微量元素的地球化学分类详解.ppt

2. 利用CI将地质样品中的REE标准化后，REE分布图应该是什么样？ Problem REE patterns Pacific pelagic sediment Values for REE normalizing 稀土元素分馏的因素 离子的晶体化学性质 离子半径减小 离子电位增大 相容性差异 2. 赋存体系的矿物组合 3.氧化还原条件 Ce和Eu的变价性，对外界氧化还原条件变化反应敏感： Ce3+ Ce4+ R：1.07?→0.94? Eu3+ Eu2+ R：0.98?→1.24? 价态变化导致离子半径相应变化，致使与REE3+整体分离 4.络离子稳定性的差异 REE可与F-、Cl-、CO32-、PO43-、SO42-等形成络阴离子，但其稳定性各异. HREE络离子稳定性＞LREE络离子稳定性. 因此LREE矿物沉淀后，HREE尚可呈络合物形式在溶液中迁移，而在较晚阶段沉淀，导致LREE与HREE的分异. 5.被吸附能力的差异 LREE被胶体、有机质和粘土矿物吸附能力大于HREE. Problem 下图中5种REE配分曲线分别反映了什么样的地质过程或地质环境？ 不同地质中的REE配分曲线 不同地质中的REE配分曲线 The end * * * Since the concentration of a trace element (unlike major elements--note Fo-Fa) in any phase is proportional to the coverall concentration of that element, a more convenient constant is commonly used for them. It is commonly referred to as D for TEs (although some authors still use KD) and is called a partition coefficient: ? D = C(S)/C(L) ? Where CS and CL are the concentration of a trace element in the solid and liquid phases, respectively (the wt% or ppm value directly). As long as the element occurs in very dilute concentrations, D is a constant. * Note that 85% Ol + Opx, but 5% Grt raises bulk D to 0.366 * A bit ambiguous, since many variables (country rx, %PM, %FX) ? Need immobile TEs, so met has no effect. Ti, Zr, Y, Hf ? apply to basic volcs to eliminate high %FX * Not exact, since D varies with the composition of mins melt * Depends on the minerals involved! Sr - melt as ol px separate - plag (Ca) not melt if plag is phenocryst phase Commonly standardized to mantle compositions (olivine, pyroxenes, and perhaps garnet) Thus the major elements Mg and Fe would usually be referred to as compatible, while K and Na as incompatible * Depends on the minerals involved! Sr - melt as ol px separate - plag (Ca) not melt if plag is phenocryst phase Commonly standardized to mantle compositions (olivine, pyroxenes, and perhaps garnet) Thus the major elements Mg and Fe would usually be referred to as compat