USGS Publications Warehouse

Geochemical, mineralogical, and isotopic evidence for multi-stage genesis of the Hicks Dome REE + Y-HFSE-fluorite deposit, Illinois, USA

Thu, 28 May 2026 14:13:31

Hicks Dome hosts breccias enriched in rare earth elements (REE), Y, Th, F, Ba, Ti, Nb, and Be, alongside spatially associated lamprophyre dikes (ca. 271 Ma). Hicks Dome is located within the Illinois–Kentucky Fluorspar District, which hosts fluorite, Pb–Zn, and barite resources. This study investigates the genetic relationships between Hicks Dome mineralization in breccias, alkaline magmatism, and Illinois–Kentucky Fluorspar District mineralization. Lamprophyre dikes are light REE–enriched with chondrite-normalized abundances decreasing from La to Lu. The Host Breccia exhibits middle and heavy REE–enriched patterns that mirror those of the principal REE–Th host minerals, including fluorapatite, xenotime, and thorite. Textural evidence suggests recrystallization of phosphates, sulfates, and Ti–Nb oxides in the Host Breccia. U–Pb geochronology constrains multiple mineralizing events, with ages of 277 ± 18 Ma from low-Th apatite interpreted as main-stage mineralization, and 121.6 ± 9.7 Ma from high-Th apatite indicating later overprinting. O–H–C stable isotope data provide evidence for multiple stages of fluid-rock interaction and fluid mixing: (1) early magmatic fluids dissolved limestone country rock, (2) mixing between magmatic fluids and basinal brines led to main-stage mineralization in the Host Breccia, and (3) late-stage mineralization occurred following mixing of meteoric water and basinal brine. These results indicate that heavy REEs, high field strength elements, and fluorine precipitated proximal to its alkaline magmatic source because of fluid–rock interactions and fluid mixing. Subsequent fluid mixing drove late-stage recrystallization and additional fluorite formation, a process that may be similar to mineralization in the Illinois-Kentucky Fluorspar District.

Modeling the seasonality of wind-driven hydrocarbon waves in Titan’s polar lakes

Wed, 27 May 2026 13:31:02

Titan, the only body in the solar system aside from Earth with standing liquids on its surface, has polar hydrocarbon lakes and seas. As Titan’s atmosphere generates light winds, there should be waves on the surface of these lakes and seas, yet, direct wave observations are scant. We introduce and use PlanetWaves, an open source 4D spectral wave model, to study Titan’s waves and create seasonal maps of wave shape and propagation on Ontario Lacus and Ligeia Mare. Titan’s modeled waves grow up to 30 times larger than terrestrial waves for the same wind speed, are seasonally present and are largest in the spring and summer when winds are strongest. Average daily winds almost never exceed the wave generation threshold of 0.5–0.7 m/s. Average storm winds (∼1.5 m/s) generate waves 15–48 cm in height with a period ranging 6–10.5 s while maximum storm winds (∼4 m/s) generate waves 2.7–3.2 m in height with a period up to 32 s. Titan’s waves become fetch-independent at ∼40 km for average storm winds occurring ∼1% of a Titan year and ∼100 kilometers for maximum storm winds occurring 2-3 times per Titan decade. On Ontario Lacus, storm winds blow nearly parallel to the eastern shore, potentially driving wave modification of the smooth eastern shoreline. On Ligeia Mare, waves rarely propagate toward a hypothesized wave modified shoreline suggesting that another process, such as tectonics, may contribute to a straight shoreline morphology.

Geochemical geodatabase of sedimentary strata (coal, coal-adjacent rocks, tuffaceous oil shale, phosphate-rich rocks) and produced water in the Uinta region, Utah and Colorado

Thu, 28 May 2026 14:50:26

The Geochemical Geodatabase of Sedimentary Strata (Coal, Coal-adjacent Rocks, Tuffaceous Oil Shale, Phosphate-rich Rocks) and Produced Water in the Uinta Region, Utah and Colorado, consists of compiled datasets acquired as part of the Carbon Ore, Rare Earth, and Critical Mineral (CORE-CM) Uinta Region assessment funded by the U.S. Department of Energy (DEFE0032046, 2021–2024; Birgenheier et al., 2024). The CORE-CM assessment focused on providing comprehensive geological and geochemical characterization of current and prospective sedimentary-hosted resources including coal, oil shale, phosphatic limestone, and produced water from oil and gas targets present in eastern Utah and northwestern Colorado (Figure 1).

