Continental Magmatism and Uplift as the Primary Driver for First-Order Oceanic 87Sr/86Sr Variability with Implications for Global Climate
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GSA Connects 2021 Presidential Address, p. 12
VOL. 32, NO. 2 | FEBRUARY 2022
Continental Magmatism and Uplift
as the Primary Driver for First-
Order Oceanic 87Sr/ 86Sr Variability
with Implications for Global Climate
and Atmospheric Oxygenation
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FEBRUARY 2022 | VOLUME 32, NUMBER 2
SCIENCE
4 Continental Magmatism and Uplift as the
Primary Driver for First-Order Oceanic
87
Sr/ 86Sr Variability with Implications for
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Continental Magmatism and Uplift as the
Primary Driver for First-Order Oceanic
87
Sr/ 86Sr Variability with Implications for
Global Climate and Atmospheric Oxygenation
Timothy Paulsen, Dept. of Geology, University of Wisconsin Oshkosh, Oshkosh, Wisconsin 54901, USA, paulsen@uwosh.edu;
Chad Deering, Dept. of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, Michigan
49931, USA; Jakub Sliwinski, Institute of Geochemistry and Petrology, Dept. of Earth Sciences, ETH Zurich, Zurich, 8092,
Switzerland; Snehamoy Chatterjee, Dept. of Geological and Mining Engineering and Sciences, Michigan Technological University,
Houghton, Michigan 49931, USA; and Olivier Bachman, Institute of Geochemistry and Petrology, Dept. of Earth Sciences, ETH
Zurich, Zurich, 8092, Switzerland
ABSTRACT 1983). According to standard models, conti- subsequently risen in association with the
Oceans cover 70% of Earth’s surface, set- nental crust is primarily formed by fluid differentiation of the crust, with rapid
ting it apart from the other terrestrial planets flux melting in the mantle wedge above increases during two principal intervals in
in the solar system, but the mechanisms driv- subducting hydrated oceanic plates as they the Precambrian, namely in the Paleo-
ing oceanic chemical evolution through time are recycled into the mantle. This is then proterozoic and Neoproterozoic (Shields
remain an important unresolved problem. followed by fractional crystallization of and Veizer, 2002) (Fig. 1A). Identifying
Imbalance in the strontium cycle, intro- mantle-derived magmas and/or partial potential drivers for these shifts in marine
duced, for example, by increases in conti- melting of preexisting crustal lithologies 87
Sr/86Sr ratios during the Precambrian is of
nental weathering associated with mountain (Hawkesworth and Kemp, 2006; Moyen et widespread interest because of possible
building, has been inferred from shifts in al., 2021). Collectively, these “distillation” links to major perturbations in the global
marine carbonate 87Sr/86Sr ratios. There are, processes have led to the development of carbon cycle and hypothetical connections
however, uncertainties about the spatial and a more felsic crust with a significant to changes in tectonism, climate, and
temporal patterns of crustal evolution in enrichment of incompatible elements, such atmospheric-oceanic oxygenation (Shields,
Earth’s past, particularly for the period lead- as rubidium and strontium, with respect 2007; Campbell and Allen, 2008; Sobolev
ing up to the Cambrian explosion of life. to the mantle as Earth has aged (Veizer, and Brown, 2019).
