地质年龄测定中高Rb／Sr样品部分除铷处理方法

介绍了地质年龄测定中对高Ｒｂ／Ｓｒ样品，用吸附了六硝基二苯胺的阴离子交换树脂除去部分铷元素的新方法，从而实现样品在阳离子交换柱上的铷锶安全分离。该方法可解决Ｒｂ／Ｓｒ〉２０样品在质谱分析测定中＾８７Ｒｂ干扰＾８７Ｓ的问题。     

安徽沙溪斑岩铜（金）矿床成岩成矿热历史探讨

采用Ｒｂ－Ｓｒ方法,测定沙溪斑岩铜（金）矿成矿岩体年龄为１４３．３７±５．１７Ｍａ;采用＾４０Ａｒ／＾３９Ａｒ快中子活化定年法,测定沙溪斑岩铜（金）矿成矿年龄为１２３．６±０．７Ｍａ;成矿岩体从固结成岩到成矿经历了２０Ｍａ。根据Ｒｂ－Ｓｒ和Ｋ－Ａｒ同位素体系封闭温度的不同,估算出沙溪岩浆热液成矿系统热衰减速率平均为２０℃／Ｍａ。单一的由成矿小岩体所提供的热能难以维持如此长时间热液成矿活动,矿区晚期     

江西进贤早官岭侵入体的地球化学特征及其成因探讨

进贤早官岭侵入体是作者近年来从事１：５万进贤图组区域地质调查所发现的。该侵入体主体岩性为黑云角闪闪长岩，全岩Ｒｂ－Ｓｒ等时线年龄为１２４０±１０Ｍａ，（￣（８７）Ｓｒ／￣（８６）Ｓｒ）＝０．７０３４，具有高Ａｌ＿２Ｏ＿３、ＴｉＯ＿２、ＣａＯ含量，低ＳｉＯ＿２含量的成分特征，其微量元素的ＭＯＲＢ标准化曲线与阿卓热斯碱性玄武岩极为相似，稀土总量较高，弱的负Ｅｕ异常。地球化学特征反映其岩浆为亏损地幔经低的部分融熔后，发生极低的结晶分异且未受地壳混染，固结后经构造运动拾升至地表。     

武当地块基性岩墙群及耀岭河群基性火山岩的Sr,Nd,Pb,O同位素研究

武当地块基性岩墙群与耀岭河群基性火山岩的Ｓｒ、Ｎｄ、Ｐｂ同位素特征反映它们具相同的混合地幔源区。前者的（＾８７Ｓｒ／＾８６Ｓｒ）ｉ＝０．６９０５￣０．７０６１,εＮｄ（ｔ）＝－１．９￣５．０,Δ＾２０８Ｐｂ／＾２０４Ｐｂ＝３５．４９￣１９０．２６,Δ＾２０７Ｐｂ／＾２０４Ｐｂ＝４￣８５,Ｔｈ／Ｔａ低,Ｌａ／Ｙｂ变化大;后者的（＾８７Ｓｒ／＾８６Ｓｒ）ｉ＝０．６４８７￣０．７０７５,εＮｄ（ｔ）＝０     

构造剪切与变质角闪石中过剩Ar的引入：北秦岭丹凤群斜长角闪岩的Sm－Nd、Rb－Sr和~（40）Ar／~（39）Ar测年证据

本文对两个北秦岭丹凤群斜长角闪岩样品进行了Ｓｍ－Ｎｄ、Ｒｂ－Ｓｒ和４０Ａｒ／３９Ａｒ测年，发现其中受构造改造轻微的黑河丹凤群斜长角闪岩样品的角闪石４０Ａｒ／３９Ａｒ年龄与其Ｒｂ－Ｓｒ、Ｓｍ－Ｎｄ矿物等时线年龄接近，而遭受强烈构造剪切作用的蒲峪丹凤群斜长角闪（片）岩的角闪石４０Ａｒ／３９Ａｒ年龄则明显高于其Ｒｂ－Ｓｒ、Ｓｍ－Ｎｄ矿物等时线年龄，指示构造剪切作用对变质角闪石中过剩氩的引入有显著影响。在利用４０Ａｒ／３９Ａｒ进行造山带年代学研究时这一问题应引起注意     

