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Mark Pecha - One of the best experts on this subject based on the ideXlab platform.
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the syn orogenic sedimentary record of the grenville Orogeny in southwest laurentia
Precambrian Research, 2017Co-Authors: Jacob A Mulder, Katherine Fletcher, Michael J Timmons, Laura J Crossey, Karl E. Karlstrom, George E. Gehrels, Matthew T Heizler, Mark PechaAbstract:Late Mesoproterozoic sedimentary sequences in southwest Laurentia range in age from 1340 to 1035 Ma and record regionally extensive intracratonic sedimentation before and during the Grenville Orogeny in southern Laurentia. This paper examines the specific links between intracratonic sedimentation and orogenesis and develops a new tectonic model for basin formation throughout southwest Laurentia during the Late Mesoproterozoic. New detrital zircon, muscovite, and biotite ages refine the provenance, depositional age, and regional correlations of Late Mesoproterozoic strata throughout southwest Laurentia. These data provide a new view of the Grenville orogen in southern Laurentia as it evolved from a continental margin arc to a continent-continent collision based on the record of inboard sedimentation. Deposition of all Late Mesoproterozoic sequences in southwest Laurentia was facilitated by far-traveled, continental-scale rivers that flowed north off the developing Grenville orogen. Sediment accumulation took place during four discrete basin forming events that can be directly linked to changes in the style of convergence and collision along the southern margin of Laurentia. The oldest basin system (lower Apache and Pahrump Groups) records distal back arc basin sedimentation at 1340–1320 Ma, synchronous with widespread magmatism along the southern margin of Laurentia. Unconformably overlying shallow marine carbonate-bearing sequences (lower Unkar Group and correlatives) were deposited between 1255 and 1230 Ma in a regionally extensive retroarc basin with clastic sediment sourced in part from an active continental arc along the southern margin of Laurentia. Shallow marine and terrestrial siliciclastic sequences (upper Unkar Group and correlatives) were deposited at 1140–1100 Ma and were sourced from unroofing thrust nappes in the orogen to the south in an extensive foreland basin system during continent-continent collision. Finally, coarse-grained siliciclastic deposits of the 1060–1035 Ma Hazel Formation represent a proximal foreland basin recording the final stages of the Grenville Orogeny in southern Laurentia.
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detrital zircon u pb geochronology and hf isotope geochemistry of paleozoic and triassic passive margin strata of western north america
Geosphere, 2014Co-Authors: George E. Gehrels, Mark PechaAbstract:U-Pb geochronologic and Hf isotopic analyses have been conducted on detrital zircons extracted from 36 samples of Neoproterozoic through Triassic passive margin strata from western North America. The data serve as an improved reference for comparison with inboard strata that accumulated on the North American craton and outboard strata belonging to potentially displaced Cordilleran terranes. As expected, this reference documents significant variations in ages and Hf isotope compositions both north-south and also through time. The data also provide insights into the provenance of Cordilleran passive margin strata. During Neoproterozoic, Cambrian, and Early–Middle Devonian time, most grains were shed from relatively local basement rocks and from Mesoproterozoic clastic strata containing 1.2–1.0 Ga grains that originated in the Grenville orogen. This pattern was interrupted during Ordovician time, when much of the Cordilleran margin was blanketed by detritus shed from the northern Canadian Shield. Beginning in Late Devonian time, and continuing through late Paleozoic and Triassic time, most regions were dominated by locally derived detritus (largely recycled from underlying strata), but also received 0.7–0.4 Ga grains that were shed from the Franklinian, Caledonian, Appalachian, and Ouachita-Marathon orogens. This pattern is complicated in southern transects as a result of mid-Paleozoic emplacement of off-shelf assemblages onto the continental margin (e.g., Antler Orogeny) and construction of Permo-Triassic magmatic arcs along the margin. Our data also provide a robust record of the crustal evolution of western North America, with significant production of juvenile crust during late Archean (3.0–2.5 Ga) and Paleoproterozoic (1.78–1.6 Ga) time and phases of mainly crustal reworking at 2.0–1.78, 1.5–1.3, 1.2–1.0, and 0.6–0.2 Ga. This history is somewhat different from that of other continents, with western Laurentia comprising a greater overall proportion of juvenile crust, punctuated by greater degrees of crustal reworking between 2.2 and 1.78 Ga and 0.3–0.2 Ga.
