Teaching Geochemistry Workshop Rock Samples and Geochemical Analysis Maria de Lourdes Rosa & Débora...

Teaching Geochemistry WorkshopTeaching Geochemistry Workshop

Rock Samples and Rock Samples and Geochemical Geochemical

AnalysisAnalysisMaria de Lourdes Rosa & Débora Correia RiosMaria de Lourdes Rosa & Débora Correia Rios Federal University of BahiaFederal University of Bahia Earth Sciences InstituteEarth Sciences Institute BrazilBrazil

Laboratório de Petrologia Aplicada à Pesquisa Mineral – CPGG – IGEO – UFBA


Geochemistry at the Geochemistry at the Federal University of Bahia - Federal University of Bahia -

BrazilBrazil


Geochemistry at the Geochemistry at the Federal University of Bahia (UFBA) - Federal University of Bahia (UFBA) -

BrazilBrazil Brief DescriptionBrief Description

• 2 Disciplines of Geochemistry2 Disciplines of GeochemistryChemistry for Geologists (first year)Chemistry for Geologists (first year)Geochemistry (fourth year)Geochemistry (fourth year)

For who?For who?• Undergraduate students of GeologyUndergraduate students of Geology

Background:Background:• Introductory GeologyIntroductory Geology


Chemistry for Geologists Chemistry for Geologists CourseCourse

Syllabus - Lectures (60%)Syllabus - Lectures (60%) Lab Activities (40%)Lab Activities (40%) 48 students/semester48 students/semester 2 Teachers2 Teachers 75 hours/semester75 hours/semester

• 30 h Lectures30 h Lectures• 45 h Laboratory Activities45 h Laboratory Activities


Laboratory ActivitiesLaboratory Activities 15 Laboratory Activities: 1 per week15 Laboratory Activities: 1 per week The laboratory practices are for students to The laboratory practices are for students to

recognize what is involved in modern recognize what is involved in modern geochemistry analyses of these geological geochemistry analyses of these geological materials:materials:

Rocks and mineralsRocks and minerals WaterWater Soil and sedimentsSoil and sediments


Goals for Lab ActivitiesGoals for Lab Activities Types of materials subject to geochemical analysis.Types of materials subject to geochemical analysis. Procedures and care in sampling.Procedures and care in sampling. Tools for sample preparation.Tools for sample preparation. Avoiding contamination and common errors.Avoiding contamination and common errors. Analytical Instruments at UFBA:Analytical Instruments at UFBA:

• ICP-AESICP-AES• AASAAS• XRFXRF• MicroprobeMicroprobe


Rock Sample Preparation: Rock Sample Preparation: AC-01AC-01

Lab Activity 01: What do geochemical analysis mean?Lab Activity 01: What do geochemical analysis mean?• Research about geochemical analysisResearch about geochemical analysis..

WebsitesWebsites Earth Sciences Institute LibraryEarth Sciences Institute Library

• At this point, we will discuss different kind geologic samples At this point, we will discuss different kind geologic samples and ways of reporting geochemistry data.and ways of reporting geochemistry data. TablesTables Qualitative versus quantitative analysesQualitative versus quantitative analyses Major, minor and trace constituentsMajor, minor and trace constituents Chemical formChemical form



Lab Activity 01: What do geochemical analysis Lab Activity 01: What do geochemical analysis mean?mean?• Students will discuss the analyses as Students will discuss the analyses as

measurements which provide quantitative measurements which provide quantitative information about the chemical composition of a information about the chemical composition of a sample and the importance of the results.sample and the importance of the results.



Lab Activity 02: SamplingLab Activity 02: Sampling• Sample CollectionSample Collection

Sample scheme: What to collect?Sample scheme: What to collect? Geochemical investigation: How to proceed?Geochemical investigation: How to proceed? How many and how much: number and size of How many and how much: number and size of

samples that I needsamples that I need Which tools should be used?Which tools should be used? Identification: Sample protocolsIdentification: Sample protocols

• Field ActivityField Activity NeighborhoodNeighborhood Granite outcropsGranite outcrops



Lab Activity 02: SamplingLab Activity 02: Sampling• Students must understand the importance of Students must understand the importance of

sampling and of a well planned field study and sampling and of a well planned field study and the importance of these steps in the the importance of these steps in the geochemical analysis.geochemical analysis.



Lab Activity 03: Classic Sample PreparationLab Activity 03: Classic Sample Preparation• Granulometric ReductionGranulometric Reduction• Polished slicePolished slice• Rock powder Rock powder • Mineral ConcentrationMineral Concentration• Effects of these choices on the resultsEffects of these choices on the results


Sample Preparation LaboratorySample Preparation Laboratory• 1 Hydraulic rock breaker1 Hydraulic rock breaker• 3 Stell crushers3 Stell crushers• And also other tools…And also other tools…

HammersHammers SievesSieves PaperPaper Storage containers…Storage containers…

Rock Sample Rock Sample Preparation: AC-03Preparation: AC-03



Reciprocating rock crusher Sample Preparation LaboratorySample Preparation Laboratory

• During these steps, During these steps, students will:students will: Perform a typical procedure Perform a typical procedure

for preparing solid rock for preparing solid rock samples for analyses.samples for analyses.

Discuss the media used to Discuss the media used to fabricate the equipments and fabricate the equipments and risks of sample risks of sample contamination.contamination.



