Possible xenolith noble gas components

A variety of components may be present in a mantle xenolith sample. As discussed in subsequent sections, considerable effort is often required to detect and confirm the presence each particular component. 

Cosmogenic Ne contributions have also been measured (Staudacher and Allegre 1991, 1993). Samples studied more recently are generally collected from where exposure was limited due either to shielding by burial or recent eruption. 

In general, in order to characterize the noble gas state of the continental lithosphere, it is necessary to measure or clearly deduce the pre-entrainment noble gas isotope inventories of xenolith samples. This first requires subtracting the effects of post-eruption 

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Distinctive lithospheric mantle He. As discussed in the Possible xenolith noble gas components section, radiogenic production within the lithosphere can lower the He/ He ratio of He derived from the convecting mantle. Therefore, the He represents a distinctive lithospheric component. This may be created in the xenolith source region, or may involve He that is remobilized in the lithosphere. As discussed below, regional studies often contend with distinguishing between distinctive asthenospheric and lithospheric sources for such He. 

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