Robert Ayuso is a Research Geologist with the USGS Geology, Energy & Minerals (GEM) Science Center in Reston, VA.
Science and Products
Radiogenic and Stable Isotope Methods
Our work focuses on collaborating with high-priority U.S. Geological Survey projects and other Federal and international agencies, and on providing radiogenic and stable isotope analyses to support mineral- and environmentally-related geologic investigations.
U-Pb Isotopic Data and Ages of Detrital Zircon Grains, Whole Rock Major and Trace-element Geochemistry, and Whole Rock Isotopic Data from Selected Rocks from the Western Alaska Range, Medfra area, and Livengood area, Alaska
This data release contains 3 data sets, U-Pb isotopic data and associated ages of detrital zircon grains for 27 sedimentary rocks, whole rock major and trace-element geochemistry for 15 igneous or phosphatic rock samples, and whole rock Sr, Nd, and Pb isotopic data for 6 igneous rock samples. The samples were collected from multiple localities across Alaska as part of geological mapping and resear
GIS and Data Tables for Focus Areas for Potential Domestic Nonfuel Sources of Rare Earth Elements
In response to Executive Order 13817 of December 20, 2017, the U.S. Geological Survey (USGS) coordinated with the Bureau of Land Management (BLM) to identify 35 nonfuel minerals or mineral materials considered critical to the economic and national security of the United States (U.S.). Acquiring information on possible domestic sources of these critical minerals is the basis of the USGS Earth Mappi
Geochemical Database for Iron Oxide-Copper-Cobalt-Gold-Rare Earth Element Deposits of Southeast Missouri
The Geochemical Database for Iron Oxide-Copper-Cobalt-Gold-Rare Earth Element Deposits of Southeast Missouri (IOCG-REE_GX) contains new geochemical data compilations for samples from IOCG-REE type deposits in which each rock sample has one "best value" determination for each analyzed species, greatly improving speed and efficiency of use. IOCG-REE_GX was created and designed to compile
Geochemistry, geochronology, mineralogy, and geology suggest sources of and controls on mineral systems in the southern Toquima Range, Nye County, Nevada
Geochemistry maps showing the distribution and abundance of 18 elements in about 1,400 rock samples, both mineralized and unmineralized, from the southern Toquima Range, Nev., indicate major structural and lithologic controls on mineralization, and suggest sources of the elements. Radiometric age data, lead mineralogy and paragenesis data, and lead-isotope data supplement the geochemical and geolo
Mineral resource potential map of the Lye Brook Wilderness, Bennington and Windham counties, Vermont
The Lye Brook Wilderness contains no significant mineral deposits. Although the Cheshire Quartzite is a potential source of low-grade silica sand and crops out in a large area within the wilderness, its degree of induration and relative inaccessibility make its use prohibitive. No major concentation of base metals exist within the Precambrian rocks, although they contain the highest metal concentr
Filter Total Items: 76
Age and tectonic setting of the Quinebaug-Marlboro belt and implications for the history of Ganderian crustal fragments in southeastern New England, USA
Crustal fragments underlain by high-grade rocks represent a challenge to plate reconstructions, and integrated mapping, geochronology, and geochemistry enable the unravelling of the temporal and spatial history of exotic crustal blocks. The Quinebaug-Marlboro belt (QMB) is an enigmatic fragment on the trailing edge of the peri-Gondwanan Ganderian margin of southeastern New England. SHRIMP U-Pb geo
Geophysical insights into Paleoproterozoic tectonics along the southern margin of the Superior Province, central Upper Peninsula, Michigan, USA
The southern margin of the Archean Superior Province in the central Upper Peninsula of Michigan was a nexus for key Paleoproterozoic tectonic events involved in the ~2.1 Ga rifting of proposed Archean supercraton Superia and subsequent assembly of Laurentia. Interpretations of the region’s tectonic history have historically been hampered by extensive Pleistocene glacial and Paleozoic sedimentary c
Shrimp U-Pb zircon and opal geochronology, isotope geochemistry, and genesis of the super large Be deposit at Spor Mountain, Utah, USA
