Constraints on early Paleozoic magmatic processes and tectonic setting of Index Inexpressible Island, Northern Victoria Land, Antarctica
at : Feb 18, 2019 09:48:28  (view:309)

Authors: CHEN Hong1,2, WANG Wei1,2 & ZHAO Yue1,2

1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;

2. Key Laboratory of Paleomagnetism and Tectonic Reconstruction of Ministry of Natural Resources, Beijing 100081, China

Corresponding author: Dr.CHEN Hong, chhzxm8281@163.com

Abstract: During the Cambrian and Ordovician, widespread magmatic activity occurred in the Ross Orogen of central Antarctica, forming the Granite Harbor Intrusives and Terra Nova Intrusive Complex. In the Terra Nova Intrusive Complex, the latest magmatic activity comprised the emplacement of the Abbott Unit (508 Ma) and the Vegetation Unit (~475 Ma), which were formed in different tectonic settings. Owing to their similar lithological features, the tectonic transformation that occurred between the formation of these two units has not been well studied. Through a detailed geological field investigation and geochemical and geochronological analyses, four types of magmatic rock—basalt, syenite, mafic veins, and granite veins—were identified on Inexpressible Island, Northern Victoria Land. Our SHRIMP zircon U–Pb ages of the basalt and the granite veins are 504.7 ± 3.1 and 495.5 ± 4.9 Ma, respectively. Major- and trace-element data indicate a continental-margin island-arc setting for the formation of these two rock types. The zircon U–Pb ages of the syenite and the monzodiorite veins are 485.8 ± 5.7 and 478.5 ± 4.0 Ma, respectively. Major- and trace-element compositions suggest a collisional setting for the former and an intracontinental extensional setting for the latter. These results elucidate the evolution from subduction to collision and intracontinental extension in Northern Victoria Land during the 20 Ma spanning the late Cambrian–Early Ordovician and improve our understanding of the tectonics and evolution of the Ross Orogen in the Transantarctic Mountains

Keywords: Northern Victoria Land, Ross Orogen, Early Paleozoic magmatism, island arc, intracontinental extension