Neoproterozoic Detrital Zircons Research Articles

Sedimentary provenance of the Upper Devonian Old Red Sandstone of southern Ireland: an integrated multi-proxy detrital geochronology study

The Devonian Old Red Sandstone (ORS) magnafacies of southern Ireland is hosted in the Early Devonian Dingle Basin and the Late Devonian Munster Basin. Following the closure of the Iapetus Ocean during the Caledonian Orogeny, the Dingle Basin developed as a pull-apart structure before being deformed by Acadian tectonic activity. The Munster Basin developed as a half-graben structure in response to post-Acadian north–south extension in the region. Thus, the Irish ORS provides insights into the region's tectonic history owing to its temporal and spatial proximity to the Caledonian ( c . 475–425 Ma), Acadian ( c . 400–390 Ma) and Variscan orogenic events ( c . 390–290 Ma). This study presents the first detrital zircon and apatite U–Pb geochronological data for the Upper ORS (UORS) in southern Ireland in addition to detrital white mica 40 Ar/ 39 Ar geochronological data to help unravel the depositional history of the Irish UORS and to assess the possible role of sedimentary recycling in Late Devonian basin development. Most UORS samples contain few late Neoproterozoic detrital zircon grains and are instead dominated by early Paleozoic and c. 1.1 Ga zircons. These populations represent recycling of northerly-derived Ordovician to Silurian strata of the Southern Uplands–Longford–Down terrane, which are of Laurentian affinity, and not recycling of Lower ORS (which contains a significant number of late Neoproterozoic detrital zircons) as previously thought. Similar detrital zircon dates have been observed in Givetian–Frasnian quartzites of the Pulo do Lobo Zone on the Iberian Peninsula, providing a possible Rheic Ocean link with the UORS.

U-Pb detrital zircon age determination and provenance of the lower Karoo succession from the Karoo Research Initiative (KARIN) borehole KWV-1, Eastern Cape Province, South Africa

Abstract In recent years, the maximum age of sedimentation and possible sources of detritus to the sedimentary successions of the Karoo Supergroup has received a lot of interest, with various authors presenting age data from across the main Karoo Basin (MKB). Our paper aims to contribute to this ever-growing geochronological database as we report weighted mean ages for the youngest zircons as well as detrital zircon age distributions for the lower Karoo Supergroup succession sampled from the Centre of Excellence for Integrated Mineral and Energy Resource Analysis (CIMERA)-Karoo Research Initiative (KARIN) drill core KWV-1. A total of 880 near concordant zircon ages were determined using Laser Ablation Quadrupole Inductively Coupled Plasma Mass Spectrometry (LA-Q-ICP-MS) from fifteen samples representing the Dwyka Group, the Collingham-, Ripon-, Fort Brown- and Waterford formations of the Ecca Group and the Koonap Formation of the Beaufort Group as intersected by this ~2 352 m deep research borehole drilled in the southeastern sector of the basin. The weighted mean ages for the youngest zircons calculated for the formations of the Ecca- and Beaufort groups compares with findings reported by other authors and with the ages reported for tuffaceous layers associated with these units. The weighted mean ages for the youngest zircons of the Dwyka Group reflect the age of the youngest source area and do not aid in constraining the maximum age of deposition. A significant change in detrital zircon age distribution was noted between the Dwyka Group and the overlying formations of the Ecca and Beaufort groups, which we interpret as a change in provenance. The major Meso-to Neoproterozoic detrital zircon age fractions present in the Dwyka Group are attributed to source areas located towards the north and northeast of the MKB, in line with regional ice flow directions. A significant late Carboniferous to Permian detrital zircon age fraction is however observed throughout the formations of the Ecca- and Beaufort groups, with a lesser fraction of older zircon ages. The prevailing youngest age fraction reflects ages associated with magmatic source areas in the Gondwanide Orogeny located towards the south of the MKB at the time of deposition, while the recycling of deformed sedimentary strata of the Cape Supergroup contained in the Cape Fold Belt is considered the source of older detritus. The source of detritus to the MKB remained unchanged during the deposition of the respective formations of the Ecca- and Beaufort groups, despite changes in the depositional environment brough on by regional tectonics.

Mesoproterozoic–Neoproterozoic chronostratigraphic framework and provenance analysis in the southeastern North China Craton and its tectonic significance