冀西北东坪金矿床含金石英脉石英流体包裹体Rb-Sr等时线及其地质意义

用石英流体包裹体Ｒｂ－Ｓｒ等时线法测得产于碱性岩体中具有超大型潜力的东坪金矿床含金石英脉的年龄为（１０３±８）Ｍａ，远晚于赋矿岩体的就位时间（元古宙），显示了成岩与成矿是两期不同构造运动的产物，两者之间没有直接的成因联系。８７Ｓｒ／８６Ｓｒ示踪结果显示成矿物质主要来源于赋矿碱性岩体。研究结果认为，东坪金矿是后期与大气降水热液有关的改造成矿作用的产物。     

东太平洋早中新世Sr87／Sr86和CaCO3的短周期旋回及其古海…

以５ｃｍ为间隔取得东太平洋５７９４岩心早中新世超微化石软泥须（２４．０６～２２．０６Ｍａ）的５５个样品,用同位素质谱仪、耦合等离子光谱仪和化学溶解当分别对尼中可溶碳酸盐组分的＾８７Ｓｒ／＾８６Ｓｒ、全岩的Ａｌ２Ｏ３和ＣａＣＯ３含量进行了测定。结果显示,＾８７Ｓｒ／＾８６Ｓｒ和ＣａＣＯ３呈反射发育了２个完整旋回和１个半旋回。＾８７Ｓｒ／８６Ｓｒ和ＣａＣＯ３短期旋回具有重要的古海洋学意义：（１）＾８７     

2.5Ma以来大陆风化强度的演变

本次研究得出了２．５ＭａＢＰ以来洛川剖面黄土－古土壤序列的酸不深物＾８７Ｓｒ／＾８６Ｓｒ、Ｒｂ／Ｓｒ、磁化率和沉积速率的变化曲线。黄土和古土壤酸不深物＾８７Ｓｒ／８６Ｓｒ、Ｒｂ／Ｓｒ和磁化率的变化具有类似的阶段性和周期性,这与晚新生代以来古气候的主要变化以及行星轨道参数相一致。研究证明,黄土和古土壤酸不深物＾８７Ｓｒ／＾８６Ｓｒ值得化学风化强度的替代指标,沉积速率是物理风化强度的替代指标。自２．５     

西天山琼阿乌孜超基性岩体的稀土元素和Sr,Nd同位素研究

对西天山琼阿乌孜超基性岩体和围岩片麻岩作了Ｓｍ、Ｎｄ、Ｒｂ、Ｓｒ同位素和稀土元素的研究，获得岩体的形成年龄为３１４±１９Ｍａ，∑ＲＥＥ约为４．０～７．６μｇ／ｇ。其主体岩石是由来源于未亏损地幔较高程度熔融而产生的岩浆在结晶分异作用中形成。其岩体的边缘［εＮｄ＝－５，（８７Ｓｒ／８６Ｓｒ）＝０．７０５５，∑ＲＥＥ＝１１１．５６μｇ／ｇ］同化了围岩［εＮｄ＝－１６．７，（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７５３７，∑ＲＥＥ＝１９６μｇ／ｇ］，并同时发生结晶作用，经历了ＡＦＣ过程，形成了特有的琼阿鸟孜超基性岩侵入体。     

