江苏省新沂市小焦榴辉岩型金红石矿床的特征及成因初探

CHARACTER AND ORIGIN OF RUTILE DEPOSIT IN ECLOGITE IN XIAOJIAO, XINYI, JIANGSU PROVINCE

江苏小焦榴辉岩型金红石矿床是苏鲁超高压变质带中发现的品位最富、连续宽度最大的大型矿床,它与超高压变质榴辉岩密切相关。矿体主要赋存在含金红石的块状榴辉岩中,呈似层状、长条状和透镜状产出。地球化学特征表明榴辉岩的原岩为来自上地幔或壳幔过渡区的基性至超基性岩。金红石在矿石中主要呈包裹体、粒间充填、蚀变残余、热液充填4种赋存形式,分别代表了4个不同的形成及演化阶段。电子探针分析结果显示,在高压、超高压变质作用期间,富含Na的深部流体对金红石的成矿可能起了重要的作用。研究表明该矿床属典型的榴辉岩型金红石矿床,在成因上与超高压变质作用有关,类似于挪威的Engebfjellet、俄罗斯的Shubino矿床和意大利的PianPaludo矿床,而不同于中国已知的主要金红石矿床。此外,通过本次研究以及对普查和勘探资料的总结,提出了该类矿床的主要找矿标志。

The eclogite type rutile deposit of Xiaojiao in Jiangsu Province is the biggest and the abundantest in Sulu ultra high pressure metamorphic belt, which is related to ultra high pressure metamorphic rock-- eclogite. The ore bodies lay in rutile bearing eclogite mass, which take shaped in layer like, strip, lens. According to geochemical characteristics,it is indicated that the origin of eclogite is basic and ultra basic rocks coming from upper mantle and transitional belt of crust mantle.Four stages of rutile mineralization in the eclogites can be recognized by four ore textures,mineral paragenesis and rutile's occurrences, respectively, as inclusions, intergranular infilling, replacement remnant, and hydrothermal infilling. The analysis results of electron microprobe shows that a Na riched liquid from deep during high and ultra high pressure metamorphism probably played an important role for genesis of rutile mineralization. It is pointed out that the typical eclogite type rutile deposit was related to ultra high pressure metamorphism in genesis, similar to those occurring at Engebfjellet eclogite bodies in Norway, Shubino Village in Russia, and Pian Paludo in Italy, but differing from the other important types in China. Moreover, according to this research, ore hunting indicators for the eclogite type rutile deposit are given in this paper.