IDENTIFICATION AND CHARACTERIZATION OF METALLIFEROUS INTERVALS WITHIN BLACK SHALE FACIES FOR THE PURPOSE OF CRITICAL MINERAL EXTRACTION ASSESSMENTS

Mineralized zones with elevated concentrations of critical mineral (CM) values (e.g., V, rare earth elements (REEs), Ni, Co, Cu) are documented within numerous black shale facies, including from black shale formations targeted for natural gas extraction. These metal-bearing intervals represent a largely unknown byproduct commodity in terms of size during oil/gas operations, but whose concomitant recovery could provide a stream of critical mineral values relatively easily recovered utilizing existing infrastructure. Additionally, oil/gas operations for black shales (e.g., hydraulic fracturing in the subsurface) are not optimized for the co-extraction and recovery of metals. The objective of this research is to collect the baseline knowledge necessary to assess critical mineral extraction from black shales, including identifying representative critical mineral mineralizations and defining baseline metal mobility under typified oil/gas operations. The work presented here represents the identification and characterization of metalliferous intervals within select black shale facies in the U.S. Appalachian Basin. Core samples were scanned with a handheld X-ray fluorescence (XRF) analyzer to build a semi-quantitative log for metalliferous targets. Selected intervals were then subjected to in-depth geochemical analyses including compositional analysis via Inductively Coupled Plasma Optical Emission Spectroscopy/Mass Spectrometry (ICP-OES/MS) and inspection via Scanning Electron Microscopy Energy Dispersive Spectroscopy (SEM-EDS). A sequential extraction procedure was applied to selected samples to parse out mineral associations based on chemical reactivities. Sedimentary layers highly enriched in V (layers with V>500 ppm) had elevated concentrations of Ca, with additional CM of interest extracted from multiple mineral phases. These highly enriched black shale intervals grade into intervals of limestone with the majority of V held within refractory phases. The majority of CM from less enriched layers (V ~100-200 ppm) were extracted from multiple phases showing moderate lability for mobilizing metal sorbed species on clays and oxide minerals or from remnant organic matter.