Evolution from carbonated melt to alkali basalt in the South China Sea

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1 In the format provided by the authors and unedited. SUPPLEMENTARY INFORMATION DOI: /NGEO2877 Evolution from carbonated melt to alkali basalt in the South China Sea Guo-Liang Zhang 1,2,3, Li-Hui Chen 4, Matthew G. Jackson 3, Albrecht W. Hofmann 5 1 Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China 2 Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China 3 Department of Earth Sciences, University of California Santa Barbara, Santa Barbara, CA, United States 4 State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China 5 Max-Planck-Institute für Chemie, Postfach, Mainz, Germany NATURE GEOSCIENCE Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

2 1. Supplementary Figures Supplementary Figure 1. Plots of total alkaline (Na 2 O+K 2 O) versus SiO 2 for Site U1431 volcanic clasts. Red star, composition of the glass of plagioclase-hosted melt inclusions (Data of spots No.35 and No.38 in S1-Table 1 of Supplementary 1) in sample 21R-1-W-(9/11). Other legends are as in Fig. 2. 2

3 Supplementary Figure 2. Plots of Al 2 O 3, Na 2 O, K 2 O, MgO, TiO 2 and CaO/Al 2 O 3 vs. SiO 2 for Site U1431 volcanic clasts. Legends as in Fig. 2. Carbonated peridotite melts experimentally derived at pressure of 3 GPa 13,26 and carbonated eclogite melts derived at pressures from GPa 15,27,28 are plotted for comparison. 3

4 Supplementary Figure 3. Plots of trace elements vs. SiO 2 for Site U1431 volcanic clasts. Legends as in Fig. 2. 4

5 Supplementary Figure 4. Correlations of trace element ratios with SiO 2 for Site U1431 volcanic clasts. Legends as in Fig. 2. 5

6 Supplementary Figure 5. Plots of 207 Pb/ 204 Pb vs. 206 Pb/ 204 Pb and εhf vs. εnd for Site U1431 volcanic clasts. Arrow indicates depletion trend towards the N-MORB samples at Site U1431 (Data are listed in Supplementary Table 2.). Legends as in Fig. 2. Sources of data for comparison: the East Pacific Rise (EPR) and Indian ridge MORBs, the South China Sea seamount basalts are from literature 23,44. NHRL, north hemisphere reference line, based on literature 45. 6

7 Supplementary Figure 6. Plots of trace element ratios (La/Yb, La/Sm, La/Nb and Sm/Hf) vs. 87 Sr/ 86 Sr for Site U1431 volcanic clasts. Legends as in Fig. 2. 7

8 Supplementary Figure 7. Plots of 87 Sr/ 86 Sr, εnd, 206 Pb/ 204 Pb and εhf vs. SiO 2 for Site U1431 volcanic clasts. Legends as in Fig. 2. Arrows indicate the depletion trend in isotopes during the transition from carbonated silicate melts to alkali basalts. 8

9 Supplementary Figure 8. Plots of P 2 O 5 and Ce/Pb vs. La/Nb showing effects of apatite fractionation. Legends as in Fig. 2. Data sources: OIBs as in Fig. 2; the oceanic carbonatites are from literature 9 ; primitive mantle (PM) are from literature 36. Sample 25R-1-W-(116/120) with the highest La/Nb ratio is selected for calculation of apatite (Ca 5 (PO 4 ) 3 (F,OH)) fractionation. The partition coefficients between apatite/melts are from literature 30. 9

