Magmatic differentiation in the Uwekahuna Laccolith, Kilauea Caldera, Hawaii

Petrographic and chemicoal studies of a suite of rocks from the Uwekahuna laccolith of Kilauea Volcano show that the original mafic tholeiitic magma differentiated into tholeiitic picrite, tholeiitic olivine gabbro, and an aphanitic rock approaching quartz-basalt in composition. Mechanisms involved were an initial gravity settling of olivine and a final filter pressing of the residual liquid. The range of composition represented by the rocks of the laccolith is as great as that found among all hitherto analysed lavas of the volcano.