Detrital Zircon Data Research Articles

Orogens and detritus: unravelling the Mesoproterozoic tectonic geography of northern Australia through coupled detrital thermo- and geo-chronometers

This study presents detrital muscovite 40Ar/39Ar data from the Mesoproterozoic Roper Group and overlying informally named successions, in the Beetaloo Sub-basin, northern Australia. Detrital muscovite chronology reveals tectono-thermal processes within source regions and provides new constraints on the basin provenance, revising previous interpretations based on detrital zircon data. Detrital thermo- and geochronology, together demonstrate three main periods when the basin paleogeography was altered that correspond to the evolving tectonic history of the North Australia Craton (NAC) through the Mesoproterozoic. The first is characterised by an increased sediment contribution from source regions that lay along the eastern margin of Proterozoic Australia. These source regions are interpreted to have formed the uplifted rift-shoulders between Proterozoic Australia and Laurentia at ca 1.45 Ga. After that, sediments derived from eastern Proterozoic Australia sources become less voluminous up-section. The youngest analysed formation from the Roper Group, the Kyalla Formation, was predominately from sources to the south of the basin, representing another modification of basin geography. This is interpreted to result from the closure/subduction of the Mirning Ocean as the West Australian Craton (WAC) approached and collided with the NAC, resulting in an uplift of the southern margin of the NAC, at ca 1.35–1.31 Ga. The uppermost Mesoproterozoic to lower Neoproterozoic sandstone successions that overlie the Roper Group were derived from the Musgrave Province. Coupled detrital zircon and muscovite data imply a rapid cooling at ca 1.20–1.15 Ga that is interpreted to reflect syn-orogenic exhumation during the Musgrave Orogeny. Furthermore, data from the Beetaloo Sub-basin suggest that the changed basin tectonic settings reshaped basin geography and result in distinctive detrital zircon and muscovite geochronology records. In this study, we used the detrital U–Pb zircon and muscovite 40Ar/39Ar age data from the Beetaloo Sub-basin and a range of other basins deposited in different tectonic environments, including the convergent, collisional and extensional settings, to reconstruct the basin tectonic geography and illustrate various tectonic controls on basin formation in different tectonic backgrounds. KEY POINTS Detrital muscovite 40Ar/39Ar data provide thermochronological constraints on basin provenance, complementing previous interpretations based on detrital zircon data. Spatial and temporal variation of provenance reconstructs the basin tectonic geography, reflecting the Mesoproterozoic tectonic history of the North Australia Craton. Coupled thermo- and geochronology constrain tectonic settings of basin deposition.

Bureya−Jiamusi−Khanka superterrane linked to the Kuunga-Pinjarra interior orogen of East Gondwana and its drift toward Northeast Asia

There is general agreement that a series of East Asian blocks has always lain outboard of both India and Australia along the North Indo−Australie peripheral orogen. However, whether the East Asian blocks were involved in the interior orogens of East Gondwana remains equivocal. The geochronology and geochemistry of Neoproterozoic−Late Triassic rocks in the Russian Far East, together with existing paleontological and detrital zircon data, offer an opportunity to determine the tectonic origin and drift history of the Bureya−Jiamusi−Khanka superterrane. Biotite and amphibole 40Ar/39Ar dating results define a distinctive episode of Late Pan-African (ca. 550 Ma) metamorphism and a local Late Triassic (ca. 219−200 Ma) episode of deformation for the Bureya−Jiamusi−Khanka superterrane. Zircon U−Pb ages and whole-rock geochemical data indicate that the Early Ordovician (483 ± 3 Ma) highly fractionated I-type monzogranites were emplaced in a post-collisional setting linked to the collapse of a Late Pan-African orogen, while the Late Triassic (ca. 234−223 Ma) A-type quartz syenites and I-type granite aplite dikes were formed in a slab-pull−induced passive continental margin of the subducting Mudanjiang oceanic plate. These crucial archives, complemented by data from the literature, reveal that the Bureya−Jiamusi−Khanka superterrane made up the northernmost Kuunga-Pinjarra interior orogen during the final assembly of East Gondwana. As a result of Devonian rifting after Early Ordovician orogen collapse, the Bureya−Jiamusi−Khanka superterrane escaped from the Kuunga-Pinjarra interior orogen and subsequently migrated to Northeast Asia by the Late Triassic to Jurassic due to the subduction and closure of the Paleo-Tethys and Paleo-Pacific oceans.

