Low-temperature Thermal History Research Articles

Late Oligocene to Pleistocene thermo-tectonic evolution of the Karakoram Fault Zone: New insights from basement and detrital apatite fission track thermochronology

The Karakoram Fault Zone displays distinctive topographic and tectonic characteristics, with intricate river drainage systems. Although there are extensive thermochronological datasets for the western Tibetan Plateau, limited investigations have been carried out to uncover the low-temperature thermal history of the Karakoram Fault Zone, which connects the Lhasa terrane with the Pamir. In this contribution, apatite fission track (AFT) thermochronology was conducted on 13 basement and 4 conglomerate samples collected from the western Gangdese batholith and the Ayi Mountain Range, on either side of the Karakoram fault. Inverse thermal history modeling results reveal that the western Gangdese batholith experienced two stages of rapid basement cooling at 27–23 Ma (late Oligocene-early Miocene) and 16–4 Ma (middle Miocene-Pliocene). The adjacent Ayi Mountain Range experienced cooling in the late Miocene (∼8 Ma) and during the Pliocene to Pleistocene (4–1 Ma). We suggest that tectonic forces associated with rollback and lateral break-off of the Indian continental lithosphere, and the dextral strike-slip activity of the Karakoram fault were responsible for the first cooling phase. The second accelerated cooling phase was due to the deep fragmentation of the Indian slab, the activity of the Karakoram normal fault, and associated ∼E-W extension. Additionally, since the late Oligocene, the Indus River incision has likely also contributed to the exhumation of the western Tibetan Plateau. Subsequently, the western Gangdese batholith reached high elevations, resulting in the reversal of the Yarlung River. The dextral-normal motion of the Karakoram fault, which is still active today, was the main cause of the Pliocene to Pleistocene accelerated cooling detected in the Ayi Mountain Range.

Apatite Triple Dating (Lu–Hf, U–Pb, FT) Constrains Deformation and Cooling in the Coompana and Madura Provinces, Western Australia

Abstract Combined apatite Lu–Hf, U–Pb, and fission track (AFT) triple dating affords the opportunity to investigate the ~60 and 730°C thermal history of a study area. Here, we apply apatite triple dating to resolve the tempo of multiple thermo-tectonic events within the Precambrian basement rocks of the Coompana (COP) and Madura (MAP) Provinces, Western Australia. Apatite Lu–Hf dates for the western COP (~1.52 Ga) and MAP (~1.36 Ga) agree with published Mesoproterozoic magmatic crystallization ages. Younger apatite U–Pb dates (~1.16–1.12 Ga) for the western COP and MAP suggest isotopic decoupling and radiogenic-Pb loss by volume diffusion in response to metamorphism at that time. Further East in the COP, the apatite Lu–Hf, and U–Pb dates are within uncertainty of each other and are interpreted to reflect recrystallization at ~1.20–1.14 Ga, coinciding with the late Mesoproterozoic Maralinga thermomagmatic event. The imprints of such an event were more pervasive towards the eastern COP, resulting in a thermally weakened crust in this area. AFT results constrain the subsequent Phanerozoic low-temperature history which has contrasting thermal trajectories on either side of the Mundrabilla Shear Zone (MSZ). Thermal history modeling suggests an early Carboniferous rapid cooling pulse (~360–330 Ma) for the COP, east of the MSZ, that is contemporaneous with the intraplate Devonian–Carboniferous Alice Springs Orogeny. In contrast, the MAP, west of the MSZ, records a protracted monotonic cooling history since the Middle Devonian, implying long-term crustal stability. The differences in low-temperature thermal histories may be preconditioned by the extent of thermal weakening during the late Mesoproterozoic, as indicated by the Lu–Hf and U–Pb results. Here, we show the value of apatite triple dating applied to grains recovered from drill core samples, demonstrating opportunities for understanding other poorly accessible terranes.

