<?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>Thomas L. Wright</dc:contributor>
  <dc:creator>Odette B. James</dc:creator>
  <dc:date>1972</dc:date>
  <dc:description>&lt;p&gt;On the basis of composition, it is possible to distinguish three major groups of Apollo 12 basaltic rocks: olivine-pigeonite basalts and gabbros, ilmenite-bearing basalts and gabbros, and feldspathic basalts. Two major groups of Apollo 11 basalts are also distinguishable: ophitic ilmenite basalts and intersertal ilmenite basalts. Compositional variations between samples within groups are generally dominated by MgO variations, whereas differences between groups are primarily inverse variations of TiO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and SiO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;or Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and FeO. Results of fractionation calculations indicate that the MgO variation trends are explained principally by low-pressure fractionation of early-crystallized olivine ± pigeonite ± chrome spinel. The Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;versus FeO trend in the basalts might possibly be explained by near-surface fractionation, but the TiO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;versus SiO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;trend is not explainable in this way. Investigations of the latter trend in terms of possible processes of high-pressure fractional melting or fractional crystallization indicate that the compositional variations cannot be the products of simple variations in depth or degree of fractionation.&lt;/p&gt;&lt;p&gt;Our data are consistent with the view that the mafic magmas formed by partial melting in the lunar interior, and that near-surface fractionation, with the exception of removal or addition of olivine, has not been extensive.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1130/0016-7606(1972)83[2357:AAMBAG]2.0.CO;2</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>GSA</dc:publisher>
  <dc:title>Apollo 11 and 12 mare basalts and gabbros: Classification, compositional variations, and possible petrogenetic relations</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>