Youngest Detrital Zircon Research Articles

Progressive changes in lithological association of the Sanbagawa metamorphic complex, Southwest Japan: Relict clinopyroxene and detrital zircon perspectives

AbstractThe main tectono‐stratigraphic unit (Shirataki unit) of the Sanbagawa metamorphic complex in central Shikoku is characterized by abundant mafic schist layers that show the mid‐ocean ridge basalt (MORB) affinity. These MORB‐derived schist layers are absent in a southern (structurally lower) domain within the unit. Instead, sporadic occurrences of small metabasite lenses that contain relict igneous minerals (Ti‐rich augite and kaersutite) indicative of alkali basalt magmatism are newly recognized in the southern domain. Compositions of relict clinopyroxene in metabasalt are useful to identify the tectonic setting and origin of the protolith basalt, and those in each unit of the Sanbagawa metamorphic complex are presented. The metamorphic grade of the Shirataki unit generally increases structurally upwards in the southern side of the highest‐grade zone, and metamorphic zonation is subparallel to lithostratigraphic succession. The protolith assemblage of the Shirataki unit shows a distinct change from the southern low‐grade domain (lower Shirataki subunit) composed of terrigenous sedimentary rocks (mudstone and sandstone) with minor alkali basalt to the northern higher‐grade domain (upper Shirataki subunit) consisting of terrigenous and pelagic sedimentary rocks with abundant MORB. The youngest detrital zircon U–Pb ages (ca 95–90 Ma) suggest that both domains have Late Cretaceous depositional ages at the trench. Progressive peeling of oceanic plate stratigraphy during subduction can account for the observed change of lithological association in the Shirataki unit.

Cadomian metasediments and Ordovician sandstone from Corsica: detrital zircon U–Pb–Hf constrains on their provenance and paleogeography

The island of Corsica, which belongs to the southern Variscan realm, was detached from southern France in the Tertiary. Alongside Alpine and Variscan edifices, it carries outliers of Neoproterozoic metasediments and Lower Paleozoic siliciclastics including Ordovician sandstone and conglomerates as well as Hirnantian diamictites in its NW sector. We investigated the U–Pb–Hf of detrital zircons of basement metasediments and overlying Ordovician sandstone and channeling conglomerate to constrain their provenance, the timing of their deposition, and to deduce the late Ediacaran to Ordovician paleogeography. The youngest detrital zircons in the metasediments are 0.55–0.53 Ga indicating their maximum age of deposition is Late Ediacaran to Early Cambrian, thus classifying the Corsica basement metasediments as Cadomian. The U–Pb analyses revealed that a preponderance of the detrital zircons in the basement micaschist and quartzite portray Neoproterozoic ages concentrating between 0.55 and 0.65 Ga. This is partly consistent with derivation from Pan-African terranes of north Africa yet the presence of detrital zircons younger than ~ 0.6 Ga indicates significant input from Cadomian magmatic arcs that resided within or at the margin of the Cadomian basin in which the metasediments of Corsica were deposited. eHf values of the Ediacaran zircons varies between samples, indicating the provenance comprised both, juvenile arcs and magmatic arcs that involved various degrees of mixing with old crustal components. The Hf-TDM ages of many of the Ediacaran-aged zircons point to a plausible involvement of Meso-Paleoproterozoic crust in the generation of these Cadomian arcs. The presence of small but fairly distinguished populations of Mesoproterozoic-aged (1.0–1.6 Ga) as well as 2.0–2.2 Ga and 2.4–2.6 Ga detrital zircons in the Cadomian metasediments farther indicates the presence of such crust in the provenance. Although Mesoproterozoic detrital zircons are usually considered the hallmark of Avalonian terranes, the presence of Hirnantian glacial sediments at the Corsican sequence indicates it resided in the vicinity of Gondwana. We therefore postulate that the Pre-Neoproterozoic zircons have sourced from exotic crustal vestiges that were entrained and accreted within the Cadomian realm itself. The transition into the overlying Ordovician sandstone and conglomerate marks a major change in the provenance, possibly pointing to lateral motions along the strike of the peripheral Cadomian domain. The youngest concordant detrital zircon in the Ordovician (“Ciuttone”) sandstone yielded an age of 0.48 Ga. The detrital zircon ages define an overwhelming concentration at 0.55 Ga, indicating the source of the Ordovician sandstone was cut off from the Gondwana hinterland and that sand was exclusively derived from a latest Ediacaran arc. In view of the sharp detrital zircon age peak, the Corsica Ordovician sandstone cannot be straightforwardly correlated with Armorican sandstone because the detrital zircon spectra of the latter are generally broader, indicating derivation from various sectors of the North Gondwana crust. eHf(t) values of the 0.55 Ga zircons are mostly positive and the corresponding TDM ages at 0.7–1.2 Ga indicating derivation from a juvenile island arc. While TDM ages of this type are common for late Ediacaran Avalonian rocks, the presence of Hirnantian diamictite in Corsica further substantiates that the aforementioned 0.55 Ga island arc evolved in the peripheral Cadomian realm. As a whole, the U–Pb–Hf zircon data from the Corsica sequences reveal the presence of juvenile Cadomian arcs alongside Cadomian arcs that recycled ancient (pre-Neoproterozoic) crust. Along strike variations of this type are known from the Japanese islands, in line with the peripheral Cadomian orogeny being an ancient analog of a Western-Pacific type plate boundary.