Several Problems in Low-Temperature Thermal History Modeling

Thermal history modeling based on low-temperature thermochronological data is widely used in the study of geology. Despite its common applications, several problems remain easy to ignore yet should not be overlooked in the execution of such models. This paper describes four key problems of thermal history modeling, namely, (1) is the best-fit thermal history the best? (2) Is the date constraint box a suitable constraint? (3) Does the bimodal distribution of the apatite fission track confined track length absolutely correspond to the cooling reheating model? (4) Is the whole thermal history path credible? Counterexamples are then provided to stress the importance of accounting for these problems in the application of thermal history modeling. Acknowledging the uncertainty and considering the geological constraints are recommended to improve the accuracy of thermal history models. Moreover, thermal historical intervals with high credibility and strong constraint ability are recommended to interpret the selected geological phenomenon.

Duluth Complex FC1 Apatite and Zircon: Reference Materials for (U‐Th)/He Dating?

The accuracy and validation of geo‐ and thermochronological dating hinges on the availability of well‐characterised age reference materials. The Mesoproterozoic gabbroic anorthosite FC1 from the Duluth Complex, Minnesota is a reference material for zircon U‐Pb and a suggested reference material for apatite fission‐track dating. We evaluate FC1 as (U‐Th)/He reference material, and determine its apatite U‐Pb, and zircon and apatite (U‐Th)/He age. Our dating results constrain the thermal history of FC1, showing that fast cooling occurred between ~ 1099 and 1040 Ma from ≥ 600 °C to ~ 200 °C. The zircon (U‐Th)/He data from air‐abraded grains give a robust isochron age of 1037 ± 25 Ma (2s) without overdispersion. The within‐grain homogeneity of U and Th, the availability of FC1 zircon, and the absence of radiation‐damage effects on the (U‐Th)/He age support its use as reference material. Unabraded zircon grains give lower and more dispersed ages, highlighting the usefulness of air abrasion to control for α‐ejection in (U‐Th)/He dating. Our apatite (U‐Th‐Sm)/He single‐grain ages vary between 180 and 300 Ma. Their wide dispersion argues against the use of FC1 apatite as (U‐Th‐Sm)/He reference material and makes the interpretation of their low‐temperature thermal history complicated.

The Process of Tectonic Inversion and Disintegration in the Dasanjiang Unified Basin, Northeast China: Constraint From Low-Temperature Thermochronology

The Dasanjiang basin group in Northeast China contains more than ten Mesozoic–Cenozoic sedimentary basins. Much evidence shows that they were a unified large-scale depression lacustrine basin in the Early Cretaceous; however, destruction processes and mechanisms after the formation of the unified lacustrine basin are some of the key issues restricting basic research and oil and gas exploration in the Dasanjiang area. In this study, we carried out low-temperature thermochronology and thermal history inversion on samples from the main basins in the Dasanjiang area to finely restore the destruction process of the unified basin. The results show that since the Early Cretaceous, the Dasanjiang area has experienced three major positive tectonic inversions: 100 Ma~90 Ma, 73 Ma~40 Ma, and 23 Ma~5 Ma. The unified basin was destroyed by compression and uplift and gradually disintegrated. The basin gradually changed from initial unified evolution to differential evolution and finally formed the isolated appearance of each basin. The aforementioned three-stage positive tectonic inversion time limits basically corresponded to the changing periods in the movement direction, subduction angle, and movement speed of the paleo–Pacific Ocean plate. It is believed that the movement and reorganization events of the plates on the Pacific side dominated the formation, destruction, and disintegration of the Dasanjiang prototype basin, which was the main dynamic mechanism of the tectonic evolution of the Mesozoic and Cenozoic basins in the study area and Northeast China.

Exhumation history of late Mesozoic intrusions in the Tongling–Xuancheng area of the Lower Yangtze region, eastern China: Evidence from zircon (U–Th)/He and apatite fission track thermochronology

