Fission Track Thermochronology Research Articles

Early Cretaceous Exhumation of the Southern Great Xing’an Range, Northeastern China: Evidence from (U-Th)/He and Fission-Track Thermochronology

Early Cretaceous Exhumation of the Southern Great Xing’an Range, Northeastern China: Evidence from (U-Th)/He and Fission-Track Thermochronology

Thermal history of the southern Antarctic Peninsula during Cenozoic oblique subduction

Apatite (U–Th)/He and apatite fission-track thermochronology is used to constrain the cooling and uplift history of the southern Antarctic Peninsula where easterly-directed subduction of the Phoenix Plate, including ridge–trench collisions, has been taking place along its western margin since the Late Cretaceous. Apatite ages and thermal history models are similar on eastern Palmer Land but are younger and vary across westernmost Palmer Land and Alexander Island. Transformation of thermal history models to a single plot shows how cooling rates varied as a function of distance from the trench zone. Eastern Palmer Land preserves a record of uplift during the Late Cretaceous that coincides with changes in Phoenix Plate convergence rates and direction. In contrast, western Palmer Land and Alexander Island experienced a period of increased rates of cooling between c. 25 and 15 Ma. This younger phase of exhumation is bounded by major fault zones related to the extension and rifting that formed the present-day George VI Sound. It was probably triggered by cessation of subduction owing to trench collision of a ridge segment NE of the Heezen fracture zone. No evidence was found for slab window influences as seen along the northernmost part of the Antarctic Peninsula. Supplementary material: QTQt thermal models, a PDF with analytical protocols and supplementary tables are available at https://doi.org/10.6084/m9.figshare.c.6086234

The Tectonic Evolution of the Paleozoic Tannuola Terrane of Tuva in the Mesozoic and Cenozoic: Data of Fission-Track Thermochronology of Apatite

The Tectonic Evolution of the Paleozoic Tannuola Terrane of Tuva in the Mesozoic and Cenozoic: Data of Fission-Track Thermochronology of Apatite

Late Mesozoic to Cenozoic exhumation of the SE South China Block: Constraints from zircon and apatite fission-track thermochronology

The late Mesozoic to Cenozoic tectonothermal history of the basin-and-range system within the Cathaysia Block in the southeastern South China Block remains poorly constrained, despite its significance in the tectonic and topographic evolution of eastern China. Zircon and apatite fission-track thermochronometers were applied to reconstruct the cooling histories of NE-trending mountain ranges mantled by late Mesozoic granites and older basement rocks in southwest Fujian. New zircon and apatite fission-track data record post-magmatic cooling of the sampled granites since their emplacement of ~164–118 Ma. Thermal modeling of the thermochronology data revealed two episodes of accelerated cooling events at ~110–85 Ma and ~40–25 Ma. The late Early Cretaceous initiation of an accelerated cooling event at rates of ~6 °C/Ma was considered to be the cause of the formation of the basin-and-range system in a back-arc extensional setting related to the rollback of the Paleo-Pacific Plate. The second cooling event at ~40–25 Ma at a rate of ~20 °C/Ma, reflected by the youngest apatite fission track ages (~25–20 Ma), was likely ascribed to headwater erosion along the drainage divide related to the intensification of the East Asian Monsoon and extensional tectonism. The sharp discrepancy in apatite fission track ages across the Zhenghe-Dapu Fault zone implies that the collapse of the late Mesozoic coastal magmatic arc in the early Eocene (51.4–45.6 Ma). This is attributed to the northward propagation of extension related to the rollback of the Paleo-Pacific Plate that formed the eastward-dipping topography. Furthermore, the long-lasting extension due to the rollback of the Pacific Plate since the ridge subduction of the Izanagi-Pacific at ~50 Ma likely drove the exhumation of the Cathaysia Block and opening of the South China Sea.