U-Pb detrital zircon geochronology of the Turee Creek Group, Hamersley Basin, Western Australia: Timing and correlation of the Paleoproterozoic glaciations

The early Paleoproterozoic Turee Creek Group (TCG), Hamersley Basin, Western Australia, records a continuous siliciclastic-dominated sedimentary sequence across the Great Oxidation Event (GOE) and contains at least two glacial horizons showing many similarities with other Paleoproterozoic glaciogenic deposits from North America (Huronian Supergroup) and South Africa (Transvaal Supergroup). The correlation between these glacial events is uncertain, however, because of a lack of geochronological constraints, contradictory stratigraphic correlations among different cratons, and the occurrence of numerous sedimentary discontinuities in the Transvaal and Huronian successions. In this study, we performed in situ U-Pb dating of detrital zircons from drill core and surface samples of the TCG, the underlying Boolgeeda Iron Formation of the Hamersley Group, and the overlying Beasley River Quartzite of the Lower Wyloo Group. Over 1500 zircons analyzed by Laser Ablation coupled to ICP-MS yielded major age peaks spanning the Archean Eon at ca. 2.45 Ga, 2.54 Ga, 2.68 Ga and minor ones at 2.81 Ga, 2.96 Ga and 3.14 Ga. A younger age of 2340 ± 22 Ma obtained at the base of the main glacial deposit of the Meteorite Bore Member, represents a maximum age for this glacial event. A meter-scale level of diamictite has previously been described in the Boolgeeda Formation at the Boundary Ridge Locality (located about 50 km to the east of the Meteorite Bore Member succession) and a similar horizon was newly identified in drill core samples from the Hardey Syncline area. The youngest detrital zircons have an age of ca. 2.45 Ga in these diamictites supporting the hypothesis that these horizons represent a different and older glacial event than the Meteorite Bore Member. Considering that the TCG and underlying Boolgeeda Iron Formation are in sedimentary continuity, these results allow establishing a correlation with the other glaciogenic deposits recorded in the North America and southern Africa basins, and reconstructing the sequence of redox and climate changes attending the early Paleoproterozoic.

Provenance shift from a continental margin to a syn-orogenic basin in the Neoproterozoic Araxá nappe system, southern Brasília belt, Brazil

In the southern Brasília belt of central Brazil, prominent east-verging systems of stacked nappes caused the thrusting and tectonic interleaving of metasedimentary rocks of different provenance, age and metamorphism. Detrital zircon U-Pb analysis of metasedimentary rocks of the Araxá Group show very distinct age spectra and provenance patterns for samples collected in different sites of the Brasília belt. While samples collected in the external zone of the belt yielded zircon age peaks mainly from 790 Ma to 2.5 Ga, samples of the internal zone of the belt, close to the Goiás Magmatic Arc, yielded important age peaks around 650 Ma. This suggests an important provenance shift recorded by the metasedimentary rocks of the Araxá nappe system. The lower and easternmost rocks might represent the western passive margin of the São Francisco paleocontinent, and thus are correlated to the Canastra Group, while the upper and westernmost rocks show a striking influence of the late Cryogenian (ca. 650 Ma) continental magmatic arc of the Brasília belt, and thus were probably deposited in a syn-orogenic basin. The variability of source areas is also recorded by distinct Sm-Nd TDM ages, between 1.4 Ga and 2.0 Ga, and 87Sr/86Sr ratios from 0.719 to 0.891. Low-grade metasedimentary rocks of the Ibiá Group in the Araxá nappe system show even younger detrital zircons, around 580 Ma, suggesting they were deposited after the metamorphic peak of the Brasília belt and represent the erosion of the thrust fronts during late-stage nappe extrusion and stacking. Therefore, the Araxá nappe system is actually composed of a tectonically interleaved package of metasedimentary rocks deposited in distinct basins during distinct evolutionary stages and, finally, assembled and metamorphosed during collisional thrusting. Recognizing such metasedimentary rocks that are petrographically similar but show distinct deposition timing, sediment source and tectonic setting is an important challenge to understand the evolution of the Brasília belt in the scenario of West Gondwana amalgamation.

