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The system peridotite-H2O-CO2 serves as a simplified model forthe phase relations of mantle peridotite involving more thanone volatile component. Run products obtained in a study ofphase relations of four mantle peridotites in the presence ofH2O- and (H2O+CO2)-bearing vapors and with controlled hydrogenfugacity (fH2) at high pressures and temperatures have beensubjected to a detailed chemical investigation, principallyby the electron microprobe. Mg/(Mg+Fe) of all phases generally increases with increasingtemperature and with increasing Mg/(Mg+Fe) of the starting material.This ratio appears to decrease with increasing pressure forolivine, and for amphibole coexisting with garnet. DecreasingfH2from that of IW buffer to that of MH buffer decreases Mg/(Mg+Fe)of the partial melt from approximately 0?85 to approximately0?50, whereas the Fo content of coexisting olivine increasesslightly less than 3 per cent and the Mg/(Mg+Fe) of clinopyroxeneincreases about 4 per cent. However, the variations in Fo contentof olivines are within those observed in olivines from naturalmantle peridotite. The chemistry of other silicate mineralsdoes not significantly reflect variations of fH2. Consequently,the peridotite mineralogy and/or chemistry is not a good indicatorfor the fH2 conditions during crystallization. All crystalline phases, except amphibole, and to some extentgarnet, show increasing Cr content with increasing temperatureand increasing Cr content of the starting material, resultingin a positive correlation with Mg/(Mg+Fe). Partial melts aredepleted in Cr2O3 relative to the crystalline phases. High Mg/(Mg+Fe)and Cr2O3 are thus expected in crystal residues after partialmelting. The absolute values depend on degree of melting andthe composition of the parent peridotite. 相似文献
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The system peridotite-H2O–CO2 serves as a simplified modelfor the phase relations of mantle peridotite involving morethan one volatile component. Run products obtained in a studyof phase relations of four mantle peridotites in the presenceof H2O- and (H2O+CO2)- bearing vapors and with controlled hydrogenfugacity (fH2) at high pressures and temperatures have beensubjected to a detailed chemical investigation, principallyby the electron microprobe. Mg/(Mg+Fe) of all phases generally increases with increasingtemperature and with increasing Mg/(Mg+Fe) of the starting material.This ratio appears to decrease with increasing pressure forolivine, and for amphibole coexisting with garnet. DecreasingfH2 from that of IW buffer to that of MH buffer decreases Mg/(Mg+Fe)of the partial melt from approximately 0-85 to approximately0.50, whereas the Fo content of coexisting olivine increasesslightly less than 3 per cent and the Mg/(Mg+Fe) of clinopyroxeneincreases about 4 per cent. However, the variations in Fo contentof olivines are within those observed in olivines from naturalmantle peridotite. The chemistry of other silicate mineralsdoes not significantly reflect variations of fH2. Consequently,the peridotite mineralogy and/or chemistry is not a good indicatorfor the fH2 conditions during crystallization. All crystalline phases, except amphibole, and to some extentgarnet, show increasing Cr content with increasing temperatureand increasing Cr content of the starting material, resultingin a positive correlation with Mg/(Mg+Fe). Partial melts aredepleted in Cr2O3 relative to the crystalline phases. High Mg/Mg+Fe)and Cr2O3 are thus expected in crystal residues after partialmelting. The absolute values depend on degree of melting andthe composition of the parent peridotite. Liquids formed by anatexis of mantle peridotite are andesiticunder conditions of XH2Ov > 0.6 to at least 25 kb total pressureand to more than 200?C above the peridotite solidus. This observationsupports numerous suggestions that andesite genesis in islandarcs may result from partial melting of underlying peridotitemantle. In contrast to basaltic rocks, the absence of amphibole(paragasitic hornblende) does not affect the silica-saturatednature of the liquids. Increasing K2O content of the startingmaterial (up to 1 wt. per cent K2O) results in increasing potassiumcontent of the amphibole (1 wt. per cent K2O) as well as theappearance of phlogopite. The liquid under these conditionsis relatively K20-poor (less than 1 wt. per cent K2O). Partial melts are olivine normative with XH2O 0.5, and initialliquids contain normative ol and ne at XH2O 0.4. The alkalinityof these liquids increases with decreasing XH2O below valuesof 0.5. The (ol+opx)-normative liquids resemble oceanic basaltswhereas (ol+ne)-normative liquids resemble olivine nepheliniteand melilite basalt. Low aHlo and high aCo2 conditions may bethose under which kimberlites and related rocks are formed inthe mantle. 相似文献
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1 ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｐｏｌａｒｒｅｇｉｏｎｉｓａｎｉｍｐｏｒｔａｎｔａｒｅａｆｏｒｅｎｅｒｇｅｔｉｃｃｏｕｐｌｉｎｇｂｅｔｗｅｅｎｓｏｌａｒｗｉｎｄａｎｄｅａｒｔｈ’ｓｍａｇｎｅｔｏｓｐｈｅｒｅ .Ｔｈｅｃｕｓｐｉｓｔｈｅｄｉｒｅｃｔｐａｔｈｆｏｒｓｏｌａｒｗｉｎｄｐｅｎｅｔｒａｔｉｎｇｉｎｔｏｔｈｅｍａｇｎｅｔｏｓｐｈｅｒｅｏｒｅｖｅｎｉｎｔｏｔｈｅｉｏｎｏｓｐｈｅｒｅａｎｄｉｔａｌｓｏｉｓａｃｏｎｖｅｒｇｅｎｔｒｅｇｉｏｎｆｏｒａｌｏｔｏｆｍａｇｎｅｔｏｓｐｈｅｒｉｃｂｏｕｎｄａ… 相似文献
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A range of options for the storage and partial processing of water samples before polymerase chain reaction (PCR) analysis were evaluated. In addition, temporal storage of extracted DNA at 4 °C was investigated. Filtering the water sample and then storing that filter at ?20 °C for up to six months before DNA extraction was equivalent to extracting DNA immediately. Freezing a water sample resulted in an immediate 1 log loss of PCR signal, although thereafter the sample was stable for at least three months. A rapid loss of detectable PCR product was found when storing a water sample at 4 °C for longer than one week. Extracted DNA could be stored at 4 °C for at least six months without considerable loss of PCR signal. 相似文献
