Upper mantle origin of plagioclase megacrysts from plagioclase-ultraphyric mid-oceanic ridge basalt

Geology ◽  
2018 ◽  
Vol 47 (1) ◽  
pp. 43-46 ◽  
Author(s):  
Mélissa J. Drignon ◽  
Roger L. Nielsen ◽  
Frank J. Tepley ◽  
Robert J. Bodnar
Keyword(s):  
Upper Mantle ◽  
Oceanic Ridge ◽  
Ridge Basalt ◽  
Mantle Origin

Upper mantle origin for Harding County well gases

Nature ◽  
1987 ◽  
Vol 325 (6105) ◽  
pp. 605-607 ◽  
Author(s):  
Thomas Staudacher
Keyword(s):  
Upper Mantle ◽  
Mantle Origin

Age and radiogenic isotopic systematics of the Borden carbonatite complex, Ontario, Canada

1987 ◽  
Vol 24 (1) ◽  
pp. 24-30 ◽  
Author(s):  
Keith Bell ◽  
John Blenkinsop ◽  
S. T. Kwon ◽  
G. R. Tilton ◽  
R. P. Sage
Keyword(s):  
Upper Mantle ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Growth Curves ◽  
Carbonatite Complex ◽  
Northern Ontario ◽  
Mantle Origin ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Isotope Correlation

Rb–Sr and U–Pb data from the Borden complex of northern Ontario, a carbonatite associated with the Kapuskasing Structural Zone, indicate a mid-Proterozoic age. A 207Pb/206Pb age of 1872 ± 13 Ma is interpreted as the emplacement age of this body, grouping it with other ca. 1900 Ma complexes that are the oldest known carbonatites associated with the Kapuskasing structure. A 206Pb–238U age of 1894 ± 29 Ma agrees with the Pb–Pb age but has a high mean square of weighted deviates (MSWD) of 42. A Rb–Sr apatite–carbonate–mica whole-rock isochron date of 1807 ± 13 Ma probably indicates later resetting of the Rb–Sr system.An εSr(T) value of −6.2 ± 0.5 (87Sr/86Sr = 0.70184 ± 0.00003) and an εNd(T) value of +2.8 ± 0.4 for Borden indicate derivation of the Sr and Nd from a source with a time-integrated depletion in the large-ion lithophile (LIL) elements. These closely resemble the ε values for Sr and Nd from the Cargill and Spanish River complexes, two other 1900 Ma plutons. The estimated initial 207Pb/204Pb and 206Pb/204Pb ratios from Borden calcites plot significantly below growth curves for average continental crust in isotope correlation diagrams, a pattern similar to those found in mid-ocean ridge basalts (MORB) and most ocean-island volcanic rocks, again suggesting a source depleted in LIL elements. The combined Nd and Sr, and probably Pb, data strongly favour a mantle origin for the Borden complex with little or no crustal contamination and support the model of Bell et al. that many carbonatites intruded into the Canadian Shield were derived from an ancient, LIL-depleted subcontinental upper mantle.

Diverse Sr isotope signatures preserved in mid-oceanic-ridge basalt plagioclase

Geology ◽  
2013 ◽  
Vol 41 (2) ◽  
pp. 279-282 ◽  
Author(s):  
Amy E. Lange ◽  
Roger L. Nielsen ◽  
Frank J. Tepley ◽  
Adam J.R. Kent
Keyword(s):  
Sr Isotope ◽  
Oceanic Ridge ◽  
Ridge Basalt

Kaersutite from San Carlos, Arizona, with comments on the paragenesis of this mineral

1968 ◽  
Vol 36 (283) ◽  
pp. 997-1002 ◽  
Author(s):  
Brian Mason
Keyword(s):  
Upper Mantle ◽  
Volcanic Rocks ◽  
Mantle Origin ◽  
Basic Volcanic ◽  
San Carlos

SummaryA 230 g kaersutite xenocryst from basalt at San Carlos, Arizona, has the composition SiO2 40·10 %, TiO2 4·44, Al2O3 14·53, Fe2O3 3·24, FeO 10·05, MnO 0·14, MgO 11·00, CaO 11·06, Na2O 2·99, K2O 1·62, H2O + 0·73, H2O − 0·10; D = 3·28; α 1·680, β 1·700, γ 1·715; a 9·858 Å, b 18·063 Å, c 5·315 Å, β 105° 14′. Kaersutite occurring as xenocrysts in basic volcanic rocks and tuffs, and as a phase in garnet-pyroxene xenoliths from such rocks, is probably of upper mantle origin, and may be the important potassium-bearing phase in this region.

scholarly journals Mantle transition zone thickness beneath Cameroon: evidence for an upper mantle origin for the Cameroon Volcanic Line

2011 ◽  
Vol 187 (3) ◽  
pp. 1146-1150 ◽  
Author(s):  
Angela Marie Reusch ◽  
Andrew A. Nyblade ◽  
Rigobert Tibi ◽  
Douglas A. Wiens ◽  
Patrick J. Shore ◽  
...  
Keyword(s):  
Transition Zone ◽  
Upper Mantle ◽  
Mantle Transition Zone ◽  
Cameroon Volcanic Line ◽  
Mantle Origin

Co–Ni arsenide deposits, with accessory gold, in ultramafic rocks from Morocco

1986 ◽  
Vol 23 (10) ◽  
pp. 1592-1602 ◽  
Author(s):  
Marc Leblanc
Keyword(s):  
Upper Mantle ◽  
Carbonate Rocks ◽  
Ultramafic Rocks ◽  
Hydrothermal Solutions ◽  
Average Content ◽  
Mantle Origin ◽  
Upper Proterozoic ◽  
Mantle Peridotites ◽  
Gold Bearing

A type of Co–Ni arsenide deposit with accessory gold and no silver can be recognized in ultramafic massifs of upper mantle origin. The Bou Azzer deposits (50 000 t Co) are distributed along the borders of serpentinite massifs in an Upper Proterozoic ophiolite (Anti-Atlas, Morocco). They consist of quartz–carbonate lenses with Co (Ni–Fe) arsenides. Gold is related to the skutterudite (8–15 ppm average content). In the Alpine lherzolite massif of Beni Bousera (Rif, Morocco) are found small chromite–Ni arsenides veins (300 t Ni) with accessory gold. They are associated with late orthopyroxene–vermiculite dikes. Several occurrences of As, arsenides, and gold-bearing carbonate rocks are found in serpentinites from various ophiolites. It is proposed that gold was leached by As- and Co2-rich hydrothermal solutions related to the serpentinization of mantle peridotites.

Sign in / Sign up

Export Citation Format

Share Document