Convergence history of the Jiamusi and Songnen-Zhangguangcai Range massifs: Insights from detrital zircon U-Pb geochronology of the Yilan Heilongjiang Complex, NE China

The Heilongjiang Complex, located between the Jiamusi and Songnen-Zhangguangcai Range massifs, has become a focus of tectonic research in recent years. Here we document new U-Pb detrital zircon age data for metasedimentary rocks from the Heilongjiang Complex in Yilan-Huanan counties. These data not only provide important constraints on the depositional timing and provenance, but also give further insights into the complicated convergence history of the Jiamusi and Songnen-Zhangguangcai Range massifs. Most zircons from the Heilongjiang Complex show “magmatic-like” zircon rare earth element patterns, with enrichment in heavy rare earth elements and positive Ce and negative Eu anomalies, suggesting a magmatic origin. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb analysis indicates that the youngest detrital zircons in these metasedimentary rocks have concordant 206Pb/238U ages of ca. 230–180Ma. Based on this finding and the Middle Jurassic metamorphic ages of the Heilongjiang Complex, we conclude that metasedimentary rocks of the Yilan Heilongjiang Complex were deposited during the Late Triassic-Early Jurassic. Approximately 55% of the detrital zircons yield ages of 297 to 180Ma, with peaks at 270–245Ma, 230–200Ma and 200–180Ma, while 27% of the detrital zircons yield ages of 544–412Ma with a peak at 500–480Ma. Proterozoic detrital zircons (~15%) were also identified, yielding ages of 2352 to 595Ma, with most being of Neoproterozoic age. These results, combined with field relationships and previously published ages, suggest that detrital zircons in the Yilan Heilongjiang Complex were sourced mainly from igneous rocks in the Jiamusi and Songnen-Zhangguangcai Range massifs. Moreover, the protoliths of the metasedimentary rocks in the Yilan Heilongjiang Complex were most likely deposited in a forearc basin setting during convergence between the Jiamusi and Songnen-Zhangguangcai Range massifs.

Variations in Zircon Provenance Constrain Age and Geometry of an Early Paleozoic Rift in the Pinjarra Orogen, East Gondwana

AbstractThe Tumblagooda Sandstone in Western Australia documents Early Paleozoic rifting in East Gondwana and provides the earliest evidence for terrestrial activity of multicellular animals on Earth. We constrain the provenance of this sequence using 737 concordant U–Pb ages of detrital zircons from two stratigraphic wells in the northern Perth Basin and Southern Carnarvon Basin and outcrops of the type sections near Kalbarri. Detrital zircon age signatures are linked to infrared spectral data and stratigraphic logs. These ages span 3,312–466 Ma, including major Precambrian age peaks at 1,079–1,544 Ma, 1,695–2,403 Ma, and 2,640–2,879 Ma, consistent with igneous sources in the West Australian Craton. Significant Early Paleozoic age peaks at 499–541 Ma suggest a North Indian Orogen source. The maximum depositional age is constrained by the youngest detrital zircon, which yields an age of 466 ± 8 Ma. Our age constraints imply that terrestrial activity of multicellular animals on Earth may not be older than Middle Ordovician (Darriwilian). Rifting resulted in the exposure of the Yilgarn Craton and the segmentation of the Pinjarra Orogen. The Northampton Complex segment of the Pinjarra Orogen constituted a basement high that separated subbasins during the onset of rifting. Discordant Archean zircons provide a consistent record of radiogenic Pb loss at ~470 Ma, which we interpret as being related to the denudation of the Yilgarn Craton. The Pb loss event suggests that intracratonic rifting in the Pinjarra Orogen was initiated in the Middle Ordovician, after the Kuunga Orogeny completed the final amalgamation of Gondwana.

Spatial and temporal variation in detrital zircon age provenance of the hydrocarbon-bearing upper Roper Group, Beetaloo Sub-basin, Northern Territory, Australia

The subsurface Beetaloo Sub-basin of the McArthur Basin, Northern Territory, Australia, comprises a succession of shallow-water, dominantly marine, clastic sedimentary rocks that formed in the main depocentre of the Mesoproterozoic Roper Group. This group contains the oldest commercial hydrocarbons known, whose presence has been linked to changing nutrient flux controlled by a changing provenance. LA-ICP-MS detrital zircon U–Pb age data presented here provide new age constraints on the upper Roper Group and reveal spatial and temporal provenance variations illustrating the evolution of the basin and its margins that are linked to a major provenance change caused by the coeval collision of the combined South Australian Craton/North Australian Craton with the West Australian Craton.The maximum depositional ages of the Bessie Creek Sandstone and the Velkerri Formation of the Roper Group are constrained to 1386 ± 13 Ma and 1308 ± 41 Ma, respectively, whereas the overlying Moroak Sandstone has no younger detrital zircons, so its maximum depositional age is also constrained as 1308 ± 41 Ma. The Kyalla Formation was deposited after 1313 ± 47 Ma, and two, as yet, informally defined and ungrouped latest Mesoproterozoic to Neoproterozoic sedimentary units, the lower and upper Jamison sandstone, have maximum depositional ages of 1092 ± 16 Ma and 959 ± 18 Ma, respectively. Large detrital zircon age datasets (of 1204 near-concordant analyses) indicate that zircons from the Maiwok Subgroup were originally sourced from Palaeoproterozoic and earliest Mesoproterozoic rocks. These are consistent with derivation from the surrounding exposed basement. Detrital zircon age variations up-section suggest a systematic temporal change in provenance. The oldest formation analysed (Bessie Creek Sandstone) has a major source dated at ca. 1823 Ma. Rocks of this age are common in northern basement exposures. Samples from the overlying Velkerri Formation, show derivation from a ca. 1590 Ma source, consistent with rocks exposed in Queensland, or the Musgrave Province. The Moroak Sandstone and the Kyalla Formation show progressively more ca. 1740 Ma detritus, which we suggest likely reflects new sources in the Arunta Region to the south.We suggest that the provenance variation initially records exposure and denudation of western Queensland rocks at ca. 1400 Ma due to rifting between Laurentia and the North Australian Craton. From then until at least ca. 1320 Ma, the increased ca. 1740 Ma detritus suggests uplift of the Arunta Region that we interpret as reflecting collision between the southern North Australian Craton and the West Australian Craton as ca. 1300–1400 Ma. This tectonically-controlled provenance change is interpreted to have included erosion of nutrient rich arc-rocks that may have caused a bacterial bloom in the Roper Seaway. The Jamison sandstone and overlying Hayfield mudstone represent a marked change in provenance and were deposited after the Musgrave Orogeny, representing a newly-recognised siliciclastic basin that may have formed a shallow, long wavelength foreland basin to areas uplifted during the Musgrave Orogeny.

