The Impact of High-Grade Metamorphism on the U-Th-Pb System of Zircons: A Case Study of Zircon Dating of Meta-Diorite in Qixia Area, Eastern Shandong Province
详细信息
- 责任者：Wan Yusheng (Beijing SHRIMP Center ; Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Liu Dunyi
- 刊名：Earth Science Frontiers
- 出版年：2011
- 卷期：18(2)
- 关键词：变闪长岩 ; epidiorite ; 铀—铅计时 ; U-Pb dating ; 钍—铀计时 ; Th-U dating ; 山东 ; Shandong Province
- 页码：p.17-25
- 图表：7 illus., 3 tables, 21 refs.
- 分类号：0802
- 出版序号：20120188
- issnNo：ISSN1005-2321
- isbnNo：CN11-3370/P
摘要
This paper presents a study of the U-Th-Pb behavior of zircons in a "dry" rock system during high-grade metamorphism in the Archean basement of eastern Shandong Province. The studied sample has a mineral assemblage of plagioclase+K-feldspar+clinopyroxene+biotite+quartz and its protolith is considered to be diorite. The zircons are stubby,equant or irregular in shape and show fir-leaf, sector, banded or oscillatory zoning. Combined with early studies, conclusions have been drawn as follows: 1) the diorite underwent two episodes of high-grade metamorphism both at the end of the Neoarchean and the Paleoproterozoic; 2) high-grade metamorphism in a "dry" rock system may partially reset the U-Th-Pb system of zircons,and in this case, the ages between the oldest and youngest are chronologically meaningless; and 3) high Th/U ratios may be common features of the zircons formed during high-grade metamorphic conditions.
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