四川大陆槽稀土矿床碳酸岩-英碱正长岩锆石U-Pb年代学和Hf同位素性质及其地质意义

川西冕宁-德昌稀土成矿带是中国最重要的稀土成矿带之一,所有稀土矿床均与碳酸岩-正长岩杂岩体有关.前人研究表明,牦牛坪、木落寨和里庄碳酸岩-碱性杂岩体成岩年龄与其相应矿床的成矿年龄基本一致,而大陆槽正长岩年龄与REE矿床的成矿年龄相差甚远.本文对大陆槽碳酸岩、英碱正长岩进行了SHRIMP U-Pb锆石年代学和LA-MC-ICPMS锆石Hf同位素原位测量,它们的形成年龄分别为12.99±0.94Ma、14.53±0.31Ma,表明两者是同时形成的,且与其成矿年龄基本一致.碳酸岩和正长岩的εHf(t)值、Hf模式年龄与它们的εNd(t)值、Nd模式年龄所展现出来的特征一致,说明在其形成过程中有地壳物质的加入.     

中祁连东段什川杂岩基的岩石化学特征及年代学研究

祁连造山带被托菜南山-了高山构造带及宗务隆山-贵得构造带分为北祁连、中祁连及南祁连构造带。什川岩基位于中祁连构造带东部,由闪长岩、斜长花岗岩、二长花岗岩组成;对二长花岗岩进行U-Pb单颗粒锆石微区LA-ICP-MS同位素测定,获得444.6Ma及414.3Ma两组加权平均年龄,前者代表岩石的形成年龄,后者代表构造热事件年龄。二长花岗岩主量元素W(SiO_2)=68.66%～80.77%,w(K_2O)/w(Na_2O)>1和A/CNK介于0.95～1.21间,总体为钾质钙碱性过铝质花岗岩。岩石富集LILE元素(K、Th、Rb、Ba等),亏损HFSE元素(Ta、Nb、Y等);稀土元素总量较高(∑REE多介于109.05×10~(-6)～322.66×10~(-6)),轻重稀土强烈分馏(∑LREE/∑HREE介于7.92～31.68),稀土元素分配模式为轻稀土富集型,具中等-强Eu负异常(δEu=0.26～0.58)。岩石矿物组合及岩石地球化学特征共同表明,什川岩基为中上地壳泥砂质岩石部分熔融而成,形成温度较低,为加厚地壳拆沉熔融成因。这为祁连造山带构造演化及其深部动力学机制研究提供了新的资料。     

滇西点苍山—哀牢山变质岩系锆石SHRIMP定年及其地质意义

滇西点苍山和哀牢山主体分别由下元古界苍山群和哀牢山群深变质岩系组成,被认为是前寒武纪结晶基底。选取点苍山的花岗闪长质糜棱岩(DCS-1)和哀牢山元江段黑云母花岗闪长质片麻岩(SM07-1)之中的锆石进行U-Pb SHRIMP定年。样品DCS-1和SM07-1测年结果分别为233±2.6Ma和239.8±2.8Ma。结合前人对滇西地区花岗质岩类所做的研究,揭示滇西地区在三叠纪经历一期在空间上广泛分布的岩浆事件,点苍山花岗质糜棱岩和哀牢山花岗质片麻岩的原岩为三叠纪侵位的花岗岩,其构造环境属于大陆裂谷,反映了滇西地区在三叠纪地壳物质的重新调整,而该变质岩系不是前寒武纪的结晶基底,其变质作用与山体出露地表过程和新生代构造作用有关。     

西藏普兰地区拉昂错蛇绿岩中辉绿岩的锆石SHRIMP U—Pb年龄及其地质意义

蛇绿岩中的辉绿岩岩墙是洋脊扩张的产物．其形成年龄代表了扩张事件的时间,也代表了蛇绿岩的形成时代？对雅鲁藏布江缝合带西段拉昂错蛇绿岩中的辉绿岩岩墙进行锆石SHRIMPU—Pb定年,得出加权平均年龄为120．2Ma±2．3Ma,代表辉绿岩的结晶年龄。结合已有的关于雅鲁藏布江蛇绿岩的形成年龄（西段休古嘎布122．3Ma±2．4Ma,中段大竹卡126．0Ma±1．5Ma、吉定123．0Ma＋_1．8Ma,东段罗布莎162．9Ma±2．8Ma）的报道,表明拉昂错地区特提斯洋海底扩张的时代与体古嘎布地区一致．雅鲁藏布江西段与中段地区洋盆的形成时代一致,但晚于东段的发育时代。这意味着整个东提斯洋盆的发育时代存在东早西晚的特点。     

Spatial variability in the primary productivity in the East China Sea and its adjacent waters