The Lower Yangtze region is one of the most important metallogenic belts in eastern China, yet there are few precise low-temperature geochronological data to constrain the evolution of the orefield. We collected samples from 12 late Mesozoic intrusions in the Tongling–Xuancheng area for zircon (U–Th)/He (ZHe) and apatite fission track (AFT) dating. These intrusions are divided into early and late periods on the basis of their emplacement ages. The ZHe and AFT ages of the early intrusions are 144.6–111.0 Ma and 123.1–89.4 Ma, respectively, and those of the late intrusions are 119.9–71.3 Ma and 96.7–66.9 Ma, respectively, with rare outliers. The ZHe and AFT age distributions and the modeled low-temperature thermal histories of these intrusions reveal that the Tongling–Xuancheng area underwent three stages of rapid cooling: during the earliest, middle, and end of the Early Cretaceous. During the earliest Early Cretaceous, rapid cooling resulted from regional compression and in situ cooling of magma. The middle Early Cretaceous phase of cooling occurred in a regional extensional regime characterized by the development of large rift basins and the emplacement of intrusions. The rapid cooling at ~ 100 Ma was concurrent with a global plate reorganization event that resulted in regional basin inversion and the development of unconformities between the Lower and Upper Cretaceous strata in East Asia. Although Cenozoic uplift is not seen in the cooling paths of our samples, regional compression since the Paleogene has uplifted the orebodies to near-surface level, favoring ore exploration and mining.

Footprints of the Alice Springs Orogeny preserved in far northern Australia: an application of multi-kinetic thermochronology in the Pine Creek Orogen and Arnhem Province

The Precambrian Pine Creek Orogen and Arnhem Province represent two of the oldest basement terrains in northern Australia and are often considered to be devoid of significant regional deformation since the cessation of regional metamorphism in the Paleoproterozoic. A major caveat in the current hypothesis of long-lived structural inactivity is the absence of published low-temperature thermochronological data and thermal history models for this area. Here we report the first apatite fission track and (U–Th–Sm)/He data for crystalline samples from both the Pine Creek Orogen and Arnhem Province, complemented with apatite geochemistry data acquired by electron microprobe and laser ablation mass spectrometry methods, and present multi-kinetic low-temperature thermal history models. The thermal history models for the Pine Creek Orogen and Arnhem Province reveal a distinct phase of denudation coeval with the Paleozoic Alice Springs Orogeny. By integrating with previous studies, we suggest that this event deformed a larger area of the Australian crust than previously perceived. Localized Mesozoic thermal perturbations proximal to the Pine Creek Shear-Zone additionally record evidence for Mesozoic reheating contemporaneous with mantle-induced subsidence and the onset of sedimentation in the Money Shoal Basin, while the Arnhem Province samples demonstrate no evidence of Mesozoic thermal perturbations. Supplementary Material: EPMA protocol comparison, AFT plots and modelling, additional geochemistry, datasets and instrumentation parameters are available at https://doi.org/10.6084/m9.figshare.c.5206664

Multistage exhumation of the Anjiayingzi gold deposit, northern North China Block: Geodynamic settings and exploration implications

Post-mineralisation exhumation is pivotal because of its strong effects on the preservation of ore deposit. The Jiguanzi quartz monzonite hosts the Anjiayingzi Au deposit at the centre of the Kalaqin Antiform (or Kalaqin metamorphic core complex) in the northern North China Block (NCB). We can link the exhumation of the deposit with regionally geodynamic events and evaluate its exploration implications using low-temperature thermochronology from the quartz monzonite host. Sericite 40Ar/39Ar dating of auriferous quartz-sulphide veins indicates that gold mineralisation timing is 130 ± 1 Ma. Zircon fission track ages of fresh samples from the host quartz monzonite vary from 118 ± 6 to 99 ± 4 Ma, and apatite fission track ages vary from 99 ± 6 to 66 ± 5 Ma. A four-stage post-mineralisation exhumation history is revealed by combining the binomial peak fitting of single-grain ages and low-temperature thermal history inverse modelling. The first exhumation event is dated at ca. 130–100 Ma, and characterised by the most rapid exhumation rate of 167 m/Ma and ca. 5 km rise. This movement is related to the top-to-NW and a SE ductile-brittle extensional deformation of the Kalaqin Antiform. Regionally, it is also contemporaneous with the formation of extensional metamorphic core complexes, development of basins, and increasing heat flow and decreasing thermal lithospheric thickness in the eastern NCB. All of these synchronous events can be linked to the back-arc setting of the subducting Izanagi Oceanic Plate and resulted geodynamic changes beneath the NCB. The relatively slow stage 2 exhumation, dated at ca. 100–65 Ma with an exhumation rate of 20 m/Ma, was triggered by the collision between the Izanagi Oceanic Plate and eastern China at ca. 100 Ma and following change in the drift direction of the Izanagi Oceanic Plate. Sedimentation of basins in the NCB was continuous during this period. Resumed stage 3 exhumation (ca. 65–45 Ma, 27 m/Ma) and synchronous sedimentary inversion are products of regional compression event related to the collision between India and the Eurasian plates. Change of the Pacific Oceanic Plate drifting direction at ca. 50 Ma finally induced the monotonic cooling and exhumation of stage 4 (19 m/Ma). The estimated post-mineralisation exhumation is ~7.1 km, and the ore-forming depth of the Anjiayingzi Au deposit is between 5.1 and 10.1 km. In combination with previously published data, the differential exhumation history, exhumation degree and preservation potential of major gold provinces in NCB are confirmed, which further indicate that their gold prospectivity must be assessed individually.

