U–Pb detrital zircon geochronology and Hf isotopic composition of Permian clastic rocks, Zhen’an basin, South Qinling belt: implications for the Paleozoic tectonic evolution of the Qinling orogenic belt (original) (raw)
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Chinese Science Bulletin, 2008
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Precambrian Research, 2015
Middle Neoproterozoic sedimentary rocks are widespread in the South China Block, especially around the periphery of the Yangtze Block. They are separated into the Sibao and Danzhou groups (and their equivalents) by a "mid-Neoproterozoic angular unconformity" in the south margin of the Yangtze Block. This unconformity, previously interpreted as the evidence of continental collision between the Yangtze and Cathaysia blocks, is crucial for understanding the early-middle Neoproterozoic tectonic regime in the South China Block. We report integrated in situ U-Pb, Hf and O isotopes analyses of detrital zircon grains from sandstones across this unconformity, and use these data to decipher their sedimentary provenances and shed new light on the basin evolution and the tectonic significance of this mid-Neoproterozoic unconformity.
Precambrian Research, 2012
The Tarim Block is an important geologic unit in the reconstruction of the tectonic evolution of the Central Asian Orogenic Belt and the Precambrian Columbia and Rodinia supercontinents. In order to examine the evolution and crustal generation of the Tarim Block, we performed detrital zircon U-Pb dating and in situ Hf isotopic analysis of Devonian sandstones of the Baluntai area in Central Tianshan, which is part of the Tarim Block. Most analyzed zircon grains show oscillatory zoning and have Th/U ratios >0.4, suggesting that they were mainly derived from igneous rocks. A total of about 400 detrital zircon analyses yielded five age populations, namely, early Paleoproterozoic (peak at 2470 Ma), middle Paleoproterozoic (peak at 1858 Ma), early Mesoproterozoic (peak at 1541 Ma), early Neoproterozoic (peak at 952 Ma), and late Neoproterozoic (820-750 Ma). These peak ages are remarkably consistent with the polyphase tectonothermal events that occurred in the Tarim Block. The peak at 2470 Ma indicates the presence of late Neoarchean to early Paleoproterozoic magmatism in the Tarim Block. The two peaks at 1858 Ma and 952 Ma coincide with the two periods of assembly of the Columbia and Rodinia supercontinents. This further suggests that the Tarim Block was part of these two supercontinents. In fact, the age peak of 1541 Ma correlates with the breakup of Columbia, and the age range of 820-750 Ma is interpreted to represent the time of the breakup of Rodinia. The zircon Hf model ages suggest three major stages of crustal evolution at 1.0-1.4 Ga, 1.8-3.3 Ga, and 3.4-3.8 Ga. The zircons exhibit a huge range of ɛ Hf (t) values from −33 to +51, suggesting that they were derived from highly diverse protoliths. However, since most detrital zircons show negative ɛ Hf (t) values, the protoliths of the Baluntai sandstones of Central Tianshan probably comprise rocks of Archean to Proterozoic crust. Owing to the similar Precambrian basement, lithology and age spectra between Central Tianshan and Tarim, it is argued that Central Tianshan belonged to the Tarim Block in the Precambrian time. Furthermore, euhedral zircons with high Th/U ratios (>0.4) yielded a prominent peak of 447 Ma. This can be correlated with an early Paleozoic arc development in Central Tianshan.
Journal of Asian Earth Sciences, 2010
a b s t r a c t U-Pb dating and Hf isotope analyses were performed on detrital zircons from the Upper Permian sandstones in the Ordos and Jiyuan basins, with aims of defining the sediment provenance, and by inference, to determine the influence of the surrounding plates on the evolution of the North China Craton (NCC). Detrital Zircons from these two basins fall into three major groups based on their U-Pb ages: Phanerozoic, Paleoproterozoic, and Neoarchean. The youngest grain from every sample is only slightly younger than the real depositional age of strata. The Phanerozoic zircons from the Jiyuan basin show e Hf (t) ranging from À30.3 to À1.3, suggesting a provenance from the Inner Mongolia Paleo-uplift (245-376 Ma, e Hf (t) = À18.9 to À1.7). A bi-modal distribution of ages and e Hf (t) is noted for detrital zircons from the Ordos basin; one resembles that of the Jiyuan basin, the other is characterized by Early Paleozoic ages and relatively high e Hf (t) values (À10.9 to 7.7). A hybrid source is thus inferred for the Ordos sediments; the Northern Qinling Orogen (428-478 Ma, e Hf (t) = À10.9-7.7) must have served as a source in addition to the Inner Mongolia Paleo-uplift source. This interpretation is consistent with the fact that the Northern Qinling Orogen was an active margin during the Early Paleozoic and suggests that the western part of the Northern Qinling Orogen was elevated relative to the center of the craton during the Late Paleozoic. It is likely that the Early Paleozoic arc-trench in the northern part of the Dabie Orogen was under-thrusted below the NCC due to the subduction of the Yangtze plate during the Triassic. The Inner Mongolia Paleo-uplift was strongly uplifted by subduction of the Paleo-Asian Ocean Plate underneath the northern NCC and functioned as a sediment source for the inner craton during the Late Paleozoic. These results reveal a heterogeneous pattern of destruction of the North China Craton, with its northern margin starting to be activated no later than Late Paleozoic.