The Sishilichangshan area of southwestern Xuhuai Basin, located in southeastern North China Craton (NCC) and to the north of the Qinling–Dabie Orogenic belts, is a key, optimal area to study the regional evolution of the NCC because of its stratigraphic differences within the NCC. An integrated approach of the field investigation, element geochemistry, and detrital zircon U–Pb–Hf isotope analysis reveals essential information on the Mesoproterozoic–Neoproterozoic tectonic‐sedimentary evolution of the Xuhuai Basin. The youngest graphical peak ages of detrital zircons from the Shouxian Formation at the top of the Bagongshan Group, the Jiuliqiao Formation at the bottom of the Huainan Group, and the Anyangshan Formation are 1003 ± 25 Ma, 991 ± 80 Ma, and 832 ± 23 Ma, respectively. New age constraints and stratigraphic correlations show that the traditional Neoproterozoic strata in the southern Xuhuai Basin consist of Late Stenian to Early Tonian Bagongshan and Huainan groups, and the Late Tonian Anyangshan Formation, which overlapped unconformably with mid‐late Ediacaran or Cambrian Series 2 strata. The Anyangshan Formation is first termed in this study, and its equivalent strata occur sporadically in the southeastern, southwestern and northwestern NCC. The Tonian Shouxian, Jiuliqiao, and Anyangshan formations are characterized by detrital zircons of multi‐stage Mesoproterozoic ages and predominantly positive εHf(t) values, with differences in mineral composition, whole‐rock geochemistry, and the Early Neoproterozoic detrital zircon age population. Their possible provenance was a Grenvillian orogen extending from the North Qinling Terrane (NQT) to the central Korean Peninsula, supporting Late Mesoproterozoic to Early Neoproterozoic initial accretion related to the continental arc between the NCC and NQT. Tectonic transition from Late Stenian to Early Tonian (~1.18–0.94 Ga) collisional basin to mid‐late Tonian (0.94–0.74 Ga) rift basin is interpreted as the response of the NCC to the assembly and extension of the Rodinia Supercontinent.

New geochronological and provenance constraints on the Late Mesozoic sedimentary formations in the western Shandong Province and Tanlu fault zone, China

We present new LA-ICP-MS detrital zircon U-Pb age and trace element data of the Late Mesozoic sedimentary sequences from the western Shandong and Tanlu fault zone, with the aim to constrain the depositional ages and sedimentary sources. The samples from the western Shandong have similar U-Pb age spectra, which can be divided into three major age groups, peaking age at circa 2,475–2,540 Ma, 1820–1870 Ma and 257–285 Ma, with minor Mesoproterozoic, Neoproterozoic and Paleozoic detrital zircon grains. The sample JN recovered from the Tanlu fault zone has an overwhelming majority of the Early Cretaceous detrital zircons with the age peak at circa 125 Ma, whereas the Archean and Paleoproterozoic detrital zircons are subordinate. The weighted average age of the youngest zircons show that the Santai Formation probably had begun deposition at circa 158 Ma and terminated deposition at circa 150 Ma, and the Tianjialou Formation of the Dasheng Group had begun deposition at circa 122 Ma. Our study indicates that the activity of the dinosaurs might occur during the Late Jurassic rather than the Cretaceous in the Shandong province. In addition, most detrital zircons of the studied samples are characterized by the high Th/U ratios and left-inclined REE patterns, revealing a magmatic origin. Morphologically, most detrital zircon grains characterized by angular to sub-rounded shapes indicate a middle-short distance transport from the source regions, whereas minor detrital zircon grains show rounded shapes, indicating a long-distance transport or multiphase recycling. According to detrital age populations in this study, combined with previously published data, we conclude that depositional provenances of the Santai Formation were mainly derived from the western Shandong and Jiao-Liao Belt, and minor detritus were derived from the northern part of the North China Craton and Xing-Meng orogenic belt. The sediments deposited in the Tanlu fault zone were mainly derived from the volcanic and subvolcanic rocks of the Qingshan period in the eastern Shandong, and subordinate depositional sources were from the Jiao-Liao and the basement uplift of the western Shandong, with minor supplier being derived from the Yinshan-Yanshan orogenic belt. The detrital provenance of the Santai Formation indicates that extension of the eastern NCC occurred during the Late Jurassic. The Neoproterozoic detrital zircons play a minor role in the studied strata, indicating that the large sinistral movement of the Tanlu fault zone might have occurred at the Early-Middle Jurassic and formed a paleogeographic separation of the western Shandong and eastern Shandong (Sulu orogenic belt).

Neoproterozoic evolution of the northwestern margin of the Siberian Platform

New geochronological, geochemical and carbon isotope data from the Igarka Uplift constrain the age and reveal geodynamic evolution of the northwestern Siberian Platform in the latest Mesoproterozoic and Neoproterozoic. Dolostones of the Medvezhy Formation, the oldest part of the sedimentary succession, correspond to the latest Mesoproterozoic (∼1000 Ma) according to stable isotopic composition. Overlaying volcano-sedimentary Ludy, Gubinskaya and Igarka formations are no older than 715 Ma according to detrital zircon ages and carbon isotope data. Chemical composition of the Igarka Formation and synchronous mafic intrusions of the Gubinskaya Formation suggest a single magma source developed in an intraplate rifting environment. The Ediacaran Chernaya Rechka and Izluchina formations unconformably cover both meso- and mid-Neoproterozoic sequences. The age of the Ediacaran units are confirmed by the Pb-Pb isochron age of 610 ± 50 Ma and large positive C-isotope anomaly in the Chernaya Rechka limestones. Abundant Neoproterozoic (950–800 Ma) detrital zircons in the studied Neoproterozoic sedimentary rock units points to the existence of a hypothetic large Neoproterozoic orogenic belt on the northeastern periphery of the Siberian Platform unexposed nowadays. The pre-Ediacaran rift trough of the Igarka Uplift and other similar structures, mark extensional environments along the present western margin of the Siberian platform in the mid-Neoproterozoic. These structures are coeval to a large igneous province (ca. 720 Ma) at the northern Laurentia associated with the Rodinia breakup.