Meso-Cenozoic growth of the eastern Qilian Shan, northeastern Tibetan Plateau margin: Insight from borehole apatite fission-track thermochronology in the Xiji Basin

The surface uplift of the Tibetan Plateau (TP) is among the most important geological events in Earth's history, but the growth of the eastern TP margin that yielded the thickened crust and abrupt topography remains controversial. In this paper, six sample apatite fission-track (AFT) analyses of three boreholes in the Xiji Basin are applied to constrain the Mesozoic-Cenozoic uplift and exhumation history of the eastern Qilian Shan, northeastern TP. Most of the AFT ages range from 134 ± 8 Ma to 117 ± 6 Ma, except for the shallowest sample, with a younger age of 65.9 ± 3.2 Ma. Thermal history modeling indicates that the eastern Qilian Shan experienced a three-phase differential cooling history: (1) widespread rapid cooling during the Middle Jurassic-Early Cretaceous (ca. 174-120 Ma, Stage 1), (2) regional cooling during the Late Cretaceous-Paleocene (ca. 80-60 Ma, Stage 2) and (3) widespread cooling during the Eocene-early Miocene (ca. 40-20 Ma, Stage 3). We conclude that the Middle Jurassic-Early Cretaceous was the main stage of the growth and thickening of the northeastern TP, which was related to the upper-crustal horizontal shortening of the eastern Qilian Shan. Thermal history modeling of the youngest sample and seismic profile analysis imply significant reactivation of the Liupanshan fault zone during ca. 80-60 Ma. This locally intense uplift and deformation on the eastern margin of the Qilian Shan during the Late Cretaceous was likely induced by the closure of the Neo-Tethys and the continued shortening of the Lhasa-Qiangtang block. Late Eocene-Early Miocene (ca. 40-20 Ma) cooling of the eastern margin of the Qilian Shan records the coeval crustal extension and exhumation of the northeastern margin of the TP as the far-field effect of subduction of the western Pacific plate. Our AFT data detect no intense late Cenozoic reactivation information for the Xiji region, which indicates that the ca. 15-7 Ma rapid uplift triggered by fault reactivation was only located in the Haiyuan-Liupanshan fault zone, along the eastern margin of the Qilian Shan, northeastern TP. This multi-phase exhumation history is not beneficial for regional hydrocarbon exploration.

Cenozoic deformation in the eastern domain of the North Qaidam thrust belt, northern Tibetan Plateau

Abstract The present topography of the northern Tibetan Plateau is characterized by the northwest-trending Eastern Kunlun Range, Qaidam Basin, and Qilian Shan, which figure importantly into the evolution and mechanism of Tibetan plateau development during Cenozoic Indo-Asian convergence. Understanding the Cenozoic deformation history and the source-to-sink relationship through time has significant implications for deciphering the growth history of the northern Tibetan Plateau. Despite decades of study, the timing, pattern, and mechanisms of deformation across the northern Tibetan Plateau are still vigorously debated. The North Qaidam thrust belt, located between the Qaidam Basin and Qilian Shan thrust belt, provides a valuable record of Cenozoic deformation in the northern Tibetan Plateau. Here, we present the results of new geologic mapping, structural and sedimentology analysis, and apatite fission track thermochronology to constrain the Cenozoic evolution history and reconstruct the paleogeomorphology of the eastern domain of the North Qaidam thrust belt and its foreland, the Wulan Basin. Our analyses reveal the North Qaidam thrust belt experienced multi-phase exhumation since the Cretaceous. A period of Eocene localized thrust-related uplift of the North Qaidam thrust belt initiated shortly after India-Asia collision, and lower erosion rates in the Oligocene allowed the thrust belt to expand along-strike eastward. Local uplift shed sediments to the southwest, directly into the Qaidam Basin. Reactivation of the proximal thrust faults and initiation of the northwest-striking right-slip Elashan fault at ca. 15–10 Ma drove the final accelerated mid-Miocene cooling and denudation to the surface. This phase of deformation established the overall framework morphology of the northeastern margin of the Tibetan Plateau, including the overall structure of the basins and ranges.

Unrecognized post-rifting deposition and uplift history of the Erlian Basin, Northern China: Evidence from seismic reflection data and apatite fission-track thermochronology

