Apatite Fission Track Ages Range Research Articles

Low-Temperature Thermochronology Records the Convergence between the Anatolide–Tauride Block and the Arabian Platform along the Southeast Anatolian Orogenic Belt

SE Anatolia is witnessing the final stage of the Wilson Cycle, where a continental collision between the Tauride–Anatolide block and Arabian platform occurred, and a 1.5 km Eastern Tauride mountain chain formed. We present new low-temperature thermochronology (LTT) ages, including eight apatite fission track (AFT) and seven apatite and zircon U-Th-Sm/He (AHe, ZHe) ages, for the metamorphic rocks from the Nappe Zone of the Southeast Anatolian Orogenic Belt. The ZHe ages vary from 51.2 ± 0.7 Ma to 30.4 ± 0.6 Ma, the AFT ages range from 33.1 ± 1.6 Ma to 18.1 ± 0.9 Ma, and the AHe ages range from 23.6 ± 2.5 Ma to 6 ± 1.9 Ma. The LTT data show a continuous slow uplift of the region. However, the thermal modeling results suggest an Eocene and middle–late Miocene fast uplift of the region. Similar to our results, the LTT studies along the SAOB show that the vertical movements initiated during the Eocene period have continued in a steady-state regime to recent times. The Eocene epoch is identified by arc–back-arc setting in the region, whereas the Miocene epoch is marked by the continental collision. Within this tectonic framework, vertical movements on the overriding plate are controlled by both extensional and compressional tectonics. The LTT data obtained along the SAOB show fingerprints of thrust propagation from north to south.

Present-Day Geothermal Regime and Thermal Evolution of the Fukang Sag in the Junggar Basin, Northwest China

The Fukang Sag in the Junggar Basin is an important petroleum exploration and exploitation region. However, the geothermal regime and tectono-thermal evolution of the Fukang Sag, which control its hydrocarbon generation and conservation, are still controversial. This study involved a systematic analysis of the present-day geothermal gradient, heat flow, and thermal history of the Fukang Sag for better further exploration. According to the well log data and well-testing temperature data, we calculated that the geothermal gradient of the Fukang Sag ranges from 16.6 °C/km to 29.6 °C/km, with an average of 20.8 °C/km, and the heat flow ranges from 34.6 mWm−2 to 64.3 mWm−2, with an average of 44.6 mWm−2. Due to the basement relief, they decrease from northeast to southwest. The weight averages of the single-grain apatite (U-Th)/He ages of the core samples are 1.3–85.2 Ma, and their apatite fission track ages range from 50.9 Ma to 193.8 Ma. The thermal modeling results revealed that the Fukang Sag experienced late Permian, late Jurassic, and late Cretaceous cooling events (although the timing and magnitude of these events varied among the samples), which were related to the continuous compression of the Junggar Basin. In addition, basin modeling indicated that the heat flow of the Fukang Sag decreased from 80 mWm−2 in the Carboniferous to the current value of 44.6 mWm−2. The Fukang Sag’s edge exhibits prolific hydrocarbon generation in the Carboniferous–Permian source rocks, while the Jurassic source rocks within the sag also undergo abundant hydrocarbon generation. This study provides new insights into the present-day geothermal field and tectono-thermal evolutionary history of the Fukang Sag, which are significant in terms of regional tectonic evolution and oil and gas resource assessment.

The influence of lithospheric inheritance and Cenozoic magmatism on Phanerozoic rock cooling in the São Francisco Craton and adjacent orogens

