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Regional fluid flow and basin modeling in northern Alaska

Project Objectives

The goal of the project was to construct hydrologic/chemical models that allow us to compare and test conceptual models for ore fluid migration and petroleum generation. The results of this study aided in understanding the petroleum maturation and mineralization history of parts of the Brooks Range that are poorly characterized and understood. This is considered essential for mineral and energy resource assessments of northern Alaska. This project expanded the scope of the current NPRA (National Petroleum Reserve - Alaska) petroleum assessment and syngenetic massive sulfide projects, and utilized data collected during the Killik River and Howard Pass AMRAP studies in the 1980/1990's. However, it is essential that new observations and data be collected. This will necessarily involve helicopter-supported field work and airborne geophysical data collection in future years. Careful examination of existing data and collection of some key samples and analyses were the primary avenue for determining areas requiring more detailed investigation.

Mineral Resources Objectives: The configuration and extent of the basin(s) that host the zinc deposits and the hydrologic mechanisms causing hydrothermal fluid migration are still largely unknown. A better understanding of processes related to the evolution of the Carboniferous Kuna basin will greatly aid mineral resource assessment. For instance, black shale basins such as that hosting Red Dog are known worldwide in Precambrian and Phanerozoic strata yet only a few contain sedimentary exhalative (sedex)-type deposits, although reasons for this are obscure. Studies that delineate the
fundamental geologic events leading to Zn-Pb-Ag ore formation can be extrapolated to analogous shale basins elsewhere, thereby enhancing our ability to conduct an accurate global resource assessment for zinc, lead, and silver. We constructed hydrologic/chemical models that allow us to compare and test conceptual models for ore formation, and to predict sites of mineral deposition.

Energy Resources Objectives: Regional modeling of deformation, thermal evolution, and fluid flow, combined with comprehensive basin analysis, lead to an enhanced understanding of Otuk and Kuna petroleum systems in the western Brooks Range and foothills. These systems are the southern extension in the Brooks Range of the fertile Ellesmerian petroleum system of the North Slope, and as such may have contributed significant amounts of hydrocarbons to the petroleum resources of Northern Alaska. Structural restorations and modeling of the source rocks for these systems were required to make estimates of the fetch and volume of source rocks, burial and maturation history, migration pathways, and timing of hydrocarbon generation for the Brooks Range component of the Ellesmerian system. This information is essential for evaluating the contribution of the Otuk and Kuna systems to the hydrocarbon resources of northern Alaska and is a critical component for future resource assessments. Generation of hydrocarbons from rich Triassic and Jurassic source rocks may be linked to thrusting and probably began in the western Brooks Range before correlative source rocks reached thermal maturity farther north. In addition, there may be an important link between mineralization and hydrocarbon generation. The association of zinc and quartz with bitumen (interpreted to have been liquid hydrocarbon) at Red Dog would suggest a possible temporal overlap between fluid migration and hydrocarbon generation. The association of mobile hydrocarbon phases and major sulfide deposition has also recently been recognized at the large Century zinc deposit in northeastern Australia (probably the second largest zinc deposit in the world after Red Dog). Perhaps there is an unrecognized geologic explanation for this spatial/temporal association of hydrocarbons with world-class zinc deposits.

Relevance & Impact

The research improved our understanding of the evolution of sedimentary basins and fluid flow processes that control the accumulation of metals and energy-related commodities. The project included a comprehensive geological, geochemical, and geophysical database for one of the economically most important group of sedimentary basins in the world. Tracing the fluid history of the basin was necessary for successful application of large and restricted-scale flow models, for integrating the sedimentological, tectonic, and geochemical crustal evolution models, and for refining exploration and exploitation strategies for mineral and oil and gas deposits. The end result was the first quantitative geochemical and hydrologic models for fluid flow in a black shale basin, and the relationship of this fluid flow to the formation of major mineral and hydrocarbon resources. This provided a significant advance in our ability to assess the sedex potential of black shale basins elsewhere in the United States, and throughout the world.

Project Contact

Karen Duttweiler Kelley
Phone: (303) 236-2467
Email Karen Kelley

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Lithofacies and thermal parameters of the Kuna and Otuk Basins

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Regional kinematic analysis and reconstruction of NW Brooks Range thrust faulting

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Ore deposit modelling

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Basin evolution, fluid flow and geochemical modeling

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Organic geochemistry: source rocks, migration pathways, and ore deposits

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Mineral Resources Program
Eastern Central Western Alaska Minerals Information Crustal Geophysics and Geochemistry Spatial Data

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