Spatial and seasonal variations in the chemistry of sediment interstitial waters in the Tamar Estuary

Chemical concentration gradients in the interstitial waters of shallow (0–10 cm), reducing sediments are reported for four stations in the Tamar Estuary over a two-year period. The products of organic matter breakdown, sedimentary redox changes and diagenetic reactions have been determined and a multicomponent analytical approach has enabled the interactions of complementary processes to be examined. While many components show spatial and seasonal patterns related to the supply of organic matter and salinity associated sulphate distribution, the effects of temperature, sediment disturbance and river flow are also apparent.Sediment stored prior to the separation of interstitial water showed significant changes in chemical composition compared to samples processed within 24 h of collection.     

提高石油化工污泥脱水性能试验研究

本研究通过污泥比阻试验及叶片吸滤试验，探讨化学调理前后污泥的脱水性能。研制并开发了改善石油化工污泥脱水性能的最佳药剂ＰｔＣ，并为石油化工污泥脱水提供了必要的运行参数。     

The Grey System and prediction of geological and mineral resources

The Grey System is a method for making quantitative predictions using the similarity between a parent sequence and a set of subsequences. It has previously been used for non-geological problems, but here we demonstrate its use in ore prediction. Our example is from our work on known Cu deposits distributed in the Panzihua-Xichang region of Sichuan Province to set up a Grey prediction model for an unknown deposit in a similar type of environment. The following steps were carried out: (1) a sift selection was first made by logical information processing of the initial data from the known deposits, (2) data on seven deposits belonging to the same general rock type were obtained, and (3) a Grey prediction model was set up and used to make predictions about an unknown deposit in the same type of environment.     

Paleolimnology of McNearney lake: an acidic lake in northern Michigan

McNearney Lake is an acidic (pH=4.4) lake in the Upper Peninsula of Michigan with low acid neutralizing capacity (ANC=-38 eq L^-1) and high SO _inf4 ^sup2- and aluminium concentrations. Oligotrophy is indicated by high Secchi transparency and by low chlorophyll a, total phosphorus, and total nitrogen concentrations. The lake water is currently acidic because base cations are supplied to the lake water at a low rate and because SO _inf4 ^sup2- from atmospheric deposition was not appreciably retained by the lake sediments or watershed and was present in the water column.This interdisciplinary paleolimnological study indicates that McNearney Lake is naturally acidic and has been so since at least 4000 years B.P., as determined from inferred-pH techniques based on contemporary diatom-pH relationships. Predicted pH values ranged from 4.7 to 5.0 over the 4000-year stratigraphy. Considerable shifts in species composition and abundance were observed in diatom stratigraphy, but present-day distributions indicate that all abundant taxa most frequently occur under acidic conditions, suggesting that factors other than pH are responsible for the shifts. The diatom-inferred pH technique as applied to McNearney Lake has too large an uncertainly and is not sensitive enough to determine the subtle recent changes in lakewater pH expected from changes in atmospheric deposition because: (1) McNearney Lake has the lowest pH in the contemporary diatom data set in the region and confidence intervals for pH predictions increase at the extremes of regressions; (2) other factors in addition to pH may be responsible for the diatom species distribution in the lake and in the entire northern Great Lakes region; (3) McNearney Lake has a well-buffered pH as a consequence of its low pH and high aluminium concentrations and is not expected to exhibit a large pH change as a result of changes in atmospheric deposition; and (4) atmospheric deposition in the region is modest and would not cause a pH shift large enough to be discernable in McNearney Lake.Elevated atmospheric deposition is indicated in recent sediments by Pb, V, and polycyclic aromatic hydrocarbon accumulation rates and to a lesser extent by those of Cu and Zn; however, these accumulation rates are substantially lower than those observed for acidified lakes in the northeastern United States. Although atmospheric loadings of materials associated with fossil fuel combustion have recently increased to McNearney Lake and apparently are continuing, the present study of the diatom subfossil record does not indicate a distinct, recent acidification (pH decrease).Order of the first two authors is alphabetical     

Low-Ti melts from the southeastern Siberian Traps Large Igneous Province: Evidence for a water-rich mantle source?

