Fabrication of Weak C-Axis Preferred AlN Thin Film for Temperature Measurement

A weak C-axis preferred AlN thin film with a lot of defects was fabricated for temperature measurement. It was found that the (002) diffraction peak of the thin film increased monotonously with the increase in annealing temperature and annealing time. This phenomenon is ascribed to the evolution of defects in the lattice of the AlN film. Therefore, the relationship between defects and annealing can be expressed by the offset of (002) diffraction peak, which can be used for temperature measurement. Furthermore, a temperature interpretation algorithm Equation based on the lattice parameter (2θ), annealing temperature and annealing time was established, and a temperature interpretation software was built with MATLAB. Visual temperature interpretation is realized by the software, and the relative error is less than 7%. This study is of great significance for promoting the accurate temperature measurement on the surface of high temperature component.

North China craton: The conjugate margin for northwestern Laurentia in Rodinia

In the Rodinia supercontinent, Laurentia is placed at the center because it was flanked by late Neoproterozoic rifted margins; however, the conjugate margin for western Laurentia is still enigmatic. In this study, new paleomagnetic results have been obtained from 15 ca. 775 Ma mafic dikes in eastern Hebei Province, North China craton (NCC). Stepwise thermal demagnetization revealed a high-temperature component, directed northeast or southwest with shallow inclinations, with unblocking temperatures of as high as 580 °C. Rock magnetism suggests the component is carried by single-domain and pseudo-single-domain magnetite grains. Its primary origin is supported by a positive reversal test and regional remanence direction correlation test, and the paleomagnetic pole (29.0°S, 64.7°E, A95 = 5.4°) is not similar to any published younger poles of the NCC. Matching the late Mesoproterozoic to early Neoproterozoic (ca. 1110–775 Ma) apparent polar wander paths of the NCC and Laurentia suggests that the NCC could have been the conjugate margin for northwestern Laurentia in Rodinia, rather than sitting off the northeast coast of the main Rodinian landmass. Geological data indicate that breakup of the NCC and Laurentia occurred between ca. 775 and 720 Ma.

Geochronological and paleomagnetic studies of small carbonatite intrusions of the Udzha uplift (Tomtor massif, northeast of the Siberian platform)

<p>Paleomagnetic data obtained from Neoproterozoic glacial and glacier-associated sedimentary rocks indicate that they were formed at near equatorial latitudes. Based on these data, the Snowball Earth hypothesis was proposed [Kirschvink, 1992]. According to this hypothesis, during the Neoproterozoic glaciations, the entire planet (including the oceans) was completely covered with ice. Although evidence is emerging that does not support this hypothesis, there is still no conclusive evidence that it is not true [Sansjofre et al., 2011].</p><p>It is worth noting that the Snowball earth hypothesis is based on paleomagnetic data. At the same time, the available paleomagnetic data for the Neoproterozoic-Early Cambrian [Meert, Van der Voo, 2001; Shatsillo et al, 2005; Abrajevitch, Van der Voo, 2010; Pavlov et al., 2018] difficult to interpret in terms of the Geocentric Axial Dipole hypothesis. This imposes serious restrictions on the possibility of correctly constructing paleomagnetic reconstructions.</p><p>For the development and testing of a model of the geomagnetic field of the Neoproterozoic, it is necessary to obtain a lot of high-quality paleomagnetic data. Data from well-dated magmatic bodies are especially valuable.</p><p>Within the framework of this work, we obtained paleomagnetic data from three carbonatite dikes (7 to 30 cm thickness) exposed in the Udzha river bank on the Udzha uplift in the northeastern part of the Siberian platform. These dikes are associated with the large alkaline Tomtor massif located 15 km to the west. Ar/Ar dating of phlogopite megacrysts gives an intrusion age of the dikes of 706.1±8.8 Ma. Coordinates of the virtual geomagnetic pole, calculated from the direction of the high-temperature component of magnetization: Φ=-20.7°; Λ=88.6°; Α95=3.4°.</p><p>Our report will present preliminary interpretation of these data, as well as their comparison with paleomagnetic data on close-aged objects in Siberia.</p><p><em>The research was supported by the Russian Science Foundation grant (19-77-10048).</em></p><p>References:</p>

