The great plume debate

It has been 40 years since Wilson [1963] first suggested that the Hawaiian Islands were produced by the oceanic lithosphere moving over a stationary ‘hot spot’ in the mantle, and 30 years since Morgan [1971] suggested that plumes exist in the Earth's mantle and play an important role in convection. Subsequently, large igneous provinces (LIPs), volcanic continental margins, and large oceanic plateaus, along with smaller-volume seamounts and ocean-island chains, have all been attributed to mantle plumes. For the last two to three decades, the tendency has been to focus research on those features of LIPs and hot spots that can be explained by the plume hypothesis and to neglect those that cannot. Many papers have treated the plume hypothesis as an a priori assumption, and there has been little questioning of the hypothesis

The effect of MgO on the liquidus temperatures of fayalite slags

The effects of minor MgO additions on the liquidus temperatures of fayalite slag have been investigated experimentally in equilibrium with metallic iron. The synthetic slags were equilibrated, quenched, and subsequently examined by using optical microscopy and electron probe X-ray microanalysis. Liquidus isotherms in the fayalite primary field and boundary lines were determined in the multicomponent systems MgO-"FeO"-CaO-SiO and AlO-MgO-"FeO"-CaO-SiO in equilibrium with metallic iron. The experimental results show that the magnesia addition expands the fayalite primary phase field in size and increases the liquidus temperatures in the fayalite primary phase field. It has been found that the effects of alumina and magnesia additions on the liquidus temperatures in the fayalite primary phase field are independent of each other