Late Neoarchean crustal growth in the northeast of the North China Craton: Evidence from the geochronology and Hf isotope composition of Banshigou supracrustal rocks.

This paper reports zircon U-Pb age, geochemistry and Hf isotopic data of Banshigou supracrustal rocks in order to discuss the tectonic setting and crustal evolution in the northeast of the North China Craton in the Late Neoarchean. The main rock types of Banshigou supracrustal rocks are include amphibolite, plagioclase gneiss, hornblende schist and magnetite quartzite. LA-ICP-MS zircon U-Pb dating shows the magmatic zircons in the amphibolite (BA-1) were crystallized at 2548 11 Ma while the magmatic zircons in the epidote-hornblende schist (BA-6) were crystallized at 2548 +/- 23 Ma, representing the formation age of supracrustal rocks. Besides, we found three captured zircons in BA-6 which age are between 2754 +/- 80Ma and 2710 +/- 92Ma, indicate Banshigou area may have occurred magmatic events during the Early Neoarchean. The protoliths of amphibolite and hornblende schist are basaltic rocks, trace element characteristics reveal that the protoliths formed in an island-arc setting. Hf isotopic data indicate that the zircons in amphibolite have positive em.(t) values between 0. 29 and 8. 89, one-stage model ages (t(DM1)) are between 2877Ma and 2544Ma, while most of the zircons in epidote-hornblende schist also have positive epsilon(Hf)(t) values between- 0.78 and 8. 03, theirs tm, are between 2871Ma and 2544Ma, implying that the magma provenance was mainly made up of materials from depleted mantle with contamination of recycled old crust. Some zircons which t are similar to theirs (207)pb/(206) Pb ages suggested Banshigou area occurred crustal growth during the late Neoarchean. Combine with the supracrustal rocks in other regions, we propose there was likely existed the Neoarchean Ji-Liao-Ji (Jilin Liaoning -Hebei) arc-continent collision orogenic belt in the North China Craton, besides, Banshigou area is one part of this orogenic belt.