Paleomagnetism of terrigenous rocks of the Volynian series (Ediacaran) from Podolia (Ukraine)

<p>We present the results of palaeomagnetic study of Ediacaran terrigenous rocks from the SW part of East European Craton (EEC), Podolia (Ukraine). Samples are represented by red tufits of Grushkinska suite by Volhynian series, which is comparable to the upper part of the Ediacaran age by the international stratigraphic scale. Samples for paleomagnetic studies were taken at the reference section of the Grushkinsky suite of the Volhynia series in the village of Grushka (48.45°N 28°E). A total of 50 oriented core samples were selected. For the entire collection of samples, the standard procedure for paleomagnetic studies was applied. The samples underwent stepwise temperature demagnetization.  Demagnetization showed that all samples are completely demagnetized at a temperature close to 700°C. The results of demagnetization showed that additionally to the viscous components of the magnetization released up to 200°C, four more stable components of NRM are released: CLM-1–component, relatively low temperature, in the range of deblocking temperatures of 200–360°C. It is characterized by south-south-west declination and negative inclination (D/I = 197.9/-28.6); CLM-2–component, is allocated in the same temperature range as component CLM-1 (200-360°С), is characterized by south-south-west declination and positive inclination (D/I = 202.4/31); CMH–component, is strictly allocated in the range of unlocking temperatures of 590–630°C. It is characterized by northwestern declination and positive inclination (D/I = 311/18.9); CH –component, a bipolar high-temperature component, is released in the temperature range of 650–700°C. The middle direction of the forward and reverse polarity is characterized by north-north-west declination and positive inclination (D/I = 296.4/71.2). The directions of normal and reverse polarity of this component are closely antipodal and successfully pass the reversal test (γ/γ<sub>c</sub> = 7.85/8.82), class “B” in accordance with [McFadden & McElhinny, 1990].</p><p>The coordinates of the virtual geomagnetic poles for the two low-temperature components, respectively, are located close to the Permian (Φ/Λ = -53.7/357.9) and Silurian part (Φ/Λ = -21.8/4.9) of the apparent polar wander path for the EEC [Torsvik et al., 2012]. The VGP, calculated from the middle-high-temperature component, is located in the Caribbean region (Φ/Λ = 33.8/271.4) and the VGP for the relatively high temperature component is located in the eastern part of the North Atlantic (Φ/Λ = -52.5/149.1) that close to the another paleomagnetic determinations with ages about 550 Ma and 570 Ma respectively for different parts of EEC.</p><p>New data demonstrate the palaeomagnetic information content of the studied rocks and the possibility of their more detailed study in order to analyze anomalous palaeomagnetic data in the ediacaran and study the evolution of the Earth's geomagnetic field.</p><p>The analysis of directions and poles indicates that the paleomagnetic results do not contradict the data on the extremely high variability of the geomagnetic field in the studied time interval.</p><p>The new paleomagnetic determinations correspond to the previous results obtained by other authors for different regions of the East European platform, thereby supplementing them.</p>

Brazing Coupling Performance of Piezoelectric Waveguide Transducers for the Monitoring of High Temperature Components

Piezoelectric waveguide transducers possess great potential for the online monitoring of high temperature critical components, in order to improve their operational safety. Due to the use of a waveguide bar, the sensory device is not susceptible to high temperature environments, which enables the long-term service of the piezoelectric transducers. However, the coupling between the waveguide bar and the high-temperature component has been proven to be the most important part of the monitoring system. In order to effectively transmit waves through the junction of the waveguide bar and the monitoring target, it is necessary to research a reliable coupling method to connect the waveguide transducers with the host structure. In the present research, the feasibility of brazing coupling for wave propagation through the junction was investigated through experiments. Piezoelectric waveguide transducers were welded using various kinds of brazing filler metals. The experimental results indicate that the coupling effects of the brazing welding depend on the filler metals. At the same time, some filler metals for the effective coupling of the transducer and the target monitoring component were identified. The brazing coupling method was verified that it can non-dispersively and effectively propagate waves into the host structure with much better reliability than the conventional dry coupling approach. Moreover, the high-temperature experimental results show that the brazing-coupled waveguide bar system can work reliably and stably in high temperatures at 300 °C for a long time. This work strives to pave a solid foundation for the application of piezoelectric waveguide transducers for the structural health monitoring of high temperature critical components.

