Zircon Dataset Research Articles

Detrital zircon tales between the Rodinia and Pangea supercontinents – Exploring connections between Avalonia, Cadomia and Central Asia

The Rodinia to Pangea supercontinent cycle represents the most recent complete cycle in the geological record and thus informs models on the processes involved in supercontinent dispersal and assembly. The terranes and/or micro-continents of the Avalonian, Cadomian and Central Asian Orogenic Belts are witnesses to this complete cycle but their relationships to Rodinia, each other, and an intermediate stage in this supercontinent cycle represented by the formation of a large (but not supercontinent) landmass, Gondwana, are at time ambiguous. One method for testing these relationships is detrital zircon geochronology; zircons are a highly resistant and easily dateable mineral and thanks to rapid instrumental advances a huge number of detrital zircon datasets are now available. These data can provide a fingerprint whereby suspect terranes and micro-continental fragments can be linked to each other and their parental continent. Nonetheless, in order to develop coherent and testable geological hypotheses from these data it is necessary to integrate the data into a consistent framework. The presented work explores the possibilities and limitations of using detrital zircon data to better understand the position of the Avalonian, Cadomian, and Central Asian terranes in Rodinia and their journey from there to Pangea.

Ultraslow cooling of an ultrahot orogen

To constrain the rate of cooling of lower-crustal rocks from an ultrahot orogen, we determined both the age and equilibration temperature of metamorphic zircon from six widely spaced samples of metasedimentary garnet−sillimanite gneiss from the Eastern Ghats Province in eastern India. For the combined data set of metamorphic zircon, concordant dates decrease continuously within 2σ uncertainty from around 950 Ma to 800 Ma, consistent with ∼150 m.y. of zircon crystallization. Ti-in-zircon temperatures for each dated spot during this period decrease with age, corresponding to linear cooling rates ranging from 0.26 to 0.90 °C/m.y. We propose that retention of heat-producing elements in the lower crust of the Eastern Ghats Province and a low net erosion rate were responsible for ∼150 m.y. of ultraslow cooling.

Generation and evolution of the Choiyoi granitic magmatism based on U-Pb zircon studies, Cordón del Portillo, Frontal Cordillera (Argentina)

Based on a relevant geochronological U-Pb zircon dataset (n = 47) from a sample (PBL-109) of the Cerro Punta Blanca pluton (CPB), which is part of a calc-alkaline suite, we corroborate the development of protracted magmatic activity with three major crystallization events for this Permian magmatism: 278 ± 1, 283 ± 2, and 289 ± 2 Ma, which outcrop in the Cordón del Portillo, Cordillera Frontal (CF) of Argentina. These ages can be assigned to the lower section of the magmatic record of the Choiyoi magmatism (ca., 290-265 Ma), while the age of 289 Ma represents the oldest known age for the Choiyoi, indicating the start of this magmatism during the Artinskiense. Considering these geochronological data, we postulate the presence of a deep mush reservoir where protracted magmatic activity permitted the prolonged crystallization of antecrysts (ca. 283–289 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber at shallow levels, where zircon autocrysts crystallized (ca. 278 Ma). Age spectra reported within individual samples support the idea of massive magma migration when conditions were favorable (e.g., thermally matured crust). In this view, the studied “older” Choiyoi magmatism represents a continuous magmatic event lasting 11 Ma and corresponds to a single magmatic episode rather than different periods of magmatic activity and subsequent emplacements. A later alkali-calcic magmatic event is recorded at 265 ± 4 Ma from a sample of the Cerro Bayo pluton (MH-0113), which could represent the end of the lower section of the Choiyoi magmatism. Whole-rock Sm-Nd, Rb-Sr, and Lu-Hf data in zircon, along with ages reported for the studied igneous and inherited zircon from the CPB; together with isotopic data and ages from the detrital zircon found in the Carboniferous accretionary complex of Chile, indicate that the source of the Permian parental magma in this region was a heterogeneous continental crust mainly formed by Devonian and Carboniferous rocks, related probably to a magmatic arc. However, some contribution from the Carboniferous accretionary complex of Chile to the parental magma should be consider.

