Detrital Zircon Research Articles

The First Results of U–Th–Pb Isotopic Dating of Detrital Zircons from the Chenka Sandstones: A Contribution to the Stratigraphy of the Cimmerides of Mountainous Crimea

The First Results of U–Th–Pb Isotopic Dating of Detrital Zircons from the Chenka Sandstones: A Contribution to the Stratigraphy of the Cimmerides of Mountainous Crimea

Provenance signature and tectono–sedimentary setting of the Permian Shihezi formation (Ordos basin, China): Insights from geochemistry and detrital zircon U–Pb dating

During the depositional period of the Permian Shihezi Formation, the southern margin of the Ordos Basin was a key location for studying the tectonic movement of the North China Craton (NCC) and South China Blocks. The sedimentary environment was the first period of complete transition from marine to continental. However, the distribution of sediments controlled by a multi–provenance supply and the response of deposition to tectonics remain ambiguous, and the restoration of paleogeography remains in the qualitative stage, restricting the study of larger-scale tectono–sedimentary patterns. Based on field profiles and core observations, the paleocurrent direction, lithic fragments, heavy mineral assemblages, rare earth element distribution patterns, 11 detrital zircon U–Pb age datasets, and discrimination diagram of major and trace elements, the provenance signature and tectono–sedimentary setting were revealed. The results indicated that there are three main provenances in the southern margin of the Ordos Basin: North Qilian and western and eastern sections of the North Qinling Orogenic Belt. The tectonic setting of the North Qilian was a continental island arc, and the North Qinling was transformed from a passive to an active continental margin. Owing to the continued intense tectonic activities of the North Qilian, a braided river delta with a large sedimentary range developed in the west, and it was mixed with detrital sediments from the western section of the North Qinling with weak tectonic activity in the central. Affected by the uplift of the southern North China Craton, the sedimentary environment in the eastern range was unstable, and the thickness distribution of sandy sediments in the braided river delta was uneven. Refinement of provenance and deposition has important implications for the study of basin–mountain coupling relationships and paleogeographic reconstruction in the southern Ordos Basin and provides a basis for the study of collision evolution of the North and South China Blocks in the Permian.

Earliest Paleoproterozoic arc magmatism in the western Yangtze Block, South China and its geological implications

The Archean – Early Paleoproterozoic tectono-magmatic history of the Yangtze Block is inadequately constrained owing to the scarcity of coeval magmatic outcrops. Herein, we report on the Earliest Paleoproterozoic (2498 ± 17 Ma) meta-diabase dike in the Bajiaojing area of the western Yangtze Block, which may represent the oldest known mafic magmatism in the block. Whole-rock geochemical and mineral chemical proxies (e.g., U/Nb, Sc/Yb, and La/Yb) demonstrated that the Bajiaojing meta-diabase was likely emplaced in a continental arc setting. Positive zircon εHf(t) values (> 8) and incompatible elemental ratios (e.g., Gd/Yb, Sm/Yb, and Lu/Hf) further indicated that the mafic dike was derived from a depleted asthenospheric mantle source, which was modified by fluid and sediment from the subducting slab. The subduction-related modification also accounted for the compositional heterogeneity in the mantle source, which was observed in the wide range of Zr/Nb (1.05–4.38), Ce/Pb (6.11–81.59), and Nb/U (7.96–78.72) values. By combining the Precambrian evolutionary history of the Yangtze Block, we determined that an essential magmatic episode occurred in the Earliest Paleoproterozoic that was likely linked to crustal growth in the block. Therefore, the 2.5 Ga magmatism represented by the Bajiaojing meta-diabase was a potential provenance for the synchronous detrital zircons from Precambrian basement rocks.

Initiation of the Unazuki Belt, Southwest Japan, during the Carboniferous as an island arc system along the North China Craton

