Whether arc mantle is more oxidized than oceanic mantle is persistently debated. The behavior of multivalent vanadium (V) is oxygen fugacity (fO 2 ) sensitive, and the ratios of V to a homovalent element (e.g., Sc, Ti, or Yb) in basalts were commonly used as fO 2 proxies. Similar ratios, such as V/Sc, between arc basalts and mid-ocean ridge basalts were previously taken as evidence for similar fO 2 s in their mantle sources. However, this claim may be problematic because elemental ratios are primarily controlled by partition coefficients (D values), which are further affected by various factors. Here we determined D values of V and other transition elements between mantle minerals and basaltic melts at typical arc T-P-H 2 O conditions and variable fO 2 s. Combining experimental results with published data, the effects of fO 2 , T, P, and phase compositions on D V , D Sc , and D Ti for olivine, orthopyroxene (opx), clinopyroxene (cpx), and spinel were evaluated using multiple linear regressions. The results show that D V values for these four minerals all increase with decreasing fO 2 and temperature, leading to higher D V /D Sc and D V /D Ti ratios at low temperatures than those at high temperatures given a certain fO 2 . Thus, similar V/Sc and V/Ti ratios between arc basalts and mid-ocean ridge basalts reflect a relatively oxidized arc mantle due to its lower melting temperatures. In light of the highly incompatible behavior of Ti during mantle melting, V-Ti systematics are regarded to be more superior than V-Sc systematics in the fO 2 estimation. Partial melting modelling results using V-Ti systematics reveal that arc mantle is, on average,~0.9 log units higher in fO 2 than oceanic mantle.Plain Language Summary The oxidation state of the Earth`s mantle, often expressed as oxygen fugacity (fO 2 ), could control the behavior of multivalent elements and thus exert a significant influence on the formation of magmatic ore deposits and the secular evolution of Earth`s atmosphere. Whether arc mantle is more oxidized than oceanic mantle remains a controversial topic. As a multivalent element, partitioning behavior of vanadium is fO 2 sensitive and is capable of tracking mantle redox state. However, except fO 2 , other factors (temperature, pressure, and phase composition) that may affect vanadium partitioning behavior have not been clearly evaluated. Here we conducted high temperature and pressure experiments to determine partition coefficients of vanadium during mantle melting under various fO 2 conditions. Combining our and published data, we evaluated the effects of fO 2 , T, P, and compositions of mineral and melt on the vanadium partitioning using multiple linear regressions. The results indicate that, in addition to fO 2 , temperature exerts a significant control on the vanadium partitioning. Additionally, we estimated fO 2 of the arc mantle via numerical modelling using appropriate partition coefficients for vanadium. Our results clarify and reconcile the discrepancies between previous studies and reveal that a...

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Suicidal behaviour in Chinese adolescents is prevalent but less than that previously reported in Western peers. While females are more likely to attempt suicide, males are more likely to use lethal methods. Multiple child and family factors are associated with suicidal behaviour. These findings highlight the importance of early screening and intervention of suicidal behaviour in Chinese adolescents.

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The general temporal-spatial consistency for the formation of adakitic rocks and lithospheric thinning in northern China provide a window to examine the processes and mechanism for the destruction of the North China Craton. With experimental petrology data, this paper demonstrates that the adakitic rocks in northern China are the products of partial melting of middle-to high-potassic metabasalts at the base of the lower continent crust. Based on the TiO 2 solubility model, many adakitic rocks in Dabie, Jiaodong and the northern part of the craton appear to have been saturated with TiO 2 . This indicates the presence of a Ti-rich accessory phase in their source regions. This phase must be rutile based on the decreasing Nb/La with increasing La/Yb in the adakitic rocks. The adakitic magmas were, thus, derived from a depth of more than 50 km, based on pressures (higher than 1.5 GPa) for the stability of rutile in a metabasalt system. Because present-day crustal thickness is generally only 35 km, we suggest that the destruction of the North China Craton may have led to at least 15 km of thinning or delamination of the crust.

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To understand Ti, Nb, and Ta mobility in supercritical fluids and Nb/Ta fractionation in subduction zones, we conducted piston cylinder experiments to determine rutile (TiO2) solubility and Nb and Ta partition coefficients (Dru/sf Nb and Dru/sf Ta) in rutile (ru)‐silica‐rich supercritical fluid (sf) systems at 1.5–2.5 GPa and 920–1150 °C over variable fluid chemistries including solute (SiO2 ± albite component), H2O, Cl, and F contents. Under the investigated conditions, TiO2 solubility in the supercritical fluids varies from 761 ± 107 to 9795 ± 448 ppm; Dru/sf Nb and Dru/sf Ta vary from 12 ± 1 to 208 ± 30 and 34 ± 5 to 2464 ± 140, respectively. Higher solute, Cl, and F contents in the systems and higher temperatures result in higher TiO2 solubilities and lower Dru/sf Nb and Dru/sf Ta, and thus, fluid chemistry and temperature exert main controls on Ti, Nb, and Ta mobility. In all cases, Dru/sf Nb/Dru/sf Ta  < 0.70, suggesting that supercritical fluids released from subducting slabs are higher in Nb/Ta relative to their protoliths. Therefore, such fluids are expected to result in higher Nb/Ta ratios in mantle wedges and arc magmas. Although Ti, Nb, and Ta could be mobile in supercritical fluids, Nb/Ta ratios in primitive arc basalts compared to those in mid‐ocean ridge basalts show that only ~10% of arc basalts are possibly disturbed by solute‐rich supercritical fluids during their generation. Therefore, if the fluids released from subducting slabs are dominantly supercritical, then most of them must be stable only in narrow P‐T spaces and hence too short‐lived to ascend very far into mantle wedges.