A modern, guano-related occurrence of foggite, CaAl(PO4)(OH)2 · H2O and churchite-(Y), YPO4 · 2H2O in Cioclovina Cave, Romania
A modern, guano-related occurrence of foggite, CaAl(PO4)(OH)2 · H2O and churchite-(Y), YPO4 · 2H2O in Cioclovina Cave, Romania
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罗马尼亚乔克洛维纳洞穴中现代与鸟粪相关的雾石、CaAl(PO4)(OH)2 · H2O 和丘石-(Y), YPO4 · 2H2O
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
I. Balasz
中科院分区：
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作者：
B. Onac;K. Ettinger;J. Kearns;I. Balasz
摘要本研究报告了罗马尼亚Ciocloplanet洞穴中与鸟粪石有关的磷酸盐存款中两个空间上分离的位置的foglitazone和churchite-（Y）。光学显微镜观察，粉末X射线衍射，电子探针分析，和FTIR的分析中使用的两种矿物。结果表明，其化学组成为Ca 0.925（Al 0.91Fe 2 +0.016）<$0.926（P 0.991Si 0.043）<$1.034O 3.74（OH）2.26 · H2O和钙镁矾-（Y）[（Y 0.830Dy 0.043Er 0.033Gd 0.029Yb 0.022）<$0.957Ca 0.009] P 1.023O 4.00·2 H2O。化学分析表明，硫氯镁石-（Y）富含偶数原子序数的镧系元素。精化后的晶胞参数用于雾度测量（斜方晶系）a = 9.264（1）<$，B = 21.334（8）<$，c = 5.197（7）<$，V = 1027.13（8）<$3（Z = 8）;（单斜晶系）：a = 5.578（8）θ，B = 15.013（6）θ，c = 6.277（8）θ，β = 117.94（4）°，V = 464.38（5）θ 3（Z = 4）。与其他已知的灰岩和钙钛矿不同，钙钛矿-（Y）的出现与水下石灰岩和各种洞穴沉积物（砂、粘土和石灰质泥）的磷酸盐化过程有关，形成了复杂的磷酸盐组合。这些矿物质可能来自富含磷酸盐的溶液，这些溶液在向下穿过沉积物时与粘土发生反应。雾晶的形成是以最初沉淀的钙硫锰矿为代价的。局部富集的钇、稀土元素和溶解的磷酸盐可能是沉淀沉淀的原因。
SummaryThis study reports foggite and churchite-(Y) from two spatially separate locations in the guano-related phosphate deposit from the Cioclovina Cave, Romania. Optical microscope observations, powder X-ray diffraction, electron microprobe analyses, and FTIR were used in the analysis of the two minerals. The chemical composition of foggite was determined to be Ca0.925(Al0.91Fe2+0.016)Σ0.926(P0.991Si0.043)Σ1.034O3.74(OH)2.26 · H2O and churchite-(Y) [(Y0.830Dy0.043Er0.033Gd0.029Yb0.022)Σ0.957Ca0.009]P1.023O4.00 · 2H2O. Chemical analyses of Cioclovina churchite-(Y) clearly revealed enrichment in lanthanides of even atomic number. The refined unit-cell parameters are for foggite (orthorhombic) a = 9.264(1) Å, b = 21.334(8) Å, c = 5.197(7) Å, and V = 1027.13(8) Å3 (Z = 8); for churchite-(Y) (monoclinic): a = 5.578(8) Å, b = 15.013(6) Å, c = 6.277(8) Å, β = 117.94(4)°, and V = 464.38(5) Å3 (Z = 4). FTIR spectrum of churchite-(Y) exhibits all the bands assigned to the vibrations of PO4, OH, and water groups.Unlike other documented occurrences of foggite and churchite-(Y), in Cioclovina Cave, the occurrence of these minerals are related to a process that phosphatized subjacent limestone and various cave sediments (sand, clay, and limy mud) to form a complex phosphate assemblage. The minerals are presumably derived from phosphate-rich solutions that reacted with clay earth while moving downward through the sediments. Foggite was formed at the expense of the originally precipitated crandallite. Locally concentrated yttrium, REE, and dissolved phosphate are probably responsible for the precipitation of churchite-(Y).