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Abstract
The Early-Middle Jurassic Yan'an Formation widely distributed in the northwestern margin of Ordos Basin, and the outcrops scattered limitedly with similar lithological features. Many disputes still exist about the source areas of Yan'an Formation due to the tremendous geological reformation since the Late Cretaceous. The zircon Laser-Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) U-Pb dating was used to determine the ages of the source areas of the Yan'an Formation in the region. There are three samples selected from the sandstone of Yan'an Formation in two areas, altogether 210 grains were dated, and 193 valid zircon ages were obtained. Most zircons from the samples of Helan Mountain showed circular belt images under the cathodoluminescence microscope and displayed the left-oblique distribution pattern of rare earth elements. Most of those zircons have the Th/U larger than 0.4 indicating the magmatic origin, and a few zircons were from the metamorphic rock in the area. Most zircon U-Pb dating ages are mainly of the Paleozoic with the major peak in the Permian. The secondary ages are of the Proterozoic. The zircons from Zhuozi Mountain area are with the similar characteristics both in the images under the cathodoluminescence microscope and in the rare earth element distribution pattern. There exists much difference in the zircon ages between the two areas. The old ages in Zhuozi Mountain possess great proportions; 66.7% are of the Late Archean-Proterozoic (mainly the Proterozoic); only 22.7% of the total ages belong to the Permian, and 10.6% are of the Early-Middle Triassic. Compared with the ages of surrounding ancient rocks, it is concluded that the main sources of the Early-Middle Jurassic in the northwest margin of Ordos Basin were the Proterozoic magmatic and metamorphic rocks in the Alashan Paleo-Block; for the north of Ordos Basin, the main source was the Hercynian granite in the Alashan Paleo-Block. The main provenance in Helan Mountain was the Hercynian magmatic rocks in the Alashan Paleo-Block, and the secondary source was the Proterozoic magmatic and metamorphic rocks(Helan Mountain complex)for its northwest. While the principal source area in the Zhuozi Mountain was Proterozoic magmatic and metamorphic rocks for the northwest and the Hercynian magmatic rocks and Early-Middle Triassic magmatic rocks acted as the minor source. There is difference in provenance ages among the two studied areas and the Ciyaobao area. More researches from the sedimentary and petrology need to be done to further describe the provenance attribute. ©, 2015, The Editorial Office of Earth Science Frontiers. All right reserved.
... 16 The Baiyunebo area features a peak age of 269 Ma for granodioritic−granitic intrusions. 16,63 In the Alxa Desert region, weakly deformed granites from the Early Permian are widely distributed, and they are concentrated in the age range of 269−289 Ma. 17 The peak age of 2370−2540 Ma corresponds to the ages of granite bodies in the Daqing-Wula Mountains in the northern part of the study area. For instance, in the Daqing Mountains region, Early Paleoproterozoic biotite granite with an age of 2430 ± 19 Ma is observed, while in the Ula Mountains region, Zisu granite with an age of 2430 ± 7.7 Ma is observed. ...
The Ordos Basin is an important sandstone-type uranium enrichment region in China, and the Lower Cretaceous Huanhe Formation has attracted significant attention as a newly discovered ore-bearing stratum. To elucidate the provenance, tectonic background, and sedimentary environment constraints on uranium enrichment in the Huanhe Formation sandstone-type uranium deposits, 10 representative sandstone samples from the study area were analyzed by using electron microscopy, X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and electron probe microanalysis. Independent uranium minerals in the Yihewusu area of Hangjin Banner were shown for the first time to be composed mainly of coffinite and titanium-uranium oxide, with trace amounts of pitchblende. The major element diagrams of the sandstone and ratios of Sr/Ba, V/Cr, and U/Th and enrichment factors of Mo and U revealed that the source rocks of the Huanhe Formation sandstone in the study area were intermediate-felsic igneous rocks. The tectonic setting is characterized as an active continental margin, with later deposition in brackish-to-marine water environments. The ore-bearing strata indicate a reducing environment, whereas the nonore-bearing strata indicate a weakly oxidizing environment. With reference to previous studies, the sedimentary material primarily originated from the medium-acidic intrusive rocks exposed in the northern portion of the basin, including the Daqing-Wula Mountains, the Yin Mountains, and middle-acidic intrusions along the eastern margin of the Alxa region in the western part of the basin. The uranium-rich granitic pluton of the source area contributed to the preenrichment of uranium in the target sandstone layer. Under oxidizing aqueous conditions, U⁶⁺ migration was activated, whereas under reducing aqueous conditions, U⁶⁺ was reduced to U⁴⁺, resulting in eventual sedimentation of coffinite as ore.
... zircon age spectra of different origin areas and distinctly different strata with different rock ages in the origin area are less similar, and the adjacent Qinling-Qilian orogenic belt, the Alashan massif, the Tianshan-Xingmeng orogenic belt, and the North China Craton platform in the study area may provide origin. By comparing and synthesizing the ages of outcrops in the neighboring areas around the perimeter of the basin with the zircon ages of the basins stratigraphic clasts, information on the origin of a stratum in the basin can be revealed [12,32] . Based on the comprehensive study and analysis of the dating results of the red sandstone samples from the upper (LZ-1), central (LZ-2) and lower (LZ-3) parts of the study area mentioned above, most of the 182 zircons with valid dating data obtained in this study are magmatic zircons, and three main age intervals (groups) can be identified on the age data histograms (Figures 4b, 4d, 4f), 252~456 Ma (Paleozoic), 1657~ 2084 Ma (Early Mesozoic-Late Paleozoic), and 2129-2538 Ma (Early-Middle Paleozoic), which record the regional tectonothermal events in the origin area or region that may be in three major periods. ...
