Early precambrian trondhjemitic suites in Western Australia and Northwestern Scotland,and the geochemical evolution of shields     

A.Y. GliksonJ.W. Sheraton 《Earth and Planetary Science Letters》1972

Sodium-rich trondhjemites and quartz keratophyres, retained as pebbles in Archaean metaconglomerates, represent some of the oldest components (up to 3 by) of the Kalgoorlie System, Western Australia. New determinations indicate high Si, Na, Na/K, Ba/Rb, Ba/K, Sr/Ca+K, Ni, Ni/Mg, and Cr/Mg, and low K, Rb, Rb/Sr, and Y, in comparison to Taylor's (1965) [1] and other' average granites and to Nockolds and Allen's (1953) [2] acid calc-alkaline rocks. Syngeosynclinal quartz keratophyres (2.6 by) studied by O'Beirne (1968) [3] show similar comparisons. Similarly, high-grade acid and intermediate gneisses of the Lewisian, Scotland, have high Na/K, K/Rb, Ba/Rb, Ba/K, Sr/Ca+K, Ni, Ni/Mg, Cr, Cr/Mg, and low K, Rb, Rb/Sr, Y and Y/Ca. Secular decrease in Na/K, K/Rb and Sr/Rb is shown by granite series in Western Australia, Transvaal, Rhodesia and the Canadian Shield. The earliest members of these series compare with sodic acid plutons of island arcs, in particular Fiji, an archipelago showing a pattern of evolution analogous to that of the proposed model (Glikson, 1971) [4]. Evidence for an origin of Archaean sodic granites from below a basic crust is furnished by the abundance of basic xenoliths, by relationships in agmatite-gneiss terrains in Greenland, Scotland, and India, by K levels lower than those of Archaean metasediments, and by low initial⁸⁷Sr/⁸⁶Sr ratios. The abundance of euhedral quartz phenocrysts in the quartz keratophyres supports origin through partial melting of eclogite [5]. In high-grade belts, the originally low abundances of K and Rb were accentuated by synmetamorphic depletion, with which the formation of late-stage K-granites may have been associated. The correlation of chemical data enables an insight into spatial and temporal relationships between low- and high-grade early Precambrian terrains, and on the geochemical evolution of shields.  相似文献   

Soil water residence times and solute uptake on a dolomite bedrock—preliminary results     

Stephen T. Trudgill  Ian M. S. Laidlaw  Peter L. Smart 《地球表面变化过程与地形》1980,5(1):91-100

Calcium and magnesium levels have been monitored in slope foot drainage waters on a dolomite bedrock. Both calcium and magnesium rich pulses occur. Short term dissolution experiments demonstrate high calcium levels in solution while other authors have suggested that long residence time groundwater has relatively high levels of magnesium due to calcite precipitation. Patterns of field fluctuations in Ca: Mg ratios can thus be tentatively interpreted in terms of short residence time water of high calcium content mixing with long residence time water of high magnesium content. Fluorometric dye tracing has been used to indicate the orders of magnitude of soil water residence times, suggesting that quickflow components are resident in the system for a few hours to a few days. Further work is in progress.  相似文献   

Geochemistry of Cenezoic volcanic rocks, Baja California, Mexico: Implications for the petrogenesis of post-subduction magmas   总被引：2，自引：0，他引：2  

A.D. Saunders  G. Rogers  G.F. Marriner  D.J. Terrell  S.P. Verma 《Journal of Volcanology and Geothermal Research》1987,32(1-3)