Early Cretaceous rift basins in Northeast Asia typically experienced varying degrees of post-rifting thermal subsidence and compressional deformation. However, previous workers believed that only a thin post-rifting sequence was developed in basins west of the Great Xing'an Range, making a proper understanding of the post-rift tectonic history in this part of Northeast Asia difficult. In this study, newly acquired shallow seismic reflection data were utilized to unravel the shallow deformation of the Erlian Basin, which to the west of the Great Xing'an Range contains a thin post-rifting sequence. Furthermore, we used apatite fission-track thermochronology to analyze the post-rifting deposition and uplift processes in the Erlian Basin, for which there are limited stratigraphic records. Our results show that the Erlian Basin experienced a typical post-rifting stage whose sequence from the Albian to the Campanian was not controlled by normal faults. The corresponding sedimentary thickness was up to 2 km, which contradicts the previously reported little or no post-rifting thermal subsidence. The current thin post-rifting sequence is the remaining stratum after 1.4–1.8 km of denudation at the end of the Erlian period. In addition, by further comparing the sedimentary thickness and time-lag in the onset of post-rifting to those of other basins in Northeast Asia, we found two driving mechanisms of rifting in Northeast Asia, which occurred simultaneously: the gravitational collapse and back-arc extension. Moreover, the basins in Northeast Asia experienced a gradual weakening in the compressional deformation from east to west during the Cenomanian to the Coniacian, and an intense compressional deformation in the east of Northeast Asia and large-scale vertical uplift in the west during the Late Cretaceous Campanian to the Eocene.

Apatite Fission Track Thermochronology of Granite from Duobaoshan Porphyry Cu (Mo) Deposit, Northeast China: Implications for Cooling History and Ore Preservation

The Duobaoshan Cu (Mo) deposit is one of the oldest super large porphyry deposits in the eastern part of the Central Asian orogenic belt. Although ore-forming processes have been extensively concerned, the post-mineralization ore preservation state was poorly focused on. In order to improve the ability of prospecting forecast, it is necessary to consider both deposit formation and deposit preservation. Here, we reported apatite fission track (AFT) data for the Duobaoshan porphyry copper deposits in the belt to reveal the cooling and exhumation history and evaluate ore preservation. The results show that the rapid cooling of the ore-hosting rock body occurred later than the surrounding rock body. The rapid cooling of the surrounding granodiorite occurred between 82 and 72 Ma, with the exhumation depth of 2.33–3.11 km and the exhumation rate of 0.25 mm/a, whereas the ore-hosting granodiorite porphyry was rapid cooling between 71.8 and 50.2 Ma, with the exhumation depth of 2.99–3.86 km and the exhumation rate of 0.22 mm/a. This differential exhumation and cooling event provide favorable geological conditions for the preservation of the ore body.

Mesozoic-Cenozoic exhumation history and its implications for the uranium mineralization in the southern Junggar Basin, North China

The phases of tectonic activity and exhumation of the southern margin of the Junggar Basin during the Cretaceous through Cenozoic shows significant relationships with the timing of uranium mineralization episodes. To clarify the succession of metallogenetic stages that were controlled by different phases of uplift and exhumation, apatite fission track (AFT) thermochronology was performed on the Jurassic through Cenozoic sediments from the Manas section in the southern Junggar Basin. The mean ages of the AFT suites range from 63 Ma to 133 Ma, and are younger than the host sediment for the Mesozoic samples and older than the host for the Cenozoic samples. The mean track lengths (MTLs) are between 10 and 11 μm. These results indicate that most of the apatite grain assemblages in these samples experienced complicated annealing histories. AFT ages were combined with thermal history modeling to unravel the timing of the multi-phase regional uplift and exhumation history and to reveal the tectonic constraints on the uranium mineralization. The populations of AFT single-grain ages display four peaks, which are interpreted as regional uplift and cooling episodes: mid-Early Jurassic (189–180 Ma), late Jurassic–early Cretaceous (157–116 Ma), late Cretaceous–early Paleocene (88–59 Ma) and late Eocene–early Oligocene (37–28 Ma). Thermal history modeling indicates two episodes of rapid cooling of the basin sediment deposits during the late Cretaceous–Paleocene (80–50 Ma) and the Pliocene (5 Ma)–Present. A synthesis of the temporal relationship between AFT age peaks, of the modeled time–temperature paths, of a compilation of age data and regional geologic events from the Tianshan mountain belt, suggests a close relationship between tectonic evolution and uranium mineralization. Uranium metallogenesis episodes occurred in conjunction with tectonic uplift and exhumation episodes along the southern margin of the Junggar Basin during the late Cretaceous–early Paleogene and during the latest Miocene-Present. The earlier episode was the primary mineralization stage, and the later episode was a partial transformation stage superimposed on the earlier one.