Experimental Replacement of Zircon by Melt‐Mediated Coupled Dissolution‐Precipitation Causes Dispersion in U–Pb Ages

ABSTRACTZircon geochronology provides critical information on the rates and durations of geological processes and enables researchers to explore deep time. However, some zircon datasets show a continuum of concordant ages (‘smear’) without well‐defined age populations. These age smears are typically interpreted to represent variable loss of radiogenic Pb or protracted geological events lasting tens of millions of years. Coupled dissolution‐precipitation replacement of zircon has been suggested as one process that may produce these complex age datasets. Here, we react fragments of the well characterised Mud Tank zircon standard with natural intermediate and mafic melts (0.9 GPa, 1100–1180°C) to test if short‐term exposure to a melt can modify the geochronological patterns of zircon. Our observations show that within a short duration (18 h to 3.5 days), most Mud Tank zircon fragments display microstructural and/or chemical evidence for modification by dissolution at fragment boundaries along with partial replacement by coupled dissolution‐precipitation processes. The replaced zircon domains have U–Pb ages that smear over one hundred million years, between 764–647 Ma, illustrating variable mobility and redistribution of the U and Pb isotopes. Our experiments demonstrate that zircon modified by coupled dissolution‐precipitation replacement may not faithfully record the age or duration of geological events and that investigation of zircon microstructure in high‐resolution backscattered electron, cathodoluminescence imaging and/or Raman mapping is needed to better understand complex zircon geochronological datasets.

Geodynamic and Climatic Forcing on Late‐Cenozoic Exhumation of the Southern Patagonian Andes (Fitz Roy and Torres del Paine massifs)

AbstractHigh‐relief glacial valleys shape the modern topography of the Southern Patagonian Andes, but their formation remains poorly understood. Two Miocene plutonic complexes in the Andean retroarc, the Fitz Roy (49°S) and Torres del Paine (51°S) massifs, were emplaced between 16.9–16.4 Ma and 12.6–12.4 Ma, respectively. Subduction of oceanic ridge segments initiated ca. 16 Ma at 54°S, leading to northward opening of a slab window with associated mantle upwelling. The onset of major glaciations caused drastic topographic changes since ca. 7 Ma. To constrain the respective contributions of tectonic‐mantle dynamics and fluvio‐glacial erosion to rock exhumation and landscape evolution, we perform inverse thermal modeling of a new data set of zircon and apatite (U‐Th)/He from the two massifs, complemented by apatite 4He/3He data for Torres del Paine. Our results show rapid rock exhumation recorded only in the Fitz Roy massif between 10 and 8 Ma, which we ascribe to local mantle upwelling forcing surface uplift and intensified erosion around 49°S. Both massifs record a pulse of rock exhumation between 7 and 4 Ma, which we interpret as enhanced erosion during the beginning of Patagonian glaciations. After a period of erosional and tectonic quiescence in the Pliocene, increased rock exhumation since 3–2 Ma is interpreted as the result of alpine glacial valley carving promoted by reinforced glacial‐interglacial cycles. This study highlights that glacial erosion was the main driver to rock exhumation in the Patagonian retroarc since 7 Ma, but that mantle upwelling might be a driving force to rock exhumation as well.

Combined geochronological U-Pb, Hf isotopes and trace element zircon studies from Piedra Alta Terrane, Rio de la Plata Craton (West Uruguay, South America): A geodynamic model

This work delves into the intricate Paleoproterozoic geological setting of Uruguay, focusing on the Rio de la Plata Craton (RPC) and its prominent constituent Piedra Alta Terrane (PAT). The PAT constitutes the core of the RPC, characterized as a complex geological entity that encompasses a granite-migmatite basement, metamorphic belts, granite intrusions, and Proterozoic magmatism. To the west, it interfaces with the Transbrasiliano-Kandi tectonic corridor, bounded by the Late-Neoproterozoic Pampia Terrane. The PAT s southeastern boundary extends to Sierra de Tandil and perhaps to Sierra de La Ventana, demarcating its limits with Phanerozoic rocks of the North Patagonian Massif. The Sarandí del Yí shear zone defines the eastern limit of the PAT. Despite varied interpretations of the Piedra Alta Terrane’s significance, it is important to note that consensus prevails regarding its four major associations: a granite-gneiss-migmatitic basement complex, three volcanosedimentary belts of low to medium metamorphic grade, diverse late igneous intrusions, and extensional Statherian magmatism (1.79 Ga), represented by tholeiitic gabbroic dikes. In this study, a novel tectonic model for the PAT evolution emerges, supported by an extensive zircon dataset comprising new U-Pb ages, Hf isotopes, and trace element geochemistry. The analytical core involves U-Pb analyses on zircon for dating igneous rocks and establishing the provenance and maximum age of deposition of metavolcanosedimentary sequences. Lu-Hf isotopic analyses on the same zircon crystals provide petrogenetic insights, revealing episodes of crustal growth and minor recycling. Trace element geochemistry and zircon εHf(t) data further accentuate these findings, hinting at mantle source enrichment due to subduction within an intraoceanic magmatic-arc arc setting.