The Unazuki Belt, Southwest Japan, is a part of the Hida Belt, which is characterized as a plutono-metamorphic complex with a continental affinity formed between the late Paleozoic and early Mesozoic. The Unazuki Belt is known to be an important tectonic unit for the tectonic correlation between the proto-Japan and East Asian continents as it records Permo–Triassic tectono-thermal events, however, comprehensive chronology of the Unazuki Belt including the timing of the initiation of this Belt is yet unclear. The present study reveals certain Carboniferous magmatic and sedimentation events from the Unazuki Belt and their tectonic implications for the first time as follows. Zircon U–Pb age dating results and whole-rock geochemical compositions show that the protoliths of metagranite and metatrachyandesite in the Unazuki Belt formed at 328.2 ± 4.4 Ma and 332.8 ± 2.2 Ma, respectively, in an arc tectonic setting. Most metasedimentary rocks of the Unazuki Belt have the youngest detrital zircon grains of ~ 300 Ma with the Carboniferous single cluster at ~ 340–300 Ma without any Pre-360 Ma detrital zircon grains. However, one metasedimentary rock with Precambrian detrital zircons (~ 20%) has the youngest detrital zircon age of ~ 252 Ma, and ~ 66% of detrital zircons show a Permian age. Most of the εHf(t) values of zircon grains from all the studied Unazuki Belt samples, including the metasedimentary and metaigneous rocks with Carboniferous ages (~ 360–300 Ma) are positive (+ 6– + 18), whereas those of the zircon grains with Permian ages (~ 280–260 Ma) show wide variations between + 16 and -23. The whole-rock geochemical compositions of the ~ 300 Ma metasedimentary rocks of the Unazuki Belt show an island arc tectonic setting, whereas those of ~ 252 Ma metasedimentary rock have a continental arc affinity. These new data suggest that (1) igneous and sedimentary rocks in the Unazuki Belt formed in the island arc tectonic setting separated from the margin of continental crust during the Carboniferous but shifted to the continental arc tectonic setting during the latest Permian, (2) the collision between the island arc and continental arc may have caused the intermediate-P/T metamorphism during the Permian in the Unazuki Belt. The Carboniferous island arc tectonic setting in the Unazuki Belt indicates that the Hida Belt, including the Unazuki Belt, formed not at the margin of the South China Craton where Carboniferous subduction is absent but on the continuous subduction zone located along the eastern margin of the North China Craton, including the eastern margin of the northern Korean Peninsula where Carboniferous subduction occurred.Graphical

Sluggish rise of the western Gangdese mountains after India-Eurasia collision

With the most prominent topography on Earth, the Tibetan Plateau has profound influences on the hydrologic cycle and climate dynamics in Asia. However, the regional uplift history of the Tibetan Plateau remains highly debated. Here, we use europium anomalies and LREE/HREE ratio in detrital zircon, combined with whole-rock La/YbN ratio, to constrain the crustal thickness and topographic evolution of the Gangdese mountains in southern Tibet. Europium anomaly, controlled by pressure-sensitive minerals plagioclase and garnet, has been shown to correlate with crustal thickness. Our results reveal contrasting crustal thickening histories of the eastern (east of ∼88°E) and western (west of ∼88°E) parts of the Gangdese. Prior to the India-Eurasia collision (∼60–55 Ma), the crust of the eastern Gangdese thickened continuously from ∼40 km to nearly 60 km, while the western Gangdese maintained a mildly thickened crust of ∼50 km. Both parts underwent substantial thinning (to 40–45 km) immediately before the India-Eurasia collision, but the eastern Gangdese re-thickened rapidly afterwards. In the western Gangdese, post-collisional thickening was delayed until ∼40–20 Ma, which resulted in a mild elevation of ∼2000 m for most areas of southern Tibet until the late Oligocene. This diachronous uplift of the Gangdese after collision may have resulted from more mantle-derived magma additions in the eastern Gangdese before collision, which could rheologically weaken its lithosphere. We suggest that the diachronous uplift of the Gangdese after the India-Eurasia collision may have dominated the moisture transfer pattern across southern Tibet through the late Eocene and intensified the South Asian monsoon through the Oligocene-Miocene boundary (∼25–20 Ma).

Regional trends and petrologic factors inhibit global interpretations of zircon trace element compositions

The trace element composition of zircon reveals information about the melt that they are derived from, as such, detrital zircon trace element compositions can be used to interrogate melt compositions, and thus the evolution of the continental crust in time and space. Here, we present a global database of detrital zircon compositions and use it to test whether average global trends for five common petrogenetic proxies truly represent secular changes in continental evolution. We demonstrate that the secular trend is broadly comparable across continental regions for Ti-in-zircon temperatures, but for other trace element ratios interrogated, secular trends are highly variable between continental regions. Because trace element ratios result from multiple petrologic variables, we argue that these petrogenetic proxies can be overinterpreted if projected to global geologic processes. In particular, we caution against the interpretation of crustal thickness from trace elements in zircon, and we argue that our results negate current hypotheses concerning secular changes in crustal thickness.