Cambrian/Ordovician boundary as a milestone in the sedimentation history of the southern Siberian craton: Evidence from U-Pb dating of detrital zircons

The paper presents petrographic, geochemical, and new U-Pb zircon (LA-ICP-MS) geochronological data on the Upper Lena Fm. sediments which make part of the Cambrian sedimentary cover of the Siberian craton. The composition of lithic fragments in these clastic sediments, including mafic and felsic volcanics and granitoids, along with the correlation of major element ratios and the values of trace-element ratios point to predominant igneous (mainly felsic) rocks in the provenance. The U-Pb ages of detrital zircons from the sampled Upper Lena Fm. sandstones are mostly Early Paleozoic (∼500 Ma), with very few Archean-Paleoproterozoic determinations and quite many Neoproterozoic zircons. Ediacaran and Earliest Cambrian clastic sediments bearing Early Precambrian and Neoproterozoic detrital zircons, as well as Neoproterozoic and Early Paleozoic complexes of the Central Asian Orogenic Belt, could provide material for the Upper Lena clastic deposition. The geochronological evidence shows that the Upper Lena Fm. sandstones were deposited over vast territories of the southern Siberian craton in the Late Cambrian, in a single sedimentary basin, and originated from the same provenance. The Upper Lena deposition event in the Late Cambrian, immediately before the Ordovician period, makes a key milestone in the geological history of Siberia: the end of a large-scale Early Cambrian transgression and the beginning of gradual uplift of the southern craton margin, at least till the Carboniferous, which was associated with the formation of the Central Asian Orogenic Belt, a major tectonic unit of Asia.

Combined U-Pb ages and Lu-Hf systematics of detrital zircons from Early Cambrian Gondwanan siliciclastic rocks in S Turkey: Provenance and correlations with coeval successions in peri-Gondwanan terranes

Detrital U-Pb age peaks and εHf(t) and TDM(Hf) of peri-Gondwanan units of S Turkey indicate that they may have been derived from Neoproterozoic igneous suites in the Sinai Peninsula (Egypt), Israel (Elat) and Eastern Desert (Egypt) part of the Nubian Shield. Early Cambrian siliciclastics in the peri-Gondwanan units of S Turkey consist of quartzites in the Menderes Massif of the Tauride-Anatolide Platform (TAP), meta-quartz arenites in the different Alpine tectonic slivers of the TAP-margin and quartz-arenites in the Southeast Anatolian Autochthon Belt (SAAB). Geochemical data indicate that these sediments are likely to be derived from sedimentary recycling processes in oxic depositional basins within a continental back-arc tectonic setting. They were opened after the formation of the Avalonian-Cadomian magmatic arc. In the TAP, the youngest detrital zircon 238U/206Pb ages are range from 530.6 + 6.3/-12.0 Ma to 549.4 ± 10 Ma and from 551.9 + 7.9/-8.4 Ma to 545.8 ± 11 Ma in the SAAB verifying the Early Cambrian maximum depositional ages for the sampled siliciclastic successions. In the TAP, meta-quartz arenites, Neoproterozoic detrital zircons make up about 75% of the total grains, whereas they constitute about 88 % in the SAAB sedimentary rocks. Tonian zircons in the TAP (>40 %) and SAAB (<32 %) reveal key populations to determine their provenance and the paleotectonic positions of the respective terranes. The combination of U-Pb age and Lu-Hf systematics in the detrital zircons of the TAP and SAAB show that age groups at 535 to 562 Ma and 888 to 3370 Ma are mainly represented by the zircons derived from evolved sources with a limited juvenile component. The predominant zircon age groups between 577 and 854 Ma in the TAP and SAAB, on the other hand, were derived from juvenile to evolved sources. Non-parametric Kolmogorov-Smirnov tests suggest that Early Cambrian successions in the TAP (except Kocaosman-Isparta) may have been located in similar paleogeographic locations with coeval successions in the SAAB during the Early Cambrian. U-Pb geochronology and Lu-Hf systematics of the Early Cambrian successions in the TAP and SAAB indicate that the dominant detrital zircon age groups were mainly sourced and transported to continental back-arc fluvial to shallow marine sedimentary environments from igneous rocks of the Nubian Shield and the Saharan Metacraton by a combination of the glaciers, eolian events and multiple-stage erosional and sedimentary recycling processes during the Early Cambrian (ca 520 Ma). The provenance of the Early Cambrian successions in the TAP and SAAB correlate with the provenance areas of the coeval siliciclastic sequences in Israel and Jordan (Arabian Shield), Iraq and Iran and the peri-Gondwanan Carpathians, rather than the Early Cambrian successions in the central and southern European peri-Gondwanan terranes.

