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1.
西成矿化集中区热水沉积岩物质来源的同位素示踪及其意义 总被引：11，自引：3，他引：11
利用硅同位素、锶同位素和碳氧同位素,对西成矿化集中区与矿体紧密伴生的热水沉积岩的物质来源进行了探讨。硅质岩的硅同位素δ3 0 SiNBS -2 8=- 0.6‰～ - 0.1‰,硅主要来源于下伏沉积岩;热水沉积岩的锶同位素比值87Sr/ 86Sr变化于 0.70 938～ 0.72 812之间,位于海洋锶和陆壳锶之间,为混合锶,其锶主要来源于下伏沉积地层柱;碳同位素组成略低于正常沉积碳酸盐岩,碳主要来源于下伏沉积地层柱在循环碳,同时又受其它来源碳的影响。同位素研究结果表明,热水沉积岩的组成物质主要来源于下伏沉积地层柱 (地壳内部 ),形成方式主要是外生沉积作用,即热水沉积岩是内生作用与外生作用共同作用的结果,是内外生矛盾的统一体。 相似文献
2.
新疆柯坪地区早古生代地层的碳、氧和锶同位素 总被引：8，自引：0，他引：8
我们系统测定了新疆柯坪地区寒武纪和奥陶纪地层的海相碳酸盐样品的碳、氧和锶同位素组成,取得了沿地层剖面的同位素组成变化曲线。研究结果表明,柯坪地区寒武纪和奥陶纪海水中碳同位素变化曲线有6个δ~(13)C负波动峰时期,它们与当时的全球生物灭绝事件和海退—海进事件的时间基本吻合,表明它们三者之间存在着必然的联系。在寒武纪和奥陶纪的大部分时间,锶同位素曲线较为平坦,反映出较少的地壳活动和板块构造作用。 相似文献
3.
未经蚀变的海相碳酸盐岩的碳，锶同位素组成代表了原始海水的同位素组成，在确定样品末经显著蚀变的基础上，本文测定了上扬子地区晚古生代７条剖面２３８个海相碳酸盐岩样品的碳、锶同位素组成，分布了它们的测试结果和演化曲线，为其他相关研究提供了可利用的基础参照数据。 相似文献
4.
浙江陈蔡群变质岩系的氢、氧、碳及锶稳定同位素研究 总被引：3，自引：0，他引：3
本文应用稳定同位素地球化学方法，对陈蔡群中变质矿物或岩石做了氢、氧、碳及锶同位素组成测定，从而探讨了变质岩的形成温度、变质水的性质和原岩的沉积环境等问题。 相似文献
5.
川东南地区石牛栏组碳、氧、锶同位素特征及其地质意义 总被引：6，自引：0，他引：6
前人对川东南地区石牛栏组地层已进行了大量的研究工作,但有关同位素地球化学方面的研究尚未见报道。本区石牛栏组沉积成因碳酸盐岩的碳同位素值与前人的研究结果一致,而氧同位素值则有所偏低;白云岩δ^13C值低,δ^18O值高,反映受成岩环境的影响较明显;裂缝中方解石的碳、氧同位素组成分布于两个不同的区间,说明不同期次裂缝充填物形成时的流体性质发生了明显的变化;沉积成因碳酸盐岩具异常低的锶同位素值,与前人研究结果有明显的差异,推测是受贫87Sr同位素的成岩流体的影响;晚期裂缝充填物锶同位素比值较高,也表明它们受到了地表淡水的影响。 相似文献
6.
7.
城门山铜、钼矿床的稳定同位素地质 总被引：1，自引：0，他引：1
城门山铜、钼矿床由斑岩型铜、钼矿床,矽卡岩型铜矿床和块状硫化物型铜矿床组成。本文从锶、铅、硫、氢、氧、碳等多种稳定同位素的组成特征,讨论矿床中成矿物质和热液的来源。 相似文献
8.
