
Philip S. NeuhoffUniversity of Florida | UF · Department of Geological Sciences
Philip S. Neuhoff
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Publications (40)
The island-arc volcanics situated in the eastern part of the Căpıîlnaş-Techereu nappe (South Apuseni Mountains, Romania) were studied to evaluate the temperature, fluid properties, and mineral chemistry during low-temperature metamorphism. Detailed observations of metamorphic mineral assemblages were conducted using powder X-ray diffraction and ele...
Most concepts of conduit development have focused on telogenetic karst aquifers, where low matrix permeability focuses flow and dissolution along joints, fractures, and bedding planes. However, conduits also exist in eogenetic karst aquifers, despite high matrix permeability which accounts for a significant component of flow. This study investigate...
Zeolites, which host large quantities of water, are among the most important rock-forming and environmental minerals in the surface and near-surface regions of the Earth. The physical properties and geochemical behavior of water confined in zeolites differs substantially from that of bulk liquid water, and the energectics of confined water exerts a...
Analcime forms in a wide range of geologic environments from alkaline lakes to primary igneous occurrences in Si-undersaturated lavas and pegmatites and is present in many radioactive waste repository settings. To evaluate its hydration state in these environments, calorimetric-hydration heat measurements, equilibrium observations, and thermodynami...
Dehydration of zeolites is a critical factor in their stability, effectiveness as storage media for thermal energy, and influence on the thermal evolution of radioactive waste repositories. Prediction of the hydration states of zeolites as a function of temperature, pressure, and water activity is often hampered by limited data on the heat capacity...
A calorimetric method for determining isothermal partial and integral heats of hydration reactions (ΔHR,T,P and ΔHR,T,P, respectively) in zeolites and other mineral hydrates is presented. The method involves immersing a dehydrated sample in a humid gas stream under isothermal conditions within a thermal analysis device that records simultaneous dif...
High-pH (9-10), 5-90°C ground waters in a Tertiary basalt province in Iceland are close to equilibrium or slightly over-saturated with many low-temperature (<100°C) Ca-zeolites. These zeolites include chabazite, thomsonite, mesolite, scolecite, heulandite and stilbite. The waters are generally under-saturated with respect to Ca-clinoptilolite and m...
The thick Paleocene basaltic lava succession exposed on Disko Island and Nuussuaq Peninsula, central West Greenland, experienced regional metamorphism shortly after volcanism followed by several events of localized hydrothermal alteration. Regional metamorphism resulted in well-developed lower zeolite facies mineral assemblages consisting primarily...
Extensive subaerial exposures of a basalt-hosted petroleum reservoir around Marraat Killiit on Nuussuaq, West Greenland, provide an unparalleled opportunity to investigate water–rock–hydrocarbon interactions in an unconventional petroleum system. Exposed sections in this locality include picritic and olivine-phyric basalts, with both subaerial and...
Rock-forming zeolites often exhibit complex solid solutions reflecting isomorphous substitutions between Si and Al in tetrahedral framework sites, between charge-balancing extraframework cations, and between water molecules and vacancies. Although the number of moles of charge on extraframework cations in a zeolite must equal the moles of Al in ord...
Basaltic lavas exhibit considerable, yet heterogeneous, porosity (typically 10-25 % in vesiculated zones, but sometimes up to 85 % in scoraceous flowtops) and concomitantly large permeabilities (0.001 to 10 darcies). The heterogeneous distribution of porosity occurs not only on the scale of a lava flow (e.g., between vesiculated flowtops and massiv...
Heulandite is a common rock-forming zeolite that exhibits wide solid solution of extra framework cations, presumably due to ready ion exchange with aqueous solutions. In order to provide a quantitative basis for interpreting and predicting the distribution of aqueous species between heulandite and aqueous solutions, ion exchange equilibrium between...
Analcime (NaxAlxSi3-xO6 ((3-x)/2)H2O, where x varies from 0.78 to 1.06) is one of the most common rock-forming zeolites. It forms in a wide range of geologic environments that span a range of temperature and pressure from ambient to magmatic conditions. Cluster variation method analysis of 29Si magic angle spinning nuclear magnetic resonance spectr...
Isothermal vapor sorption experiments under controlled partial pressures of H2O (between 0.1 and 30 mbar, at 23.4, 30.1, 49.5, 64.5, and 79.3 °C) and liquid water immersion calorimetry experiments at 25.0 °C were conducted to determine standard molar thermodynamic properties of hydration of the W1 and W5 sites in laumontite that host hydrogen-bonde...
Analcime (Na_xAl_xSi3-xO_6\cdot[(3-x)/2]H_2O, where x varies from ˜0.78 to ˜1.06) is one of the most common rock-forming zeolites. It forms in a wide range of geologic environments that span a range of temperature and pressure from ambient to magmatic conditions. Substantial Si-Al substitution occurs in analcime, and in most analcimes the degree of...
Quantitative determination of the abundance of Si(nAl) tetrahedral structural units (where n = 0, 1, 2, 3, or 4) through analysis of 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectra was used to assess the state of Si-Al disorder in the
zeolites analcime [(NaAl)xSi48−xO96·16H2O], chabazite [(Ca0.5,Na,K)xAlxSi12−xO24·12H2O], and...
Hydrate minerals (those containing molecular water; e.g., expandable clays, zeolites, hydrated salts) are important phases in surficial and near-surface Earth systems. These phases can undergo reversible dehydration and dehydration as temperature, pressure, and water fugacity vary, which can have a profound effect on the rheological, hydrological,...
