<?xml version="1.0"?>
<!DOCTYPE article SYSTEM "journalpublishing.dtd">
<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.1991.055.379.02</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Mineralogy and Geochemistry</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Zoned Hibonites from Punalur, South India</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Santosh</surname>
<given-names>M.</given-names>
</name>
<aff>Department of Geosciences, Faculty of Science, Osaka City University, Osaka 558, Japan Centre for Earth Science Studies, Akkulam, Trivandrum 695 031, India</aff></contrib>
<contrib contrib-type="author">
<name>
<surname>Sandiford</surname>
<given-names>M.</given-names>
</name>
<aff>Department of Geology and Geophysics, University of Adelaide, Adelaide, G.P.O. Box 498, South Australia, Australia</aff></contrib>
<contrib contrib-type="author">
<name>
<surname>Reed</surname>
<given-names>S. J. B.</given-names>
</name>
<aff>Department of Earth Sciences, Bullard Laboratories, Cambridge CB3 0EZ, U.K.</aff></contrib></contrib-group>
<pub-date pub-type="ppub">
<month>6</month>
<year>1991</year>
</pub-date>
<volume>55</volume>
<issue>379</issue>
<fpage>159</fpage>
<lpage>162</lpage>
<history>
<date date-type="received">
<day>5</day>
<month>7</month>
<year>1990</year>
</date>
<date date-type="rev-recd">
<day>28</day>
<month>8</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>Zoned hibonites from a kalsilite, leucite, spinel, corundum, perovskite gneiss from the southern Indian granulite terrain near Punalur, Kerala, have rims that are the most Ti-rich yet recorded (0.83&#x2013;0.87 Ti atoms per 19 O) and are essentially free of <italic>REE</italic> elements (&#x03A3;<italic>REE</italic> &#x003C; 0.01 atoms per 19 O) while the cores are the most <italic>REE</italic>-rich compositions yet recorded (&#x03A3;<italic>REE</italic> = 0.55&#x2013;0.65 atoms per 19 O). Within the limits of analytical uncertainty, the compositions of the hibonite can be related to the theoretical end-member CaAl<sub>12</sub>O<sub>19</sub> by the substitutions <italic>REE R</italic><sup>2+</sup> &#x21CC; CaAl and <italic>R</italic><sup>2+</sup><italic>R</italic><sup>4+</sup> &#x21CC; Al<sub>2</sub> with the <italic>REE</italic>-rich cores containing in excess of 50% of the <italic>REE R</italic><sup>2+</sup> Al<sub>11</sub>O<sub>19</sub> end member. Minor substitution of Na for Ca occurs in the rims, while non-stoichiometry in both the cores and rims is indicated by partial 12-fold site occupancy. Ion-microprobe analysis of the <italic>REE</italic>-rich hibonites reveals strong enrichment in <italic>LREE</italic> with La/Lu <italic>c.</italic> 250 000.</p></abstract>
<kwd-group>
<title>Keywords</title>
<kwd>hibonite</kwd>
<kwd>rare earth elements</kwd>
<kwd>titanium</kwd>
<kwd>zoning</kwd>
<kwd>ion-microprobe analysis</kwd>
<kwd>India</kwd>
</kwd-group>
</article-meta>
</front>
</article>
