Partial Resetting Research Articles

Partial stochastic resetting with refractory periods

Abstract The effect of refractory periods in partial resetting processes is studied. Under Poissonian partial resets, a state variable jumps to a value closer to the origin by a fixed fraction at constant rate, $x\to a x$. Following each reset, a stationary refractory period of arbitrary duration takes place. We derive an exact closed-form expression for the propagator in Fourier-Laplace space, which shows rich dynamical features such as connections not only to other resetting schemes but also to intermittent motion. For diffusive processes, we use the propagator to derive exact expressions for time dependent moments of $x$ at all orders. At late times the system reaches a non-equilibrium steady state which takes the form of a mixture distribution that splits the system into two subpopulations; trajectories that at any given time in the stationary regime find themselves in the freely evolving phase, and those that are in the refractory phase. In contrast to conventional resetting, partial resets give rise to non-trivial steady states even for the refractory subpopulation. Moments and cumulants associated with the steady state density are studied, and we show that a universal optimum for the kurtosis can be found as a function of mean refractory time, determined solely by the strength of the resetting and the mean inter-reset time. The presented results could be of relevance to growth-collapse processes with periods of inactivity following a collapse.

Recurrent partial resetting of quartz OSL signal by earthquakes: a thermochronological study on fault gouges from the Atotsugawa Fault, Japan

Optically stimulated luminescence (OSL) dating utilises the detection of trapped charge in minerals, and has an ultralow closure temperature. There is the potential for direct dating of fault movement using fault gouges, because frictional heating caused by large earthquakes can reduce the OSL signal intensity of minerals within gouges. In this study, we conducted quartz OSL dating on four fault gouge and breccia samples from a surface outcrop of the Atotsugawa Fault, one of the most active dextral strike-slip faults in central Japan, where the last large earthquake occurred in AD1858, with an estimated magnitude of 7. The natural OSL signal intensity of fine-grained quartz was clearly below the signal saturation level, with the fraction of saturation (n/N) between 0.30 ± 0.02 and 0.39 ± 0.03, indicating there was signal resetting by past earthquakes. However, the apparent OSL ages ranged from 22 ± 1 to 72 ± 4 ka, two orders of magnitude older than the age of the last earthquake. To explain the significant age overestimation, we measured the thermal stability of the OSL signal, and used a thermal model with punctuated episodic losses to constrain the average shear heating temperature experienced during an individual faulting event. For an independently known recurrence interval of 2.5 ka and a presumed shear heating duration of 1 s, the observed n/N and the measured thermal stability of the OSL signals correspond to a resetting temperature of ~ 300 °C during a single earthquake event.Graphical

Entanglement Dynamics in Monitored Systems and the Role of Quantum Jumps

Monitored quantum many-body systems display a rich pattern of entanglement dynamics, which is unique to this nonunitary setting. This work studies the effect of quantum jumps on the entanglement dynamics beyond the no-click limit corresponding to a deterministic non-Hermitian evolution. To this aim, we introduce a new tool that looks at the statistics of entanglement-entropy gain and loss after and in between quantum jumps. This insight allows us to build a simple stochastic model of a random walk with partial resetting, which reproduces the entanglement dynamics, and to dissect the mutual role of jumps and non-Hermitian evolution on the entanglement scaling. We apply these ideas to the study of measurement-induced transitions in monitored fermions. We demonstrate that significant deviations from the no-click limit arise whenever quantum jumps strongly renormalize the non-Hermitian dynamics, as in the case of models with U(1) symmetry at weak monitoring. On the other hand, we show that the weak-monitoring phase of the Ising chain leads to a robust subvolume logarithmic phase due to weakly renormalized non-Hermitian dynamics. Published by the American Physical Society 2024

