Hydrothermal vein distribution in skarn type alteration zone of area X at PT. Freeport Indonesia

Kucing Liar is an economic skarn altered deposited located in Tembagapura, Papua. This deposit was found on Late Cretaceous to Miocene sedimentary rocks of Kembelangan Group and Papua New Guinea Limestone Group. The alteration from this deposit can be divided into groundmass alteration, named penetrative alteration, and selvage alteration forming hydrothermal veins. The penetrative alteration is divided into 9 zones, meanwhile the hydrothermal veins are classified by its mineral composition into 5 types of anhydrite veins, calcite, quartz, sulphide, and gypsum veins. Each vein type will associate the most with different penetrative alteration zone due to its protolith composition and on what stage the vein formed. The anhydrite and quartz veins are found to be associated the most with calc-silicate hornfels zone with the anhydrite sources came from calcite and quartz sources came from the surrounding rocks which the alteration fluid passed through. The sulphide and calcite veins are found to associate the most with dolomitization zone with calcite sources came from the surrounding rock and sulphide deposited filling the open spaces, such as fracture, in crystalline dolostone. Gypsum veins are found to associate the most with fault zone because it formed from the alteration of calcite by faulting process.