Mikko Nironen - One of the best experts on this subject based on the ideXlab platform.
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the bothnian coupled oroclines of the svecofennian orogen a palaeoproterozoic terrane wreck
Terra Nova, 2014Co-Authors: Raimo Lahtinen, Stephen T Johnston, Mikko NironenAbstract:The accretion of magmatic arcs gives rise to elongate, linear orogens and is a key process in forming new continental crust. Many Precambrian continents are, however, presently equidimensional or have large areas without any clear linearity, such as the central part of the Palaeoproterozoic Svecofennian Orogen (1.92–1.77 Ga). One way of forming an equidimensional continental domain is by buckling of a linear orogen about vertical axes of rotation into one or more coupled oroclines. Here, we reinterpret existing data and demonstrate the occurrence of coupled Bothnian oroclines in the Svecofennian Orogen. Palinspastic restoration of the southern and northern Bothnian oroclines brings a 1000-km-long segment of the Svecofennian Orogen into an originally linear, NW-striking geometry that restores the lithological belts, metamorphic zones and structural vergences to a common direction, and which indicates that the orogen consists of a SW-facing arc, which has been shortened along NE-verging folds and thrust faults.
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the svecofennian orogen a collage of microcontinents and island arcs
Geological Society London Memoirs, 2006Co-Authors: Annakaisa Korja, Raimo Lahtinen, Mikko NironenAbstract:Abstract Based on an integrated study of geological and geophysical data, a tectonic model for the Palaeoproterozoic evolution of the Svecofennian orogen within the Fennoscandian Shield at the northwestern corner of the East European Craton is proposed. The Svecofennian orogen is suggested to have formed during five, partly overlapping, orogenies: Lapland-Savo, Lapland-Kola, Fennian, Nordic and Svecobaltic. The Svecofennian orogen evolved in four major stages, involving microcontinent accretion (1.92-1.88 Ga), large-scale extension of the accreted crust (1.87-1.84 Ga), continent-continent collision (1.87-1.79 Ga) and finally gravitational collapse (1.79 and 1.77 Ga). The stages partly overlapped in time and space, as different processes operated simultaneously in different parts of the plates. In the Lapland-Savo and Fennian orogenies, microcontinents (suspect terranes) and island arcs were accreted to the Karelian microcontinent, which itself was accreting to Laurentia in the Lapland-Kola Orogeny. The formation of the Svecofennian orogen was finalized in two continental collisions producing the Nordic orogen in the west (Fennoscandia-Amazonia) and Svecobaltic orogen in the SSW (Fennoscandia- Sarmatia). The collisions were immediately followed by gravitational collapse.
Zhengxiang Li - One of the best experts on this subject based on the ideXlab platform.
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magmatic and metamorphic events during the early paleozoic wuyi yunkai Orogeny southeastern south china new age constraints and pressure temperature conditions
Geological Society of America Bulletin, 2010Co-Authors: Zhengxiang Li, Xianhua Li, Joanne Wartho, Chris Clark, Wuxian Li, Chuanlin ZhangAbstract:The early Paleozoic Wuyi-Yunkai orogen in South China is a major orogenic belt in East Asia that formed at a similar time as the classic Caledonian Orogeny in Europe. Despite the possibility of its being one of the few examples of intraplate orogenesis in the world, details about the orogen remain poorly defined. In this study, we provide age constraints on metamorphic and magmatic events in the eastern segment of the orogen, and the protoliths of the amphibolite-facies metamorphic rocks found there. By combining previous work with our new metamorphic and petrogenetic analyses, we present the following findings: (1) the Wuyi-Yunkai Orogeny occurred between mid-Ordovician (>460 Ma) and earliest Devonian (ca. 415 Ma) time; (2) amphibolite-facies metamorphism in the eastern Wuyi-Yunkai orogen occurred between ca. 460 and 445 Ma, whereas cooling below 500–300 °C occurred by ca. 420 Ma; (3) the orogen exhibits a clockwise pressure-temperature ( P - T ) path and a maximum pressure of >8 kbar, indicating crustal thickening during the Orogeny; (4) protoliths of the high-grade metamorphic rocks in the eastern segment of the orogen were dominantly Neoproterozoic (840–720 Ma) volcanic and volcaniclastic rift successions and younger deposits formed in a failed rift, and Paleoproterozoic rocks account for only a small proportion of the outcrops; and (5) the analyzed granites indicate a mixed source of Paleoproterozoic basement and Neoproterozoic continental rift rocks, with elevated melt temperatures of >800 °C, which are interpreted as reflecting dehydration melting of basin sediments taken to below midcrustal levels.
