Keywords: δ88Sr, 87Sr/86Sr, carbonate, seawater
The radiogenic Sr isotopic composition (87Sr/86Sr) of the Phanerozoic seawater has been fluctuated according to global tectonics and/or climate change. The major Sr fluxes to drive 87Sr/86Sr in seawater are three-fold; i.e., weathering of highly radiogenic continental silicates, non-radiogenic submarine hydrothermal fluid, and weathering of less radiogenic carbonates and basalts from island arc/oceanic island. During the Phanerozic, seawater 87Sr/86Sr changed most dramatically around the Middle/Late Permian boundary marked by a major mass extinction. Stable Sr isotope (δ88Sr) in seawater is recently recognized as an useful proxy for estimating ancientburial/dissolution of marine carbonate. The δ88Sr values were consistently low in the Middle Permian and began to increase during the Late Permian. The timing of thistrend change across the G-LB corresponds to that of 87Sr/86Sr. This significant change of ocean Sr budget in the Phanerozoic might be explained by increase/decrease of carbonate weathering on continental shelves with respect to the long-term cooling/warming associated with global sea level change.