The Danxia landform area of Jingbian Wave Valley is located in the central part of Ordos Basin. The near-red Danxia landform consisting of sandstone in this area is a new discovery in geological circles at home and abroad, and its depositional age and genesis remain a hot topic of discussion at present. As the material basis for its development, red sandstone is of great importance to the in-depth study on its formation date and origin. The paper explores the origin, tectonic significance and paleogeographic pattern of the red sandstone through field geological investigation and zircon U-Pb dating analysis of the red sandstone of the Luohe Formation. The results show that the original materials of the red sandstone was formed in three main age intervals, 252~456 Ma, 1657~2084 Ma, and 2129~2538 Ma, and regional tectonothermal events in the origin area during the three periods were recorded, among which the events in Mesoproterozoic and Paleoproterozoic periods were the most active. The comparative analysis of zircon U-Pb age spectra shows that for the sediment of red sandstone, the early origin is near-origin and late origin is distant-origin. The main origin areas in the study area are the Xingmeng orogenic belt, the North China massif and the Alashan massif; the vertical section reflects that the origin area has the strongest erosion and transport in the upper deposition period, the smallest erosion and transport in the middle deposition period, and the moderate erosion and transport in the lower deposition period. With origins system dominated by the northern origins and the paleogeographic pattern of multi-period and cyclonic, the area mainly experienced four tectonic movement cycles, such as Wutai, Lvliang, Caledon and Haixi.
... U-Pb dating of detrital zircons informs provenance analysis and regional tectonic evolution (Gehrels et al. 1995;Zhao et al. 2015;Guo et al. 2018). Therefore, the focus of this work is to compare the provenance on the east and west sides of the Middle Permian Lower Shihezi Formation in the northern Ordos Basin through systematic petrological and quantitative mineralogical analysis. ...
Temporal constraints on the closure of the eastern segment of the Palaeo-Asian Ocean along the northern margin of the North China Craton (NCC) remain unclear. As a part of the NCC, the sedimentation and tectonic evolution of the Late Palaeozoic Ordos Basin were closely related to the opening and closing of the Palaeo-Asian Ocean. We use petrology, quantitative mineralogical analysis, U–Pb geochronology and trace element signatures of detrital zircons of the Lower Shihezi Formation from two sections in the eastern north Ordos Basin and two sections in the western north Ordos Basin to reconstruct the sedimentary provenance and tectonic background of the northern Ordos Basin. The results show that the sediments of the western sections were mainly derived from the Yinshan orogenic belt and Alxa block, and that those in the eastern sections only came from the Yinshan orogenic belt. The trace element ratios in detrital zircons from the Late Palaeozoic sandstones indicate that the source areas were mainly subduction-related continental arcs, closely related to the continued subduction of the Palaeo-Asian Ocean in the Late Palaeozoic. Since the main Late Palaeozoic magmatic periods vary on the east and west sides of the northern margin of the Ordos Basin, two main collisions related to Palaeo-Asian Ocean closure are recorded. The collision on the west side occurred significantly earlier than that in the east. This study implies that the Palaeo-Asian Ocean began to subduct beneath the NCC in the Carboniferous and gradually closed from west to east thereafter.
... The northern region (region A in Fig. 8) is located in the northern-central part of the WOB, as evidenced by four samples. Three samples from the Ciyaobao and Helanshan sections are very special because they exclusively contain zircons of the group 282, while the other age groups are negligible and can be ignored (Guo, 2010;Zhao et al., 2015). One sample in the Zhuozishan section is distinct from the three samples as it has two additional age groups that peak at 2468 Ma and 1847 Ma, suggesting additional provenances for this sample. ...
The western Ordos Basin (WOB), situated in a tectonic transition zone in the North China Craton, acts as an excellent example for studying the Mesozoic intraplate sedimentation and deformation in Asia. In this study, U-Pb ages for 1203 detrital zircons of 14 sandstone samples collected from 11 sections are presented to unravel the sediment source locations and paleogeographic environments of the Early-Middle Jurassic coal-bearing Yan'an Formation in the WOB. Data show that there are five prominent age groups in the detrital zircons of the Yan'an Formation, peaking at ca. 282 Ma, 426 Ma, 924 Ma, 1847 Ma, and 2468 Ma. Samples from the northern, middle, and southern parts of the WOB contain these five age categories in various proportions. In the northern region, the Yan'an Formation exclusively contains Early Permian detrital zircons with a single age group peaking at 282 Ma, matching well with the crystallizing ages of the widespread Early Permian granites in the Yinshan Belt to the north and the Alxa Block to the northwest. While in the southern region, the Yan'an Formation mainly contains three groups of detrital zircons, with age peaks at 213 Ma, 426 Ma, and 924 Ma. These zircon ages resemble those of the igneous rocks in the Qilian-Qinling Orogenic Belt to the south-southwest. Samples in the middle region, characterized by a mixture age spectrum with peaks at 282 Ma, 426 Ma, 924 Ma, 1847 Ma and 2468 Ma, are previously thought to have mixed derivations from surrounding ranges. However, by referring to the detrital-zircon age compositions of the pre-Jurassic sedimentary successions and combining with paleontological and petrographic analysis, we firstly propose that the sediments of the Yan'an Formation in the middle region were partly recycled from the Triassic and Paleozoic sedimentary strata in the WOB. The occurrence of recycled sedimentation suggests that the Late Triassic-Early Jurassic intraplate compressional deformation was very intense in the WOB, especially for regions in front of the Qilian Orogenic Belt. © 2017 China University of Geosciences (Beijing) and Peking University.
