Sediment Recycling Research Articles

MARS CHRONOLOGY DERIVED FROM CRATERS HETEROGENEITY AT GALE CRATER

Craters sample into diachronic surfaces and different depths on Mars and other planetary surfaces. These surfaces are affected by cosmonuclide radiation that offers one of the most reliable age anchors to date. Craters also accumulate, evolve and display an universal characteristic that can be measured at any scale, regardless of the geologic unit they sample, in the form of the heterogeneity parameter (Capitan, 2021). Here we use an age equation, which is based on the measurements of craters diameter, depths and area they occupy, to derive the ages of deposits that are sampled by medium-scale craters (meters to few hundred meters in diameter). We show that units sampled by the deepest craters near MSL exploration area are formed during the early stages of Gale crater formation before 2870 Ma. In contrast, units sampled by shallower craters were formed during the stages that correspond to the time of sediment recycling and lithification periods, near 2129 Ma to present. Given the heterogeneity of initial formation conditions of craters of diverse diameters and their different depths of sampling, our proposed synchronous ages with ground-truth ages has the potential to redefine the paradigm of using the impact crater morphometry as a tool to date the planetary surfaces.

Tracing drainage capture between the two large tributaries of the Yangtze River in the southeastern Tibetan plateau: Insights from detrital apatite fission-track thermochronology

The evolution of drainage patterns in the southeastern Tibetan Plateau remains a highly controversial topic. In this study, we provide solid evidence that the Dadu and Anning Rivers, located in the southeastern Tibetan Plateau, have undergone reorganization after the plateau uplift. Through detrital apatite fission-track dating on modern sediments from both rivers, as well as the upper Pliocene - lower Pleistocene Xigeda Formation of the Anning, we reveal that the modern sediments of the Dadu River are dominated by young AFT ages (<5 Ma), consistent with the bedrock ages in its drainage basin. Similarly, the Anning modern sediments and the Xigeda Formation exhibit a significant portion of young ages (peaking at 4.2 and 4.4 Ma, respectively), contrasting with the older ages observed in the bedrocks of the Anning drainage basin but comparable to those of the Dadu drainage basin. We conclude that the Anning and Dadu Rivers were connected during the deposition of the Xigeda Formation, and the modern Anning River receives significant recycled sediments from this formation.

Timing and evolution of structures within the southeastern Greater Caucasus and Kura Fold-Thrust Belt from multiproxy sediment provenance records

The Greater Caucasus (GC) mountains are the locus of post-Pliocene shortening within the northcentral Arabia-Eurasia collision. Although recent low-temperature thermochronology constrains the timing of orogen formation, the evolution of major structures remains enigmatic—particularly regarding the internal kinematics within this young orogen and the associated Kura Fold-Thrust Belt (KFTB), which flanks its southeastern margin. Here we use a multiproxy provenance analysis to investigate the tectonic history of both the southeastern GC and KFTB by presenting new data from a suite of sandstone samples from the KFTB, including sandstone petrography, whole-rock geochemistry, and detrital zircon (DZ) U-Pb geochronology. To define source terranes for these sediments, we integrate additional new whole-rock geochemical analyses with published DZ results and geological mapping. Our analysis reveals an apparent discrepancy in up-section changes in provenance from the different methods. Sandstone petrography and geochemistry both indicate a systematic up-section evolution from a volcanic and/or volcaniclastic source, presently exposed as a thin strip along the southeastern GC, to what appears similar to an interior GC source. Contrastingly, DZ geochronology suggests less up-section change. We interpret this apparent discrepancy to reflect the onset of sediment recycling within the KFTB, with the exhumation, weathering, and erosion of early thrust sheets in the KFTB resulting in the selective weathering of unstable mineral species that define the volcaniclastic source but left DZ signatures unmodified. Using the timing of sediment recycling and changes in grain size together as proxies for structural initiation of the central KFTB implies that the thrust belt initiated nearly synchronously along strike at ~2.0–2.2 Ma.

