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The food source of hadal endemic fauna provides an insight into the carbon cycle in trenches and a biological adaptation to the impoverished and harsh trench environment. Here, we present the first Delta C-14 results of hadal amphipods from three trenches in the Pacific to define the organic matter source in these remote ecosystems. Amphipod muscle tissues contain a bomb C-14 signature (Delta C-14 from 10 +/- 2 parts per thousand to 65 +/- 2 parts per thousand), thereby revealing a dietary preference for labile and fresh organic matter derived from the surface water. Thus, the carbon cycle in the deepest ocean trench has a tight linkage with the surface ocean via the food chain. The bomb C-14 dating result suggests that hadal amphipods have a low tissue turnover rate and an unexpectedly long lifetime (>10 years), at more than 4 times higher than the common longevity (similar to 2 years) of amphipods in shallow waters. Plain Language Summary Hadal trenches (depth > 6,000 m) are the remotest and the least explored places on our planet, with characteristics of low temperatures, high pressure, limited food, and frequent geological activity. Knowing the source of organic matter for hadal life is key in understanding the ocean carbon cycle and the biological adaptation in trenches. We report the first C-14 results of hadal amphipods from three trenches in the West Pacific, including the deepest ocean trench, Mariana, which indicates that the organic matter for amphipods is mostly from the surface water. This tight linkage between the organic matter within the hadal fauna and in surface water points out that the anthropogenic pollution can reach the deepest ocean trench rapidly via the food chain. Moreover, the bomb C-14 dating method can be applied to hadal amphipods, thereby suggesting a low tissue turnover rate and an unexpectedly long lifetime, which might be a result of an adaptation to the impoverished and harsh environment.

The East Taiwan Ophiolite (ETO) occurs as blocks and thrust sheets associated with the Lichi Melange in the Coastal Range of eastern Taiwan. The blocks consist of serpentinized harzburgite, serpentinite breccia, gabbro, dikes of dolerite and plagiogranite, pillow basalts, and red clay within a mud-and serpentinite-rich melange matrix. New U-Pb zircon dating of a pegmatite gabbro yields a weighted mean age of 16.65 +/- 0.20 Ma. This age is earlier than the North Luzon Arc but overlaps with the late-stage spreading of the South China Sea. ETO glassy basalt has low K2O, MgO and high CaO contents, similar to MORB. REE and trace element patterns show both N-MORB patterns with LREE depletion and E-MORB patterns with slight LREE enrichment. A few samples show slight depletion in Nb-Ta and Ti and enrichment in Rb, Ba, U and Sr, indicating a hint of subduction influence. Most ETO basalt plots within the overlapping fields of N-MORB and BABB on Ti-V, Cr-Y, Nb/Yb-Th/Yb, and Hf/3-Th-Ta discrimination diagrams. These geochemical compositions are emblematic of mid-ocean ridge or back-arc lava, like South China Sea basalt. We interpret ETO basalt and gabbro as fragments of the subducted South China Sea basement that were scrapped off and accreted to the Luzon forearc during the process of subduction initiation along the Manila Trench. Blocks of mantle material in the melange may originate from the upper plate of the arc-continent collision and were mixed with lower plate crustal material in a subduction channel now represented by the Lichi Melange.

The Yap subduction zone is a distinctive erosive margin with an extremely slow convergence rate. The high relief of the subducting plate, generated by horst and graben structures and seamounts, leads to attenuation of the crust. In this study, we present the latest geophysical data, collected by the Chinese research vessel Kexue, to investigate subduction erosion at the Yap subduction zone and develop subduction models for Yap subduction zone structures. We show an anomalous distance between the Yap Trench and the adjacent volcanic arc, the steep slope of the trench arcward, a frontal prism, and rare sediment in the trench, all typical features of erosive margins. We propose that the high-relief subducting plate has led to erosion of the overlying plate and that different subduction processes, controlled locally by the topography of the subducting plate, have modified the Yap subduction zone. Numerous normal faults increase the relief of the seafloor entering the trench, and an anomalously large slope angle along the trench reflects uplift of the fore-arc high via seamount subduction. In addition, the thin crust of the subducted horst and graben structures, along with the normal faults, might have eroded the fore-arc crust and subsequently eroded the Yap arc crust during subduction. These subduction erosional processes at the Yap Trench provide one of the best cases of an erosive margin in the world, particularly for a subduction zone with an extremely slow convergence rate.

The genesis of seamount chains along fossil spreading ridges reflects the mantle melting dynamics of dying spreading center. The South China Sea developed a seamount chain along its fossil ridge shortly after cessation of spreading. International Ocean Discovery Program Expedition 349 has recovered three volcanic layers, a shallow volcanic breccia layer and two deeper (upper and lower sections) basalt layers, at Site U1431 near the fossil ridge of the South China Sea. Despite the mid-ocean ridge basalt (MORB)-like geochemistry of the lower and upper section basalts, they show distinct geochemical differences that indicate a change of mantle source and a transition from spreading to intraplate volcanism. While the lower section basalts could reflect the last stage volcanism before the cessation of ridge spreading, the upper section basalts with whole-rock MgO up to 20wt.% were formed by intraplate volcanism with significant olivine accumulation once the spreading center had become inactive. The MORB type basalts at Site U1431 have Hawaii-like high olivine Ni and Fe/Mn and low olivine Ca and Mn and bulk-rock low CaO that are distinctly different from normal global MORBs, suggesting an anomalous mantle source in lithology. We suggest that an eclogite-/pyroxenite-rich component, possibly sourced from the Hainan hot spot, played a fundamental role in the transition from spreading to intraplate volcanism of the dying spreading ridge of the South China Sea.