LA-ICP-MS zircon U–Pb and muscovite K–Ar ages of basement rocks from the south arm of Sulawesi, Indonesia

The zircon U–Pb and muscovite K–Ar age from the Bantimala, Barru and Biru basement complexes in the South Arm of Sulawesi, Indonesia provide new information regarding the timing of magmatism, metamorphism and sedimentation in this region and have implications for the origin and evolution of the study area. The study area is at the juncture between the southeast margin of Sundaland and Bird's Head-Australia. The age of both the zircon U–Pb of detrital materials in the Bantimala Complex and the muscovite K–Ar of amphibolite in the Biru Complex fall in the Late Early Cretaceous (between 109 and 115Ma), which is a similar age range to previous data for both the sedimentary and metamorphic rocks. The youngest detrital zircon in the schist samples from the Barru Complex fall into the Triassic in age (between 243 and 247Ma). These age data indicate that the protolith of all three basement complexes were involved in the subduction system and metamorphosed in the late Early Cretaceous, but there are several differences in their deposition environment under and out of the influence of the late Early Cretaceous magmatism in the Bantimala and Barru Complexes, respectively. Felsic igneous activities are confirmed in the Late Cretaceous and the Eocene by the zircon U–Pb age of igneous rocks intruding or included as detrital fragments in three basement complexes. These dates are similar to those reported from the Meratus Complex of South Kalimantan. The detrital zircon age distributions of the basement rocks in the South Arm of Sulawesi display predominant Mesozoic (Cretaceous and Triassic) and Paleozoic populations with a small population of Proterozoic ages supporting the hypothesis that the West Sulawesi block originated from the region of the circum Bird's Head-Australian, namely the Inner Banda block. The absence of Jurassic zircon age population in the South Arm of Sulawesi suggests the division of the South Arm of Sulawesi from the Inner Banda block in early stage of rifting. Western Sulawesi is composed of several blocks separated from Inner Banda block with different histories, which is supported by the varieties of zircon population distribution in the basement rocks in the Western Sulawesi and also difference of general orientations of structural features between the Bantimala and Barru Complexes.

Detrital zircon U-Pb-Hf isotopes and provenance of Late Neoproterozoic and Early Paleozoic sediments of the Simao and Baoshan blocks, SW China: Implications for Proto-Tethys and Paleo-Tethys evolution and Gondwana reconstruction

Early Paleozoic evolution of the northern Gondwana margin is interpreted from integrated in situ U-Pb and Hf-isotope analyses on detrital zircons that constrain depositional ages and provenance of the Lancang Group, previously assigned to the Simao Block, and the Mengtong and Mengdingjie groups of the Baoshan Block. A meta-felsic volcanic rock from the Mengtong Group yields a weighted mean 206Pb/238U age of 462±2Ma. The depositional age for the previously inferred Neoproterozoic Lancang and Mengtong groups is re-interpreted as Early Paleozoic based on youngest detrital zircons and meta-volcanic age. Detrital U-Pb zircon analyses from the Baoshan Block define three distinctive age peaks at older Grenvillian (1200–1060Ma), younger Grenvillian (~960Ma) and Pan-African (650–500Ma), with εHf(t) values for each group similar to coeval detrital zircons from western Australia and northern India. This suggests that the Baoshan Block was situated in the transitional zone between northeast Greater India and northwest Australia on the Gondwana margin and received detritus from both these cratons. The Lancang Group yields a very similar detrital zircon age spectrum to that of the Baoshan Block but contrasts with that for the Simao Block. This suggests that the Lancang Group is underlain by a separate Lancang Block. Similar detrital zircon age spectra suggest that the Baoshan Block and the Lancang Block share common sources and that they were situated close to one another along the northern margin of East Gondwana during the Early Paleozoic. The new detrital zircon data in combination with previously published data for East Gondwana margin blocks suggests the Early Paleozoic Proto-Tethys represents a narrow ocean basin separating an “Asian Hun superterrane” (North China, South China, Tarim, Indochina and North Qiangtang blocks) from the northern margin of Gondwana during the Late Neoproterozoic-Early Paleozoic. The Proto-Tethys closed in the Silurian at ca. 440–420Ma when this “Asian Hun superterrane” collided with the northern Gondwana margin. Subsequently, the Lancang Block is interpreted to have separated from the Baoshan Block during the Early Devonian when the Paleo-Tethys opened as a back-arc basin.

