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Vils, Flurin; Tonarini, Sonia; Kalt, Angelika; Seitz, Hans-Michael (2009): (Table 1) Li, B and Sr isotopic composition and concentration in ODP Leg 209 samples [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.789079, Supplement to: Vils, F et al. (2009): Boron, lithium and strontium isotopes as tracers of seawater–serpentinite interaction at Mid-Atlantic ridge, ODP Leg 209. Earth and Planetary Science Letters, 286(3-4), 414-425, https://doi.org/10.1016/j.epsl.2009.07.005

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Abstract:
Spinel harzburgites from ODP Leg 209 (Sites 1272A, 1274A) drilled at the Mid-Atlantic ridge between 14°N and 16°N are highly serpentinized (50-100%), but still preserve relics of primary phases (olivine >= orthopyroxene >> clinopyroxene). We determined whole-rock B and Li isotope compositions in order to constrain the effect of serpentinization on d11B and d7Li. Our data indicate that during serpentinization Li is leached from the rock, while B is added. The samples from ODP Leg 209 show the heaviest d11B (+29.6 to +40.52 per mil) and lightest d7Li (-28.46 to +7.17 per mil) found so far in oceanic mantle. High 87Sr/86Sr ratios (0.708536 to 0.709130) indicate moderate water/rock ratios (3 to 273, on the average 39), in line with the high degree of serpentinization observed.
Applying the known fractionation factors for 11B/10B and 7Li/6Li between seawater and silicates, serpentinized peridotite in equilibrium with seawater at conditions corresponding to those of the studied drill holes (pH: 8.2; temperature: 200 °C) should have d11B of +21.52 per mil and d7Li of +9.7 per mil. As the data from ODP Leg 209 are clearly not in line with this, we modelled a process of seawater-rock interaction where d11B and d7Li of seawater evolve during penetration into the oceanic plate. Assuming chemical equilibrium between fluid and a rock with d11B and d7Li of ODP Leg 209 samples, we obtain d11B and d7Li values of +50 to +60 per mil, -2 to +12 per mil, respectively, for the coexisting fluid. In the oceanic domain, no hydrothermal fluids with such high d11B have yet been found, but are predicted by theoretical calculations. Combining the calculated water/rock ratios with the d7Li and d11B evolution in the fluid, shows that modification of d7Li during serpentinization requires higher water/rock ratios than modification of d11B.
Extremely heavy d11B in serpentinized oceanic mantle can potentially be transported into subduction zones, as the B budget of the oceanic plate is dominated by serpentinites. Extremely light d7Li is unlikely to survive as the Li budget is dominated by the oceanic crust, even at small fractions.
Project(s):
Coverage:
Median Latitude: 15.371105 * Median Longitude: -45.824010 * South-bound Latitude: 15.094430 * West-bound Longitude: -46.676360 * North-bound Latitude: 15.647780 * East-bound Longitude: -44.971660
Date/Time Start: 2003-06-07T07:45:00 * Date/Time End: 2003-06-18T21:45:00
Minimum DEPTH, sediment/rock: 0.89 m * Maximum DEPTH, sediment/rock: 146.69 m
Event(s):
209-1272A  * Latitude: 15.094430 * Longitude: -44.971660 * Date/Time Start: 2003-06-07T07:45:00 * Date/Time End: 2003-06-12T07:30:00 * Elevation: -2559.8 m * Penetration: 131 m * Recovery: 37.5 m * Location: South Atlantic Ocean * Campaign: Leg209 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 27 cores; 131 m cored; 0 m drilled; 28.6 % recovery
209-1274A  * Latitude: 15.647780 * Longitude: -46.676360 * Date/Time Start: 2003-06-15T00:30:00 * Date/Time End: 2003-06-18T21:45:00 * Elevation: -3939.8 m * Penetration: 155.8 m * Recovery: 34.65 m * Location: South Atlantic Ocean * Campaign: Leg209 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 28 cores; 155.8 m cored; 0 m drilled; 22.2 % recovery
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
Event labelEvent
Sample code/labelSample labelVils, FlurinDSDP/ODP/IODP sample designation
DEPTH, sediment/rockDepth sedmGeocode – mbsf
δ11Bδ11B‰ SRMVils, Flurin
δ11B, standard deviationδ11B std dev±Vils, Flurin
Strontium-87/Strontium-86 ratio87Sr/86SrVils, Flurin
Strontium-87/Strontium-86 ratio, error87Sr/86Sr e±Vils, Flurin
Sample amountN#Vils, Flurin87Sr/86Sr
BoronBmg/kgVils, Flurin
10 Water in rockH2O%Vils, Flurin
11 LithiumLimg/kgVils, Flurin
12 Lithium, standard deviationLi std dev±Vils, Flurin
13 δ7Liδ7LiVils, Flurin
14 δ7Li, standard deviationδ7Li std dev±Vils, Flurin
15 Sample amountN#Vils, Flurind7Li
Size:
236 data points

Data

Download dataset as tab-delimited text — use the following character encoding:


Event

Sample label

Depth sed [m]
(mbsf)

δ11B [‰ SRM]

δ11B std dev [±]

87Sr/86Sr

87Sr/86Sr e [±]

N [#]
(87Sr/86Sr)

B [mg/kg]
10 
H2O [%]
11 
Li [mg/kg]
12 
Li std dev [±]
13 
δ7Li []
14 
δ7Li std dev [±]
15 
N [#]
(d7Li)
209-1272A OD 261.7532.360.410.7089540.000010258.716.100.070.00-28.460.133
209-1272AOD 676.5337.640.710.7088730.000035160.315.400.100.01-14.251.374
209-1272AOD 6/276.5337.820.40
209-1272AOD 780.1837.990.360.480.007.170.784
209-1272AOD 1189.9235.790.410.7087920.000010253.916.400.210.00-4.340.763
209-1272AOD 1599.8534.090.430.7091300.000036159.315.100.200.011.240.893
209-1272AOD 15/299.850.220.01-0.031.374
209-1272AOD 18110.1938.470.710.7085990.000027159.815.300.520.112.311.534
209-1272AOD 18/2110.1939.000.240.520.08-3.371.055
209-1272AOD 22120.0535.350.260.7088200.000123165.015.200.810.13-0.380.463
209-1272AOD 26125.0839.130.210.7090640.000022161.513.000.460.04-3.370.193
209-1272AOD 29129.4235.000.330.7089830.000041250.313.800.570.04-6.831.474
209-1272AOD 29/2129.420.520.05-4.881.354
209-1274A OD 320.890.7087920.00003121.040.20-6.801.024
209-1274AOD 3417.2734.680.260.7085480.000010231.212.700.560.08-16.550.724
209-1274AOD 3827.5440.660.190.7085360.000013217.513.100.560.04-15.571.063
209-1274AOD 4232.140.7071730.000010313.893.370.772.841.763
209-1274AOD 4536.4533.690.480.7080700.000010210.410.901.130.19-1.180.203
209-1274AOD 4869.7932.241.120.7086540.000010338.512.200.900.05-12.131.513
209-1274AOD 48/269.7932.610.33
209-1274AOD 4994.1134.111.070.7087480.000010336.615.000.280.06-4.880.753
209-1274AOD 49/294.1134.310.50
209-1274AOD 52146.6929.720.300.7085390.00001730.870.12-0.861.254