Partial Resetting Research Articles

Apollo 12 breccia 12013: Impact-induced partial Pb loss in zircon and its implications for lunar geochronology

Apollo 12 breccia 12013 is composed of two portions, one grey in colour, the other black. The grey portion of the breccia consists mainly of felsite thought to have formed during a single crystallisation event, while the black part is characterized by presence of lithic fragments of noritic rocks and individual plagioclase crystals. In this study, U-Pb analyses of Ca-phosphate and zircon grains were conducted in both portions of the breccia. The zircon grains within the grey portion yielded a large range of ages (4154 ± 7 to 4308 ± 6 Ma, 2σ) and show decreasing U and Th concentrations within the younger grains. Moreover, some grains exhibit recrystallisation features and potentially formation of neoblasts. The latter process requires high temperatures above 1600–1700 °C leading to the decomposition of the primary zircon grain and subsequent formation of new zircon occurring as neoblasts. As a result of the high temperatures, the U-Pb system of the remaining original zircon grains was most likely open for Pb diffusion causing partial resetting and the observed range of 207Pb/206Pb ages. The event that led to the Pb loss in zircon could potentially be dated by the U-Pb system in Ca-phosphates, which have a weighted average 207Pb/206Pb age across both lithologies of 3924 ± 3 Ma (95% conf.). This age is identical within error to the combined average 207Pb/206Pb age of 3926 ± 2 Ma that was previously obtained from Ca-phosphates within Apollo 14 breccias, zircon grains in Apollo 12 impact melt breccias, and the lunar meteorite SaU 169. This age was interpreted to date the Imbrium impact. The zircon grains located within the black portion of the breccia yielded a similar range of ages (4123 ± 13 to 4328 ± 14 Ma, 2σ) to those in the grey portion. Given the brecciated nature of this part of the sample, the interpretation of these ages as representing igneous crystallisation or resetting by impact events remains ambiguous since there is no direct link to their source rocks via textural relationships or crystal chemistry. Similarly, the currently available zircon data set for all lunar samples may be distorted by partial Pb loss, resulting in meaningless and misleading age distribution patterns. Therefore, it is crucial to fully understand and recognize the processes and conditions that may lead to partial resetting of the U-Pb system in zircon in order to better constrain the magmatic and impact history of the Moon.

A 100-m.y.-long window onto mass-flow processes in the Patagonian Mesozoic subduction zone (Diego de Almagro Island, Chile)

Diego de Almagro Island was formed by the subduction and accretion of several seafloor-derived tectonic slices with very heterogeneous ages and pressure-temperature-time (P-T-t) paths. The highest element of the pile (the Lazaro unit) evidences subduction in the high-P granulite field (∼1.3 GPa, 750 °C) at ca. 163 Ma. Below it, a thin tectonic sliver (the Garnet Amphibolite unit) preserves eclogite-facies remnants (∼570 °C and ∼1.7 GPa) formed at ca. 131 Ma (in situ U-Pb zircon rim ages). Peak assemblages were nearly fully amphibolitized during decompression down to ∼1.2 GPa and ∼600 °C at 125–120 Ma (Rb-Sr multimineral dating). The underlying Blueschist unit has ∼50 m.y. younger metamorphic ages and exhibits slightly cooler peak burial conditions (∼520 °C, 1.7 GPa; ca. 80 Ma, in situ white mica Ar-Ar ages and multimineral Rb-Sr dating) and is devoid of amphibolitization. The mylonites from the sinistral strike-slip Seno Arcabuz shear zone bounding Diego de Almagro Island to the east also exhibit amphibolite-facies (∼620 °C and ∼0.9 GPa) deformation at ca. 117 Ma (multimineral Rb-Sr ages). In situ white mica Ar-Ar dating and multimineral Rb-Sr dating of low-T mylonites (∼450 °C) along the base of the Lazaro unit reveal partial resetting of high-T assemblages during tectonic displacement between 115 and 72 Ma and exhumation of the slice stack. Detrital zircon U-Th-Pb ages indicate that the material accreted on Diego de Almagro Island has been mostly recycled from a Permian–Triassic accretionary wedge (Madre de Dios accretionary complex) exposed along the subduction buttress. Geological and geochronological constraints suggest that the rocks of the Seno Arcabuz shear zone and the Lazaro unit were tectonically eroded from the buttress, while the underlying Garnet Amphibolite and Blueschist units instead derive from the subducted oceanic basin, with increasingly younger maximum depositional ages. The very long residence time of the rocks (∼90 m.y. for the Lazaro unit) along the hanging wall of the subduction interface recorded long-term cooling along the Patagonian subduction zone during the Mesozoic. Diego de Almagro Island therefore represents a unique window onto long-term tectonic processes such as subduction interface down-stepping, tectonic erosion, and episodic underplating near the base of an accretionary wedge (40–50 km).