Thermodynamic work of partial resetting

Partial resetting, whereby a state variable x(t) is reset at random times to a value ax(t) , 0⩽a⩽1 , generalizes conventional resetting by introducing the resetting strength a as a parameter. Partial resetting generates a broad family of non-equilibrium steady states (NESS) that interpolates between the conventional NESS at strong resetting (a = 0) and a Gaussian distribution at weak resetting (a → 1). Here such resetting processes are studied from a thermodynamic perspective, and the mean cost associated with maintaining such NESS are derived. The resetting phase of the dynamics is implemented by a resetting potential Φ(x) that mediates the resets in finite time. By working in an ensemble of trajectories with a fixed number of resets, we study both the steady-state properties of the propagator and its moments. The thermodynamic work needed to sustain the resulting NESS is then investigated. We find that different resetting traps can give rise to rates of work with widely different dependencies on the resetting strength a. Surprisingly, in the case of resets mediated by a harmonic trap with otherwise free diffusive motion, the asymptotic rate of work is insensitive to the value of a. For general anharmonic traps, the asymptotic rate of work can be either increasing or decreasing as a function of the strength a, depending on the degree of anharmonicity. Counter to intuition, the rate of work can therefore in some cases increase as the resetting becomes weaker (a→1) although the work vanishes at a = 1. Work in the presence of a background potential is also considered. Numerical simulations confirm our findings.

A conceptual model for the evolution of a magmatic system based on U-Pb zircon studies on the devonian granites of Sierra de San Luis, Argentina

ABSTRACT It is widely acknowledged that thermal models clearly demonstrate that crustal magma bodies should solidify rapidly upon emplacement. Small plutons can cool below the solidus in thousands of years, while even large plutons require hundreds of thousands of years, but not more than a million years. However, recent U-Pb zircon geochronological data contradict these results, strongly suggesting that magmatic systems are often characterized by protracted events. Therefore, a conceptual framework that reconciles thermal models and the geochronology data is necessary. The Devonian foreland magmatism of the Sierra de San Luis is made up of two distinctive suites, the Monzonite suite (<65 wt.% SiO2) and the Granite suite (>65 wt.% SiO2), both emplaced at ca. 3.7 kbar. Classification of the studied Devonian granitoids is debatable because they have a hybrid I- to A-type granite signature. Based on a robust geochronological U-Pb zircon dataset we corroborate the development of a protracted magmatic activity with three major crystallization events for this Devonian magmatism: 391 ± 1, 384 ± 1, and 379 ± 2 Ma. Considering these geochronological data, we postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the prolonged crystallization of antecrysts (ca. 395–384 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located at shallow levels, where zircon autocrysts crystallized (ca. 379 Ma). Age spectra reported within individual samples support the idea of a massive migration of magma when conditions were favourable (e.g. thermally matured crust). Individual crystallization ages recorded by monazites hosted in two-mica granites are comparable to those obtained from zircons, supporting the presence of a long-lasting hot source. Additional geochronological data indicate that a later thermal event (ca. 353 Ma) could have partially affected some areas of the Devonian magmatic zircons promoting Pb loss, with subsequent partial resetting of the isotopic clock.

Reconstructing the thermal history of the Morondava Basin, Madagascar, after Gondwanan breakup as resolved through detrital zircon (U–Th)/He and U–Pb geochronology

Formation of the Phanerozoic basins of Madagascar coincided with the initial stages of Permian break-up of Gondwana. The largest of these, the Morondava Basin, records the tectonic history of rifting, drifting, and uplift of the Malagasy terrane over the last 300 Myr. Herein, we have applied detrital zircon U–Pb geochronology and (U–Th)/He low-temperature thermochronology to resolve the thermal history of the basin as Madagascar separated from Africa and subsequently India. Coarse-grained siliciclastic samples were taken along two transects parallel to the Morondava River in the central basin, including from the Permo-Triassic failed rift basin and from post-Jurassic passive margin sequences. Detrital zircon U–Pb age distributions are defined by common Neoarchean and Neoproterozoic populations which suggests input from the basement terranes of the Malagasy Central Highlands (Antananarivo domain). Samples also contain Paleo-to Mesoarchean and Cambrian populations likely associated with metamorphic terranes amalgamated during the Pan-African orogeny. Single crystal zircon (U–Th)/He dates are 503 ± 17 Ma to 40 ± 1 Ma with effective uranium (eU) values ranging from 35 to 1760 ppm, which exhibit a strong negative date-eU relationship that indicates partial resetting of the He systematics in zircon throughout the basin. Inverse and forward thermal history models from the data reveal separate thermal histories for strata on either side of basin-dividing Illovo Fault. Under an elevated geothermal gradient, temperatures did not exceed 180 °C either during post-Gondwanan burial of Jurassic rift strata or during Late Cretaceous burial of Early Cretaceous passive margin strata. Intrusion of Turonian-age dikes and sills related to the Marion hot spot likely promoted subtle yet widespread heating. The time of latest cooling during the Paleogene recorded in the basin is poorly constrained by the detrital zircon thermochronology.

