新疆阿尔泰山南缘沙尔布拉克一带早二叠世花岗岩的年龄、地球化学特征及地质意义
Early Permian granite age and geochemical characteristics in Shaerbulake of Xinjiang's Altay area and its geological significance
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摘要: 对出露于阿尔泰山南缘沙尔布拉克一带的布可萨拉岩体和索尔库都克岩体中的似斑状黑云母二长花岗岩进行了锆石LA-ICP-MS U-Pb定年，206Pb/238U年龄分别为277.0Ma±2.4Ma和280.9Ma±4.3Ma，表明形成于早二叠世。岩石地球化学特征表明，该期花岗岩具有富碱、高钾的特征，属高钾钙碱性系列，为具有I—A、I—S过渡特点的I型花岗岩，稀土元素含量较高(∑REE为184.68×10-6～221.49×10-6)，轻稀土元素富集(LREE/HREE为4.52～8.45)，Eu负异常明显(δEu为0.47～0.68)，富集大离子亲石元素，具Nb、Ta、Sr、P、Ti等元素负异常。结合区域资料分析，该期岩体形成于碰撞造山后的拉张构造环境，属于后造山花岗岩。阿尔泰南缘早二叠世花岗岩是在后造山拉张背景下，地幔物质减压熔融形成岩浆上涌，底侵于新生地壳之下，使地壳熔融形成岩浆沿深断裂带上侵形成的。
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关键词:
- 早二叠世花岗岩 /
- 锆石LA-ICP-MS年龄 /
- 地球化学特征 /
- 阿尔泰山南缘
Abstract: he zircons LA-ICP-MS U-Pb dating of the spotted adamellite biotite granite from Bukesala and Suoerkuduke plutons in Shaerbulake, southern margin of Altay, was performed, yielding the 277.0±2.4Ma 206Pb/238U age in Bukesala ,and 280.9±4.3Ma 206Pb/238U age in Suoerkuduke, suggesting that their formation in the Early Permian. Geochemical characteristics indicate that the granite has a rich base, potassium, is a high-K calc-alkaline series, as with I-A and I-S transition characteristics of I-type granite, high content of REE (ΣREE to 184.68×10-6~221.49×10-6), LREE enrichment (LREE/HREE 4.52~8.45), marked negative Eu anomalies (δEu as 0.47-0.68), enriched in large ion lithophile elements, with Nb, Ta, Sr, P, Ti and other elements of negative anomalies. Combined with regional data, the rock formed in the collision of post-orogenic extensional tectonic setting are post-orogenic granite. The Early Permian granites in the post-orogenic context of decompression melting of mantle material upwelling of magma, crustal underplating in the newborn under the crust formed by melting of magma intrusion along the deep fault zone. -
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