Cooling, exhumation, and deformation in the Hindu Kush, NW Pakistan: New constraints from preliminary 40Ar/39Ar and fission track analyses

Asian crust in the Hindu Kush region in northern Pakistan records a protracted history of rifting, subduction and collision not commonly preserved within the Himalaya. Because of this, it is key to understanding the development of the southern Eurasian margin both prior to and after collision with India. New mica 40Ar/39Ar and apatite fission track geochronologic data from this region provide constraints on the kinematics of the Hindu Kush. 40Ar/39Ar muscovite and biotite ages from the late Cambrian Kafiristan pluton are 379.7 ± 1.7 Ma and 47.2 ± 0.3 Ma, respectively. The muscovite age may record cooling or partial resetting, while the biotite age is interpreted to record a thermal disruption associated with the early stages of continental collision in the Himalayan system. A 111.0 ± 0.6 Ma muscovite age from the northern part of the Tirich Mir pluton (∼123 Ma old; U-Pb) is interpreted to indicate a recrystallization event ∼12 Myrs after its intrusion. In addition, a younger muscovite age of 47.5 ± 0.2 Ma was derived from the opposite side of the same pluton in the immediate hanging wall of the Tirich Mir fault. This Eocene age is interpreted to represent the time of recrystallization during fault (re)activation in the early stages of India-Asia continent-continent collision. 40Ar/39Ar biotite analysis from the Buni-Zom pluton yields an age of 61.6 ± 1.1 Ma and is interpreted to reflect cooling at mid-upper crustal levels subsequent to the pluton’s emplacement in the middle Cretaceous. Finally, 17.1–21.3 Ma 40Ar/39Ar ages from the Garam Chasma pluton and surrounding metapelites indicate cooling immediately following crystallization of the leucogranite body in the earliest Miocene/latest Oligocene.The younger cooling history is resolved by fission track dating of apatite (AFT). In the vicinity of the bounding Tirich Mir fault, the Tirich Mir pluton yields an AFT age of 1.4 ± 0.3 Ma, which is consistent with active exhumation associated with the surface uplift of the 7700+ m Tirich Mir peak. The Garam Chasma pluton has a young age of 3.5 ± 0.2 Ma, which also records rapid rock uplift and exhumation in the area. Finally, an AFT age of 9.1 ± 2.1 Ma was extracted from a metapelite in the footwall of an east verging thrust fault separating it from the Garam Chasma pluton to the west. The difference in ages, Pliocene vs. late Miocene, reflect differential cooling/exhumation paths across that structure.

Partial reset HDR image sensor with improved fixed pattern noise performance

An efficient method is presented to achieve 4T pixel dynamic range extension whilst keeping the fixed pattern noise (FPN) low. The method utilizes the floating diffusion node as a secondary photocharge integration node with a partial reset applied to the floating diffusion node. The output image signal is a recombination of the linear signal integrated in the photodiode node, and a compressed signal integrated in the floating diffusion node. The recombination algorithm suppresses the FPN stemming from the variable transfer gate potential barrier height. An image sensor array of 1344x1008 pixels was built in 0.11um technology. We demonstrate the preservation of low light sensitivity of 4T pixels, a dark noise of 3.5e-, and a dynamic range for the current sensor of 115 dB, with potential to greatly exceed 120-dB. Further, the FPN stemming from the transfer gate potential barrier height variation does not degrade the image; the pixel compressive response can be controlled on a per frame basis depending on the scene, and the HDR scene is captured during one frame. The sensor combines the properties that are crucial for automotive and other machine vision applications.

Understanding phengite argon closure using single grain fusion age distributions in the Cycladic Blueschist Unit on Syros, Greece

The preservation of 40Ar/39Ar ages of high pressure (HP) metamorphic white mica reflects an interplay of processes that mobilise 40Ar, either through mica recrystallisation or by diffusive 40Ar loss. The applicability of resulting ages for dating tectonic processes is critically dependent on whether either of these processes can be proven to be efficient and exclusively active in removing 40Ar from mica. If not, preservation of an inherited or mixed age signal in a sample must be considered for interpretation. The Cycladic Blueschist Unit on Syros has become a new focal area in the discussion of the geological significance of argon age results from multi-grain step heating experiments. While some argue that age results can directly be linked to deformation or metamorphic growth events, others interpret age results to reflect the interplay of protracted recrystallisation and partial resetting, preserving a mixed age signal. Here, we demonstrate the potential of a new approach of multiple single grain fusion dating. Using the distribution of ages at the sample, section and regional scale, we show that in Northern Syros mica ages display systematic trends that can be understood as the result of three competing processes: 1) crystallisation along the prograde to peak metamorphic path, 2) a southward trend of increasing 40Ar loss by diffusion and 3) localised and rock type dependent deformation or metamorphic reactions leading to an observed age spread typically limited to ∼10 Myr at the section scale. None of the sections yielded the anomalously old age results that would be diagnostic for significant excess 40Ar. The recorded trends in ages for each of the studied sections reflect a range of P–T conditions and duration of metamorphism. Diffusion modelling shows that in a typical subduction metamorphic loop, subtle variations in P–T–t history can explain that age contrasts occur on a regional scale but are limited on the outcrop scale. Our new approach provides a comprehensive inventory of the range of ages present in different rocks and at different scales, which results in a more refined understanding of argon retention and isotopic closure of phengite and the geological significance of the ages. We verify the added value of our new approach by comparison with multi-grain step heating experiments on selected samples from the same sections.