Here we show that U-Pb age and trace ele- 1989; McDermott and Hawkesworth, 1990). The average Sr isotopic composition of
ment data from a global compilation of detri- However, the questions of how the conti- the present oceanic crust is relatively uni-
tal zircons are consistent with marine car- nental crust has evolved chemically over form (~0.703), but the Sr isotopic composi-
bonate 87Sr/86Sr ratios, suggesting changes time and how it has influenced Earth’s tion of today’s continental crust (~0.73 on
in radiogenic continental input into Earth’s oceans and atmosphere remain as funda- average) is spatially highly variable (~0.703
oceans over time. Increases in riverine Sr mental unresolved problems. to >0.73) due to a heterogeneous rock record
input were related to the break-up and dis- Earth’s present oceans have a uniform that includes juvenile and ancient, evolved
persal of continents, with increased weather- Sr isotopic composition (87Sr/86Sr = 0.7092) crustal components (Veizer and Mackenzie,
ing and erosion of a higher proportion of that primarily reflects the balance between 2014). The average Sr isotopic composition
radiogenic rocks and high-elevation conti- radiogenic Sr input from weathering of the of today’s rivers (~0.711) reflects a balance
nental crust. Tectonic processes exert a continents and unradiogenic Sr input from of the weathering of such sources on a
strong influence on the chemical evolution of hydrothermal alteration of oceanic crust global scale (Veizer and Mackenzie, 2014),
the planet’s oceans over geologic time scales (Veizer and Mackenzie, 2014). Although but the dynamic nature of the solid Earth
and may have been a key driver for concomi- 87
Sr/86Sr ratios in marine carbonates are has likely led to changes in the proportion
tant increases in atmosphere-ocean oxygen- better documented for Phanerozoic versus of radiogenic rocks being weathered on
ation and global climate cooling. Precambrian marine limestones, oceanic Earth’s surface over time. This notion is
87
Sr/86Sr ratios appear to have departed from supported by recent analyses of a global
INTRODUCTION mantle values as early as ca. 2.8 Ga (Shields detrital zircon database, which have led to
Planetary differentiation has led to two and Veizer, 2002) (Fig. 1A). This transition the conclusion that, at least for the past 1.0
fundamental types of crust on Earth: (1) has been interpreted to mark a change Ga, increases in the 87Sr/86Sr ratios recorded
continental, which tend to survive over long from mantle- to river-buffered oceans as in marine limestones generally coincide
periods acquiring ancient rock records and the continents rose and hydrothermal with decreases in the εHf composition of
evolved compositions; and (2) oceanic, circulation of oceanic crust decreased as zircons produced by increased magmatic
which tend to be juvenile and rapidly recy- heat dissipated from Earth with time (Veizer reworking of preexisting radiogenic crust
cled by subduction (Campbell and Taylor, and Mackenzie, 2014). 87Sr/86Sr ratios have (Bataille et al., 2017). Decreases in zircon
GSA Today, v. 32, https://doi.org/10.1130/GSATG526A.1. CC-BY-NC.
4 GSA TODAY | February 2022
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/86Sr evolution of Earth’s oceans (see
Supplemental Material1 for data, sources,
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) 87Sr/86Sr evolution of seawater from marine limestones and fossils with respect to the rocks associated with magmatic recycling
mantle contribution (Shields and Veizer, 2002). Red data points are poorly constrained in age (greater
than ± 50 Ma). (B) Normalized marine 87Sr/86Sr evolution from Shields (2007) with respect to kernel
of older radiogenic crust (Barth et al., 2013).
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 87Sr/86Sr ratios trace element ratios indicative of increased (Fig. 2A). The results suggest a higher
(Bataille et al., 2017). Increases in oceanic crustal reworking and thickness recorded in proportion of magmas characterized by
87
Sr/86Sr 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 87Sr/86Sr ratios recorded assimilation and thickness from Antarctica trolled by the amount of crustal recycling in
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.
www.geosociety.org/gsatoday 5
reflect processes such as weathering and
erosion. The zircon trace element data are,
therefore, consistent with the hypothesis
that increases in the proportion of evolved
magmas along convergent margins have
had an important influence on radiogenic
Sr input into Earth’s oceans during these
time intervals.
PATTERNS OF CRUSTAL
THICKENING
Increases in magmatic reworking of pre-
existing radiogenic crust should occur asso-
ciated with thermal maximums as the crust
thickens (DeCelles et al., 2009). Garnet is a
mineral found in crustal magmas that is
highly sensitive to pressure and incorporates
heavy rare earth element (HREE)+Yb rela-
tive to other trace elements (Ducea et al.,
2015). Therefore, changes in Yb/Gd ratios
in zircon, for example, are thought to cor-
relate with changes in the crustal thickness
during magmatism (Barth et al., 2013). The
trace element record retained within the zir-
con data shows that the lowest Yb/Gd ratios
in the data set (Fig. 2C) correlate well with
the Paleoproterozoic and Neoproterozoic
Th/Yb and εHf peaks. These crustal thick-
ness patterns are similar to those presented
recently based on La/Yb ratios for a global
compilation of 5587 detrital zircons (Balica
et al., 2020). In particular, both analyses
show Paleoproterozoic and Neoproterozoic
peaks in crustal thickness that are separated
by an intervening interval from ca. 1.8 Ga
to 0.8 Ga during a period of environmen-
tal stasis known as the “boring billion”
(Holland, 2006). The trace element data are
therefore consistent with increased assimi-
lation of radiogenic crust during periods of
increased crustal thickness along conver-
gent margins. Increases in crustal thickness
are in turn associated with mountain build-
ing driven by tectonic shortening along
Earth’s major convergent plate boundaries
involving advancing states of subduction and
collisions. Thus, the patterns in the zircon
trace element data are also consistent with
Figure 2. (A) Average Th/Yb (crustal input proxy); (B) εHf (crustal input proxy; note axis the hypothesis that increases in the propor-
reversal); and (C) Yb/Gd (crustal thickness proxy) with their 95% confidence envelopes tion of radiogenic rocks (e.g., older base-
determined by Monte Carlo bootstrap resampling of zircons in 0.1-Gyr time brackets
compared to normalized marine 87Sr/86Sr evolution. εHf data from Puetz and Condie (2019).
