•The Kontinentale Tiefbohrung reveals defects of the apatite fission-track method.•Near-isothermal holding lasts since the Late Cretaceous to Palaeocene exhumation.•Fossil tracks in natural apatite ...do not etch as induced tracks in annealed apatite.•Surface-intersecting and confined fission tracks are sampled with different bias.•None of the annealing models can claim decisive support from geological data.
Deep boreholes serve as natural laboratories for testing thermochronometers under geological conditions. The Kontinentale Tiefbohrung (KTB) is an interesting candidate because the geological evidence suggests that approximate isothermal holding since the last documented exhumation in the Late Cretaceous to Palaeocene is a reasonable assumption for the thermal histories of the KTB samples. We report 30 new apatite fission-track ages and 50 new mean confined track lengths determined on cores from the 4km deep pilot hole. The ϕ- and ζ-external detector ages are consistent with the population ages from earlier studies and together define a clear age profile. The mean track lengths from this and earlier studies reveal the effects of experimental factors. The measured age and length profiles are compared with the predictions of 24 annealing models for isothermal holding. There are clear discrepancies between the measured and calculated profiles. Down to 1.5km depth, the measured mean track lengths are shorter than the predicted. The balance of methodological evidence indicates that this is due to seasoning, i.e., a shortening of the fossil confined tracks without attendant age reduction. From 2.5 to 4.0km depth, the mean track lengths are longer than the predictions. This suggests that the bias model that weights the probabilities of observing tracks of different length and which is based on experiments relating surface track densities to mean track lengths is not appropriate for confined tracks. Experimental and methodological factors are sometimes difficult to disentangle, but present a sufficient margin for there to be no need to go against the independent geological evidence. Unknown geological events cannot be ruled out but their existence cannot be inferred from the fission-track data alone, much less can the nature or magnitude of such events be specified.
The results of apatite fission-track modelling are only as accurate as the method, and depend on the assumption that the processes involved in the annealing of fossil tracks over geological times are ...the same as those responsible for the annealing of induced fission tracks in laboratory experiments. This has hitherto been assumed rather than demonstrated. The present critical discussion identifies a number of methodical problems from an examination of the available data on age standards, borehole samples and samples studied in the framework of geological investigations. These problems are related to low- (<60°C) and high-temperature (>60°C) annealing on a geological timescale and to the procedures used for calculating temperature–time paths from the fission-track data. It is concluded that it is not established that the relationship between track length and track density and the appearance of unetchable gaps, observed in laboratory annealing experiments on induced tracks, can be extrapolated to the annealing of fossil tracks on a geological timescale. This in turn casts doubt on the central principle of equivalent time.
That such uncertainties still exist is in no small part due to an insufficient understanding of the formation, structure and properties of fission tracks at the atomic scale and to a lack of attention to the details of track revelation. The methodical implications of discrepancies between fission track results and the independent geological evidence are rarely considered. This presents a strong case for the re-involvement of track physicists in fundamental fission track research.
The Middle to Late Cretaceous central Anatolian granitoids intrude the supra-subduction zone-type central Anatolian ophiolite and medium- to high-grade metasediments of central Anatolian crystalline ...complex and are overlain by Late Palaeocene to Early/Middle Eocene sediments. Their single-zircon
207Pb–
206Pb evaporation ages define three clusters: (1) Cenomanian–Turonian (weighted-mean age: 94.9
±
3.4 Ma), (2) Turonian–Santonian (85.5
±
5.5 Ma) and (3) Campanian (74.9
±
3.8 Ma). Their hornblende and biotite
40Ar–
39Ar and K–Ar cooling ages cluster around 80–65 Ma. The close hornblende and biotite ages reflect rapid exhumation of a mid-crustal section during the Campanian–Maastrichtian. Early to Middle Palaeocene (57–62 Ma) apatite fission-track age clusters date the tail end of this exhumation episode. It is proposed that the central Anatolian granitoid melts were generated in a post-collisional extensional setting following the docking of an oceanic island arc onto the Tauride–Anatolide platform. Campanian–Maastrichtian to Early/Middle Palaeocene rapid exhumation event is considered to result from continent–continent collisions between Eurasian plate and the Tauride–Anatolide platform along the İzmir–Ankara–Erzincan suture zone.