... Unlike most studied sections like the Helanshan-Zhuozishan (Darby & Gehrels, 2006;Darby & Ritts, 2002;Ritts et al., 2004;Zhang, Li, Li, & Ma, 2009;Zhao et al., 2015) Neoproterozoic, the Helan aulacogen, as the failed branch of the paleo-Qilian Sea, developed in the WOB (Lin, Yang, & Li, 1995;Sun & Liu, 1983). In the subsequent Paleozoic, regional extension and transgression occurred twice in the WOB Lin et al., 1995). ...
U-Pb detrital zircon data from the Jurassic strata in the western Ordos Basin (WOB) show significant age differences between formations, from lower to upper including the Yan'an, Zhiluo, Anding, and Fenfanghe formations. The main peaks in the detrital zircon age spectra of the Yan'an Formation are at ca. 245, 444, 1813, and 2,387 Ma, which resemble those of the underlying Triassic strata in the WOB. Combined with the occurrence of reworked sporopollen and carbonate debris, the sediments of the Yan'an Formation are interpreted to be potentially recycled from the residual Triassic highlands. The overlying Zhiluo Formation contains detrital zircons mostly in the 260-290 Ma age range with only one peak at 269 Ma, reflecting primary derivations from the Permian granites in the Yinshan Belt to the north and/or the Alxa Block to the northwest. The detrital zircon age compositions of the Anding Formation, however, are most varied, with one prominent age peak at 274 Ma and several other minor peaks at 348 Ma, 447, 932, 1641, 2143, and 2514 Ma, reflecting complex origins. The uppermost syntectonic Fenfanghe Formation, contains detrital zircons with similar age compositions with the Yan'an Formation, once again interpreted as the result of recycled sedimentation. These two phases of multicycle sedimentation in the WOB reveals two intense tectonic events in the Late Triassic and Late Jurassic, whereas the provenance transition between the Yan'an and Zhiluo formations implies a less intense but extensive event in the Middle Jurassic. The complex age composition of the Anding Formation, however, are possibly as the result of climate change corresponding to the change of petrology and sediment colour. These Early-Middle Mesozoic tectonic events evidenced by the U-Pb ages record the tectonic transition of the North China Block from the Tethys to the paleo-Pacific tectonic domains.
The Ordos Basin is located in the western part of the North China Craton, and was developed based on Paleozoic shallow marine sediments and Mesozoic continental deposits. In the southwestern Ordos Basin (SWOB), Paleozoic to Mesozoic sedimentary successions are well preserved and display variable deformation. However, the Cretaceous source-to-source evolution of the SWOB is poorly known but is significant to understand the tectonic evolution of the Ordos Basin. In this study, U–Pb ages and Hf isotopic analyses on detrital zircons from sandstones of the Cretaceous succession in the SWOB were performed, with an aim to trace the Cretaceous sediment provenances and the tectonic–paleogeographic configuration of the Ordos Basin. The new analyses clearly reveal four major age peaks for detrital zircons from Cretaceous sedimentary rocks in the SWOB: 274, 438, 1852, and 2474 Ma, and two minor peaks at 880–950 Ma and >3000 Ma. These zircons have εHf(t) values with a normal distribution from −15.8 to 11.4 and TDM2 ages with multiple peaks mostly at 2985–2720 Ma. Combined with the paleogeographic reconstruction and tectonic evolution of the Ordos Basin, the isotopic analyses prove that the detrital zircons in the Cretaceous succession were mostly sourced from the Alxa Block, Qilian Orogenic Belt, and Yinshan Orogenic Belt, and secondarily from the Qinling Orogenic Belt. Influenced by the formation of the Late Jurassic-Early Cretaceous paleo-uplifts, the Cretaceous sedimentary rocks in the SWOB were sourced from these paleo-uplifts and recycled from the underlying pre-Cretaceous rocks situated in the western Ordos Basin. The migration of the Mesozoic sedimentary depocenter and provenance in the Ordos Basin was controlled by the regional compression of multiple directions.
