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: 78
Containing arsenic-enriched groundwater tracing lead isotopic compositions of common arsenical pesticides in a coastal Maine watershed
Arsenical pesticides and herbicides were extensively used on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Lead arsenate was the most heavily used arsenical pesticide until it was officially banned. Lead arsenate, calcium arsenate, and sodium arsenate have similar Pb isotope compositions: 208Pb207Pb = 2.3839-2.4722, and 206Pb207Pb = 1.1035-1.2010
Authors
Robert A. Ayuso, Nora K. Foley, Glipin R. Robinson, A.S. Colvin, G. Lipfert, A.S. Reeve
Emplacement of the Kodiak batholith and slab-window migration
The Kodiak batholith is one of the largest, most elongate intrusive bodies in the forearc Sanak-Baranof plutonic belt located in southern Alaska. This belt is interpreted to have formed during the subduction of an oceanic spreading center and the associated migration of a slab window. Individual plutons of the Kodiak batholith track the location and evolution of the underlying slab window. Six U/P
Authors
David W. Farris, Peter J. Haeussler, Richard Friedman, Scott R. Paterson, R. W. Saltus, Robert A. Ayuso
U-Pb zircon ages and Pb isotope geochemistry of gold deposits in the Carolina slate belt of South Carolina
Volcanic rocks of the Persimmon Fork Formation host the largest known gold mines of the Carolina slate belt. U-Pb (SHRIMP) zircon ages have been obtained from rocks closely associated with pyrite-enargite-gold deposits at Brewer (quartz-topaz rhyolite breccia from the argillic alteration zone in the Brewer pit and felsic ash-flow tuff from the quartz sericite alteration zone), from the disseminate
Authors
Robert A. Ayuso, Joseph L. Wooden, Nora K. Foley, Robert R. Seal, A. Krishna Sinha
Oceanic Pb-isotopic sources of Proterozoic and Paleozoic volcanogenic massive sulfide deposits on Prince of Wales Island and vicinity, southeastern Alaska
Volcanogenic massive sulfide (VMS) deposits on Prince of Wales Island and vicinity in southeastern Alaska are associated with Late Proterozoic through Cambrian volcanosedimentary rocks of the Wales Group and with Ordovician through Early Silurian felsic volcanic rocks of the Moira Sound unit (new informal name). The massive sulfide deposits in the Wales Group include the Big Harbor, Copper City, C
Authors
Robert A. Ayuso, Susan M. Karl, John F. Slack, Peter J. Haeussler, Peter E. Bittenbender, Gregory A. Wandless, Anna Colvin
Multistage hydrothermal silicification and Fe-Tl-As-Sb-Ge-REE enrichment in the Red Dog Zn-Pb-Ag district, northern Alaska: Geochemistry, origin, and exploration applications
Geochemical analyses of major, trace, and rare earth elements (REE) in more than 200 samples of variably silicified and altered wall rocks, massive and banded sulfide, silica rock, and sulfide-rich and unmineralized barite were obtained from the Main, Aqqaluk, and Anarraaq deposits in the Red Dog Zn-Pb-Ag district of northern Alaska. Detailed lithogeochemical profiles for two drill cores at Aqqalu
Authors
J. F. Slack, K. D. Kelley, V.M. Anderson, J.L. Clark, R. A. Ayuso
Origin of the Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska: Evidence from regional Pb and Sr isotope sources
Pb and Sr isotope data were obtained on the shale-hosted Zn-Pb-Ag Red Dog deposits (Qanaiyaq, Main, Aqqaluk, and Paalaaq), other shale-hosted deposits near Red Dog, and Zn-Pb-Ag sulfide and barite deposits in the western and central Brooks Range. The Red Dog deposits and other shale-hosted Zn-Pb-Ag deposits near Red Dog are hosted in the Mississippian Kuna Formation, which is underlain by a sequen
Authors
R. A. Ayuso, K. D. Kelley, D. L. Leach, L. E. Young, J. F. Slack, G. Wandless, A.M. Lyon, J.L. Dillingham
Textural, compositional, and sulfur isotope variations of sulfide minerals in the Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska: Implications for Ore Formation
The Red Dog Zn-Pb deposits are hosted in organic-rich mudstone and shale of the Mississippian Kuna Formation. A complex mineralization history is defined by four sphalerite types or stages: (1) early brown sphalerite, (2) yellow-brown sphalerite, (3) red-brown sphalerite, and (4) late tan sphalerite. Stages 2 and 3 constitute the main ore-forming event and are volumetrically the most important. Su
Authors
K. D. Kelley, D. L. Leach, C.A. Johnson, J.L. Clark, M. Fayek, J. F. Slack, V.M. Anderson, R. A. Ayuso, W.I. Ridley
Use of spatial statistics and isotopic tracers to measure the influence of arsenical pesticide use on stream sediment chemistry in New England, USA
