印度尼西亚塔里亚布铁矿床的磁铁矿成因矿物学特征

Genetic mineralogical characteristics of magnetite from Taliabu iron deposit, Indonesia

以光学显微镜、单矿物化学分析、X线衍射分析、扫描电镜和流体成分分析等手段对印尼塔里亚布铁矿床的矿浆型、接触交代型及热液脉型3种磁铁矿进行成因矿物学特征研究。结果表明:矿区磁铁矿属贫钒低钛富锰镁型。矿浆型磁铁矿贯入充填成矿,锆石与赤铁矿为特征矿物,磁铁矿全Fe含量66.08%～68.01%,以致密细粒晶体为主,三晶嵌连为特征结构,晶胞参数0.839 2～0.839 9 nm,流体富含碱金属离子及挥发性组分;接触交代型磁铁矿产于花岗岩与碳酸盐岩接触带附近,矿石矿物组合复杂,以镁质矽卡岩矿物为特征,磁铁矿SiO2和Mg含量较高,以菱形十二面体、立方体晶形为主,晶胞参数0.839 8～0.840 2 nm,流体富含H2和K+;热液脉型磁铁矿呈中粗-粗晶脉状充填产出,磁铁矿Mn含量4.78%～6.22%,八面体裂理发育,晶胞参数0.840 1～0.840 7 nm,流体成分总量最低,是成矿系统最晚阶段。

The genetic mineralogical characteristics of ore magma, contact metasomatic and hydrothermal vein types different magnetite were researched by means of optical microscope, monomineralic chemical analysis, X-ray diffraction （XRD）, scanning electronic microscopy （SEM） and fluid inclusions compositions analysis from Taliabu iron deposit, Indonesia. The results show that these magnetites belong to poor vanadium, low-Ti, rich magnesium and manganese type. Ore magma type magnetite is formed by injection and filling. Ziron and hematite are the characteristic minerals. The magnetite is high in Fe （66.08%-68.01%）. The crystal form of magnetites is mainly in dense, fine grained and xenomorphic. Triple junction is the characteristics texture. The cell parameter is between 0.839 2 and 0.839 9 nm. The fluid compositions are high in alkali metal ion and volatile components. Skarn magnetite occurs in the contact zone between granite and carbonatite. The mineral assemblage is very complex and characteristic of magnesium skam minerals. The magnetite is high in SiO2 and Mg. The crystal form of magnetites is mainly in granatohedron and cube with cell parameter between 0.839 8 nm and 0.840 2 nm. The fluid compositions are high in H2 and K＋. Hydrothermal vein type magnetite occurs in veins composed by medium- and coarse-magnetite with high content of Mn （4.78%-6.22%）. Octahedral parting is developed very well with cell parameter between 0.840 1 and 0.840 7 nm. The lowest fluid compositions show that it is the last stage of the metallogenic system.