Zircon continues to grow in importance as a probe of the crust, both its current architecture and the parts of it that have been lost to erosion over deep time. A wide array of applications in the earth sciences, ranging from tectonic reconstructions of modern-day crustal terranes to investigation of Earth’s earliest crust in the Hadean Eon, benefit from being able to fully exploit the information trapped in zircon about its source rocks and the environments in which they formed. One less-explored avenue for reconstructing zircon source rocks is the mineral inclusions trapped in them, whose interpretation is somewhat complicated compared to direct age and isotopic results from the host zircons themselves. This talk presents three projects showing different applications of inclusions in detrital zircon that were derived from igneous rocks. First, the proportion of apatite in a zircon inclusion assemblage can help to predict how felsic the source magma was, and avoids some of the biases that impede this when the prediction is made using the major minerals quartz and feldspar. Second, the Fe-Ti oxides trapped as inclusions in zircon reflect the redox state of the magma from which the zircon grew, and can help to reconstruct the source magma when other indicators such as trace elements in the host zircon are more ambiguous or overprinted. Third, the proportion of inclusion phases made up of highly incompatible trace elements helps to predict whether a detrital population had significant provenance from highly felsic leucogranites, which are significant both in the context of crustal maturation and mineral exploration. Future applications involving inclusions in zircon will be able to exploit the trace element and isotopic information that is available on increasingly smaller spatial scales due to tools like the ion microprobe.

Xenon isotopes trace Earth’s deep volatile history, but present-day mantle Xe observations display a paradox: atmospheric-like isotopic ratios require substantial regassing, while the low concentration requires limited regassing. Previous models resolved this by invoking early limited regassing, but this is hard to reconcile with evidence for early plate tectonics, higher Xe concentrations in the ancient atmosphere, and incomplete noble gas removal from subducting slabs. We use a parameterized thermal evolution and material recycling framework to explore time-dependent degassing and regassing histories, including Xe loss through continental crust extraction, mid-ocean ridge and plume melting, and Xe recycle via subduction. We show that strong early Xe loss driven by rapid early continental crust generation reduces the bulk mantle concentration enough to make later regassing effective at reproducing the isotopic ratios. Fissiogenic Xe constraints and the required intense early degassing together favor lower initial mantle uranium concentration, pointing to starting compositions with at least an enstatite-chondrite component rather than purely CI-chondritic material. Analytical solutions with simplified approximation and machine learning analysis confirm that these requirements are linked: low uranium and large early crustal extraction are coupled, and early degassing controls the timescale over which the system transitions to moderate degassing or regassing. Our results show that a major early degassing episode with prolonged moderate regassing can explain both the isotopic ratios and concentrations, offering an alternative to limited regassing scenarios and new constraints on Earth’s starting materials and early history.