Igneous rock area and age in continental crust

Shanan E Peters,Oliver Shorttle,Robert R Gaines,Daven P Quinn,Craig R Walton,Jon M Husson,C Brenhin Keller

doi:10.1130/g49037.1

Abstract

Abstract Rock quantity and age are fundamental features of Earth's crust that pertain to many problems in geoscience. Here we combine new estimates of igneous rock area in continental crust from the Macrostrat database (https://macrostrat.org/) with a compilation of detrital zircon ages in order to investigate rock cycling and crustal growth. We find that there is little or no decrease in igneous rock area with increasing rock age. Instead, igneous rock area in North America exhibits four distinct Precambrian peaks, remains low through the Neoproterozoic, and then increases only modestly toward the recent. Peaks in Precambrian detrital zircon age frequency distributions align broadly with peaks in igneous rock area, regardless of grain depositional age. However, detrital zircon ages do underrepresent a Neoarchean peak in igneous rock area; young grains and ca. 1.1 Ga grains are also overrepresented relative to igneous area. Together, these results suggest that detrital zircon age distributions contain signatures of continental denudation and sedimentary cycling that are decoupled from the cycling of igneous source rocks. Models of continental crustal evolution that incorporate significant early increase in volume and increased sedimentation in the Phanerozoic are well supported by these data.

Highlights

Quantitative constraints on the age-varying properties of rocks in Earth’s crust are critical for generating and testing hypotheses about the long-term evolution of Earth systems
The more salient similarities between igneous rock area in global maps and North American columns involve temporal patterns (Fig. 2), including shared late Archean and late Paleoproterozoic peaks followed by a decrease into the Mesoproterozoic and a smaller mid- to late Phanerozoic rise
Data on igneous-metaigneous rock area in the continental surface and subsurface combined with detrital zircon (DZ) age distributions have several implications

Summary

Introduction

Quantitative constraints on the age-varying properties of rocks in Earth’s crust are critical for generating and testing hypotheses about the long-term evolution of Earth systems. Columns can include igneous rocks of different ages and lithologies through a thickness of crust that is covered by sediment, a more volumetrically relevant representation of igneous rock quantity than that provided by maps (Fig. 1).

Results

Conclusion