马达加斯加石墨矿床控矿构造特征与找矿模型

马达加斯加石墨矿床主要分布于马达加斯加岛中东部及南部,矿床类型丰富且成矿地质条件优越,具有良好的找矿前景。综合研究表明,石墨矿床成矿作用经历了自新太古代至新元古代沉积、变质变形及岩浆叠加改造三个阶段。控矿构造研究表明,中部石墨矿床主要受由于紧密同斜褶皱改造的变质片理构造控制,矿体翼部薄而转折端较厚。东部石墨矿床受同斜褶皱及顺变质片理的剪切带控制,并被后期沿脆性断裂迁移的热液叠加富集。南部石墨矿床由于受深层次剪切变形带的影响而延伸稳定。在控矿构造研究的基础上,提出针对石墨矿床"层带复合-岩浆叠加"为主体的区域找矿模型。结合已有矿化时空分布规律及成矿条件,提出了马达加斯加4个主要的成矿远景区。

MAIN ORE-CONTROLLING STRUCTURAL CHARACTERISTICS AND PROSPECTING MODEL OF MADAGASCAR GRAPHITE DEPOSIT

Madagascar graphite deposits are mainly distributed in the Middle-East and south of Madagascar Island. There are abundant types of graphite deposits and favorable metallogenic geological conditions in this area, which have good prospecting prospects. The comprehensive study shows that the metallogenesis of graphite deposits has gone through three stages: Neoarchean to Neoproterozoic sedimentation, metamorphic deformation and magmatic superimposition and transformation. The study of ore-controlling structure shows that the central graphite deposit is mainly controlled by metamorphic schistosity transformed by tight isoclinal folds, with thin wings and thick hinge zone. The eastern graphite deposits are controlled by shear zones of synclinal folds and metamorphic schistosities, and are enriched by hydrothermal superimposition of later migration along brittle faults. The southern graphite deposit extends steadily due to the influence of deep shear deformation zone. Based on the study of ore-controlling structures, a regional prospecting model for graphite deposits is proposed, in which the main body is "zonal composite-magmatic superimposition". Based on the existing spatial and temporal distribution of mineralization and metallogenic conditions, four major metallogenic prospects in Madagascar are divided in this paper.