早三叠世作为地球发展史上一个高度的反常时期,人们对其关注程度远不及二叠纪/三叠纪界线。海相碳酸盐的碳、锶同位素组成与演化是了解重大突变期的生态环境事件和地球过程的重要切入点。根据前人公布的川东地区早三叠世锶、碳同位素数据,绘制同位素演化散点图,根据曲线的演化特征以及不同地区的对比,分析其控制因素和地质过程。研究表明,川东地区早三叠世锶同位素演化曲线单调上升,具有很高的全球一致性,由河流注入到海水的高放射成因的锶含量增加是加剧87Sr/86Sr比值单调上升的主要原因。碳同位素演化曲线在短时间内发生的一系列高频率、大幅度波动,大量的磷酸盐注入海洋使菌藻类大量繁殖,海洋的初级生产力增强,有机碳埋藏量增大,使δ13C偏高。甲烷水合物吸收与释放等暂时性效应不是引起曲线来回波动的主要因素,海洋水体倒转等持续性效应可以很好地解释曲线异常,但对其驱动机制有待进一步研究。此外δ13Ccarb和δ13Corg的同步研究并参考早寒武世是下一步研究的重点。 相似文献
9.
扬子地台西缘宁蒗泸沽湖地区志留系沉积旋回及锶、碳、氧同位素特征 总被引：10，自引：1，他引：10
本系统研究了扬子地台西缘宁蒗泸沽湖地区志留系沉积旋回及海相碳酸盐岩的锶、碳、氧同位素特征，并对同位素曲线演化规律与海平面变化和区域地壳运动的关系进行了探讨。研究结果表明，本区志留系除底部有少量细碎屑岩沉积外，主要为浅海潮坪相碳酸盐岩沉积，其锶、碳、氧同位素值变化范围分别是0．7093～0．7196、-1．28‰～2．74‰和-1．302‰～-10．721‰；平均值分别是0．7114、0．984‰和-7．810‰。由于受区域地壳隆升运动的影响，同位素组成和同位素演化规律与海平面变化的关系并不明显。 相似文献
10.
新型柯坪地区早古生代地层的碳,氧和锶同位素 总被引：1，自引：0，他引：1
我们系统测定了新疆柯坪地区寒武纪和奥陶纪地层的海相碳酸盐样品的碳，氧和锶同位素组成，取得了沿地层剖面的同位素组成变化曲线，研究结果表明，柯坪地区寒武纪和奥陶纪海水中碳同位素变化曲线有６个δ＾１３Ｃ负波动峰时期，它们与当时的全球生物灭绝事件和海退－海进事件的时间基本吻合，表明它们三者之间存在着必然的联系，在寒武纪和奥陶纪的大部分时间，锶同位素曲线较为平垣，反映出较少的地壳活动和板块构造作用。 相似文献
11.
Peter Stille Anne-Désirée Schmitt François Labolle Marie-Claire Pierret Sophie Gangloff Florian Cobert Eric Lucot Florence Guéguen Laure Brioschi Marc Steinmann François Chabaux 《Comptes Rendus Geoscience》2012,344(5):297-311
The combination of the Sr, Nd and Pb isotope systems, recognized as tracers of sources, with the Ca isotope system, known to reveal biology-related fractionations, allowed us to test the reliability of spruce (Picea abies) growth rings as environmental archives through time (from 1916 to 1983) in a forest ecosystem affected by acid atmospheric deposition. Sr and Pb isotopes have already been applied in former tree-ring studies, whereas the suitability of Nd and Ca isotope systems is checked in the present article. Our Sr and Nd isotope data indicate an evolution in the cation origin with a geogenic origin for the oldest rings and an atmospheric origin for the youngest rings. Ca isotopes show, for their part, an isotopic homogeneity which could be linked to the very low weathering flux of Ca. Since this flux is weak the spruces’ root systems have pumped the Ca mainly from the organic matter-rich top-soil over the past century. In contrast, the annual growth rings studied are not reliable and suitable archives of past Pb pollution. 相似文献
12.