Primary productivity in the East China Sea and its adjacent area was measured by the¹³C tracer method during winter, summer and fall in 1993 and 1994. The depth-integrated primary productivity in the Kuroshio Current ranged from 220 to 350 mgC m⁻²d⁻¹, and showed little seasonal variability. High primary productivity (above 570 mgC m⁻²d⁻¹) was measured at the center of the continental shelf throughout the observation period. The productivity at the station nearest to the Changjiang estuary exhibited a distinctive seasonal change from 68 to 1,500 mgC m⁻²d⁻¹. Depth-integrated primary productivity was 2.7 times higher in the shelf area than the rates at the Kuroshio Current. High chlorophyll-a specific productivity (mgC mgChl.-a⁻²d⁻¹) throughout the euphotic zone was mainly found in the shelf area rather than off-shelf area, probably due to higher nutrient availability and higher activity of phytoplankton at the subsurface layer in the shelf area.     

用铀系定年法测定南永1井珊瑚礁年龄

运用铀系定年法首次对南水1井珊瑚礁岩心中的两个层位进行测年,结果与~(14)C测年一致,证实在晚更新世与全新世之间存在沉积间断面。     

渤海湾沿岸泥炭沼泽形成机制与时空分布

渤海湾沿岸的海陆过渡带，优越的水文地理环境有利于泥炭沼泽的形成与发育。海洋海退导致的海岸线变迁，是控制泥炭沼泽发育时间和空间分布的主导因素。间冰期和冰后期的海面上升期间，自海向陆发育了海侵基底泥炭；中全新世高海面期，在山前扇缘洼地和沟谷有泥炭沼泽发育；晚全新世海面下降期，泥炭沼泽主要发育在沿岸的海湾、泻湖、三角洲汊河间洼地及平原上的河滩、阶地、古河道等地。     

Seasonal Variations in Benthic Community Metabolism and Nitrogen Dynamics in a Shallow, Organic-Poor Danish Lagoon

The dynamics of benthic primary production and community respiration in a shallow oligotrophic, marine lagoon (Fællestrand, Denmark) was followed for 1·5 years. The shape of the annual primary production cycle was explained primarily by seasonal changes in temperature (r² = 0·67-0·72) and daylength (r² = 0·63), whereas temperature almost explained all variation in benthic community respiration (r² = 0·83-0·87). On a daily basis the benthic system was autotrophic during spring and summer supplied by 'new' and 'regenerated' nitrogen and predominantly heterotrophic during fall and winter caused by light and nutrient limitation. The linear depth-relationship between porewater alkalinity and ammonium indicated that the C:N ratio of mineralized organic matter is low in spring and summer (3-6) and high in fall and winter (9-16). This is inversely related to net primary production and thus the input of labile, nitrogen-rich algal cells. Accordingly, mineralization occurred predominantly in the upper 2-5 cm of the sediment. The pool of reactive material (microalgal cells) was estimated to account for 12% of total organic carbon in the upper 3 cm, and had an average turnover time of less than 1 month in summer. Assimilation of organic carbon by benthic animals was equivalent to about 30% of the annual gross primary production. Grazing reduced chlorophyll a concentration in the sediment during summer and spring to values 30-40% lower than in winter, but maintained a 3-4 times higher specific microalgal productivity. The rapid turnover of organic carbon and nitrogen, and important role of benthic microalgae showed that the benthic community in this oligotrophic lagoon is of a very dynamic nature.     

海洋沉积样品~(14)C测年差异来源及其结果解释

~(14)C测年已为海洋研究工作广泛应用,但由于时有不合理取样或在运用数据时没有充分考虑各种海洋环境和动力因素,因而产生无法使用数据作合理解释的现象。本文试从海洋样品本身和海洋各种营力作用分析各种数据差异的来源,认为海洋环境特别是海岸带环境的复杂性是造成海洋样品~(14)C测年数据差异的主要原因,它可能影响样品的代表性或使数据解释时得出错误结论.并指出在运用年代结果时一定要充分考虑地质地理和各种营力作用因素。     

C网格嵌套技术及其在海洋波动传播模拟中的应用

采用粗细嵌套的ArakawaC网格模拟Klevin波和Rossby波沿赤道传播的过程，研究在粗细网格嵌套边界产生数值振荡和反射的原因及其消减方法，得到合理的并能用于复杂海洋模式的ArakawaC网格下的嵌套方案。数值实验结果表明：波形在粗细网格边界产生数值振荡的原因是波形在不同分辨率下的形态有差异，在粗网格下波形趋向于平坦化，而细网格下趋向于锐化。采用双向嵌套和粗细网格交界处加松弛的方法可以有效地消减数值振荡和反射。