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Phase Relations on the Actinolite-Pargasite Join 总被引:1,自引:0,他引:1
Phase relations along the join Ca2Mg4Fe2+Si8O22 (OH)2 (Actinolite)-NaCa2Mg3?2Fe0?82+AlSi6Al2O22(OH)2 (Pargasite) have been studied at PH2O = 1 kb andthe oxygen fugacities defined by the iron-wustite(IW) buffer. Actinolite and bornblende are separated by a solvus and thefield of actinolite+hornblende+vapor is present in the regionbetween Ac85Pa15 and Ac55 Pa45 at 680 ?C. Complete miscibilityis achieved at 720 ?C. At temperatures higher than the solvusthere is a continuous solid solution series between the twoend members. The stability field of amphibole solid solutiongradually increases with increasing pargasite content in actinolite.The phase assemblages at temperatures higher than those of asolid solution series between the two end members change withincreasing pargasite content in the bulk composition as follows;Act+Cpx+Qz+V, ActHbl+Cpx+Opx+Qz+V, Hbl+Cpx+Opx+Pl+V and Hbl+Cpx+Pl+Ol+V. In comparison with the Fe-free system, the extent of the miscibilitygap between actinolite and hornblende is reduced by an increasein the Fe2+ content. The present study should provide an adequatebasis for the interpretation of actinolite-hornblende pairsin metamorphic rocks. 相似文献
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