Hf-W isotope systematics of enstatite chondrites: Parent body chronology and origin of Hf-W fractionations among chondritic meteorites

Five enstatite chondrites, including two EH4 (Abee, Indarch) and three EL6 samples (Hvittis, Khairpur, Pillistfer), were investigated for their Hf-W isotope systematics to constrain the chronology and thermal evolution of their parent bodies and to assess the nature and extent of Hf-W fractionations among chondritic meteorites. The Hf-W ages range from ∼4.5 Ma to ∼10 Ma after CAI formation, where Pillistfer exhibits an older Hf-W age (∼4.5 Ma) than the other two EL6 chondrites (∼8.5–10 Ma), probably reflecting rapid cooling after impact excavation. The ∼8 Ma Hf-W age of the EH4 chondrite Indarch overlaps with those of the younger EL6 chondrites, indicating a similar cooling timescale despite the lower metamorphic grade. By contrast, Abee shows evidence for only partial resetting of the Hf-W system during metamorphism, and the 182W composition of Abee's metal still records the time of chondrule formation at ∼2 Ma after CAI formation. Thus, the thermal and cooling histories of enstatite chondrites do not appear to be a simple function of their metamorphic grade.Despite their distinct Fe-metal contents, EH and EL chondrites and their precursor material have uniform Hf/W ratios. This most likely reflects the early and proportional removal of refractory metal and silicate components from the enstatite chondrite formation region, which left the Hf/W ratio unchanged. As such, the Hf/W ratio of enstatite chondrites provides a good estimate for the average composition of primitive chondritic material from the inner solar system. All carbonaceous chondrites except CI chondrites have higher Hf/W ratios, reflecting admixture of CAIs or metal-silicate fractionation during chondrule formation. Using the Hf/W ratio of enstatite chondrites, rather than carbonaceous chondrites, in the calculation of Hf-W core formation model ages makes these ages up to ∼0.7 Ma younger, shifting the core formation ages for non-carbonaceous iron meteorites closer to those of carbonaceous iron meteorites.

On the virtues and pitfalls of combined laser ablation Rb–Sr biotite and U–Pb monazite–zircon geochronology: an example from the isotopically disturbed Cape Woolamai Granite, SE Australia

Abstract Different mineral clocks in granite can provide age information reflecting various aspects of rock formation, including cooling or post-emplacement fluid–rock interaction. However, the dating tool chosen can yield inconclusive age information due to differences in closure temperatures and susceptibility to fluid alteration among chronometers. This has led to an inferred superiority of U–Pb in zircon over U–Pb in monazite or Rb–Sr in mica. Here, we investigate age systematics using Rb–Sr biotite grains, U–Pb in monazite and zircon in a Devonian granite from Australia. Single-grain laser ablation ICP-MS/MS biotite analyses are combined with zircon–monazite U–Pb ages and trace element systematics. Textural and trace element evidence combined with age systematics reveals a Rb–Sr closure age of c. 360–330 Ma relative to a putative 364 Ma emplacement age, suggesting hydrothermal alteration of the granite. Trace element systematics and magnetic susceptibility in biotite grains reflect their partial chemical reset and fluid overprint in the granite. However, similar systematics are also observed for zircon and monazite. Our multiple chronometer dating approach, studied with modern laser-ablation methods, highlights the need for detailed investigation of isotope and trace element systematics in single grains and that individual ages should be used cautiously when dating altered granitoids.

