Mantle-derived K-rich melts had intrigued most of the founders of petrology and many of the later experts in field and experimental geology, because they are sometimes associated with carbonatites and even diamond. They tend to contain anomalous concentrations of many such elements as K, Rb, Sr, U.F.P. etc. along with Ni, Co, and Cr indicating a mixture of crust and mantle. For key isotopic indicators like Sr86/Sr87, O16/O18, they show great variability. In addition most of these rocks are young with few ancient examples. Is this real or the result of a sampling problem? Modern observations leave no doubt that sediments must be subducted on a large scale. There is now evidence that the upper mantle (and perhaps even the lower mantle) is not homogeneous but rather like a fruit cake, and that thermal anomalies in the mantle resulting from deep mantle plumes or deep subduction, can release these unusual rocks clearing the mantle of left over subduction material. This volume, written for those interested in the geochemistry of K-rich melts from the deep earth, reviews the present state of knowledge of these unique volcanic rocks.
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