Annite-phlogopite

Figure 5.51 fo2 stability field of biotite. (A) Pseudobinary phlogopite-annite mixture. Numbers at experimental points indicate observed Fe/(Fe + Mg) atom ratio. (B) Annite. HM = hematite-magnetite buffer NNO = Ni-NiO buffer MW = magnetite-wuestite buffer QFM = quartz-fayalite-magnetite buffer. From Wones and Eugster (1965). Reprinted with permission of The Mineralogical Society of America. 

According to Wones (1972) and Mueller (1972), the mixture KMgjAlSijOjo (OH)2-KFe3AlSi30io(OH)2 (phlogopite-annite) is virtually ideal. 

Hazen R. M. and Burnham C. W. (1973). The crystal structure of 1 layer phlogopite and annite. 

Rancourt DG, Ping JY, Berman RG (1994) Mossbauer spectroscopy of minerals. III. Octahedral-site Fe quadrapole splitting distributions in the phlogopite-annite series. Phys Chem Minerals 21 258-267 Rancourt DG, Scorzelli RB (1995) Low-spin Y-Fe-Ni(YLs) proposed as a new mineral in Fe-Ni-bearing meteorites Epitaxial intergrowth of yls and tetrataenite as a possible equilibrium state at 20-40 at % Ni. J Magnet Magnetic Mater 150 30-36... 

For large cations such as Cs and Rb (e.g., Cs-tetra-ferri-annite, Rb-,Cs-rich phlogopite, and nanpingite) the small a value corresponds to a large interlayer separation, whereas for small cations such as Na and Ca (e.g., preiswerkite, paragonite, and... 

In K-rich trioctahedral micas, both a and interlayer separation increase from norrishite to tetra-ferriphlogopite (and aluminian phlogopite) toward values for Fe-rich polylithionite, Fe-rich phlogopite, Mg-rich annite, and phlogopite. Annite deviates from the trend of trioctahedral true micas owing to a larger interlayer separation. In the Ba-rich brittle mica, ferrokinoshitalite (M sites mainly occupied by Fe ), a- and interlayer-separation values are smaller with respect to those of kinoshitalite (M sites mostly occupied by Mg). With respect to trioctahedral micas, the interlayer separation in both muscovite and celadonitic muscovite is smaller, but a values are similar. To explain this behavior, the octahedral, tetrahedral, and 0(4) site chemistry must be considered. 

Ordering of tetrahedral cations is quite unusual in the common mica species such as muscovite-2Mi, phlogopite-lM and annite-lM (Bailey 1975, 1984c), whereas it is common in brittle micas. Margarite, bityite and anandite are examples of minerals with Si,Al (or Fe ) tetrahedral ordering (Guggenheim 1984). 

Figure 16. Mean electron count (m.e.c.) of M(2) [M(2) = M(3)] vs. m.e.c. of M(l) site. Symbols filled circles = annite filled circles, x-hair =magnesian annite open circle, x-hair = ferroan phlogopite open circles = phlogopite. Estimated average standard deviation +0.3 e".

Figure 17. Difference between M(l) and M(2) site mean bond distance in mica crystals of the phlogopite-annite join. Symbols and samples as in Fignre 16. The average standard deviation on

Hazen RM, Burnham CW (1973) The crystal structures of one-layer phlogopite and annite. Am Mineral 58 889-900... 

In Table 3, the compressibility of the lattice parameters and of the polyhedral building units are reported, along with other structural parameters useful to understand the high-pressure behavior of Cs-annite, Rb-annite and phlogopite. The points outlined below show the effect of how different structural units of trioctahedral micas relate with one another, and then respond as a whole to pressure ... 

The tetrahedra are nearly rigid units, and tend to relax under pressure by rotations described by the a angle. These rotations are sensitive to composition, as Table 3 shows. In particular, the tetrahedral sheets adjacent to the Fe-bearing octahedral sheet, in Cs-annite, exhibit a significantly smaller a rotation than in phlogopite. This... 

F-phlogopite (Takeda and Morosin 1975) phlogopite (Russell and Guggenheim 1999) phlogopite (Tutti et al. 2000) Cs-annite (Comodi et al. 1999)... 

Figure 6. Bulk modulus as a function of interlayer cation size, calculated using the interlayer chemical composition. Na(Pg) paragonite (Comodi and Zanazzi 1997) Na(mu) Na-rich muscovite (Comodi and Zanazzi 1995) K(phl) phlogopite (Hazen and Finger 1978) K(mu) K-muscovite (Comodi and Zanazzi 1995) Cs(Cs-tfa) Cs-tetra-ferri-annite (Comodi et al. 1999) Rb(Rb-tfa) Rb-tetra-feni-annite (Comodi et al. 2001).

Figure 5. (A) Mossbauer spectrum of annite from Devil s Slide, Pikes Peak, Colorado, U.S.A. This sample most closely resembles the ideal Fe end member analogue of phlogopite. (B) Mossbauer spectmm of biotite from Cape Ann, Massachusetts, which contains both t e" and These are newly collected spectra on the same mounts used by Dyar and Bums (1986).

Redhammer GJ, Dachs E, Amthauer G (1995) Mossbauer spectroscopic and X-ray powder diffraction studies of synthetic micas on the join annite KFe3AlSi30io(OH)2-phlogopite KMg3AlSi30io(OH)2. Phys Chem Minerals 22 282-294... 

Table 1. Observed absorption bands in cm and suggested band assignments for the synthetic micas phlogopite (Jenkins 1989), annite (Redhammer et al. 2000), muscovite and margarite (Langer et al. 1981) in the mid-lR lattice vibrational region. Horizontal lines band positions within 10 cm . [Al] = Al in octahedral coordination libr = librational mode.

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