Metamorphic K-feldspar in low-grade metasediments from the Ogcheon metamorphic belt in South Korea
Metamorphic K-feldspar in low-grade metasediments from the Ogcheon metamorphic belt in South Korea
复制标题
DOI：
10.1016/s1342-937x(05)70918-7
复制
发表时间：
2002-10
影响因子：
6.1
通讯作者：
S. Kim;T. Itaya;H. Hyodo;T. Matsuda
中科院分区：
文献类型：
--
作者：
S. Kim;T. Itaya;H. Hyodo;T. Matsuda
变质钾长石是在韩国乌川变质带的低品位泥质岩中发现的。它以极细粒度晶体（宽5-15毫米，长15-25毫米）的形式出现，与细粒度白云母和黑云母密切相关。利用电子探针微量分析仪对它们的微观结构关系进行了分析，结果表明，钾长石是在Ogcheon变质过程中与白云母和黑云母共存的稳定相，直接从基质相中生长出来的。白云母中白云石成分在400℃时约为4.2 kbar，为中P/T变质作用。白云母2 ~ 4和4 ~ 8 mm两个粒径分馏体的K-Ar年龄分别为153.4±3.3和156.7±3.4 Ma。黑云母分选物年龄为156.5±3.3 Ma。采用激光探针步进加热技术，采用40ar /39Ar法对黑云母晶体进行了分析。高原年龄为158.2±0.5 Ma，与K-Ar白云母和黑云母年龄相同。这些资料与前人的工作相结合，表明中侏罗统奥川变质带为中侏罗统右走滑断层运动的中P/T型变质带。
Metamorphic K-feldspar was found in the low-grade pelitic rocks from the Ogcheon metamorphic belt in South Korea. It occurs as extremely fine-grained crystals (5-15 mm in width and 15-25 mm in length) closely associated with fine-grained muscovite and biotite. Their micro structural relations by X-ray mapping analyses using an electron-probe microanalyzer strongly suggest that K-feldspar has grown directly from the matrix phases as a stable phase coexisting with muscovite and biotite during the Ogcheon metamorphism. The phengite component in muscovite indicates about 4.2 kbar at 400°C, suggesting intermediate P/T type of metamorphism. Muscovite separates of two size fractions, 2-4 and 4-8 mm, give K-Ar ages of 153.4±3.3 and 156.7±3.4 Ma, respectively. The biotite separate is 156.5±3.3 Ma in age. Coarse-grained biotite crystal (ca. 0.5 mm) often occurs and it was analyzed by40Ar/39Ar method using a laser probe step heating technique. It gives a plateau age of 158.2±0.5 Ma that is the same as the K-Ar muscovite and biotite ages. These data, including the previous works, suggest that intermediate P/T type of Ogcheon metamorphic belt exhumed in Middle Jurassic with the dextral strike-slip fault movement.