Regional trends and petrologic factors inhibit global interpretations of zircon trace element compositions

Abstract

The trace element composition of zircon reveals information about the melt that they are derived from, as such, detrital zircon trace element compositions can be used to interrogate melt compositions, and thus the evolution of the continental crust in time and space. Here, we present a global database of detrital zircon compositions and use it to test whether average global trends for five common petrogenetic proxies truly represent secular changes in continental evolution. We demonstrate that the secular trend is broadly comparable across continental regions for Ti-in-zircon temperatures, but for other trace element ratios interrogated, secular trends are highly variable between continental regions. Because trace element ratios result from multiple petrologic variables, we argue that these petrogenetic proxies can be overinterpreted if projected to global geologic processes. In particular, we caution against the interpretation of crustal thickness from trace elements in zircon, and we argue that our results negate current hypotheses concerning secular changes in crustal thickness.

Continental Crust Rejuvenation Across the Paleo‐Mesoarchean Transition Resulted From Elevated Mantle Geotherms

“…This potentially indicates that early Mesoarchean zircon crystallized from a hotter magma compared to zircon from prior and subsequent periods. Furthermore, Eu/Eu* in zircon has been argued to directly correlate to crustal thickness (Tang et al, 2020), although this correlation has also been questioned (Roberts et al, 2024;Triantafyllou et al, 2022;Yakymchuk et al, 2023). Using the same zircon trace element compilation (Table S8), we demonstrate that mean Eu/Eu* ratios peak during this Paleoarchean to Mesoarchean transition, with a secular trend resembling the MgO contents in global komatiites (Figure 3d).…”

“…These lines of evidence indicate that both mantle plumes and the ambient mantle had anomalously elevated thermal states at the transitional time. Despite Ti-based zircon crystallization temperatures being controlled by a number of factors beyond temperature (Roberts et al, 2024;Siégel et al, 2018), it is also noteworthy that calculated zircon crystallization temperatures based on a compilation of detrital zircon trace elements show a gradual increase to a vertex during the early Mesoarchean (Figure S8 in Supporting Information S1). This potentially indicates that early Mesoarchean zircon crystallized from a hotter magma compared to zircon from prior and subsequent periods.…”