Implications of εNd—La／Nb,Ba／Nb,Nb／Th Diagrams to Mantle Heterogeneity—Classification of Island—arc Basalts and Decomposition of EMII Component

A group of εNd/Nb,Ba/Nb,Nb/Th diagrams are used to study mantle heterogeneity.Island-arc basalts(IAB) are distributed in a triangle of these diagrams. Three end-member components (the MORB-type depleted mantle, the fluid released from subducted oceanic crust and the sediments from the continental crust) of the source of IAB may be displayed in these diagrams. Two types of IAB are identified .They are of the two-component type (with little continental sediments), such as the basalts from Aletians and New Britain ,and the three-compeonent type, such as those from Sunda, Lesser Antilles and Andes. In addition ,the EMII type mantle-derived rocks may also be divided into two groups. One is exemplified by continental flood basalts and some peridotite xenoliths, similar to IAB, with high La/Nb and Ba/Nb and low Nb/Th ratios, The other includes the Samoa-type oceanic island basalts, with low La/Nb and Ba/Nb and high Nb/Th ratios. The corresponding two sub-components of EMII are EMIIM, which is related to the metasomatism of lithosphere mantle by fluids released from the subducted oceanic crust, and EMIISR, related to the intervention of recycling continental sediments into the convective mantle.     

白云鄂博矿区磷灰石氧同位素研究

通过新建立的BiPO4转化法，笔者分析了白云鄂博矿区部分磷灰石的氧同位素组成，其变化范围为6．3‰～9．4‰，并通过与各种产状磷灰石及不同时代磷酸盐沉积的氧同位素对比、磷灰石形成温度的计算，以及磷灰石Sr－Pb同位素数据的分析，推断矿区磷灰石的形成可能与热水沉积作用有关。     

安徽省泮汤温泉研究

通过对泮汤地区地质、水文地质调查、地温测量、物探测量研究,对该区地下热水赋存的水文地质条件、控水构造等提出初步的认识。     

大别山造山带核部九资河-天堂寨花岗岩的成因和时代

近十余年来,众多国内外著名学者、专家对大别山造山带进行了深入研究,一些长期争论不休的问题逐渐取得了一致意见。如大别山造山带是华北地块与扬子地块于印支期陆—陆碰撞的产物［１～３］,但是,仍有相当多的重大地质问题还未取得共识。如伴随造山带形成的“天堂寨混...     

长江中下游晚中生代中基性岩的铅同位素特征:富集地幔的证据

长江中下游东段庐枞、怀宁、繁昌、铜陵和宁芜地区的中基性岩属于碱性系列 ,具有高的U ,Th含量和Th/Pb ,U/Pb比值 ,分别平均为 2 .82× 10 -6,9.5 6× 10 -6和 0 .6 35 ,0 .184。样品的初始铅同位素 (130Ma)组成为 :(2 0 6Pb/ 2 0 4Pb) i=17.6 5～ 18.6 0 ,(2 0 7Pb/ 2 0 4Pb) i=15 .4 2～ 15 .5 0 ,(2 0 8Pb/ 2 0 4Pb) i=37.6 7～ 38.0 4。形成中基性岩的原始岩浆来源于富集的岩石圈地幔 ,具有EMⅠ和EMⅡ ,且以EMⅡ为主的特征。和长江中下游西段黄石地区以及大别地块西南部玄武岩的比较表明 ,长江中下游地区岩石圈地幔高的Th/Pb和U/Pb比值可能和俯冲板片析出流体的交代有关。晚中生代时期 ,华北板块岩石圈地幔以EMⅠ特征为主 ,华南板块岩石圈地幔以EMⅡ特征为主 ,岩石圈地幔性质的区域性分布与印支期扬子板块深俯冲事件密切相关。虽然中国东部新生代玄武岩因岩石圈大规模减薄表现了亏损特征 ,但残留的富集岩石圈地幔在中国东部新生代玄武岩的Pb同位素中仍有所反映     

An Experimental Calibration on the Sphalerite-Galena Sulfur Isotope Geothermometer

A new experimental calibration was undertaken in this study to get a more reliable sphalerite-galena sulfur isotope geothermometer. The experimental conditions selected in study were very similar to those of natural hydrothermal solution. The high-precision SF6 method was used in sulfur isotope analyses. The obtained calibration curve for sulfur isotope fractionation between sphalerite and galena can be expressed with the equation 10001nαSp-Gn= 0.74×106T-2+0.08.     

