Auxiliary Material for
Assessment of relative Ti, Ta and Nb (TITAN) enrichments in ocean island
basalts
Bradley J. Peters*, James M.D. Day
Scripps Isotope Geochemistry Laboratory, Geosciences Research Division, Scripps Institution of
Oceanography, La Jolla, CA 92093-0208, United States of America
*Corresponding author:
Email: bpeters@ucsd.edu
Phone: +1-858-534-8580
Submitted to: Geochemistry, Geophysics, Geosystems
Introduction
These supplementary materials provide additional information for methods discussed in the main
text of the paper and cite data sources for the compilation highlighted in the main text. The
authors consider this additional discussion prudent as it clarifies the treatment of a large quantity
of published data. Four specific topics are addressed:
1. Data sources for OIB compilation (text, table S1)
2. Discussion of quantitative methods for determining compositions of parental magmas
(text, figures S1-S5)
3. Iron oxidation state recalculation method from analytically determined total iron (text,
figures S6-S11).
4. Discussion of partial melting-AFC model of trace element and radiogenic isotope
compositions of OIB (text, tables S2-S4).
Index of auxiliary files:
TITANaux-text01
TITANaux-fs01
TITANaux-fs02
TITANaux-fs03
TITANaux-fs04
Contains all written supplementary information in titled sections with
references to supplementary tables and figures
Contains Supplementary Figure 1. Caption: Example of visual
determination of reference MgO using Canary Island OIB. Black boxes
represent areas in which the inflection point is expected to occur. Preferred
reference MgO for this hotspot is 10 wt. %.
Contains Supplementary Figure 2. Caption: Olivine compositions and
corresponding whole-rock Mg# from hotspots. A number of olivines lie
outside the narrow range of experimental equilibrium determined by
Roeder & Emslie [1970]. For a more detailed explanation of the
calculation of FeO from measured total Fe, please see Supplemental
Information text.
Contains Supplementary Figure 3. Caption: Comparison of parental
TITAN anomalies determined from reference MgO determined by two
methods: a visual estimate of reference MgO and olivine equilibria (see
text for explanation of each method). Both methods result in similar
calculated parental TITAN anomalies.
Contains Supplementary Figure 4. Caption: Comparison of parental
TITAN anomalies determined from visually-determined reference MgO
contents and either direct or component calculation, as described in the
text. Anomalies directly regressed against reference MgO values are
systematically higher than those determined by regression of reference
MgO against TITAN-involved elements and recalculation of parental
TITAN anomalies (or the inverse of this).
TITANaux-fs05
TITANaux-fs06
TITANaux-fs07
TITANaux-fs08
TITANaux-fs09
TITANaux-fs10
TITANaux-fs11
TITANaux-fs12
Contains Supplementary Figure 5. Caption: Parental TITAN anomalies (as
in Figure 5) versus hotspot “scorecards” [Courtillot et al., 2003;
Anderson, 2005] for a plume origin to OIB volcanism. All parental
anomalies show poor to very poor correlations, indicating that the
primitive component possibly proxied by a higher score is not present in
the source of the positive TITAN anomalies. Symbols as in Figure 5.
Contains Supplementary Figure 6. Caption: Relative abundance of FeO
relative to total Fe in OIB and a subset of picritic (primitive) OIB.
Contains Supplementary Figure 7. Caption: (a) Theoretical Fe redox state
based on olivine accumulation in typical categories of geological
materials. (b) Linear and quadratic approaches to recalculating Fe
oxidation state and absolute deviation between the two methods.
Contains Supplementary Figure 8. Caption: Propagated deviation on
whole-rock Mg# for various values of total Fe content over a range of
typical MgO contents for OIB using the two methods described in
Supplementary Information text Percent deviation remains below 1% even
for very high Fe contents.
Contains Supplementary Figure 9. Caption: Comparison of methods of
determining FeO (and, by this, Fe2+) from total Fe data when propagated
to calculations of Mg# (Mg# = Mg / (Mg+Fe2+)). A 1:1 line (solid, bold)
and other lines of constant ratio (dashed) are given with their respective
slopes.
