The partitioning of Mg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺ and Zn²⁺ between spinel group minerals (spinel and magnetite) and 2M aqueous chloride solutions was experimentally investigated in the temperature range of 500 to 800°C, 1 kb. The experimental results were analyzed thermodynamically taking into consideration the aqueous speciation.
The partition coefficient - ionic radius (PC-IR) diagrams are drawn based on the experimental results. PC-IR curve for magnetite is parabola-shaped with a maximum between Co²⁺ and Fe²⁺, whereas Ni²⁺ and Zn²⁺ deviate from such a trend. The anomaly of Zn²⁺ and Ni²⁺ may be attributable to their tetrahedral and octahedral site preferency, respectively. The PC-IR curve becomes gentle with increasing temperature. This means that the element partitioning becomes weak with increasing temperature. On the other hand, PC-IR curve for spinel shows a maximum between Ni²⁺ and Mg²⁺, but Zn²⁺ shows no anomaly unlike the case of magnetite. This is because the element partitioning occurs in the tetrahedral site in the case of spinel.

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The Goshikigahara volcano, situated at the northern part of the Tomuraushi volcano group in Central Hokkaido, Japan, is a large Quaternary composite volcano consisting of a basal volcanic edifice (Kaundake volcano) and three overlying volcanic edifices (Ponkaundake, Chubetsudake, and Goshikidake volcanoes). The volcanic activity began with eruptions of andesitic and dacitic lava flows and pyroclastics, and produced a large stratovolcano Kaundake (ca. 1.1 Ma - 0.95 Ma). Subsequent to this activity, a dacitic stratovolcano Ponkaundake has grown on the western flank of the Kaundake cone. The main part of the Ponkaundake cone constructed prior to about 0.8 Ma. The next period of volcanic activity began at the eastern and southeastern flanks of the Kaundake cone, building up two andesitic lava plateaus, Chubetsudake (0.75 Ma) and Goshikidake (0.74 Ma), concurrently.
The rock types of the Goshikigahara volcano are medium-K, calc-alkaline, two-pyroxene andesites and dacites. The eruptives from each of the four eruption centers show distinct whole-rock major element trends. Differences also exist between the modal characteristics of the eruptive products from the four centers. The petrographic and geochemical differences between the four volcanoes suggest each volcanic center had its own crustal magma chamber.

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