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| 1 | Rare earth element and yttrium compositions of the Paleoproterozoic Yuanjiacun BIF in the Lüliang area and their implications for the Great Oxidation Event(GOE)显示文摘In China, most Precambrian banded iron formations(BIFs) are situated in the North China Craton. The Yuanjiacun iron deposit, located in the Lüliang area, is arguably the most representative Superior-type BIF. This iron deposit is coherent with the sedimentary rock succession of the Yuanjiacun Formation in the lower Lüliang Group, and was interpreted to be deposited at 2.3–2.1 Ga, based on ages of overlying and underlying volcanic strata. This age overlaps with the time range of the Great Oxidation Event(GOE, 2.4–2.2 Ga). The Yuanjiacun BIF consists mainly of subhedral-xenomorphic magnetite and quartz and rarely other minerals with a lower degree of metamorphism, from greenschist to lower amphibolite facies. The geochemical characteristics of this BIF are similar to those of Superior-type BIFs. Prominent positive La, Y, and Eu anomalies normalized by the Post Archean Australian Shale(PAAS) indicate that the primary chemical precipitate is a result of solutions that represent mixtures of seawater and high-T hydrothermal fluids. The contamination from crustal detritus found is negligible based on low abundances of Al2O3 and TiO2(<0.5%) and of trace elements such as Th, Hf, Zr, and Sc(<1.5 ppm), as well as the lack of co-variations between Al2O3 and TiO2. In particular, the Yuanjiacun BIF samples do not display significant negative Ce anomalies like those of the Archean iron formations, but rather, the Yuanjiacun BIF samples exhibit prominent positive Ce anomalies, low Y/Ho ratios, and high light to heavy REE((Pr/Yb)SN) ratios, which are essentially consistent with the late Paleoproterozoic(<2.0 Ga) BIFs around the world. These characteristics of the Yuanjiacun BIF samples imply that the ancient ocean(2.3–2.1 Ga) was redox-stratified from oxic shallow water to deeper anoxic water. The specific redox conditions of the ancient ocean may be related to the GOE, which gave rise to the oxidation of Ce and Mn in the upper water, and to the presence of a Mn oxide shuttle in the ocean, resulting in varying REE patterns due to the precipitation and dissolution of this Mn oxide shuttle under different redox states. Therefore, the Yuanjiacun BIF appears to have formed near the redoxcline and lower-level reduced marine water. | WANG ChangLe ZHANG LianChang LAN CaiYun DAI YanPei | 2014 | Science China Earth Sciences2014，57，10： | 13 |
| 2 | The Early Jurassic magmatism in northern Guangdong Province, southeastern China: Constraints from SHRIMP zircon U-Pb dating of Xialan complex显示文摘This paper reports SHRIMP zircon U-Pb ages of 196±2 Ma for granite, and 195±1 Ma for gabbro from the Xialan complex in the Meizhou area, northern Guangdong Province. These results shed new light on the calm stage of magmatic activity in southeastern China during 200-180 Ma, and revealed that the back-arc extension induced by the subduction of the western Pacific plate may have begun at 195 Ma at least. Field observation on the fresh outcrops allows us to recognize some features formed by magma mixing. A part of the gabbro has a fine-grained rim of 20-30 cm at the margin, and thins gradually to-ward the granite; numerous dark fine-grained to microcrystalline dioritic enclaves developed in the granite. These enclaves vary in shape and size, dark minerals concentrated at the margin of enclaves, and the contact between enclaves and host rock is either obvious or obscure, or gradational. In addi-tion, needle-shaped apatites are included in the enclaves. The REE patterns of gabbros, as well as the trace element patterns, are generally consistent with those of granitic rocks. The above characters further suggest that in the Early Jurassic the injection of basic magma had melted deep continental crust and produced acidic magma, and the Xialan complex was produced by the mixing of them. | YU XinQi DI YongJun WU GanGuo ZHANG Da ZHENG Yong DAI YanPei | 2009 | Science China Earth Sciences2009，52，4： | 12 |
| 3 | Formation age and tectonic setting of the Shirengou Neoarchean banded iron deposit in eastern Hebei Province: Constraints from geochemistry and SIMS zircon U–Pb dating显示文摘 | Lianchang Zhang Mingguo Zhai Xiaojing Zhang Peng Xiang Yanpei Dai Changle Wang Franco Pirajno | 2011 | Precambrian Research2011，，： | 1 |
| 4 | Formation age and tectonic setting of the Shirengou Neoarchean banded iron deposit in eastern Hebei Province: Constraints from geochemistry and SIMS zircon U–Pb dating显示文摘 | Lianchang Zhang Mingguo Zhai Xiaojing Zhang Peng Xiang Yanpei Dai Changle Wang Franco Pirajno | 2011 | Precambrian Research2011，，： | 1 |
| 5 | New geochronological data from the Paleozoic and Mesozoic nappe structures, igneous rocks, and molybdenite in the North Wuyi area, Southeast China显示文摘 | Xinqi Yu Ganguo Wu Xixi Zhao Da Zhang Yongjun Di Junting Qiu Yanpei Dai Chunlin Li | 2011 | Gondwana Research2011，，2： | 1 |
| 6 | Steep subduction of the Indian continental mantle lithosphere beneath the eastern Himalaya revealed by gravity anomalies显示文摘The geometry and deformation of the Indian continental mantle lithosphere(ICML)beneath the India-Eurasia collision zone are critical to understanding the accommodation of continent-continent convergence.In this paper,the distribution of residual gravity anomalies in the upper mantle of southern Tibet is estimated using the gravity data and seismic velocity models,and the heterogeneous density distribution of the upper-mantle is then recovered through three-dimensional gravity inversion.The results reveal a low-density anomaly(~300 km W-E and~100 km N-S)in the upper mantle under the eastern Himalaya,while there is no obvious density anomaly under the western Himalaya.The western boundary of the low-density anomaly coincides with the Yadong-Gulu Rift(YGR)on the surface(89°–90°E),and its southern boundary is located at~28°N,approximately 130 km southward from the Indus-Yarlung suture,probably representing the mantle suture at depth.This observation indicates that,in contrast to the western ICML which is probably underthrusting at a shallow angle,the eastern ICML be likely subducting steeply,accompanying asthenosphere upwelling.Such a laterally varying geometry suggests that a major tearing of the ICML may have taken place from the intersection of the mantle suture and the YGR in the upper mantle.The tearing and the steep subduction of the ICML might be associated with the magmatic and mineralization events in the eastern Himalaya-Gangdese and the formation of the YGR. | Shengxian LIANG Xuben WANG Zhengwei XU Yanpei DAI Yonghua WANG Jing GUO Yanjie JIAO Fu LI | 2023 | Science China Earth Sciences2023，66，9： | 0 |
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