尼雄地区早白垩世磁铁矿伸展成矿地质背景及成矿模型
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本文为国家自然科学基金(编号41773026)和中国地质调查项目(编号DD20190053)联合资助的成果。


Metallogenic background and metallogenic model of the Early Cretaceous magnetite deposit in the Nixiong area, Tibet
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    摘要:

    尼雄地区早白垩世磁铁矿以成矿岩体及矿床研究偏多,忽略围岩时代及其成矿地质背景分析。尼雄早白垩世磁铁矿可分为矽卡岩型和热液脉型,而达及藏布地区热液脉型磁铁矿与基性岩脉密切相关,通过共生辉长岩岩脉锆石U- Pb年龄(120. 1±1. 7 Ma)限定热液脉型磁铁矿成矿时代约120 Ma,与已经确定成矿时代的矽卡岩型铁矿成矿时代一致,指示尼雄矿田两种类型磁铁矿受控于相同的地质背景。通过尼雄岩体碎屑岩围岩(原上二叠统敌布错组)碎屑锆石测年,获得其沉积时代介于130~120 Ma之间,故将上二叠统敌布错组重新厘定为下白垩统则弄群。结合区域地层及岩浆岩新资料,认为冈底斯中部则弄群火山岩与侵位于其中的岩体构成一个早白垩世火山侵入杂岩体系,其与尼雄矿田早白垩世磁铁矿密切相关。该早白垩世火山侵入杂岩地球化学特征及尼雄附近浅表层次构造共同指示冈底斯中部在早白垩世处于伸展构造背景。最后,依据伸展构造背景新认识建立了尼雄地区早白垩世磁铁矿成矿地质模型。

    Abstract:

    The Nixiong Iron Mine, a large magnetite deposit in the central Gangdese belt, was mainly formed in the Early Cretaceous. This paper will discuss the metallogenic background of Early Cretaceous Nixiong magnetite deposit that can be divided into the Skarn type and the hydrothermal vein type. Gabbro dyke in mining area yielded the UPb age of 120. 1±1. 7 Ma which limits the mineralization era of the hydrothermal vein magnetite to about 120 Ma and is fully consistent with the determined mineralization era of Skarn magnetite deposit, indicating that a similar tectonic setting controlled both types magnetite deposits. Clastic rocks, as the wall rock of the Nixionggranitoid from the Upper Permian Dibucuo Formation, yielded a detrital zircon UPb age of 130~120 Ma with the youngest peak age of 131.25 Ma which was prior to the emplacement age of the Nixiong rock (~120 Ma) suggesting that the Upper Permian Dibucuo Formation should be renamed to be the Lower Cretaceous. Combined with the new regional stratigraphic and magmatic data, we propose that an Early Cretaceous volcanicintrusive complex system consisted of volcanic rocks from the Zenong Group and emplacing granitoid in the Zenong Group in the Central Gangdese belt. This Early Cretaceous metallogenic magmatic system is closely related to the Early Cretaceous Nixiong magnetite deposit. Both geochemical characteristics of the Early Cretaceous igneous rocks and the shallow surface structure show an extensional tectonic setting in the Central Gangdese belt in the Early Cretaceous. Based on the new understanding of the tectonic background in Nixiong area, a metallogenic geological model of the Early Cretaceous Nixiong magnetite deposit was established.

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刘函,李俊,崔浩杰,苟正彬,李奋其,张士贞,段瑶瑶.2020.尼雄地区早白垩世磁铁矿伸展成矿地质背景及成矿模型[J].地质学报,94(8):2383-2399.
LIU Han, LI Jun, CUI Haojie, GOU Zhengbin, LI Fenqi, ZHANG Shizhen, DUAN Yaoyao.2020. Metallogenic background and metallogenic model of the Early Cretaceous magnetite deposit in the Nixiong area, Tibet[J]. Acta Geologica Sinica,94(8):2383-2399.

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  • 收稿日期:2019-11-23
  • 最后修改日期:2020-01-01
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  • 在线发布日期: 2020-06-18
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