Constraints on genetic relationships between organic-rich black shales and Zn-Pb mineralization in the Mid-Continent Region, U.S.A.

University Of Arkansas, Fayetteville AR

Investigators

Abstract

Mississippi Valley-type (MVT) ores are important worldwide, especially in developing countries that are utilizing their natural resources to create jobs and develop infrastructure. The US technologic and economic interests are critically reliant on a continuation of prospecting, discovery and exploitation of new strategic ore deposits. Resources of this type necessitate investigation since they are part of our effort to ensure societal development on a sustainable Earth. Constraining the source(s) of metals in the MVT deposits is very important for a better understating of how this significant class of ores form. Understanding the mechanism can lead to modeling and predicting where they may be concentrated and may result in identification of yet-to-be-found deposits. The PI’s intent is to emphasize the education and training of economic geologists and will integrate research with an effort to enhance students’ preparation and understanding in the natural resources area. Research will also include student training in the radiogenic isotope class 100 clean lab and use of the state-of-the-art technology, including a Nu Plasma MC-ICP-MS and Thermo Scientific iCAP Q ICP-MS. The PI is using this research as a platform to contribute to ongoing outreach efforts focused on training and recruiting high-quality students of under-represented minorities of historically Black Colleges and Universities and Hispanic Serving Institutions. This project is jointly funded by the Petrology and Geochemistry Program the Established Program to Stimulate Competitive Research (EPSCoR). A genetic link between black shales and MVT ores has long been thought to exist because of (1) the presence of mature hydrocarbon and brine fluid inclusions within many MVT ores, (2) the association of the hydrothermal fluids that are linked to MVT ore formation with organic compounds and oil-like droplets, and (3) the highly radiogenic nature of the ores. Research aims to provide a better understanding of the genetic relationship between metal-rich black shales in large sedimentary basins and sulfide mineralization associated with (1) major MVT ores in carbonate sequences and (2) minor occurrences of ores in shales. A secondary goal is to better constrain the sources of metals in the MVT ores. The main hypothesis to be tested is that metal-rich black shales deposited in large sedimentary basins are the source of metals for Pb-Zn mineralization in the Mid-Continent Region of the United States. Preliminary Pb isotope and trace element data suggest that U-enriched black shales represent a potential source for radiogenic Pb to be mobilized in the ores and that different depositional environments within the larger shale body may explain the patterns of metal occurrence in the black shales and their movement into adjacent strata. Recognition and proof that these shales may be a major source of metals in ores may cause a paradigm shift of the basic concepts of how and where these deposits form. Understanding MVT deposits can also lead to enhanced knowledge about presence and relevant characteristics of metal-bearing black shales. This project is jointly funded by the Petrology and Geochemistry Program the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.