Geological characteristics, ages of host rocks and its geological significance of the Zhoutaizi iron deposit in Luanping, Hebei Province
河北滦平周台子条带状铁矿地质特征、围岩时代及其地质意义

Zhoutaizi iron deposit lies on the northern margin of the North China Craton, which is located in Luanping, Hebei Province. The iron deposit occurred in the metamorphic rocks, Dantazi Group of Precambrian. And the deposit which has obvious banded iron formations is an Anshan type iron deposit. The banded structure is obvious in ore rock, whereas striate and massive structure is rare. The quartz magnetite type is the main ore rock type which contains 30%~35% irons. The main wall rock is the metamorphic rocks in Precambrian including biotite plagiogneiss, amphibolite and granitic gneiss. The granitic gneiss is characterized as SiO2>56%, MgO<3%, Al2O3>15%, Sr>500×10-6, Yb>1.9×10-6, obvious fractionation between HREE and LREE, HREE depleted strongly, inconspicuous negative Eu anomalies. It is indicated that the granitic gneiss is geochemically similar to adakite. Zircon U-Pb analysis has shown several different ages, which are 2512±21Ma, 2452±9.6Ma, 2394±55Ma, respectively. First of all, the ages around 2512Ma represent the volcanic eruption event and the sedimentary age of BIF deposit. Secondly, the ages around 2452Ma represent the crystallization age of TTG granitic gneiss. At last the ages around 2394Ma represent a metamorphic event which resulted in the modification of original rocks and ore rocks. The Hf isotope data indicates that the magma source of amphibolite and TTG granitic gneiss may be contaminated by ancient crustal material. And therefore the tectonic setting of Zhoutaizi iron deposit was extensional related to rifts.