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Yong-fei Zheng - One of the best experts on this subject based on the ideXlab platform.

  • paleoproterozoic tectonic evolution of the northern yangtze craton from oceanic subduction through Continental Collision to Continental rifting geochronological and geochemical records of metabasites from the tongbai orogen in central china
    Precambrian Research, 2020
    Co-Authors: Qiangqiang Zhang, Yong-fei Zheng, Xiaoying Gao, Shaobing Zhang
    Abstract:

    Abstract We report for the first time the existence of multistage Paleoproterozoic Collision- and rift-related tectonothermal events in the northern margin of the Yangtze craton. This is achieved through an integrated study of geochronology and geochemistry for Phanerozoic metabasites from the Tongbai orogen in central China. Zircon U-Pb dating and trace element analysis reveal two episodes of magmatism and one episode of metamorphism from ca. 1.96 Ga to 1.63 Ga. Whole-rock geochemistry indicates that the 1.96 Ga metabasite shows typical arc-like trace elemental distribution patterns with enrichment in LREE but depletion in HFSE, whereas the 1.63 Ga metabasites are characterized by enriched mid-ocean ridge basalts (MORB)- or ocean island basalts (OIB)-like trace element distribution patterns with enrichment in LREE but no depletion in HFSE. In addition, a 1.84 Ga granulite facies metamorphic event is recorded by sector zoned domains of zircon from the 1.96 Ga metabasites, showing flat HREE patterns with markedly negative Eu anomalies and a high formation temperature of 825 °C. Integrating the available data from the northern Yangtze craton, we suggest that the 1.96 Ga metabasite was produced by decompressional melting of the metasomatic mantle domain subsequent to exhumation of the high-pressure metamorphic rocks, the 1.84 Ga granulite facies metamorphism was induced by asthenospheric upwelling in response to post-Collisional extension, and the 1.63 Ga magmatism was associated with lithospheric extension due to Continental rifting. Therefore, the Paleoproterozoic metabasites in the Tongbai orogen witness the tectonic evolution from oceanic subduction through Continental Collision to Continental rifting, indicating that the northern margin of the Yangtze craton was involved in the assembly and breakup of supercontinent Columbia. In comparison to the coeval rift-related igneous rocks in other blocks, the geochemical features of 1.63 Ga metabasites in the northern Yangtze craton are similar to those in the northern Australia, but are significantly different from those in the southern Siberia and the northern Laurentia. This indicates a possible connection between the northern Yangtze and the northern Australia before the Columbia breakup.

  • the timing of Continental Collision between india and asia
    Chinese Science Bulletin, 2018
    Co-Authors: Yong-fei Zheng
    Abstract:

    Abstract The timing of Continental Collision between India and Asia has been controversial for a long time because of the difficulty in screening isotopic ages for different types of tectonothermal event along the convergent Continental boundary. After distinguishing the Collisional orogeny from the preCollisional accretionary orogeny and the postCollisional rifting orogeny, an age range of 55 ± 10 Ma is obtained to mark the Collisional orogeny in the Early Cenozoic rather than throughout the Cenozoic. This age range provides the resolution to the timing of tectonic reactivation not only for reworking of the marginal arc systems in the Early Cenozoic but also for overprinting of granulite facies metamorphism on eclogites in the Late Cenozoic. In particular, superimposition of the rifting orogeny on both accretionary and Collisional orogens in the Late Cenozoic is the key to the reactivation of both Gangdese and Himalayan orogens for contemporaneous metamorphism and magmatism at high thermal gradients. Therefore, rise of the plateau may be caused by underplating of the asthenospheric mantle for rifting orogeny in the composite Himalayan–Tibetan orogens after foundering of their roots in the Late Cenozoic.

