TY - JOUR AU - Gilluly, James AB - The structures of continental plates and of oceanic basins suggested by several seismologists are utilized to estimate the relative volumes of sial and sima in the earth's crust. It seems that sial of the composition of the average igneous rock constitutes fully 26% and perhaps as much as 43% of the total crust. This ratio is far higher than seems likely if the sial had been entirely derived through fractional crystallization of a basaltic magma. The relative paucity of intermediate rocks as compared with granite and gabbro in the crust points in the same direction. The tentative conclusion is reached that the sial owes a large part of its volume to some process other than fractional crystallization of basalt—possibly to the emanation of low-melting constituents such as water, silica, potassa, soda, and alumina directly from the mantle to the crust. TI - Composition of the continental plates JF - Mineralogy and Petrology DO - 10.1007/BF01140407 DA - 2005-01-27 UR - https://www.deepdyve.com/lp/springer-journals/composition-of-the-continental-plates-3ObgTaFDQ7 SP - 360 EP - 369 VL - 4 IS - 4 DP - DeepDyve ER -