Geochemistry of the Baishitouquan Amazonite—and Topaz—bearing Granite in the Mid—Tianshan Belt,Xinjiang,China |
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摘 要: |
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关 键 词: | 绿长石 黄玉 花岗岩 铷 氟 新疆 天山地区 地球化学 氧同位素 锶同位素 |
Geochemistry of the Baishitouquan amazonite- and topaz-bearing granite in the Mid Tianshan belt,Xinjiang, China |
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Authors: | Gu Lianxing Yang Hao Gou Xiaoqin Guo Jichun Wang Jinzhu |
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Institution: | (1) Department of Earth Sciences, Nanjing University, 210008 Nanjing;(2) Geological Brigade No.6, Bureau of Geology and Mineral Resources, 839000 Xinjiang Uygur Autonomous Region |
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Abstract: | The Baishitouquan amazonite and topaz-bearing granite is one of the typical high-rubidium and high-fluorine granites in the
eastern part of the Mid-Tianshan belt. This intrusion is in sharp contact with Mid-Proterozoic schists, gneisses and marbles,
and is composed of four zones transitional from the bottom upwards: leucogranite, amazonite granite, topaz-bearing amazonite
granite and topaz quartz albitite.
The Baishitouquan granite contains highly ordered K-feldspar, Li-rich mica, Mn-rich garnet, α-quartz and low temperature zircon
and is chemically high in Si, K, Na, Al, Li, Rb, Cs and F, and low in Ti, Fe, Ca, Mg, P, Co, Ni, Cr, V, Sr and Ba, with Na2O<K2O. Amazonite from the amazonite granite zone contains 1867 ppm Rb. The F contents of bulk rocks are 3040 and 4597 for the
amazonite granite and topaz-bearing amazonite granite zones, respectively. These two zones have δ18O values of 8.97–9.85‰ (SMOW) and show flat REE distribution patterns with strong Eu depletion. K-Ar and Rb-Sr ages of this
intrusion are 226. 6 Ma and 209. 6 Ma respectively, with an initial87Sr/86Sr ratio of 0.987±0.213.
The Baishitouquan granite is the product of crystallization of a low temperature, and water, rubidium and fluorine-rich magma,
which may have been derived from partial melting of muscovite-rich crustal rocks. Consolidation of this granite involved two
contrasting and successive stages: melt crystallization and hydrothermal metasomatism and precipitation. Various geological
features of this granite were formed during the transition from the magmatic to the hydrothermal stage. |
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Keywords: | amazonite topaz granite rubidium fluorine Xinjiang Uygur Autonomous Region |
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