Meteorite Oslo - Regolith compaction and fluid alterations

Meteorite Oslo is an H3-6 ordinary chondrite breccia, that samples regolith of an S-type asteroid. These asteroids are basically anhydrous, but ordinary chondrites contain minerals that suggest that some fluid alteration may have affected the bodies. Based on the chemistry of phosphates, and in rare cases of halite, it is supposed that Cl-rich ‘dry’ fluids circulated in the regolith.

Sources of these fluids and time of alteration, as well as processes that drive fluid circulation, are not fully understood, however. Oslo meteorite, with its light-dark structure, is a primer example of a regolith breccia that recorded lithification probably accompanied by ‘dry fluid’ circulation. The two contrasting lithologies in Oslo – the dark H3 and light H6, differ in equilibration degree, structure and general chemistry of halogen-bearing minerals.

The project would investigate the history of brecciation and lithification of meteorite and put the formation of phosphates and other minerals capturing fluid alteration in the context of the regolith gardening processes.
 

Aims:

The aim of the project is to understand the distribution of fluid alteration minerals in Oslo regolith breccia and by this to further our understanding of the processes that redistribute halogens and volatiles in S-type asteroids.

Objectives:

1. To reconstruct brecciation of the chondrite and to provide context for lithification history.
2. To study chemistry and structure of phosphate minerals in various lithologies of Oslo.
3. To correlate halogen chemistry and deformation record with processes responsible for lithification and regolith gardening

Data

The project will generate EDX maps on several thin sections, EPMA point data of chosen minerals and EBSD maps of selected examples. All data will be collected in correlated workflow required for reconstruction of the process.

Tools and methods:

• Project is mainly analytical. EDX, EPMA and EBSD will be used.
• Depending on previous experience and skills of the student HR-XCT may be incorporated to the workplan.

Learning outcomes:

• State-of-the art analytical techniques, application, data reduction and interpretation
• Ability to work in a correlated analytical workflow, important to deal with a limited amount of extraterrestrial material
• Knowledge of current problems in studies of small solar system bodies dynamics and structure
•  Familiarization with problems of fluid alterations and shock metamorphism
   

Recommended skills:

• Knowledge of mineralogy and petrology.
• Basic knowledge of microbeam techniques.
• Interest in planetary geology and meteorites.
• Basic knowledge of planetary science is advantageous, but not required for start.

Project organization:

• Literature review and required course work
• Familiarization with EDX, EPMA EBSD
• Chemical composition – EDX and EPMA data collection
• Data reduction and interpretation
• EBSD data collection and interpretation
• Interpretation in the broader-scale context
• Inferring conclusions regarding fluid alteration time and potentially triggering processes
• Preparing a publishable manuscript with the results