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    <pubDate>Tue, 09 Apr 2024 21:16:12 +0100</pubDate>
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      <title><![CDATA[L504
Garnet schist]]></title>
      <link>https://wserv3.esc.cam.ac.uk/p1acollections/items/show/38</link>
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        <h3>Title</h3>
                    <div class="element-text"><h2><strong>L504</strong></h2>
<h2>Garnet schist</h2></div>
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        <div id="dublin-core-subject" class="element">
        <h3>Subject</h3>
                    <div class="element-text"><h3>Age</h3>
<div class="element-text">
<p>Pre-Devonian</p>
<h3>Location</h3>
<div class="element-text">
<p>Ny-Friesland, Spitsbergen</p>
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        <div id="dublin-core-description" class="element">
        <h3>Description</h3>
                    <div class="element-text"><div class="element">
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<h3>Hand Specimen</h3>
<div class="element-text">
<p>Strongly developed planar<span> </span><a href="/p1acollections/items/show/192">fabric</a><span> </span>made up of<span> </span><a href="/p1acollections/items/show/237">platy</a><span> </span>biotite mica and muscovite mica grains and lenses of quartz grains. Fabric wraps around large,<span> </span><a href="/p1acollections/items/show/189">euhedral</a><span> </span>garnets, typically ~2mm across. Quartz, the most soluble mineral, has recrystallised at the corners of the “eyes”, in the pressure shadows of the garnets.</p>
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<div class="element">
<h3>Thin-section</h3>
<div class="element-text">
<p>Bands of interlocking quartz grains and some feldspar (plagioclase and alkali,<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a><span> </span>and<span> </span><a href="/p1acollections/items/show/170">alteration</a>), alternate with bands composed of needles of biotite mica and muscovite mica, about 50:50.</p>
<p>Quartz displays<span> </span><a href="/p1acollections/items/show/263">undulose extinction</a>, and being the most soluble mineral in this rock has recrystallised into the pressure shadows around the garnets.</p>
<p>The fabric is interrupted by large<span> </span><a href="/p1acollections/items/show/189">euhedral</a><span> </span>garnet crystals. Characteristically the garnets are<span> </span><a href="/p1acollections/items/show/213">isotropic</a><span> </span>and have high<span> </span><a href="/p1acollections/items/show/247">relief</a>. They contain<span> </span><a href="/p1acollections/items/show/210">inclusions</a><span> </span>of quartz and mica.</p>
<p>Accessory minerals:<span> </span><br />- chlorite<span> </span><br />-<span> </span><span>staurolite</span><span> </span><br />- tourmaline</p>
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<div class="element">
<h3>Rock History</h3>
<div class="element-text">
<p>This schist contains large quantities of muscovite indicating that it had a pelitic protolith. This pelite was subjected to high pressures and temperatures during regional metamorphism, resulting in the crystallisation and alignment of metamorphic minerals.</p>
<p>The<span> </span><a href="/p1acollections/items/show/198">foliation</a><span> </span>of this schist may be due to original compositional banding in the pelite; the quartz-rich layers having been sandy layers, while the mica-rich layers were muddy.</p>
<p>Some evidence for post-metamorphic deformation: quartz displaying undulose extinction; micas are wrapped around the garnet grains.</p>
<p>Tiny grains of chlorite found around the edges of the garnets indicate that some retrogradation has taken place. Chlorite is a common break-down product of garnets.</p>
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<h3>Advanced Notes</h3>
<div class="element-text">
<p>In thin-section<span> </span><span>staurolite</span><span> </span>is pale-golden in colour. It has high relief, and displays straight<span> </span><a href="/p1acollections/items/show/190">extinction</a><span> </span>and 1st order birefringence colours.</p>
</div>
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<div class="element"></div>
<div class="element"></div>
<div class="element">
<h3>Rock Name</h3>
<div class="element-text">garnet schist</div>
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</div></div>
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      <pubDate>Mon, 17 Jun 2019 12:33:59 +0100</pubDate>
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