Analysis of Partial Melting ^ of CR and R Chondritic Meteorites

Courtney King,

Kathryn Gardner-Vandy,

Dante Lauretta

Lunar and Planetary Laboratory, University of Arizona

Objectives

• The study of meteoritics is important in order to learn about materials and environments of the early Solar System

• Understand the origin of oxidized (Fe2+) igneous meteorites– Brachinites– Other primitive

achondrites

Background

• Types of meteorites: – Chondrites (undifferentiated)– Primitive Achondrites– Achondrites (differentiated)

• CR chondrite group– Aqueous alteration

• R chondrite group– Highly oxidized: Olivines

and sulfides

• Brachinites– Sulfides and oxides present– Fe in Olivine

Steps for Analyzing a Meteorite• Receive sample from Meteorite

Working Group (MWG)• Cut sample into pieces and

weigh• Mount a piece in epoxy and

polish until smooth• View/analyze the mounted

sample using Electron Microprobe

• Perform a partial melting experiment

• Repeat mounting process to analyze partially melted sample using probe

Renazzo• CR2

– Type 2: Low grade aqueous alteration

• Rim of metals/sulfides– Kamacite < 6% Ni– Taenite > 6% Ni

• Chondrule– Kamacite next to Taenite – Kamacite next to sulfides

Pyrrhotite, Troilite• Stoichiometric

Equilibrium• Presence of a Sulfur gas

mixture: sulfurization of FeNi alloy (FeS)

Experimental Set-up

• Temperature Controller

• Pyrometer• Induction Furnace• Thermocouple• Gas flow Ar• QMS• Close up:

– Al2O3 crucible– Platinum

Experiments

• Partially melted R chondrite– 1200º C, Ar gas– Found: veins of troilite

(FeS) surrounding unmelted olivine (FeMg)2SiO4

– Texture: coagulated

• Temperature calibrations– Halite, Troilite– Ag, Cu

Photo courtesy: Kathryn Gardner-Vandy

Implications of the Data

• Question: What happens when a meteorite containing reduced iron (Fe0) and aqueous alteration is heated?– Possibility of producing oxidized iron (Fe2+); Olivine

• Metal/sulfide textures respond rapidly to melting• What to look at:

– Kamacite < 6% Ni – Taenite > 6% Ni– Kamacite Troilite (FeS)

• Sulfur gas, H2S

Thank you!

– Dante Lauretta

– Kathryn Gardner-Vandy

– Katrina Jackson