Zn-rich spinel in association with quartz in the al-rich metapelites from the Mashan khondalite series, NE China

Abstract

Al-rich metapelites from the Mashan khondalite series are characterized by the assemblage Spl+Grt+Sil+Crd+Bt+Pl (An72)+Kfs+Quartz+graphite. Large amounts of spinel+quartz assemblages occur as inclusions in garnet and prismatic sillimanite in the Al-rich metapelites of the Mashan complex, NE China. The chemical composition of spinel is characterized by Zn-rich (X Zn=0.33–0.40. X Zn=Zn/Zn+Mg+Fe*) (Fe*=Fe2++Fe3+) and Fe3+ rich (up to 0.31 p.f.u.). The characteristic chemical composition and the mineral association indicated that the formation of spinel and quartz assemblage may be due to the breakdown of Zn-rich staurolite. The geothermobarometers studies show that the peak temperature of the Mashan complex is around 820 °C and the peak pressures is 8.0 kbar. The Mashan complex shows a typical orogen style P-T path.