Neoarchean to Paleoproterozoic continental evolution and tectonic history of the North China Craton: a review

摘要

Rocks of Archean age are widely distributed in the North China Craton (NCC) and can be divided into high-grade regions and granite-greenstone belts, even though most underwent amphibolite to granulite facies metamorphism. Quartzo-feldspathic gneisses occupy 70 to 85% of the total exposure of Archean rocks in the craton. Supracrustal rocks commonly consist of intercalated volcano-sedimentary rocks, including metabasites, meta-intermediate to acid rocks, banded iron formations, metapelites and minor marbles. The oldest rocks outcrop over a small area of ～4 km~2 and are a quartzite-amphibolite sequence that yield 3.8-3.5 Ga isotopic ages. Chemical and geochronological data constrain the earliest main crust-forming episode at ca. 2.9-2.7 Ga, when most rocks were metamorphosed to upper amphibolite or granulite facies at moderate pressures. Mafic granulites can be classified into two textural types, referred to as near-isobaric cooling (IBC) and near-isothermal decompression (ITD) types. High-pressure granulites and retrograded eclogites occur mainly near the junction of the provinces of Hebei, Shanxi and Inner Mongolia in the central NCC, and in eastern Shandong Province of the eastern NCC, as well as locally in Henan Province in the southern NCC. These high-pressure rocks show clockwise P-T paths, indicating decompression from > 14 kb to 5-6 kb. An exposed section, interpreted as representing Precambrian continental lower crust has also been identified in the northern part of the craton. Although some mafic-ultramafic metamorphic rocks have been interpreted as remnants of ancient oceanic crust and mantle by a number of geologists, geochemical and petrological evidence demonstrates that many supracrustal/orthogneiss associations have island arc affinities. Therefore, several tectonic models have been proposed, including continent-continent collision and island arc terrain accretion achieved by arc-arc or arc-microcontinent collision. The NCC underwent multiple high-grade metamorphic events of which the two most important took place during the intervals 2600-2450 Ma and 1950-1750 Ma, which are considered to be related to early Precambrian supercontinental cycles.