The South American Platform encompasses the São Francisco Craton (SFC) and the Araçuaí-Ribeira orogenic system (AROS) located in the eastern Brazil. These geologic domains hold records of differential exhumation, sedimentation, volcanic activity, and post-rift reactivation of faults and shear zones. Therefore, these terranes provide outstanding opportunities for studying the dynamics of lithospheric processes, particularly in their interaction zones, characterized by the transition from cratonic to orogenic lithosphere. To investigate the processes involved in the contrasting behavior of the upper crust, we provide 23 new apatite fission track (AFT) ages and thermal histories from the northern segment of the AROS and from the eastern area of the SFC. The AFT ages range from 154.4 ± 20.1 and 37.1 ± 3.0 Ma and the mean track lengths range from 10.9 and 13.2 μm. We compiled thermal information from previous thermochronological analysis from 357 sites and constructed inverse distance weighted maps that depict the spatial distribution of AFT ages and the temperature evolution from 360 to 30 Ma. The results indicate that the SFC experienced its final exhumation within the apatite partial annealing zone (APAZ) at temperatures ranging from 110 °C to 60 °C during the late Paleozoic. In contrast, the AROS went through its last cooling within the APAZ during the Mesozoic or even in the Cenozoic. This suggests that reactivation and reheating, possibly associated with the South Atlantic rift, influenced the orogenic basement of the passive margin. We highlight that the reheating associated to the Abrolhos magmatic province in the northern segment of the AROS caused the youngest AFT ages of the study area. Our work demonstrates the importance of considering contrasting rheology when analyzing regional exhumation patterns, the structural fabric of orogens through reactivation of crustal discontinuities generating heating and exhumation, and how volcanism can disrupt the thermal record, inducing crustal reheating.

Contrasting thermal histories in the Dom Feliciano Belt triggered by magmatism related to the Paraná-Etendeka LIP and fracture zone proximity

The present-day southern Brazilian continental margin rests on top of the Dom Feliciano Belt (DFB) and adjacent cratons. This belt formed through the collision of the Rio de La Plata, Kalahari, Paranapanema, Congo and Luis Alves paleoplates in the Neoproterozoic. Several low-temperature thermochronology works were executed in the area, although none of them demonstrated how the basement temperature of the entire DFB evolved through time. To this end, this work aims to provide new Apatite Fission Track (AFT) and Apatite (UTh)/He (AHe) ages for samples collected in the Catarinense Shield, in the northern DFB, and to perform inverse modeling in those samples. Besides, the collection of the basement temperature of 128 locations across the entire belt and adjacent cratons provided thermal information to create inverse-distance weighted interpolation maps documenting the progression of the temperature from 360 to 30 Ma. New AFT ages range from 126.6 ± 24.1 to 60.3 ± 6.03 Ma, whereas AHe ages span from 153.0 ± 9.2 to 62.5 ± 3.7 Ma. Mean track lengths are short to medium, suggesting complete thermal annealing of apatite crystals. Apatite single-grain eU concentration range from 4.5 to 96 μg/g and display a sparse correlation with AHe ages. Interpolation maps evidence a contrasting temperature evolution of the northern DFB and bordering cratons relative to the southern segment and surrounding cratons. Near-surface exposure of the basement in the northern segment was possibly much earlier than in the south, followed by partial burial by the sedimentary successions of the Paraná Basin. The emplacement of volcanic rocks of the Paraná-Etendeka Large Igneous Province and associated dyke swarms and alkaline volcanic plugs related to the Florianópolis Fracture Zone raised and sustained higher basement temperatures until 30 Ma, resetting low-temperature thermochronometers in the northern DFB, which was minor to absent in the southern DFB.

Prolonged post-orogenic extension in the southeastern Canadian Cordillera: Miocene reactivation of the Columbia River Fault

