| Summary: | Due to limited exposure and the challenges of field access, the magmatic record of the Ross Orogeny along the Transantarctic Mountains, Antarctica remains ill-constrained. This results in a lack of clarity for Gondwanan tectonics and geodynamics along the paleo-Pacific margin. To better understand spatiotemporal trends in the timing, duration, and source(s) of magmatism, whole-rock geochemistry, U-Pb ages, and Lu-Hf isotopes were measured on zircon in 132 granitoids and 40 gneisses from northern Victoria Land (nVL), the Miller Range (MR), and the Ohio Range (OHR) mountains, spanning ~4,000 km of the Antarctic segment of the paleo-Pacific margin of Gondwana. U-Pb data reveal magmatism in the northern Transantarctic Mountains at nVL initiated by at least ca. 552 Ma, lasting until ca. 467 Ma, magmatism in the central Transantarctic Mountains (cTAM) at the MR spans ca. 573 Ma to ca. 487 Ma, and, the OHR in the southern Transantarctic Mountains (sTAM) records magmatism from ca. 540 Ma to ca. 423 Ma. These age ranges suggest that the duration of magmatism was near-synchronous along the entire margin, but that magmatism first initiated in the cTAM through sVL (ca. 595-590 Ma), before migrating northward and southward into nVL (ca. 552 Ma) and sTAM (i.e., OHR, ca. 540 Ma), respectively. Termination of magmatism followed a similar trend, ending in the cTAM through sVL ca. 485 Ma, then in nVL ca. 467 Ma, and finally in OHR ca. 423 Ma. Thus, our data do not support the long-held suggestion of arc magmatism decreasing in age northward along the margin.Zircon Hf isotope data indicate different magma sources contributed to magmatism as it migrated along the margin. Granitoids from nVL contain minimal mantle input, and were instead dominantly sourced from melting of (meta-)sedimentary source(s). Granitoids from the Ohio Range contain some juvenile input from a relatively young mantle source and contain almost no inherited zircon xenocrysts. Magmatic and metamorphic rocks from the Miller Range (MR) reveal abundant crustal ...
|
|---|