answer is A. Pls refer to the following passage for details: For example, G10 garnets,
a type of garnet typically found in (45) diamond-rich pipes, are lower in calcium and higher in chrome than garnets from barren pipes. Geo- chemists John Gurney showed thatgarnets with this composition were(50) formed only in the diamond-stabilityfield; more commonly found ver-sions came from elsewhere in the mantle. |