accuracy of the thermal history models is assessed by comparisons with previous geological models, and comparisons with pre-existing and newly acquired U/Pb (titanite and rutile), 40Ar/39Ar (muscovite) and low temperature thermochronological data. This study also examines the feasibility of using a large, regionally dispersed apatite U-Pb data set to obtain continuous thermal history paths along a long-lived (>500 Ma) Active Margin. A second aim of this study is to further test the hypothesis that the dominant mechanism for Pb displacement through apatite is volume diffusion, as opposed to aqueous fluid interaction. The thermal history models derived from the Triassic anatectites exposed in the Andes of Colombia and Ecuador are entirely consistent with lower temperature thermochronological constraints, and previously established geochronological and geochemical constraints. They reveal and quantify trench parallel changes in the amount of Jurassic – Early Cretaceous extension, significantly bolstering and adding to previous tectonic interpretations. Confirmation of the utility of U-Pb thermochronology provides geologists with a powerful tool for investigating the high-temperature thermal evolution of accessory minerals.
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Detrital zircon fingerprint of the Proto-Andes: Evidence for a Neoproterozoic Active Margin?
Precambrian Research, 2008Co-Authors: David Chew, Richard Alan Spikings, Tomas Magna, Christopher L. Kirkland, Aleksandar Mišković, Agustín Cardona, Urs SchalteggerAbstract:Neoproterozoic Palaeogeographic reconstructions of Rodinia conventionally place the western (Proto- Andean) Margin of Amazonia against the eastern (Appalachian) Margin of Laurentia. Separation and formation of the Iapetus Ocean is generally considered to have occurred later at ∼550 Ma. We exam- ine the U-Pb detrital zircon "fingerprint" of autochthonous rocks from the northern and central segments of the Proto-Andean Margin, which formed part of the western Margin of Amazonia during the Late Neoproterozoic-Phanerozoic. The Proto-Andean Margin is clearly the most feasible source region for most of the zircon grains, except for a 550-650 Ma sub-population, broadly age-equivalent to the Brasiliano/Pan- African Orogeny in eastern Amazonia. No obvious source for this detritus is known in the northern and central Andes. Derivation from eastern Amazonia is considered unlikely due to the stark paucity of detritus derived from the core of the Amazonian craton. Instead, we propose that a Late Neoproterozoic magmatic belt is buried beneath the present-day Andean belt or Amazon Basin, and was probably covered during the Eocene-Oligocene. If this inferred Neoproterozoic belt was an Active Margin, it would record the initiation of Proto-Andean subduction and imply at least partial separation of West Gondwana from its conjugate rift Margin of eastern Laurentia prior to ca. 650 Ma. This separation may be linked to the ca. 770-680 Ma A-type magmatism found on eastern Laurentia in the southern Appalachians, and on the Proto-Andean Margin in the Sierra Pampeanas and the Eastern Cordillera of Peru.
Gerald H. Haug - One of the best experts on this subject based on the ideXlab platform.
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turbiditic trench deposits at the south chilean Active Margin a pleistocene holocene record of climate and tectonics
Earth and Planetary Science Letters, 2008Co-Authors: Susanne Blumberg, Helmut Echtler, Frank Lamy, Helge W Arz, Michael Wiedicke, Gerald H. Haug, Onno OnckenAbstract:The Active plate Margin of South America is characterized by a frequent occurrence of large and devastating subduction earthquakes. Here we focus on marine sedimentary records off Southern Chile that are archiving the regional paleoseismic history over the Holocene and Late Pleistocene. The investigated records – Ocean Drilling Program (ODP) Site 1232 and SONNE core 50SL – are located at ~40°S and ~38°S, within the Peru–Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. On the basis of the sedimentological characteristics and the association with the Active Margin of Southern Chile, we assume that the turbidites are mainly seismically triggered, and may be considered as paleo-megaearthquake indicators. However, the long-term changes in turbidite recurrence times appear to be strongly influenced by climate and sea level changes as well. During sea level highstands in the Holocene and Marine Isotope Stage (MIS) 5, recurrence times of turbiditic layers are substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability. In addition, segmented tectonic uplift changes and related drainage inversions likely influenced the postglacial decrease in turbidite frequencies. Glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), on the other hand, are within the same order of magnitude as earthquake recurrence times derived from the historical record and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were high enough to enable recording of the complete sequence of large earthquakes in Southern Chile. Our data thus suggest that earthquake recurrence times on the order of 100 to 200 years are a persistent feature at least during the last glacial period. © 2008 Elsevier B.V. All rights reserved.
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Turbiditic trench deposits at the South-Chilean Active Margin: A Pleistocene–Holocene record of climate and tectonics
Earth and Planetary Science Letters, 2008Co-Authors: Susanne Blumberg, Helmut Echtler, Frank Lamy, Helge W Arz, Michael Wiedicke, Gerald H. Haug, Onno OnckenAbstract:The Active plate Margin of South America is characterized by a frequent occurrence of large and devastating subduction earthquakes. Here we focus on marine sedimentary records off Southern Chile that are archiving the regional paleoseismic history over the Holocene and Late Pleistocene. The investigated records – Ocean Drilling Program (ODP) Site 1232 and SONNE core 50SL – are located at ~40°S and ~38°S, within the Peru–Chile trench, and are characterized by frequent interbedded strata of turbiditic and hemipelagic origin. On the basis of the sedimentological characteristics and the association with the Active Margin of Southern Chile, we assume that the turbidites are mainly seismically triggered, and may be considered as paleo-megaearthquake indicators. However, the long-term changes in turbidite recurrence times appear to be strongly influenced by climate and sea level changes as well. During sea level highstands in the Holocene and Marine Isotope Stage (MIS) 5, recurrence times of turbiditic layers are substantially higher, primarily reflecting a climate-induced reduction of sediment availability and enhanced slope stability. In addition, segmented tectonic uplift changes and related drainage inversions likely influenced the postglacial decrease in turbidite frequencies. Glacial turbidite recurrence times (including MIS 2, MIS 3, cold substages of MIS 5, and MIS 6), on the other hand, are within the same order of magnitude as earthquake recurrence times derived from the historical record and other terrestrial paleoseismic archives of the region. Only during these cold stages sediment availability and slope instability were high enough to enable recording of the complete sequence of large earthquakes in Southern Chile. Our data thus suggest that earthquake recurrence times on the order of 100 to 200 years are a persistent feature at least during the last glacial period. © 2008 Elsevier B.V. All rights reserved.
