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Post-collisional adakitic biotite plagiogranites from Guangtoushan pluton (Mianxian, central China): Petrogenesis and tectonic implication |
| QIN Jiangfeng, LAI Shaocong, LI Yongfei |
| State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi′an 710069, China; |
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Abstract The post-collisional Guangtoushan pluton intruded into the Mianlue suture, Central China. Geochemically, the Guangtoushan biotite plagiogranites show many close compositional similarities to high-silica adakites from the supra-subduction zone setting, but tend to have a higher concentration of K2O (3.22%&ndashi;3.84%). Chondrite-normalized rare earth element patterns are characterized by high ratios of (La/Yb)N, concave-upward shapes of the heavy rare earth element (HREE), and a lack of significant Eu anomalies. In conjunction with high abundances of Ba and Sr, as well as low abundances of Y and HREE, these patterns suggest a feldspar-poor, garnetv?ohibole-rich fractionation mineral assemblage. Coupled with previous studies, we suggest that the Guangtoushan biotite plagiogranites were likely to be caused by subducting slab break-off during the late orogenic stage in the West Qinling orogenic belt.
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Issue Date: 05 September 2007
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