Detrital Ages Research Articles

Cryogenian Magmatic Arc Detrital Ages and Superposition of Metamorphic Events in Metasedimentary Rocks from the Andrelândia and Juiz de Fora Domains, Juiz de Fora, Minas Gerais

Cryogenian Magmatic Arc Detrital Ages and Superposition of Metamorphic Events in Metasedimentary Rocks from the Andrelândia and Juiz de Fora Domains, Juiz de Fora, Minas Gerais

Sedimentary provenance and U-PB detrital zircon in the mesozoic record of the Parecis Basin, Rôndonia and Juruena sub-basin

Sediment provenance analysis is a tool increasingly used in the study of basins. This technique allows identifying the mineralogical and lithological composition of source areas, inferring paleogeography, climate and relief, determining the main sand distribution routes, and estimating the distance and transport time. The Mesozoic volcanic-sedimentary packages of the Parecis Basin mark a significant part of the South American Platform evolution, regarding tectonism, subsidence, sedimentation, basic and alkaline magmatism, uplift and erosion. Also, these packages registers the initial stages of Andean Orogeny subduction. Different authors have established opposite stratigraphic proposals for Parecis Basin regional correlations, and also for its tectonics evolution. Given this context, there are controversies regarding the chronostratigraphic positioning and relationships between the intervals, especially the units called Salto das Nuvens and Utiariti formations. This article presents the faciological framework and facies association, heavy mineral assemblage, ZTR index and sediment sources, and U-Pb detrital zircon ages to both sub-basins. Detrital Zircon data reveal minimum ages of 124 Ma for the Rondônia sub-basin and 245 Ma for the Juruena sub-basin for sedimentary deposition attributed to the base of the Cretaceous units. The detrital age of zircons points to a varied contribution, between elements from different provinces and ages of the Amazon Craton, the Paraguay Fold Belt and records of alkaline magmatism of ages Permo-Triassic and Cretaceous in the different kimberlithic fields of Rondônia and Mato Grosso.

Detrital muscovite 40Ar/39Ar geochronology and provenance of Cenozoic deposits in the Qaidam basin, northern Tibetan Plateau and comparison with detrital zircon and apatite records

The single-grain detrital multi-mineral dating techniques are powerful tools for tracing sediment provenance. However, natural biases in sediment source-to-sink systems may lead to heterogeneous sink signals based on detrital single-grain ages. Differing provenance interpretations may arise from detrital multi-mineral geochronologic data because of the potentially diverse origins and transport behaviors of the analyzed detrital minerals. To test this hypothesis, we present new single-grain detrital muscovite 40Ar/39Ar dating results from the Cenozoic Qaidam basin and compile published detrital muscovite 40Ar/39Ar, detrital zircon U-Pb, and detrital apatite fission track age data to interpret muscovite provenance and to explore the potential inconsistencies among multi-dating results and related controlling mechanisms. Our results indicate that detrital muscovite grains from most Cenozoic deposits have a similar, dominated 300–400 Ma age range, with subordinate 200–300 Ma and 400–500 Ma. The new and compiled 40Ar/39Ar age data demonstrate that detrital muscovite records from the Cenozoic Qaidam basin are stratigraphically variable. Samples from middle fine-grained deposits-dominated strata, representing the paleo-megalake period, exhibit a relatively wider age range compared to those from lower and upper coarse-grained deposits-dominated strata, indicating a probable control of sedimentary environments. Comparisons of detrital muscovite, zircon, and apatite records indicate that the detrital zircon age spectra have the oldest ages, the widest age ranges, and the largest number of age groups. Detrital zircon and apatite age spectra exhibit higher spatial variations than detrital muscovite records, likely due to the distinct source-to-sink behaviors of these minerals. The magmatic, metamorphic, and uplift history of source terranes, along with system closure temperatures, originally determine detrital mineral age records, i.e., high-temperature systems yield older ages, and vice versa. Parent-rock types, mineral fertility, and weathering resistance control the numbers and probabilities of the detrital age clusters. Differences in mineral shape, density, and transport and depositional processes (i.e., different transport loads of light, platy minerals vs. heavy, granular minerals) may cause variations in age spectra. These differences in detrital mineral behaviors warrant more attention in multi-mineral dating-based sediment provenance studies. Additionally, 40Ar/39Ar age data compilation based on global Cenozoic sedimentary basins and modern rivers indicates that detrital muscovite records have potentials to determine tectonic settings, but climate-induced exhumation signals need to be distinguished before interpretation.

A Scottish provenance for the Altar Stone of Stonehenge.

