印尼爪哇之新生代岩漿活動與區域構造演化研究

Cenozoic magmatism in Java Island were formed from the Indo-Australian Plate subducted beneath the Eurasian Plate. According to the tectonic structures, Java can be separated into three blocks, i.e., the West Java, the Central Java, and the East Java. This study focus on five volcanic bodies from the western West Java area: Danau Volcanic Complex, North Bayah Dome, South Bayah Dome, Gede Volcanic Complex, and Ciemas Area. A total 55 volcanic rock samples were collected, and 19 of them were finished the petrography study while 14 of them were dated by zircon U-Pb method. Petrography study show that almost all samples content the plagioclase, hornblende, orthopyroxene, and clinopyroxene and some samples show additional quartz or olivine phenocrysts. Most of these samples content groundmass less than 50%, and some of them went through the metasomatism or alteration. Zircon U-Pb results show that two young (<0.6 Ma) samples in Danau Volcanic Complex. One inherited zircon age (~140 Ma) and several magmatic satges (i.e., 0.7 Ma, 5.4 Ma, 9.3-9.9 Ma, and 11.4-11.6 Ma) can be identified in the North Bayah Dome. South Bayah Dome has several magmatic stages (12.3-12.6 Ma, 14.2 Ma, and 16.7 Ma). One magmatic zircon age could be found in the Ciemas Area. Based on our results, the distribution of Cenozoic magmatism in the western West Java area show different characteristics between the Tertiary and Quaternary volcanics. In Bayah Dome area, Tertiary magmatism shows progressively younger from south (16-12 Ma) to north (11-5.4 Ma). Quaternary magmatism could be found in the whole western West Java. In addition, the inherited zircons (~140 Ma) in the northern part of this area could provide evidence to prove that the Cretaceous volcanic arc in the southern Sumatra exactly extended to the West Java.