Disordering of Si and Al in natrolite, scolecite, mesolite, and gonnardite was investigated with 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The results indicate that with the exception of
one sample of natrolite (from San Benito County, California), the natrolite, mesolite, and scolecite samples studied al...
Disordering of Si and Al in natrolite, scolecite, mesolite, and gonnardite was investigated with Si-29 and Al-27 magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The results indicate that with the exception of one sample of natrolite (from San Benito County, California), the natrolite, mesolite, and scolecite samples studied...
Zeolite A provides a unique opportunity to explore the relationship between structural parameters and 17O nuclear magnetic resonance (NMR) isotropic chemical shifts (δISO) because differences in site multiplicity for framework oxygens often permit unambiguous site assignments. Strontium exchanged zeolite A and hydrated and dehydrated K- and Na-A we...
We present here high-resolution solid state NMR spectra of several oxide and silicate materials that illustrate the improvements obtainable with very high external fields (18.8 and 21.1 T), with probes capable of tuning to a wide frequency range that allow observations of nuclides from high to low magnetogyric ratio. We discuss 27Al MAS spectra for...
Standard state thermodynamic data for stilbite (Ca2NaAl5Si13O36∗16H2O) and stellerite (Ca2Al4Si14O36∗14H2O), together with mixing properties of the stilbite -stellerite solid solution (stilbite SS) are derived through assessment of geological observations of stilbite SS compositions in metabasalts, experimental phase equilibria, and calorimetric ob...
Configurational entropies (Scon) arising from disordering of Si and Al in the frameworks of FAU and LTA zeolites were calculated from published 29Si MAS NMR spectra using the cluster variation method (CVM). The calculations indicate that Scon is a systematic function of aluminum mole fraction (XAl) and predict that Scon becomes zero at XAl=0 and 0....
The utilization of higher magnetic fields for nuclear magnetic resonance (NMR) (e.g., 14.1 and 18.8 T) can enhance both resolution and sensitivity in studies of disordered materials. When used in conjunction with fast magic angle spinning (MAS), high-field NMR can yield structural information not always available from NMR experiments of glasses at...
Fast amplitude modulation (FAM) shifted-echo pulse sequences for 3Q- and 5Q-MAS NMR experiments were compared for resolution of 17O on chemically and/or crystallographically distinct framework oxygen sites (i.e., Si–O–Si, Si–O–Al) in zeolites 13X, 4A, and a natural analcime (Na1.01Al1.01Si1.99O6·H2O). Significantly better sensitivity is afforded by...
In the beginning the surface of the Earth was extremely hot, because the Earth as we know it is the product of a collision between two planets, a collision that also created the Moon. Most of the heat within the very young Earth was lost quickly to space while the surface was still quite hot. As it cooled, the Earth's surface passed monotonically t...
Stratigraphic, geochemical and mineralogical characterization of pyroclastic deposits on the Gronau West Nunatak of East Greenland indicates that both alkaline and basaltic tephras occurred during the eruption of flood basalts associated with the opening of the North Atlantic ocean in the early Tertiary. Within the exposed section of Gronau West Nu...
Laumontite is a common zeolite mineral indicative of low-grade metamorphism of lavas and volcaniclastic sediments. Stoichiometric laumontite (CaAl2Si4O12.4.5H2O) dehydrates in air at 298.15 K, 1 bar to leonhardite (CaAl2Si4O12.3.5H2O) via loss of water from the W1 crystallographic site. Consideration of reported X-ray diffraction and calorimetric d...
Detailed analyses of crystalline, hydrated, and precipitated strontium compounds and an aqueous strontium solution by synchrotron extended X-ray absorption fine structure (EXAFS) were used to quantify local thermal and static disorder and to characterize strontium coordination in a variety of oxygen-ligated bonding environments. Analysis of anharmo...
Zeolites are among the most common products of chemical interaction between groundwaters and the Earth's crust during diagenesis and low-grade metamorphism. The unique crystal structures of zeolites result in large molar volumes, high cation-exchange capacities, and reversible dehydration. These properties influence both the stability and chemistry...
Low-grade alteration of basaltic lavas at Teigarhorn, eastern Iceland, resulted in three distinct stages of mineral paragenesis that correlate to events in the burial and intrusive history of Icelandic crust. Metasomatism and brittle deformation during the paragenetic stages dramatically affected the paleo- hydrology of the lavas and formed tempora...
The 1997 summer season saw continued petroleum geological activities in the Disko-Nuussuaq-Svartenhuk Halvø area, onshore West Greenland. These activities mainly took the form of a geological field project led by the Geological Survey of Denmark and Greenland (GEUS), whereas the continued exploration by grøn- Arctic Energy Inc. (grønArctic) in the...
Zeolite isograds delineating regionally extensive metamorphic mineral
zones occur throughout most of the early Tertiary flood basalts in
central East Greenland. Mineralogic zones defined by isograds are
essentially uniform in thickness throughout the province, parallel
paleotopographic surfaces, and transgress lava stratigraphy. The
distribution of...
A patient presenting in the first year of life with feeding difficulties and failure to grow had variable but persistent lactic acidemia noted at age 20 months. Nonspecific nutritional and biochemical therapy was accompanied by improvement in general clinical status, growth, gait, and development. However, she died in a catastrophic illness at the...
The groundwater system in the Oak Ridge Reservation (ORR) area is stratigraphically controlled and divisible into aquitards, where flow is through fractures only, and aquifers, where flow is in karst conduits. An electromagnetic borehole flowmeter was used to survey 60 piezometer wells and 12 coreholes on the ORR. Piezometer well depths ranges from...