Fission Track Analysis Research Articles

Structural evolution and exhumation events recorded in the Huingancó Granodiorite, Cordillera del Viento, Southern Central Andes, Argentina

This study seeks to unravel the exhumation history of Permian granodiorites corresponding to the Huingancó volcano-plutonic Complex in the southern sector of the Cordillera del Viento (∼37°S), located within the Chos Malal fold-thrust belt. In this context, mineral chemistry analyses were conducted on the granodiorites using electron microprobe data to infer the P-T conditions of emplacement, resulting in 700–900 °C and pressures ranging between 1 and 2.4 kbar. Employing a geostatic gradient of 3.7 km/kbar, these values give an estimate of emplacement depths between 4 and 9 km. In order to understand their exhumation path, five samples from the Huingancó Granodiorite were taken along the Huaraco creek on the western flank of the Cordillera del Viento anticline to perform apatite fission track (AFT) analysis. This analysis yielded new cooling ages for the study area ranging between 50 and 80 Ma. Furthermore, inverse thermal modeling using the fission track data revealed two significant exhumation events during the Andean cycle: one during the Late Cretaceous-Paleocene and the other in Miocene times, separated by a period of gradual cooling or stability during Eocene-Oligocene times. These important cooling events are associated with the main construction phases of the Cordillera del Viento. Finally, to characterize its deformation evolution, a structural kinematic model is proposed based on a balanced structural section and its reconstruction to its non-deformed pre-Cretaceous state. The resulting model allows us to identify the structures and mechanisms of uplift rising the Cordillera del Viento, and their association with the main exhumation events depicted in the inverse thermal modeling. The main structure of the Cordillera del Viento corresponds to a fault bending fold that involves the basement in the deformation. Subsequently, its insertion as an intracutaneous wedge is related with the development of the thin-skinned structures at the internal sector of the Chos Malal fold and thrust belt.

Apatite Fission-Track Dating: A Comparative Study of Ages Obtained by the Automated Counting LA-ICP-MS and External Detector Methodologies

Abstract Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in combination with developments in digital microscopy, image analysis, and computer software has allowed the implementation of an automated counting approach for the apatite fission-track (AFT) analysis. We refer to this approach as the “automated counting-LA-ICP-MS” (ACLA) method. Two major components comprise the ACLA method: (i) the digital counting of spontaneous tracks performed on high-resolution images captured from apatite grains and (ii) the measurement of 238U content in apatite by LA-ICP-MS. This study includes ACLA analyses from Fish Canyon Tuff (FCT) and Durango apatite standard crystals. Furthermore, a comparative age study between the ACLA and conventional external detector method (EDM) strategies was performed on a set of thirteen granitoid samples from northwestern Mexico and four granitic samples from the eastern Dharwar craton (EDC), India. ACLA analyses on FCT yielded an AFT age of 28.1 ± 0.6 (1σ) and 28.8 ± 1.1 (1σ) Ma for Durango apatite, whereas reported EDM ages are 27.5 ± 0.5 and 31.4 ± 0.5 Ma, respectively. Calculated AFT ages using the ACLA method from northwestern Mexico samples range from 11.1 ± 1.1 to 42.0 ± 3.6 Ma (EDM ages range from 10.0 ± 0.8 to 54.0 ± 3.0 Ma), whereas AFT ages from the EDC samples range from 147 ± 3.1 to 220.5 ± 12.5 Ma (EDM ages range from 120.9 ± 4.5 to 197.1 ± 19.4 Ma). Based on a statistical comparison with ages previously determined by the conventional EDM on the same samples and considering their 2σ uncertainties, these ages are in good agreement.

Thermochronological constraints on the tectonic history of the Polda Basin

The Polda Basin is a narrow, east–west striking intracontinental basin that extends ~400 km from the onshore Eyre Peninsula in South Australia to the offshore Great Australian Bight and contains up to 5 km of strata, with a thick sequence of Neoproterozoic rocks overlain by unconformably-bound sequences of Carboniferous-Permian, Jurassic and Cenozoic strata. Though the Polda Basin has witnessed limited exploration for hydrocarbons, it is attracting renewed interest due to the potential for underground hydrogen storage in Neoproterozoic halites, whilst surrounding regions of the Gawler Craton are considered prospective for natural hydrogen. To date however, knowledge of the tectonic history of the Polda Basin, which is critical to assessing its potential role in the energy transition, is limited. Here we present results from a regional apatite fission track analysis study of the Eyre Peninsula, focussing on data from the onshore Kilroo-1A borehole, which provide insights into the burial and exhumation history of the Polda Basin. Results indicate that the preserved Upper Jurassic sequence was thicker prior to Late Cretaceous exhumation, which may have supplied sediment to the adjacent Ceduna Sub-basin. Our results highlight a complex history of Phanerozoic vertical motions in this region, which have implications for both resource and energy storage potential.

