Abstract
Quartz occurs ubiquitously in felsic plutons. The development of a methodology to reveal the quartz growth process in a granitic body provides essential insights into magma chamber processes. Cathodoluminescence (CL) characterization combined with Ti concentration of quartz crystals in granite is a prevalent tool for identifying the crystal growth and crystallization temperature of quartz in granitic magmas. This study focused on quartz crystal growth in the Kuki granite (KKG), northeast Japan, and Kurobegawa granite (KBG), central Japan. In the KKG quartz crystals, the difference in luminescence corresponds to Ti concentration: high luminescence corresponds to high Ti concentrations, which is consistent with our previous studies on the Toki and Okueyama granites. In the KBG quartz crystals, the Ti concentrations do not correspond to the luminescence level, whereas the Al concentrations are negatively correlated with the luminescence level. Therefore, quartz crystallizations in KKG and KBG are characterized by Ti- and Al-diffusion-controlled growth, respectively. Using the difference in the time-temperature history among the target rock bodies, this study provides insight into the nature of the relationship between quartz crystallization and magma chamber processes. Quartz crystallizations in the KKG were accompanied by gradual variations from oscillatory zonation through gradual zonation to homogeneous CL patterns with decreasing temperature in the cooling magma chambers. The quartz internal structure of the KBG was resulted from the rapid cooling of the KBG magma and the scarcity of Ti and enrichment of Al in the magma during quartz crystallization.