Sedimentary response to the early Silurian (Rhuddanian-Aeronian) post-glacial transgression and Kwangsian Orogeny in the Upper Yangtze region, South China

Unlike the lowermost Silurian ‘hot’ shales deposited in many other regions of the world, the early Silurian (Rhuddanian-Aeronian) succession in South China exhibits a distinctive lithofacies transition from organic-rich black siliceous mudstone in the early Rhuddanian, to interlaminated siltstone and mudstone with relatively low total organic carbon content in the late Rhuddanian, and finally to organic-lean argillaceous mudstone or calcareous mudstone in the late Aeronian. The interlaminated siltstone and mudstone interval has been the subject of a long-standing dispute over its nature, whether it belongs to turbidite or contourite. In this study, we employed a range of approaches, including petrographic analyses, UPb dating of detrital zircons, and measurements of paleocurrent directions to generate a dataset that reveals: (1) four typical fine-grained facies developed within the interlaminated siltstone and mudstone interval, (2) detrital zircon UPb ages yielding a wide age range from Archean (∼2.50 Ga) to early Paleozoic (0.42 Ga), with a predominant peak of ca. 447 Ma based on 516 detrital zircon UPb analyses, and (3) paleocurrent directions indicate the presence of current circulation in the Upper Yangtze region. The results of this study demonstrated that the detritus of the interlaminated siltstone and mudstone interval originated from concurrent explosive volcanic eruptions along the southeastern margin of the South China Craton. It was deposited and reworked by bottom currents under the background of the early Silurian post-glacial transgression. We suggest that the occurrence of the interlaminated siltstone and mudstone interval is indicative of a far-field sedimentary response to the onset and progradation of the Kwangsian Orogeny in the Upper Yangtze region.

Cenozoic tectonosedimentary evolution of the Linxia Basin, northeast Tibetan Plateau based on an analysis of detrital zircon provenance

The Linxia Basin is an important region for understanding the tectonism and uplift history in the northeast Tibetan Plateau, and also contains rich mammalian faunas of evolutionary significance. In this paper, we conduct a provenance study of Cenozoic sediments, relying primarily on U-Pb dating of detrital zircons, to investigate the exhumation history of surrounding terranes and to gain a better understanding of the relationship between tectonism, basin development and paleoenvironment.Samples were collected from the Maogou section in the central Linxia Basin, which has been recently dated by magnetostratigraphy. Detrital zircon populations show five UPb age groups of 65–350 Ma, 350–600 Ma, 600–1600 Ma, 1600–2200 Ma and 2200–2600 Ma; however, UPb age patterns varied up-section, indicating different sources at different times.Sediments from the lower part of the section (>27.8 Ma) were sourced from multiple regions, including the distal East Kunlun Shan, Qilian Shan, and Songpan–Ganzi terranes, and as well as the proximal West Qinling region. Contributions from the Songpan–Ganzi terrane increased considerably during the late Oligocene (27.8–23 Ma), as a result of strong tectonic movements of the northeastern Tibetan Plateau. During the early Miocene (23–17.2 Ma), the northern sources of the Laji Shan–Maxian Shan region supplied more sediments to the basin, indicating the uplift and exhumation of these mountain ranges. Until the middle Miocene (17.2–12.8 Ma), the Songpan-Ganzi terrane and the northern sources dominated the basin sediments, while the northern sources and the Jishi Shan region became increasingly important sources at around 11.6 Ma. This study explores the tectonosedimentary evolution of the Linxia Basin in the northeastern Tibetan Plateau, providing a reference for further research of the paleoclimate and mammalian evolution in this critical region.

