陕南马岭关杂岩中斜长角闪岩的矿物学特征及其对Fe-Ti矿化的启示

Mineralogical Characteristics of the Plagioclase Amphibolites of the Malingguan Complex in Southern Shaanxi Province and Their Implications for Fe- Ti Mineralization

陕南安康地区马岭关杂岩中分布有大量的变质基性岩（斜长角闪岩）,其Ti O2含量变化较大,在1.80%-5.95%之间,可划分为低钛与高钛两种类型。岩石学、矿物学、地球化学的详细研究表明,有利于Fe-Ti成矿的是高钛斜长角闪岩,其源岩为富Fe-Ti基性岩类。矿物化学研究表明,钛铁氧化物主要以钛铁矿形式存在,化学成分上具富锰贫镁特征,与攀西地区岩浆型钒钛磁铁矿中钛铁矿的特征明显不同,是海底基性火山活动形成的产物后又经区域变质作用改造形成的,其Fe-Ti矿化作用经历了原岩的初始富集、板块深俯冲过程中的进变质Fe-Ti矿化作用和后期退变质Fe-Ti矿化作用三个主要成矿阶段。

There exist many metabasic rocks（ plagioclase amphibolites） in the Malingguan complex in the Ankang area,southern Shaanxi Province.Their Ti O2 contents are highly variable,ranging 1. 80% - 5. 95%. They can be divided into two types of high-Ti and low-Ti plagioclase amphibolites.Detailed petrological,mineralogical and geochemical studies show that Fe- Ti mineralization is favorably related to Ti-high plagioclase amphibolites. The results of electronic probe show that Fe- Ti oxides consist mostly of ilmenite with higher content of Mn O and lower Mg O,and are obviously different from that of ilmenite in the vanadium-titanium-magnetite ore deposits of the magmatic type in the Panzihua area. They formed in a marine environment that was genetically related to basic volcanism and later were subjected to regional metamorphism. The Fe- Ti mineralization of plagioclase amphibolites experienced three stages： primary Fe- Ti enrichment in protolithes of plagioclase amphibolites,Fe- Ti mineralization during prograde metamorphism of plate deep subduction and Fe- Ti mineralization during the later retrograde metamorphism.