内蒙古自治区巴林左旗老房身铅锌矿矿床中闪长岩地球化学特征及其地质意义

Geochemical and Geological Significance of Diorite in Laofangsheng Lead-Zinc Deposits Bahrain Zuoqi, Inner Mongolia

内蒙古巴林左旗老房身铅锌矿矿床位于兴蒙造山带内,矿区内出露脉状闪长岩,地球化学分析表明该地区闪长岩属于低TiO_2和高Al_2O_3钙碱性玄武岩系列,富集Rb、Ba、K大离子亲石元素(LILE),亏损Nb、Ta、Ti、P等高场强元素,具有典型弧岩浆岩的特征。结合区域地质资料及对比分析前人成果,认为石炭世末期巴林左旗地区在强烈拉张的裂谷环境下存在一个有限洋盆,由于洋盆发育不成熟或边伸展边向两侧俯冲-消减,形成了巴林左旗地区类似大陆边缘弧玄武岩特征的闪长岩。

Laofangsheng Lead-Zinc Deposits Bahrain Zuoqi,Inner Mongolia is located in the Xingmeng orogenic belt.There are some veins of diorite.Geochemical of diorite samples show high Al2O3values but low TiO2values,and are thus classified as calc-alkali basalt series.These samples are characterized by low REE abundance and slight LREE enrichment.They also show LILE enrichment,HFSE depletion and distinctly negative Nb and Ta anomalies.Based on geochemical characteristics of these samples in this study,combined with regional geological data and previous research results,the authors hold that,in the late Early-Carboniferous,there was a new limited ocean basin under an intensely extensional rift setting.Consequently,as the newly formed ocean basin was still immature or experienced subduction-related contamination and metasomatism,the Late Carboniferous quartz diorites of Bahrain Zuoqi exhibited the continental margin-arc-like enriched signatures.