We report preliminary results of a geochemical study on banded iron formations （BIFs） in the Zhaojiayangpo （赵家阳坡） area from the Kongling （崆岭） Group in the northern Huangling （黄陵） anticline, on the nort...We report preliminary results of a geochemical study on banded iron formations （BIFs） in the Zhaojiayangpo （赵家阳坡） area from the Kongling （崆岭） Group in the northern Huangling （黄陵） anticline, on the northern margin of the Yangtze craton. The CL （cathodoluminescence） images of zircons mostly have sector zoning, fir-tree zoning and patched zoning, and a few show core-rim tex-tures with rims having patched zoning. The calculated formation temperatures using the Ti-in-zircon thermometer are 660-808 ℃ （714 ℃C in aver-age）, all indicating that the BIFs underwent granulite facies metamorphism. The age of zir-cons with granulite facies metamorphism is 1 990±14 Ma by LA-ICP-MS U-Pb dating, indi-cating that there was a significant granulite fa-cies tectonothermal event in the northern Huangling anticline in the Paleoproterozoic, which may be related with tectonic thermal events of the metamorphism caused by the as-sembly of the Columbia supercontinent with South China. Moreover, the REE pattern ischaracterized by depletion in LREE while relatively flat in HREE, LaN/YbN=0.26, with a positive Eu anomaly （Eu/Eu^＊---1.59）, which reveals its hydrothermal sedimentation origin and it may have formed in the environment of submarine exhalation.展开更多
基金supported by the Postdoctoral Science Foundation (No. 20100471203)the Ministry of Land and Resources(No. 1212010670104)+1 种基金the National Natural Science Foundation of China (Nos. 91014002, 40821061, 41272242)Ministry of Education of China (Nos. B07039, TGRC201024)
文摘We report preliminary results of a geochemical study on banded iron formations （BIFs） in the Zhaojiayangpo （赵家阳坡） area from the Kongling （崆岭） Group in the northern Huangling （黄陵） anticline, on the northern margin of the Yangtze craton. The CL （cathodoluminescence） images of zircons mostly have sector zoning, fir-tree zoning and patched zoning, and a few show core-rim tex-tures with rims having patched zoning. The calculated formation temperatures using the Ti-in-zircon thermometer are 660-808 ℃ （714 ℃C in aver-age）, all indicating that the BIFs underwent granulite facies metamorphism. The age of zir-cons with granulite facies metamorphism is 1 990±14 Ma by LA-ICP-MS U-Pb dating, indi-cating that there was a significant granulite fa-cies tectonothermal event in the northern Huangling anticline in the Paleoproterozoic, which may be related with tectonic thermal events of the metamorphism caused by the as-sembly of the Columbia supercontinent with South China. Moreover, the REE pattern ischaracterized by depletion in LREE while relatively flat in HREE, LaN/YbN=0.26, with a positive Eu anomaly （Eu/Eu^＊---1.59）, which reveals its hydrothermal sedimentation origin and it may have formed in the environment of submarine exhalation.