Understanding the provenance of megaliths used in the Neolithic stone circle at Stonehenge, southern England, gives insight into the culture and connectivity of prehistoric Britain. The source of the Altar Stone, the central recumbent sandstone megalith, has remained unknown, with recent work discounting an Anglo-Welsh Basin origin1,2. Here we present the age and chemistry of detrital zircon, apatite and rutile grains from within fragments of the Altar Stone. The detrital zircon load largely comprises Mesoproterozoic and Archaean sources, whereas rutile and apatite are dominated by a mid-Ordovician source. The ages of these grains indicate derivation from an ultimate Laurentian crystalline source region that was overprinted by Grampian (around 460 million years ago) magmatism. Detrital age comparisons to sedimentary packages throughout Britain and Ireland reveal a remarkable similarity to the Old Red Sandstone of the Orcadian Basin in northeast Scotland. Such a provenance implies that the Altar Stone, a 6 tonne shaped block, was sourced at least 750 km from its current location. The difficulty of long-distance overland transport of such massive cargo from Scotland, navigating topographic barriers, suggests that it was transported by sea. Such routing demonstrates a high level of societal organization with intra-Britain transport during the Neolithic period.

A revised stratigraphic model for the ∼ 1910–1835 Ma Tanami Group, the Northern Territory, Australia: Implications for exploration targeting

The Paleoproterozoic Tanami Group of the Granites—Tanami Orogen hosts a known endowment of > 20 Moz of gold mineralization across numerous deposits. Throughout the region, host lithologies impart a first-order control on the style, grade and endowment of mineralization. However, the genetic relationship and regional distribution of three regionally correlative formations (the Dead Bullock, Mount Charles and Stubbins formations) remains enigmatic. Here, we combine lithostratigraphic analysis, lithogeochemistry, detrital zircon geochronology and geophysical observations to propose a new evolutionary model for the Tanami Group. We find that the Tanami Group was deposited in a continental back-arc basin setting and developed in four stages. Package A marked the onset of the rifting of the continental Archean basement. Sedimentary rocks within Package A are dominantly felsic in composition and display a unimodal detrital zircon age population at ∼ 2530 Ma. Package B marks the onset of mafic volcanism; consequently, volcaniclastic and sedimentary rocks within Package B display a distinct mafic geochemical signature. Detritus shed from an Archean basement persisted throughout this period, and a unimodal detrital age component at ∼ 2530 Ma persists. Package C marked the waning stages of voluminous mafic volcanism across the Tanami Basin. Sedimentary volcaniclastic rocks within Package C display a mixed mafic and felsic composition. Detrital zircon age spectra record multiple peaks at ∼ 2500, 3000 and 3350 Ma, which may reflect erosion of older Archean basement domains or changes in paleo-drainage. Package D marked a significant change in the source of detritus entering the basin from dominantly Archean to Paleoproterozoic, with dominant detrital age peaks at ∼ 1860 Ma. Despite significant lithofacies variations, the presented model highlights multiple correlations between the Dead Bullock and Mount Charles formations. The Mount Charles Formation likely represents a volcanic source-proximal, high-energy depocenter. In contrast, the Dead Bullock Formation was deposited in a lower energy setting, distal to volcanic centers. These observations are important to mineral exploration. Notably, the Mount Charles Formation is distributed over a significantly greater area than previously thought, and the under-represented Hangingwall and Footwall sequences of this formation are interpreted to host significant gold mineralization at the Oberon and Groundrush deposits.

How to Quantify Heavy Mineral Fertility From Point‐Counting Data

AbstractHeavy minerals (HM) are widely used in provenance studies, for example, for reconstructing source areas and quantifying sediment budgets. Source rock mineral fertility influences the composition and concentration of HM in sediments. The resulting bias is of particular interest when interpreting single‐grain data such as detrital age distributions. However, the quantification of fertility is complex and there are no robust data for most HM, which prevents the routine implementation of fertility in many studies. In this study, we test whether mineral fertility can be assessed by quantifying mineral concentrations in detrital samples through point counting and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN). The challenge is to transform the resulting area percentage into mass percentage, which is a prerequisite for comparing those data with grain size or geochemical data. We suggest overcoming this problem by recording grain‐size and shape metrics of minerals using image analysis, and applying several transformation steps. We test our method by (a) using a series of detrital grain mixtures of known density and mass, and (b) applying it to a natural sediment from the European Alps. Our results agree with existing methods developed for apatite and zircon, that is, the quantification of fertility through geochemistry (with P2O5 and Zr concentrations as proxies for apatite and zircon) and the separation of pure apatite and zircon concentrates using additional separation steps. The advantage of our method is its applicability to all HM (not only apatite and zircon) and the redundancy of additional separation steps, which might create bias.