西南极利文斯顿岛百耳斯半岛中生代火山岩地球化学特征

西南极利文斯顿岛百耳斯半岛中生代火山岩是晚侏罗纪至晚白垩纪三期火山活动的产物。岩石普遍贫钾,轻稀土元素略为富集,但轻重稀土分馏不强烈;Ｓｒ、Ｋ、Ｒｂ、Ｂａ、Ｔｈ等大离子亲石元素（ＬＩＬ）明显富集,Ｎｂ和Ｔａ明显亏损,过渡金属族元素Ｃｒ和Ｎｉ强烈亏损,表明它们属于火山弧环境中生成的钙碱性系列岩石。白垩纪中期和白垩纪晚期岩石的８７Ｓｒ／８６Ｓｒ比值主要在０．７０３９～０．７０５３之间变化,εＮｄ＞０,８７Ｓｒ／８６Ｓｒ相对１／Ｓｒ、Ｒｂ、Ｋ和ＳｉＯ２等的变化不大,表明其源区岩浆可能直接来自上地幔,很少受到壳源物质的混染。而晚侏罗纪火山岩的Ｓｒ同位素比值较高,说明早期岩浆可能受到少量地壳物质的混染。但在Ｔｈ／Ｔａ－Ｔｈ和Ｔｈ／Ｓｍ－Ｔｈ图解上所有岩石的投影点分布趋势相同,趋势线的斜率＞０。百耳斯半岛中生代火山岩是上地幔部分熔融生成的同源岩浆不同期的产物     

RbSr studies of CI and CM chondrites

RbSr whole rock analyses have been performed on 2 CI and 3 CM chondrites. Four of these stones (Ivuna, Orgueil, Cold Bokkeveld and Erakot) were previously studied in this laboratory and were shown to be discordant from a 4.6 Gyr isochron. The fifth, Murchison, was not previously studied. The new data support the discordance of the first four stones, and indicate that Murchison is also discordant. Studies of Sr isotope ratios in unspiked Orgueil show that the discordance is not due to inhomogeneities in the $\text{Sr}{}^{84}\text{Sr}{}^{86}$ ratio caused by incomplete mixing of nucleosynthesis products.In order to gauge the effects of weathering, two leaching experiments were performed on fresh, interior samples of Murchison; one for a period of 1.5 hr and the other for 117 hr. The results indicate that the relative solubility of nonradiogenic Sr is approximately twice that of Rb and radiogenic Sr is more soluble than the nonradiogenic Sr. This gives the residue a lower model age than the whole rock both by increasing the $\text{Rb}\text{Sr}$ ratio and by decreasing the $\text{Sr}{}^{87}\text{Sr}{}^{86}$ ratio. This result is in contrast to that expected from studies of ordinary chondrite finds, which generally show higher model ages than falls. The constancy of $\text{K}\text{Rb}$ and $\text{K}\text{Sr}$ ratios between the two leaching experiments, and their difference from the unaltered whole rock ratios suggest that the bulk ratios are produced by dissolution of a single phase, and the higher radiogenic Sr content by selective leaching of other phases.     

Rb/Sr geochronology in the Eastern Alps

New Rb/Sr data on mineral and whole rock samples from in and around the south-east corner of the Tauern Window are presented. Pennine orthogeneisses yield an Rb/Sr whole rock age of 279±9 m.y., while orthogneiss samples from the Altkristallin Sheet near Innerkrems, Carinthia, yield an age of 381±30 m.y. by the same technique. The apparent mineral age break across the margins of the Tauern Window is investigated in an area of good structural and petrofabric control. The post-Palaeozoic history of the Eastern Alps is then discussed in the context of the available Rb/Sr data. It is argued that the bulk of the Katschberg Phyllites are of pre-Mesozoic age; that the major overthrusting movements of the Austroalpine Units were completed by 60–65 m.y.; and that the Peri-Adriatic intrusives can be little older than middle Tertiary.     

The relation between Rb,Ba and Sr in granitic rocks

The ternary relation between the elements Rb, Ba and Sr in granitoid rocks is discussed. This relation proved to be useful in tracing differentiation trends in acidic suites. Moreover, it has a potentiality for being used as a criterion in genetic problems of granites, i.e. in distinguishing magmatic from metasomatic or granitized granites. The averages of these three elements in the various types of granites are calculated. The Turekian and Wedepohl (1961) two-fold subdivision of granites into high- and low-Ca rocks is elaborated so as to comprise four distinctive types: quartz diorites and granodiorites, normal granites, strongly differentiated granites beside the group of anomalous granites.     