Improvement of SET variability in TaOx based resistive RAM devices

Improvement or at least control of variability is one of the key challenges for Redox based resistive switching memory technology. In this paper, we investigate the impact of a serial resistor as a voltage divider on the SET variability in Pt/Ta2O5/Ta/Pt nano crossbar devices. A partial RESET in a competing complementary switching (CS) mode is identified as a possible failure mechanism of bipolar switching SET in our devices. Due to a voltage divider effect, serial resistance value shows unequal impact on switching voltages of both modes which allows for a selective suppression of the CS mode. The impact of voltage divider on SET variability is demonstrated. A combination of appropriate write voltage and serial resistance allows for a significant improvement of the SET variability.

Mass transport and fractionation during monazite alteration by anisotropic replacement

The present experimental study investigates the causes of anisotropic replacement and its impact on the element mass transfer during monazite alteration by combining in situ characterization of solid and fluid products. Starting material of standard Manangotry monazite was placed at 200MPa with 18O doped fluids, at temperature (T) between 300 and 600°C, for durations between 14 and 114days, in some cases with hematite-magnetite buffer, and in presence of pre-fractured quartz crystals. For all experiments with NaOH at T>400°C, monazite products show a replacement rim (altered domain), but with complex microstructures that are best explained by nanoscale observations. At 400°C (and 500°C), replacement propagates anisotropically through the unaltered domain, due to preferentially oriented dissolution and/or fracturing at the reaction interface. The altered domain corresponds to nanochannels of secondary monazite (Mnz2) intruding primary monazite (Mnz1), with nanopores filled by amorphous Si-rich inclusions at the reaction front (interface). At 600°C, the altered domain increases in volume and becomes homogeneous and non-porous, due to textural (and chemical) reequilibration. However, nanoscale observations reveal an anisotropic propagation associated with dislocations and preservation of Mnz1 relics within the apparently homogeneous altered domain. Textural equilibration leads to transient pores/inclusions, which preferentially move toward the reaction front. In all experimental products, the abundant porosity attests to significant mass transfer during monazite replacement. Nanomixture within altered domains hampers accurate determination of Mnz2 composition, and is assumed to be responsible for the Pb measured in the rim, due to Mnz1 contribution. However, composition measurements indicate that Mnz2 contains higher light rare earth elements (LREE), higher Th/U ratio but lower Y, Th, U, Pb and Ca contents compared to Mnz1. Elements released in the fluid by monazite replacement are mobilized from the reaction front toward the grain boundary, and then redistributed between secondary Th-silicates and phosphates, Si-rich gel-like material and aqueous fluids. At T>500°C, analyses of inclusions trapped in replaced quartz confirm an efficient REE solubility in the alkaline solutions. The Si-rich gel-like inclusions contain high amounts of REE (e.g. 950–4600ppm Ce), Th (4480–6170ppm) and U (30–110ppm), while aqueous fluid inclusions have high concentrations of REE and Th (around 100s of ppm) compared to common natural brines. There is a fractionation of Th and U during Mnz1 replacement (Th/U ~70) with low Th/U ratios in the aqueous fluid (7–23) compared to the secondary solid products (up to 150), independently of the initial presence of hematite-magnetite buffer. This accounts for a fractionation within the isotopic Th-Pb and U-Pb ages within the altered domain. In natural samples observed microscopically, the complex anisotropic geometry of the replacement can lead to a nanomixture within apparently homogeneous altered domains (with partial resetting of the U-Th-Pb geochronometer), and to misleading interpretations of secondary inclusions within apparently unaltered domain.

