Teaching Geochemistry with a Lab: Problems, Pitfalls, and Potential Solutions?

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Teaching Geochemistry with a Lab Problems,
Pitfalls, and Potential Solutions?

• Aley El-Shazly
• Geology Department
• Marshall University

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Background and History

• Four person department offering BS degrees with
  emphasis in
• Geology
• Engineering Geology
• Environmental Geosciences
• Average 25 30 majors
• Geochemistry is a 400 level class required for
  environmental geoscience emphasis

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Background and History

• Geochemistry is 4 credit units with a lab
• Offered every other year
• Pre-requisites are Physical Geology Chem I II.
• Enrollment is very low typically 2 3 students!

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Why a Lab?

• Most Geochem classes offered w/o a lab!
• Environmental issues their importance to WV!
• Marshall fairly well equipped for an
  undergraduate program of this size!

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Equipment
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Equipment

• II- Scanning electron microscope
• Capable of
• imaging at magnifications up to 200,000 X.
• Qualitative analysis for all elements with atomic
  number higher than 8
• Quantitative analysis of spots in solids as small
  as 2 ?m

JSM-5310LV SEM with an Oxford Instruments EDS
detector, and ISIS 300 software
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equipment

• III- Varian Liberty 110 Inductively Couples
  Atomic Emission Spectroscope (ICP-OES)
• Capabilities
• Useful for analysis of dilute solutions
• Elements (mostly metallic) are detected at the
  parts per million level (ppm).

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Equipment

• IV- Varian Spectra AA 600 Zeeman Graphite Furnace
  Atomic Absorption Spectrometer (GF-AAS)
• Useful for the analysis of dilute aqueous
  solutions
• Concentrations of cations detected at the part
  per billion (ppb) level .

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Equipment

• 1960s GE XRD/XRF
• Spex Mill standard equipment for crushing,
  grinding, sieving, sawing, and polishing rocks
• Frantz Isodynamic separator separatory funnels
  heavy liquids Centrifuge
• Muffle furnaces
• Wet Chemistry lab w/ pH meter water chemistry
  kits digital titrators pipettes all
  necessary glassware
• ICP-AES
• ZGF-AAS
• SEM with EDS
• Access to Hach spectrophotometers
• Access to TEM and AFM in Biotechnology Center,
  and portable spectrophotometers

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The early attempts an ambitious (unrealistic?)
syllabus!

• Introduction Basic chemical principles. Basics
  of calculus.
• Cosmochemistry Origin of the Solar system
  nucleosynthesis Cosmic abundance of elements
  Meteorites Differentiation of the Earth, Origin
  of atmosphere hydrosphere
•  Mineral and Crystal Chemistry Types of bonding,
  coordination numbers, crystal structures,
  polymorphism Isomorphism, Goldschmidts rules
  for substitution Camouflage, capture admission
• Distribution and Association of elements The
  Periodic Table of elements Goldschmidts
  classification Distribution of elements in
  igneous, sedimentary, and metamorphic rocks
  Partition coefficients, Trace elements in igneous
  petrology
• Chemical equilibrium The Phase rule, Phase
  diagrams, Reversible and irreversible chemical
  reactions, Balancing reactions, Law of Mass
  Action, Le Chateliers principle, Solubility
  products, Common ion effect, Activity, Fugacity
•  Thermodynamics 1st, 2nd, and 3rd laws Gibbs
  Free Energy, Enthalpy, Entropy, Heat capacity,
  thermal expansion, compressibility. Some key
  relations. Applications.
•  Water chemistry Properties of water Acids
  bases pH, Dissociation constants, Ionic
  concentrations, Buffers, pH-pC diagrams  
•  Solution Mineral equilibria carbonates
  silicates Chemistry of groundwater chemistry of
  seawater, Analysis of water samples, Mixing,
  Dilution, Evaporation. Activity - activity
  diagrams weathering and mineral stability
•  Kinetics Diffusion Nucleation Growth
•  Oxidation and Reduction Eh pH diagrams
•  Radioactive isotopes Age dating techniques
•  Stable Isotopes Principles, applications
•  Organic Geochemistry

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The early attempts an ambitious (unrealistic?)
LAB syllabus!
Topic Equipment
Basic principles and objectives safety measures Grand tour of the labs
Sample crushing, sieving and separation of minerals Frantz Isodynamic separator
Principles of X-ray Diffractometry Tutorial for HW 2 3 XRD
First MT exam
Acid digestion preparation of standard solutions Wet Chemistry Lab
Analysis of aqueous solutions ICP-AES
Analysis of aqueous solutions GF-AAS
Water chemistry pH meter spectrophotometers
Second MT Exam
Analysis of minerals in thin section SEM
Other techniques (XRF, EPMA, ICP-MS). Work on projects
Work on projects/ tutorials for homeworks XRD, SEM, ICP-AES.
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The early attempts an ambitious (unrealistic?)
syllabus!

