SODIC-FERRI-FERROPEDRIZITE AND FERRI-CLINOFERROHOLMQUISTITE: MINERAL DATA AND DEGREE OF ORDER OF THE A-SITE CATIONS IN Li-RICH AMPHIBOLES
SODIC-FERRI-FERROPEDRIZITE AND FERRI-CLINOFERROHOLMQUISTITE: MINERAL DATA AND DEGREE OF ORDER OF THE A-SITE CATIONS IN Li-RICH AMPHIBOLES
复制标题
钠铁矿和铁斜铁矿：富锂角闪石中 A 位阳离子的矿物数据和有序度
DOI：
10.2113/gscanmin.41.6.1345
复制
发表时间：
2003
影响因子：
0.9
通讯作者：
L. Ottolini
中科院分区：
文献类型：
--
作者：
R. Oberti;F. Cámara;J. Caballero;L. Ottolini
通过对西班牙瓜达拉马山脉Pedriza地块中变质表面岩的系统研究，发现了两种不同的富锂C2/m角闪石。它们可以通过同价交换M1(Fe2+Mg−1)和M2(Fe3+Al−1)与先前描述的物种相关，并代表该组成空间中最富Fe的成分。铁斜铁石的理想式为A-B Li2C(Fe3+·2Fe2+)TSi8O22 X(OH)2，钠铁矿式为ANa BLi2C(Fe3+·2Fe2+·C2Li)TSi8O22X(OH)2，Z=2.Hol型铁斜铁石(IMA-CNMMN 2001-066)A(Na0.28K0.00)∑0.28B(Li1.90Na0.08Ca0.02)∑2.00C(Fe3+1.68Fe2+1.55Mg1.06Li0.28Al0.26Ti0.01Mn2+0.14Zn0.02)∑5.00TSi8.00O2203(OH1.79F0.24)∑2.03，有a 9.462(6)，b 17.898(9)，c 5.302(3)A，β101.88(4)°，V 17.898(2)A3。正型钠铁钙铁矿型(IMA-CNMMN2001-068)，A(Na0.53K0.03)∑0.56B(Li1.82Na0.15Ca0.03)∑2.00C(Fe3+0.55Fe2+1.49Mg0.95Li0.58Al0.21Ti0.13Mn2+0.07Zn0.01)∑4.99TSi8.00O22X(OH1.45F0.52)∑1.97，具有a 9.496(4)，b 17.883(8)，c 5.297(2)A，β102.06(3)°，V 5.297(2)A3。钠铁镁铁闪锌矿和铁斜长铁方铁矿均为黑色，具有玻璃光泽。它们具有灰色条纹，在长短波紫外光下不显示荧光；它们脆性，断口不均匀，具有单斜角闪石的特征{110}解理。密度计算值分别为3.23g/cm~3和3.24g/cm~3，平均折射率分别为1.708和1.710。A位的电子密度形状随着B Li和C Li含量的变化而变化，这表明阳离子有序性受到局域键价要求的强烈影响。系统的键价键强度计算证实了这一特征，支持(M4‘Li-O3f-Am Na)&Gt；(M4’Li-O3OH-Am Na)择优局域构型序列。
A systematic examination of metamorphic episyenites in the Pedriza Massif, Sierra de Guadarrama, Spain, allowed detection of two more distinct Li-rich C 2/ m amphibole species. They can be related to previously described species via the homovalent exchanges M 1(Fe2+Mg−1) and M 2(Fe3+Al−1), and represent the compositions richest in Fe in this compositional space. The ideal formula of ferri-clinoferroholmquistite is A □ B Li2 C (Fe3+ 2Fe2+ 3) T Si8 O22 X (OH)2, and that of sodic-ferri-ferropedrizite is A Na B Li2 C (Fe3+ 2Fe2+ 2Li) T Si8 O22 X (OH)2, with Z = 2. Holotype ferri-clinoferroholmquistite (IMA–CNMMN 2001–066), A (Na0.28K0.00)∑0.28 B (Li1.90Na0.08Ca0.02)∑2.00 C (Fe3+ 1.68Fe2+ 1.55Mg1.06Li0.28Al0.26Ti0.01Mn2+ 0.14Zn0.02)∑5.00 T Si8.00 O22O3(OH1.79F0.24)∑2.03, has a 9.462(6), b 17.898(9), c 5.302(3) A, β 101.88(4)°, V 878.6(2) A3. Holotype sodic-ferri-ferropedrizite (IMA–CNMMN 2001– 068), A (Na0.53K0.03)∑0.56 B (Li1.82Na0.15Ca0.03)∑2.00 C (Fe3+ 1.55Fe2+ 1.49Mg0.95Li0.58Al0.21Ti0.13 Mn2+ 0.07Zn0.01)∑4.99 T Si8.00 O22 X (OH1.45F0.52)∑1.97, has a 9.496(4), b 17.883(8), c 5.297(2) A, β 102.06(3)°, V 879.6(2) A3. Sodic-ferri-ferropedrizite and ferri-clinoferroholmquistite are both black, with a vitreous luster. They have a gray streak and do not show fluorescence under long-and short-wave ultraviolet light; they are brittle with an uneven fracture, and have the characteristic {110} cleavage of monoclinic amphiboles. The calculated values of density are 3.23 and 3.24 g/cm3, and the calculated mean indices of refraction are 1.708 and 1.710, respectively. The shape of the electron density at the A sites changes as a function of the B Li and C Li contents, suggesting that cation ordering is strongly affected by local bond-valence requirements. This feature is confirmed by systematic bond-valence – bond-strength calculations, which support the sequence ( M 4′Li–O3F– Am Na) > ( M 4′Li–O3OH– Am Na) of preferred local configurations.