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1.
Variations of δ18O in the snow which accumulates at a Nordic temperate glacier during the win-ter are not entirely eliminated after a few months of ablation in the following summer. Survive of isotopicsignals closely relates to the re-freezing capacity of snow accumulated in winter when its temperature wasbelow 0 ℃. The melt-water re-freezing ice layers formed in winter hindered subsequent melt-water percolation in summer when snow temperature was at melting point and, therefore, varied isotopic record wasreserved between these ice layers. The isotopic record in snow pack can provide an estimate of the ap-proximate trend of the most recent winter season temperatures. The relationship between regional tem-perature changes and δ18O values in the snow pack is affected by many natural factors, but 1989-1990 (aglacier balance year) winter air temperatures were reflected in the snow which remained on the glacierAustre Okstindbreen at an altitude of 1 350 m in July 1990. There was larger amplitude of variations ofδ18O values in the 4. 1 m of snow above the 1989 summer surface, but variations in the underlying firnwere relatively small. Melt water percolation modifies the initial variations of δ18O values in the snowpack. At a site below the mean equilibrium line altitude on Austre Okstindbreen, increased isotopic bom-ogenization within a ten-day period in July accompanied an increase of the mean δ18O value. Although theisotopic record at a temperate glacier is likely to be influenced by more factors than is that at polar glac-iers, it can provide an estimate of the approximate trend of recent local temperature variations. 相似文献
2.
DU Shaorong ZHENG Mianping Lü Yuanyuan ZHANG Yongsheng ZHANG Xuefei MIAO Zhongying LI Mingming 《《地质学报》英文版》2022,96(6):2028-2039
The Lanping?Simao Basin is located on the southeastern Tibetan Plateau, China, and contains massive evaporites. The origin of evaporites in the basin has been hotly debated because of the strong transformation by tectonic movement. Forty halite samples from borehole MK-3 in the Mengyejing area of the basin were collected and analyzed using XRD, Cl-Sr isotopes and chemical compositions to trace the origin of the evaporites in the basin. The Br × 103/Cl ratios of the halite samples are between 0 and 0.55, most of which are synchronized with the law of seawater evaporation and at the stage of halite precipitation from seawater, indicating that the evaporites are mainly of marine origin. The 87Sr/86Sr ratios range from 0.707489 to 0.711279; after correction, the 87Sr/86Sr 145 Ma ratios range from 0.704721 to 0.707611, equivalent with the 87Sr/86Sr ratios of seawater at 145 Ma, indicating a marine origin. The decay of 87Rb in the evaporite during deposition, change of the depositional environment and the unsealed environment at a later period resulted in the present 87Sr/86Sr ratios of some samples being high. The δ37Cl value compositions range from ?0.38‰ to 0.83‰, which is consistent with the δ37Cl value composition of the world marine halite (?0.6‰ to 0.4‰), further confirming that seawater is the main origin. In addition, the high δ37Cl value of some samples at the boundary of the upper and lower evaporite layers might be related to the influence of δ37Cl-rich brine and the incomplete dissolution of the halite. 相似文献
3.
A Late Quaternary Climate Record Based on Multi-Proxies Analysis from the Jiaochang Loess Section in the Eastern Tibetan Plateau, China 总被引：1，自引：0，他引：1 
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下载免费PDF全文 We compared the stable carbon isotopic records from a loess transect of the Jiaochang in the eastern Tibetan Plateau, spanning the last ~21,000 years, with multiproxy data for pedogenesis, including magnetic susceptibility, clay fraction, Fed/Fet ratio, carbonate and total organic carbon content, in order to probe the mechanisms of δ13C values of organic matter and Late Quaternary climate variations in the eastern Tibetan Plateau. Our results indicate that there is no simple relationship between δ13C of organic matter and summer monsoon variations. The change in δ13C values of organic matter (in accordance with the ratios of C3 to C4 plants) results from the interaction among temperature, aridity and atmospheric pCO2 level. Drier climate and lower atmospheric pCO2 level contribute to positive carbon isotopic excursion, while negative carbon isotopic excursion is the result of lower temperature and increased atmospheric pCO2 level. Additionally, our results imply that the Tibetan monsoon may play an important role in climate system in the eastern Tibet Plateau, which specifically reflects frequently changing climate in that area. The results provide new insights into the forcing mechanisms on both the δ13C values of organic matter and the local climate system. 相似文献
4.