Compositional effects on etching of fossil confined fission tracks in apatite

Abstract Fission-track analysis is a thermochronologic method for dating rocks and reconstructing their low-temperature thermal histories. We investigate the influence of the apatite composition on the etching of fossil confined fission tracks, and its consequences for the fission-track method. We conducted step-etch experiments with 5.5 M HNO3 at 21 °C on samples with etch pit diameters (Dpar) spanning most of the range for natural apatites (Panasqueira: 1.60 µm, Slyudyanka: 2.44 µm, Brazil: 3.92 µm, and Bamble: 4.60 µm) to determine their apatite etch rates vR (the rate at which each lattice plane is displaced parallel to itself) as a function of crystallographic orientation (ϕ’). Our measurements revealed significant differences between the four samples. We fitted three-parameter functions, vR = a(Dpar) ϕ’ eb(Dpar)ϕ’ + c, describing vR as a function of the angle to the apatite c-axis for our hexagonal samples (excluding Bamble) and Durango apatite. The parameters a and b both exhibit a linear correlation with Dpar, whereas the constant c is small (~0.1 µm.min-1) and its between-sample variation negligible at the resolution of our measurements. Bamble exhibits a different, bimodal relationship between vR and ϕ’, which we fitted with a sum of two sine functions. In all cases, including Bamble, there is a striking correlation between the angular frequencies of horizontal confined tracks and the magnitude of the apatite etch rate vR perpendicular to the track axes. This shows that the sample of confined tracks selected for measurement and modeling is to a much greater degree determined by the etching properties of the apatite sample than by geometric or subjective biases. The track etch rate vT is constant along most of the track length but varies from track to track. The mean vT correlates with Dpar, so that tracks etch to their full lengths in a shorter time in faster etching apatites. The mean rate of length increase between etch steps, vL, also correlates with Dpar. The length increments of individual tracks are however irregular. This points to an intermittent structure at the ends of the tracks.

A Complex Meso–Cenozoic History of Far-Field Extension and Compression: Evidence from Fission Track Analysis in the Helanshan Mountain Tectonic Belt, NW China

The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and adjacent basins remain unclear. To better assess the connections between the temporal and structural activity in HTB, apatite fission-track (AFT) and zircon fission-track (ZFT) analyses were conducted in this study. The lack of adequate FT data from the HTB is a source of contention and dispute. This paper collected samples for AFT and ZFT techniques from the central and southern HTB, trying to improve the research. The ZFT and AFT ages could be divided into the following 7 groups: 279 Ma, 222–213 Ma, 193–169 Ma, 151–147 Ma, 130–109 Ma, 92–77 Ma, and 65–50 Ma. The inverse modeling results of AFT indicate 4 fast cooling episodes of 170–120 Ma, 120–95 Ma, 66–60 Ma, and ~10–8 Ma to the present. Combining the results of FT analysis with radial plot and inverse modeling of AFT, the following eight age groups are believed to reveal the distinct tectonic activities in HTB: the first age group of 279 Ma mainly represented the back-arc extension of the southern HTB; the age group of 222–213 Ma was bounded with NNE-SSE trending contraction between the South China block and North China Craton; the event of 193–169 Ma responded to the post-orogenic collapse followed after the second event; the 151–147 Ma group was interpreted as the eastward extrusion induced by the subduction between Qiangtang and Lhasa blocks; the Early Cretaceous (130–109 Ma) group was not only affected by the rollback of the Pacific Plate, but also denoted the collapse of the thickened lithosphere formed in the Late Jurassic; the Late Cretaceous (92–77 Ma) group was attributed to long-distance impact from the subduction of the Pacific Plate beneath the Eurasian Plate; the event during 65–50 Ma was a correspondence to far-field effect of the onset collision between the Eurasian and Indian Plates; and from 10–8 Ma to the present, the progressive collision of the Indian and Eurasian Plates have a significant impact on the HTB and the northeastern Tibetan Plateau.

