Chentaigou BIF-Type Iron Deposit, Anshan Area Associated with Archean Crustal Growth: Constraints from Zircon U-Pb Dating and Hf Isotope
详细信息
- 责任者：Dai Yanpei (Key Laboratory of Mineral Resources ; Institute of Geology and Geophysics ; Chinese Academy of Sciences ; Beijing 100029 ; China) ; Zhang Lianchang
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：铁矿 ; iron ores ; 增生楔 ; accretionary wedges ; 铀—铅计时 ; U-Pb dating ; 辽宁 ; Liaoning Province
- 页码：p.2537-2550
- 图表：9 illus., 4 tables, 55 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Located in the Anshan area,Liaoning Province,the newly discovered Chentaigou concealed iron deposit mainly consists of banded iron ores,with the roof rock of chlorite-quartz schist and the bottom rock of biotite-quartz schist.Geochemical data show the iron ore and magnetite are enriched in HREE characterized by positive La,Eu and Y anomaly without apparent negative Ce anomaly,indicating that the ore-forming materials were derived from mixtures of high-T hydrothermal fluids (～ 0.1%) and seawater,and implying that the seawater was under anoxic condition during the deposition.Typomorphic studies indicate that the iron ore and magnetite are metamorphosed sedimentary-type or BIF-type.The protolith of chlorite-quartz schist was acid volcanic rock while that of biotite-quartz schist was pelitic or arenaceous rocks,which are all enriched in Rb,Th,U and LREE,and depleted in Nb,Ta and Ti.The protolith of these schists was formed under island arc setting,suggesting that the Chentaigou BIF was deposited in island arc setting.LA-ICP-MS zircon U-Pb dating shows the magmatic zircons were crystallized at 2551 ± 10Ma,representing the formation age of the Chentaigou BIF,while the metamorphic zircons were formed at 2469 ± 23Ma,reflecting the age of later metamorphic event.Hf isotopic data indicate that most of the zircons have positive ε Hf (t) values between-2.23 and 7.54,implying that the magma provenance was mainly made up of materials from depleted mantle with contamination of recycled old crust.Two-stage model ages (t DM2) are primarily between 3133Ma and 2580Ma.Combined with Hf isotopic data of other deposits,it is suggested that Neoarchean (～2.55Ga) crustal growth occurred in the Anshan-Benxi area.To sum up,we propose that the Chentaigou iron deposit belongs to the Algoma-type BIF,which represents a large-scale Neoarehean BIF metallogenic event widely distributed in the North China craton.
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