Detrital zircons from phanerozoic rocks of the Songliao Block, NE China: Evidence and tectonic implications

Abstract

Rocks that crop out in the northern part of the Songliao Block are mainly consist of high-grade metamorphic gneiss, Paleozoic strata and Mesozoic granites. They are essentially similar to rocks reported from beneath the Songliao Basin that occupies the majority of the Songliao Block. Four samples of Paleozoic metasedimentary rocks from Tieli in the north-eastern part of the Songliao Block yield detrital zircon U–Pb ages ranging from 2690 to 501Ma, with four age populations at: 2071–2690Ma, with a peak at 2585Ma; 1776–1997Ma, with a peak at 1890Ma; 719–991Ma, with a peak at 800Ma; and 501–592Ma, with a peak at 518Ma. These are similar to age populations in other parts of the Central Asian Orogenic Belt (CAOB), although sediments from the Songliao Block contain more abundant Archean and Proterozoic detrital zircons than the neighboring Jiamusi–Khanka Block to the east and Xing’an Block to the west. This may indicate that rocks of this age comprise a minor component of the Songliao Block. The Pan-African zircon ages from the Songliao Block, taken together with ∼500Ma magmatic and high-grade metamorphic zircons obtained from the nearby Erguna, Xing’an and Jiamusi–Khanka blocks, indicate that Pan-African events affected all blocks of the CAOB in NE China. This suggests that these blocks not only share a common basement, but that they had a common history. An extensive Late Pan-African (∼500Ma) orogenic terrane thus occupies much of the CAOB in NE China.