Sedimentary and tectonic evolution of the southern Qiangtang basin: Implications for the Lhasa‐Qiangtang collision timing

AbstractThe Mesozoic stratigraphic record of the southern Qiangtang basin in central Tibet records the evolution and closure of the Bangong‐Nujiang ocean to the south. The Jurassic succession includes Toarcian‐Aalenian shallow‐marine limestones (Quse Formation), Aalenian‐Bajocian feldspatho‐litho‐quartzose to feldspatho‐quartzo‐lithic sandstones (shallow‐marine Sewa Formation and deep‐sea Gaaco Formation), and Bathonian outer platform to shoal limestones (Buqu Formation). This succession is truncated by an angular unconformity, overlain by upper Bathonian to lower Callovian fan‐delta conglomerates and litho‐quartzose to quartzo‐lithic sandstones (Biluoco Formation) and Callovian shoal to outer platform limestones (Suowa Formation). Sandstone petrography coupled with detrital‐zircon U‐Pb and Hf isotope analysis indicate that the Sewa and Gaaco formations contain intermediate to felsic volcanic detritus and youngest detrital zircons (183–170 Ma) with εHf(t) ranging widely from +13 to −25, pointing to continental‐arc provenance from igneous rocks with mixed mantle and continental‐crust contributions. An arc‐trench system thus developed toward the end of the Early Jurassic, with the southern Qiangtang basin representing the fore‐arc basin. Above the angular unconformity, the Biluoco Formation documents a change to dominant sedimentary detritus including old detrital zircons (mainly >500 Ma ages in the lower part of the unit) with age spectra similar to those from Paleozoic strata in the central Qiangtang area. A major tectonic event with intense folding and thrusting thus took place in late Bathonian time (166 ± 1 Ma), when the Qiangtang block collided with another microcontinental block possibly the Lhasa block.

Extensive oxidative weathering in the aftermath of a late Neoproterozoic glaciation – Evidence from trace element and chromium isotope records in the Urucum district (Jacadigo Group) and Puga iron formations (Mato Grosso do Sul, Brazil)

The massive Fe and Mn deposits of the Urucum district (Banda Alta Formation) and the iron formations from Fazenda São Manoel (Puga Formation) in Mato Grosso do Sul, Brazil, are associated with glacigenic deposits and represent the youngest and largest sedimentary Fe and associated Mn formation (IF;MnF) deposits of Cryogenian age in the world. The Urucum district IFs studied are predominantly composed of pure classical plane-parallel and stratified hematite–chert–iron - and intercalated manganese (cryptomelane) micro- and mesobands, whereas the IFs at Fazenda São Manoel are closely associated with diamictites and shales. Although the precise depositional age is unknown, maximum age constraints for the Puga IFs are defined by the youngest detrital zircon with an U-Pb age of 706±9Ma (Babinski et al., 2013), a result which we here confirm by a U-Pb age of the youngest zircon of 695±17Ma from within shaly beds in the Urucum district IF succession. Redox-sensitive trace element signatures and tendency to hump-shaped Rare Earth Element+Yttrium (REY) patterns with negative Ce- but without Eu anomalies support the presence of an oxic surface water layer, fertilized by low temperature hydrothermal fluids injected from submarine thermal springs and/or, alternatively, by significant fresh water input directly derived from glacial meltdown. Strongly positively fractionated, authigenic chromium isotope signatures (average δ53Cr=1.10±0.4‰; n=16; 2σ) prevailing throughout the entire stratigraphic section indicate that riverine supply of continentally-derived Cr, remained more or less constant throughout the glacier meltdown and IF depositional period. Cycling across a redoxcline and predominant deposition of the IF in anoxic deeper seawater of the Jacadigo basin is supported by the peculiar presence of subchondritic Y/Ho ratios, by decreased negative Ce anomalies and by shifts of LREE patterns towards higher values in the Urucum district IFs that are independent of detrital contamination.The strongly positively fractionated Cr isotope signatures measured in these iron formations are compatible with those from other iron formations and black shales deposited during the late Neoproterozoic and Precambrian-Cambrian transition worldwide and are in support of prevailing high atmospheric O2 levels following the late Neoproterozoic glaciations that accompanied the evolution of macroscopic multicellular organisms.

Detrital zircon U-Pb dating of Suining Formation sandstone from the Daba Mountains, northeastern Sichuan and its stratigraphic implications

The non-marine Jurassic–Cretaceous boundary in the Sichuan Basin in southwestern China has a long and highly controversial history. According to the dominant opinion, the Suining and Penglaizhen Formations are the Upper Jurassic, and the Chengqiangyan Group is the Lower Cretaceous. Based on detrital zircon U-Pb dating of the Suining Formation sandstone from the Daba Mountains, the upper limit of the deposition of the Suining Formation is given by the detrital zircon U-Pb ages. The youngest detrital zircon U-Pb age is ∼120Ma, which reflects a depositional age of younger than ∼120Ma. The detrital zircon U-Pb age of the Suining Formation shows that this widespread formation should be assigned to the Cretaceous, not the Jurassic. This study sheds new light on the location of the Suining Formation in the stratigraphic column. Additionally, these ages are very important for the regional stratigraphic correlation and tectonic evolution studies.

