# HIERARCHY_SUMMARY

STRUCTURAL_CONTROL:
Crustal extension in area bordering Co Plateau

PETROGENESIS:
Sub-continental lithosphere. Transition zone magmas melt dominated. Recent subduction not ruled out. Ancient rather than recent subduction

HOT_SPOT_POS:
No well constrained relationship to hot spot

REE:
High ratios of LIL to high field strgth elements. High Ba with higher Ba/Nb ratios, low TiO2.

TRACE_ELEM:
Rb, Ba, Nb similar to subduction related basalts


ROCK_TYPE_RANGE:
Tholeiite, basaltic andesite, trachyandesite, rhyolite

COMP_EVOLUTION:
Early basalts and basaltic andesite to local sequeunces of trachydacite and rhyolite w/ late olivine basalt.

PETROGENESIS:
Early mafic flows derived from subcontinental lithosphere enriched by subduction

HOT_SPOT_POS:
South of hot spot tract (south opening zipper)

87SR_86SR_RANGE:
.7050-basal part of early mafic flows; .7064, upper part early flows; .7078, trachydacite; .7081, rhyolite


COMP_EVOLUTION:
Time transgr seq frm silicic ignimbrites erupted frm calderas; calderas young to NE within SRP, to basalts and sediments that covered ignimbrites.

PETROGENESIS:
Crustal assimilation accompanied by fract crystallization of accessory phases; rx chem similar to oceanic basalts derived frm enriched sources attributed to mantle plumes. Metasomatism of hybrid lithospheric mantle in wake of Yellowstone Plume.

REE:
Preferential enrichments of LREE and HREE w/ respe

238Ur/238Th:
.7723 (2 Ka, craters of Moon andesite) to 1.0158 (GR Basalt)


ROCK_TYPE_RANGE:
High silica rhyolite: Intermidiate to Basaltic comp overlap rhyolites

COMP_EVOLUTION:
Coalesced or isolated domes and lava flows, flow dome complexes, flowbanded plugs. Underlying tuff is common.

PETROGENESIS:
Fract. Crystalliz. Of initially less silicic rhyolite w/ .2 wt% fluorine involving extensive fract. Of major phases sanidine, qrtz, plag, biotit, Fe-Ti oxides, zircon, apatite with allanit, monazite or titanite

HOT_SPOT_POS:
No well constructed relationship to Hot Spots

REE:
LREE, no greater than 200x chondrite, less than 100. REE patterns commonly flat, La/Ybn 1 to 3, negative Eu anomalies

TRACE_ELEM:
K, Rb, U, Th, Y, Be Li, Zr, Nb, Ta, Hf, Ba, Sm, Eu, Ti, Co, Ni, Cr, Zr, Hf

HYD_PHASES:
Commonly biotite & hornblende. Several examples are iron rich; topas as vapor phase and devitrification product.

MINERAL_DEP:
Be, U, F, Li Sn. Some examples resemble Climax typ

ISOTOPIC_AGE:
Preceded but overlap age of NNR rx (22Ma to .5Ma)


STRUCTURAL_CONTROL:
Episodic intervals of increasing crustal extension with time


# INSTITUTION

DEPARTMENT:
Economic Geology, Geologic Mapping/Geologic Framew


INSTITUTION:
New Mexico Bureau of Mines and Mineral Resources


DEPARTMENT:
School of Earth & Environmental Sciences


# REFERENCE

TITLE:
Peralkaline Ash Flow Tuffs and Calderas of the McDermitt Volcanic Field, Southeast Oregon and North Central Nevada


TITLE:
Miocene and Early Pliocene Epithermal Gold-Silver Deposits in the Northern Great Basin, Western United States: Characteristics, Distribution, and Relationship to Magmatism


TITLE:
New Perspectives on the Geology and Origin of the Northern Nevada Rift

BOOK_TITLE:
Geology and Ore Deposits 2000: The Great Basin and Beyond Proceedings, May 15-18, 2000

BOOK_EDITORS:
Cluer, J.K., Price, J.G., Struhsacker, E. M., Hardyman, R.F., and Morris, C.L.


TITLE:
Geologic Map of the Emigrant Pass Quadrangle, Nevada


TITLE:
Geologic map of the southern part of the Toe Jam Mountain Quadrangle, Nevada Map 117, scale 1:24,000

JOURNAL:
Nevada Bureau of Mines and Geology Map 117


TITLE:
Snowstorm Mountains, Elko and Humbolt Counties, Nevada unpublished 2005


TITLE:
Geologic map of the Willow Creek Reservoir quadrangle, Elko County, Nevada

JOURNAL:
Nevada Bureau of Mines and Geology Map 135 scale 1:24,000


TITLE:
Geologic map of the Willow Creek Reservoir SE quadrangle, Elko, Eureka, and Lander Counties, Nevada

JOURNAL:
Nevada Bureau of Mines and Geology Map 136 scale 1:24,000


TITLE:
Diverse mid-Miocene Silicic Volcanism AssociatedwiththeYellowstone-Newberry Thermal Anomaly

BOOK_TITLE:
Petrogenesis and volcanology of anorogenic rhyolites in the northwest intermountain USA


TITLE:
Crystallization behavior of Basalt Magma, Santa Rosa Range, Nevada,


TITLE:
Geologic Map of the Izzenhood Spring Quadrangle, Lander County, Nevada, Geological Investigation Series, I2668


TITLE:
Are Cenozoic topaz rhyolites the erupted equivalents of Proterozoic rapakivi granites?  Examples from the western United States and Finland


TITLE:
Geochemical evolution of topaz rhyolites from the Thomas Range and Spor Mountain, Utah


TITLE:
A model for the origin of red beryl in topaz rhyolite, Wah Wah Mountains, Utah, USA.

JOURNAL:
Unpublished MS Thesis, Brigham Young University


TITLE:
Geochemistry of Volcanic Rocks in the Marysvale Volcanic Field, West-Central Utah


TITLE:
Magmatic Evolution of the Pine Grove Porphyry Molybdenum System, Southwestern Utah

JOURNAL:
Unpublished PhD. Thesis Univ. of Wisconsin-Madison


TITLE:
The geology and geochemistry of Cenozoic topaz rhyolites from western United States


# SAMPLE

SAMPLE_COMMENT:
cliff on S side of trough; Izzenhood type


SAMPLE_COMMENT:
older rhyolite under Tlh and Tkc N of SSMtn


SAMPLE_COMMENT:
upper Midas canyon at saddle (new sample)


SAMPLE_COMMENT:
black vitrophyre along margin of rhyolite dome


ROCK_CLASSIFICATION:
Bullion Canyon volcanics north assemblage


ROCK_CLASSIFICATION:
Bullion Canyon volcanics east assemblage


ROCK_CLASSIFICATION:
Bullion Canyon volcanics south assemblage


