Pyrolite is a term used to characterize a model composition of the Earth's upper mantle. The definition varies, but it is generally considered as being 1 part tholeiitic basalt and 3 parts dunite (the term is derived from the mineral names PYR-oxene and o-LI-vine). If fused experimentally, this mix yields high pressure tholeiitic basaltic melts, and intermediate pressure alkaline basalts. The hypothetical pyrolite compositions are not compatible with trace element, isotopic and chondritic abundance data, and are also difficult to reconcile with the evidence for mantle heterogeneity.
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