北京市泉水的水化学、同位素特征及其指示作用

对北京市泉水的水温、溶解氧、电导率、氧化还原电位、pH值、总溶解固体等进行了现场检测,对泉水中的K+、Na+、Ca2+、Mg2+、Cl-、SO42-、HCO32-、NO3-离子,D、18O组成和Sr、87Sr/86Sr比值等进行了实验室检测,对泉水按成因进行了分类,并与30年前的泉水普查资料作了对比。调查表明,曾以泉多著称的北京市,1980s初存在的几乎全部二类泉和60%的一类泉如今已消失,仅存的13眼泉的出水量也明显减小,这与降水量的减少和大规模开采地下水有关。水质分析表明,现在绝大部分泉水水质良好,物理和水化学指标与30年前相比变化甚微,明显没有受人类活动的污染;泉水仅在浅部循环,在地下滞留时间较短,更新能力强;泉水接受大气降水补给,与浅层地下水联系密切,构成了统一的地下水系统;泉水中的Sr为碳酸盐岩风化来源。     

The Impact of Aqueous Medium on Gas Yields and Kinetic Behaviors of Hydrogen Isotope Fractionation during Organic Matter Thermal Degradation

In order to recognize the impact of aqueous medium on gas yields and the kinetic behaviors of hydrogen isotope fractionation during organic matter thermal degradation, the gold tube apparatus was used to conduct thermal simulation experiments by mixing the nC18 with the water of different properties and proportions. The yields of natural gas components, the relation among hydrogen isotope composition of each component and the experimental temperatures vs. heating rates have been obtained, and the results indicate that under the higher temperature conditions, the hydrous experiment has obvious impact on gas yields, such as when more water is added, higher amounts of hydrocarbon gas and H2 are yielded, and the existence of water obviously prolongs the temperature interval with the existence of heavy hydrocarbon gas. It also shows that the hydrogen isotope of hydrocarbon gas generated by the hydrous experiment is obviously lighter than that generated by the anhydrous experiment, and with the increasing amount of added water, the δD value of hydrocarbon gas gradually decreases. Compared with gas yields, the variation of δD value is more sensitive to aqueous medium in the thermal simulation experiment. However, compared with the amount of the added water, the aqueous medium property has smaller impact on the gas yields, which still shows the inherit effect on hydrogen isotope composition of aqueous medium. Through the model simulation and the isotope fractionation behavior analysis, it is validated that the hydrogen isotope fractionation process can be well described by the chemical kinetic model. The difference of reaction fraction of normal methane and D-containing methane is large, corresponding to the same activation energy. The content of normal methane is obviously higher in the part with lower activation energy, while the content of D-containing methane is higher in the part with higher activation energy. Therefore, it will result in larger hydrogen isotope fractionation amplitude, and the δD values will be more sensitive to the variation of maturity. Meanwhile, the average activation energy of methane generation from nC18 in the hydrous experiment is higher than that in the anhydrous experiment, and the greater amount of added water, the larger the average activation energy of methane generation reaction. This has laid foundation for its exploratory application in the study of gas reservoir forming history and the gas-source correlation, which indicates the research and application prospects in this orientation.     

中更新世气候转型期南海北部和南部的气候变化差异

选取大洋钻探ODP184航次在南海北部采集的1144站为研究材料,通过分析中更新世0.4～1.4Ma期间506个样品中浮游有孔虫氧、碳稳定同位素的变化特征,并与南海南部ODP 1143站和西太平洋暖池ODP 807站的同位素资料进行比较,发现南海北部的氧、碳稳定同位素及其差值的变化响应中更新世气候转型事件,在中更新世距今约0.9Ma之后100ka的偏心率周期明显增强。在中更新世气候转型之前,南海北部、南海南部和赤道西太平洋都呈现出典型的热带气候特征,具有岁差和半岁差的气候周期;转型之后,随着北半球冰盖的进一步扩张,南海北部受东亚冬季风增强的影响而导致温度下降、温跃层变深,但南海南部与赤道西太平洋的温度变化较小且温跃层变浅,说明同属季风区的南海北部和南部对气候变化的响应有所不同。     

金红石U-Pb同位素稀释法定年技术的改进

介绍了金红石U-Pb定年方法,并对影响本底的各方面因素、同位素分馏效应、干扰峰影响等环节做了分析和讨论,提出了相关的流程改进措施,并利用改进的方法对大别山超高压榴辉岩中的金红石做了测定,获得了218.2±1.2 Ma的高精度金红石UPb年龄.