geochemistry 2012

Tanta University Faculty of Science

Department of Geology

Geochemistry 2012 4th year- 2nd term

Submitted byMohamed Mahmoud Ahmed El-Shora

Isotopes

REE

Mineral Chemistry

Geochemistry

Isotopes

IsotopesMineral Chemistry

REE

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:

Isotopes

Stable isotopes

Unstable isotopes

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• عدد في لتغير نتيجة العنصر لنفس نظائر ايالنيترونات

• 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• لعملية نتيجة اخر لعنصر عنصر من يتغير العنصر اياالشعاع

Unstable isotopes

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

Isochron diagram

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

Ex:

القيم عمودمتشابهه الغير

المتشابهه القيم عمود

Select data, then press insert

Press Scatter

Right-click on the points

The Result

• τ= 1/λ ln ( slope +1)

• القانون هذا عوضفيالعمر هو والناتج

The End Of Isotopes

REE

Mineral Chemistry

Isotopes

REE

Man

tle Residual“HREE”

Melt“LREE”

Partly melting

Types of melting

• 1- Fractional Melting When melt leave magma chamber without react with residualSo HREE ˃ LREE• 2- Batch Melting When melt still in magma chamber and react with residualSo LREE ˃ HREE

1Fractional Melting

HREE ˃ LREEشديد الخط انحدار

BATCH MELTINGLREE ˃ HREE

خفيف الخط انحدار

Normalization

EuLa Lu

LREE HREE

Normalization = conc in rock / conc in PM

PM : Primitive Mantle

1Enrichment

Depletion

Metasomatism“Rock was attacked by

Melt”

REE

1

2

1

2

Press here

1

2

After inserting the the value of

each element

press "Enter"

1

2

After inserting the the value of

each element

press "Enter"

1

2

1

2

3

1Fractional Melting

HREE ˃ LREEشديد الخط انحدار

BATCH MELTINGLREE ˃ HREE

خفيف الخط انحدار

Normalization

EuLa Lu

LREE HREE

Normalization = conc in rock / conc in PM

PM : Primitive Mantle

1Enrichment

Depletion

Metasomatism“Rock was attacked by

Melt”

Enrichment

Depletion

Metasomatism

BATCH MELTING

BATCH MELTING

Mineral Chemistry

Isotopes

REE

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)

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

SiO2

General Formula• Pyroxene Group

• Feldspar Group

• Amphibole Group

Pyroxene Group

Feldspar Group

Types of Feldspar:

General Formula

Feldspar Group

Feldspar Group

Amphibole Group

Example for Amphibole Group

Sample 2 Sample 1 Oxides

52.05 53.44 SiO2

0.21 0.23 TiO2

2.02 1.29 Al2O3

12.24 9.11 FeO

0.27 0.16 MnO

10.52 15.25 MgO

23.75 20.24 CaO

0.44 0.51 Na2O

Example for Pyroxene Group

Example for Feldspar GroupSample 2 Sample 1 Oxides

64.1 65.98 SiO2

- - TiO2

22.66 19.58 Al2O3

0.14 - Fe2O3

0.17 - FeO

- 0.21 MnO

0.25 0.12 MgO

3.26 0.49 CaO

9.89 5.9 Na2O

0.05 7.88 K2O

Minpet 2.02

To Create File

Enter the data for the sample No. one

After inserting the the value of

each element

press "Enter"

Enter the data for the sample No. two

After inserting the the value of

each element

press "Enter"

or

To calculate the general formula from minpet

Press here

T=Z , M1=Y , M2=X

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

T=Z , M1=Y , M2=X

P-T Condition In Pyroxene sample

Ca

FeMg

Cations بـــــ بشتغل

recalculation

In Pyroxene sample

PL-Amphiboleالقانون في بيها واعوض طلعت اللى الكاتيون نسبة باخد

الرسم في واوقع

PL-Amphibole

Amphibole onlyWt%

Amphibole only

• Wt% بـــــــ بنشتغل• العينة هي التقاطع نقطة• الـــ واشوف انزل• Temp & Pressure• يكون ان البد التوقيع

للخطوط موازي.األساسية

IsotopesMineral Chemistry

REE

Best RegardsMohamed M Elshora

President of AAPG-TUSCPhone (+2)01112078926 OR (+2)01280048933Mail : mohamed_elshora35@yahoo.com