Geology, petrology and age determination of Archaean-Proterozoic basement rocks of western Uganda

该项目旨在通过增进我们对火山岩及其内部超镁铁质结核生成的了解，评估鲁文佐里山脉的隆升与Toro Ankole火山田火山活动的形成之间的关系。火山岩由一种不寻常的钾质碱性火成岩组成，称为卡马辉石，可以通过云母的部分熔融和富含单斜辉石的地幔组合来解释，这些组合与火山岩中发现的捕虏体相似。锶、钕和锶的同位素将被用来评估地壳和岩石圈地幔的吸收，从而评估地壳或地幔岩浆室的可能驻留。Re-Os将进一步阐明熔融的地幔的性质，即软流圈或旧岩石圈及其富集度。对含云母和单斜辉石包体的岩石学和矿物化学特征将确定这些岩石是来自地幔的包体，还是来自卡马辉石的地壳堆积体。如果是地幔包体，将使用矿物化学，包括微量元素，来研究它们是橄榄岩普遍交代的结果，还是局限于矿脉。该地区普遍存在地幔交代作用，导致岩石圈体积大幅增加，这可能是卢旺达山脉抬升的原因之一。

This project aims to assess the relationship of the uplift of the Rwenzori mountains to the generation of volcanism in the Toro Ankole volcanic field by improving our understanding of the generation of the volcanics and of the ultramafic nodules within them. The volcanics comprise an unusual type of potassic alkaline igneous rock known as kamafugite that may be explained by partial melting of mica and clinopyroxene-rich mantle assemblages similar to those found as xenoliths within the volcanics. Isotopes of Sr, Nd and Os will be used to assess the uptake of crust and lithospheric mantle and therefore the possible residence in crustal or mantle magma chambers. Re-Os will shed further light on the nature of the mantle that melted, namely asthenosphere or old lithosphere and the extent of its enrichment. Petrological and mineral chemical characterization of the mica- and clinopyroxenebearing xenoliths will ascertain whether these rocks are xenoliths from the mantle or crustal cumulates from the kamafugites. If mantle xenoliths, the mineral chemistry, including trace elements, will be used to investigate whether they are the result of pervasive metasomatism of peridotite or are restricted to veins. Pervasive metasomatism of the mantle has been proposed in this area to result in a large volume increase in the lithosphere - a possible reason for the uplift of the Rwenzoris.