10 2. Supplementary 1- Petrography and Lithology Summary for sampling and analyses The International Ocean Discovery Program (IODP Exp_349) Site U1431 drilled into the mid-ocean ridge basalt (MORB) basement near the fossil spreading ridge of South China Sea (SCS). Before reaching the basement, a layer of volcanic breccia ( mbsf) was recovered. The volcanic breccia is inter-bedded with multiple layers of pelagic sediment. Fossils in the sediment constrain ages between 12.8 Ma 7.4 Ma (Fig. 1). Clasts of the volcanic breccia vary in diameter from several millimeters to ~10 centimeters. The volcanic clasts from the lower layer (the early stage) have the most abundant globules, which are generally spherical and dumbbell-shaped and less commonly irregular-shaped (as shown in S1-Fig. 1, S1-Fig. 2 in this file). The abundance of globules decreases towards the top where the clasts have rare/no globules. Judging from the observation on the groundmass of the thin sections under microscope, these clast samples are fresh or very slightly altered. The clast sample 21R-1-W-(9/11) from the lower part of the breccia layer has the most abundant globules (S1-Fig. 1-B). The diameter of globules in this sample vary from <0.1mm to 3 mm. Its whole-rock has the most abundant CaO (25.6 wt%) and P 2 O 5 (6.76 wt%), strongest enrichments of light rare earth elements (LREEs), and negative anomalies of high field strength elements (HFSEs). Based on petrographical observation (S1-Fig. 2), Sample 21R-1-W-(9/11) was analyzed for and measured by electron microprobe (EMPA) for major elements (S1-Fig. 3&4) and laser ablation of inductively coupled plasma mass spectrometry (LA-ICP-MS) for trace elements (S1-Fig. 6). Results of EMPA analyses are shown in S1-Table 1 and results of LA-ICP-MS analyses are shown in S1-Table 2. Analytical methods for EMPA and LA-ICP-MS are shown in Supplementary 2-Methods. Evidence for primary magmatic origin of the carbonatites in this study (A - G) A. Phases resulted from conjugate immiscible melts within globules Results of EMPA analyses on sample 21R-1-W-(9/11), the sample with the highest abundance 10

11 of primary magmatic, carbonatite-rich globules, show four phases in typical globules. These phases are all primary magmatic in composition: 1) Carbonate. The center of globules is typically filled with calcium calcite crystals (CaO of ~50 wt%) (representative analyses of spot 1 in S1-Fig. 3A, Spot in S1-Fig. 3B) surrounded by MgO-rich ( wt%) calcite (representative analyses of spot 5 in S1-Fig. 3A, spot 21 in S1-Fig. 3B). 2) P 2 O 5 -CaO-Ti-F rich glass. Additionally, the globules host glass enriched in CaO (33.8 wt% to 48.3 wt%), P 2 O 5 (17.1 wt% to 24.4 wt%) and F (up to 2.4 wt%), and with TiO 2 of up to 4.0 wt% and Na 2 O up to 0.9 wt%, but mostly depleted in SiO 2 and most of other oxides (representative analyses of spot 6 in S1-Fig. 3A, spot 18 in S1-Fig. 3B, spot 27 in S1-Fig. 3C). 3) MgO-FeO t rich, low-cao silicate glass. A different glass composition, which is a silicate, is also found in the globules, and is enriched in MgO (13.8 wt% to 16.3 wt%) and FeO t (10.4 wt% to 14.1 wt%) and depleted in CaO (<1.6 wt%) (representative analyses of spots 3 and 7 in S1-Fig. 3A; spots 10, 15 and 22 in S1-Fig. 3B). 4) K 2 O-Na 2 O rich, low CaO silicate glass. A second type of silicate glass in the globules is enriched in K 2 O (~2.4 wt%) and Na 2 O (~3.9 wt%) and depleted in CaO (~1.0 wt%) (representative analyses of spot 2 in S1-Fig. 3A). Major element compositions of the glassy phases above are plotted in S1-Fig. 5 for comparison. The two types of silicate glasses have contrasted compositions. One is enriched in MgO-FeO t but depleted in K 2 O-Na 2 O (S1-Fig. 5), while the other is enriched in K 2 O-Na 2 O but has very low MgO and FeO t (S1-Fig. 5). Thus, these two types of glass are complementary in compositions of MgO, FeO t, K 2 O and Na 2 O, suggesting compositional gap between conjugate immiscible melts (Kjarsgaard and Peterson, 1991; Lee and Wyllie, 1997; Panina et al., 2008; Lester et al., 2013). The MgO-FeO t rich glass has lower SiO 2 and Al 2 O 3 than the K 2 O-Na 2 O rich glass, while both types of silicate glass contain low P 2 O 5 (<0.02 wt%) and CaO (<1.6 wt%). Importantly, the carbonate phase (high CaO concentration) is complementary in CaO concentration to the two types of silicate glass, which have low CaO concentrations. Also, the glass of the third type (i.e., the non-silicate glass) has high P 2 O 5 -CaO-F but very low SiO 2 (S1-Fig. 5) is also conjugate to the two types of silicate glass in P 2 O 5, CaO and SiO 2 concentrations. The P 2 O 5 -CaO-F glass in this study is also generally enriched in TiO 2 and Na 2 O, which corroborate its 11