Detrital zircon U–Pb ages and Hf isotope analyses of modern and Quaternary sediments in China: A new dataset with preliminary analysis

AbstractDevelopments of detrital zircon geochronology have resulted in an explosion of publications that report or discuss detrital zircon data. Combined detrital zircon U–Pb ages with Hf isotope analyses from modern and Quaternary sediments have been widely carried out with the aim of characterizing continental crustal evolution and tracing sediment provenance. Although several detrital zircon databases have compiled U–Pb and Hf data on global scale, the dataset of detrital zircon with a special focus on modern sediment has rarely been compiled. Here, we publish a new detrital zircon dataset of modern and Quaternary sediments in China with 59,535 U–Pb ages and 4,971 Hf isotope data, with detailed information of isotope ratios, ages, Th/U, etc. Four types of sediments have been classified according to sedimentary environments, including fluvial, marine, aeolian and alluvial sediments. Preliminary analysis is carried out on these compiled data to provide new insights into sedimentary provenance and crustal evolution in China. Eight age populations are identified corresponding to tectonic–thermal or magmatic events, including 2,300–2,700 Ma, 1,800–2,000 Ma, 700–1,000 Ma, 400–500 Ma, 200–300 Ma, 120–200 Ma, 80–120 Ma and < 60 Ma. Accompanying with quantitative comparison between sediments from various sedimentary environments, these U–Pb age distributions reveal the provenance link between “source” and “sink” in both exorheic and endorheic drainages. The compiled εHf(t) data reflect that the crustal history of China is apparently episodic, whose pattern is similar to that of global record. Further work will be implemented for database construction, including the integration of latest literatures, AI‐based data extraction and data aggregation.

U-Pb dating of detrital zircons from the Datangpo Formation, South China: Implications for Sturtian deglaciation age and Nanhua stratal provenance

U-Pb dating of detrital zircons from the Datangpo Formation, South China: Implications for Sturtian deglaciation age and Nanhua stratal provenance

Strike-slip influenced stratigraphic and structural development of the Foula Sandstone Group, Shetland: implications for offshore Devonian basin development on the northern UK continental shelf

The island of Foula, located 25 km SW of Shetland, preserves a gently folded, 1.6 km thick sequence of Middle Devonian sandstones spectacularly exposed in kilometre-long cliff sections >350 m high. These rocks unconformably overlie likely Precambrian-age amphibolite facies basement rocks that are intruded by sheeted granites. The onshore succession is similar in age to the nearby Lower Clair Group offshore to the west. New mapping, incorporating the use of drone imagery in the inaccessible cliff sections, uses down-plunge projections to show that growth folding and faulting on Foula were contemporaneous with sedimentation during basin filling. The large-scale structural geometry is consistent with the regional constrictional strain due to the sinistral transtension associated with movements along the Walls Boundary–Great Glen fault zone system during the Mid-Devonian. Detrital zircon provenance studies indicate that the Devonian sequences of Foula (and nearby Melby in western Shetland) show similarities with the Clair Group and Orkney successions. We suggest that NE–SW transtensional fold development contemporaneous with regional subsidence in the Devonian basins of Scotland may be more widespread than previously realized. Large, kilometre-scale folds previously interpreted to be related to Permo-Carboniferous inversion may therefore have initiated earlier in the basin evolution sequence than previously realized. Supplementary material: Appendices A, Methodologies; B, Regional stratigraphic correlation table; C, Heavy mineral data; D, Detrital zircon data; and E, 3D virtual outcrop models are available at https://doi.org/10.6084/m9.figshare.c.6442552

Late Oligocene Formation of the Pearl River Triggered by the Opening of the South China Sea

AbstractThe Pearl River is one of the largest rivers entering the South China Sea, yet its initiation time remains debated, a topic we address using Pb isotopes in detrital K‐feldspar. Based on these Pb data, Eocene and Early Oligocene sandstones from the northern South China Sea are interpreted to have been supplied with sediment by proximal rivers draining the Cathaysia Block. In contrast, the Late Oligocene and Miocene sandstones are mainly derived from the western Pearl tributaries (e.g., Hongshui River), suggesting that the Pearl River had formed by the Late Oligocene. Detrital zircon data from the Beibuwan Basin previously suggested that the western tributaries flowed into this basin before being captured by the paleo‐Pearl River. These lines of evidence suggest that progressive headward erosion of the eastern Pearl River and late Oligocene integration of this large fluvial system can be linked to contemporaneous sea‐floor spreading of the South China Sea.

Detrital zircon geochronology from the Nueva Segovia Schist, Nicaragua: evidence for the tectonic evolution of the Chortis Block?

