VISUALIZATION OF HAFNIUM ISOTOPES IN ZIRCON USING BIG DATA AND PLATE RECONSTRUCTION MODELS AS A TOOL TO LINK MAGMATISM TO TECTONICS

The global distribution of igneous rocks generated by subduction and collision magmatism holds information about the relationship between magma composition and plate tectonics. These rocks located in high-elevation orogenic belts can also influence the isotopic composition of seawater through erosion and chemical weathering. Yet, existing compilations of igneous rocks or zircons through geologic time lack spatial information about their distribution on ancient tectonic plates.

In this study, we used a global database of igneous and detrital zircons, along with the plate reconstruction models, to map the original locations of samples on tectonic plates using their paleo-latitudes and longitudes. The data was processed and filtered using Python Pandas library. The pyGPlates library was used to restore the samples’ paleo-localities. Preliminary results show that from 550 Ma to ~400-350, during the formation and the breakup of the Gondwana supercontinent, the global zircon Hf isotopic composition (εHf(t)) show overall evolved isotopic signatures as the subduction and collision mostly involving old continents. From ~250 Ma to ~35 Ma, during the formation and the breakup of the Pangea supercontinent, global zircon εHf(t) show overall juvenile isotopic signatures suggesting the subduction and collision during this period involved accreted, young oceanic terranes that served as the juvenile basements for arc and collisional magmatism. These findings align with other studies that suggest the supercontinent cycle influences the isotopic signatures in igneous rocks. As a result, chemical weathering of the igneous rocks can influence the isotopic composition of seawater as suggested by the correlation between seawater Sr and zircon εHf(t) curves.

Similar approach can be applied to proxies such as Sr/Y and La/Yb ratios to investigate how arc parameters, such as crustal thickness, can be linked to plate-scale processes. The visualization approach is also a great educational tool demonstrating how flare-ups and cessation of arcs at different geologic times reflect the changing configuration of tectonic plates.