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Karen Duttweiler Kelley

Publications and source records attributed to Karen Duttweiler Kelley.

4 recordsLinked to original sources
USGS2018

Sulfur isotopes of host strata for Howards Pass (Yukon–Northwest Territories) Zn-Pb deposits implicate anaerobic oxidation of methane, not basin stagnation

A new sulfur isotope stratigraphic profile has been developed for Ordovician-Silurian mudstones that host the Howards Pass Zn-Pb deposits (Canada) in an attempt to reconcile the traditional model of a stagnant euxinic basin setting with new contradictory findings. Our analyses of pyrite confirm the up-section 34 S enrichment reported previously, but additional observations show parallel depletion of carbonate 13 C, an increase in organic carbon weight percent, and a change in pyrite morphology. Taken together, the data suggest that the 34 S enrichment reflects a transition in the mechanism of pyrite formation during diagenesis, not isotopic evolution of a stagnant water mass. Low in the stratigraphic section, pyrite formed mainly in the sulfate reduction zone in association with organic matter–driven bacterial sulfate reduction. In contrast, starting just below the Zn-Pb mineralized horizon, pyrite formed increasingly within the sulfate-methane transition zone in association with anaerobic oxidation of methane. Our new insights on diagenesis have implications for (1) the setting of Zn-Pb ore formation, (2) the reliability of redox proxies involving metals, and (3) the source of ore sulfur for Howards Pass, and potentially for other stratiform Zn-Pb deposits contained in carbonaceous strata.

Northwest Territories, Yukon↗
USGS2018

Strategic and critical metals in produced geothermal fluids from Nevada and Utah

Herein we summarize the results of an investigation dealing with the concentrations and inventories of strategic, critical and valuable materials (SCVM) in produced fluids from geothermal and hydrocarbon reservoirs (50-250° C) in Nevada and Utah. Water samples were collected from thirty-four production wells across eight geothermal fields, the Uinta Basin oil/gas province in northeast Utah, and the Covenant oil field in southwestern Utah; additional water samples were collected from six hot springs in the Sevier Thermal Belt in southwestern Utah. Most SCVM concentrations in produced waters range from <0.1 to 100 µg/kg; the main exception is lithium, which has concentrations that range from <1000 to 25,000 ug/kg. Relatively high concentrations of gallium, germanium, scandium, selenium, and tellurium are measured too. Geothermal waters contain very low concentrations of REEs, below analytical detections limits (0.01 µg/kg), but the concentrations of lanthanum, cerium, and europium range from 0.05 to 5 µg/kg in Uinta basin waters. Among the geothermal fields, the Roosevelt Hot Spring reservoir appears to have the largest inventories of germanium and lithium, and Patua appears to have the largest inventories of gallium, scandium, selenium, and tellurium. By comparison, the Uinta basin has larger inventories of gallium. The concentrations of gallium, germanium, lithium, scandium, selenium, and tellurium in produced waters appear to be partly related to reservoir temperature and concentrations of total dissolved salts. The relatively high concentration and large inventory of lithium occurring at Roosevelt Hot Springs may be related to granitic-gneissic crystalline rocks, which host the reservoir. Analyses of calcite scales from Dixie Valley indicate enrichments in cobalt, gallium, gold, palladium, selenium and tellurium, and these metals appear to be depositing at deep levels in production wells due to boiling. Comparisons with SCVM mineral deposits suggest that brines in sedimentary basins, or derived from lacustrine evaporites, enable aqueous transport of gallium, germanium, and lithium.

Conference Paper↗
USGS2017

The hyper-enrichment of V and Zn in black shales of the Late Devonian-Early Mississippian Bakken Formation (USA)

Black shales of the Late Devonian to Early Mississippian Bakken Formation are characterized by high concentrations of organic carbon and the hyper-enrichment (> 500 to 1000s of mg/kg) of V and Zn. Deposition of black shales resulted from shallow seafloor depths that promoted rapid development of euxinic conditions. Vanadium hyper-enrichments, which are unknown in modern environments, are likely the result of very high levels of dissolved H 2 S (~ 10 mM) in bottom waters or sediments. Because modern hyper-enrichments of Zn are documented only in Framvaren Fjord (Norway), it is likely that the biogeochemical trigger responsible for Zn hyper-enrichment in Framvaren Fjord was also present in the Bakken basin. With Framvaren Fjord as an analogue, we propose a causal link between the activity of phototrophic sulfide oxidizing bacteria, related to the development of photic-zone euxinia, and the hyper-enrichment of Zn in black shales of the Bakken Formation.

Manitoba, Montana, North Dakota, Saskatchewan, Sou↗