ALBERT

Description: Volatiles are important for planetary geodynamics, climate, and habitability. The C/N ratio of the bulk silicate Earth (BSE) is superchondritic, which provides a useful tool for understanding the origin of Earth’s volatiles. The Earth accreted largely from differentiated planetesimals and embryos, and the fate of nitrogen and carbon in magma oceans (MOs) of such rocky bodies is key in shaping the BSE’s C/N ratio. Here we present experiments performed at 0.3–3 GPa and 1400–1600 ◦C to determine both the solubility and partitioning of nitrogen and carbon between Fe-rich metallic and silicate melts at graphite-saturation and the saturation of N 2 -rich gas. The quenched samples were analyzed by electron microprobe, secondary ion mass spectrometry, and Raman spectroscopy for their N–C–H–O contents and speciation. Our results show that the C/N solubility ratios of the silicate melts (ppm/ppm by wt.) are a multi-function of pressure, temperature, silicate melt composition, and mainly oxygen fugacity ( f O2 ), and increase from 0.01 to 1.6 with increasing f O2 from IW-3.7 to IW+0.4 (IW refers to the iron–wüstite buffer). Raman spectra and theoretical considerations reveal that the main species in silicate melts are N 2, N 3−, and N–H in the case of nitrogen, and CO, CO32−, and C–H in the case of carbon. Nitrogen and carbon may also form complex species, which, however, could not be identified presently. The metal/silicate partition coefficients of nitrogen and carbon D metal/silicate N,C are 1–114 and 34–3050, respectively. The D metal/silicate C /D metal/silicate N ratios are 1.5–1100, which decrease with increasing pressure,fO2, and the water content in silicate melts. Our results imply that N–C fractionation could occur during core-formation and silicate MO degassing. For a rocky body starting with a chondritic C/N ratio, core-formation would result in a superchondritic C/N ratio in its core if that rocky body is S- and Si-poor. However, a superchondritic C/N ratio can also be achieved in the silicate mantle through C-saturation coupled with preferential nitrogen degassing and loss into space, if the rocky body is oxidized and has a S-rich core, or is reduced and has a Si-rich core. Both Earth’s accretion of planetesimals and embryos with cores as the major nitrogen and carbon reservoirs, and Earth’s disequilibrium accretion of C-saturated embryos through core–core merging, could have helped establish the BSE’s superchondritic C/N ratio. During Earth’s accretion of the last few giant impactors, multiple episodes of MO degassing and erosion-induced atmospheric loss would have also favored the formation of a superchondritic C/N ratio in the BSE, due to the oxidized nature of Earth’s surface MO ( f O2 〉 IW) and the preferential loss of nitrogen into space. Finally, we emphasize that oxidization of emulsified planetesimal cores in Earth’s upper mantle during its final accretion stages could have further helped establish the BSE’s superchondritic C/N ratio. Accordingly, the BSE’s superchondritic C/N ratio may be an outcome of combined processes operating both on the accreted planetesimals and embryos and on the proto-Earth itself.

Description: Hydrothermal alteration is crucial in the formation of many ore deposits, with potassium (K) mobilization and cycling being prevalent. Potassic metasomatism of wall rocks generally forms K-bearing minerals, such as hydrothermal feldspar and mica. However, determining the source and redistribution of K (and other elements transported by the same fluid) in hydrothermal systems is challenging. K isotopes offer a potential solution to this problem. This study presents new K isotope data from two K-rich alteration assemblages — K-feldspar and sericite-quartz-pyrite — in the Jiaodong gold province of China. The data covers a compositional range from unaltered granites to syn-magmatic potassic alteration (formation of K-feldspar) and post-magmatic syn-mineralization phyllic alteration (formation of sericite). Potassic alteration in granite correlates with significant K addition, whereas phyllic alteration of earlier phases of magmatic and hydrothermal K-feldspar resulted in K loss. K-feldspar altered granites display similar δ41K values (–0.55 to –0.42 ‰ for whole-rocks and –0.56 to –0.48 ‰ for K-feldspar separates) as unaltered granite (–0.52 to –0.47 ‰). The narrow δ41K range suggests that magmatic fluid exsolution and magmatic-hydrothermal alteration have a minor effect on δ41K of the altered rock. Phyllic alteration of K-feldspar altered precursor rock leads to K loss and elevated δ41K values ranging from –0.36 to –0.19 ‰ for whole-rocks and –0.34 to –0.17 ‰ for sericite mineral separates. As sericite preferentially incorporates 41K, sericite will have higher δ41K values than the precursor K-feldspar, whereas the fluids will have lower δ41K values. Our study demonstrates that hydrothermal alteration may affect the K isotope composition of altered rocks in several ways, contingent on the nature of the involved phases, making K isotopes a promising tool for studying hydrothermal alteration and associated mineralization.

