基隆火山群為臺灣著名的熱液礦床區域，且位於東北季風盛行地帶，本研究依據不同高程及火成岩產狀有系統採集樣品，利用岩象、X光繞射分析法、能量分散式螢光光譜儀以及風化及蝕變指數，探討位處於熱液礦床區域的安山岩在風化作用下的特徵。
本研究結果顯示，基隆火山群有三種安山岩，分別含石英普通角閃石玄武質安山岩、含石英普通角閃石安山岩及含石英直輝石普通角閃石玄武質安山岩。基隆山、本山及牡丹山所屬岩性相當，然而，草山及雞母嶺含鐵鎂礦物的種類多及含量高，因此，前者以風化指數 (Parker’s Index)，後者則以斜長石風化指數 (PIA)能夠清楚表達地球化學元素變化與礦物轉變。另外，本研究中以蝕變作用為主時，會有方矽石產生；而以風化作用為主時，會出現蒙脫石及綠泥石。
The Keelung Volcano Group is famous hydrothermal deposit of Taiwan, and it sites in the northeast monsoon zone. This study systematically collected samples from different elevation and occurrence by petrography, X-ray diffraction, energy dispersive X-ray fluorescence and indexes of weathering and alteration. Finally, this research aims to understand the characteristics of andesite in hydrothermal deposit of weathering.
The results of this study shown that there have hornblende basaltic andesite with quartz, hornblende andesite with quartz and orthopyroxene hornblende basaltic andesite with quartz in the The Keelung Volcano Group. The KeelungShan, BenShan, and MutangShan belong to the hornblende (basaltic) andesite with quartz that Parker’s index would be displayed the characteristics of geochemistry and mineral assemblages. However, the TsaoShan and Chimuling are orthopyroxene hornblende basaltic andesite with quartz that plagioclase index would be presented the variation of geochemistry and mineral assemblages. Additionally, the cristobalite shown in hydrothermal alteration, and montmorillonite and chlorite displayed in weathering.
