TY - JOUR
T1 - EXTREMELY AL-DEPLETED CHLORITES FROM DOLOMITE CARBONATITES OF THE KOVDOR ULTRAMAFIC-ALKALINE COMPLEX, KOLA PENINSULA, RUSSIA
AU - Chukanov, Nikita V.
AU - Krzhizhanovskaya, Maria G.
AU - Pekov, Igor V.
AU - Varlamov, Dmitry A.
AU - Van, Konstantin V.
AU - Ermolaeva, Vera N.
AU - Vozchikova, Svetlana A.
N1 - Chukanov, N.V., Krzhizhanovskaya, M.G., Pekov, I.V. et al. EXTREMELY AL-DEPLETED CHLORITES FROM DOLOMITE CARBONATITES OF THE KOVDOR ULTRAMAFIC-ALKALINE COMPLEX, KOLA PENINSULA, RUSSIA. Clays Clay Miner. 68, 81–88 (2020). https://doi.org/10.1007/s42860-019-00055-8
PY - 2020/2/1
Y1 - 2020/2/1
N2 - 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 Na0.05Ca0.05(Fe2+ 3.01Mg2.01Ti0.14Fe3+ 0.04)Σ6.00[(Si3.53Fe3+ 0.41Al0.06)Σ4.00O10](OH)8·nH2O (Sample 1) and Na0.05Ca0.01(Fe2+ 3.26Mg1.97Fe3+ 0.75Mn0.01Ti0.01)Σ6.00[(Si3.16Fe3+ 0.75Al0.09)Σ4.00O10](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-1T 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 , 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) Å3, 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.
AB - 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 Na0.05Ca0.05(Fe2+ 3.01Mg2.01Ti0.14Fe3+ 0.04)Σ6.00[(Si3.53Fe3+ 0.41Al0.06)Σ4.00O10](OH)8·nH2O (Sample 1) and Na0.05Ca0.01(Fe2+ 3.26Mg1.97Fe3+ 0.75Mn0.01Ti0.01)Σ6.00[(Si3.16Fe3+ 0.75Al0.09)Σ4.00O10](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-1T 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 , 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) Å3, 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.
KW - Chlorite
KW - Cronstedtite
KW - Crystal structure
KW - Dolomite carbonatite
KW - Infrared spectroscopy
KW - Kovdor Complex
KW - Rietveld refinement
UR - http://www.scopus.com/inward/record.url?scp=85083419472&partnerID=8YFLogxK
U2 - 10.1007/s42860-019-00055-8
DO - 10.1007/s42860-019-00055-8
M3 - Article
AN - SCOPUS:85083419472
VL - 68
SP - 81
EP - 88
JO - Clays and Clay Minerals
JF - Clays and Clay Minerals
SN - 0009-8604
IS - 1
ER -