This paper mainly analyzed the isotopic effect of precipitation in the Yarlung Zangbo River.On the whole,the isotopic compositions of most water samples fall on the upper right of the global meteoric water line.According to δD and δ18O data of the samples,the precipitation equation is figured out as δD=8 δ18O+10,showing that they are derived from precipitation but have experienced intensive evaporation.With obvious region-continental effect(a continuous depletion in heavy isotopes in water bodies occurs with increasing distance from the coast),the water presents a reducing trend of δD and δ18O westwards and southwards.Altitudinal effect is evident here,occur-ring in both trunk stream and main branches of the Yarlung Zangbo River.The distribution of water isotopic compo-sitions is concerned with the movement of precipitation clouds from the Bay of Bengal and the Nujiang River and is affected by the topographic and climatic conditions of the Tibetan Plateau. 相似文献
5.
YANG Yuncheng SHEN Zhaoli WENG Dongguang HOU Guangcai ZHAO Zhenhong WANG Dong PANG Zhonghe 《《地质学报》英文版》2009,83(1):103-113
Hundreds of precipitation samples collected from meteorological stations in the Ordos Basin from January 1988 to December 2005 were used to set up a local meteoric water line and to calculate weighted average isotopic compositions of modern precipitation. Oxygen and hydrogen isotopes, with averages of ?7.8‰ and ?53.0‰ for δ18O and δD, respectively, are depleted in winter and rich in spring, and gradually decrease in summer and fall, illustrating that the seasonal effect is considerable. They also show that the isotopic difference between south portion and north portion of the Ordos Basin are not obvious, and the isotope in the middle portion is normally depleted. The isotope compositions of 32 samples collected from shallow groundwater (less than a depth of 150 m) in desert plateau range from ?10.6‰ to ?6.0‰ with an average of ?8.4‰ for δ18O and from ?85‰ to ?46‰ with an average of ?63‰ for δD. Most of them are identical with modern precipitation. The isotope compositions of 22 middle and deep groundwaters (greater than a depth of 275 m) fall in ranges from ?11.6‰ to ?8.8‰ with an average of ?10.2‰ for δ18O and from ?89‰ to ?63‰ with an average of ?76‰ for δD. The average values are significantly less than those of modern precipitation, illustrating that the middle and deep groundwaters were recharged at comparatively lower air temperatures. Primary analysis of 14C shows that the recharge of the middle and deep groundwaters started at late Pleistocene. The isotopes of 13 lake water samples collected from eight lakes define a local evaporation trend, with a relatively flat slope of 3.77, and show that the lake waters were mainly fed by modern precipitation and shallow groundwater. 相似文献
6.
The relationship between δ18O in precipitation and climatic factors is analyzed based on the observation of δ18O in precipitation and meteorological data in the four years from 1992 to 1995 at Tuotuohe Meteorological Station, Tibetan Plateau. Almost all the precipitation on the Tibetan Plateau is concentrated on the warm period of the year, while in the dry cold period, there is only a few precipitation events. Because the factors affecting δ18O in precipitation is rather complicated and the air temperature does not change too much in the precipitation season, the distribution of δ18O in precipitation with air temperature is therefore scattered. In this paper, the relationship between the averages of each meteorological factor and the corresponding δ18O in precipitation is analyzed. The analysis results indicate that there is an obvious positive correlation between the monthly δ18O and temperature in the 4 years: whenever the air temperature increases 1℃, δ18O in precipitation will increase 0. 5‰. No correlation can be observed between relative humidity and B18O in precipitation. There still can not find any correlation between the annual air temperature and annual δ18O in precipitation in the 4 years probably due to the very short time series of the observation and the little annual air temperature variations. 相似文献
7.
Yunchao LANG Congqiang LIU Jianghong WU Hiroshi Satake Siliang LI 《中国地球化学学报》2006,25(B08):173-173
A groundwater system in a karstic terrain is easily subject to pollution and its remediation is difficult once contaminated by human activities. The groundwater samples collected in both winter and summer seasons at Guiyang, SW China, show a wide range of variations in chemical composition and dominance of Ca^2＋, Mg^2＋, SO4^2-, and HCO3^- ions. The anthropogenic inputs include Cl^-, NO3^-, SO4^2-, Na^＋, and K^＋, as judged from the relationships between different elemental ratios and sewage samples. Cl^- concentrations of all water samples in the study area vary from 0 to 3.9 mmol/L in winter and are higher than in summer. In most of the samples, SO4^2- concentrations are high, ranging from 0.1 to 11 mmol/U The studies show that the cycling of sulfur plays an important role in controlling water chemistry and fate of contaminants in groundwater. In order to understand the source of SO4^2- and the geochemical cycling of some elements in the karstic groundwater environment, we have carried out a study on the variations of S and Cl isotope compositions, in addition to other isotopic tracers such as ^87Sr/^86Sr and δ^13C studied previously. The δ^37Cl values of the groundwater samples present a seasonal variation, ranging from 0.00‰ to ＋2.03‰ in winter and from -1.46‰ to ＋0.29‰ in summer. The surface water samples show a similar range of variations as observed for groundwater. Two rainwater samples collected at Guiyang have a distinct isotopic signature （mean value is -3‰） compared to the δ^37Cl values reported in literature. These results indicate that ground water is mainly derived from precipitation and suggest a fast recharge of the karst system by surface water. 相似文献
8.
