halt as silica becomes unavailable, and Reaction 2b takes over. When olivine is abundant, silica activity drops low enough that talc begins to react with olivine:

This reaction requires higher temperatures than those at which brucite forms.

The final mineralogy depends both on rock and fluid compositions, temperature, and pressure. Antigorite forms in reactions at temperatures that can exceed 600 C during metamorphism, and it is the serpentine group mineral stable at the highest temperatures. Lizardite and chrysotile can form

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