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Hokkaido University Collection of Scholarly and Academic Papers >
Graduate School of Science / Faculty of Science >
Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy >
Vol.XXII, No.3 >
Cr-rich and Al-rich Spinels in the Kibi-kogen Alkali Basalts, Southwest Japan
| Title: | Cr-rich and Al-rich Spinels in the Kibi-kogen Alkali Basalts, Southwest Japan |
| Authors: | Fujibayashi, Norie Browse this author |
| Issue Date: | Feb-1989 |
| Publisher: | 北海道大学 |
| Journal Title: | 北海道大学理学部紀要 |
| Journal Title(alt): | Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy |
| Volume: | 22 |
| Issue: | 3 |
| Start Page: | 503 |
| End Page: | 517 |
| Abstract: | Cr-rich spinel (Cr2O3 11～33 wt%, Al2O3 18～39 wt%) and Al-rich spinel (Cr2O3<2 wt%, Al2O3 48～65 wt%) occur in the Kibi-kogen alkali basalts. The latter is extremely high in Al2O3 and plots near the Al end of the Fe+3-Al side of Cr-Fe+3-Al diagram. The occurrence and chemistry of the spinels indicate that the Cr-rich spinel crystallized as a near-liquidus phase, whereas the Al-rich one formed subsequently. The calculation in terms of the Rayleigh fractional crystallization model resulted in notable depletion of Cr in the residual liquid with progress of crystallization of the Kibi-kogen alkali basalt magma. Thus, when the Cr content of the magma became less than the solubility limit of Cr, the Cr-rich spinel may have ceased from crystallization and the Al-rich spinel in turn crystallized as an aluminous phase prior to the appearance of plagioclase. The composition of the near-liquidus Cr-rich spinel depends mainly on the Cr content of host magma rather than the Al content and Si/Al ratio. |
| Type: | bulletin (article) |
| URI: | http://hdl.handle.net/2115/36762 |
| Appears in Collections: | Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy > Vol.XXII, No.3
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