1 10 2 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/3a045ee9b56d4f42ca318e0623d82bac.jpg 9de28fb8f3aa176785607b86ed35a349 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/ad163c9708faad229d3b45dfe05cc6d2.jpg c1d47de48160ed5d95eaa51938891095 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/9a8a6274518a04739a23711773ab19ae.jpg 9d09b58110825fcd56646bf1cec98d2b Physical Object An inanimate, three-dimensional object or substance. Note that digital representations of, or surrogates for, these objects should use Moving Image, Still Image, Text or one of the other types. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource <h2><strong>L172<br /></strong></h2> <h2>Ultramafic cumulate</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text">Precambrian<br /><br /><h3>Location</h3> <div class="element-text">Lewisian Complex, Dyke<br />Assynt, Sutherland</div> </div> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <div class="element"> <div class="element-text five columns omega"> <h3>Hand Specimen</h3> </div> </div> <div class="element"> <div class="element-text five columns omega"> <div class="element-set"> <div class="element"> <div class="element-text">Greenish black, coarse-grained rock, comprising olivine, clinopyroxene and plagioclase.<br />Grains typically 1-2 mm across.<span> </span></div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Olivine<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/256">Subhedral</a><span> </span>to<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/189">euhedral</a><span> </span>grains making up ~45% of the rock.<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/170">Alteration</a><span> </span>to magnetite and serpentine, particularly along the curving cracks. Cracks across the thin-section, could be due to expansion of the rock as the olivine was altered.</p> <p>Clinopyroxene<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/211">Interstitial</a><span> </span>phase making up ~35% of the rock. Moderate<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/247">relief</a>, inclined<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/190">extinction</a> and first order pink to second order orange interference colours.</p> <p>Plagioclase feldspar<span> </span><br />- Interstitial phase making up ~20% of the rock. Low first order interference colours and<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/169">lamellar twinning</a>.</p> <p>Accessory minerals - Biotite, small, interstitial grains, altered.</p> <p>This is a cumulate rock. It has undergone late-stage shear banding.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Olivine<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/236">phenocrysts</a><span> </span>crystallised first.<span> </span><br />Clinopyroxene grew around the olivine phenocrysts.<span> </span><br />Interstitial feldspar filled in the remaining gaps.<span> </span><br />Shearing of the rock produced bands of deformation.<span> </span><br />Hydrothermal alteration.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">ultramafic cumulate</div> </div> </div> </div> </div> </div> </div> </div> alteration euhedral interstitial shear ultramafic https://wserv3.esc.cam.ac.uk/p1acollections/files/original/19912665ea9a172bdcbf89f42f8bfd51.jpg 02578476b62cb5d6f8f83c4fd82c21b1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/fd32bc8c9301390886cfc2d1b5039e5b.jpg d750b6043096fff00dfac9d769fd8306 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/e296e547f6d79fa4ce77b4b16eaafdb2.jpg 6c3117dea0a91029411225c36498d477 Physical Object An inanimate, three-dimensional object or substance. Note that digital representations of, or surrogates for, these objects should use Moving Image, Still Image, Text or one of the other types. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource <h2><strong>L112<br /></strong></h2> <h2>Rhyolite, banded</h2> Subject The topic of the resource <div class="element-text"> <h3>Location</h3> <div class="element-text"> <p>Glacial boulder, North Wales</p> </div> </div> Description An account of the resource <div class="element"> <h3>Hand Specimen</h3> <div class="element-text"> <p>Pink-brown, fine-grained rock.<span> </span><br />Strong planar shear<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/192">fabric</a>, produced by flow: streaks of dark red-brown and black-brown in the<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/205">groundmass</a>, and siliceous streaks and lenses.<span> </span><br />Gold-coloured,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/224">metallic</a><span> </span>pyrite, and a black mineral are associated with the quartz-filled lenses.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Plagioclase feldspar<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/236">Phenocrysts</a>, fairly fresh,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/258">tabular</a>, typically 1-2 mm long, with characteristic<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/169">lamellar twinning</a>.</p> <p>Opaques<span> </span><br />- Grains associated with the quartz-filled lenses. Range of sizes from<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/205">groundmass</a><span> </span>up to ~0.5 mm. These are a mixture of pyrite, FeS2, (tending to have a cubic<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/206">form</a>) and the unidentified black mineral, both seen in hand specimen.</p> <p>Groundmass<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/184">Cryptocrystalline</a>, almost glassy, speckled with tiny, irregular quartz and feldspar crystals. Probably devitrified<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/200">glass</a>. Plagioclase altered to white mica.</p> <p>Secondary quartz<span> </span><br />- Narrow veins and lenses of quartz, considerably coarser than the groundmass. The grains of quartz have<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/257">sutured contacts</a>, and may have been injected after consolidation of the lava. Some of these clumps are rimmed with inward pointing needles of feldspar.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Phenocrysts crystallised in a magma chamber. The magma erupted and cooled very rapidly to a fine-grained, glassy groundmass, preserving<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/197">flow banding</a><span> </span>texture. Injection of quartz-rich fluid, which precipitated quartz in lenses and veins.</p> <p>Very high temperature hydrothermal<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/170">alteration</a><span> </span>caused devitrification of the glassy groundmass.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text"> <p>banded rhyolite<br />rhyloite flow</p> </div> </div> devitrification flow shear