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
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
Authors
A. Consenza, A. Lima, Robert A. Ayuso, Nora K. Foley, S. Albanese, A. Messina, B. De Vivo
Geochemical and mineralogical characteristics of REE in granite-derived regolith: a model for the Southeast United States
Rare earth element (REE) ion-adsorption clay deposits are of global economic importance because they currently supply a significant portion of the world’s annual production of both light (LREE) and heavy REE (HREE). There is considerable ambiguity regarding the origin of
this deposit type: The main criteria include the presence of large, generally granitic, igneous suites; long periods of intense
Authors
Nora K. Foley, Carleton R. Bern, Robert A. Ayuso, Bernard E. Hubbard, Anjana K. Shah
REE enrichment in granite-derived regolith deposits of the southeast United States: Prospective source rocks and accumulation processes
The Southeastern United States contains numerous anorogenic, or A-type, granites, which constitute promising source rocks for REE-enriched ion adsorption clay deposits due to their inherently high concentrations of REE. These granites have undergone a long history of chemical weathering, resulting in thick granite-derived regoliths, akin to those of South China, which supply virtually all heavy RE
Authors
Nora K. Foley, Robert A. Ayuso
Reconstruction of an early Paleozoic continental margin based on the nature of protoliths in the Nome Complex, Seward Peninsula, Alaska
The Nome Complex is a large metamorphic unit that sits along the southern boundary of the Arctic Alaska–Chukotka terrane, the largest of several micro continental fragments of uncertain origin located between the Siberian and Laurentian cratons. The Arctic Alaska–Chukotka terrane moved into its present position during the Mesozoic; its Mesozoic and older movements are central to reconstruction of
Authors
Alison B. Till, Julie A. Dumoulin, Robert A. Ayuso, John N. Aleinikoff, Jeffrey M. Amato, John F. Slack, W.C. Pat Shanks
Geochemical and Nd-Sr-Pb isotopic evolution of metabasites from rifting of continental lithosphere, Seward Peninsula, Alaska, and implications for paleogeographic reconstruction
The chemical character of mafic rocks from the Arctic Alaska–Chukotka terrane records rifting of continental crust during the early Paleozoic, possibly during the Ordovician. The mafic rocks are part of a metamorphosed Neoproterozoic to Devonian continental margin sequence preserved in a Mesozoic metamorphic terrane, the Nome Complex, of Seward Peninsula, Alaska. Protoliths of the mafic rocks incl
Authors
Robert A. Ayuso, Alison Till
Pb isotope geochemistry of stratabound Zn-Pb(-Ag-Au-Ba-F) deposits and occurrences in the Nome Complex, Seward Peninsula, Alaska: Metal sources and regional comparisons
A detailed study of the Pb isotope geochemistry of Zn-Pb(-Ag-Au-Ba-F) stratabound sulfide deposits within metasedimentary rocks of the Neoproterozoic to Mississippian(?) Nome Complex provides key information for understanding deposit genesis and crustal evolution. A total of 106 new analyses of galena (and other sulfi des) and metasedimentary rocks hosting the deposits shows that (1) Pb isotope si
Authors
Robert A. Ayuso, Alison Till, John F. Slack, Francesca Forni
Pb-Sr-Nd isotopes in surficial materials at the Pebble Porphyry Cu-Au-Mo Deposit, Southwestern Alaska: can the mineralizing fingerprint be detected through cover?