Siberian Traps Large Igneous Province (STLIP) is one of the most voluminous volcanic provinces on Earth. The dominant erupted rocks are low-Ti basalts, which make up 80% by volume of the classical Noril’sk lava sequence. In the west Siberian basin and Maymecha-Kotuy area, the low-Ti basalts make up about 99% and 50% by volume, respectively. Dolerite sills in the Angara-Taseevskaya Syncline at the southeastern STLIP exhibit trace element patterns and Sr isotope ratios typical of the low-Ti basalts of the Noril’sk sequence. The most Mg-rich (MgO 9.5–11 wt%) and hence least differentiated dolerites are characterized by trace element patterns with Ta-Nb depletion, low Ce/Pb and high Sr/Pr. These trace element features are similar to water-saturated, mantle wedge-derived island arc basalts. These imply an important role of subduction fluid-derived trace elements in the source of melting beneath the Angara-Taseevskaya Syncline and other regions of the STLIP. Less magnesium rocks (MgO 3.8–6.1 wt%) with less prominent Ta-Nb depletion, higher Ce/Pb and lower Sr/Pr could be produced via olivine-plagioclase fractionation of primary high-magnesium melts.     

Age and duration of ultrahigh-temperature metamorphism in the Anápolis–Itauçu Complex, Southern Brasília Belt, central Brazil – constraints from U–Pb geochronology, mineral rare earth element chemistry and trace-element thermometry

Integrated petrographic and chemical analysis of zircon, garnet and rutile from ultrahigh‐temperature (UHT) granulites in the Anápolis–Itauçu Complex, Brazil, is used to constrain the significance of zircon ID‐TIMS U–Pb geochronological data. Chondrite‐normalized rare earth element (REE) profiles of zircon cores have positive‐sloping heavy‐REE patterns, commonly inferred to be magmatic, whereas unambiguous metamorphic grains and overgrowths have flat to slightly negatively sloping heavy‐REE patterns. However, in one sample, a core of zircon interpreted as having formed prior to garnet crystallization and a metamorphic zircon formed within microstructures involving garnet breakdown both display elevated heavy‐REE (and Y) with positive‐sloping patterns. D_REE(zrc/grt) partition coefficients suggest an approximation to equilibrium between zircon and garnet cores, although progressive enrichment in heavy REE towards garnet rims occurs in two of the samples investigated. Titanium‐in‐zircon thermometry indicates zircon growth during both the prograde and post‐peak evolution, but not at peak temperatures of the UHT metamorphism. By contrast, zirconium‐in‐rutile thermometry of inclusions armoured by garnet records crystallization temperatures, based on the upper end of the interquartile range of the data, of ～890 to 870 °C and maximum temperature around 980 °C, indicating prograde and retrograde growth close to and after peak conditions. Rutile located in retrograde microstructures records crystallization temperatures of 850 to 820 °C. Rutile intergrown with ilmenite and included within orthopyroxene, which is associated with exsolved zircon, records temperatures ～760 °C, consistent with Ti‐in‐zircon crystallization temperatures. ID‐TIMS U–Pb geochronological data from two of the four samples investigated define upper intercept ages of 641.3 ± 8.4 Ma (MSWD 0.91) and 638.8 ± 2.5 Ma (MSWD 1.03) that correlate with periods of zircon growth along the prograde segment of the P–T path. Individual zircon U–Pb dates retrieved from all samples range from 649 to 634 Ma, indicating a maximum duration of c. 15 Myr for the UHT event. This period is interpreted as recording modest thickening of hot backarc lithosphere located behind the Arenópolis Arc at the edge of the São Francisco Craton consequent upon terminal collision of the Parána Block with the arc during the amalgamation of West Gondwana.     

Petrogenesis of Volcanic Rocks from Saipan and Rota, Mariana Islands, and Implications for the Evolution of Nascent Island Arcs