Abstract The Chortis Block of Central America is a cratonic-type peri-Gondwanan terrane and is commonly included in Neoproterozoic–Paleozoic palaeogeographical reconstructions. At present, most research has focused on the Mesozoic evolution of the Chortis Block, however, its earlier history remains poorly constrained. As a result, there is considerable debate surrounding the internal complexities of the Chortis Block and its tectonothermal evolution has not been well established by geochronological and geochemical data. New field investigations from the Nueva Segovia Schist (Northern Nicaragua), considered one of the oldest exposed parts of the Chortis Block, reveal it is composed primarily of deformed sequences of greenschist facies marine clastic and chemical sediments in conformable contact with felsic volcanics. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) detrital zircon data from two samples taken from the Nueva Segovia Schist reveal a youngest age peak of c. 250 Ma with other significant peaks at c. 500 Ma, c. 1.0 Ga and c. 1.2 Ga. Taken together with field observations, these data suggest the Nueva Segovia Schist was likely deposited between c. 250 and 110 Ma proximal to Amazonia during the Late Paleozoic, and they support a Precambrian age for the basement of the East Chortis Terrane. Taken together the data support a Pangaean position of the Chortis Block, adjacent to Amazonia inboard of Oaxaquia.

Geochemistry and geochronology of the Bay of Islands metamorphic sole, Newfoundland, Canada: Protoliths and implications for subduction initiation

The Bay of Islands complex, Newfoundland, Canada, represents a fossil subduction system that was obducted onto the Laurentian margin during the Taconic Orogeny. We present whole-rock geochemistry and geochronology for the Bay of Islands metamorphic sole from the Table Mountain and North Arm Mountain massifs. The Bay of Islands metamorphic sole can be subdivided into three units: a high metamorphic-grade Grt-Cpx amphibolite and Grt-Cpx granulite unit, a medium metamorphic-grade common amphibolite unit, and a medium metamorphic-grade metasedimentary-dominated unit. Based on their major and trace element contents, two types of protoliths can be inferred for the Bay of Islands sole metabasites: cumulate gabbroic protoliths with high Mg numbers and depleted trace element contents, and basaltic protoliths with trace element contents defining a normal mid-oceanic-ridge basalt (N-MORB) affinity. Titanite in situ U-Pb analyses of two common amphibolite samples yield dates of 486 ± 7 Ma and 484 ± 4 Ma, which are interpreted as a metamorphic age (ca. 485 Ma). One sample from the metasedimentary unit yields detrital zircon dates that range from Archean to Ordovician, with the youngest dates defining the most dominant peak at ca. 490 Ma. This youngest peak is consistent with an arc-related source that may be linked with arc magmatism of the upper plate during the Taconic Orogeny. These observations suggest that (1) the subduction responsible for the formation of the Bay of Islands complex nucleated in an oceanic domain before ca. 485 Ma; and (2) the sediments that form the metasedimentary unit were partly sourced from the upper plate and were deposited on the lower plate while subduction was active.

A database of detrital zircon U–Pb ages and Hf isotopes for the Middle East (Iranian and Arabian plates)

AbstractThe detrital zircon records significant information in the ‘source‐sink’ system. With the application of in situ laser ablation technology, a large number of high‐quality detrital zircon data have been published since 2000. In this study, a total of 41,342 detrital zircon U–Pb ages and 6,129 Hf isotopes were compiled from the published literatures of the Middle East (Iranian and Arabian plates). Through data filtering and recalculation, valid data were employed for further analysis. The detrital zircons from the Middle East show a Cambrian–Precambrian age population of 500–1,000 Ma, with a major age peak of ~620 Ma and dispersed εHf(t) values of −35 to +20. The Alborz Mountains and central Iran terrane show a Permo–Triassic age range of 200–300 Ma. The Mesozoic–Cenozoic detrital zircons are mostly occurred in the Zagros orogenic belt and Makran accretionary complex, with three obvious age ranges of 145–180 Ma, 80–110 Ma and 15–65 Ma. The Mesozoic zircons yield positive εHf(t) values, while Cenozoic zircons have varied εHf(t) values. This database allows for the further exploration of the provenance analysis and application in constraining the timing of the major tectonic events in the Middle East, and may also help to explore the affinities of plates, thus guiding future palaeogeographic research efforts.