12 magmatic origin, because seawater has extremely low/no TiO 2. Thus, compositions of the four phases within the globules point to origin from immiscibility (unmixing) of a phosphor-fluorine rich carbonated silicate melt. There are two major stages of melt immiscibility, one of which is formation of the globule as immiscible melt, the other is differentiation of the melt in the globule into the four immiscible phases mentioned above. B. Alkaline (Na-K) feldspar precipitated from immiscible melt in globules Alkaline (Na 2 O-K 2 O) feldspars (S1-Fig. 3C, EMPA spots 28 and 29) are common in the globule for sample 21R-1-W-(9/11), which is very similar in major element compositions to the above mentioned K 2 O-Na 2 O-rich silicate glass (S1-Fig. 5). This type of alkaline feldspar is usually found within the globules in this study, and in the same globule there are phases of carbonate and silicate glass (enriched in P 2 O 5 -MgO-FeO t but strongly depleted in Na 2 O-K 2 O-SiO 2 -Al 2 O 3, see spot 27 in S1-Fig. 3C). Also, there is no Na 2 O-K 2 O rich silicate glass in this type of globule (S1-Fig. 3C). Thus, it is reasonable to propose that the alkaline feldspar has precipitated from the above-mentioned immiscible Na 2 O-K 2 O rich silicate melt (glass) in the globule, corroborating genesis of the above-mentioned Na 2 O-K 2 O-rich silicate melt through immiscibility of a phosphor-fluorine rich carbonated silicate melt. C. P 2 O 5 -CaO-TiO 2 -F rich silicate glass in plagioclase-hosted melt inclusions There are many well-preserved melt inclusions (MI) in plagioclase phenocrysts in sample 21R-1-W-(9/11). Here we show results of the EMPA analyses on representative melt inclusion glasses hosted in the plagioclase phenocryst (S1-Fig. 4). Based on the backscatter image, the melt inclusion shown in S1-Fig. 4a has precipitated a thin layer of plagioclase on the wall of the host mineral. The melt inclusion is composed of two phases: (1) a homogenous silicate glass (bright zone in the backscatter image in S1-Fig. 4a) enriched in P 2 O 5 -CaO-F-Na 2 O-K 2 O-TiO 2 (P 2 O 5 of up to 16.5 wt%, F of up to 3.3 wt%, CaO of up to 28.5 wt%, and TiO 2 of up to 4.8 wt%) (see spots 35 and 38 in S1-Fig. 4) (see S1-Fig. 5 for comparison with other silicate glasses), and (2) the other phase is (i.e., the spherical, dark zone in the backscatter image in S1-Fig. 4a) is enriched in MgO-FeO t but depleted in P 2 O 5 -CaO-F-Na 2 O-K 2 O-TiO 2 (see spot 36 in S1-Fig. 4). The total weight percent (wt%) of major element concentrations for the two kinds of phases 12

13 in the plagioclase-hosted melt inclusions are always much lower than 100 wt%, indicating a significant amount of volatiles (e.g., CO 2 ) in the inclusions. Despite loss of CaO from the melt inclusion due to fractionation of plagioclase to the wall of host plagioclase, the melt inclusion still has an extremely high content of CaO (~28.5 wt%), which is higher than the whole-rock concentration of CaO (25.6 wt%) of this sample. This type of melt inclusion (bright glass) also has P 2 O 5 much higher than, MgO similar to, and SiO 2 lower than the whole-rock composition of its host rock (see S1-Fig. 5). Compared with the whole-rock compositions of this sample suite on Total Alkaline vs. SiO 2, the melt inclusion glass is more primitive (Extended Data Fig. 1). The compositions of the plagioclase-hosted melt inclusion glass suggest that the host rock (sample 21R-1-W-(9/11)) is P 2 O 5 -CaO-TiO 2 -F-rich carbonated silicate melt. The P 2 O 5 -CaO-TiO 2 -F-rich melt inclusions further suggest a primary magmatic origin of the P 2 O 5 -CaO-TiO 2 -F glass in the globules of sample 21R-1-W-(9/11). The compositions of plagioclase-hosted melt inclusions support that the above-mentioned immiscible phases are derived from a P 2 O 5 -CaO-F-rich carbonated silicate melt. D. Dumbbell shape globules formed by immiscible melt droplet evolution In addition to spherical globules, there are also many dumbbell-shaped globules (S1-Fig. 2). The existence of dumbbell shape phases in the sample is consistent with evolution of an immiscible melt droplet (melt 2) in another melt (melt 1) (S1-Fig. 6). Modeling result of Guido and Greco (2004) on the shape evolution of an initially spherical drop of immiscible melt is shown in S1-Fig. 6. Under shear flow, the immiscible melt droplet (melt 2) experiences necking before breaking up into two separated melt droplets, thus forming a dumbbell shaped droplet. The dumbbell shaped immiscible melt droplet evolution has been verified by experimental studies on silicate-dominated system (e.g., Lester et al., 2013), and by field observation on immiscible carbonate melts (e.g., Kjarsgaard and Hamilton, 1989). Thus, the presence of dumbbell shaped globules in sample 21R-1-W-(9/11) is consistent with the morphology of immiscible melts. E. Two coexisting carbonate phases Two types of coexisting carbonates (calcium calcite, MgO-rich calcite; see S1-Fig. 3 & S1-Table 1) are common in the globules of sample 21R-1-W-(9/11). The calcium calcite generally 13