An ⁴⁰Ar/³⁹Ar age of 45·1 Ma determined for lavas fromnorthern Saipan confirms that these high-silica rhyolites eruptedduring the ‘proto-arc’ stage of volcanism in theIzu–Bonin–Mariana system, which is characterizedelsewhere by eruption of boninitic lavas. Incompatible traceelement concentrations and Sr, Hf, Nd, and Pb isotope ratiosfor these rhyolites are transitional between those of c. 48Ma boninitic lavas and post-38 Ma ‘first-arc’ andesitesand dacites from Saipan and Rota that have typical subduction-relatedcompositions. These transitional compositions are modeled bycrystal fractionation of parental tholeiitic basalt combinedwith assimilation of young boninitic crust. A second stage ofRayleigh fractionation in the upper crust is required by SiO₂concentrations that exceed 77 wt % and near-zero compatibleelement concentrations. First-arc magma compositions are consistentwith fractionation of basalt and assimilation of crust similarin composition to the first-arc magmas themselves. The mantlesources of the proto-arc and first-arc lavas from Saipan andRota are similar to those of Philippine back-arc basin basaltsbased on Nd and Hf isotopic compositions. The Pb isotope compositionsof these lavas are between those of Pacific sea-floor basaltsand Jurassic and younger cherty and clay-rich sediments. Thiscontrasts with the boninitic proto-arc volcanic rocks from Guamand Deep Sea Drilling Project Sites 458 and 459 that have Pbisotope compositions similar to Pacific basin basalts and volcaniclasticsediments. The preferred explanation for the difference in thenature of proto-arc volcanism between Saipan and other fore-arclocations is that the crust ceased extending 3–4 Myr earlierbeneath Saipan. This was caused by a change from mantle upwelling,fore-arc extension, and shallow melting to an environment dominatedby more normal mantle wedge convection, stable crust, and deepermelting. KEY WORDS: rhyolite; andesite; Mariana arc; isotope ratios; trace elements     

地球化学组成揭示的杜蒙沙地化学风化和沉积再循环特征及其对风尘物质贡献的指示

对杜蒙沙地的河流冲积砂、河漫滩泥质粉砂、沙质古土壤和风成沙等不同类型沉积物进行了采样（27组）,对这些样品的细颗粒组分（<63 μm）进行了常量元素、微量元素、稀土元素（REE）和Sr-Nd同位素比值等地球化学分析,就杜蒙沙地的化学风化、沉积再循环特征及其对风尘物质的贡献等展开了讨论。结果显示,杜蒙沙地的地球化学组成表现出空间的均一性,低的化学蚀变指数CIA（48~56,平均52）及A-CN-K和A-CNK-FM图解均表明了杜蒙沙地仅遭受了低级的化学风化程度。沙地的成分成熟度较低,大部分河流沉积物表现出初次循环沉积特征,系大兴安岭东侧中酸性岩浆母岩风化剥蚀的产物经嫩江搬运堆积形成;古土壤表现出与河流沉积物相同的初次循环特征,表明古土壤的成土母质是河流沉积物,这与野外地层出露情况一致;风成沙表现出再循环沉积特征,系河流沉积物就地起沙搬运堆积形成。不活动元素比值、REE和Sr-Nd同位素比值等物源判别图解,结合植被和地貌状况,一致表明杜蒙沙地与东北平原中东部的风尘物质没有地球化学亲缘关系,其对该地区（甚至下风向更远地区）的大气风尘的贡献很小。     

OBSERVATIONAL STUDIES ON SAND-DUST STORM IN HELAN MOUNTAINOUS AREA

According to the observation of the number and mass concentration spectra of atmosphericaerosols,the total suspended particulates (TSP) and their size distribution,micrometeorology,and the solar spectroscopic radiation,even neutron activation treatment of sand dust samples inHelan Mountainous area.the formation law of floating dust,blowing sand and sandstorm weatherand the characteristics of climatic variation in this area and the influence of the Helan Mountain arecounted and analyzed.In addition,the spectrum characteristics,optical depth and chemicalcomposition of sand aerosol particles are also analyzed and discussed.     

Prediction of minesite-drainage chemistry through closure using operational monitoring data

Post-mining drainage chemistry depends strongly on geochemical and hydrologic processes that occur during the operational years. Where routine operational monitoring data are abundant, the dominant processes can often be evaluated with no additional, special studies. Thus, post-mining drainage chemistry can be predicted with confidence based on the operational data. This is referred to here as ‘empirical drainage-chemistry modelling’ (EDCM).This paper presents examples of EDCM using routine monitoring databases from several minesites, each containing thousands of analyses and spanning up to 30 years of mine operation and closure. Simple statistical interpretations in the EDCM can reveal annual cycles and trends that aqueous concentrations display during operation and into closure.A new compilation of 12 EDCM equations for copper versus pH is presented to illustrate similar trends with pH among the sites. However, this compilation also shows that average-annual copper concentrations at a particular pH can vary by three orders of magnitude, reflecting site-specific factors. Also, a new case study comparing actual closure concentrations to those predicted with EDCM in 1991 demonstrates that predictive accuracy is within a factor of two.