Results 171 to 180 of about 299,133 (214)

Isotope disequilibrium during partial melting of metasedimentary rocks

Geochimica et Cosmochimica Acta, 2019
Abstract The chemical composition of partial melts is buffered by the rock forming minerals that participate in the melting reactions and by the solubility of accessory phases in these melts. Both depend on the melting conditions. The chemical composition of restite depends on the restite mineralogy and may be highly variable.
Mathias Wolf, Rolf L. Romer, Johannes Glodny   +2 more
openaire   +3 more sources

Partial melting of common metasedimentary rocks: A mass balance approach

Contributions to Mineralogy and Petrology, 1980
Materials balance calculations are presented to document the progressive bulk chemical changes in metagreywacke and metapelite with separation of increments of granite of minimum melt composition. During partial melting, enrichment of Fe relative to Mg in granite and strong absorption of water leave residual rocks with increasing proportions of such Mg-
MacRae, N. D., Nesbitt, H. W.
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Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks

Nature Geoscience, 2013
The Archaean rocks of Isua, West Greenland, contain graphite, but its origins are debated. Geochemical and microscopic analyses suggest that the graphite was formed from biologically formed carbon that was deposited at least 3.7 billion years ago.
Ohtomo, Yoko, Kakegawa, Takeshi, Ishida, Akizumi, Nagase, Toshiro, Rosing, Minik Thorleif   +4 more
openaire   +2 more sources

Late Precambrian Metasedimentary Rocks of Egan Range, Nevada

AAPG Bulletin, 1963
ABSTRACT Approximately 8,450 feet of polymetamorphic Late Precambrian strata are exposed at Heusser Mountain in the central northern Egan Range, Nevada. These rocks were regionally metamorphosed to slates, argillites, phyllites, metasiltstones, and quartzites; they were later contact-metamorphosed to grades as high as the biotite-zone
openaire   +1 more source

Geochronology of sedimentary and metasedimentary Precambrian rocks of the West African craton

Precambrian Research, 1982
Abstract This contribution summarizes current knowledge of the geochronology of the Upper Proterozoic sedimentary rocks covering the West African craton. This was done by using direct dating methods. Correlations between the northern edge of the Tindouf basin and the northern and southern part of the Taoudeni basin, as well as the Volta basin, are ...
Norbert Clauer, Renaud Caby, Daniel Jeannette, Roland Trompette   +3 more
openaire   +1 more source

Subsolidus segregation of quartz in metamorphic differentiation of metasedimentary rocks

Doklady Earth Sciences, 2017
Thermodynamic modeling of the SiO2–TiO2–Al2O3–Fe2O3–MnO–MgO–CaO–Na2O–K2O–P2O5–H2O (STAFMMCNKPOH) system at 600°C, 5 kbar has been applied to investigate dissolution and re-precipitation of quartz. Comparing silica molality in the STAFMMCNKPOH and SiO2–H2O systems, there is seen to be no effect of mineral assemblage on quartz solubility.
openaire   +1 more source

Whole-Rock Rb-Sr Age of Metasedimentary Rocks Below the Stillwater Complex, Montana

Geological Society of America Bulletin, 1969
Eight metasedimentary rocks selected from a suite collected below the Stillwater Complex in the Beartooth Mountains, Montana, yield a whole-rock Rb-Sr age of 2730 ± 150 m.y. (λ = 1.39 × 10 −11 /yr). The samples represent rocks located 0.4 to 6 miles from the lower contact of the Complex, and the nearer samples are definitely within the contact ...
J. L. POWELL, W. R. SKINNER, DAVID WALKER   +2 more
openaire   +1 more source

GRAPHITIZATION OF METASEDIMENTARY ROCKS IN THE WESTERN KONYA

2015
The Paleozoic-Mesozoic metasedimentary rocks in the study area are metacarbonate, metachert, metapelite, metasandstone and metaconglomerate. Graphite layers are 1cm to 2m thick, extend laterally for tens of meters and are intercalated with metasedimentary rocks.
KURT, Hüseyin, EREN, Yaşar
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Fold growth and transposition in metasedimentary rocks of the southeastern Adirondacks: Summary

Geological Society of America Bulletin, 1980
INTRODUCTION Most of the estimates of the pressure and temperature for Adirondack metamorphism fall in the range of 650 to 800 °C and 7 to 9 kbar (Whitney and McLelland, 1973; Essene and others, 1977; Boone, 1978; Valley and Bohlen, 1979; Whitney and others, 1979), suggesting an elevated geothermal gradient comparable to oceanic gradients (Mercier and
JAMES W. GRANATH, NOEL BARSTOW
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MICROSTRUCTURES AND COMPOSITION OF ANATECTIC MELT INCLUSIONS IN METASEDIMENTARY ROCKS

2011
Melt inclusions (MI) investigation represents a widely used approach to gain information on a number of igneous processes on the Earth system. The recent finding of crystallized and glassy MI in high-grade, partially melted metapelites and metagraywackes opened up the possibility to investigate also anatectic processes with the same method. The present
Ferrero S, Bartoli O, Cesare B, Salvioli Mariani E, AcostaVigil A, Cavallo A, Groppo C, Battiston S   +7 more
openaire   +1 more source