14 has regular crystal shape and is always surrounded by MgO-rich calcite (S1-Fig. 3). It is well known that Mg 2+ can substitute Ca 2+ in the CaO-dominated calcite. According to the phase diagram of CaCO 3 -MgCO 3 (e.g., Irving and Wyllie, 1975), calcite (CaCO 3 ) has higher melting point than MgO-rich calcite for a given pressure, thus, crystallization of a CaO-MgO-bearing carbonated melt will precipitate calcium calcite first; then, as temperature drops and precipitation of calcium calcite proceeds, Mg 2+ will participate in crystallization. Crystallization of calcium calcite followed by MgO-rich calcite in carbonatite melt has also widely been verified by field observations (e.g., Le Bas, 1989 and references therein). Thus, the coexisting and contact relationships of these two classes of carbonates are consistent with a magmatic origin. F. High Sr/Ca ratio calcium carbonate LA-ICP-MS analyses of carbonate in this study show that the calcium calcite has extremely high Sr concentration ( ppm) (S1-Fig. 7 & S1-Table 2). Here, we use the ratio of Sr/Ca to distinguish primary carbonate from seawater-derived secondary carbonates. The partition coefficient D Sr (where D Sr = (Sr/Ca) calcite /(Sr/Ca) solution ) of the Sr/Ca ratio between calcite and solution has been shown to exhibit a relatively narrow range of values (0.02 to 0.05) under temperature of <50 C (Malone and Baker, 1999 and references therein). Thus, for a given Sr/Ca ratio of a solution, we can calculate the Sr/Ca ratio of the equilibrium carbonate that precipitates from it. More importantly, global seawater has widely been shown to have relatively constant Sr ( mg/kg) and Ca (~410 mg/kg) concentrations (Nagaya et al., 1971 and references therein; Besson et al., 2014) and thus a relatively constant Sr/Ca ratio (De Villiers, 1999). Here we use the standard seawater Sr (7.9 mg/kg) and Ca (412 mg/kg) concentrations of Summerhayes et al (1996), and we use an average D Sr of Thus, the calculated Sr/Ca for calcite precipitated from seawater would be This ratio is similar to the Sr/Ca ratio measured for seawater-derived secondary carbonates (e.g., see carbonates in altered basalts from ODP hole 801C in S1-Fig. 8). Compared to seawater-derived calcite, the carbonates in this study have much higher Sr/Ca ratio ( to ) (S1-Fig. 8). Such high Sr/Ca ratios require unrealistic high Sr/Ca ratio (25 to 50 times of seawater) in the seawater, and, thus, present strong evidence that the calcites in the globules in this study are not seawater-derived secondary carbonate. Moreover, the Sr/Ca 14