Navigating the complexity of detrital rutile provenance: methodological insights from the Neotethys Orogen in Anatolia

Abstract. Sedimentary provenance is a powerful tool for reconstructing convergent margin evolution. However, single mineral approaches, like detrital zircon, have struggled to track sediment input from mafic and metamorphic sources. Detrital rutile complements detrital zircon datasets by offering a path forward in sedimentary provenance reconstructions where metamorphic terranes are potential source regions. However, U–Pb geochronology in rutile can be difficult due to low uranium concentrations and incorporation of common Pb, and multiple workflows are currently in use. Here, we investigate U–Pb and trace element data reduction, processing, and common Pb correction workflows using new detrital rutile U–Pb geochronology and trace element geochemistry results from the Late Cretaceous to Eocene Central Sakarya and Sarıcakaya basins in Anatolia. A significant number of analyses were rejected (54 %) due to signal intensity limitations, namely low U, low Pb, anomalous signal, and inclusions. We identify this as a universal limitation of large-n detrital rutile studies and recommend the systematic reporting of the amount of discarded analysis and the processes for rejection in all studies using detrital rutile U–Pb geochronology. Additionally, we show that (1) the 208Pb and 207Pb common Pb reduction schemes produce similar age distributions and can be used interchangeably, while (2) the Stacey–Kramers distance is a suitable metric for quantifying U–Pb discordance, but a discordance filter is not recommended. (3) Instead, filtering U–Pb data by a power law function based on the corrected date uncertainty is appropriate. (4) The exclusion of low uranium concentration rutile biases date distributions and favors pelitic-derived, higher Zr-in-rutile temperature, and higher U–Pb concordance grains. (5) Paired U–Pb and trace elements can be used to evaluate potential bias in U–Pb data rejection, which reveals that data rejection does not bias the provenance interpretations. Finally, (6) The signature of sediment recycling can be identified through U–Pb dates and Zr-in-rutile temperatures. To better navigate the complexity of detrital rutile datasets and to facilitate the standardization of data reporting approaches, we provide open-access code as Jupyter notebooks for data processing and analysis steps, including common Pb corrections, uncertainty filters, discordance calculations, and trace element analysis.

A conceptual model for the evolution of a magmatic system based on U-Pb zircon studies on the devonian granites of Sierra de San Luis, Argentina

ABSTRACT It is widely acknowledged that thermal models clearly demonstrate that crustal magma bodies should solidify rapidly upon emplacement. Small plutons can cool below the solidus in thousands of years, while even large plutons require hundreds of thousands of years, but not more than a million years. However, recent U-Pb zircon geochronological data contradict these results, strongly suggesting that magmatic systems are often characterized by protracted events. Therefore, a conceptual framework that reconciles thermal models and the geochronology data is necessary. The Devonian foreland magmatism of the Sierra de San Luis is made up of two distinctive suites, the Monzonite suite (<65 wt.% SiO2) and the Granite suite (>65 wt.% SiO2), both emplaced at ca. 3.7 kbar. Classification of the studied Devonian granitoids is debatable because they have a hybrid I- to A-type granite signature. Based on a robust geochronological U-Pb zircon dataset we corroborate the development of a protracted magmatic activity with three major crystallization events for this Devonian magmatism: 391 ± 1, 384 ± 1, and 379 ± 2 Ma. Considering these geochronological data, we postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the prolonged crystallization of antecrysts (ca. 395–384 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located at shallow levels, where zircon autocrysts crystallized (ca. 379 Ma). Age spectra reported within individual samples support the idea of a massive migration of magma when conditions were favourable (e.g. thermally matured crust). Individual crystallization ages recorded by monazites hosted in two-mica granites are comparable to those obtained from zircons, supporting the presence of a long-lasting hot source. Additional geochronological data indicate that a later thermal event (ca. 353 Ma) could have partially affected some areas of the Devonian magmatic zircons promoting Pb loss, with subsequent partial resetting of the isotopic clock.

