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Experimental studies on the phase relations of manganese silicate minerals and their application to the natural occurrences
| Title: | Experimental studies on the phase relations of manganese silicate minerals and their application to the natural occurrences |
| Other Titles: | マンガン珪酸塩鉱物間における相関係の実験鉱物学的研究及びその鉱物生成条件解明への応用 |
| Authors: | Takahashi, Kosei1 Browse this author |
| Authors(alt): | 高橋, 興世1 |
| Issue Date: | 26-Dec-1994 |
| Publisher: | Hokkaido University |
| Abstract: | Experimental studies on the phase relations of Si - rich braunite and manganese pyroxenoids have been carried out to analyse their natural occurrences． The Si - rich braunite with maximum 12.37 wt% SiO2 component has been found at the Hikari mine in south west Hokkaido， Japan． The single crystal of braunite shows the zonal variation of SiO2 content and the increase of divalent cation contents from the core to the edge． The Si - rich composition is represented by the formula Mn3+6-2x(Mn2+， Mg， Ca)1+x Si1+xO12 where x is up to O.22．The formula represents the substitution of 2Mn3+ ⇔( Mn2+， Mg， Ca ) ＋ Si4+． The Mg substitution seems to be deeply correlated with Si substitution， while the Ca content is independent of Si substitution in Si - rich braunite．Experimental study for confirming the solubility of ”MgSiO3” molecule in braunite has been carried out at 1100 ℃ in open air circamstances． The solubility limit was determined to be x ＝ O．2 of the formula (Mn3+6－2xMgx Six)Mn2+SiO12 from the change of the cell parameters． For x > O.2 braunite coexists with tephroite which has a constant composition of (Mn1.4 Mg0.6) SiO4. Phase relations in the manganese rich portion of the system MnSiO3- MgSiO3-CaSiO3 have been determined experimentally under the conditions of 700 ℃ - 1200 ℃ and O - 10 kb． The phases present were rhodonite， pyroxmangite， bustamite and kanoite． Each phase showed a limited solid solution and its stability field was changed depending on pressure and temperature． Phase assemblages， rhodonite-pyroxmangite， rhodonite-bustamite， pyroxmangitekanoite， kanoite-bustamite and rhodonite-pyroxmangite-bustamite were found to be stable under the conditions． From these results， distribution coefficient KD for respective coexisting phases were determined． The two - phase region of pyroxmangite-rhodonite shifts toward the Mn-rich and Mg-poor side in the Mn - Mg - Ca diagram with incre，asing pressure and/or decreasing temperature． The two phase region of pyroxmangite-rhodonite at 700℃-4kbar showed a good agreement with the compositional range of naturally coexisting pairs of pyroxmangite and rhodonite from the Tatehira mine， southwestern Hokkaido， Japan． The formation temperatures ot pressures of coexisting two phases from other 10calities were also estimated using the experimentally deterrnined KD． |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第3495号 |
| Degree Level: | 博士 |
| Degree Discipline: | 理学 |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/58184 |
| Appears in Collections: | 学位論文 (Theses) > 博士 （理学）
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Submitter: 高橋 興世
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