Late Cenozoic volcanism in Baja California records the effects of cessation of subduction at a previously convergent, plate margin. Prior to 12.5 m.y., when subduction along the margin of Baja ceased, the predominant volcanic activity had a calc-alkaline signature, ranging in composition from basalt to rhyolite. Acidic pyroclastic activity was common, and possibly represented the westermost, distal edge of the Sierra Madre Occidental province. After 12.5 m.y., however, the style and composition of the magmatic products changed dramatically. The dominant rock type within the Jaraguay and San Borja volcanic fields is a magnesian andesite, with up to 8% MgO at 57% SiO₂, low Fe/Mg ratios, and high Na/K ratios. These rocks have unusual trace-element characteristics, with high abundances of Sr (up to 3000 ppm), low contents of Rb; K/Rb ratios are very high (usually over 1000, and up to 2500), and Rb/Sr ratios are low (less than 0.01). Furthermore, La_n/Yb_n ratios are high, consistent with derivation from a mantle source with fractionated REE patterns. ⁸⁷Sr/⁸⁶Sr ratios are less than 0.7048, and usually less than 0.7040, whereas the pre-12.5 m.y. lavas have ⁸⁷Sr/⁸⁶Sr ratios between 0.7038 and 0.7063. We have previously termed these rocks bajaites, in order to distinguish them from other magnesian andesites. Bajaites also occur in southernmost Chile and the Aleutian Islands, areas which also have histories of attempted or successful ridge subduction.It is proposed that the bajaite series is produced during the unusual physico-chemical conditions operating during the subduction of young oceanic lithosphere, or subduction of a spreading centre. During normal subduction, the oceanic crust dehydrates, releasing volatiles (water, Rb and other large-ion lithophile elements) into the overlying wedge. Subduction of younger crust will result in a progressive decrease, and eventual cessation of the transfer of volatiles when subduction stops. Thermal rebound of the mantle may cause the slab to melt, perhaps under eclogitestable conditions. The resulting melt will be heavy-REE-depleted, perhaps dacitic, but will otherwise inherit MORB-like Rb/Sr and K/Rb ratios. The ascending melt will react with the mantle to form the source of the bajaitic rocks. Furthermore, any amphibole in the mantle, stabilised during the higher PH₂O conditions of earlier subduction, will break down and contribute a high-K/Rb ratio component.The implications of this study are that firstly, the subducted slab does not contribute a highly fractionated REE component in most modern arcs (i.e. the slab does not melt); secondly, Rb has a very short residence time in the mantle, and its abundance in arc rocks is a direct reflection of the input from the dehydrating slab; and thirdly, bajaitelike rocks may provide recognition of attempted or successful ridge subduction in the geologic past.  相似文献   

Evaluation of groundwater hydrochemical characteristics and mixing behavior in the Daying and Qicun geothermal systems,Xinzhou Basin     

D.M. Han  X. Liang  M.G. Jin  M.J. Currell  X.F. Song  C.M. Liu 《Journal of Volcanology and Geothermal Research》2010,189(1-2):92-104

This paper examines groundwater hydrochemical characteristics during mixing between thermal and non-thermal groundwater in low-to-medium temperature geothermal fields. A case study is made of Daying and Qicun geothermal fields in the Xinzhou basin of Shanxi province, China. The two geothermal fields have similar flow patterns, with recharge sourced from precipitation in mountain areas heated through a deep cycle, before flowing into overlying Quaternary porous aquifers via fractures. Hydrochemical features of 60 ground- and surface water samples were examined in the context of hydrogeologic information. The average temperatures of the deep geothermal reservoirs are estimated to be 125 °C in Daying field, and 159 °C in Qicun field, based on Na–K–Mg geothermometry, while slightly lower estimates are obtained using silica geothermometers. Hydrochemical features of thermal water are distinct from cold water. Thermal groundwater is mainly Cl·SO₄–Na type, with high TDS, while non-thermal groundwater is mostly HCO₃–Ca·Mg and HCO₃–Ca type in the Daying and Qicun regions, respectively. Hydrogeochemical processes are characterized by analyzing ion ratios in various waters. Higher contents of some minor elements in thermal waters, such as F, Si, B and Sr, are probably derived from extended water–rock interaction, and these elements can be regarded as indicators of flow paths and residence times. Mixing ratios between cold and thermal waters were estimated with Cl, Na, and B concentrations, using a mass balance approach. Mixing between ascending thermal waters and overlying cold waters is extensive. The proportion of water in the Quaternary aquifer derived from a deep thermal source is lower in Daying geothermal field than in Qicun field (5.3–7.3% vs. 6.3–49.3%). Mixing between thermal and non-thermal groundwater has been accelerated by groundwater exploitation practices and is enhanced near faults. Shallow groundwater composition has also been affected by irrigation with low-temperature thermal water.  相似文献   

