Detrital Zircon Age Distributions Research Articles

Provenance Analysis of the Cenozoic Sedimentary Successions in the Ningnan Basin, NE Tibetan Plateau: Constraints on Sedimentological and Tectonomorphological Evolution

AbstractThe evolution and reforming history of the Cenozoic basins in the northeastern Tibetan Plateau (NETP) are significant for understanding the northeastward growth of the Tibetan Plateau. The sediments in these basins archived the spatial‐temporal patterns of the surface uplift and deformation processes in response to remote effects of growth of the NETP. Here, we present an integrated provenance analysis of the Ningnan basin in the NETP to provide direct insights into the basin evolution and further constraints of the Tibetan Plateau's northeastward growth. In this study, the Cenozoic strata (the Sikouzi, Qingshuiying, Zhang'enpu and Ganhegou formations) in the Ningnan basin yield complex detrital zircon age distributions featured by predominant age populations at 200–360 Ma and 360–540 Ma with minor Precambrian ages. Detrital zircon U‐Pb ages indicate that the southwestern Ordos Block, the western Qinling orogenic belt, and the eastern Qilian orogenic belt are primary source areas. Additionally, adjacent local paleo‐uplifts (e.g., Xi‐nanhuashan, Xiangshan, Liupan mountains.) also provided minor volumes of sediment. In addition, conglomerates and paleocurrent directions of the Sikouzi–Ganhegou formations exhibit an apparent change since the late Mocene, revealing an obvious provenance shift. The quantitatively determined mixing proportions of the surrounding source areas also reveals that the early source‐to‐sink system was replaced during the deposition of the Ganhegou Formation. Combined with previous studies, we suggest that the formation of the Ningnan basin was controlled by normal faults in extension setting and experienced continued sediment accumulation during the Qingshuiying–Zhang'enpu period; since the late Miocene, the significant provenance shift reflects the obvious northeastward growth of the NETP and led to the extinction of the Ningnan basin.

ПЕРВЫЕ ДАННЫЕ О ПОЗДНЕМЕЛОВЫХ ТЕРРИГЕННЫХ ОТЛОЖЕНИЯХ ВЕРХНЕЙ ЧАСТИ РАЗРЕЗА ЖУРАВЛЕВСКО-АМУРСКОГО ТЕРРЕЙНА В НИЖНЕМ ПРИАМУРЬЕ (ПО РЕЗУЛЬТАТАМ U/PB ДАТИРОВАНИЯ ЦИРКОНА)

The study was performed on the age and composition of little-studied Cretaceous terrigenous deposits of lower Priamurie, which are part of the Zhuravlevka-Amur terrane and are referred to the Berriasian-Valanginian Komsomolsk Series. U/Pb dating of detrital zircons yielded reliable dates of 99 and 90 Ma for the Gorin and Pioneer formations, respectively. Thus, for the first time, a Late Cretaceous age of sedimentation was identified for the sedimentary complex within the Sikhote-Alin orogenic belt based on U/Pb dating of detrital zircons. In terms of composition and detrital zircon age distribution patterns, the studied rocks are similar to the sediments of the upper Hauterivian-Albian part of the Zhuravlevka-Amur terrane section, and not the Berriasian-Valanginian. In rocks of the Pioneer Formation, the youngest population of zircon with an age of about 90 Ma accounts for more than 40 % of all the dated grains. Andesites of the Bolba Formation and granitoids of the Nizhneamurskii Complex, which are distributed nearby are probably the main source of clastic material of this age. Felsic rocks of the Albian-Cenomanian igneous province of Pacific Asia were probably the source of detritus for sediments of the Gorin Formation of about 99 Ma. The issue of inconsistency between the Late Cretaceous age obtained by us and the paleontologically established Berriasian-Valanginian stratigraphic age of the formations requires additional research. New data on the Late Cretaceous age of sediments of the Zhuravlevka-Amur pull-apart continental margin basin invite further investigations to better understand the geologic evolution of the terrane and the Sikhote-Alin orogenic belt as a whole.

Geochronology, provenance, and tectonic setting of the meta-sedimentary rocks from the North Shahrekord metamorphic Complex, Iran

