Characteristics of the banded iron formation (BIF) and its zircon chronology in Yangzhuang, western Shandong
鲁西杨庄条带状铁建造特征及锆石年代学研究

The Taishan Group, mainly distributed in the western Shandong Province, is an important part of western Shansong granite-greenstone belt. Some sedimentary metamorphic iron ores have been found in Yangzhuang, Yishui County, the iron bodies are resident in the Liuhang Formation. This paper studied characteristics of BIF in the Yishui area, determined ages of this BIF by LA-ICP-MS U-Pb method from BIF strata and magmatic intrusion of the upper member of the Taishan Group. Results show that zircon ages of in amphibolite are concentrated in about 2.6Ga, its formation age is considered to be 2615±61Ma; an upper intercept zircon age of 2527±66Ma is obtained from biotite quartz schist, zircon dating of migmatitic granite yields an age of 2469±34Ma. These indicate that the upper member of the Liuhang Formation, Taishan Group, formed from earlier than 2.6Ga to Early Paleoproterozoic. Accordingly, we suggest that the "Liuhang Group" in western Shandong, could be further separated into two parts, i.e., the lower part of amphibolites (with magnetite formation) formed at c.a. 2.6Ga in Late Archean, and the upper part of surficial rock sequences (mainly with schist), formed at c.a. 2.5Ga in Early Paleoproterozoic. The formation of migmatitic granite of Early Paleoproterozoic could fill the inactive period of global geological evolution gap. The metamorphic sequences represented by the Taishan Group are distributed deep or covered by Mid-Late Proterozoic rocks, are important for research of early evolution of North China Craton and iron deposits (BIF) in China.