15 ratios in this study are similar to oceanic carbonatites (Hoernel et al., 2002), which indicates that high Sr/Ca ratios in this study can be a magmatic origin (see S1-Fig. 8). G. Anomalously positive high-sr-ba, low-rees carbonate formed by melt immiscibility Results of trace element of carbonates (S1-Fig. 7) analyzed by LA-ICP-MS are shown in S1-Table 2. Notable features of the dataset in S1-Table 2 is that the carbonates in this study have strongly positive Sr and Ba anomalies, and many of the trace elements, including rare earth elements (REEs), are extremely low. Concentrations of REEs of these carbonates are much lower than the whole-rock compositions of oceanic carbonatites reported in Hoernle et al (2010) (S1-Fig. 9a), and they are even much lower than those of secondary carbonates formed in the altered basalts at ODP Hole 801C (S1-Fig. 9a). Despite the low REE concentrations, the patterns are similar to oceanic carbonatites and distinct from the secondary carbonates from ODP Hole 801C (S1-Fig. 9a). Additionally, the extremely positive Sr and Ba anomalies of the carbonates in this study are distinct from the secondary carbonates formed by alteration (S1-Fig. 9a). REEs are strongly compatible in carbonatite melts during solid mantle melting (e.g., carbonatite melt in equilibrium with solid peridotite or eclogite) (Hammouda et al., 2009; Dasgupta et al., 2009). However, partition of elements between coexisting carbonatite and silicate melts are different from between carbonate melt/solid mantle phases. Increasing studies show that REEs (especially for HREEs) and many other trace elements (except for Sr and Ba) are very incompatible in carbonatite melt between immiscible carbonatite/silicate melts (S1-Fig. 9a) (Veksler et al., 1998; Veksler et al., 2012; Martin et al., 2013). This is supported by the observation in Oldoinyo Lengai that the immiscible natrocarbonatites have much lower trace element abundances (except for Sr, Ba) than the conjugate nephelinite (Veksler et al., 2012). Moreover, the presence of phosphate and/or fluorine in carbonatite melts strongly increase the compatibility of REEs (Ryabchikov et al., 1993; Suk, 1997, 1998 and 2001), however, in the immiscible melts of phosphate (fluorine)/carbonate/silicate, REEs are strongly compatible in phosphate (fluorine) melt and incompatible in carbonate and silicate melts (S1-Fig. 9b) (Suk, 1997, 1998 and 2001; Veksler et al., 2012). In the globule of sample U1431E-21R-1-W-(9/11), there is a P-F-glass phase, two silicate glass phases and a carbonate phase (see discussions above). 15

16 According to the strong incompatibility of REEs and strong compatibility of Sr and Ba in carbonate among immiscible silicate-melt/p-f-melt/carbonate-melt (S1-Fig. 9b), it is reasonable for carbonate melt in the globules of this study to have extremely low REEs and positive Sr and Ba. Thus, the low concentrations of REEs (especially HREEs) and positive Sr and Ba ((S1-Fig. 9a) of carbonates in the globules in this study are consistent with an origin of melt immiscibility. The Mg-rich calcite is predicted to have formed after the calcium calcite according their contact relationship (S1-Fig. 7). This is consistent with previous observation that carbonatite melts first crystallize Sr-rich calcium carbonate (Sr is highly compatible in calcium carbonate), which is followed by Mg-rich low-sr carbonate (Le Bas, 1989). Compared with seafloor secondary carbonates (ODP 801C), the carbonates in the globules of this study have distinctively high Sr content and ratios of Ba/Y and Ce/Y (S1-Fig. 10), which exclude origin of seawater-derived carbonates. Moreover, the carbonates in this study are within the range of whole-rock compositions of oceanic carbonatites on plots of Ce/Y vs. Ba/Y and Sr vs. Ba/Y (S1-Fig. 10), suggesting a magmatic origin of carbonates in the globules of this study. 16

17 S1-Figure 1. Hand specimens photos of volcanic clasts at Site U1431. The volcanic clasts from the bottom to the top of the volcanic breccia layer are: A, 26R-2-W-(92/94), mbsf, composed of groundmass and globules (light color) types of glass; B, 21R-1-W-(9/11), mbsf, composed of partial crystalline groundmass and abundant globules (light color and mostly spherical); C, 10R-1-W-(41/44), mbsf, microcrystalline volcanic clast with rare globules. 17

18 S1-Figure 2. Microphotographs of sample 21R-1-W-(9/11). A, C and E are under plane polarized light, B, D and F are under crossed polarized light. The sample has abundant globules, which contain multiple phases, including glass (they are extinction under crossed polarized light) and carbonate. 18

