The internal field trip of SEG UGM SC was held in Gupit, Kebonsari, Magelang at 23rd April 2016. The fieldtrip was guided by Mrs. Dian Yesy Fatimah, S.T. Fieldtrip started at 10 am until 2.30 pm. The first observation placed on Dusun Ngadiharjo. The first location was interpreted by the previous observer as high sulfidation epithermal deposits. High sulfidation epithermal deposits is result from hydrothermal fluid activity in the hipabisal depth at 1-1,5 kilometers, with low temperature that about 50-300 C. High sulfidation epithermal deposits controlled by geological structural in this zone because, the hydrothermal fluid can move upward through the weak zone and usually the weak zone is fault. High sulfidation epithermal deposits is characterized by vuggy silica texture and clay mineral that formed in high temperature condition such as dickite, alunite, pyrofilit. The hydrothermal alteration that happened in Gupit Hill is consisting of Propilitic, Argilic, Advance Argilic and silicification alteration.
In the first STA, we can see the Propylitic alteration that has some typical mineral, such as chlorite, epidote. In the first STA, there is a body rock that already controlled by geological structure, that is joint. The joint caused the hydrothermal fluid move upward, so the wall rock’s texture and minerals are replaced and become new minerals. In the first STA, we saw the altered rock that consist some minerals like chlorite and epidote, also oxide mineral that have black red color.