Post-orogenic extension in the southeastern Canadian Cordillera manifested in the form of metamorphic core complexes exhumed during the Paleocene–Eocene, but new thermochronology data suggest this interval may be longer. The Columbia River Fault is a brittle-ductile normal fault bounding the eastern margin of the Monashee Complex, southeastern British Columbia. Vertical motions along this fault are investigated here using apatite fission-track and (U-Th)/He thermochronology and samples from two elevation profiles. Apatite fission track ages range from 29.3 to 17.7 Ma, and apatite (U-Th)/He ages range from 26.6 to 7.0 Ma. Inverse thermal history modeling of these profiles suggests the footwall underwent rapid cooling between 18 and 16 Ma, whereas the hanging wall experienced more protracted cooling since 40 Ma, with two small cooling pulses at 20 and 10 Ma. These new data suggest the Columbia River Fault was reactivated in the early Miocene and continued to exhume the Monashee Complex an additional ∼2 km. Combining all thermochronology data from the region suggests three phases of accelerated cooling in the Monashee Complex; 1) Eocene (56–40 Ma); 2) Miocene (20–16 Ma); and 3) Pliocene to recent. Thermal history modeling of thermochronometric data reported from elevation profiles from across the wider region of the southern Canadian Cordillera find early Miocene cooling phases contemporaneous with that seen along the Columbia River Fault. This widespread exhumation coincides with early Miocene plate tectonic reorganization of the Pacific-North American margin which resulted in increased transtension in northwestern North America. We propose that the early Miocene reactivation of the Columbia River Fault is a splay fault associated with dextral strike slip faulting along the Rocky Mountain Trench, driven by an increase in transtensional stresses along the Pacific-North American plate boundary. Building on earlier models, pre-existing gravitational instabilities in the southeastern Canadian Cordillera aided in lateral extension of the upper crust along unstable inherited structures throughout the Shuswap Metamorphic Core Complex

A two phase escarpment evolution of the Red Sea margin of southwestern Saudi Arabia. Insights from low-temperature apatite thermochronology

Rifting of the Red Sea resulted in the formation of one of the highest escarpments on our planet: the Great Escarpment of southwestern Saudi Arabia. Published low-temperature geochronology ages are around the Paleogene-Neogene transition, but geomorphic features like the height, the steepness and the preservation of the escarpment may indicate a younger aspect to the exhumation history. Here we use apatite fission track (AFT) and (U-Th-Sm)/He (AHe) cooling ages in combination with a geomorphic analysis of the region from Jeddah to Jizan to test this idea. Pooled AFT ages range from 352.1±17.6 to 13.2±1.7 Ma (1σ). The base of the AFT partial annealing zone prior to rock uplift is at ∼200 m elevation in most of the studied area, but track length data show that the amount of exhumation is insufficient to affect all coastal plain samples. Consistent with earlier estimates in the literature, the total amount of rock uplift is estimated to be ∼4 km. Single grain AHe ages range from 264.5±19.6 to 2.8±0.3 Ma (1σ) and do not have a clear trend with distance from the escarpment. Overall, the distribution of data appears to indicate widespread downwearing of the elevated topography around the rift flank. In contrast, geomorphic analysis that indicates escarpment retreat including a flexural uplift response. We suggest that the conflict between geomorphological and geochronological data can be resolved by invoking a two-stage erosion model. The first stage involved dome-shaped rift flank uplift since initiation of the Afar plume, downwearing of this topography and cooling recorded by the AFT ages. The second stage involved the massive erosion that excavated the present day Saudi escarpment and reset the AHe ages. We suggest that this second stage is related to the formation of oceanic lithosphere since 13 Ma in the Red Sea, associated downwarping of the margin and flexural updoming of the eastern rift flank. The consequential orographic precipitation initiated asymmetric erosion and formation of a retreating escarpment. This model is consistent with the large age difference between Miocene AFT and Pliocene AHe ages and the geomorphic metrics.

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 two-phase topographic growth of the northeastern Tibetan Plateau derived from two thermochronologic transects across the southern Qilian Shan thrust belt

The formation of high topography on the northeastern margin of the Tibetan Plateau (the Qilian Shan) constrains the evolutionary history of the plateau. Although prominent exhumation occurred in the middle–late Miocene, the time at which deformation and relief development began in the Qilian Shan during the Cenozoic remains highly debated. Here, we use low-temperature thermochronology to reveal the histories of topographic growth in the Qilian Shan. Two transects were sampled in two primary thrust belts (Qaidam Shan and Danghenan Shan) in the southern Qilian Shan. New apatite fission track ages range from 16.6 to 113 Ma, and apatite (U-Th)/He ages range from 8.4 to 63.5 Ma. Age–elevation relationships and thermal modeling show enhanced rock exhumation in the late Paleocene–early Eocene and middle–late Miocene in both transects. The results indicate two pulses of enhanced thrusting on the major thrust belts in the southern Qilian Shan in the late Paleocene–early Eocene and middle–late Miocene. Our findings imply an early Cenozoic onset of topographic growth in the northeastern Tibetan Plateau, which was quasi-synchronous with the India–Asia collision.

