Lesson 1X-ray diffraction (XRD): phase identification goals and sample preparation notesCover XRD for BIF, aiming at phase spotting, measuring iron oxides, carbonates, silicates, and spotting non-crystalline parts. Stress sampling, grinding, and avoiding alignment issues.
Choosing representative XRD samplesPowder preparation and grain-size controlInstrument settings and scan parametersIdentifying iron oxides, carbonates, silicatesSemi-quantitative phase estimation limitsLesson 2Stable isotopes (O, Si, C): what each proxy reveals about temperature, fluid sources, and diagenesisLook at stable oxygen, silicon, carbon isotopes in BIF materials, what they say about temps, fluid origins, rock-water reactions, and alteration, plus combining multi-isotope data with thin section views.
Sampling carbonates, cherts, and silicatesO isotope constraints on fluid temperatureSi isotopes and silica source signalsC isotopes in associated carbonatesCombining isotopes with petrographyLesson 3Dating approaches relevant to BIF studies: U-Pb on intercalated volcanics or zircons, Re-Os on sulfides, and stratigraphic correlation methodsReview dating for BIF layers, like U-Pb on zircons in volcanic layers, Re-Os on sulphides, chemostratigraphy, and rock matching, noting strengths, doubts, and combining methods.
Selecting datable interlayered unitsU-Pb zircon sampling and interpretationRe-Os sulfide sampling and limitationsChemostratigraphic correlation in BIFsIntegrating ages with regional stratigraphyLesson 4Designing a sampling plan: sample spacing in outcrop and core, targeting cycles, and strategies for composite sectionsPlan BIF sampling in outcrop and core, with spacings, aiming at cycles, facies changes, and composite sections that keep stratigraphy while being practical.
Defining scientific questions and scalesSampling spacing in outcrop and coreTargeting facies and cycle boundariesBuilding composite stratigraphic sectionsDocumenting locations and metadataLesson 5Optical petrography: objectives, thin-section techniques (transmitted and reflected light), and key textures to documentIntroduce microscope study for BIF, using transmitted and reflected light on thin sections to show minerals, textures, tiny structures from deposition, alteration, deformation, fluids.
Objectives of BIF petrographic studiesPreparing transmitted light thin sectionsPreparing reflected light polished sectionsRecognizing primary banding and laminationIdentifying diagenetic and metamorphic texturesLesson 6Iron isotope analyses and their interpretive use for redox and source studiesIntroduce iron isotope work in BIF, sampling, cleaning, mass spec, and how Fe isotope values pin down redox, sources, microbes, alterations in old basins.
Sampling strategies for Fe isotopesChemical purification of iron fractionsMC-ICP-MS measurement considerationsInterpreting δ56Fe in depositional settingsRecognizing diagenetic isotope overprintsLesson 7Types of samples: bulk rock, oriented slabs, thin sections, polished mounts, and targeted micro-drilled powdersDefine BIF sample kinds and uses, from whole rock and slabs to thin sections, polished blocks, micro-drills, each for petrography, chemistry, isotopes.
Bulk rock samples for whole-rock chemistryOriented slabs for structural contextStandard and doubly polished thin sectionsPolished mounts for reflected light and EMPAMicro-drilled powders for isotope analysesLesson 8Whole-rock major and trace element geochemistry (XRF/ICP-MS): elements to measure, expected ranges, and redox-sensitive proxies (Fe, Si, Mn, P, rare earth elements)Explain whole-rock XRF/ICP-MS for BIF, targets, ranges, redox proxies like Fe, Si, Mn, P, REE to read deposition and alteration conditions.
Sampling and contamination avoidanceFusion and dissolution preparation methodsKey major elements and Fe/Si ratiosTrace elements and REE pattern metricsRedox-sensitive elemental proxy selectionLesson 9Electron microprobe and SEM-EDS: mineral chemistry, zoning, and micro-texture documentationDetail electron probe and SEM-EDS for BIF, mineral chemistry, zoning, tiny textures. Design lines, read maps, link to whole-rock chemistry.
Sample polishing and coating requirementsBackscattered and secondary electron imagingPoint analyses and line transectsElemental mapping of mineral zoningLinking microtextures to bulk chemistry