  • tectonic evolution from oceanic subduction to Continental Collision during the closure of paleotethyan ocean geochronological and geochemical constraints from metamorphic rocks in the hong an orogen
    Gondwana Research, 2015
    Co-Authors: Ligang Zhou, Yong-fei Zheng, Renxu Chen, Qiongxia Xia, Yueheng Yang
    Abstract:

    Abstract A combined study of whole-rock major-trace elements and Sr–Nd isotopes as well as zircon U–Pb ages, trace elements and Lu–Hf isotopes was carried out for high-pressure (HP) and ultrahigh-pressure (UHP) eclogite-facies metamorphic rocks in the Hong'an orogen, China. The results provide insights into the tectonic evolution from oceanic subduction to Continental Collision during the closure of Paleotethyan ocean between the South and North China Blocks. Based on the whole-rock geochemistry, eclogites in the Hong'an orogen are categorized into Continental- and oceanic-type, respectively. The Continental-type eclogites widely occur in the whole orogen, exhibiting general enrichments of LILE and LREE but depletion of HFSE and HREE. Zircon U–Pb dating yields protolith ages of about 750 to 1200 Ma, demonstrating a tectonic affinity to the South China Block. They have both positive and negative e Nd (t) and e Hf (t) values for whole-rock and zircons, suggesting that their protoliths were originated from both juvenile and ancient crustal rocks. The oceanic-type eclogites only occur in the northwestern edge of the orogen, exhibiting mid-ocean ridge basalt (MORB)-like flat REE patterns and arc-like trace element patterns. Zircon U–Pb dating on the relict zircon cores of magmatic origin yields protolith ages of ~ 420 Ma. They have variable e Nd (t) and positive e Hf (t) values and slightly high ( 87 Sr/ 86 Sr) i ratios. These geochemical features suggest that their protoliths are equivalent to backarc basin basalts (BABB) in a Continental margin. The eclogite-facies metamorphic ages and grade are also different for these two types of eclogites. The oceanic-type eclogites were only metamorphosed under HP conditions in the Carboniferous whereas the Continental-type eclogites were mostly metamorphosed under HP to UHP conditions in the Triassic. Thus, the two types of eclogites record the tectonic transition from oceanic subduction to Continental Collision during the closure of the Paleotethyan ocean between the South and North China Blocks. It is possible that the backarc basins were developed in the northern margin of the SCB during the Early Paleozoic, and then became a new subduction zone in which both backarc basin basalts and overlying terrigenous sediments were carried to a depth in the Carboniferous for the HP eclogite-facies metamorphism. Afterwards the Continental crust would start to subduct northwards, eventually leading to the HP to UHP eclogite-facies metamorphism in the Triassic. Therefore, the Hong'an orogen is a composite one that is tectonically different not only from the Qinling–Tongbai orogens to the west but also from the Dabie–Sulu orogens to the east. The occurrence of both oceanic-type and Continental-type eclogites in the Hong'an orogen suggests that the subduction of Continental crust would be gravitationally pulled by the subduction of oceanic crust at the same subduction zone and the HP eclogite-facies metamorphic melange would be exhumed together along the same subduction channel.

  • developing plate tectonics theory from oceanic subduction zones to Collisional orogens
    Science China-earth Sciences, 2015
    Co-Authors: Yong-fei Zheng, Yixiang Chen, Liqun Dai, Zifu Zhao
    Abstract:

    Crustal subduction and Continental Collision is the core of plate tectonics theory. Understanding the formation and evolution of Continental Collision orogens is a key to develop the theory of plate tectonics. Different types of subduction zones have been categorized based on the nature of subducted crust. Two types of Collisional orogens, i.e. arc-continent and continent-continent Collisional orogens, have been recognized based on the nature of Collisional blocks and the composition of derivative rocks. Arc-continent Collisional orogens contain both ancient and juvenile crustal rocks, and reworking of those rocks at the post-Collisional stage generates magmatic rocks with different geochemical compositions. If an orogen is built by Collision between two relatively old Continental blocks, post-Collisional magmatic rocks are only derived from reworking of the old crustal rocks. Collisional orogens undergo reactivation and reworking at action of lithosphere extension, with inheritance not only in the tectonic regime but also in the geochemical compositions of reworked products (i.e., magmatic rocks). In order to unravel basic principles for the evolution of Continental tectonics at the post-Collisional stages, it is necessary to investigate the reworking of orogenic belts in the post-Collisional regime, to recognize physicochemical differences in deep Continental Collision zones, and to understand petrogenetic links between the nature of subducted crust and post-Collisional magmatic rocks. Afterwards we are in a position to build the systematics of Continental tectonics and thus to develop the plate tectonics theory.

