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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 1
Chapter 2 Analysis of clay minerals using X-ray diffraction (XRD)
2.1 X-ray diffractometer2.2 Sample preparation2.3 XRD analysis2.4 Data processing
X-ray diffractometer
X-ray generator
goniometer
X-ray detector
Reference:Holtzapffel, T., 1985. Les minéraux argileux: Préparation, analyse diffractométrique et determination. Soc. Géol. Nord Publ, 12. 136 pp.
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2.1 X-ray diffractometer
X-ray generator: produce X-rays under high output power Goniometer: rotate the sample (or X-ray detector arm) and
measure diffraction angles X-ray detector: count circuits to detect, amplify and measure the
diffracted radiation. 2
Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 2
X-ray generator tube
High voltage
Tungsten filamentX rays
Electron
Target (Cu)
X rays
Cooling water
λmin λIntensity
Continuous spectrum
Characteristic spectrum
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Characteristic X-rays
N
M
K
L
Kγ
Kα
Kβ
Lα
Lβ
K series excitation
L series excitation λmin λ
Intensity
Continuous spectrum
Characteristic spectrum
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 3
X-rays filtering
Kα
Kβ
Kα
Kβ
I
λ λ
A crystal monochromator is used to absorb other spectrum and produce monochromatic radiation, mostly as K characteristic spectrum.
filter filter
K X-ray (Cu target)
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 4
X-ray diffraction
K X-ray (Cu target)
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Bragg’s Law:
n 2d sin
n = an integer (1, 2, 3, …)= wavelength (Cu 1.54Å)d = interplanar spacingincidence angle(”)
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 5
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2.2 Sample preparation Significance of oriented mounts of clay particles: to identify clay minerals, it
is essential to record their diagnostic basal reflections, the intensities of which are enhanced if the platy clay minerals of the sample lie generally parallel to the plane surface of the diffractometer.
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 6
Separation of fine-grained fraction, i.e. <2 m
Stokes equation:t = 190 x/d2
t = time of sedimentation (minutes)d = diameter of targeted particles (m)x = distance of particles descend
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Oriented mounts making method 1: filtration
Advantage: thick clay film.
Disadvantage: differential setting, difficult operation (to remove filter); not good quality on oriented mounts surface; relative large amount of sample request.
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 7
Oriented mounts making method 2: dropping
Advantage: very quick and easy operation, small amount of sample request.
Disadvantage: differential setting, too thin clay film.
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Oriented mounts making method 3: smearing
Advantage: thick clay film, relative easy operation, excellent quality of oriented amounts surface.
Disadvantage: relative large amount of sample request.
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 8
Power (non-oriented) mounts making method
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Ethylene-glycol solvation (24 hours)
Heating (490ºC, 2 hours)
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 9
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PANalytical X’Pert PRO Multi-Purpose Diffractometer
2.3 XRD analysis
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 10
Receiving slit + detector
Polycrystalline sample
Line focus
Divergence slitScan directionScan direction
Classical geometry (Bragg-Brentano)
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Polycrystalline sample
X’Celerator
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 11
Polycrystalline sample
X’Celerator
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Polycrystalline sample
X’Celerator
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 12
2.4 Data processing
Identification
Calculation
Multiple X-ray diffractograms of a typical sample from the South China Sea. Liu et al. (2010, Mar. Geol.) 23
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 13
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 14
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 15
Semi-quantitative calculation of clay minerals
1. Selection of peakssmectite (001), illite (001), kaolinite (001), chlorite (002)
2. Calculation methods(1) Ratio of peak areas: Biscaye (1965, GSA Bull.)(2) Ratio of integrated peak areas:
Petschick et al. (1996, Mar. Geol.)
(3) Ratio of peak heights: Fagel and Boës (2008, Palaeo-3)(4) Weighting factors:
Biscaye (1965)smectite × 1, illite × 4, kaolinite × 2, chlorite × 2
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(1) Ratio of peak areas and weighting factors: Biscaye (1965, GSA Bull.)
(2) Ratio of integrated peak areas: Petschick et al. (1996, Mar. Geol.)
(3) Ratio of peak heights: Fagel and Boës (2008, Palaeo-3)
(4) Ratio of peak areas (without weighting factors): Liu et al. (2010, Mar. Geol.)
Homework:Semi-quantitative calculation of clay minerals
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 16
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Clay Sedimentology, Prof. Zhifei Liu 2017-10-17
School of Ocean and Earth Science, Tongji University 17
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