Pleistocene magmatism in a lithospheric transition area: petrogenesis of alkaline and peralkaline lavas from the BaringoBogoria Basin, central Kenya Rift
Pleistocene magmatism in a lithospheric transition area: petrogenesis of alkaline and peralkaline lavas from the BaringoBogoria Basin, central Kenya Rift
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岩石圈过渡区的更新世岩浆作用：肯尼亚裂谷中部巴林戈博戈里亚盆地碱性和过碱性熔岩的岩石成因
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发表时间：
2003
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通讯作者：
J. Cotten
中科院分区：
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作者：
J. Clement;M. Caroff;C. Hemond;J. Tiercelin;C. Bollinger;H. Guillou;J. Cotten
介绍了肯尼亚裂谷中部BaringoBogoria盆地玄武岩、辉绿岩、过碱性粗面岩和白云岩的新岩石学、地质年代学和地球化学数据。KAr测年结果表明，火山岩侵位时代为894±13~92±5ka。~(87)Sr/~(86)Sr为0.70304~0.70692，~(143)Nd/~(144)Nd为0.51237~0.51295，~(206)Pb/~(204)Pb为18.4~19.8，~(207)Pb/~(204)Pb为15.46~15.70，~(208)Pb/~(204)Pb为38.2~40.5。尽管采样区域相当有限，时间跨度相对较短(820ka)，但矿物学和地球化学变化与熔岩之间的简单同源联系并不一致。研究区位于两个不同岩石圈区域(坦桑尼亚克拉通和巴拿马活动带)之间的过渡带。我们认为，所研究熔岩的岩石学和地球化学变化本质上与下伏岩石圈的性质有关。一些玄武岩产品遭受了碳酸盐污染，可能是在岩石内部。
New petrological, geochronological, and geochemical data on basalts, mugearites, peralkaline trachytes, and phonolites from the BaringoBogoria Basin, central Kenya Rift, are presented. KAr dating indicates that the volcanic rocks were emplaced between 894 ± 13 and 92 ± 5 ka. 87Sr/86Sr ranges from 0.70304 to 0.70692, 143Nd/144Nd from 0.51237 to 0.51295, 206Pb/204Pb from 18.4 to 19.8, 207Pb/204Pb from 15.46 to 15.70, and 208Pb/204Pb from 38.2 to 40.5. Despite a rather restricted sampling area and a relatively short time span (820 ka), the mineralogical and geochemical variations are not consistent with a simple cogenetic link between the lavas. The studied area is located in a transition zone between two different lithospheric domains (Tanzanian Craton and Panafrican Mobile Belt). We propose that the petrological and geochemical variations of the studied lavas are essentially linked to the nature of the underlying lithosphere. Some basaltic products underwent carbonate contamination, possibly within the c...