<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Joseph J. Fahey</dc:contributor>
  <dc:contributor>Angelina C. Vlisidis</dc:contributor>
  <dc:creator>A. F. Buddington</dc:creator>
  <dc:date>1963</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Partial chemical analyses of the accessory iron oxide and iron-titanium oxide minerals from more than one hundred samples of Adirondack igneous, metamorphic, and metasomatic rocks portray the degree of oxidation of the minerals and afford a basis for a discussion of their relation to the accompanying silicate assemblage and petrogeny. Among the granitic igneous rocks, the green pyroxenic facies have the least oxidized iron-titanium oxide minerals and a pink potassium-rich microperthitic microcline facies the most oxidized. Granites and syenites may crystallize with either an iron-rich variety of hornblende (or pyroxene) plus ilmenite, or with an iron-magnesium variety of hornblende (or of pyroxene) plus magnetite plus ilmenite, depending on the degree of oxidation. The granite facies of the orthogneisses of the Diana Complex (Precambrian) have a more oxidized mineral assemblage than the syenitic and quartz syenitic facies. The anorthosites and gabbro anorthosites have relatively oxygen-rich oxide minerals. Orthogneisses in the granulite facies have a lower ratio of Fe&amp;nbsp;&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;O&amp;nbsp;&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;/FeO than similar gneisses in the amphibolite facies. At least part of this lower ratio is due to metamorphism at higher temperatures and pressures. A regional belt of granitic orthogneiss metamorphosed in the amphibolite facies has a magnetite-sphene instead of a magnetite-ilmenite assemblage. Metasomatism of biotite-quartz-plagioclase gneiss to sillimanitic quartz-microcline gneisses is accompanied by decrease in mafic silicates and a series of changes of minerals in intermediate stages such that, in general, biotite yields with increasing degrees of oxidation successively such assemblages as (1) biotite, garnet, magnetite, hemo-ilmenite, and ilmeno-hematite; (2) pale brown mica, sillimanite, magnetite, and ilmeno-hematite; and (3) rutilo-hematite, rutile, and meagre silicates including sillimanite, muscovite, and chlorite. Diabase altered to monzodiorite by potassium-bearing solutions has ilmeno-magnetite partly altered to ilmeno-maghemite.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1093/petrology/4.1.138</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Oxford University Press</dc:publisher>
  <dc:title>Degree of oxidation of adirondack iron oxide and iron-titanium oxide minerals in relation to petrogeny</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>