Geochemistry and Geochronology of Early Paleozoic Intrusive Rocks in the Terra Nova Bay Area, Northern Victoria Land, Antarctica

Abstract

The Terra Nova Intrusive Complex (TNIC) in northern Victoria Land, Antarctica, results from widespread magmatism during the Early Paleozoic Ross Orogeny. According to field relationships, geochemistry, and geochronology data, the northern part of the TNIC comprises the Browning Intrusive Unit (BIU), which is associated with an arc crustal melting including migmatization of the Wilson Metamorphic Complex, and the later Campbell Intrusive Unit (CIU), which is attributed to the mantle and crustal melting processes. Zircon U-Pb ages suggest Late Neoproterozoic to Early Cambrian protolith with Late Cambrian metamorphism (502 +/- 15 Ma) in the WMC, Late Cambrian formation (similar to 500 Ma) of the BIU, and Early Ordovician formation (similar to 480-470 Ma) of the CIU. Sr-Nd isotopic characteristics of the BIU indicate predominant crustal component (epsilon Nd-(t) = -8.7 to -8.9), whereas those of the CIU reflect both mantle (epsilon Nd-(t) = 1.8 to 1.6) and crustal (epsilon Nd-(t) = -4.0 to -7.5) compositions. These results suggest that the northern TNIC magmatism occurring at similar to 500-470 Ma originated from partial melting of the mantle-mafic crust components and mixing with felsic crust components. By integrating the results with previous studies, the TNIC is considered to be formed by a combination of the mantle and mafic crust melting, crustal assimilation, felsic crust melting, and magma mixing during the Ross Orogeny.