The provenance and tectonic setting of the Lower Devonian sandstone of the Danlin Formation in southeast Yangtze Plate, with implications for the Wuyi-Yunkai orogeny in South China Block

The South China Block was subject to widespread tectonic and magmatic events during the middle Ordovician to earliest Devonian which are collectively called the Wuyi-Yunkai orogeny. Two different hypotheses were formulated about the origin of the orogeny: collisional orogenesis and intracontinental orogenesis. Ages of 215 detrital zircons were obtained from quartz sandstones in the Lower Devonian Danlin Formation exposed in Dushan County, south Guizhou Province. The results show that the detrital zircons came from multiple source areas but with little indication of the Wuyi-Yunkai orogeny. The detrital zircons of early Paleozoic age account only for 1.9% of all samples. These zircons range from 476 to 402Ma and originated from the early Paleozoic granites situated east of Dushan County. The mean 206Pb/238U age of the two youngest detrital zircons was 404Ma, which constrains the maximum depositional age of the Danlin Formation. The detrital zircons are mostly within Neoproterozoic age (59.5%) and in the range 997 to 557Ma. The zircon age pattern, morphology, and trace element characteristics combined with paleogeographic reconstruction interpret that these detrital zircons were supplied from igneous rocks in the Neoproterozoic Sibao and Danzhou Groups within the west Jiangnan orogen to the east of the study area. Mesoproterozoic zircons made up 20.9% of the grains and range from 1569 to 1055Ma; the ages of most of these zircons coincide with those of zircons indicating the Grenvillian orogeny (1300–1000Ma) in the Cathaysia Plate. The detrital zircon age data reveal that the study area was located in an intracontinental tectonic setting, both before and after the Wuyi-Yunkai orogeny. Therefore, the Cathaysia Plate was not separated from the Yangtze Plate by an ocean and the study area received sediments primarily from the Cathaysia Plate located to the southeast since the middle Ordovician. By the early Devonian, the sediments were supplied by the west Jiangnan orogen. Although a source change was caused by Wuyi-Yunkai orogeny, our data imply that this orogeny represented an intracontinental event rather than an orogenesis involving subduction-collision and joining of the Yangtze and Cathaysia Plates during the early Paleozoic.

New constraints on orogenic models of the southern Central Andean Plateau: Cenozoic basin evolution and bedrock exhumation

We present a multidisciplinary study that constrains the development history of the southern part of the Central Andean Plateau, a prototypical noncollisional orogenic system. In the Antofagasta de la Sierra region of NW Argentina, data from sedimentary geology, sandstone modal composition, detrital zircon U-Pb geochronology, and apatite fission-track and (U-Th-Sm)/He thermochronology indicate that sediments accumulated in the late Eocene to early Oligocene, with a maximum depositional age of ca. 39–38 Ma provided by the youngest detrital zircon U-Pb dates. Provenance data, including paleocurrent indicators, sandstone modal composition, and detrital zircon U-Pb ages, point to prevailing western sources, including the Sierra de Quebrada Honda (a proximal source), the Ordovician to Late Cambrian Famatinian magmatic arc in western Argentina and Chile (a distal source), and the Permian–Triassic plutonic and volcanic rocks in coastal Chile (a distal source). Along the western basin margin, these strata were deformed by a basement-involved thrust fault that was active at ca. 25–20 Ma, as constrained by apatite fission-track and (U-Th-Sm)/He data. Analysis of new and existing U-Pb geochronologic data from both detrital and basement samples across the Puna suggests that the Sierra Laguna Blanca, a major mountain range in the southern Puna, remained buried during the late Eocene to early Oligocene. Our multidisciplinary data indicate that the southern Central Andean Plateau may have hosted a regional basin primarily formed by lithospheric flexure during the late Eocene to early Oligocene. Furthermore, this study refines the history of basin compartmentalization and exhumation of the major mountain ranges in the southern Puna, revealing propagation of deformation from the west to east, starting as early as the late Eocene and continuing to the mid-late Miocene.

Mesozoic age of the Gilyui Metamorphic Complex in the junction zone of the Selenga–Stanovoi and Dzhugdzhur–Stanovoi superterranes, Central Asian fold belt

The Gilyui Complex includes sedimentary and volcanic rocks metamorphosed to amphibolite and epidote–amphibolite facies, which constitute blocks confined to the main structural sutures of the Dzhugdzhur–Stanovoi superterrane in the Central Asian fold belt. In recent stratigraphic scales, they are considered as being Neoarchean in age with Nd model age values of 1.5–3.0 Ga. The youngest detrital zircons from metamorphosed mudstone of the Gilyui Complex yield a date of 285 ± 4 Ma, which determines the lower age limit for the formation of its protolith. The age of crystallization of rhyolites from the Gilyui Complex is determined to be 231 ± 4 Ma. If the rhyolites form volcanic flow units or sills, the Gilyui Complex is approximately 230 Ma or 231 ± 4 to 285 ± 4 Ma old, respectively.

