Source region analyses of the morainal detritus from the Grove Mountains: Evidence from the subglacial geology of the Ediacaran–Cambrian Prydz Belt of East Antarctica

Abstract

The Grove Mountains are the inland exposures of the Prydz Belt in East Antarctica. Although the 550–500Ma orogenic event was recognized as the latest major magmatic–metamorphic activity in the Prydz Belt, its subduction–collision origin was not confirmed until the discovery of high-pressure (HP) mafic granulite erratic boulders in the glacial moraines from the Grove Mountains. Because no HP metamorphic bedrock is exposed in this area, an understanding the regional geology required a thorough study of the morainal debris mineralogy and detrital zircon U–Pb chronology. Detrital zircon U–Pb age histograms show 550–450Ma, 900–800Ma, and 1100–1000Ma modes from three morainal deposits and one paleosol samples. The oldest ages were 2300 to 2420Ma. Detailed electron probe microanalyses (EPMA) for the detrital mineral grains were compared with the minerals from the nearby exposed bedrock. The mineral chemistry indicates that the exposed bedrock in the Grove Mountains was not the sole source for morainal materials. This new U–Pb zircon geochronology and microprobe mineral data support the previous interpretation that the 550–500Ma tectonic activity was the final collisional event that formed the Prydz Belt and amalgamated East Antarctica.