Petrography of iron skarn at Khao Lek Amphoe Nong Bua, Changwat Nakhon Sawan

Abstract

Skarn is a metamorphic rock occurred by contact metasomatism between igneous and country rocks which generally is carbonate host. It usually forms as replacement both in igneous, endoskarn, and in country rocks, exoskarn. In exoskarn, it commonly has mineral zonation based on dominant minerals in each zone. Those zones commonly consist of garnet skarn, pyroxene skarn and wollastonite or pyroxenoid skarn. Moreover, from previous works, they found that ore mineralization is commonly formed at boundary between endo- and exoskarn or between exoskarn and non-metasomatized rocks. Khao Lek Fe skarn deposit situates in the western part of Loei Fold Belt. Its host rocks of Khao Lek skarn consists of volcanic and carbonate rocks. So, study about skarn zonation in different types of host rock and its evolution maybe help us to interpret and identify location of ore zone. According to petrographic study and field observation, the result that Khao Lek skarn is iron skarn deposit. The result shows that types of host affected to skarn extension and mineralization also. Skarn in volcanic host commonly extended less than in carbonate host. Moreover, from microscopic observation, the proximity of skarn caused petrographical variation in garnet crystals. The proximal zone is usually containing anisotropic and zoned garnet rather than in distal zone. The interpretation of Khao Lek skarn evolution and is that the magma causing iron skarn deposit should come as small intrusive body because it is occurred as local scale.