Formation age of the Neoarchaean Jining Group(banded iron formation) in the western Shandong Province:Constraints from SHRIMP zircon U-Pb dating
2010; Science Press; Linguagem: Inglês
ISSN
2095-8927
Autores Tópico(s)Geochemistry and Geologic Mapping
ResumoThe Jining Group,located in the Jining area,western Shandong Province,is covered by young sediments and was once considered to be formed during the Early Palaeoproterozoic.Much attention was paid on the supracrustal rocks because of the discovery of a huge banded iron formation(BIF) through drilling and geophysical study in recent years.There were arguments about the formation age and origin of the BIF.This paper reports SHRIMP U-Pb zircon ages for the metamorphic rocks of the Jining Group.A pebble-bearing chlorite sericite phyllite sample has detrital zircons mainly of～2.7Ga,with a grain with a believable age of 2.61±0.01Ga.An upper intercept age of 2.56±0.02Ga was obtained for magmatic zircons from meta-felsic volcanic rock.These indicate that the Jining Group was formed at the end of Neoarchaean,not Palaeoproterozoic,as thought before.In the North China Craton,BIFs were mainly formed during the Late Neoarchaean.The Jining Group is different in rock association and metamorphism from the BIF-bearing supracrustal rcoks in the Anshan,eastern Hebei and Wutai areas,but similar to ones in the Nanfen-Benxi area.This is important for the research and exploration of Archaean BIF-type iron deposits in China.
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