Metasomatically altered peridotite xenoliths from the Hessian Depression (Northwest Germany)

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90196-R· OSTI ID:6702184

Hartmann, G; Wedepohl, K H ^[1]

---

1. Univ. of Goettingen (Germany, F.R.)

A set of 36 spinel lherzolite and spinel harzburgite xenoliths from 7 occurrences of Tertiary alkali olivine basalt and olivine nephelinite have been investigated for modal composition, major elements, and 39 minor elements. The periodotites were depleted during former partial melting events. The proportion of clinopyroxene, elements indicating depletion, and compatible trace elements are on average close to the means of the worldwide subcontinental lithosphere. The metasomatic alteration of the sampled mantle varies in a complicated three-dimensional pattern without vertical layering. Mobilization of elements in mantle fluids and accumulation in certain peridotites is a complex open-system process. The exceptional behavior of high field-strength elements might be controlled by the formation of Ti minerals. The metasomatic transport can be explained by extraction of the incompatible elements either from mantle minerals or from subducted crustal sources into water-rich fluids. Chlorine in phlogopite has equilibrated with fluids containing chloride concentrations close to seawater. Values of {delta}{sup 18}O in bulk peridotites and in phlogopite exceeding typical mantle compositions probably reflect a crustal contribution to the metasomatic fluids. Nd and Sr isotopic ratios of both peridotites and alkali basalts received a crustal signature from an environment with time-integrated LREE accumulation and Rb depletion.

• OSTI ID: 6702184
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:1; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ABUNDANCE
BASALT
CENOZOIC ERA
CHEMICAL COMPOSITION
ELEMENT ABUNDANCE
EUROPE
FEDERAL REPUBLIC OF GERMANY
GEOLOGIC AGES
GEOLOGIC HISTORY
HYDROTHERMAL ALTERATION
IGNEOUS ROCKS
MAGMATISM
METAMORPHISM
PERIDOTITES
PETROCHEMISTRY
PETROGENESIS
PLUTONIC ROCKS
ROCK-FLUID INTERACTIONS
ROCKS
TERTIARY PERIOD
VOLCANIC ROCKS
VOLCANISM
WESTERN EUROPE