Local Singularity Spectrum: An Innovative Graphical Approach for Analyzing Detrital Zircon Geochronology Data in Provenance Analysis

Detrital zircon geochronology plays a crucial role in provenance analysis, serving as one of the fundamental strategies. The age spectrum of detrital zircons collected from the sedimentary unit of interest is often compared or correlated with that of potential source terranes. However, biases in the age data can arise due to factors related to detrital sampling, analysis techniques, and nonlinear geological mechanisms. The current study reviewed two sets of detrital zircon datasets established in 2011 and 2021 to discuss the origins of the Tibetan Plateau. These datasets collected from different media effectively demonstrate a progressive understanding of provenance affinity among the main terranes on the Tibetan Plateau. This highlights issues regarding weak and unclear temporal connections identified through analyzing the age spectrum for provenance analysis. Within this context, a local singularity analysis approach is currently employed to address issues associated with unclear and weak provenance information by characterizing local variations in nonlinear behaviors and enhancing detection sensitivity towards subtle anomalies. This new graphical approach effectively quantifies temporal variations in detrital zircon age populations and enhances identification of weak provenance information that may not be readily apparent on conventional age spectra.

Implications of high-grade metamorphism on detrital zircon data sets: A case study from the Fraser Zone, Western Australia

Detrital zircon grains provide a useful tool to determine the maximum age of sedimentary strata and can elucidate tectonic setting and basin evolution. However, high-grade metamorphism can overprint the mineral chemistry of the detrital cargo and reset both primary age and compositional information. Incomplete resetting of the U–Pb isotopic system, fluid alteration, and complex internal structures due to granulite-facies metamorphism makes dating and interpretation of the obtained zircon ages challenging. Here, we use trace element chemistry, U–Pb geochronology (LA-ICP-MS and SHRIMP), textural observations, and inclusion characterization from detrital zircon crystals in the Snowys Dam Formation (Albany–Fraser Orogen; AFO) to deconvolve its strongly overprinted sedimentary history, and to evaluate the likely geodynamic setting for basin genesis. Detrital zircons that survived metamorphic overprinting show that the main detrital load was sourced from Paleoproterozoic lithologies from neighbouring regions, with rare Archean Yilgarn crystals. The youngest detrital grains correlate with the age of plagiogranites in the Madura Province to the east of the AFO and imply a maximum depositional age of c. 1390 Ma, indicating that the Fraser Zone temporally correlates to an oceanic arc and thus best fits a back-arc basin setting. High-grade metamorphism during Stage I of the orogeny (c. 1330–1260 Ma) promoted recrystallization of pre-existing detrital zircons together with neoblastic growth of metamorphic zircon rims. At c. 1245 Ma, during early Stage II of the AFO, anatexis of the metasedimentary rocks produced rare neocrystallized magmatic zircon. Late-stage fluids are indicated by elevated LREE for these grains, which also contain a hydrous inclusion assemblage. High volume sampling techniques such as LA-ICP-MS often drilled through multiple age domains that can hinder geological interpretation. Thus, a lower volume sampling technique (e.g., SHRIMP) and verification with mineral chemistry is highly instructive in accurately resolving primary age groups in high-grade terrains.

A detrital zircon dataset for the eastern Central China Orogenic Belt (East Qinling, Dabie and Sulu orogens)

AbstractThe Qinling‐Dabie‐Sulu orogen is the eastern part of the Central China Orogenic Belt. Looking back on previous studies of the sedimentary record we systematically compiled the dataset of detrital zircon U–Pb ages and Hf isotopes for this orogenic belt. The dataset incorporates a comprehensive compilation of 32,449 detrital zircon U–Pb ages and 979 Hf isotopes. The findings demonstrate that distinct tectonic units within the orogenic belt exhibit unique tectonic evolution histories during various geological epochs. This dataset can be used to constrain the tectonic framework and orogenic evolution including ocean subduction, continental collision and orogen exhumation. It can be integrated with other geological datasets to improve our understanding of the Central Orogenic Belt in China, and possibly plate tectonics globally.