ABSTRACT The meta-sedimentary rocks from the North Shahrekord metamorphic Complex (NSMC) comprise micaschists, paragneisses, quartz-feldspathic schists, and marbles. Detrital zircons from the paragneisses yield ages of ca. 2811–507 Ma with most of the dated grains belonging to the Late Neoproterozoic to Cambrian, suggesting a maximum depositional age of the sedimentary protolith during the Late Ediacaran to the Early Cambrian times (543 ± 12 Ma). In contrast, detrital zircons from the quartz-feldspathic schists are mostly dominantly 692–577 Ma and a few at ca. 2369–703 Ma, suggesting that the maximum depositional age of 577 ± 9 Ma, Late Neoproterozoic. The age distribution of detrital zircons suggests that their main provenance was located within the Arabian-Nubian Shield and adjacent terranes. Rutiles from a paragneiss give a U-Pb lower-intercept age of 181 ± 3 Ma, indicating the occurrence of a high-pressure metamorphic event during the Early Jurassic. The trace element contents of the two rock units show enrichment in LREE relative to HREE and negative Eu anomalies, indicating upper continental crustal sources. The geochemical evidence (e.g. low to moderate Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration, high Index of Compositional Variability (PIA), and low Th/U) suggests that the quartz-feldspathic schists and paragneisses originated from an immature, and immature to less mature, respectively, intermediate-felsic igneous source and their protolith experienced a simple sedimentary recycling history with relatively weak to moderate chemical weathering. Geochemical and petrographic data also suggest that the precursor to the quartz-feldspathic schists and paragneisses were deposited in a continental island arc and a back-arc basin setting, respectively. Our new data, including depositional age, provenance, and geochemical evidence, provide perspectives on palaeogeographic affinities (provenance of sediments with different weathering and recycling materials), and paleotectonic reconstructions (from arc to back-arc) of the Iranian basement, exposed in the Sanandaj-Sirjan Zone, during Ediacaran.

U–Pb detrital zircon ages from Cretaceous - Paleogene white sandstone member in Western Tabei Uplift (China) as provenance indicators

The Western Tabei Uplift is one of the largest first-level structural units in the Tarim Basin with great potential for oil and gas resources. Previous studies have established sedimentary provenance of the upper and lower strata in the unconformity of the Cretaceous Bashijiqike Formation and Paleogene Kumugeliemu Group in the Western Tabei Uplift. However, little attention has been paid to the light-colored, white-ish sandstone at the interface of this unconformity, whose sedimentary provenance remains to be investigated. Based on morphology, U–Pb age and trace element analyses of detrital zircon, our study reveals five age peaks in detrital zircon age distribution, ∼300 Ma, ∼420 Ma, ∼820 Ma, ∼1.8–1.9 Ga, ∼2.4 Ga. Potential sources of white sandstone include the Quruqtagh region to the east (E-source), the South Tianshan to the north (N-source), the west of East Tianshan and the north part of Quruqtagh to the north-east (NE-source). Their detrital zircon U–Pb age information is collected and compared with those from the white sandstone. The detrital zircon age comparison demonstrates that the E-source is the primary sedimentary source area for the white sandstone, the N-source may also provide some additional sediments. The detrital zircon age pattern also indicates that the origin of the NE-source is probably supplied by both the E-source and N-source together. Our finding could shed new light on the provenance and sedimentary model of Cretaceous-Paleogene white sandstone member in the Western Tabei Uplift and provide a theoretical basis for further exploration of lithological oil reservoirs in this section.

Detrital zircons of the vast Triassic Snadd and De Geerdalen formations, Barents Shelf, reveal temporal changes in sediment source

Studies of detrital-zircon age distributions from Triassic sedimentary rock successions on the Arctic Barents Shelf have resulted in different provenance interpretations. Here, we provide new U–Pb/Hf detrital-zircon data from eleven samples of the Snadd and De Geerdalen formations, covering the Barents Shelf in a north–south transect, that help refine the provenance of these sedimentary rocks and show how stratigraphic variations reflect changing source regions. The sample locations cover different stratigraphic levels and geographic locations within the formations. The detrital-zircon age spectra in the lower part (lowest Ladinian and lower Carnian) are dominated by two age peaks at 300 and 540 Ma, whereas the zircon distributions in the stratigraphically younger deposits (latest Carnian and early Norian) are dominated by a 235 Ma age peak and two minor peaks at 300 and 425 Ma. The apparent relative contribution of detritus of different ages changes gradually from lower to higher stratigraphic levels, marked by an increase in both the 235 and 425 Ma age peaks, a decrease in the 300 Ma component and a progressive loss of the 540 Ma age peak. The zircon Hf-isotopic compositions display predominantly juvenile zircon populations, except for a mixed juvenile and evolved signature in the youngest Permo-Triassic grains. A regional comparison of detrital-zircon age spectra in latest Carnian/early Norian deposits extends the depositional system into the Sverdrup Basin, supporting a much larger depositional system than hitherto known. The gradual change in detrital-zircon age spectra likely represents a gradual shift in zircon provenance. We interpret these variations to reflect an early source region in the north Urals, gradually changing to a dominant source region in the Taimyr Peninsula region.

A combined methodology for reconstructing source-to-sink basin evolution, exemplified by the Triassic Songpan–Ganzi basin, central China

