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Map showing the distribution and characteristics of plutonic rocks in the Tonopah 1 degree by 2 degrees Quadrangle, central Nevada

Miscellaneous Field Studies Map 1877-J

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Abstract

Plutonic rocks, mostly granite and granodiorite, are widely distributed in the west two-thirds of the Tonopah 1 degree by 2 degree quadrangle, Nevada. These rocks were systematically studied as part of the Tonopah CUSMAP project. Studies included field mapping, petrographic and modal analyses, geochemical studies of both fresh and altered plutonic rocks and altered wallrocks, and K-Ar and Rb-Sr radiometric dating. Data collected during this study were combined with previously published data to produce a 1:250,000-scale map of the Tonopah quadrangle showing the distribution of individual plutons and an accompanying table summarizing composition, texture, age, and any noted hydrothermal alteration and mineralization effects for each pluton.

The main areas mapped as part of this study, mapped along with collaborators listed in parentheses, were the Paradise Range (N.J. Silberling), north Cedar Mountain (R.A. Armin), the east side of the Toiyabe Range (G. F. Brem and R. A. Armin), and the south end of the Toquima Range (R.A. Armin). Most mapping was done at a scale of 1:24,000. These maps were combined with previously published maps and other maps of the Tonopah CUSMAP project to produce this pluton map

The accompanying table includes the name (if any) of the pluton and its location, the age of the pluton (either a radiometric age or an age inferred from field relations), modal composition, texture, mineralogy, hydrothermal alteration and mineralization related to the pluton, the source of mapping shown on this map, and published references on the pluton. Radiometric ages are either published K-Ar and fission track ages or new whole-rock Rb-Sr ages determined by A. C. Robinson on samples collected either for this study or as part of regional Sr-isotope studies by R.W. Kistler and A.C. Robinson. K-Ar ages published prior to 1977 are corrected using the new I.U.C.S. constants (Steiger and Jager, 1977). Muscovite alteration ages are reported for several plutons and represent minimum ages for emplacement of these plutons. Compositional classification follows the T. J. G.S. system (“Streckeisen, 1976) and is based either on modal analyses of slabs or estimates from hand specimens. All modes, unless otherwise noted, were measured in this study. The number of modes determined is shown in parentheses, and the range in volume percent of major minerals is given. Where no modal data are available, the color index (percentage of mafic minerals) and major mafic minerals are given for most plutons. Data tabulated on hydrothermal alteration and mineralization related to plutons are based on observations made during field studies for this project. Clear genetic relation between granitic plutonism and several mineral deposits previously attributed to granitic plutonism were not substantiated, and these inconsistencies are noted in the table.

Study Area

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Map showing the distribution and characteristics of plutonic rocks in the Tonopah 1 degree by 2 degrees Quadrangle, central Nevada
Series title:
Miscellaneous Field Studies Map
Series number:
1877
Chapter:
J
Year Published:
1987
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Description:
Plate: 34.05 x 50.01 inches
Scale:
250000
Online Only (Y/N):
N
Additional Online Files (Y/N):
N