990 resultados para 338.064


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华南大陆从印支期进入陆内活化阶段,形成一系列沿断裂分布的印支期花岗岩。该期花岗岩代表陆内活化期的开发,在岩石地球化学和形成构造环境上以及岩石的形成方式上都与该期以后的花岗质岩石存在一定的差异。表明华南中生代陆内活化构造环境的复杂性和多阶段性。本文以湘东北印支期花岗质侵入岩为例,分析其成岩构造环境,用以反映该区陆内开始活化时的构造环境和活化方式。湘东北印支期花岗质岩石以花岗闪长岩-二长花岗岩岩石系列为主,以相对较低的SiO2、K2O和较高的TiO2、P2O5及负铕异常不明显区别于中生代其它侵入期次岩石,具有陆壳重熔型花岗岩特征,其形成为陆内俯冲导致陆壳物质在俯冲前缘重熔的结果,表明陆内俯冲作用是导致湘东北陆内开始活化的主要方式之一,其构造环境以逆冲式推覆挤压为主。

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The sedimentary-volcanic tuff (locally called "green-bean rock") formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements ( REE), as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.

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自然界锂同位素分馏强烈,这使得它在很多方面都得到了应用,如地球化学、天体化学和核工业等。所有这些领域都要求精确的测定6Li/7Li的比值。但由于锂是微量元素,而且在测试过程中还存在明显的干扰,因此在进行锂同位素比值测定之前必须对样品进行分离和富集。本文以锂元素标准样品和钾、钠、钙、镁元素标准样品的混合溶液为主要研究对象,采用阳离子交换树脂AG-50W-X8来分离富集锂,探索在不同淋洗介质条件下锂分离纯化的最佳介质条件。初步得出以下结论: 1、本次研究建立了相对简单、高效的锂同位素分离方法。用单一的柱子分离、提纯样品锂;用低浓度的盐酸(0.15M HCl)直接作为淋洗介质,操作过程简单。 2、对锂同位素比值测定产生潜在影响因素,如基体效应、回收率、流程空白等进行了实验研究,证实这些影响因素对于本次研究所建立的方法来说都是可以忽略不计的。 3、用MC-ICP-MS测定样品的锂同位素组成,分析结果的准确度和精度与现阶段所报道数据相同。测定海水的锂同位素组成(+31.6±1.0‰,2σ)与Tomoscak 等(+31.8±1.9‰,2σ)的分析值相近。 4、该方法也适用于低含量的样品。我们分离并测定了不同类型样品的锂同位素组成,样品锂含量在0.064µg/g和132µg/g之间,说明该方法也同样适用于低含量地质样品的分析测定。

