广西及邻区泥盆系碳酸盐岩碳,氧同位素组成特征及意义

广西及邻区下泥盆统至下石炭统稳定碳同位素组成逐渐增大，由埃姆斯阶（Ｄ１）－１‰－４‰增至法门阶，杜内阶的＋０．５‰－＋２．５‰。同时期δ＾１８Ｏ呈“Ｗ”型分布在艾菲尔阶和弗拉斯阶两个负向波动；在埃姆斯阶，吉维特阶和法门阶、杜内阶三个正向波动。     

湖相碳酸盐碳、氧同位素与团簇同位素的研究进展

总结近年来传统碳、氧同位素及新兴团簇同位素在湖相碳酸盐中的研究进展,梳理湖相环境中碳酸盐同位素组成变化的影响因素及两种同位素方法在地质研究中的应用,探讨当前研究中存在的问题。湖相碳酸盐氧同位素组成受温度的影响较小,主要与湖盆水体的蒸发量和大气降水量有关,碳同位素组成则受湖水蒸发咸化作用以及湖泊有机质与无机质相互作用的共同控制;团簇同位素仅受温度单一因素的影响,是良好的碳酸盐温度计。指出湖相碳酸盐碳、氧同位素研究的两大方向:一是解决团簇同位素理论研究中存在的问题,尤其是埋藏改造过程中团簇同位素温度的重置机理;二是将传统的碳、氧同位素指标与新兴的团簇同位素指标相结合,进行多指标的地球化学综合分析,有效地避免二者在地质研究中的局限性。     

塔里木盆地奥陶系碳酸盐岩碳氧稳定同位素地球化学特征

中-下奥陶统碳酸盐岩储层是塔里木盆地塔中地区的主要油气产层.利用碳氧稳定同位素的分布特征和变化规律,可分析影响碳酸盐岩沉积环境和成岩作用的因素.中-下奥陶统的碳酸盐岩可在垂向上把δ13C和δ18O值的变化趋势划分为三段,二者的变化趋势是一致的.中-上奥陶统岩层碳氧稳定同位素比值明显下降,证明中-下奥陶统经历过一次短暂的抬升暴露和随后的大面积海水加深淹没事件.海水淹没时期,大量C转到海水之中,海水中沉淀出的碳酸盐岩的δ13C值相对较低.     

腕足化石壳体氧、碳同位素生命效应问题研究

利用产于四川龙门山地区中泥盆统吉维特阶的腕足化石,在保证测试分析精度相同的条件下,对原始生活环境相同、保存程度相同的化石进行了科、属、种3个级别上氧、碳同位素组成的对比,所研究的化石都没有显示出可检测的同位素生命效应.已有的腕足化石具有氧、碳同位素生命效应的认识很可能源于原始生活环境不尽相同和(或)保存程度不同的腕足化石的对比研究.因此腕足化石壳体是研究碳酸盐岩原始氧、碳同位素组成的较为理想的样品.     

内陆湖泊贝壳碳酸盐碳氧同位素组成与古气候研究

通过对江川湖盆沉积物中螺壳化石样品的处理和分析,测定了贝壳碳酸盐的δ~(13)C值和δ~(18)O值。结合孢粉资料,研究贝壳碳酸盐碳氧同位素分布及变化,对江川湖盆的古气候及盆地演化提供有用的信息。     

玉北地区奥陶系碳酸盐岩碳氧同位素特征及成岩环境分析

基于大量碳、氧稳定同位素(δ13C,δ18O)数据,利用岩心分析、岩石薄片单偏光、阴极发光以及扫描电镜等实验方法,结合玉北地区成岩环境特点,研究了该区奥陶系各类成岩环境的地球化学特征。研究结果表明:玉北地区奥陶系碳酸盐岩都是在稳定的海相环境中形成的,且基本上保持了原始环境的碳、氧同位素组成,其成岩埋藏深度经历了先上升后下降的过程,沉积地层由鹰山期至良里塔格期,对应着海平面的上升。用Z值作为定量指标来解释古盐度的相对变化精确度较低。三大类成岩环境中,近地表成岩环境的δ13C和δ18O普遍较高,表生淡水成岩环境的δ13C和δ18O普遍较低,中—深埋藏和热液成岩环境的δ13C和δ18O介于前两者之间。     