Meteorite cloudy zone formation as a quantitative indicator of paleomagnetic field intensities and cooling rates on planetesimals

Metallic microstructures in slowly-cooled iron-rich meteorites reflect the thermal and magnetic histories of their parent planetesimals. Of particular interest is the cloudy zone, a nanoscale intergrowth of Ni-rich islands within a Ni-poor matrix that forms below ∼350°C by spinodal decomposition. The sizes of the islands have long been recognized as reflecting the low-temperature cooling rates of meteorite parent bodies. However, a model capable of providing quantitative cooling rate estimates from island sizes has been lacking. Moreover, these islands are also capable of preserving a record of the ambient magnetic field as they grew, but some of the key physical parameters required for recovering reliable paleointensity estimates from magnetic measurements of these islands have been poorly constrained. To address both of these issues, we present a numerical model of the structural and compositional evolution of the cloudy zone as a function of cooling rate and local composition. Our model produces island sizes that are consistent with present-day measured sizes. This model enables a substantial improvement in the calibration of paleointensity estimates and associated uncertainties. In particular, we can now accurately quantify the statistical uncertainty associated with the finite number of islands acquiring the magnetization and the uncertainty on their size at the time of the record. We use this new understanding to revisit paleointensities from previous pioneering paleomagnetic studies of cloudy zones. We show that these could have been overestimated by up to one order of magnitude but nevertheless still require substantial magnetic fields to have been present on their parent bodies. Our model also allows us to estimate absolute cooling rates for meteorites that cooled slower than <10,000°CMy−1. We demonstrate how these cooling rate estimates can uniquely constrain the low-temperature thermal history of meteorite parent bodies. Using the main-group pallasites as an example, we show that our results are consistent with the previously-proposed unperturbed, conductive cooling at low temperature of a ∼200-km radius main-group pallasite parent body.

Tectonothermal history of the Holy Cross Mountains (Poland) in the light of low‐temperature thermochronology

AbstractThe low‐temperature thermal history of the Holy Cross Mountains (HCM) is investigated by apatite fission track and apatite and zircon (U–Th)/He thermochronology. Our results provide constraints on the deformation history of Palaeozoic basement rocks in the transition area from Precambrian to Palaeozoic Europe that are exposed from beneath Permian–Mesozoic sediments within the HCM. Late to post‐Variscan cooling of the Palaeozoic strata from maximum temperatures is shown to be a major feature of the HCM. This cooling likely followed a heating event related to burial and/or hot fluid circulation along the Holy Cross Fault in the late Carboniferous. The central part of the HCM shows a rapid cooling event caused by tectonic inversion, which started in the Late Cretaceous. However, this event was less pronounced in the western margin of the HCM, where slow cooling continued throughout the Mesozoic with only minor acceleration of the cooling rate since the latest Cretaceous.

