新疆磁海铁矿床中黑柱石的发现及其地质意义

Finding and Significance of Ilvaite in the Cihai Iron Deposit, Xinjiang Autonomic Region,China

黑柱石是一种不常见的夕卡岩标型矿物,本次研究在新疆磁海矿区首次发现黑柱石。本文对磁海矿区的黑柱石产出地质环境、矿物共生组合、化学成分、光学性质等进行了研究。化学成分均由电子探针分析求得,计算化学简式为Ca0.98(Fe1.72Mn0.07Mg0.11)1.902+(Fe0.95Al0.03)0.983+[Si2.00O7]O(OH)。磁海矿区黑柱石的形成与基性次火山热液活动有关,是一种特殊的退变质(蚀变)夕卡岩矿物;在成矿作用晚期,随着热液活动加强,早期夕卡岩矿物可退变质形成黑柱石。黑柱石形成时间较晚,对早期形成的磁铁矿起贫化作用。将磁海矿区黑柱石与国内外其它矿区黑柱石的化学成分进行了对比,认为磁海矿区黑柱石为普通黑柱石。黑柱石在常用的矿物中较少提及,应该引起重视。

Ilvaite,an uncommon type of skarn typomorphic mineral,was first found in Cihai iron deposit.In this study geological occurrence,mineral association,chemical composition and optical property of ilvaite in Cihai area were discussed.The mineral chemical composition by EPMA showed that the molecular formula of the Cihai ilvaite is Ca0.98（Fe1.72Mn0.07Mg0.11）1.90^2＋（Fe0.95Al0.03）0.98^3＋ [Si2.00O7]O（OH）,which belonging to normal ilvaite species.It is considered that the ilvaite was related with mafic subvolcanic rocks and with the hydrothermal metallogeny as a kind of typical retrograde,postskarn mineral.At the end of mineralization,the early skarn minerals can be metasomated and substituted by ilvaite.Ilvaite of the Cihai deposit was formed in later mineralization stage and had a dilution effect to the early magnetite.It is suggested that ilvaite is a kind of important mineral in mineralogy and should be paid more attention.