In order to unravel the Mesozoic sedimentation in response to multistage deformation of the western Ordos fold-thrust belt, combined zircon U-Pb and fission track analyses of single zircon grain are conducted for seven sandstone samples in the Helanshan area. Zircon FT ages are calculated using absolute uranium concentration determined by LA-ICP-MS during the procedure of zircon U-Pb dating. The newly-obtained zircon FT data show age features that are comparable with the previous zircon FT ages obtained by conventional FT methods (by which uranium contents are determined through an external detector to map induced fission tracks). The newly-obtained zircon FT ages have four subordinate FT age peaks (i.e., 225 Ma, 165 Ma, 125 Ma and 80 Ma) which are well matched with the regional geodynamic events occurred in the Late Triassic, Late Jurassic, Late Cretaceous and Early Cenozoic, respectively; and the zircon U-Pb ages have two main peaks at the Paleoproterozoic and the Late Paleozoic. The zircon U-Pb ages, integrating with the FT ages and available paleocurrents, suggest that the Paleoproterozoic basement rocks and Late Paleozoic plutonic rocks of the Alxa Block are the source rocks for the Triassic sandstones, and the Jurassic sandstones are associated with a multi-cycling sedimentation. The Jurassic sandstones contain recycled zircons that firstly deposited in the Triassic strata and subsequently exhumed during the Late Triassic-Early Jurassic.
The Jurassic stratigraphy in China is dominated by continental sediments. Marine facies and marine-terrigenous facies sediment have developed locally in the Qinghai-Tibet area, southern South China, and northeast China. The division of terrestrial Jurassic strata has been argued, and the conclusions of biostratigraphy and isotope chronology have been inconsistent. During the Jurassic period, the North China Plate, South China Plate, and Tarim Plate were spliced and formed the prototype of ancient China. The Yanshan Movement has had a profound influence on the eastern and northern regions of China and has formed an important regional unconformity. The Triassic-Jurassic boundary (201.3 Ma) is located roughly between the Haojiagou Formation and the Badaowan Formation in the Junggar Basin, and between the Xujiahe Formation and the Ziliujing Formation in the Sichuan Basin. The early Early Jurassic sediments generally were lacking in the eastern and central regions north of the ancient Dabie Mountains, suggesting that a clear uplift occurred in the eastern part of China during the Late Triassic period when it formed vast mountains and plateaus. A series of molasse-volcanic rock-coal strata developed in the northern margin of North China Craton in the Early Jurassic and are found in the Xingshikou Formation, Nandailing Formation, and Yaopo Formation in the West Beijing Basin. The geological age and markers of the boundary between the Yongfeng Stage and Liuhuanggou Stage are unclear. About 170 Ma ago, the Yanshan Movement began to affect China. The structural system of China changed from the near east-west Tethys or the Ancient Asia Ocean tectonic domain to the north-north-east Pacific tectonic domain since 170–135 Ma. A set of syngenetic conglomerate at the bottom of the Haifanggou or Longmen Fms. represented another set of molasse-volcanic rock-coal strata formed in the Yanliao region during the Middle Jurassic Yanshan Movement (Curtain A1). The bottom of the conglomerate is approximately equivalent to the boundary of the Shihezi Stage and Liuhuanggou Stage. The bottom of the Manas Stage creates a regional unconformity in northern China (about 161 Ma, Volcanic Curtain of the Yanshan Movement, Curtain A2). The Jurassic Yanshan Movement is likely related to the southward subduction of the Siberian Plate to the closure of the Mongolia-Okhotsk Ocean. A large-scale volcanic activity occurred in the Tiaojishan period around 161–153 Ma. Note that 153 Ma is the age of the bottom Tuchengzi Formation, and the bottom boundary of the Fifth Stage of the Jurassic terrestrial stage in China should have occurred earlier than this. This activity was marked by a warming event at the top of the Toutunhe Formation, and the change in the biological assembly is estimated to be 155 Ma. The terrestrial Jurassic-Cretaceous boundary (ca. 145.0 Ma) in the Yanliao region should be located in the upper part of Member 1 of the Tuchengzi Formation, the Ordos Basin in the upper part of the Anding Formation, the Junggar Basin in the upper part of the Qigu Formation, and the Sichuan Basin in the upper part of the Suining Formation The general characteristics of terrestrial Jurassic of China changed from the warm and humid coal-forming environment of the Early-Middle Jurassic to the hot, dry, red layers in the Late Jurassic. With the origin and development of the Coniopteris-Phoenicopsis flora, the Yanliao biota was developed and spread widely in the area north of the ancient Kunlun Mountains, ancient Qinling Mountains, and ancient Dabie Mountain ranges in the Middle Jurassic, and reached its great prosperity in the Early Late Jurassic and gradually declined and disappeared and moved southward with the arrival of a dry and hot climate.
For detrital-zircon provenance studies, we present a new methodology that combines low-temperature fission-track with high-temperature U-Pb single-grain dating methods. This approach removes single-technique-based bias which can lead to misinterpretation of source. By obtaining data from the same samples and/or grains, it is possible to identify both the underlying age structure of the source terrane and subsequent thermotectonic events. Using detrital zircons from sediments belonging to the Khorat Basin in Thailand, we show how a combined approach to zircon dating can be used to better understand the temporal association between source and depositional site---information that is integral to improving models of basin formation.