19 S1-Figure 3. Backscatter image and EMPA analyses position of Site U1431 clast sample 21R-1-W-(9/11) (A-C). Results of EMPA analyses are shown in S1-Table 1. A. Composed of four phases in the globule: carbonate (MgO-poor and MgO-rich calcite) (spot 5), silicate glass enriched in K 2 O-Na 2 O and depleted in CaO (spot 2), silicate glass enriched in MgO-FeO t and depleted in CaO (spot 3,7), and P 2 O 5 -CaO-enriched glass (spot 6); B. Composed of three phases of in the globule: carbonate (MgO-rich calcite (spot 8,9,14 and 21) and/or MgO-poor calcite (spot 19,20)), silicate glass enriched in MgO-FeO t and depleted in CaO (spot 10,16,22), and P 2 O 5 -CaO-F-riched silicate glass (spot 18), and the groundmass surrounding globules is also P 2 O 5 -CaO-F-rich silicate glass (spot 24); C. Composed of three phases in the globules: alkaline (K 2 O-Na 2 O) feldspar (spot 28,29), carbonate (calcite) (spot 30) and P 2 O 5 -CaO-rich silicate glass (spot 27). 19

20 S1-Figure 4. Backscatter image and EMPA analyses of representative plagioclase-hosted melt inclusions. A. The melt inclusion is composed of two glassy phases, one of P 2 O 5 -CaO-F-Na 2 O-K 2 O-TiO 2 -rich silicate glass (spots 35, 38), the other of MgO-FeO t -rich P 2 O 5 -CaO-F-Na 2 O-K 2 O-TiO 2 -poor silicate glass (spots 36, 37). B. The melt inclusion is composed of P 2 O 5 -CaO-F-rich silicate glass. 20

21 S1-Figure 5. Plots of SiO 2 vs. (a) MgO, (b) FeO t, (c) K 2 O, (d) Na 2 O, (e) CaO, (f) P 2 O 5 and (g) TiO 2 for typical glass and alkali feldspar in globules and glass of plagioclase-hosted melt inclusion (MI). 21

22 S1-Figure 6. The shape evolution of an initially spherical drop of immiscible melt 1 in melt 2 and formation of dumbbell-shaped globule under shear flow based on Guido and Greco (2004). 22

23 S1-Figure 7. Positions of LA-ICP-MS analyses on carbonates in sample U1431E-21R-1-W-(9/11). Yellow circles indicate high Sr-Ba group compositions and blue circles indicate low Sr-Ba group compositions. S1-Figure 8. Plots of Sr/Ca vs. Sr for calcium calcite in this study compared with secondary carbonate at ODP 801C (data from oceanic carbonatite (Hoernle et al., 2002), and calculated calcite in equilibrium with standard seawater (Summerhayes et al., 1996). 23

24 S1-Figure 9. (a) Trace element patterns of carbonates of sample U1431E-21R-1-W-(9/11). The average composition of whole-rock oceanic carbonatites from Hoernle et al (2002), and the average composition of secondary carbonate from ODP Hole 801C (data from are plotted for comparison. Data of primitive mantle for normalization are from McDonough and Sun (1995). (b) Patterns of partition coefficient (D) between carbonate melt/silicate melt, between phosphate melt/silicate melt, and between fluoride melt/silicate melt. Data of partition coefficient are from Veksler et al (2012). 24

25 S1-Figure 10. Comparison of carbonate data in this study with whole-rock oceanic carbonatite (Hoernle et al., 2010) and oceanic secondary carbonate (ODP 801C) (data from on plots of (a) Sr vs. Ba/Y, and (b) Ce/Y vs. Ba/Y. Selection of elements for comparison is based on the relatively high concentrations that allow better data quality. References of Supplementary 1 Besson, P., et al. Calcium, Na, K and Mg Concentrations in Seawater by Inductively Coupled Plasma Atomic Emission Spectrometry: Applications to IAPSO Seawater Reference Material, Hydrothermal Fluids and Synthetic Seawater Solutions. Geostandards and Geoanalytical Research 38(3), (2014). De Villiers, S. Seawater strontium and Sr/Ca variability in the Atlantic and Pacific oceans. Earth and Planetary Science Letters 171(4), (1999). Dasgupta, R., Hirschmann, M. M., McDonough, W. F., Spiegelman, M. & Withers, A. C. Trace element partitioning between garnet lherzolite and carbonatite at 6.6 and 8.6 GPa with applications to the geochemistry of the mantle and of mantle-derived melts. Chemical Geology 262(1), (2009). Guido, S. & Greco, F. Dynamics of a liquid drop in a flowing immiscible liquid. Rheology Reviews (2004). Hammouda, T., Moine, B. N., Devidal, J. L. & Vincent, C. Trace element partitioning during 25