Sample Preparation LaboratorySample Preparation Laboratory• During these steps, students will see:During these steps, students will see:

Representative fractions of sample to analyzeRepresentative fractions of sample to analyze Sample storageSample storage Possible sources of systematic errorsPossible sources of systematic errors


Shatter Box

Mineral Concentration LaboratoryMineral Concentration Laboratory• 2 Swing mills2 Swing mills

Tungsten carbide potTungsten carbide pot Agate potAgate pot

• 1 Ball mill1 Ball mill Hardened steel ballsHardened steel balls

• 1 Mineral Separator Table1 Mineral Separator Table• 2 Frantz 2 Frantz

Isodynamic magnetic separatorIsodynamic magnetic separator• Heavy LiquidsHeavy Liquids

BromophormBromophorm




Mineral Concentration LaboratoryMineral Concentration Laboratory• Other skills and goals for this activity are to concentrate mineral Other skills and goals for this activity are to concentrate mineral

grains. Students will be taught that some geochemical procedures grains. Students will be taught that some geochemical procedures require a pure mineral sample and that a single mineral can be require a pure mineral sample and that a single mineral can be physically separated from the rock.physically separated from the rock.



Lab Activity 03: Classic Sample PreparationLab Activity 03: Classic Sample Preparation• At the end of this step, students will At the end of this step, students will

be able to prepare their samples:be able to prepare their samples: Thin sectionsThin sections PowderPowder Mineral concentrationMineral concentration

• Now, they have samples ready for Now, they have samples ready for XRF (powder - solid disc) and XRF (powder - solid disc) and Electron Microprobe analysis (thin Electron Microprobe analysis (thin section).section).



Lab Activity 04: Sample decomposition-solutionLab Activity 04: Sample decomposition-solution

• The Lab environmentThe Lab environment Safety in the geochemistry Safety in the geochemistry

lab lab Equipments Equipments Glasses Glasses Reagent purity and blanks Reagent purity and blanks

• Here, following the physical preparation Here, following the physical preparation procedures, students will perform one or more procedures, students will perform one or more stages of chemical processing. stages of chemical processing.



Lab Activity 04: Sample decomposition-solutionLab Activity 04: Sample decomposition-solutionAcid digestion (open and closed systems)Acid digestion (open and closed systems)Alkaline fusionsAlkaline fusions



Lab Activity 04: Sample Decomposition-Lab Activity 04: Sample Decomposition-SolutionSolution• By the end of this activity, rock samples were By the end of this activity, rock samples were

converted into solution by a variety of procedures.converted into solution by a variety of procedures.• Therefore, we will emphasize the procedures Therefore, we will emphasize the procedures

producing solutions suitable for analysis by ICP-AES producing solutions suitable for analysis by ICP-AES and AAS.and AAS.


Geochemical Analyses: Geochemical Analyses: AC-05AC-05

Lab Activity 05: Running SamplesLab Activity 05: Running Samples• ICP-AES – AAS – XFR – MicroprobeICP-AES – AAS – XFR – Microprobe

ICP-AES AAS


Geochemical Analyses: Geochemical Analyses: AC-05AC-05

Lab Activity 05: Running SamplesLab Activity 05: Running Samples• From the analytical viewpoint, students will perform From the analytical viewpoint, students will perform

the analyses using the instrumental methods the analyses using the instrumental methods available at the Federal University of Bahia.available at the Federal University of Bahia.

• Additionally they will be able to evaluate the Additionally they will be able to evaluate the differences in methods and results by comparisondifferences in methods and results by comparisonTime to get an analysisTime to get an analysisPrecision and accuracyPrecision and accuracyCostsCosts


Student EvaluationStudent Evaluation Students work in groups of four (3 groups Students work in groups of four (3 groups

per class)per class)• For each activity a preliminary reportFor each activity a preliminary report• A seminar bA seminar by the end of the term including:y the end of the term including:

A final write-up: first time they are expected to A final write-up: first time they are expected to write up their own datawrite up their own data

An oral presentationAn oral presentation Seminars allow comparison between the groups. Seminars allow comparison between the groups.

Each one uses a distinct analytical method.Each one uses a distinct analytical method.


DifficultiesDifficulties Restricted fundsRestricted funds Time for assessment this discipline is Time for assessment this discipline is

insufficient insufficient Absence of Technical SupportAbsence of Technical Support

• Labs off-routineLabs off-routine Students missing classesStudents missing classes References:References:

• ScarcityScarcity• Native language: EnglishNative language: English


SolutionsSolutions

Limit field activities to nearby the UniversityLimit field activities to nearby the University Buy some books ourselvesBuy some books ourselves Limiting the course reference to the ones Limiting the course reference to the ones

availableavailable Resuming and translating some texts and making Resuming and translating some texts and making

them available to studentsthem available to students Emphasizing operating methodsEmphasizing operating methods Looking for working labs in other institutesLooking for working labs in other institutes


Nice News…Nice News…

The GeoChronos Net: The GeoChronos Net: • A Brazilian national Earth Sciences Project creating the A Brazilian national Earth Sciences Project creating the

Geochronological, Geodynamic and Environmental Net. Geochronological, Geodynamic and Environmental Net.


The GeoChronos NetThe GeoChronos Net

SHRIMP

LA-ICP-MS

• University of São Paulo

• Federal University of Pará• University of Brasilia• Federal University of RS


AcknAcknwledgmentswledgments

510

Date post:	07-Apr-2016
Category:	Documents
Upload:	carmem-martinho-affonso
View:	216 times
Download:	0 times

Teaching Geochemistry Workshop Rock Samples and Geochemical Analysis Maria de Lourdes Rosa & Débora...

Documents