Differential exhumation of cratonic and non-cratonic lithosphere revealed by apatite fission-track thermochronology along the edge of the S\xe3o Francisco craton, eastern Brazil

Lithosphere of cratons and orogens generally reacts differently to tectonic events. Although these differences are mostly clear during the orogenic phases, understanding how they respond to tectonic reactivation is still challenging. Here, we report the first detailed apatite fission-track (AFT) study pinpointing the gradual transition between cratonic and orogenic lithosphere, using the case study of the São Francisco craton (SFC) and the adjacent Araçuaí-West Congo Orogen (AWCO), eastern Brazil. The collision that built the AWCO partially affected the inherited rift structures of the Paramirim Aulacogen, embedded in the São Francisco-Congo paleocontinent. Our data reveal a differential Phanerozoic exhumation between closely interspaced areas affected and not affected by the AWCO deformation. Samples from the SFC present slow and protracted basement cooling during the Phanerozoic, while samples from the orogen display rapid exhumation since the Eocene. An intermediate ~ N–S zone of c.40 km shows lower magnitude basement cooling during the Cenozoic, possibly because the propagation of AWCO deformation decreases towards the craton interior. Within the orogen, the Rio Pardo salient is the main reactive structure and probably results from the deformation of a master fault, inherited from its precursor rift. Here, we show how the magnitude of Phanerozoic denudation may be deeply associated with previous events of lithosphere weakening.

Miocene development of the Main Boundary Thrust and Ramgarh Thrust, and exhumation of Lesser Himalayan rocks of the Kumaun-Garhwal region, NW-Himalaya (India): Insights from Fission Track Thermochronology

• New FT ages suggest that the MBT and Saleri Thrust were initiated during ∼14 Ma. • The Amritpur granite was emplaced over the Siwalik along the MBT during late Miocene . • The Ramgarh Thrust sheet was emplaced over the LHMS zone along the RT during ∼24 Ma. • Old ZFT ages suggest that the metamorphism of the outer LHMS zone occurred < 250 °C. • Reactivation of the MBT and its associated faults occurred since Plio-Plistocene time. Bounded between the northeast dipping Main Boundary Thrust (MBT) at the base and the Saleri Thrust (ST) at the top, the Amritpur granite in the Kumaun-Garhwal region, NW-Himalaya is emplaced over the Siwalik sediments. As it is devoid of microscopic/mesoscopic imprints of the Himalayan tectonics, there is a debate regarding its emplacement along the MBT. While some interpret it as a klippe, others describe it as an intrusive body. The new apatite (AFT) and the zircon (ZFT) fission-track thermochronological data from the Amritpur granite provide similar age ranges and trends from the MBT to the ST. AFT ages range between 11.3 ± 1.6 and 14.7 ± 1.0 Ma with a weighted mean of 13.4 ± 1.5 Ma and ZFT ages range between 12.4 ± 1.2 and 15.4 ± 1.7 Ma with a weighted mean of 13.9 ± 1.2 Ma. Such age ranges and trends could be explained by rapid upliftment and exhumation of the Amritpur granite as horse rooted from the basement along the MBT from a depth of ∼8–10 km during mid-Miocene (∼14 to 13 Ma). We interpret this age as the time of development of the MBT. The new ZFT ages from the Jaunsar Group of the outer Lesser Himalayan meta-sedimentary (LHMS) zone range between 49.4 ± 2.0 and 80.3 ± 4.1 Ma (with a weighted mean of 67.5 ± 4.01 Ma) while the AFT ages range between 1.7 ± 0.2 and 4.2 ± 1.0 Ma (with a weighted mean of 3.17 ± 0.6 Ma). The old ZFT ages indicate that the outer LHMS zone underwent low-grade pre-Himalayan metamorphism (∼250 °C) around ∼67–72 Ma and the ZFT age of outer LHMS was not reset during the Himalayan orogeny. Young AFT ages from the Jaunsar Group of the outer LHMS zone reflect accelerated exhumation, likely due to reactivation of the MBT and its associated faults, since Plio-Pleistocene time. The new ZFT ages from the Ramgarh Thrust (RT) sheet range between 23.2 ± 2.4 and 24.2 ± 2.7 Ma with a weighted mean of 23.7 ± 2.5 Ma. The mean ZFT age of the RT sheet is similar to the age range of the Main Central Thrust (MCT) movements. This indicates that the RT sheet has been thrusted along the RT during 24 Ma followed by the exhumation of the RT sheet.

