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Stable Strontium Isotope (δ Sr) Fractionation
in the Marine Realm: A Pilot Study

zur Erlangung des Doktorgrades
Dr. rer. nat.

der Mathematisch-Naturwissenschaftlichen Fakultät
der Christian-Albrechts-Universität zu Kiel

Vorgelegt von
André Krabbenhöft
Kiel, 2011

… dedicated to my family

Referent: Prof.Dr. Anton Eisenh auer
Korreferent: Priv.Doz.Dr. Thor Han steen
Tag der mündlichen Prüfung: 22.03.2 011
Zum Druck genehmigt: Kiel, 22.03 .2011

Der Deka n

Hiermit erkläre ich, dass ich die vorlrairebgenidte sDeolktbostständig und ohne
Zuhilfenahme unerlaubter Hilfsmittel Weresdteerl dlite shea eine ähnliche Arbeit
wurde an einer anderen Abteilung oder Hochs cRhauhlmeen ieimnes Prüfungsverfahrens
vorgelegt, veröffentlicht oder zur Verö ffveorntgeliecgth.u ngFerner versichere ich, dass die
Arbeit unter Einhaltung der Regeln guter fwtilssiecnhsecrh a Praxis der Deutschen
Forschungsgemeinschaft entstanden ist.

Kiel, den 22.3.2011

André Krabbenhöft A BSTRACT
The determination of the isotopic compotsuirtailo ns uobfs tnances is an important field of research
within isotope geochemistry. Especialgaltiyo nt hoef itnhvee satlikaline earth element s trontium (Sr)
plays an important role in geologicala lan dr egseeoacrhcemhi. cIn order to quantify the degree of
natural stable Sr isotope fractionatiiokn e a tedocuhbnilqeu es pwas developed in the frame of this
study. This technique allows the preciosne odfe tneartmiurnalt Sr isotope fractionation without
87 86 88 86
normalizing theSr / Sr to a fixeSdr / Sr ratio in order to correct for instrumental mass
fractionation. Variations in the starbaltie oS ra ries optorpese nted in the common δ-notat ion in per
mill [‰] deviation from standard material NIST 987 SRM
88/86 88 86 88 86
(δ Sr[‰]=((Sr/ Sr) /( Sr/ Sr) –1)∙1000). Measurements were carried out at- the IFMsample standard
GEOMAR in Kiel using a thermal ionizationt rmoamsest esrp e(cTIMS). Long term measurements of
the coral standard JCp-1 and the seawaterI AsPtSOa nrdearsudl ted in Srδ=0.194±0.025‰ and
δ Sr=0.389±0.026‰ (2SD), respectively. Thdiss tcoo rarne spimopnrovement of measurement
precision of at least a factor of 2 woh emnu lctomip acroeldl tector inductively coupled plasma mass
spectrometer (MC-ICP-MS) measurements using briancg ksetandardI E(TFZK Eand IESENHAUER , 2006).
The precise determination of natural Src tiosnoattoipoen fardads a new dimension to the well
established radiogenic Sr isotope systema.n d Semaawraitenre carbonates show significant
differences in their stable Sr isotop iwch iccoh mpwoesrie tinoont accessible by applying the
87 86
radiogenic Sr/ Sr ratio alone. In order to constraingl aglciacalia lc/hainngetse rin the marine Sr
budget the isotope composition of modern sneda wmaotder n amarine biogenic carbonates are
compared with the corresponding values ofe rrsi vaenrd whaytdrothermal solutions in a triple
88/86 87 86 87 86 88/86
isotope pδlotS r( vs. Sr/ Sr). The Sr sourceSrs/ (Sr ~ 0.71±060.0008,δ Sr ~ 0.±310.01‰)
87 86
show a heavier isotopic composition compiarned ctaor bmoanratesSr /( Sr ~ 0.7092±06.00002,
δ Sr ~ 0.±201.02‰), representing the main Sr sink. Thitso priefcl deictsse quisloibrium with
respect to Sr inputs and outputs. In ec omnotdrearsnt otcoe ant,h isotope equilibrium between
inputs and outputs was achieved during ctihael l maasxti mgluma (10-30 kyr before present). This can
be explained by invoking three times thsi ghferro m Sra iunpiquuely “glacial” source: weathering of
shelf carbonates exposed at low sea lae vealres .a lOusro cdaontsistent with the “weathering peak”
hypothesis that invokes enhanced Sr inpg utfrs omr ewseualthteirning of post-glacial abundant fine-
grained material left exposed by the rmeastsreesa t(iANVnCEg iecte al., 2009).
Furthermore, the temperature dependency Sro f iδn cultured and temperature controlled (21°C
to 29°C) warm water corAaclrosp o(ra sp.) was investigated. A strict lirneeparor terde nbd yl ike
(FIETZK Eand IESENHAUER , 2006;Ü GGREBERG et al., 2008) could not be confirmed. iOnu r this study
measurements rather revealed a nonlinear irpel atbietonwsehen temperature andS r δ
88/86 2 2
(δ Sr=0.001∙T – 0.039∙T + 0.692=0,. 4r7) whereas the Sr/Ca ratio shows the eixpneeacrt ed l
88/86 18
trend. Moreover, we determined Srδ-, δO- and Sr/Ca-ratios of a fossil (1P5o rikteysr spB. P.)
coral originating from Tahiti (French-hPeol Syr/neCas iaas) .w eTll as the isotope ratios shows a
similar seasonal variabiPl oirit eys .s pFo.s si(δlSr =0.205±0.017‰, 2SEM) and rePcoerintets mean
sp. represented in this study by the cJCopra-l1 (sδtSarndar=d0.194±0.009‰, 2SEM) show JCp-1
88/86 88/86
connatural mean δSr values. The average Srδ is obviously not affected by enhanced
weathering and elevated Sr fluxes from exvpeoss eddu rsihnegl glacial times like it is the case for
Sr/Ca elemental ratios. Therefore, stable e frSra ctisoontaotpion can potentially serve as
independent and unbiased parameter for rengc opnsatlreuoc-tsiea-surface-temperatures.


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