Magnesite (MgCO3) is a likely main host of carbonates in the mantle and plays an important role in the transport and storage of carbon in the Earth's mantle. Its physical properties at high pressure and high temperature (PT) are crucial for understanding the deep carbon cycle. Here we investigated thermodynamic and elastic properties of magnesite under the mantle PT conditions using first-principles calculations with local density approximation (LDA). Magnesite has the seismic velocities close to those of forsterite. The effect of the magnesite on seismic velocity of the carbonated peridotite and eclogite is subtle in the upper mantle. However, magnesite has much smaller seismic velocities and far larger elastic anisotropy than major minerals in the transition zone and lower mantle. The enrichment of magnesite in the transition zone and lower mantle will likely produce seismically detectable low-velocity zone and velocity anisotropy.

Adakitic rocks with high MgO content and lower crust affinity at convergent margins provide important constraints on arc crust evolution and regional tectonics. An integrated study on the only adakitic pluton with high MgO content and its mafic microgranular enclaves (MMEs) in the Early Paleozoic North Qinling arc terrane was conducted in this paper. Zircons from 2 host rock samples yielded identical weighted mean ages of 428 Ma. The MMEs contain two types of zircons: type 1 zircons share similar morphology, chemical composition, and indistinguishable age with those from the host rock; type 2 zircons yielded an older age of 450 Ma. The similarity in zircon Hf isotopic composition for these zircons indicates a cognate origin of the MMEs. However, the lower Ce4+/Ce3+, higher crystallization temperature and the LREE overabundance of type 2 zircons indicate that mafic intrusions in the lower arc crust were subjected to a post-magmatic event at similar to 450 Ma. Samples from the Tangzang pluton are characterized by typical adakitic geochemical features, and high MgO (Mg#: 50-52), Cr, Ni, and Ba contents. Considering their similar isotopic compositions with the Neoproterozoic metabasites in the North Qinling terrane, we argue that the Tangzang pluton was generated by crustal anatexis of two sources with contributions from the metasomatized mantle wedge. The mantle connection was achieved by aqueous melt-fluxed melting of a "hot zone'' in the lower arc crust. This implies that andesitic continental crust with Mg# of similar to 0.5 may also be associated with fluxed-melting of the lower arc crust.

Mantle peridotites show that Ca is isotopically heterogeneous in Earth's mantle, but the mechanism for such heterogeneity remains obscure. To investigate the effect of partial melting on Ca isotopic fractionation and the mechanism for Ca isotopic heterogeneity in the mantle, we report high-precision Ca isotopic compositions of the normal Mid-Ocean Ridge Basalts (N-MORB) from the southern Juan de Fuca Ridge. Ca-44/40 of these N-MORB samples display a small variation ranging from 0.750.05 to 0.860.03 (relative to NIST SRM 915a, a standard reference material produced by the National Institute of Standards and Technology), which are slightly lower than the estimated Upper Mantle value of 1.050.04 parts per thousand and the Bulk Silicate Earth (BSE) value of 0.94 +/- 0.05 parts per thousand. This phenomenon cannot be explained by fractional crystallization, because olivine and orthopyroxene fractional crystallization has limited influence on Ca-44/40 of N-MORB due to their low CaO contents, while plagioclase fractional crystallization cannot lead to light Ca isotopic compositions of the residue magma. Instead, the lower Ca-44/40 of N-MORB samples compared to their mantle source is most likely caused by partial melting. The offset in Ca-44/40 between N-MORB and BSE indicates that at least 0.1-0.2 parts per thousand fractionation would occur during partial melting and light Ca isotopes are preferred to be enriched in magma melt, which is in accordance with the fact that Ca-44/40 of melt-depleted peridotites are higher than fertile peridotites in literature. Therefore, partial melting is an important process that can decrease Ca-44/40 in basalts and induce Ca isotopic heterogeneity in Earth's mantle.