Investigating the Paleozoic–Mesozoic low-temperature thermal history of the southwestern Canadian Arctic: insights from (U–Th)/He thermochronology

The Arctic Amerasia Basin, located between the Canadian margin and Alaska, formed by purported Jurassic–Cretaceous rifting related to the rotation of the Arctic Alaska – Chukotka microcontinent from northern Laurentia. Rifting may have been accompanied by rift shoulder uplift and cooling that is recorded in low-temperature thermochronometers. Furthermore, the southwestern Canadian Arctic has a widespread Devonian–Cretaceous unconformity with a poorly understood burial-unroofing history. We evaluate new zircon (U–Th)/He thermochronology (ZHe) and organic maturity (vitrinite reflectance (VRo)) data from Neoproterozoic strata of the Amundsen Basin, Cambrian strata of the Arctic Platform, and Devonian strata of the Franklinian Basin to help resolve the sedimentary thickness deposited and eroded during the time represented by the regional unconformity. ZHe and VRo models identify the thermal maximum occurring between the late Paleozoic – Mesozoic interval. Proximal to the rifted Canadian margin, models estimate 3.7–4.5 km of deposition between the Devonian–Cretaceous, in marked contrast to &lt;1 km towards the craton. Jurassic–Cretaceous exhumation is estimated at 2.3–3.5 km and is more uniform across the region. Although the magnitude of burial and erosion can be resolved by modelling, the timing of these events cannot be elucidated with confidence. The thermochronology models can be satisfied by either (1) late Paleozoic – early Mesozoic burial with a thermal maximum prior to Jurassic rifting, followed by cooling; or (2) Late Devonian maximum burial, with gradual unroofing until Cretaceous sedimentation. Although continued deposition into the Mesozoic towards the craton interior seems unlikely, it remains possible that there was continued deposition proximal to the rifted Canadian margin.

The evolution of eastern Sichuan basin, Yangtze block since Cretaceous: Constraints from low temperature thermochronology

In Yangtze block (South China), there is a well-developed Mesozoic thrust system extended through the Xuefeng and Wuling mountains in the southeast to the Sichuan basin in the northwest. We present 11 apatite fission-track (AFT) data and 11 (U–Th–Sm)/He ages to unravel the low temperature thermal history of a part of the system located in the eastern Sichuan basin. The fission-track data are interpreted using a grain-age deconvolution algorithm with inverse thermal modeling of track length, grain ages and mineral composition proxy data. Results suggest that apatite fission-track ages range between 99.3±8.1 and 51.0±4.0Ma, and the apatite (U–Th–Sm)/He ages between 58.3±3.5Ma and 14.2±0.9. The spatial distribution of these ages shows a trend decreased from SE to NW gradually, which supports the idea of a prolonged, steady-state rock uplift and erosion process across the eastern Sichuan basin. Thermal history modeling of the combined FT and (U–Th–Sm)/He datasets reveal a common three stage cooling history: (1) initial stage of rapid cooling that younger to the east during pre-Cretaceous, (2) following by a period of relative (but not perfect) thermal stability at ∼65–50°C, (3) and then a new rapid cooling stage that initiated in all samples between ∼15 and 20Ma. The first rapid cooling at a rate of ⩾1.5°C/Ma is associated with coeval tectonism in nearby regions, which result in folds and faults of the eastern Sichuan basin. Early-mid Cenozoic thermal stability is contributed to the extension widely occurring in the eastern China continent at which the average cooling rate decreased to ∼0.16°C/Ma. Causes for speculative accelerated cooling after ca. 20–15Ma with a rate of ⩾1.2°C/Ma may be a far-field effect of upward and eastward growth of the Tibetan Plateau but could also be related to climate effects. In a whole, this paper analyzes the several Mesozoic and Cenozoic tectonic events influence to the patters of regional denudation.