Arsenical pesticides and herbicides, principally Pb arsenate, Ca arsenate, and Na arsenate with lesser use of other metal-As pesticides, were widely applied on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Agricultural census data for this time period is used to define an agricultural index that identifies areas that are inferred to have used ars
Authors
G. R. Robinson, R. A. Ayuso
Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy
We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: "Protohistoric" (3550 y B.P. to 79 A.D.), "Ancient Historic" (79 to 472 A.D.) and "Medieval" (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that
Authors
M. Cortini, R. A. Ayuso, B. de Vivo, P. Holden, R. Somma
The late cretaceous Donlin Creek gold deposit, Southwestern Alaska: Controls on epizonal ore formation
The Donlin Creek gold deposit, southwestern Alaska, has an indicated and inferred resource of approximately 25 million ounces (Moz) Au at a cutoff grade of 1.5 g/t. The ca. 70 Ma deposit is hosted in the Late Cretaceous Kuskokwim flysch basin, which developed in the back part of the arc region of an active continental margin, on previously accreted oceanic terranes and continental fragments. A hyp
Authors
Richard J. Goldfarb, Robert A. Ayuso, Marti L. Miller, Shane W. Ebert, Erin E. Marsh, Scott A. Petsel, Lance D. Miller, Dwight C. Bradley, Chad Johnson, William C. McClelland
Arsenic in New England: Mineralogical and geochemical studies of sources and enrichment pathways
Detailed mineralogical, geochemical and radiogenic isotopic studies of iron-sulfide and secondary iron oxy-hydroxide minerals in natural bedrock in coastal Maine and New Hampshire test the link between arsenic-rich sulfide minerals in bedrock and secondary oxy-hydroxide minerals. Samples were selected from over 70 bedrock localities, including 22 within the regionally extensive and sulfide-mineral
Authors
Robert A. Ayuso, Nora K. Foley
Anthropogenic vs. natural pollution: An environmental study of an industrial site under remediation (Naples, Italy)
Heavy metal concentrations and Pb isotopic composition were determined in the soils, slags, scums and landfill materials from a shut down industrial (brownfield) site. This was the second largest integrated steelworks in Italy, and is now under remediation by a Government project. It is located in the outskirts of Napoli on the Bagnoli-Fuorigrotta plain (BFP), which is part of the Campi Flegrei (C
Authors
M. Tarzia, B. de Vivo, R. Somma, R. A. Ayuso, R.A.R. McGill, R.R. Parrish
Science and Products
Filter Total Items: 78
Containing arsenic-enriched groundwater tracing lead isotopic compositions of common arsenical pesticides in a coastal Maine watershed
Arsenical pesticides and herbicides were extensively used on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Lead arsenate was the most heavily used arsenical pesticide until it was officially banned. Lead arsenate, calcium arsenate, and sodium arsenate have similar Pb isotope compositions: 208Pb207Pb = 2.3839-2.4722, and 206Pb207Pb = 1.1035-1.2010
Authors
Robert A. Ayuso, Nora K. Foley, Glipin R. Robinson, A.S. Colvin, G. Lipfert, A.S. Reeve
Emplacement of the Kodiak batholith and slab-window migration
The Kodiak batholith is one of the largest, most elongate intrusive bodies in the forearc Sanak-Baranof plutonic belt located in southern Alaska. This belt is interpreted to have formed during the subduction of an oceanic spreading center and the associated migration of a slab window. Individual plutons of the Kodiak batholith track the location and evolution of the underlying slab window. Six U/P
Authors
David W. Farris, Peter J. Haeussler, Richard Friedman, Scott R. Paterson, R. W. Saltus, Robert A. Ayuso
U-Pb zircon ages and Pb isotope geochemistry of gold deposits in the Carolina slate belt of South Carolina
Volcanic rocks of the Persimmon Fork Formation host the largest known gold mines of the Carolina slate belt. U-Pb (SHRIMP) zircon ages have been obtained from rocks closely associated with pyrite-enargite-gold deposits at Brewer (quartz-topaz rhyolite breccia from the argillic alteration zone in the Brewer pit and felsic ash-flow tuff from the quartz sericite alteration zone), from the disseminate
Authors
Robert A. Ayuso, Joseph L. Wooden, Nora K. Foley, Robert R. Seal, A. Krishna Sinha
Oceanic Pb-isotopic sources of Proterozoic and Paleozoic volcanogenic massive sulfide deposits on Prince of Wales Island and vicinity, southeastern Alaska
Volcanogenic massive sulfide (VMS) deposits on Prince of Wales Island and vicinity in southeastern Alaska are associated with Late Proterozoic through Cambrian volcanosedimentary rocks of the Wales Group and with Ordovician through Early Silurian felsic volcanic rocks of the Moira Sound unit (new informal name). The massive sulfide deposits in the Wales Group include the Big Harbor, Copper City, C
Authors