Source-to-sink evolution of a basin is a key to understand sedimentary processes, especially in a complex regional orogenic setting. Detrital zircon populations can be traced from their primary sources to their depositional settings. The resulting interpretations are enhanced by calculation of the adjacent orogen's paleoaltimetry, which provides additional insights into paleogeography. In this study, we present a combined methodology which aims to reconstruct source-to-sink evolution by the analysis of detrital zircon age distribution in sandstones, together with the calculation of paleo-elevation of surrounding orogens based on the chemical compositions of coeval magmatic rocks. We test the method using detrital zircon U–Pb geochronological data sets from the Triassic Songpan–Ganzi basin in central China, combined with whole-rock geochemical data from intermediate-composition magmatic rocks in adjacent crustal blocks. Application of the combined methodology supports a syn-collisional basin model for the formation of the Triassic Songpan-Ganzi basin in preference to a continental back-arc basin. The clastic sediments, mainly deep-marine turbidites, accumulated in a remnant Paleotethyan Ocean that was surrounded by the converging North China Block, South China Block, East Kunlun Orogenic Belt and the Qiangtang Block. The North China Block and the North Qaidam Block were major proto-sources of detrital zircons to the basin, contributing on average 12 % and 15 %, respectively. Triassic magmatic rocks in the East Kunlun and Qiangtang regions were major sources of igneous zircons, up to 68 % for the former and up to 56 % for the latter. Despite being located at a calculated elevation of ca. 4000 m, the Qinling Orogenic Belt contributed only ca. <10 % of the zircons, mostly restricted to the eastern depocenter of the basin. In contrast, supply from the North Qiangtang Block, despite its calculated lower elevation (1000–3000 m), accounts for 2–10 % of the detrital zircons in the basin, suggesting high erosion rates of this block. The minimal supply of zircons from the South China Block, restricted to 3–6 % in the central and western depocenters, is inconsistent with the zircon abundances predicted in the alternative back-arc basin model of the Songpan–Ganzi basin.

Late Paleozoic sedimentary and tectonic evolution of the Linxi basin in the eastern Inner Mongolia, eastern Central Asian Orogenic Belt

The eastern Central Asian Orogenic Belt (CAOB) encompasses a vast region from northeast China to Inner Mongolia, where there were many Late Paleozoic sedimentary basins that can provide key constraints to tectonic evolution of the eastern CAOB. Analysis of sedimentary sequence and environment of eight measured sections from the Linxi basin, Inner Mongolia indicates that there were shallow marine clastic-carbonate sedimentary facies, delta and littoral facies and terrestrial facies during the Early, Middle and Late Permian, respectively, and no oceanic sedimentary facies was found. Sedimentary sequence from the initial clastic-carbonate rocks to marine volcanic rocks reveals a transgression process during 300–270 Ma, while clastic and carbonate rocks with conglomerates and plant fossils represent a regression process during 270–250 Ma. According to the detrital zircon (DZ) age distribution of twenty-two samples (1610 zircons), the northern and southern provenances of the Permian sedimentary strata have been recognized, respectively. These DZ samples express the dispersed polymodal age populations and are attributed to a divergent dominated tectonic setting, implying the Linxi basin is an intracontinental extension basin during the Permian. This is consistent with an extensional process revealed by the syn-depositional deformed structures, coarse clastic sediments and olistostrome successions in the Linxi basin during the Early to Middle Permian and also similar to the speculation that there was an extension setting based on studies of volcanic rocks and intrusions in the Linxi basin. Combined with previous studies on the West Ujimqin basin, the Late Carboniferous to Permian tectonic frame of the eastern Inner Mongolia expresses extensional tectonics characterized by alternating combination of basins and uplifts superimposed on a pre-existing Early-Middle Paleozoic orogenic lithosphere and Precambrian basement, rather than a single ocean basin of Paleo Asian Ocean (PAO), which provides constraints for understanding sedimentary and tectonic evolution of the eastern CAOB during the Late Paleozoic.

Concurrence of Late Triassic lithostratigraphic, radioisotopic, and biostratigraphic data support a Carnian age for the Popo Agie Formation (Chugwater Group), Wyoming, USA

The Upper Triassic Popo Agie Formation of the Chugwater Group of Wyoming, northeastern Utah, and northwestern Colorado has been an enigmatic unit since its definition and is commonly excluded from large-scale studies of continental Upper Triassic strata in the western USA. Lithostratigraphic correlations of Popo Agie Formation outcrops are documented from west-central Wyoming through northeastern Utah and northwestern Colorado, which demonstrates the presence of the Popo Agie Formation throughout this region. Unique detrital zircon age distributions have led previous workers to hypothesize a paleodrainage connecting basal units of the Dockum in west Texas and eastern New Mexico, USA, with the Gartra Grit, a basal unit of the Popo Agie in northeastern Utah. Biostratigraphically informative taxa such as parasuchid phytosaurs in the absence of leptosuchmorph phytosaurs support an assignment of the Gartra Grit and Popo Agie Formation to the Otischalkian estimated holochronozone. We present the first detrital zircon age distributions for the Popo Agie Formation. Multidimensional scaling analysis of zircon populations shows that the Popo Agie samples are similar to other Upper Triassic units surrounding the Ancestral Uncompahgre Highlands, Central Colorado Trough, and the Ancestral Front Range. Additionally, we present the first maximum depositional ages (youngest population) for the Popo Agie Formation at a location where the top of the ochre unit is no older than 225 ± 4 Ma, and the upper purple to ochre transition is no older than 230 ± 5 Ma. By leveraging existing biostratigraphy, regional lithostratigraphy, and new radioisotopic ages we temporally constrain the Popo Agie Formation, enabling us to integrate the upper Chugwater Group, Chinle Formation, and Dockum Group strata into a testable Late Triassic chronostratigraphic framework for the western USA. The consilience of data support a Carnian age for the majority (if not entirety) of the Popo Agie Formation, making this—and equivalent strata in the Dockum Group (i.e., Camp Springs Conglomerate, and strata of the Tecolotito and Los Esteros members of the Santa Rosa Formation)—among the oldest continental Late Triassic stratigraphic units in the western USA.

