Robert Ayuso
Robert Ayuso is a Research Geologist with the USGS Geology, Energy & Minerals (GEM) Science Center in Reston, VA.
Science and Products
Filter Total Items: 82
A geochemical isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius Volcano, southern Italy A geochemical isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius Volcano, southern Italy
No abstract available.
Authors
Renato Somma, Robert A. Ayuso, B. de Vivo
Radiogenic isotopes and the Eastern Mineral Resources Program of the U.S. Geological Survey Radiogenic isotopes and the Eastern Mineral Resources Program of the U.S. Geological Survey
Radiogenic isotope geology relies on a small group of naturally occurring but unstable elements that naturally produce energy and disintegrate or decay to more stable atoms of different elements. Because this phenomenon occurs at a known rate, is unaffected by most physical and chemical processes, and takes place over periods of time comparable to the age of the Earth, these elements can...
Authors
Robert A. Ayuso
Carolina slate belt gold deposits in Virginia, North Carolina, South Carolina, and Georgia Carolina slate belt gold deposits in Virginia, North Carolina, South Carolina, and Georgia
The Southeastern United States, in particular, the Carolina slate belt of Virginia, North Carolina, South Carolina, and Georgia, has been an important region of mineral production (fig. 1). This region is thought to have major potential for containing large undiscovered deposits of gold and silver, as well as copper, lead, zinc, molybdenum, and tin. Gold production from the major mines...
Authors
Robert A. Ayuso
Geochemical and isotopic (Nd-Pb-Sr-O) variations bearing on the genesis of volcanic rocks from Vesuvius, Italy Geochemical and isotopic (Nd-Pb-Sr-O) variations bearing on the genesis of volcanic rocks from Vesuvius, Italy
Alkaline volcanism produced by Monte Somma-Vesuvius volcano includes explosive plinian and subplinian activity in addition to effusive lava flows. Pumice, scoria, and lava (150 samples) exhibit major- and trace-element gradients as a function of SiO2 (58.9-47.2 wt%) and MgO (0-7.8 wt%); Mg value are ???50. Internally gradational chemical groups or cycles are distinguished by age: (1) 25...
Authors
R. A. Ayuso, B. de Vivo, G. Rolandi, R.R. Seal, A. Paone
The Spruce Head composite pluton: An example of mafic to silicic Salinian magmatism in coastal Maine, northern Appalachians The Spruce Head composite pluton: An example of mafic to silicic Salinian magmatism in coastal Maine, northern Appalachians
No abstract available.
Authors
Robert A. Ayuso, Joseph G. Arth
Pb and O isotopic constraints on the source of granitic rocks from Cape Breton Island, Nova Scotia, Canada Pb and O isotopic constraints on the source of granitic rocks from Cape Breton Island, Nova Scotia, Canada
Pb isotopic compositions of leached feldspars from twenty-three plutons in Cape Breton Island can be divided into two groups: anorthosite, syenite, and granite in the Blair River Complex, which have the least radiogenic compositions on the Island, and granitic rocks from terranes (Aspy, Bras d'Or, and Mira) to the south. Pb isotopic data for the Blair River Complex (206Pb/204Pb = 17.399...
Authors
Robert A. Ayuso, S. M. Barr, Frederick J. Longstaffe
Recommendations for assessments of undiscovered mineral resources Recommendations for assessments of undiscovered mineral resources
No abstract available.
Authors
Paul B. Barton, D. A. Brew, S. D. Ludington, D. A. Lindsey, R. A. Ayuso, E. R. Force, B. M. Gamble, R.J. Goldfarb, D. A. John, K. M. Johnson
Petrography and mineral chemistry of the composite Deboullie Pluton, northern Maine, USA: implications for the genesis of Cu-Mo mineralization Petrography and mineral chemistry of the composite Deboullie Pluton, northern Maine, USA: implications for the genesis of Cu-Mo mineralization
Biotite and apatite mineral chemistry, particularly halogen abundances and ratios, are used to investigate the relation of the two contrasting parts of the Deboullie composite pluton (syenite-granodiorite) located in northern Maine. Biotite mineral chemistry helps to classify the weakly developed porphyry-style mineralization (Cu-Mo) associated with syenitic rocks of the Deboullie pluton...
Authors
P. J. Loferski, R. A. Ayuso
Lead isotope compositions as guides to early gold mineralization: The North Amethyst vein system, Creede district, Colorado Lead isotope compositions as guides to early gold mineralization: The North Amethyst vein system, Creede district, Colorado
The North Amethyst vein system, which is hosted by approximately 27 Ma Carpenter Ridge Tuff and approximately 26 Ma Nelson Mountain Tuff, has two mineral associations separated by brecciation and sedimentation in the veins. The early association consists of quartz, rhodonite, hematite, magnetite, electrum (Au (sub 0.3-0.5) Ag (sub 0.7-0.5)) , and Mn carbonate, Au-Ag sulfide, Ag sulfosalt...