Method of Estimating the Integral Roundness Index for Detrital Zircons: A Case Study of Cimmeride Sedimentary Sequences in the Crimean Mountains

Method of Estimating the Integral Roundness Index for Detrital Zircons: A Case Study of Cimmeride Sedimentary Sequences in the Crimean Mountains

New insights into the origin and depositional setting of the Haerdaban Pb[sbnd]Zn deposit, Chinese western Tianshan: Evidence from geology, chert geochemistry, and detrital zircon U[sbnd]Pb geochronology

The Haerdaban PbZn deposit (with an ore reserve of 10.93 Mt. at 1.0–25.65 % Zn and 0.7–12.29 % Pb) is hosted in weakly metamorphosed clastic‑carbonate rocks from the Proterozoic Haerdaban Group. It represents a significant addition of the sediment-hosted PbZn deposits in the Yili block, Chinese western Tianshan. Currently, there are ongoing debates regarding its genesis, with a particular focus on the crucial metallogenic mechanism (syngenetic sedimentary exhalation or epigenetic reworking) responsible for the primary sulfide mineralization. Mineralization at Haerdaban primarily occurs as banded to stratiform ore layers or lenses conformably sandwiched in their host rocks. Vein and stockwork ores occur locally below the stratiform ore layers. A syn-sedimentary fault trending SN was identified based on abrupt lateral changes in lithofacies and thickness of the stratigraphic units. The ore mineralogy is dominated by sphalerite, galena, quartz, and dolomite, with a small amount of pyrite, barite, and organic matter. Detrital zircon LA-ICP-MS UPb dating of the Haerdaban siltstones obtained a maximum depositional age of about 604 Ma. Their geochemical composition similar to the passive continental margin signatures, with rare earth element (REE) patterns enriched in LREE and negative Eu anomalies (Eu/Eu* = 0.50–1.14). Stratiform beds of chert that host disseminated ores have relatively high contents of hydrothermal components (e.g., Ba, Zn), with apparent positive Eu anomalies (Eu/Eu* = 7.38–49.34) and negligible negative Ce anomalies (Ce/Ce* = 0.85–0.98). They are thus interpreted to be hydrothermal sedimentary rocks (exhalites) deposited in a suboxic-anoxic environment proximal to the hydrothermal vents. Integrated geological and geochemical evidence indicates that the Haerdaban PbZn deposit is a typical vent-proximal sedimentary exhalative (SEDEX) deposit formed in a Neoproterozoic Sinian (Ediacaran) passive continental margin rift basin. Post-depositional metamorphism and deformation in the Paleozoic may have caused partial remobilization of primary ores but did not significantly alter the morphology of the orebodies. Furthermore, establishing a genetic model for the Haerdaban deposit has important implications for the exploration of similar deposits preserved in the equivalent stratigraphy within the Chinese western Tianshan region.

Mineralization of Zr-REE-Y in the Ngaoumbol iron formations, central Cameroon: Insights from petrography, mineral chemistry and whole rock geochemistry

The increasing importance of rare earth elements (REE) and critical metals in contemporary society has led us to investigate the mineral potential of the Ngaoumbol area, located within Cameroon's Central African Fold Belt (CAFB). In this study, we have conducted a comprehensive analysis that includes petrography, whole rock geochemistry, and mineral chemistry, along with the application of an outlook coefficient known as Koult, with the aim to evaluate the prospectivity of the Ngaoumbol iron formations as a potential source of REE-Y resources. This coefficient is defined as the ratio of the relative abundance of critical Rare Earth Elements to the relative abundance of excess REE. The iron formations in the Ngaoumbol area are fine-to medium-grained foliated rocks with alternating magnetite and actinolite bands and quartz bands, suggesting a sedimentary parentage. These rocks have an average REE-Y content of 1438.43 ppm and a Koult of 0.77, indicating their potential as raw sources for REE. Furthermore, the investigated samples exhibit high average Zr content (7748 ppm), suggesting that the rocks may host potentially economic Zr ore. The Zr-REE-Y mineralization in the Ngaoumbol area is hosted in detrital zircon, monazite and xenotime, probably deriving from the weathering of alkaline/subalkaline rocks surrounding the deposits. Our findings suggest that the Ngaoumbol area has promising REE and Zr resources. However, further exploration and evaluation are necessary to determine the extent and economic viability of these resources.

