Rb-Sr and K-Ar age determinations of the granitic rocks in the southern part of the Kyeongsang basin, Korea: Implication for cooling history and evolution of granitic magmatism during late Cretaceous
Rb-Sr and K-Ar age determinations of the granitic rocks in the southern part of the Kyeongsang basin, Korea: Implication for cooling history and evolution of granitic magmatism during late Cretaceous
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韩国庆尚盆地南部花岗岩的 Rb-Sr 和 K-Ar 年龄测定：对晚白垩世花岗质岩浆作用冷却历史和演化的启示
DOI：
10.2343/geochemj.29.363
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发表时间：
1995
影响因子：
0.8
通讯作者：
K. Nagao
中科院分区：
文献类型：
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作者：
J. I. Lee;H. Kagami;K. Nagao
对韩国庆尚盆地南部晚白垩世花岗质岩石进行了Rb-Sr全岩等时线年龄和K-Ar矿物年龄测定。根据岩石学特征，将花岗岩分为4个区域（马山、镇海、金海和釜山）的7种。5个岩体的Rb-Sr全岩等时线年龄和同位素初始比值测定结果如下： Rb-Sr全岩年龄 初始Sr比率Masan Hbbtgr 100.1 ± 7.1 Ma 0.70489 ± 0.00012 Jinhae Btgr 70.5 ± 1.9 Ma 0.70497 ± 0.00006 Kimhae Hbbtgr 83.9 ± 9.0 Ma 0.70538 ± 0.00021釜山Btgr（YS） 70.6 ± 4.2 Ma 0.70531 ± 0.00029釜山Btgr（KP） 68.8 ± 3.4 Ma 0.70579 ± 0.00028 Rb-Sr全岩年龄随着长英质含量的增加和规模的减小而逐渐变年轻，反映了源区熔融程度随时间的推移而逐渐降低。各岩体的初始Sr比值从西部向东部逐渐增大，与其年龄无关。这意味着由于下地壳物质的贡献很大，花岗岩岩浆更多地向东部地区演化。黑云母的K-Ar年龄约为300 ~ 1500万年。各深成单元的Rb-Sr全岩等时线年龄小于Rb-Sr全岩等时线年龄。各岩体的平均冷却速率与岩体体积成正比。大的热反差引起的热传导损失和浅部花岗岩体与围岩之间循环的大气降水被认为直接影响了每个岩体的平均冷却速率。研究区花岗岩的初始Sr同位素比值与九州中部至北方和日本西南部的北带具有良好的相关性。从九州中部（120-100 Ma）到北方（115-90 Ma）再到庆尚盆地南部（100-70 Ma），白垩纪花岗岩的Rb-Sr等时线年龄逐渐变年轻。阳三断层东侧70 Ma的花岗质岩浆活动与日本西南部北带的花岗质岩浆活动有较好的对应关系。
Abstract-Rb-Sr whole rock isochron ages and K-Ar mineral ages have been determined for late Cretaceous granitic rocks distributed in the southern part of the Kyeongsang basin, Korea. The granitic rocks are grouped into seven in four areas (Masan, Jinhae, Kimhae and Busan) based on their petrological features. In the five plutons, Rb-Sr whole rock isochron ages and isotopic initial ratios were determined as follows: Rb-Sr whole rock age Initial Sr ratioMasan Hbbtgr 100.1 ± 7.1 Ma 0.70489 ± 0.00012Jinhae Btgr 70.5 ± 1.9 Ma 0.70497 ± 0.00006Kimhae Hbbtgr 83.9 ± 9.0 Ma 0.70538 ± 0.00021Busan Btgr (YS) 70.6 ± 4.2 Ma 0.70531 ± 0.00029Busan Btgr (KP) 68.8 ± 3.4 Ma 0.70579 ± 0.00028 Rb-Sr whole rock ages become younger toward more felsic and smaller plutons, which is thought to reflect progressive lowering in melting degree at the source with time. Initial Sr ratios of each pluton progressively increase from the western to eastern areas, regardless of their ages. This means that the granitic magmas have been more evolved toward the eastern area due to much contribution from lower crustal materials. K-Ar ages of biotite are about 3 to 15 m.y. younger than Rb-Sr whole rock isochron ages in each plutonic unit. Average cooling rate of each body is directly proportional to the volume of granitic body. The conduction-loss of heat due to large thermal contrast and the circulating meteoric water between a granitic body and the country rock at shallow levels are thought to have directly affected the average cooling rate of each body. Initial Sr isotopic ratios of the granitic rocks in the study area are well correlated with those of the central to northern Kyushu and the North Zone of Southwest Japan. Rb-Sr isochron ages of the Cretaceous granitic rocks became younger from central Kyushu (120-100 Ma) through northern Kyushu (115-90 Ma) to southern part of the Kyeongsang basin (100-70 Ma). The granitic magmatism having 70 Ma ages on the eastern side of the Yangsan Fault is thought to be better correlated with those of the North Zone of Southwest Japan.
影响因子：
3.5
作者：
H. Kagami;S. Iizumi;Y. Tainosho;M. Owada
通讯作者：
H. Kagami;S. Iizumi;Y. Tainosho;M. Owada
刘J.G.；王晓敏；科尔曼，R.G.；张Zh.M.；Maruyama，S.：构造学。
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