ment) uplifted and exposed along conver-
Age of “boring billion” from Holland (2006). UHP—ultrahigh-pressure. gent margins have had an important
influence on radiogenic Sr input into Earth’s
oceans (Richter et al., 1992).
large detrital zircon data set (n = 70,656) normalized to model 87Sr/86Sr ratios of the
show that significant negative deviations global river and mantle inputs, shows CRUSTAL THICKNESS AND Sr FLUX
of εHf values correlate with these Th/Yb increases that post-date the peaks in crustal Geologists have long recognized that the
peaks (Fig. 2B). The 87Sr/86Sr isotope assimilation indicated by zircon Th/Yb and widespread generation of continental topo-
curve shown in Figures 2A–2B, which is εHf values—a time lag that may in part graphic relief, which increases the overall
6 GSA TODAY | February 2022
surface area and potential energy, should Emergence of Emergence of paired
correlate with increases in sedimentary flux blueschist & UHP high dT/dP & interm. dT/dP
metamorphism metamorphism
into Earth’s oceans. Analysis of Phanerozoic 8 Snow Snow
ball ball Wilson A
sedimentary rock records suggests that cycle
Earth Earth onset
increasing sedimentary flux correlates with
increases in 87Sr/86Sr ratios in marine lime- 20
stones (Hay et al., 2001). Detrital zircon age 12
peaks have been attributed to increases in Boring billion
sedimentary flux associated with wide-
% S-Type
Yb/Gd
spread continental collisions and convergent
margin magmatism (Campbell and Allen, 16
2008; McKenzie et al., 2016). However, other 10
authors have favored increases in preserva-
tion for these age peaks (Hawkesworth et
al., 2009), and zircon abundance does not 20
always correlate with increases in 87Sr/86Sr
ratios in Earth’s oceans over time (Fig. 1B).
0
Increases in sedimentary flux derived
from weathering of a greater proportion of PG R N Su
K Wilson B
Sc cycle
elevated continental crust should, however, 1.0 onset 0
occur associated with an increase in flysch Boring billion
deposition. Flysch successions include inter-
bedded graywackes and shales rich in quartz 0.8 500
and feldspars, which, when water-saturated,
Th/Yb
are fertile sources for the generation of
S-type granites (Collins and Richards, 2008; 0.6 1000
Zhu et al., 2020). Thus, S-type granite pro-
duction may serve as a proxy for previous
4.0
intervals of increased flysch deposition. We 1500
0.4
Atmosphere
identified zircons that are likely to have been
O2 (atm)
derived from S-type granite using the trace NOE GOE
O2 O2 O2
element discrimination procedure of Zhu et 2000
al. (2020), wherein S-type granites typically 0.2 0
Rift-Drift Rift-Drift Rift-Drift
have elevated phosphorus concentrations rel- K Wilson C
ative to I-type granites because apatite 1.9 PG R N Sc
Su cycle
onset 140
[Ca5(PO4)3(OH,F,Cl)] crystallization is sup-
Number of Passive Margins
pressed in the S-type magmas. To test the
hypothesis that the peaks in crustal thickness 1.5
were associated with an increase in S-type Boring billion
granites, we integrated S-type zircons iden- 51
U/Yb
tified within our data set with those found
through an examination of zircons from 52 1.1
38
of Earth’s major rivers (Zhu et al., 2020).
Peaks in S-type zircon percentages overlap 25
or even postdate the latter stage of increases 0.7
in crustal thickness identified here (Fig. 3A).