Contains Supplementary Figure 10. Caption: Olivine and whole-rock data
for global OIB plotted with experimental equilibrium bounds of Roeder &
Emslie (1970). (a) shows Mg# calculated using FeO determined by the
method described in Section 3 of the Supplementary Information; (b)
shows Mg# using a constant ratio of FeO/(FeO + Fe2O3) = 0.9.
Contains Supplementary Figure 11. Caption: Comparison of Mg#
calculated from measured redox states of Fe and re-calculations of redox
state using the method described in Section 3 of the Supplementary
Information and a constant ratio of FeO/(FeO + Fe2O3) = 0.9. A 1:1 line
(solid, bold) and other lines of constant ratio (dashed) are given with their
respective slopes. Mg# calculated using the method described in Section 3
of the Supplementary Information are a closer statistical fit with measured
data than are Mg# calculated using a constant ratio of FeO to total Fe.
Contains Supplementary Figure 12. Caption: Re-ordering of trace element
spider diagrams based on relative incompatibilities of elements in OIB
with various accumulations of olivine, clinopyroxene and oxide
phenocryst phases for (A) typical ordering, (B) oxide accumulation >3 vol.
%; (C) <10 vol.%; (D) between >3 vol. % and (E) >20 vol. % olivine and
clinopyroxene. Accumulation of oxides, which strongly prefer HFSE
(Table S5, S7), generally cause TITAN anomalies of the highest
magnitude. In all cases, re-ordering the elements based on overall
compatibility results in Ta and Nb being shifted to the far left, indicating
that they are the most incompatible elements in these systems; this new
position means that Ta and Nb anomalies can no longer be calculated.
Titanium shifts variably, and in all cases Ti/Ti* becomes closer to 1.
These re-ordering options are not meant to suggest re-use, but show how
modal abundance of mineral phases in OIB may cause relative elemental
incompatibilities that differ from those presented in a traditional
spidergram; the most appropriate ordering of incompatible trace elements
may be closely linked to modal mineral abundances.
TITANaux-ts01
TITANaux-ts02
TITANaux-ts03
TITANaux-ts04
TITANaux-ts05
Contains Supplementary Table 1. Caption: Table of the nine hotspots
primarily studied and corresponding indexed references. References are
listed in Supplementary Information text.
Contains Supplementary Table 2. Caption: Example of the number of
samples filtered using criteria mentioned in Supplementary Information.
Some samples are excluded by multiple factors.
Contains Supplementary Table 3. Caption: Example of TITAN
calculations using various normalization schemes. PM: primitive mantle
(McDonough, 2000), CI: chondrite Ivuna (Wasson & Kallemeyn, 1988);
BE: bulk Earth (McDonough, 2000). The largest difference between PMnormalized TITAN values (preferred) and another normalization reservoir
are for CI-normalized Ta and Nb anomalies, which arise due to the low
Sm and Tb contents of CI relative to PM. Maximum variation is less than
20%.
Contains Supplementary Table 3. Caption: Partition coefficients for
numerical modeling of partial melting and references (bracketed).
References: [1] Adam & Green (2006); [2] McKenzie & O’Nions (1991);
[3] Elkins, et al. (1991); [4] Hart & Brooks (1974); [5] Kelemen, et al.
(1993); [6] Day (2013).
Literature compositions of primitive mantle as comparisons to the starting
point selected for the models (McDonough, 2000). None of the
calculations results in a TITAN anomaly that is substantially different
from 1.00; in the case of Nb/Nb*, partial melt models show that the
increase in Nb/Nb* well exceeds the difference from 1.00 shown here
(Figure 7).
TITANaux-ts06
TITANaux-ts07
Contains Supplementary Table 6. Caption: Model parameters for OIB
hotspot localities. For an explanation of variables, please see the text of
Supplementary Information.
Contains Supplementary Table 7. Caption: Partition coefficients for
numerical modeling of AFC processes and references (bracketed).
References: [1] McKenzie & O’Nions (1991); [2] Villemant, et al. (1981);
[3] Hart & Brooks (1974); [4] Nikogosian & Sobolev (1997); [5] Adam &
Green (2006); [6] Sobolev, et al. (1996); [7] Heber, et al. (2007); [8] Day
(2013); [9] Nielsen (1992); [10] Ewart & Griffin (1992); [11] Nash &
Crecraft (1985); [12] Okamoto (1979); [13] Lemarchand, et al. (1987).