大别山麻粒岩和TTG片麻岩的Sr,Nd,Pb同位素地球化学 总被引：4，自引：1，他引：4
北大别4个麻粒岩和4个TTG片麻岩样品的Sr,Nd同位素分析结果表明，样品普遍具有较高的锶同位素比值（^87Sr/^86Sr=0.7066-0.7461)，较低的Nd同位素比值（^143Nd/^144Nd=0.5108-0.5124)，表现出明显的壳源特征，结合铅同位素的组成来看，北大别麻粒岩及TTG片麻岩的同位素成分相当于－下地壳。岩石的特源为古老的地壳，大约在2－3Ga之间，少数样品的同位素特征可能暗示源区有年轻地壳物质的加入。 相似文献
13.
对赛利普地区新生代火山岩Sr,Nd,Pb同位素资料分析,揭示了赛利普新生代火山岩同位素组成在时代和岩石组合上存在的规律性变化.总体上,随时代变新,Sr,Pb同位素呈递增,Nd同位素呈递减趋势,火山岩中地壳物质贡献明显增加.本区新生代火山岩与青藏高原北部(班公湖-怒江缝合带以北)相比,Sr,Nd和Pb同位素组成存在一定差异,尤其是新近纪以来钾质火山岩显著高87Sr/86Sr、极低143Nd/144Nd值,208Pb/204Pb值普遍偏高,古近纪火山岩这种差别则不明显.揭示了新生代以来,在印度大陆岩石圈向北俯冲过程中,拉萨地块比青藏高原北部融入了更多喜马拉雅大陆地壳端元成分.中新世早中期,印度大陆板块向北A型俯冲到拉萨地块基底西段,并发生岩石圈不同层次部分熔融、岩石圈断离等作用. 相似文献
14.
高Rb/Sr岩石样品中Sr同位素多接收等离子体质谱分析校正方法研究 总被引：1，自引：1，他引：0
在利用多接收电感耦合等离子体质谱(MC-ICPMS)进行Sr同位素研究中,87Rb对于87Sr干扰严重。岩石样品经化学分离后,若Rb/Sr≤0.0005,可以采用传统的Rb干扰扣除方法对87Sr/86Sr测定值进行准确校正;但如果样品经化学分离后仍含有较高的Rb/Sr比,同量异位素的干扰不能完全消除,则无法准确校正87Sr/86Sr测定值,直接影响测试结果的准确度。本文针对Rb含量较高的地质样品设计两组实验,确定了87Sr/86Sr同位素比值与Rb/Sr元素含量比值的关系曲线,并在理论分析的基础上,提出包含同位素分馏校正在内的重叠干扰校正方法。通过实际地质样品验证,该校正方法在较高含量Rb元素共存(Rb/Sr<0.2)的Sr纯化液中,能够较为准确地测量87Sr/86Sr同位素比值,降低了MC-ICPMS分析地质样品中Sr同位素时对化学分离步骤的要求。而对于Rb/Sr>0.2的地质样品,因仪器分馏效应和记忆效应影响,测试精确度大大降低,无论采用何种校正方法均无法得到准确的Sr同位素组成。 相似文献
15.
《Applied Geochemistry》2002,17(3):285-300
Strontium and particularly 87Sr/86Sr ratios in stream water have often been used to calculate weathering rates in catchments. Nevertheless, in the literature, discharge variation effects on the geochemical behavior of Sr are often omitted or considered as negligible. A regular survey of both Sr concentrations and Sr isotope ratios of the Strengbach stream water draining a granite (Vosges mountains, France) has been performed during one year. The results indicate that during low water flow periods, waters contain lower Sr concentrations and less radiogenic Sr isotope ratios (Sr=11.6 ppb and 87Sr/86Sr=0.7246 as an average, respectively) than during high water flow periods (Sr= 13 ppb and 87Sr/86Sr=0.7252 as an average, respectively). This is contrary to expected dilution processes by meteoric waters which have comparatively lower Sr isotopic ratios and lower Sr concentrations. Furthermore, 87Sr/86Sr ratios in stream water behave in 3 different ways depending on moisture and on hydrological conditions prevailing in the catchment. During low water flow periods (discharge < 9 l/s), a positive linear relationship exists between Sr isotope ratio and discharge, indicating the influence of radiogenic waters draining the saturated area during storm events. During high water flow conditions, rising discharges are characterized by significantly less radiogenic waters than the recession stages of discharge. This suggests a large contribution of radiogenic waters draining the deep layers of the hillslopes during the recession stages, particularly those from the more radiogenic north-facing slopes. These results allow one to confirm the negligible instantaneous incidence of rainwater on stream water chemistry during flood events, as well as the existence in the catchment of distinct contributive areas and reservoirs. The influence of these areas or reservoirs on the fluctuations of Sr concentrations and on Sr isotopic variations in stream water depends on both moisture and hydrological conditions. Hence, on a same bedrock type, 87Sr/86Sr ratios in surface waters can be related to flow rate. Consequently, discharge variations must be considered as a pre-requisite when using Sr isotopes for calculating weathering rates in catchments, particularly to define the range of variations of the end-members. 相似文献
16.