Image segmentation and classification for fission track analysis for nuclear forensics using U-net model

AbstractThis study introduces a novel methodology for the detection and classification of fission track (FT) clusters in microscope images, employing state-of-the-art deep learning techniques for segmentation and classification (Elgad in nuclear forensics—fission track analysis—star segmentation and classification using deep learning, Ben-Gurion University, 2022). The U-Net model, a fully convolutional network, was used to carry out the segmentation of various star-like patterns in both single-class and multi-class scenarios.

New insights into Cenozoic evolution of the Shijiutuo uplift, Bohai Bay basin, China: Constraints from apatite fission track analysis and seismic data

The Shijiutuo Uplift within the Bohai Bay Basin(BBB)has experienced a complex evolutionary history since the Cenozoic. Studies of the Cenozoic evolution of the Shijiutuo Uplift are important for basin tectonics and petroleum geology. The formation of uplifts in rift basins is generally controlled by regional tectonic event and fault-block tilting. In this study, apatite fission track (AFT) data from fourteen samples and seismic data analysis were used to study the processes of regional uplift and fault-block tilting. We further investigated the Cenozoic evolution and formation mechanism of the Shijiutuo Uplift. The results indicated that the Shijiutuo Uplift experienced a two-phase differential tectonic uplift and erosion history (1) Widespread rapid uplift and erosion during the early Cenozoic (65–55 Ma) (2) Widespread uplift and erosion from 40 Ma to 16 Ma. The uplift and erosion substages of 40–38 Ma and 26–16 Ma were mainly caused by regional uplift, whereas those of 38–26 Ma resulted from fault-block tilting. Since the end of the third member from the Eocene Shahejie Formation, the Shijiutuo Uplift began to rise, causing the greater Bozhong Depression to be separated into the independent Qinnan and Bozhong Sags. These tectonic uplift and erosion events have a wide range of responses and regional dynamics in eastern China. The findings of this study will lead to a better understanding of the evolution and formation of uplifts within the BBB.

Interpreting and reporting fission-track chronological data

Abstract Fission-track dating is based on the analysis of tracks—linear damage trails—produced by the spontaneous fission of 238U in a range of natural accessory minerals and glasses. The retention of tracks is sensitive to elevated temperatures, and the data serve principally as a tool for recording thermal histories of rocks, potentially over the range of ~20–350 °C, depending on the specific minerals studied. As such, in most cases, fission-track data generally bear little or no direct relationship to the original formation age of the material studied. The age range of fission-track dating is related to the product of age and uranium content, and ages from several tens of years to older than 1 Ga are reported. Fission-track analysis led to the development of powerful modeling techniques. When used with appropriate geological constraints, these modeling techniques allow important geological processes to be addressed in a broad range of upper crustal settings. Since early attempts to standardize the treatment of fission-track data and system calibration over more than 30 years ago, major advancements were made in the methodology, necessitating the development of new, updated data reporting requirements. Inconsistencies in reporting impede public data transparency, accessibility and reuse, Big Data regional syntheses, and interlaboratory analytical comparisons. This paper briefly reviews the fundamentals of fission-track dating and applications to provide context for recommended guidelines for reporting and supporting essential meta fission-track data for publication and methodological archiving in structured formats that conform with FAIR (Findable, Accessible, Interoperable, and Reusable) data principles. Adopting such practices will ensure that data can be readily accessed, interrogated, and reused, allowing for further integration with other numerical geoscience techniques.

Post-rifting uplift and inversion of an intra-plate basin: The Doseo basin, Central Africa

There is a growing recognition that the post-rifting phase of basin evolution is far from being tectonically quiescent, as it can involve episodic uplift. However, the dynamic mechanisms responsible for this phenomenon remain a subject of controversy, particularly for intra-plate basins situated distant from active plate boundaries. Accurately determining the timing and magnitude of uplift is essential for elucidating the driving model behind these processes. In this study, we document the thermal history of the Doseo basin within the West and Central Africa Rift System (WCARS) using a combination of apatite fission track analysis and vitrinite reflectance data. Our findings reveal a period of accelerated exhumation during the late Eocene to Miocene epoch (∼45-20 Ma), characterized by kilometer-scale uplift, which corresponds to the formation of angular unconformities, folds, and fault-related anticlines. This specific time interval appears to be critical for the Cenozoic petroleum system, coinciding with the peak maturation of source rocks and the simultaneous formation of compressional traps. When integrated with the seismic data and previously published thermochronological data, our research reveals two significant cooling and uplift events in WCARS: a Santonian extrusion event and a late Eocene exhumation event. Both of these events have the potential to impact the entire tectonic plate, and Tethys realm. Furthermore, this two-stage exhumation event aligns closely with the timing of the Africa-Europe convergence collision. Consequently, we come to conclude that far-field lateral compression emerges as the dominant driving mechanism for intra-plate uplift, outweighing the influence of the mantle model.

