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
Sulfur and lead isotope geochemistry of hypogene mineralization at the Barite Hill Gold Deposit, Carolina Slate Belt, southeastern United States: A window into and through regional metamorphism
The Barite Hill gold deposit, at the southwestern end of the Carolina slate belt in the southeastern United States, is one of four gold deposits in the region that have a combined yield of 110 metric tons of gold over the past 10 years. At Barite Hill, production has dominantly come from oxidized ores. Sulfur isotope data from hypogene portions of the Barite Hill gold deposit vary systematically w
Authors
Robert R. Seal, Robert A. Ayuso, Nora K. Foley, Sandra H. B. Clark
Major, trace element and isotope geochemistry (Sr-Nd-Pb) of interplinian magmas from Mt. Somma-Vesuvius (Southern Italy)
Major, trace element and isotopic (Sr, Nd, Pb) data are reported for representative samples of interplinian (Protohistoric, Ancient Historic and Medieval Formations) activity of Mt. Somma-Vesuvius volcano during the last 3500 years. Tephra and lavas exhibit significant major, trace element and isotopic variations. Integration of these data with those obtained by previous studies on the older Somma
Authors
R. Somma, R. A. Ayuso, B. de Vivo, G. Rolandi
Pb isotopes and toxic metals in floodplain and stream sediments from the Volturno river basin, Italy
We present results of a stratigraphic and environmental geochemistry study of the eastern sector of the Volturno river basin (Italy) using stream sediment and floodplain drill core samples. The cores, dated back to 7,000 years B.P., have been used to evaluate background (baseline) values. Pb isotopic compositions and toxic metal abundances have been determined to discriminate natural versus anthro
Authors
B. DeVivo, R. Somma, R. A. Ayuso, G. Calderoni, A. Lima, S. Pagliuca, A. Sava
Minimum age of the Neoproterozoic Seven Hundred Acre Island Formation and the tectonic setting of the Islesboro Formation, Islesboro block, Maine
Two plat formal stratigraphic sequences occur on Islesboro, Penobscot Bay, Maine. The older Seven Hundred Acre Island Formation is at least 200 m thick, its base is not exposed, and it makes up fault-bounded blocks of siliceous colour-banded dolomitic marble, muscovite-rich quartzite, coarse-grained splendent muscovite-garnet-staurolite-andalusite schist, and calcareous metapelite, with minor garn
Authors
David B. Stewart, Robert D Tucker, Robert Ayuso, Daniel R. Lux
Isotope geochemistry and fluid inclusion study of skarns from Vesuvius
We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd isotope data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopit
Authors
H.A. Gilg, A. Lima, R. Somma, H. E. Belkin, B. de Vivo, R. A. Ayuso
A metallogenic survey of alkalic rocks of Mt. Somma-Vesuvius volcano
Somma-Vesuvius is an alkaline volcano whose products (pumice, scoria and lava) have alkaline (Na2O+K2O) contents between 6 and 16 wt%, Mg number
Authors
A. Paone, R. A. Ayuso, B. de Vivo
Remnant colloform pyrite at the haile gold deposit, South Carolina: A textural key to genesis
Auriferous iron sulfide-bearing deposits of the Carolina slate belt have distinctive mineralogical and textural features-traits that provide a basis to construct models of ore deposition. Our identification of paragenetically early types of pyrite, especially remnant colloform, crustiform, and layered growth textures of pyrite containing electrum and pyrrhotite, establishes unequivocally that gold
Authors
N. Foley, R. A. Ayuso, R.R. Seal
Stratigraphy, geochemistry and tectonic significance of the Oligocene magmatic rocks of western Oaxaca, southern Mexico
In Western Oaxaca, Tertiary magmatic activity is represented by extensive plutons along the continental margin and volcanic sequences in the inland region. K-Ar age determinations reported previously and in the present work indicate that these rocks correspond to a relatively broad arc in this region that was active mainly during the Oligocene (~ 35 to ~ 25 Ma). In the northern sector of western O
Authors
B. Martiny, R. G. Martinez-Serrano, D. J. Moran-Zenteno, C. MacIas-Romo, R. A. Ayuso
Pb isotopes and toxic metal abundances in the floodplain and stream sediments from the Volturno River basin (Campania, Italy); natural and anthropogenic contributions
No abstract available.
