Plate tectonic control of strontium concentration in Phanerozoic and Neoproterozoic seawater: Evidence from fluid inclusions in marine halite

Seafloor hydrothermal systems control long-term changes in seawater [Li + ]: Evidence from fluid inclusions

“…2, Table 1, table S1, and data S1; see Materials and Methods). Fluid inclusions from the same halites were used to document the major ion chemistry (7,(24)(25)(26)(27)(28)(29) and Sr concentration (30) of Mesozoic and Cenozoic seawater. The 87 Sr/ 86 Sr ratios from these fluid inclusions (30) and associated sulfate minerals (31)(32)(33) lie on the marine curve, supporting the seawater origin of the brines from which halite precipitated (Fig.…”

“… [Li + ] in seawater from fluid inclusions versus relative MOR fluid flux ( A ) ( 38 ), seawater [Ca 2+ ] ( B ) ( 7 , 24 , 25 ), Mg 2+ /Ca 2+ ( C ) ( 7 , 24 , 25 ), [Sr 2+ ] ( D ) ( 30 ), 87 Sr/ 86 Sr ( E ) ( 2 ), and δ 7 Li ( F ) ( 3 ). Ages in million years adjacent to symbols show average values of seawater [Li + ], [Ca 2+ ], Mg 2+ /Ca 2+ , [Sr 2+ ], 87 Sr/ 86 Sr, and δ 7 Li with 1σ (2SE for [Sr 2+ ]) and 2σ (δ 7 Li) error bars.…”

“…S3), well documented for major ion chemistry (Mg 2+ , Ca 2+ , Na + , K + , SO 4 2− , Clˉ) ( 7 , 24 – 28 ), were reanalyzed to obtain Li + /Mg 2+ ratios and Li + concentrations (table S1 and data S1). Petrographic, geochemical, and paleontological criteria used to characterize the marine origin of the fluid inclusions in the halites studied include the following: (i) Brˉ concentrations in halite ( 24 – 29 ), (ii) δ 34 S in sulfate minerals interbedded with halite ( 24 – 27 , 31 , 63 ), (iii) 87 Sr/ 86 Sr in sulfate minerals ( 31 – 33 ) and in fluid inclusions in halite ( 30 ), and (iv) marine fossils preserved in underlying carbonate/marl units ( 24 , 25 , 64 ). These records show that the parent waters of the inclusion brines reported here were marine in origin, especially because the 87 Sr/ 86 Sr ratio in halite fluid inclusions is the same as contemporaneous seawater ( Fig.…”

“…Experiments with solar evaporation of Black Sea water and Mediterranean seawater showed that Li + increased conservatively up to a DE of 117 ( 65 ) and 870 ( 35 ), respectively. Halite analyzed in this study was not associated with Mg-bearing salts ( 30 ); thus, the Li + /Mg 2+ ratio measured in fluid inclusions in halite is assumed to be the same as the ratio in unevaporated seawater.…”

“…Error bars are the uncertainty of the data (minimum/maximum for [Li + ] SW and Mg 2+ /Ca 2+ ). Red circles show 87 Sr/ 86 Sr values from fluid inclusions in marine halite (table S2) ( 30 ); red squares show 87 Sr/ 86 Sr values in sulfates interbedded with halite ( 31 – 33 ).…”