Sedimentology, geochronology and provenance of the late Permian and Triassic Mitu Group in Peru—The evolution of continental facies along a transform margin

AbstractIn the late Permian and Triassic, the continental Mitu Group formed in extensional basins along the length of the Cordillera Oriental and Altiplano of present‐day Peru. Given the presence of coeval arc systems only in northern Chile and southern Ecuador but not in Peru the tectonic setting of the Mitu basin has been interpreted variably as orthogonal continental rift, sinistral transtensional rift, aulacogen and back‐arc basin. The Mitu Group comprises continental mass flow and alluvial fan, fluvial, aeolian and minor lacustrian facies and hosts thick piles of subalkaline and alkaline intermediate and felsic ignimbrites and mafic lavas. The age of the Mitu Group had originally been established as ranging from the Late Permian to the late Triassic on the basis of structural considerations and scarce biostratigraphic data. Recently, U–Pb zircon ages from ignimbrites and sedimentary rocks have been taken to constrain the Mitu Group to the Middle and Late Triassic. We performed a sedimentological, heavy mineral, and zircon geochronological and Lu‐Hf isotope study of the Mitu Group in 14 sections mainly in southern and central Peru, and one section in northern Peru. Ten new U–Pb concordia ages on ignimbrites intercalated in the Mitu Group successions offer a new robust stratigraphic framework and constrain the stratigraphy of the Mitu Group between 260 and 205 Ma. In combination with maximum likelihood ages of deposition derived from detrital zircon, U–Pb geochronology places the deposition of the Mitu Group between ca. 270 and 194 Ma (lower Guadalupian into the Sinemurian). Detrital zircon U–Pb age distributions and heavy mineral assemblages reflect a strongly recycled Precambrian Amazonian and Palaeozoic proto‐Andean provenance. The Palaeozoic detrital age patterns are highly variable, and temporally and spatially random. A local provenance can generally not be identified. εHf(t) values in zircon obtained from ignimbrites and sedimentary rocks indicate variable degrees of crustal recycling. In the course of the Palaeozoic, εHf(t) values become on average progressively less negative, with a large proportion particularly of Mitu age zircons' εHf(t) values encompassing less evolved and moderately juvenile compositions. Along strike of the basin stratigraphic thicknesses, and rates and times of accumulation vary strongly with larger thicknesses and rates being registered in southern Peru. This suggests that the Mitu basin had been divided into a number of subbasins with individual histories of subsidence, accumulation, and volcanism. Absent a magmatic arc, late Permian–Triassic Peru evolved in a sinistral plate tectonic and regional framework expressed particularly in the sinistral Late Gondwanide orogeny predating the Mitu Group. We interpret that a sinistral transform fault linked the subduction zones in southern Ecuador and northern Chile and that the Mitu Group basin has formed by sinistral transtensional and transpressional movements along a related transcurrent fault inboard of the transform margin. In the broader framework of the accretionary Terra Australis orogen along the western Gondwana margin, this interpretation fits its evolution in the Andean segment in an internally consistent way.

Provenance shifts in bauxitic clay from Zibo, North China Craton, links tectonics and climate to environmental perturbation

Abstract In the eastern North China Craton, the Zibo bauxitic clay deposits are situated between Permian sandstones. These deposits exhibit distinct characteristics in two horizons. The lower horizon consists of disordered kaolinite with anhedral–subhedral, rounded morphologies that indicate a detrital origin. The upper horizon, however, contains ordered kaolinite. Detrital zircon grains in the lower horizon indicate a unimodal age spectrum with a mean age of ca. 290 Ma and εHf(t) values ranging from −20.8 to −6.0. These findings suggest a continental volcanic arc source on the northern margin of the North China Craton. In contrast, detrital zircon grains in the upper section exhibit a multi-modal detrital age spectrum with significant age peaks at 2500 Ma, 1850 Ma, and 310 Ma that originates from the local basement. The zircon dating establishes a maximum depositional age of ca. 280 ± 3 Ma, which indicates denudation of the source area in the northern North China Craton during the Artinskian stage. The relative abundance of detrital kaolinite indicates a warm and humid climate during the late Artinskian (ca. 283 Ma) to Early Kungurian (ca. 280 Ma), while cold and dry conditions prevailed during the mid–late Kungurian (ca. 277 Ma). The northern North China Craton, which supplied source material to the lower section of Zibo bauxitic clay, experienced rapid uplift and exhumation and underwent intense weathering under high humidity and warm temperatures during the late Artinskian to Early Kungurian. However, the source area shifted from the north to a more central region as the climate transitioned to cold and dry conditions in the mid–late Kungurian. Considering that detrital clay formation is indicative of specific climatic conditions, the Permian bauxitic clay deposits in Zibo provide a valuable record of environmental changes during the late Paleozoic ice age (LPIA; ca. 360–260 Ma).