Paleozoic-Mesozoic multistage tectonic evolution of the North Qilian Shan revealed by detrital zircon U-Pb and fission-track double dating

Knowledge of the tectonic history of the North Qilian Shan contributes to our understanding of the formation of the Tibetan Plateau. However, when the North Qilian Shan were formed has been controversial. We report new detrital zircon U-Pb (n = 899) and double dating fission track and U-Pb (n = 450) results from nine samples of Lower Cretaceous and Oligocene sandstone units, integrating with published geochronology and thermochronology data in order to reconstruct the evolution history of the North Qilian Shan. Nine samples from this unit show detrital zircon fission track age populations that center at: 636–603, 495, 406–331, 290–266, 247–224, 193–151, and 144–102 Ma. These fission track data are older than their corresponding depositional ages, suggesting that the fission track ages are unreset and record magmatic-related cooling or exhumation stages of the North Qilian Shan since the Late Neoproterozoic. Deconvolved fission track peak ages document major cooling events associated with the opening of the North Qilian Ocean at 636–603 Ma. Late Cambrian peak age (495 Ma) is attributed to the early phase of the subduction of the North Qilian Ocean. The Devonian period exhibited a cooling phase between 406 and 381 Ma, corresponding to the collision event between the Qaidam terrane, Central Qilian Shan, and Alxa Block. The peak age of 331 Ma signifies the cooling event associated with the subduction of the Paleo-Asian Ocean. The peak ages during the Early-Middle Permian period (290–266 Ma) provide evidence of significant exhumation events that occurred during the Late Paleozoic era. These events were linked to the subduction of the Paleo-Tethys Ocean to the south and the Paleo-Asian Ocean to the north. The Triassic peak ages (247–224 Ma) unveil exhumation signals in the North Qilian Shan region that were generated by the far-field effect of the collision between the Qiangtang and Kunlun terranes. During the Jurassic (193–151 Ma) and the Early Cretaceous periods (144–102 Ma), the exhumation of the North Qilian Shan region was a consequence of the subduction of the Neo-Tethys Ocean and the collision between the Lhasa and Qiangtang blocks, respectively. The peak ages of the Xinminpu Formation in the Early Cretaceous (123–121 Ma) are in close proximity to their depositional age (125–105 Ma), indicating that the North Qilian Shan underwent rapid exhumation during this period. The peak ages observed in the Oligocene Baiyanghe Formation (31–24 Ma) from 144 to 102 Ma, indicate that it has been influenced by the recycled sediments originating from the Cretaceous Xinminpu Formation. The North Qilian Shan gradually emerged during the late Paleozoic and Mesozoic eras, providing the foundation for its subsequent reactivation in the Cenozoic era. The multi-stage cooling or exhumation events of North Qilian Shan since Late Neoproterozoic reflect the complex formation process of the northeastern margin of Tibetan Plateau.

Evolution process of chemical weathering and sediment sources in the Makran Continental margin since the Younger Dryas

The chemical weathering processes and sedimentary source evolution since the Younger Dryas (YD) in the low-latitude arid continental margin have been investigated. Two sediment cores, MK07G and MK09G, were retrieved from the Makran continental margin in the northern Arabian Sea and subjected to analyses of major and trace elements, along with AMS14C dating. The results show that since the YD, the weathered parent rocks of Makran sediments have remained relatively stable, predominantly consisting of felsic rocks, with some contributions from mafic rocks. The Makran sediments exhibit initial to moderate weathering, with no discernible effects from grain size sorting or disturbances from sediment recycling, indicating primary deposition. Significant contributions of terrigenous eolian dust from surrounding continents (e.g., the Indian subcontinent, Arabian Peninsula, and northeastern Africa) were identified, along with riverine inputs from the Dasht River and fine-grained components from the Late Pleistocene Indus delta sediment, as well as proximal basin sedimentation. The evolution of sediment sources in the study area is significantly influenced by the Indian Monsoon and westerly wind systems, with intensified monsoon phases and westerly conditions correlating with increased fluvial input. Furthermore, chemical weathering processes since the YD are closely linked to local precipitation patterns, where intensified rainfall enhances weathering intensity. Records from the Makran continental margin indicate a teleconnection between chemical weathering and sedimentary processes in the Arabian Sea and Bond events in the North Atlantic, highlighting the extensive influence of Northern Hemisphere climate fluctuations.