Growth of the imbrication zone along the southeast Anatolian orogenic belt: evidencefrom fission track thermochronology from Gölbaşı region (SE Turkey)

One of the major components of continental collision zones is their imbricated zones. Such a zone along the Southeast Anatolian Orogenic Belt (SAOB) is solely controlled by a still-active convergence and accretion system between the Anatolian Plate and Arabian platform since at least Late Cretaceous. The zone is characterized by NEE/SWW-trending, northward-dipping thrust slices that are squeezed between the Tauride Block to the north and the Arabian platform to the south. The units cropping out within the zone comprise Neo-Tethysrelated magmatic, ophiolitic, sedimentary and metamorphic rocks with Late Cretaceous to Miocene formation/metamorphism ages. The Karanlıkdere granitoid intrudes into Late Cretaceous Meydan ophiolite, Helete volcanics, and Malatya metamorphics. These units thrust over Cenozoic volcanic and sedimentary rocks. Although various scenarios have been proposed for the late Cretaceous to Neogene evolution of the complex region, quantitative data aiming to understand the growth mechanism of the imbrication zone in the region are limited. The zircon U-Pb and the apatite fission track (AFT) thermochronology were applied to the Karanlıkdere granitoid within the imbrication zone of the Southeast Anatolian Orogenic Belt (SAOB). The LA-ICP-MS zircon U-Pb age yields 79.67 ± 0.24 Ma with 0.23?0.65 Th/U ratios. This age is slightly younger than the previously published ages, indicating that the main body of the Karanlıkdere granitoid formed 3-4 Ma later than the small dikes intruded into other units. The AFT ages are directly controlled by altitude and range between 40.38 ± 3.4 Ma and 22.81 ± 0.63 Ma. The oldest AFT age has the highest altitude, whereas the youngest has the lowest height. The age-temperature models show a slow uplift rate between 40 Ma and 22 Ma. The results indicate that the growth of the imbrication zone in front of the Nappes of the SAOB continued in a steady-state mode with a slow uplift rate of 0.02 ± 0.005 mm/a, during middle-late Eocene to early Miocene and increasing uplift rate during early-middle Miocene, which might be explained by continental collision during early-middle Miocene.

Meso-Cenozoic thermo-tectonic evolution of the Yili block within the Central Asian Orogenic Belt (NW China): Insights from apatite fission track thermochronology

The Yili block in the Central Asian Orogenic Belt (CAOB), forms the easternmost part of the Kazakhstan collage system. Exploring its thermo-tectonic history is important to reconstruct the intra-continental evolution of the Tianshan belt. In this contribution, we report new apatite fission track (AFT) data from the basement rocks from the northern (i.e. the Wenquan complex) and southern (i.e. the Dahalajunshan - Nalati range) margins of the Yili block. Thermal history modeling reveals that the Wenquan complex underwent moderate basement cooling in the Cretaceous, possibly due to far-field effects of the Tethys-deformation and the following Lhasa-Qiangtang collision. These events at the southern Eurasian margin propagated tectonic stress to the northern Yili and triggered localized deformation. Early Triassic-middle Jurassic moderate cooling is also identified in the Dahalajunshan - Nalati range, and is interpreted to be related to the post-orogenic strike-slip motion along the major shear zones and the effects of the Qiangtang and Kunlun-Qaidam collision. Combined with the published thermochronological data, it is suggested that the northern and southern parts of the Yili block experienced different Mesozoic thermo-tectonic evolution. Basement cooling of the northern Yili block generally took place before the Cretaceous, exhuming shallower crustal levels as compared with the southern one. The intermontane Yili basin may have accommodated substantial propagated contraction induced by the Cretaceous collisional events. Based on our new results and the previously published thermochronological data, it is suggested that the intra-continental reactivation of the North Tianshan and Nalati faults probably did not invoke significant regional exhumation during the Meso-Cenozoic. Instead, small-scale brittle faults controlled localized enhanced denudation.