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early history of the eastern sibao orogen south china during the assembly of rodinia new mica 40ar 39ar dating and shrimp u pb detrital zircon provenance constraints
Precambrian Research, 2007Co-Authors: Zhengxiang Li, Xianhua Li, Joanne Wartho, Chuanlin Zhang, Sandra Occhipinti, Jian WangAbstract:Abstract The Sibao Orogen in South China is one of the poorest known Grenville-aged orogenic belts through which the Neoproterozoic supercontinent Rodinia assembled. We report here the first UV laser spot 40Ar/39Ar mica and SHRIMP U–Pb zircon ages from a rare Grenville-aged metamorphic complex, the Tianli Schists, in the eastern Sibao Orogen. Our U–Pb zircon provenance ages indicate that the protolith of the Tianli Schists was a clastic sedimentary succession most likely derived from the Yangtze Block. The depositional age of the protolith is younger than 1530 Ma, as constrained by the youngest detrital zircon grains, but is older than 1040 Ma as constrained by the oldest 40Ar/39Ar muscovite ages. The Yangtze Block provenance for the Tianli Schists suggests that the Sibaoan ophiolitic complexes in northeastern Jiangxi, the ca. 970 Ma Xiwan adakitic granite intrusions, and the ca. 900 Ma(?) Xiwan blueschists, all to the northwest of the study region, were likely formed during the closure of a back-arc basin along the margin of the Yangtze Block. Our in situ UV laser 40Ar/39Ar results from S1 and S2 muscovites suggest that the Tianli Schists underwent metamorphism and deformation at 1042 ± 7 Ma to 1015 ± 4 Ma, the oldest known metamorphic event in the eastern Sibao Orogen. Muscovite/biotite cooling ages of ca. 968 ± 4 and 942 ± 8 Ma are recorded by deformed and recrystallised muscovite and biotite, respectively, indicating tectonic reactivation before 900 Ma, during the later stages of the Sibao Orogeny. Together with previous results from the western Sibao Orogen, our work suggests that the closure of the ocean between the Yangtze and Cathaysia Blocks during the assembly of Rodinia was diachronous: ≥1000 Ma at the western Sibao Orogen and ca. 900 Ma at the eastern Sibao Orogen.
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formation of the 1300 km wide intracontinental orogen and postorogenic magmatic province in mesozoic south china a flat slab subduction model
Geology, 2007Co-Authors: Zhengxiang Li, Xianhua LiAbstract:We propose a flat-slab subduction model for Mesozoic South China based on both new sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon data and a synthesis of existing structural, geochronological, and sedimentary facies results. This model not only explains the development of a broad (∼1300-km-wide) intracontinental orogen that migrated from the coastal region into the continental interior between ca. 250 Ma and 190 Ma, but can also account for the puzzling chain of events that followed: the formation of a shallow-marine basin in the wake of the migrating foreland fold-and-thrust belt, and the development of one of the world's largest Basin and Range–style magmatic provinces after the Orogeny. The South China record may serve as an example of the multiple effects of flat-slab subduction, including migrating orogenesis and foreland flexure, synorogenic sagging behind the active orogen, postdelamination lithospheric rebound, and the development of a Basin and Range–style broad magmatic province.
Peter A. Cawood - One of the best experts on this subject based on the ideXlab platform.
