Silvialite, a new sulfate-dominant member of the scapolite group with an Al-Si composition near the I4/m−P42/n phase transition
Silvialite, a new sulfate-dominant member of the scapolite group with an Al-Si composition near the I4/m−P42/n phase transition
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Silvialite，方柱石族中以硫酸盐为主的新成员，其 Al-Si 成分接近 I4/m−P42/n 相变
DOI：
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发表时间：
1999
影响因子：
2.7
通讯作者：
F. Hawthorne
中科院分区：
文献类型：
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作者：
D. K. Teertstra;M. Schindler;B. Sherriff;F. Hawthorne
硅铝石，理想的是Ca 4Al 6Si 6 O24 SO 4，为四方晶系，I4/m，Z = 2，a = 12.160（3），c = 7.560（1）Ω，V = 1117.9（8）Ω 3，c：a = 0.6217：1，ω= 1.583，Ω = 1.558（单轴负），Dm = 2.75 g/cm 3，Dcalc = 2.769 g/cm 3，H（莫氏）= 5.5。它是透明的，略带黄色，具有良好的{100}解理，软骨状断裂，白色条纹和玻璃光泽。产于澳大利亚北昆士兰州麦克布赖德省上地幔石榴麻粒岩捕虏体中。由电子探针分析得出的经验公式为（Na_（1.06）Ca_（2.86））（Al_（4.87）Si_（7.13））O_（24）[（SO_4）_（0.57）（CO_3）_（0.41）]。晶体结构精修显示沿四重轴沿着的无序碳酸酯和硫酸酯基团。硅铝石是碱性玄武岩在900 - 1000°C和8 - 12 kbar高fSO_2和fO_3条件下析出的主要堆积相。目前在文献中用来描述镁灰岩的硫酸盐类似物的名称silvialite是由Brauns（1914）提出的。
Abstract Silvialite, ideally Ca4Al6Si6O24SO4, is tetragonal, I4/m, Z = 2, with a = 12.160(3), c = 7.560(1) Å, V = 1117.9(8) Å3, c:a = 0.6217:1, ω= 1.583, Ɛ= 1.558 (uniaxial negative), Dm = 2.75 g/cm3, Dcalc = 2.769 g/cm3 and H (Mohs) = 5.5. It is transparent and slightly yellow, has a good {100} cleavage, chonchoidal fracture, white streak and a vitreous lustre. It occurs in upper-mantle garnet-granulite xenoliths hosted by olivine nephelinite, from McBride Province, North Queensland, Australia. The empirical formula, derived from electron-microprobe analysis, is (Na1.06Ca2.86)(Al4.87Si7.13)O24 [(SO4)0.57(CO3)0.41]. Crystal-structure refinement shows disordered carbonate and sulfate groups along the fourfold axis. Silvialite is a primary cumulate phase precipitated from alkali basalt at 900−1000°C and 8−12 kbar under high fSO₂ and fO₂ . The name silvialite, currently used in literature to describe the sulfate analogue of meionite, was suggested by Brauns (1914).