A brief introduction to the detrital zircon U–Pb and Hf isotopic datasets for mainland China and adjacent regions

AbstractImprovements in analytical technique and data processing lead to a large deposit of detrital zircon U–Pb and Hf isotopic data in published journal articles, thesis and reports. With the support of Deep‐time Digital Earth Big Science Program, OneSediment Project conducted a team‐working effort to assemble the detrital zircon U–Pb and Hf isotopic data for mainland China and adjacent regions. Entity‐relationship diagram was constructed for detrital zircon data to determine what information need to be collected. Researchers and students from 13 institutions were organized together to fulfil this task and generated 13 detrital zircon datasets. The assembled datasets totally include 6635 samples and 560,596 analyses. The samples were checked in terms of lithology and stratigraphy according to the latest stratigraphic framework. Collected detrital zircon U–Pb and Hf isotopic data were recalculated for the best U–Pb age and εHf(t) values. They can be used to track crustal growth, tectonic evolution, provenance analysis and palaeogeographical change in regional and, when combined with other dataset, global scales.

Dataset of detrital zircon U–Pb ages and Hf isotopic compositions for the late Paleozoic–Mesozoic strata in the North China block

AbstractThe construction of databases of detrital zircon is important for Earth science research. A total of 27,915 U–Pb ages and 4,968 Hf isotopic compositions of detrital zircons from the upper Paleozoic–Mesozoic strata of the North China Block were compiled from articles in the Web of Science and the China National Knowledge Infrastructure. This dataset yields five age groups, at 3.9–1.0 Ga, 1,000–540 Ma, 540–360 Ma, 360–240 Ma and 240–95 Ma. The 3.9–1.0 Ga group has two peaks at ~2.5 and ~ 1.85 Ga. The 1,000–540 Ma and 540–380 Ma groups have three peaks at ~920 Ma, 780–750 Ma and ~ 440 Ma. Detrital zircon grains with ages of 360–240 Ma have multiple age peaks at ~380, ~320, ~280 and ~250 Ma. The group with ages of 240–95 Ma yields four peak ages at ~220, ~180, ~160 and ~120 Ma. Corresponding εHf(t) values range from −81.3 to +41.9, with two‐stage Hf model ages (TDM2) of 4,335–204 Ma. This dataset provides a comprehensive and systematic archive of detrital zircon data for Paleozoic–Mesozoic successions in the North China Block, which can be used to track tectono‐sedimentary and crustal evolution. In using this dataset, two issues need to be considered. First, the number of detrital zircon analyses from each sample varies markedly, which may influence the interpretation of the dataset. Second, there may be large uncertainties in the stratigraphic ages assigned to the samples.

Sediment provenance signal of the discontinuous retroarc topography in the northern Andes during the Early Cretaceous

AbstractA large dataset of detrital zircon U–Pb ages (N = 5940) of Aptian‐Albian strata of the Colombian‐Ecuadorian retroarc region suggests that these rocks were sourced from Proterozoic cratonic and Permian–Triassic to Cretaceous rocks of the Andean proto‐Cordilleras. The nonconformity between Aptian‐Albian strata and Proterozoic rocks of the Garzón Massif indicates the existence of positive relief in this region. Topographic highs could have caused local basin compartmentalization and the prevalence of a localized provenance of coeval strata. Areas of positive relief were seemingly exposed to intense chemical weathering as suggested by the high Chemical Index of Alteration values, and low Rb/Sr and SiO2/Al2O3 ratios of analysed strata. Our results highlight the value of provenance analysis to study the ancient topography of retroarc systems and open the avenue for further research on the role of extensional tectonics in the topographic and basin evolution in the Andes.

Southwest Borneo, an autochthonous Pangea-Eurasia assembly proxy: Insights from detrital zircon record

Abstract The current tectonic model for Borneo in SE Asia suggests that the SW Borneo block rifted from NW Australia at ca. 190 Ma and drifted across the Tethyan Ocean to collide with Eurasia in the Early Cretaceous. But, the global zircon Hf trend after 200 Ma indicates that circum-Pacific-style accretionary orogens prevail. The SW Borneo detrital zircon data set, which combines our new data with previous data, shows consistent age peaks (ca. 250 Ma, 1.9–1.8 Ga, and 2.5–2.4 Ga) in late Permian to Early Cretaceous samples. The Banda terranes, a notable block derived from NW Australia, have distinct detrital zircon age peaks for pre-breakup and post-breakup. Available Borneo detrital zircon εHf(t) values for ca. 1.8 Ga and 2.4 Ga are indistinguishable from those of NW Australia sources, but εHf(t) values for 300–200 Ma are more negative than those from the Gondwanide orogen and are more similar to those from the Peninsular Malaysia Indosinian orogen. We suggest SW Borneo is a Triassic accretion zone at eastern Cimmeria that rifted from NW Australia in the Permian. The ca. 250 Ma negative εHf(t) values present in samples are characteristic of Tethyan-style collisional orogens and show participation in Pangea assembly. SW Borneo underwent further autochthonous accretion along its SE margin (ca. 186 Ma and ca. 140 Ma) in a Jurassic Meso-Tethys and Paleo-Pacific supra–subduction zone setting. Our revision locates SW Borneo with other SE Tethysides blocks in Eurasia where accretionary orogens have influenced rises after 200 Ma.

