Geophysical Resea ch Abs ac s, Vol. 5, 09206, 2003
c
Eu opean Geophysical Socie y 2003
CHARACTERIZATION OF NH4-BEARING MICAS
IN CARPHOLITE METAPELITES FROM
AMORGOS (GREECE)
Nie o, F (1); Ma a, M. P.(2); Go é, B (3); Azañón, J. M.(1)
(1) Ins i u o Andaluz de Ciencias de la Tie a, Uni . G anada, CSIC. A . Fuen enue a, 18002
G anada, Spain. (2) Dp o. Geología. Fac. Ciencias del Ma . P o. Real (Cádiz), Spain. 11510 (3)
UMR 8538, Lb. Geologie, ENS, 24, Rue Lhomond, F-75231 Pa is, Cedex 05, F ance
( nie o@ug .es)
Phengi ic micas om some HP se ing ca pholi e-bea ing ocks in he Alpine domain
ha e been shown o ha e anomalous low-K con en (0–9 o 0.55 p u.) which may in
pa , be explained by a pi ophili ic (illi ic) subs i u ion. P elimina y EMPA analyses
show ha phengi ic micas om Amo gos (G eece) ep esen one o he mos ex eme
cases o an in e laye de ici in his se o samples, in e laye con en anges om 0.65
o 0.55 p u. In o de o e alua e he possibili y o signi ican obeli ic subs i u ion o in-
e g ow h wi h o he phyllosilica es, de ailed XRD, IR, BSE and TEM-EDS analyses
ha e been pe o med. BSE images show an in e g ow h o wo ypes o mica: pa ag-
oni ic and low-K (phengi ic) mica which eplace ca pholi e c ys als. XRD analyses
in <2 m ac ions show basal spacings co esponding o 9.623 Å (pa agoni e) and a
la ge basal spacing (10.102 Å) co esponding o a NH4-bea ing mica. In ensi y a ios
(I001:I002:I003)∼(4:1:1) a e cha ac e is ic o NH4-bea ing mica in compa ison o
musco i e a ios o app oxima ely 4:1:3. In a ed abso p ion bands a 1430 cm−1and
in he ange o 3000–3400 cm−1a e also cha ac e is ic o NH4-bea ing micas. TEM
images co obo a e he ex u es obse able in BSE images showing wo kinds o mi-
cas as disc e e and sepa a e hick packe s and no in e g ow h a la ice scale wi h any
o he phase. On he basis o he p e ious c i e ia, he de ici o he in e laye ca ions
can be accoun ed o by a obeli ic NH4subs i u ion. Acco ding o he basal spacing,
he calcula ion o he NH4con en can be as high as 30%, which is in good acco dance
wi h he EMPA in e laye de ici o ca. 40%. The es o he in e laye de ici can be
jus i ied by a pi ophili ic (illi ic) subs i u ion. Al hough he mos common in e laye
ca ion o low-g ade dioc ahed al micas a e K Na and Ca, he p esence o NH4 ep e-
sen s a ou h signi ican componen , as poin ed ou by Guido i and Sassi, 1998. The
a i y o NH4in Amo gos mica is ela ed o i s occu ence in non-coal ela ed peli es.
A ques ion hus eme ges, is Amo gos mica a amdom case o does NH4 ep esen a
mo e common in e laye componen in me amo phic sequences, e en in hose which
a e no ela ed o o ganic ma e ?