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The kimberlites of Riley County, Kansas contain xenoliths of upper mantle and crustal rocks. The kimberlite probably originated below the Low Velocity Zone (LVZ). Deep seated xenoliths include ilmenite-pyroxene symplectites, lherzolite, and eclogite. Other xenoliths from below the Moho include pyroxenites, plagioclase-bearing eclogites, and several types of granulites. Above (or near) the Moho (35 kilometers depth) occur granulites overlain by metanorites which in turn are overlain by noritic-gabbroic rocks and diorites. Metamorphic amphibolite and schistose xenoliths are rare, as too are granitic rocks. Presumably the granites occur below the Rice Formation (Arkosic Rocks) and Clay Formation (Basaltic Rocks) which are in fault contact with each other and extend into the midcontinental region from the Lake Superior Province. Above the Precambrian basement, there occurs approximately 1.7 kilometers of Paleozoic shales and limestones; xenoliths of these rocks are common in the kimberlite diatremes. |
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