AGE CONSTRAINTS AND SOURCE AREAS FOR THE PRECAMBRIAN TO CAMBRIAN STRATA OF THE SOUTHERN YENISEI RIDGE (REDKOLESNAYA AND OSTROVNOY FORMATIONS)

The Precambrian to Cambrian strata at the southwestern margin of the Siberian Platform are ubiquitously characterized by a gradual transition from red-colored alluvial and deltaic deposits to shallow-marine carbonates, reflecting a transgressive infill of the accommodation space of the foreland basin. However, a supposed synchronicity of the Early Precambrian marine transgressive events calls for verification by geochronological and bio- and chemostratigraphic dating. The herein-presented data on small skeletal fossils, trace fossils and variations in the carbon isotope composition of carbonates from the mixed carbonate-terrigenous succession (Redkolesnaya and Ostrovnoy formations) in the southern Yenisei ridge show that the base of the Cambrian Fortunian stage is placed within the Redkolesnaya formation. Age distribution of detrital zircons in the studied succession suggests the Siberian craton to be a major source of the clastic material in the foreland basin during the development of the Redkolesnaya formation. An increase in the amount of zircons derived from "non-Siberian" sources, located at the southwestern periphery of the paleocontinent at that time, in the coeval strata of the northern part of the southern Yenisei ridge, indicates a complex morphology of the paleobasin and considerable differentiation among the sources of clastic material therein.

U–Pb geochronology of detrital zircon from the Ediacaran and Cambrian sedimentary successions of NE Estonia and Volyn region of Ukraine: Implications for the provenance and comparison with other areas within Baltica

Trends in detrital zircon age distribution patterns are used to constrain the paleotectonic and paleogeographic conditions during deposition of the late Ediacaran - Early Cambrian sedimentary successions in northwestern, western, and southwestern Baltica. Detrital zircons from three sandstone samples collected from a drill-core drilled in northeastern Estonia and four sandstone samples collected from three drill-cores located in the Volyn region of Ukraine were dated using the U-Pb LA-ICP-MS isotope technique. The resulting age patterns are compared with the published data for southwestern Ukraine and Moldova, eastern Poland, Belarus, and northwestern Russia to constrain the late Ediacaran - Early Cambrian evolution of the sedimentary basins developed on Baltica. All sedimentary basins from these areas of Baltica show a transition during that interval from a passive continental margin to collisional settings, which has been triggered by the pre-Schythides and Santacrusades orogenies along the south-southwestern and, to a lesser extent, by the Timanian Orogeny along the north-northeastern and eastern (in modern coordinates) margins of Baltica.

Mantle plume heat flux and surface motion periodicities and their implications for the growth of continental crust

About 40% of Earth's surface is covered by continental crust. It has been found that the global detrital zircon age distribution is dominated by multiple periodicities from <100 Myr to ∼800 Myr, suggesting that continental crust may have been produced periodically. However, what causes the periodic growth of continental crust remains unclear. Continental crust is produced mainly by arc magmatism at subduction zones and plume-induced magmatism. With 3D global mantle convection models, we investigate the long-term evolution of heat flux of mantle plumes and surface flow velocity, which can be respectively related to plume-induced magmatism and arc magmatism. About 10-30 plumes are present in our models, with significant spatial and temporal variations of heat flux for individual plumes. Both the temporal variations of the total plume heat flux and the root-mean-square (rms) of the surface velocity in our models have periodicities that decrease with the vigor of mantle convection. When extrapolated to conditions with Earth-like vigor of convection, the total plume heat flux and the rms of the surface velocity vary with periodic cycles of ∼90-200 Myr and ∼300 Myr, respectively. Therefore, the ∼90-200 Myr and the ∼300 Myr periodic cycles in the growth of continental crust as suggested by the global detrital zircon age distribution may be respectively caused by plume-induced magmatism and arc magmatism.

Provenance analysis of Paleozoic strata in the Falkland/Malvinas Islands: Implications for paleogeography and Gondwanan reconstructions

