Publications

The spatial extent of mixing between separately emplaced batches of magma is a key component in understanding the incremental assembly of plutons. Potassium feldspar megacrysts (>3 cm length) in granodioritic rocks are hypothesized to record magma mixing and transport over hundred kyr timescales. CA-ID-TIMS U-Pb dates from zircon inclusions within 11 new megacryst samples and their...

The origin of prolific ca. 1.4 Ga ferroan magmatism between the southwestern USA and eastern Canada is enigmatic and has been explained by various models, including extensional, mantle plume, and convergent plate-margin models. Rare mafic plutons are associated with the ferroan plutons, which may help constrain their mantle source and tectonic setting. In the southwestern USA, only two...

Coal mining and reclamation can have a profound influence on hydrogeologic systems, with clear consequences for groundwater quality, yet their long-term influence on downgradient water quality over time following reclamation is less well documented. Geochemical trends were evaluated in water quality downgradient of a fully reclaimed landscape at the former Big Sky Mine in the Rosebud...

Gravity data require submeter elevation accuracy for data processing, and differential global navigation satellite system (dGNSS) equipment is commonly used to acquire three-dimensional positional data to achieve such accuracy. However, lidar (light detection and ranging) data are commonly used to develop digital elevation models (DEMs) of Earth’s surface. Therefore, using elevations...

Some earth science data are naturally grouped by region, and it is often desirable to map these data by region. However, if there are only a few samples within each region, then the map should be smoothed in an appropriate way to mitigate the problems that arise from having only a few samples. A smoothing algorithm based on a Bayesian hierarchical model is developed and presented in this...

Eocene magmatic systems contemporaneous with world-class Carlin-type Au deposits in Nevada (USA) have been proposed by some researchers as a key ingredient for Au mineralization, though evidence conclusively demonstrating their genetic relationship remains tenuous. This study provides the first direct evidence of the pre-eruptive metal budget of volatile- and metal-charged silicic magmas

Coastal Louisiana is known for saltwater intrusion that threatens wetlands, aquifers, and rivers. However, the extent of saltwater intrusion is not well understood. This study develops an innovative framework with airborne electromagnetic (AEM) data to map chloride concentration distributions for wetlands in the Mississippi River deltaic plain and Chenier plain as well as for the...

No abstract available.

In situ Re–Os geochronology by LA-ICP-MS/MS was previously demonstrated by reacting Os with CH4 or N2O reaction gasses. However, for both reactions, a minor proportion of the Re parent isotope also reacts, potentially leading to significant isobaric interferences of 187Re on 187Os, especially for young samples with little radiogenic in-growth. Here we present an interlaboratory...

Earth has experienced three complete icehouse-greenhouse turnovers in the Phanerozoic, with the Late Paleozoic Ice Age (LPIA) recognized as the last and most extreme icehouse. The nature, scale and dynamics of the LPIA are characterized by periods of intense glaciation, which are often interrupted by short-lived (1–2 Myrs) intervals associated with ice-free or distal from ice conditions...

Some of the highest-grade uranium deposits in the United States occur in breccia pipes that formed by solution and collapse of sedimentary strata, which occur in the southern portion of the Colorado Plateau in northwestern Arizona. The host breccia pipes are up to 1200 m in vertical extent, average about 90 m in diameter, and can cross-cut strata from their base in the Mississippian...

Borehole nuclear magnetic resonance (bNMR) data are typically used to infer in situ hydrologic properties. Partial water content as a function of pore size is estimated by fitting the measured NMR response to a multi-exponential T2 distribution, and the sum of estimated T2 amplitudes equals the total volumetric water content. From these estimated parameters, several empirical...