New 1.72-1.76 GA paleointensity data obtained on Proterozoic volcanic rocks from the Ukrainian Shield

<p>The Precambrian period occupies ≈ 85% of the Earth’s geological history and accommodates all the main formation stages of the Earth as a planet, including the emergence of its magnetic field. Variations in the time-averaged geomagnetic dipole moment have the potential to learn about the long-term development of the geodynamo and its response to mantle forcing and thermal evolution of the core. But determinations of paleointensity (Banc) of the geomagnetic field during this period are sparse and of limited reliability. Here we report detailed palaeomagnetic and paleointensity studies combined with comprehensive investigations of magnetic properties of Proterozoic volcanic rocks from the Ukrainian Shield.</p><p>The Ukrainian Shield comprises the crust of the Palaeoproterozoic protocraton Volgo-Sarmatia, which together with the Fennoscandian crustal segment constitutes the East European Craton (Baltica). The different megablocks of Ukrainian Shield can be treated as a coherent unit since 1.77 Ga.  Our studies has been performed on gabbro-anorthosite complexes from Ingul megablock within the Korsun-Novomigorodsky Pluton (ages 1.75-1.72 Ga) and North-Western megablock within the Korosten Pluton (age ca 1.76 Ga). The high-temperature stable ChRM component was isolated in the interval of blocking temperatures of 500-580°C by more than 300 samples from 7 sites. The presence of dual-polarity high-temperature component, lack of signs of metamorphism and good agreement of the mean palaeomagnetic pole position obtained from the Ingul block with age ca.1.75 Ga (Φ=22.5º, Λ=167.3º, dp/dm=4.0/7.7) with previous studies of anorthosites (Elming et al., 2001) of similar age suggests a primary origin of ChRM.</p><p>Comprehensive investigations of magnetic properties of rocks, the electron microscopic images of thin sections and X-ray diffractograms were performed. Rocks demonstrate thermally stable successive Msi(T) curves with clearly pronounced near-magnetite Tc. The carriers of remanent magnetization are fine magnetite isolated needle-like and/or lamellar ferromagnetic particles dispersed in plagioclas. According to the thermomagnetic criterion, high-temperature pTRMs show typical SD-PSD behavior. Palaeointensity determinations were successful on samples from 5 sites carrying well-identified ChRM components using the Thellier-Coe method with pTRM checks and the Wilson protocols. Reliable Banc values give generally low palaeofield (3.7-6.6 µT) with corresponding VDM values in the range (0.93-1.6)×10<sup>22</sup> Am<sup>2</sup>. These findings agree with our previous results for Proterozoic rocks of Kola Peninsula (age 1.86 GA) and with the data reported in the World paleointensity databases (http://wwwbrk.adm.yar.ru/palmag/index_e.html and others data), which also provide a noticeably low paleofield intensity with mean VDM = 3.2×10<sup>22</sup> Am<sup>2</sup> for the Paleo-Proterozoic period. Thus, our new data support the Proterozoic dipole low hypothesize by Biggin et al., 2009. The work was supported by the state assignment 17-05-00259 and the RFBR grant 19-05-00433.</p>

Magnetostratigraphy of the Eocene Jianchuan Basin in southeast Tibet: A preliminary result