Authors
Nora K. Foley, Robert A. Ayuso
Geochemistry and argon thermochronology of the Variscan Sila Batholith, southern Italy: source rocks and magma evolution Geochemistry and argon thermochronology of the Variscan Sila Batholith, southern Italy: source rocks and magma evolution
The Sila batholith is the largest granitic massif in the Calabria-Peloritan Arc of southern Italy, consisting of syn to post-tectonic, calc-alkaline and metaluminous tonalite to granodiorite, and post-tectonic, peraluminous and strongly peraluminous, two-mica??cordierite??Al silicate granodiorite to leucomonzogranite. Mineral 40Ar/39Ar thermochronologic analyses document Variscan...
Authors
R. A. Ayuso, A. Messina, B. de Vivo, S. Russo, L. G. Woodruff, J. F. Sutter, H. E. Belkin
A Coast Mountains provenance for the Valdez and Orca groups, southern Alaska, based on Nd, Sr, and Pb isotopic evidence A Coast Mountains provenance for the Valdez and Orca groups, southern Alaska, based on Nd, Sr, and Pb isotopic evidence
Nd, Sr, and Pb isotopic data were obtained for fourteen fine- to coarse-grained samples of accreted flysch of the Late Cretaceous and early Tertiary Valdez and Orca Groups in southern Alaska to determine the flysch provenance. Argillites and greywackes from the Orca Group, as well as compositionally similar but higher metamorphic grade rocks from the Valdez Group, show a restricted range...
Authors
G. L. Farmer, R. Ayuso, George Plafker
The Northeast Kingdom batholith, Vermont: magmatic evolution and geochemical constraints on the origin of Acadian granitic rocks The Northeast Kingdom batholith, Vermont: magmatic evolution and geochemical constraints on the origin of Acadian granitic rocks
Five Devonian plutons (West Charleston, Echo Pond, Nulhegan, Derby, and Willoughby) that constitute the Northeast Kingdom batholith in Vermont show wide ranges in elemental abundances and ratios consistent with major crustal contributions during their evolution. The batholith consists of metaluminous quartz gabbro, diorite and quartz monzodiorite, peraluminous granodiorite and granite...
Authors
R. A. Ayuso, Joseph G. Arth
Science and Products
Filter Total Items: 82
A geochemical isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius Volcano, southern Italy A geochemical isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius Volcano, southern Italy
No abstract available.
Authors
Renato Somma, Robert A. Ayuso, B. de Vivo
Radiogenic isotopes and the Eastern Mineral Resources Program of the U.S. Geological Survey Radiogenic isotopes and the Eastern Mineral Resources Program of the U.S. Geological Survey
Radiogenic isotope geology relies on a small group of naturally occurring but unstable elements that naturally produce energy and disintegrate or decay to more stable atoms of different elements. Because this phenomenon occurs at a known rate, is unaffected by most physical and chemical processes, and takes place over periods of time comparable to the age of the Earth, these elements can...
Authors
Robert A. Ayuso
Carolina slate belt gold deposits in Virginia, North Carolina, South Carolina, and Georgia Carolina slate belt gold deposits in Virginia, North Carolina, South Carolina, and Georgia
The Southeastern United States, in particular, the Carolina slate belt of Virginia, North Carolina, South Carolina, and Georgia, has been an important region of mineral production (fig. 1). This region is thought to have major potential for containing large undiscovered deposits of gold and silver, as well as copper, lead, zinc, molybdenum, and tin. Gold production from the major mines...
Authors
Robert A. Ayuso
Geochemical and isotopic (Nd-Pb-Sr-O) variations bearing on the genesis of volcanic rocks from Vesuvius, Italy Geochemical and isotopic (Nd-Pb-Sr-O) variations bearing on the genesis of volcanic rocks from Vesuvius, Italy
Alkaline volcanism produced by Monte Somma-Vesuvius volcano includes explosive plinian and subplinian activity in addition to effusive lava flows. Pumice, scoria, and lava (150 samples) exhibit major- and trace-element gradients as a function of SiO2 (58.9-47.2 wt%) and MgO (0-7.8 wt%); Mg value are ???50. Internally gradational chemical groups or cycles are distinguished by age: (1) 25...
Authors
R. A. Ayuso, B. de Vivo, G. Rolandi, R.R. Seal, A. Paone
The Spruce Head composite pluton: An example of mafic to silicic Salinian magmatism in coastal Maine, northern Appalachians The Spruce Head composite pluton: An example of mafic to silicic Salinian magmatism in coastal Maine, northern Appalachians
No abstract available.
