Xenoliths mineral suites

Along with studies of melt inclusions, the study of mantle xenoliths (samples of mantle material entrained and brought to the surface in eruption magmas) and exhumed mantle rocks is one of the most common applications of SIMS for trace element analysis. SIMS is ideally suited to this task, as there is no need to try to make mineral separates from what are often limited amounts of sample, alteration can be prevented, and zoning easily studied. 

Cr-poor variety widespread, locally abundant (e.g.. Monastery). Garnets, clino- and orthopyroxenes, phlogopite and ihnenite most common, zircon and olivine rarer. Debatable whether phlogopite and olivine are members of Cr-poor suite. Wide range in chemistry but Cr-poor, Fe-Ti-rich relative to type I (low-Z) peridotite minerals. Mineral chemistry and estimated equilibration P/Ts overlap those of type V (high-Z) Iherzolites. Some Slave craton Cr-poor megacrysts show mineral chemistry links to type II megacrystalline pyroxenite xenoliths. See review of Schulze (1987). 

Studies of mantle xenoliths have confirmed the view from seismology that peridotite is volumetrically the dominant component of the Earth s shallow mantle (<400 km) (see Chapter 2.02). This is because xenolith suites in almost all tectonic environments are dominated by peridotites. Even at localities where other lithologies such as eclogite dominate the intact xenolith suite, mineral concentrate studies show that peridotite dominates the inventory of entrained mantle material (Schulze, 1989). Major- and trace-element studies of mineral concentrates from mined kimberlites have also been used to illustrate... 

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