Anatomy of Shaku–dake high–Mg diorite, southwest Japan: Lithofacies variations and growth process of high–Mg diorite stock

The Shaku–dake body represents a two–pyroxene diorite (TPD) located in the Northern Kyushu region southwest Japan and is member of Cretaceous batholith. Layered structures feeder dikes wall TPD are recognized as magma plumbing systems that result from pulses. pulses were likely provided localized anomalous spots, which have been horizontal variations modal, major, trace element compositions body. Vertical variation indicates irregular changes, differentiated facies rich modal quartz K–feldspar appear at altitudes 300–450 m; however, mafic pyroxenes MgO, Cr, Ni contents also present same altitude. Field observation, petrography, geochemical features suggest could formed by multiple injections several sites. On other hand, exsolution texture clinopyroxene appears center body, indicating slow cooling. Overall, prolonged supra–solidus state. A sheet–on–sheet intrusion model was most plausible mechanism for addition andesitic to reservoir. Multiple may involved formation chamber, where cooled quickly left layered structure; additionally, caused cooling interior.