Provenance, paleoweathering, sediment maturity, and depositional environment of intertrappean sediments in Angot–Gazo volcanic plateau, northeastern Ethiopia: Evidence from field mapping, petrography and geochemistry

Numerous intertrappean beds have been reported in different sections of the Ethiopian highlands; however, their detailed paleo-sedimentological characteristics have not been fully examined. This study investigates the source rock composition, tectonic setting, degree of past weathering, paleoclimatic conditions, sediment maturity, and depositional environments of the Angot–Gazo terrestrial sediments through geological mapping, mineralogical analysis, and geochemical approaches. Two terrestrial beds, consisting of mudrock and sandstone, were identified. The sandstone is characterized by massive, medium to coarse, and poorly sorted grains that range from sub-rounded to angular shapes. Minerallogically, the sandstone comprises quartz, feldspar, and lithic fragments grains with a proportional amounts of ash material. Both mineralogical (Q–F–R) and geochemical classification plots categorize the sandstone as arkosic to lithic greywacke. Felsic volcanic rocks are the main source material for the investigated sediments, as evidenced by multiple discrimination plots (DF1 vs. DF2, V–Ni–Th∗10, La–Th–Sc, Cr/Th–Th/Sc, La/Co–Th/Co, La/Sc–Th/Co and Y/Ni–Cr/V), LREE/HREE patterns, elemental ratios, and the appearance of abundant felsic-derived lithic fragments within the sandstone. A new bivariate discriminant function plot from DF1 vs. DF2 analysis, coupled with ternary diagrams of Zr/10–Th–Sc for the studied intertrappean sediments, revealed a continental rift setting, particularly a passive continental margin. Ternary diagram of A–CN–K, binary plots of Al₂O₃/Na₂O vs. average values of weathering indices (CIA, CIW, PIA, & MIA), and SiO2 vs. Al2O3+K2O + Na2O plot demonstrate slight to moderate degree of weathering for the sandstone, and deep weathering for the mudrock under semi-arid paleoclimatic conditions. The binary schemes of SiO2/Al2O3 and Ni–TiO2 ratio, along with the significant abundance of angular to sub-angular framework grains, reflect both immaturity and initial sediment recycling. Finally, the examined sediments were deposited in freshwater under oxic conditions, as evidenced by binary plots of Sr/Ba, Th/U, U/Th, and Ni/Co.

Continental rift evolution and drainage reorganization along the Dead Sea rift since the Miocene

The Dead Sea fault is a section of the Arabian-African plate boundary. Widespread field relations indicate that three major drainage systems (stages) occupied the landscape west of the Dead Sea fault since its initiation at ca. 20 Ma. Specifically, (1) an early to middle Miocene drainage system, only minorly reconfigured by the fault (all sediments of this system belong to the Hazeva Formation); (2) a late Miocene to early Pleistocene fault-parallel drainage system named Paran-Neqarot (all sediments of this system belong to the Arava and Zehiha Formations; and (3) the early Pleistocene to present drainage configuration. The temporal and spatial frameworks of drainage stage 1 are generally constrained by radiometric dating of interfingering volcanic units, and the onset and temporal and spatial frameworks of drainage stage 3 are well constrained by cosmogenic 10Be surface exposure ages. The timing and longevity of the rift-parallel drainage (stage 2) have until now been evasive to direct dating. The overall time gap between stages 1 and 3 is ∼12−13 million years. Thus, an early age (within this time gap) of stage 2 would imply an immediate response of drainage reorganization to rift tectonics, while a later age of this drainage system would imply a delayed response. We present 11 10Be-26Al cosmogenic burial ages of alluvial and colluvial units related to the fault-parallel drainage system (stage 2), which collectively constrain the time of deposition of the Arava Formation sediments in the central Negev to ca. 8 Ma. The general lack of stratigraphic order, together with the large dispersion of ages both across and within the sampling sites, attests to significant recycling of sediments from drainage stage 1 into the Arava Formation deposits. The termination of Arava and Zehiha Formation sediment deposition at ca. 1.8 Ma was determined previously using cosmogenic exposure ages of desert pavements that cover the formations. Combining the previously published data with our new data, we established the longevity and character of the Paran-Neqarot drainage system. This framework highlights the temporal aspect of drainage system build-up and collapse as it responded to transform and extensional plate boundary tectonics during the Neogene.

