"Rock of the Month # 65, posted for November 2006" ---

The Odegardens Verk apatite mines in south Norway (Cappelen, 1965) display an altered metagabbro known as odegaardite (odegardite). Sample 321.12 (to the right), collected 01 April 1975, is composed of circa 60% scapolite and 40% hornblende, plus traces of rutile and apatite. It is a recrystallized rock, with brown pleochroic hornblende and scapolite veining. Sample 321.9 (at left) is a chloritic, presumably retrograded variant. The phosphates at the locality are well-documented (e.g., Dunn, 1977; Lieftink et al., 1994; Warnock et al., 1997).

The Bamble sector along the south coast of Norway is noted for its excellent exposure of diverse lithologies subjected to upper amphibolite to granulite facies regional metamorphism. This deep crustal terrane includes a range of gabbroic rocks of broadly Grenvillian (Sveconorwegian, circa 1100 Ma) age. The area has been subject to Sveconorwegian metamorphism (O'Nions and Baadsgaard, 1971). The local mid-Proterozoic mafic intrusions range from subordinate ultramafic rocks to a variety of gabbros and norites, often displaying corona textures (Alirezaei and Cameron, 2002). See also the entry for krageroite (another metagabbro).

References

Alirezaei,S and Cameron,EM (2002) Mass balance during gabbro-amphibolite transition, Bamble sector, Norway: implications for petrogenesis and tectonic setting of the gabbros. Lithos 60, 21-45.

Cappelen (1965) Cappelens Bil-og Turistkart, dobbeltblad 1-2. J.W. Cappelens forlag, Oslo, tourist map, sheets 1-2 (1:325,000 scale).

Dunn,PJ (1977) Apatite: a guide to species nomenclature. Mineral.Record 8 no.2, 78-82.

Lieftink,DJ, Nijland,TG and Maijer,C (1994) The behaviour of rare-earth elements in high-temperature Cl-bearing aqueous fluids: results from the Odegardens Verk natural laboratory. Can.Mineral. 32, 149-158.

O'Nions,RK and Baadsgaard,H (1971) A radiometric study of polymetamorphism in the Bamble region,Norway. Contrib.Mineral.Petrol. 34, 1-21.

Warnock,AC, Zeitler,PK, Wolf,RA and Bergman,SC (1997) An evaluation of low-temperature apatite U-Th/He thermochronometry. Geochim. Cosmochim. Acta 61, 5371-5377.