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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.1985.049.354.03</article-id>
<title-group>
<article-title>Compositional Variation in H&#x00F6;gbomites from North Connemara, Ireland</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Angus</surname>
<given-names>N. S.</given-names>
</name></contrib>
<contrib contrib-type="author">
<name>
<surname>Middleton</surname>
<given-names>R.</given-names>
</name></contrib>
<aff>Department of Geology, The University, Hull, HU6 7RX</aff></contrib-group>
<pub-date pub-type="ppub">
<month>12</month>
<year>1985</year>
</pub-date>
<volume>49</volume>
<issue>354</issue>
<fpage>649</fpage>
<lpage>654</lpage>
<history>
<date date-type="received">
<day>14</day>
<month>11</month>
<year>1984</year>
</date>
<date date-type="rev-recd">
<day>4</day>
<month>3</month>
<year>1985</year>
</date></history>
<copyright-statement>Copyright &#x00A9; 1985, The Mineralogical Society</copyright-statement>
<copyright-year>1985</copyright-year>
<abstract>
<title>Abstract</title>
<p>H&#x00F6;gbomite occurs in two contrasting mineral assemblages within the Currywongaun-Dough-ruagh intrusion of north Connemara: a cordierite-rich pelitic xenolith and an orthopyroxenite. In the latter, h&#x00F6;gbomite and green spinel form blebs within magnetite-ilmenite grains. The h&#x00F6;gbomite displays significant compositional variation from grain to grain: TiO<sub>2</sub> (3.0&#x2013;6.3%), FeO (21.6&#x2013;21.3%), MgO (10.0&#x2013;7.5%), ZnO (3.6&#x2013;2.4%). This chemical heterogeneity appears to represent variable degrees of partial substitution of Mg and Zn by Ti, in the replacement of spinel by h&#x00F6;gbomite. By contrast, in the cordierite-hornfels, the h&#x00F6;gbomite compositions are more notably enriched in iron: TiO<sub>2</sub> (4.7&#x2013;7.0%), FeO (29.6&#x2013;24.3%), MgO (4.2&#x2013;6.2%), ZnO (2.7&#x2013;2.1%). This iron-rich h&#x00F6;gbomite appears to have formed primarily by interaction between opaque ore and adjacent cordierite, rather than by replacement of spinel.</p>
<p>Two high-grade metamorphic episodes appear to be necessary for h&#x00F6;gbomite growth, one determining chemical composition and the other appropriate physical parameters. In the Connemara occurrences thermal metamorphism and partial melting, coupled with contamination of the surrounding magma, controlled the formation of mineral assemblages rich in Fe, Mg, Al, Ti, and Zn. Emplacement of the intrusion was accompanied by amphibolite facies regional metamorphism and it is to this metamorphic event that the growth of h&#x00F6;gbomite may be attributed.</p></abstract>
<kwd-group>
<title>Keywords</title>
<kwd>h&#x00F6;gbomite</kwd>
<kwd>orthopyroxenite</kwd>
<kwd>cordierite-hornfels</kwd>
<kwd>Connemara</kwd>
<kwd>Ireland</kwd>
</kwd-group>
</article-meta>
</front>
</article>
