摘要
帕莱通铁矿床是老挝万象—呵叻中新生代盆地中最大规模的铁矿床,分为东、西2个矿段,西矿段为豆状、块状富磁铁矿矿体,东部则主要发育角砾状贫赤铁矿矿体。其中,西矿段主要产于新生代富铁质玄武岩中。文章对西矿段中豆状、块状磁铁矿进行了详细的野外地质调查和显微结构分析,发现块状磁铁矿具有细粒他形结构特征,豆状磁铁矿具有球粒同心圆状结构特征。对较为新鲜的磁铁矿进行电子探针(EPMA)以及激光剥蚀电感耦合等离子质谱(LA-ICP-MS)分析显示:帕莱通铁矿床磁铁矿TiO2-Al2O3-MgO三角图落入岩浆岩区域;微量元素富集V、Ti、Cr、Co、Ni及Ga等元素,亏损Sr、Ba及Mg等不相容元素;w(Co)和w(Ni)较高,且较高的Ni/Co比值可以反映成因与深源物质;w(Ti)较高且Ni/Cr比值≤1,在Ti-Ni/Cr图中落入了热液型磁铁矿的范围;Ga-Sn图解表明磁铁矿属于斑岩型热液成因;(Ca+Al+Mn)-(Ti+V)或Ni/(Cr+Mn)-(Ti+V)成因判别图显示该矿床兼具Kiruna型和斑岩型矿床的特征;w(V)表明磁铁矿在较低氧化环境中形成;(Al+Mn)-(Ti+V)形成温度判别图表明磁铁矿形成温度处于300~500℃范围内。文章认为帕莱通铁矿床成矿物质主要源于岩浆演化作用形成的富铁流体,后期由于岩浆热液流体的交代作用,使得磁铁矿具有了热液成因的特征。岩浆型矿床类型在老挝及邻区分布较为广泛,研究帕莱通铁矿的成因,对于总结区域成矿规律,指导同类型矿床找矿预测具有重要意义。
The PaLayThong iron deposit,the largest iron deposit in the Vientiane-Korat Meso-Cenozoic basin in Laos,can be divided into two ore blocks:the west ore block is a bean-shaped and block-shaped magnetite-rich orebody,and the east ore block is a brecciform poor hematite orebody.Of them,the west ore block is mainly produced in the Cenozoic iron-rich basalt.In this paper,the detailed field geological survey and microstructure analysis of the pea-shaped and block-shaped magnetite in this section were carried out.The relatively fresh magnetite was analyzed by electron microprobe(EPMA)and laser ablation inductively coupled plasma mass spectrometry(LA-ICPMS),and the results are as follows:TiO2-Al2O3-MgO magnetite from the PaLayThong iron ore deposit falls into the magmatic rock zone on the triangle diagram.The trace elements are enriched in V,Ti,Cr,Co,Ni and Ga and depleted in Sr,Ba,Al and Mg incompatible elements.w(Co)and w(Ni)are higher,and the higher Ni/Co ratio can reflect the origin and deep source materials.w(Ti)is high and Ni/Cr ratio≤1,which falls into the range of hydrothermal magnetite on the Ti-Ni/Cr diagram.Ga-Sn diagram shows that magnetite belongs to porphyry hydrothermal origin.The genetic discriminant diagram of(Ca+Al+Mn)-(Ti+V)or Ni/(Cr+Mn)-(Ti+V)shows that the deposit has the characteristics of both Kiruna type and porphyry type deposits.V content indicates that magnetite was formed in a low oxidation environment;(Al+Mn)-(Ti+V)formation temperature discrimination diagram shows that magnetite was formed in a temperature range of 300℃to 500℃.It is considered that the ore-forming materials of the PaLayThong iron deposit mainly came from the iron-rich fluid formed by magmatic evolution,and the magnetite had the characteristics of hydrothermal genesis attributed to the metasomatism of magmatic hydrothermal fluid.The magmatic deposits are widely distributed in Laos and its adjacent areas.The study of the genesis of the PaLayThong iron ore deposit is of great significance for summarizing the regional metallogenic regularity and guiding the prospecting and prediction of the same type of deposits.
作者
孙策
彭惠娟
熊富浩
侯林
SUN Ce;PENG HuiJuan;XIONG FuHao;HOU Lin(Key Laboratory of Structural Metallogeny,Chengdu University of Technology,Chengdu 610059,Sichuan,China;Chengdu Geological Survey Center,CGS,Chengdu 610081,Sichuan,China)
出处
《矿床地质》
CAS
CSCD
北大核心
2020年第3期523-546,共24页
Mineral Deposits
基金
中国地质调查局成都地质调查中心“老挝、柬埔寨及邻区矿产资源潜力评价”项目(编号:DD20160107)
国家自然科学青年基金项目(编号:4150020521)联合资助。
