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: 77
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) 25 000 to 14
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
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 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 = 17.399-18.107; 20
Authors
Robert A. Ayuso, S. M. Barr, Frederick J. Longstaffe
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
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. Biotite
Authors
P. J. Loferski, R. A. Ayuso
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, and base
Authors
Nora K. Foley, Robert A. Ayuso
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 emplacement and c
Authors
R. A. Ayuso, A. Messina, B. de Vivo, S. Russo, L. G. Woodruff, J. F. Sutter, H. E. Belkin
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, and strongl
Authors
R. A. Ayuso, Joseph G. Arth
Rock chemistry and fluid inclusion studies as exploration tools for ore deposits in the Sila batholith, southern Italy
The Sila batholith is the focus of an extensive petrogenetic research program, which includes an assessment of its potential to host granite-related ore deposits. Univariate and multivariate statistical techniques were applied to major- and minor-element rock geochemical data. The analysis indicates that the highest potential for mineralization occurs in corundum-normative, peraluminous, unfoliate
Authors
B. de Vivo, R. A. Ayuso, H. E. Belkin, A. Lima, A. Messina, A. Viscardi
A method of quantitative analysis of trace elements in silicate rocks by energy-dispersive X-ray fluorescence spectroscopy
No abstract available.
Authors
J.C. Jackson, R. A. Ayuso
White mica geochemistry of the Catheart Mountain porphyry copper deposit, Maine
White micas from hydrothermally altered and mineralized zones in the Catheart Mountain Cu-Mo porphyry deposit have regular compositional variations that are generally related to the contents of copper, total iron, and sulfur in the whole rock. Micas in unmineralized rocks exhibit no such relationship. White mica compositions reflect primarily the control imposed by the celadonitic substitution AII
Authors
Robert A. Ayuso
Lead-isotopic evidence for distinct source of granite and for distinct basement in the northern Appalachians, Maine
Lead-isotopic compositions of feldspars in plutons of the coastal lithotectonic block (Avalonian basement), central Maine (Merrimack) synclinorium, and Connecticut Valley-Gaspé synclinorium in northern Maine (Granville basement) indicate the presence of three fundamentally different sources of Devonian granitic rocks in Maine. Plutons in the coastal lithotectonic block have the most radiogenic va
Authors
R. A. Ayuso
Science and Products
Filter Total Items: 77
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) 25 000 to 14
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
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 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 = 17.399-18.107; 20
Authors
Robert A. Ayuso, S. M. Barr, Frederick J. Longstaffe
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
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. Biotite
Authors
P. J. Loferski, R. A. Ayuso
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, and base
Authors
Nora K. Foley, Robert A. Ayuso
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 emplacement and c
Authors
R. A. Ayuso, A. Messina, B. de Vivo, S. Russo, L. G. Woodruff, J. F. Sutter, H. E. Belkin
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, and strongl
Authors
R. A. Ayuso, Joseph G. Arth
Rock chemistry and fluid inclusion studies as exploration tools for ore deposits in the Sila batholith, southern Italy
The Sila batholith is the focus of an extensive petrogenetic research program, which includes an assessment of its potential to host granite-related ore deposits. Univariate and multivariate statistical techniques were applied to major- and minor-element rock geochemical data. The analysis indicates that the highest potential for mineralization occurs in corundum-normative, peraluminous, unfoliate
Authors
B. de Vivo, R. A. Ayuso, H. E. Belkin, A. Lima, A. Messina, A. Viscardi
A method of quantitative analysis of trace elements in silicate rocks by energy-dispersive X-ray fluorescence spectroscopy
No abstract available.
Authors
J.C. Jackson, R. A. Ayuso
White mica geochemistry of the Catheart Mountain porphyry copper deposit, Maine
White micas from hydrothermally altered and mineralized zones in the Catheart Mountain Cu-Mo porphyry deposit have regular compositional variations that are generally related to the contents of copper, total iron, and sulfur in the whole rock. Micas in unmineralized rocks exhibit no such relationship. White mica compositions reflect primarily the control imposed by the celadonitic substitution AII
Authors
Robert A. Ayuso
Lead-isotopic evidence for distinct source of granite and for distinct basement in the northern Appalachians, Maine
Lead-isotopic compositions of feldspars in plutons of the coastal lithotectonic block (Avalonian basement), central Maine (Merrimack) synclinorium, and Connecticut Valley-Gaspé synclinorium in northern Maine (Granville basement) indicate the presence of three fundamentally different sources of Devonian granitic rocks in Maine. Plutons in the coastal lithotectonic block have the most radiogenic va
Authors
R. A. Ayuso