The problem to be solved is whether Al is a necessary component of Fe-Mg chlorites. Very unusual Al-depleted and Fe-enriched trioctahedral chlorites with the empirical formulae Na 0.05 Ca 0.05 (Fe 2+ 3.01 Mg 2.01 Ti 0.14 Fe 3+ 0.04 ) Σ6.00 [(Si 3.53 Fe 3+ 0.41 Al 0.06 ) Σ4.00 O 10 ](OH) 8 · n H 2 O (Sample 1) and Na 0.05 Ca 0.01 (Fe 2+ 3.26 Mg 1.97 Fe 3+ 0.75 Mn 0.01 Ti 0.01 ) Σ6.00 [(Si 3.16 Fe 3+ 0.75 Al 0.09 ) Σ4.00 O 10 ](OH) 8 (Sample 2) have been discovered in Al-depleted dolomite carbonatites of the Kovdor complex of ultramafic, alkaline rocks and carbonatites, Kola Peninsula, Russia. The presence of substantial amounts of Ti in Sample 1 is another unusual feature of this mineral. In both samples, chlorites are intimately intergrown with cronstedtite-1 T which is an indication of a low stability of chlorite structure in the absence of aluminum in the tetrahedral sheet. The crystal structure of chlorite in Sample 1 was solved by the Rietveld method. The mineral is triclinic (IIb-4-module), space group C - 1 $$ 1 $$ , a = 5.4153(4), b = 9.3805(7), c = 14.5743(12) Å, α = 90.137(5)°, β = 96.928(5)°, γ = 90.043(6)°, V = 734.95(10) Å 3 , and Z = 2. A problem to be solved is how stable are Al-free chlorites belonging to the clinochlore–chamosite solid-solution series and whether their existence in natural mineral assemblages is possible. The results obtained indicate that even though Al-depleted chlorites belonging to the clinochlore–chamosite solid-solution series exist in Nature as metastable phases, these minerals are extremely rare and much less stable than Al-poor serpentines.

中文翻译：

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来自俄罗斯科拉半岛 KOVDOR 超碱性复合体的白云石碳酸盐的极度贫铝的亚氯酸盐

需要解决的问题是Al是否是Fe-Mg亚氯酸盐的必要成分。非常不寻常的贫铝和富铁三八面体绿泥石，其经验公式为 Na 0.05 Ca 0.05 (Fe 2+ 3.01 Mg 2.01 Ti 0.14 Fe 3+ 0.04 ) Σ6.00 [(Si 3.53 Fe 3+ 0.040 Σ) Al 0.40 Al O 10 ](OH) 8 · n H 2 O（样品 1）和 Na 0.05 Ca 0.01 (Fe 2+ 3.26 Mg 1.97 Fe 3+ 0.75 Mn 0.01 Ti 0.01 ) Σ6.00 [(Si 3.16 Fe 59 Al 3+ 0.05 ) Σ4.00 O 10 ](OH) 8 （样品 2）已在俄罗斯科拉半岛的 Kovdor 超基性、碱性岩石和碳酸盐岩复合体的贫铝白云岩碳酸盐岩中被发现。样品 1 中存在大量 Ti 是这种矿物的另一个不同寻常的特征。在两个样本中，绿泥石与 cronstedtite-1 T 密切共生，这表明四面体片中没有铝时绿泥石结构的稳定性低。样品 1 中亚氯酸盐的晶体结构通过 Rietveld 方法求解。矿物为三斜晶系 (IIb-4-模), 空间群 C - 1 $$ 1 $$ , a = 5.4153(4), b = 9.3805(7), c = 14.5743(12) Å, α = 90.137(5) )°, β = 96.928(5)°, γ = 90.043(6)°, V = 734.95(10) Å 3 , and Z = 2. 需要解决的问题是属于斜绿石的无铝亚氯酸盐的稳定性如何– 菱镁矿固溶体系列以及它们是否可能存在于天然矿物组合中。获得的结果表明，即使属于斜绿石-菱镁矿固溶体系列的贫铝绿泥石在自然界中作为亚稳相存在，