This Data Series includes a geodatabase that consists of analytical geochemical data collected September 2021 through December 2024 via portable X-ray fluorescence (pXRF), and laboratory measured analyses produced by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The coal-related geochemical data are derived primarily from the Cretaceous Blackhawk Formation and Ferron Sandstone of Utah, and the Mesaverde Group of Colorado. Additional non-coal resources assessed include oil shale-bearing strata of the Eocene upper Green River Formation (Utah and Colorado), phosphate-rich limestone of the Permian Park City Formation (Utah) and produced water from oil and gas-bearing strata of the Eocene Green River and Wasatch Formations (Uinta Basin) and the Pennsylvanian Paradox Formation (Paradox Basin) (Table 1). The CORE-CM assessment included a wide range of lithologies present in the coal, oil shale, and phosphate geologic resource systems whether or not the specific lithology has current economic value. Geochemical analyses of produced water from oil and gas wells focused on current and emerging hydrocarbon targets in the central Uinta Basin and northern Paradox Basin. A total of 13,092 geochemical analyses from these geologic systems is provided in the included geodatabase. A series of coal quality data (e.g., composition and maceral analyses) is also included in the database and was digitized from archived coal samples from the Utah Geological Survey (Appendix A).

A hierarchical approach for finding undiscovered populations of an endangered bumble bee

Thu, 7 May 2026 15:00:45

Understanding the distributions of rare species is necessary to guide monitoring and inform species recovery efforts. The rusty patched bumble bee (RPBB; Bombus affinis, Cresson) is an endangered species with an extant, known distribution centered around urban areas of the Midwestern United States. We tested a novel approach for finding undocumented RPBBs outside of urban centers and estimated the species occurrence at two scales that are relevant to management. We confirmed presence of RPBBs at 54% of the sampled 100 km² grid cells where the species was previously undocumented, expanding the species’ known distribution by 5700 km². After accounting for imperfect detection, our occupancy model estimated the number of occupied grid cells was 67 of 105 sampled grids, suggesting our methods were effective for finding undiscovered RPBB sites. Occupancy within 100 km² grids was positively related to the number of occupied neighboring units but was not related to the area of developed land within 100km² grid cells or smaller subunits (i.e. 3.14 ha patches or roadside transects). We highlight the utility of our approach for guiding future survey efforts by identifying an additional 145 grid cells where the occupancy status of RPBB is unknown but we predict a relatively high likelihood of RPBB occurrence. Our approach can be extended to find undiscovered RPBB sites in other areas and applied to other bee species where occurrence information is lacking outside of their core distribution.

Assessment of groundwater quantity and quality contributions to Lake Huron

Kaemming, Bridget; Ford, Chanse; Martin, Sherry — Fri, 24 Apr 2026 18:36:33

Lake Huron, one of the five Great Lakes, borders the United States and Canada, with Michigan as the only U.S. State on its shoreline. Like other freshwater lakes, it faces water-quality challenges from nutrients and chemicals applied across its drainage basin. Although past studies focused on surface-water sources, groundwater contributions remain less understood. To address this gap, the U.S. Geological Survey, as part of the Cooperative Science and Monitoring Initiative, classified drainage basins to Lake Huron into eight hydrogeologic zones based on bedrock rock type and glacial sediment transmissivity. Utilizing existing data and empirical field data, we quantified groundwater discharge and identified areas of concern for loading of chloride and nitrate to Lake Huron. Groundwater contributions, including indirect and shoreline discharge, ranged from 5.8 to 11.5 inches annually, totaling 1.9 cubic miles and 0.09 cubic mile, respectively. Hydrogeologic zones with higher glacial sediment transmissivity yielded greater indirect groundwater discharge. Chloride levels above the U.S. Environmental Protection Agency’s 250-mg/L recommendation were mainly in the Saginaw lowlands, whereas nitrate above the 10-mg/L standard was rare—found in only 11 wells. Together, the analysis of where groundwater discharge is occurring in the Lake Huron Basin and the identification of areas with potential groundwater-quality concerns can help prioritize areas that are critical to protecting the long-term health of Lake Huron.