川西地区栖霞组白云岩成因及其与峨眉山玄武岩喷发热事件关系颇有争论。在野外剖面、岩心观察基础上,通过岩石学、全岩及矿物微区地球化学分析方法对其研究,结果表明川西地区栖霞组白云岩（石）可分为残余砂屑白云岩、晶粒白云岩以及鞍状白云石、脉体充填白云石四类。残余砂屑白云岩与晶粒白云岩均呈块状,阴极发光较暗,稀土配分模式与泥微晶灰岩相似,δ13C、87Sr/86Sr多处于同期海水范围内,δ18O略偏负,Ce负异常,残余砂屑白云岩Eu呈负异常,而晶粒白云岩Eu多为正异常。微区δ13C、δ18O分析显示,残余砂屑白云岩的白云石雾心与亮边内δ13C均处于同期海水范围内,δ18O亮边较雾心偏负;晶粒白云岩中不同大小的晶粒白云石微区δ13C、δ18O显示相近特征,表明这两类白云岩均为海水浅埋藏成因,但受到后期热流体叠加改造。曲面他形粗晶鞍状白云石充填于裂隙与溶蚀孔洞内,镜下具波状消光特征,发亮红色光,δ13C与二叠纪海水相近,δ18O明显负偏,Eu呈正异常,指示鞍状白云石为热液成因。脉体白云石岩石学与地球化学特征表明其为晚期埋藏成因。川西地区栖霞组白云岩主体为浅埋藏成因,峨眉山玄武岩喷发期热液对其叠加改造,仅西南地区充填裂隙与溶洞的鞍形白云石为热液成因。 相似文献
17.
重庆秀山寒武系锶同位素演化曲线及全球对比 总被引：15，自引：0，他引：15
本文评述了国际上已有的寒武纪海相碳酸盐的锶同位素演化曲线，公布了重庆秀山寒武系海相碳酸盐的锶同位素分析结果，尽管对样品进行了成岩蚀变检测和必要的筛选，但样品仍可能不同程度地经历了成岩蚀变，锶同位素组成与地层厚度投点图显得较为离散，笔者主要利用87Sr/86Sr比值较低的样品建立的寒武纪海水的锶同位素演化曲线在长期旋回上与国际上已公布的同时代锶同位素演化曲线仍具有较好相似性和可比性，说明全球事件是海水锶同位素组成的主要控制因素，海水的87Sr/86Sr比值在盆内对比，盆间对比，以及全球对比中都具有潜在价值。根据锶同位素地层学的基本原理，笔者尝试确定了重庆秀山寒武纪剖面一些关键点的年龄，累积厚度1340m处的年龄为503－509Ma，累积厚度1950m处的年龄为496－498Ma，这对秀山寒武纪剖面下，中寒武统和中、上寒武统界线的确定具有参考价值。 相似文献
18.
