The O¹⁸/O¹⁶ ratio of quartz in metasedimentary detrital rocks and iron formations is related to the modal abundance of quartz or iron oxides in the rocks. The relationship is explained according to a hypothesis of local, closed-system recrystallization of metastable detrital material derived from a high-temperature source mixed with varying proportions of isotopically heavy material (clays, carbonates, and siliceous and ferruginous ooze) in low-temperature isotopic equilibrium with seawater. Oxygen isotopic equilibrium attainment during prograde metamorphism is commonly limited to dimensions less than meters and may generally be limited to dimensions less than centimeters. Small-scale disequilibrium, if undetected, can lead to errors in deduced "isotopic temperatures" of the order of 100°C. Such errors can generally be avoided by selecting small, fine-grained, homogeneous samples.
No takes yet. Share an insight, caveat, or question.
A. T. Anderson (1967) studied this question.
Synapse has enriched 5 related papers. Consider them for comparative context: