Detachment folding in a Lower Cambrian–Upper Permian karst reservoir: 3D model of the Yubei 3D area (eastern Markit Slope,Tarim Basin,Northwest China)

A three-dimensional (3D) structural modeling of the Lower Cambrian–Upper Permian Yubei 3D area was performed to understand its structural evolution. This model reproduces the present-day structure of the basin and comprises 11 horizons within Lower Cambrian to Upper Permian rocks. The analysis is based on 3D depth views and faults. The results image salt movements due to tectonics and/or burial. From these observations, this paper deduces that salt structures are correlated to the main faults and tectonic events. From the model analysis, we interpret the timing and geometry of Tarim Basin tectonics. The fault geometry can be resolved based on the strike of the fault, the morphology of hanging wall strata, and the stratigraphic distribution. Emphasis is placed on gypsum rock detachment, considering its movements during the Middle Caledonian event and decoupling effects during tectonic evolution. Moreover, we point to the structural control of the Paleozoic basement and the crustal architecture (Yubei 3D Zone) on the geometry of the Tarim Basin.     

水产动物雷帕霉素受体信号通路的研究进展

雷帕霉素受体信号通路(mTOR信号通路)广泛存在于真核生物细胞中,能够接收来自营养素、生长因子或者环境胁迫等的信号,通过调控细胞的合成代谢和分解代谢,实现对细胞生长和生理活动的精确调控。在mTOR信号通路的研究中,水产养殖动物mTOR信号通路的研究仅见于少数几种鱼类、对虾和蟹类,且其研究深度远远落后于模式生物。本文综述了近年来mTOR信号通路的研究进展,包括TOR蛋白的发现与组成,以及参与mTOR信号通路的信号因子和信号通路调控生命过程的机制。同时,本文重点阐述了mTOR信号通路在水产动物细胞中的研究现状,说明了水产动物mTOR信号通路研究的必要性,以期为水产养殖动物mTOR信号通路的进一步研究提供参考。     

Iron Reduction Along an Inundation Gradient in a Tidal Sedge (<Emphasis Type="Italic">Cyperus malaccensis</Emphasis>) Marsh: the Rates,Pathways, and Contributions to Anaerobic Organic Matter Mineralization

Incubation experiments were adopted to characterize the rates and pathways of iron reduction and the contributions to anaerobic organic matter mineralization in the upper 0–5 cm of sediments along a landscape-scale inundation gradient in tidal marsh sediments in the Min River Estuary, Southeast China. Similar sediment characteristics, single-species vegetation, varied biomass and bioturbation, distinct porewater pH, redox potential, and electrical conductivity values have resulted in a unique ecogeochemical zonation along the inundation gradient. Decreases in solid-phase Fe(III) and increases in nonsulfidic Fe(II) and iron sulfide were observed in a seaward direction. Porewater Fe²⁺ was only detected in the upland area. High rates of iron reduction were observed in incubation jars, with significant accumulations of nonsulfidic Fe(II), moderate accumulations of iron sulfides, and negligible accumulations of porewater Fe²⁺. Most of the iron reduction was microbially mediated rather than coupled to reduced sulfides. Microbial iron reduction accounted for 20–89 % of the anaerobic organic matter mineralization along the inundation gradient. The rate and dominance of microbial iron reduction generally decreased in a seaward direction. The contributions of microbial iron reduction to anaerobic organic matter mineralization depended on the concentrations of bioavailable Fe(III), the spatial distribution of which was significantly related to tidal inundation. Our results clearly showed that microbial iron reduction in the upper sediments along the gradient is highly dependent on spatial scales controlled primarily by tidal inundation.     

Theoretical calculation of equilibrium Mg isotope fractionation between silicate melt and its vapor

Isotope fractionation during the evaporation of silicate melt and condensation of vapor has been widely used to explain various isotope signals observed in lunar soils, cosmic spherules, calcium–aluminum-rich inclusions, and bulk compositions of planetary materials. During evaporation and condensation, the equilibrium isotope fractionation factor (α) between high-temperature silicate melt and vapor is a fundamental parameter that can constrain the melt’s isotopic compositions. However, equilibrium α is difficult to calibrate experimentally. Here we used Mg as an example and calculated equilibrium Mg isotope fractionation in MgSiO₃ and Mg₂SiO₄ melt–vapor systems based on first-principles molecular dynamics and the high-temperature approximation of the Bigeleisen–Mayer equation. We found that, at 2500 K, δ²⁵Mg values in the MgSiO₃ and Mg₂SiO₄ melts were 0.141?±?0.004 and 0.143?±?0.003‰ more positive than in their respective vapors. The corresponding δ²⁶Mg values were 0.270?±?0.008 and 0.274?±?0.006‰ more positive than in vapors, respectively. The general \(\alpha - T\) equations describing the equilibrium Mg α in MgSiO₃ and Mg₂SiO₄ melt–vapor systems were: \(\alpha_{{{\text{Mg}}\left( {\text{l}} \right) - {\text{Mg}}\left( {\text{g}} \right)}} = 1 + \frac{{5.264 \times 10^{5} }}{{T^{2} }}\left( {\frac{1}{m} - \frac{1}{{m^{\prime}}}} \right)\) and \(\alpha_{{{\text{Mg}}\left( {\text{l}} \right) - {\text{Mg}}\left( {\text{g}} \right)}} = 1 + \frac{{5.340 \times 10^{5} }}{{T^{2} }}\left( {\frac{1}{m} - \frac{1}{{m^{\prime}}}} \right)\), respectively, where m is the mass of light isotope ²⁴Mg and m′ is the mass of the heavier isotope, ²⁵Mg or ²⁶Mg. These results offer a necessary parameter for mechanistic understanding of Mg isotope fractionation during evaporation and condensation that commonly occurs during the early stages of planetary formation and evolution.     

U–Pb zircon age of the base of the Ediacaran System at the southern margin of the Qinling Orogen

Global abrupt climate change from Marinoan snowball Earth to greenhouse Earth, recorded as cap carbonate overlain on diamictite, had shed the first light on Cambrian bio-radiation. The most documented cap carbonate sections are typical with comprehensive δ¹³C negative values and ubiquitous sedimentary structures, such as tepee-like, sheet-crack etc., which are associated with successive glacial eustatic variation caused by isostatic rebound in shallow-water facies. Here we report a deep-water basinal cap carbonate section with strong negative δ¹³C values in the southern margin of the Qinling Orogen, Heyu, Chengkou County, Chongqing in China, which consists of massive dolostone with abundant carbonaceous laminae. However, it lacks the sedimentary structure as mentioned above and is overlain by thin-bedded silicious shales and cherts. A K-bentonite bed was discovered within the base of cap carbonates, about 0.7 m above the top of the Marinoan diamictite. Magmatic zircons that were separated from the K-bentonite bed yield a SIMS concordia U–Pb age of 634.1 ± 1.9 Ma (1σ, MSWD_CE = 0.31, Probability_CE = 1.000, n = 20). The age is in good agreement with previously reported TIMS U–Pb ages for the termination of Marinoan glaciation and provides a geochronological constraint for the Ediacaran successions in the Qinling Orogen.