Recycling of terrigenous sediments recorded in late Permian-early Triassic Fe-rich intrusions from Yunkai Massif, South China

The origin of Fe-rich intrusion remains debatable regarding the respective role of magmatic evolution and Fe enrichment in the source. Here, we report detailed mineral and bulk-rock geochemistry of Permian-Triassic (251–250 Ma) mafic intrusions from the Tengxian area in Yunkai Massif, South China. These rocks consist of hornblende norites, show Fe-rich affinities with high FeO*(FeO* = FeOt / (FeOt + MgO) in weight ratio, >0.8, based on total iron oxide in the rock), and exhibit significant enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) but depletion in Sr and high field strength elements (HFSEs), resembling subduction-related magmas. In addition, they show remarkable features that include very high δ18O values in zircon (δ18O = 8.8–10.6 ‰) and apatite (δ18O = 8.7–10.8 ‰), and extremely enriched SrPb [e.g. 87Sr/86Sr(i) = 0.7181–0.7196, 207Pb/204Pb(i) = 15.77–15.78, 208Pb/204Pb(i) = 38.95–39.05] and nonradiogenic NdHf isotopic compositions [e.g. εNd(t) = −11.1 ~ − 10.1, εHf(t) = −8.8 ~ −7.3] in bulk rocks. These characteristics distinguish the Tengxian norites from modern arc basalts and subduction-related magmas in the Paleo-Pacific Tectonic Domain. Instead, they are isotopically similar to Cenozoic Tibetan and Mediterranean potassic to ultrapotassic rocks in the Tethys Tectonic Domain. Regardless of variable influence by orthopyroxene and plagioclase accumulation, the intrinsically low SiO2 and high FeOt and Fe/Mn ratios in these rocks were likely attributed to significant contribution of a Fe-rich mantle component such as Si-poor pyroxenite, which might have formed through crystal accumulation of mafic magmas at mantle conditions. The highly evolved Sr-Nd-Pb-Hf isotopic signatures and very high δ18O values in zircon and apatite required substantial (10–20 %) involvement of recycled crust in the mantle source. The combined mineral and bulk-rock geochemical data suggest that the parental magmas for the Tengxian norites originated from a metasomatized mantle wedge through addition of terrigenous sediment-derived melt following the subduction of Paleo-Tethys Ocean beneath the Yunkai Massif.

Detrital zircon in Pleistocene aeolianite of the Isipingo Formation at Cape Vidal, KwaZulu-Natal, South Africa, gives age and Hf isotope signatures without provenance significance

Abstract Pleistocene (50 to 70 ka) aeolianite of the Isipingo Formation (Maputaland Group) at Cape Vidal, northern KwaZulu-Natal province, South Africa, contains a combination of three detrital zircon age fractions (A: 940 to 1150 Ma, B: 470 to 720 Ma, C: 230 to 280 Ma) that are also known from Holocene sediments in eastern South Africa, Mesozoic – Cenozoic sandstones in southern Mozambique and from the Carboniferous to Jurassic Karoo Supergroup. Archaean and Palaeoproterozoic bedrock of the Kaapvaal Craton, which is exposed in the drainage basins of rivers that have provided detritus to coastal sedimentary basins, is represented by one single Archaean zircon. Combined laser Raman micro-spectroscopy and estimates of accumulated alpha radiation dose from U and Th concentrations indicate that the virtual absence of zircon older than late Mesoproterozoic cannot be attributed to selective removal of radiation-damaged zircon grains by abrasion during erosion and transport. The Isipingo Formation sandstone at Cape Vidal is a product of sedimentary recycling, potentially involving river transport from the continental hinterland, water- and wind-borne drift parallel to the coast and local recycling. Because of the similarity in detrital zircon distribution patterns of the sandstone and all of its potential Palaeozoic to Cretaceous sedimentary precursors, detrital zircon data cannot provide useful information on the relative importance of these processes, or on the routing of detritus to its final site of deposition.