Time to reconsider the enigmatic tail of eastern Paleo-Tethys: New insights from Borneo

The rise of Tibet and growth of Asia resulted from successive accretion of Gondwana-derived continental fragments at the expense of Tethyan oceans, yet how and where the eastern Paleo-Tethys closed in SE Asia remain controversial. Here we report new and synthesized detrital zircon data from Borneo and relevant regions revealing that West and SW Borneo show consistent Precambrian age profiles resembling that of Northern Australia (Kimberley to Pine Creek), but contrasting with those of NW/NE Australia, Bird's Head, and Cathaysia/Indochina. Considering the questionable suture between West and SW Borneo, we suggest a united Borneo basement that originated from Northern Australia, with a position between Sumatra and Timor. Surprisingly, Borneo lacks NE Australia-sourced ca. 1700–1400 and 400–280 Ma zircons that prevail in Triassic-Jurassic strata of Timor, Babar, and Tanimbar offshore Northern Australia, which may be best explained by pre-Triassic rifting of the Borneo basement from Northern Australia. Combining with recent investigations, we propose a new tectonic scenario involving a Permian separation of Borneo (probably together with Sumatra) from northern Gondwana through opening of the Meso-Tethys Ocean followed by a Triassic docking with Eurasia that closed the eastern Paleo-Tethys. Thus, assembly of Sundaland (continental core of SE Asia) completed in the Late Triassic, rather than Cretaceous as previously thought, and the tail (or the southeasternmost section) of eastern Paleo-Tethys lies within the Kuching zone of Borneo. Our new reconstruction challenges current understanding of Gondwana dispersion and Asian accretion, shedding new light on Asian climate change and biogeographic diversity.

Cadomian to Cenerian accretionary orogenic processes in the Alpine basement: the detrital zircon archive

New whole-rock geochemical and detrital zircon U–Pb and Lu–Hf data of metasedimentary sequences of the Silvretta Nappe, Orobic Alps, Strona-Ceneri Zone, Gotthard Massif and Venediger Nappe are presented. These units seem to share a common early to middle Paleozoic geological record, which has alternatively been interpreted as the result of intraplate or orogenic processes. Detrital zircon data mainly indicate late Ediacaran to early Ordovician maximum sedimentation ages for the studied sequences, suggesting that they were intimately related to Cadomian and Cenerian orogenic processes along the northwestern Gondwana margin. The common presence of late Ediacaran to Cambrian Cadomian ages associated with variable subchondritic to suprachondritic Lu–Hf compositions points to recycling processes of Cadomian sequences, further supported by geochemical data indicating a relatively low to moderate maturity of sedimentary protoliths. The occurrence of Cenerian arc-related intrusions in Austroalpine and South Alpine basement unit points to an arc/back-arc position in the early Paleozoic Cenerian orogen, except for the Strona-Ceneri Zone, which was likely located closer to the forearc region, as indicated by the presence of high-pressure metamorphism. Younger sequences, such as the Landeck Quartz-phyllite, document post-Cenerian sedimentation, whereas those of the Venediger Nappe more likely record the early stages of Variscan subduction, as indicated by Devonian maximum deposition ages.

Depositional environment and provenance of Early Carboniferous clastic sedimentary rocks at McIsaacs Point, Nova Scotia: implications for syntectonic basin development during the formation of Pangaea

Abstract Following the collision of Gondwana and Laurussia to form Pangaea, a large system of regional-scale strike-slip faults developed which resulted in the formation of transtensional syncollisional basins. One such basin, the Antigonish Basin, contains late Devonian fluvial, marine and lacustrine sedimentary rocks, including sandstone, conglomerate and shale. LA-ICP-MS U–Pb detrital zircon data from three samples from the lower and middle of the McIsaacs Point section have a strong Silurian–Devonian ( c. 440–380 Ma) population whereas the top of the section lacks these age populations and is instead dominated by Neoproterozoic ( c. 630–550 Ma) grains. Detritus was derived from a mix of local Avalonian and more distal Meguma terrane sources. Detrital zircon and field data show that sediments were deposited in a braided to meandering fluvial system transitional to a proximal braided stream environment followed by evolution to a more distal braided stream environment. As the basin evolved, the source of detritus shifted from a dominantly Meguma terrane source to a more local Avalonian source. This temporal evolution in provenance and depositional environment attests to the complex depositional processes associated with syntectonic basin evolution during the formation of Pangaea.