  • fluid rock interaction and geochemical transport during protolith emplacement and Continental Collision a tale from qinglongshan ultrahigh pressure metamorphic rocks in the sulu orogen
    American Journal of Science, 2014
    Co-Authors: Yixiang Chen, Yong-fei Zheng, Long Li, Renxu Chen
    Abstract:

    Ultrahigh-pressure (UHP) metamorphic rocks from the Qinglongshan region of the Sulu orogen are comprehensively studied for their whole-rock geochem- istry, mineral O isotopes and zirconology. The metamorphic minerals, which experi- enced eclogite- to amphibolite-facies metamorphism, exhibit low to negative 18 O values, suggesting that the 18 O-depletion of UHP rocks was acquired from their igneous protolith due to high-T meteoric-hydrothermal alteration during the Neopro- terozoic. The O isotope heterogeneity in the protolith was not homogenized during the Triassic UHP metamorphism, indicating very limited fluid flow during orogenesis. However, the fluid flow is locally significant during exhumation of the UHP rocks, resulting in the formation of quartz veins, symplectites and coronas. Geochemical transport due to fluid action is evident in whole-rock geochemistry and mineralogical composition. The UHP rocks exhibit unreasonably low 87 Sr/ 86 Sr ratios at t1 750 Ma but much radiogenic Sr isotopes at t2 230 Ma, suggesting the mobility of water- soluble elements due to hydrothermal alteration during protolith emplacement and metamorphic dehydration during Continental Collision. Fluid-rock interaction during exhumation would also have mobilized Al, Si, Ca and LREE, resulting in the formation of high-pressure veins in the UHP eclogites. The protolith zircon of magmatic origin underwent different types of metamorphic recrystallization in response to fluid- mineral interaction, leading to differential redistribution of trace elements and O-Hf isotopes. Newly grown zircons of metamorphic origin exhibit negative 18 O values, indicating precipitation from negative 18 O fluids that were likely generated by metamor- phic dehydration of the hydrothermally altered negative 18 O rock-forming minerals during the Triassic. The metamorphic zircons exhibit relatively homogeneous Hf isotope compositions, suggesting that fluid Hf isotopes originated from the same Hf isotope composition of the protolith. Relict zircon domains of magmatic origin exhibit both positive Hf (t) and negative Hf (t) values, indicating that the protolith of UHP rocks formed by reworking of both juvenile and ancient crustal rocks.

Yaoling Niu - One of the best experts on this subject based on the ideXlab platform.

  • ttg and potassic granitoids in the eastern north china craton making neoarchean upper Continental crust during micro Continental Collision and post Collisional extension
    Journal of Petrology, 2016
    Co-Authors: Chao Wang, Yaoling Niu, Shuguang Song, Chunjing Wei
    Abstract:

    As the major component, Archean granitoids provide us with an insight into the formation of the early Continental crust. We report the study of a series of Neoarchean granitoids, including tonalite- trondhjemite-granodiorite (TTG) and potassic granitoids, in the Xingcheng region of the eastern North China Craton. Zircon U-Pb dating shows that the TTG granitoids were emplaced in the Neoarchean within a 75 Myr period (2595-2520 Ma), with coeval mafic magmatic enclaves, followed by intrusion of potassic granitoids. The geochemistry of the TTG granitoids is consistent with partial melting of Mesoarchean enriched mafic crustal sources at different depths (up to 10-12 kbar equivalent pressure) during a Continental Collision event. The potassic granitoids are derived from either low-degree melting of Mesoarchean enriched mafic crustal sources or remelting of Mesoarchean TTGs in response to post-Collisional extension, and were hybridized with Neoarchean mantle-derived mafic melts to various degrees. The TTG and potassic granitoids in the Xingcheng region record the evolution from Collision of micro-Continental blocks to post-Collisional extension, consistent with other studies, suggesting that the amalgamation of micro-Continental blocks is what gave rise to the cratonization of the North China Craton at the end of the Archean. The rock assemblage of these granitoids resembles those of syn-and post-Collisional magmatism in Phanerozoic orogenic belts, and the estimated average composition is similar to that of the present-day upper Continental crust, suggesting that a prototype upper Continental crust might have been developed at the end of the Archean from a mixture of TTG and potassic granitoids. Together with concurrent high-grade metamorphism in the North China Craton, we conclude that Collisional orogenesis is responsible for Continental cratonization at the end of the Archean in the North China Craton.

