Fagel, Alleman, Granina, Hatert, Thamo-Bozso, Cloots and André (2004)

Vivianite formation and distribution in Lake Baikal sediments

Fig. 1. Location of investigated cores (stations are shown by open circles) in Lake Baikal, Siberia. In addition, the shaded region highlights the area where the accumulations of vivianite were found at the stations shown by numbers (Romashkin et al., 1993, Granina and Callender, 2001 and Granin and Granina, 2002; A. Gvozdkov, personal communication). This area located opposite the Selenga Delta is noted “vivianite area” in the text.

Fig. 2. Simplified lithological columns of investigated sediment cores (plotted from South to North). Modified from Hauregard, unpublished data. The tentative correlation between the cores is based on lithology and magnetic susceptibility (Hauregard, unpublished data; Demory et al., 2004-this issue). The depths of concretion-rich layers are reported with regard to the lithological columns. Plain line: direct observation of X-radiographs; dotted line: observations after >63 μm sieving.

Fig. 3. Vivianite morphology at different scales. (A) X-radiograph photography—Distribution of concretions in sediment core: the concretions are concentrated at specific depths along the core, defining repeated laminations every few millimetres. Sample: Diatom-rich level from VER98-1-3, Academician Ridge. (B) Thin section image—Concretion showing a colour zonation from a blue central part to a yellow border. Sample: Short core from Posolsky site, CON01-427-8 (X. Boes, unpublished data). (C) SEM microphotography-Fine lamellar structure of a blue, fresh concretion. Sample: Diatom ooze from VER98-1-3, Academician Ridge, 705 cm. (D) Microprobe photography—Colour and structural zonation of one concretion: its center part displays a lighter and lamellar structure, its border is darker with no visible internal structure. Sample: Diatom ooze with clays from VER98-1-3, Academician Ridge, 208.5 cm.

Fig. 4. Bulk geochemical signature of sediments from cores CON01-604 (Posolsky Bank), CON01-603 (Continent Ridge), VER98-1-3 and VER98-1-14 (Academician Ridge). Data from ICP-AES (MRAC, Belgium). (A) MnO vs. P₂O₅ (wt.%) diagram; P-rich samples compared with the background samples. (B) SiO_{2 xs} vs. P₂O₅ (wt.%) diagram. The excess of silica is an estimation of biogenic silica and consequently reflects the diatom abundance in the sediments. It is defined as followed: SiO_{2 xs}=SiO_{2 total}−SiO_{2 detrital}; SiO₂ detrital is estimated from measured Al₂O₃ and reference Si/Al crustal ratio (Taylor and McLennan, 1985). The diagram emphasizes the range of biogenic silica content of the P-rich samples. The P-rich samples do not coincide with the richest diatom-samples in any of the core sediment samples.

Fig. 5. Infrared spectra of vivianite (VER 98-1-3, 728 cm) and santabarbaraite (VER 98-1-3, 208.5 cm) from Lake Baikal.

Fig. 6. Shales-normalised geochemical signature of isolated vivianite concretions from Lake Baikal sediment cores. Analyses by ICP-AES (Mn content, data from Table 3a) or ICP-MS (trace elements, data from Table 3b). The composition of the vivianite from Anlua, Cameroon (MRAC collection) is plotted for comparison. The Lake Baikal concretions are usually enriched with respect to the Cameroun vivianite. See text for discussion.

Fig. 7. Evolution of Mn content (normalised wt.%) measured on isolated concretions from Lake Baikal cores, i.e., from South to North: CON01-604 (Posolsky Bank), VER98-1-14 (Academician Ridge), VER98-1-3 (Academician Ridge) and CON01-603 (Continent Ridge). Analyses by microprobe (UCL, Belgium) or ICP-AES (MRAC, Belgium). Data from Table 3a. The Mn content is calculated taking into account only the measured % of FeO, MnO and, P₂O₅ (the sum being at 100%). For Lake Baikal data, each core is identified by the same symbol. Within the same core, the label indicates the depth of the sample. Data from literature are also reported: for Academician Ridge and North Baikal, from (Deike et al., 1997); Bolivia from (Rodgers et al., 1993); Greece from (Stamatakis and Koukouzas, 2001). The composition of vivianite from Cameroon (MRAC collection) has been determined during the same analytical run as the Lake Baikal vivianite samples. In Lake Baikal, the Mn content is highly variable throughout a core and from one site to another. The concretions from the Academician Ridge display the highest measured Mn content (up to 19% Mn). The Lake Baikal samples (except one reported by Deike et al., 1997) are enriched in Mn with respect to worldwide vivianites. See text for explanation.

Fig. 8. Relation between Mn and (Fe²⁺+Mg+Zn) per formula unit, for selected vivianite and santabarbaraite samples. ×: vivianite from Lake Baikal, •: santabarbaraite from Lake Baikal, □: vivianites from Cameroon, Greece (Stamatakis and Koukouzas, 2001), and Bolivia (Rodgers et al., 1993).

Table 2: Composition of major oxide in bulk sediments from lake Baikal: ICP-AES data from P-rich samples [Download]

Table 3a: Major composition (wt.%) of concretions, ICP-AES measurements [Download] 

Table 3b: Trace element composition of concretions, ICP–MS measurements [Download]

Table 4: Unit-cell parameters and Mn(Fe+Mn) ratios of vivianites from Lake Baikal [Download]

Table 5: Selected electron-microprobe analyses of vivianite and santabarbaraite from Lake Baikal [Download]   

References

P.A. Romashkin, D.F. Williams, E.B. Karabanov and A.H. Gvozdkov, Geochemical evidence of diagenetic changes and climatic events in Lake Baikal sediments, IPPCCE Newsl. 7 (1993), pp. 17–24.

L.Z. Granina and E. Callender, Formation of authigenic vivianite in Baikal bottom sediments, Geology of Seas and Oceans. XIV Intern. School on Marine Geology, GEOS Publ., Moscow (2001), pp. 250–251 (in Russian).

N.G. Granin and L.Z. Granina, Gas hydrates and gas venting in Lake Baikal, Russ. Geol. Geophys. 43 (2002), pp. 629–637.

F. Demory, N.R. Nowaczyk, A. Witt and H. Oberhänsli, High-resolution magnetostratigraphy of late Quartenary sediments from Lake Baikal, Siberia: timing of intracontinental paleoclimatic responses, Glob. Planet. Change 46 (2004), pp. 167–186.

S.R. Taylor and S.M. McLennan, The Continental Crust: its Composition and Evolution, Blackwell (1985).

R.G. Deike, L. Granina, E. Callender and J.J. McGee, Formation of ferric iron crusts in Quaternary sediments of Lake Baikal, Russia, and implications for paleoclimate, Mar. Geol. 139 (1997), pp. 21–46. doi:10.1016/S0025-3227(96)00096-5

K.A. Rodgers, H.W. Kobe and C.W. Childs, Characterization of vivianite from Catavi, Llallagua Bolivia, Mineral. Petrol. 47 (1993), pp. 193–208.

M.G. Stamatakis and N.K. Koukouzas, The occurrence of phosphate minerals in lacustrine clayey diatomite deposits, Thessaly, Central, Greece, Mar. Geol. 139 (2001), pp. 33–47. doi:10.1016/S0037-0738(00)00154-8

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