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地球动力学与成矿关系的研究是地球科学研究的前沿领域,而陆内岩石圈伸展与成矿的关系的研究则是该领域相对比较薄弱的环节。 华南地区于白垩—古近纪发生了岩石圈强烈的伸展减薄事件,且岩石圈伸展减薄与该区同时期形成的众多金属和非金属矿床有密切的成因联系,尤其是华南地区的花岗岩型热液铀矿床,显示了与该区岩石圈伸展作用可能有多方面的成因联系。粤北下庄铀矿田位于位于南岭铀-多金属成矿带的南部,是华南地区典型的花岗岩型热液铀矿区,本次研究在深入细致的野外地质工作的基础上,运用流体包裹体地球化学、元素地球化学、同位素地球化学等方法手段,开展了对下庄铀矿田成矿流体性质、成矿过程中元素的活动规律、成矿流体来源及演化等方面的系统研究,初步探讨了岩石圈伸展对该区铀成矿的制约机制,并建立了可能的矿床成因模式。通过研究,本次工作获得了以下几点主要认识: (1)通过对下庄铀矿田部分铀矿床流体包裹体显微测温、激光拉曼光谱及液相成分分析研究,查明了下庄矿田铀矿床矿前期热液属中高温(200℃~350℃)、低盐度(0.72%~5.95%NaCl)、密度中等(0.703~0.830g/cm3)、活动深度较深(2.29km~5.74km)、富∑CO2、相对还原性质的流体;成矿期热液属中低温(主要为154℃ ~250℃)、低盐度(0~1.83%NaCl)、密度中等(0.628~0.867g/cm3)、活动深度较浅(0.19km~1.62km)、富F-、相对氧化性质的流体。 (2)矿石矿矿物电子探针测试分析及岩、矿石的微量元素地球化学分析研研究表明,本区铀矿床主要的原生铀矿物为沥青铀矿、铀石、钛铀矿,铀矿物的形成与Si、Ca、W等元素有密切的关系,而其它金属元素未显示明显地富集。矿石、脉石矿物部分继承了原岩的稀土元素组成,且在原岩基础上又有高度的演化。 (3)进行了矿区内碳酸盐的C、O同位素和黄铁矿的He、Ar稀有气体同位素的分析研究。研究表明,矿化剂∑CO2主要为幔源,大量的He、Ar等稀有气体也来自于地幔。矿区发育的深大断裂构造可能控制了幔源挥发份的加入。 (4)脉石矿物碳酸盐和萤石的Sr、Nd同位素地球化学研究显示,成矿流体中的这些元素主要源于地壳,南区矿床(338、339)的Sr、Nd组成则为富含壳源Sr、Nd的流体与幔源基性脉岩不同程度的水—岩反应所致。另外,碳酸盐铅同位素研究显示,下庄矿区成矿物质铀可能来自帽峰式后期流体交代的花岗岩体。 (5)岩石圈伸展与下庄矿田铀成矿有关系密切:下庄矿田铀矿床明显受伸展构造控制,伸展构造既为导矿构造,又为储矿构造;岩石圈伸展导致的地温梯度升高,大地热流平均值加大,驱动热液流体的流动,为铀成矿提供了主要的热驱动力;岩石圈伸展产生的深大断裂导通了壳幔间的联系,使幔源脱气成因挥发份(主要为∑CO2)沿断裂上升,加入壳源热水循环系统,从而参与了铀成矿。 (6)初步建立了下庄矿田“岩石圈伸展体系下大陆热水系统铀矿床成因模式”。模式认为,华南地区白垩—古近纪岩石圈伸展作用引发区内热水流体的大规模循环,且伸展引起的幔源脱气作用产生的挥发份(主要为ΣCO2)加入了贫铀、贫矿化剂的循环的地下热水中,形成了富矿化剂热水。富矿化剂热水从富铀花岗岩中浸出铀(氧化作用),变为富矿化剂、富铀热液流体,这种热液流体在伸展引起的热驱动下沿构造上升,热液流体上升到浅部时,由于地球化学障、流体压力释放等因素的影响,U被还原沉淀,并在有利部位富集成矿。

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The aim of the present study was to assess the factors which may influence the timing of the introduction of solid food to infants. The design was a prospective cohort study by interview and postal questionnaire. Primiparous women (n 541) aged between 16 and 40 years were approached in the Forth Park Maternity Hospital, Fife, Scotland. Of these, 526 women agreed to participate and seventy-eight were used as subjects in the pilot study. At 12 weeks we interviewed 338 women of the study sample. The postal questionnaire was returned by 286 of 448 volunteers. At 12 weeks 133 of 338 mothers said that they had introduced solids. Those that said that they had introduced solids early (<12 weeks) were compared with those who had introduced solids late (>12 weeks) by bivariate and multiple regression analysis. Psychosocial factors influencing the decision were measured with the main outcome measure being the time of introduction of solid food. The early introduction of solids was found to be associated with: the opinions of the infant's maternal grandmother; living in a deprived area; personal disagreement with the advice to wait until the baby was 4 months; lack of encouragement from friends to wait until the baby was 4 months; being in receipt of free samples of manufactured food. Answers to open-ended questions indicated that the early introduction appeared to be influenced by the mothers’ perceptions of the baby's needs. Some of the factors influencing a woman's decision to introduce solids are amenable to change, and these could be targeted in educational interventions.

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Burnley, M, Doust, J and Jones, A (2005) Effects of Prior Warm-up Regime on Severe-Intensity Cycling Performance. Medicine and Science in Sports and Exercise, 37 (5). pp. 838-845. ISSN 1530-0315 RAE2008

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Burnley, M., Doust, J. and Jones, A. (2006). Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise. Journal of Applied Physiology. 101(5), pp.1320-1327 RAE2008

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En Tomo V. 2 h. de grabados calcográficos representando monedas de Huesca.

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18 fotografías a color.