New U-Pb geochronological, Hf isotopic, heavy mineral, and sandstone petrographic results for Paleozoic clastic deposits of the Falkland/Malvinas Islands help address renewed debates on the plate tectonic history, regional paleogeography, and basin evolution of this geologic enigma prior to Mesozoic breakup of Gondwana. The Falkland/Malvinas Islands have been considered either an autochthonous part of the South American continent or part of an independent microplate displaced from the southeastern corner of Africa. We report detrital zircon U-Pb results (n = 1306 LA-ICPMS ages) for 11 sandstone samples from the Silurian-Devonian West Falkland Group (N = 7 samples, n = 837 grains) and Carboniferous-Permian Lafonia Group (N = 4 samples, n = 469 grains). Detrital zircon age distributions for the West Falkland Group point to consistent contributions from Neoproterozoic-Cambrian (650–520 Ma) and Mesoproterozoic (1100–1000 Ma) sources. Heavy mineral assemblages and sandstone petrographic data from these samples indicate significant input from recycled sediments. A potential shift in sediment sources during deposition of the Lafonia Group is indicated by the appearance of late Paleozoic (350–250 Ma) and Proterozoic (2000–1200 Ma) age populations, decreased proportions of stable heavy minerals, and a shift to juvenile Hf values for < 300 Ma zircons. The provenance change can be attributed to the onset of subduction-related arc magmatism and potential regional shortening and crustal thickening in southwestern Gondwana during the Permian transition of a passive margin into an active, retro-arc foreland basin. The detrital zircon age distributions identified here reflect potential source regions in southern Africa and/or the Transantarctic Mountains in Antarctica. These results are most readily accommodated within a Gondwana reconstruction that includes the Falkland/Malvinas Islands as a rotated microplate originating on the eastern side of southern Africa as part of the Gondwanide fold-thrust belt spanning from the Ventania region of Argentina through the Cape region of South Africa and into the Ellsworth and Pensacola mountains of Antarctica.

Tectonic Background of Carboniferous to Early Permian Sedimentary Rocks in the East Kunlun Orogen: Constraints from Geochemistry and Geochronology

The formation of the East Kunlun Orogen (EKO) was related to the tectonic evolution of the Proto-Tethys and Paleo-Tethys Oceans. However, how the Paleo-Tethys Ocean transited from the Proto-Tethys Ocean, and whether the Paleo-Tethys Ocean subducted northward beneath the East Kunlun–Qaidam Terrane in Carboniferous to Permian times, is still highly debated. Early Carboniferous Halaguole and Late Carboniferous to Early Permian Haoteluowa formations are extensively outcropped in the EKO, north Tibetan Plateau, and have thus recorded key information about the tectonic processes of the Paleo-Tethys Ocean that have implications for the reconstruction of the Northern Paleo-Tethys Ocean (Buqingshan Ocean). Siliciclastic rocks within these formations are collected for petrogeological, geochemical, and detrital zircon U–Pb dating research. Our results show that sandstones from Halaguole and Haoteluowa formations have an average total quartz–feldspar–lithic fragment ratio of Q67F12L21 and Q50F20L30, respectively, indicating relatively high compositional maturity. The geochemical results suggest that the average values of the Chemical Index of Alteration (CIA) are 57.83 and 64.66; together with their angular to subangular morphology, this indicates that their source rocks suffered from weak weathering and the sandstones are the result of proximal deposition. Geochemical features such as the low La/Th, TiO2, and Ni values suggest that the parental rocks in the provenance area are mainly acidic igneous rocks with minor intermediate igneous and old sedimentary components. The detrital zircon U–Pb age spectrum of these samples is dominated by age peaks at ~405–503 Ma and ~781–999 Ma, with subordinate age peaks at ~1610–2997 Ma and ~1002–1529 Ma, which show tectono–thermal events similar to those of the North Qimatag Belt (NQB), North Kunlun Terrane (NKT), and South Kunlun Terrane (SKT). These features suggest a contribution from the Early Paleozoic magmatic arc and Proterozoic basements in the NQB, NKT, and SKT to the Halaguole and Haoteluowa formations in these areas. In addition, the youngest zircon age of ~440 Ma from these sandstones is greater than the depositional age of Halaguole and Haoteluowa formations, which is a typical basin depositional feature in a passive continental margin. Geochemical tectonic discrimination diagrams, based on a major and trace element Ti/Zr–La/Sc plot, in combination with a detrital zircon age distribution pattern, all suggest a passive continental margin setting. Considering this together with the previous data, we argue that the Paleo-Tethys Ocean did not begin to subduct northward and that there was no oceanic subduction zone in the south EKO during Carboniferous to Early Permian times. Combining this information with that from previous studies suggests that the initial opening of the Paleo-Tethyan Ocean may have occurred before the Early Carboniferous time, and all the branches of the Paleo-Tethys Ocean constituted a complex ocean–continent configuration across parts of what is now Asia during the Early Carboniferous to Early Permian.

PROVENANCE AND AGE CONSTRAINTS OF THE RIPHEAN SANDSTONES FROM THE IVANOVSKY GRABEN (THE KOLA PENINSULA) BASED ON THE U-Pb LA-ICP-MS DATING AND RAMAN SPECTROSCOPY OF DETRITAL ZIRCON

