The δ¹⁷O and δ¹⁸O values of some international silicate reference materials such as NBS-28 quartz, NBS-30 biotite, UWG2 garnet, San Carlos olivine and some mineral separates of terrestrial origin were re-evaluated on the VSMOW-SLAP scale using the CO₂-laser fluorination technique. To report their δ¹⁸O values on the VSMOW-SLAP scale, the δ¹⁷O and δ¹⁸O values of O₂ directly derived from VSMOW and SLAP were measured using the same preparation line as used for the silicates. Application of the VSMOW-SLAP scale to the above silicate reference samples resulted in the δ¹⁸O values of NBS-28 quartz, NBS-30 biotite, UWG2 garnet and San Carlos olivine that are 9.18, 4.88, 5.59 and 5.28‰, respectively. The data form a straight line in the 10³ ln(1 + δ¹⁷O/10³) vs. 10³ ln(1 + δ¹⁸O/10³) plot with a slope of 0.526 ± 0.003 (standard error at 95% confidence limit), but the line for the waters (VSMOW, GISP, SLAP and MSA-6) seems to have a slightly steeper slope of 0.528 ± 0.001, although difference of the slopes is not statistically significant.

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In the present study, lithogenic/biogenic and anthropogenic elements were determined in five sediment cores collected at the SW Iberian Continental Shelf in order to investigate the spatial and temporal heavy metal distribution and to associate them with specific continental influences/events. Elemental concentrations suggest a heavy metal (Cu, Zn and Pb) enrichment at the upper sections of all the cores. This enrichment is larger for cores localised closer to the coastline and probably exposed to a stronger continental influence. The geochemical regional background values for the studied elements are reached at ∼25-30 cm for all the studied cores with one exception (core 8), which showed to be metal-enriched down to ∼80 cm. It is worthnoting that core 8 is located closer to the coastal area, in a different fine sedimentary deposit, in which the deposition rates seem to be considerably higher. Enrichment factors (EF) calculated by using the natural background value determined at the deeper layers show that the EF values vary at the upper sections of cores, between 1.0 and 4.5 and the spatial distribution of the sediment cores show a similar behaviour in the heavy metal distribution patterns along this area of the continental shelf. Cu, Zn and Pb are heavy metals associated with mining exploitation along the Iberian Pyrite Belt, one of the most important mining areas of southwestern Europe, with massive orebodies of these metals. The combination of enrichment factors downcore profiles with sedimentation rate values signifies the beginning of heavy metal pollution in shelf sediments (∼200-250 years ago) and is coincident with the mining exploitation reactivation during the XIX century.

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Hydrogen isotope ratios were measured on terrigenous alkanes (n-C₂₅ to n-C₃₁) extracted from recent lake surface sediments from the climatically and environmentally distinct basins Qiangyong Glacier Lake, Yamzho Lake, Nam Co Lake, Keluke Lake and Xiao Qaidam Lake along a S-N transect in the Tibetan Plateau to explore the climatic implication of these biomarkers. δD values of these n-alkanes are compared to that of precipitation spanning a wide range from -167‰ to -51‰ and clearly correlate with δD values of meteoric water, indicating that terrigenous alkanes record the precipitation signal. The fractionation between precipitation and n-C₂₅, n-C₂₇ alkanes cover a range from -45‰ to -70‰ whilst that between precipitation and n-C₂₉, n-C₃₁ alkanes varies from -70‰ to -95‰ both being fairly constant along the S-N Tibetan transect with the mean at -57‰ and -82‰ respectively. By comparison with the fractionation of -130‰ along the S-N European transect, it implies that the hydrogen isotopic fractionation between meteoric water and terrestrial n-alkanes along the Tibetan transect represent distinct character.

