摘要
前寒武纪条带状铁建造(BIF)铁矿是我国最为重要的铁矿类型,冀东地区是国内重要铁矿开采基地之一。南山铁矿位于冀东迁安北部,是一大型铁矿床,也是该区最为典型的BIF铁矿。铁矿体赋存于晚太古代变质岩系中,矿体形态复杂,与斜长角闪片麻岩互层,矿石类型主要为磁铁石英岩,具有典型的条带状构造。南山铁矿体与斜长角闪片麻岩呈互层产出,表明二者在时间空间具有相关性。对斜长角闪片麻岩中的锆石进行了U-Pb定年分析,结果表明其原岩(火山岩)喷出时代为2 513.2±8.4Ma,从而推测南山铁矿形成于约2 513 Ma,随后在2 492±4 Ma受到变质作用的改造。南山铁矿原始沉积成矿的年龄为2.5Ga,与华北克拉通以及世界上的BIF铁矿成矿高峰期同时,此时期的BIF形成峰期不仅仅指示了华北克拉通的拼贴聚合,也可能与更大范围克拉通的形成有关。
The precambrian banded iron formation(BIF)is the most important iron deposit type in the world.Eastern Hebei province is one of the most important iron ore provinces in China.The Nanshang iron deposit,located at Qian'an,is a large and typical BIF-type iron deposit.The Nanshang mine exploits a BIF hosted by the Archean metamorphic rocks,and the orebodies are interlayered with plagioclase-hornblende gneiss and mainly consist of magnetite quartzite with clear banded structure.The Nanshang BIF is interlayered with plagioclase-hornblende gneiss,indicating that these two lithologies are temporally closely associated.U-Pb dating of zircons from the plagioclase-hornblende gneiss suggests that the Nanshang BIF was formed at ca.2 513.2±8.4 Ma and was subjected to metamorphism at 2 492±4 Ma.The Nanshang BIF formed at 2.5 Ga and is coeval with other BIFs in north China and in other cratons in the world.We further point out that the 2.5 Ga global BIF formation peak not only predates the amalgamation of the north China craton,but probably also record an ancient supercontinent event.
出处
《中国矿业》
北大核心
2017年第S2期252-255,259,共5页
China Mining Magazine