Low-temperature constraints on the Cenozoic thermal evolution of the Southern Rhodope Core Complex (Northern Greece)

The South Rhodope Core Complex (SRCC) of Northern Greece is probably the most studied metamorphic core complex of the Rhodope Massif, and yet its geological evolution has not yet been fully unravelled, especially the later stages of its thermotectonic evolution. We applied the fission-track method on apatite and zircon and the [U–Th–(Sm)]/He method on apatite in order to reconstruct the low-temperature thermal history. The main detachments responsible for the unroofing of the core complex are the Kerdilion and the Strymon Valley detachments. The Kerdilion detachment initiated the exhumation of the SRCC at the latest at 42 Ma and controlled it until about 24 Ma. Between 24 and 12 Ma, the Strymon Valley detachment accommodated the exhumation. Since 12 Ma brittle normal faults, some of them cutting the Strymon Valley detachment were responsible for the final cooling of the basement rocks in the studied area and the formation of syn-tectonic sedimentary basins. Activity along these brittle normal faults lasted until 6 Ma or probably even until today, as indicated by recent seismic activity in the area.

A new Poissonian algorithm for the determination of fission-track ages

Fission-track (FT) thermochronology has been widely used since the 1970s to constrain the low-temperature thermal history of rocks in numerous geological settings. Statistical problems associated with this method have been addressed since the 1980s. Today, with the improvements brought to the technique, new questions arise which require the adaptation of previously established statistical methods. Samples used for FT thermochronology are typically composed of minerals (e.g. apatite, zircon, titanite, etc.) with a wide variability in uranium (U) concentration. In this work we propose a new statistical methodology, called p-partition, that even assuming grains of a same sample could have different uranium concentrations. We apply our methodology to fission-track ages standards, in-situ and detrital samples. For standards we found that the new estimated age is closer to the independently determined K–Ar age, for detrital samples we applied our methodology to existent and published data for the case of the Venezuelan Andes. Our results were compared with other decomposition methods for the fission-track ages distributions, they show robustness, and in some particular case our method has more resolution in comparison with conventional methods. In this work we present a methodology and algorithms that attempt to solve mathematically the problem of decomposition of data with Poisson mixtures.

Paleotopographic reconstruction on the basis of low-temperature thermochronological thermal history modelling

The traditional paleotopographic explanation of mountain belts from low-temperature thermochronology is based on the simulation of low-temperature age data, the main defect of which is that we cannot make comparisons at the same time between the samples. In this article, we intend to make paleotopographic reconstruction on the basis of thermal history modelling. We first digitalize the thermal history curve and take contemporary temperatures for comparison, then reconstruct the paleotopography according to the distribution of the samples’ temperatures. The finite difference method is used to solve the diffusion equation for heat in the reconstruction process. Our paleotopography reconstruction method can restore the topography over time. However, due to the nature of thermal history modeling and the noise in the data, the accuracy of this reconstruction is currently limited.

Low-temperature thermal history and landscape development of the eastern Adirondack Mountains, New York: Constraints from apatite fission-track thermochronology and apatite (U-Th)/He dating

