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The concentrations of rare earth elements in the waters and suspended particles from two alkaline lakes in a carbonate drainage basin of the South China Karst region were determined via ICP-MS. Sequential chemical extraction experiments were conducted on the suspended matter to investigate water-particle interaction processes. Due to their high pH, the alkaline lakes have lower concentrations of dissolved rare earth elements than those reported for most other terrestrial surface waters of the world. Linear regressions between pH and the rare earth element (REE) concentrations over a wide pH range show a “three stage model,” implying the geochemical behavior of dissolved REEs in surface waters is mainly controlled by pH. Shale-normalized patterns of dissolved REEs mainly show a marked enrichment in heavy REEs (HREE), while acid-extracted and organic REEs mainly show convex patterns and the residual fractions have flat patterns. Distinct positive La anomalies were observed in the Lake Aha and its river waters, which also exhibit a very high Mn concentration, indicating severe redox and scavenging conditions. Both negative and positive Ce anomalies were clearly observed in the dissolved phase and extracted fractions of suspended particulate matter. The positive correlation of Ce anomalies with Mn indicates that redox reactions control these Ce anomalies.

Chemical properties and reactivity of fluorescent dissolved organic matter (FDOM) are examined in this paper. They are key issues to understand the biogeochemical processes in the aquatic environments. Typically, FDOM undergoes photochemical transformation and is recalcitrant to microbial degradation, except for the aromatic amino acids that are microbiologically degraded under dark conditions. Experimental results demonstrate that the fluorescence intensity of various FDOM components is depleted upon irradiation (in the hours to 70 days time scale), approximately by 20‐85% for fulvic acid, by 12‐95% for fluorescent whitening agents (FWAs) or commercial detergents, and by 5‐60% for trytophan. Microbial degradation is able to decompose the amino acid tryptophan and similar compounds, by approximately 13‐24% in unfiltered river waters, 67% in unfiltered sewerage samples, and 11% in filtered river samples. The photoreactivity of FDOM is greatly decreased when passing from freshwater (river and lakes) to marine waters, but deep waters in lakes or marine environments are often more sensitive to photodegradation processes than surface waters. The high reactivity of FDOM toward photodegradation could be understood on the basis of its (however complex) chemical structure, considering that many FDOM components can undergo photoionization or otherwise photosensitized oxidation under sunlight. The controlling factors to the photochemical and microbial degradation of FDOM for a variety of waters are extensively discussed. One of the important functions of FDOM is the formation of complexes with transition metals in the aquatic environments, and this review discusses the mechanisms by which FDOM interacts with metals. Further investigations on FDOM, namely the identification of still unknown FDOM components, the metal-FDOM interactions as well as the photochemical and microbial reactivity will give invaluable information on the DOM dynamics in the aquatic environments.

l ‐1 in the epilimnion and 1.4‐41.0 µg l ‐1 in hypolimnion with the maximum level in July when water temperature (WT) was the highest of the year. DOC concentrations were significantly correlated with Chl a and WT. Chl a was well correlated with WT in the epilimnion of Lake Hongfeng, suggesting that biological activities might be a major DOC source in the lake waters. DOC concentrations were weakly correlated or not correlated with fulvic acid-like fluorescence in the epilimnion, but they were significantly correlated with tryptophan-like fluorescence, indicating that the tryptophan-like fluorescent material was from new DOM in the lakes during the summer period. But these correlations were often insignificant or absent in the waters of Lake Baihua except peaks T and TUV, which may be caused by the input of organic contaminants from the industrial activities near Lake Baihua. This study may assist to better understand the sources of lake DOM and the effects of organic matter pollution on the biogeochemical cycling of DOM in lake environments.