Robert A. Ayuso, Susan M. Karl, John F. Slack, Peter J. Haeussler, Peter E. Bittenbender, Gregory A. Wandless, Anna Colvin
Multistage hydrothermal silicification and Fe-Tl-As-Sb-Ge-REE enrichment in the Red Dog Zn-Pb-Ag district, northern Alaska: Geochemistry, origin, and exploration applications
Geochemical analyses of major, trace, and rare earth elements (REE) in more than 200 samples of variably silicified and altered wall rocks, massive and banded sulfide, silica rock, and sulfide-rich and unmineralized barite were obtained from the Main, Aqqaluk, and Anarraaq deposits in the Red Dog Zn-Pb-Ag district of northern Alaska. Detailed lithogeochemical profiles for two drill cores at Aqqalu
Authors
J. F. Slack, K. D. Kelley, V.M. Anderson, J.L. Clark, R. A. Ayuso
Origin of the Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska: Evidence from regional Pb and Sr isotope sources
Pb and Sr isotope data were obtained on the shale-hosted Zn-Pb-Ag Red Dog deposits (Qanaiyaq, Main, Aqqaluk, and Paalaaq), other shale-hosted deposits near Red Dog, and Zn-Pb-Ag sulfide and barite deposits in the western and central Brooks Range. The Red Dog deposits and other shale-hosted Zn-Pb-Ag deposits near Red Dog are hosted in the Mississippian Kuna Formation, which is underlain by a sequen
Authors
R. A. Ayuso, K. D. Kelley, D. L. Leach, L. E. Young, J. F. Slack, G. Wandless, A.M. Lyon, J.L. Dillingham
Textural, compositional, and sulfur isotope variations of sulfide minerals in the Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska: Implications for Ore Formation
The Red Dog Zn-Pb deposits are hosted in organic-rich mudstone and shale of the Mississippian Kuna Formation. A complex mineralization history is defined by four sphalerite types or stages: (1) early brown sphalerite, (2) yellow-brown sphalerite, (3) red-brown sphalerite, and (4) late tan sphalerite. Stages 2 and 3 constitute the main ore-forming event and are volumetrically the most important. Su
Authors
K. D. Kelley, D. L. Leach, C.A. Johnson, J.L. Clark, M. Fayek, J. F. Slack, V.M. Anderson, R. A. Ayuso, W.I. Ridley
Use of spatial statistics and isotopic tracers to measure the influence of arsenical pesticide use on stream sediment chemistry in New England, USA
Arsenical pesticides and herbicides, principally Pb arsenate, Ca arsenate, and Na arsenate with lesser use of other metal-As pesticides, were widely applied on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Agricultural census data for this time period is used to define an agricultural index that identifies areas that are inferred to have used ars
Authors
G. R. Robinson, R. A. Ayuso
Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy
We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: "Protohistoric" (3550 y B.P. to 79 A.D.), "Ancient Historic" (79 to 472 A.D.) and "Medieval" (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that
Authors
M. Cortini, R. A. Ayuso, B. de Vivo, P. Holden, R. Somma
The late cretaceous Donlin Creek gold deposit, Southwestern Alaska: Controls on epizonal ore formation
The Donlin Creek gold deposit, southwestern Alaska, has an indicated and inferred resource of approximately 25 million ounces (Moz) Au at a cutoff grade of 1.5 g/t. The ca. 70 Ma deposit is hosted in the Late Cretaceous Kuskokwim flysch basin, which developed in the back part of the arc region of an active continental margin, on previously accreted oceanic terranes and continental fragments. A hyp
Authors
Richard J. Goldfarb, Robert A. Ayuso, Marti L. Miller, Shane W. Ebert, Erin E. Marsh, Scott A. Petsel, Lance D. Miller, Dwight C. Bradley, Chad Johnson, William C. McClelland
Arsenic in New England: Mineralogical and geochemical studies of sources and enrichment pathways
Detailed mineralogical, geochemical and radiogenic isotopic studies of iron-sulfide and secondary iron oxy-hydroxide minerals in natural bedrock in coastal Maine and New Hampshire test the link between arsenic-rich sulfide minerals in bedrock and secondary oxy-hydroxide minerals. Samples were selected from over 70 bedrock localities, including 22 within the regionally extensive and sulfide-mineral
Authors
Robert A. Ayuso, Nora K. Foley
Anthropogenic vs. natural pollution: An environmental study of an industrial site under remediation (Naples, Italy)
Heavy metal concentrations and Pb isotopic composition were determined in the soils, slags, scums and landfill materials from a shut down industrial (brownfield) site. This was the second largest integrated steelworks in Italy, and is now under remediation by a Government project. It is located in the outskirts of Napoli on the Bagnoli-Fuorigrotta plain (BFP), which is part of the Campi Flegrei (C
Authors
M. Tarzia, B. de Vivo, R. Somma, R. A. Ayuso, R.A.R. McGill, R.R. Parrish