The preservation mechanism of the Duolong ore district in northwest Tibet: Evidence from the low temperature thermochronological study

The Early Cretaceous Duolong porphyry-epithermal copper ore district is one of the largest copper ore districts in the central Tibetan Plateau. In order to investigate the preservation mechanism of Early Cretaceous porphyry-epithermal mineralization, new apatite and zircon fission track dating and (U-Th)/He dating of pre-ore sandstone, ore-related and barren intrusive rocks, and post-ore igneous rock, thermal modeling together with previous thermochronological data of the Duolong ore district were combined to study the burial and exhumation processes. Apatite fission track ages range from 68 ± 4 to 40 ± 4 Ma, with mean track lengths varying from 12.1 ± 2.0 to 12.8 ± 2.4 μm. Zircon fission track ages range from 106 ± 4 to 86 ± 4 Ma. In addition, apatite (U-Th)/He yields average age ranging from 62.7 ± 4.2 to 22.6 ± 1.2 Ma, and zircon (U-Th)/He yields average age of 112.3 ± 5.1 Ma. The thermal modeling shows that the Duolong ore district experienced two periods of exhumation and two stages of burial. The first period of exhumation with rate of 0.14 km/m.y. took place immediately after the ore formation which caused the erosion of orebody. Two periods of burial are thought to be related to northeast-southwest striking fault and thrust nappe structure induced by Lhasa-Qiangtang collision between 110 and 65 Ma when the overlying rocks of orebodies were thickened to 4 km. The last period of exhumation with rate of 0.062 km/m.y. (since 65 Ma) is attributed to lithospheric delamination related to India-Asia collision. The preservation of the Duolong ore district mainly benefited from the burial related to the Lhasa-Qiangtang collision. The exhumation and uplift of Duolong ore district was mainly attributed to the India-Asia collision since Paleocene.

Late Neoproterozoic-to-recent long-term t–T-evolution of the Kaoko and Damara belts in NW Namibia

This research aims to reconstruct the Late Neoproterozoic-to-recent long-term time–temperature-evolution of the NW Namibian Kaoko and Damara belts combining numerical modeling of new thermochronological data with previously published geochronological data, i.e., U–Pb, Sm–Nd, and Rb–Sr analyses, and K/Ar, 40Ar/39Ar low-temperature thermochronology. Consequently, we retrieve a coherent long-term time–temperature-evolution of the NW Namibian Neoproterozoic basement rocks including rates of exhumation and subsidence periods over the last ~ 500 Myr. Neoproterozoic basement rocks indicate fast post-Pan African/Brasiliano cooling and exhumation, reheating, or rather subsidence during the development of the Paleozoic-to-Mesozoic SW Gondwana intraplate environment and a significant thermal overprint of the rocks during South Atlantic syn- to post-rift processes, and therefore, resemble the opponent SE Brazilian time–temperature-evolution. We provide an overview of thermochronological data including new apatite and zircon fission-track data derived from Neoproterozoic, Late Paleozoic, and Lower Cretaceous rocks. Apatite fission-track ages range from 390.9 ± 17.9 Ma to 80.8 ± 6.0 Ma in the NW Kaoko Belt with youngest ages confined to the coastal area and significant age increase towards the inland. New zircon apatite fission-track data reveal ages between 429.5 ± 47.8 and 313.9 ± 53.4 Ma for the rocks of the Kaoko Belt. In the central Damara Belt, new apatite fission-track ages range between 138.5 ± 25.3 Ma to 63.8 ± 4.8 Ma. Combined apatite fission-track age distributions from Angola to Namibia and SE Brazil correlate for both sides of the South Atlantic passive continental margin and the reset AFT ages overlap with the lateral Parana–Etendeka dike swarm distribution.

