Zircon LA-ICP MS dating of volcanic rocks from Tianmushan basin in the lower Yangtze region and its geological significances
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摘要: 天目山盆地是下扬子江南隆起带保存较完整的中生代火山盆地,中生代火山岩系岩性自下而上主要为流纹岩-英安岩-安山岩。对盆地内黄尖组下段流纹岩和英安岩分别进行了锆石 LA-ICP MS定年,分别获得了133.6±1.5 Ma(MSWD=0.73)和135.0±2.1 Ma(MSWD=0.78)的锆石U-Pb年龄,指示天目山盆地黄尖组火山岩时代为早白垩世。天目山盆地火山活动起始时间和长江中下游地区晚中生代火山活动基本一致,说明江南隆起带和长江中下游地区在早白垩世均处于强烈拉张环境。
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关键词:
- 火山岩 /
- 锆石LA-ICP MS定年 /
- 天目山盆地 /
- 下扬子
Abstract: Tianmushan basin is a relatively well preserved Mesozoic volcanic basin in Jiangnan uplift of the Lower Yangtze region .The rock types of Mesozoic volcanic rock series are mainly rhyolite ,dacite and andesite from below .Zircon LA-ICP-MS U-Pb isotopic dating of the rhyolite and dacite from the lower part of Huangjian Formation gives ages of 133 .6 ± 1 .7 Ma (MSWD=0 .73) and 135 .0 ± 2 .1 Ma (MSWD=0 .78) ,respectively ,indicating that the age of volcanic rocks of the Huangjian Formation in the Tianmush-an basin is early Cretaceous .The starting time of volcanic eruption in the Tianmushan basin was consistent with those in volcanic basins in the middle-lower reaches of the Yangtze River ,suggesting that the Jiang-nan uplift and the middle-lower reaches of the Yangtze River were in a similar tectonic setting during early Cretaceous . -
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