Northward expansion of the West Kunlun orogenic belt during the Cenozoic and its implications for the evolution of the northwest Tibetan Plateau: Constraints from sediment dispersal patterns in the Buya Basin, China

The West Kunlun orogenic belt, which defines the northwestern margin of the Tibetan Plateau, holds important information on plateau growth. Despite its significance, views about its uplift history continues to be under debate, with two competing hypotheses involving episodic uplift or northward expansion, related to a fixed or movable plateau boundary, respectively. The Buya Basin, a small basin located between the North and South Kunlun terranes, is key to understanding the Cenozoic uplift history of the West Kunlun orogenic belt. In this study, we conducted sedimentary and detrital zircon UPb geochronological analyses on the Cenozoic sediments of the Buya Basin. According to the findings of the sedimentary investigation, the Cenozoic strata of the basin generally show gradual changes from low- to high-energy deposition interrupted by a reverse trend in the Anjuan Formation. Moreover, the detrital zircon UPb geochronological results indicate that the Buya Basin received sediments initially from the Songpan–Ganzi and South Kunlun terranes during the deposition of the Keziluoyi to Pakabulake formations and then from the South and North Kunlun terranes during the deposition of the Artux Formation. This change in sediment dispersal patterns demonstrates that the uplift of the West Kunlun orogenic belt has expanded northwards to the North Kunlun terrane, which suggests that the northwestern boundary of the Tibetan Plateau has been a northward-moving feature in the context of India–Eurasia convergence. Along with previous studies, we suggest that the northward expansion of the northwest Tibetan Plateau is accommodated by decoupling deformation along the southern Tarim Basin, with northward thrusting of the foreland fold-and-thrust belts in the upper crust and southward underthrusting in the lower plate.

Early–Middle Devonian paleomagnetic results from the Zhongba microterrane, Tibetan Plateau: Evidence for its origin from the northern margin of Greater India

Abstract The initial disintegration of Gondwana during the Paleozoic laid the foundation for the formation of the Tibetan Plateau in the Cenozoic. Determining the relative positions of the microterranes in Gondwana during the Paleozoic not only informs the subsequent drift and accretion processes of these microterranes but is also crucial to the paleogeographic reconstruction of Gondwana. However, the lack of paleomagnetic constraints on the Devonian paleogeography of the microterranes in the northern part of Gondwana makes this effort challenging. Here, we report paleomagnetic results for the first time from the Early–Middle Devonian sediments of the Zhongba microterrane. The site-mean direction is declination (Ds) = 310.7°, inclination (Is) = −67.2°, ks = 31.2, α95 = 8.3°, and n = 11, in stratigraphic coordinates. Positive fold and reversal tests, together with rock magnetism results and microscopic observations, strongly suggest that the remanence carriers are of depositional origin. The paleomagnetic results meet the paleomagnetic reliability criteria and therefore can be used for tectonic reconstructions. Our results constrain the paleolatitude of the Zhongba microterrane to be 50.0°S ± 11.7°S in the Early–Middle Devonian. Combined with published detrital zircon ages as well as paleomagnetic results and geological data, our data indicate that the Zhongba microterrane, which had no tectonic affinity with the Lhasa terrane, was part of the northern margin of Greater India during 408–388 Ma and coupled with the South Qiangtang terrane, Tethyan Himalayas, and other terranes to form the continuous northern continental margin of East Gondwana.

Sedimentation tempo in an Early Jurassic erg system: Refined chronostratigraphy and provenance of the Clarens Formation of southern Africa

AbstractThe Clarens Formation is a widespread aeolianite deposited over southern Gondwana and represents the final phase of erg evolution in the main Karoo Basin during the Early Jurassic. Previous age assessments of the formation hinge on limited detrital zircon data, supplemented by relative ages from the biostratigraphy and geochronology of the adjacent Karoo units. This study refines the depositional history of the Clarens Formation, including its sediment source dynamics as well as basin‐wide geochronological framework, based on U–Pb dating of detrital zircon grains, together with petrographic and sedimentological characterization. The abundant presence of heavy minerals like zircon, tourmaline and rutile suggests large‐scale detritus recycling, while the uniform sandstone composition on a regional scale is an indication of sediment homogenisation across the basin. Based on the prominent detrital zircon age fractions, the sediments are interpreted as having been reworked from pre‐existing rocks of the Karoo Supergroup (Permian), the Damara and Saldania Orogenic belts (650–490 Ma), whereas minor sources can be assigned to the Namaqua‐Natal Mobile Belt (1.35–1.1 Ga) and the western Sierras Pampeanas (1.30–1.33 Ga). Unstable minerals (hornblende, garnet, titanite, feldspar) provide evidence for a nearby granitic source east and southeast of the basin, related to likely Grenvillian rocks (1.0–1.3 Ga). An Early Jurassic zircon age fraction is linked to volcanic activity in the Chon Aike Magmatic Province that, at the time, was situated south and southwest of the study area. Maximum depositional ages derived from these detrital zircon dates suggest that the sedimentation of the Clarens Formation spanned an interval of ~10 Ma during the Pliensbachian and early Toarcian. More specifically, the lower part of the formation is of early Pliensbachian age or younger (~191–192), while the upper part is of early Toarcian age or younger (~181–183 Ma). These age patterns are particularly prominent in the south of the basin that was situated closer to the volcanic source.