Mesozoic–Cenozoic thermal evolution of the Linqing Sub‐basin, Bohai Bay Basin (eastern North China Craton): Constraints from vitrinite reflectance data and apatite fission track thermochronology

The Linqing Sub‐basin is situated in the south‐west of the Bohai Bay Basin (BBB), which is the centre of lithospheric destruction and thinning of the eastern North China Craton (NCC). It is also one of China's premier hydrocarbon‐bearing basins. To better understand the Mesozoic–Cenozoic thermal history of the Linqing Sub‐basin, 178 vitrinite reflectance (Ro) data from nine wells and six apatite fission track (AFT) ages have been used. The effective AFT ages range from 53.5 to 107.7 Ma, with mean track lengths of 10.6 μm, recording the tectonic–thermal events from the Early Cretaceous to the Palaeogene. The thermal modelling results of AFT show that the Linqing Sub‐basin experienced two rapid cooling events during the Late Cretaceous (100–70 Ma) and Middle Eocene–Miocene (40–20 Ma), respectively, which are closely related to the subduction and rollback of the Pacific Plate. The thermal modelling results of Ro indicate that the Linqing Sub‐basin has experienced two heat flow peaks during the Early Cretaceous and the Palaeocene–Late Eocene, with the heat flow values of 80 and 86 mW/m2, respectively. These heat flow values were consistent with the destruction peak of the North China Craton and the extension peak of the Bohai Bay Basin. The Carboniferous source rocks experienced a large‐scale hydrocarbon generation stage from the early Mesozoic to the Late Cretaceous and the Shahejie 3 Formation source rocks from the Middle Eocene to the Late Oligocene. Our study provides new geothermal evidence for the process of the destruction of the North China Craton.

New Evidence of ‘Anomalous' Vertical Movements along the Hinterland of the Atlantic NW African Margin

AbstractLow‐temperature thermochronology studies revealed major exhumation events affecting domains in the hinterland of the Central Atlantic margins, where Palaeozoic and/or Precambrian basement is exposed. Thus, domains traditionally assumed to be stable since at least the Variscan and juxtaposed to subsiding Meso‐Cenozoic basins, appear to be affected by km‐scale vertical movements during the Atlantic rifting and after the Early Jurassic breakup in the Central Atlantic. In this contribution, we investigate the extent and the magnitude of these motions along the NW African margin by presenting the first low‐temperature thermochronology data from west Mauritania. The analysed 22 samples were collected along the Mauritanides, a N‐S trending Variscan Belt separating the cratonic Taoudeni Basin in the east from the Atlantic coastal basin in the west. The obtained apatite fission track (AFT) ages range between 236 and 90 Ma, with mean track lengths between 11.22 and 12.81 μm and Dpar comprised between 1.6 and 2.1 μm. The uncorrected (U‐Th‐Sm)/He (AHe) ages vary between 261 and 33 Ma. Inverse thermal modelling of the AFT and AHe data indicates that the hinterland of the Mauritanian Atlantic margin experienced (i) burial between the Permian and the Late Triassic, (ii) km‐scale exhumation during Middle‐Late Jurassic and Early Cretaceous, (iii) burial during the Palaeogene–early Miocene, and (iv) exhumation between mid‐Miocene and present‐day. We argue that these vertical movements are primarily driven by the tectonic evolution of the Atlantic rift and the subsequent geodynamic evolution of the Central Atlantic Ocean and the African plate.

Late Mesozoic and Cenozoic tectono-thermal history and geodynamic implications of the Great Xing’an Range, NE China