<p>Early Cenozoic continental sediments deposited contemporaneously or soon after the onset of India-Asian collision provide an obvious target for gaining insight into the early stages of the growth of the Tibetan plateau. These continental sequences are generally found in an arcuate belt that extends from the central plateau into the western Yunnan province (e.g. Nangqian-yushu Basin, Gongjo Basin and Jianchuan Basin). With limited exposure and elusive datable horizons except for a few dikes cross-cutting stratigraphy and interbedded lava flows, there were few constraints on absolute time of these Cenozoic sediments, limiting further studies of the tectonic, topographic and environmental evolution in southeast Tibet. Here, we focus on the Jianchuan basin, the age of which was mapped from the Paleocene up to the Pliocene but recently reassigned to the Paleocene/Eocene as a whole. The Xinsong section with 1547 meters in thickness was measured at the meter scale to determine vertical changes through the depositional facies. The lower part of the section consists of 1027 m thick red-colored, massive siltstone with many fine sandstone interlayers, while the upper part of the section is composed by a series of basal-scoured, upward-fining and stacked sand bodies with the thickness of 520 m. A total of 981 standard paleomagnetic oriented samples were collected. Samples were subjected to stepwise thermal demagnetization that revealed either two or three component magnetizations with the high temperature component (HTC) unblocked at ∼660-680 °C. Our preliminary results show multiple polarity reversals that can be well correlated with the Geomagnetic Polarity Time Scale (GPTS) between ca. 50 and ca. 40 Ma. We interpret that these sediments were deposited in a restricted, narrow basin in the footwalls of thrust fault where the depositional environments were highly related to the compressional deformation. Our new result may be of great significance for understanding the kinematic and dynamic models of the deformation and evolution of the Tibetan plateau.</p>

Prospects of paleomagnetic studies of the Riphean intrusive bodies of the Bashkirian megazone (Southern Urals)

<p>         The studied objects are located in the core of the Bashkirian megazone and related to the Riphean stage of rift magmatism of the East European craton. Paleomagnetic studies of the Bashkirian megazone intrusive bodies can be a source of new information on the East European platform position in the Riphean, as well as on the process of remagnetization during the Late Paleozoic folding on the Southern Urals. At this moment, 42 thin basic intrusions and the Main Bakal dyke were investigated.</p><p>         According to the results of our previous paleomagnetic studies two remanence components were isolated in Bashkirian megazone intrusions. First, the primary remanence component of Middle Riphean age was isolated in 8 thin bodies. Pole for the boundary of the Early and Middle Riphean of the East European Craton was calculated from high-temperature component of remanence of 8 sheet intrusions. This pole is close to the known paleomagnetic poles of East European craton for close ages and agrees with U-Pb age of one of the studied bodies (1349 ± 11 Ma). Also, arguments in favor of the primary origin of the remanence and the absence of significant tectonic dislocations in the sampling area are discussed. In other 4 intrusive bodies, paleomagnetic directions that are close but slightly different from the Middle Riphean directions were found. Second, the Late Paleozoic directions were found in the studied objects. These directions are widespread in the Bashkirian megazone rocks and have been reported by other researchers. Presumably it is the result of the Late Paleozoic syn-collisional remagnetization.</p><p>            According to the new results another component of remanence was detected in the intrusive bodies of the Bashkirian megazone. In 2 sheet bodies and the Main Bakal dyke a component close to the Late Riphean identified earlier in sedimentary rocks of the same region was found (Pavlov, Gallet, 2009; Danukalov et al., 2019). Furthermore, in total 20 thin intrusive bodies and the Main Bakal dyke have paleomagnetic directions close to the Late Paleozoic directions. The comparison of mean paleomagnetic directions for the different studied regions demonstrates the absence of any traces of essential rotation of blocks within the Bashkirian megazone in the Later Paleozoic.</p><p>            At this moment the origin of the remanence of 8 thin bodies is unclear, the nature of the other components of remanence requires additional research. It is planned to sample more intrusive bodies and to perform the isotopic dating of the key objects.</p><p>References:</p><ul><li>1) Pavlov V.E., Gallet Y. Katav limestones: A unique example of remagnetization or an ideal recorder of the Neoproterozoic geomagnetic field. Izvestiya, Physics of the Solid Earth, 2009, vol. 45, no. 1, pp. 31-40</li> <li>2) Danukalov K. N., Salmanova R. Y., Golovanova I. V., Parfiriev N. P. New paleomagnetic data on sedimentary rocks of the Inzer and Zilmerdak formations in the Southern Urals// Materials of the XXV anniversary All-Russian School-Seminar on problems of paleomagnetism and magnetism of rocks. – IPE RAS Moscow, 2019. – P. 108-113</li> </ul>