12
Thus, increasing radiogenic Sr input into
Earth’s oceans appears to be related to (1) the
0.3 0
weathering of a greater proportion of radio- 0 1.0 2.0 3.0 4.0
genic rocks produced and exposed as the Age (Ga)
crust thickened during the Paleoproterozoic
and Neoproterozoic time intervals, and (2) Figure 3. (A) Average Yb/Gd (crustal thickness proxy) compared to the percentage of S-type zircons
concomitant increases in continental weath- with its 95% confidence envelope. (B) Th/Yb (crustal input proxy) compared to a global compilation of
ages versus temperature/pressure (T/P) (°C/GPa) of high dT/dP (granulite−ultrahigh temperature
ering and sedimentary flux into the oceans. [UHP]) (red); intermediate dT/dP (eclogite−high-pressure granulite) (purple); and low dT/dP (high-
The results reviewed above provide pressure−UHP) metamorphism (blue) from Brown and Johnson (2018). (C) U/Yb (crustal input and fluid
input proxy) compared to a global compilation of passive margin abundance from Bradley (2008).
important confirmation that increases in Sr Tenure of supercontinent/cratons from Bradley (2011), increases in atmospheric oxygen, early “whiffs”
recorded in marine carbonates correlate of oxygen (green arrows) and intervening boring billion from Holland (2006) and Lyons et al. (2014), and
snowball Earth glaciations adapted from Sobolev and Brown (2019). Supercontinent/craton
with first-order changes in convergent mar- abbreviations: K—Kenor; Su—Superia; Sc—Sclavia; N—Nuna; R—Rodina; G—Gondwana; P—Pangea.
gin tectonism over time (Bataille et al., NOE—Neoproterozoic oxygenation event; GOE—Great oxygenation event.
www.geosociety.org/gsatoday 7
2017; Gernon et al., 2021). Increasing leading edge of continents by driving them by global changes in plate margin networks.
87
Sr/86Sr ratios in Cenozoic marine lime- into advancing compressional states of sub- Increasing 87Sr/86Sr compositions in Cenozoic
stones have been associated with decreases duction and collisions involving arcs and marine sediments have also been associated
in unradiogenic Sr flux related to lower continental blocks that favor crustal thicken- with glaciation (Palmer and Elderfield, 1985).
seafloor spreading rates (Van Der Meer et ing (Lee et al., 2013). Increases in crustal Snowball Earth deglaciation likely contrib-
al., 2014) and cooler ocean temperatures recycling and thickness identified in the zir- uted to the Paleoproterozoic and Neo-
(Coogan and Dosso, 2015), suggesting that con proxy data correlate with an increase in proterozoic Sr excursions (Sobolev and
the cause of increased 87Sr/86Sr ratios in the passive margin abundance (Bradley, 2008) Brown, 2019), but the data reviewed here
oceans may be multifactorial. The ancient (Fig. 3C). These increases around the suggest that tectonism played a major role.
ocean crust record is in large part lost due to Proterozoic-Phanerozoic time interval also Collectively, the balance of these processes
subduction (Scholl and von Huene, 2009), correlate with a decrease in thermal gradi- is likely recorded in today’s continental rock
but our results suggest that increases in ents of high dT/dP metamorphism (Brown record by the great unconformities at the
87
Sr/86Sr ratios in oceans have been strongly and Johnson, 2018). Collectively, these Precambrian-Phanerozoic and Archean-
influenced by a continental component. If patterns are consistent with superconti- Proterozoic boundaries (Windley, 1984;
the increases in the proportion of radio- nent break-up driving a greater proportion Peters and Gaines, 2012).
