Lamproltes include a range of compositions which have high Mg-nuraber, N1 and Cr, and carry mantle-derived ultramaflc nodules, and thus appear to represent little-modified mantle-derived liquids. These range in SlOo content from about 40 wt% to at least 51 wt%, and experimental work has indicated that leucite lamproltes as silica-rich as 55 wt% could be in equilibrium with mantle minerals at high pressures [ Barton and Hamilton 1982]. Petrogenetlc models must explain this range of apparently

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... mary magmas, which may be greater than 10 wt% Si02 within a single volcanic field, such as the West Kimberley region of Western Australia.