History of crustal growth in Africa and the Americas from detrital zircon and Nd isotopes in glacial diamictites

Diamictites produced by continental glaciations were deposited in the Mesoarchean (∼2.9 Ga), Paleoproterozoic (∼2.4–2.2 Ga), Neoproterozoic (∼0.75–0.58 Ga), and Paleozoic (∼0.3 Ga), and, with the exception of the Mesoarchean, occur on multiple modern continents. We examine the provenance of a selection of these diamictites from all four time periods and three continents via detrital zircon U-Pb geochronology and Hf isotope and whole-rock Nd isotope analyses. Mesoarchean samples from South Africa contain mostly Mesoarchean zircon, with a much smaller number of Paleoarchean grains. Zircon Hf and whole-rock Nd point towards their derivation from reworked Paleoarchean crust. Paleoproterozoic samples from North America share a similar unimodal zircon age distribution, with a peak at 2.7 Ga and a narrow range in Hf isotopes that is slightly superchondritic. Coupled with whole-rock Nd results, these data point to their derivation from reworked juvenile Mesoarchean crust. By contrast, the Nd isotope data and existing published detrital zircon U-Pb data for Paleoproterozoic diamictites from South Africa indicate a mix of Neoarchean and Mesoarchean sources. Neoproterozoic samples from Namibia share a Paleoproterozoic detrital zircon population with variable but subchondritic Hf isotope compositions, indicating derivation from reworked Neoarchean crust. Most samples also have Mesoproterozoic and Neoproterozoic zircon with both positive and negative εHf(i), and all have Nd isotope compositions yielding Paleoproterozoic model ages. A Neoproterozoic sample from Canada contains mostly Neoproterozoic detrital zircon with variable Hf isotope compositions, indicating a mix of juvenile and reworked Mesoproterozoic crust. Samples from different parts of the Paleozoic Dwyka Group in South Africa show significantly different provenance, with a western locality containing only zircon older than 2.0 Ga and a Neoarchean Nd model age. By contrast, eastern samples have Paleoproterozoic model ages and published detrital zircon ages are largely Mesoproterozoic and younger. Paleozoic samples from Bolivia have a Paleoproterozoic Nd model age.Overall, the difference between zircon initial Hf isotope compositions and the depleted mantle is smallest for Archean zircons, indicating major episodes of crustal reworking followed shortly after crust formation (perhaps reflecting the last stage of cratonization). Hf and Nd data together record major episodes of juvenile crust formation at 3.2, 2.8–2.7, 2.0–1.7, and 1.3–0.9 Ga, consistent with previously documented global crust formation events. The diamictites provide no evidence for pre-3.6 Ga felsic crust in these regions.

ИСТОЧНИКИ КЛАСТИЧЕСКОГО МАТЕРИАЛА И УСЛОВИЯ НАКОПЛЕНИЯ ОСАДОЧНЫХ ПОРОД ДАУРСКОЙ СЕРИИ АРГУНСКОГО КОНТИНЕНТАЛЬНОГО МАССИВА

The paper presents the results of geochemical and isotopic-geochemical (Sm-Nd) studies of the Upper Riphean (?) (in the Stratigraphic Scale of Russia) sedimentary rocks of the Urulungui and Dyrbylkey formations of the Daur Series in the Argun continental Massif, as well as U-Th-Pb and Lu–Hf isotopic studies of detrital zircons from these formations. Rocks of the Urulungui and Dyrbylkey formations differ significantly in mineral composition and content of the main elements, which is probably due to the degree of chemical weathering of the source rocks. Analysis of concentrations of trace elements in sedimentary rocks of the Urulungui and Dyrbylkey formations enabled to establish that they were formed in a subduction-related setting. The presence of conglomerate-breccias, conglomerates, gravelstones, fragments of igneous and volcanic rocks, a weak degree of roundness of clastic material, as well as abundant Neoproterozoic detrital zircons in the formations is evidence of tectonic and igneous activities in the region during sedimentation. Sedimentary rocks of the Urulungui Formation are characterized by two-stage model ages TNd(DM2) = 2.0–2.1 Ga, and the Dyrbylkei Formation – TNd(DM2) = 1.6–1.8 Ga according to the results of Sm-Nd isotopic-geochemical studies. The abundant Neoproterozoic zircons in sandstones of the Urulungui and Dyrbylkey formations suggest that Neoproterozoic igneous rocks widely developed within the western Argun continental Massif were the main source of clastic materials. At the same time, the presence of Early Precambrian detrital zircons is evidence that Early Precambrian rocks were also present in the source area. However, Early Precambrian igneous and metamorphic associations whose age would be reliably determined from geochronological data have not yet been found so far within the Argun continental Massif, and thus it is not out of the question that rocks of the Daur Series form a «detached block» intruded in the Argun Massif.

Early Neoproterozoic tectonic evolution of northern Yangtze Block: Insights from sedimentary sequences from the Dahongshan area