Detecting bumble bees in the wild using environmental DNA: Development and validation of a qPCR assay for the endangered Franklin’s bumble bee (Bombus franklini)

Mon, 20 Apr 2026 13:25:30

Environmental DNA (eDNA) sampling is a noninvasive alternative to conventional methods of surveying insects that may be particularly useful for detecting pollinators. We developed a quantitative polymerase chain reaction (qPCR) assay to detect the DNA of Franklin’s bumble bee (Bombus franklini) from flower samples and conducted an initial test of the assay using samples collected within and around the historical range of the species. We further analyzed all samples using metabarcoding. Our qPCR assay successfully amplified B. franklini DNA and exhibited no cross-reactivity with nontarget bumble bee DNA during in silico and in vitro testing. We did not detect B. franklini DNA from field-collected flower samples using either qPCR or metabarcoding. However, metabarcoding analysis revealed DNA of at least 16 other bumble bee species. This finding underscores the potential utility of eDNA sampling for surveying bumble bees. Nondetection of B. franklini from field-collected flower samples may be due to the extreme rarity of the species; B. franklini is endangered and has not been observed in the wild since 2006. Our B. franklini assay is among the first bee-specific qPCR assays ever developed and provides proof of concept for additional assays that may improve detection rates of rare and endangered bees.

Initial condition uncertainty exerts a large and persistent influence on model simulations of ecosystem carbon dynamics in California

Selmants, Paul; Sleeter, Benjamin M.; Daniel, Colin — Wed, 22 Apr 2026 14:41:53

Uncertainties in terrestrial ecosystem models limit their predictive power. Efforts to reduce projection error have rarely focused on constraining uncertainty in the initial state of the ecosystem, however, despite evidence that matching model initial conditions to real-world observations reduces overall model bias. Here we use an integrated land change and carbon gain-loss model to evaluate the influence of initial condition uncertainty on simulations of California wildland ecosystems during the years 1985–2020. We generated 36 initial conditions scenarios by varying the source data used to initialize state variables and then ran simulations based on each of these scenarios under a constant set of historical conditions. We found that discrepancies in initial forest extent and initial forest age among scenarios generated wide uncertainty ranges in model estimates of terrestrial ecosystem carbon stocks and flux rates at the outset of the simulation period, but differences in initial forest composition had no impact. Over time, forest age became more homogeneous across model scenarios leading to exponential rates of decline in the uncertainty ranges of live biomass and dead wood carbon but little to no impact on uncertainties in litter and soil organic carbon. Uncertainties in individual carbon flux rates were consistent with uncertainties in their source pools. In contrast, model estimates of ecosystem carbon balance demonstrated a shift in system behavior not apparent in trends for individual carbon stocks and fluxes. Specifically, estimates of ecosystem carbon balance converged across scenarios for the first 20 years of the simulation period but then began to diverge at an accelerating rate, possibly due to weakened resilience to the increased frequency and severity of climate-driven disturbances. Our results demonstrate that uncertainty in the initial state of the system can have large and persistent impacts on the predictability of ecosystem carbon dynamics, and that ongoing shifts in external forcing by climate and climate-driven disturbances can exacerbate these impacts.

Evaluating ichthyoplankton sampling as an effective method for early detection of novel aquatic invasive species in large bays of western Lake Erie

Bowser, Jessica; VanScoyoc, Haley; DeBruyne, Robin; Briggs, Andrew — Thu, 21 May 2026 14:28:36

Early detection and monitoring are critically important for effective management of invasive species in the Laurentian Great Lakes. Specifically, Lake Erie is at high-risk for aquatic invasive species introductions due to many factors such as shoreline development, warm water temperatures, and transoceanic shipping traffic. Rare species captured are often used as a surrogate to assess sampling effectiveness for new or rare invasive species in vulnerable areas, such as Maumee and Sandusky bays of western Lake Erie. We compared species catches from multiple larval fish collection methods to those from adult and juvenile fish sampling. The specific objectives of this study were to: 1) evaluate the effectiveness of larval fish sampling for aquatic invasive species early detection in two bays of western Lake Erie: Maumee Bay and Sandusky Bay; 2) evaluate the effectiveness of passive and active sampling techniques at capturing different larval fish taxa; and 3) compare effectiveness of larval sampling techniques to juvenile and adult fish sampling methods for detecting new and rare species. While no new non-native species were captured during the study, we found that larval fish sampling techniques were not effective for detecting new or rare species but could be used with other life-stage sampling. Active sampling with bongo nets was more effective than light trap sampling, capturing a higher number of individuals and taxa. Juvenile and adult fish sampling methods provided higher precision in fish identification without the use of genetic tools. Because of the finer taxonomic resolution possible when identifying juvenile and adult fishes, sampling for adult and juveniles was found to be more robust and reliable for early detection of new and rare species compared to larval fish sampling. However, larval fish sampling can still be appropriate depending on study goals and objectives or as emerging technologies allow for greater taxonomic resolution of sampled fish.