The Mesozoic–Cenozoic tectonics of Northeastern China involves complex multistage interaction of different tectonic domains and has long been controversial. The tectono-thermal evolutionary history recorded by the widespread outcropped granitoids in the Great Xing’an Range (GXR) may provide significant constraints on the tectonics, illuminating the deep geodynamic process. Here, we present new low-temperature thermochronology data from the GXR, and thus, reconstruct the detailed thermal history. Zircon fission-track dating yielded a group of central ages ranging from 80 ± 4 to 185 ± 10 Ma, while apatite fission-track ages range from 55 ± 3 to 75 ± 5 Ma. The modeled time–temperature paths of all the samples reveal two relatively rapid cooling events at ~100–60 Ma and ~50–0 Ma, and one intervening reheating episode at ~60–50 Ma. The initial uplift, exhumation, and induced cooling events, which represent strong orogenic activity, are related mainly to closure of the Mongol–Okhotsk Ocean in the north and were subsequently influenced by the Paleo-Pacific plate subduction in the east. The evolution of the basin–mountain system consisting of the Songliao Basin and GXR, as well as the accretion, metamorphism, and magmatism at the Northeast Asian continental margin, are all dominated or indirectly influenced by the Paleo-Pacific subduction. This indicates that the Paleo-Pacific subduction had affected the evolution of the GXR to the west since the Jurassic. The significant reheating episode during the Late Paleocene to Eocene may be related to the heat flux derived from asthenosphere upwelling and igneous activity.

Low-temperature thermochronology of the Carlin-type gold deposits in southwestern Guizhou, China: Implications for mineralization age and geological thermal events

The Dian-Qian-Gui area in southwestern China is the second-largest concentration of the Carlin-type gold deposits in the world, and the southwestern Guizhou is the most important gold-producing district of the Dian-Qian-Gui area. Dating of the Carlin-type gold deposits is always a challenge due to the lack of ore-stage minerals which are suitable for conventional radiometric dating. Low-temperature thermochronometers, including fission track and (U-Th)/He, are temperature-sensitive radiometric dating techniques and have been successfully applied to elucidate many aspects of ore deposits, including the timing and duration of mineralization processes.In this study, zircon fission track, zircon (U-Th)/He and apatite fission track dating techniques were applied to the Carlin-type gold deposits in southwestern Guizhou. Samples for zircon and apatite analyses were collected from mineralized or altered sedimentary rocks in Shuiyindong, Taipingdong, Bojitian, Yata and Getang gold deposits. Four groups of thermochronological ages were obtained, i.e., 192–216 Ma, 132–160 Ma, 88 Ma, and 19–40 Ma, which are considered to be the records of four geological thermal events. Of them, most zircon fission track ages and all zircon (U-Th)/He ages concentrate in 132–160 Ma. Thermochronological constraints, combined with field relationships, suggest that the mineralization of the Carlin-type gold deposits in southwestern Guizhou most likely occurred in this period. Partial zircon fission track ages are in 192–216 Ma. They may record the cooling timing of a pre-ore thermal event caused by the Indosinian orogeny, which is supported by the paleogeotemperature restoration. A few zircon grains with high U content yield fission track age of 88 Ma, which may record a post-ore thermal event associated with the intrusion of local mafic dykes. All apatite fission track ages range in 19–40 Ma, which may record a lower temperature but extensive hydrothermal superimposition in the Cenozoic. Additionally, a corresponding relationship between zircon fission track ages and stratigraphic sequences was identified in the Huijiabao anticline, which is considered to reflect the decrease of temperature and duration of ore-forming hydrothermal activity from lower to upper stratigraphic sequences.

New insights into the Gondwana breakup at the Southern South America by apatite fission-track analyses

Abstract. Apatite fission-track (AFT) analyses, applied to Southern Brazil and Uruguay samples, was employed aiming to understand the low temperature history of the Dom Feliciano Belt Segment. The Dom Feliciano Belt formed during the Neoproterozoic to Early Paleozoic, linked to the Brasiliano/Pan-African Orogeny. Twenty-four samples were dated, and confined track lengths of twenty samples were measured. The spatial distribution of ages shows three domains with different evolution cut by shear zones and, or suture zones in the Dom Feliciano Belt. The Western Domain exhibits AFT ages > 250 Ma (Permian to Devonian) while the Eastern Domain shows AFT ages < 230 Ma (Paleogene to Triassic). In the Central Domain, the AFT ages range from ∼196 to 130 Ma (Jurassic to Early Cretaceous). The thermal modeling in the domains revealed a complex evolution, with cooling and reheating phases, and a denudation of ∼2600 m. The AFT ages clearly postdate the Gondwanide, Paraná-Etendeka and Rio Grande Cone exhumation history of the Dom Feliciano Belt.