genic sources and sedimentary flux repre- of convergent margins into compressional
sent a coupled suite of processes as we advancing states and collisions with magma- BROADER IMPLICATIONS
contend, then they raise the question as to tism in thicker crust. High 87Sr/86Sr ratios in Our results suggest that increases in
why convergent margin tectonism changed oceans during these periods are presumably 87
Sr/86Sr ratios in oceans occur when a
during these time periods. Insight into this due to increases in the proportion of exposed greater proportion of continental crust is
issue comes from an examination of model- radiogenic sources and sedimentary flux thick and high, leading to increases in
ing and other proxy data sets to which we from the continents associated with a reorga- evolved felsic magmatism, radiogenic base-
now turn. nization of riverine drainage networks. ment exposure, and riverine sedimentary
The correlations between the zircon proxy flux. From a broader perspective, the results
SUPERCONTINENT PATTERNS AND data and processes involving subduction out- raise the important question of whether solid
SR FLUX lined above warrants an examination of the Earth processes play a fundamental role in
Modeling studies suggest that supercon- U/Yb ratio in the zircon data set. The U/Yb modulating global climate and atmospheric
tinent tenures should be marked by elevated ratio in zircon has been used as a proxy for oxygenation over geologic time scales. If the
temperatures in the underlying subconti- crustal reworking (Verdel et al., 2021) but correlations outlined above are representa-
nental mantle with convergent margins in may also reflect the amount of subducting tive of a global tectonic pattern as we con-
retreating states with arcs on thinner crust slab fluid addition in magmas, because U is tend, then the generation of continental relief
in outboard locations with respect to the a fluid-mobile large-ion lithophile element highlights the introduction of a significant
continents (Lenardic et al., 2011; Lee et al., (LILE; K, Sr, Rb, Cs, Ba, Pb, U) extracted silicate weathering sink associated with the
2013; Lenardic, 2016). Temporal consider- from slabs, and is, therefore, enriched rela- drawdown of CO2 and associated transi-
ations based on multiple proxy data sets tive to HREE such as Yb (Barth et al., 2013). tion into periods of global glaciation
suggest that the lows in crustal recycling U/Yb increases correlate with the increases (Hoffman and Schrag, 2002) (Fig. 3). Uplift
and thickness identified in the zircon proxy in crustal assimilation and thickness we have associated with convergent margin tecto-
data overlap with the tenure of superconti- identified (Fig. 3C), consistent with a higher nism may therefore have further enhanced
nents over Earth’s history (Figs. 3A–3B) amount of crustal recycling and flux of sub- CO2 drawdown associated with the exhuma-
(Bradley, 2011). For example, the low in duction fluid along a greater proportion of tion and weathering of rocks associated with
crustal recycling and thickness during the convergent margins during these periods. continental rifting and dispersal (Donnadieu
boring billion correlates with the tenure of We, therefore, conclude that the increases in et al., 2004; DeLucia et al., 2018). Continental
Nuna during a period dominated by high riverine Sr input into Earth’s oceans were uplift has also been previously postulated to
dT/dP metamorphism (Fig. 3B) and higher related to geodynamic changes in convergent be linked to steps in oxygenation of Earth’s
thermal gradients (Brown and Johnson, margin networks, which were required to atmosphere during the Paleoproterozoic and
2018). This pattern may reflect superconti- accommodate the birth and maturation of Neoproterozoic through enhanced erosion
nent insulation of the mantle (Brown and new ocean basins created by supercontinent and nutrient supply to the oceans, as well as
Johnson, 2018) associated with the devel- break-up and dispersal. These episodes were changes in the proportion of subaerial volca-
opment of hot back-arc environments associated with increased weathering and nism (Campbell and Allen, 2008; Gaillard et
(Hyndman et al., 2005) and a greater pro- erosion of radiogenic rocks along convergent al., 2011) (Fig. 3B). Oxygenation may have
portion of convergent margins in retreating margins and greater expanses of uplifted, fostered the decrease of CH4, a potent green-
states with arcs on thinner crust in outboard higher-elevation radiogenic crust found house gas (Fakhraee et al., 2019), while
localities (Roberts, 2013; Paulsen et al., along the leading edges of continents. uplifts along convergent margins promoted
2020; Tang et al., 2021). Increases in riverine Sr were likely amplified nascent glaciation in cooler, high-elevation
Supercontinent break-up, by contrast, by the exhumation of continental crust asso- habitats, providing further feedback (albedo)
should lead to a release of potential energy ciated with rifting (DeLucia et al., 2018), for a runaway global glaciation. The ultimate
stored in the underlying mantle (Lenardic, which is consistent with the general thesis drivers for these important steps in Earth’s
2016). Thermal release of the mantle induces supported here, that increases in riverine Sr evolution are controversial and likely
changes in the geodynamic state of the are primarily driven by tectonism induced involved a complex set of variables and
8 GSA TODAY | February 2022
inextricably linked feedbacks. However, Science Letters, v. 415, p. 38–46, https://doi.org/ Jellinek, A.M., Lenardic, A., and Pierrehumbert,
in general terms, potential links between the 10.1016/j.epsl.2015.01.027. R.T., 2020, Ice, fire, or fizzle: The climate foot-
solid Earth and the evolution of its climate, DeCelles, P.G., Ducea, M.N., Kapp, P., and Zandt, print of Earth’s supercontinental cycles: Geo-
G., 2009, Cyclicity in Cordilleran orogenic chemistry Geophysics Geosystems, v. 21, p. 1–45,
atmosphere, and oceans are highlighted by systems: Nature Geoscience, v. 2, https://doi.org/ https://doi.org/10.1029/2019GC008464.
