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Petrological and isotope geochronological study on the uplift of the Hidaka Mountains, Hokkaido, Japan

日本北海道日高山脉隆起的岩石学和同位素年代学研究

基本信息

批准号：
02640590
负责人：
ARITA Kazunori
金额：
$ 1.22万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02640590/
关键词：
Hidaka metamorphic belt mountain uplift Fission track dating K-Ar isotope dating Thrust movement 日高山脈フィッショントラック年代グラニュライト相岩石

项目摘要

The Hidaka metamorphic belt(H. idaka Mountains), Hokkaido, Japan consist of easists -steeply dipping thrust sheet of island arc. The belt increases in metamorphic grade westward up to the granulite facies and thrust over the metamorphosed ophiolite complex on the west along the Hidaka Main Thrust. Sixteen and two K-Ar dates on biotites and hornblendes, respectively and five fission-track dates on zircons have been obtained from tonalites and gneisses and schists of various grades collected from localities with different altitudes on a traverse section through Mt. Kamuiekuutikaushi(1979m)in central part of the Hidaka metamorphic belt in order to examine the uplift(erosion)process and rate of the Mountains.The isotope geochronological data lead to the following conclusions :1. All of K-Ar biotite ages almost agree(17.9-16.3Ma)regardless of their metamorphic grade and altitudes. The fact means that the Present eastward-steeply dipping structure of the metamorphic belt had been already made up before the middle Miocene. Therefore, thrusting of the Hidaka island arc along the Hidaka Main Thrust had begun before that time.2. K-Ar dates on hornblendes and biotites from western granulite-facies rocks reveal the uplift(erosion)rate of the western part of the metamorphic belt reaches up to 6.7mm/a between l8Ma and 17Ma.3. Fission-track ages on zircons range from 15.7Ma Lo 12.4Ma with an exception of 10.9Ma which occurs near a thrust. These ages become younger with increase in altitude of sample locality. The tendency, which is the reverse of what observed generally, suggests that the uplift of the Mountains since middle Miocene age is not simple btit of rotational type.4. K-Ar and fission-track ages show uplift rates of the Mountains to be 3.5-0.8mm/a during the middle Miocene and 0.5-0.3mm/a during interval from the middle Miocene to the present. Thus, the uplift rate of the Hidaka Mountains decreases with time since the end of the early Miocene.

日本北海道日高变质带（H.idaka Mountains）由岛弧状的东亚急倾冲断片组成。该带变质程度向西增加，直至麻粒岩相，并沿日高主冲断层向西逆冲至变质蛇绿岩杂岩上。为了考察日高变质带中部卡姆依库提考西山(1979m)的横断面，在不同海拔地区采集的不同等级的英云闪岩、片麻岩和片岩中，分别获得了16个黑云母和2个角闪石的K-Ar测年以及5个锆石裂变径迹测年。山脉的抬升（侵蚀）过程和速率。同位素年代学数据得出以下结论： 1．所有K-Ar黑云母年龄几乎一致（17.9-16.3Ma），无论其变质程度和海拔高度如何。这一事实表明，现今的东陡变质带构造在中新世之前就已形成。因此，日高岛弧沿日高主冲断带的逆冲在此之前就已开始。2．西部麻粒岩相岩石角闪石和黑云母的K-Ar测年表明，18Ma至17Ma期间，变质带西段的抬升（侵蚀）速度高达6.7mm/a。3。锆石上的裂变径迹年龄范围为 15.7Ma 至 12.4Ma，但逆冲附近出现的 10.9Ma 除外。随着样本所在地海拔的升高，这些年龄变得更年轻。这一趋势与一般观察相反，表明中新世中期以来山脉的隆升并非简单的旋转型隆升。 4． K-Ar和裂变径迹年龄显示，中中新世中期山脉的抬升速率为3.5-0.8mm/a，中中新世至今的抬升速率为0.5-0.3mm/a。因此，自中新世早期结束以来，日高山脉的隆升率随着时间的推移而降低。