To provide a better understanding of potential hazard of effluent detritus, both at the present and in the future, the dispersal and accumulation of sewage-derived materials in the receiving river should be addressed. For the goals, we determined concentrations and isotopic compositions of sedimentary organic carbon (SOC) and nitrogen (SON) and those of effluents in an urban river (Nanming River, China). In the river, the two major sources of sedimentary organic matter (SOM) are effluent detritus (δ 13 C: ‐25.0‰; δ 15 N: +8.5‰; C/N: 8.1) and C3 plants growing along the river bank (δ 13 C: ‐27.7‰; δ 15 N: ‐0.9‰; C/N: >28). Isotopic difference between the two end-members was observed to be 9.4‰ for nitrogen, compared with 2.7‰ for carbon, and hence nitrogen isotopic difference between end-members is large enough to be used as a tracer for source recognition of SOM. Using a mixing model, we found that at outfalls sewage-derived SON accounted for >60% of the bulk SON. At site 40 km far from outfall, fraction of sewage-derived SON was still high to 50%. But at most sites, though about 450,000 m 3 sewage effluents per day discharge into the river, effluent detritus and C3 plants contributed nearly the same to SOM, indicated that natural contribution from C3 plants should be also paid attention to.

Several types of granites including alkaline granites and alkali feldspar granites are distributed in the Karamaili tectonic belt of East Junggar, Xinjiang, China. Some medium-small tin deposits are located within or near the contact zones of the granitic intrusions. The alkaline granites share all the features commonly observed in peralkaline A-type granites. They contain alkalic mafic minerals such as riebeckite and aegirine; have high contents of SiO2, alkalis, Rb, Th, Zr, Hf, REE (except Eu), and high ratios of FeO*/MgO and Ga/Al; and show strong depletions in Ba, Sr, Eu in the spidergrams. Laser ablation-ICPMS U-Pb zircon geochronology indicates a crystallization age of ca. 305 Ma for the granites; TIMS analyses of the granites found high eNd(T) values of +5.9 to +6.5. Considering their geochemical features, alkaline granites most likely formed by fractional crystallization of granodioritic magmas, which were probably produced by partial melting of lower crustal basaltic to andesitic rocks formed from oceanic crustal materials that were deeply buried during late Paleozoic subduction and accretion. Six molybdenite samples from the Sareshike tin deposit in East Junggar yielded an isochron age of 307 ± 11 Ma (2σ) and a weighted mean model age of 306.5 ± 3.4 Ma, consistent with zircon U-Pb ages of the alkaline granites. Low Re contents (0.323-0.961 ppm) in the molybdenite suggest that they originated from crustal sources related to the alkaline granites. Considering their identical ages, close spatial distribution, and similar sources, we argue that the A-type granites have a genetic relationship with the tin mineralization, and that the same association may be important elsewhere.

The Maoniuping REE deposit is the second largest light rare earth elements deposit (1.45 million tons of REE2O3) in China, located in the Panxi rift, Sichuan Province. It is a vein-type deposit hosted within, and genetically related to the Himalayan alkalic carbonatite-syenite complex. The initial 206Pb/204Pb and 208Pb/204Pb ratios from the Maoniuping carbonatites are similar to syenites, which, however, show more radiogenic 207Pb/204Pb ratios. This could not only be attributed to contamination by crustal materials. The Pb-Pb isotope plots from carbonatites and syenites define a linear array between EM1 and EM2. It suggests their sources were located in a heterogeneous lithospheric mantle and produced by the mixture of EM1 with EM2. The initial 206Pb/204Pb and 208Pb/204Pb ratios from fluorites, galenas, pyrites and feldspar are similar to carbonatites and syenites, and different from granites. Their 207Pb/204Pb ratios also plot to between syenites and carbonatites. This suggests the REE ore-forming fluids were derived from carbonatite and syenite magmas. The Pb isotopic results are consistent with a model for REE deposition involving mixing of the F-rich, syenite-derived fluid with Ca-, CO2-bearing fluid evolved from carbonatite magma. The early fluorites have higher 207Pb/204Pb ratio than the later ones, which shows that the REE ore-forming fluids were not contaminated by country rocks fluids.