Description: As a consumed and influential natural plant beverage, tea is widely planted in subtropical and tropical areas all over the world. Affected by (sub) tropical climate characteristics, the underlying surface of the tea distribution area is extremely complex, with a variety of vegetation types. In addition, tea distribution is scattered and fragmentized in most of China. Therefore, it is difficult to obtain accurate tea information based on coarse resolution remote sensing data and existing feature extraction methods. This study proposed a boundary-enhanced, object-oriented random forest method on the basis of high-resolution GF-2 and multi-temporal Sentinel-2 data. This method uses multispectral indexes, textures, vegetable indices, and variation characteristics of time-series NDVI from the multi-temporal Sentinel-2 imageries to obtain abundant features related to the growth of tea plantations. To reduce feature redundancy and computation time, the feature elimination algorithm based on Mean Decrease Accuracy (MDA) was used to generate the optimal feature set. Considering the serious boundary inconsistency problem caused by the complex and fragmented land cover types, high resolution GF-2 image was segmented based on the MultiResolution Segmentation (MRS) algorithm to assist the segmentation of Sentinel-2, which contributes to delineating meaningful objects and enhancing the reliability of the boundary for tea plantations. Finally, the object-oriented random forest method was utilized to extract the tea information based on the optimal feature combination in the Jingmai Mountain, Yunnan Province. The resulting tea plantation map had high accuracy, with a 95.38% overall accuracy and 0.91 kappa coefficient. We conclude that the proposed method is effective for mapping tea plantations in high heterogeneity mountainous areas and has the potential for mapping tea plantations in large areas.

Description: This article was originally published online on 17 July 2023 with an error in the Acknowledgment section.

Description: Chimera states in spatiotemporal dynamical systems have been investigated in physical, chemical, and biological systems, while how the system is steering toward different final destinies upon spatially localized perturbation is still unknown. Through a systematic numerical analysis of the evolution of the spatiotemporal patterns of multi-chimera states, we uncover a critical behavior of the system in transient time toward either chimera or synchronization as the final stable state. We measure the critical values and the transient time of chimeras with different numbers of clusters. Then, based on an adequate verification, we fit and analyze the distribution of the transient time, which obeys power-law variation process with the increase in perturbation strengths. Moreover, the comparison between different clusters exhibits an interesting phenomenon, thus we find that the critical value of odd and even clusters will alternatively converge into a certain value from two sides, respectively, implying that this critical behavior can be modeled and enabling the articulation of a phenomenological model.

Description: The complex phase interactions of the two-phase flow are a key factor in understanding the flow pattern evolutional mechanisms, yet these complex flow behaviors have not been well understood. In this paper, we employ a series of gas–liquid two-phase flow multivariate fluctuation signals as observations and propose a novel interconnected ordinal pattern network to investigate the spatial coupling behaviors of the gas–liquid two-phase flow patterns. In addition, we use two network indices, which are the global subnetwork mutual information (⁠ ⁠) and the global subnetwork clustering coefficient (⁠ ⁠), to quantitatively measure the spatial coupling strength of different gas–liquid flow patterns. The gas–liquid two-phase flow pattern evolutionary behaviors are further characterized by calculating the two proposed coupling indices under different flow conditions. The proposed interconnected ordinal pattern network provides a novel tool for a deeper understanding of the evolutional mechanisms of the multi-phase flow system, and it can also be used to investigate the coupling behaviors of other complex systems with multiple observations.