External geodynamic evolution of the Mongolian Accretionary Collage: Insights from petro-chronology of zircon

Evolution of internal or external oceanic domains can bring decisive indications into the mode of formation of supercontinents, which is key to understand the supercontinent cycle. Defining the type of ocean evolving in the Central Asian Orogenic belt (CAOB) is thus critical to better understand the Earth’s supercontinental evolution. In this contribution, we provide systematic and combined U-Pb, trace-element in zircon and hafnium-in-zircon analyses of four turbidites of the Altai accretionary wedge. These turbiditic rocks provide constraints into the early Paleozoic subduction-accretionary stages of the Mongolian Accretionary Collage (MAC) and show a major detrital age peak in the Cambro-Ordovician (∼490–500 Ma), with minor Neo- and Paleo-Proterozoic to Archean peaks. The zircon trace-elemental patterns are consistent with derivation mostly from magmatic arc (with granitoids affinity), interpreted as detritus sourced from the Ikh-Mongol continental arc system further north-east (present coordinates). The main detrital zircon peak together with the zircon magmatic arc origin suggest that the subduction-accretionary stage was active from 550 to 430 Ma showing mixed εHf(t) values (-20 to + 15). A summary of the detrital zircon εHf(t) values from 550 to 430 Ma suggests a continuous increase of εHf(t) mean values from + 0.2 to + 6.1 towards younger ages. The younging juvenile trend can be compared to the evolution of external orogeny, therefore consistent with a Pacific-type accretionary system facing an external ocean. At last, the results combined with two paleo-geographic reconstructions from the literature imply that the MAC may have been part of the Peri-Siberian accretionary orogeny in the early Paleozoic.

U-Pb Zircon Geochronology of Detrital and Ash Fall Deposits of the Southern Paraná Basin: A Contribution for Provenance, Tectonic Evolution, and the Paleogeography of the SW Gondwana

Zircon U-Pb geochronology was applied to investigate the provenance, depositional ages, and paleogeography of the southwestern Gondwana in detrital and ash fall sediments from Carboniferous to Jurassic succession of the southern Paraná Basin. Four detrital age populations suggest provenance from local and distal sources located to the south, southeast, and southwest: (i) Archean to Paleoproterozoic zircons from the Rio de La Plata Craton, Nico Peres and Taquarembó terranes; (ii) Grenvillian zircons from the basement of the Gondwanides and Namaqua–Natal belts; (iii) Neoproterozoic grains from the Don Feliciano Belt; and (iv) Phanerozoic populations from Paleozoic orogenic belts and related foreland systems in Argentina, as well as eroded units of the Paraná Basin. The paleogeographic reconstruction indicates an evolution in three distinct stages: (1) a gulf open to the Panthalassa Ocean during the Carboniferous; (2) an epicontinental sea with the rise of the Gondwanides Orogeny during the Permian; and (3) continental deposits controlled by an intra-plate graben system during the Triassic. Permian–Triassic volcanogenic zircons provide constrained maximum depositional ages and attested persistent volcanism, related to the Choiyoi magmatism and effects of the climate change episodes. During the Triassic, the extensional graben system recorded the uplift of the basement through regional northwest and northeast fault systems, and the recycling of Permian zircons, modifying source-to-sink relationships.

Sedimentary provenance in continental rifts: U–Pb detrital zircon, Nd and Sr isotopes and lithogeochemistry of the Eocene alluvial sandstones of the Resende Basin, SE–Brazil