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

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

Editorial to the Special Collection “Controls and Biasing Factors in Sediment Generation, Routing, and Provenance: Models, Methods, and Case Studies”

AbstractClastic sediment composition constitutes a key archive of Earth history, controlled by allogenic and autogenic processes that impact weathering, erosion, sediment transfer, and deposition. Deciphering those processes can provide valuable insights into ancient and modern tectonic, geomorphic, climatic, and anthropogenic controls that shape sediment routing systems over a wide range of temporal and spatial scales. However, in order to clearly identify the controls on sediment composition, it is necessary to exclude sources of bias that may mask or diminish the original provenance signal. Such biases may be natural, including mineral fertility, sediment recycling, and grain size, or analytical. This special collection arises from the fifth meeting of the working group on sediment generation held at the University Milano‐Bicocca in Milan, Italy, from 28 to 30 June 2022. The collation includes studies that investigate biasing factors affecting all steps of the sediment cascade and all stages of sample collection, preparation, and analysis, as well as case studies that aim to disentangle original provenance signals from geological, environmental, or analytical noise.

Mineralogical and geochemical characteristics of mudstones from the Lower Cretaceous Prosopis Formation in the Bongor basin, Chad: Implications for provenance, paleoenvironment and organic matter enrichment

The Cretaceous greenhouse represents the largest global warming event since the Phanerozoic, significantly affecting the provenance, weathering, regional climate, and paleoenvironment of lake basins globally. During the period of global warming, the control of regional paleoenvironment over organic matter enrichment is still unclear. The Lower Cretaceous Prosopis Formation in the Bongor Basin features thick lacustrine organic-rich mudstones as major effective hydrocarbon source rocks with excellent hydrocarbon potential in the basin. However, the provenance, paleoclimate, paleoenvironment and mechanism of organic matter accumulation in this location have not yet been systematically studied. In this study, 22 dark gray mudstone samples were collected from three cored wells. Clay mineralogy, along with organic and inorganic elemental geochemical analyses were jointly carried out to determine the characteristics of the provenance, paleoclimate and paleoenvironment as well as the major controlling factors for organic matter enrichment. The results imply that the Prosopis Formation mudstones are mainly composed of clay minerals such as illite, kaolinite, chlorite, and illite/smectite mixed layers (I/S). Organic geochemistry indicated that all the studied mudstones reached the standard of good to excellent source rocks (the total organic carbon content ranged from 1.27% to 7.41%). Inorganic elemental geochemistry is characterized by high enrichment of Fe, Mg, P, Mn, Ti, Na, Ca, V, Co, Cu, Sr, Ba and B relative to UCC and PAAS, whereas rare earth elements (REEs) show enrichment of light rare earth elements (LREEs) and a deficiency of heavy rare earth elements (HREEs) relative to chondrite. The source composition of the mudstones is predominantly intermediate-felsic igneous rocks that have not undergone sediment recycling. The parent rocks experienced weak to moderate weathering, corresponding to semiarid paleoclimatic conditions of transitional nature. The organic-rich mudstones were deposited in fresh to brackish waters with paleoredox conditions ranging from weakly oxic to anoxic semi-deep to deep lake environments having relatively low initial productivity. Comprehensive study indicates that paleoredox and paleoclimate are important parameters affecting the enrichment of organic matter in lake basins during global warming. The aridification of climate is one of the most important reasons for the high input and efficient preservation of organic matter. The relatively semiarid climate both increased the supply of terrigenous nutrients to the lake basins and provided a driving force for the increase in salinity, thereby providing better sources and preservation conditions for organic matter.

Tracing uplift and erosion in orogenic settings using quartz luminescence sensitivity: Insights from the Northern Andes uplift