The Cretaceous Pebble porphyry Cu-Au-Mo deposit is covered by tundra and glacigenic sediments. Pb-Sr-Nd measurements were done on sediments and soils to establish baseline conditions prior to the onset of mining operations and contribute to the development of exploration methods for concealed base metal deposits of this type. Pebble rocks have a moderate range for 206Pb/204Pb = 18.574 to 18.874, 2
Authors
Robert A. Ayuso, Karen D. Kelley, Robert G. Eppinger, Francesca Forni
Gold deposits of the Carolina Slate Belt, southeastern United States--Age and origin of the major gold producers
Gold- and iron sulfide-bearing deposits of the southeastern United States have distinctive mineralogical and geochemical features that provide a basis for constructing models of ore genesis for exploration and assessment of gold resources. The largest (historic) deposits, in approximate million ounces of gold (Moz Au), include those in the Haile (~ 4.2 Moz Au), Ridgeway (~1.5 Moz Au), Brewer (~0.2
Authors
Nora K. Foley, Robert A. Ayuso
Understanding processes affecting mineral deposits in humid environments
Recent interdisciplinary studies by the U.S. Geological Survey have resulted in substantial progress toward understanding the influence that climate and hydrology have on the geochemical signatures of mineral deposits and the resulting mine wastes in the eastern United States. Specific areas of focus include the release, transport, and fate of acid, metals, and associated elements from inactive mi
Authors
Robert R. Seal, Robert A. Ayuso
Formation of cordierite-bearing lavas during anatexis in the lower crust beneath Lipari Island (Aeolian arc, Italy)
Cordierite-bearing lavas (CBL;~105 ka) erupted from the Mt. S. Angelo volcano at Lipari (Aeolian arc, Italy) are high-K andesites, displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and/or processes. CBL consist of megacrysts of Ca-plagioclase and clinopyroxene, euhedral crystals of cordierite and garnet, microphenocrysts of orthopyroxene and p
Authors
Martino C. Di, F. Forni, M.L. Frezzotti, R. Palmeri, J.D. Webster, R. A. Ayuso, F. Lucchi, C.A. Tranne
Geochemical and isotopic study of soils and waters from an Italian contaminated site: Agro Aversano (Campania)
Lead isotope applications have been widely used in recent years in environmental studies conducted on different kinds of sampled media. In the present paper, Pb isotope ratios have been used to determine the sources of metal pollution in soils and waters in the Agro Aversano area. During three different sampling phases, a total of 113 surface soils (5-20. cm), 20 samples from 2 soil profiles (0-1.
Authors
M.A. Bove, R. A. Ayuso, B. de Vivo, A. Lima, S. Albanese
Lead isotopes in soils and groundwaters as tracers of the impact of human activities on the surface environment: The Domizio-Flegreo Littoral (Italy) case study
The isotopic signature of geogenic and anthropogenic materials, in combination with concentration data for pollutants, can help trace the origin and the extent of contamination in the environment. This approach is particularly effective if naturally occurring and anthropogenically introduced metals have different isotopic ratios. Lead isotope analysis on soils from 7 profiles (1 m depth) and on gr
Authors
G. Grezzi, Robert A. Ayuso, B. de Vivo, A. Lima, S. Albanese
Science and Products
Filter Total Items: 77
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
Authors
A. Consenza, A. Lima, Robert A. Ayuso, Nora K. Foley, S. Albanese, A. Messina, B. De Vivo
Geochemical and mineralogical characteristics of REE in granite-derived regolith: a model for the Southeast United States
Rare earth element (REE) ion-adsorption clay deposits are of global economic importance because they currently supply a significant portion of the world’s annual production of both light (LREE) and heavy REE (HREE). There is considerable ambiguity regarding the origin of
this deposit type: The main criteria include the presence of large, generally granitic, igneous suites; long periods of intense
Authors
Nora K. Foley, Carleton R. Bern, Robert A. Ayuso, Bernard E. Hubbard, Anjana K. Shah
REE enrichment in granite-derived regolith deposits of the southeast United States: Prospective source rocks and accumulation processes
The Southeastern United States contains numerous anorogenic, or A-type, granites, which constitute promising source rocks for REE-enriched ion adsorption clay deposits due to their inherently high concentrations of REE. These granites have undergone a long history of chemical weathering, resulting in thick granite-derived regoliths, akin to those of South China, which supply virtually all heavy RE
Authors
Nora K. Foley, Robert A. Ayuso
Reconstruction of an early Paleozoic continental margin based on the nature of protoliths in the Nome Complex, Seward Peninsula, Alaska
The Nome Complex is a large metamorphic unit that sits along the southern boundary of the Arctic Alaska–Chukotka terrane, the largest of several micro continental fragments of uncertain origin located between the Siberian and Laurentian cratons. The Arctic Alaska–Chukotka terrane moved into its present position during the Mesozoic; its Mesozoic and older movements are central to reconstruction of
Authors
Alison B. Till, Julie A. Dumoulin, Robert A. Ayuso, John N. Aleinikoff, Jeffrey M. Amato, John F. Slack, W.C. Pat Shanks
Geochemical and Nd-Sr-Pb isotopic evolution of metabasites from rifting of continental lithosphere, Seward Peninsula, Alaska, and implications for paleogeographic reconstruction
The chemical character of mafic rocks from the Arctic Alaska–Chukotka terrane records rifting of continental crust during the early Paleozoic, possibly during the Ordovician. The mafic rocks are part of a metamorphosed Neoproterozoic to Devonian continental margin sequence preserved in a Mesozoic metamorphic terrane, the Nome Complex, of Seward Peninsula, Alaska. Protoliths of the mafic rocks incl
Authors
Robert A. Ayuso, Alison Till
Pb isotope geochemistry of stratabound Zn-Pb(-Ag-Au-Ba-F) deposits and occurrences in the Nome Complex, Seward Peninsula, Alaska: Metal sources and regional comparisons
A detailed study of the Pb isotope geochemistry of Zn-Pb(-Ag-Au-Ba-F) stratabound sulfide deposits within metasedimentary rocks of the Neoproterozoic to Mississippian(?) Nome Complex provides key information for understanding deposit genesis and crustal evolution. A total of 106 new analyses of galena (and other sulfi des) and metasedimentary rocks hosting the deposits shows that (1) Pb isotope si
Authors
Robert A. Ayuso, Alison Till, John F. Slack, Francesca Forni
Pb-Sr-Nd isotopes in surficial materials at the Pebble Porphyry Cu-Au-Mo Deposit, Southwestern Alaska: can the mineralizing fingerprint be detected through cover?