  • syn Collisional granitoids in the qilian block on the northern tibetan plateau a long lasting magmatism since Continental Collision through slab steepening
    Lithos, 2016
    Co-Authors: Hui Huang, Yaoling Niu
    Abstract:

    In this paper we present a new model that can explain the large zircon age spectrum of similar to 510-420 Ma within a single sample from the Gangcha (Gcha) biotite granodiorite and the Huangyuan (HY) two-mica monzogranite on the northern Tibetan Plateau. The large age spread recorded in zircons is characteristic of granitoid samples from the studied region, which is best explained by the long-lasting magmatism since the onset of Continental Collision at similar to 500 Ma, followed by slab steepening and the ultimate slab break-off at similar to 450 Ma. These granitoids have a large major and trace element compositional variation, but limited initial Sr (I-sr[450] = 0.709 to 0.715), Nd (epsilon(Nd[450]) = -6.5 to -3.7), Hf (epsilon(Hf[450]) = -4.3 to -1.5) and Pb (Pb-206/Pb-204([450]) = 17.70 to 17.17; Pb-207/Pb-204([450]) = 15.60 to 15.69; Pb-208/Pb-204([450]) = 38.04 to 38.73) isotopic variation. The small negative whole rock epsilon(Nd[450]) and epsilon(Hf[450]) values are most consistent with the granitoid source being dominated by subducted seafloor materials. The inherited zircons with large negative epsilon(Hf[450]) values (e.g. -50) are indicative of input from the lower Continental crust and subducted sediments. The correlated variations among major elements, trace elements and radiogenic isotopes are best interpreted as reflecting melting-induced mixing of a compositionally heterogeneous source with superimposed effect of varying extent of fractional crystallization and crustal assimilation. The inherited zircons of Palaeo-Proterozoic age and the Archean crustal model ages signify the involvement of ancient basement rocks. (C) 2016 Elsevier B.V. All rights reserved.

  • magmatism during Continental Collision subduction exhumation and mountain collapse in Collisional orogenic belts and Continental net growth a perspective
    Science China-earth Sciences, 2015
    Co-Authors: Shuguang Song, Yaoling Niu, Mengjue Wang, Cao Wang
    Abstract:

    Continental orogens on Earth can be classified into accretionary orogen and Collisional orogen. Magmatism in orogens occurs in every periods of an orogenic cycle, from oceanic subduction, Continental Collision to orogenic collapse. Continental Collision requires the existence of prior oceanic subduction zone. It is generally assumed that the prerequisite of Continental deep subduction is oceanic subduction and its drag force to the connecting passive-margin Continental lithosphere during Continental Collision. Continental subduction and Collision lead to the thickening and uplift of crust, but the formation time of the related magmatism in orogens depends on the heating mechanism of lithosphere. The accretionary orogens, on the other hand, have no strong Continental Collision, deep subduction, no large scale of crustal thrusting, thickening and uplift, and no UHP eclogite-facies metamorphic rocks related to Continental deep subduction. Even though arc crust could be significantly thickened during oceanic subduction, it is still doubtful that syn- or post-Collisional magmatism would be generated. In Collisional orogens, due to Continental deep subduction and significant crustal thickening, the UHP metamorphosed oceanic and Continental crusts will experience decompression melting during exhumation, generating syn-Collisional magmatism. During the orogen unrooting and collapse, post-Collisional magmatism develops in response to lithosphere extension and upwelling of asthenospheric mantle, marking the end of an orogenic cycle. Therefore, magmatism in orogens can occur during the Continental deep subduction, exhumation and uplift after detachment of subducted oceanic crust from Continental crust, and extensional collapse. The time span from Continental Collision to collapse and erosion of orogens (the end of orogenic cycle) is 50-85 Myr. Collisional orogens are the key sites for understanding Continental deep subduction, exhumation, uplift and orogenic collapse. Magmatism in Collisional orogens plays important roles in Continental reworking and net growth.

