摘要
镜铁山铁(铜)矿床是我国西北地区发现和勘探最早的大型铁(铜)矿床。对于铁矿床的成因,目前还存在不同的观点。笔者等对镜铁山铁铜矿床赋矿地层开展了岩石学和岩石化学成分分析,结果显示:变质石英砂岩的SiO_(2)平均含量为96.95%、Al_(2)O_(3)平均为1.36%、Fe_(2)O_(3)平均为0.31%,SiO_(2)/Al_(2)O_(3)平均值为73.26,K_(2)O/Na_(2)O平均值为12.54;除Sn以外,其他微量元素平均含量均低于后太古宙澳大利亚页岩(PAAS)值,稀土元素总量显著低于PAAS值,具有弱的Eu正异常,Ce异常不明显;铁碧玉岩SiO_(2)平均含量为85.67%、Fe_(2)O_(3)平均含量为10.19%、SiO_(2)/Al_(2)O_(3)平均为430.47、K_(2)O/Na_(2)O平均为0.79;除Cu、Ba和Pb平均含量显著高于PAAS外,其他微量元素平均含量均低于PAAS,具有极低的稀土总量、较明显的Eu正异常和不明显的Ce异常;千枚岩SiO_(2)平均为63.56%、Al_(2)O_(3)平均为14.35%、Fe_(2)O_(3)平均为5.04%,K_(2)O平均为5.08%,MgO平均为2.46%,SiO_(2)/Al_(2)O_(3)=4.2~4.95,平均为4.44,除了Cu、Sr和U外,其他微量元素均高于PAAS,尤其是Sn和Ba显著高于PAAS。稀土元素总量与PAAS相当,Ce和Eu异常不明显。认为镜铁山群下岩组千枚岩和变质石英砂岩为陆源石英质沉积岩和中—中酸性火成岩在半干旱—潮湿的气候条件下经历了中等—强烈的风化并在被动大陆边缘的氧化—贫氧—次氧化水体环境沉积而成,铁碧玉岩源岩主要为火成岩,形成于氧化的水体环境,为典型的热水成因。镜铁山铁矿为SEDEX型矿床,其形成与哥伦比亚超大陆裂解有关。
The Jingtieshan Iron( copper) deposit is the large iron( copper) deposit discovered and explored earliest in Northwest China.There are still different views on the genesis of iron deposit.The petrological and petrochemical characteristics of the ore bearing strata of the deposit are analyzed.The average contents of SiO_(2),Al_(2)O_(3),Fe_(2)O_(3),SiO_(2)/Al_(2)O_(3) and K_(2)O/Na_(2)O ratio of metamorphic quartz sandstone is 96.95%,1.36%,0.31%,73.26 and 12.54 respectively;Except Sn,the average contents of Trace and rare earth elements are lower than the Post Archaean Australian Shale( PAAS) value,with weak Eu positive anomaly and no obvious Ce anomaly.The average contents of SiO_(2),Fe_(2)O_(3),SiO_(2)/Al_(2)O_(3)and K_(2)O/Na_(2)O in the metamorphic quartz sandstone are 85.67%,10.19%,430.47 and 0.79;Cu,Ba and Pb were significantly higher than PAAS value;it has obvious Eu positive anomaly,and has not obvious Ce anomaly.The average contents of SiO_(2),Al_(2)O_(3),Fe_(2)O_(3),K_(2)O and MgO in phyllite are 63.56%,14.35%,5.04%,5.08% and 2.46%,respectively;SiO_(2)/Al_(2)O_(3) is relatively stable,and K_(2)O/Na_(2)O ratio vary significantly;The contents of Trace and rare earth elements are high.Most of the components are higher than PAAS value except Cu,Sr and U,and Inconspicuous Eu and Ce abnormalities.It is considered that the phyllite and metamorphic quartz sandstone of the Lower Rock Formation of the Jingtieshan Group are terrigenous sedimentary and igneous rocks,which have undergone moderate to strong weathering under semi-arid and humid climatic conditions and deposited in the oxidation—dysoxic —suboxic water environment on the passive continental margin.The iron jasper rock is formed in the oxidized water environment and is a typical hydrothermal origin.The Jingtieshan iron deposit is a SEDEX-type deposit,which is related to the breakup of the Columbia super continent.
作者
赵建仓
吴雯辉
何谋惷
丁振举
胡新露
宫勇军
ZHAO Jiancang;WU Wenhui;HE Mouchun;DING Zhenju;HU Xinlu;GONG Yongjun(Mining Research Institute,Jiuquan Iron and Steel Co.,Jiayuguan,Gansu,735100;Gansu Provincail Key Laboratory of Refractory Iron Ore Resource Utilization,Jiayuguan,Gansu,735100;School of Earth Resources China University of Geosciences,Wuhan,430074;National Demonstration Center for Experimental Mineral Exploration Education(China University of Geosciences(Wuhan)),Wuhan,430074)
出处
《地质论评》
CAS
CSCD
北大核心
2023年第2期727-746,共20页
Geological Review
基金
酒泉钢铁(集团)有限责任公司科技项目“镜铁山铁铜矿床成矿机理研究”(编号:10305035)的成果。
关键词
镜铁山群
沉积物物源
构造环境
北祁连构造带
哥伦比亚超大陆
Jingtieshan Group
provenance
tectonic environment
north Qilian orogenic belt
Columbia supercontinent