Isotopic behavior and age interpretations of U-Pb, Sm-Nd, and 40Ar/39Ar systems in polymetamorphic granulite terranes: A case study from the Prydz Belt and adjacent Vestfold Block, East Antarctica

A combined zircon U-Pb, garnet-based mineral−whole-rock Sm-Nd, and hornblende/biotite 40Ar/39Ar geochronological study was conducted on polymetamorphic granulite-facies rocks from the Prydz Belt and adjacent Vestfold Block in East Antarctica. Zircon U-Pb data and zircon-garnet rare earth element distributions indicate that granulite-facies mineral assemblages of the Meknattane Nunataks−Hamm Peak area and the Reinbolt Hills in the Prydz Belt were formed at ca. 1000−900 Ma. Some Grenville-aged (i.e., late Mesoproterozoic to early Neoproterozoic) zircons underwent partial U-Pb resetting, without new growth, during Pan-African-aged (i.e., late Neoproterozoic to Cambrian) metamorphism. Mineral−whole-rock Sm-Nd dating yielded isochron ages of 865−672 Ma for the Meknattane Nunataks−Hamm Peak area, 504−483 Ma for the Reinbolt Hills, and 670−589 Ma for the Vestfold Hills. These results suggest that Pan-African-aged reworking was inhomogeneous, leading to either partial or complete resetting of the garnet Sm-Nd isotopic system in different areas. Apparently, Sm-Nd ages might have geological meaning only when the isotopic system of garnet (including other contemporaneous minerals) has been completely reset. In this regard, garnet-based Sm-Nd geochronology is less robust when applied to polymetamorphic granulite terranes. Hornblende 40Ar/39Ar dating produced an older age of 526 Ma for the Vestfold Hills, whereas biotite 40Ar/39Ar ages showed slight differences among the studied areas, with ages of 514−497 Ma for the Meknattane Nunataks−Hamm Peak area, 482−467 Ma for the Reinbolt Hills, and 520−509 Ma for the Vestfold Hills. These age patterns imply that 40Ar/39Ar dating of minerals can constrain the cooling time of the latest metamorphic event only, and cooling times to the Ar closure temperature of biotite differ among different parts of the Prydz Belt. Integration of the new results with available Sm-Nd and 40Ar/39Ar data indicates that the Prydz Belt underwent rapid tectonic uplift and cooling from lower to mid- and upper-crustal depths during postorogenic evolution. The Vestfold Block might have been located at the margin of the high-temperature Prydz Belt and underwent relatively low-temperature reworking and earlier cooling during the Pan-African-aged orogeny.

Time-dependent probability density function for partial resetting dynamics

Stochastic resetting is a rapidly developing topic in the field of stochastic processes and their applications. It denotes the occasional reset of a diffusing particle to its starting point and effects, inter alia, optimal first-passage times to a target. Recently the concept of partial resetting, in which the particle is reset to a given fraction of the current value of the process, has been established and the associated search behaviour analysed. Here we go one step further and we develop a general technique to determine the time-dependent probability density function (PDF) for Markov processes with partial resetting. We obtain an exact representation of the PDF in the case of general symmetric Lévy flights with stable index . For Cauchy and Brownian motions (i.e. ), this PDF can be expressed in terms of elementary functions in position space. We also determine the stationary PDF. Our numerical analysis of the PDF demonstrates intricate crossover behaviours as function of time.

An Unusually Warm Upper‐Crust in the Late Paleozoic North China Continental Arc: Implications for the Thermal Modification of the Giant Bayan Obo REE Deposit

AbstractThe genesis and timing of formation of the giant Bayan Obo deposit, the world's largest rare earth element (REE) deposit in the western part of the late Paleozoic northern North China continental arc (NCA), are highly controversial due to complex mineral assemblages and reported ages of mineralization. We conducted new zircon U‐Pb and40Ar/39Ar dating of metamorphic and igneous Neoarchean to Permian mid‐to upper‐crustal rocks exhumed along a north−south corridor across the western NCA and its retroarc foreland. The results show that the mid‐ to upper‐crust of the western part of the NCA has been strongly affected by thermal modifications during arc construction in the late Paleozoic, while the retroarc foreland remained thermally stable. Our results first reveal an unusually warm upper‐crust around Bayan Obo during the late Paleozoic with high geothermal gradients of 50.0 ± 8.3 to 88.3 ± 8.3°C/km and strong thermal modification of the upper‐crust during arc construction. This unusually warm upper‐crust and high geothermal gradients resulted in intensive thermal perturbations and recrystallization of REE‐bearing minerals in the Bayan Obo deposit, as well as formation of high‐grade REE ores and complete or partial resetting (U‐)Th‐Pb isotopic systems of REE minerals. Our identification of the unusually warm upper‐crust and high geothermal gradients in the western part of the NCA provides important constraints on genesis, timing and thermal modification of the giant Bayan Obo deposit, as well as other REE deposits with complex isotopic ages.