  • adakitic tonalitic trondhjemitic magmas resulting from eclogite decompression and dehydration melting during exhumation in response to Continental Collision
    Geochimica et Cosmochimica Acta, 2014
    Co-Authors: Shuguang Song, Yaoling Niu, Chunjing Wei, Lifei Zhang
    Abstract:

    Modern adakite or adakitic rocks are thought to result from partial melting of younger and thus warmer subducting ocean crust in subduction zones, with the melt interacting with or without mantle wedge peridotite during ascent, or from melting of thickened mafic lower crust. Here we show that adakitic (tonalitic-trondhjemitic) melts can also be produced by eclogite decompression during exhumation of subducted and metamorphosed oceanic/Continental crust in response to Continental Collision, as exemplified by the adakitic rocks genetically associated with the early Paleozoic North Qaidam ultra-high pressure metamorphic (UHPM) belt on the northern margin of the Greater Tibetan Plateau. We present field evidence for partial melting of eclogite and its products, including adakitic melt, volumetrically significant plutons evolved from the melt, cumulate rocks precipitated from the melt, and associated granulitic residues. This "adakitic assemblage" records a clear progression from eclogite decompression and heating to partial melting, to melt fractionation and ascent/percolation in response to exhumation of the UHPM package. The garnetite and garnet-rich layers in the adakitic assemblage are of cumulate origin from the adakitic melt at high pressure, and accommodate much of the Nb-Ta-Ti. Zircon SHRIMP U-Pb dating shows that partial melting of the eclogite took place at similar to 435-410 Ma, which postdates the seafloor subduction (>440 Ma) and temporally overlaps the UHPM (similar to 440-425 Ma). While the geological context and the timing of adakite melt formation we observe differ from the prevailing models, our observations and documentations demonstrate that eclogite melting during UHPM exhumation may be important in contributing to crustal growth. (C) 2014 Elsevier Ltd. All rights reserved.

  • Continental Collision zones are primary sites for net Continental crust growth a testable hypothesis
    Earth-Science Reviews, 2013
    Co-Authors: Yaoling Niu, Zhidan Zhao, Di-cheng Zhu
    Abstract:

    The significance of the Continental crust (CC) on which we live is self-evident. However, our knowledge remains limited on its origin, its way and rate of growth, and how it has acquired the "andesitic" composition from mantle derived magmas. Compared to rocks formed from mantle derived magmas in all geological environments, volcanic arc rocks associated with seafloor subduction share some common features with the CC; both are relatively depleted in "fluid-insoluble" elements (e.g., Nb, Ta and Ti), but enriched in "fluid-soluble" elements (e.g., U, K and Pb). These chemical characteristics are referred to as the "arc-like signature", and point to a possible link between subduction-zone magmatism and CC formation, thus leading to the "island arc" model widely accepted for the origin of the CC over the past 45 years. However, this "island arc" model has many difficulties: e.g., (1) the bulk arc crust (AC) is basaltic whereas the bulk CC is andesitic; (2) the AC has variably large Sr excess whereas the CC is weakly Sr deficient; and (3) AC production is mass-balanced by subduction erosion and sediment recycling, thus contributing no net mass to the CC growth, at least in the Phanerozoic. Our recent and ongoing studies on granitoid rocks (both volcanic and intrusive) formed in response to the India Asia Continental Collision (similar to 55 +/- 10 Ma) show remarkable compositional similarity to the bulk CC with the typical "arc-like signature". Also, these synCollisional granitoid rocks exhibit strong mantle isotopic signatures, meaning that they were recently derived from a mantle source. The petrology and geochemistry of these synCollisional granitoid rocks are most consistent with an origin via partial melting of the upper ocean crust (i.e., last fragments of underthrusting ocean crust upon Collision) under amphibolite facies conditions, adding net mantle-derived materials to form juvenile CC mass. This leads to the logical and testable hypothesis that Continental Collision produces and preserves the juvenile crust, and hence maintains net CC growth.

