
doi: 10.1007/bf00371463
Experimental investigation of the fluid absent melting reaction biotite+plagioclase+A12SiOs+quartz~ garnet + K-feldspar + melt at 10 kbar, indicated that melt- ing began between 760 and 800~ and was extensive at 850 ~ C. This reaction apparently has a positive dP/dT at least up to 10 kbar, compared to a calculated backbending in a simplified system. Natural biotites are stabilised to higher dehydration melting temperatures probably by Ti. Consequently, metapelites undergo two-stages of fluid-ab- sent melting even in thickened, continental crust. The two stages firstly as muscovite, and secondly as biotite react, appear to persist to at least 17 kbar, depending upon biotite composition. This lies well within the stability field of kya- nite migmatites. Thus, complex petrogenetic grids can be computed from the little available data over a wide range of P-T-Xroek-XH20 conditions. Microprobe analyses indicate good correlations with the Fe/Mg garnet + biotite exchange thermometer and the garnet +plagioclase +A12SiO5 + quartz barometer at 850 ~ C, 10 kbar. Furthermore, micro- probe analyses show that vGar'" Liq .~.yBio in fluid-absent ~x Fe f Fe t- .l Fe as well as in HzO-saturated pelite anatexis. Thus intermedi- ate Fe/Mg compositions, containing Bio, Gar, Als, Plg, Ksp, Qtz will eutectically melt before Fe-richer or Mg-richer metapelites. If the partition VG,r/vLiq reverses with increas- " Fe /~x Fe
550.geology, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU.PE] Sciences of the Universe [physics]/Earth Sciences/Petrography, Article
550.geology, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU.PE] Sciences of the Universe [physics]/Earth Sciences/Petrography, Article
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