Abstract

The widespread migmatites in the Precambrian basement of the North Qinling Belt are products of crustal partial melting, and record tectono-thermal response to the Late Paleozoic collision along the Shangdan suture. The morphology and trace element geochemistry of zircons from the migmatites suggest their metamorphic origin related to partial melting. The zircons from leucosome, melanosome and banded migmatites yield U-Pb weighted mean ages of 408 ± 2 Ma, 403 ± 2 Ma and 400 ± 2 Ma, respectively, constraining the timing of migmatization. The granitic dyke intruded into the migmatite gives zircon U-Pb weighted mean age of 396 ± 2 Ma, constraining the minimum time of migmatization. Zircons from the melanosome and banded migmatite yield upper intercept ages of 1088–1061 Ma, representing the protolith ages of the basement of North Qinling Belt. The zircon rims of the melanosome and banded migmatite predominantly display negative and positive εHf(t) values, respectively, suggesting variable input of mantle material. Together with regional geology and previous geochronological data, we propose that the thickening and partial melting in the North Qinling Belt was induced by the collision along the Shangdan suture between the North and South China Blocks during ca. 408–400 Ma.

Supplementary material: LA-ICP-MS U-Pb data, Lu-Hf isotopic compositions, and trace elements geochemistry of zircons and Ti–in–zircon thermometry are available at https://doi.org/10.6084/m9.figshare.c.4521389.

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