U–Pb detrital zircon geochronology has been used to identify provenance and document sediment delivery systems during the deposition of the early Late Triassic Yanchang Formation in the south Ordos Basin. Two outcrop samples of the Yanchang Formation were collected from the southern and southwestern basin margin respectively. U–Pb detrital zircon geochronology of 158 single grains (out of 258 analyzed grains) shows that there are six distinct age populations, 250–300 Ma, 320–380 Ma, 380–420 Ma, 420–500 Ma, 1.7–2.1 Ga, and 2.3–2.6 Ga. The majority of grains with the two oldest age populations are interpreted as recycled from previous sediments. Multiple sources match the Paleozoic age populations of 380–420 and 420–500 Ma, including the Qilian–Qaidam terranes and the North Qilian orogenic belt to the west, and the Qinling orogenic belt to the south. However, the fact that both samples do not have the Neoproterozoic age populations, which are ubiquitous in these above source areas, suggests that the Late Triassic Yanchang Formation in the south Ordos Basin was not derived from the Qilian–Qaidam terranes, the North Qilian orogenic belt, and the Qinling orogenic belt. Very similar age distribution between the Proterozoic to Paleozoic sedimentary rocks and the early Late Triassic Yanchang Formation in the south Ordos Basin suggests that it was most likely recycled from previous sedimentary rocks from the North China block instead of sediments directly from two basin marginal deformation belts.
To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (<0.07) Th/U zircons, consistent with crystallization under UHP conditions, are rare in eastern Songpan-Ganzi complex zircon, and U-Pb ages of low Th/U zircons are incompatible with a Dabie terrane source. An unweighted pair group method with arithmetic mean nearest-neighbor analysis of Kolmogorov-Smirnov two-sample test results reveals that the eastern Songpan-Ganzi complex is not a single contiguous turbidite system but is instead composed of three subsidiary depocenters, each associated with distinct sediment sources. The northeastern depocenter contains zircon ages characterized by Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south-to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south-to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are interpreted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan shear zone that bounds the Dabie terrane to the north. The central depocenter deposits reflect a later influx of bimodally distributed Precambrian zircon, signifying either a decrease in the influx of Paleozoic zircon grains due to stalled UHP exhumation and/or dilution of the same influx of Paleozoic zircons by spilling of Precambrian zircon from the northeastern depocenter into the central depocenter basin, perhaps due to infilling and bypass of sediment from the northern depocenter or due to initial collapse and constriction of the eastern Songpan-Ganzi complex basin. The southeastern depocenter of the eastern Songpan-Ganzi complex bears significant Paleozoic, Neoproterozoic, and Paleoproterozoic zircon populations derived from the South China block and Yidun arc complex, likely recording nascent uplift of the Longmenshan deformation belt due to impingement of the Yidun arc complex upon the western margin of the South China block.
Isotopic, geochemical and U–Pb zircon geochronological characteristics of the Nawa Domain in the South Australian Craton, Australia, have been determined to place constraints upon Palaeoproterozoic reconstruction models. U–Pb detrital zircon analysis of the Nawa Domain metasedimentary rocks indicates deposition between ca. 1740 and 1720Ma. Sedimentary rocks are shown to be enriched in REE and sourced from evolved crust (ɛNd(1.6Ga)=−7.0 to −4.3). The combination of geochemical, Nd-isotope and U–Pb detrital zircon age data indicate the dominant source for the studied metasedimentary rocks is likely to be the Arunta region of the North Australian Craton. This indicates the Nawa Domain crustal segment was proximal to the North Australian Craton during the period ca. 1740–1720Ma. Provenance correlations drawn between the Nawa Domain metasedimentary rocks, lower part of the Willyama Supergroup in the Curnamona (Broken Hill) region and Maronan Supergroup in the Mount Isa region suggest contiguity of these crustal terranes during the late Palaeoproterozoic. These spatial and temporal constraints negate some reconstructions of Palaeoproterozoic Australia suggested for this period, and indicate further refinement of other models is needed. Further, the intra-continental nature and Australian sourced detritus of the lower sections of these basins limits their use as piercing points between eastern Australia and possible neighbouring continents in the Palaeo- and Mesoproterozoic.
The provenance of detrital zircons in nineteen littoral and sedimentary deposits in eastern Australia is determined in terms of their isotopic ages measured by Sensitive High Resolution Ion MicroProbe (SHRIMP). Principal component analysis of the age data reveals four `age groupings' whose occurrence and distribution have wider implications for regional tectonics and general provenance studies. A 100–175 Ma age grouping is correlated with Jurassic/Cretaceous volcanism along the eastern Australian margin. A 225–350 Ma age grouping is correlated with the New England Orogen. A 350–500 Ma age grouping is correlated with magmatism in the Lachlan Orogen. The ultimate source of the Pacific–Gondwana 500–700 Ma age grouping is enigmatic, but is tentatively identified as a Neoproterozoic orogeny along the eastern Antarctic margin. The geochronology of detrital zircon reveals a strong regional variation along the eastern coast with the Lachlan Orogen age grouping stronger in the south, mixing with the 500–700 Ma age grouping in the central sector, and then a New England Orogen age grouping in the north. The Pacific–Gondwana age grouping on the central coast is derived from the Middle Triassic Hawkesbury Sandstone of the Sydney Basin. This distribution of the Pacific–Gondwana age grouping via the Sydney Basin is one example of how a favourable sedimentary pathway can have greater control over provenance than proximity. The other example occurs with Jurassic/Cretaceous age grains are prominent in the Murray Basin, around 1200 km from the protosource along the eastern margin, but not in sediments now accumulated on that same margin.