26 partial melting of carbonated eclogites. Physics of the Earth and Planetary Interiors 174(1), (2009). Hoernle, K., Tilton, G., Le Bas, M. J. & Garbe-Schönberg, D. Geochemistry of oceanic carbonatites compared with continental carbonatites: mantle recycling of oceanic crustal carbonate. Contributions to Mineralogy and Petrology 142, (2002). Irving, A.J. & Wyllie, P. J. Subsolidus and melting relationships for calcite, magnesite and the join CaCO 3 -MgCO 3 36 kb. Geochimica et Cosmochimica Acta 39(1), (1975). Kjarsgaard, B. A. & Hamilton, D. L. The genesis of carbonatites by immiscibility. Page In Carbonatite, Edited by Keith Bell. ISBN: (1989). Kjarsgaard, B. & Peterson, T. Nephelinite-carbonatite liquid immiscibility at Shombole volcano, East Africa: Petrographic and experimental evidence. Mineralogy and Petrology, 43(4), (1991). Lee, W. J. & Wyllie, P. J. Liquid immiscibility between nephelinite and carbonatite from 1.0 to 2.5 GPa compared with mantle melt compositions. Contributions to Mineralogy and Petrology 127 (1-2), 1 16 (1997). Le Bas, M. J. Diversification of carbonatite. Page In Carbonatite, Edited by Keith Bell. ISBN: (1989). Lester, G. W., Clark, A. H., Kyser, T. K. & Naslund, H. R. Experiments on liquid immiscibility in silicate melts with H 2 O, P, S, F and Cl: implications for natural magmas. Contributions to Mineralogy and Petrology 166(1), (2013). Malone, M.J. & Baker, P. A. Temperature dependence of the strontium distribution coefficient in calcite; an experimental study from 408 degrees to 2008 degrees c and application to natural diagenetic calcites. Journal of Sedimentary Research 69(1), (1999). Martin, L. H., Schmidt, M. W., Mattsson, H. B. & Guenther, D. Element partitioning between immiscible carbonatite and silicate melts for dry and H2O-bearing systems at 1 3 GPa. Journal of Petrology 54(11), (2013). McDonough, W. F., Sun, S. S. The composition of the Earth. Chemical Geology 120 (3-4), (1995). Nagaya, Y., Nakamura, K. & Saiki, M. Strontium concentrations and strontium-chlorinity ratios in sea water of the North Pacific and the adjacent seas of Japan. Journal of the Oceanographical 26

27 Society of Japan 27(1), (1971). Panina, L. I. & Motorina, I. V. Liquid immiscibility in deep-seated magmas and the generation of carbonatite melts. Geochemistry International 46(5), (2008). Ryabchikov, I. D., Orlova, G. P., Senin, V. G. & Trubkin, N. V. Partitioning of rare earth elements between phosphate-rich carbonatite melts and mantle peridotites. Mineralogy and Petrology 49(1-2), 1 12 (1993). Suk, N. I. Behavior of ore elements (W, Sn, Ti and Zr) in layered immiscible silicate salt systems. Petrology 5, (1997). Suk, N. I. Distribution of ore elements between immiscible liquids in silicate-phosphate systems (experimental investigation). Acta Universitatis Carolinae Geologica (1998). Suk, N. I. Experimental study of liquid immiscibility in silicate-carbonate systems. Petrology 9(5), (2001). Summerhayes, C. P. & Thorpe, S. A. Oceanography An Illustrated Guide, Chapter 11, (1996). Veksler, I. V. et al. Partitioning of elements between silicate melt and immiscible fluoride, chloride, carbonate, phosphate and sulfate melts, with implications to the origin of natrocarbonatite. Geochimica et Cosmochimica Acta 79, (2012). Veksler, I. V., Petibon, C., Jenner, G. A., Dorfman, A. M. & Dingwell, D. B. Trace element partitioning in immiscible silicate carbonate liquid systems: an initial experimental study using a centrifuge autoclave. Journal of Petrology 39(11-12), (1998). 27