Authors
Robert A. Ayuso, Joseph G. Arth
Pb and O isotopic constraints on the source of granitic rocks from Cape Breton Island, Nova Scotia, Canada Pb and O isotopic constraints on the source of granitic rocks from Cape Breton Island, Nova Scotia, Canada
Pb isotopic compositions of leached feldspars from twenty-three plutons in Cape Breton Island can be divided into two groups: anorthosite, syenite, and granite in the Blair River Complex, which have the least radiogenic compositions on the Island, and granitic rocks from terranes (Aspy, Bras d'Or, and Mira) to the south. Pb isotopic data for the Blair River Complex (206Pb/204Pb = 17.399...
Authors
Robert A. Ayuso, S. M. Barr, Frederick J. Longstaffe
Recommendations for assessments of undiscovered mineral resources Recommendations for assessments of undiscovered mineral resources
No abstract available.
Authors
Paul B. Barton, D. A. Brew, S. D. Ludington, D. A. Lindsey, R. A. Ayuso, E. R. Force, B. M. Gamble, R.J. Goldfarb, D. A. John, K. M. Johnson
Petrography and mineral chemistry of the composite Deboullie Pluton, northern Maine, USA: implications for the genesis of Cu-Mo mineralization Petrography and mineral chemistry of the composite Deboullie Pluton, northern Maine, USA: implications for the genesis of Cu-Mo mineralization
Biotite and apatite mineral chemistry, particularly halogen abundances and ratios, are used to investigate the relation of the two contrasting parts of the Deboullie composite pluton (syenite-granodiorite) located in northern Maine. Biotite mineral chemistry helps to classify the weakly developed porphyry-style mineralization (Cu-Mo) associated with syenitic rocks of the Deboullie pluton...
Authors
P. J. Loferski, R. A. Ayuso
Lead isotope compositions as guides to early gold mineralization: The North Amethyst vein system, Creede district, Colorado Lead isotope compositions as guides to early gold mineralization: The North Amethyst vein system, Creede district, Colorado
The North Amethyst vein system, which is hosted by approximately 27 Ma Carpenter Ridge Tuff and approximately 26 Ma Nelson Mountain Tuff, has two mineral associations separated by brecciation and sedimentation in the veins. The early association consists of quartz, rhodonite, hematite, magnetite, electrum (Au (sub 0.3-0.5) Ag (sub 0.7-0.5)) , and Mn carbonate, Au-Ag sulfide, Ag sulfosalt...
Authors
Nora K. Foley, Robert A. Ayuso
Geochemistry and argon thermochronology of the Variscan Sila Batholith, southern Italy: source rocks and magma evolution Geochemistry and argon thermochronology of the Variscan Sila Batholith, southern Italy: source rocks and magma evolution
The Sila batholith is the largest granitic massif in the Calabria-Peloritan Arc of southern Italy, consisting of syn to post-tectonic, calc-alkaline and metaluminous tonalite to granodiorite, and post-tectonic, peraluminous and strongly peraluminous, two-mica??cordierite??Al silicate granodiorite to leucomonzogranite. Mineral 40Ar/39Ar thermochronologic analyses document Variscan...
Authors
R. A. Ayuso, A. Messina, B. de Vivo, S. Russo, L. G. Woodruff, J. F. Sutter, H. E. Belkin
A Coast Mountains provenance for the Valdez and Orca groups, southern Alaska, based on Nd, Sr, and Pb isotopic evidence A Coast Mountains provenance for the Valdez and Orca groups, southern Alaska, based on Nd, Sr, and Pb isotopic evidence
Nd, Sr, and Pb isotopic data were obtained for fourteen fine- to coarse-grained samples of accreted flysch of the Late Cretaceous and early Tertiary Valdez and Orca Groups in southern Alaska to determine the flysch provenance. Argillites and greywackes from the Orca Group, as well as compositionally similar but higher metamorphic grade rocks from the Valdez Group, show a restricted range...
Authors
G. L. Farmer, R. Ayuso, George Plafker
The Northeast Kingdom batholith, Vermont: magmatic evolution and geochemical constraints on the origin of Acadian granitic rocks The Northeast Kingdom batholith, Vermont: magmatic evolution and geochemical constraints on the origin of Acadian granitic rocks
Five Devonian plutons (West Charleston, Echo Pond, Nulhegan, Derby, and Willoughby) that constitute the Northeast Kingdom batholith in Vermont show wide ranges in elemental abundances and ratios consistent with major crustal contributions during their evolution. The batholith consists of metaluminous quartz gabbro, diorite and quartz monzodiorite, peraluminous granodiorite and granite...
Authors
R. A. Ayuso, Joseph G. Arth