Detrital zircon and rutile of southern Mexico Cambrian–Ordovician sandstone: Their significance for sediment provenance and Rheic Ocean evolution

The Cambrian–Ordovician Tiñú Formation of southern Mexico is key for identifying sediment sources along the northern margin of Gondwana, enhancing our understanding of early Paleozoic paleogeography and linking it with age-equivalent units in terranes with Gondwanan affinity. This study integrates detrital zircon U–Pb ages, Hf isotope signatures, and heavy mineral chemical data. U–Pb detrital zircon ages indicate sources from Stenian–Tonian (900–1200 Ma) to Calymmian (1400–1600 Ma) ages. The Stenian to Tonian zircon population, with peak ages around 1.0 Ga and model ages ranging from 1.68 to 1.90 Ga, suggests a provenance from the metaigneous rocks of the Oaxacan and Guichicovi complexes. The presence of the Calymmian zircon population, tourmaline crystals, and rutile grains displaying lower crystallization temperatures compared to the high-temperature rutile from the Oaxacan Complex suggests additional sources. Hf isotope signatures from Calymmian-aged zircon grains, with model ages between 1.95 and 2.30 Ga, match well with the Paleo-Mesoproterozoic Catarina Unit in the southern Chiapas Massif Complex. Further potential sources may include the basement of the Putumayo Province in Colombia and igneous rocks from the western Guiana Shield and the Rio Negro-Juruena Province. The Tiñú Formation provenance is comparable to coeval metasedimentary units across the northwestern margin of Gondwana found in Belize, the southern Chiapas Massif Complex, and Guatemala. The Tiñú Formation was likely deposited adjacent to the rifted margin of the Rheic Ocean. The results also emphasize combining U–Pb–Hf isotope analysis and trace elements in detrital zircon and rutile as effective provenance tracers.

Zircon petrochronological evidences for diachronous tectonic switch and orogenic keel collapse of the Tongbai-Dabie-Sulu orogens

Migmatites can be produced in different stages of orogeny and thus have a great significance to constrain the evolution of an orogenic belt. Migmatites widely occur in the Tongbai orogen, but their formation ages and geological significance have not been well constrained. In this study, a combination of cathodoluminescence (CL) imaging, U-Pb-Hf-O isotopes and trace elements of zircons were carried for migmatites in the Tongbai orogen. Most inherited cores in a melanosome show variable UPb ages and Hf isotope compositions with high δ18O values, suggesting they might be detrital zircons from its protolith. Whereas other relict cores in this sample have nebulously zoning or no zoning, flat HREE patterns with insignificant Eu anomalies and relatively low formation temperatures, indicating their formation under eclogite-facies conditions. They yield UPb ages of 228 ± 3 Ma, providing direct evidence for the involvement of Triassic subducted continental materials. The overgrowth rims and some new grown grains in the migmatites show euhedral shapes, low CL luminescence, high Th/U ratios, clear negative Eu anomalies and steep HREE patterns, suggesting they are anatectic zircons formed during partial melting. They yield UPb ages from 139 ± 2 to 132 ± 1 Ma. Combined with previous studies, we suggest that migmatization mainly occurred at 139–130 Ma in the Tongbai orogen. The anatectic zircons in the leucosomes show much lower δ18O values (5.79 ± 0.23‰ vs. 8.94 ± 0.16‰) and higher 176Hf/177Hf ratios (0.282302–0.282648 vs. 0.281728–0.282504) than the zircons in adjacent melanosomes, suggesting that the leucosomes might be externally sourced. According to a compilation of the geochronological information of migmatite and magmatism, the Tongbai-Dabie-Sulu orogens have a spatial and temporal variation of partial melting and magma activities in the post-collisional stage. These might result from the diachronical tectonic switch and collapse of the orogenic lithospheric keels caused by the subduction and rollback of the Paleo-Pacific slab.

