Petrogenesis of Intrusive Rocks in Galela, North Halmahera Regency, North Maluku Province

Abstract

Halmahera Island has a row of volcanoes stretching from North to South, known as the Halmahera volcanic belt. In general, intrusive rocks in the belt are associated with the potential for mineral deposits such as those in the Gosowong gold deposit (PT. NHM). This condition provides an opportunity to find considerable mineral resource potential in North Halmahera, so research related to the genesis of intrusive rocks carrying mineralization (host-rock) needs to be carried out comprehensively to understand the genesis to the characterization of magma. The study aims to understand the genesis and characterization of magma and to conduct initial investigations related to the fertilization of magma in the research location. The study was conducted using the surface mapping and sampling of intrusive rocks carrying mineralization in the research area. Furthermore, it was analyzed petrographically and geochemically—geochemical analysis using X-ray fluorescent (XRF) to determine the levels of oxide elements in rock samples. From the petrographic data, the rocks in the research area can be classified as a hornblend diorite. The whole-rock geochemical analysis (XRF) results show an average composition of SiO2 (49.87-55.18 wt.%), Al₂O₃ (17.74-20.00 wt. %), CaO (9.25-13.03 wt. %), Fe₂O₃ (5.57-10.14 wt. %), Na₂O (3.31-4.22 wt. %), MgO (1.96-2.95 wt. %), K₂O (1.20-2.60 wt. %), TiO₂ (0,79-1.06 wt. %), MnO (0.18-0.31 wt. %), P₂O₅ (0.13-0.31 wt. %). Based on the geochemical classification of intrusive rocks in the research area, they are included in the gabbroic-diorite group. In general, intrusive rocks in the research area are affiliated with a series of calc-alkaline magmas with intermediate characteristics formed in tectonic settings associated with oceanic arcs.