1 10 1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/e3160631658548f9f2dc6e1becea70da.jpg d95ec5a176a934d2c3e57276e230693c https://wserv3.esc.cam.ac.uk/p1acollections/files/original/e2173d02d96267ba32160e6fdf7413e7.jpg 6064d39c4c259244a0f9ee941313b06b https://wserv3.esc.cam.ac.uk/p1acollections/files/original/01845924716bedfe0fd182d669f227cd.jpg 29966d5660a6a3fe8f268bf574236f17 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/16d925108b74372b95b4fdde50676900.jpg 5258ac41a282f9310c3fe1c4115cc800 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f8b28219498294d826754ab3542fb00f.jpg c99a49a3bc0d2fc2234806df01cd66c1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/ac59d17b2a65340795a83853876e0422.jpg 27acfdf84cb9a638c01a6ee7daebba0e 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>L102<br /></strong></h2> <h2>Hornblende biotite granite</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text"> <p>Caledonian, Devonian</p> <h3>Location</h3> <div class="element-text"> <p>Glencoe</p> </div> </div> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <div class="element-set"> <div class="element"> <div class="element-text"> <h3><span style="font-size:14px;">Hand Specimen</span></h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text"> <p>Medium to coarse-grained rock with a<span> </span><a href="/p1acollections/items/show/203">granular</a><span> </span>texture.<span> </span><br />White feldspar<span> </span><a href="/p1acollections/items/show/215">laths</a><span> </span>2-4 mm long are clearly visible.<span> </span><br />Other phases: pink feldspar, black biotite mica, black hornblende amphibole and pale grey quartz. These grains are more<span> </span><a href="/p1acollections/items/show/188">equant</a>, typically 1-2 mm across.<span> </span><br />Biotite may be distinguished from hornblende by its flaky<span> </span><a href="/p1acollections/items/show/206">habit</a><span> </span>and one good<span> </span><a href="/p1acollections/items/show/180">cleavage</a>. It is shinier than hornblende.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Plagioclase feldspar<span> </span><br />- The larger laths (2-4 mm long) are strongly<span> </span><a href="/p1acollections/items/show/267">zoned</a>. The cores of these laths, which display clear<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a>, have been<span> </span><a href="/p1acollections/items/show/232">overgrown</a><span> </span>by rims of more feldspar. Some<span> </span><a href="/p1acollections/items/show/170">alteration</a><span> </span>to white mica.</p> <p>Biotite mica<span> </span><br />- Grains typically 1 mm across. Strongly pleochroic in reddish brown and pale straw. Often associated with small grains of an opaque accessory mineral, probably magnetite.</p> Quartz<span> </span><br />- Grains are 1-2 mm across,<span> </span><a href="/p1acollections/items/show/173">anhedral</a>, and display<span> </span><a href="/p1acollections/items/show/263">undulose extinction</a>. <p>Alkali feldspar<span> </span><br />- Anhedral grains up to 5mm long. Some alteration to white mica. Some grains display a<span> </span><a href="/p1acollections/items/show/228">microperthite texture</a>.</p> <p>Hornblende amphibole<span> </span><br />- Pale green, anhedral. Grains appear to have been “eaten away”, reducing their<span> </span><a href="/p1acollections/items/show/246">prismatic</a><span> </span>form (diamond) to a ragged anhedral<span> </span><a href="/p1acollections/items/show/206">form</a>. Amphiboles have two cleavage planes which intersect at 56°.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text">This coarse-grained rock must have cooled slowly as part of an intrusion.<br /><br />Its granitic composition (essential quartz and feldspar) indicates that it was produced in a continental setting.<br /><br />Strongly zoned plagioclase crystals and “eaten away” appearance of the hornblende could be due to a change in the composition of the liquid from which the phases crystallised; perhaps due to magma mixing or degassing of volatiles from the magma.<span> </span><br /><br />Presence of hornblende and biotite indicate that this is a wet granite, probably from a subduction zone.<br /><br />Hydrothermal alteration of feldspars to white mica.</div> </div> <div class="element"> <h3>Advanced Notes</h3> <div class="element-text"> <p>This rock is classified as an<span> </span><span>adamellite</span><span> </span>because it contains roughly equal proportions of alkali feldspar and plagioclase feldspar, with additional quartz and biotite.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text"> <p>hornblende biotite granite<br />adamellite</p> </div> </div> </div> </div> </div> </div> arc biotite coarse granite hornblende subduction