A fluvial‐aeolian system in response to aridification during the Late Mesozoic, Junggar Basin, Central Asia

AbstractAridification of Central Asia in the Late Mesozoic led to drastic environmental changes characterized by widespread aeolian deposits. We systematically investigated fluvial‐aeolian deposits in the Middle Jurassic Toutunhe Formation, Upper Jurassic Kalazha Formation, and Lower Cretaceous Tugulu Group in the Junggar Basin to the north of the Tianshan Orogenic Belt via unmanned aerial vehicle‐based photogrammetry, scanning electron microscope, grain‐size analysis, and detrital zircon geochronology. Paludal and deltaic environments transitioned to a fluvial‐aeolian environment from the late Middle Jurassic to the Late Jurassic. Fan delta and incisive braided river deposits accumulated in the earliest Cretaceous and evolved into a lacustrine environment with aeolian deposits in the lakeshore. Aeolian deposits are characterized by moderate‐ to well‐sorted and subangular to subround sandstones with large‐scale, high‐dip cross‐bedding, inversely graded lamination, dominant saltation grains, crescent‐shaped, and dish‐shaped impact structures. Aeolian deposits contain heavy minerals including more ilmenite, zircon, garnet, and, tourmaline and less magnetite and epidote than the fluvial deposits. The preserved aeolian sediments of the Kalazha Formation extend west–east for more than 100 km, suggesting a wide desert area during the latest Jurassic. The detrital zircon age patterns indicate that the provenance of the aeolian deposits was similar to that of coeval fluvial deposits. The cooccurrence of fluvial and aeolian deposits and the similar provenances but orthogonal flow directions indicate that the aeolian deposits were mainly sourced from the nearby fluvial material within the basin. The evolution of the fluvial‐aeolian system responded to a complete base‐level cycle controlled by the aridification and tectonics. Due to decreased sediment supply caused by aridification, the base level rose, leading to the change from braided rivers to meandering rivers, along with the deposition of aeolian sediments. Due to the tectonic reactivation in the Late Jurassic, the base level fell, causing the occurrence of alluvial fans and the expansion of the aeolian sediments. Previous studies revealed that the Tianshan in the Jurassic exhibited low relief. The fluvial‐aeolian system played an important role in maintaining the limited relief in southern Central Asia.

Impact of sediment provenance and depositional setting on chlorite content in Cretaceous turbiditic sandstones, Norway

AbstractChlorite minerals, mainly in the form of clay coats, play a critical role in determining the reservoir quality of siliciclastic rocks. They can positively influence reservoir quality by preserving porosity during deep burial, but they can also play a negative role by reducing permeability through pore filling. The main aim of this research is to determine the optimal conditions for chlorite growth in sedimentary basins. This study investigates the Lower Cretaceous turbidite sandstone of the Agat Formation in the North Sea. We used a source‐to‐sink approach to investigate the impact of sediment source composition, chemical weathering and depositional environment on chlorite formation. Understanding the interplay between these processes can help refine exploration and exploitation strategies, optimise hydrocarbon recovery, and reduce exploration risks. Representative samples from two hydrocarbon fields (the Duva and Agat fields) were investigated using petrography, geochemistry, heavy mineral identification and quantification, and U–Pb geochronology of detrital zircons. Our results show a strong heterogeneity in the sediment provenance between the two turbidite systems. In the Duva field, the sandstone is derived from a mixture of mafic and felsic sources, producing Fe‐rich sediments. Intense chemical weathering generates fine fraction materials rich in kaolinite, vermiculite, and hydroxy‐interlayered clays, which are transported into shallow marine settings. Subsequent interaction with seawater results in the formation of glauconitic materials, Fe‐illite, and phosphatic concretions. These Fe‐rich materials are remobilised into deep marine settings, providing precursors for the development of authigenic Fe‐clays such as berthierine and chlorite. Conversely, in the Agat field, the sandstone is predominantly sourced from felsic rocks that underwent low chemical weathering, producing sediment rich in quartz and feldspar with a low amount of clays. With few Fe‐rich materials transported into the basin, the development of chlorite in the Agat field was less pervasive. Basin configuration and depositional environment exerted additional control on chlorite distribution. In the confined turbidite system (e.g. Duva field), chlorite is typically found as coating, whereas in less confined turbidite systems (e.g. Agat field) chlorite shows complex distribution related to depositional environment and dewatering processes. Our findings demonstrate the importance of considering the entire sediment routing system, from source to sink, when predicting chlorite occurrence and its impact on reservoir quality in deep marine settings. This integrated approach can guide exploration and development efforts in deepwater clastic reservoirs.