Meso‐Cenozoic Tectonic History of the Altai: New Insights From Apatite U‐Pb and Fission Track Thermochronology for the Fuyun Area (Xinjiang, China)

AbstractThe Altai is an enigmatic, relatively young mountain belt with sharp relief (up to 4,500 m high) that developed thousands of kilometers away from the nearest current plate margins. The Fuyun area, at the interface between the southern margin of the Chinese Altai and the Junggar Basin, represents a key locality for understanding the Meso‐Cenozoic deformation and exhumation history of the Altai. The complex structural architecture of the Fuyun area suggests that multiple deformation events affected the area, which ultimately led to the exhumation of the Altai. Furthermore, the area hosts orogenic‐type mineralization, suggesting a history of fluid alteration. However, in contrast to the well‐constrained Palaeozoic history, the timing of Meso‐Cenozoic deformation, metasomatism and exhumation has not been comprehensively studied. This study presents new apatite U‐Pb, trace element and fission track data for the Fuyun area and integrates these with previous studies for the Altai to shed more light on the Meso‐Cenozoic tectonic history. The apatite U‐Pb dates, associated with LREE‐depleted trace element profiles, suggest that a phase of Middle–Late Jurassic (∼170–160 Ma) metasomatism affected the Keketuohai area, which is potentially linked to the timing of rare‐metal mineralization. The apatite fission track results and thermal history models reveal rapid early Late Cretaceous (∼100–75 Ma) cooling linked to tectonic exhumation throughout the Chinese Altai, associated with distant plate‐margin processes. In addition, samples taken in vicinity to the frontal thrusts of the Altai record evidence for Cenozoic partial resetting of the apatite fission track system.

Prevalent putative chromatin bivalency and partial resetting of H3K27me3 in plant sperm.

Prevalent putative chromatin bivalency and partial resetting of H3K27me3 in plant sperm.

Dating hydrothermal processes related to the formation of the Lagoa Real uranium deposits using in situ U–Pb dating of andradite and titanite

To understand the mechanisms and origin of ore deposits, it is essential to know their age. However, the processes responsible for ore formation do not always leave a geochronological record, with hydrothermal processes often either not affecting zircon or causing only partial resetting. The Lagoa Real uranium province hosts the most important U resource in Brazil. The U mineralization is hosted by Na-rich rocks known as albitite, which also contain variable amounts of garnet, clinopyroxene, biotite, amphibole, magnetite and titanite. These rocks are presumed to be the result of hydrothermal alteration of the Lagoa Real intrusive suite, a group of A-type granitic rocks emplaced between 1740 and 1720 Ma. Despite the economic importance of these rocks, determining the age of metasomatism and U mineralization has been extremely difficult, with previous attempts using a variety of methods and targeting the whole rock, titanite, uraninite, heavy-mineral concentrates and zircon, yielding a wide variety of ages in the range of 1.5 to 0.9 Ga. This study is the first to directly date metasomatic minerals (garnet and titanite) with the in situ U–Pb dating method. Garnet and titanite from an unmineralized sample gave U–Pb ages of ca. 545 Ma and ca. 520 Ma, respectively. U–Pb dating of zircon from two other unmineralized samples yielded ages of 1740–1720 Ma, interpreted as igneous ages. Electron-microprobe dating of uraninite from mineralized samples produced ages of 530–520 Ma. Altogether, these results suggest that both metasomatism and U mineralization occurred as a result of fluids associated with the gravitational collapse phase (ca. 530–480 Ma) of the Araçuaí–West Congo orogen. This study illustrates the utility of U–Pb dating of andradite garnet for determining the age of mineralization related to metasomatism.