Comments on “Devonian to Permian post-orogenic denudation of the Brasília Belt of West Gondwana: Insights from apatite fission track thermochronology” by Fonseca et al. (2020)

In a recent paper published in the Journal of Geodynamics (vol. 137, June 2020, 101733), Fonseca et al. (2020) proposed a thought-provoking model aiming to elucidate the exhumation history of the Neoproterozoic Brasília Fold Belt (BFB) between the Devonian and Cretaceous periods. Exclusively based on information from the literature and new thermochronological data, Fonseca et al. (2020) presented an alternative model that tries to bind tectonic uplift, erosion, and the influx of clastic material coming from the BFB into the intracratonic Paraná Basin. Although the welcome proposal and reliable quality of the analytical data, the hypothesis presented diverges from several previously published works. In the light of the presented apatite fission-track ages, we disagree with their paleogeographical model, which puts the Brasília Fold Belt as a major source for clastic detritus to the Paraná Basin between the Devonian to Permian. The primary goal of our comments is to clarify the state-of-art of the intricate source-to-sink system of the Paraná Basin. Secondarily, we try to demonstrate why the model proposed by Fonseca et al. (2020) presents some geodynamic and interpretative problems and do not characterize an adequate paleogeographic scenario for southwest Gondwana between the Devonian to Permian periods.

Reply to the comment on “Devonian to Permian post-orogenic denudation of the Brasília Belt of West Gondwana: insights from apatite fission track thermochronology” by Alessandretti and Warren, 2021

Here we reply to the comment by Alessandretti and Warren, (2021) on the paper “Devonian to Permian post-orogenic denudation of the Brasília Belt of West Gondwana: insights from apatite fission track thermochronology” by Fonseca et al. (2020). We have the impression that many of the remarks, at least to some extent stem from a misunderstanding of our manuscript, also considering that they did not propose any alternative hypothesis for interpretation of our results presented in the aforementioned paper. We, thus, reiterate our interpretations from our low-temperature thermochronology data. The basement of the Brasilia Belt was subject to a significant exhumation during the Devonian to the Permian through erosion, and was likely a source area for detrital sediments deposited in parts of the northeastern Paraná Basin at that time. Apatite fission-track data show that Meso-Cenozoic events had limited effect on post-orogenic exhumation of the Brasília Belt, in contrast to e.g. the Araçuaí Belt.

Mesozoic–Cenozoic Uplift/Exhumation History of the Qilian Shan, NE Tibetan Plateau: Constraints From Low-Temperature Thermochronology

The Qilian Shan, which is located along the northeastern margin of the Tibetan Plateau, plays a key role in understanding the dynamics of the outward and upward growth of the plateau. However, when and how tectonic deformation evolved into the geographic pattern which is currently observed in the Qilian Shan are still ambiguous. Here, apatite fission track (AFT) thermochronology and sedimentology were conducted to interpret the low-temperature tectonic deformation/exhumation events in well-dated Late Miocene synorogenic sediment sequences in the Xining Basin, which is adjacent to the southern flank of the Qilian Shan. These new low-temperature thermochronological results suggest that the Qilian Shan experienced four stages of tectonic exhumation during the late Mesozoic–Cenozoic. The Late Cretaceous exhumation events in the Qilian Shan were caused by the diachronous Mesozoic convergence of the Asian Plate and Lhasa Block. In the early Cenozoic (ca. 68–48 Ma), the Qilian Shan quasi-synchronously responded to the Indian–Asian plate collision. Subsequently, the mountain range experienced a two-phase deformation during the Eocene–Early Miocene due to the distal effects of ongoing India–Asia plate convergence. At ca. 8 ± 1 Ma, the Qilian Shan underwent dramatic geomorphological deformation, which marked a change in subsidence along the northeastern margin of the Tibetan Plateau at that time. Our findings suggest that the paleogeographic pattern in the northeastern Tibetan Plateau was affected by the pervasive suture zones in the entire Qilian Shan, in which the pre-Cenozoic and Indian–Asian plate motions reactivated the transpressional faults which strongly modulated the multiperiodic tectonic deformation in northern Tibet during the Cenozoic. These observations provide new evidence for understanding the dynamic mechanisms of the uplift and expansion of the Tibetan Plateau.

