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Reading: Brearley (2006)

1. Brearley makes a distinction between what he calls aqueous alteration and fluid-assisted metamorphism.  What is this difference?

2. How does the author reconcile evidence for large chemical fractionations between matrix and CI chondrite bulk compositions (Fig. 2) and the generally solar compositions of chondritic meteorites?  What does he say this implies for fluid flow in parent bodies?  For where alteration occurred?

3. Create a table listing the main alteration products (minerals) for the following meteorite groups and classes:
 

group or class	main alteration minerals
CI
CM2
CM1
CR
CO
CVoxA
CVoxB
CVred
ordinary

Indicate by an asterisk those phases produced by fluid-assisted metamorphism.

4.  Summarize how alteration is thought to proceed in the well-studied CM chondrites.  Mention phases being destroyed and created and other chemical and isotopic changes.

5. Contrast the results of aqueous alteration models for ²⁶Al heating of icy bodies.  What effect do variations in initial ice and ²⁶Al content have on alteration timescales and temperatures?  What effect does parent body size have (e.g., consider bodies <50 km and >50 km in diameter)?