A similar system exists in seawater, where by 44Ca/40Ca has a tendency to rise when the speed of removal of Ca2+ by mineral precipitation exceeds the enter of recent calcium to the ocean. In 1997, Skulan and DePaolo introduced the 1st evidence of alter in seawater 44Ca/40Ca about geologic time, https://waterqualitystandardsinri27641.actoblog.com/28690817/rumored-buzz-on-ca