The complexities of zircon crystllazition and overprinting during metamorphism and anatexis: An example from the late Archean TTG terrane of western Shandong Province, China

There are different viewpoints on metamorphic and anatectic zircons recording ages of 2.45–2.48Ga or even younger in some areas of the North China Craton where both late Neoarchean and late Paleoproterozoic tectono-thermal events are well developed. These are: 1) partial resetting of the U-Pb isotopic system in the late Neoarchean zircons, 2) metamorphism lasting from the late Neoarchean to the earliest Paleoproterozoic, and 3) earliest Paleoproterozoic metamorphism as separate different event. Western Shandong Province is an area where the late Neoarchean tectono-thermal event is widely developed but the late Paleoproterozoic event has not been identified. This provides an opportunity to understand the geological processes around the Archean-Proterozoic boundary. Based on a field study, we carried out SHRIMP U-Pb zircon dating on seventeen samples of ∼2.5Ga old metamorphic and anatectic rocks, including tonalite, trondhjemite, granodiorite, gabbro, quartz diorite, granite and paragneiss with primary emplacement or depositional ages of 2.52–2.68Ga. Anatectic zircons show some textural and compositional features: a) Homogenous or blurred oscillatory zoning, b) high U contents and low in Th/U ratios (commonly <0.3), c) rare idiomorphic morphologies, and d) commonly containing inherited (xenocrystic) cores. We conclude that the strong late Neoarchean event is widespread in western Shandong and is limited between ∼2.50 and 2.54Ga. In contrast, apparent 2.45–2.48Ga metamorphic zircon ages in some other areas of the North China Craton may be the result of overprinting and partial recrystallization of Neoarchean metamorphic zircons during the late Paleoproterozoic event. The Archaean rocks of western Shandong can be divided into three belts, namely Belts A, B and C from the northeast to the southwest. The difference between Belts A and B in ∼2.5Ga metamorphic and anatectic intensity may indicate that the former was elevated to a higher crustal level compared with the latter at the end of the Neoarchean.

Modeling of the multilevel conduction characteristics and fatigue profile of Ag/La1/3Ca2/3MnO3/Pt structures using a compact memristive approach

The hysteretic conduction characteristics and fatigue profile of La1/3Ca2/3MnO3 (LCMO)-based memristive devices were investigated. The oxide films were grown by pulsed laser deposition (PLD) and sandwiched between Ag and Pt electrodes. The devices exhibit bipolar resistive switching (RS) effect with well-defined intermediate conduction states that arise from partial SET and RESET events. The current-voltage curves are modeled and simulated using a compact memristive approach. Two equations are considered: one for the electron transport based on the double-diode equation and the other for the memory state of the device driven by the play operator with logistic ridge functions. An expression that accounts for the remnant resistance of the device is obtained after simplifying the model equations in the low-voltage limit. The role played by the power dissipation in the LCMO reset dynamics as well as the asymmetrical reduction of the resistance window caused by long trains of switching pulses are discussed.

Ductile–brittle deformation effects on crystal-chemistry and U–Pb ages of magmatic and metasomatic zircons from a dyke of the Finero Mafic Complex (Ivrea–Verbano Zone, Italian Alps)

A detailed microstructural, geochemical and geochronological study was performed on zircon grains from plagioclase-rich dioritic dykes discordantly intruded within meta-diorites/gabbros forming the External Gabbro unit of the Finero Mafic Complex (Italian Alps). This unit is exposed as part of a near complete crustal section spanning from mantle rocks to upper crustal metasediments (Val Cannobina, Ivrea–Verbano Zone, Italy). The leucocratic dykes consist mainly of plagioclase (An18–24Ab79–82Or0.3–0.7) with subordinate amounts of biotite and spinel defining melanocratic layers. Zircon and corundum are common accessory phases. Both the dykes and the surrounding meta-diorites/gabbros show evidence of ductile deformation under amphibolite-facies conditions.Zircon grains/fragments (up to 2mm in length) occur as porphyroclasts surrounded by fine-grained plagioclase within the leucocratic domains and may occur within the melanocratic layers completely or partially surrounded by biotite and spinels. Fractures are common within zircon, define networks and have associated displacements occasionally and/or they can be filled by secondary minerals.Cathodoluminescence (CL) images reveal that zircon grains from the leucocratic layers show relicts of primary magmatic (i.e. oscillatory and or sector) zoning generally related with the crystal shapes or crystallographic orientation, whereas those from the melanocratic domains do not. In both cases, zircon shows secondary CL features, i.e. mosaic-like textures, due to deformation. EBSD maps confirmed a profuse mosaic texture, resulting in an internal misorientation of ca. 10°, generally associated with fractures. Locally, zircon shows clear evidence of crystal-plastic deformation at the edges, with a gradual misorientations of up to 12°, suggesting an origin prior fragmentation.Trace elements and U–Pb analyses were carried out by LA-ICP-MS directly on petrographic thin sections. Such in situ investigations revealed a strong correlation between internal zircon structures, chemistry, U–Pb isotope ratios and mylonitic fabric.U–Pb data return highly discordant and variable ages. The 206Pb/238U ages may range from ca. 297 to 198Ma within the same zircon grain from the leucocratic layers, whereas 206Pb/238U younger than 250Ma were systematically obtained from zircon within the melanocratic layers. The 206Pb/238U data younger than ca. 240Ma from zircon grains within the leucocratic layers were obtained from narrow axial stripes observed in CL images and oriented parallel or at low-angle with respect to the foliation planes. These stripes are characterized by an overall HREE, Y, U and Th enrichment possibly reflecting deformation of the grain in presence of interstitial fluid phases. Combining U–Pb data, microstructure and zircon CL features, we suggest a multistage evolution of the dykes whereby the melanocratic layers are the result of a Late Permian metasomatic event promoting modification of the pre-existing mineral assemblage of the (Late Carboniferous–Early Permian?) dykes and deformation and partial resetting of zircon porphyroclasts. This has important implications in the geology of the Ivrea–Verbano Zone because, having the dyke intruded the External Gabbro unit before Triassic (probably during Carboniferous–Permian), the latter cannot be considered a Triassic intrusion. At least part of the External Gabbro unit is Carboniferous–Permian as the other mafic bodies of the Ivrea–Verbano Zone.