Precambrian sedimentary strata are widely distributed along the periphery of the Yangtze Block. However, the age, provenance and tectonic setting of the sedimentary successions on the northern margin still remain unclear, which exerted considerable influence on the understanding of Precambrian crustal evolution of the Yangtze Block. Here we report integrated detrital zircon U-Pb dates and Lu-Hf isotopes from the Dahongshan area to the northeast of the nuclei (i.e. the Kongling Complex) of the Yangtze Block. The youngest U-Pb dates of 995 Ma and 810 Ma of detrital zircon grains place constraints on the maximum depositional ages of the underlying Dagushi Group and the overlying Huashan Group, respectively. Both groups show pre-Mesoproterozoic age populations at ca. 2050 Ma and ca. 2700 Ma and corresponding εHf(t) values varying from –24.1 to + 2.3, consistent with counterparts of the Kongling Complex and Yangpo Complex in northern Yangtze Block. The εHf(t) values of Neoproterozoic (1000–800 Ma) detrital zircon grains in the Huashan Group show a decrease after ca. 880 Ma (from + 13.5 to –18.5), possibly indicating a transition from arc-continent collision to continental arc setting on the northern margin of the Yangtze Block. In combination with sedimentary characteristics and the new isotopic results, the Dagushi Group probably formed in a shallow marine basin setting and received dominant detritus from the Kongling and Yangpo complexes. In contrast, the Huashan Group received sediments recycled from the underlying Dagushi Group and contemporary igneous rocks in the Dahongshan and Kongling areas. The changes in provenance and tectonic setting recorded in the two sedimentary sequences suggest a tectonic transition from late Mesoproterozoic passive continental margin to Neoproterozoic subduction and accretion in response to the amalgamation of Rodinia supercontinent. On the basis of distinct location and history, Pre-Nanhua Neoproterozoic sedimentary sequences distributed in the periphery of Yangtze Block are dispersed into four separate domains. Through bivariate kernel density estimates and bootstrap resampling method, we have identified that these domains were characterized by asynchronous igneous impulse and heterogeneous character of igneous activity in early Neoproterozoic along with varying degrees of integration of crustal growth and reworking.

A missing piece between Laurentia and the North China Craton in Rodinia: Evidence from metasedimentary rocks of the North Qinling Terrane in central China

The North Qinling Terrane was a microcontinent in the Late Neoproterozoic and then subducted northwards beneath the North China Craton for regional metamorphism in the Early Paleozoic. In order to constrain its location in supercontinent Rodinia, metasedimentary rocks were sampled from it for a combined study of whole-rock major and trace elements as well as zircon U-Pb ages and Lu-Hf isotopes. The metasedimentary rocks show greywacke compositions with A/CNK ratios of 0.99–1.28 and upper continental crust-like trace element patterns. They have metamorphic ages of ca. 510–490 Ma, recording continental collision for the regional metamorphism. The youngest detrital zircon U-Pb ages from three metasedimentary rocks are 1161 ± 54 Ma, 954 ± 15 Ma, 861 ± 10 Ma, respectively. In combination with ages of granitic intrusions of 960 to 890 Ma in the target region, their deposition ages are constrained to be 1110–960 Ma, ca. 960 Ma and ca. 860 Ma, respectively. The cumulative proportions of the difference between the detrital zircon crystallization ages and the deposition ages for the sediments of ca. 960 Ma and ca. 860 Ma suggest their deposition in a collisional setting. Detrital zircon age spectrum from the Qinling Group yields two major populations at 1000–900 Ma and 1700–1400 Ma and three subordinate populations at 900–800 Ma, 1300–1200 Ma and 1800–1700 Ma with rare Neoarchean grains. Neoproterozoic detrital zircons mainly have negative εHf(t) values, consistent with Neoproterozoic granitoids in the North Qinling Terrane. On the other hand, Mesoproterozoic detrital zircons mainly have positive εHf(t) values, similar to those in East Laurentia and East Greenland. This means that the major provenance of sediments in the Qinling Group was the North Qinling Terrane itself and East Laurentia, supporting the connection between the North Qinling Terrane and East Laurentia in Rodinia prior to its breakup. In combination with the coeval strata in the southern margin of the North China Craton, we propose that the North Qinling Terrane is a missing piece connecting the southern margin of the North China Craton with the northern part of East Laurentia in Rodinia in the early Neoproterozoic.

Zircon U-Pb ages and Hf isotope analysis of Neoproterozoic Yaolinghe Group sedimentary rocks in the Chengkou area, South Qinling: Provenance and paleogeographic implications

The Yaolinghe Group sedimentary rocks exposed along the Dabashan fault zone are rich in pyroclastics and are thousands of meters thick. They provide key information for studying the tectonic location relationship between the Yangtze and Qinling blocks and the tectonic-sedimentary environment of the late Neoproterozoic continental margin. This study reports U–Pb and Lu-Hf isotope data of 438 and 408 detrital zircons from five samples of Yaolinghe Group sedimentary rock, collected in the Chengkou area, China. Combining the youngest detrital zircon U–Pb age for gravelly sandstone with data from previous studies, we constrained the maximum depositional time of the Yaolinghe Group sedimentary rocks in this area to ca. 650–635 Ma (i.e., Neoproterozoic Cryogenian). In the Chengkou area, the predominantly Neoproterozoic (1000–635 Ma) detrital zircons, with wide εHf(t) values ranging from −31.03 to 13.07 and an average of 2.00, were primarily derived from the adjacent regions of exhumed igneous rock in the South Qinling and Northern Yangtze blocks. Several minor age peaks at more than 1000 Ma indicate that this formation contains a small amount of recycled zircon. Further study indicates that the Yaolinghe Group sedimentary rocks were formed by near-source accumulation in a rift setting, located at the north margin of the Yangtze Block, during the breakup of Rodinia. As in previous studies, the retreat of the subducted slab may have led to continental rifting and extension of the Northern Yangtze Block, and the Yaolinghe Group sedimentary rocks in the Chengkou area recording the history of the last stage of Rodinia breakup.

