The north-eastern Polish anorthosite massifs: petrological, geochemical and isotopic evidence for a crustal derivation
✍ Scribed by Janina Wiszniewska; Stefan Claesson; Holly Stein; Jacqueline Vander Auwera; Jean-Clair Duchesne
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 775 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0954-4879
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✦ Synopsis
ABSTRACT Deeply buried 1.5 Ga Polish anorthosites, accessible only by bore holes, reveal diagnostic features of some massif‐type anorthosites (polybarism, jotunitic parent magma), diapirically emplaced in the mid crust together with the rapakivi granites of the EW‐trending Mazury complex, intruded along a major crustal discontinuity. Geochemical modelling and isotope data corroborate recent experimental work on the basaltic system in dry conditions: the source rock of the parental magma is a gabbronorite, necessarily lying in the lower crust. Since no Archaean crust is known in the region, high initial ^188^Os/^187^Os ratios for sulphide‐oxide isochrons and negative ε~Nd~ values are best accounted for by melting a ∼ 2.0 Ga mafic crust.