28 S1-Table 1. Results (wt%) of EMPA analyses of spots shown in S1-Fig. 3&4. ND, not detected; NA, not analysed. Spot Mineral Phases Positions SiO 2 CaO Al 2 O 3 P 2 O 5 MgO FeO t Na 2 O K 2 O TiO 2 MnO F Total 1 calcite within globule ND ND ND 0.01 NA silicate Glass within globule ND 0.04 NA silicate Glass within globule NA calcite within globule ND NA Mg-rich Calcite within globule ND ND ND ND ND NA P-Ca-F-Na glass within globule silicate Glass within globule NA Mg-rich Calcite within globule ND ND 0.01 ND NA Mg-rich Calcite within globule ND ND ND ND 0.01 NA silicate Glass within globule NA Mg-rich Calcite within globule NA calcite within globule NA calcite within globule ND NA Mg-rich Calcite within globule ND ND ND 0.02 ND silicate Glass within globule ND silicate Glass within globule silicate Glass within globule ND P-Ca-F-Fe-Na glass within globule calcite within globule ND ND ND ND calcite within globule ND ND ND ND

29 S1-Table 1. (To be continued) Spot Mineral Phases Positions SiO 2 CaO Al 2 O 3 P 2 O 5 MgO FeO t Na 2 O K 2 O TiO 2 MnO F Tota 21 Mg-rich calcite within globule ND ND ND silicate glass within globule ND silicate glass groundmass ND P-Ca-F-Ti-Na glass groundmass silicate glass groundmass ND plagioclase groundmass ND P-Ca-Mg-Fe-Ti-Na glass within globule NA alkali Feldspar within globule ND NA alkali Feldspar within globule ND ND NA calcite within globule ND ND 1.33 NA plagioclase host Plagioclase ND ND P-Ca-F-Mg-Ti silicate glass melt inclusion (MI) silicate Glass gray zone of MI bubble ND dark zone of MI bubble ND P-Ca-F-Mg-Fe-Ti silicate melt Inclusion (MI)

30 S1-Table 2. Results (ppm) of LA-ICP-MS analyses on carbonates in the globules of sample 21R-1-W-(9/11). 3-5 and are calcium calcite; 1, 2, 6-11, and are MgO-rich calcite. Blanks, not detected. Position Sr Y Zr Nb Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb

31 3. Supplementary 2- Results of analyses on standard reference material S2-Table 1. Whole-rock Major (wt%) and minor element (Cr, Sr, V, Ba and Zn) (ppm) analyses of standard reference material. See for recommended values for the standard. BHVO-2 Standard Recommend Result1 Result2 Result3 Result4 Result5 SiO 2 (wt%) 49.9(±0.6) Al 2 O (±0.2) TFe 2 O (±0.2) CaO 11.4(±0.2) MgO 7.23(±0.12) K 2 O 0.52(±0.01) Na 2 O 2.22(±0.08) MnO TiO (±0.04) P 2 O (±0.02) LOI Total Ba (ppm) 130(±13) Sr 389(±23) Cr 280(±19) V 317(±11) Zn 103(±6)

32 S2-Table 2. Whole-rock trace element analyses (ppm) of standard reference materials. See and for recommended values for standards. Standard BHVO-2 GSR-3 Recommend Result 1 Result 2 Result 3 Result 4 Recommend Result 1 Result 2 Be 0.99(±0.1) (±0.6) Co 45.0(±3) (±5.2) Ni 119(±7) (±11) Ga 22(±2) (±1.3) Rb 9.8(±0.04) (±6) Y 26(±2) (±5) Zr 178(±11) (±30) Nb 18.1(±1) (±12) Cs 0.10(±0.01) La 15(±1) (±7) Ce 38(±2) (±12) Pr 5.3(±0.2) (±1.6) Nd 25(±1) (±5) Sm 6.2(±0.4) (±0.7) Eu 2.1(±0.2) (±0.3) Gd 6.3(±0.3) (±0.7) Tb 0.92(±0.03) (±0.2) Dy 5.3(±0.2) (±0.3) Ho 0.98(±0.04) (±0.05) Er 2.54(±0.1) (±0.3) Tm 0.33(±0.01) (±0.04) Yb 2.0(±0.2) Lu 0.27(±0.01) Hf 4.36(±0.14) Ta 1.4 (±0.1) (±0.6) Pb 1.6 (±0.3) Th 1.2(±0.1) (±1.2) U 0.40(±0.01) (±0.4)

33 S2-Table 3. Results (ppm) of in situ analyses on standards, BHVO and NIST612, during analyses of LA-ICP-MS. Standard Sr Y Zr Nb Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb BHVO BHVO BHVO BHVO BHVO BHVO BHVO BHVO BHVO BHVO NIST NIST NIST NIST NIST NIST NIST NIST