Pre-Pampean metasedimentary rocks from the Argentinian Puna: Evidence for the Ediacaran margin of Gondwana or the Arequipa–Antofalla–Western Pampeanas block

Quartzites exposed in the southern Puna (northwest Argentina) form faulted contacts with Late Ordovician volcaniclastic rocks and are discordantly overlain by Permo-Carboniferous red-beds. These strongly recycled rocks lack sedimentary structures and fossils. Therefore, a geochemical approach was preferred for this study. U–Pb isotope analysis of detrital zircon yielded an unusual age population. Ten grains lie within error of 570 and 590Ma—with the youngest detrital zircon at 571±14Ma—and are therefore interpreted as defining the maximum sedimentation age range.There is no evidence of Pampean orogeny event detritus (c. 550–520Ma). Therefore, we argue that these rocks are unlikely to be syn-tectonic with the event, or even younger. Alternatively, it can be argued that this component is absent due to differences in paleocurrent direction, sorting during transportation, or a hypothetical structural high; all of which could have blocked the Pampean provenance signal from reaching the depositional basin. Sorting related to the depositional environment can be excluded as the sample is a combination of all occurring grain sizes. There is no preserved geological evidence of an obstruction, which allows us to envisage different scenarios for deposition of these rocks.The most likely interpretation is that these successions predate the Pampean orogeny and deposition of the Cambrian Puncoviscana Formation. Consequently, the rocks could either have been deposited within the (passive) margin of the Arequipa–Antofalla–Western Pampeanas terrane (western Gondwana) or MARA block; or are unusual, reworked sedimentary rocks related to the active continental margin of the Pampean orogen.

The Orosirian-Statherian banded iron formation-bearing sequences of the southern border of the Espinhaço Range, Southeast Brazil

The Serra da Serpentina and the Serra de São José groups are two distinct banded iron formation-bearing metasedimentary sequences along the eastern border of the southern Espinhaço Range that were deposited on the boundary between the Orosirian and Statherian periods.The Serra da Serpentina Group (SSG) has an Orosirian maximum depositional age (youngest detrital zircon grain age = 1990 ± 16 Ma) and consists of fine clastic metasediments at the base and chemical sediments, including banded iron formations (BIFs), on the top, corresponding to the Meloso and Serra do Sapo formations, respectively, and correlating with the pre-Espinhaço Costa Sena Group. The SSG represents sedimentary deposition on an epicontinental-epeiric, slow downwarping sag basin with little tectonic activity.The younger Serra de São José Group (SJG) is separated from the older SSG by an erosional unconformity and was deposited in a tectonically active continental rift-basin in the early stages of the opening of the Espinhaço Trough. The Serra do São José sediments stretch along the north-south axis of the rift and comprise a complete cycle of transgressive sedimentary deposits, which were subdivided, from base to top, into the Lapão, Itapanhoacanga, Jacém and Canjica formations. The Itapanhoacanga Formation has a maximum depositional age of 1666 ± 32 Ma (Statherian), which coincides with the maximum depositional age (i.e., 1683 ± 11 Ma) of the São João da Chapada Formation, one of the Espinhaço Supergroup's basal units. The Serra de São José Rift and the Espinhaço Rift likely represent the same system, with basal units that are facies variations of the same sequence.The supracrustal rocks have undergone two stages of deformation during the west-verging Brasiliano orogeny that affected the eastern margin of the São Francisco Craton and generated a regional-scale, foreland N–S trending fold-thrust belt, which partially involved the crystalline basement. Thrust faults have segmented the terrain into a large number of tectonic blocks, where the stratigraphic sequence was nevertheless well preserved.

The Mesoproterozoic to early Neoproterozoic passive margin Lajeado Group and Apiaí Gabbro, Southeastern Brazil

The Lajeado Group in the Ribeira Belt, southeastern Brazil, corresponds to an open-sea carbonate platform, comprised of seven overlapping siliciclastic and carbonatic formations, intruded in its upper portion by the Apiaí Gabbro. These rocks have a Neoproterozoic tectonometamorphic overprint related to arc magmatism and the Brasiliano collisional orogeny. Geochronological constraints are given by new U-Pb SHRIMP and LA-ICP-MS data for Lajeado Group detrital zircons and for magmatic zircons from the Apiaí Gabbro. The youngest detrital zircons in the Lajeado Group are 1400–1200 Ma, and constrain its maximum age of deposition to be <1200 Ma, whereas the 877 ± 8 Ma age for magmatic zircons in the Apiaí Gabbro give the minimum age. Detritus source areas are mainly Paleoproterozoic (2200–1800 Ma) with some Archean and Mesoproterozoic contribution (1500–1200 Ma), with distal or tectonic stable cratonic character. The Lajeado Group should be a Stenian–Tonian carbonate platform passive margin of a continent at this time, namely the Columbia/Nuna or the Rodinia. The Apiaí Gabbro displays similar age to other intrusive basic rocks in the Lajeado and Itaiacoca groups and represents tholeiitic MORB-like magmatism that we relate to the initial break-up of a Mesoproterozoic continent and the formation of the Brasiliano oceans.

