Petrology and thremochronological study for youngest exposed pluton of the World

本文对第四纪泷谷花岗闪长岩和晚上新世黑河花岗岩进行了热年代学古地磁和地质研究，以阐明它们的冷却历史和侵位机制。主要研究结果如下：泷谷花岗闪长岩和黑北川花岗闪长岩的古地磁方向由于其剩磁不稳定而无法确定。2 .上述花岗质岩体顶板火山岩由于飞驒山脉东半部地区的东倾作用，剩磁极性反转，方向东移。这两个花岗岩岩体在其西部接触处沿南北向逆断层表现出强烈的糜棱岩化结构。Takidani花岗云母的K-Ar年龄（1.4 ~ 1.0 Ma）系统地向底部年轻化，可以用深部冷却开始较慢来解释。这样的降温历史可能受到飞驒山脉东半部地区的东倾和隆升的影响。约1.0 Ma时，泷谷岩体在冷却过程中发生糜棱岩位移。

Thermochronological paleomagnetic and geological studies have been carried out on the Quaternary Takidani Granodiorite and the Late Pliocene Kurobegawa Granite in order to elucidate their cooling history and the mechanism for emplacement. Major results are as follows.1. Paleomagnetic directions for both the Takidani Granodiorite and the Kurobegawa Granite could not determine for unstability of remanent magnetization of them.2. Roof volcanic rocks of the above granitic pluton show reversed polarities of remanent magnetization with east-shifted directions as the result of eastward tilting of eastern-half area of the Hida Mountain Range.3. Both the granitic pluton show strongly mylonitized texture along the N-S tending reverse faults at their western contact.4. Systematic bottomward younging of biotite K-Ar ages (1.4 Ma to 1.0 Ma) for the Takidani Granodairite can be explained by the slower start in cooling at deeper level of the pluton. Such a cooling history may be affected by the eastward tilting and uplifting of the eastern-half area of the Hida Mountain Range. Mylonitic displacement took place during the cooling process of the Takidani Pluton about 1.0 Ma.