Mineralogy and Petrology (2001) 72: 77±111 Phase relations of calc-silicate assemblages in the Auerbach marble, Odenwald Crystalline Complex, Germany E. Schma Èdicke 1 , M. Okrusch 2 , W. Schubert 2 , B. Elwart 2 ,and U.GoÈrke 2 1 Institut fu Èr Mineralogie, Technische Universita Èt Darmstadt, Darmstadt, Federal Republic of Germany 2 Mineralogisches Institut, Universita Èt Wu Èrzburg, Wu Èrzburg, Federal Republic of Germany With 9 Figures Received July 29, 1999; accepted March 28, 2000 Summary In the Odenwald Crystalline Complex, calc-silicate rocks are concentrated at the marginsof the marblelayer of Auerbach.They werepresumably formedby metasomatic exchange between the calcite marble and the neighbouring granodioritic and quartz-dioritic intrusives. The investigated samples contain thecharacteristic mineral assemblages: garnetclinopyroxeneepidote/clinozoisitecalcitequartz titanite (1) and wollastoniteclinopyroxenegarnetcalcitequartzepidote/clinozoi- sitetitanite (2).Microprobe analyses revealed the following compositional ranges: garnet grs 40ÿ98 adr 2ÿ55 alm <5:5 sps <5:5 pyp <1 ; clinopyroxene di 46ÿ88 hed 9ÿ47 joh 0ÿ5 cats 0ÿ6 ; epidote/clinozoisite ps 20ÿ80 . Differentphase diagrams were calculated in the system CaO-MgO-Al 2 O 3 -TiO 2 -SiO 2 -CO 2 -H 2 O (CMATSCH) to decipher the P-T-X CO 2 para- meters of metamorphism: isobaric T-X CO 2 sections and a P-T projection with mixed volatiles. The phase diagrams illustrate that the observed assemblages can only form in the presence of an H 2 O-rich volatile phase. The assemblages are stable over a large range of temperatures, from 580C to < 400C (at 4 kbar) and at X CO 2 values of less than 0.055 (at 4 kbar). Higher temperatures can be inferred from reaction textures which indicate that garnetplagioclase (T > 580 C, at 4 kbar) and wollastoniteplagioclase (T > 660C, at 4 kbar)coexisted during an early metamorphic stage. A minimum pressure of 3.5 kbar can be inferred for the early high-temperature stage. Furthermore, on the basis of the calculated phase diagrams, combined with modal abundances in thin sections, it is possible to evaluate ¯uid behaviour; in the investigated specimens, in®ltration of ¯uids from an external reservoir occurred. A minimum ¯uid : rock ratio of 3.6 : 1 can be estimated.