紫坪铺水库沉积物Sr同位素及元素组成变化对2008年汶川大地震的响应     

陈晨  金章东  徐阳  李良波  苟龙飞  张飞 《湖泊科学》2020,32(6):1882-1890

2008年5月12日里氏7.9级汶川大地震引发了超过56000多个山体滑坡,在龙门山地区产生巨量的碎屑物质,极大地影响了流域的地表过程.然而,地震对河流碎屑物质组成及沉积过程的改变却知之甚少.紫坪铺水库超高沉积速率（平均74 cm/a）的沉积物完整记录了汶川地震前后的沉积过程,为研究2008年汶川地震对流域地表物质搬运及沉积物组成的影响提供了宝贵的素材.本研究测试了汶川地震前后紫坪铺水库沉积物的Sr同位素以及元素组成,结果表明其在地震之后均发生了显著变化.震后沉积物⁸⁷Sr/⁸⁶Sr与Rb/Sr比值同步降低,并且和沉积物化学蚀变指数（CIA）呈正相关性,反映了地震滑坡导致的新鲜物质对沉积物的贡献,特别是地震后强径流的2010—2011年.地震前后沉积物组成的差异性,为利用沉积物反演水文气候和构造事件及其环境效应提供了基础和潜在指标.  相似文献   

Sources of Ground Water Salinization in Parts of West Texas     

《Ground Water Monitoring & Remediation》1987,7(4):75-84

Abstract
Determination of chemical constituent ratios allows distinction between two salinization mechanisms responsible for shallow saline ground water and vegetative-kill areas in parts of west Texas. Mixing of deep-basin (high Cl) salt water and shallow (low Cl) ground water results in saline waters with relatively low Ca/Cl, Mg/Cl, SO₄4/ Cl, Br/Cl, and NO₃/Cl ratios. In scattergrams of major chemical constituents vs. chloride, plots of these waters indicate trends with deep-basin brines as high Cl end members. Evaporation of ground water from a shallow water table, in contrast, results in saline water that has relatively high Ca/Cl, Mg/Cl, SO₄/Cl, and Br/CL ratios. Trends indicated by plots of this water type do not coincide with trends indicated by plots of sampled brines. Leaching of soil nitrate in areas with a shallow water table accounts for high NO₃ concentrations in shallow ground water.  相似文献   

Effect of exchangeable Mg on saturated hydraulic conductivity, disaggregation and clay dispersion of disturbed soils   总被引：2，自引：0，他引：2  

X. C. Zhang  L. D. Norton 《Journal of Hydrology》2002,260(1-4):194-205

Different opinions exist regarding the specific effect of Mg on soil physical and chemical properties. We hypothesized that Mg²⁺, compared with Ca²⁺, reduces saturated hydraulic conductivity (K_s) via promoting clay swelling, disaggregation, and clay dispersion. Two soils (mixed, mesic Typic Hapludalfs) in packed soil columns were leached with either Ca- or Mg-containing solutions at the successive concentrations of 250, 10, 2, 0.5, and 0 mM. Critical flocculation concentration (CFC) in either Ca or Mg systems was determined with flocculation series tests. Aggregate stability and mean weight diameter (MWD) were assessed by wet-sieving. The CFCs were higher in Mg than in Ca for both soils, indicating that Mg is more dispersive than Ca. The MWDs measured using 1–2 mm aggregates of both soils were significantly larger for Ca-soils than for Mg-soils (P=0.05). The K_sr (normalized with initial K_s) started to decline at higher concentrations for Mg than for Ca, and the reduction was much greater in Mg than in Ca above 0.5 mM. The K_sr and percent transmittance (inversely related to turbidity) of leachate at a given eluted pore volume following ‘steady state’ were higher in Ca than in Mg for both soils (P=0.1), indicating lower permeability and more clay dispersion with the Mg treatment. Swelling and disaggregation, which reduced large pores, appeared to be the dominant process causing the rapid initial decline of K_sr. Clay dispersion and subsequent pore plugging became progressively important when electrolyte concentration was reduced to below CFCs.  相似文献   

⁸⁷Sr/⁸⁶Sr ratios in hydrothermal waters and deposits from the East Pacific Rise at 21°N     

F. Albarède  A. Michard  J.F. Minster  G. Michard 《Earth and Planetary Science Letters》1981,55(2):229-236

⁸⁷Sr/⁸⁶Sr ratios of three hydrothermal waters collected on the East Pacific Rise at 21°N define a mixing line between seawater and a hydrothermal end-member at 0.7030 which is derived by seawater-basalt interaction at ca. 350°C and water/rock ratio of about 1.5. Sr concentrations are not affected in the process while Mg uptake from seawater is almost complete. Up to2/3 of this hydrothermal component is involved in anhydrite precipitation while the Sr isotopic ratio in sulfides (chalcopyrite + sphalerite) cannot be distinguished from that of sulfate. It is estimated that ca. 1 × 10¹⁰ moles of strontium are yearly cycled in the hydrothermal systems of mid-oceanic ridges, thereby affecting the⁸⁷Sr/⁸⁶Sr budget of seawater. Mass balance between river runoff, limestone precipitation and ridge basalt alteration suggests that the⁸⁷Sr/⁸⁶Sr ratios of the river runoff are in the range 0.7097–0.7113, and are largely dominated by limestone alteration.  相似文献   

Hydrological characteristics of a moso-bamboo (Phyllostachys pubescens) forest in south china     

Yanhui Wang  Yongmin Liu 《水文研究》1995,9(7):797-808

Since 1986 the multiple benefits of moso-bamboo forest, a special forest type found mainly in south China, have been investigated in a small 11.7 ha watershed in Fenyi County, Jiangxi Province. The mean annual precipitation in the study area is 1593.3 mm. For the 0–60 cm soil layer the average soil bulk density is 1.00 g/cm³, and the mean values for other soil properties are: total porosity 71.74%; non-capillary porosity 5.81%; and water retention capacity 430 mm. The maximum effective water retention capacity of 313 mm is 28% higher than that for Chinese fir (Cunninghamia lanceolata) plantations and natural broadleaved forest in the neighbouring area. The parameters f₀, f_c and k, in Horton's infiltration equation, measured using the double-ring method under drought conditions, are 29.10 mm/min, 8.28 mm/min and 0.2391, respectively. These infiltration properties are more favourable than those under nearby Chinese fir plantations. Compared with a Chinese fir plantation, the canopy interception ratio of moso-bamboo is lower, but the stemflow ratio is higher. The annual canopy interception ratio is 11.1%. Because of snowfall, the interception ratios in January, February and March are higher, with values of 12.1–17.2%, whereas during the period of leaf fall in April, May and June the interception ratios are lower with values of 9.2–9.5%. During the other months they are relatively constant. The annual stemflow ratio is 4.4%. Again, because of snowfall, the stemflow ratios in January, February and March are lower with values of 2.8–2.9%, whereas during the remaining months they are fairly constant. Runoff analysis shows that the annual runoff ratio in this research watershed is 54.8%, but the ratio for quick runoff, composed of direct runoff and surface runoff, is only 0.8%. The upper interflow ratio is 15% and the ratio for the slow runoff composed of deeper interflow and underflow is 39%. The moso-bamboo forest is very effective in reducing peak runoff and increasing low flows. The annual nutrient element inputs (kg/ha) to the moso-bamboo forest ecosystem associated with throughfall and stemflow are N 17.7, P 0.38, K 56.5, Ca 31.,4, Mg 4.8 and SiO₂ 26.2, respectively. All the measured element inputs, with the exception of P, are higher than those associated with precipitation in the open, where typical values are N 10.1, P 0.89, K 18.8, Ca 25.8, Mg 3.1 and SiO₂ 10.1. The annual outputs in streamflow are N 3.0, P 0.28, K 16.6, Ca 38.9, Mg 8.3 and SiO₂ 125.7, indicating that for N, P and K the moso-bamboo forest ecosystem is an accumulating system, whereas for Ca, Mg and SiO₂ the reverse applies. All the pH values associated with precipitation in the open, throughfall, stemflow, surface runoff from runoff plots and streamflow in the research watershed vary between 6.45 and 7.60 and are close to neutral.  相似文献   