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paleoproterozoic magmatic and metamorphic events link yangtze to northwest laurentia in the nuna supercontinent
Earth and Planetary Science Letters, 2016Co-Authors: Peter A. Cawood, Meifu Zhou, Wei Wang, Jun Hong ZhaoAbstract:Abstract Zircons from granitic gneisses in North Vietnam have magmatic cores dated at 2.28–2.19 Ga, and constitute the first reported evidence of continental crust with these ages in the Yangtze Block of the South China Craton. Overgrowths on zircon rims indicate two periods of metamorphism at 1.97–1.95 Ga and ∼1.83 Ga. These events, along with a previously reported ∼2.36 Ga metamorphic overgrowth on ∼2.9 Ga crystallized zircons from the same region, suggest a sequence of events similar to that recorded for the northwestern region of Laurentia and possibly Siberia, which are associated with assembly of the Nuna supercontinent. These include the 2.4–2.3 Ga Arrowsmith Orogen and a range of events in the interval 2.32–1.80 Ga, including accretionary magmatism in northwestern Laurentia and Siberia (2.32–2.07 Ga), the Thelon Orogeny (2.02–1.96 Ga) and the 1.85–1.80 Ga collision between the Superior and Hearne–Rae cratons during the Trans-Hudson Orogen in Laurentia, and the Akitkan Orogen in Siberia (2.03–1.86 Ga). Subsequent attempted breakup of Nuna may be represented by ca. 1.80 to 1.59 Ga consanguineous extension related sedimentation and magmatism in the southwestern Yangtze Block and northwestern Laurentia. These correlations favor location of the Yangtze Block adjacent to northwest Laurentia, and possibly Siberia, within the Nuna supercontinent.
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neoproterozoic Orogeny along the margin of rodinia valhalla orogen north atlantic
Geology, 2010Co-Authors: Peter A. Cawood, R A Strachan, Kathryn Cutts, P D Kinny, Martin Hand, Sergei PisarevskyAbstract:Latest Mesoproterozoic to mid-Neoproterozoic (1030–710 Ma) sedimentation and orogenic activity that developed on the northeast Laurentian substrate around the North Atlantic borderlands and is currently exposed in Scotland, Shetland, East Greenland, Svalbard, and Norway, is herein defined as the Valhalla orogen. The site for the orogen was initiated by ∼95° of clockwise rotation of Baltica with respect to Laurentia at the end of the Mesoproterozoic. This created a triangular ocean basin, the Asgard Sea, which received orogenic detritus from the Grenville-Sveconorwegian-Sunsas orogen. Sedimentary successions within the orogen accumulated during two cycles at 1030–980 Ma and 910–870 Ma, with each cycle terminated and the successions stabilized during tectonothermal episodes involving crustal thickening and igneous activity, some of calc-alkaline affinity, associated with the Renlandian (980–910 Ma) and Knoydartian (830–710 Ma) orogenic events. The Valhalla orogen represents an exterior accretionary orogen that developed along the margin of Laurentia and the Asgard Sea. The early stages of the Valhalla orogen are coeval with the final stages of the Grenville-Sveconorwegian-Sunsas orogen to the south, but are tectonically discrete; they constitute part of an exterior orogen that is entirely distinct from the interior orogen formed between collision of Laurentia, Baltica, and Amazonia.
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terra australis orogen rodinia breakup and development of the pacific and iapetus margins of gondwana during the neoproterozoic and paleozoic
Earth-Science Reviews, 2005Co-Authors: Peter A. CawoodAbstract:Abstract The Pacific Ocean formed through Neoproterozoic rifting of Rodinia and despite a long history of plate convergence, this ocean has never subsequently closed. The record of ocean opening through continental rifting and the inception of ocean convergence through the initiation of subduction are preserved in the Neoproterozoic to late Paleozoic Terra Australis Orogen. The orogen had a pre-dispersal length along the Gondwana margin of approximately 18,000 km and was up to 1600 km wide. It incorporates the Tasman, Ross and Tuhua orogens of Australia, Antarctica and New Zealand, respectively, the Cape Basin of Southern Africa, and Neoproterozoic to Paleozoic orogenic elements along the Andean Cordillera of South America. The Terra Australis Orogen can be divided into a series of basement blocks of either continental or oceanic character that can be further subdivided on the basis of pre-orogenic geographic affinity (Laurentian vs. Gondwanan) and proximity to inferred continental margin sequences (peri-Gondwanan vs. intra-oceanic). These divisions reflect initial tectonic setting and provide an insight into the character of the orogen through time. The orogen incorporates elements that are inferred to have lain outboard of both West and East Laurentia within Rodinia. Subduction of the Pacific Ocean was established at, or close to, the Gondwana margin by around 570 Ma and occurred at about the same time as major global plate reorganization associated with final assembly of Gondwana and the opening of the Iapetus Ocean. The termination of the Terra Australis Orogen at around 300–230 Ma was associated with the assembly of Pangea. It is represented by the Pan-Pacific Gondwanide Orogeny and is marked in east Gondwana by a stepping out in the position of the plate boundary and commencement of the classic late Paleozoic to Mesozoic Gondwanide Orogen. The Pacific has been cited as an example of the declining stage of the Wilson cycle of ocean basins. However, its protracted history of ongoing subduction and the absence of any indication of major continental collisions contrasts with the clear evidence for opening and closing of oceans preserved in the Iapetus/Atlantic and Tethyan realms. The Terra Australis and other orogens that bound the Pacific are accretionary orogens and did not form through the classic Wilson cycle.