Polyphase Exhumation of the East Kunlun Orogenic Belt: Evidence from Modern River Detrital Zircon and Apatite Fission Track Dating

Abstract The East Kunlun Orogenic Belt (E-KOB) stands out as one of the most prominent basin-mountain geomorphic features in the northern interior of the Tibetan Plateau. It records a series of accretion-collision events from the Mesozoic to the Cenozoic. In particular, with the uplifting of the Tibetan Plateau, the E-KOB experienced intracontinental deformation and exhumation in the Cenozoic. Clarifying the exhumation history of the E-KOB is crucial to define the growth time and mechanism of the Tibetan Plateau. In this study, we apply detrital zircon fission-track (ZFT) and apatite fission-track (AFT) analyses on modern river sands in order to constrain the regional exhumation history of the eastern E-KOB. Four peak ages have been identified and interpreted as results of rapid exhumation correlated with intracontinental deformation. Two older peak ages at 144.7–141.0 and 114.6–82.1 Ma are in good accordance with the collision time of the north-south Lhasa-Qiangtang Block along the Bangong-Nujiang suture zone and the subsequent progressive deformation stage toward the north. Peak age at 60.9–45.3 Ma is coeval with the initial timing of the India-Asia collision. The youngest peak age at 25.1–18.3 Ma matches well with the extensive outward and upward growth of the Tibetan Plateau during the Oligocene to Miocene time. The Cretaceous and early Cenozoic rapid exhumations suggest that the E-KOB has been involved in the intracontinental deformation induced by collisions of the Lhasa-Qiangtang and India-Asia from the south. It implies that the northern Tibetan Plateau likely has been elevated or was a structural high before the Eocene. In addition, some of our detrital samples show a younger ZFT peak age than the AFT peak age. We attributed this data bias to the contribution of hydrodynamic sorting and/or lithological difference. The combination of ZFT and AFT dating has advantages in eliminating interfering age signals in detrital thermochronology.

Simulation tools for improvement of the fission track analysis method for nuclear forensics

Simulation tools for improvement of the fission track analysis method for nuclear forensics

A MODEL OF THE LATE MESOZOIC AND CENOZOIC THERMOTECTONIC EVOLUTION OF THE PRE-MESOZOIC BASEMENT ROCKS IN SOUTH TUVA

Thermotectonic modeling was performed for the crystalline rocks of South Tuva using the apatite fission-track analysis. Thermotectonic modeling made it possible to visualize the Late Mesozoic and Cenozoic cooling history of the Pre-Mesozoic basement rocks, and to reconstruct the chronology and scale of the denudational processes over the last 125 myr and the evolution of paleorelief of South Tuva over the last 100 myr. The modeling results depicted several Mesozoic-Cenozoic episodes of cooling due to differential denudation and exhumation of the Pre-Mesozoic basement rocks. A differential denudation is related to an asynchronous activation of fault structures controlling the tectonic evolution of South Tuva. It is shown that the Early Cretaceous (~125–100 Ma) activation of the Agar-Dag-Oka thrust fault zone could result from the post-collisional processes after the collision between Siberia and Amuria and/or consecutive collision between the Cimmerian blocks. An intense activation of the Agar-Dag-Oka fault zone in the Late Cretaceous (~100–75 Ma), accompanied by significant basement rock exhumation in the eastern South Tuva to absolute heights of 1200 m, could be caused by the Karakoram-Pamir collision in the south of Eurasia. The Late Cenozoic (25–0 Ma) activation of the main fault zones of South Tuva represents a far-field effect of the Indo-European collision on the southern Eurasian continent. At the same time, there were the maximum basement uplift in the junction zone between the South Tannuola and Ubsunur-Bii-Khem fault zones and the transformation of relief of South Tuva from moderately dissected, with absolute heights of 500 to 1400 m, to modern, with absolute heights of 800 to 2600 m.