The Lang Shan, North-Central China, has experienced a complex Mesozoic to recent history of intraplate deformation and sedimentation. Well-exposed cross-cutting relationships document Jurassic right-lateral strike-slip faulting (transtension) followed by several tens of kilometers of Late Jurassic to Early Cretaceous north-northwest–south-southeast crustal shortening and development of an associated foreland basin. Since the Early Cretaceous, the south-central Lang Shan has undergone two phases of extension. The first, which occurred along north–south oriented structures, may represent collapse of an overthickened crust. The youngest deformation is represented by the active Cenozoic mountain-front normal fault system. This compound history may be the result of the complicated far-field effects of plate interactions combined with structural inheritance in a region adjacent to a rigid and undeformed crustal block, the Ordos block.
Paleogene clastic sedimentary rocks in the Puna plateau of northwestern
Argentina contain valuable information about the timing and location of
early mountain building in the central Andes. Because these rocks
generally lack tuffaceous facies, only paleontological ages have been
available. We present U-Pb ages from detrital zircons in the
conglomeratic Eocene Geste Formation of the central Puna plateau. The
zircon ages indicate that the Geste Formation was derived from nearby
high-relief ranges composed of Ordovician metasedimentary rocks. A small
population of ca. 37 35 Ma grains also confirms the late Eocene
stratigraphic age of the Geste Formation, and suggests that U-Pb
detrital zircon ages may provide a new tool for determining depositional
ages and provenance of widespread Paleogene deposits in the central
Andes.
The Helanshan Complex is located at the westernmost segment of the Khondalite Belt, a continent–continent collisional belt along which the Yinshan Block in the north collided with the Ordos Block in the south to form the Western Block of the North China Craton. The complex consists of S-type granites and high-grade pelitic granulite/gneiss, felsic paragneiss, quartzite, calc-silicate rock and marble, together called the Khondalite Series rocks. LA-Q-ICP-MS U–Pb geochronology and LA-MC-ICP-MS Lu–Hf isotopic data of zircons, combined with cathodoluminescence (CL) imaging, enable the resolution of magmatic and metamorphic events that can be directed towards understanding the formation and evolution of the Khondalite Belt in the Western Block of the North China Craton. CL images reveal the coexistence of magmatic-type detrital zircons and metamorphic zircons in most of the Khondalite Series rocks, of which the metamorphic zircons occur as either single grains or overgrowth rims surrounding and truncating magmatic-type detrital zircon cores. LA-Q-ICP-MS U–Pb analyses on magmatic-type detrital zircons reveal two distinct age populations, with one in the Archaean (2.85–2.53 Ga) and the other in the Palaeoproterozoic (2.2–2.0 Ga), suggesting that the sedimentary protoliths of the Khondalite Series rocks in the Helanshan Complex must have been deposited at some time after 2.0 Ga. The Hf analyses show that the Archaean detrital zircons possess negative εHf(t) values from − 7.64 to − 0.15 with depleted mantle model ages ranging from 3.34 to 3.10 Ga. This implies the existence of a Paleo-Mesoarchaean (3.34–3.10 Ga) crust in the Western Block, which underwent a recycling event in the period 2.85–2.53 Ga. Nearly all Palaeoproterozoic (2.2–2.0 Ga) detrital zircons possess positive εHf(t) values (0.86–9.38) with depleted mantle model ages of 2.45–2.15 Ga, suggesting a significant crustal growth event in the Western Block in the Palaeoproterozoic. Metamorphic zircons yield two groups of age, with one at ~ 1.95 Ga and the other at ~ 1.87 Ga, of which the former is considered as the timing of the collision between the Yinshan and Ordos Blocks to form the Western Block, whereas the latter is consistent with the age of ~ 1.86 Ga from two S-type granites which are considered to have formed by the partial melting of pelitic granulites/gneisses at the stage of the exhumation of the Helanshan Complex.
Detrital zircons from the Wulashan khondalites in the Ordos Terrane, western block of the North China Craton, give U–Pb ages between 1.84 and 2.32 Ga, showing that their provenance was dominated by Paleoproterozoic rocks, much younger than those exposed in the Eastern Block. These zircons have oscillatory growth zoning and possess εHf values between − 8 and + 9, suggesting derivation of their precursor magmas from old crust and juvenile materials from the mantle. The lowest εHf values of zircons with different ages give a line that intersects the depleted mantle line at about 2.6 Ga in a εHf vs. time diagram. This may imply that the precursor magma source in the deep level of the crust was largely separated from the mantle ∼2.6 Ga ago and therefore 2.6 Ga may be an important crustal formation period for the terrane. One khondalite sample has detrital zircons with a single age population at ∼2.0 Ga and positive εHf values from + 1 to + 9, clearly recording the significant addition of juvenile materials at ∼2.0 Ga in the source region. This may inspire us to seek whether there was a connection between a mantle superevent and the formation of Columbia supercontinent. Data of this study exclusively demonstrate that the Ordos Terrane was developed independently from the Eastern Block until assembly of the Columbia supercontinent. Therefore, tectonic models involving that the whole North China Craton was cratonized 2.5 Ga ago should be dismissed.