M Santosh - One of the best experts on this subject based on the ideXlab platform.

  • multi stage crustal melting from late permian back arc extension through middle triassic Continental Collision to late triassic post Collisional extension in the east kunlun orogen
    Lithos, 2020
    Co-Authors: M Santosh, Xu Zhao, Junhao Wei, Jan Marten Huizenga, Jiajie Chen, Dianzhong Wang
    Abstract:

    Abstract The East Kunlun Orogen is an important part of the East Tethys region and has received significant attention with regards to the evolution of the Tethys Ocean. This contribution presents geochronological, whole-rock major and trace element geochemical, and Sr-Nd-Hf isotopic data of magmatic rocks within the Kengdenongshe polymetallic deposit in the eastern part of the East Kunlun Orogen. Here, we report zircon U Pb ages of ca. 257 Ma and ca. 211 Ma for granite porphyry intrusions, and ca. 240 Ma for the rhyolitic tuff. These rocks are characterized by high SiO2, variable Al2O3 and K2O, low Na2O, MgO and CaO contents, and high A/CNK ratios, which is typical of S-type granitic rocks. They exhibit large-ion lithophile element enrichment, depletion of high field strength elements, have low (La/Yb)N ratios, and negative Eu anomalies. They also display variable (87Sr/86Sr)i ratios (0.709981 to 0.720907), negative eNd (t) values (−8.7 to −5.5), and a wide (enriched) zircon eHf (t) range (−10.1 to −0.8). The geochemical and isotope data indicate magma derivation through dehydration melting of heterogeneous crustal sources including clay-poor meta-sedimentary rocks and amphibolite, which are both parts of the East Kunlun Orogen basement. These results provide evidence for the evolution of the Paleo-Tethys Ocean in the East Kunlun Orogen including Late Permian (266–255 Ma) back-arc extension, Late Permian to Middle Triassic (255–240 Ma) subduction, Middle Triassic (240–225 Ma) Continental Collision, and Late Triassic (

  • early palaeozoic high pressure granulites from the dunhuang block northeastern tarim craton constraints on Continental Collision in the southern central asian orogenic belt
    Journal of Metamorphic Geology, 2012
    Co-Authors: K Q Zong, M Santosh, Z M Zhang, Yongsheng Liu, W Wang
    Abstract:

    The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary collages in the world, and records a prolonged sequence of subduction-accretion and Collision processes. The Tarim Craton is located at the southernmost margin of the CAOB. In this study, the discovery of early Palaeozoic high-pressure (HP) granulites from the Dunhuang block in the northeastern Tarim Craton is reported, and these rocks are characterized through detailed petrological and geochronological studies. The peak mineral assemblage of the HP mafic granulite is garnet + clinopyroxene + plagioclase + quartz + rutile, which is overprinted by amphibolite facies retrograde metamorphic assemblages. The calculated P-T conditions of the peak metamorphism are � 1.4-1.7 GPa and � 800 � C. The retrograde P-T conditions are � 0.7 GPa and � 700 � C. The metamorphic zircon grains from the HP mafic granulite show homogeneous CL-images, low Th ⁄ U ratios and flat HREE patterns and yield a weighted mean 206 Pb ⁄ 238 U age of 444 ± 5 Ma. The metamorphic zircon grains from the associated kyanite-bearing garnet gneiss and garnet-mica schist show a similar 206 Pb ⁄ 238 U age of 429 ± 3 and 435 ± 4 Ma, respectively. The c. 440-430 Ma age is interpreted to mark the timing of HP granulite facies metamorphism in the Dunhuang block. The results from this study suggest that the Dunhuang block experienced Continental subduction prior to the early Palaeozoic Collisional orogeny between the northeastern Tarim Craton and the southern CAOB, and the Dunhuang area could be considered as the southward extension of the CAOB. It is suggested that the Continental Collision in the eastern part involving the Dunhuang block of the southern CAOB may have occurred c. 120 Ma earlier than in the western part involving the Tianshan orogen.