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Assembling and reactivating the Proterozoic Capricorn Orogen: lithotectonic elements, orogenies, and significance
Precambrian Research, 2004Co-Authors: Peter A. Cawood, I.m. TylerAbstract:Abstract The Capricorn Orogen was initiated during Palaeoproterozoic suturing events that brought together the Archaean Yilgarn and Pilbara cratons to form the West Australian Craton. The orogen comprises Palaeoproterozoic plutonic and medium- to high-grade metamorphic rocks of the Gascoyne Complex, a series of Palaeoproterozoic volcano-sedimentary and sedimentary basins, including the Ashburton, Blair, Yerrida, Bryah, Padbury and Earaheedy basins, and the deformed margins of the Pilbara and Yilgarn cratons. Major pulses of deformation and metamorphism took place during the ca. 2200 Ma Ophthalmian Orogeny, the 2000–1960 Ma Glenburgh Orogeny, the 1830–1780 Ma Capricorn Orogeny, and a more localized unnamed event at the end of the Palaeoproterozoic (∼1670–1620 Ma). The orogen has been the site of repeated intracratonic reactivation with renewed basin formation, magmatism and Orogeny during the Mesoproterozoic and the Neoproterozoic. The exhumed Palaeoproterozoic components of the orogen are unconformably overlain by the intracratonic Mesoproterozoic Edmund and Collier Basins (Bangemall Supergroup), which have been deformed during the Neoproterozoic Edmundian Orogeny. The Ophthalmian and Glenburgh orogenies affected the northern and southern margins of the orogen, respectively. The former resulted in the development of a foreland basin along the Pilbara Craton margin, whereas the latter is associated with accretion of an allochthonous element, the Glenburgh Terrane of the Gascoyne Complex, to the northwestern margin of the Yilgarn Craton. Effects of the Capricorn Orogeny extended across the entire orogen and provide a younger limit for amalgamation of the Yilgarn and Pilbara cratons. A number of basins developed along both the northern and southern margin of the orogen during this event, and were filled with sediment eroded from the Yilgarn Craton, the Gascoyne Complex, and a presently unexposed early Palaeoproterozoic terrane. The Capricorn Orogeny corresponds with a major phase of continental collision both in Australia and world wide, which appears to mark a major phase of supercontinent assembly. Mineralization within the orogen includes a wide variety of deposit types that can be related to collisional settings, including the world-class iron orebodies of the Hamersley Basin.
Xianhua Li - One of the best experts on this subject based on the ideXlab platform.