The results of U-Pb LA-ICP-MS dating of 150 detrital zircon grains from the Precambrian (Riphean?) sandstones of the Kildin group on the coast of the Ivanovka Bay (northeastern Kola Peninsula) are presented. A group of three youngest grains yielded constraint on the sandstone maximum depositional age of 1179±45 Ma. Detrital zircon age distribution is dominated by three maximums of 1.9, 2.4 and 2.7 Ga. The authors consider two complementary scenarios of interpretation of the data obtained. The first scenario involves the contribution of distant provenance out of granitoids in the Lapland-Kola orogen (~1.9 Ga) and adjacent areas of the Kola-Karelia region (~2.7 Ga), Imandra-Varzuga structure (~2.4 Ga), and Sveconorwegian belt (~1.2 Ga); the off-Baltic (Greenland?) sources of the detrital zircon also cannot be excluded. According to the second scenario, the Ivanovsky graben received zircons also from the proximal sources – sialic complexes formed upon melting of granite-gneiss substratum of the upper crust of the Murmansk craton during largescale episodic mafic magmatism 1.86, 2.50 and 2.68 Ga. The Raman spectroscopy showed that about 25 % of the analyzed detrital zircon grains experienced a 1.4-Ga-old thermal effect which did not lead to Pb losses but partially restored the crystalline structure of zircon. This result can be used as an additional constraint in the detailed provenance analysis of the northeastern East European Platform sedimentary basins and is indicative of 1.4-Ga-old large-scale magmatic events related to the breakup of the supercontinent Nuna.

The Assabet barcode: Mesoproterozoic detrital zircons in Neoproterozoic strata from Mauritania, West Africa

Detrital zircon data are reported from Mesoproterozoic to Ordovician strata from two tectonic domains in Mauritania: 14 samples from the Taoudeni Basin of the West African Craton and 15 samples from the Mauritanide orogen. Taoudeni Basin samples show four sequential, distinctive detrital zircon age distributions, which we refer to as “barcodes”. From old to young these are the Char, Assabet, Téniagouri, and Oujeft barcodes, each named for a constituent stratigraphic unit. Zircon age maxima are as follows, with the dominant ones in italics. The Char barcode, from Mesoproterozoic (<i>ca.</i> 1100 Ma) strata including the Char Group, yielded zircon age maxima at 2941, 2871, 2703, <i>2447</i>, <i>2076</i>, and <i>2041</i> Ma, all potentially traceable to sources in the West African Craton. The Assabet barcode is from strata, including the eponymous Assabet el Hassiane Group, that were deposited between <i>ca</i>. 883 and <i>ca.</i> 570 Ma; it has age maxima at 2137, 2053, 1769, 1510, <i>1212</i>, 1021, and 936 Ma and a pronounced minimum during Geon 16 (1699–1600 Ma). The Assabet9s Mesoproterozoic to early Neoproterozoic zircons cannot have come from the West African Craton or any of its surrounding orogens. The Téniagouri barcode, which takes its name from the Téniagouri Group, was deposited at <i>ca.</i> 569 Ma; it has dominant maxima at 1983, 1872, <i>1522</i>, <i>1215</i>, 1109, 988, and 601 Ma and resembles the Assabet barcode but with the addition of the youngest population. The Oujeft barcode, named for the Oujeft Group, is from strata deposited between 541 or slightly earlier and 444 Ma or younger, has age maxima at 2124, 2053, 1197, <i>624</i> and <i>579</i> Ma. The Téniagouri and Oujeft barcodes record input from Pan-African orogens. In the Mauritanide orogen, most of the metasedimentary rock units that were sampled yielded detrital zircon age spectra that match one of the Taoudeni Basin barcodes. These results imply new depositional age constraints based on barcode correlation and suggest affinities between Mauritanide strata and the West African Craton. Detrital zircon age distributions that broadly resemble the Assabet barcode occur in the Neoproterozoic of Morocco, Ghana, Greece, Russia, Brazil, and, in the Appalachian orogen of Canada and the United States, Avalonia and Ganderia. The recent Rodinia reconstruction of Evans (2021) restores these far-flung localities to a more compact area, with Avalonia, Ganderia, and other peri-Gondwanan terranes occupying an oblong area between Amazonia, Laurentia, Baltica, and West Africa. Our preferred explanation is that most of these places received detritus via the same continent-scale fluvial system as the West African craton. Among the craton9s nearest Rodinia neighbors in the Evans (2021) reconstruction for 900 Ma, Amazonia has known igneous rocks corresponding to all of the major Assabet age populations, and also a lull, though not a complete magmatic gap, during Geon 16. This is consistent with overall north-directed paleocurrents in the Assabet El Hassiane Group and its correlatives on the West African Craton.

Provenance of pre- and Carboniferous sequences of the Esquel-Arroyo Pescado-Tepuel regions (Argentine Patagonia): A combined U–Pb and Hf isotope study of detrital zircon and constraints on depositional setting

