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<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.1982.045.337.26</article-id>
<title-group>
<article-title>Cryptic Variation in the Kapalagulu Layered Intrusion, Western Tanzania</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Wadsworth</surname>
<given-names>W. J.</given-names>
</name>
<aff>Department of Geology, University of Manchester, Manchester M13 9PL, England</aff></contrib>
<contrib contrib-type="author">
<name>
<surname>Dunham</surname>
<given-names>A. C.</given-names>
</name>
<aff>Department of Geology, University of Hull, Cottingham Road, Hull HU6 7RX, England</aff></contrib>
<contrib contrib-type="author">
<name>
<surname>Almohandis</surname>
<given-names>A. A.</given-names>
</name>
<aff>Department of Geology, Riyadh University, Riyadh, Saudi Arabia</aff></contrib></contrib-group>
<pub-date pub-type="ppub">
<year>1982</year>
</pub-date>
<volume>45</volume>
<issue>337</issue>
<fpage>227</fpage>
<lpage>236</lpage>
<copyright-statement>Copyright &#x00A9; 1982, The Mineralogical Society</copyright-statement>
<copyright-year>1982</copyright-year>
<abstract>
<title>Abstract</title>
<p>The Kapalagulu intrusion displays the following sequence of cumulus phase layering in a stratigraphic sequence of 1400 m: <italic>Basal Zone</italic> (BZ) olivine &#x00B1; chromite &#x2192; <italic>Intermediate Zone</italic> (IZ) olivine + plag + opx &#x2192;, olivine + plag + opx + cpx &#x2192; <italic>Main Zone</italic> (MZ) plag + opx + cpx &#x2192; plag + cpx + Fe/Ti oxide + apatite. The corresponding cryptic variation is <italic>olivine</italic> Fo<sub>83 &#x2212; 77</sub> (limited to BZ and IZ), <italic>orthopyroxene</italic> En<sub>82 &#x2212; 56</sub>, <italic>clinopyroxene</italic> Ca<sub>46</sub>Mg<sub>45</sub>Fe<sub>9</sub> to Ca<sub>43</sub>Mg<sub>37</sub>Fe<sub>21</sub> and <italic>plagioclase</italic> An<sub>88 &#x2212; 80</sub>. Reversals of the cryptic variation occur at the base of MZ (minor reversal) and in the middle of MZ (major reversal), and are attributed to the influx of relatively primitive magma. The major reversal indicates that progressive mixing of fresh and residual magmas occurred. Because of the major reversal, inverted pigeonite appears twice in the layered sequence, but at different compositions (En<sub>65</sub> and En<sub>56</sub>). Unlike the cumulus olivine and pyroxene, cumulus plagioclase exhibits a wide range of composition (5&#x2212;10% An) in individual rocks and even in single crystals.</p></abstract>
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