Leak Stopper

To alleviate high energy dissipation of unnecessary snooping accesses, snoop filters have been designed to reduce snoop lookups. These filters have the problem of decreasing filtering efficiency, and thus usually rely on partial or whole filter reset by detecting block evictions. Unfortunately, the reset conditions occur infrequently or unevenly (called passive filter deletion ). This work proposes the concept of revitalized snoop filter (RSF) design, which can actively renew the destination filter by employing a generation wrapping-around scheme for various reference behaviors. We further utilize a sampling mechanism for RSF to timely trigger precise filter revitalizations, so that unnecessary RSF flushing can be minimized. The proposed RSF can be integrated to various existent inclusive snoop filters with only a minor change to their designs. We evaluate our proposed design and demonstrate that RSF eliminates 58.6% of snoop energy compared to JETTY on average while inducing only 6.5% of revitalization energy overhead. In addition, RSF eliminates 45.5% of snoop energy compared to stream registers on average and only induces 2.5% of revitalization energy overhead. Overall, these RSFs reduce the total L2 cache energy consumption by 52.1% (58.6% -- 6.5%) as compared to JETTY and by 43% (45.5% -- 2.5%) as compared to stream registers. Furthermore, RSF improves the overall performance by 1% to 1.4% on average compared to JETTY and stream registers for various benchmark suites.

Assessing the Risks Associated with MRI in Patients with a Pacemaker or Defibrillator

BackgroundThe presence of a cardiovascular implantable electronic device has long been a contraindication for the performance of magnetic resonance imaging (MRI). We established a prospective registry to determine the risks associated with MRI at a magnetic field strength of 1.5 tesla for patients who had a pacemaker or implantable cardioverter–defibrillator (ICD) that was “non–MRI-conditional” (i.e., not approved by the Food and Drug Administration for MRI scanning).MethodsPatients in the registry were referred for clinically indicated nonthoracic MRI at a field strength of 1.5 tesla. Devices were interrogated before and after MRI with the use of a standardized protocol and were appropriately reprogrammed before the scanning. The primary end points were death, generator or lead failure, induced arrhythmia, loss of capture, or electrical reset during the scanning. The secondary end points were changes in device settings.ResultsMRI was performed in 1000 cases in which patients had a pacemaker and in 500 cases in which patients had an ICD. No deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI. One ICD generator could not be interrogated after MRI and required immediate replacement; the device had not been appropriately programmed per protocol before the MRI. We observed six cases of self-terminating atrial fibrillation or flutter and six cases of partial electrical reset. Changes in lead impedance, pacing threshold, battery voltage, and P-wave and R-wave amplitude exceeded prespecified thresholds in a small number of cases. Repeat MRI was not associated with an increase in adverse events.ConclusionsIn this study, device or lead failure did not occur in any patient with a non–MRI-conditional pacemaker or ICD who underwent clinically indicated nonthoracic MRI at 1.5 tesla, was appropriately screened, and had the device reprogrammed in accordance with the prespecified protocol. (Funded by St. Jude Medical and others; MagnaSafe ClinicalTrials.gov number, NCT00907361.)

Inferring a Neoproterozoic orogeny preceding the Rodinia break-up in the Sirohi Group, NW India

Abstract Recent studies indicate the Delhi Orogeny to be a Grenvillian-age collision event in the NW Indian Shield. West of the southern part of the South Delhi Fold Belt, aeromagnetic anomalies show a high-angle relationship with the Delhi Fold Belt trend. We examined an argillaceous–calcareous metamorphosed sequence exposed within and adjacent to this aeromagnetic anomaly. This sequence, deposited over a granitic basement, is reported as the Sirohi Group. The basement granite is dated to be 892±10 Ma (Erinpura age) and this was partially reset at 815±43 Ma. The metapelites preserve a low- to medium-grade metamorphic assemblage (peak temperature of c. 460°C) and the metamorphism took place at 822±29 Ma, which was partially reset at 723±65 Ma. The partial resetting can be ascribed to the Malani eruption. Control of accessory minerals on the garnet trace element chemistry is evident in the Y distribution of the two analysed garnets. It is contended that the Rodinia break-up, marked by Malani Igneous Suite, was preceded by an orogenic event (the Sirohi Orogeny) which marked the culminating mountain-building event in the cratonization of the NW Indian Shield.