Multiproxy analysis of detrital minerals is a powerful tool for unravelling the source-to-sink evolution of syn-rift sedimentary basins that represent important depositional settings during major rift events. The Cenozoic Resende half-graben in SE Brazil is a classic example of a syn-rift basin developed under oblique extension, which preserves evidence of tectonic episodes and palaeoclimatic conditions during the opening of the Atlantic. Sediment in the basin was sourced from the surrounding basement rocks, which to the faulted margin consists of older Proterozoic orthogranulites and orthogneisses, whilst to the flexural margin is characterised by Neoproterozoic passive margin paragneisses. Cretaceous intra-plate alkaline stocks crop out at the western edge and in the central-south basement of the basin and represent a distinct provenance fingerprint. This study uses new detrital zircons U–Pb ages combined with previously published elemental and Nd and Sr isotopic data to characterise the sedimentary provenance of Eocene alluvial deposits and to understand how sediment sourcing has changed throughout the evolution of the basin. U–Pb detrital zircon analyses from samples collected across the Resende Basin are presented herein. Samples yield a spread of detrital age spectra from the Archaean to the Cretaceous. Precambrian zircons range from ca. 3228 Ma to ca. 542 Ma. Cretaceous zircons yield ages between ca. 138 Ma and ca. 67 Ma. The sediment source location is interpreted by comparing the yielded detrital zircon spectra with the age spectra of zircons from the basement rocks. The dominance of detrital zircons yielding ages of ca. 1500 Ma and ca. 1000 Ma is interpreted to be sourced from the Neoproterozoic basement rocks to the flexural border of the half-graben. Cretaceous zircons from samples with whole rock εNd40Ma > −10 are found in both the western and eastern portions of the half-graben but not in the central portions. It is interpreted that an along-axis fluvial system was responsible for a small increase in the compositional maturity of the Resende sandstones from west to east, resulting in the progressive dilution of Cretaceous alkaline igneous detritus along the basin axis. Preserved metamorphic rims in zircon grains indicate low transport abrasion, suggesting that Cretaceous zircons in the eastern depocentre could be associated with other small proximal sources. U–Pb zircon analyses and Nd and Sr isotopes provide reliable insights regarding sediment provenance and transport processes, whilst element geochemistry supplies evidence for hydraulic sorting effects. Consequently, the data represents a more robust estimation of the provenance patterns of the Resende Basin, showing chemical and geochronological differences that support the division of the basin into three depocentres (western, central, and eastern) connected by a longitudinal fluvial system sourced mostly by sediments coming from the south-western flexural border. This study highlights the usefulness of using multiple provenance proxies to unravel the complex development of rift basins, assessing multiple source terrains and the variable degrees of mixing in sedimentary basins.

Short communication: The Wasserstein distance as a dissimilarity metric for comparing detrital age spectra and other geological distributions

Abstract. Distributional data such as detrital age populations or grain size distributions are common in the geological sciences. As analytical techniques become more sophisticated, increasingly large amounts of distributional data are being gathered. These advances require quantitative and objective methods, such as multidimensional scaling (MDS), to analyse large numbers of samples. Crucial to such methods is choosing a sensible measure of dissimilarity between samples. At present, the Kolmogorov–Smirnov (KS) statistic is the most widely used of these dissimilarity measures. However, the KS statistic has some limitations such as high sensitivity to differences between the modes of two distributions and insensitivity to their tails. Here, we propose the Wasserstein-2 distance (W2) as an additional and alternative metric for use in geochronology. Whereas the KS distance is defined as the maximum vertical distance between two empirical cumulative distribution functions, the W2 distance is a function of the horizontal distances (i.e. age differences) between observations. Using a variety of synthetic and real datasets, we explore scenarios where the W2 may provide greater geological insight than the KS statistic. We find that in cases where absolute time differences are not relevant (e.g. mixing of known, discrete age peaks), the KS statistic can be more intuitive. However, in scenarios where absolute age differences are important (e.g. temporally and/or spatially evolving sources, thermochronology, and overcoming laboratory biases), W2 is preferable. The W2 distance has been added to the R package, IsoplotR, for immediate use in detrital geochronology and other applications. The W2 distance can be generalized to multiple dimensions, which opens opportunities beyond distributional data.

Cretaceous source to sink system reconstruction of northeastern Asian continental margin: Insight from integrated detrital geochronology in NE China

The Cretaceous sedimentary successions in NE China are largely incomplete as the basins are inverted and younger strata are eroded. Except for the Songliao Basin, whose depositional record has remained relatively intact, the burial record to the east was interrupted in the late Early or Late Cretaceous. There is still controversy on the possible connection between the Songliao Basin and the eastern basin group, as well as the extent of the previously suggested “pan-Sanjiang” proto-basin that covered most current eastern satellite basins. To address these questions, we studied modern river catchments of variable sizes from sediment-supplying basement highs that cover most of eastern NE China to track the intense denudation events and provenance changes through the Cretaceous. We found a great inconsistency between detrital age patterns of the modern river sands and the spatial proportions of the source units. The detrital age distributions allow to re-evaluate the basement units that are mostly composed of the Triassic–Jurassic igneous suite and some metasedimentary units with Paleozoic ages, but the contribution from Proterozoic formations is negligible. Combining the newly dated modern catchment detrital U-Pb ages, the region-wide compilation of the basement emplacement ages, and the U-Pb ages in the Cretaceous formations in NE China, we systematically refine the Cretaceous provenance history. In the Early Cretaceous, the eastern satellite basins accumulated sediments from the Lesser Xing’an range (LXR) in the west, Zhangguangcai range (ZGCR) in the south, and the Nadanhada terrane (NT) in the east. The sediment of the southern Songliao Basin derived from the North China Craton (NCC) and from ZGCR but barely from the Great Xing’an Range (GXR). The Jiamusi uplift (JU) did not provide sediments to the eastern satellite basins and the Songliao Basin.In the Late Cretaceous, the eastern satellite basins received sediments from the exhumed JU but barely from ZGCR and LXR. The Songliao Basin still accumulated the sediments from the NCC, some south part of ZGCR, and GXR but minor from the central and northern ZGCR and LXR. Between the latest Early Cretaceous and early Late Cretaceous, a much wider proto-basin was suggested in NE China than previously assumed. It covered during its maximum extension period the current Songliao Basin, the eastern satellite basins, the LXR, ZGCR, JU, and partial GXR basement areas. The provenance change is induced by the Paleo-Pacific plate motion change, i.e., with the subduction direction change, the roll-back, and two-stage limited flat slab subduction trigged the formation of the basin-and-range system in NE China since the Early Cretaceous. Moreover, we suggest conducting modern sand provenance analysis to detect, verify or re-classify the ages of the zircon-bearing units, especially at a reconnaissance prospecting on areas covered by imprecise large-scale geological maps only to reveal the catchment better.