Two-step exhumation of Caucasian intraplate rifts: A proxy of sequential plate-margin collisional orogenies

Intraplate structural deformation is diagnostic of tectonic stress regime changes linked to plate interactions and can result from superposed tectonic events whose single contributions are hardly distinguishable. In this paper, we present a set of integrated thermochronologic inverse models along a 140 km-long transect across the central Greater Caucasus and the adjacent Adjara-Trialeti fold-and-thrust belt of Georgia, two intraplate orogens produced by structural inversion of parallel continental rift zones located on the Eurasian plate. Our dataset allows to distinguish discrete and superposed deformation episodes and quantify their respective contributions to orogenic exhumation. The integration of (U-Th)/He analysis on apatite and zircon, fission-track analysis on apatite, and peak-temperature determinations (clay mineralogy, organic matter petrography, Raman spectroscopy) shows that structural inversion was punctuated by two incremental steps starting respectively in the latest Cretaceous and the mid-Miocene. Latest Cretaceous partial inversion of the Greater Caucasus is documented here for the first time and placed in a geographically wider context of coeval deformation. The two episodes of intraplate structural inversion, exhumation, and sediment generation are chronologically and physically correlated with docking of (i) the Anatolide-Tauride-Armenian terrane (Late Cretaceous - Paleocene) and (ii) Arabia (Miocene hard collision) against the southern Eurasian plate margin. Intraplate deformation in the Caucasian domain was triggered by far-field propagation of plate-margin collisional stress which focused preferentially along rheologically weak rift zones.

Two-phase kinematic evolution of the Qilian Shan, northern Tibetan Plateau: Initial Eocene−Oligocene deformation that accelerated in the mid-Miocene

The Cenozoic growth of the Tibetan Plateau and the distribution of deformation across it are a consequence of India-Asia collision and continued convergence, which have implications for studies of continental tectonics. The spatio-temporal development of Cenozoic deformation along the northern margin of the plateau is an important issue that can be better understood by testing various models of plateau growth. The northern Tibetan Plateau is bounded by the Cenozoic Qilian Shan thrust belt and the Haiyuan left-slip fault. We conducted geologic mapping, field observations, electron spin resonance (ESR) dating, and apatite (U-Th)/He (AHe) and apatite fission-track (AFT) analysis in the Qilian Shan thrust belt to improve our understanding of the timing of brittle faulting and range exhumation in the northern Tibetan Plateau. We document the first direct age constraints for Oligocene deformation within the central Qilian Shan via ESR dating, which correlates with AHe-AFT cooling ages in adjacent ranges. We demonstrate that the Qilian Shan thrust belt experienced a two-phase growth history, including Eocene−Oligocene fault-related uplift shortly after the India-Asia convergence, and mid-Miocene regional overprinting deformation that reactivated the proximal thrust faults. This deformational pattern suggests that the Qilian Shan thrust belt has experienced out-of-sequence development since the Eocene−Oligocene and has persisted as the stationary northeastern boundary of the Himalayan-Tibetan Orogen throughout the Cenozoic. The Paleozoic Qilian suture systems acted as a pre-existing weakness and played a decisive role in controlling the lithospheric rheology, which therefore impacted the timing, pattern, and strain distribution of Cenozoic deformation across the northern Tibetan Plateau.

Meso–Cenozoic Exhumation in the South Qinling Shan (Central China) Recorded by Detrital Apatite Fission-Track Dating of Modern River Sediments

