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of Sr from the continental reservoir. This
represents a potentially important suite of
coupled processes operating outside of the
steady-state, and hence warrants investiga-
tion on a global scale.
This study integrates detrital zircon U-Pb
age and trace element proxies for an excep-
tionally large global detrital zircon data set
(n = 24,206) from samples derived from
Earth’s major continental landmasses to
develop a better understanding of the
petrotectonic evolution of continental crust
through time and its potential link to the
87 Sr/ Sr evolution of Earth’s oceans (see
86
Supplemental Material for data, sources,
1
and methods). The cumulative zircon age
distribution binned in 0.1-Gyr age intervals
in Figure 1B shows a series of age peaks
similar to other global U-Pb detrital zircon
age data sets (Campbell and Allen, 2008).
The majority of zircons in this data set
(Th/U >0.1) are expected to be derived from
felsic igneous rocks formed along conver-
gent margins, which represent the primary
source for zircons within the geologic
record (Lee and Bachmann, 2014).

PATTERNS OF CRUSTAL
REWORKING
Thorium is an incompatible element that
becomes enriched relative to other elements
as continental crust matures (McLennan
and Taylor, 1980). Therefore, increases in
Th/Yb ratios in zircon should correlate with
increases in the production of evolved felsic
Figure 1. (A) Sr/ Sr evolution of seawater from marine limestones and fossils with respect to the rocks associated with magmatic recycling
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mantle contribution (Shields and Veizer, 2002). Red data points are poorly constrained in age (greater of older radiogenic crust (Barth et al., 2013).
than ± 50 Ma). (B) Normalized marine Sr/ Sr evolution from Shields (2007) with respect to kernel
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density estimate plot and histogram (Vermeesch, 2012) of cumulative U-Pb age data (n = 24,190) for the Monte Carlo bootstrap resampling of the
global compilation of detrital zircons analyzed in this study. Emergence of paired high dT/dP-intermediate trace element record (to minimize the effect
dT/dP metamorphism and widespread ultrahigh-pressure (UHP) and blueschist metamorphism (cold
subduction) from Brown and Johnson (2018), and Wilson cycle onset from Shirey and Richardson (2011). of sampling bias presented by zircon age
peaks) shows that increased Th/Yb ratios
are generally associated with two principal
εHf have been found to correlate with shown to correlate with changes in zircon periods in the Precambrian since 3.0 Ga
increases in whole-rock Sr/ Sr ratios trace element ratios indicative of increased (Fig. 2A). The results suggest a higher
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(Bataille et al., 2017). Increases in oceanic crustal reworking and thickness recorded in proportion of magmas characterized by
86
87 Sr/ Sr ratios have, therefore, been linked Neoproterozoic to Triassic sandstones from increased assimilation of radiogenic crust at
to the production, and weathering, of exten- Antarctica (Paulsen et al., 2020). Increases 2.5–1.9 Ga and 0.7–0.5 Ga. Igneous zircon
sive felsic igneous rocks along convergent in crustal thickness lead to increases in Th contents may be influenced by the pres-
margins involving subduction or collisions continental elevation (mountain building), ence of rare accessory phases (e.g., allanite)
(Bataille et al., 2017). A plausible causal which has in turn been associated with that compete to incorporate Th during crys-
link exists because such rocks tend to be increased Sr runoff into Earth’s oceans tallization (Kirkland et al., 2015). However,
eroded rapidly due to their high elevations (Edmond, 1992; Richter et al., 1992; Raymo this pattern is also recognized on a global
above sea level in proximity to oceans and Ruddiman, 1992; Shields, 2007). scale in the zircon Hf isotope record, the
(Milliman and Syvitski, 1992). Therefore, the record of increases in crustal isotopic value of which is primarily con-
Increases in the Sr/ Sr ratios recorded assimilation and thickness from Antarctica trolled by the amount of crustal recycling in
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in marine limestones have recently been may point to significant, punctuated releases magmas. εHf-age values from a separate
1 Supplemental Material. Table S1 (detrital zircon U-Pb age and trace element ratio global compilation, sample location maps, methods, and data sources). Go to https://
doi.org/10.1130/GSAT.S.16942894 to access the supplemental material; contact editing@geosociety.org with any questions.

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