Jiři Konopasek - One of the best experts on this subject based on the ideXlab platform.

  • anticlockwise metamorphic pressure temperature paths and nappe stacking in the reisa nappe complex in the scandinavian caledonides northern norway evidence for weakening of lower Continental crust before and during Continental Collision
    Solid Earth, 2019
    Co-Authors: Carly Faber, Erling J. K. Ravna, Holger Stunitz, Deta Gasser, Petr Jeřabek, Katrin Kraus, Fernando Corfu, Jiři Konopasek
    Abstract:

    This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kafjord, and Nordmannvik nappes) in northern Troms, Nor-way. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure-temperature (P-T) conditions of deformation and metamorphism during nappe stacking that facilitated crustal thickening during Continental Collision. Five samples taken from different parts of the RNC reveal an anticlockwise P-T path attributed to the effects of early Silurian heating (D 1) followed by thrusting (D 2). At ca. 439 Ma during D 1 the Nordmannvik Nappe reached the highest meta-morphic conditions at ca. 780 • C and ∼ 9-11 kbar inducing kyanite-grade partial melting. At the same time the Kafjord Nappe was at higher, colder, levels of the crust ca. 600 • C, 6-7 kbar and the Vaddas Nappe was intruded by gabbro at > 650 • C and ca. 6-9 kbar. The subsequent D 2 shearing occurred at increasing pressure and decreasing temperatures ca. 700 • C and 9-11 kbar in the partially molten Nordman-nvik Nappe, ca. 600 • C and 9-10 kbar in the Kafjord Nappe, and ca. 640 • C and 12-13 kbar in the Vaddas Nappe. Multi-stage titanite growth in the Nordmannvik Nappe records this evolution through D 1 and D 2 between ca. 440 and 427 Ma, while titanite growth along the lower RNC boundary records D 2 shearing at 432±6 Ma. It emerges that early Silurian heating (ca. 440 Ma) probably resulted from large-scale magma underplating and initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual thrust slices (nappe units). This tectonic style contrasts with subduction of mechanically strong Continental crust to great depths as seen in, for example, the Western Gneiss Region further south.

  • Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower Continental crust before and during Continental Collision
    Solid Earth, 2019
    Co-Authors: Carly Faber, Erling J. K. Ravna, Holger Stunitz, Deta Gasser, Petr Jeřabek, Katrin Kraus, Fernando Corfu, Jiři Konopasek
    Abstract:

    This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kafjord, and Nordmannvik nappes) in northern Troms, Nor-way. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure-temperature (P-T) conditions of deformation and metamorphism during nappe stacking that facilitated crustal thickening during Continental Collision. Five samples taken from different parts of the RNC reveal an anticlockwise P-T path attributed to the effects of early Silurian heating (D 1) followed by thrusting (D 2). At ca. 439 Ma during D 1 the Nordmannvik Nappe reached the highest meta-morphic conditions at ca. 780 • C and ∼ 9-11 kbar inducing kyanite-grade partial melting. At the same time the Kafjord Nappe was at higher, colder, levels of the crust ca. 600 • C, 6-7 kbar and the Vaddas Nappe was intruded by gabbro at > 650 • C and ca. 6-9 kbar. The subsequent D 2 shearing occurred at increasing pressure and decreasing temperatures ca. 700 • C and 9-11 kbar in the partially molten Nordman-nvik Nappe, ca. 600 • C and 9-10 kbar in the Kafjord Nappe, and ca. 640 • C and 12-13 kbar in the Vaddas Nappe. Multi-stage titanite growth in the Nordmannvik Nappe records this evolution through D 1 and D 2 between ca. 440 and 427 Ma, while titanite growth along the lower RNC boundary records D 2 shearing at 432±6 Ma. It emerges that early Silurian heating (ca. 440 Ma) probably resulted from large-scale magma underplating and initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual thrust slices (nappe units). This tectonic style contrasts with subduction of mechanically strong Continental crust to great depths as seen in, for example, the Western Gneiss Region further south.

