Phosphate and silicate inclusions in apatite and pyroxene from the Precambrian nelsonite and jotunite of NE Poland

Melt inclusions were investigated in apatite from nelsonite from the Suwałki anor-thosite massif and in pyroxene from the Fe–Ti–P-rich monzodiorite (jotunite) from the Sejny massif, both of Proterozoic age and occurring within the ranges of the Mazury crystalline complex in NE Poland. The melt inclusions in apatite were filled by an agg-regate of pyroxene, apatite, calcite, plagioclase, biotite, halite, sylvite, ore mineral plus aqueous solution and gas bubble. At 880oC in the inclusions two melts: silicate and phosphate one, were observed which neither homogenized nor changed their propor-tions up to 1080oC. This indicated the formation of nelsonite from the melt composed of two immiscible phases. Inclusions in pyroxene from jotunite were filled by pyroxene, feldspar, apatite, carbonate and ore mineral with gas bubble. Their homogenization tem-peratures were from 1090 to 1180oC; at 1000 to 1030oC in silicate melt small droplets of carbonate and phosphate melt were visible, homogenizing subsequently in one melt phase. The behaviour of the two melts in the studied inclusions may indicate a genetic affinity of nelsonite with monzodioritic rocks.