The Qinling Shan is located between the North China Craton and the South China Block. Not only is investigating the exhumation process of the Qinling Shan beneficial for comprehending the tectonic collision history of mainland China but also for enhancing our understanding of the development of the Yellow and Yangtze Rivers. Previous studies have predominantly focused on bedrock analysis in the Qinling Shan. However, modern fluvial detrital samples offer a more extensive range of thermal history information. Therefore, we gathered modern fluvial debris samples from the Hanjiang River, which is the largest river in the South Qinling Shan. Subsequently, we conducted apatite fission-track analysis using the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method. A total of 214 valid track ages were obtained, with an age distribution ranging from 9.5 to 334.0 Ma. The Density Plotter software was employed to decompose the data and generate four prominent age peaks: 185, 103, 69, 35, and 12 Ma. The exhumation events of the Early Jurassic (185 Ma) and Cretaceous (103–69 Ma) in the Southern Qinling Shan were strongly influenced by the collision between the South China Block and the North China Craton, as well as the subduction of the West Pacific Plate, respectively. The far-field effect of the collision between the Indian Plate and the southern Asian continent influenced the exhumation of the South Qinling Shan during the Late Eocene (35 Ma) and Middle Miocene (12 Ma), respectively. In conjunction with the reported findings, we comprehensively analyzed the geological implications of the Mesozoic and Cenozoic exhumations of the Qinling Shan. The Qinling Shan emerged as a watershed between the Ordos and Sichuan Basins in the early Mesozoic and Cenozoic, respectively. However, the exhumation and expansion of the Tibetan Plateau has forced the Yangtze River to flow eastward, resulting in its encounter with the South Qinling Shan in the late Cenozoic. The exhumation of the Qinling Shan has resulted in fault depression in the southern Ordos Basin. This geological process has also contributed to the widespread arid climatic conditions in the basin. During the Miocene, the Yellow River experienced limited connectivity due to a combination of structural and climatic factors. As a result, the Qinling Shan served as an obstacle, dividing the connected southern Yangtze River from the northern segment of the Yellow River during the late Cenozoic era.

New advances in the understanding of Bulgarian geology through fission-track analysis – a review

The paper is focused on the development and application of fission-track analysis in Bulgaria from the first experiments in the 1980s to the present. The results from two different approaches (the conventional method and fission-track analysis using LA-ICP-MS), obtained for deciphering the thermal and tectonic evolution of several zones of the Balkanides, are summarized. They demonstrate the significance of the method and its considerable contribution to the understanding of Bulgarian geology.

LA-ICP-MS APATITE FISSION-TRACK DATING OF THE SIBERIAN TRAPS INTRUSIONS: METHOD, FIRST RESULTS AND THEIR INTERPRETATION

In this paper we present the results on apatite fission-track dating, which was first performed at the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, using the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS, Dobretsov Geological Institute, Siberian Branch of the Russian Academy of Sciences) for two intrusions of the Siberian Permian-Triassic large igneous province: Magan alkaline-ultramafic pluton (two samples) and Kontay intrusion (one sample). The obtained AFT ages are 217.6±18.6 and 238.8±35.8 Ma (95% confidence) for the Magan intrusion and 150.0±23.0 Ma for the Kontay intrusion and mark the time since they have been cooled below 120 °C. The distributions of track lengths in apatite grains from the studied samples indicate their rapid cooling to near-surface temperatures. We provide a detailed description of the method used, and also demonstrate that the results of fissiontrack analysis performed on the "sample-to-sample" principle by the classical external detector method (EDM) and the LA-ICP-MS method in the modification of the zeta calibration coincide within the age uncertainty.

Tectonic-Thermal Evolution of the Wadi El-Dahal Area, North Eastern Desert, Egypt: Constraints on the Suez Rift Development

The Suez Rift developed as a northern extension of the Red Sea rift during the Oligocene-Miocene, whose flanks were constructed from the Neoproterozoic basement rocks of the Arabian–Nubian Shield. These basement rocks are comprised of the whole tectonic history since their formation. The Suez Rift initiation model and proposed thermal overprint role in the rifting process and flank development remain uncertain. Additionally, the amplitude of different regional tectonic events’ effects on the region is still debatable. Integration of fission-track thermochronology data with modeling of the time-temperature history has demonstrated efficiency in addressing such issues. In the context of this study, eleven representative samples were collected from the different rock units in the Wadi El-Dahal area at the northern tip of the western flank of the Suez Rift. These samples revealed Carboniferous zircon fission-track cooling ages of 353 ± 9 Ma and 344 ± 11 Ma. Meanwhile, the apatite fission-track analysis provided two spatially separated age groups: Permian-Triassic and Late Cretaceous, with average ages of 249 ± 11 Ma and ca. 86 ± 10 Ma, respectively. The time-temperature modeling revealed four possible cooling pulses representing exhumation events, which were initiated as a response to four tectonic activities: the accretion-subsequent event of erosion during the Neoproterozoic, the Hercynian (Variscan) tectonic event during the Devonian-Carboniferous, the Mid-Atlantic opening during the Cretaceous, and the Suez Rift opening during the Oligocene-Miocene. The western flank of the Suez Rift suggests a passive mechanical type with no extra thermal overprint, as indicated by the dominance of older thermochronological ages, modest rift flank elevations, and a reduction in the heat flow.