乌尔逊凹陷构造层序界面的识别与划分

探讨乌尔逊凹陷的构造特征及其演化规律,采用地震解释方法对构造层序界面进行识别与划分。结果表明乌尔逊凹陷发育四个区域性构造层序界面,将盖层划分出四个构造层。得出乌尔逊凹陷经历了4个形成期和3个改造期的构造演化阶段。     

安固里淖自生碳酸盐碳氧同位素组成与环境

湖泊自生碳酸盐碳氧同位素变化是反映内陆湖泊水环境与气候环境的重要指标．通过在河北坝上安固里淖钻取沉积样柱,分样进行自生碳酸盐矿物类型分析和碳氧同位素分析,结合剖面的纹层年代以及粒度分析和易溶盐分析,对湖泊地区的全新世古环境进行了探讨：8507—7909 a B．P．,湖区气温较高,蒸发量大,夏季风先减弱随后增强．7909—7004 a B．P．,冬季风较强,气温低,蒸发量小,湖水盐度高;7004—5491 a B．P．,气温较高,降雨量大,湖水冰冻时间短,相当于大暖期鼎盛阶段;5491—4617 a B．P．,大气湿度低,气温低,冬季风较强,湖泊冰冻时间长,代表大暖期气候剧烈波动阶段;4617—574 a B．P．,冬季风较强,降水量少,河流补给少,湖泊冰冻时间较长;574 a B．P．至今,冬季风较弱,冰冻时间缩短,气候向暖湿发展．安固里淖自生碳酸盐碳氧同位素反映的环境变化与我国北方地区的全新世环境以及海平面的变化基本一致。     

镇安西口地区二叠纪碳氧同位素特征及意义

文章对镇安西口地区二叠纪剖面进行了碳酸盐岩稳定同位素和烧失量的测定,探讨了“年代效应”的校正和古盐度、古温度的计算问题.结果表明古盐度Z值大于120,为海相沉积,与沉积环境的研究结论一致;用校正后的δ18O计算出灰岩形成时的古海水温度为13.4～35.1℃,与前人的计算结果基本一致;碳氧同位素值在少数层位有较大的偏差;...     

轮古西地区奥陶系碳酸盐岩古岩溶储层碳、氧同位素地球化学特征

中—下奥陶统鹰山组碳酸盐岩古岩溶储层是塔里木盆地轮古西地区的主要油气产层 .为了弄清储层的成因类型、储层古岩溶过程中的流体性质和古水文条件 ,为预测和评价此类储层提供有关的地球化学信息 ,讨论了储层形成过程中记录的碳、氧稳定同位素特征 .结果表明 :轮古西地区奥陶系鹰山组碳酸盐岩古岩溶储层中的δ13C和δ18O值的变化范围较大 ,δ13C值为 -0 .70‰～ -6.5 0‰ ,平均值 -1 .76‰ ;δ18O值为 -3 .75‰～ -1 7.1 0‰ ,平均值 -9.42‰ .碳酸盐岩基质、冲积岩和方解石胶结物的δ13C和δ18O分布具有一定的差异 .三类样品的δ18O值均具有明显偏负特征 ,表明在碳酸盐岩成岩过程中受到大气成因的淡水影响 ,反映了当时的风化壳岩溶成岩环境 .冲积岩样品的δ13C值的偏负程度较高 ,其物源可能来自石炭—二叠系地层     

用碳氧同位素对沱沱河盆地古近纪及新近纪早期气候变化的研究

鉴于目前对位于青藏高原上的沱沱河盆地研究不多,作者试用碳氧同位素比值的方法研究该地区新生代的始新世到中中新世这一时段内的气候环境变化情况.经过数据计算、图解和分析表明,沱沱河盆地从始新世到中中新世的气候环境变化可划分为两个阶段,即始新世-渐新世的炎热干燥气候期和中中新世的温暖湿润气候期.此研究结果将为进一步研究该地区的古环境变化提供依据.     