Research Article| March 01, 2011 Low-temperature thermal history and landscape development of the eastern Adirondack Mountains, New York: Constraints from apatite fission-track thermochronology and apatite (U-Th)/He dating Joshua P. Taylor; Joshua P. Taylor † Department of Earth Sciences, 204 Heroy Geology Laboratory, Syracuse University, Syracuse, New York 13244, USA †E-mail: jtaylo03@syr.edu Search for other works by this author on: GSW Google Scholar Paul G. Fitzgerald Paul G. Fitzgerald Department of Earth Sciences, 204 Heroy Geology Laboratory, Syracuse University, Syracuse, New York 13244, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Joshua P. Taylor † Department of Earth Sciences, 204 Heroy Geology Laboratory, Syracuse University, Syracuse, New York 13244, USA Paul G. Fitzgerald Department of Earth Sciences, 204 Heroy Geology Laboratory, Syracuse University, Syracuse, New York 13244, USA †E-mail: jtaylo03@syr.edu Publisher: Geological Society of America Received: 24 Jul 2009 Revision Received: 31 Jan 2010 Accepted: 08 Mar 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (3-4): 412–426. https://doi.org/10.1130/B30138.1 Article history Received: 24 Jul 2009 Revision Received: 31 Jan 2010 Accepted: 08 Mar 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Joshua P. Taylor, Paul G. Fitzgerald; Low-temperature thermal history and landscape development of the eastern Adirondack Mountains, New York: Constraints from apatite fission-track thermochronology and apatite (U-Th)/He dating. GSA Bulletin 2011;; 123 (3-4): 412–426. doi: https://doi.org/10.1130/B30138.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Adirondack Mountains in northern New York State form an elongate, domal exposure of mainly high-grade metamorphic tectonites in a mountainous setting with topographic relief of ∼1 km. The origin of the Adirondack Mountains and this relief has long been enigmatic, since the Adirondacks presently lie within an intracratonic setting, inboard of the North American passive margin and far from any active plate boundaries. Through the application of apatite fission-track (AFT) thermochronology and apatite (U-Th)/He (AHe) dating within the eastern Adirondack Mountains, this study provides constraints on both the thermal and erosional effects of Mesozoic passage near a hotspot and the timing of relief development.AFT thermochronology and AHe dating record relatively stable thermal conditions within the eastern Adirondacks from the Middle Jurassic into the Early Cretaceous. During the Early Cretaceous (ca. 130–120 Ma), the region underwent heating associated with progressive movement near the Great Meteor hotspot, resulting in the temporary establishment of an elevated geothermal gradient. Following regional heating, cooling rates increased considerably (ca. 105–95 Ma), likely due to both thermal doming, producing an increase in erosion rate, and the relaxation of isotherms after passage near the hotspot.The regional distribution of AFT ages across the eastern Adirondacks reveals no systematic age gradient from core to periphery, which would be expected under conditions of persistent high relief during the decay of a crustal root over many tens to hundreds of millions of years. Instead, thermochronological data suggest that the present relief developed during the Late Cretaceous–Cenozoic through plateau dissection during periodic base-level changes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Annealing kinetics of Kr-tracks in monazite: Implications for fission-track modelling

This paper reports data related to the potential of the mineral monazite for reconstructing the low-temperature thermal histories of geological samples from confined fission-track length measurements. The data are derived from isothermal annealing experiments on 300 MeV 86Kr tracks. Simplified versions of the favoured annealing models for apatite are adequate for describing the dataset. A non-compositional model predicts that: (1) track accumulation sets in when a sample cools under ~ 100 °C; (2) a substantial reduction (~ 2.5 μm) takes place at ambient and lower temperatures on a geological timescale; (3) an additional reduction of similar magnitude (~ 2.5 μm) takes place during exposure for a geological time span to the annealing conditions in the earth's upper crust; and (4) etching at elevated or room temperature is expected to affect the length of induced fission tracks but not that of fossil tracks.

The low-temperature thermal history of northern Switzerland as revealed by fission track analysis and inverse thermal modelling

New zircon and apatite fission track (FT) data from four boreholes, which penetrate the Mesozoic and pre-Mesozoic sediments and crystalline basement of northern Switzerland, are presented. Inverse thermal modelling of the measured apatite FT parameters unravels the low-temperature (below ~120°C) thermal history of the crystalline basement of northern Switzerland. Zircon FT central and single-grain ages cluster around 250 Ma, thus maximum palaeotemperatures did not exceed ∼ 330°C after late-Variscan consolidation of the crystalline basement. Apatite FT central ages vary between 25 and 87 Ma. Confined mean track lengths range between 9.3 μm and 11.6 μm, suggesting substantial track annealing within all apatite samples. Modelled time-temperature paths offer a clear picture about the low-temperature thermal history of the crystalline basement of northern Switzerland: Cretaceous cooling is followed by an Eocene heating event and subsequent cooling to present-day temperatures. The Eocene heating episode is contemporaneous with the initial rifting stage of the nearby Upper Rhine Graben and the associated increasing volcanic activity. Crustal-scale faults of the Permo-Carboniferous Trough of northern Switzerland could have acted as major pathways for circulating hydrothermal fluids giving rise to the observed Middle to Late Eocene thermal event.