A comparison of fast pulse and conventional LA-ICP-MS detrital zircon geochronology: A large n detrital zircon study from the Centralian Superbasin, northwestern Australia

Over ten thousand detrital zircon U–Pb analyses on thirty four samples were undertaken using a fast pulse laser ablation protocol from the Neoprotoerozoic rocks of the largely unexposed Yeneena and northwestern Officer Basins in Western Australia. In addition, conventional laser ablation detrital zircon U–Pb geochronology was carried out on three of the samples. A comparison of the two datasets demonstrated that no statistical significant difference was observed in the detrital zircon spectra between the two techniques.The results of the detrital zircon analyses reveal that after an intial pulse of material dominated by Archean detritus the sediment are dominated by Mesoproterozic sources. This indicates that there is little variation in source materials within and between the identified formations. The major age peaks coincide with magmatic rock ages from within Australia. The results indicate that either the Palaeoproterozoic and Mesoproterozoic terranes remained sources throughout the deposition of the Yeneena and northwestern Officer Basins during the Neoproterozoic, or that recycling of zircons occurred within a quasi-closed system for the duration of sedimentation. The remaining 10 % of grains are difficult to reconcile with magmatic suites of any significant volume within Australia. However, when considering the broader palaeogeographic context at the time the sediments are inferred to have been deposited, rocks from Dronning Maud Land and the Kalahari Craton can supply grains of appropriate ages and are consistent with the known paleocurrent directions.This work demonstrates that there is no significant disadvantage in the application of the fast pulse technique when applied to the collection of U–Pb detrital zircon datasets for the purpose of detrital zircon fingerprinting. However, there is a large upside related to the significant amount of data that can be collected for a given amount of time compared to other more conventional techniques.

Light fractions can also be heavy hitters: Comparison of detrital zircon U–Pb and detrital K‐feldspar Pb–Pb as provenance indicators—A case study from Cretaceous strata of southern Utah, USA

AbstractComparison of detrital zircon U–Pb geochronology and detrital K‐feldspar Pb–Pb isotopic data from Upper Cretaceous sandstones of southern Utah reveals important provenance information that is unrecorded by more chemically and physically durable detrital minerals like zircons. To better understand these signals, we also present an updated database of Pb‐isotopic ratios in ores, whole rocks and feldspars, for potential sediment source terranes in North America. Detrital K‐feldspar Pb‐isotopes indicate sediment provenance of the Western Cordillera/Mojave, Yavapai‐Mazatzal and Wyoming terranes, with limited input from recycled Sevier fold‐thrust belt strata. The K‐feldspar data broadly support previous interpretations, largely based on detrital zircon datasets, of a Cretaceous palaeo‐river system transporting sediment from the southwest. However, the light‐fraction data also provide important, complementary and otherwise unrecognized perspectives as compared to detrital zircon datasets. For example, K‐feldspars indicate a stronger apparent influence of Western Cordillera/Mojave and Wyoming terrane sources than previously interpreted. We interpret the K‐feldspar Wyoming terrane signal as the result of south‐directed longshore drift, with preferential loss of zircons due to hydraulic sorting processes. As relatively new detrital K‐feldspar detrital methods continue to be developed, this multi‐proxy approach to provenance could be informative in other sedimentary basins where suitable source terranes can be identified.

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 &lt; 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.

