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Economic Mineral Occurrences in Layered intrusion
A new sub section of the Layered intrusion article, to be placed after the causes of layering section.

Layered intrusions have potential to be economically significant for the occurrence of nickel-copper-platinum group element (Ni-Cu-PGE), chormitite, and iron-titanium oxide (Fe-Ti oxide) ore deposits.

Economic Ni-Cu-PGE minerals occur in mafic-ultramific rock within igneous rock-hosted magmatic sulfides emplaced near or at the bottom of the intrusions, in regard to the original orientation of the intrusive complex. The standard magmatic sulfide assemblage is composed of pyrrhotite, pentlandite, and chalcopyrite, with lesser to trace amounts of pyrite, cubanite and magnetite. The respective minerals that make up the copper and nickel ores are chalcopyrite and pentlandite. The platinum group elements are associated with the typical magmatic sulfide assemblage, these platinum group minerals (PGM) occur as sulfides, arsenides, alloys, and native metals.

In Chromium rich layered intrusions, the chromium bearing mineral chromitite can form discrete monomineralic cumulate layers. In local portions of the intrusive suite or in systems lacking chromium, it may occur as chromitite clasts associated with base metal magmatic sulfides. Similar to chromium occurrences, iron and titanium rich systems may form discrete cumulate layers composed primarily of magnetite and ilmenite.

There are significant Ni-Cu-PGE ores within the country rock spatially associated with the layered complex, the nickel, copper, and PGM's occur within sulfide veins in the foot-wall of the layered complex. Whether or not there is a direct relationship between igneous and country rock-hosted magmatic sulfides is still a debated topic.

Citations for Quaternary geology

 * 1) Ehlers, J., Gibbard, P. L., Hughes, P. D., & Gibbard, P. L. (Philip L. (2011). Quaternary glaciations extent and chronology : a closer look. Elsevier. (Intro section)
 * 2) for the dating methods of lichenometry and dendrochronology
 * 3) for the dating method of amino acid geochronology
 * 4) for the dating methods of dendrochronology
 * 5) for the dating methods of lichenometry

Added citations for the chemical and biological Quaternary geochronological dating methods.