THE GEOCHEMISTRY OF THE STABLE CARBON ISOTOPES

摘要: Abstract Several hundred samples of carbon from various geologic sources have been analyzed in a new survey the variation ratio C13/C12 nature. Mass spectrometric determinations were made on instruments developed by H. C. Urey and his co-workers utilizing two complete feed systems with magnetic switching to determine small differences isotope ratios between standard gas. With this procedure variations can be determined an accuracy ±0.01% ratio. The results confirm previous work few exceptions. range is 4.5%. Terrestrial organic carbonate rocks constitute well defined groups, carbonates being richer C13 some 2%. Marine lies intermediate these groups. Atmospheric CO2 than was formerly believed. Fossil wood, coal limestones show no correlation age. If petroleum marine origin considerable change isotopic composition has probably occurred. Such seems occurred black shales carbonaceous schists. Samples graphites, diamonds, igneous gases Yellowstone Park analyzed. graphite cannot ratios. terrestrial distribution isotopes sediments discussed reference available meteoritic determinations. Isotopic fractionation iron carbide meteorites may indicate mechanism which early deep seated surface