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Mary R Croke

Physical Science Technician

Geology, Energy & Minerals Science Center

Office Phone: 703-648-6454

John W Powell FB
12201 Sunrise Valley Drive
Reston , VA 20192-0002

Supervisor: Robert Matthias
To test if reflectance increases to sedimentary organic matter (vitrinite) caused by broad ion beam (BIB) milling were related to molecular aromatization and condensation, we used Raman and Fourier transform infrared (FTIR) spectroscopies to evaluate potential compositional changes in the same vitrinite locations pre- and post-BIB milling. The same locations also were examined by atomic force microscopy (AFM) to determine topographic changes caused by BIB milling (as expressed by the areal root-mean-square roughness parameter Rq). Samples consisted of four medium volatile bituminous coals. We used a non-aggressive BIB milling approach with conditions of [(5 min, 4 keV, 15°incline, 360° rotation at 25 rpm and 100%...
Solid organic matter (OM) in sedimentary rocks produces petroleum and solid bitumen when it undergoes thermal maturation. The solid OM is a 'geomacromolecule', usually representing a mixture of various organisms with distinct biogenic origins, and can have high heterogeneity in composition. Programmed pyrolysis is a common conventional method to reveal bulk geochemical characteristics of the dominant OM while detailed organic petrography is required to reveal information about the biogenic origin of contributing macerals. Despite advantages of programmed pyrolysis, it cannot provide information about the heterogeneity of chemical compositions present in the individual OM types. Therefore, other analytical techniques...
Petroleum within unconventional source-rock reservoirs is hosted in organic matter and mineral pore space as well as in voids and microfractures. Recent work has shown that for source-rock reservoirs in the dry gas window, significant portions of methane (CH4), the main component of petroleum at elevated maturities, can be stored within fine organic matter porosity. However, within reservoirs at lower thermal maturities (e.g., peak oil or wet-gas conditions), the distribution and behavior of CH4 and the higher alkanes that comprise gas condensates across pore sizes is unclear, especially for fine pores with diameters <50 nm. Understanding CH4 within these settings provides insight for petroleum generation, movement,...
Germanium (Ge) is an increasingly important element used in critical technologies for communication, defense, and computing. However, Ge is scarce, and there is no United States (U.S.) primary production. Additionally, the environmental behavior of Ge is poorly understood. Germanium does not generally form its own minerals, but is instead recovered as a byproduct of zinc mining or of coal fly ash. It has been deemed critical by the U.S. and globally, and investigations of its geologic concentration, environmental fate and transport, and potential for recovery are crucial for maintaining a sustainable supply. A relevant study site to explore questions of environmental behavior and the potential to recover...
At recent technical conferences, many coal geoscientists in academia and government institutions as well as in industry organizations have expressed concern about the dwindling number of students and young staff members interested in careers in coal geoscience. To better understand what is driving these trends and to identify potential ways that the community can increase interest and participation in coal geoscience, two different surveys were sent to 94 coal geoscientists who were current or past members of The Society of Organic Petrology (TSOP) in February 2020. As the trends and perceptions in industry and government organizations may be different than in universities, one distinct survey was sent to members...
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