cig_2020_poster_emmanuel_njinju.pdf

The impact of a plume head beneath the lithosphere generally results in intense melting of plume materials, producing large igneous provinces (LIPs; White & McKenzie, 1995) such as in the Eastern Branch of the East African Rift (EAR; Alayew & Gibson, 2009). However, the Western Branch of the EAR is characterized by limited and sparse magmatism and the melt source is contentious. Geochemical studies of past eruptions of the Rungwe Volcanic Province (RVP) in the Western Branch, indicate plume signatures (elevated mantle potential temperatures; Rooney et al., 2011 and high 3He/4He; Hilton et al., 2011). The plume signatures of the RVP remain enigmatic, mainly because the volcanism is highly localized, unlike the LIP in the Eastern Branch. We use 3D geodynamics models to investigate plume-lithosphere interactions beneath the RVP, to better understand the sources of the enigmatic plume signatures.

岩石圈下方的地幔柱头部通常会引发地幔柱物质的强烈熔融，进而形成大火成岩省（large igneous provinces, LIPs；White & McKenzie, 1995），以东非裂谷（East African Rift, EAR）东支区域为典型代表（Alayew & Gibson, 2009）。但东非裂谷西支的岩浆作用却局限且稀疏，其熔融源区仍存在争议。针对西支伦圭火山省（Rungwe Volcanic Province, RVP）过往火山喷发的地球化学研究显示，其存在地幔柱相关地球化学特征（如升高的地幔位温：Rooney等, 2011；以及偏高的³He/⁴He比值：Hilton等, 2011）。然而伦圭火山省的地幔柱特征仍颇具谜团，这主要是因为其火山活动高度局限，与东支的大火成岩省特征截然不同。本研究采用三维地球动力学模型，对伦圭火山省下方的地幔柱-岩石圈相互作用开展模拟研究，以期更清晰地解析这一神秘地幔柱特征的成因。