Tectono-Thermal Evolution and Morphodynamics of the Central Dronning Maud Land Mountains, East Antarctica, Based on New Thermochronological Data

The lack of preserved Mesozoic–Cenozoic sediments and structures in central Dronning Maud Land has so far limited our understanding of the post-Pan-African evolution of this important part of East Antarctica. In order to investigate the thermal evolution of the basement rocks and place constraints on landscape evolution, we present new low-temperature thermochronological data from 34 samples. Apatite fission track ages range from 280–85 Ma, while single-grain (U-Th)/He ages from apatite and zircon range from 305–15 and 420–340 Ma, respectively. Our preferred thermal history models suggest late Paleozoic–early Mesozoic peneplanation and subsequent burial by 3–6 km of Beacon sediments. The samples experienced no additional burial in the Jurassic, thus the once voluminous continental flood basalts of western Dronning Maud Land did not reach central Dronning Maud Land. Mesozoic–early Cenozoic cooling of the samples was slow. Contrary to western Dronning Maud Land, central Dronning Maud Land lacks a mid-Cretaceous cooling phase. We therefore suggest that the mid-Cretaceous cooling of western Dronning Maud Land should be attributed to the proximity to the collapse of the orogenic plateau at the Panthalassic margin of Gondwana. Cooling rates accelerated considerably with the onset of glaciation at 34 Ma, due to climate deterioration and glacial denudation of up to 2 km.

Evolution of the Southwestern Angolan Margin: episodic burial and exhumation is more realistic than long-term denudation

There are two main points of view regarding how continental margins evolve. The first one argues that the present-day margins have been developed by long-term denudation since a major exhumation episode, probably driven by rifting or another relevant tectonic event. The second one argues that continental margins underwent alternating burial and exhumation episodes related to crustal tectonic and surface uplift and subsidence. To demonstrate that the proximal domain of the southwestern Angolan margin has evolved in a polycyclic pattern, we present a review of geological and thermochronological information and integrate it with new combined apatite fission-track and (U-Th)/He data from Early Cretaceous volcanic and Precambrian basement samples. We also provide hypotheses on the possible mechanisms able to support the vertical crustal movements of this margin segment, which are also discussed based on some modern rifting models proposed for Central South Atlantic. The central apatite fission-track ages range from 120.6 ± 8.9 to 272.9 ± 21.6 Ma, with the mean track lengths of approximately 12 µm. The single-grain apatite (U-Th)/He ages vary between 52.2 ± 1 and 177.2 ± 2.6 Ma. The integration of the thermochronological data set with published geological constraints supports the following time-temperature evolution: (1) heating since the Carboniferous–Permian, (2) cooling onset in the Early Jurassic, (3) heating onset in the Early Cretaceous, (4) cooling onset in the Mid- to Late Cretaceous, (5) heating onset in the Late Cretaceous, and (6) cooling onset in the Oligocene–Miocene. The thermochronological data and the geological constraints, support that the proximal domain of the southwestern Angolan margin was covered in the past by pre-, syn-, and post-rift sediments, which were eroded during succeeding exhumation events. For this margin segment, we show that a development based on long-term denudation is less realistic than one based on burial and exhumation episodes during the last 130 Myr.

Mesozoic and Cenozoic thermal history of the Western Reguibat Shield (West African Craton)

AbstractUsing low‐temperature thermochronology on apatite and zircon crystals, we show that the western Reguibat Shield, located in the northern part of the West African Craton, experienced significant cooling and heating events between Jurassic and present times. The obtained apatite fission track ages range between 49 and 102 Ma with mean track lengths varying between 11.6 and 13.3 μm and Dpar values between 1.69 and 3.08 μm. Zircon fission track analysis yielded two ages of 159 and 118 Ma. Apatite (U–Th)/He uncorrected single‐grain ages range between 76 and 95 Ma. Thermal inverse modelling indicates that the Reguibat Shield was exhumed during the Early Cretaceous, Late Cretaceous, Palaeocene–Eocene and Quaternary. These exhumation events were coeval with regional tectonic and geodynamic events, and were probably driven by a combined effect of plate tectonics and mantle dynamics.