Provenance and stratigraphic age of pre-Carboniferous or pre-glacial (Esquel and Arroyo Pescado formations) and Carboniferous glacial (Valle Chico Formation) metasedimentary units exposed in the southwestern sector of the North Patagonian Argentine region are analyzed by sedimentary petrology and combined U–Pb and Lu–Hf isotope on detrital zircons. Additionally, a sample of the Jaramillo Formation (Tepuel Group) allowed comparison and correlation to the Carboniferous deposits in the type area of the Tepuel-Genoa basin.Despite differences, samples of all units studied indicate deposition linked to an arc tectonic environment using ternary petrological diagrams. U–Pb detrital zircon age distribution of the Esquel Formation show a dominance of Famatinian, Pampean-Brazilian and Mesoproterozoic ages, whereas the Arroyo Pescado Formation displays a predominant Mesoproterozoic data cluster. On the other hand, the Valle Chico Formation records a main input of post-Famatinian or Chanic (Devonian) ages and minor Gondwanic (Carboniferous) ages. The Jaramillo Formation is unique due to the remarkable unimodal concentration of Gondwanic ages (Carboniferous) and the scarcity of older than Famatinian detrital zircon ages. The maximum sedimentation age is Lochkovian (Lower Devonian) for the Esquel Formation and, Tournaisian and Tournaisian-Visean (lower Carboniferous) for the Valle Chico and Jaramillo formations, respectively; the youngest records for the Arroyo Pescado Formation indicate a middle Cambrian to Middle Ordovician age. Most Mesoproterozoic zircon grains show a remarkable juvenile Hf isotopic character and a slight age difference between U–Pb and Hf TDM data. These records are equivalent to those identified in different units of the Paleozoic of the Patagonian region and the Malvinas/Falkland Islands, where the Mesoproterozoic detrital zircons with positive εHf (t) values indicative of a juvenile character are present. The conspicuous participation of Mesoproterozic zircons ages within the pre-Carboniferous units supports the probable existence of an unexposed Mesoproterozoic crust in the North Patagonian region, as mentioned by previous authors.The allochthonous or autochthonous character of South Patagonia is tested using combined U–Pb ages and initial Hf-isotope compositions of single zircons. The allochthonous alternative of South Patagonia in the pre-Carboniferous stage, favours contributions from eastern Antarctica, South Africa, Malvinas/Falkland Islands and local sources such as the Deseado Massif and the suspected Chaitenia terrane. An autochthonous scenario suggests that the North Patagonian, Deseado Massifs, Malvinas/Falkland Islands and local areas (Chaitenia terrane) were the main source for the pre-Glacial and Glacial studied units, with minor influence from distant regions of South America.

Geochemical and detrital zircon age constraints on Meso- to Neoproterozoic sedimentary basins in the southern Yangtze Block: Implications on Proterozoic geodynamics of South China and Rodinia configuration

The late Mesoproterozoic to early Neoproterozoic sedimentary sequences in the southwestern Yangtze Block, represented by the Julin, Huili, and Kunyang groups, provide vital evidence for deciphering the tectonic evolution of the Yangtze Block that have implications on the reconstruction of the Rodinia supercontinent. Zircon geochronological data reveal that the Julin and Huili groups were deposited at 1167–982 Ma and 1176–958 Ma, respectively. The Haizishao Formation, the conventionally thought the upper most of the Julin Group, was deposited after 982 Ma. The stratigraphicphic position of the Haizishao Formation basal conglomerate and diversity in its detritus source, and tectonic setting, suggest that the Haizishao Formation may not be a part of the Julin Group but represents an independent sedimentary event. Geochemical tectonic discrimination characteristics based on major elements, Th-Sc-Zr/10, Ti/Zr-La/Sc, La/Th-Hf and Sc/Th-La/Sc plots, in combination with detrital zircon age distribution pattern and bimodal magmatism, point toward a transition from continental rift to passive continental margin setting followed by an active continental margin setting for Julin and Huili groups. However, the Huili Group is significantly different from both the Julin and Kunyang groups in terms of lithological composition, depositional environment, detrital zircon age distribution, and tectonic setting, implying that the Julin and Huili basins may have been located in different microcontinents during the late Mesoproterozoic - early Neoproterozoic times.Detrital zircon U-Pb ages and Lu-Hf isotopic characteristics of Julin and Huili groups indicate detritus sourced from the continental interior and exotic terranes, such as the Yudongzi, Douling, and Kongling complexes and magmatic rocks at the southwestern margin of Yangtze Block, the Gawler Craton in Australia, the Transantarctic Mountains in East Antarctica, and the Ongole domain in the Eastern Dharwar Craton of India. Combining provenance analyses and comparison of detrital zircon data, the Yangtze Block was paleogeographically placed in the external position to the Rodinia supercontinent, close to north-central India, Australia, and East Antarctica during the late Mesoproterozoic to early Neoproterozoic.

