Detailed petrology of the Buchanan massif, Llano and Burnet counties, Texas

dc.contributor.advisorRogers, John J. W.en_US
dc.creatorCook, Beverly Kay Gatlinen_US
dc.date.accessioned2016-04-22T21:59:52Zen_US
dc.date.available2016-04-22T21:59:52Zen_US
dc.date.issued1967en_US
dc.description.abstractThe Buchanan massif is a Precambrian pluton in the central Texas area, midway between the towns of Llano and Burnet, It shows a roughly concentric zonation over its outcrop area of about; 100 square miles. The general zonation is from fine-grained rocks in the interior of the pluton to coarse-grained and porphyritic rocks near the margin, and the trends of modal composition indicate an increase in acidity toward the margins. This reverse zonation is here explained by an equilibrium (equal fugacity) distribution of water in the intruded magma shortly after emplacement, The higher water content of the cooler, outer zones depresses the crystallization temperature of the magma below the actual temperature in the outer regions, thus allowing the interior to crystallize first. Progressive crystallization outward further increased the water content of the margins, and pegmatitic segregations attest to the saturation of the melt in the outer regions. The high water content maintained crystallization in the two-phase, subsolidus feldspar region throughout most of the pluton. The Enchanted Rock batholith and other less well-known plutons in the central Texas area exhibit the same textural and modal trends as the Buchanan massif, and it is proposed that their crystallization histories are similar. The high water content of the magmas may be indicative of derivation from remelting of crustal rocks.en_US
dc.format.digitalOriginreformatted digitalen_US
dc.format.extent37 ppen_US
dc.identifier.callnoThesis Geol. 1967 Cooken_US
dc.identifier.citationCook, Beverly Kay Gatlin. "Detailed petrology of the Buchanan massif, Llano and Burnet counties, Texas." (1967) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/90129">https://hdl.handle.net/1911/90129</a>.en_US
dc.identifier.digitalRICE1165en_US
dc.identifier.urihttps://hdl.handle.net/1911/90129en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.titleDetailed petrology of the Buchanan massif, Llano and Burnet counties, Texasen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentEarth Scienceen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Artsen_US
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