Although metasedimentary successions are widely distributed across the North China Craton, those of Palaeoproterozoic age are restricted to three orogenic belts, namely: the Trans-North China Orogen, the Khondalite Belt and the Jiao-Liao-Ji Belt. Prior to this work, some of those successions were considered to be Archaean in age. The Palaeoproterozoic metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3.0 to 2.1 Ga, with the majority recording an age between 2.3 and 2.0 Ga. This latter group define a series of magmatic events that occurred between formation of the Archaean basement and deposition of the metasedimentary rock protoliths. The metasedimentary rocks occur as two associations; older volcano-sedimentary units that formed between 2.37 and 2.0 Ma, and younger sedimentary units that formed mainly between 2.0 and 1.88 Ga. All these rock associations were then subjected to metamorphism during the Late Palaeoproterozoic (1.88 and 1.85 Ga) tectonothermal event, named the Lüliang Movement in early Chinese literature, which was a continent–continent collision that led to the amalgamation of the North China Craton.
Clastic sedimentary rocks are samples of the exposed continental crust. In order to characterize the crustal growth history of North China and its possible regional variations, 479 concordant detrital zircons in three sand samples from the lower reach of the Yellow River (which drains the Tibet–Qinghai Plateau, the Western Qinling Orogen, the Qilian Orogen and the North China Craton) and two sand samples from the Luan River and the Yongding River (which run entirely within the North China Craton) were measured for U–Pb age and Lu–Hf isotopic compositions by excimer laser-ablation ICP-MS and MC-ICP-MS. Although regional variations exist, concordant detrital zircons from the Yellow River reveal three major age groups of 2.1–2.5 Ga, 1.6–2.0 Ga, and 150–500 Ma. Detrital zircons from the smaller Luan and Yongding Rivers show three broadly similar major age groups at 2.3–2.6 Ga, 1.6–2.0 Ga, and 140–350 Ma, but with narrower age ranges. Compared to the Luan and Yongding River zircons, the Yellow River zircons are characterized by a significant number of Neoproterozoic grains. Although Hf isotopic compositions show both juvenile crustal growth and crustal reworking for all age groups, much of the crustal growth of North China occurred in the Neoarchean and Mesoproterozoic. All three rivers are characterized by a common prominent group of Hf crust formation model ages at 2.4–2.9 Ga with a peak at 2.7–2.8 Ga. A less significant age group lies between 1.4 and 1.8 Ga for the Yellow River, and between 1.6 and 1.9 Ga for the Yongding River and Luan River. Crustal growth rates based on Hf continental crust formation model ages suggest 45% and 90% of the present crustal volume was formed by 2.5 Ga and 1.0 Ga, respectively, for the drainage area of the Yellow River. In comparison, 60% and 98% of the present crustal volume of the North China Craton was generated by 2.5 Ga and 1.0 Ga, respectively, for the Luan and Yongding Rivers. The 2.7–2.8 Ga age peak observed in all river samples agrees well with the coeval major peak for global crustal growth. However, the other suggested global peaks of crustal growth at 3.4 and 3.8 Ga are insignificant in North China. Taken together with our previous studies of the Yangtze Craton, which show insignificant crustal growth at 2.7–2.8 Ga, we suggest that these advocated worldwide crust formation peaks be re-examined and treated carefully. Our results also show that Phanerozoic zircons may have been derived from crustal sources separated from the mantle up to 2.0 Ga ago before the zircons crystallized, suggesting long-term preservation, reworking and recycling of the continental crust.
Zircom U-Pb age and Hf isotope analyses were made on gneissic granite and garnet-mica two-feldspar gneiss from the Helanshan Group in the Bayan Ul-Helan Mountains area, the western block of the North China Craton (NCC). Zircons from the gneissic granite commonly show core-mantle-rim structures, with magmatic core, metamorphic mantle and rim having ages of 2323±20 Ma, 1923±28 Ma and 1856±12 Ma, respectively. The core, mantle and rim show similar Hf isotope compositions, with single-stage depleted mantle model ages (T
DM1) of 2455 to 2655 Ma (19 analyses). Most of the detrital zircons from the garnet-mica two-feldspar paragneiss have a concentrated U-Pb age distribution, with a weighted mean 207Pb/206Pb age of 1978±17 Ma. A few detrital zircons are older (2871 to 2469 Ma). The age for metamorphic overgrown rim was not determined because of strong Pb loss due to their high U content. The zircons show large variation in Hf isotope composition, with T
DM1 ages of 1999 to 3047 Ma. In combination with previous studies, the main conclusions are as follows: (1) protolith of the khondalite series in the Helanshan Group formed during Palaeoproterozoic rather than the Archaean as previously considered; (2) The results lend support to the contention that there is a huge Palaeoproterozoic Khondalite (metasedimentary) Belt between the Yinshan Mountains Block and the Ordos Block in the Western Block of NCC; (3) The widely-distributed bodies of early Palaeoproterozoic orthogneisses in the Khondalite Belt might be one of the important sources for detritus material in the khondalite series; (4) Collision between the Yinshan Block, the Ordos Block and the Eastern Block occurred in the same tectonothermal event of late Palaeoproterozoic, resulting in the final assembly of the NCC.
