1. No category

How to calculate mineral formula for 2 members
dioctahedral mixed layers from
EDX-analysis by TEM: Example - Friedland clay
Nguyen, Thanh Lan*, Joern Kasbohm**, Hoang, Thi Minh Thao***
* Institute of Geography and Geology, University of Greifswald. D-17487 Greifswald, Germany;
** GeoENcon Ltd., D-17489 Greifswald, Germany
*** Faculty of Geology, Hanoi University of Science, Thanh Xuan, Hanoi, Vietnam
Introduction
TEM ‐ Results
ratio
„IS : diVS“
IS‐ml
diVS‐ml
For more information to INTRODUCTION (purpose, sample) see below for FLYER
TEM – Methodology
0.8
0.6
0.4
0.8
20
0.6
10
0.4
diVS‐ml
0
0.2
IS-ml
after ~ 10,000 y
(± closed system)
IS‐ml
10
30
1
ratio
„IS : diVS“
0
= randomly interstratified illite-smectite mixed layer phase (see INTRODUCTION)
0.2
Interlayer charge for certain members of IS-ml
Interlayer charge for certain members of diVS-ml
diVS-ml = dioctahedral vermiculite-smectite mixed layer phase (see INTRODUCTION)
Interlayer ccharge (O10(OH)2 )
40
diVS‐ml
IS‐ml
diVS‐ml
20
(e.g. small different in ratio ‚IS-ml vs. diVS-ml‘
as indicator for that)
IS‐ml
diVS‐ml
30
BUT
# parameter ‚open system‘ (rain water)
could exceed parameter ‚time‘ in comparison to ‚closed systems‘ (glacial water)
after few decades of years already
impact by glacial water
1
after < 10 y
(± open system)
Fre
equency (%)
40
(check ratio and missing smectite-rich
members of diVS-ml in diagram
‚impact by glacial water‘)
0.2
IS‐ml
HOW IS THIS PROCESS TO RECOGNIZE?
Here: TEM – particle‐wise EDX‐analyses – see TEM‐Methodology and
TEM‐Results
XRD – oriented mounts (EG) – see XRD‐Proofs
Fre
equency (%)
diVS‐ml = K‐deficient IS‐ml
diVS‐ml = charge‐deficient IS‐ml
commonly VIAl3+‐enriched
ratio
„IS : diVS“
4. Rate of Alteration
# deepest degree by glacial water impact
representing parameter ‚time‘
Illite
0
impact by rain water
IS‐ml in senso of Środon et al. 1992
interlayer charge of illite: 0.89
interlayer charge of smectite: 0.40
diVS‐ml
0.4
ML80
Mg
3. Illitization
# diVS-ml show a higher degree
of illitization (compare the different
maxima for IS-ml and diVS-ml)
ML60
2+
0.6
10
ML40
+
0.8
IS‐ml
Mg22+
diVS-ml)
ML20
Fe
4+
reduced Si
Si 4+
reduced
20
Montm.
Mg2+
3+
2. Interlayer Charge
# diVS-ml show a reduced interlayer
charge (check
for IS-ml vs.
for
Interlayer ccharge (O10(OH)2)
IS-ml
+ Al
3+
diVS
S-ml
increased Al
increased
Al3+3+
Frequency (%)
(see small ratio-bars in left corners of
each diagram)
What is to recognize here?
1
origin
Interlay
yer charge ((O10(OH)2)
30
1. Ratio ‚IS-ml : diVS-ml‘
# IS-ml is altering into diVS-ml
ML80
ML20
What is to recognize here?
diVerm
Changing of ratio IS‐ml and diVS‐ml and interlayer charge ML60
Alteration of illite‐smectite mixed layer phases (IS‐ml) into dioctahedral vermiculite‐smectite mixed layer phases (diVS‐ml)
ML40
FREQUENCY / DIVERSITY OF IS‐ml AND diVS‐ml
Montm.
INTERACTION OF CLAY AND WATER
.
ML10 = 10% of illitic layers
in this class of ml
XRD – Proofs
ŚRODON et al., 1992: S
,
( )
max (%) DETERMINES CHEMISTRY ALTERATION OF SWELLING PHASE VIA RATIO ‘17Å:10Å’
concerning IVAl3+, XIIK (FIX) and interlayer charge
in XRD patterns from ethylene glycol saturated (EG) specimen
origin
2.86
EG
d=17Å, Illite
e
<
d=17Å, IS-ml
Ratio ‚17Å:10Å‘
# Height of 17Å-peaks is decreasing
in comparison to mica (10Å)
d=7Å, Kaolinite
<
What is to recognize here?
rain water impact
after < 10 y (± open system)
after ~ 10,000 y (± closed system)
from 600 Å to 120 Å per stack
from 400 Å to 90 Å per stack
Illite
from 60 Å to 45 Å per stack
+ Illite – Smectite and dioctahedral Vermiculite – Smectite mixed layer phases show mostly a lognormal distribution
+ Illite – Smectite mixed layer altered into dioctahedral Vermiculite – Smectite mixed layer phases in contact with water
+ duration
d ti off contact
t t is
i determining
d t
i i the
th degree
d
off alteration:
lt ti
glacial
l i l water
t (~ 10,000
10 000 y)) > rain
i water
t (<
( 10 y))
+ alteration could be faster in open systems than in closed system (see high degree of alteration already after < 10 years in contact with rain water)
+ selective exploitation is now possible , e.g. to offer optimized products for UV‐protection creams and for filtering of vegetable oil (low charges required)
= particle‐wise TEM‐EDX analysis is a very sensitive tool to recognize alteration processes in clay mineral matter
Acknowledgments
We thank colleagues of TEM‐laboratory at Institute of Geography and Geology (Greifswald). Funding for this project was provided by GRS mbH.
d=10Å, Illite
d=7Å, Kaolinite
XRD by
y J. Kroos
IS-ml
diVS-ml
1.31
<
d=17Å, IS-ml
d=7Å, Kaolinite
d=10Å, Illite
d=17Å, IS-ml
<
Characterization of Peak Shape
(by Dehlez et al. (1993)
Conclusions
Contact email: [email protected]
glacial water impact
<
<
What is the proof for reduction of
thickness?
Already 1 month contact time with water is reducing
the thickness of EG-saturated (001) BRAGG peak:
For more information to TEM-METHODOLOGY (equations, control-values) see below for FLYER
Reduced thickness of particles
# Interpretation:
Reduction of particle thickness
during alteration of IS-ml into diVS-ml
by breaking at smectitic interlayers and
lower interlayer charge than in IS-ml
EG
EG
2.00
What is the interpretation?