recent modeling that suggests that global cli- 10.1038/ngeo469. Kirkland, C.L., Smithies, R.H., Taylor, R.J.M., Evans,
mate may ultimately be modulated by DeLucia, M.S., Guenthner, W.R., Marshak, S., N., and McDonald, B., 2015, Zircon Th/U ratios in
changes in outgassing and weathering sinks Thomson, S.N., and Ault, A.K., 2018, Thermo- magmatic environs: Lithos, v. 212–215, p. 397–414,
associated with mantle thermal states during chronology links denudation of the Great Uncon- https://doi.org/10.1016/j.lithos.2014.11.021.
formity surface to the supercontinent cycle and Lee, C.T.A., and Bachmann, O., 2014, How impor-
the assembly and break-up of superconti- snowball Earth: Geology, v. 46, p. 167–170, tant is the role of crystal fractionation in making
nents (Jellinek et al., 2020). While the oceans https://doi.org/10.1130/G39525.1. intermediate magmas? Insights from Zr and P
have played a fundamental role in the Donnadieu, Y., Goddéris, Y., Ramstein, G., Nédélec, systematics: Earth and Planetary Science Let-
geochemical evolution of the continents A., and Meert, J., 2004, A “snowball Earth” cli- ters, v. 393, p. 266–274, https://doi.org/10.1016/
(Campbell and Taylor, 1983), the continents mate triggered by continental break-up through j.epsl.2014.02.044.
changes in runoff: Nature, v. 428, p. 303–306, Lee, C.T.A., Shen, B., Slotnick, B.S., Liao, K.,
have, in turn, shaped the oceans and perhaps
https://doi.org/10.1038/nature02408. Dickens, G.R., Yokoyama, Y., Lenardic, A., Das-
major evolutionary steps in Earth’s global Ducea, M.N., Saleeby, J.B., and Bergantz, G., 2015, gupta, R., Jellinek, M., Lackey, J.S., Schneider,
climate and the oxygenation of its ocean- The architecture, chemistry, and evolution of con- T., and Tice, M.M., 2013, Continental arc-island
atmosphere system. tinental magmatic arcs: Annual Review of Earth arc fluctuations, growth of crustal carbonates,
and Planetary Sciences, v. 43, p. 299–331, https:// and long-term climate change: Geosphere, v. 9,
doi.org/10.1146/annurev-earth-060614-105049. p. 21–36, https://doi.org/10.1130/GES00822.1.
ACKNOWLEDGMENTS
Edmond, J.M., 1992, Himalayan tectonics, weather- Lenardic, A., 2016, Plate tectonics: A superconti-
We thank Jay Chapman and two anonymous re-
ing processes, and the strontium isotope record in nental boost: Nature Geoscience, v. 10, p. 4–5,
viewers for comments that improved this manuscript.
marine limestones: Science, v. 258, p. 1594–1597, https://doi.org/10.1038/ngeo2862.
This work was supported by the Faculty Development
https://doi.org/10.1126/science.258.5088.1594. Lenardic, A., Moresi, L., Jellinek, A.M., O’Neill,
Program at the University of Wisconsin, Oshkosh.
Fakhraee, M., Hancisse, O., Canfield, D.E., C.J., Cooper, C.M., and Lee, C.T., 2011, Conti-
Crowe, S.A., and Katsev, S., 2019, Proterozoic nents, supercontinents, mantle thermal mixing,
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Minerals Matter: Science, Technology, and Society
Barbara L. Dutrow, Dept. of Geology & Geophysics, E-235 Howe-Russell Geoscience Complex, Louisiana State University, Baton
Rouge, Louisiana 70803-4101, USA, dutrow@lsu.edu
The expertise of earth scientists is crucial for solving some of The expansive subject of minerals is familiar to Geological
today’s most pressing challenges, including global warming and the Society of America (GSA) audiences. Several past presidents have
climate crises, natural hazard reduction, water and soil quality, spoken on minerals and related topics, presumably beginning with
exploration for critical elements for our technological society, and the second president of GSA, James Dwight Dana, in 1890—
many others. perhaps best known for his enduring textbook The Manual of
Mineralogy, first published in 1848 (J.C. Wiley and Sons), and now
INTRODUCTION in its twenty-third edition (Klein and Dutrow, 2007). Why should
Minerals, the solid material comprising planet Earth, are within we continue to care about mineral sciences in the twenty-first cen-
the intellectual realm of earth scientists but are much more funda- tury? Because minerals still matter.
