Studies on the U-Pb ages and Hf isotopes of zircons in the Aoyitake plagioclase granite, west Tarim
| 作者: |
Li, G.W., et al. |
| 期刊名称: |
Acta Petrologica Sinica |
| 发表年度: |
2009 |
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25 |
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1 |
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| 页码: |
166-172 |
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| 摘要: |
In situ U-Pb ages and I-If isotopes of Aoyitake plagioclase granite in west Kunlun were analyzed on the basis of mircro-district studies upon zircons selected from two samples. Zircon U-Pb ages of the two samples are 337.5 +/- 6.5Ma and 339.2 +/- 6.5Ma, respectively with their Th/U ratio of 0.3 similar to 1.0, which is consistent with the SHRIMP ages tested by Zhang et al. ( 2006). The Aoyitake plagioclase granite zircons, with their Hf-176/Hf-177 ratios varying in 0.2829 similar to 0.2831, have high positive epsilon(Hf) (12 similar to 17) and depleted mantle model ages (averaged at 359.1 Ma), which is almost equal to their U-Pb ages. In the Hf-176/Hf-177-epsilon(Hf) discrimation diagrams, these zircons were plotted on the depleted mantle evolution line, indicating that this granite was derived from the new basaltic lower crust which is originated from depleted mantle, through a series of crystallization differentiations. Compared with current data from studies on the layered complex mass in Bachu- Kashgar zone, Aoyitake granite bears similar characteristics of its primary magma with the former, which were supposed to be originated from partial melting of the young basaltic lower crust related to the mantle plume action during the carboniferous Tianshan rift period.
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