Ongoing studies of the Spor Mountain beryllium (Be) deposit are focused on (1) characterizing the role of igneous rocks in the genesis of the ore zones, (2) determining the timing and duration of magmatic-hydrothermal events, and (3) establishing processes related to beryllium transport and accumulation. The Spor Mountain Formation (SMF) hosts the deposit, which is the largest known volcanic rock-
The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska
The youngest part of the Farewell terrane in interior Alaska (USA) is the enigmatic Devonian–Cretaceous Mystic subterrane. New U-Pb detrital zircon, fossil, geochemical, neodymium isotopic, and petrographic data illuminate the origin of the rocks of this subterrane. The Devonian–Permian Sheep Creek Formation yielded youngest detrital zircons of Devonian age, major detrital zircon age probability p
Lead and strontium isotopes as monitors of anthropogenic contaminants in the surficial environment
Isotopic discrimination can be an effective tool in establishing a direct link between sources of Pb contamination and the presence of anomalously high concentrations of Pb in waters, soils, and organisms. Residential wells supplying water containing up to 1600 ppb Pb to houses built on the former Mohr orchards commercial site, near Allentown, Pennsylvania, United States, were evaluated to discern
Geochemical and Pb isotopic characterization of soil, groundwater, human hair, and corn samples from the Domizio Flegreo and Agro Aversano area (Campania region, Italy)
A geochemical survey was carried out to investigate metal contamination in the Domizio Littoral and Agro Aversano area (Southern Italy) by means of soil, groundwater, human hair and corn samples. Pb isotope ratios were also determined to identify the sources of metals. Specifically, the investigation focused on topsoils (n = 1064), groundwater (n = 26), 25 human hair (n = 24) and corn samples (n =
Regional geologic and petrologic framework for iron oxide ± apatite ± rare earth element and iron oxide copper-gold deposits of the Mesoproterozoic St. Francois Mountains terrane, southeast Missouri, USA
This paper provides an overview on the genesis of Mesoproterozoic igneous rocks and associated iron oxide ± apatite (IOA) ± rare earth element, iron oxide-copper-gold (IOCG), and iron-rich sedimentary deposits in the St. Francois Mountains terrane of southeast Missouri, USA. The St. Francois Mountains terrane lies along the southeastern margin of Laurentia as part of the eastern granite-rhyolite p
Geochemistry, Nd-Pb Isotopes, and Pb-Pb Ages of the Mesoproterozoic Pea Ridge Iron Oxide-Apatite–Rare Earth Element Deposit, Southeast Missouri
Iron oxide-apatite and iron oxide-copper-gold deposits occur within ~1.48 to 1.47 Ga volcanic rocks of the St. Francois Mountains terrane near a regional boundary separating crustal blocks having contrasting depleted-mantle Sm-Nd model ages (TDM). Major and trace element analyses and Nd and Pb isotope data were obtained to characterize the Pea Ridge deposit, improve identification of exploration t
Beryllium—A critical mineral commodity—Resources, production, and supply chain
Beryllium is a lightweight metallic element used in a wide variety of specialty and industrial applications. As a function of its unique chemical and physical properties, such as a high stiffness-to-weight ratio, resistance to temperature extremes, and high thermal conductivity, beryllium cannot be easily replaced by substitute materials in applications where combinations of these properties make
Pb-Sr isotopic and geochemical constraints on sources and processes of lead contamination in well waters and soil from former fruit orchards, Pennsylvania, USA: A legacy of anthropogenic activities
Isotopic discrimination can be an effective tool in establishing a direct link between sources of Pb contamination and the presence of anomalously high concentrations of Pb in waters, soils, and organisms. Residential wells supplying water containing up to 1600 ppb Pb to houses built on the former Mohr orchards commercial site, near Allentown, PA, were evaluated to discern anthropogenic from geoge
Soil geochemical survey of abandoned mining sites in the Eastern-Central Peloritani Mountains, Sicily, Italy
This investigation focused on topsoils (n = 122) and vertical profiles (n = 6) distributed over an area of 250 km2 in the eastern-central Peloritani Mountains, northeastern Sicily. Georeferenced concentration of 53 elements (including potentially harmful ones), determined by ICP-MS after an aqua regia leach, were used to produce geochemical maps by means of a GIS-aided spatial interpolation proces