闪锌矿铷 锶同位素等时线讨论

通过对闪锌矿铷锶同位素等时线形成机制的讨论,若为同源、同期、待测同位素封闭的体系,因混合形成的直线为等时线具有定年意义,但若非同源、非同期或非封闭的体系亦可因混合形成直线,但该直线为无年代学意义的混合线。作为铷锶同位素定年矿物,闪锌矿可能仅充当“容器”的角色,因此利用闪锌矿进行定年时,必须进行细致的物相研究。闪锌矿中的碳酸盐、硅酸盐等矿物微粒可能对铷锶定年产生极大的影响,如不能对其进行成因鉴别或配合其他同位素定年方法加以系统研究,闪锌矿铷锶法直线拟合结果很难反映成矿时间。     

Rb and Sr partitioning between haplogranitic melts and aqueous solutions

Rubidium and strontium partitioning experiments between haplogranitic melts and aqueous fluids (water or 1.16-3.56 m (NaCl + KCl) ± HCl) were conducted at 750-950 °C and 0.2-1.4 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. In addition, we studied if the applied technique (rapid and slow quench, and in-situ determination of trace element concentration in the fluid) has a bearing on the obtained data. There is good agreement of the data from different techniques for chloridic solutions, whereas back reactions between fluid and melt upon cooling have a significant effect on results from the experiments with water.The Rb fluid-melt partition coefficient shows no recognizable dependence on melt composition and temperature.For chloridic solutions, it is ∼0.4, independent of pressure. In experiments with water, it is one to two orders of magnitude lower and increases with pressure. The strontium fluid-melt partition coefficient does not depend on temperature. It increases slightly with pressure in Cl free experiments. In chloridic fluids, there is a sharp increase in the Sr partition coefficient with the alumina saturation index (ASI) from 0.003 at an ASI of 0.8 to a maximum of 0.3 at an ASI of 1.05. At higher ASI, it decreases slightly to 0.2 at an ASI of 1.6. It is one to two orders of magnitude higher in chloridic fluids compared to those found in H₂O experiments. The Rb/Sr ratio in non-chloridic solutions in equilibrium with metaluminous melts increases with pressure, whereas the Rb/Sr ratio in chloridic fluids is independent of pressure and decreases with fluid salinity.The obtained fluid-melt partition coefficients are in good agreement with data from natural cogenetic fluid and melt inclusions. Numerical modeling shows that although the Rb/Sr ratio in the residual melt is particularly sensitive to the degree of fractional crystallization, exsolution of a fluid phase, and associated fluid-melt partitioning is not a significant factor controlling Rb and Sr concentrations in the residual melt during crystallization of most granitoids.     

流体包裹体RbSr等时线定年的可靠性

通过对Rb-Sr等时线原理应用的必要条件及流体包裹体样品的成因特点的分析，认为是否可以用流体包裹体Rb-Sr定年在理论上尚需解决以下问题：（1）因矿物中常有不同期次、不同成因的流体包裹体存在，必须保证所选择的各流体包裹体样品具有相同的初始Sr同位素比值；（2）流体包裹中Rb与Sr的分异机理以及分异程度问题，即流体中Rb与Sr之间是否存在分异和分异程度是否可以达到Sr同位素分析的精度分析。已有的流体包裹体的Rb-Sr等时线年龄研究资料和数据的分析检验结果普遍存在以下问题：等时线图上数据点分散；拟合年龄较老；等时线拟合品质参数的MSWD偏大，可靠性低。     

