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The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt.Five banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U-Pb zircon dating,which yielded protolith emplacement ages of 2469±22Ma,2479±12 Ma,2497±21 Ma,2501±17 Ma and 2509±14 Ma,respectively.An important peak age of~2.48 Ga was also obtained for a metasedimentary rock in the same region.These discoveries suggest the occurrence of magmatic activity of2.51–2.47 Ga at the northern margin of the Yangtze craton.The age-correctedεHf(t)values obtained from in situ zircon Hf isotopic analysis are mainly between 5.5 and+0.3,and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga.Considering two important periods of~3.3–3.2 Ga and~2.95–2.90 Ga for the continental crustal growth in the Yangtze craton,we infer that the dioritic-granitic gneisses from the Douling Complex are the products of reworking of Paleo-to Mesoarchean crust at the northern margin of the Yangtze craton at~2.5 Ga.In addition,metamorphic ages of 837±8 Ma and 818±10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock,indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic,although its geological meaning remains ambiguous.
The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt. FIVE banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U -Pb zircon dating, which yielded protolith emplacement ages of 2469 ± 22 Ma, 2479 ± 12 Ma, 2497 ± 21 Ma, 2501 ± 17 Ma and 2509 ± 14 Ma, respectively. An important peak age of ~ 2.48 Ga was also obtained for a metasedimentary rock in the same region.These discoveries suggest the occurrence of magmatic activity of 2.51-2.47 Ga at the northern margin of the Yangtze craton.The age-correctedεHf (t) values obtained from in situ zircon Hf isotopic analysis are mainly between 5.5 and + 0.3, and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga.Considering two important periods of ~3.3-3.2 Ga and ~ 2.95-2.90 Ga for the continental crustal growth in the Yangtze craton, we infer that the dioritic-granitic gneisses f rom the Douling Complex are the products of reworking of Paleo-to Mesoarchean crust at the northern margin of the Yangtze craton at ~ 2.5 Ga. addition, metamorphic ages of 837 ± 8 Ma and 818 ± 10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock, indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic, although its geological meaning remains ambiguous.