Analysis of carbon isotopes in airborne carbonate and implications for aeolian sources

Methods were developed to determine the mass ratios of carbon isotopes in trace amounts of aerosol carbonate. A Finnigan MAT 252 mass spectrometer fitted with an on-line Kiel device was to determine the ^13C/^12C ratio in CO2 produced from the carbonate. A study using these methods was conducted to characterize the carbonate carbon isotopes in aerosol samples collected in Xi‘an on dusty and normal days during March and April 2002. Results of the study demonstrate that insights into the origin of the dust can be deduced from its isotopic composition. That is, the δ^13C ofcarbonate for dust storm samples ranged from -1.4‰ to -4.2‰, and this is consistent with sandy materials in dust source regions upwind. In contrast, for non-dusty days δ^13C ranged from -7.5% to -9.3‰, which is more similar to fine particles emitted from local surface soils. Comparisons of dust storm aerosols with surface soils from source regions and with aerosol samples collected downwind indicate that the δ^13C values did not change appreciably during longrange transport. Therefore, carbon isotopes have the potential for distinguishing among source materials, and this approach provides a powerful new tool for identifying dust provenance.     

Variations of sulfur and carbon isotopes in seawater during the Doushantuo stage in late Neoproterozoic

The Doushantuo Formation of the Sinian System in the Yangtze area is the first sedimentary stratigraphic unit after the Neoproterozoic Snowball Earth event[1], named the Nantuo Glaciation in south China. There are not only phosphorite and manganese mineralized beds[2], but also a series of biome which represents the biological radiation in Neoproterozoic[3] found in this formation. It is important to study the palaeoenvironment and the early biological evolution implied in the Doushantuo …     

Stable carbon and oxygen isotopic compositions of carbonates in middle Mesoproterozoic Wumishan Formation and sea-level change

δ13C of dolostones from the Wumishan Formation (1 310-1 207 Ma) in the Ming Tombs area near Beijing ranges from - 1.5 to 1.5‰ (PDB), and generally, the δ18O ranges from - 4 to - 5‰ (PDB). The secular variation of stable carbon isotopic compositions is cyclic. δ13C displays positive shifts from a sequence boundary to 1.5 per mil (PDB), then a negative shifts to - 1.5 per mil (PDB). In some unit, where δ13C values of the rocks are negative, they have relatively high δ18O values close to -4.0‰ (PDB). These characteristics of the carbon and oxygen isotopic compositions may be associated with sea-level changes.     

Vegetational ecotype of the Gyirong Basin in Tibet, China and its response in stable carbon isotopes of mammal tooth enamel

Carbon isotope analysis of modern herbaceous plants in the Gyirong Basin (Tibet, China) indicates that although C3 plants are dominant, C4 plants rarely comprise of the vegetation in the area at 4000 m above sea level. The C4 plants discovered in the Gyirong Basin are Salsola nepalensis of Chenopodiaceae and Pennisetum flaccidum of Gramineae, affirming that C4 plants affected by high solar gain can be distributed at high altitude, which supports the opinion that some C4 plants can exist in areas of high elevation. Carbon isotope analysis of herbivore tooth enamel from the Gyirong Basin indicates that carbon isotopes of structural carbonate in biogenic apatite at high altitude still keep a stable enrichment relationship with those of plants in their diet. Carbon isotopes in tooth enamel are therefore an accurate proxy for vegetation ecotypes and should reflect climatic and environmental features.     

浅层测温在地热勘查开发中的应用

采用浅层测温方法,辅助地球物理勘探和氢氧同位素方法,论述了夏县南山底地热田开发利用的前景。     

Discovery of seep carbonate nodules as new evidence for gas venting on the northern continental slope of South China Sea

The geotectonic evolution of the northern South China Sea (SCS) is controlled by the Eurasian, the Pa-cific and the Indian-Australian Plates. With regard to its tectonic evolution, the northern margin composed of faulted terraces and basins and deposited …