Detrital zircon U–Pb geochronology and Hf isotopes of Mesozoic through Cenozoic sandstones from the southern Junggar Basin, NW China: Implications for the provenances and uranium source

Junggar Basin is an important exploration zone for sandstone‐hosted uranium deposits in north‐west China. However, neither the provenance of the host sandstone nor the uranium supply capacity of the potential source rocks have been well evaluated. To determine the provenances of the Mesozoic to Cenozoic sandstone grains and to evaluate relationships between the uranium source and the detritus provenances, a field investigation was performed at the Honggou section in the southern Junggar Basin. U–Pb geochronology and Hf isotopes were obtained from populations of detrital zircons from Jurassic through Palaeogene sandstones. The detrital zircon U–Pb ages display three main groups: 145–190 Ma, 250–360 Ma, and 360–460 Ma. The detrital zircon age distributions and the Hf isotopic characteristics of the sandstones correspond to different igneous rock units within the North and Central Tianshan Mountains. Therefore, the changes in the relative proportions of the zircon age populations indicate that there were major shifts of the provenance areas for the sandstones throughout the Early Jurassic to Palaeogene interval. The majority (92%) of Hf isotope εHf(t) values are positive and in the range of +0.7 to +15.5, which indicates that the majority of the zircons had crystallized in igneous rocks that were mainly derived from juvenile crust or depleted mantle. The majority (93%) of the two‐stage model ages (TDM2) are less than 1.8 Ga, thereby indicating the source of the majority of the igneous rocks was from the melting of ancient Meso‐Proterozoic juvenile crust. Carboniferous–Permian intermediate‐felsic igneous rocks in the Tianshan Mountains may be the primary source of released mobilized uranium and uranium‐enriched siliciclastics into the southern Junggar Basin. This study will assist in future uranium prospecting in this region.

Provenance of Devonian–Carboniferous strata of Colorado: The influence of the Cambrian and the Proterozoic

ABSTRACT We report new LA-ICP-MS U–Pb detrital zircon ages and sedimentary petrology of silty to sandy limestones and dolostones, as well as calcareous to dolomitic sandstones of the Devonian–Carboniferous (Mississippian) Chaffee Group. We also report new detrital zircon ages from the late Cambrian Sawatch Quartzite, and a U–Pb zircon crystallization age on a late Mesoproterozoic (1087.9 ± 13.5 Ma) granitoid of underlying basement from the Eagle Basin of northwest Colorado. Grain populations in the Chaffee Group are mostly bimodal. More than 84% of zircons centered around a Paleoproterozoic (ca. 1.78 Ga) mode typical of the Yavapai province that forms much of the basement of Colorado and an early Mesoproterozoic (ca. 1.42 Ga) mode typical of A-type granites that intrude this region. A notable late Mesoproterozoic (ca. 1.08 Ga) mode exists in some Chaffee samples, giving those samples a trimodal detrital zircon age distribution. These bipartite or tripartite detrital zircon age modes exist in Cambrian, Devonian, and Carboniferous strata from paleogeographically adjacent successions, but the correlation between the Chaffee zircons is highest with the region’s basal Cambrian sandstones of the Sawatch Quartzite, Flathead Sandstone, and Ignacio Quartzite, which have similar (ca. 1.08 Ga, 1.43 Ga, 1.70 Ga, respectively) zircon populations, and a paucity of &amp;gt; 1.8 Ga grains. This similarity suggests that most grains in the Chaffee Group derive from recycling of these basal sandstones, and that little sediment was derived directly from thenexposed Precambrian basement highs, from the Wyoming craton to the north, or from Paleoproterozoic arcs and orogens to the west and northeast. Minor Mesoarchean to early Paleoproterozoic (ca. 3.00 to 2.40 Ga) grains exist in the Chaffee Group, an attribute shared by the Late Ordovician Harding Sandstone of Colorado’s Front Range, but that is absent from the region’s underlying Cambrian sandstones—suggesting some recycled mixture of Cambrian and Ordovician sedimentary rocks. No near-depositional age grains are present in the Chaffee Group. The youngest grain is Early Devonian (~417 Ma), &amp;gt; 45 million years (m.y.) older than these strata. Additionally, Paleozoic grains are extremely uncommon (&amp;lt; 0.1%; n = 2,927 grains).

Age and origin of the H9 member from the Bayan Obo Group: Implications for the genesis of the giant Bayan Obo Fe-Nb-REE deposit, China

The Bayan Obo deposit hosted in a set of metamorphic sedimentary strata contains the world’s largest rare earth reserve. However, the genesis of its ore-bearing dolomites remains controversial. The temporal and spatial relationships and compositions of the surrounding strata could provide indirect genetic indications for ore-bearing dolomites, particularly the overlying H9 member. Our data suggest that the compositions of H9 member are complex, consisting of quartz sandstone, biotite shist, metamorphic volcanic rocks and alkaline rocks. The origin and genesis of different lithologies in the H9 member are different. Based on the age distribution of detrital zircons, the basement rocks from the Bayan Obo region are presumed to be the material sources for the quartz sandstone in the H9 member. The biotite schist is the alteration products of wall rocks reacting with the fluids extracted from the ore-bearing dolomite. Metamorphic volcanic rocks and alkaline rocks are also distinguished in the H9 member. Th-Pb dating of zircons from the H9 volcanic rocks indicates its formation age is around 1.4 Ga, which is earlier than the mineralization age of the ore body, and the H9 member is also affected by the Caledonian tectonic compression recorded by the age of 427 Ma. According to the temporal and spatial distribution of H9 member and ore-bearing dolomites, the dolomites are considered to be magmatic origin. H9 member acts as the caprocks of the ore-bearing dolomite, and the contribution of its material composition and entrapment play an important role in the formation of the Bayan Obo deposit.