Late Triassic Tectonic Setting in Northeastern Margin of North China Craton: Insight into Sedimentary and Apatite Fission Tracks

The closure timing of the Paleo-Asian Ocean and the terminal stage of the Central Asian Orogenic Belt have been widely debated in the geological community. It’s known that the gradual scissor-like closure of the Paleo-Asian Ocean occurred from west to east during the Paleozoic period. However, it was not until the Triassic period that the complete closure of the ocean occurred at the northeastern margin of the North China Craton. Nevertheless, there is still much uncertainty regarding the Late Triassic tectonic setting in Northeast China. In this study, we focused on the Upper Triassic Dajianggang Formation, located in the Shuangyang area of central Jilin Province, which is situated on the northeastern margin of the North China Plate. Our aim was to determine the formation age of the Dajianggang Formation by analyzing the detrital particle composition, petrogeochemistry, detrital zircon U-Pb isotope dating, and apatite fission track thermochronology. Our results indicated that the primary sandstone provenance area of the Dajianggang Formation in the Shuangyang area is the island arc orogenic belt. The tectonic background of the sandstone provenance area is mainly a continental island arc environment. The provenance area is mostly composed of felsic rocks with sedimentary tendencies, and some of its material may have originated from the northern margin of the North China Craton or the eroded recycle orogenic belt. LA-ICP-MS U-Pb dating of detrital zircons shows that the Dajianggang Formation formed after 226.8 ± 5 Ma. Moreover, analysis of the thermal evolution history modelling shows that the Dajianggang Formation in the Shuangyang area continued to be deposited and heated in the early stage, and then experienced rapid exhumation around 30 Ma. This suggests that the study area underwent an orogenic process during the early stage of formation, but then transitioned into a post-orogenic extension period, which constrained the final closure of the Paleo-Asian Ocean prior to the Late Triassic period. In addition, our study indicates that the remote effect of the Pacific subduction did not reach the study area until 30 Ma. The central age of the detrital apatite fission track of sample 19DJ-1 is 94.2 ± 8.3 Ma, which is younger than its corresponding stratigraphic age. The two peak ages of the fission track analysis are 62.9 ± 5.4 Ma and 126 ± 11 Ma. These findings provide new evidence for the tectonic evolution of Northeast China and shed light on the Late Triassic tectonic setting, as well as the influence time of subsequent tectonic domains in the southern part of Northeast China.

A grain-by-grain comparison of apatite fission-track analysis by LA-ICP-MS and the External Detector Method

Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is increasingly used in fission-track analysis to determine the uranium content of host mineral specimens, particularly apatite. Fission-track dating by LA-ICP-MS (LAFT) has several advantages over the conventional External Detector Method (EDM), particularly in terms of sample turn-around times and the fact that neutron irradiations and the handling of radioactive materials are no longer necessary, while providing a similar level of in-situ information about parent nuclide (238U) concentrations. In addition, it facilitates the simultaneous measurement of multiple isotopes for double or triple-dating approaches or compositional characterisation. While it is often implicitly assumed that the EDM and LAFT fission-track dating approaches produce equivalent results, this assertion has yet to be adequately tested. We present an extensive dataset of apatite fission track results from 17 samples representing a large range of fission-track ages (∼0–2 Ga), 238U concentrations (0.14–410 ppm) and thermal histories that were analysed grain-by-grain using both techniques in order to investigate whether they yield concordant results during routine fission-track analysis.Apart from a few outliers, our data show that 238U concentrations measured by the EDM and LAFT techniques yield indistinguishable results across at least three orders of magnitude when a similar calibration system against rapidly cooled standards (e.g., Durango) is used. Comparison of single grain pooled and central ages reveals that LAFT ages are within error of EDM ages for apatite fission track standards such as Fish Canyon Tuff or Durango, as well as for a range of other samples whose shorter mean confined track lengths (<13 μm) and broader track distributions indicate they experienced more complex cooling histories. The most important conclusion here is that both the conventional EDM and LAFT methods can be expected to yield identical results for the breadth of ages, 238U concentrations, and underlying thermal histories commonly found in real world apatites.Importantly, the aggregate empirical calibrations for EDM and LAFT mask an underlying assumption that the mean etchable range of fission fragments is a constant having the mean value observed for spontaneous tracks in age standards such as the Durango apatite. Given that this assumption is known to be false in the great majority of samples, it is our view that empirically derived EDM and LAFT fission-track ages are best considered as model ages and that there should be greater clarity about the assumptions involved in their calculation.