The optically stimulated luminescence (OSL) sensitivity of the fast component in quartz has been increasingly used in provenance analysis of Quaternary sediments. Quartz OSL natural sensitization is thought to be mainly controlled by the formation conditions of the source bedrock and surface processes occurring mainly in sediment source areas. Thus, quartz OSL sensitivity can be linked to distinct sediment source regions, based on their tectonic setting and erosion conditions. In this way, changes in quartz OSL sensitivity within siliciclastic successions would track variations in sediment provenance. So far, few works evaluated how the OSL sensitivity of quartz sand grains varies in sedimentary successions that experienced long-term cycles of deep burial, exhumation, and erosion. Therefore, this work aims to characterize the sensitivity of the fast OSL component of quartz sand grains retrieved from the Cenozoic sedimentary rocks of the Northern Andes basins and assess its spatiotemporal changes. We found that quartz grains with the lowest OSL sensitivity are sourced by crystalline and volcanic rocks related to the Andean Continental Arc emplaced in the Colombian Central Cordillera, reflecting the onset of denudation in orogenic sources during the Paleocene. Subsequently, increasing trends in OSL sensitivity are related to the sedimentary recycling during the Andean orogeny, reaching maximum values as a result of the progressive unroofing of Cretaceous rocks in the Colombian Eastern Cordillera, originally sourced from the low-relief Amazon Craton. Changes in quartz OSL sensitivity measured in the Cenozoic sedimentary basin-fill sequences of the Northern Andes vary according to the shifts in sediment provenance related to the orogenic construction and sediment recycling of the Andean range.

Using quartz OSL signals from SAR cycles for sediment provenance studies

Quartz optically stimulated luminescence (OSL) sensitivity is varied and related to Earth surface processes and, thus, it has been shown to be a useful tool for appraising sediment recycling and provenance investigations. These investigations are mainly based on OSL data purposely measured for sensitivity calculations. However, it has been recently shown that the relative sensitivity of the quartz OSL fast component (%BOSLF) from the first test dose (Tn) signal from an OSL dating measurement using the Single Aliquot Regenerative-dose (SAR) protocol can be used to discriminate sediment sources. Here, we investigate the possibility of characterizing %BOSLF for provenance purposes using not only Tn signals but all other OSL signals obtained over SAR protocol cycles from OSL dating measurements. We address the %BOSLF behaviour over SAR cycles (if conservative or not), the %BOSLF dependency on dose-size, differences between %BOSLF values given by natural/regenerative and test dose signals, and %BOSLF application for provenance studies. Quartz sand grains data from twenty Late Quaternary sediment samples, representing orogenic and cratonic sources and diverse depositional contexts from South America, Africa, and Asia, are included in the analysis. All calculations were performed using data that have been previously obtained for equivalent dose estimation. The key finding is that the averaged %BOSLF of all SAR signals was representative of the samples' characteristic sensitivity and could satisfactorily discriminate samples from known sources, mainly in the case of high-sensitivity samples. We could distinguish sediment source areas by averaging the %BOSLF of OSL signals from SAR natural/regenerative and test doses together. Likewise, laboratories worldwide could produce regional/global sediment provenance fingerprinting reference data using their dating measurements accumulated throughout the last decade.

Carbon cycling during the India-Asia collision revealed by δ26Mg−δ66Zn−δ98Mo evidence from ultrapotassic volcanoes in NW Tibet

India-Asia continental collision−induced volcanic gas emissions are thought to have played an important role in driving Cenozoic atmospheric CO2 variations, yet the details of how the deep carbon cycle may influence volcanic CO2 degassing are not understood. We present a novel study employing Mg-Zn-Mo isotopic compositions of Cenozoic ultrapotassic lavas from NW Tibet. The negative Mg-Zn isotope correlation (δ26Mg = −0.39‰ to −0.19‰; δ66Zn = +0.27‰ to +0.36‰), bolstered by petrographic analysis of mantle-derived xenoliths from these lavas, demonstrates that the ultrapotassic magmas originated from a lithospheric mantle source that had been enriched by recycled carbonate-bearing sediments rich in calcite and dolomite. Very low δ98Mo values (−0.78‰ to 0‰) relative to the average continental crust (δ98Mo = +0.10‰ to +0.35‰) further indicate that the sedimentary components were derived from the subducted Indian continental crust after its dehydration. Monte Carlo modeling estimates that the input flux of carbon (elemental C) from such sediments into the lithospheric mantle is ∼5.6 Mt/yr, with a predicted CO2 emission rate of ∼15.5 Mt/yr. We suggest that the still ongoing subduction of the Indian tectonic plate has played a crucial role in introducing substantial quantities of carbonate-rich sediments into the Tibetan lithospheric mantle, leading to the sequestration of large amounts of CO2 via carbonatite metasomatism. Hence, partial melting of such a carbon-rich mantle reservoir in an orogenic setting provides the positive feedback mechanism that can explain the high flux of volcanic CO2 during India-Asia collision. These findings not only highlight the importance of continental subduction, sediment recycling, and mantle metasomatism by carbon-rich melts/fluids in the generation of Tibetan ultrapotassic volcanism, but they also show how the deep carbon cycle influences volcanic CO2 degassing.