Provenance of the conglomerate and siliciclastic rocks from the Gadag Greenstone Belt, Western Dharwar Craton, India: Implications for understanding Neoarchean basin margin sedimentation

Petrographic, whole‐rock geochemical and geochronological analysis of polymictic conglomerate, associated siltstone and greywacke in the Neoarchean Gadag Greenstone Belt in the Western Dharwar Craton, India, provides new insights into sedimentary provenance and tectonic setting. The polymictic conglomerate contains granitic, gneissic, felsic and mafic volcanic, quartzite and banded ferruginous chert clasts within a quartzo‐feldspathic matrix. Framework grains in the siltstone and greywacke are quartz, feldspar with rock fragments, embedded in a chlorite‐dominant matrix. The chemical index of alteration values (~70) and A‐CN‐K plot for the rocks suggest a low‐to‐moderate degree of weathering. Rare earth element (REE) patterns show moderate fractionation (LaN/YbN ~ 12.31) with a weak negative europium anomaly (0.82). Enrichment in transition elements (Ni, Cr, Co, Sc) and depletion in high‐field‐strength elements, as well as relatively low La/Co (0.62), moderate to high Th/Yb (3.06), La/Th (5.16), La/Yb (17.5), and La/Sc (~2.37) ratios, suggest a mixed felsic‐mafic provenance. U–Pb dating of detrital zircon from the conglomerate and greywacke revealed major age peaks at ca. (3.2, 2.9, 2.8, 2.6, 2.5 Ga) and a maximum age of deposition of 2,508 ± 26 Ma, 2,493 ± 20 Ma, respectively. The above data suggest low to moderately weathered proximal sources for both conglomerate and greywacke, indicating that these two rock types were not deposited simultaneously, but rather separately. The association of these conglomerates and greywacke with continental arc‐related volcanics indicates the closing of an arc at the time of sedimentation. Complex provenance consisting of recycled and magmatic arc during basin closure confirm the notion of modern style plate tectonics operating during Neoarchaean.

Sequence stratigraphy and underlying tectonism of the Northern Richardson Mountains and adjacent Mackenzie Delta related to the formation of the Arctic Ocean

Abstract Jurassic-Cretaceous rifting within Arctic North America that eventually resulted in the formation of the Amerasia Basin greatly affected deposition within nearshore terrestrial basins in surrounding areas, such as the Brooks-Mackenzie Basin and the Sverdrup Basin. In this paper, four measured stratigraphic sections and detrital U-Pb zircon data (N = 14; n = 3339) from outcrops within the Northern Richardson Mountains are integrated with well-log and core data from the adjacent Mackenzie Delta to establish a model-independent sequence stratigraphic framework for the Brooks-Mackenzie Basin. This framework is used to elucidate the underlying tectonic forces responsible for the observed stratigraphy, relating patterns of deposition to various phases of rift development. The proposed interpretation classifies the sub-Jurassic unconformity as a first-order sequence boundary, demarcating a change in tectonic setting from pre-rift to rift, meaning it is also classified as the rift onset unconformity for the Amerasia Basin. The overlying Bug Creek Group is largely progradational, representing a first-order lowstand systems tract corresponding to early syn-rift strata. Detrital zircon data from the Bug Creek Group lacks syn-depositional detrital zircon and resembles the underlying Permian, suggesting a recycled source of sediment. A change in the detrital zircon signature is observed within the uppermost Aklavik Formation, representing a new source. This also coincides with a rapid transition from shoreface sandstones of the Aklavik Formation to the lower offshore deposits of the Husky Formation caused by normal faulting in the Husky Lakes Fault Zone which is associated with a dramatic basin expansion. Maximum transgression occurs above the Arenaceous Member of the Husky Formation, likely near the Jurassic-Cretaceous boundary, representing a first-order maximum flooding surface and rift-climax. Above the maximum flooding surface, the overall progradational signature represents a first-order highstand systems tract and early post-rift deposits. The sub-Hauterivian basal Kamik unconformity is observed at the base of the subsequent falling stage systems tract. This first-order sequence boundary is approximately time equivalent to the breakup unconformity for the Arctic Ocean, with the overlying Kamik Formation resembling the Isachsen Formation in the Sverdrup Basin.

