High-pressure alteration of eclogites from the Austroalpine basement north of Merano-Meran (Eastern Alps)
European Journal of Mineralogy Volume 3 Number 5 (1991), p. 895 - 898
published: Oct 2, 1991
manuscript accepted: Apr 25, 1991
manuscript received: Mar 19, 1991
ArtNo. ESP147050305011, Price: 29.00 €
Abstract Records of an eclogite stage followed by high-pressure alteration (HPA) of the eclogitic mineral assemblage were recognized in some metabasic rocks outcropping within the Austroalpine Merano-Mules basement. During HPA, Cpx I and phengitic mica, both phases belonging to the eclogitic mineral assemblage, were altered to symplectites due to the reactions : (1) Cpx I + K+ + H2O = Cpx II + Pl + Am II + Na+ + Ca2+, (2) Phe + Qtz + Na+ + Ca2+ = Bt + Pl + K+ + H2O. The pressure conditions prevailing during reaction (1) were evaluated by the Jd content of Cpx II, giving an equilibrium pressure of 9 kbar.