日本列島を構成する地質体の岩石密度：岩石物性データベースPROCKに基づく見積もり

抄録

Mean dry and wet bulk densities of the rocks of various ages and occurrences in Japan were estimated by sorting a set of reliable data retrieved from the database PROCK. Within the limited data, dry bulk density of clastic sedimentary rocks obviously increases up to 2.7×10³ kg·m⁻³ with increasing age; largely from recent to early Miocene time and slightly in earlier times. Wet bulk density is larger than dry bulk density for younger clastic rocks, especially for younger sandstone. The difference, however, becomes negligible with increasing age, perhaps due to increasing porosity reduction by compaction and chemical precipitation. No obvious difference in variation of density is found between sandstone and mudstone and between their occurrences. Felsic and mafic volcanic rocks slightly increase in dry and wet bulk densities from 2.4 to 2.6×10³ kg·m⁻³ and from 2.5 to 2.8×10³ kg·m⁻³ with increasing age. Dry and wet densities of felsic plutonic rocks are between 2.6 and 2.7 ×10³ kg·m⁻³. Only few data is available for mafic plutonic rocks and ultramafic rocks. The dry or wet bulk densities of crystalline schist and gneiss are close to 2.7 and 2.8×10³ kg·m⁻³. Few density data are available for other types of metamorphic rocks.