The Liaodong gold province, along the eastern margin of the North China craton, is a large productive base of gold in China. The Wulong gold deposit hosted in granitoid is a famous Au-bearing quartz vein gold deposit in this region, and located at the northern side of Sanguliu granite. The ages of Sanguliu granite determined by the conventional Rb-Sr isochron and U-Pb zircon methods are 131 ′ 4.5 Ma and 129 ′ 2.9 Ma respectively, thus the comprehensive isotopic age of Sanguliu granite is 130 Ma. Lode gold deposits commonly consist of pyrite and lesser amounts of galena and sphalerit sulfides accompanied by quartz and calcite. Here we use direct Rb-Sr dating of pyrite from Wulong gold deposit, and determined the age of Wulong gold deposit. A positive correlation between present-day 8 7 Sr/ 8 6 Sr and 8 7 Rr/ 8 6 Sr ratios of pyrite from the Wulong gold deposit corresponds to an age of 120 ′ 3 Ma, which dates the age of gold mineralization. The Sr initial ratios (0.714816 to 0.7148927 of Sanguliu granite and 0.715280 to 0.715504 of pyrites in Au-bearing quartz veins) and Pb isotopic compositions in pyrites and Sanguliu granite indicates that lead was derived partially from the similar magmatic source, and the liner array of Pb isotope composition in pyrite show a incorporation of two end members (may be incorporation of basic and acid wall rocks). The studies of H and O isotopes of fluid inclusions in auriferous quartz veins demonstrate that the magmatic water predominates in ore fluids, and also reflect a little formation waters.

REE and other trace elements in altered and unaltered phyllites, orebodies and quartz veins in the Yinshan deposit were determined in order to examine behaviors of trace elements during hydrothermal alteration. REE, especially LREE, were selectively leached from the phyllites that had been undergone recrystallization dominantly of the major minerals during hydrothermal alteration. The greater the degree of alteration was, the stronger the leaching of REE would be. LREE were leached from the rocks that are close to the intrusions and re-deposited in the part far away from the intrusions. Nevertheless, Eu was systematically leached from the rocks, resulting in strong negative Eu anomalies in the altered phyllites. The lower total REE contents in the altered rocks close to the intrusions, compared to those from the further part is probably attributed to the dilution of REE-barren minerals (quartz and sulfides), and the removement of REE from the rocks by hydrothermal alteration. REE in the hydrothermal solutions are characterized by enrichment in LREE, strong positive Eu anomalies and (La/Yb)N ratios much smaller than those of the phyllites. The addition of REE from the hydrothermal solutions into the altered rocks resulted in the observed smaller (La/Yb)N ratios in the altered phyllites than that of the unaltered equivalent. For other trace elements, Y behaved similarly to HREE. The LIL elements such as Rb, Sr and Ba behaved differently, which may be attributed to the different fates of their main hosting minerals. The ore-forming elements such as Cu, Pb, Zn, Ag and Sn were remarkably added to the altered phyllites, while Hf, Th, U, Nb, and Zr remained rather constantly during hydrothermal alteration. It is suggested by the REE features that ore-forming fluids probably found their ways upwards from the depth through faults to the locus of ore deposition. The degree of REE mobility increases with the sizes of the orebodies. Thus, REE is probably an effective geochemical indicator for distinguishing between small and large orebodies at the later stage of exploration.

Sr, Nd, Ce and O isotopic ratios and trace element abundances were measured for Cenozoic SiO2- and (Na2O + K2O)-rich volcanic rocks from Yutian of Xinjiang, Yumen of Gansu and Tengchong of Yunnan, Western China. All samples investigated, especially the samples from Yutian of Xinjiang, are highly enriched in LREE and other incompatible elements, and are characterized by higher 87Sr/86Sr (0.706-0.709) and lower 143Nd/144Nd (0.5121-0.5126) ratios as compared with MORB and OIB. High 138Ce/142Ce ratios (0.0225767-0.0225810) were also found for the volcanic rocks from Yutian of Xinjiang and Yumen of Gansu provinces. The volcanic rocks from the three areas are concluded to have been derived from LILE (large ion lithophile element)-enriched mantle source regions without significant crustal contamination. Their high δ18O, and low HFSE (high field strength element)/LILE ratio characters imply a crust-like component existing in their mantle source regions, and hence the isotope variations of the volcanic rocks are modeled with mixing between two end members; depleted mantle and crust-like component. The mantle source region below western China, which indicates integration of subduction-related mantle, is disclosed to be clearly different from that below eastern China.