mental to science, technology, and society. From the beginnings of
humankind, Earth’s minerals have been essential for technological
advances. Prior to written language, paintings made of mineral pig-
ments adorned caves. The advent of human-produced fire owes its
source to two minerals: pyrite and flint. Early Homo species were
likely the first mineralogists, separating different minerals into
useful tools based on their physical properties to identify, in part,
those minerals that perfectly fractured when worked. Utilization of
different minerals through melting, smelting, or physical manipula-
tion defines the Ages of Man: Stone, Bronze, Iron, and Technology.
Minerals are important basic resources that can inform us about
how solid materials work on the atomic level and be modified to
humanity’s benefit. They serve as templates for technologically
advanced materials, necessary to fulfill many societal needs.
The attributes of minerals to science, technology, and society are
illustrated by a single mineral, elbaite. Elbaite is a species of the
tourmaline supergroup that incorporates nearly the entire periodic Figure 2. Banded iron formation, a source for iron, a critical component of
table in its structure (Fig. 1). For geoscientists, it embeds unparal- steel and other manufactured materials. Iron was one of the earliest mined
and smelted minerals.
leled geologic information when properly interpreted; for technol-
ogy, it was utilized during WWII as a pressure sensor to monitor
underwater explosions due to its piezoelectric properties; and for ESSENTIAL BUT UNDERVALUED
society, it is a mineral that contains lithium, an element critical to Minerals are vastly underappreciated, and the science of mineral-
powering modern electronic devices. ogy is disappearing despite their centrality to society and to the
earth sciences. Minerals (continue to) power our lives. They are
used in nearly every aspect of our lives, yet do we think of minerals
when we walk on planet Earth or answer the cell phone or turn on
the lights or start the car? The U.S. Geological Survey (USGS)
reports that an average automobile “contains more than a ton of iron
and steel, 240 lbs of aluminum, 50 lbs of carbon, 42 lbs of copper,
22 lbs of zinc, and 30 other mineral commodities” (USGS, 2021).
These materials do not include the cerium used to polish mirrors or
the other components in hybrid or electric vehicles. One primary
reason for their underappreciation is that, for the most part, we do
not use minerals, per se; we utilize their contents—their chemical
constituents (Fig. 2). From aluminum to zinc, the elements extracted
from minerals form the basis for advanced materials for our ever-
improving standard of living.
While mineralogy, or mineral sciences, has been taught largely
Figure 1. Elbaite crystal, a species of the tourmaline supergroup contain-
ing lithium, showing its noncentrosymmetic growth along the long axes as an underpinning subject or in support of other earth-science
(c) which is responsible for its piezoelectric (and pyroelectric) properties, fields (e.g., petrology or geochemistry), its utility to all facets of sci-
contributing to its utility as a technological material. Color change
reflects incorporation of different chemical elements in response to its
ence, technology, and society elevates this discipline well beyond
host environment. the geosciences. As industry and governments look to a sustainable
GSA Today, v. 32, no. 2, https://doi.org/10.1130/GSATPrsAdrs21.1. CC-BY-NC.