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magmatic and metamorphic events during the early paleozoic wuyi yunkai Orogeny southeastern south china new age constraints and pressure temperature conditions
Geological Society of America Bulletin, 2010Co-Authors: Zhengxiang Li, Xianhua Li, Joanne Wartho, Chris Clark, Wuxian Li, Chuanlin ZhangAbstract:The early Paleozoic Wuyi-Yunkai orogen in South China is a major orogenic belt in East Asia that formed at a similar time as the classic Caledonian Orogeny in Europe. Despite the possibility of its being one of the few examples of intraplate orogenesis in the world, details about the orogen remain poorly defined. In this study, we provide age constraints on metamorphic and magmatic events in the eastern segment of the orogen, and the protoliths of the amphibolite-facies metamorphic rocks found there. By combining previous work with our new metamorphic and petrogenetic analyses, we present the following findings: (1) the Wuyi-Yunkai Orogeny occurred between mid-Ordovician (>460 Ma) and earliest Devonian (ca. 415 Ma) time; (2) amphibolite-facies metamorphism in the eastern Wuyi-Yunkai orogen occurred between ca. 460 and 445 Ma, whereas cooling below 500–300 °C occurred by ca. 420 Ma; (3) the orogen exhibits a clockwise pressure-temperature ( P - T ) path and a maximum pressure of >8 kbar, indicating crustal thickening during the Orogeny; (4) protoliths of the high-grade metamorphic rocks in the eastern segment of the orogen were dominantly Neoproterozoic (840–720 Ma) volcanic and volcaniclastic rift successions and younger deposits formed in a failed rift, and Paleoproterozoic rocks account for only a small proportion of the outcrops; and (5) the analyzed granites indicate a mixed source of Paleoproterozoic basement and Neoproterozoic continental rift rocks, with elevated melt temperatures of >800 °C, which are interpreted as reflecting dehydration melting of basin sediments taken to below midcrustal levels.
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early history of the eastern sibao orogen south china during the assembly of rodinia new mica 40ar 39ar dating and shrimp u pb detrital zircon provenance constraints
Precambrian Research, 2007Co-Authors: Zhengxiang Li, Xianhua Li, Joanne Wartho, Chuanlin Zhang, Sandra Occhipinti, Jian WangAbstract:Abstract The Sibao Orogen in South China is one of the poorest known Grenville-aged orogenic belts through which the Neoproterozoic supercontinent Rodinia assembled. We report here the first UV laser spot 40Ar/39Ar mica and SHRIMP U–Pb zircon ages from a rare Grenville-aged metamorphic complex, the Tianli Schists, in the eastern Sibao Orogen. Our U–Pb zircon provenance ages indicate that the protolith of the Tianli Schists was a clastic sedimentary succession most likely derived from the Yangtze Block. The depositional age of the protolith is younger than 1530 Ma, as constrained by the youngest detrital zircon grains, but is older than 1040 Ma as constrained by the oldest 40Ar/39Ar muscovite ages. The Yangtze Block provenance for the Tianli Schists suggests that the Sibaoan ophiolitic complexes in northeastern Jiangxi, the ca. 970 Ma Xiwan adakitic granite intrusions, and the ca. 900 Ma(?) Xiwan blueschists, all to the northwest of the study region, were likely formed during the closure of a back-arc basin along the margin of the Yangtze Block. Our in situ UV laser 40Ar/39Ar results from S1 and S2 muscovites suggest that the Tianli Schists underwent metamorphism and deformation at 1042 ± 7 Ma to 1015 ± 4 Ma, the oldest known metamorphic event in the eastern Sibao Orogen. Muscovite/biotite cooling ages of ca. 968 ± 4 and 942 ± 8 Ma are recorded by deformed and recrystallised muscovite and biotite, respectively, indicating tectonic reactivation before 900 Ma, during the later stages of the Sibao Orogeny. Together with previous results from the western Sibao Orogen, our work suggests that the closure of the ocean between the Yangtze and Cathaysia Blocks during the assembly of Rodinia was diachronous: ≥1000 Ma at the western Sibao Orogen and ca. 900 Ma at the eastern Sibao Orogen.
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formation of the 1300 km wide intracontinental orogen and postorogenic magmatic province in mesozoic south china a flat slab subduction model
Geology, 2007Co-Authors: Zhengxiang Li, Xianhua LiAbstract:We propose a flat-slab subduction model for Mesozoic South China based on both new sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon data and a synthesis of existing structural, geochronological, and sedimentary facies results. This model not only explains the development of a broad (∼1300-km-wide) intracontinental orogen that migrated from the coastal region into the continental interior between ca. 250 Ma and 190 Ma, but can also account for the puzzling chain of events that followed: the formation of a shallow-marine basin in the wake of the migrating foreland fold-and-thrust belt, and the development of one of the world's largest Basin and Range–style magmatic provinces after the Orogeny. The South China record may serve as an example of the multiple effects of flat-slab subduction, including migrating orogenesis and foreland flexure, synorogenic sagging behind the active orogen, postdelamination lithospheric rebound, and the development of a Basin and Range–style broad magmatic province.