High-grade complexes record the Late Permian-Middle Triassic arc metamorphism in the southernmost Altaids: Implications for the final closure of the Paleo-Asian Ocean

High-grade metamorphic complexes or terranes in orogens play a vital role in reconstructing orogenic dynamics and tectonic history of Earth's past owing to their multi-tectono-thermal recording capacity. The Chijin Complex, located in the southernmost Altaids and composed of intensely deformed medium- to high-grade meta-volcanic rocks including (garnet-bearing) mica-quartz schists, felsic gneisses, and amphibolitic schists and gneisses, imposes crucial constraints on the fiercely disputed timing and tectonic architecture of the Paleo-Asian Ocean's (PAO) terminal evolution. This Complex has long been interpreted as the Precambrian basement of a microcontinent in tectonic reconstructions. Our detailed field investigations, geochemical research, and detrital age spectrum analyses of the Chijin Complex reveal structural-lithological-geochemical affinities to volcanic-magmatic extrusions originating from a continental arc regime. Anti-clockwise P-T paths and high T/P geothermal gradients (~24–37 °C/km), reconstructed by thermodynamic modeling and geothermobarometry for the Complex, reveal magmatic underplating mechanism from prograde “hot” T/P metamorphism resulting from thermal intrusion and finite arc crustal thickening to in-situ retrograde isobaric cooling. Hornblende and biotite 40Ar/39Ar and zircon UPb dating demonstrates that the continental arc system was still active as during the Early to Middle Triassic (~252–237 Ma) as a result of continuing southward subduction of the PAO, thereby constraining the final amalgamation of the Altaids to the Late Triassic. This study proposes a new perspective for redefining high-grade rocks at the southernmost Altaids as arc-metamorphic complexes rather than “reputed” ancient microcontinent, as well as a potential template example for discerning tectonic nature of semblable metamorphic complexes or terranes with distinct origins in global orogens.

Detrital composition and sedimentary provenance of Early Carboniferous Al-bearing rock series in central Guizhou

The Early Carboniferous Al-bearing rock series in central Guizhou is an important bauxite ore-bearing and Li-rich stratigraphic unit. The origin and correlation of detrital zircon ages from different types of Al-bearing rock series will provide new insights into the sedimentary processes and metallogenic mechanisms. We present the detrital zircon U-Pb ages and Hf isotopic compositions from the Early Carboniferous Al-bearing rock series and underlying Ordovician clastic rocks (Tongzi and Meitan Formation). The early Carboniferous Al-bearing rock series in the central Guizhou show two dominant age peaks at ca. 980–960 Ma and 540–530 Ma and several subordinate age peaks (ca. 2500 Ma, 820–780 Ma, and 630–610 Ma). The deposition of the Al-bearing rock series occurred near the direct source and the provenance of the Jiujialu Formation mainly originated from the recycled sedimentary bedrock of underlying Ordovician stratigraphic units. Most recycled clastic materials of the Early Carboniferous Al-bearing rock series originated from external sources outside the South China Block. Ferrous clay rocks and Aluminous clay rocks show two age peaks at ca. 540 Ma and 970 Ma. Detrital zircon from the bauxite diposits shows multiple detrital age peaks, reflecting the supply of multiple provenances. Aluminous or Ferrous clay rocks are more widespread in the southern segment of central Guizhou may be related to the early carboniferous transgression.

