极地研究

极地研究 ›› 2023, Vol. 35 ›› Issue (1): 1-14.DOI: 10.13679/j.jdyj.20210077

• 研究论文 •    下一篇

东南极西福尔丘陵冰碛物中磁铁石英岩的识别与地质意义

王晓虎1,2  王伟1,2  保红1,2  刘晓春1,2  胡健民1,2  赵越1,2   

  1. 1中国地质科学院地质力学研究所, 北京 100081;
    2自然资源部古地磁与古构造重建重点实验室, 北京 100081
  • 出版日期:2023-03-31 发布日期:2023-03-09
  • 通讯作者: 王伟
  • 作者简介:王晓虎, 男, 1983年生。副研究员, 主要从事构造与成矿研究。E-mail: wangzykc@yeah.net
  • 基金资助:
    国家自然科学基金(41941004, 42172068)、国家重点研发计划(2021YFC2901805)和地质调查项目(DD20221810)资助

Identification and geological significance of magnetite quartzite in Vestfold Hills moraines, East Antarctica

Wang Xiaohu1,2, Wang Wei1,2, Bao Hong1,2, Liu Xiaochun1,2, Hu Jianmin1,2, Zhao Yue1,2   

  1. 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China; 
    2Laboratory of Paleomagnetism and Tectonic Reconstruction, Ministry of Natural Resources, Beijing 100081, China
  • Online:2023-03-31 Published:2023-03-09

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摘要： 广袤的南极大陆发育丰富的岩石类型, 也蕴藏着丰富的自然资源。但南极大陆大部分地区常年被冰雪覆盖, 难以进行直接研究; 而散布在冰川周缘的冰碛物包含各种岩石类型, 携带丰富的冰下地质信息, 对理解南极大陆岩石组成、构造演化及成矿作用具有不可替代的作用。通过对东南极西福尔丘陵冰碛物研究, 识别出了两种磁铁石英岩(条带状铁建造的组成岩石, 简称BIF), 分别为浅暗红色富赤铁矿磁铁石英岩和浅灰色磁铁石英岩。浅暗红色富赤铁矿磁铁石英岩的石英条带和磁铁矿条带相间分布, 界线较为平直, 矿物组合主要包括石英、磁铁矿、赤铁矿、褐铁矿等, 含少量绢云母、磷灰石; 赤铁矿含量约3%, 分布在磁铁矿颗粒边缘或裂隙中, 或呈颗粒状分布于石英条带中。浅灰色磁铁石英岩的石英条带和磁铁矿条带相间分布, 条带边缘不平直, 矿物组合主要包括石英、磁铁矿、赤铁矿、褐铁矿, 含少量透辉石、透闪石、阳起石; 赤铁矿含量很少(＜1%), 分布在磁铁矿颗粒裂隙内, 或呈颗粒状分布于石英条带中。根据已有的结果初步推断东南极西福尔丘陵两种样式BIF具有相似的沉积环境, 属阿尔戈马型。BIF中赤铁矿可能是由磁铁矿经历了一定程度的氧化作用形成, 且赤铁矿形成时地球环境中氧气含量应处于上升过程。根据已有的资料推测, 西福尔丘陵BIF形成时代在25亿年前, 或可追溯至30亿年前, 其形成机理与环境有助于解释地球早期地质及环境演化规律, 值得将来深入研究。

关键词: 南极, 西福尔丘陵, 磁铁石英岩, 条带状铁建造(BIF)

Abstract: Because the Antarctic continent is covered by a permanent ice cap, its geology cannot be studied comprehensively. Moraines scattered around the glacier preserve substantial subglacial geological information, critical to understand the Antarctic geological and tectonic evolution. By studying moraines in the Vestfold Hills of east Antarctica, we identified two types of magnetite quartzite (banded iron formation, BIF); a light red, hematite-rich BIF, and a light gray BIF. The light red, hematite-rich BIF is mainly composed of magnetite, hematite, quartz, limonite, with small amounts of sericite and apatite. Quartz bands and magnetite bands are distributed alternately with nearly straight boundaries, whereas hematite is distributed in the edges or cracks of magnetite particles or in the quartz bands with a granular shape. The light gray BIF consists mainly of magnetite, hematite, quartz and limonite, with small amounts of diopside, tremolite, and actinolite. Quartz bands and magnetite bands are also distributed alternately, but the band edges are not straight. Hematite is distributed in the cracks of magnetite particles or in the quartz bands with a granular shape. Our analysis revealed that both BIFs formed in similar sedimentary environments. The samples may correspond to the Algoma type BIFs and the included hematite may result from early magnetite oxidation. We inferred that the environmental oxygen content was increasing when the hematite formed. Both Vestfold Hills samples likely formed 2.5 Ga, 3.0 Ga before present. Further study of BIF types in that region will improve our understanding of earth’s early geological and environmental evolution.
Keywords  Antarctica, Vestfold Hills, magnetite quartzite, banded iron formation (BIF)

Key words: Antarctica, Vestfold Hills, magnetite quartzite, banded iron formation (BIF)