Eoarchean to Neoproterozoic Detrital Zircons from the South of Meiganga Gold-Bearing Sediments (Adamawa, Cameroon): Their Closeness with Rocks of the Pan-African Cameroon Mobile Belt and Congo Craton

The core of detrital zircons from the southern Meiganga gold-bearing placers were analyzed by Laser Ablation Split Stream analytical techniques to determine their trace element abundances and U-Pb ages. The obtained data were used to characterize each grain, determine its formation condition, and try to trace the provenance. The Hf (5980 to 12,010 ppm), Y (27–1650 ppm), U (25–954 ppm), Th (8–674 ppm), Ti (2–256 ppm), Ta, Nb, and Sr (mainly &lt;5 ppm), Th/U (0.06–2.35), Ti zircon temperature (617–1180 °C), ∑REE (total rare earth element) (98–1030 ppm), and Eu/Eu* (0.03 to &lt;1.35) are predominant values for igneous crustal-derived zircons, with very few from mantle sources and of metamorphic origin. Crustal igneous zircons are mainly inherited grains crystallized in granitic magmas (with some charnockitic and tonalitic affinities) and a few from syenitic melts. Mantle zircons were crystallized in trace element depleted mantle source magmatic intrusion during crustal opening. Metamorphic zircons grown in sub-solidus solution in equilibrium with garnet “syn-metamorphic zircons” and in equilibrium with anatectic melts “anatectic zircons” during crustal tectono-metamorphic events. The U-Pb (3671 ± 23–612 ± 11 Ma) ages distinguish: Eoarchean to Neoproterozoic igneous zircons; Neoarchean to Mid Paleoproterozoic anatectic zircons; and Late Neoproterozoic syn-metamorphic grains. The Mesoarchean to Middle Paleoproterozoic igneous zircons are probably inherited from pyroxene-amphibole-bearing gneiss (TTGs composition) and amphibole-biotite gneiss, whose features are similar to those of the granites, granodiorites, TTG, and charnockites found in the Congo Craton, south Cameroon. The youngest igneous zircons could be grains eroded from Pan-African intrusion(s) found locally. Anatectic and syn-metamorphic zircons could have originated from amphibole-biotite gneiss underlying the zircon-gold bearing placers and from locally found migmatized rocks that are from the Cameroon mobile belt, which could be used as proxies for tracking gold.

Pre-orogenic connection of the foreland domains of the Kaoko–Dom Feliciano–Gariep orogenic system

Neoproterozoic metasedimentary rocks in the foreland domains of the Kaoko–Dom Feliciano–Gariep orogenic system record sedimentation from the breakup of Rodinia to the amalgamation of Gondwana, and thus provide ideal subjects for investigation of the mutual pre-orogenic positions of rifted margins of the African and South American cratonic blocks. U–Pb isotopic dating of zircon in the Brusque Complex of the northern Dom Feliciano Belt, Brazil, provides new constraints on the timing and sources of Neoproterozoic sedimentation along the eastern margin of the Luis Alves Craton. The minimum age of sedimentation is constrained by a U–Pb zircon age of 811 ± 6 Ma from a dyke cross-cutting the Brusque Complex. U–Pb detrital zircon analysis reveals two distinct groups: one with ages ca. 2.2–2.0 Ga consistent with erosion of the adjacent Luis Alves Craton, and another with ages ca. 2.1–1.8 and 1.6–1.0 Ga consistent with erosion of Paleoproterozoic to Mesoproterozoic igneous provinces and/or supracrustal sequences at the edge of the Congo Craton. The age distributions match with analogous rocks of the central Dom Feliciano Belt and the Kaoko Belt, and show similarities with the Gariep Belt, suggesting deposition in a system of coeval and spatially related paleobasins around the time of Rodinia breakup. The absence of Neoproterozoic detrital zircon close to the age of sedimentation suggests deposition in an intracontinental rift or passive margin. A third group contains a significant proportion of Neoproterozoic ca. 670–560 Ma zircon, suggesting similarities with the adjacent Itajaí Basin syn-orogenic foreland sedimentary rocks. This indicates that foreland basin sediments were partly tectonically interleaved with the pre-orogenic metasediments of the Brusque Complex during late-stage orogenic deformation. The findings support an intracontinental rifting model for the formation of the Kaoko–Dom Feliciano–Gariep basin system. The data further indicate that the Luis Alves Craton was in close proximity to the Congo Craton, and likely with the Nico Pérez Terrane and the Kalahari Craton, at the onset of Tonian rifting and the breakup of Rodinia.

U-Pb ages of detrital zircons in lower Palaeozoic quartzites of the Taebaeksan Basin, eastern Sino–Korean Block: sediment provenance response to relative sea-level changes