Multimethod provenance analysis using detrital zircon and rutile U-Pb geochronology across Devonian basin systems in the Tasmanides of eastern Australia

The Devonian represents a period of transition for the accretionary orogens of the Australian Tasmanides where the largest and inboard Thomson Orogen became stabilised and orogenic processes became focused in the outboard and newly developing New England Orogen. The end of tectonic activity in the Thomson and the adjacent Delamerian and Lachlan orogens culminated with the development of several overlying intracratonic sedimentary basins. We examine the two largest cover basins, the Adavale and Darling, using stratigraphic logging, sandstone petrography, detrital zircon and rutile U-Pb geochronology to fingerprint sediment sources to test whether the basins were once connected and part of a much larger cover basin system. Sediment provenance in the Adavale Basin is characterised by (i) continuous input from a basement-derived Ordovician (∼480 Ma) igneous zircon source, (ii) reworking of metasedimentary basement rocks with a ‘Pacific-Gondwana’ age signature (iii) reworking of detrital rutile from Cambro-Ordovician sedimentary rocks in the Thomson Orogen ultimately sourced from the Musgrave Block and (iv) an addition of syn-depositional volcanic zircon from contemporary volcanism between ∼380 and 360 Ma. Sediment provenance of the Darling Basin is dominated by reworking of (meta)sedimentary basement, evident from large proportions of rounded zircons exhibiting a ‘Pacific-Gondwana’ age signature and detrital rutile with Peterman Orogeny ages. A much less significant age population of syn-depositional volcanic detrital zircons suggests input from contemporary volcanic sources which were more distal and extra-basinal.The comparison of sandstone compositions and detrital age information indicate both basins record similar provenance signals in terms of reworking of their respective hinterlands and receiving contributions from relatively distal syn-depositional volcanism. However, the comparison of sediment provenance proxies, suggests that the Adavale and Darling basins were not connected during the Devonian and that the basins are intracratonic or cover basins, recording the stabilisation of the Thomson and Lachlan orogens, respectively.

Exhumation of the Higher Himalaya: Insights from Detrital Zircon U–Pb Ages of the Oligocene–Miocene Chitarwatta Formation, Sulaiman Fold–Thrust Belt, Pakistan

This study reports the detrital zircon U–Pb ages of the post collisional Chitarwatta Formation, exposed along the western margin of the Indian plate at the Sulaiman fold–thrust belt (SFB), Pakistan. The Chitarwatta Formation overlies the shallow marine carbonate sequence of the Kirthar Formation and represents an Oligocene–Miocene transitional marine sequence. The sequence consists of sandstone, siltstone, and mudstone. The sandstone consists predominantly (79–82%) of quartz grains. The framework grains are sub-angular to sub-rounded and show recycled orogenic provenance. The detrital zircon U–Pb age data show the dominant population between 390 Ma and ~1100 Ma, which is ~70% of the total population. In addition to this, a significant percentage of the younger detrital ages exist between ~40 Ma and ~120 Ma. This younger age cluster indicates the northern sources, including the Kohistan–Ladakh arc (KLA) and Karakoram block (KB), whereas the provenance for the 390–1100 Ma detrital zircon is likely the Higher Himalaya (HH), with contribution from Tethyan Himalaya (TH). This post-collisional scenario suggests that the Chitarwatta Formation received detritus from the northern sources through a drainage system, named as the Indus drainage system. A comparison with the coeval units in the north (Murree Formation, Dagshai Formation, and Dumre Formation) suggests that the sediments may have been delivered through the same drainage system that shares similar detritus. Relying on the contribution of the HH detritus, we propose that the HH uplifted during the Oligocene–Miocene along the Main Central Thrust (MCT) and provided detritus to the foreland basin.

New insights on the interpretation of the provenance and evolution of the Silurian units in the central Precordillera, Argentina

In the central region of the Precordillera, San Juan Province, Silurian silicoclastic sedimentites of the Los Espejos Formation crop out in the Jáchal River area. To the south of this region, an equivalent unit is recognized in the San Juan River area (Tambolar Formation). Both units present similar lithological characteristics, however, it has not yet been defined if they share source areas of detrital contributions. On the other hand, for the Jáchal River sector, it is proposed to establish if there were changes in the regions from where the sub-basin received sediment contributions during the Devonian, which can be seen reflected in the detrital zircon contribution patterns of the overlying unit (Talacasto Formation). The present work is part of a series of studies tending to determine the nature and provenance of the Silurian-Devonian sequences of the Central Precordillera. On this occasion, detrital zircon patterns of the detrital sources of the Los Espejos Formation are analyzed and compared with the information obtained for the Silurian Tambolar Formation (San Juan River area) and the overlying Devonian Talacasto and Punta Negra formations (Jáchal and San Juan rivers areas). To characterize and compare the studied units, different methodologies were applied, namely sedimentary petrography, heavy minerals studies, and morphological and isotopic analyses of detrital zircons. The analysis of thin sections allowed determining textural and compositional parameters. Through the predominance of detrital minerals, it was possible to establish that the studied units are composed of quartzite-type rocks coming from mature areas, with low percentages of lithic components and abundant opaque heavy minerals of the hematite group. The study of heavy minerals, especially morphological and typological parameters of detrital zircons, allowed to establish recycled and plutonic sources as main modes, as well as the changes that occurred during the basin filling dynamics for Silurian and Devonian times. On the other hand, U–Pb isotopic analysis in detrital zircons indicate that the Pampean-Brasiliano orogenic cycle composes the main source of detritus with ages between 511 and 816 Ma. In second place are the Mesoproterozoic ages, represented by the interval from 1000 to 1350 Ma. The youngest detrital ages show a maximum sedimentation age of 478.5 ± 4.4 Ma (Tremadocian), indicating that younger sources of contribution correspond to the Famatinian Orogen. The Kolmogorov-Smirnoff test revealed that the studied Silurian-Devonian units studied have similar patterns of sedimentary contributions, which suggests that the sources of provenance were common in both regions and remained active throughout the entire time interval, without significant changes.