西藏羊八井地热水的氢、氧稳定同位素组成及氚含量 总被引：4，自引：0，他引：4
Isotopic data on drill hole water and surface water samples from the Yengbajain geothermal area as well as an ice sample from the glacial amphitheater in the Mt. Nyainqintanglha to the northwest of the Yangbajain basin are presented in this paper. In consideration of isotopic fractionation during steam separation, the hydrogen and oxygen isotopic ratios for thermal waters collected at the mouths of drill holes have been calibrated. The D/H ratio of thermal waters is similar to that of local precipitation, indicating their meteoric origin. The δ D and δ^18O values of the thermal waters of --150--160 and -17-20‰, respectively are the lowest among those well-known geothermal fields in the world.The recharge area of the geothermal system is at elevation of about 4,800--5,000 m. Drill holes along the axis of a tongueshaped zone where loose Quaternary sediments have been cemented by siliceous material show greater δ D and δ^18O values and discharge tritiumfree thermal waters. It is suggested that the thermal waters may be derived from superhcated water and steam which find their way upwards along the tectonic fractures within the granitic base overlain by Quaternary sediments. The classification of drill hole geothermal waters have been made in accordance with their δ D and δ^18O values and chloride contents. The “oxygen shift” of the thermal waters seems to be 2‰, due to isotopic exchange reactions between geothermal waters and reservoir rocks 相似文献
9.
西藏东部大气降水氧同位素组成特征 总被引：24，自引：0，他引：24
The Xizang Plateau, with a common altitude of more than 4000 m sbove sea level,has long been celebrated as “The Roof of the World”. In order to study oxygen isotopic composition of meteoric water in the Xizang Plateau Region and its relationship with the attitude, we made an investigation tour to the Xizang Plateau, starting from Guizhow, during 1979 from July to October, and 79 meteoric Water samples were collected, including brook, well, lake, snow, firn, spring and running waters, at different altitudes. Oxygen isotope analyses indicate that the isotopie composition of meteoric water in the areas more than 4000g and in the western parts of SichuanGaizhow shows remarkable altitude effect. There is a negative correlation between δ^28O and altitude, which is reflected by --δ^18O = 0.0026H 7.75. The average δ^18O value for metcoric water in the areas: more than 4000m above sea level turns out to be --18.15‰ is evident that δ^18O value for lake water on the plateau is related to its water supply. δ^18O value for lake water, in which the evaporation is greater than supply,is approximately three or four times higher than that of supplied water, averaging -5.74‰. Oxygen isotopic compasition of geothermal water can be compared with that of local meteoric water, but shows certain δ^18O-shift, suggesting that the main water-supply source seems to be meteoric water in the same area. 相似文献
10.
The method of determining the nitrogen isotopic composition of granites in the northeastern part of China is described.The content and isotopic values of nitrogen released from granite samples by stepwise heating were determined as well.The results showed that the diferent areas of northeastern China hae a great difference in nitrogen content and isotopic composition.Nitrogen released from the granites is 1.64-6.23μL/g ,with the maximum at about 600℃,from rhyolite and granophyre is 108.98-755.96μL/g,with the maximum at about 900℃,It is proved that fluid is characterized by heterogeneity in the deep crust of the different areas in northeastern China.The nitrogen isotopic compositions in different ranges of temperautes are wweighted.And the nitrogen isotopic compositions in different anges of temperatures are weighted.And the nitrogen isotopic values are 9.2‰ to 17.0‰,with a variation range of 7.8‰,The nitrogen isotopic ratios may have been fractionated during degassing and the fluid released from granites is the residual component. 相似文献
11.
CSAMT 法在辽西康杖子区深部探矿中的应用 总被引：5，自引：0，他引：5
可控源音频大地电磁法(CSAMT)具有探测深度大、横向分辨率高、抗干扰能力强的特点,在深部找矿勘探中有着重要的指导意义。肖家营子铜钼矿床是辽西地区一个大型矽卡岩型金属矿床,大部分矿体是隐伏矿体,矿区外围的康杖子区与本区有相似的成矿地质环境,成矿地质条件优越.矿体与围岩电性差异明显,通过应用CSAMT,矿体具有低电阻特点,根据成果推断解释,对深部有利成矿部位进行了钻探验证,取得了理想的探矿效果,在矿区外围取得第二深度空间找矿重大突破。 相似文献
12.
Trends in landslide occurrence in Nepal 总被引：2，自引：0，他引：2
David N. Petley Gareth J. Hearn Andrew Hart Nicholas J. Rosser Stuart A. Dunning Katie Oven Wishart A. Mitchell 《Natural Hazards》2007,43(1):23-44
Nepal is a mountainous, less developed kingdom that straddles the boundary between the Indian and Himalayan tectonic plates.
