Actual Fe-Li mica series as a series with ☐VI constant but not with AlIV or AlVI

Sun, Shengsi; Yu, Jie

doi:10.1180/002646100549607

Cited by 3 publications

(1 citation statement)

References 17 publications

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“…Their crystal structure accommodates a plethora of elements, leading to a large and diverse mineral group. The compositional diversity of micas has led to numerous attempts at classification and graphical presentation (Foster, 1960a,b;Tröger, 1962;Rieder et al, 1970Rieder et al, , 1998Koval et al, 1972;Gottesmann and Tischendorf, 1978;Č erný and Burt, 1984;Monier and Robert, 1986;Jolliff et al, 1987;Burt, 1991;Tischendorf et al, 1997Tischendorf et al, , 2004Sun Shihua andYu Jie, 1999, 2000).…”

Section: Introductionmentioning

confidence: 99%

True and brittle micas: composition and solid-solution series

Tischendorf¹,

Förster²,

Gottesmann³

et al. 2007

Mineral. mag.

151

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Micas incorporate a wide variety of elements in their crystal structures. Elements occurring in significant concentrations in micas include: Si, IVAl, IVFe3+, B and Be in the tetrahedral sheet; Ti, VIAl, VIFe3+, Mn3+, Cr, V, Fe2+, Mn2+, Mg and Li in the octahedral sheet; K, Na, Rb, Cs, NH4, Ca and Ba in the interlayer; and O, OH, F, Cl and S as anions. Extensive substitutions within these groups of elements form compositionally varied micas as members of different solid-solution series. The most common true K micas (94% of almost 6750 mica analyses) belong to three dominant solid-solution series (phlogopite–annite, siderophyllite–polylithionite and muscovite–celadonite). Theirclassification parameters include: Mg/(Mg+Fetot) [=Mg#] formicas with VIR >2.5 a.p.f.u. and VIAl <0.5 a.p.f.u.; Fetot/(Fetot+Li) [=Fe#] formicas with VIR >2.5 a.p.f.u. and VIAl >0.5 a.p.f.u.; and VIAl/(VIAl+Fetot+Mg) [=Al#] formicas with VIR <2.5 a.p.f.u. The common true K micas plot predominantly within and between these series and have Mg6Li <0.3 a.p.f.u. Tainiolite is a mica with Mg6Li >0.7 a.p.f.u., or, fortr ansitional stages, 0.3–0.7 a.p.f.u. Some true K mica end-members, especially phlogopite, annite and muscovite, form binary solid solutions with non-K true micas and with brittle micas (6% of the micas studied). Graphical presentation of true K micas using the coordinates Mg minus Li (= mgli) and VIFetot+Mn+Ti minus VIAl (= feal) depends on theirclassification according to VIR and VIAl, complemented with the 50/50 rule.

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Section: Introductionmentioning

confidence: 99%

True and brittle micas: composition and solid-solution series

Tischendorf¹,

Förster²,

Gottesmann³

et al. 2007

Mineral. mag.

151

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Hydrothermal water–rock interaction and the redistribution of Li, B and Cl in the Taupo Volcanic Zone, New Zealand

Reyes

Trompetter

2012

Chemical Geology

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A new graphical presentation and subdivision of potassium micas

et al. 2004

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A system based on variation of the octahedrally coordinated cations is proposed for graphical presentation and subdivision of tri- and dioctahedral K micas, which makes use of elemental differences (in a.p.f.u.): (Mg – Li) [= mgli] and (Fetot + Mn + Ti – VIAl) [= feal]. All common true tri- and dioctahedral K micas are shown in a single polygon outlined by seven main compositional points forming its vertices. Sequentially clockwise, starting from Mg3 (phlogopite), these points are: Mg2.5Al0.5, Al2.167□0.833, Al1.75Li1.25, Li2Al (polylithionite), Fe22+Li, and Fe32+ (annite). Trilithionite (Li1.5Al1.5), Li1.5Fe2+Al0.5, Fe22+ Mg, and Mg2Fe2+ are also located on the perimeter of the polygon. IMA-siderophyllite (Fe2+2Al) and muscovite (Al2□) plot inside.The classification conforms with the IMA-approved mica nomenclature and differentiates among the following mica species according to their position in a diagram consisting of mgli and feal axes plotted orthogonally; trioctahedral: phlogopite, biotite, siderophyllite, annite, zinnwaldite, lepidolite and tainiolite; dioctahedral: muscovite, phengite and celadonite. Potassium micas with [Si] <2.5 a.p.f.u. including IMA-siderophyllite, KFe22+ AlAl2Si2O10(OH)2, and IMA-eastonite, KMg2AlAl2Si2O10(OH)2 seem not to form in nature.The proposed subdivision has several advantages. All common true, trioctahedral and dioctahedral K micas, whether Li-bearing or Li-free, are shown within one diagram, which is easy to use and gives every mica composition an unambiguously defined name. Mica analyses with Fe2+, Fe3+, Fe2+ + Fe3+, or Fetot can be considered, which is particularly valuable for microprobe analyses. It facilitates easy reconstruction of evolutionary pathways of mica compositions during crystallization, a feature having key importance in petrologically oriented research. Equally important, the subdivision has great potential for understanding many of the crystal-chemistry features of the K micas. In turn this may allow one to recognize and discriminate the extent to which crystal chemistry or bulk composition controls the occurrence of some seemingly possible or hypothetical K mica.

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Actual Fe-Li mica series as a series with ☐_VI constant but not with Al_IV or Al_VI

Cited by 3 publications

References 17 publications

True and brittle micas: composition and solid-solution series

True and brittle micas: composition and solid-solution series

Hydrothermal water–rock interaction and the redistribution of Li, B and Cl in the Taupo Volcanic Zone, New Zealand

A new graphical presentation and subdivision of potassium micas

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