12 GSA TODAY | February 2022future and Environmental Social Governance (ESG) guides busi- While mineralogy is deeply embedded in most aspects of the earth
ness decisions, the earth sciences, specifically mineral sciences, are sciences (Fig. 4), mineralogy bridges disciplinary boundaries and
ever more important to provide foundational information. connects earth sciences to other science, technology, engineering,
Yet, the study of minerals has dwindled, gradually disappearing and mathematics (STEM) fields. One such example was recently
from the earth-science curriculum, particularly in the U.S. (e.g., released by the American Chemical Society in their “reaction” series
Nietzel, 2020; Bierman, 2021). Commonly viewed as “too tradi- titled “Are we standing on a quadrillion diamonds?” (ACS, 2021).
tional,” mineralogy classes have been reduced in many curricula, Chemists are capitalizing on the inspiration and engagement of
compressed into another class (e.g., “earth materials”), or aban- chemical reactions to make (natural) minerals—clearly trying to take
doned altogether and expunged from the curriculum, with the con- the spotlight from the geosciences. Much of materials science and
comitant loss of critical expertise. No funding agency supports advanced materials research is built on templates from nature (i.e.,
“mineralogical research” per se. One recent editorial described how minerals). This approach has been largely in the domain of chemists
difficult it is to find properly trained mineralogists in the U.S. and physicists—yet earth scientists have much to contribute. Because
(R. Ewing, personal commun., 2021). of my mineral-science background, I had the pleasure of serving as a
This short article provides a case for mineralogical expertise and Ph.D. committee member in the chemistry department for a candi-
implores earth scientists to re-engage with this discipline, because its date studying the crystal structure of MoS2, which mineral geoscien-
foundational knowledge and skill sets are integral to earth-science tists know as molybdenite. During the questioning, I asked the candi-
solutions required to tackle some of society’s most challenging prob- date if they could identify the shiny, gray, foliated sample of MoS2
lems. Additionally, embracing mineralogy in all its forms, by sup- I proffered. He looked at me quizzically and replied that he had no
porting mineralogical research and education, provides fundamental idea that MoS2 was an actual mineral that occurred naturally on
information required to help solve many of Earth’s most closely Earth. Clearly, geoscientists with a mineralogical background can
guarded secrets. The criticality of mineralogical knowledge is dem- inform the STEM community about mutually beneficial subjects.
onstrated by connecting the mineral sciences across scientific disci- Geoscientists understand complex, heterogeneous, multicompo-
plines and into the realm of humankind by providing select examples nent, and natural materials over ranges of spatial scales and through
in science, technology, and society. time, and are superb analysts, providing natural connections to
To geoscientists, the value of minerals to science is broadly rec- these disciplines. As such, mineralogy is a translational science,
ognized. Resulting from complex planetary processes, minerals are within and outside of the earth sciences.
extraordinary archives of Earth’s mysteries, allowing scientists to
decipher ~4.5 billion years of embedded history. For example, the Paleoclimatology Geochemistry
minerals in a pallasite meteorite contain clues to the composition, Environmental
formation conditions, and evolution of the early Solar System, with Mineralogy, Geology Petrology
implications for core-mantle development of Earth. Glacial ice, a
Paleontology Meteoritics
mineral, shapes continents, modulates Earth’s surface tempera- Geomicrobiology Planetary Studies
tures, and moderates climate variations; it also traps gas bubbles
Mineralogy
that sample prehistoric CO2 and CH4 levels. Other minerals, such as
Structural Geology
calcite, can record in their oscillatory zoning patterns the thermal, Geofluids, Hydrology
Tectonics
chemical, and mechanical interactions in complex geosystems.
Portions of the biosphere, such as pollen grains, invertebrate exo- Materials Science Economic Geology
skeletons, and vertebrate bones and teeth are (bio)minerals. Their Mineral Physics Geophysics
former presence, now as fossilized remnants of past life, owe their
persistence to mineral replacement (Fig. 3).
Figure 4. Centrality of mineralogy to earth-science disciplines (modified
from Klein and Dutrow, 2007).
MINERALS AND CLIMATE
Although a myriad of examples is available to demonstrate the
value of minerals in technology and society, this article focuses on
Figure 3. Belemnite, replaced select mineralogical contributions that will serve as integral compo-
by the mineraloid opal, pre- nents to mitigate the climate crises. These examples include (1) min-
serves former remnants of
life. Early Cretaceous: 135 eral trapping as one method for carbon capture and long-term
Ma. From Coober Pedy, storage; (2) mineral constituents as essential materials for the energy
South Australia. © Jeff Scovil
photo. Rob Seilecki speci- transformation, highlighting renewable energy and electric vehicles;
men. Used with permission. and (3) minerals as templates for advanced functional materials.
Mineral Trapping
As the world struggles with the impact of climate change, carbon
capture and long-term storage are required for reducing greenhouse
gas emissions into the atmosphere, stabilizing and lowering carbon
dioxide levels, and ensuring a more robust sustainable climate path
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