Mineralogy of clinozoisite amphibolites in the Khitoostrov occurrence of corundum-bearing rocks

[Marco E. Ciriotti]

Referenza:
▪ Akimova, E.Yu. & Skublov, S.G. (2023): Mineralogy of Clinozoisite Amphibolites in the Khitoostrov Occurrence of Corundum-bearing Rocks (Fenno-Scandinavian Shield). Zapiski RMO, 152(3), 59-81.

Abstract:
A study was carried out of the mineral composition (major and rare earth elements) of clinozoisite amphibolites, closely associated with corundum-bearing rocks at the Khitoostrov occurrence (North Karelia). Clinozoisite amphibolites contain ferruginous phlogopite containing more Al than ferruginous phlogopite from the host garnet amphibolites; calcium amphibole of the tschermakite–pargasite–sadanagaite series; Basic plagioclase, absent in the host rocks, and margarite appear. Reaction relationships between minerals are noted: plagioclase-amphibole symplectites around garnet porphyroblasts, the development of clinozoisite over calcium amphibole. Some of the minerals (clinozoisite, calcium amphibole) acquire distribution spectra of rare earth elements (REE) that are not characteristic of them, inheriting them from the replaced minerals in the areas of distribution of reaction structures: calcium amphibole inherits the spectrum of garnet, and clinozoisite inherits the spectrum of calcium amphibole. The hypothesis about the metasomatic origin of clinozoisite amphibolites and the redistribution of REE under the influence of fluid are discussed.