The Ancient Configuration of the Southern Central Andes and Paleogeographic Reconstruction of the Late Cretaceous Foreland Basin at 34°40’S

AbstractThe early stages of Andean construction have been barely recognized due to a long history of tectonic superposition during the growth of the orogen. In this work, we present a multi‐method approach integrating sedimentological, geochronological, structural, and provenance analyses to reconstruct the architecture of the Late Cretaceous foreland basin at 34°40’S. We identified a new depocenter located in an inner position of the Late Cretaceous foreland basin, a strategic location to understand the sedimentation dynamics near the topographic front of the orogen. Two sandstone samples from the basal and upper sections of the Diamante Formation were collected for detrital zircons dating, which yielded maximum depositional ages between 98 Ma and 91 Ma. The provenance analyses based on U‐Pb zircons ages indicated a main source area located to the west, in the incipient orogenic belt, with a complementary contribution from basement rocks, located to the east. Moreover, growth strata documented in these deposits were compared with structural kinematic models, which suggest that some of these deposits are associated with inherited structures, reactivated during the tectonic inversion of the extensional Jurassic Atuel depocenter. Our paleogeographic model comprises an Andean Cordillera flanked by a hinterland basin to the west and a foreland basin to the east, with a deformational front positioned further east compared to previous models.

Sedimentary age and paleoenvironment restoration of paleogene and cretaceous oil and gas reservoirs in the Termit Basin, Niger

The Termit Basin is a typical rift basin of the Mesozoic-Cenozoic era and is considered the most promising area for hydrocarbon exploration in the West African Rift System. This region's Paleozoic and Upper Cretaceous Formations have relatively complete source-reservoir-cap assemblages. This study aims to provide an in-depth understanding of the excellent environmental conditions and background that are conducive to the preservation of hydrocarbons in the Paleocene and Upper Cretaceous Formations. The study aims to explore various aspects of the sedimentary age, depositional environment, source direction, and hydrodynamic conditions in the area.In this study, zircon dating, geochemical characterization, and particle size analysis were performed on samples collected from two high-quality exploration areas, the Paleocene and Upper Cretaceous Formations. The Sokor-2 Formation of the Paleocene and the Madama and Yogou Formations of the Upper Cretaceous were the principal strata under investigation. The zircon dating results show that the primary rocks of detrital zircons experienced the Garidonian movement, with primary peaks in the Cambrian period. Geochemical characterization reveals that the sedimentary environment in the area was oxygen-rich, low-salinity, and warm. Particle size analysis helps identify the direction of material sources and hydrodynamic conditions in the palaeoenvironment.The experimental results indicate that the Paleogene and Upper Cretaceous Formations are high-quality exploration layers for oil and gas. These findings provide valuable data support for future hydrocarbon discoveries in the region.

Early Orosirian belts of the central Guiana Shield, northern Amazonian Craton: U-Pb geochronology and tectonic implications

