Abstract The Adwa – Yeha felsic plugs and domes are chain of towering inverted cone-shaped isolated plugs and circular domes with wide basal diameters and steep-sided, narrow tops. They form contrasting prominent topography from the Trap basalt ridges of the Adwa – Axum - Tekeze volcanic ridge, located just west of the Northern Afar Depression. The felsic plugs and domes are concentrated in the Adwa – Yeha area, in a zone of about 20 km wide and 30 km long and generally aligned along NNE-SSW direction, parallel to the regional structural grain of the Precambrian basement and the Miocene - Pliocene rift margin faults. In this study, we investigated these felsic plugs and domes using petrological and major and trace element geochemical methods in order to constrain their petrogenetic evolution. Their possible tectonic link to the Western Afar Margin has also been investigated combining our geochemical data, with assessment of regional tectonic setting and geochronological data from previous studies. The results ascertain that the felsic plugs and domes are peralkaline trachytes and peralkaline to sub-alkaline rhyolites, formed by Assimilation Fractional Crystallization (AFC) of basaltic magma which involved removal of olivine, pyroxene, plagioclase, and Fe–Ti oxides, and moderate amount of crustal input. The eruption of the felsic plugs and domes occurred along reactivated Precambrian weakness zones during the formation of the western Afar boundary faults.

中文翻译：

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Adwa – Yeha 长英质柱塞和圆顶，提格雷 – 埃塞俄比亚北部的地球化学：对其岩石成因和构造环境的影响

摘要 Adwa-Yeha长英质栓塞和圆顶是由高耸的倒锥形孤立栓塞和圆形圆顶组成的链，基部直径宽，顶部陡峭，顶部狭窄。它们与 Adwa-Axum-Tekeze 火山脊的 Trap 玄武岩脊形成对比鲜明的地形，位于北阿法尔洼地以西。长英质塞和穹窿集中在 Adwa-Yeha 地区，宽约 20 公里，长约 30 公里，大致沿 NNE-SSW 方向排列，平行于前寒武纪基底和中新世-上新世的区域构造颗粒裂谷断层。在这项研究中，我们使用岩石学和主要和微量元素地球化学方法研究了这些长英质柱塞和圆顶，以限制它们的岩石演化。还结合我们的地球化学数据以及对先前研究的区域构造环境和地质年代学数据的评估，研究了它们与西阿法尔边缘可能存在的构造联系。结果确定长英质柱塞和圆顶是过碱性粗面岩和过碱性至亚碱性流纹岩，由玄武岩岩浆的同化分步结晶 (AFC) 形成，包括橄榄石、辉石、斜长石和 Fe-Ti 氧化物的去除，以及适量的地壳输入。在西阿法尔边界断层形成期间，长英质柱塞和圆顶的喷发发生在重新激活的前寒武纪薄弱带。结果确定长英质柱塞和圆顶是过碱性粗面岩和过碱性至亚碱性流纹岩，由玄武岩岩浆的同化分步结晶 (AFC) 形成，包括橄榄石、辉石、斜长石和 Fe-Ti 氧化物的去除，以及适量的地壳输入。在西阿法尔边界断层形成期间，长英质柱塞和圆顶的喷发发生在重新激活的前寒武纪薄弱带。结果确定长英质柱塞和圆顶是过碱性粗面岩和过碱性至亚碱性流纹岩，由玄武岩岩浆的同化分步结晶 (AFC) 形成，包括橄榄石、辉石、斜长石和 Fe-Ti 氧化物的去除，以及适量的地壳输入。在西阿法尔边界断层形成期间，长英质柱塞和圆顶的喷发发生在重新激活的前寒武纪薄弱带。