Authors
Renato Somma, R. A. Ayuso, B. de Vivo, S. Pagliuca
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 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 be used i
Authors
Robert A. Ayuso
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 (Haile, Bre
Authors
Robert A. Ayuso
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Filter Total Items: 78
Sulfur and lead isotope geochemistry of hypogene mineralization at the Barite Hill Gold Deposit, Carolina Slate Belt, southeastern United States: A window into and through regional metamorphism
The Barite Hill gold deposit, at the southwestern end of the Carolina slate belt in the southeastern United States, is one of four gold deposits in the region that have a combined yield of 110 metric tons of gold over the past 10 years. At Barite Hill, production has dominantly come from oxidized ores. Sulfur isotope data from hypogene portions of the Barite Hill gold deposit vary systematically wAuthorsRobert R. Seal, Robert A. Ayuso, Nora K. Foley, Sandra H. B. ClarkMajor, trace element and isotope geochemistry (Sr-Nd-Pb) of interplinian magmas from Mt. Somma-Vesuvius (Southern Italy)
Major, trace element and isotopic (Sr, Nd, Pb) data are reported for representative samples of interplinian (Protohistoric, Ancient Historic and Medieval Formations) activity of Mt. Somma-Vesuvius volcano during the last 3500 years. Tephra and lavas exhibit significant major, trace element and isotopic variations. Integration of these data with those obtained by previous studies on the older SommaAuthorsR. Somma, R. A. Ayuso, B. de Vivo, G. RolandiPb isotopes and toxic metals in floodplain and stream sediments from the Volturno river basin, Italy
We present results of a stratigraphic and environmental geochemistry study of the eastern sector of the Volturno river basin (Italy) using stream sediment and floodplain drill core samples. The cores, dated back to 7,000 years B.P., have been used to evaluate background (baseline) values. Pb isotopic compositions and toxic metal abundances have been determined to discriminate natural versus anthroAuthorsB. DeVivo, R. Somma, R. A. Ayuso, G. Calderoni, A. Lima, S. Pagliuca, A. SavaMinimum age of the Neoproterozoic Seven Hundred Acre Island Formation and the tectonic setting of the Islesboro Formation, Islesboro block, Maine
Two plat formal stratigraphic sequences occur on Islesboro, Penobscot Bay, Maine. The older Seven Hundred Acre Island Formation is at least 200 m thick, its base is not exposed, and it makes up fault-bounded blocks of siliceous colour-banded dolomitic marble, muscovite-rich quartzite, coarse-grained splendent muscovite-garnet-staurolite-andalusite schist, and calcareous metapelite, with minor garnAuthorsDavid B. Stewart, Robert D Tucker, Robert Ayuso, Daniel R. LuxIsotope geochemistry and fluid inclusion study of skarns from Vesuvius
We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd isotope data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopitAuthorsH.A. Gilg, A. Lima, R. Somma, H. E. Belkin, B. de Vivo, R. A. AyusoA metallogenic survey of alkalic rocks of Mt. Somma-Vesuvius volcano
Somma-Vesuvius is an alkaline volcano whose products (pumice, scoria and lava) have alkaline (Na2O+K2O) contents between 6 and 16 wt%, Mg numberAuthorsA. Paone, R. A. Ayuso, B. de VivoRemnant colloform pyrite at the haile gold deposit, South Carolina: A textural key to genesis
Auriferous iron sulfide-bearing deposits of the Carolina slate belt have distinctive mineralogical and textural features-traits that provide a basis to construct models of ore deposition. Our identification of paragenetically early types of pyrite, especially remnant colloform, crustiform, and layered growth textures of pyrite containing electrum and pyrrhotite, establishes unequivocally that goldAuthorsN. Foley, R. A. Ayuso, R.R. SealStratigraphy, geochemistry and tectonic significance of the Oligocene magmatic rocks of western Oaxaca, southern Mexico
In Western Oaxaca, Tertiary magmatic activity is represented by extensive plutons along the continental margin and volcanic sequences in the inland region. K-Ar age determinations reported previously and in the present work indicate that these rocks correspond to a relatively broad arc in this region that was active mainly during the Oligocene (~ 35 to ~ 25 Ma). In the northern sector of western OAuthorsB. Martiny, R. G. Martinez-Serrano, D. J. Moran-Zenteno, C. MacIas-Romo, R. A. AyusoPb isotopes and toxic metal abundances in the floodplain and stream sediments from the Volturno River basin (Campania, Italy); natural and anthropogenic contributions
No abstract available.AuthorsRenato Somma, R. A. Ayuso, B. de Vivo, S. PagliucaA 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.AuthorsRenato Somma, Robert A. Ayuso, B. de VivoRadiogenic 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 be used iAuthorsRobert A. AyusoCarolina 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 (Haile, BreAuthorsRobert A. Ayuso