The geochemistry of S, Se, Te, Mg, Tl and Bi - their determination by thermal neutron analysis and their geochemical significance

The volatile elements S, Se, Te, Hg, Tl and Bi have been measured in a wide range of terrestrial, lunar and meteoritic materials using thermal neutron activation analysis and their geochemical distribution is reported. Terrestrial samples studied include a large number of ultramafic kimberlite and eclogite nodules of possible upper mantle or lower crustal origin, and gossaniferous and nickel sulphide material from Western Australia. The concentrations of the elements studied were normally below 1 ppm. A method using destructive thermal neutron activation analysis was therefore developed and is reported for the simultaneous determination of S, Se, Te, Hg, Tl and Bi, with a sensitivity approaching 10-9 gm/gm. The technqiue involved sample dissolution using either alkaline fusion or acid attack in a sealed Teflon bomb, followed by a series of rapid and specific radiochemical separations and purifications. The Allende sample data (particularly from the calcium-aluminium rich inclusions) have been used to support the theoretical models for the accretion and early evolution of the solar system. A formation model, with the appearance of the calcium-aluminium inclusions resulting from the gradual loss of energy from the cooling solar plasma is supported. Element distribution in terrestrial samples was used to obtain geological information on the rock types and the evolutionary processes occurring in the upper mantle/lower crustal region