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Table 1. Nomenclature for lithologic units within the field trip area.
Descriptive Field Nomenclature1 General Petrologic Nomenclature2 Charnockitic Nomenclature3
Yfqj low-silica charnockite (5) monzogranite to quartz monzodiorite farsundite to quartz jotunite
Yaf alkali feldspar granite4 (4)

Ygr Old Rag magmatic suite (3) alkali feldspar granite to syenogranite alkali feldspar charnockite to charnockite
Ygg garnetiferous alkali feldspar granite and syenogranite (1) alkali feldspar granite to syenogranite
Ylgg leucogranite gneiss (5) alkali feldspar granite
Ybg biotite granitoid gneiss (3) monzogranite to quartz monzonite and quartz monzodiorite
Yfh Flint Hill Gneiss (1) syenogranite to monzogranite
Yfpg foliated pyroxene granite (1) monzogranite farsundite
Ylgn layered granodiorite gneiss (1) granodiorite opdalite
Ypqd pyroxene quartz diorite (1) quartz diorite orthopyroxene quartz diorite
Ycf high-silica charnockite (2) syenogranite to monzogranite charnockite to farsundite
Yg garnetiferous granite gneiss (2) syenogranite to monzogranite charnockite to farsundite
Ygn garnetiferous gneiss (4)

Ylg leucocratic granitoid and foliated megacrystic leucocratic granite (4) alkali feldspar granite to syenogranite

1Number following nomenclature refers to the 7.5-minute quadrangle containing the reference locality within the area of new mapping: (1) Chester Gap, (2) Thornton Gap, (3) Old Rag Mountain, (4) Madison, and (5) Fletcher.
2Nomenclature determined using molar normative compositions calculated on basis of Fe2+/Fe(total) = 0.9 plotted on Q' vs ANOR plot of Streckeisen and Le Maitre (1979).
3Nomenclature following recommendations of Le Maitre and others (1989).
4Leucocratic rocks are indicated by italics.

U.S. Department of the Interior, U.S. Geological Survey
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