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
Significance of tourmaline-rich rocks in the Grenville Complex of St. Lawrence County, New York
Feldspathic quartzite and metapelite of Middle Proterozic age north of Gouverneur, N.Y., contain abundant dravite-uvite (magnesian tourmaline). These rocks, more than 1,000 feet thick, are regionally metamorphosed to the upper amphibolite facies, are pyritic, and locally contain porphyroblastic scapolite. The rocks are underlain by talctremolite schist and a thick sequence of calcitic and dolomiti
Authors
C. Ervin Brown, Robert A. Ayuso
Manganese-rich red tourmaline from the Fowler talc belt, New York.
Red uvite containing up to 4.34 wt.% MnO is found in the Arnold talc mine near Fowler, New York, USA. Microprobe analyses give a composition of 51% uvite in the uvite-dravite series. Associated minerals in this manganiferous metamorphic assemblage (possibly an evaporite) are manganese-rich tremolite (hexagonite) braunite and quartz.-R.A.G.
Authors
R. A. Ayuso, C. Erwin Brown
Comparative geochronology in the reversely zoned plutons of the Bottle Lake Complex, Maine: U-Pb on zircons and Rb-Sr on whole rocks
The Bottle Lake Complex is a composite granitic batholith emplaced into Cambrian to Lower Devonian metasedimentary rocks. Both plutons (Whitney Cove and Passadumkeag River) are very coarse grained hornblende and biotite-bearing granites showing petrographic and geochemical reverse zonation. Two linear whole rock Rb/Sr isochrons on xenolith-free Whitney Cove and Passadumkeag River samples indicate
Authors
R. A. Ayuso, Joseph G. Arth, A.K. Sinha, J. Carlson, D. R. Wones
Lye Brook Wilderness, Vermont
The Lye Brook Wilderness, in the Green Mountains of Vermont is underlain by gneisses, quartzites, schists, and amphibolites of Precambrian to Ordovician age. A mineral-resource survey determined that only one commodity, quartzite, is present in large quantities and could be a source of dimension stone or crushed stone. Although an anomalously high radioactive area occurs within the Precambrian bas
Authors
Robert A. Ayuso, D. K. Harrison
Field relations, crystallization, and petrology of reversely zoned granitic plutons in the Bottle Lake Complex, Maine
No abstract available.
Authors
R. A. Ayuso
Quartz-molybdenite veins in the Priestly Lake granodiorite, north-central Maine
Quartz-molybdenite veins up to 15 cm in width occur in fine to medium-grained porphyritic biotite-hornblende granodiorite at Priestly Lake north-central Maine. An area of about 150 m x 150 m contains quartz-molybdenite veins; a larger area is characterized by barren quartz veins. Quartz-molybdenite veins are concentrated within the most felsic variants of the intrusion as suggested by lower mafic
Authors
Robert A. Ayuso, Stephen G. Shank
Science and Products
Filter Total Items: 78
Significance of tourmaline-rich rocks in the Grenville Complex of St. Lawrence County, New York
Feldspathic quartzite and metapelite of Middle Proterozic age north of Gouverneur, N.Y., contain abundant dravite-uvite (magnesian tourmaline). These rocks, more than 1,000 feet thick, are regionally metamorphosed to the upper amphibolite facies, are pyritic, and locally contain porphyroblastic scapolite. The rocks are underlain by talctremolite schist and a thick sequence of calcitic and dolomiti
Authors
C. Ervin Brown, Robert A. Ayuso
Manganese-rich red tourmaline from the Fowler talc belt, New York.
Red uvite containing up to 4.34 wt.% MnO is found in the Arnold talc mine near Fowler, New York, USA. Microprobe analyses give a composition of 51% uvite in the uvite-dravite series. Associated minerals in this manganiferous metamorphic assemblage (possibly an evaporite) are manganese-rich tremolite (hexagonite) braunite and quartz.-R.A.G.
Authors
R. A. Ayuso, C. Erwin Brown
Comparative geochronology in the reversely zoned plutons of the Bottle Lake Complex, Maine: U-Pb on zircons and Rb-Sr on whole rocks
The Bottle Lake Complex is a composite granitic batholith emplaced into Cambrian to Lower Devonian metasedimentary rocks. Both plutons (Whitney Cove and Passadumkeag River) are very coarse grained hornblende and biotite-bearing granites showing petrographic and geochemical reverse zonation. Two linear whole rock Rb/Sr isochrons on xenolith-free Whitney Cove and Passadumkeag River samples indicate
Authors
R. A. Ayuso, Joseph G. Arth, A.K. Sinha, J. Carlson, D. R. Wones
Lye Brook Wilderness, Vermont
The Lye Brook Wilderness, in the Green Mountains of Vermont is underlain by gneisses, quartzites, schists, and amphibolites of Precambrian to Ordovician age. A mineral-resource survey determined that only one commodity, quartzite, is present in large quantities and could be a source of dimension stone or crushed stone. Although an anomalously high radioactive area occurs within the Precambrian bas
Authors
Robert A. Ayuso, D. K. Harrison
Field relations, crystallization, and petrology of reversely zoned granitic plutons in the Bottle Lake Complex, Maine
No abstract available.
Authors
R. A. Ayuso
Quartz-molybdenite veins in the Priestly Lake granodiorite, north-central Maine
Quartz-molybdenite veins up to 15 cm in width occur in fine to medium-grained porphyritic biotite-hornblende granodiorite at Priestly Lake north-central Maine. An area of about 150 m x 150 m contains quartz-molybdenite veins; a larger area is characterized by barren quartz veins. Quartz-molybdenite veins are concentrated within the most felsic variants of the intrusion as suggested by lower mafic
Authors
Robert A. Ayuso, Stephen G. Shank