The Fuxing hypabyssal suite of igneous rock in early Miocene age is exposed in Fuxing Bridge, Chiaopanshan area of Taoyuan County, Taiwan. Several studies were conducted for mineralogy, petrology, and geology of Fuxing hypabyssal suite in last several decades. Previous studies suggest that the Fuxing hypabyssal suite occurs as a laccolith and igneous rocks (picrite, diabase, trachydiabase, and soda trachyte from bottom to top) are differentiated from one source after one magma activity. However, according to the field investigation and optical analysis of this study show that picrite and trachyte with cumulative and poikilitic texture, so we modify the name of rocks as a picrite porphyry and soda trachyte porphyry. Noted that obvious prehnite – pumpellyite and other minerals occur in picrite porphyry and diabase, abundant chlorite and calcite occur in soda trachyte porphyry. Their difference is indicating that two types of ultramafic/basic rock have been altered by very low - grade metamorphism into prehnite – pumpellyite facies, but the intermediate rock (soda trachyte porphyry) underwent diagenesis/zeolite (?) facies. The result of this study reveals that those two rocks could be derived from different igneous activities.