ABSTRACT The Cambrian–Ordovician Taebaeksan Basin overlies the Precambrian basement of the Sino–Korean Block (North China Craton) in the central–eastern Korean peninsula. This corresponds to the occurrence of the global marine transgression over the Great Unconformity in the Cambrian, which is widely recognized. However, the palaeogeography of the Sino–Korean Block during the Early Cambrian–Ordovician remains unclear. This study aimed to identify the provenances and reconstruct the palaeogeography of the eastern Sino–Korean Block. For this purpose, we investigated U-Pb ages of detrital zircons in the lower Cambrian–Ordovician successions using samples collected from the Danyang (i.e. Jangsan), Jeongseon, and Dongjeom areas. Detrital zircons from all samples clearly exhibited predominant clusters of Paleoproterozoic ages (ca. 1875–1861 Ma) and a minor cluster of Neoarchean ages (ca. 2500 Ma). The age spectra from the lower quartzites (Jangsan and Jeongseon formations) are partly distinguished from those in the Taebaeksan Basin, showing bimodal Precambrian peaks, which indicates the preferred drainage system within the Sino–Korean Block. A lack of young detrital zircon ages representing maximum depositional ages in the lower quartzites indicates that there were little igneous activity and little influx of external detritus. The age spectra from the lower quartzites, in contrast, are different from those of the conformably overlying shale (i.e. ~510 Ma Myobong Formation) consisting mainly of Neo–Mesoproterozoic detrital zircons derived from East Gondwana. Paleoproterozoic detrital zircons in the upper quartzite (Dongjeom Formation) were repetitively predominant without Neoproterozoic detrital zircons. The reappearance of predominant Paleoproterozoic zircons is most likely associated with uplifts possibly due to the subduction of the Paleo-Asian Ocean (PAO). We suggest that progressive changes along the eastern margin of the Sino–Korean Block were affected by the regional tectonism, regardless of the global transgression during the Cambrian–earliest Ordovician (ca. 480–500 Ma).

Internal versus external locations of the South China Craton within Rodinia during the Cryogenian: Provenance history of the Nanhua Basin

AbstractContrasting models for internal versus external locations of the South China Craton (SCC) in the supercontinent Rodinia and associated mantle plume or ocean subduction dominated tectonic processes can be resolved by detrital zircon U-Pb dating and Lu-Hf isotopic analyses on the Cryogenian Nanhua Supergroup in the central SCC. Our results show that samples from the lower Liantuo, Tiesi’ao, and Datangpo formations of the Nanhua Supergroup show three age peaks at 2.50 Ga, 2.05 Ga, and 0.85 Ga, and those of the upper Nantuo Formation yield four peaks at 2.50 Ga, 2.05 Ga, 0.85 Ga, and 0.65 Ga. The Archean and Paleoproterozoic (1.80–2.10 Ga) zircons have εHf(t) values of −16.3 to +4.7 and −23.0 to +4.2, and may be sourced from the Kongling and Douling complexes and Paleoproterozoic intrusions in the northern Yangtze Block, respectively. Early Neoproterozoic (0.70–0.96 Ga) zircon grains show variable εHf(t) values of −20.0 to +15.0. In combination with the absence of Mesoproterozoic detrital zircons in the Nanhua Supergroup, huge volumes of Neoproterozoic granitic intrusions in the northern Yangtze Block are the potential sources for the 0.70–0.96 Ga detrital zircons. Only the siltstone of the Nantuo Formation has late Neoproterozoic (0.63–0.69 Ga) detrital zircons with high and positive εHf(t) values (+7.9 to +9.4). Several granitoid intrusions (0.63–0.68 Ga) in the Wudang and Ankang uplift of the South Qinling belt in the northern Yangtze Block provide the late Neoproterozoic detrital zircons of the Nantuo Formation. These provenance analyses of the Nanhua Supergroup indicate an interior source from the SCC, rather than an exterior source from the Laurentia and Australia cratons. The Neoproterozoic rift basins and magmatic rocks in the SCC were produced by secular episodic subductions and back-arc extensions, rather than a Neoproterozoic super-mantle plume. The SCC occupied a peripheral position adjacent to northern India in Rodinia during the Neoproterozoic. These conclusions will promote our understanding of genetic mechanism and distribution prediction of the several Cryogenian–Cambrian black-shale layers and excellent source rocks in the SCC.

Iapetan Oceans: An analog of Tethys?

Abstract The Iapetus Ocean opened during the breakup of Rodinia by the separation of the major continental blocks of Laurentia (LA), Baltica, and Amazonia (AM). Relics of protracted continental extension to rifting from 750 to 530 Ma are observed along those continental margins, including two distinct phases of rifting: (1) at 750–680 Ma, and (2) at 615–550 Ma. Conventionally, the second phase is thought to have led to the opening of the Iapetus, while the first phase marked a failed rifting attempt. We challenge this concept on the basis of a new review of the geological observations from those margins and propose the successive opening of two “Iapetan” ocean basins. First, a “Paleo-Iapetus” opened between LA and AM at ca. 700 Ma, followed by the opening of the “Neo-Iapetus” at 600 Ma, which led to the final disaggregation of the supercontinent Rodinia. This scenario better explains the absence of the second rifting phase in western AM, as well as an otherwise enigmatic late Neoproterozoic detrital zircon age fraction in Phanerozoic sediments along that margin. We further propose that the opening of the Neo-Iapetus led to the detachment of small terranes from LA and their drift toward AM, following subduction of the Paleo-Iapetus mid-ocean ridge and the arrival of a mantle plume around 615 Ma. This could be a direct, deep-time analog of the opening of the Neo-Tethys Ocean in the late Paleozoic.