Science and Products
- Science
Radiogenic and Stable Isotope Methods
Our work focuses on collaborating with high-priority U.S. Geological Survey projects and other Federal and international agencies, and on providing radiogenic and stable isotope analyses to support mineral- and environmentally-related geologic investigations. - Data
U-Pb Isotopic Data and Ages of Detrital Zircon Grains, Whole Rock Major and Trace-element Geochemistry, and Whole Rock Isotopic Data from Selected Rocks from the Western Alaska Range, Medfra area, and Livengood area, Alaska
This data release contains 3 data sets, U-Pb isotopic data and associated ages of detrital zircon grains for 27 sedimentary rocks, whole rock major and trace-element geochemistry for 15 igneous or phosphatic rock samples, and whole rock Sr, Nd, and Pb isotopic data for 6 igneous rock samples. The samples were collected from multiple localities across Alaska as part of geological mapping and researGIS and Data Tables for Focus Areas for Potential Domestic Nonfuel Sources of Rare Earth Elements
In response to Executive Order 13817 of December 20, 2017, the U.S. Geological Survey (USGS) coordinated with the Bureau of Land Management (BLM) to identify 35 nonfuel minerals or mineral materials considered critical to the economic and national security of the United States (U.S.). Acquiring information on possible domestic sources of these critical minerals is the basis of the USGS Earth MappiGeochemical Database for Iron Oxide-Copper-Cobalt-Gold-Rare Earth Element Deposits of Southeast Missouri
The Geochemical Database for Iron Oxide-Copper-Cobalt-Gold-Rare Earth Element Deposits of Southeast Missouri (IOCG-REE_GX) contains new geochemical data compilations for samples from IOCG-REE type deposits in which each rock sample has one "best value" determination for each analyzed species, greatly improving speed and efficiency of use. IOCG-REE_GX was created and designed to compile - Maps
Geochemistry, geochronology, mineralogy, and geology suggest sources of and controls on mineral systems in the southern Toquima Range, Nye County, Nevada
Geochemistry maps showing the distribution and abundance of 18 elements in about 1,400 rock samples, both mineralized and unmineralized, from the southern Toquima Range, Nev., indicate major structural and lithologic controls on mineralization, and suggest sources of the elements. Radiometric age data, lead mineralogy and paragenesis data, and lead-isotope data supplement the geochemical and geoloMineral resource potential map of the Lye Brook Wilderness, Bennington and Windham counties, Vermont
The Lye Brook Wilderness contains no significant mineral deposits. Although the Cheshire Quartzite is a potential source of low-grade silica sand and crops out in a large area within the wilderness, its degree of induration and relative inaccessibility make its use prohibitive. No major concentation of base metals exist within the Precambrian rocks, although they contain the highest metal concentr - Publications
Filter Total Items: 76
Age and tectonic setting of the Quinebaug-Marlboro belt and implications for the history of Ganderian crustal fragments in southeastern New England, USA
Crustal fragments underlain by high-grade rocks represent a challenge to plate reconstructions, and integrated mapping, geochronology, and geochemistry enable the unravelling of the temporal and spatial history of exotic crustal blocks. The Quinebaug-Marlboro belt (QMB) is an enigmatic fragment on the trailing edge of the peri-Gondwanan Ganderian margin of southeastern New England. SHRIMP U-Pb geoGeophysical insights into Paleoproterozoic tectonics along the southern margin of the Superior Province, central Upper Peninsula, Michigan, USA
The southern margin of the Archean Superior Province in the central Upper Peninsula of Michigan was a nexus for key Paleoproterozoic tectonic events involved in the ~2.1 Ga rifting of proposed Archean supercraton Superia and subsequent assembly of Laurentia. Interpretations of the region’s tectonic history have historically been hampered by extensive Pleistocene glacial and Paleozoic sedimentary cShrimp U-Pb zircon and opal geochronology, isotope geochemistry, and genesis of the super large Be deposit at Spor Mountain, Utah, USA