Identifying sources of non-unique detrital age distributions through integrated provenance analysis: An example from the Paleozoic Central Colorado Trough

AbstractTo address the longstanding issue of provenance interpretation of non-unique detrital zircon age populations, we integrated zircon U-Pb, rare earth element (REE), and εHf(t) data from upper Paleozoic strata in the northern Central Colorado Trough and Cambrian intrusions with petrography, paleocurrent data, and structural and stratigraphic observations. This data set indicates that Cambrian sediment was shed by multiple local sources instead of distant sources hundreds of kilometers away, and it reveals a detailed history of tectonic drainage reorganization in the northern Central Colorado Trough during Ancestral Rocky Mountain deformation. During the Early–Middle Pennsylvanian, Cambrian detrital zircons were a minor constituent of northern Central Colorado Trough sediment. However, during the Late Pennsylvanian–early Permian, westward advancement of the adjacent Apishapa Uplift deformation front precipitated drainage reorganization, which resulted in an episode of dominant Cambrian detrital zircon sourcing. Paleocurrent and petrographic data indicate that the source of Cambrian detritus was shed by an igneous rock body that was ≤15 km northeast of the depocenter, which has since been eroded away or mantled by Tertiary volcanic rocks. The addition of zircon petrochronology to the data set applied here was critical in confirming this hidden source of detritus and elucidating the compositional characteristics of that igneous rock. Zircon εHf(t) provided a regional provenance indicator of a western Laurentian affinity, and REE composition aided in discriminating possible local sources of Cambrian zircon. Furthermore, this work serves as a case study of a dominant Cambrian detrital zircon signature sourced from outside of the wellknown Amarillo-Wichita Uplift, and it has implications for the interpretation of such detrital spectra in the context of a direct-from-basement source or the recycling of Cambrian zircon-dominated rocks. In summary, we demonstrate the utility of this multi-provenance proxy approach in interpreting a complex structural history of a dynamic hinterland and concomitant drainage reorganization through an in-depth investigation into the basin record.

U-Pb zircon ages from metasedimentary and plutonic rocks in the Bras d'Or terrane of Cape Breton Island, Nova Scotia, Canada: insights into the Ediacaran–Cambrian tectonomagmatic evolution of Ganderia

The Bras d'Or terrane of central Cape Breton Island, Nova Scotia, Canada, contains a well-preserved record of the Ediacaran to early Cambrian evolution of Ganderia, a Gondwana-derived terrane in the northern Appalachian orogen. A complex assemblage of low- to high-grade metasedimentary rocks has varied detrital zircon signatures from laser ablation inductively coupled plasma mass spectrometry U-Pb zircon dating, but combining three or more samples yielded representative age spectra that support correlation of the low- and high-grade metasedimentary rocks throughout the Bras d'Or terrane and the corresponding Ganderian Brookville terrane of southern New Brunswick. In quartzite samples from the McMillan Flowage Formation in the northwestern Bras d'Or terrane, the youngest detrital zircons have ages >900 Ma, in contrast to previously studied psammitic and semipelitic samples from correlative units in the eastern Bras d'Or terrane in which youngest detrital ages are 620–600 Ma. Both quartzite and semipelitic samples from the McMillan Flowage Formation contain Neoproterozoic dates from zircon rims, which reflect metamorphic overgrowths during peak metamorphism at ca. 550 Ma, providing a robust age for peak metamorphism in the Bras d'Or terrane that supports similar, albeit sparse, ages reported previously from monazite and titanite samples. This metamorphism is coeval with the emplacement of voluminous dioritic to granitic plutons that occur throughout the Bras d'Or terrane and form in an Andean-type continental margin subduction zone. New U-Pb zircon ages presented here from plutons in the northern Bras d'Or terrane, combined with previously published ages, are consistent with subduction-related magmatism and associated metamorphism between ca. 575 and 540 Ma.