Re. garnets as indicator minerals: Try this page out for starters, as a brief educational source:
syd.dem.csiro.au
Diamond Exploration
Geochemical methods of diamond exploration rely on recognizing indicator minerals that formed in the earth's upper mantle, within the diamond stability field, and were entrained in rapidly rising volatile-rich magmas and emplaced in or on the crust (Fig. 1). Diamond is only stable at high pressure. Therefore, diamond exploration commonly targets prospects containing high pressure minerals, such as low-Ca, high-Cr ("G10") garnets and high-Cr chromites, similar to inclusions in diamonds. However, this procedure can be ambiguous; some barren pipes contain abundant "G10" garnets, while such garnets are extremely rare in the Argyle pipe, the world's largest diamond producer. Similarly, high-Cr chromites are shed by a wide variety of barren rock types...
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Also,
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NRC - Kimberlite indicator minerals in till (NWT) -
sts.gsc.emr.ca
- Plenty there, including:
sts.gsc.emr.ca
Introduction
Diamond exploration in glaciated terrain differs from precious or base metal exploration in that it uses indicator minerals and boulders, instead of till geochemistry, to detect glacial dispersal from a kimberlite...
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Lots more at the links -- hope it helps some, anyway.
Cheers,
-j
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