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Phyllic alteration
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<h2 id="variation-with-depth">Variation with depth</h2> <p>Phyllic alteration typically forms in the <a href="/facts/Base_metal/H1EpE5DU">base-metal</a> zone of a porphyry system.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Alteration assemblages vary with depth and with degree of fluid interaction. In deep environments, the most highly altered areas are veins and thin <i>selvages</i>, or halos, that surround them. The selvages are generally <10 cm in diameter and composed of major sericite and minor quartz. Vein orientation is preserved from original rock, but minerals within are mostly replaced by pyrite.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> With decreasing depth, selvages widen (10 cm - 1m) and contain more quartz and pyrite. </p><p>Outside of selvages, most alteration occurs in replacement of mafic minerals by <a href="/facts/Chlorite/EYtQI4wC">chlorite</a> and of plagioclase by sericite.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <p><a href="http://www.mindat.org/min-9252.html">Sericite at Mindat</a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Yant, Marcella (2009). "Hydrothermal Alteration". www.indiana.edu. Indiana University. <a href="http://www.indiana.edu/~sierra/papers/2009/yant.html" target="_blank">http://www.indiana.edu/~sierra/papers/2009/yant.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Damian, Floarea (2003). "The Mineralogical Characteristics and the Zoning of the Hydrothermal Types of Alteration from the Nistru Ore Deposit, Baia Mare Metallogenic District". scholarcommons.usf.edu. Studia Universitatis Babeş-Bolyai. Retrieved 18 April 2014. <a href="http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia" target="_blank">http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Damian, Floarea (2003). "The Mineralogical Characteristics and the Zoning of the Hydrothermal Types of Alteration from the Nistru Ore Deposit, Baia Mare Metallogenic District". scholarcommons.usf.edu. Studia Universitatis Babeş-Bolyai. Retrieved 18 April 2014. <a href="http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia" target="_blank">http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Damian, Floarea (2003). "The Mineralogical Characteristics and the Zoning of the Hydrothermal Types of Alteration from the Nistru Ore Deposit, Baia Mare Metallogenic District". scholarcommons.usf.edu. Studia Universitatis Babeş-Bolyai. Retrieved 18 April 2014. <a href="http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia" target="_blank">http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Parry, W. T.; Jasumback, M.; Wilson, P. N. (2002). "Clay Mineralogy of Phyllic and Intermediate Argillic Alteration at Bingham, Utah". Economic Geology. 97: 221–239. doi:10.2113/gsecongeo.97.2.221. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Damian, Floarea (2003). "The Mineralogical Characteristics and the Zoning of the Hydrothermal Types of Alteration from the Nistru Ore Deposit, Baia Mare Metallogenic District". scholarcommons.usf.edu. Studia Universitatis Babeş-Bolyai. Retrieved 18 April 2014. <a href="http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia" target="_blank">http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1192&context=geologia</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Parry, W. T.; Jasumback, M.; Wilson, P. N. (2002). "Clay Mineralogy of Phyllic and Intermediate Argillic Alteration at Bingham, Utah". Economic Geology. 97: 221–239. doi:10.2113/gsecongeo.97.2.221. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Parry, W. T.; Jasumback, M.; Wilson, P. N. (2002). "Clay Mineralogy of Phyllic and Intermediate Argillic Alteration at Bingham, Utah". Economic Geology. 97: 221–239. doi:10.2113/gsecongeo.97.2.221. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> </ol>