CRITICAL METALS IN MARINE MUDSTONES: INSIGHTS FROM THE UPPER DEVONIAN OF WESTERN NEW YORK STATE, USA

The rising demand for critical minerals necessitates the need to understand their abundance in potential, non-traditional ores like mudstones. The interbedded black and gray Upper Devonian shale succession of western New York provides a natural laboratory to understand the accumulation and distribution of critical metals in fine-grained marine strata. In this study, we evaluated mineralogy using X-ray diffraction and elemental composition using inductively coupled plasma mass-spectrometry of gray and black shale, detrital pyrite lags, and diagenetic pyrite from the top of the gray shale-dominated Hanover Shale of the Java Group (the Point Gratiot bed and overlying Beaver Meadow beds) to approximately one meter above the base of black shale-dominated Dunkirk Shale of the Canadaway Group. Hand samples and 41 mm diameter cores were collected along a series of lakeshore and creek exposures across a 75 km transect from Dunkirk to Java Village, NY. The eastward-thickening wedge of gray shale hosts numerous thin black shale beds, detrital pyrite lags, and diagenetic pyrite worm tubes, concretions, and nodules. Total sulfide content ranges from less than 1% in gray shale to nearly 28% in detrital pyrite lags. Clay content ranges from approx. 12% in detrital pyrite lags to over 50% in gray shale and is composed mostly of illite with subordinate chlorite and kaolinite. We investigated the occurrence of rare-earth elements and yttrium (REE+Y), lithium, and battery metals (Co, Cu, Ni) relative to gray shale, black shale, and pyrite within the section. Average REE+Y, Li, and Co+Cu+Ni concentrations range from 123 to 228, 35 to 68, and 90 to 291 ppm, respectively. Both REE+Y and Li occur at roughly average shale values. However, their abundance is lowest in pyrite lags, and most abundant in gray shale. Their covariance with aluminum suggests an association with clay minerals. The battery metals concentrations are 2 to 6.5 times higher than the average shale in pyrite lags and are mostly depleted in gray shale facies. Covariance of Co+Cu+Ni with Fe and S suggests these metals are associated with pyrite. This work provides insight into the occurrence of critical minerals in fine-grained marine sediments which will aid in the exploration of these metals in sedimentary basins.