Geological Journal, 2019
The temporal-spatial framework of arc amalgamation is an important key for understanding the anatomy of orogenic collages, present and past. The Junggar-Balkhash Ocean was a major branch of the southern Paleo-Asian Ocean where several arcs were amalgamated. Among them, the Dananhu arc with its characteristic juvenile magmatism and lack of Precambrian basement is an efficient recorder of the evolutional history. From our U-Pb and Lu-Hf isotopic analyses of Devonian to Triassic sediments in the Dananhu arc and Permian sediments in the Yamansu-Central Tianshan arc, we discovered two major changes in detrital zircon provenance of the Dananhu arc: (a) An increasing input of Precambrian ages from the Mongolia collage at 850, 1,850, and 2,500 Ma, together with Phanerozoic zircons ranging from 420 to 480 Ma with negative εHf(t) value since ca. 288 Ma; (b) the presence of the Yamansu-Central Tianshan arclike Precambrian age cluster of 1,400-1,600 Ma around 243 Ma. In combination with regional tectonothermal events, these two changes correspond to the formation of the Harlik-Dananhu composite arc in the latest Carboniferousearly Permian followed by its collision with the Yamansu-Central Tianshan arc in the latest Permian-early Triassic, which marks the termination of the eastern Junggar-Balkash Ocean. Analysis of the sedimentary successions within the intraoceanic arcs sheds light on the amalgamation history of the Central Asian Orogenic Belt.
Late Paleozoic tectonic evolution of the northern West Chinese Tianshan Belt
Geodinamica Acta, 2006
The northern West Chinese Tianshan is divided into three subunits: Carboniferous turbidite, ophiolitic mélange and Yili magmatic arc. Stratigraphical and petrological studies suggest that the turbidite and ophiolitic mélange form a subduction complex. The ophiolitic mélange that forms the North Tianshan suture was a result of intra-oceanic tectonism and subsequent redeposition and deformation during the subduction of the North Tianshan oceanic basin. The Yili arc-type granitoids are constained by single zircon U-Pb radiochronology between 361 and 309 Ma. The first-hand kinematic results on the deformed turbidite suggest that this suture zone was reworked by a Permian ductile dextral strike-slip fault. An evolutionary model of the study area allows three events to be distinguished: 1) Late Devonian to Carboniferous subduction of the oceanic basin below the Yili Block producing Yili magmatic rocks and subduction complex, 2) Late Carboniferous complete closure of this basin, 3) Permian right-lateral strike-slip faulting generating pull-apart basins and alkaline magmatism. A prominent reactivation during the Indo-Eurasia collision provoked the northward thrusting of the Paleozoic units upon the Cenozoic sediments of the Junggar Basin, consequently, hiding the bulk of this Late Paleozoic suture.
Lithos, 2009
Southwestern Yunnan is a key region for the understanding of the complex geological evolution of the Paleo-Tethys and the Eurasia-Gondwana collision at the end of the Paleozoic. The southern Lancangjiang zone near the city of Jinghong at the Laotian border hosts MORB-like basaltic andesites and gabbros (Nanlianshan volcano-plutonic complex). Fine-grained gabbro with a U-Pb zircon age of 292 ± 1 Ma and ε Nd (t) of 5.3 is indicative of early Permian sea-floor spreading. The Jinghong area also hosts small granodiorite intrusions which have U-Pb zircon ages of 284 ± 1 Ma to 282 ± 1 Ma, ε Nd (t) of − 3.1 to − 3.6, and initial Sr isotopic ratios of 0.709-0.710. The chemical and isotope signature of the granodiorite is characteristic for an arc setting and is similar to arc-like andesites from the same area. Both the earlier MORB-type magmatism and the granodiorite intrusions can be correlated in time and composition with ophiolites and trondhjemites several 100 km north and point to Permian subduction of oceanic crust between the Lincang Block and the Lanping-Simao Block. The regionally distributed peraluminous Triassic Lincang granite batholith marks the closure of the Paleo-Tethys. The northern Lincang granite gave a zircon U-Pb age of 239 ± 1 Ma, similar to the Baimaxueshan granodioritic intrusion about 250 km north of the Lincang granite, which likely represents the northward extension of the Lincang granite. Nd-model ages range from 1.7 to 2.1 Ga and point to Paleoproterozoic basement which probably represents a fragment of the Yangtze Block. Our data suggest a complex Permo-Triassic history of continental rifting, subduction and collision at the southern border of the Yangtze Block.