The Cretaceous Pebble porphyry Cu-Au-Mo deposit is covered by tundra and glacigenic sediments. Pb-Sr-Nd measurements were done on sediments and soils to establish baseline conditions prior to the onset of mining operations and contribute to the development of exploration methods for concealed base metal deposits of this type. Pebble rocks have a moderate range for 206Pb/204Pb = 18.574 to 18.874, 2
Authors
Robert A. Ayuso, Karen D. Kelley, Robert G. Eppinger, Francesca Forni
Gold deposits of the Carolina Slate Belt, southeastern United States--Age and origin of the major gold producers
Gold- and iron sulfide-bearing deposits of the southeastern United States have distinctive mineralogical and geochemical features that provide a basis for constructing models of ore genesis for exploration and assessment of gold resources. The largest (historic) deposits, in approximate million ounces of gold (Moz Au), include those in the Haile (~ 4.2 Moz Au), Ridgeway (~1.5 Moz Au), Brewer (~0.2
Authors
Nora K. Foley, Robert A. Ayuso
Understanding processes affecting mineral deposits in humid environments
Recent interdisciplinary studies by the U.S. Geological Survey have resulted in substantial progress toward understanding the influence that climate and hydrology have on the geochemical signatures of mineral deposits and the resulting mine wastes in the eastern United States. Specific areas of focus include the release, transport, and fate of acid, metals, and associated elements from inactive mi
Authors
Robert R. Seal, Robert A. Ayuso
Formation of cordierite-bearing lavas during anatexis in the lower crust beneath Lipari Island (Aeolian arc, Italy)
Cordierite-bearing lavas (CBL;~105 ka) erupted from the Mt. S. Angelo volcano at Lipari (Aeolian arc, Italy) are high-K andesites, displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and/or processes. CBL consist of megacrysts of Ca-plagioclase and clinopyroxene, euhedral crystals of cordierite and garnet, microphenocrysts of orthopyroxene and p
Authors
Martino C. Di, F. Forni, M.L. Frezzotti, R. Palmeri, J.D. Webster, R. A. Ayuso, F. Lucchi, C.A. Tranne
Geochemical and isotopic study of soils and waters from an Italian contaminated site: Agro Aversano (Campania)
Lead isotope applications have been widely used in recent years in environmental studies conducted on different kinds of sampled media. In the present paper, Pb isotope ratios have been used to determine the sources of metal pollution in soils and waters in the Agro Aversano area. During three different sampling phases, a total of 113 surface soils (5-20. cm), 20 samples from 2 soil profiles (0-1.
Authors
M.A. Bove, R. A. Ayuso, B. de Vivo, A. Lima, S. Albanese
Lead isotopes in soils and groundwaters as tracers of the impact of human activities on the surface environment: The Domizio-Flegreo Littoral (Italy) case study
The isotopic signature of geogenic and anthropogenic materials, in combination with concentration data for pollutants, can help trace the origin and the extent of contamination in the environment. This approach is particularly effective if naturally occurring and anthropogenically introduced metals have different isotopic ratios. Lead isotope analysis on soils from 7 profiles (1 m depth) and on gr
Authors
G. Grezzi, Robert A. Ayuso, B. de Vivo, A. Lima, S. Albanese