Experimental determination of kyanite-andalusite and andalusite-sillimanite equilibria; the aluminum silicate triple point

The low-pressure partial-melting behaviour of natural boron-bearing metapelites from the Mt. Stafford area, central Australia

“…4) Neither quartz, nor andalusite was completely consumed in the melting reactions of MTS7 and MTS8, indicating the persistance of andalusite to temperatures significantly higher than those of the wet solidus temperatures and also the proposed andalusite-sillimanite curves proposed by Holdaway (1971), Pattison (1992) or even the highest temperature position of the boundary proposed by Richardson et al (1969). This metastability of andalusite is supported by field evidence (Greenfield et al, 1998) and petrogenetic evidence (White et al, 2003).…”

“…This suggests that boron influx into a high-grade metasediment, for example as a component in an infiltrating fluid phase, at near solidus conditions would result in tourmaline precipitation, not substantial partial melting. It is possible that the andalusite to sillimanite transition preserved at Mt Stafford does not occur at the same conditions as the many calculated or experimentally derived andalusite to sillimanite reactions and the metastable persistence of aluminosilicate minerals outside their stability range is well documented in a number of studies (Richardson et al, 1969;Holdaway, 1971;Pattison & Harte, 1985Kerrick & Spear, 1988;Kerrick, 1990;Pattison & Tracy, 1991;Pattison, 1992;Kerrick, 1990;Pattison , 2001;Cesare et al, 2003;Droop & Moazzen, 2007). Field evidence suggests that andalusite may persist, along with sillimanite, in many of the Mt Stafford rocks to Zone 4 conditions (Greenfield et al, 1998), which corresponds to approximately 680 ˚C at 3 kbar.…”

“…Several of these studies of metapelitic andalusite-sillimanite phase equilibria in low-pressure settings (relavant to andalusite + melt stability) rejected the Holdaway (1971) curve because it was impossible to reconcile the andalusite stability field with other phase equilibrium constraints (Vernon, 1982;Vernon et al, 1990;Pattison & Tracy, 1991;Pattison, 1992;Johnson & Vernon, 1995), but Pattison (1992) provided a calculated position midway between the Holdaway (1971) and Richardson et al (1969) positions. This allows for an andalusite + haplogranitic melt stability field below 3 kbar, without the need of F, B, Li or excess Al components in the melt (Clarke et al, 2005).…”

Andalusite and Na- and Li-rich cordierite in the La Costa pluton, Sierras Pampeanas, Argentina: textural and chemical evidence for a magmatic origin

“…7). Moreover, the field for potentially magmatic andalusite is even larger and probably more realistic, if the Richardson et al (1969) andalusite-sillirnanite equilibriurn curve is considered ( Fig. 7; curve R69).…”

Metamorphic development of cordierite-bearing layered schist and mica schist in the vicinity of Savonranta, eastern Finland

“…The triple point of the aluminosilicate polymorphs used in Figure 5 is that calibrated by Holdaway (1971) at 501°C and 3.76 kb. The other triple point commonly used in the literature is that of Richardson et al (1969) at c. 630°C and 5.5 kb, but this greatly reduces the size of the silliminate stability field below the minimum melting curve for AbOr-Qtz (c.f. Thompson 1976).…”