Tracing and identifying recycled carbonates is a key issue to reconstruct the deep carbon cycle. To better understand carbonate subduction and recycling beneath the southeastern Tibetan Plateau, high-K cal-alkaline volcanic rocks including trachy-basalts and trachy-andesites from Tengchong were studied using Mg and Ca isotopes. The low Mg-26 (-0.310.03 to -0.380.03) and Ca-44/40 (0.67 +/- 0.07 parts per thousand to 0.80 +/- 0.04 parts per thousand) values of these volcanic rocks compared to those of the mantle (-0.25 +/- 0.07 parts per thousand and 0.94 +/- 0.05 parts per thousand, respectively) indicate the incorporation of isotopically light materials into the mantle source, which may be carbonate-bearing sediments with low Mg-26 and Ca-44/40 values. In addition, no correlations of Mg-26 and Ca-44/40 with either SiO2 contents or trace element abundance ratios (e.g., Sm/Yb and Ba/Y) were observed, suggesting that limited Mg and Ca isotopic fractionation occurred during cal-alkaline magmatic differentiation. A binary mixing model using Mg-Ca isotopes shows that 5-8% carbonates dominated primarily by dolostone were recycled back into the mantle. Since Tengchong volcanism is still active and probably related to ongoing plate tectonic movement, we propose that the recycled carbonates are derived from oceanic crust related to the ongoing subduction of the Indian plate.

Hydrothermal experiments were performed at 311 degrees C and 3.0 kbar on natural olivine and peridotite to investigate the kinetics of serpentinization. The results show that the rates of reaction strongly depend on grain sizes of solid reactants, with smaller grain sizes resulting in faster kinetics. After 27 days of reaction, the reaction extent was 99% for peridotite with grain sizes of

The study presents δ65Cu and δ97Mo isotope values from cogenetic chalcopyrite and molybdenite found in veins and breccias of the Dahutang W-Cu-Mo ore field in China. The samples span a 3–4 km range. Both isotopes show a significant degree of fractionation. Cu isotope values in the chalcopyrite range from −0.31‰ to +1.48‰, and Mo isotope values in the molybdenite range from −0.03‰ to +1.06‰. For the cogenetic sulfide veined samples, a negative slope relationship exists between δ65Cu and δ97Mo values, which suggest a similar fluid history. Rayleigh distillation models the vein samples' change in isotope values. The breccia samples do not fall on the trend, thus indicating a different source mineralization event. Measured fluid inclusion and δD and δ18O data from cogenetic quartz indicate changes in temperature, and mixing of fluids do not appear to cause the isotopic shifts measure. Related equilibrium processes associated with the partitioning of metal between the vapor-fluid in the hydrothermal system could be the probable cause for the relationship seen between the two isotope systems.

It is well-known that nitric oxide ( NO) is an important component in nitrogen biogeochemical cycling produced through biological process of nitrification and denitrification in soils, but the production and the consumption processes of NO in sodic saline soil are less understood. Through a series of laboratory experiments focusing on NO biogenic emissions from four kinds of saline sodic soils of different land use in western Songnen Plain northestern China, we found that the optimum soil moisture for the maximum NO production and emission were 14.0%, 9.0%, 9.5%, and 18% water-filled pore space (WFPS) for soil samples from natural pasture, man-made pasture, paddy field of saline sodic soil mixed sandy soil, and paddy field of pure saline sodic soil, respectively. For a given moisture, NO fluxes increased exponentially with soil temperature at any given soil moisture. The optimum soil moisture for the maximum NO emission for a certain soil type, however, was constant and independent of soil temperature. The NO consumption processes for different land uses were similar in all studied saline sodic soils since the difference of NO consumption rate constant in these soils was small ( ranged from 1.07 x 10(-6) to 7.45 x 10(-6) m 3 kg(-1) s(-1)). The NO emission potential for paddy field soils was about 1.2-2-fold higher than pasture soils. On the basis of laboratory results and field monitoring data of soil water content and soil temperature, the average NO fluxes from these saline sodic soils in the region were estimated to be 1.3-4.9 ng m(-2) s(-1) for an entire plant growth period. NO fluxes for pastures mainly occurred in the dry season and were about threefold higher than that for paddy fields, which was strongly influenced by field management.

[1] In temperate climates, up to ∼50–70% of the total annual nitrous oxide (N2O) flux occurs in winter, which is mainly attributed to freezing-thawing processes of frozen soils. To investigate the nature of the enhanced N2O emission in winter, we monitored gas fluxes at two plots of freshwater marshes in northeastern China (47°35′N, 133°31′E), using a static chamber method at weekly to monthly intervals from 2002 to 2004. The results show that the big emission burst of N2O coupled with peak emission of CH4 occurred in late July to early August, which is about 1 week after the soil thawed out completely. Further observations show that the N2O and CH4 were continuously produced underneath the frozen soil. The gas-producing layer was continuously depressed downward during the progressive freezing. The highest concentrations of N2O and CH4 were first observed when the frozen layer reached its maximum depth of ∼90 cm in early February and remained there with roughly constant concentrations until June. We propose that at the beginning the frozen soil limits the transportation of oxygen from atmosphere to soil, while freezing increases the nutrient supplies, producing an anoxic organic-rich environment underneath the frozen layer, which promotes the net formation of N2O and CH4 through denitrification and anoxic digestion of organic matters, respectively. In contrast, after the frozen layer reached the organic-poor gley layer and there is no further supply of nutrients through freezing, the formation of N2O and CH4 stopped shortly after.

We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties (at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive (isotope dilution) and comparative bulk (e.g., INAA, ICPMS, SSMS) and microanalytical (e.g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented.