https://bereket-haileab.geology.sites.carleton.edu/files/original/74f44554fb2f133dc9a3142fce982bb6.jpg 16f8b2f2310024e055144882af7c33b6 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 Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample 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 BH250-233 Subject The topic of the resource Dike (phonolitic compostion) Description An account of the resource Major Minerals: aegirine, aegirine-augite, riebeckite, orthoclase, plagioclase, nepheline<br />Minor Mineral: sphene, glass (<em>devitrified glass)</em><br /><br /> <p>Near<span>&nbsp;</span><span>Lead</span><span>&nbsp;</span>in the northern<span>&nbsp;</span><span>Black Hills</span>, the phonolitic dike sample<span>&nbsp;</span>BH250-233<span><strong>&nbsp;</strong></span>belongs to a suite of alkaline intrusive rocks emplaced during the Paleocene to Eocene. These dikes are much younger than the Precambrian metamorphic basement rocks they cut and were likely intruded during the later stages of the<span>&nbsp;</span><span>Laramide Orogeny</span>, when regional uplift and crustal fracturing created pathways for magma ascent. Their presence records a phase of post-uplift magmatism in the Black Hills, when small volumes of unusual magma rose through deep fractures and solidified as narrow intrusive sheets.</p> <p data-start="673" data-end="1268">Chemically, phonolite is a distinctive alkali-rich, silica-undersaturated igneous rock enriched in sodium and potassium relative to more common volcanic rocks. Typical compositions contain moderate silica (about 52–60 wt.% SiO₂), high Na₂O + K₂O, and relatively low calcium and magnesium. Because the magma lacked sufficient silica to form quartz, feldspathoid minerals crystallized instead. BH250-233, as a phonolitic rock, was likely enriched in trace elements such as barium, strontium, zirconium, niobium, and rare earth elements, reflecting derivation from evolved alkaline magma sources.</p> <p data-start="1270" data-end="1886" data-is-last-node="" data-is-only-node="">Mineralogically,<span>&nbsp;</span>BH250-233<span>&nbsp;</span>is composed chiefly of alkali feldspar (commonly sanidine) together with nepheline, the key feldspathoid mineral diagnostic of phonolite. Dark minerals commonly include aegirine or aegirine-augite pyroxene, with minor biotite. Accessory minerals may include sodalite, nosean, titanite, apatite, and iron oxides. In hand sample, the rock is fine grained and gray to greenish-gray, while thin sections often reveal a feldspar-rich groundmass with scattered feldspar phenocrysts and slender green pyroxene crystals, textures characteristic of rapid cooling within a narrow dike intrusion.<br /><br /></p> <br /><iframe width="1800" height="100" src="https://docs.google.com/spreadsheets/d/e/2PACX-1vS4nyqCmZQGn3t6vX4g4nhDPwHMBaKrigt1LaY2pykWbBGXB1wNb6FYArx625I-JTtD7lyg4uz1OS1r/pubhtml?gid=1426176328&amp;single=true&amp;widget=true&amp;headers=false"></iframe> Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Lead, South Dakota, USA Nearby Geographic Feature: Black Hills, South Dakota GPS Coordinates: 44.356578, -103.787958 Type The nature or genre of the resource Thin section and hand sample Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 233. Housed at Carleton College in Minnesota. Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=7a82c46580864c219db49a33e6197783" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=7a82c46580864c219db49a33e6197783">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1SHcrNlT1lfmm5vGgHg5sev9euhCokIWd/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1lbpA3g_WtKKSmHAXRkOUwn60ohUaY6K4/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1DUO0TgcmCh7ZS23oTtyQrKNhJP5uXe_E/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1t3PVw-g5b30EoACb9DSr-yfAGfawa1xj/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ZW6QQMOgIMrEhudQhYfr13I_wHNQLsdh/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1W1qCBBLFLisToouT849nabSUZ66d48If/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1wFcogJnpNN5dfrdQNXcYoVzyJ2OGPpsv/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1-8sG72eltFsA0CVnjNZdAaubwnVF7aEb/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1X-RJEKT3MFOpWXygpwoG6mra8UyZTn99/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1PPmtUe5QJnaJXUquz0yxUG3zwtYWc7RE/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hl_DR_BawFfcsu7JkGaQtoeNry2_gcc_/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/11hiP5T677KAWfWbzmy-t3xWIrsnDeK53/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Vo8OWVvCx1o70dHc1UyH9sgGtjCrwDbU/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1i-YUpDfq9_n69VUBde8zKXgMWUfrSZ4b/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1FwrHZ0uC1VgpGbC7_I9KPIxZFRNOeCGs/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1iIby9ZeDURmKr-43ACHaIlFbLPzXQTuC/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ZkCwl9vS1A7QleNEOJDrxRGeQS12a3pc/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Aegirine Aegirine Augite alkali feldspar Alkaline igneous rock Black Hills devitrification Devitrified Glass dike igneous Lead South Dakota mafic Nepheline orthoclase phonolite Phonolitic Dike plutonic Sanidine Sodalite Sphene Titanite