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The Abaga volcanic field is one of the largest and least known areas of late Cenozoic intraplate igneous activities in eastern China. Twenty-seven Abaga basaltic rocks were analyzed for major and trace element contents, Sr-Nd-Pb isotopic compositions, and K-Ar dating. These basalts predominantly consist of alkali basalt with subordinate transitional olivine tholeiite and rare quartz tholeiite. Combining our data of ten K-Ar dates with previously published data showed that the time of the principal volcanic eruption was from the Miocene to the Quaternary (14.57∼0.19 Ma). A large amount of volcanic activity is believed to have begun in the northwestern portion of the AVF and gradually migrated southeastwards with geological time. The Abaga basalts exhibit chondrite-normalized REE patterns, incompatible elements and isotopic ratios (⁸⁷Sr/⁸⁶Sr of 0.703654∼0.704286 and ¹⁴³Nd/¹⁴⁴Nd of 0.512845∼0.512891) affiliated with oceanic island basalts (OIBs). In general, they have relatively homogenous Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb of 18.409∼18.521, ²⁰⁷Pb/²⁰⁴Pb of 15.514∼15.546, and ²⁰⁸Pb/²⁰⁴Pb of 38.259∼38.447), indicating that these lava suites have a similar source. But the alkali basalts are relatively enriched in incompatible elements when compared to the tholeiites. This compositional difference may be attributable to the different degrees of partial melting in the mantle source. The Sr-Nd-Pb isotopic data indicated that the mantle sources of the late Cenozoic Abaga basalts display a DMM-EM2 array similar to those of Southeast Asia. The ²⁰⁸Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb plot was also significantly displaced above the Northern Hemisphere reference line in a pattern clustering near the less-depleted end of the field for the Indian Ocean mid-oceanic ridge basalt (MORB) that shows Dupal signatures. Therefore, we suggest that the Abaga basaltic magmas were dominantly derived from an Indian Ocean MORB-like depleted asthenospheric source with fewer contributions of an enriched mantle component (EM2) from the subcontinental lithospheric mantle.

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Rare earth element and yttrium in hydrothermal fluids sampled from six high temperature vents and two diffuse flow sites on the Endeavour segment, Juan de Fuca Ridge by US-CHINA Joint Deep Dive Cruise in Aug. 2005 were analyzed by ICP-MS after being pre-concentrated by 20-fold. According to the species distributions calculated by GWB, the chondrite-normalized REE patterns (REE_CN) of these fluids are characterized by LREE enrichment and positive Eu anomalies, which are mainly controlled by complexing with chloride. The (La/Yb)_CN ratio does not correlate significantly with fluoride. Sulfate content are low in most high temperature fluids except in Gremlin vent fluids. Certain amounts of REE are complexed with sulfate that likely originates from oxidation of magmatic SO₂ and/or H₂S in Gremlin. Sulfates, mostly come from seawater, are also responsible of large percentage of REE complexes in diffuse fluids. It is shown by the character of REY concentrations and the Y/Ho ratios that REE removed by Fe, Mn-oxyhydroxides is negligible in most of high temperature vent fluids. However, the Y/Ho ratios in Gremlin (Y/Ho = 160) and Faulty Towers (Y/Ho = 140) vent fluids are higher than that in other high temperature vent fluids, suggesting REE removal controlled by coprecipitation and scavenging. The negative Ce anomalies in diffuse fluids also result from the scavenging of mineral particles in the oxidizing conditions when mixing with seawater. Compared to ideal mixing fluids calculated by Mg content, two diffuse fluids display LREE-depleted patterns and enhanced positive Eu anomalies. Based on the REE characteristics of anhydrite, the REE distribution patterns of diffuse fluids are probably influenced largely by anhydrite precipitation under the seafloor at diffuse fluids sites. It is interesting to notice that the HREE_CN pattern of Mothra vent fluids is similar to sediments but different from the sediment-starved hydrothermal fluids, suggesting they are likely remolded by the sediments in water-rock interaction zone and/or upflow zone nearby Mothra vent field. The provenance and character of these sediments bears further investigation.

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Nine publications showing REE data in groundwaters and river water were examined to understand the general condition of terrestrial water where a negative Ce anomaly develops. It was found that the negative Ce anomaly only appeared when Fe, Mn and dissolved organic carbon (DOC) concentrations were low (Fe and Mn < 5 × 10^-5 mol/L and DOC < 10 mg/L). Assuming that Ce³⁺ and Fe²⁺ concentrations were limited by the formation of cerianite and ferrihydrite, respective redox potential (Eh) was calculated from each of Ce³⁺ and Fe²⁺ concentrations. For data sets displaying Ce anomalies, the calculated Ehs (cEhs) showed a 1:1 relationship between Ce and Fe. This relationship indicates that the absolute concentration of Ce in natural water may be thermodynamically determined in situ by Eh and pH when concentrations of Fe, Mn and DOC are poor.

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