An artificial recharge experiment in the San Jacinto basin, Riverside, southern California     

Tien-Chang Lee  Alan E. Williams  Chuching Wang 《Journal of Hydrology》1992,140(1-4):235-259

During a 3 month recharge experiment related to conjunctive use of water resources, 1.5 × 10⁶ T of imported water were percolated through a pond of 128 m by 128 m in the San Jacinto basin. The infiltration rates, which declined with time, averaged 1.9 m day⁻¹, equivalent to four times the lowest laboratory-measured hydraulic conductivity of the fluvial deposits. Ponding altered the unimodal grain-size distribution at the ground surface to types without a dominant mode, but this redistribution did not always lead to reduction in conductivities, which varied over at least three orders of magnitude. The water table 80 m downstream from the ponding edge began to rise slowly 1 month after the start of ponding; it leveled off at 8 m above the pre-recharge water table depth of 75 m and did not recede 2 months after termination of ponding. Water levels in wells bottomed in the original vadose zone suggested that an inverted water table migrated downward to meet the rising water table. Minor, local perching occurred at 14 m depth, as indicated by the presence of moist ground near one monitoring well and by hydraulic responses during a 20 day intermission in percolation. As it percolated through the sediments, the imported northern California water gained Ca but lost Mg, so that the Mg/Ca ratio resembled that of local ground water. Such cation exchange has also been demonstrated by leaching experiments in the laboratory. However, the characteristics of the original source waters appear to be retained by D/H isotope ratios and Cl concentrations, as well as cross-plots of SO₄ vs. Cl and B vs. Cl. Such unreactive tracers could serve to monitor transport and mixing of the chemically diverse water used in future recharge programs in the San Jacinto basin.  相似文献   

Multiple‐indicator study of groundwater flow and chemistry and the impacts of river and paddy water on groundwater in the alluvial fan of the Tedori River,Japan          下载免费PDF全文

Yumi Iwasaki Yoshioka  Kimihito Nakamura  Takanori Nakano  Haruhiko Horino  Ki‐Cheol Shin  Satoko Hashimoto  Shigeto Kawashima 《水文研究》2016,30(16):2804-2816

To investigate the source, flow paths, and chemistry of rich resources of high‐quality, shallow groundwater in the alluvial fan between the Tedori and Sai rivers in central Japan, we analysed stable isotope ratios of H, O, and Sr and concentrations of major dissolved ions and trace elements in groundwater, river water, and paddy water. The ⁸⁷Sr/⁸⁶Sr ratios of the groundwater are related to near‐surface geology: groundwater in sediment from the Tedori River has high ⁸⁷Sr/⁸⁶Sr ratios (>0.711), whereas that from the Sai River in the north of the fan has low ⁸⁷Sr/⁸⁶Sr ratios (<0.711). δ²H and δ¹⁸O values and ⁸⁷Sr/⁸⁶Sr ratios indicate that groundwater in the central and southern fans is recharged by the Tedori River, whereas recharge in the north is from the Sai River. Mg²⁺, Ca²⁺, Sr²⁺, HCO₃^?, and SO₄^2? concentrations and δ²H and δ¹⁸O values in the groundwater are high in the central fan and, except for the northern area, tend to increase with distance from the Tedori River. There are linear relationships between ⁸⁷Sr/⁸⁶Sr ratio and the reciprocal concentrations of Sr²⁺, Mg²⁺, and Ca²⁺. These geochemical characteristics suggest that as groundwater recharged from the Tedori River flows towards the central fan, it mixes with waters derived from precipitation and paddy water that have become enriched in these components during downward infiltration. These results are consistent with our hydrological analysis and numerical simulation of groundwater flow, thus verifying the validity of the model we used in our simulation of groundwater flow. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis     