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.

Lithotectonic setting, paleoweathering, maturity, sediment recycling and paleoredox conditions of quaternary alluvium from Mayo Sina (Tchad). A geochemical approach

The alluvial material in the two PITs of the Mayo Sina in the southern part of Chad, were subjected to a geochemical analysis in order to determine the source rock lithological composition, tectonic context, degree of weathering, type of climate at the period of weathering, and cycles of sedimentation and maturity. Plotting source lithology charts with values of La/Sc, Th/Sc, La/Co, and Cr/Th indicated that the sediments originated from a felsic source rock composition. The Enrichment of LREE/HREE and a negative chondrite Eu anomaly confirm the felsic source rock composition. A passive tectonic context for the source rock of the sediments is revealed by binary charts (SiO2 versus K2O/Na2O) in conjunction with innovative discrimination plots (DF 1 and DF 2 (Arc-Rift-Col)M1, DF (A-P)M, and DF (A-P)MT). The exceptional degree of plagioclase removal and weathering is demonstrated by the results of the Plagioclase Index of Alteration (PIX) and Chemical Index of Alteration (CIX). The proportion of SiO2/Al2O3 and the new index of compositional variation (ICVnew), which exclude iron and calcium oxides from the formula, indicate that the sediments are immature to mature. Schematic representations of K2O/Na2O ratio indicate that the sediments have undergone both primary to secondary phases of sedimentation.

Feasibility of constructed soils for tree planting – A pilot study in New York City

Constructed soils are soils that are created with a mixture of various materials. An innovative soil exchange program - the Clean Soil Bank (CSB) in New York City allows recycling of clean glacial outwash sediments excavated from depth at construction sites. One previous study showed that soils constructed from CSB sediment and compost can effectively support crop growth in community gardens, but no research has been conducted on its potential usage as a medium for tree growth. Moreover, biochar has been used to improve soil quality, but its efficacy for street trees incorporated into constructed soils has largely not been quantified in the field. The objective of this project was to evaluate the feasibility of using soils constructed from the CSB and compost for tree planting and to investigate the impact of biochar on tree performance. Thirty-six trees of two species (Maackia amurensis and Zelkova serrata) were planted in 2019, on the sidewalks of a residential-business neighborhood in Bronx, New York. Each tree pit contains one of three soil types: type A - existing and purchased topsoil mixed with 33% compost and biochar, type B - CSB sediment mixed with 33% compost, and type C - CSB sediment mixed with 33% compost and biochar. Soil samples were collected in 2019 (before planting) and in 2021. Tree health assessments were conducted in September 2020 and July 2021 using a protocol developed by the USDA Forest Service. Other tree health parameters collected include diameter at breast height (DBH), crown diameter, tree height, photosynthetic capacity, and foliar chemistry. Significant differences in bulk density, water holding capacity, and K, Fe, and Zn concentrations were found among the three soil types. However, comparison of tree performance and foliar chemistry showed no systematic differences among the three soil types. The results indicate that CSB sediment mixed with compost can be an effective replacement for purchased topsoil for tree growth. No evidence was found that biochar provides additional benefits to street tree performance. Considering the abundant availability of glacial outwash sediment at low cost to the city, as well as access to locally produced compost, constructed soils can be a reliable source of material for urban forestry programs.

Detrital mode and geochemical constraints on the provenance, paleoweathering and tectonic setting of the Surma sediments of Chittagong-Tripura fold belt, Tripura, India

The Chittagong Tripura Fold Belt (CTFB), the folded eastern part of the Bengal Basin is critical for understanding sediments origin and tectonic evolution linked to interactions among the Indian, Eurasian, and Burma plates. The upper Bhuban and Bokabil sediments (Surma Group) from Atharamura anticline, Tripura, India were analyzed using whole-rock geochemistry and petrography to assess their provenance, tectonics, weathering, and depositional milieu in this least explored area. Petrographic study indicates sub-lithic arenite to sub-arkosic composition, with moderate-high quartz, feldspar poor containing metamorphic and sedimentary lithic fragments (Bh Q88.3F3.0L8.6; Bk Q83.5F7.6L8.8), indicating significant recycled orogen source. Geochemical characteristics such as Eu/Eu* (0.6, 0.7), La/Sc (3.2, 2.4), Th/Sc (1.7, 1.4), Th/Co (1.9, 1.8), CIA/WIP (∼1–2), high Hf, Zr/Sc, low K2O/Al2O3 and enriched LREEs, depleted HREEs, and negative Eu anomalies, indicate a recycled provenance of felsic origin that underwent moderate to intense chemical weathering in active continental margin settings. Radiolarian chert, volcanic lithic fragments with Barail-like recycled sediments strongly suggests an additional detritus from uplifted Indo-Burman Ranges from the east. Elevated Th/U and Th/Rb ratios, sediment immaturity and poor sorting suggest first-cycled detritus. This study indicate that Tripura Neogene sediments are chiefly Himalayan-derived, with minor inputs from IBR and Meghalaya Plateau. Sediments were deposited under brackish near shore to shallow marine oxic basins to the west of the uplifted IBR during the Miocene. The study offers insights into regional geological processes, facilitating correlation of foreland Neogene basins and enhances understanding of the geological evolution of the CTFB.

Carboniferous–Early Permian volcano-sedimentary units from the northern margin of the North China Craton recorded subduction initiation in the Paleo-Asian Ocean

The precise timing of subduction initiation of the Paleo-Asian Ocean (PAO) in the northern margin of the North China Craton (NCC) remains controversial. In this study, we have conducted zircon UPb dating, whole-rock major and trace elements, and zircon Hf isotope analyses on metadacites and metamorphic greywackes from the Changde volcano-sedimentary rocks, feldspar quartz sandstones and argillaceous siltstones from the Luquantun Formation and the Sidao sedimentary rocks in central-eastern Jilin Province (NE China), to constrain the initial closure of the PAO. We obtained Early Carboniferous zircon UPb ages (345 ± 2 Ma and 351 ± 7 Ma) from the Changde volcano-sedimentary rocks. The metadacites are characterized by the enrichment in light rare earth elements and large ion lithophile elements, depletion in heavy rare earth elements and high field strength elements, and rare earth element ratios similar to those of the continental crust, indicating that these rocks originated from crustal melting. The metadacites exhibit affinity with the peraluminous A-type granite, with high zircon εHf(t) values (+3.46 − +12.21) and TDM2 of 1132–571 Ma, suggesting that they formed in a post-collisional extensional setting. Detrital zircon UPb ages from the Luquantun Formation and Sidao sedimentary rocks constrain their maximum depositional ages to the Late Carboniferous (319 ± 5 Ma) and Early Permian (284 ± 4 Ma), respectively. Most detrital zircons have age peaks at 1800 Ma with negative zircon εHf(t) values, and 2500 Ma with positive zircon εHf(t) values, suggesting that the Carboniferous–Early Permian sediments from these two formations were mainly sourced from the NCC. Moreover, the chemical index of alteration, index of compositional variability, and plagioclase index of alteration values suggest that the sediments of the Changde volcano-sedimentary rocks originated from a mafic igneous source with a low degree of weathering and a sedimentary recycling history, while the samples from the Luquantun Formation and Sidao sedimentary rocks were sourced from an intermediate-felsic igneous rock with a moderate to intense degree of weathering and mainly influenced by source composition. The crystallization age curves and summary plots of detrital zircons indicate that the Early Carboniferous metamorphic greywackes from the Changde Formation were mainly deposited in a passive margin, while the Carboniferous–Early Permian sediments of the Luquantun Formation and Sidao sedimentary rocks were mainly deposited in an active margin. We suggest that the tectonic transition from passive to active margin occurred at ∼333 Ma, marking subduction initiation in the PAO close to the northern margin of the NCC.