The effect of pH modifier on the flotation of celestite with sodium oleate and sodium metasilicate
Abstract This paper studies the influence of two pH modifiers, namely sodium hydroxide (NaOH) and sodium carbonate (Na 2 CO 3 ), on the flotation of celestite ore using sodium oleate as the collector and sodium silicate (Na 2 SiO 3 ) as the depressant. The use of Na 2 CO 3 provides the best results for the concentration of celestite, under the same experimental conditions.
Separation of sillimanite from beach sands contaminated with shell
Sillimanite is a very important raw material for the manufacture of refractory bricks used in iron and steel, 
cement and glass industries. In some coastal stretches of 
south India, the beach sand is contaminated with shell. After recovering heavy minerals like ilmenite, rutile, zircon and garnet by various physical separation techniques, the final sand containing sillimanite, quartz and shell is presently dumped as waste. Separation of sillimanite from these rejects was studied by flotation process using oleic acid and octylhydroxamate as collectors for selective flotation of sillimanite. Starch and tannin were tried as depressants for shell and sodium silicate as dispersant for quartz. Though the quartz could be depressed effectively, the shell was found to float along with sillimanite both in the presence of oleic acid and octylhydroxamate. When starch or tannin was added to suppress the shell flotation, the floatability of 
sillimanite and in turn its recovery was drastically affected. Alternatively shell was totally removed by treating with dilute hydrochloric acid and sillimanite was separated from quartz using oleic acid and sodium silicate. The concentrate analyzing 97% sillimanite free from shell were achieved from the initial sand assaying 48 % sillimanite, 46 % quartz and 3.3% shell.
Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview
Abstract The northern African Tethyan margin registered three major rifting episodes from the latest Palaeozoic-earliest Mesozoic to the earliest Cenozoic. Break-up of Gondwana was initiated in the late Carboniferous. Along the northern African-Arabian plate margin rifting propagated westward from the northeastern Arabian margin to Morocco during the Permian and Triassic, and was accompanied by Mid-Late Triassic-earliest Liassic extensive alkaline flow basalts. Rifting continued during the Liassic, e.g. in the Moghrebian Atlas troughs. A second stage of rifting occurred in the Late Jurassic and continued into, or was rejuvenated during, the Early Cretaceous. Along the east Mediterranean margin, some large E-W trending rifts formed, often with associated volcanism, e.g. southern Sirt and Abu Gharadig. Most researchers believe the oceanization of the eastern Mediterranean basin occurred at this time. Flexural subsidence affected the Moghrebian Atlas, including the Riffian-Tellian domain, where a thick flysch series was deposited. Two short-lived, but widespread and tectonically important, compressional or wrench-dominated events occurred during the Santonian and the latest Maastrichtian. From Morocco to Oman, most sedimentary basins were folded and inverted at these times. The Santonian event resulted from onset of the collision between the African-Arabian and Eurasian plates. New stress-fields favoured NE-SW extension along the African plate margin, generating or rejuvenating some rifts, e.g. in the Euphrates trough and in the Libya-Tunisia region (northwestern Sirt, Pelagian Sea). Rifting and magmatism continued in these regions into the Paleocene. During the Mesozoic, therefore, the northern margin of the African-Arabian plate registered both rifting resulting in the oceanization of the Tethys and rifting resulting from the initiation of the closure of the Tethys. The intraplate domain exhibited echoes of the tectonic events affecting the margin.