The composition of peridotite tectonites from the Ivrea Complex, northern Italy: Residues from melt extraction

Journal Article · Thu Apr 01 00:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90112-A· OSTI ID:6458845

Hartmann, G; Wedepohl, K H ^[1]

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1. Univ. of Goettingen (Germany)

Peridotite tectonites have been analyzed for major elements, forty minor elements, mineral composition, and a subset a samples have been investigated for [delta]D, [delta][sup 18]O, [delta][sup 34]S, and [sup 87]Sr/[sup 86]Sr ratios. The spinel lherzolites from Balmuccia and Baldissero contain on average 56% olivine, 28% orthopyroxene, 14% clinopyroxene, and 1.5% spinel. They have a neodymium and strontium isotopic signature similar to MORB (oceanic ridge basalt). These peridotites were moderately depleted in Al and Ca and highly depleted in incompatible elements by the separation of 4.5% P-MORB. The MORB in excess to the formation and subduction of the oceanic crust fractionated into a tonalitic continental crust and a pyroxenitic residue which was recycled into the mantle. The crustal mass fraction of the upper mantle-crust system is 2.8%. A primitive mantle composition can be calculated from 97.2% Balmuccia model peridotite plus 2.8% bulk crust. The new set of primitive mantle concentrations is in accordance, within about 10%, with the data from fertile peridotite xenoliths and primitive meteorites for the elements Li, Mg, Si, Ca, Sc, V, Mn, Fe, Co, Ni, Zn, Ga, Y, Zr, La, Ce, Nd, Eu, Tb, Dy, Yb, Lu and Hf. Larger differences occur for the elements F, Na, P, Ti, Cr, and Cu. The bulk crust concentrations of the highly incompatible and mobile elements K, Rb, Ba, Th, and U exceed those being supplied from a primitive upper mantle reservoir of 660 km depth. An additional lower mantle source is required for about half of the crustal accumulation of these elements. Moderately depleted peridotite bodies with a cross section of 3 km can be sufficiently well homogenized in compatible and moderately incompatible elements to represent MORB producing upper mantle. Concentrations of Na, Sc, Ti, V, Ga, Y, Zr, and Yb are well correlated with the Al abundance so that primitive mantle values can also be estimated using the cosmically derived primordial Al concentration.

• OSTI ID: 6458845
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:8; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
EARTH MANTLE
CHEMICAL COMPOSITION
PERIDOTITES
QUANTITATIVE CHEMICAL ANALYSIS
ABSORPTION SPECTROSCOPY
CONTINENTAL CRUST
FLUORESCENCE SPECTROSCOPY
GAMMA SPECTROSCOPY
ITALY
OCEANIC CRUST
OLIVINE
PLATE TECTONICS
PYROXENES
SPINELS
STRONTIUM
STRONTIUM 86
STRONTIUM 87
SULFUR 34
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
BETA DECAY RADIOISOTOPES
CHEMICAL ANALYSIS
DEVELOPED COUNTRIES
EARTH CRUST
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EMISSION SPECTROSCOPY
EUROPE
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIGHT NUCLEI
METALS
MINERALS
NUCLEI
OXIDE MINERALS
OXYGEN COMPOUNDS
PLUTONIC ROCKS
RADIOISOTOPES
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPECTROSCOPY
STABLE ISOTOPES
STRONTIUM ISOTOPES
SULFUR ISOTOPES
TECTONICS
400102* - Chemical & Spectral Procedures