U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong
This paper carried out a study on U–Th–Pb behavior of zircons in a “dry” rock system during high-grade metamorphism in the Archean basement of eastern Shandong. The studied sample has a mineral assemblage of plagioclase + K-feldspar + clinopyroxene + biotite + quartz and its protolith is considered...
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Elsevier
2011-04-01
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| Series: | Geoscience Frontiers |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S1674987111000259 |
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| author | Yusheng Wan Dunyi Liu Chunyan Dong Shoujie Liu Shijin Wang Enxiu Yang |
| author_facet | Yusheng Wan Dunyi Liu Chunyan Dong Shoujie Liu Shijin Wang Enxiu Yang |
| author_sort | Yusheng Wan |
| collection | DOAJ |
| description | This paper carried out a study on U–Th–Pb behavior of zircons in a “dry” rock system during high-grade metamorphism in the Archean basement of eastern Shandong. 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, sectorial, banded or oscillatory zoning. They contain inclusions, including mineral assemblages of clinopyroxene + orthopyroxene + hornblende + quartz and plagioclase + K-feldspar + biotite + quartz. Fifty SHRIMP analyses were performed on 34 zircon grains, which commonly yielded high Th/U ratios (mostly >0.5). Most analyses are distributed along concordia from 2.54 to 2.25 Ga, with the youngest age being ∼1.95 Ga. Compositions and ages show large variations even in a same zircon grain. Combined with early studies, conclusions can be drawn as follows: 1) the diorite underwent two episodes of high-grade metamorphism, at the end of the Neoarchean and the Paleoproterozoic (∼2.50 Ga and ∼1.95 Ga or slightly later); 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 zircons formed during high-grade metamorphic conditions. |
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| institution | Directory Open Access Journal |
| issn | 1674-9871 |
| language | English |
| last_indexed | 2024-03-12T18:29:21Z |
| publishDate | 2011-04-01 |
| publisher | Elsevier |
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| series | Geoscience Frontiers |
| spelling | doaj.art-cdf488d4dbb8459e8feb61fb1f93c8dd2023-08-02T08:23:36ZengElsevierGeoscience Frontiers1674-98712011-04-012213714610.1016/j.gsf.2011.02.004U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern ShandongYusheng Wan0Dunyi Liu1Chunyan Dong2Shoujie Liu3Shijin Wang4Enxiu Yang5Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, ChinaBeijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, ChinaBeijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, ChinaBeijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, ChinaShandong Geological Survey, Jinan 250013, ChinaShandong Geological Survey, Jinan 250013, ChinaThis paper carried out a study on U–Th–Pb behavior of zircons in a “dry” rock system during high-grade metamorphism in the Archean basement of eastern Shandong. 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, sectorial, banded or oscillatory zoning. They contain inclusions, including mineral assemblages of clinopyroxene + orthopyroxene + hornblende + quartz and plagioclase + K-feldspar + biotite + quartz. Fifty SHRIMP analyses were performed on 34 zircon grains, which commonly yielded high Th/U ratios (mostly >0.5). Most analyses are distributed along concordia from 2.54 to 2.25 Ga, with the youngest age being ∼1.95 Ga. Compositions and ages show large variations even in a same zircon grain. Combined with early studies, conclusions can be drawn as follows: 1) the diorite underwent two episodes of high-grade metamorphism, at the end of the Neoarchean and the Paleoproterozoic (∼2.50 Ga and ∼1.95 Ga or slightly later); 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 zircons formed during high-grade metamorphic conditions.http://www.sciencedirect.com/science/article/pii/S1674987111000259ZirconsU–Th–Pb systemResetHigh-grade metamorphismSHRIMP datingEarly Precambrian |
| spellingShingle | Yusheng Wan Dunyi Liu Chunyan Dong Shoujie Liu Shijin Wang Enxiu Yang U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong Geoscience Frontiers Zircons U–Th–Pb system Reset High-grade metamorphism SHRIMP dating Early Precambrian |
| title | U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong |
| title_full | U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong |
| title_fullStr | U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong |
| title_full_unstemmed | U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong |
| title_short | U–Th–Pb behavior of zircons under high-grade metamorphic conditions: A case study of zircon dating of meta-diorite near Qixia, eastern Shandong |
| title_sort | u th pb behavior of zircons under high grade metamorphic conditions a case study of zircon dating of meta diorite near qixia eastern shandong |
| topic | Zircons U–Th–Pb system Reset High-grade metamorphism SHRIMP dating Early Precambrian |
| url | http://www.sciencedirect.com/science/article/pii/S1674987111000259 |
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