Yue‐Heng Yang Ming Yang Klaus Peter Jochum Shi‐Tou Wu Han Zhao Lie‐Wen Xie Chao Huang Xiu‐Chun Zhan Jin‐Hui Yang Fu‐Yuan Wu 《Geostandards and Geoanalytical Research》2020,44(3):567-579
To assess the homogeneity of and provide the first Sr‐Nd‐Hf‐Pb isotopic reference values for the Chinese Geological Standard Glasses CGSG‐1, CGSG‐2, CGSG‐4 and CGSG‐5, we measured these isotopes in several measurement sessions over the course of nearly 3 years. The results were obtained by high‐precision MC‐ICP‐MS and TIMS. Our investigation indicates that these CGSG glass reference materials are homogenous with regard to Sr‐Nd‐Hf‐Pb isotopic distribution and are therefore suitable geochemical materials for Sr‐Nd‐Hf‐Pb isotope measurements. Clear differences in Sr‐Nd‐Hf‐Pb isotopic composition were observed between the glasses and the original powdered rock reference materials (CGSG‐2 and GSR‐7, and especially CGSG‐5 and GSR‐2) because of flux addition during preparation of the glasses. The new Sr‐Nd‐Hf‐Pb isotope data provided here might be useful to the geochemical community for in situ and bulk analysis. 相似文献
19.
Sr, C, and O isotope geochemistry of Ordovician brachiopods: a major isotopic event around the Middle-Late Ordovician transition 总被引：2，自引：0，他引：2
Graham A Shields Giles A.F Carden Jαn Veizer Tõnu Meidla Rong-Yu Li 《Geochimica et cosmochimica acta》2003,67(11):2005-2025
Here we present Sr, C, and O isotope curves for Ordovician marine calcite based on analyses of 206 calcitic brachiopods from 10 localities worldwide. These are the first Ordovician-wide isotope curves that can be placed within the newly emerging global biostratigraphic framework. A total of 182 brachiopods were selected for C and O isotope analysis, and 122 were selected for Sr isotope analysis. Seawater 87Sr/86Sr decreased from 0.7090 to 0.7078 during the Ordovician, with a major, quite rapid fall around the Middle-Late Ordovician transition, most probably caused by a combination of low continental erosion rates and increased submarine hydrothermal exchange rates. Mean δ18O values increase from −10‰ to −3‰ through the Ordovician with an additional short-lived increase of 2 to 3‰ during the latest Ordovician due to glaciation. Although diagenetic alteration may have lowered δ18O in some samples, particularly those from the Lower Ordovician, maximum δ18O values, which are less likely to be altered, increase by more than 3‰ through the Ordovician in both our data and literature data. We consider that this long-term rise in calcite δ18O records the effect of decreasing tropical seawater temperatures across the Middle-Late Ordovician transition superimposed on seawater δ18O that was steadily increasing from ≤−3‰ standard mean ocean water (SMOW). By contrast, δ13C variation seems to have been relatively modest during most of the Ordovician with the exception of the globally documented, but short-lived, latest Ordovician δ13C excursion up to +7‰. Nevertheless, an underlying trend in mean δ13C can be discerned, changing from moderately negative values in the Early Ordovician to moderately positive values by the latest Ordovician. These new isotopic data confirm a major reorganization of ocean chemistry and the surface environment around 465 to 455 Ma. The juxtaposition of the greatest recorded swings in Phanerozoic seawater 87Sr/86Sr and δ18O at the same time as one of the largest marine transgressions in Phanerozoic Earth history suggests a causal link between tectonic and climatic change, and emphasizes an endogenic control on the O isotope budget during the Early Paleozoic. Better isotopic and biostratigraphic constraints are still required if we are to understand the true significance of these changes. We recommend that future work on Ordovician isotope stratigraphy focus on this outstanding Middle-Late Ordovician event. 相似文献
20.
微量元素锶及其同位素的地球化学研究与应用前景 总被引：19，自引：0，他引：19
锶元素的浓度和同位素组成在自然界的碳酸盐、水体和生物体中有很大的变化范围,这种变率和定量的相关性可能是沉积速率、介质环境、矿物结晶体生长机制和生物聚集或选择吸收作用的函数。随着测量分析技术的提高,以及锶元素含量和同位素组成变化的地球化学理论模式的逐步完善,锶元素和同位素组成的地球化学特征成为研究水文循环、碳酸盐成岩作用机制、以及由此引出的古环境评价和现代环境的监测与示踪等方面的重要工具。主要介绍了锶元素及其同位素在以上各方面的研究进展及其应用前景。 相似文献