Geochronology and geochemistry of the Essimingor volcano: Melting of metasomatized lithospheric mantle beneath the North Tanzanian Divergence zone (East African Rift)
Geochronology and geochemistry of the Essimingor volcano: Melting of metasomatized lithospheric mantle beneath the North Tanzanian Divergence zone (East African Rift)
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埃西明戈尔火山的地球年代学和地球化学：北坦桑尼亚分歧带（东非裂谷）下方交代岩石圈地幔的融化
DOI：
10.1016/j.lithos.2012.09.009
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发表时间：
2012
期刊：
影响因子：
3.5
通讯作者：
C. Swisher
中科院分区：
文献类型：
--
作者：
Sara Mana;T. Furman;M. J. Carr;G. Mollel;R. Mortlock;M. Feigenson;B. Turrin;C. Swisher
北坦桑尼亚辐散带（NTD）位于东非大裂谷东部分支的南端，是地球上目前少数几个活跃的大陆内裂谷系统之一。NTD保存了裂谷活动早期复杂的构造-岩浆演化过程。NTD中报告的最古老的岩浆活动与位于中心的埃西明戈火山有关。虽然主要元素的氧化物显示狭窄的成分变化，建议分步结晶，微量元素丰度和Sr-Nd-Pb同位素数据具有复杂的分布，需要开放系统的过程。较原始的样品（MgO> 9 wt.%）可能反映了以残留石榴石、金云母和少量角闪石为特征的交代岩石圈地幔的部分熔融。放射成因铅同位素组成的范围表明，存在混合之间的这个源和东非裂谷（托罗Ankole和维龙加）的西部分支的岩石圈。对选定样品的激光增量加热得到的40 Ar/39 Ar年龄范围为5.76±0.02Ma至5.91±0.01Ma，这表明该年龄比以前报道的年龄大约年轻200万年。
The North Tanzanian Divergence zone (NTD), at the southern end of the eastern branch of the East African Rift, is part of one of Earth's few currently active intra-continental rift systems. The NTD preserves a complex tectono-magmatic evolution of a rift in its early stage of activity. The oldest magmatism reported in the NTD is associated with the centrally located Essimingor volcano. Although major element oxides show narrow compositional variations suggesting fractional crystallization, trace element abundances and Sr–Nd–Pb isotopic data have complex distributions that require open-system processes. The more primitive samples (MgO>9wt.%) likely reflect partial melting of a metasomatized lithospheric mantle characterized by residual garnet, phlogopite and minor amphibole. The range of radiogenic Pb isotopic compositions indicates the presence of mixing between this source and the lithosphere of the western branch of the East African Rift (Toro Ankole and Virunga). Laser-incremental heating of selected samples gives40Ar/39Ar ages that range from 5.76±0.02Ma to 5.91±0.01Ma, suggesting an age roughly 2myr younger than previously reported.