Geobody architecture, genesis and petrophysical characteristics of the Budakalász travertines, Buda Hills (Hungary)

Subsurface Pre-salt Lower Cretaceous reservoir systems encountered offshore Brazil and Angola that consist of porous continental carbonates are difficult to access because of the limited core material that is under concession. Therefore, it is important to study comparable continental carbonate analogues, such as travertines and lacustrine carbonates, that potentially possess similar porosity and permeability characteristics. The Budakalasz Pleistocene travertines (Buda Hills, Hungary) have been studied from a sedimentological, geochemical and reservoir properties point of view in order to understand their formation, petrophysical properties and 3D reservoir architecture. The three-dimensional geobody architecture of the Budakalasz travertines illustrates the potential complexity of kilometre scale continental carbonate systems. Heterogeneous low angle sloping travertine lobes consisting of terrace slope, smooth slope and reed facies, are covered by a lime mudstone dominated, gastropod- and charophyte-rich marsh-pool facies. The observed facies represent a change from a subaerial travertine to a palustrine to lacustrine system, reflecting the ceasing of the system due to tectonic uplift. The dominant paleo-flow direction of the sloping lobes was towards the Danube depression, with several subordinate flow systems identified. The SrCO isotope geochemical signatures reflect travertine precipitation at ambient to superambient temperatures from meteoric derived fluids with a mixed CO2 origin of the marine carbonate substrate rocks, a potential atmospheric and a soil-derived component. Although the uniform signatures of the stable oxygen and carbon isotopes, in addition to petrographic observations suggest partial diagenetic isotopic resetting, the primary isotope trends seem to have been preserved. A reservoir-oriented facies evaluation in the three-dimensional geobody frame of the Budakalasz carbonates based on porosity and permeability core plug analyses reveals their heterogeneous nature. Terrace, smooth slope and marsh-pool facies have considerable porosities of 5–15%, while the porosity of the reed facies may reach up to 27%. Permeability of all facies is strongly anisotropic, mainly controlled by a better connectivity along layer-parallel primary pores. The reconstruction of the 3D geobody architecture of the Budakalasz lobe complex coupled to its geochemical and petrophysical properties provides a unique dataset that contributes in understanding fossil travertine systems.

On the geometric relationship between deformation microstructures in zircon and the kinematic framework of the shear zone

We present novel microstructural analyses of zircon from a variety of strained rocks. For the first time, multiple plastically deformed zircon crystals were analyzed in a kinematic context of the respective host shear zones. Our aim was to derive how the orientation of zircon grains in a shear zone affects their deformation, based on careful in situ observations. For sampling, we selected zircon-bearing rocks that were deformed by simple shear. Samples covered a range of P–T conditions and lithologies, including various meta-igneous and meta-sedimentary gneisses.Microstructural analyses of zircon crystals in situ with scanning electron backscatter diffraction mapping show strong geometrical relationships between orientations of: (i) the long axes of plastically deformed zircon crystals, (ii) the crystallographic orientation of misorientation axes in plastically deformed zircon crystals and (iii) the foliation and lineation directions of the respective samples. We assume that zircon crystals did not experience post-deformation rigid body rotation, and thus the true geometric link can be observed. The relationships are the following: (a) plastically deformed zircon crystals usually have long axes parallel to the mylonitic foliation plane; (b) crystals with <c> axes oriented at an angle>15° to the foliation plane are undeformed or fractured.Zircon crystals that have <c> axes aligned parallel or normal to the stretching lineation within the foliation plane develop misorientation and rotation axes parallel to the [001] crystallographic direction. Zircon grains with the <c> axis aligned at 30–60° to the lineation within the foliation plane often develop either two low Miller indices misorientation axes or one high Miller indices misorientation axis. Host phases have a significant influence on deformation mechanisms. In a relatively soft matrix, zircon is more likely to develop low Miller indices misorientation axes than in a relatively strong matrix.These relationships are independent of zircon's grain size and shape, and reflect the strong geometric control of the macroscopic kinematic rotation axis on the crystal-plastic deformation behavior of zircon and on the geometry of its slip systems. We describe previously unknown rheological and crystallographic properties of zircon, which suggest a tool for deriving an orientation of the plastically deformed zircon crystals with respect to the associated foliation and stretching lineation. Additionally, relationships between zircon deformation microstructures and the macroscopic kinematic framework have implications for zircon geochronology. If deformation events result in zircon distortion and, as a consequence, partial or complete resetting of the zircon isotopic system, the age of deformation can be accurately dated.

