Apatite (U-Th)/He Thermochronology Evidence for Two Cenozoic Denudation Events in the Eastern Part of the Sulu Orogenic Belt.

International audienceThe Sulu orogenic belt, located between the North China and South China plates, is one of the most prominent intracontinental orogenic belt in eastern China. Therefore, the denudation history of Sulu orogenic belt provides significant insight into the basin-mountain evolution in eastern China and their dynamic mechanism. Due to the apatite (U-Th)/He system has low closure temperature (ca. 70 °C), it can constrain the cooling processes of geological bodies more accurately in the upper crust. In this study, the apatite (U-Th)/He method was used to analyze the exhumation time of rocks on the Duofu and Juchi Mountains located in the eastern parts of Sulu orogenic belt. The apatite (U-Th)/He age-elevation relationship and thermal history simulation results showed that the exhumation occurred in the Early-Middle Eocene (54-43 Ma) and Oligocene (35-27 Ma) for the Duofu and Juchi Mountains, respectively. These cooling episodes were synchronized with the exhumation time of the western part of the Sulu orogenic belt. Combined with the results reported in the region, it is showed that the eastern China was influenced by the Pacific and Indian plates subduction into Eurasia, and the extensive exhumation process occurred in the Early Cenozoic, which established the basin-mountain distribution pattern during this time

Early Cenozoic drainage evolution in the Jianghan Basin: Constraints from detrital zircon U-Pb ages of surface rivers and cores in the basin

Objective The evolution of large rivers is closely linked to the interactions between tectonic and climatic processes. Understanding the evolutionary history of these rivers is crucial for uncovering the influence of deep dynamic processes on the Earth's surface. In the Jianghan Basin, the preserved Cenozoic strata provide valuable insights into the evolutionary history of the Han and Yangtze Rivers. Methods By conducting a systematic analysis of detrital zircon U-Pb ages (n=690) in the Hanjiang River Basin, the sediments in the lower reaches of the Hanjiang River contain a mixture of fluvial detrital signals from the Qinling and Dabie mountains. The detrital zircon U-Pb ages of these samples from the lower reaches of the Hanjiang River are more representative for determining their provenance. We have compared these new data with previously published fluvial sedimentary zircon U-Pb ages from the Jianghan Basin, as well as detrital zircon U-Pb ages from drilling cores obtained from Early Eocene strata in the basin. Results Provenance analysis reveals that the detrital material in the Jianghan Basin during the Early Eocene was primarily derived from the Qinling-Dabie Mountains. This can be attributed to the significant difference in elevation between the depression within the Jianghan Basin and the surrounding uplifted orogenic belts, which provided the necessary conditions for the development of large rivers. It is important to note that the Wuling Mountain and Huangling Anticline rivers did not serve as the main sources of sediment supply for the central, eastern, and southern depressions of the Jianghan Basin during this time period. Additionally, the Yangtze River, located west of the Huangling Anticline, did not flow into the Jianghan Basin in the Early Eocene. Conclusion Overall, the sediments in the Jianghan Basin were predominantly proximal deposits sourced from the adjacent orogenic belt, which can be attributed to the exhumation of the orogenic belt and a monsoon-like climate in the early Cenozoic era

Changing provenance of late Cenozoic sediments in the Jianghan Basin

The Yangtze River is one of the most important components of the East Asia river system. In this study, sediments in the Jianghan Basin, middle Yangtze River, were selected for trace element and rare earth element (REE) measurements, in order to decipher information on the change of sediment provenance and evolution of the Yangtze River. According to the elemental variations, the late Cenozoic sediments of the Jianghan Basin could be divided into four parts. During 2.68–2.28 Ma and 1.25–0 Ma, provenance of the sediments was consistent, whereas sediments were derived from variable sources during 2.28–1.25 Ma. Comparison of the elemental compositions between the Pliocene and Quaternary sediments revealed a change in sediment source from a more felsic source area to a more basic source area around the Pliocene–Quaternary boundary. Input from the Emeishan LIP should account for this provenance change. Based on the provenance analysis of sediments in the Jianghan Basin, we infer that the Yangtze River developed into a large river with its drainage basin extended to the Emeishan LIP no later than the Pliocene–Quaternary boundary

Human impact on erosion patterns and sediment transport in the Yangtze River

Sediment load in rivers is an indicator of erosional processes in the upstream river catchments. Understanding the origin and composition of the sediment load can help to assess the influence of natural processes and human activities on erosion. Tectonic uplift, precipitation and run-off, hill slopes and vegetation can influence erosion in natural systems. Agriculture and deforestation are expected to increase the sediment yield, but dams and reservoirs can trap much of this sediment before it reaches the ocean. Here, we use major element composition and 40Ar/39Ar ages of detrital muscovites to constrain the sediment contribution of various tributaries to sedimentation in the Yangtze delta. The sediment contribution calculated from muscovite data was compared with that estimated from current sediment load data from gauging stations. Muscovite data show that the main contributor to the Yangtze delta sands is the Min River, while the current sediment load suggests that the Jinsha and Jialing rivers are the most important current contributors to delta sediments. We suggest that this difference reflects an "old" and "young" erosion pattern, respectively as medium grained muscovite could be transported much slower than suspended sediment load in the complex river-lake systems of the Yangtze River basin. These two different erosion patterns likely reflect enhanced human activity (deforestation, cultivation, and mining) that increasingly overwhelmed long-time natural factors controls on erosion since ~1900 cal years B.P

Simultaneous Enhancement of Thermoelectric Power Factor and Phase Stability of Tin-Based Perovskites by Organic Cation Doping

Tin-based halide perovskites are promising room-temperature thermoelectric materials due to their ultralow thermal conductivity and propensity for doping. However, poor phase stability and inferior electrical transport properties hinder their practical application. Herein, we found that organic cation formamidinium (FA) doping, which is not possible by high-temperature processing, could simultaneously enhance the stability and electrical conductivity of CsSnI3 films through a simple solution process. The carrier concentration of 3 × 1019 cm–3 was obtained in FA-doped films, which leads to an 8× enhancement in electrical conductivity to 26.5 S cm–1 but maintains a Seebeck coefficient as high as 131 μV K–1, resulting in a power factor of 45.53 μW m–1 K–2. A further theoretical calculation shows that the enhanced carrier concentration originates from the lowered transition energy of tin vacancies in the doped films. More importantly, remarkable phase stability is achieved under an ambient atmosphere, which stems from a sharply decreased free energy of the B-γ phase compared to the Y phase by FA doping. This work suggests that organic cation doping by facile solution processing is an avenue for the simultaneous improvement of the thermoelectric power factor and phase stability of tin-based halide perovskite. It is applicable for flexible and wearable thermoelectric generators to harvest energy from low-grade heat sources.</p

Impact of hydraulic sorting and weathering on mica provenance studies: An example from the Yangtze River

Detrital muscovite and biotite 40Ar/39Ar analyses are useful tools for studying regional tectonic histories, sediment provenances and paleo-drainage reconstructions. During transport and recycling of detrital micas physical and chemical weathering occurs. This process effects the grain size and age populations ultimately found in river sediments, but is often ignored in provenance studies. Here, we present detrital muscovite and biotite 40Ar/39Ar results of 15 modern sediments from the Yangtze River to address the impact of grainsize on provenance age populations. The beam intensities of 39Ar, formed from 39K by neutron capture reaction during sample irradiation, have been used as an index for grain size. We found that relatively older detrital mica ages of the Yangtze River are often characterized by small 39Ar signals (i.e., grain sizes), and large grain sizes correspond to younger grains. This observation is also revealed by reanalysis of previously reported detrital mica studies in other major river systems (Red and Brahmaputra rivers) and sediments (Scotian Basin, Canada and Antarctic) and probably results from physical and chemical weathering during transport and recycling. Our Yangtze results indicate that detrital muscovite and biotite ages of grainsize ranging from 100 to 1000 μm cover all age components as identified in all dated grains (with a size of >100 μm), and thus indicate that detrital mica 40Ar/39Ar analyses should include also small grains from >100 μm to reduce the effects of hydraulic sorting and weathering. Grainsizes smaller than 100 μm have not been tested in this study, but will be more difficult to date due to both smaller beam intensities and possible recoil effects

New insight into oxygen vacancy and synergism in CuCeO_x catalysts based on the toluene oxidation

Cu-Ce based catalysts is an important type of catalyst due to its high activity, and the exploration of Cu-Ce synergistic effect is always on the focus. This study provides a new insight into the synergistic effect between copper and cerium based the toluene combustion properties over CuCeOx catalysts prepared with different methods. The catalyst synthesized by sol-gel method exhibits the best synergistic effect, and post calcination of the physically mixed catalyst can strengthen the formation of Cu-O-Ce solid solution. Under low temperature conditions (TT-50). The lattice oxygen in the Cu-O-Ce bond is active under relative high temperature, owing that lattice distortion weakens the metal oxygen bond, making it easier to participate in reaction or transfer from bulk phase to catalyst surface

Influence of Rare-Earth Promoters (Ce, Zr and La) on Catalytic Performance of Copper-Based Catalyst in Toluene Oxidation

Copper-infused mixed metal oxides have been identified as powerful catalysts for eliminating volatile organic compounds (VOCs) due to their widespread availability and cost-effectiveness. The copper metal oxide catalysts were synthesized using the sol-gel method and promoted with rare earth elements, La, Ce, and Zr, to catalyze the oxidation of toluene. Compared to all tested catalysts, CuLaOx demonstrates the least activity igniting activity even though La appears to enhance copper dispersion and generate a large number of oxygen species on the surface. CuZrOx displays remarkable thermal stability, resulting in a minimal amount of lattice oxygen participating in toluene oxidation. The introduction of Ce into the CuCeOx catalyst enhances its activity significantly, attributed to the exceptional reducibility of copper species. Therefore, the TOF for the CuCeOx, CuLaOx and CuZrOx catalysts are 9.23-24.8 x 10-3 s-1, 1.29-6.22 x 10-3 s-1, and 1.05-10.03 x 10-3 s-1 at 200-400 degrees C, respectively. The infrared spectra, observed at varying temperatures during toluene oxidation, were presented. Interestingly, all catalysts demonstrated a comparable reaction pathway. The catalytic oxidation mechanism is expected to proceed via the intermediates of toluene-alkoxide-aldehydic-carboxylic acid, ultimately culminating in complete degradation to CO2 and H2O. This study establishes a theoretical foundation for the judicious selection of suitable rare earth elements as promoters, enabling the development of copper-based catalysts for efficient volatile organic compound (VOC) removal in industrial settings

Biodegradable materials and green processing for green electronics

There is little question that the “electronic revolution” of the 20th century has impacted almost every aspect of human life. However, the emergence of solid-state electronics as a ubiquitous feature of an advanced modern society is posing new challenges such as the management of electronic waste (e-waste) that will remain through the 21st century. In addition to developing strategies to manage such e-waste, further challenges can be identified concerning the conservation and recycling of scarce elements, reducing the use of toxic materials and solvents in electronics processing, and lowering energy usage during fabrication methods. In response to these issues, the construction of electronic devices from renewable or biodegradable materials that decompose to harmless by-products is becoming a topic of great interest. Such “green” electronic devices need to be fabricated on industrial scale through low-energy and low-cost methods that involve low/non-toxic functional materials or solvents. This review highlights recent advances in the development of biodegradable materials and processing strategies for electronics with an emphasis on areas where green electronic devices show the greatest promise, including solar cells, organic field-effect transistors, light-emitting diodes, and other electronic devices.</p

Biodegradable Materials and Green Processing for Green Electronics

There is little question that the “electronic revolution” of the 20th century has impacted almost every aspect of human life. However, the emergence of solid-state electronics as a ubiquitous feature of an advanced modern society is posing new challenges such as the management of electronic waste (e-waste) that will remain through the 21st century. In addition to developing strategies to manage such e-waste, further challenges can be identified concerning the conservation and recycling of scarce elements, reducing the use of toxic materials and solvents in electronics processing, and lowering energy usage during fabrication methods. In response to these issues, the construction of electronic devices from renewable or biodegradable materials that decompose to harmless by-products is becoming a topic of great interest. Such “green” electronic devices need to be fabricated on industrial scale through low-energy and low-cost methods that involve low/non-toxic functional materials or solvents. This review highlights recent advances in the development of biodegradable materials and processing strategies for electronics with an emphasis on areas where green electronic devices show the greatest promise, including solar cells, organic field-effect transistors, light-emitting diodes, and other electronic devices.</p