Rb−Sr age of Gaik granite,Ladakh batholith,northwest Himalaya

The Gaik Granite is a part of the Ladakh batholith outcropping between Gaik and Kiari in NW Himalaya. This is a pink porphyritic granite rich in biotite and poor in hornblende. Rb-Sr analyses have been made on six whole-rock samples of the Gaik Granite. Though the samples are poorly enriched in radiogenic Sr, they define a reliable isochron corresponding to an age of 235±13 (2σ) m.y. and initial⁸⁷Sr/⁸⁶Sr ratio of 0·7081±0·0004 (2σ). Biotite, plagioclase and potash feldspar fractions separated from two of the samples have yielded a much younger mineral isochron at 30±1·5 m.y. indicating a nearly complete redistribution of Sr isotopes between mineral phases at a time much later than the primary emplacement of the granite. The present results show that at least some components of the Ladakh batholith are of Permo-Triassic age. These rocks were isotopically re-equilibrated on a mineral scale during Upper Oligocene in response to the Himalayan orogeny.     

Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate

Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain-size fractions and chemical forms. Results show that Rb is quite rich in the fraction of less than 2μm, and exits only in the residual phase, while Sr is distributed in sand and silt fractions, occurring in the residual and carbonate phases. Therefore, variations of the concentrations of Rb and Sr in loess and palaeosols are closely related not only to dustfall compositions depending on winter monsoon wind strength but also to summer monsoon-induced pedogenic intensity. This indicates that variations of Rb/Sr ratio in Chinese loess sequences represent cyclic alternations of East Asian summer and winter monsoon climates on the orbital time-scale. Variations in Sr concentrations along the sequence bear a high similarity to the oxygen isotope record of the deep sea sediments over the past 2.5 Ma, whereas variations in Rb concentrations are in good agreement with the record of     

Clinopyroxene-matrix partitioning of K,Rb, Cs,Sr and Ba

Extremely pure samples of clinopyroxene phenocrysts from two volcanic rocks have been analyzed for K, Rb, Cs, Sr and Ba. In conjunction with matrix concentrations, partition coefficients are obtained which are in the range 0.001–0.004 for K, Rb, Cs and Ba. These values are lower than those in the literature by factors of 6–100 but are in good agreement with values determined experimentally at pressures of 15–30 kb by Shimizu (Geochim. Cosmochim. Acta38, 1974). Values for partition coefficients measured on separates of impure or cloudy pyroxenes from these same rocks were higher and similar to those in the literature. We suggest this effect is related to ‘trapping,’ during crystal growth, of liquid which is enriched in the larger ions (such as Rb and Cs) due to lack of diffusion equilibrium in the liquid. Partition coefficient values for olivine and plagioclase from one of these same rocks were also determined.     

K-A and RbSr geochronology and Sr isotopic study of the Alnö alkaline complex,northeastern Sweden

K-A ages from a variety of alkaline rocks, carbonatites (sövites) and alnöites from the Alnö complex range between 370 and 605 m.y. but the most meaningful ages concentrate between 546 and 578 m.y. Most nephelinites, phonolites and alkali trachytes that occur in a dike complex surrounding the main intrusion give a middle Cambrian RbSr whole-rock isochron age of 553±6 m.y. (2σ). Some samples (deleted from the age regression) were contaminated by radiogenic strontium. Plutonic pyroxenites, ijolites and nepheline syenites that form most of the core of the intrusion formed at about the same time and from the same parental magma as the dike rocks. Sövites and alnöites that crosscut the dike and core rocks did not intrude significantly later and may have formed from the same parent magma or mantle source. Many samples show evidence of either mixing or isotopic exchange of the magma with the country rocks during intrusion (fenitisation?) or open system behavior after crystallization. These processes resulted in some scatter of the data points about the best-fit RbSr isochron lines and in some anomalous K-A ages. Fenites have higher Rb/Sr and ⁸⁷Sr/⁸⁶Sr ratios than the alkaline rocks, making it unlikely that the latter were the remobilized products of extreme fenitization, as suggested by von Eckermann (1948). The Alnö intrusion is about the same age as the Fen complex of southern Norway, but is significantly older or younger than many other apparently similar intrusions in Scandinavia.