Large detrital zircon data set investigation and provenance mapping: Local versus regional and continental sediment sources before, during, and after Ancestral Rocky Mountain deformation

The increasing number and size of detrital geochronology data sets offer new opportunities for increased accuracy and resolution of sediment routing models. However, the new opportunities come coupled with challenges in large data integration and visualization. We address these challenges by outlining two novel approaches that aid in analyzing and interpreting large detrital geochronology data sets: (1) combination of bottom-up and top-down detrital zircon source modeling, and (2) sediment provenance mapping. Combining source-modeling methods provides guidance in identifying empirical detrital zircon sources and determining source proportions. Provenance mapping integrates source proportions from modeling results and complimentary geologic data (e.g., paleocurrents, paleogeography, and stratal thickness maps) to extrapolate provenance information through areas with sparse or ambiguous data, thus mitigating issues of data distribution heterogeneity. Sediment provenance maps also provide a synoptic view of data that, along with detrital zircon source modeling, aids in circumventing lengthy descriptions of individual age modes for data sets containing hundreds of samples, which can obscure underlying trends in the data. We apply this approach to late Paleozoic−early Mesozoic strata, using 329 published and new U-Pb detrital zircon samples, and document five sediment-routing episodes in the core zone of intraplate deformation in western Laurentia (i.e., the Ancestral Rocky Mountains (ARM)). The transitions between these episodes are defined by changes in sediment source distribution, which are illustrated by provenance maps that show (1) the degree and extent of ARM basin isolation from transcontinental sediment sources and (2) ARM-driven changes in transcontinental sediment routing systems. We map possible sediment pathways of distally derived sediment around the ARM core, illustrating that ARM uplifts diverted transcontinental systems around areas of intense intraplate deformation. Further, the evolution of sediment routing in western Laurentia before, during, and after ARM deformation provides an example of the interaction between transcontinental sediment routing and intraplate deformation.

Insights into the evolution of the southeastern Dom Feliciano Belt and its connection to the Pan-African Orogeny based on new U-Pb and Lu-Hf zircon data

The Neoproterozoic supracrustal units of the Dom Feliciano Belt in southern Brazil and eastern Uruguay provide a record of the tectonic evolution of the Brasiliano/Pan-African cycle in terms of sedimentation, deformation, and metamorphism during the western Gondwana supercontinent assembly. From the northern Punta del Este Terrane (Jaguarão Domain) and neighboring Herval Complex were acquired new LA-ICPMS U-Pb and Lu-Hf zircon data from significant samples of metasedimentary rocks and intrusive granites. The central units of the domain are the Arroio Telho and Arroio Grande metasedimentary complexes, which have detrital zircon data ranging in age from 3.2 to 0.7 Ga, with prominent age peaks at 2.2–1.7 Ga, 1.5–1.0 Ga, and 1.0–0.7 Ga. The Herval Complex samples revealed a similar provenance of detrital zircon ages, with two main intervals of 1.5–1.1 Ga and 1.0–0.7 Ga, and also minor Paleoproterozoic (2.0–1.7 Ga) and Archean (2.8–2.4 Ga) ages. The maximum depositional age of the supracrustal complexes is constrained to age populations between 700 and 650 Ma. The mylonitic intrusive peraluminous granites yielded crystallization ages of ca. ∼570 Ma. The Neoproterozoic metamorphic zircon overgrowths range from 680 to 570 Ma. The Lu-Hf data from the meso- to Paleoproterozoic zircons have εHf(t) values ranging from −10 to +10, with the dominance of slightly positive results, and Hf(t) model ages from Paleoproterozoic to Archean. The εHf(t) values in Neoproterozoic zircons are dominantly negative (−15 to +5) with meso- to Paleoproterozoic Hf(t) model ages. These results demonstrate that sedimentary deposition ceased and underwent metamorphism during the development of the Cryogenian/Ediacaran arc-related magmatism of the Dom Feliciano belt. Given the scarcity of Mesoproterozoic rocks in the Mantiqueira Province and nearby cratonic areas, the obtained data suggest that these detrital populations originated in southwestern African rocks. The Congo/Kalahari cratons (Africa) are the most likely source area for Paleoproterozoic and Archean detrital zircons. The geological context and isotopic results of the investigated supracrustal complexes point to a prior extensional tectonic setting during the Tonian (∼800 Ma), with regional deformation and metamorphism linked with the Dom Feliciano Belt accretionary and collisional stages (660–570 Ma).

