Patchy charnockites from Jenapore, Eastern Ghats granulite belt, India: Structural and petrochemical evidences attesting to their relict nature

The charnockite patches that occur within leptynite host, in and around Jenapore, northern sector of the Eastern Ghats granulite belt, are disposed in a linear fashion and generally have sharp lithological contact with the host leptynite. Sometimes the patches and foliations of the host are cofolded. Also, the patches sometimes have the internal S1 foliation, while the host leptynite records only S2 foliation. Mineralogically and chemically patchy charnockites and host leptynites are distinct entities, and cannot be related by any prograde and retrograde reactions. Particularly important is the peraluminous granitic composition and high Rb/Sr ratios of the leptynites, presumably resulting from biotite-dehydration melting; as against metaluminous granodioritic to tonalitic composition and low Rb/Sr ratios of the patchy charnockites, presumably resulting from hornblende-dehydration melting. The charnockite patches here can be interpreted as caught up patches or xenolith within granitic melt (leptynite). Mg-rich rims of garnet in the charnockite patch were probably caused by heat from the crystallising melt or decompression during ascent of melt.