Technical note: colab_zirc_dims: a Google Colab-compatible toolset for automated and semi-automated measurement of mineral grains in laser ablation–inductively coupled plasma–mass spectrometry images using deep learning models

Abstract. Collecting grain measurements for large detrital zircon age datasets is a time-consuming task, but a growing number of studies suggest such data are essential to understanding the complex roles of grain size and morphology in grain transport and as indicators for grain provenance. We developed the colab_zirc_dims Python package to automate deep-learning-based segmentation and measurement of mineral grains from scaled images captured during laser ablation at facilities that use Chromium targeting software. The colab_zirc_dims package is implemented in a collection of highly interactive Jupyter notebooks that can be run either on a local computer or installation-free via Google Colab. These notebooks also provide additional functionalities for dataset preparation and for semi-automated grain segmentation and measurement using a simple graphical user interface. Our automated grain measurement algorithm approaches human measurement accuracy when applied to a manually measured n=5004 detrital zircon dataset. Errors and uncertainty related to variable grain exposure necessitate semi-automated measurement for production of publication-quality measurements, but we estimate that our semi-automated grain segmentation workflow will enable users to collect grain measurement datasets for large (n≥5000) applicable image datasets in under a day of work. We hope that the colab_zirc_dims toolset allows more researchers to augment their detrital geochronology datasets with grain measurements.

Orogenic eclogites record relative magnitude of deep crustal flow and extent of migmatite-eclogite interaction

In exhumed orogens, refractory mafic rocks have the potential to preserve a record of petrogenesis and high-pressure (H P ) metamorphism that is commonly obliterated in quartzofeldspathic rocks owing to re-equilibration at high-temperature, low-pressure (L P –H T ) conditions. In the Montagne Noire (France) migmatite dome, located in the foreland of the Variscan orogen, eclogite is exposed in both the core and margin of the dome. In this study, we combine in situ U Pb petrochronology and oxygen-isotope analyses of key eclogite phases to demonstrate that eclogites from the two distinct domains had different protoliths and source regions, traveled relatively variable distances in the deep crust, and differentially interacted with surrounding migmatite prior to exhumation. Dome-margin eclogite zircons are small (~40 μm) with well-preserved inherited cores and thin (<15 μm) rims, compared to larger (40–120 μm) neo- and recrystallized dome-core zircons with small relict cores and wide (15–30 μm) recrystallized rims. Protolith and H P metamorphism ages were determined using in situ zircon and rutile petrochronology (LASS-ICP-MS). Both eclogites formed in a continental setting; dome margin protolith zircon cores formed at 442.5 ± 3.4 Ma (steep HREE slope, no Eu-anomaly) whereas zircon cores of the dome-core eclogites yielded scattered dates suggesting protolith crystallization between ~500–400 Ma (steep HREE slope, pronounced Eu-anomaly). Both eclogites experienced H P metamorphism at c. 320–310 Ma in garnet-stable, plagioclase-absent conditions. Most analyzed rutile yielded dates of 307–304 Ma associated with cooling. The record of H P fluid conditions was determined by O-isotope (SIMS) analyses of garnet and zircon. Dome-margin zircon cores and rims have δ 18 O of ~8.2–8.5 ‰, indistinguishable within uncertainty, in isotopic equilibrium with isotopically unzoned garnet (δ 18 O ~ 8.0–8.2 ‰). In contrast, zircons in dome-core eclogites have systematically lower zircon-core δ 18 O values compared to their rims and neocrystallized grains, and zircon cores were in equilibrium with major-cation zoned garnet with respect to oxygen. The two dome-core eclogite samples yielded zircon and garnet δ 18 O values of ~8.6–9.5 ‰ and ~ 9.7–10.5 ‰. Based on these results and existing H P fabric data for these eclogites, we propose that (1) gabbro protoliths for the two eclogites were emplaced at different depths in a Cambro-Ordovician continental crustal package; and (2) dome-core eclogites interacted extensively with surrounding gneiss during burial and foreland-vergent crustal flow, whereas the dome-margin eclogite was sourced proximally to the dome-emplacement location and had minimal chemical interaction with surrounding gneiss. At least parts of the Montagne Noire migmatite dome were deeply sourced, but rocks exhumed in the core had a more extensive and protracted history of deep-crustal flow than deep-crustal rocks exhumed at the margin. • Eclogites in migmatite dome retain memory of deep crust history. • Zircon (re)crystallization extent reveals distinct eclogite source, flow paths. • Petrochronology and O-isotopes record migmatite-eclogite interaction at depth. • Integrated garnet, zircon datasets reveal protolith, peak, exhumation histories. • Domes may exhume crust laterally-sourced >100 s of km from emplacement location.