Controls on Early Cretaceous desert sediment provenance in south‐west Gondwana, Botucatu Formation (Brazil and Uruguay)

AbstractThe Lower Cretaceous Botucatu Formation records the development of widespread dry–aeolian desert sedimentation throughout the Paraná Basin in south‐west Gondwana. To reconstruct the provenance of the aeolian sediment, petrography, granulometric analysis, U‐Pb detrital zircon ages have been determined from along the southern basin margin in Rio Grande do Sul state (southern Brazil) and Uruguay (Tacuarembó region). The dataset reveals a mean composition Qt89F8L3, comprising very fine to medium‐grained quartozose and feldspatho‐quartzose framework. Heavy mineral analysis reveals an overall dominance of zircon, tourmaline and rutile grains (mean ZTR0.84) with sporadic garnet, epidote and pyrolusite occurrences. The detrital zircon U‐Pb ages are dominated by Cambrian to Neoproterozoic (515 to 650 Ma), Tonian to Stenian (900 to 1250 Ma) and Orosirian to Rhyacian (1.8 to 2.2 Ga) material. The detrital zircon dataset demonstrates a significant lateral variation in sediment provenance: Cambrian to Neoproterozoic detrital zircons dominate in the east, while Tonian to Stenian and Orosirian to Rhyacian ages predominate in the west of the study area. Sandstones are quartz‐rich with dominantly durable zircon, tourmaline and rutile heavy mineral suite, with subtle but statistically significant along‐strike differences in heavy mineral populations and detrital mineralogy which are thought to record local sediment input points into the aeolian system. The similar age spectra of Botucatu desert with proximal Paraná Basin units, the predominance of quartzose, and zircon, tourmaline and rutile components, suggests that recycling is the mechanism responsible for the erg feeding.

From Breakup of Nuna to Assembly of Rodinia: A Link Between the Chinese Central Tianshan Block and Fennoscandia

AbstractThe transition from breakup of Nuna (or Columbia, 2.0–1.6 Ga) to assembly of Rodinia (1.0–0.9 Ga) is investigated by means of U‐Pb and Lu‐Hf data of detrital zircons from three Neoproterozoic metasedimentary rocks in the Central Tianshan Block (CTB), NW China. These data yield six age peaks around 1.0, 1.13, 1.34, 1.4–1.6, 1.75, and 2.6 Ga. Few zircons are detected between 2.0 and 2.5 Ga. The Paleoproterozoic to Neoproterozoic detrital zircons have Hf isotopic compositions (−22.1 to +13.0) similar to those of coeval magmatic rocks in the CTB, indicating a proximal provenance. These results, together with the geological evidence and the presence of 1.4 Ga orogenic granitoids in the CTB, rule out most cratons as the CTB sources but support a Fennoscandia ancestry. Zircon U‐Pb ages and Hf isotopic compositions from the CTB and Fennoscandia suggest that from 1.8 to 1.4 Ga, the εHf(t) values increased toward more positive values, consistent with an exterior orogen characteristic that the lower crust was replaced by a juvenile arc crust. In contrast, from 1.4 to 0.9 Ga, zircon εHf(t) values decreased to more negative values, reflecting an interior orogen, characterized by enhanced contribution of recycled crustal material from collided continental fragments. This marked shift most likely reflected a transition from breakup of Nuna to assembly of Rodinia, accomplished by a transformation from an exterior orogen to an interior one.

Detrital zircon provenance and palaeogeographic implications of the Ediacaran Shigu Group in the Zhongza Terrane, SW China

ABSTRACT The palaeogeographic positions of South China in the Rodinia and Gondwana supercontinents have long been controversial. We report petrological, detrital zircon U-Pb geochronological, trace element geochemical and Lu-Hf isotopic compositions for metasedimentary rocks from the Shigu Group in the Zhongza Terrane, SW China. The Shigu Group has been regarded as the Precambrian basement of the Zhongza Terrane, and comprises mainly a suite of medium-/low-grade metamorphosed terrigenous clastic rocks. The youngest zircon age population of two metasedimentary rock samples from the bottom Shigu Group yields a weighted average age of 633 ± 9 Ma, indicative of a late Neoproterozoic (ca. 630 Ma) maximum deposition age. The youngest detrital zircon age of a metasedimentary rock from the upper Shigu Group is 597 ± 7 Ma, it may suggesting a considerably later deposition. Detrital zircon age distribution patterns of the Shigu Group metasedimentary rocks are similar to those of coeval sedimentary rocks in the western Yangtze Block. According to Hf isotope compositions and zircon morphology, the Neoproterozoic Shigu Group detritus may have sourced from Neoproterozoic magmatic rocks in the western Yangtze Block, whilst the pre-Neoproterozoic zircons might originate from recycling of the underlying metasedimentary rocks. Our results indicate that the basement of the Zhongza Terrane was a continuation of the Yangtze Block, which implies that Precambrian Yangtze basement rocks were present beyond the current boundary of the Block. In the late Neoproterozoic (ca. 630–570 Ma), the western Yangtze Block may have been facing the Proto-Tethys and received detritus mainly from the local Neoproterozoic magmatic rocks. During the late Neoproterozoic-earliest Palaeozoic (ca. 570–520 Ma), the seaway closure between the Yangtze (incl. Zhongza) Block and northern India likely created new pathways for delivery of the earliest Neoproterozoic and Pan-African detrital zircons into the lowermost Palaeozoic sequences in South China.