| Mineral chemistry, geochemistry and U-Pb SHRIMP zircon data of the Yangxin monzonitic intrusive in the foreland of the Dabie orogen |
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| 基金项目： | 国家自然科学基金;中国科学院基金 |
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| 摘 要： | The lower Yangtze River area, situated at the fore-land of the Qinling-Dabie orogen, is an important re-gion for high-grade mineral deposits in Cen-tral-Eastern China. Nearly 300 different types of Cu and Au polymetal, Fe, and S mineral deposits have been found and mined in this zone1,2]. The overall distribution of these deposits follows the trend of the Mesozoic igneous rocks, suggesting their fundamental controls on the formation of these deposits. Geo-physical and geologic observatio…
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| 收稿时间： | 9 June 2005 |
| 修稿时间： | 13 September 2005 |
Mineral chemistry, geochemistry and U-Pb SHRIMP zircon data of the Yangxin monzonitic intrusive in the foreland of the Dabie orogen |
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| Authors: | XUE Huaimin DONG Shuwen JIAN Ping |
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| Institution: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
2. Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The Yangxin composite intrusive consists of three generations of plutons, among which 90% are the second generation intrusions.
The second generation intrusion has U-Pb SHRIMP zircon age of 134±2 Ma, substantially younger than the early stage of the
Yanshanian. Amphibole and biotite, major mafic minerals in the Yangxin plutons, are rich in magnesium, suggesting a deep source
of their parental magma, possibly derived from the upper mantle. Whole rock geochemical data on these rocks show that they
have high Al2O3 (15.92%–16.38%), relatively high alkali (Na2O+K2O = 6.95%–7.37%) and higher Na2O contents than K2O (Na2O/K2O = 1.47–1.94). They also have high Sr contents (816–897 μg/g) are enriched in strong incompatible elements such as Rb, U,
Th, K and LREE, but depleted in HREE and Y. Strong fractionation of LREE from HREE as indicated by high (La/Yb)N ratios ranging from 17.83 to 20.86. Although with little difference, the whole characteristics of the Yangxin intrusive body
are greatly similar to the adakite, referring that the formation of the parental magma may relate with the partial melting
of the basalt underplating from the mantle after delamination of the mountain root of the Dabie orogen. The body has been
uplifted about 5 km since cooling concretion, the average rate was only about 0.04 mm/a, much slower than that of the Dabie
orogen in late Mesozoic, but the rates of denudation in two area are similar in Cenozoic. |
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| Keywords: | zircon SHRIMP Yangxin intrusive foreland Dabie orogen |
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