H. Elderfield  J. Yu  P. Anand  T. Kiefer  B. Nyland   《Earth and Planetary Science Letters》2006,250(3-4):633-649

Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5 °C. Mg/Ca ratios are consistently lower, by  0.2 mmol/mol, in samples cleaned using oxidative and reductive steps than using oxidative cleaning. Differences between Cibicidoides species have been identified: Mg/Ca of Cibicidoides robertsonianus > Cibicidoides kullenbergi > Cibicidoides wuellerstorfi. Comparison with bottom water temperatures support observations of lowered Mg/Ca of C. wuellerstorfi at temperature below  3 °C compared with values predicted by published calibrations and from other Cibicidoides species. Hydrographic data shows that carbonate ion saturation (Δ[CO₃²⁻]) decreases rapidly below this temperature. An empirical sensitivity of Δ[CO₃²⁻] on Mg/Ca has been established for C. wuellerstorfi of 0.0086 ± 0.0006 mmol/mol/μmol/kg. A novel application using modern temperatures and Last Glacial Maximum temperatures derived via pore fluid modelling supports a carbonate ion saturation state effect on Mg incorporation. This may significantly affect calculated δ¹⁸O_seawater obtained from foraminiferal δ¹⁸O and Mg/Ca temperature.  相似文献   

An assessment of an environmental gradient using coral geochemical records, Whitsunday Islands, Great Barrier Reef, Australia     

Lewis SE  Brodie JE  McCulloch MT  Mallela J  Jupiter SD  Williams HS  Lough JM  Matson EG 《Marine pollution bulletin》2012,65(4-9):306-319

Coral cores were collected along an environmental and water quality gradient through the Whitsunday Island group, Great Barrier Reef (Australia), for trace element and stable isotope analysis. The primary aim of the study was to examine if this gradient could be detected in coral records and, if so, whether the gradient has changed over time with changing land use in the adjacent river catchments. Y/Ca was the trace element ratio which varied spatially across the gradient, with concentrations progressively decreasing away from the river mouths. The Ba/Ca and Y/Ca ratios were the only indicators of change in the gradient through time, increasing shortly after European settlement. The Mn/Ca ratio responded to local disturbance related to the construction of tourism infrastructure. Nitrogen isotope ratios showed no apparent trend over time. This study highlights the importance of site selection when using coral records to record regional environmental signals.  相似文献   

Temporal distributions of anthropogenic Al, Zn and Pb in Hong Kong Porites coral during the last two centuries     

Wang BS  Goodkin NF  Angeline N  Switzer AD  You CF  Hughen K 《Marine pollution bulletin》2011,63(5-12):508-515

A 182-year long record of trace metal concentrations of aluminum, zinc and lead was reconstructed from a massive Porites coral skeleton from southeastern Hong Kong to evaluate the impacts of anthropogenic activity on the marine environment. Zn/Ca and Pb/Ca ratios fluctuate synchronously from the early 19th century to the present, indicating that the marine environment has been anthropogenically influenced since industrialization. Additionally, land reclamation, mining, and ship building activities are recorded by elevated Al/Ca ratios from 1900 to 1950. The coral record indicates that high levels of Zn, Pb and Al occur coincidentally with local wars, and may have contributed to partial colony mortality. Pb/Ca does not correlate well with hemispheric proxy records after 1950, indicating that coastal corals may be recording local rather than hemispheric contamination. Pb/Ca levels in Hong Kong, Guangdong and Hainan corals imply a continuous supply of Pb-based contamination to southern China not reflected in hemispheric signals.  相似文献