Cadomian basement and Paleozoic to Triassic siliciclastics of the Taurides (Karacahisar dome, south-central Turkey): Paleogeographic constraints from U–Pb–Hf in zircons

The Tauride block in Turkey is a peri-Gondwana, Cadomian-type terrane that rifted from the Afro-Arabian margin of Gondwana in the Permo-Triassic and re-accreted to Arabia in the Neogene. In the Karacahisar dome in the southern-central Taurides, Neoproterozoic basement metasediments and intrusive rocks are overlain by Cambro-Ordovician, Carboniferous and Triassic sediments. We studied U–Pb–Hf in zircons from major rock units exposed in Karacahisar in order to constrain the Cadomian crustal evolution of the Taurides, to evaluate the provenance of the Neoproterozoic and overlying sediments, to constrain the paleogeography of the Taurides, and to assess their linkage to Gondwana.The Neoproterozoic metasediments are low-grade metamorphic wacke-type turbidites that evolved in a broad back-arc basin peripheral to Afro-Arabia. Their detrital zircon U–Pb signal comprises a preponderance (40–68%) of Neoproterozoic-aged zircons (peak ages defined at 635 and 830Ma), indicating that the sedimentary pile was built mainly from the erosion of Pan-African terranes from Afro-Arabia. The εHf values of the younger population (635Ma) are mostly positive, indicating derivation from a juvenile arc, whereas Cryogenian–Tonian detrital zircons spread vertically (−25<εHf<15), indicating a different provenance where mixing of juvenile magmas with Paleoproterozoic to Neoarchean crust was widespread.An unusually high proportion of pre-Neoproterozoic zircons is found in all Cadomian metasediments, including up to 31% Grenvillian-aged (ca. 1.0Ga) and up to 35% of ca. 2.5Ga zircons; about a third of the latter possess positive εHf values. Because only minor exposures of 1.0 and 2.5Ga crustal vestiges are currently known in North Africa and Arabia, we infer that pre-Neoproterozoic terranes were dispersed within the Cadomian realm itself.The youngest detrital zircons in all Cadomian metasediments concentrate at 0.58Ga, indicating that the proto-Cadomian back-arc basin was formed towards the Late Ediacaran. The termination of Neoproterozoic sedimentation is marked by the intrusion of dyke swarms yielding a U–Pb zircon age of 544±4Ma, coeval with magmatism in other Cadomian basement units in the Taurides (e.g., Sandıklı and Menderes massif). Shortly afterwards the Tauride basement was overstepped by the Cambro-Ordovician platform.From the Cambrian to the Triassic, the U–Pb–Hf detrital zircon signal of the cover sediments in the Taurides in Karacahisar portrays remarkable resemblance to that of typical North Gondwana Cambro-Ordovician cover sediments, and shows that the Taurides accreted to Afro-Arabia by the onset of the Cambrian. The short time interval between Cadomian basin fill and deposition of the Cambrian platform implies that the Taurides evolved within a short distance from their present position relative to the Afro-Arabian margin of Gondwana. The Gondwana provenance of the Tauride sedimentary cover is maintained through the Upper Triassic, indicating that Neo-Tethys rifting was incipient at that time, allowing Afro-Arabian detritals to reach the Taurides.

A hidden Tonian basement in the eastern Mediterranean: Age constraints from U–Pb data of magmatic and detrital zircons of the External Hellenides (Crete and Peloponnesus)

A newly discovered Precambrian basement of the External Hellenides (Peloponnesus) is composed of mica schist, quartzite and meta-greywackes intruded by Cambrian granitoids (524+6/−5Ma). As such Cambrian intrusions are frequent in the eastern Mediterranean, but are lacking in northern Africa, they are interpreted to result from a Cadomian magmatic arc that was situated along the northern margin of East Gondwana. This arc was rifted off from Gondwana in Early Paleozoic times. The sedimentation age of the meta-greywackes is bracketed between the age of their youngest detrital zircons (541±7Ma, Crete; 546±7Ma, Peloponnesus) and the intrusion of the Cambrian granitoids. The detrital zircon age spectra are dominated by two significant age peaks at ca. 600Ma and ca. 1Ga, which are characteristic for Cambrian platform sediments of Jordan, Israel and Lybia and for the Minoan-type terranes with an East Gondwana provenance. The high amount of 1Ga old zircons points to a Tonian basement as provenance, which is situated at the northern margin of the Arabian Nubian Shield (N'Sinai) and the Sahara Metacraton, today hidden under Mesozoic cover. There is a good correlation between the detrital age spectra of the Late Ediacaran/Cambrian basement of the External Hellenides and of the eastern Mediterranean realm. Apart from the Hellenides and Turkey (Menderes, Sakarya), the Minoan-type terranes have also been found in Sicily, Sardinia, and NW Iberia. Our review of detrital zircon ages obtained from Europe and northern Africa revealed four different domains during Early Cambrian times, which have affinities to (1) Baltica, (2) South-America (Avalonian-type terranes), (3) W Africa (Armorican-type terranes), and (4) E Gondwana (Minoan-type terranes and the platform sandstones of E Africa).