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<article article-type="research-article">
<front>
<journal-meta>
<journal-id journal-id-type="archive">gsminmag</journal-id>
<journal-title>Mineralogical Magazine</journal-title>
<abbrev-journal-title abbrev-type="full">Mineralogical Magazine</abbrev-journal-title>
<issn pub-type="ppub">0026-461X</issn>
<publisher>
<publisher-name>Mineralogical Society</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1180/minmag.1991.055.381.05</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Mineralogy</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Phase Relations of Aenigmatite Minerals in a Syenitic Ejectum, Wonchi Volcano, Ethiopia</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Gaeta</surname>
<given-names>Mario</given-names>
</name></contrib>
<contrib contrib-type="author">
<name>
<surname>Mottana</surname>
<given-names>Annibale</given-names>
</name></contrib>
<aff>Dipartimento di Scienze della Terra, Universit&#x00E0;, di Roma &#x2018;La Sapienza&#x2019;, Piazzale A. Moro, 5, I-00185 Roma RM, Italy</aff></contrib-group>
<pub-date pub-type="ppub">
<month>12</month>
<year>1991</year>
</pub-date>
<volume>55</volume>
<issue>381</issue>
<fpage>529</fpage>
<lpage>534</lpage>
<history>
<date date-type="received">
<day>14</day>
<month>5</month>
<year>1990</year>
</date>
<date date-type="rev-recd">
<day>22</day>
<month>11</month>
<year>1990</year>
</date></history>
<copyright-statement>Copyright &#x00A9; 1991, The Mineralogical Society</copyright-statement>
<copyright-year>1991</copyright-year>
<abstract>
<title>Abstract</title>
<p>Wonchi volcano (Ethiopia) is the second locality for wilkinsonite, the new mineral related to aenigmatite via the coupled substitution 2Fe<sup>3+</sup> = TiFe<sup>2+</sup>. Wilkinsonite occurs as relics surrounded by rims of riebeckite and biotite in a syenitic ejectum which also contains microphenocrysts of aenigmatite. The two minerals do not represent an equilibrium pair. They both formed in the magma chamber under plutonic to hypabyssal conditions, but during two following stages of crystallisation separated by a major drop in <italic>&#x0192;</italic><sub>O<sub>2</sub></sub> conditions.</p></abstract>
<kwd-group>
<title>Keywords</title>
<kwd>aenigmatite</kwd>
<kwd>wilkinsonite</kwd>
<kwd>syenitic ejectum</kwd>
<kwd>Wonchi volcano</kwd>
<kwd>Ethiopia</kwd>
</kwd-group>
</article-meta>
</front>
</article>