Ongoing studies of the Spor Mountain beryllium (Be) deposit are focused on (1) characterizing the role of igneous rocks in the genesis of the ore zones, (2) determining the timing and duration of magmatic-hydrothermal events, and (3) establishing processes related to beryllium transport and accumulation. The Spor Mountain Formation (SMF) hosts the deposit, which is the largest known volcanic rock-The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska
The youngest part of the Farewell terrane in interior Alaska (USA) is the enigmatic Devonian–Cretaceous Mystic subterrane. New U-Pb detrital zircon, fossil, geochemical, neodymium isotopic, and petrographic data illuminate the origin of the rocks of this subterrane. The Devonian–Permian Sheep Creek Formation yielded youngest detrital zircons of Devonian age, major detrital zircon age probability pLead and strontium isotopes as monitors of anthropogenic contaminants in the surficial environment
Isotopic discrimination can be an effective tool in establishing a direct link between sources of Pb contamination and the presence of anomalously high concentrations of Pb in waters, soils, and organisms. Residential wells supplying water containing up to 1600 ppb Pb to houses built on the former Mohr orchards commercial site, near Allentown, Pennsylvania, United States, were evaluated to discernGeochemical and Pb isotopic characterization of soil, groundwater, human hair, and corn samples from the Domizio Flegreo and Agro Aversano area (Campania region, Italy)
A geochemical survey was carried out to investigate metal contamination in the Domizio Littoral and Agro Aversano area (Southern Italy) by means of soil, groundwater, human hair and corn samples. Pb isotope ratios were also determined to identify the sources of metals. Specifically, the investigation focused on topsoils (n = 1064), groundwater (n = 26), 25 human hair (n = 24) and corn samples (n =Regional geologic and petrologic framework for iron oxide ± apatite ± rare earth element and iron oxide copper-gold deposits of the Mesoproterozoic St. Francois Mountains terrane, southeast Missouri, USA
This paper provides an overview on the genesis of Mesoproterozoic igneous rocks and associated iron oxide ± apatite (IOA) ± rare earth element, iron oxide-copper-gold (IOCG), and iron-rich sedimentary deposits in the St. Francois Mountains terrane of southeast Missouri, USA. The St. Francois Mountains terrane lies along the southeastern margin of Laurentia as part of the eastern granite-rhyolite pGeochemistry, Nd-Pb Isotopes, and Pb-Pb Ages of the Mesoproterozoic Pea Ridge Iron Oxide-Apatite–Rare Earth Element Deposit, Southeast Missouri
Iron oxide-apatite and iron oxide-copper-gold deposits occur within ~1.48 to 1.47 Ga volcanic rocks of the St. Francois Mountains terrane near a regional boundary separating crustal blocks having contrasting depleted-mantle Sm-Nd model ages (TDM). Major and trace element analyses and Nd and Pb isotope data were obtained to characterize the Pea Ridge deposit, improve identification of exploration tBeryllium—A critical mineral commodity—Resources, production, and supply chain
Beryllium is a lightweight metallic element used in a wide variety of specialty and industrial applications. As a function of its unique chemical and physical properties, such as a high stiffness-to-weight ratio, resistance to temperature extremes, and high thermal conductivity, beryllium cannot be easily replaced by substitute materials in applications where combinations of these properties makePb-Sr isotopic and geochemical constraints on sources and processes of lead contamination in well waters and soil from former fruit orchards, Pennsylvania, USA: A legacy of anthropogenic activities
Isotopic discrimination can be an effective tool in establishing a direct link between sources of Pb contamination and the presence of anomalously high concentrations of Pb in waters, soils, and organisms. Residential wells supplying water containing up to 1600 ppb Pb to houses built on the former Mohr orchards commercial site, near Allentown, PA, were evaluated to discern anthropogenic from geogeSoil geochemical survey of abandoned mining sites in the Eastern-Central Peloritani Mountains, Sicily, Italy
This investigation focused on topsoils (n = 122) and vertical profiles (n = 6) distributed over an area of 250 km2 in the eastern-central Peloritani Mountains, northeastern Sicily. Georeferenced concentration of 53 elements (including potentially harmful ones), determined by ICP-MS after an aqua regia leach, were used to produce geochemical maps by means of a GIS-aided spatial interpolation proces