The Cauarane-Coeroeni Belt (CCB), the Orocaima Igneous Belt (OIB) and the Rio Urubu Belt (RUB) are the main tectonic features of the central part of the Guiana Shield. The CCB is a sinuous NW-SE/NE-SW/NW-SE trending high-grade supracrustal belt, bordered to the north by the OIB, formed by volcanics and high-crustal level granitoids, and to the south by the RUB, made up of deeply emplaced granitoids and gneisses. We present 27 new U-Pb SHRIMP and LA-ICP-MS zircon ages for these belts.The geochronological data obtained for 10 granitoid samples of the OIB indicate that magma pulses of different typologies were coeval along the belt and confirm its continental scale extension. Crystallization ages obtained for the high-K calc-alkaline granitoids vary from 1990 ± 5 Ma to 1957 ± 17 Ma and those of reduced A-type granites vary from 1980 ± 14 Ma to 1974 ± 8 Ma.Only four samples of granitoids and gneisses of the RUB were analysed. Crystallization ages of 1964 ± 7 Ma and 1956 ± 8 Ma were calculated respectively for a granodiorite and for an orthogneiss and are in agreement with the 1.96–1.92 Ga age period regionally considered for the evolution of the RUB. However, an age of 1973 ± 7 Ma was calculated for a foliated S-type granite, indicating that slightly older granitoid rocks are also present within the RUB. In addition, an age of 1935 ± 10 Ma was calculated for the high-grade metamorphism along the belt.A microgranitic dyke that crosscuts the foliation of a gneiss of the RUB was dated at 1884 ± 7 Ma, and probably represents one of the feeder dykes for the large 1.89–1.87 Ga Uatumã magmatic event.Twelve samples of the CCB were analysed. The data for the detrital nuclei of the zircon crystals of the paragneisses and schists suggest an overall similar inheritance pattern along the length of the CCB, recording the contribution of Archean to early Orosirian sources, with a major participation of Rhyacian domains.The oldest detrital zircon crystals yielded an age of 3.65 Ga, but the age of most of the Archean zircon grains fall in the 3.50–2.50 Ga range and they were probably derived from the Imataca and Amapá blocks. Results in the 2.50–2.30 Ga age interval were obtained for detrital zircon grains of many samples, indicating the contribution of Siderian source-areas, possibly the Bacajá Domain, located outside the shield. Those terranes formed within the shield during the Rhyacian phase of the Transamazonian Cycle were probably the source of the 2.30–2.05 Ga detrital zircon grains. In addition, zircon grains with ages between 2.05 Ga and 2.03 Ga were possibly derived from the Trairão-Anauá terranes.The U-Pb SHRIMP zircon dating allowed to better constrain the metamorphic events along the CCB. The syn-kinematic M1 high-grade metamorphic phase could not be directly dated, and we suggest it occurred between 2025 Ma and 2000 Ma. The imprint of the thermal M2 metamorphic event is recorded by the presence of rims and cores of zircon crystals with very low Th/U ratios (<0.1), showing secondary texture. Upper intercept ages of 1983 ± 9 Ma, 1978 ± 9 Ma and 1967 ± 27 Ma were obtained for M2. Zircon grains with secondary textures and very low Th/U ratios (<0.1) from a sample collected in the vicinities of the RUB yielded an upper intercept age of 1955 ± 14 Ma, tentatively interpreted as reflecting M3.The ages obtained for the M2 and M3 metamorphic phases coincide, respectively with those measured for the rocks of the OIB and for the high-grade metamorphism in the RUB. We envisage that the M2 and M3 metamorphic overprints in the paraderived rocks of the CCB reflect important fluid input and thermal perturbation respectively during the emplacement of the OIB granitoids to the north, and the assemblage of granitoid bodies of slightly different ages, deformation and high-grade metamorphism within the RUB, south of the CCB.The early Orosirian terranes of the central part of the Guiana Shield were formed during Akawai Orogeny. The 2.04–2.03 Ga Trairão-Anauá terranes and the CCB supracrustal rocks represent the pre-collisional and collisional stages of the orogeny, the OIB records post-collisional, late-orogenic magmatism. The RUB is probably reflecting a post-collisional setting associated with transpressive deformation. The Akawai Orogeny is interpreted as the late stage of the Transamazonian Cycle, after the main Rhyacian orogeny of the cycle, and was responsible for the final amalgamation of this part of the Columbia paleocontinent.

Early Paleozoic accretionary history of the Pearya terrane: New insights from igneous and detrital zircon signatures of the Kulutingwak Formation, Ellesmere Island, Nunavut, Canada

The juxtaposition of the composite Pearya terrane and the northern Laurentian margin at Ellesmere Island, Nunavut, Canada, has significant ramifications for the Paleozoic tectonic history of the circum-Arctic region. Published tectonic models rely upon interpretation of the subduction-related Kulutingwak Formation as an indicator of Ordovician and/or Silurian accretion (Trettin, 1998). New igneous and detrital zircon U-Pb and Lu-Hf isotopic data from 16 samples collected in the Yelverton Inlet–Kulutingwak Fiord region of northern Ellesmere Island suggest that the Kulutingwak Formation of Trettin (1998) contains structural blocks derived from both the Pearya terrane and Silurian strata associated with the ancestral Laurentian margin. Data from this study demonstrate a complex provenance history for rocks within the Petersen Bay, Kulutingwak Fiord, and Emma Fiord fault zones, with age probability peaks of ca. 470 Ma, 650 Ma, and 960–980 Ma that suggest affinity with the Pearya terrane, and age probability peaks of ca. 1800 Ma and 2700 Ma that indicate connections to the Laurentian margin. The combination of these signatures in Kulutingwak Formation rocks suggests that the Pearya terrane was proximal to the northern Laurentian margin by Late Ordovician time. Silurian and younger strike-slip displacement on the major fault zones resulted in the incorporation of blocks derived from the Pearya terrane basement and Silurian clastic rocks into the Kulutingwak Formation. Silurian displacement along these strike-slip faults, which are integral components of the Canadian Arctic transform system, is recorded by syndepositional deformation structures in the Danish River Formation and prevented the transition from soft to hard collision of the Pearya terrane. The two-stage model for the Pearya terrane—accretion followed by significant translation—provides a process for developing complex steep terrane boundaries with contentious displacement histories that are common in accretionary orogens.