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Helium and carbon isotopes in fluorites: implications for mantle carbon contribution in an ancient subduction zone 总被引:1,自引:0,他引:1
Junji Yamamoto Makoto Watanabe Yoshiyuki Nozaki Yuji Sano 《Journal of Volcanology and Geothermal Research》2001,107(1-3)
The concentrations of helium and carbon in fluorite associated with Cretaceous to Neogene (90–13 Ma) granitic magmatism in the Japanese arc have been measured. Concentrations of Li, U, Th and Gd were measured to correct for secondary generated 3He. The CO2/3He of fluorites are almost uniform (1.5×1010–4×1010) and in fair agreement with the range of present island arc volcanic gases. The calculated mantle C contribution in the Mesozoic subduction zone appear to have been identical to the present one (7–19%) indicating that the C flux from the mantle in supra-subduction zone environments has remained fairly constant during the past 70 million years. 相似文献
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四川牦牛坪稀土矿床萤石Sr、Nd同位素对地幔成矿流体的指示意义 总被引:14,自引:0,他引:14
萤石是四川牦牛坪稀土矿床主要的脉石矿物之一,其形成贯穿了整个稀土成矿过程,因此同位素的研究对探讨萤石和稀土成矿流体的来源具有重要的价值。矿区6件萤石样品的Sr、Nd同位素组成没有明显差异,结合围岩(碳酸岩-正长岩,花岗岩)同位素组成特征研究表明,不同颜色、来自不同矿石类型、具有不同REE类型的萤石为同源产物,稀土成矿流体来源于富集地幔,与区内碳酸岩-正长岩岩浆活动密切相关。 相似文献
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