Diffusion with partial resetting.

Inspired by many examples in nature, stochastic resetting of random processes has been studied extensively in the past decade. In particular, various models of stochastic particle motion were considered where, upon resetting, the particle is returned to its initial position. Here we generalize the model of diffusion with resetting to account for situations where a particle is returned only a fraction of its distance to the origin, e.g., half way. We show that this model always attains a steady-state distribution which can be written as an infinite sum of independent, but not identical, Laplace random variables. As a result, we find that the steady-state transitions from the known Laplace form which is obtained in the limit of full resetting to a Gaussian form, which is obtained close to the limit of no resetting. A similar transition is shown to be displayed by drift diffusion whose steady state can also be expressed as an infinite sum of independent random variables. Finally, we extend our analysis to capture the temporal evolution of drift diffusion with partial resetting, providing a bottom-up probabilistic construction that yields a closed-form solution for the time-dependent distribution of this process in Fourier-Laplace space. Possible extensions and applications of diffusion with partial resetting are discussed.

Exponential Stability of Switched Neural Networks with Partial State Reset and Time-Varying Delays

This paper mainly investigates the exponential stability of switched neural networks (SNNs) with partial state reset and time-varying delays, in which partial state reset means that only a fraction of the states can be reset at each switching instant. Moreover, both stable and unstable subsystems are also taken into account and therefore, switched systems under consideration can take several switched systems as special cases. The comparison principle, the Halanay-like inequality, and the time-dependent switched Lyapunov function approach are used to obtain sufficient conditions to ensure that the considered SNNs with delays and partial state reset are exponentially stable. Numerical examples are provided to demonstrate the reliability of the developed results.

Structure, metamorphism, and mica40Ar/39Ar thermochronology of the southern Purcell anticlinorium and its transition into the central Kootenay arc, Omineca belt, southeastern British Columbia

The Purcell anticlinorium (PA) and the Kootenay arc (KA) are two adjacent Mesozoic tectonic domains in the southeastern Omineca belt of the Canadian Cordillera. Mesoproterozoic rocks of the Belt-Purcell Supergroup (BPSG) core the PA and have open, upward-facing structures. Deeper levels of the BPSG (Aldridge Formation) preserve a Mesoproterozoic phyllitic cleavage (S1) and biotite zone mineral assemblages. The KA, on the west flank of the PA, has a younger Neoproterozoic through Paleozoic stratigraphy. The central part of the KA, the focus of this study, experienced Jurassic recumbent folding and greenschist facies metamorphism that was overprinted by Early Cretaceous ductile deformation (S2schistosity) and Barrovian metamorphism. The interface between the PA and KA is taken as the easternmost occurrence of the S2schistosity. K–Ar and40Ar/39Ar mica dates in the PA range from 1318 to 240 Ma and show no consistent spatial distribution. They are interpreted to reflect partial resetting of Ar following initial cooling in the Mesoproterozoic, indicating that the PA was never sufficiently buried or heated during younger tectonism to uniformly reset the mica cooling ages. In the KA,40Ar/39Ar dates range from 139 to 55 Ma and reflect previously documented periods of Mesozoic and Cenozoic metamorphism, magmatism, and exhumation. The PA–KA interface occurs above a west-dipping ramp in the Laurentian basement. The thick Mesoproterozoic sequence of turbidites and sills in the PA may have acted as a rigid buttress against which the more ductile rocks of the central KA “piled up” during Early Cretaceous compressional orogenesis.

