This document discusses mineral isotopes and chemistry from the Department of Geology at Tanta University in Egypt. It was submitted by Mohamed Mahmoud Ahmed El-Shora and covers topics including radioactivity, stable and unstable isotopes, geochronology using isotope dating, rare earth elements in minerals, and partial melting. Diagrams are included showing isotope ratios and rare earth element patterns in primitive mantle and residual and melt fractions during mantle melting. Methods for calculating mineral formulas based on oxide percentages are also outlined.

1. Tanta University
Faculty of Science
Department of Geology
Submitted by
Mohamed Mahmoud Ahmed El-Shora

2. Mineral Isotopes
Chemistry
REE

3. Mineral Isotopes
Chemistry
REE

4. Radioactivity (Isotope)
• Isotope analysis
• Isotope: are atoms having the same atomic number “Z” but different
masses “A” due to difference in number of neutrons “N”.
• Ex:
• Isobars: atoms having the same mass “A” but different “Z” and “N”.
• Ex:
• Isotones: atoms having the same “N” but different “A” and “Z”.
• Ex:

6. Stable
isotopes
• Atoms do not change into other atoms, but
the only change is the number of “N”
• Have low life time
• Ex: O, H, S, C, N
•

7. Unstable
isotopes
• Parent atom is changed into daughter atom
U……….P
• Associated with the emission of α, β, µ
• Have great life times
• Ex: Sr, Rb, U, Pb
• Present decay process
•

8. Geochronology
• Another importance of
radiogenic isotopes is
usage of them is age dating
of rocks.
• This can be done using the
isochron diagram.
• Rubidium – Strontium
system
Parent atom is changed into daughter atom U……….P

9. Isochron diagram
• τ= 1/λ ln ( slope +1)
• Where:
τ the age
λ the decay constant

10. Ex:

14. Select data, then press insert

15. Press Scatter

17. Right-click
on the
points

22. The Result
• τ= 1/λ ln ( slope +1)
•

24. Isotopes REE
Mineral
Chemistry

25. Mantle Residual
“HREE”
Melt
“LREE”
Partly melting

26. Types of melting
• 1- Fractional Melting
When melt leave magma chamber without react
with residual
So HREE ˃ LREE
• 2- Batch Melting
When melt still in magma chamber and react
with residual
So LREE ˃ HREE

27. 1
La Eu Lu

28. PM
PM : Primitive Mantle
1

29. REE

39. Press here

43. After
inserting the
the value of
each
element
press "Enter"

46. After
inserting the
the value of
each
element
press "Enter"

52. 1
La Eu Lu

53. PM
PM : Primitive Mantle
1

54. BATCH MELTING
BATCH MELTING

58. Mineral
REE Chemistry
Isotopes

59. Calculate the general formula of
group of mineral “Manual”
• The following steps must be performed:
• 1-calculation of the molecular proportion (M.P)
M.P=(WT%/Mwt)*1000
• 2-atomic proportion (ATP)
ATP=M.P*no of (O) oxygen atoms in oxide
• 3-Factor (F)
F=no of (O) in general formula/Sum of ATP
• 4-Number of anions = F*ATP
• 5-Number of Cations =
no of anions*(no of cations/no of (O) in each oxide)

60. Notes
• 5-Number of Cations =
no of anions*(no of cations/no of (O) in each oxide)
EX
• (no of cations/no of (O) in each oxide)= 1/2

61. General Formula
• Pyroxene Group
• Feldspar Group
• Amphibole Group

62. Pyroxene Group

63. Feldspar Group
General Formula
Types of Feldspar:

64. Feldspar Group

65. Feldspar Group

66. Amphibole Group

67. Example for Amphibole Group

68. Example for Pyroxene Group
Oxides Sample 1 Sample 2
SiO2 53.44 52.05
TiO2 0.23 0.21
Al2O3 1.29 2.02
FeO 9.11 12.24
MnO 0.16 0.27
MgO 15.25 10.52
CaO 20.24 23.75
Na2O 0.51 0.44

69. Example for Feldspar Group
Oxides Sample 1 Sample 2
SiO2 65.98 64.1
TiO2 - -
Al2O3 19.58 22.66
Fe2O3 - 0.14
FeO - 0.17
MnO 0.21 -
MgO 0.12 0.25
CaO 0.49 3.26
Na2O 5.9 9.89
K2O 7.88 0.05

70. Minpet 2.02

82. Enter the
data for
the
sample
No. one

83. After
inserting the
the value of
each
element
press "Enter"

84. Enter the
data for
the sample
No. two

87. After
inserting the
the value of
each
element
press "Enter"

108. or

113. Press here

114. 5-Number of Cations =
no of anions*(no of cations/no of (O) in each oxide)

116. P-T Condition
In Pyroxene sample
Cations
Ca
recalculation
Mg Fe

117. In Pyroxene sample

118. PL-Amphibole

119. PL-Amphibole

120. Amphibole only
Wt%

121. Amphibole only
• Wt%
•
•
• Temp & Pressure
•

122. Mineral Isotopes
Chemistry
REE

123. Mohamed M Elshora
President of AAPG-TUSC
Phone (+2)01112078926
OR (+2)01280048933
Mail :
mohamed_elshora35@yahoo.com