The Lassi mass, Southeast of lake singkarak is a complex rock assemblage of permo-Carboniferous volcanics and sediments and Triassic Duringg Permo-Carboniferous volacanic and sediments and Triassic deposits, intruted by plutons and partly overlain by Tertiary sediments. During Permo-Carboniferous time this area was occupied by an elongated sea basin…