A re-evaluation of the Meso-Cenozoic thermo-tectonic evolution of Bogda Shan (Tian Shan, NW China) based on new basement and detrital apatite fission track thermochronology

ABSTRACT Bogda Shan is a mountain belt located at the eastern extremity of the Chinese Tianshan and records a complex and debated exhumation history. Previous studies have reported a young Cenozoic thermal history for the exhumation of Bogda Shan, which is in conflict with the observation of preserved Mesozoic erosion surfaces in the area. This study re-evaluates the Meso-Cenozoic thermo-tectonic evolution of Bogda Shan using apatite fission track (AFT) thermochronology. Palaeozoic basement (meta-sandstone) samples collected from the northern and southwestern flanks of the mountain ranges reveal apparent Mesozoic AFT ages ranging from ~202 Ma to ~97 Ma. Inverse thermal history modelling results reveal slow to moderate basement cooling during the early Mesozoic, corresponding to relatively low levels of exhumation. This accounts for the preservation of low-relief Mesozoic peneplanation surfaces recognized at elevations of ~3500–4000 m. None of the presented AFT data and thermal history models show any evidence for significant deep Cenozoic exhumation. In the neighbouring Junggar Basin, a Middle Jurassic sandstone sample records partial resetting of the AFT system during the Cretaceous. This observation conflicts with previous data (from the same Jurassic strata) where complete resetting of the AFT clock during the Cenozoic was suggested. Furthermore, Lower Cretaceous and Palaeogene sediments from the Turpan-Hami Basin show non-reset detrital AFT age populations of ~197, ~135, and ~104 Ma, which are coincident with the main pulses of exhumation recorded in the Chinese North Tianshan. Based on a comprehensive summary of the published data, we argue for a Mesozoic building of the Bogda–Balikun–Harlik mountain chain in the eastern Chinese Tianshan. Subsequent Cenozoic exhumation must have been relatively modest at most (<2 km) as it was not recorded by AFT thermochronology.

Decline of Lanna ceramic group production in northern Thailand (Ban Bo Suak site) confined by radiocarbon and luminescence dating

The Lanna group is a traditional ceramic production style from Southeast Asia, with several kiln sites found distributed all over present northern Thailand. However, its origin and development are considered controversial and chronological constraints are scarce. Applied here are radiocarbon dating to charcoal remains and luminescence dating to ceramics, kiln wall material, and fluvial sediments from the Ban Bo Suak archaeological site near Nan, northern Thailand. The site has been suspected to have been abandoned due to destruction by a flood. Unexpectedly, the ceramic samples lack proper thermoluminescence signal properties and only two samples could be dated using optically stimulated luminescence (OSL). These ages in combination with published radiocarbon ages point towards a ceramic production around AD 1700. The kiln wall material and fluvial sediments reveal evidence for partial resetting of the OSL signal, which is unexpected for heated material. Supported by some radiocarbon ages, the OSL ages imply a temporal connection between the last use of the kilns and the flood deposits, during the fifteenth century AD. Besides general methodological considerations, the data reported here indicates that while a flood apparently dismantled several kiln sites, this did not stop the production of Lanna style ceramics in the region.

Detrital zircon analysis of metasedimentary rocks of the Staré Město Belt, Sudetes: implications for the provenance and evolution of the eastern margin of the Saxothuringian terrane, NE Bohemian Massif

The Staré Město Belt (SMB) in the Central Sudetes forms a Variscan tectonic boundary zone that is located between the Saxothuringian and Brunovistulian terranes of the Bohemian Massif. The three thrust-bounded upper, middle and lower lithotectonic units of the SMB are composed of metasedimentary and Late Cambrian metavolcanic rocks. A new LA-ICPMS zircon geochronology supported by zircon typology studies of the mica schists of the upper unit and the migmatitic paragneisses of the middle unit provides new insights into the provenance and evolution of the SMB. Our new data were obtained from metasedimentary rocks and compared to the previously published zircon ages of the SMB metavolcanic rocks. The results indicate that the metasedimentary and bimodal metavolcanic rocks in the separate lithotectonic units of the SMB originally formed Late Cambrian volcano-sedimentary successions. The source areas of the sedimentary basins studied were dominated by Neoproterozoic and Paleoproterozoic crystalline rocks that were presumably located near the West African Craton of Gondwana. A comparison of the detrital age spectra obtained with those previously published from the region indicates a strong association of the entire SMB with the Saxothuringian terrane of the Bohemian Massif. During partial melting of the metasedimentary rocks of the middle unit of the SMB, Cambrian and older zircon grains were affected by solid-state transformations that caused partial resetting of the U-Pb dates, changes in internal zircon textures and reductions in Th/U ratios.