Mesozoic and Cenozoic tectono-thermal reconstruction of the western Bohai Bay Basin (East China) with implications for hydrocarbon generation and migration

Studies on the tectono-thermal evolution of the western Bohai Bay Basin (WBBB), including the Jizhong Sub-basin and Cangxian Uplift, are important for further petroleum exploration and exploitation. This study aims to reconstruct the tectono-thermal history of the WBBB based on a combination of 125 vitrinite reflectance (Ro) data and seven apatite fission track (AFT) and nine apatite (U-Th)/He (AHe) ages. The effective AFT ages range from 60.3 to 97.0Ma, with mean track lengths of 10.86–12.64μm. The variable single-grain AFT ages are explained to be due to the parameter Dpar. The effective AHe ages range from 21.1Ma to 75.0Ma. Two rapid cooling events revealed by the thermal modeling results occurred during the Early-Late Cretaceous (130–90Ma) and Late Eocene-Early Miocene (40–18Ma), respectively. The Fuping Complex, which is located in the western margin of the WBBB and mainly composed of the Paleo-proterozoic high-grade gneisses, experienced the intensive extension-detachment during the Early-Late Cretaceous along with the subduction of the Izanagi Plate, that was probably responsible for the first cooling event. The second cooling event was caused by the subduction of the Pacific Plate during the Middle Eocene-Early Miocene (43–23Ma), as well as the collision of the Indian and Eurasian Plates and the rollback of the subducting Pacific Plate during the Early Miocene (23–18Ma). The WBBB experienced two heat flow peaks of ∼75 and ∼80mW/m2 during the Early Cretaceous and the Late Eocene, respectively. During the Late Eocene-Early Miocene, rapid subsidence in the Baxian Depression (one secondary tectonic unit of the Jizhong Sub-basin) coupled with the rapid uplift in the Cangxian Uplift caused the Shahejie Formation of the middle-upper Eocene to generate gas during the Early Miocene. Meanwhile, tectonic movement during the Early Miocene also caused faults to become migration paths, as revealed by the homogenization temperature of the fluid inclusion. This study provides new insights regarding the tectonic and hydrocarbon evolution of the WBBB.

South Menderes Monocline: Low-temperature thermochronology constrains role of crustal extension in structural evolution of southwest Turkey

We report apatite and zircon fission-track data across the contact zones between the Menderes nappes, the Cycladic blueschist unit, and the Ören nappe, in the Anatolide belt of southwest Turkey. These data resolve previous debate on the deformation history of these Cretaceous to Eocene nappe contacts, including whether they were reactivated during late Oligocene to Miocene crustal extension. Apatite fission-track ages range from 18 to 28Ma in the Menderes nappes, and 31 to 42Ma in the Ören nappe. Zircon fission-track ages are 29 to 31Ma in the Menderes nappes, 30 to 33Ma in the Cycladic blueschist unit, and between 93Ma and 129Ma in the Ören nappe. The data reveal that the tectonic contacts within the Menderes nappes, and with the overlying Cycladic blueschist unit have been sealed since ~35–30Ma. In the Ören nappe, zircon fission-track ages are distinctly older (with mixed single grain ages between ~300 and 75Ma) reflecting partial to full resetting during late Cretaceous high-pressure metamorphism. The contact between the Cycladic blueschist unit and the Ören nappe shows no significant tectonic movement in the brittle crust after ~70Ma. These data reveal that the nappe boundaries in the southern Menderes Massif have undergone no significant differential offset relative to the Earth's surface since the Oligocene and therefore were not reactivated during late Oligocene to Miocene continental extension. We interpret the steeply dipping portion of the nappe pile in the southern Menderes Massif as a tilted crustal section, which we name the ‘South Menderes Monocline’. We speculate this monocline formed by differential uplift in the Miocene, either at the hinge zone of a plateau, or by unloading of the Simav detachment footwall.