In Nepal, landslides represent a major constraint on development, causing high levels of economic loss and substantial numbers
of fatalities each year. There is a general consensus that the impacts of landslides in countries such as Nepal are increasing
with time, but until now there has been little or no quantitative data to support this view, or to explain the causes of the
increases. In this paper, a database of landslide fatalities in Nepal has been compiled and analysed for the period 1978–2005.
The database suggests that there is a high level of variability in the occurrence of landslides from year to year, but that
the overall trend is upward. Analyses of the trends in the data suggest that there is a cyclicity in the occurrence of landslide
fatalities that strongly mirrors the cyclicity observed in the SW (summer) monsoon in South Asia. Perhaps surprisingly the
relationship is inverse, but this is explained through an inverse relationship between monsoon strength and the amount of
precipitation in the Hill District areas of Nepal. It is also clear that in recent years the number of fatalities has increased
dramatically over and above the effects of the monsoon cycle. Three explanations are explored for this: land-use change, the
effects of the ongoing civil war in Nepal, and road building. It is concluded that a major component of the generally upward
trend in landslide impact probably results from the rural road-building programme, and its attendant changes to physical and
natural systems. 相似文献
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2010年,美国铀矿总共施工7 209个钻孔,总进尺1 493 520 m;生产铀1 628.55 t;铀矿业总支出费用为2.773亿美元,其中铀矿地勘费支出为3 450万美元,占铀矿业总费用的12.44%。铀矿地勘钻探费用为4 460万美元,占铀矿业总费用的16.08%。 相似文献
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环境地球化学学科在中国生态文明和美丽中国建设、国际环境公约履约及过去全球变化研究中发挥着越来越大的作用。本文简要回顾了中国过去十年在环境地球化学领域的部分研究进展,介绍了汞、持久性有机污染物和其他重金属污染物长距离传输研究进展;总结了汞、镉、锑、铊等非传统稳定同位素在地表生物地球化学循环过程中的同位素分馏规律及污染来源和环境过程示踪方面的研究进展;回顾了传统稳定同位素地球化学与污染示踪及过去全球变化方面的研究进展。指出了以上研究方向还存在的问题及未来研究方向。 相似文献
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Radon is a radioactive gas emanating naturally from uranium rich granites and shales. It may be emitted from the ground surface into the atmosphere as a gas, or it may be dissolved into stream water and transported over distance. The levels of radon gas in soils at ground surface depend on a number of factors relating to the source of the gas and to its transmission. Igneous rocks contain the highest mean concentrations of radium and uranium. The depth of cover is relevant also. Surveys over the years by the National Radiological Protection Board (NRPB) and others have indicated that the highest concentrations in the United Kingdom occur in Cornwall, Devon and northeast Scotland. However, recent reports have indicated that high concentrations of the gas may be detected in small pockets in counties outside of those considered at high risk. This survey relates to a series of measurements taken in and around Darlington, County Durham. The results showed the presence of small areas with strong concentrations of radon in soil gas, but only minor levels of dissolved gas in stream waters. 相似文献
18.
环境和灾害是威胁人类生存的两大挑战性问题。由人类活动导致的自然环境破坏和恶化是一个长期累积的过程,类似于人体所患的慢性疾病,对其认识和解决不仅依靠多种条件,也需要很长时间的持久努力。自然灾害的发生一般是短时间内的突然事件,类似人体的急性疾病。为最大限度地减轻自然灾害给人类社会造成的损失,需要实施事先预防、灾前预警、灾时应急和灾后重建的系统工程,其中地球科学家的责任之一是找出有效的宣传演练,使社会各界充分认识灾害的危险性,做好必要的防灾准备。最近20 a来中国的减灾实践经验还说明,为进一步提高减灾的效益,要用科学观念指导各领域的减灾工作,在国家一级层次上要实行多部门协调、多学科合作的综合管理,并注重对灾害发生的规律性研究。例如对群发性灾害链过程及其潜在影响的估计,这对制定区域性可持续发展规划具有重要意义。 相似文献
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古昌蛇绿岩中的斜长花岗岩特征 总被引：1，自引：0，他引：1
古昌蛇绿岩中首次发现斜长花岗岩。斜长花岗岩的地质特征和岩石学、岩石化学、地球化学特征反映出异常洋脊花岗岩的属性,岩浆源自地幔,与古昌蛇绿岩中的变质橄榄岩、基性岩墙、基性熔岩的岩浆同源,是基性—超基性岩浆分异的残余,应属古昌蛇绿岩中的浅色岩组分,是蛇绿岩的端元岩石。 相似文献