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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Animas River (1)
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North America
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Rocky Mountains
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U. S. Rocky Mountains
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Sawatch Range (1)
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Yukon-Tanana Terrane (1)
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United States
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Alaska
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Alaska Range (1)
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Colorado
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San Juan County Colorado (1)
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Sawatch Range (1)
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Midcontinent (1)
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Mississippi Valley
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Upper Mississippi Valley (1)
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Missouri
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Saint Francois Mountains (1)
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Viburnum Trend (1)
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Montana
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Jefferson County Montana (1)
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Ozark Mountains (1)
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U. S. Rocky Mountains
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Sawatch Range (1)
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commodities
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metal ores
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copper ores (1)
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gold ores (1)
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lead ores (1)
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lead-zinc deposits (1)
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silver ores (1)
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mineral deposits, genesis (1)
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elements, isotopes
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isotope ratios (1)
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isotopes
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radioactive isotopes
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Pb-206/Pb-204 (2)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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stable isotopes
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Pb-206/Pb-204 (2)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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S-34/S-32 (2)
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metals
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aluminum (1)
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copper (1)
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iron (1)
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lead
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Pb-206/Pb-204 (2)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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sulfur
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S-34/S-32 (2)
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geologic age
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Paleozoic
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Cambrian
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Upper Cambrian
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Bonneterre Formation (1)
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Lamotte Sandstone (1)
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Devonian (1)
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metamorphic rocks
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metamorphic rocks
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schists (1)
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minerals
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minerals (1)
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phosphates
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apatite (1)
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sulfides
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galena (1)
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Primary terms
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ground water (2)
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hydrology (1)
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isotopes
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radioactive isotopes
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Pb-206/Pb-204 (2)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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stable isotopes
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Pb-206/Pb-204 (2)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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S-34/S-32 (2)
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metal ores
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copper ores (1)
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gold ores (1)
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lead ores (1)
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lead-zinc deposits (1)
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silver ores (1)
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metals
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aluminum (1)
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copper (1)
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iron (1)
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lead
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Pb-206/Pb-204 (2)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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metamorphic rocks
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schists (1)
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metamorphism (1)
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metasomatism (1)
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mineral deposits, genesis (1)
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minerals (1)
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North America
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Rocky Mountains
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U. S. Rocky Mountains
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Sawatch Range (1)
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Yukon-Tanana Terrane (1)
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orogeny (1)
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Paleozoic
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Cambrian
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Upper Cambrian
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Bonneterre Formation (1)
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Lamotte Sandstone (1)
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Devonian (1)
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paragenesis (1)
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pollution (2)
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reclamation (1)
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sedimentary rocks (1)
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sulfur
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S-34/S-32 (2)
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United States
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Alaska
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Alaska Range (1)
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Colorado
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San Juan County Colorado (1)
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Sawatch Range (1)
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Midcontinent (1)
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Mississippi Valley
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Upper Mississippi Valley (1)
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Missouri
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Saint Francois Mountains (1)
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Viburnum Trend (1)
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Montana
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Jefferson County Montana (1)
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Ozark Mountains (1)
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U. S. Rocky Mountains
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Sawatch Range (1)
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weathering (1)
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sedimentary rocks
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sedimentary rocks (1)
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Metal contamination and post-remediation recovery in the Boulder River watershed, Jefferson County, Montana
Abstract Historical production of metals in the western United States has left a legacy of acidic drainage and toxic metals in many mountain watersheds that are a potential threat to human and ecosystem health. Studies of the effects of historical mining on surface water chemistry and riparian habitat in the Animas River watershed have shown that cost-effective remediation of mine sites must be carefully planned. of the more than 5400 mine, mill, and prospect sites in the watershed, ∼80 sites account for more than 90% of the metal loads to the surface drainages. Much of the low pH water and some of the metal loads are the result of weathering of hydrothermally altered rock that has not been disturbed by historical mining. Some stream reaches in areas underlain by hydrothermally altered rock contained no aquatic life prior to mining. Scientific studies of the processes and metal-release pathways are necessary to develop effective remediation strategies, particularly in watersheds where there is little land available to build mine-waste repositories. Characterization of mine waste, development of runoff profiles, and evaluation of ground-water pathways all require rigorous study and are expensive upfront costs that land managers find difficult to justify. Tracer studies of water quality provide a detailed spatial analysis of processes affecting surface- and ground-water chemistry. Reactive transport models were used in conjunction with the best state-of-the-art engineering solutions to make informed and cost-effective remediation decisions. Remediation of 23% of the high-priority sites identified in the watershed has resulted in steady improvement in water quality. More than $12 million, most contributed by private entities, has been spent on remediation in the Animas River watershed. The recovery curve for aquatic life in the Animas River system will require further documentation and long-term monitoring to evaluate the effectiveness of remediation projects implemented.
Lead and sulfur isotope investigation of Paleozoic sedimentary rocks from the southern Midcontinent of the United States; implications for paleohydrology and ore genesis of the Southeast Missouri lead belts
Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana Terrane, eastern Alaska Range, Alaska
Geologic Relationships, K-Ar Ages, and Isotopic Data from the Willow Creek Gold Mining District, Southern Alaska
Abstract The Willow Creek mining district is located in the Peninsular terrane in Alaska, on the southwestern margin of the Talkeetna Mountains batholith. The district contains exposures of tonalite (74-73 Ma) and adamellite (67-65 Ma) of the batholith and an older unit of schist that has no nearby correlative units. The tonalite (quartz diorite) and schist both host gold-bearing quartz veins in fractures and shears, whereas the adamellite (quartz monzonite) appears to be barren of gold mineralization. Our data suggest that there is a previously unmapped fault along the contact between the mineralized tonalite and schist. The fault may have provided a conduit for mineralizing fluids. Ceologic relations and K-Ar ages indicate that at least two periods of mineralization occurred at 66 and at 57 to 55 Ma. At 66 Ma, the intruding adamellite provided heat and possibly fluids to the tonalite as suggested by K-Ar ages from a gold-bearing quartz vein and from dikes in the tonalite. At 57 to 55 Ma, the source of heat is uncertain. Both periods of mineralization occurred during right-oblique subduction of the Kula plate beneath the Peninsular terrane and some mineralizing fluids may have originated in zones of metamorphism and partial melting in the descending Kula plate, Fluids of deep origin, magmatic and/or met amorphic, could have moved through a deeply rooted fault system and out into the host rocks along splays and fractures related to a fault separating the schist and tonalite. Oxygen isotope data suggest that the mineralizing fluids were similar in their oxygen isotope composition to the tonalite, and perhaps the adamellite, but were unlike the schist. This similarity could have resulted if the fluids equilibrated with a plutonic body (tonalite or adamellite) at temperatures high enough that fractionation approached zero. The measured values of δ 18 O from quartz in gold-bearing veins are 13.2 to 15.8 per mil, with one low value of 9.2 per mil from a pegmatite, and the calculated fluid values are 6.3 to 8.9 per mil. These values occur in veins with ages of 66 Ma, as well as in undated veins. The Pb isotope compositions of sulfides from two veins in the tonalite resemble each other but differ from those in the schist. These compositions suggest that the Pb in veins in the tonalite had a common source. In the schist, the gold-bearing veins may have farmed from the same mineralizing fluid that was modified in Pb isotope composition by circulation through the schist, or from a fluid that was different from the one that produced gold-bearing quartz veins in the tonalite.