Stability of simultaneously block triangularisable switched systems with partial state reset

ABSTRACTWe study the stability of a certain class of switched systems where discontinuous jumps (resets) on some of the state components are allowed, at the switching instants. It is known that, if all components of the state are available for reset, the system can be stabilisable by an adequate choice of resets. However, this question may have negative answer if there are forbidden state components for reset. We give a sufficient condition for the stabilisability of a switched system, under arbitrary switching, by partial state reset in terms of a block simultaneous triangularisability condition. Based on this sufficient condition, we show that the particular class of systems with partially commuting stable system matrices is stabilisable by partial state reset. We also provide an algorithm that allows testing whether a switched system belongs to this particular class of systems.

Partial resetting of the U-Th-Pb systems in experimentally altered monazite: Nanoscale evidence of incomplete replacement

Research Article| June 01, 2016 Partial resetting of the U-Th-Pb systems in experimentally altered monazite: Nanoscale evidence of incomplete replacement Alexis Grand’Homme; Alexis Grand’Homme 1ISTerre (Institut des Sciences de la Terre), University Grenoble Alpes, 38058 Grenoble Cedex 9, France Search for other works by this author on: GSW Google Scholar Emilie Janots; Emilie Janots * 1ISTerre (Institut des Sciences de la Terre), University Grenoble Alpes, 38058 Grenoble Cedex 9, France *E-mails: janotse@ujf-grenoble.fr; anne.magali.seydoux@univ-st-etienne.fr. Search for other works by this author on: GSW Google Scholar Anne-Magali Seydoux-Guillaume; Anne-Magali Seydoux-Guillaume * 2Laboratoire Magmas et Volcans LMV (UMR 6524 CNRS-UBP-UJM1 IRD), 42023 Saint-Etienne, France *E-mails: janotse@ujf-grenoble.fr; anne.magali.seydoux@univ-st-etienne.fr. Search for other works by this author on: GSW Google Scholar Damien Guillaume; Damien Guillaume 2Laboratoire Magmas et Volcans LMV (UMR 6524 CNRS-UBP-UJM1 IRD), 42023 Saint-Etienne, France Search for other works by this author on: GSW Google Scholar Valérie Bosse; Valérie Bosse 3Laboratoire Magmas et Volcans LMV (UMR 6524 CNRS-UBP-UJM-IRD), 63038 Clermont-Ferrand, France Search for other works by this author on: GSW Google Scholar Valérie Magnin Valérie Magnin 1ISTerre (Institut des Sciences de la Terre), University Grenoble Alpes, 38058 Grenoble Cedex 9, France Search for other works by this author on: GSW Google Scholar Geology (2016) 44 (6): 431–434. https://doi.org/10.1130/G37770.1 Article history received: 08 Feb 2016 rev-recd: 12 Apr 2016 accepted: 12 Apr 2016 first online: 09 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 Alexis Grand’Homme, Emilie Janots, Anne-Magali Seydoux-Guillaume, Damien Guillaume, Valérie Bosse, Valérie Magnin; Partial resetting of the U-Th-Pb systems in experimentally altered monazite: Nanoscale evidence of incomplete replacement. Geology 2016;; 44 (6): 431–434. doi: https://doi.org/10.1130/G37770.1 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 SocietyGeology Search Advanced Search Abstract Alteration experiments on natural monazite crystals (Manangotry standard, Madagascar) under alkali conditions at 300, 400, 500 and 600 °C and 200 MPa were conducted to clarify mechanisms behind incomplete resetting of U-Th-Pb geochronological systems in monazite replaced by dissolution and precipitation processes. Above 400 °C, experimental products show typical replacement textures: a compositionally distinct monazite rim, referred as altered rim, surrounds the primary monazite (Mnz1). Isotopic and electron microprobe U-Th-Pb in situ dating of the altered rim yields intermediate ages between pristine monazite (555 Ma) and complete experimental resetting (0 Ma). Lead is systematically detected in altered rims, with concentration decreasing from 400 °C to 600 °C. The origin of incomplete resetting is elucidated with transmission electron microscope images that reveal an incomplete replacement of Mnz1 by a secondary monazite (Mnz2) within the altered rim. With increasing temperature, the size and volume of the Mnz2 within the altered rim become more important. Because no structural Pb or Pb nanoinclusions were observed, Pb in the altered rim is attributed to the Mnz1 component. Partial resetting of U-Th-Pb systems depends on the nanomixture of different Mnz1 proportions in the analyzed volume, and explains the higher rejuvenation at 600 °C than at lower temperatures. Although microanalytical techniques have the spatial resolution to date micrometer-sized rims, they are unable to resolve a nanoscale mixture of pristine and secondary monazite that could occur in altered rims formed by fluid-driven replacement, especially at low temperatures. Porosity and/or inclusions and complex age scattering in zoned monazite are significant markers that can indicate a possible nano-sized partial replacement. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A systematic evaluation of the Zr-in-rutile thermometer in ultra-high temperature (UHT) rocks