Low temperature thermochronology of the southern East Greenland continental margin: Evidence from apatite (U–Th)/He and fission track analysis and implications for intermethod calibration

The southern coast of East Greenland is characterized by high topographic relief and deep fjords, but the evolution of the landscape and the low-temperature thermochronology of the region is not well understood. Here we present apatite fission-track and (U–Th)/He ages that suggest several important features of the long-term geomorphic history of this region, but which also illustrate an important discrepancy in the thermal histories derived from each technique. Apatite from bedrock of the southern coast of East Greenland between 62°N and 67°N has fission-track ages ranging from 60 to 840 Ma and (U–Th)/He ages ranging from 21 to 250 Ma. The ages generally increase with elevation and distance from the coast, and fission-track analyses show significant differences in thermal histories for the different regions. In the Kangertittivatsiaq area (c. 66–67°N) apatite fission track data and models suggest two separate periods of slow cooling: prior to c. 200 Ma and between c. 160 Ma and the late Cenozoic (more recently than c. 20 Ma), each of which was followed by a period of rapid cooling and inferred exhumation. Apatite He data in the Kangertittivatsiaq region, including crystal-size–age correlations in low-elevation samples, are most simply interpreted as recording an incision event of at least 1.5 km later than 20 Ma near the coast. This may have been caused by glacial erosion. The (U–Th)/He data also indicate an earlier phase of rapid exhumation at c. 250 Ma. In the Skjoldungen/Kap Møsting area (c. 62–64°N) approximately 200 km south of the Kangertittivatsiaq, apatite fission-track data suggest slow exhumation from c. 200 Ma into the Neogene followed by fast exhumation. The similarity of fission track ages (200 Ma) at sea level in the fjords in the Skjoldungen area (c. 62–64°N) do not suggest tilting in the hinterland related to the breakup of the East Greenland continental margin. Furthermore, the Cenozoic fission track ages and modeling fission track data suggest that pre-breakup basins may have covered the outer coast. Despite the broadly similar topographic implications of the fission-track and (U–Th)/He data, the thermal histories derived from these systems are inconsistent. Fission-track data require thermal histories that predict He ages younger than observed, and He data require thermal histories that predict fission-track ages older than observed. Similar discrepancies have also been observed in other settings characterized by long-term low-temperature thermal histories, and may reflect changes in annealing or diffusion behavior (or both) that either develop or become more apparent in such cases.

Low-temperature (

The paucity of Phanerozoic rock sequences in the Proterozoic Mt Isa and Murphy Inliers in northern Australia renders it difficult to determine their Phanerozoic tectonic histories. However, thermochronological methods provide a means to assess this problem. Apatite fission track ages vary from 390 to 218 Ma, and mean track lengths range between 11.1 and 13.6 μm. These results record a non-linear cooling history below about 110 ± 10°C. Forward modelling of the fission track data suggests that the first episode of relatively rapid cooling since the Early Carboniferous occurred between ca 350 and 250 Ma at rates of ∼0.9°C/million years and was synchronous with intracontinental deformation associated with the Alice Springs Orogeny and tectonics at the contemporaneous eastern margin of Australia. This event resulted in ≥ 2 km of exhumation across both inliers. Cooling rates also increased after 100 Ma, although estimates of the amount of cooling and exhumation across trhe inliers obtained by forward modelling of the fission track data exceed those determined by constraints provided by the 40Ar/39Ar ages of weathering profiles. This observation adds to the growing amount of evidence that the fission track annealing model employed overestimates cooling rates at low temperatures (<60 – 70°C). The spatial variation of apatite fission track data within the Mt Isa Inlier indicates the three major structural belts, the Western Fold Belt, Kalkadoon – Leichhardt Belt and the Eastern Fold Belt, which are separated by major north – south faults, experienced similar thermal histories on a regional scale. This suggests that the main faults bounding the belts have not experienced major reactivation in a vertical sense, as a single large-scale fault plane, since ca 350 Ma. However, adjacent smaller scale, fault-bounded blocks within the structural belts demonstrate variable cooling histories, suggesting that reactivation of favourably oriented minor faults in the inlier, including segments of the major faults, has occurred over this time interval. Variations in apatite fission track data show that up to 1.5 km of vertical displacement occurred along parts of the Mt Isa Fault Zone and the Pilgrim Fault between 350 and 250 Ma.