1. Geochemistry 319
Table of Contents
1. Introduction and Periodic Table
2. Abundance of elements ( Crust Universe and Whole Earth)
3. Recalculation of Mineral Formulae
4. Radiometric dating of rocks
5. Interpretation of chemical analyses. Use of Niggli Values
Mid-Term Exam
6. Interpretation of chemical analyses. Use of CIPW Norm Calculations
7. Interpretation of chemical analyses. CIPW Norm Calculations (Mafic Rocks)
8. Continuation of CIPW Norm Calculations (Ultramafic Rocks)
9. Classification and Naming of the Igneous Rocks
10. Use of ACF Diagrams to Interpret Metamorphic Rocks
The Final
2.
3. Periodic Table
• The periodic table is divided into four blocks (s, p, d, f) based on
which sublevel is in the process of being filled. Alkali metals, alkaline
earth metals, halogens, and noble gases are the common names of
groups 1, 2, 17, and 18.
• Electro positive and electronegative elements
4.
5. • The electron configuration of an element describes how electrons are
distributed in its atomic orbitals. Electron configurations of atoms
follow a standard notation in which all electron-containing atomic
subshells (with the number of electrons they hold written in
superscript) are placed in a sequence.
• 1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s<5f<6d<7p
• I: 1s22s22p63s23p64s23d104p65s24d105p5
• or
• I: [Kr]5s24d105p5
6. subshell number of orbitals
total number of
possible electrons
in each orbital
s 1 2
p 3 (px, py, pz) 6
d
5 (dx
2
-y
2
, dz
2
, dxy, dxz,
dyz)
10
f
7 (fz
3
, fxz
2
, fxyz, fx(x
2
-
3y
2
), fyz
2
, fz(x
2
-y
2
),
fy(3x
2
-y
2
)
14
28. Q 2. Follwing is the chemical analysis of a feldspar mineral. You are
required to
Calculate the chemical formula on the basis of 24 Oxygens.
Calculate the mole percent of Ab , An and Or.
Predict the type and name of feldspar by plotting on the triangular
(ternary) diagram.
31. Isotopes
• Isotopes are variants of a particular chemical element which differ in neutron
number, and consequently in nucleon number. All isotopes of a given element
have the same number of protons but different numbers of neutrons in each
atom.
• The abundances of parent and daughter isotopes in a sample can be measured
and used to determine their age. This method is known as radiometric dating.
The amount of time that it takes for half of the parent isotope to decay into
daughter isotopes is called the half-life of an isotope
• Radiometric dating, often called radioactive dating, is a technique used to
determine the age of materials such as rocks. It is based on a comparison
between the observed abundance of a naturally occurring radioactive isotope
and its decay products, using known decay rates.
• Carbon, uranium, and potassium are just a few examples of elements used in
radioactive dating. Each element is made up of atoms, and within each atom is a
central particle called a nucleus. Within the nucleus, we find neutrons and
protons; but for now, let's just focus on the neutrons
32.
33. The ratio of parent to daughter after one half-life will be 1:1. After two half-lives,
half of the remaining half will decay, leaving one-quarter of the original
radioactive parent atoms. Those transformed atoms bring the tally
of daughter atoms to three-quarters of the crop of parent plus daughter atoms.
34.
35.
36. Radiocarbon dating is also simply called carbon-14 dating. Carbon-14 is a
radioactive isotope of carbon, with a half-life of 5,730 years (which is very short
compared with the above isotopes), and decays into nitrogen.
When an organism dies, it ceases to take in new carbon-14, and the existing isotope decays
with a characteristic half-life (5730 years). The proportion of carbon-14 left when the
remains of the organism are examined provides an indication of the time elapsed since its
death.
The rate of decay is conveniently expressed in terms of an isotope's half-life, or the time it
takes for one-half of a particular radioactive isotope in a sample to decay.
Most radioactive isotopes have rapid rates of decay (that is, short half-lives) and lose their
radioactivity within a few days or years.
40. https://youtu.be/rQVzNynZ9vM
Radiocarbon dating (also referred to as carbon dating or carbon-14
dating) is a method for determining the age of an object containing
organic material by using the properties of radiocarbon,
a radioactive isotope of carbon. ... The development
of radiocarbon dating has had a profound impact on archaeology.
https://youtu.be/5aX2YcOjyKE
46. • . Using the decay equation and the calculated slope from the
isochron plot:
• Slope = λt; or t = Slope/ (1.42 x 10-11)
•
• For the Cathedral Peak Batholith, the calculated slope is: 0.001336;
• the calculated Sri (intercept) is: .7063
•
• t = (.00136)/(1.42 x 10-11) = 9.58 x 107 ≈ 96 Ma (million years)
