Geology and metallization of the White River Area, King and Pierce Counties, Washington
Bedrock of the White River area is dominated by Miocene age volcanics of andesite to rhyolite composition, which may be in part coeval with plutonic phases of the nearby 26 - 14 m.y. Tatoosh batholith. These volcanic rocks host two spatially distinct and gold-bearing epithermal deposits of the acid-sulfate type that are structurally, temporally, and genetically related to the formation and resurgent magmatic activity at the margin of an early Miocene caldera (22.6 - 19.1 m.y.). The age of hydrothermal activity is 20.4 +/- 0.1 m.y. based on UAr/TZAr analysis of hypogene alunite from the mineralized zone. Hydrothermal alteration and metallization of both deposits is chemically and mineralogically similar and consists of a central core of pervasive silicification that grades outward into zones of advanced argillic, argillic, and propylitic alteration. The largest of the two target areas is defined by a silica capping. Sulfur isotope analyses of cogenetic alunite-pyrite-enargite demonstrate a (34)S of +28.8 per thousand for the alunite-pyrite mineral pair. This large fractionation corroborates other field and mineralogic evidence for the hypogene origin of the alunite, and provides a geologically reasonable isotopic temperature estimate of 190 C for this epithermal deposit. Fold was introduced in at least 3 distinct episodes of structural-hydrothermal activity. The highest concentration of gold is within a zone measuring 1600 by 300-600 feet, and is localized in parts of the similar capping that contain outcrops of matrix-supported explosion breccias and veins having anomalous concentrations of up to 480 ppb Au, 13.7 ppm Ag, 1900 ppm As, 213 ppm Sb, 7.5 ppm Hg, and 10 ppm Mo.
- Research Organization:
- Oregon State Univ., Corvallis (USA)
- OSTI ID:
- 6409406
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC DEPOSITS
GEOCHEMISTRY
HYDROTHERMAL ALTERATION
WASHINGTON
AGE ESTIMATION
ANTIMONY
ARSENIC
GEOLOGIC HISTORY
GOLD
ISOTOPE RATIO
MERCURY
MINERALOGY
MOLYBDENUM
PALEOTEMPERATURE
SILVER
SULFUR 34
TERTIARY PERIOD
VOLCANIC ROCKS
CENOZOIC ERA
CHEMISTRY
ELEMENTS
EVEN-EVEN NUCLEI
FEDERAL REGION X
GEOLOGIC AGES
IGNEOUS ROCKS
ISOTOPES
LIGHT NUCLEI
METALS
NORTH AMERICA
NUCLEI
ROCKS
SEMIMETALS
STABLE ISOTOPES
SULFUR ISOTOPES
TRANSITION ELEMENTS
USA
580100* - Geology & Hydrology- (-1989)
580400 - Geochemistry- (-1989)