The Nd isotope composition of chemical and clastic sediments surviving from the Archaean
provides no evidence for the existence of pre-4,000-Myr continental crust. Either the …

THE quest for evidence of life processes, past or. present, in extraterrestrial enviromnents is
of considerable interest to-day. Isoprenoid alkanes have boon proposed as' biological …

THERE has been considerable debate as to whether isotopically enriched continental crust
was an important geochemical reservoir in earliest Archaean times. Fundamental questions …

The study of neodymium model ages of sedimentary rocks has added considerably to our
understanding of crustal growth and evolution. So far, however, the possible effects of …

Samarium-neodymium and rubidium-strontium isotopic systematics, together with plausible
assumptions regarding the geochemical evolution of continental crust material, have been …

The concentrations of heavy metals in seawater are exceedingly low and commonly less
than 10− 9 g per g. In marked contrast, their concentrations in pelagic clays and …

Siderophilic element concentrations are high in sediments from the Cretaceous–Tertiary
boundary. An extraterrestrial source is indicated. Concentrations are too high to be …

The metalliferous sediment deposits of the Atlantis II Deep in the Red Sea are an example of
submarine hydrothermal deposits at a spreading centre. The brine salinities (∼ 270% for the …

Anomalous isotopic composition has been reported for the carbon in carbonate minerals of
banded iron formations. Well studied examples show an enrichment in the light isotope of …

Avarying fraction of the sediment accumulating on the ocean floor consists of solids formed
by precipitation from solution in the-sea water, at the sediment surface, and in the sediment …