A Thickness Gauge for the Lithosphere Based on Ce/Yb and Sm/Yb of Mantle–Derived Magmatic Rocks

A new method for determining the partial melting depth of mantle-derived magma and lithospheric thickness in continental regions is derived from REE geochemistry. This effective technique uses variations in the Ce/Yb and Sm/Yb ratios found in mainly volcanic rocks in continental China. The ratios change with the depth of origin consistent with the correlation between lithospheric thickness and the Ce/Yb and Sm/Yb ratios found in oceanic basalt. These ratios increase exponentially with the depth of origin, the lithospheric thickness, of a wide variety of Cenozoic volcanic basalt and Paleozoic kimberlite in the North China Craton, northeastern China continent and vicinity. This functional relationship with depth is shown in a plot of the ratios that forms a concordia curve, which is closely expressed by formulas using 8–degree polynomials. These provide a more accurate gage in measuring the lithospheric thickness than the traditional geophysical methods. When applied to volcanic rock of different ages it also reveals how the thickness has changed over time and thus, greatly aids the understanding of the tectonic history. Relations between the CO_2 content, mineral reactions and pressure in the upper asthenosphere beneath the base of the lithosphere appears to affect the proportions of REE in partial melts and brings about a close correlation between lithospheric thickness and the Ce/Yb and Sm/Yb ratios in mantle–derived magmatic rock. This thickness gauge, for both continental and oceanic lithosphere, provides a new approach in analyzing the lithospheric thickness in different tectonic settings and geologic times.

基于合作能量传递的Sm^(2+)离子上转换发光

报道了Sm^(2+)离子的上转换发光。在实验上证明了变价镧系离子同样可以作为上转换材料的发光中心。在近红外光的激发下,复合Ba FCl_(0.5)Br_(0.5)∶1%Sm^(2+)-Ca F_2∶1%Yb^(3+)化合物发出红色上转换发光。上转换发射光谱中位于631,644,665,689,704,729 nm的特征发射分别来自于样品中Sm^(2+)的~5D_i(i=0,1)→~7F_j(j=0,1,2)特征跃迁。根据动力学分析及光子数拟合的结果,我们将二价Sm离子的上转换过程归因于合作能量传递,即:两个同时被激发的Yb^(3+)离子合作将能量传递给一个Sm^(2+)离子。

Low-temperature heat capacities and thermodynamic properties of rare-earth triisothiocyanate hydrates (Ⅲ)——Sm(NCS)_3·6H_2O,Gd(NCS)_3·6H_2O,Yb(NCS)_3·6H_2O and Y(NCS)_3·6H_2O

The heat capacities of four RE isothiocyanate hydrates,Sm( NCS)3 6H2O,Gd( NCS)3 6H2O,Yb(NCS)3 6H2O and Y( NCS)3 6H2O,have been measured from 13 to 300 K with a fully-automated adiabatic calorimeter No obvious thermal anomaly was observed for the above-mentioned compounds in the experimental tem-peiatnre ranges.The polynomial equations for calculating the heat capacities of the four compounds in the range of 13-300K were obtained by the least-squares fitting based on the experimental Cp data.The Cp values below 13 K were estimated by using the Debye-Einstem heat capacity functions.The standard molar thermodynamic functions were calculated from 0 to 300 K.Gibbs energies of formation were also calculated.

微波消解-电感耦合等离子体质谱法(ICP-MS)测定蛇床子中16种稀土元素

目的:建立电感耦合等离子体质谱法(ICP-MS)同时测定蛇床子中16种稀土元素(钪、钇、镧、铈、镨、钕、钐、铕、钆、铽、镝、钬、铒、铥、镱、镥)的含量。方法:蛇床子(12批)经微波消解后采用ICP-MS测定,射频功率为1 300 W,采样深度为6.8 mm,辅助气、等离子体气和载气流速分别为1.0、16.0和1.17 L·min^(-1),雾化室温度为2℃;通过在线加入内标铼(Re)和铑(Rh)元素的方法来校正基质效应和干扰。结果:各元素在各自检测质量浓度范围内线性关系良好(r均不低于0.999 3),检出限为0.03~0.32μg·kg^(-1),回收率为90.1%~105.7%,重复性RSD值为0.9%~3.1%。不同产地的蛇床子中各元素含量差别较大。结论:经方法学验证,本法可用于蛇床子中16种稀土元素的检测,为其质量控制提供参考依据。

西秦岭中生代花岗岩类岩浆作用及成矿

西秦岭是我国重要的有色金属和贵金属成矿省。本文论述了该地区主要矿床的空间分布特点；分析讨论了主要成矿带和矿集区中的矿化组合及其与花岗岩类的空间、时间和成因关系。提出该地区大规模成矿作用出现在220-100Ma之间，最高峰值为170Ma左右。花岗岩类岩浆作用及成矿相应的地球动力学背景为陆一陆碰撞造山运动的晚期表现为一侧陆壳向另一侧陆壳之下的俯冲叠置过程。中生代花岗岩类在成因上与陆壳的俯冲有联系，大多属高钾钙碱性系列。部分为钾玄武岩系列，它们来自加厚的下地壳。部分花岗岩类具壳幔混合成因。一个地区花岗岩类Pb-Sm-Nd同位素主要受该地区源岩基底地层的控制，因此同一地区花岗岩类具有相近的Pb-Sm-Nd同位素特征。基底地层对花岗岩类的分布成因类型、有关的成矿作用具有重要的控制作用。依据花岗岩sr和Yb的含量，本文将该地区花岗岩类大致分为两类：埃达克岩和喜马拉雅型花岗岩。铜钼矿大都同埃达克岩有关，而两类花岗岩均可形成金矿。