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The limited preservation of ancient crustal material poses a challenge for understanding the composition of Earth’s early crust. As a result of poor preservation and near-ubiquitous overprinting by later geological events, deciphering the early evolution of our planet often relies on the isotopic composition of resistive minerals, such as zircon. Although the isotopic information recorded by zircon grains has proved an invaluable asset to workers seeking to understand the geological evolution of the Earth, it is limited by the range of elements easily incorporated into the structure of the mineral. One way to overcome these limitations is by analysing inclusions of other minerals that were trapped within the zircon during crystallisation. Apatite has great potential in this respect, as it is commonly found as inclusions in magmatic zircon and records a variety of useful isotopic information. Here we present an approach for investigating igneous petrogenesis and crustal evolution by combining 87Sr/86Sr measurements of apatite inclusions with U–Pb and Hf isotope analysis of their host zircon crystal. The Sr isotope information contained in the apatite can be accessed by applying a novel SIMS technique we developed for this purpose. A case study applying this new approach to Eoarchean igneous rocks of the Narryer Terrane in the northern Yilgarn Craton of Western Australia demonstrates how this can be used to understand the evolution of this key locality, with implications for both regional geology and the growth of the continental crust.

The processes that facilitate the production of granitoids are elucidated by the study of exposed lower crustal sections. The focus of this study is an exposure of the lower crustal portion of Albany-Fraser-Orogen (AFO) of Western Australia. This outcrop, located at Whale Head Rock in the western AFO, preserves the interface between an intrusive body and migmatised sedimentary rocks. Detailed mapping, petrography and thermodynamic modelling are combined to characterize the sources and distribution of melt generations in the aureole. U-Pb dating of zircon indicates that the tonalite crystallisation and migmatization of the metapelitic units were coeval at ca. 1.3 Ga. While thermodynamic modelling yields conditions of ca. 820°C and 0.5 GPa, in metapelites throughout the area. The contact zone evolves from igneous dominated textures to migmatitic sediments, dominated by concordant, internally derived leucosomes. The distribution of mineral assemblages and mineral chemistry across this section indicates that the mixing between intrusive and internally generated melt is structurally constrained. The back reaction with late stage, more evolved, melts within this mixing zone indicates that it acts as a pathway for continued melt removal and transport. This study represents and outcrop scale model for the complex processes that are involved in the production of granitoids at high temperature, medium pressure conditions. Giving further insight into the generation and extrapolation of melt from thinned crustal settings.

Supporting descriptive text, summary data and plots for the apatite fission track analysis, apatite U-Pb dating, and the thermal history modelling

Supplementary B: Detailed methodology and geo/thermochronology results.

Supplementary A: Detailed geological map of central Madagascar.

This Article contains errors in Reference 40 which is incorrectly given as: Palyvos, N., Pantosti, D. & Zabci, C. Paleoseismological evidence of recent earthquakes on the 1967 Mudurnu Valley earthquake segment of the North Anatolian fault. Bull. Seis. Soc. Am. 97, 1646–1661 (2007).