Exhumation of the passive margin of the DR Congo during pre- and post- Gondwana breakup: Evidence from low-temperature thermochronology, geology and geomorphology

The Lower Congo region encompasses the South Atlantic passive margin of the Democratic Republic of Congo (Central Africa). It is host to the lowermost course of the Congo River, cutting through the Central African Atlantic Swell (CAAS). The region is underlain by litho-structural units of the Pan-African West Congo Belt, which consists of different tectono-metamorphic domains. The Precambrian basement is covered to the west by marine deposits of the South Atlantic Ocean and to the east by continental deposits of the Congo Basin. In this study we aim to constrain the timing of uplift and exhumation of the CAAS by using apatite fission track (AFT) thermochronology in combination with an updated overview of the geology and geomorphology of the Lower Congo region. AFT ages vary widely between 108 and 312 Ma. Short track lengths (11–12 μm) and broad, complex track length distributions indicate mixed ages between multiple thermal events. We derive the timing of exhumation from inverse thermal history models, that show that the Lower Congo region experienced a first exhumation event before Gondwana breakup during the Carboniferous to Middle Jurassic. This event is probably related to compressive forces at the boundaries of Gondwana. Both rifting and subsequent opening of the South Atlantic Ocean do not seem to have had a pronounced effect on the CAAS region. During the Late Cretaceous to Palaeogene, a slight reheating is suggested and could be due to subsidence and consequential modest reburial of the Lower Congo rocks. A second phase of exhumation initiated around the Palaeogene–Neogene and eventually emplaced the sampled rocks at surface temperatures. The multi-phased differential denudation results from reactivation of fault-bounded tectono-metamorphic blocks of the Precambrian basement, controlled by the combination of two systems of faults related to the Cretaceous South Atlantic Ocean opening and Pan-African orogeny respectively. Differential denudation of the Lower Congo region is also well-marked by independent qualitative indicators of the present-day geomorphology including distinct knickpoints and steep valleys along the course of the Lower Congo River, reworking of erosion surfaces and associated laterite crust and contrasting karst morphology.

Mesozoic-Cenozoic multistage tectonic deformation of the Qilian Shan constrained by detrital apatite fission track and zircon U[sbnd]Pb geochronology in the Yumu Shan area

The Qilian Shan on the northeastern edge of the Tibetan Plateau contains structural, sedimentary and tectonothermal records of plateau formation and growth in response to the Indian-Asian continental collision. In this study, we reveal the tectonic deformation evolution of the Qilian Shan by detrital apatite fission track (AFT) thermochronology and provenance analysis of a sedimentary section on the northern flank of the Qilian Shan based on paleocurrent measurements and detrital zircon UPb geochronology. The unannealed detrital AFT peak ages span ~154–10 Ma, and the zircon UPb ages range between ~3260 Ma and ~ 178 Ma. Detrital AFT ages showing that the initial exhumation occurs ca. 154–135 Ma and ca. 105–81 Ma and abundant ages of ca. 61–24 Ma indicate the prominent exhumation of the sedimentary provenance from the Qilian Shan at those times. Zircon UPb analysis suggests that the sediments were generally sourced from the Qilian Shan to the south, with moderate provenance changes at ~10 Ma and 5.1 Ma. These geochronological datasets imply that the Qilian Shan experienced multistage deformation during the Mesozoic-Cenozoic, i.e., late Jurassic-early Cretaceous (153.6–135.2 Ma), late Cretaceous (104.5–80.9 Ma), late Paleocene-Oligocene (61–43.1 Ma;38.2–24.6 Ma), mid-late Miocene (10 ± 4 Ma) and Pliocene (5.1–3.6 Ma). During the Cenozoic, the deformation initiated in the late Paleocene reflects the synchronous far-field response of the northeastern Tibetan Plateau margin to the Indian-Asian plate collision.

Intensified Late Miocene Deformation in the Northern Qaidam Basin, Northern Tibetan Plateau, Constrained by Apatite Fission-Track Thermochronology

The Cenozoic tectonic evolution of the North Qaidam-Qilian Shan fold-thrust belt in the northern Tibetan Plateau is important to understanding the tectonic rejuvenation of orogeny and growth of the plateau. However, the deformation processes in this region remain controversial. This study presents new apatite fission track (AFT) data from Paleogene strata in the northern Qaidam Basin to investigate the time of deformation in this site. Thermal modeling of these partially annealed detrital AFT ages shows a thermal history with a noticeable transition from heating to cooling after ∼10 Ma. This transition is attributed to the intensified thrusting and folding of the northern Qaidam Basin since ∼10 Ma. Integrated with published tectonics and thermochronology results, we suggest the North Qaidam-Qilian Shan fold-thrust belt experienced prevailing tectonism since the late Miocene.

Apatite and zircon fission-track thermochronology constraining the interplay between tectonics, topography and exhumation, Arunachal Himalaya

Apatite and zircon fission-track thermochronology constraining the interplay between tectonics, topography and exhumation, Arunachal Himalaya