• Grading
• 3 tests 50
• Homeworks 20 8 problem sets covering
• Cosmochemistry
• Periodic table Crystal chemistry
• Trace elements in igneous rocks
• Phase rule phase diagrams
• Balancing chemical reactions
• Thermodynamics
• Water chemistry
• Weekly Labs 15.
• Lab project term paper 15

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The early attempts

• Major Problems
• Ran out of time! Organic geochemistry was not
  covered in lecture!
• Students who have not had Mineralogy struggled!
• Students failed to turn in homeworks on time
  homeworks were very painful!
• There was little time for tutorials
• Labs took longer than the 2 hour period allocated
• SEM and ZGFAAS how much did they really learn?
• Usual annoying comments about thermodynamics in
  students evaluations

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New Approach Split lab from lecture!

• Designed a separate 300 level lab class called
  Lab techniques in Geology and Environmental
  Science
• Class is aimed at familiarizing students with
  capabilities of equipment in Geology/ CoS.
• Lab caters to all Science majors who may make use
  of our equipment for their capstone projects
• Only pre-requisite is Physical Geology and Earth
  Materials Lab
• Lab is worth 2 credit hours lab period is 3
  hours long, meeting once a week.
• Lab starts with a theoretical background of
  equipment to be used for 45 minutes.
• Enrollment limited to 6

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GLY 320L Lab techniques in Geology and
Environmental Science
Topic Equipment
Basic principles and objectives safety measures Grand tour of the labs
Sample crushing, sieving and separation of minerals Frantz Isodynamic separator
Principles of X-ray Diffractometry XRD
Analysis of aqueous solutions I Mixing Dilution Preparation of standards analysis for Al, Mn, Fe. ICP-AES
Analysis of aqueous solutions II Standard Addition techniques ICP-AES
Analysis of aqueous solutions III Trace amounts GF-AAS
Chemistry of Natural waters Cations anions pH meter spectrophotometers Hach digital titrator and kits
Bulk chemical analysis of rock samples major elements ICP-AES
Bulk chemical analysis of rock samples trace elements ICP-AES
Analysis of minerals in thin section Principles imaging SEM
Analysis of minerals in thin section quantitative analysis SEM
Microthermometry of fluid inclusions Linkam Stage
Other techniques (XRF, EPMA, ICP-MS). Lecture only
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GLY 320L Lab techniques in Geology and
Environmental Science

• I- Grading
• Weekly lab reports 85
• Final Exam 15

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II- Examples SEM Lab Exercise
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II- Examples SEM Lab Exercise

• Students are asked to obtain
• A BSEI w/ mafic and felsic minerals identify all
  minerals in your picture with the help of the
  EDS.
• A Secondary electron image of the same area.
• An X-ray image of a zoned plagioclase feldspar
• A linescan of the same zoned plagioclase feldspar
  crystal.
• A quantitative analysis of one mineral Hb/Bt vs.
  Pl/Or
• Stoichiometry of the Pl, Or, Bt, or Hb
• A 2 page report on this sample with all the
  results that you obtained.
•  

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GLY 320L Lab techniques in Geology and
Environmental Science

• III- Student Comments
• Would prefer a project over a final exam!
• All would opt for a project of major element
  analysis using the ICP-AES!
• All enjoyed the SEM work the most!
• Most enjoyed major element analysis of rocks and
  the use of GCDkit or Petrograph!

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GLY 320L Lab techniques in Geology and
Environmental Science

• IV- Pitfalls to avoid
• Objectives make sure that they are clearly
  stated for each lab
• Using your (current) research samples do not
  attempt to get meaningful data through the
  student lab
• Sample Preparation provide the students with
  pre-prepared (and preferably pre-analyzed)
  samples
• Data manipulation/ interpretation factor the
  time needed for that .. provide sufficient PC
  support
• Projects Have those ready for students, chances
  are most wont be able to come up with ones in
  the course of the semester

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GLY 320L Lab techniques in Geology and
Environmental Science

• IV- Outstanding Problems
• Very time-consuming Need to prepare and analyze
  solutions ahead of time best if you had a
  technician/ TA.
• Students must be supervised at all times if they
  work in pairs, that triples your contact hours!
• Students w/o a background in Mineralogy struggle
  with mineral separation/ SEM lab/ stoichiometry/
  XRD lab.

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Outstanding Problems with teaching Geochemistry
(w/ or w/o lab)

• A good comprehensive textbook?
• Thermodynamics! Calculus!
• Lack of background in Mineralogy is a serious
  problem ? Two year rotation?
• Low enrollments?
• How can we measure our true success?

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• Thank You!