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Freshly excreted droppings from Canada geese (n=80), black swans (n=80), ducks (n=80) and gulls (n=80) were collected from sites around New Zealand. The droppings were enumerated for Escherichia coli, enterococci and Salmonella spp., and for the presence/absence of Cryptosporidium spp. Overall prevalence of E. coli and enterococci in samples was 95% and 94%, respectively. Cryptosporidium spp. was detected in 2% of the samples, whereas no Salmonella spp. were detected in the survey. Preliminary estimates of daily microbial outputs suggest that ducks will produce the highest loadings of E. coli and enterococci per bird, whereas Canada geese will produce the highest loadings of Campylobacter spp. per bird. This study provides the first set of indicator and pathogen counts for one of the largest sources of diffuse faecal contamination of natural waters in New Zealand. 相似文献
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A garnet websterite nodule from the Honolulu volcanic series,Oahu, Hawaii, has been melted in the presence of nearly pureH2O. The solidus is intermediate between that of peridotiteand gabbro. The curve displays a temperature minimum around20 kb reflecting the breakdown of plagioclase. The Iiquidusis between 1130 ?C and 1150 ?C between 10 and 20 kb vapor pressure.Amphibole (pargasitic hornblende) has an extensive stabilityfield, reaching a maximum temperature about 20 ?C below thegarnet websterite liquidus at 15 kb and a maximum pressure of27.5 kb at 950 ?C. The amphibole-out curve intersects the soliduswith a positive slope. Liquids formed by partial melting of garnet websterite are quartz-normativewithin the stability field of amphibole, but become olivine-normative(tholeiitic) with increasing temperature. Amphibole and clinopyroxeneare enriched in Tschermak's molecule at higher temperatures,pargasite content of amphibole increases with increasing pressure. A garnet websterite-rich upper mantle containing modal olivineyields quartz-normative (13–16 per cent), aluminous (21–4wt. per cent A12O3) melts at 17 P 10 kb and in the presenceof nearly pure H2O. However, the presence of amphibole controlsthe liquid composition, a situation not found for liquids formedfrom wet peridotite. In contrast to many basalt liquids, liquidof garnet websterite composition cannot fractionate to andesiteby precipitation of amphibole, as amphibole is not a liquidusphase. 相似文献
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Balshaw S Edwards JW Ross KE Ellis D Padula DJ Daughtry BJ 《Marine pollution bulletin》2008,56(12):2009-2017
Two empirical models are presented to elucidate the mechanisms driving reductions in the mercury concentration of southern bluefin tuna (SBT) during culture. Model 1 predicts temporal fluctuations in mercury concentration in response to growth dilution. Model 2 predicts the combined effects of growth dilution and linear mercury accumulation. Model 2 was found to be the more accurate model. Over a typical farming period of 136 days, growth dilution resulted in a reduction in mean mercury concentration of SBT edible tissues from 0.51 mg/kg down to 0.33 mg/kg. Extended culture beyond 136 days resulted in an increase in mercury concentration due to the combined effects of mercury accumulation and seasonal lipid depletion. Results indicate that under current industry practice, cultured SBT can be consumed twice as frequently as that of wild caught SBT while maintaining total dietary mercury intake below national recommendations. 相似文献
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THE ROLE OF ATMOSPHERIC CIRCULATION PATTERNS IN AGROCLIMATE VARIABILITY IN FINLAND, 1961–2011 
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下载免费PDF全文 MASOUD IRANNEZHAD DELIANG CHEN BJØRN KLØVE 《Geografiska Annaler: Series A, Physical Geography》2016,98(4):287-301
This study evaluates interannual variations and trends in growing season daily temperature sum and daily precipitation sum in Finland during 1961–2011, and their connections to well known atmospheric circulation patterns. Changes in summer (June–August) climate partially explain changes in growing season daily temperature sum and daily precipitation sum over Finland, which naturally decreased from south to north. On a national scale, growing season warmed and became wetter during 1961–2011, as growing season daily temperature sum and daily precipitation sum significantly (p < 0.05) increased by 5.01 ± 3.17°C year–1 and 1.39 ± 0.91 mm year–1, respectively. The East Atlantic pattern was the most influential atmospheric circulation pattern for variations in growing season daily temperature sum (rho = 0.40) across Finland and the East Atlantic/West Russia pattern was most influential for growing season daily precipitation sum variability (rho = –0.54). There were significant (p < 0.05) increasing trends in growing season daily temperature sum and daily precipitation sum throughout Finland during 1961–2011. Increased growing season daily temperature sum was mainly observed in northern, central, western, eastern and coastal areas of south‐western Finland. This warming was positively associated with the East Atlantic pattern in the north, centre and south, but negatively associated with the East Atlantic/West Russia pattern in eastern Finland. Increased GSP mostly occurred in southern, eastern, western, central, northern and north‐western Finland. These wetting trends were positively correlated with the East Atlantic pattern in the north and negatively correlated with the Polar pattern in the south and the East Atlantic/West Russia pattern in the east, west, centre and north‐east of Finland. The overall agroclimatic year‐to‐year variability in Finland between 1961 and 2011 was mostly linked to variations in the East Atlantic and East Atlantic/West Russia patterns. 相似文献