Carly Faber - One of the best experts on this subject based on the ideXlab platform.

  • anticlockwise metamorphic pressure temperature paths and nappe stacking in the reisa nappe complex in the scandinavian caledonides northern norway evidence for weakening of lower Continental crust before and during Continental Collision
    Solid Earth, 2019
    Co-Authors: Carly Faber, Erling J. K. Ravna, Holger Stunitz, Deta Gasser, Petr Jeřabek, Katrin Kraus, Fernando Corfu, Jiři Konopasek
    Abstract:

    This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kafjord, and Nordmannvik nappes) in northern Troms, Nor-way. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure-temperature (P-T) conditions of deformation and metamorphism during nappe stacking that facilitated crustal thickening during Continental Collision. Five samples taken from different parts of the RNC reveal an anticlockwise P-T path attributed to the effects of early Silurian heating (D 1) followed by thrusting (D 2). At ca. 439 Ma during D 1 the Nordmannvik Nappe reached the highest meta-morphic conditions at ca. 780 • C and ∼ 9-11 kbar inducing kyanite-grade partial melting. At the same time the Kafjord Nappe was at higher, colder, levels of the crust ca. 600 • C, 6-7 kbar and the Vaddas Nappe was intruded by gabbro at > 650 • C and ca. 6-9 kbar. The subsequent D 2 shearing occurred at increasing pressure and decreasing temperatures ca. 700 • C and 9-11 kbar in the partially molten Nordman-nvik Nappe, ca. 600 • C and 9-10 kbar in the Kafjord Nappe, and ca. 640 • C and 12-13 kbar in the Vaddas Nappe. Multi-stage titanite growth in the Nordmannvik Nappe records this evolution through D 1 and D 2 between ca. 440 and 427 Ma, while titanite growth along the lower RNC boundary records D 2 shearing at 432±6 Ma. It emerges that early Silurian heating (ca. 440 Ma) probably resulted from large-scale magma underplating and initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual thrust slices (nappe units). This tectonic style contrasts with subduction of mechanically strong Continental crust to great depths as seen in, for example, the Western Gneiss Region further south.

  • Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower Continental crust before and during Continental Collision
    Solid Earth, 2019
    Co-Authors: Carly Faber, Erling J. K. Ravna, Holger Stunitz, Deta Gasser, Petr Jeřabek, Katrin Kraus, Fernando Corfu, Jiři Konopasek
    Abstract:

    This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kafjord, and Nordmannvik nappes) in northern Troms, Nor-way. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure-temperature (P-T) conditions of deformation and metamorphism during nappe stacking that facilitated crustal thickening during Continental Collision. Five samples taken from different parts of the RNC reveal an anticlockwise P-T path attributed to the effects of early Silurian heating (D 1) followed by thrusting (D 2). At ca. 439 Ma during D 1 the Nordmannvik Nappe reached the highest meta-morphic conditions at ca. 780 • C and ∼ 9-11 kbar inducing kyanite-grade partial melting. At the same time the Kafjord Nappe was at higher, colder, levels of the crust ca. 600 • C, 6-7 kbar and the Vaddas Nappe was intruded by gabbro at > 650 • C and ca. 6-9 kbar. The subsequent D 2 shearing occurred at increasing pressure and decreasing temperatures ca. 700 • C and 9-11 kbar in the partially molten Nordman-nvik Nappe, ca. 600 • C and 9-10 kbar in the Kafjord Nappe, and ca. 640 • C and 12-13 kbar in the Vaddas Nappe. Multi-stage titanite growth in the Nordmannvik Nappe records this evolution through D 1 and D 2 between ca. 440 and 427 Ma, while titanite growth along the lower RNC boundary records D 2 shearing at 432±6 Ma. It emerges that early Silurian heating (ca. 440 Ma) probably resulted from large-scale magma underplating and initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual thrust slices (nappe units). This tectonic style contrasts with subduction of mechanically strong Continental crust to great depths as seen in, for example, the Western Gneiss Region further south.