The Zr-in-rutile geothermometer is potentially a widely applicable tool to estimate peak metamorphic temperatures in rocks from diverse geological settings. In order to evaluate its usefulness and reliability to record and preserve high temperatures in granulite facies rocks, rutile from UHT rocks was investigated to assess different mechanisms of Zr (re-)distribution following cooling from high temperature. Granulite facies paragneisses from the lowermost part of the Ivrea Zone, Italy, incorporated as thin sheets into the extensive basaltic body of the Mafic Complex were selected for this study. The results show that Zr-in-rutile thermometry, if properly applied, is well suited to identify and study UHT terranes as it preserves a record of temperatures up to 1190 °C, although the thermometer is susceptible to partial post-peak metamorphic resetting by Zr diffusion. Texturally homogeneous rutile grains preserve Zr concentrations corresponding to temperatures of prograde rutile growth. Diverse rutile textures and relationships between some rutile host grains and included or adjacent Zr-bearing phases bear testimony to varying mechanisms of partial redistribution and resetting of Zr in rutile during cooling and link Zr-in-rutile temperatures to different steps of the metamorphic evolution. Rutile grains that equilibrated their Zr concentrations at temperatures above 1070 °C (i.e. 1.1 wt% Zr) could not retain all Zr in the rutile structure during cooling and exsolved baddeleyite (ZrO2). By subsequent reaction of baddeleyite exsolution lamellae with SiO2, zircon needles formed before the system finally closed at 650–700 °C without significant net loss of Zr from the whole host rutile grain. By reintegration of zircon exsolution needles, peak metamorphic temperatures of up to 1190 °C are derived for the studied rocks, which demonstrates the suitability of this solution thermometer to record UHT conditions and also confirms the extraordinary geological setting of the lowermost part of the Ivrea Zone.

An impulsive dynamical systems framework for reset control systems

ABSTRACTImpulsive dynamical systems is a well-established area of dynamical systems theory, and it is used in this work to analyse several basic properties of reset control systems: existence and uniqueness of solutions, and continuous dependence on the initial condition (well-posedness). The work scope is about reset control systems with a linear and time-invariant base system, and a zero-crossing resetting law. A necessary and sufficient condition for existence and uniqueness of solutions, based on the well-posedness of reset instants, is developed. As a result, it is shown that reset control systems (with strictly proper plants) do not have Zeno solutions. It is also shown that full reset and partial reset (with a special structure) always produce well-posed reset instants. Moreover, a definition of continuous dependence on the initial condition is developed, and also a sufficient condition for reset control systems to satisfy that property. Finally, this property is used to analyse sensitivity of reset control systems to sensor noise. This work also includes a number of illustrative examples motivating the key concepts and main results.

Zirconolite, zircon and monazite-(Ce) U-Th-Pb age constraints on the emplacement, deformation and alteration history of the Cummins Range Carbonatite Complex, Halls Creek Orogen, Kimberley region, Western Australia

In situ SHRIMP U-Pb dating of zirconolite in clinopyroxenite from the Cummins Range Carbonatite Complex, situated in the southern Halls Creek Orogen, Kimberley region, Western Australia, has provided a reliable 207Pb/206Pb age of emplacement of 1009 ± 16 Ma. Variably metamict and recrystallised zircons from co-magmatic carbonatites, including a megacryst ~1.5 cm long, gave a range of ages from ~1043–998 Ma, reflecting partial isotopic resetting during post-emplacement deformation and alteration. Monazite-(Ce) in a strongly foliated dolomite carbonatite produced U-Th-Pb dates ranging from ~900–590 Ma. Although the monazite-(Ce) data cannot give any definitive ages, they clearly reflect a long history of hydrothermal alteration/recrystallisation, over at least 300 million years. This is consistent with the apparent resetting of the Rb-Sr and K-Ar isotopic systems by a post-emplacement thermal event at ~900 Ma during the intracratonic Yampi Orogeny. The emplacement of the Cummins Range Carbonatite Complex probably resulted from the reactivation of a deep crustal structure within the Halls Creek Orogen during the amalgamation of Proterozoic Australia with Rodinia over the period ~1000–950 Ma. This may have allowed an alkaline carbonated silicate magma that was parental to the Cummins Range carbonatites, and generated by redox and/or decompression partial melting of the asthenospheric mantle, to ascend from the base of the continental lithosphere along the lithospheric discontinuity constituted by the southern edge of the Halls Creek Orogen. There is no evidence of a link between the emplacement of the Cummins Range Carbonatite Complex and mafic large igneous province magmatism indicative of mantle plume activity. Rather, patterns of Proterozoic alkaline magmatism in the Kimberley Craton may have been controlled by changing plate motions during the Nuna–Rodinia supercontinent cycles (~1200–800 Ma).