The "Taihua Group" is a collective term for a series of old terranes scattered along the southern margin of the North China
Craton. The timing of formation and thermal overprinting of the Taihua Group have long been contentious, and its relationship
with the Qinling orogenic belt has been unclear. In this study, new data from integrated in-situ U–Pb dating and Hf isotope
analysis of zircons from an amphibolite (from the Xiong’ershan terrane) and a biotite gneiss (from the Lantian-Xiaoqinling
terrane) indicate that the Upper Taihua Group formed during the Paleoproterozoic (2.3–2.5Ga) and thus was originally part
of the southern edge of North China Craton, detached during the Mesozoic Qinling orogeny and displaced about 100km north
from its original location. This suggests that the Taihua Group became part of the tectonic terrane associated with the Qinling
orogeny and now forms part of the overthrust basement section of the Qinling belt. Before the Qinling orogeny, the Taihua
Group was metamorphosed at 2.1Ga. The initial Hf-isotope compositions of zircons, together with positive εNd(t) values for
the whole-rocks, imply that the original magmas were derived from a juvenile source with some assimilation of an Archean crustal
component.
Analyses of zircon grains from the Queureuilh Quaternary tephras (pumice) provide new information about their pre-eruptive history. U–Pb dating was performed in situ using two methods: SHRIMP and LA-MC-ICPMS equipped with a multi-ion counting system. Both methods provided reliable 207Pb/206Pb and 206Pb/238U ratios as well as U and Th abundances required for U–Pb Concordia intercept age determination, after initial 230Th disequilibrium correction. The new LA-MC-ICPMS method was validated by dating a reference zircon (61.308B) and zircons from a phonolitic lava dated independently with the two techniques. A time resolution of about 20 kyr for 1 Ma zircon crystals was achieved for both methods.
The Qianlishan Complex is located in the westernmost part of the Khondalite Belt, a continent–continent collisional belt along which the Yinshan Block in the north and the Ordos Block in the south amalgamated to form the Western Block, which then collided with the Eastern Block along the Trans-North China Orogen to form the North China Craton. The complex is dominated by high-grade supracrustal rocks and minor S-type granites, of which the supracrustals consist of graphite-bearing sillimanite-garnet gneiss, garnet quartzite, felsic paragneiss, calc-silicate rock and marble. CL images reveal the existence of detrital and metamorphic zircons in major rocks of the Qianlishan Complex. In most cases, detrital zircons occur as either single grains with oscillatory zoning or oscillatory zoning cores, typical of igneous origin, which are surrounded by metamorphic overgrowth rims that are structureless, high bright and low in Th/U ratio. Detrital zircons from the Qianlishan Complex yield nearly concordant 207Pb/206Pb ages ranging from 2.3 to 2.0 Ga, suggesting that the protoliths of the high-grade supracrustal rocks in the Qianlishan Complex were deposited at some time after 2.0 Ga. Metamorphic zircons yield two age populations with one at ∼1.95 Ga and another at ∼1.92 Ga, of which the former is interpreted as the timing of the collision between the Yinshan and Ordos Blocks to form the Western Block, whereas the later is considered to be the age of subsequent post-orogenic extensional event. Minor S-type granites were emplaced at ∼1.88 Ga, as a result of partial melting of supracrustals at the stage of the exhumation of the Qianlishan Complex. These new zircon ages, combined with structural and metamorphic considerations, enable resolution of the tectonothermal events involving the collision between the Yinshan and Ordos Blocks to form the Western Block, followed by the post-collisional extension and subsequent exhumation of the Khondalite Belt.
LA-ICP-MS U–Pb zircon dating and cathodoluminescene (CL) image analysis were carried out to determine the protolith and metamorphic ages of high-grade Al-rich gneisses, named as “khondalites”, from the Jining Complex of the North China Craton (NCC). The analytical results of more than 200 detrital zircon grains from the khondalites show three main age populations: 2060 Ma, 1940 Ma and 1890 Ma. These data indicate that the provenance of the Jining khondalites is Paleoproterozoic in age, but not Archean as previously suggested, and the sediments were derived from a provenance different from the Eastern Block and the Yinshan Terrane of the NCC. The nearly concordant youngest age of 1842 ± 16 Ma (207Pb/206Pb age) for the detrital zircons is interpreted as the maximum depositional age of the khondalites. Overgrowth rims of detrital zircons yield an age of 1811 ± 23 Ma, which we interpret as the metamorphic age. The new age data are consistent with the recent three-fold tectonic subdivision of the NCC and support that the Eastern and Western Blocks collided at ∼1.8 Ga to form the coherent NCC.
Provenance analysis of sediments is aimed at reconstructing the parent-rock assemblages of sediments and the climatic-physiographic conditions under which sediments formed. Inferring sediment provenance from the final product, a basin fill, is anything but straightforward because the detrital spectrum evolves as the sediment is transported along the pathway from source to basin. Successful provenance analysis requires that the nature and extent of compositional and textural modifications to the detrital spectrum be recognised, if not quantified. The history of quantification in sediment-provenance studies is summarised and illustrated by tracking two fundamental ideas: the concept of the sediment-petrological province or petrofacies, and the relation between sandstone composition and (plate) tectonic environment. Progress in sedimentary provenance analysis has been closely linked with advancements in measurement technology. A brief survey of modern data-acquisition tools illustrates the possibilities and limitations of modern provenance research. An operational definition of Quantitative Provenance Analysis (QPA) is presented in which the central role of mass balance is acknowledged. Extension of this definition to include quantitative predictions obtained by forward modelling (computer simulation) of sediment production, as well as methodological improvements in data acquisition and processing is needed to cover likely future developments in QPA. The contributions to the special issue "Quantitative Provenance Analysis of Sediments" illustrate the intrinsic multidisciplinarity and rapid expansion of QPA.