熱水性炭酸塩鉱物の相関係と希土類元素の循環過程

稀土元素在地圈中的分布和行为是稀土元素地球化学条件和迁移过程的良好指示。稀土氟碳酸盐矿物氟碳铈矿（Ln（CO3）F）和氟碳铈矿（CaLn 2（CO3）3F2）产于日本中部Toki花岗岩中方解石（CaCO3）的热液蚀变脉中。氟碳铈矿在副基质中呈层状结构。这些矿物应与方解石沉淀的热液中含有稀土元素，钙和碳酸根离子。氟碳铈矿、氟碳铈矿和钙钛矿（CaLn（CO_3）_2F）的组成可表示在方解石-氟碳铈矿二元体系中。这些稀土矿物与方解石的相关系是了解稀土元素在方解石-饱和热液体系中迁移和固定条件的基础背景，方解石-饱和热液体系是地球圈中元素循环最常见和最活跃的过程之一。 ...更多信息 通过冷封压力容器对具有钯-（La）组成的起始材料进行反应。起始物料由碳酸镧和CaF2试剂制备，并用蒸馏水密封在Ag胶囊中。实验条件为：350 ℃~650 ℃，30 MPa~100 MPa，66 h~910 h。通过粉末X射线衍射和扫描电子显微镜观察，确定了运行产品中的矿物相。在400 ℃~600 ℃、100MPa和350 ℃~500 ℃、30MPa条件下，产物中存在氟碳铈矿和方解石。碳酸镧和CaF_2试剂经实验分解后，方解石晶体长出数十微米以上。在650 ℃、100MPa和600 ℃、30MPa条件下，氟碳铈矿不稳定，产物中含有氧化镧、萤石和方解石。在任何运行的产品中均未检测到Paramount。氟碳铈矿在本研究条件下应比氟碳铈矿更稳定。过氧化氢的形成可以通过CO2的分压来控制。少

Distribution and behavior of rare earth elements in geosphere is a good indicator of geochemical conditions and migration processes of rare earth elements. Rare earth fluorocarbonate minerals, bastnaesite (Ln (CO3) F) and parisite (CaLn2 (CO3) 3F2) occur in the hydrothermal alteration veins with calcite (CaCO3) in Toki granite, central Japan. Bastnaesite shows lamellae-like texture in the parisite matrix. These minerals should be precipitated with calcite from hydrothermal fluid containing rare earth elements, calcium and carbonate ions. Compositions of bastnaesite, parisite and synchysite (CaLn (CO3) 2F) can be expressed in the calcite-bastnaesite binary system. Phase relations of these rare earth minerals with calcite is fundamental background to understand migration and fixation conditions of rare earth elements under calcite-saturated hydrothermal system, which is one of the most common and active process to circulate elements in geosphere.In this study, hydrothermal synthesis expe … More riments are carried out on starting materials with parisite-(La) composition by cold-seal pressure vessels. Starting materials are prepared from La carbonate and CaF2 reagents and sealed in Ag capsules with distilled water. Experimental conditions are as follows : 350〜650 degree C, 30〜100 MPa and 66〜910 hours. Mineral phases in the run products are identified by powder X-ray diffraction and observed by scanning electron microscopy. Bastnaesite and calcite occur in the run products between 400 degree C and 600 degree C, 100MPa and between 350 degree C and 500 degree C, 30MPa. La carbonate and CaF2 reagents are decomposed by the experiments, and calcite crystals grow more than tens of micrometers in length. At 650 degree C, 100MPa and 600 degree C, 30MPa, bastnaesite is unstable, and La oxide, fluorite and calcite are found in the run products. Parisite is not detected in any run products. Bastnaesite should be more stable than parisite under the conditions of this study. Formation of perisite may be controlled by partial pressure of CO2. Less