Dating and forward modelling of the fission-track data of apatite samples from the Dereli–Şebinkarahisar region, south of Giresun in the Eastern Turkish Pontides, provides quantitative data on the ...regional tectonics resulting from the closure of neo-Thetys and the collision of Eurasia and Gondwana. The age vs. elevation profiles identified Senonian (80.7±3.2 to 62.4±2.5 Ma) slow uplift and denudation, interpreted as the result of the diapiric ascent of subduction-related plutons above the neo-Tethyan subduction zone beneath the Eurasian continent. This was followed by rapid differential uplift during the Palaeocene–Early Eocene (57.4±2.4 to 47.8±2.4 Ma), which juxtaposed granitoid units of different ages, compositions, and emplacement levels in the crust, and is thought to be related to the collision between the Pontide (Eurasian) and Anatolide (Gondwana) basements. The modelling results must be interpreted with caution, but appear to indicate a period of Mio-Pliocene (ca. 5 Ma) reheating related to volcanism associated with the westward escape of the Anatolian plate and uplift from the Pliocene (ca. 3.5 Ma) up to the present.
Apatite fission-track (AFT) and structural data outline the Late Cretaceous−Cenozoic history of the southern Tan-Lu fault zone (TLFZ), one of Asia's major faults, the Triassic–Jurassic Dabie orogen, ...Earth's largest track of ultrahigh-pressure rock exposure, and its foreland, the Yangtze foreland fold-thrust belt. The fission-track analyses utilized the independent (
φ-),
Z- and
ξ-methods for age determination, which yielded within error identical ages. Ages from Triassic–Jurassic syn-orogenic foreland sediments are younger than their depositional age and thus were reset. A group of ages records rapid cooling following shallow emplacement of granitoids of the widespread latest Jurassic−Early Cretaceous “Yanshanian” magmatism. Most ages are 90 to 55 Ma and document cooling following reheating at 110–90 Ma, the time when the basement units of the Dabie Shan were last at >200 °C. This cooling coincides with rifting marked by the Late Cretaceous−Eocene red-bed deposition in eastern China. During this period, the Dabie basements units exhumed in the footwall of the Tan-Lu fault with the Qianshan basin in the hanging wall; the associated stress field is transtensional (NW-trending principal extension direction). The youngest fission-track ages and temperature–time path modeling point to enhanced cooling in the footwall of the Tan-Lu and associated faults at 45±10 Ma. The related stress field is transtensional, with the principal extension direction changing trend from NW to W. It may be the far-field expression of the India–Asia collision superposed on the back-arc extension setting in eastern China. A regional unconformity at ∼25 Ma marks an upper bound for the inversion of the Late Cretaceous−Eocene rift structures. During the Neogene, further subsidence in the eastern China basins was accommodated by sub-horizontal NE–SW extension, and followed by the presently active NW–SE extension. The Tan-Lu fault along the eastern edge of the Dabie Shan had normal and then sinistral-transpressive motion during the Late Cretaceous−Eocene. Its motion changed during the Neogene from sinistral transtensive to normal and then to its present dextral transtensive activity.
In order to evaluate the effect of repeated cleaning on EUV reticles, specifically, on the etched Mo/Si multilayer, wafer-based test structures with a mimic of this etched Mo/Si multilayer ...(“black-border”) were fabricated. The resistance of Mo and Si towards alkaline chemistries was tested and quantified using these test structures. The initial passivating film on Mo seems to play a role in delaying the Mo to further oxidize and dissolve in alkaline solutions. For the cleaning times used (minutes) the Mo surface, and thus the black-border edges, will probably stay passivated by that protective oxide in alkaline solution (pH 11), with no or only very limited Mo loss. Stirring and the amount of oxygen or other oxidizing species like H2O2 in solution could increase the oxidation rate of the Mo and/or Mo oxides into soluble Mo(VI) species.
Three major technological lithography options have been reviewed for high volume manufacturing at the 32 nm half pitch node: 193 nm immersion lithography with high index materials, enabling NA > 1.6; ...193 nm double patterning and EUV lithography. In this paper the evolution of these three options over 2008 is discussed. The extendibility of these options beyond 32 nm half pitch is important for the final choices to be made. During 2008, the work on high index 193 nm immersion lithography has been stopped due to lack of progress in high index optical material and high index liquid development. Double patterning has made a lot of progress but cost concerns still exist. Preferred are those resists which support pattern or image freezing techniques in order to step away from the complex litho-etch-litho-etch approach and make double patterning more cost effective. For EUV, besides the high power light source, the resist materials need to meet very aggressive sensitivity specifications and need to maintain simultaneously performance in terms of resolution and line width roughness. Furthermore, EUV reticles encounter serious challenges, primarily related to mask defectivity.
The superconducting state of a material can be suppressed by either increasing the temperature (T) or applying a magnetic field (H). Measurements of the superconducting H-T phase boundary of a range ...of mesoscopic aluminum structures show clearly the effect of sample topology.
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