The critical role of recycling of post-Grenvillian, Neoproterozoic sediments for Phanerozoic Laurentian clastic systems: evidence from detrital-zircon and -monazite geochronology and textures

ABSTRACT Lithic and quartz arenites of the Central Appalachian Basin deposited by late Paleozoic Laurentian fluvial systems are widely interpreted to be sourced by recycling of late Precambrian and early Paleozoic clastic sequences in the Appalachian Orogen. U-Pb and (U-Th)/He age distributions for detrital-zircon and Th-Pb age distributions for detrital-monazite, detrital-zircon and monazite textures (including detrital diagenetic monazite, which prove recycling), sandstone petrology, heavy-mineral abundances, and other detrital proxies are all accounted for by the following: 1) lithic arenite is directly sourced from late Neoproterozoic metasediments in the proximal Appalachian fold and thrust belt via transverse drainages, 2) the late Neoproterozoic sediments were recycled from early Neoproterozoic, post-Grenvillian clastic sequences, 3) Cambrian quartz arenites along the Laurentian margin were recycled from Neoproterozoic sequences with local cratonic input, 4) although dominated by sediment of ultimate Grenvillian age, quartz arenites require ∼ 40% of Paleoproterozoic and Archean input, interpreted to be recycled from late Neoproterozoic to Devonian clastic sequences of the northern Appalachians and/or southern (Scottish–Irish) Caledonides in the distal reaches of a longitudinal drainage system. Ordovician to Mississippian clastic sequences and their metamorphosed equivalents in the Appalachian crystalline core were also likely sediment sources. Quartz arenite does not result from mixing of lithic arenite with other sources because of differences in textural and compositional maturity, and in heavy-mineral characteristics. Input from the Laurentian craton, commonly cited as the source for Paleoproterozoic and Archean detrital zircon in the eastern Laurentian clastic systems, is untenable here because of: 1) the presence of Paleozoic monazite derived from Appalachian Neoproterozoic and early Paleozoic metasediments, 2) abundant detrital chromite, and 3) abundant Paleozoic detrital muscovite. Multiple recycling explains all observed sedimentologic and mineralogic characteristics of the two lithic types. Incorporation of published detrital-zircon data for Paleozoic to modern clastic sequences in eastern Laurentia reveals that Grenville-age zircons experienced at least five and potentially ten recycling events since entering the clastic system in the Neoproterozoic. Recycling also explains the abundance of quartz pebbles in conglomerates of the quartz-arenite lithofacies, and the range of detrital-muscovite 40Ar/39Ar ages in quartz arenites of the Appalachian Basin.

Mesoproterozoic basins (Yukon, Canada) in the evolution of supercontinent Columbia

Geochemical and geochronological data from the Pinguicula Group and unit PR1 of the lower Fifteenmile Group (Yukon, Canada) provide information on sediment provenance and timing of break-up of supercontinent Columbia and seaway development on Laurentia’s northwestern margin. The older unit PR1, in the Coal Creek inlier, has a near-unimodal detrital zircon population with an age of 1499 ± 3 Ma. The Pinguicula Group detrital zircon data, in the Wernecke and Hart River inliers, display a polymodal detrital zircon population with a maximum age of <1322 ± 23 Ma. Using detrital zircon signatures, Sm–Nd isotopic data, and C-isotopic signatures, lithostratigraphic correlations between the Pinguicula Group in the Wernecke and Hart River inliers are confirmed, whereas the Pinguicula Group and unit PR1 are no longer considered correlative. The zircon population in unit PR1 requires a proximal source, but sources of this age are not known in western Laurentia. Based on detrital zircon and Sm–Nd data, sediment in unit PR1 was derived from the Mt. Isa inlier in northeastern Australia sometime after 1460 Ma. Unit PR1 correlates with older Mesoproterozoic successions, including the Belt-Purcell, that were deposited during break-up of supercontinent Columbia, and contain sediment from Australia and the Mawson continent. Mesoproterozoic successions deposited after 1.45 Ga, including the Missoula Group, lack North American Magmatic Gap (NAMG)-aged zircon and instead record sediment provenance from southern Laurentia, as north Australia and the Mawson continent rifted from Laurentia’s western margin. The Pinguicula Group has few NAMG-aged grains that were probably recycled from older Mesoproterozoic basins.