Late Palaeozoic mineralization and tectonic evolution of the West Junggar metallogenic belt, Central Asia: constraints from Re–Os and ⁴⁰Ar/³⁹Ar geochronology

<p>The West Junggar Metallogenic Belt (WJMB) is located between the Tianshan fault system and the Ertix fault system in the western part of the Central Asian Metallogenic Domain (CAMD). The belt features widespread late Palaeozoic granitic plutons, strike-slip faults, and porphyry copper and orogenic gold deposits. We collected nine molybdenite samples from the Baogutu III–IV Cu–Mo deposit and the Suyunhe Mo–W deposit, and 12 granitoid samples from the Jiaman, Kangde, Kulumusu, Bieluagaxi, Hatu, Akbastau, Miaoergou, Baogutu, Karamay, and Hongshan plutons in the WJMB. Molybdenite Re–Os dating gives metallogenesis ages of 312.7 and 299.7 Ma for the Baogutu III–IV and Suyunhe deposits, respectively. ⁴⁰Ar/³⁹Ar thermochronology yields biotite ages ranging from 326 to 302 Ma and K-feldspar ages from 297 to 264 Ma, indicating a regional medium-temperature cooling history in the WJMB during the late Carboniferous to middle Permian. By integrating these data with previous zircon U–Pb, amphibole ⁴⁰Ar/³⁹Ar, and zircon and apatite fission-track ages, we reconstruct the whole thermal history of the WJMB, which includes late Palaeozoic intrusive magmatism, porphyry Cu and W–Mo mineralization, and late Mesozoic tectonic uplift and exhumation of the WJMB. The regional ⁴⁰Ar/³⁹Ar cooling ages are consistent with the timing of regional sinistral strike-slip faulting, thereby indicating the tectonic significance of the cooling ages. We suggest that the biotite ⁴⁰Ar/³⁹Ar ages represent the static cooling of the granitic plutons after emplacement, since the ages are consistent with the U–Pb ages of the plutons. Thereafter, the oldest K-feldspar ⁴⁰Ar/³⁹Ar age may record the initiation of sinistral strike-slip movement on the Darabut, Mayile, and Baerluke faults. The regional faulting resulted in significant uplift of the WJMB during the early and middle Permian.</p

Electromechanical Coupling of Murine Lung Tissues Probed by Piezoresponse Force Microscopy

Elastin is a major constituent of lung that makes up approximately 30% of lung’s dry weight, and the piezoelectricity of elastin is expected to be exhibited in lung tissues. Because hundreds of millions of cycles of inhalation and exhalation occur in one’s lifetime, such piezoelectric effect leads to hundreds of millions of cycles of charge generations in lung tissues, suggesting possible physiological significance. Using piezoresponse force microscopy (PFM), we show that the murine lung tissues are indeed piezoelectric, exhibiting predominantly first harmonic piezoresponse in both vertical and lateral modes. The second harmonic response, which could arise from ionic motions, electrochemical dipoles, and electrostatic interactions, is found to be small. The mappings of amplitude, phase, resonance frequency, and quality factor of both vertical and lateral PFM are also obtained, showing small fluctuation in frequency, but larger variation in quality factor, and thus energy dissipation. The phase mapping is confined in a small range, indicating a polar distribution with preferred orientation. It is also found that the polarity of the electromechanical coupling in lung tissues can be switched by an external electric field, resulting in characteristic hysteresis and butterfly loops, with a presence of internal bias in the polar structure. It is hypothesized that the piezoelectric charge generation during inhalation and exhalation could play a role in binding of oxygen to hemoglobin, and the polarity switching can help damp out the possible sudden increase in air pressure. We hope such observation of piezoelectricity and its polarity switching in lung lay the foundation for the subsequent studies of its physiological significance

Large Scale Two-Dimensional Flux-Closure Domain Arrays in Oxide Multilayers and Their Controlled Growth

Ferroelectric flux-closures are very promising in high-density storage and other nanoscale electronic devices. To make the data bits addressable, the nanoscale flux-closures are required to be periodic via a controlled growth. Although flux-closure quadrant arrays with 180° domain walls perpendicular to the interfaces (V-closure) have been observed in strained ferroelectric PbTiO₃ films, the flux-closure quadrants therein are rather asymmetric. In this work, we report not only a periodic array of the symmetric flux-closure quadrants with 180° domain walls parallel to the interfaces (H-closure) but also a large scale alternative stacking of the V- and H-closure arrays in PbTiO₃/SrTiO₃ multilayers. On the basis of a combination of aberration-corrected scanning transmission electron microscopic imaging and phase field modeling, we establish the phase diagram in the layer-by-layer two-dimensional arrays versus the thickness ratio of adjacent PbTiO₃ films, in which energy competitions play dominant roles. The manipulation of these flux-closures may stimulate the design and development of novel nanoscale ferroelectric devices with exotic properties

Enhancement of Local Piezoresponse in Polymer Ferroelectrics <i>via</i> Nanoscale Control of Microstructure

Polymer ferroelectrics are flexible and lightweight electromechanical materials that are widely studied due to their potential application as sensors, actuators, and energy harvesters. However, one of the biggest challenges is their low piezoelectric coefficient. Here, we report a mechanical annealing effect based on local pressure induced by a nanoscale tip that enhances the local piezoresponse. This process can control the nanoscale material properties over a microscale area at room temperature. We attribute this improvement to the formation and growth of β-phase extended chain crystals <i>via</i> sliding diffusion and crystal alignment along the scan axis under high mechanical stress. We believe that this technique can be useful for local enhancement of piezoresponse in ferroelectric polymer thin films