New stratigraphic subdivisions and redefinition of subdivisions of late Archean and early Proterozoic metasedimentary and metavolcanic rocks of the Sierra Madre and Medicine Bow Mountains, southern Wyoming

1992 ◽  
Author(s):  
R.S. Houston ◽  
K.E. Karlstrom ◽  
P.J. Graff ◽  
A.J. Flurkey
Keyword(s):  
Early Proterozoic ◽  
Medicine Bow Mountains ◽  
Metavolcanic Rocks ◽  
Sierra Madre

An early Proterozoic volcanic arc succession in southeastern Wyoming

1984 ◽  
Vol 21 (4) ◽  
pp. 415-427 ◽  
Author(s):  
Kent C. Condie ◽  
Craig A. Shadel
Keyword(s):  
Fractional Crystallization ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Alkaline Basalt ◽  
Calc Alkaline ◽  
Early Proterozoic ◽  
Enriched Mantle ◽  
Sierra Madre ◽  
Felsic Volcanic

The Green Mountain Formation of early Proterozoic age in the Sierra Madre Range of southeastern Wyoming comprises a bimodal mafic and felsic volcanic assemblage. The rocks, which are chiefly breccias, agglomerates, flows, and volcaniclastic sediments, represent both subaerial and submarine eruptions and in part were redeposited in fluvial and nearshore marine environments. Volcanic rocks are clearly calc-alkaline in character and share a large number of geochemical features in common with continental-margin arcs or evolved oceanic-arc systems.The low Mg numbers and Ni contents of the basalts require 30–40% olivine fractional crystallization, and the high contents of the most incompatible elements, high (La/Sm)N ratios, and low Zr/Nb ratios require an undepleted or enriched mantle source. Geochemical data are consistent with an origin for the felsic volcanics and associated Encampment River granodiorite by shallow fractional crystallization of calc-alkaline basalt in a tectonic setting similar to modern arc systems. The near absence of andesites may reflect the retention of andesitic magma in crustal reservoirs during fractional cyrstallization.

Review of isotope data for Precambrian rocks from the Disko Bugt region, West Greenland

1999 ◽  
pp. 41-47 ◽  
Author(s):  
Feiko Kalsbeek ◽  
Paul N. Taylor
Keyword(s):  
Sr Isotope ◽  
Yield Model ◽  
Original Series ◽  
Early Proterozoic ◽  
West Greenland ◽  
Precambrian Rocks ◽  
Isotope Data ◽  
Metavolcanic Rocks ◽  
Granitoid Rocks ◽  
Data Yield

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kalsbeek, F., & Taylor, P. N. (1999). Review of isotope data for Precambrian rocks from the Disko Bugt region, West Greenland. Geology of Greenland Survey Bulletin, 181, 41-47. https://doi.org/10.34194/ggub.v181.5110 _______________ Pb-Pb and Rb-Sr isotope data yield whole-rock isochron ages of c. 2800 Ma for two localities of granitoid rocks in the Disko Bugt region, with little evidence of strong later disturbance. Rb-Sr isotope data on Archaean metasediments from two localities, however, were strongly disturbed during the early Proterozoic. Sm-Nd whole-rock data for acid metavolcanic rocks within Archaean supracrustal sequences yield model ages of c. 2800 Ma. The early Proterozoic age of a younger sequence of supracrustal rocks (the Anap nunâ Group) is confirmed by Sm-Nd data, and Rb-Sr whole-rock data for albitised siltstones show that albitisation took place hundreds of millions of years after the peak of early Proterozoic orogenic activity.

scholarly journals Nd-isotopic stratigraphy of early Proterozoic Amisk Group metavolcanic rocks from the Flin Flon Belt, Manitoba and Saskatchewan

1992 ◽  
Author(s):  
R A Stern ◽  
E C Syme ◽  
A H Bailes ◽  
A G Galley ◽  
D J Thomas ◽  
...  
Keyword(s):  
Early Proterozoic ◽  
Metavolcanic Rocks ◽  
Flin Flon

Preliminary report on radioactive conglomerates of Middle Precambrian age in the Sierra Madre and Medicine Bow Mountains of southeastern Wyoming

1977 ◽  
Author(s):  
Robert Stroud Houston ◽  
P.J. Graff ◽  
K.E. Karlstrom ◽  
Forrest Root
Keyword(s):  
Preliminary Report ◽  
Medicine Bow Mountains ◽  
Sierra Madre

U–Pb geochronology of the Hope Bay – Elu Inlet area, Bathurst Block, northeastern Slave Structural Province, Northwest Territories

1991 ◽  
Vol 28 (12) ◽  
pp. 1925-1930 ◽  
Author(s):  
Mary Lou Bevier ◽  
James S. Gebert
Keyword(s):  
Northwest Territories ◽  
Isotopic Ratios ◽  
Magmatic Activity ◽  
Early Proterozoic ◽  
Metavolcanic Rocks ◽  
Felsic Volcanism ◽  
Hope Bay

U–Pb ages for six felsic samples from the dominantly mafic Hope Bay and Elu Inlet metavolcanic belts of the Bathurst Block provide the first constraints on the timing of felsic volcanism (2685–2677 Ma) and plutonism (2672–2608 Ma) in the northeastern corner of the Slave Structural Province. Gold veins that cut a pluton in the eastern Hope Bay belt are younger than 2672 Ma. Early Proterozoic magmatic activity is recorded in a pegmatite dyke that crosscuts metavolcanic rocks of the northern Hope Bay belt. Initial Nd and Sr isotopic ratios from the Hope Bay and Elu Inlet belts indicate a juvenile source for the magmas.

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