海南石碌铁矿床构造变形特征及其与铁多金属成矿富集的关系

Structural deformation of the Shilu iron ore deposit in Hainan,southern China,and its relationship with the formation and enrichment of iron-polymetallic metals

海南石碌铁矿曾被誉为"亚洲最大的富铁矿",其形成、定位与褶皱变形及伴随的剪切、塑性流动等构造密切相关。石碌矿区构造变形大致分为早期(D1)复式向斜的形成时期、晚期(D2)褶皱叠加和剪切变形时期。后者又进一步分为韧-脆性变形(D2a),脆-韧性变形、层间滑脱断层形成(D2b)和脆性变形、矿体破坏(D2c)3个阶段。石碌铁矿床受NW—SE向复式向斜及其与NE—NNE向褶皱叠加所形成的横跨或斜跨褶皱的严格控制;褶皱过程所伴随的剪切变形和高温塑性流动是富铁矿形成的重要机制。复式向斜轴部,尤其是2期向斜褶皱轴的叠加部位往往可发现厚大的富铁矿体。

Shilu iron ore deposit,which is situated at the western Hainan Province of southern China,has been reputed as the biggest hematite-rich ore deposit in Asia.The formation and location of the deposit have close relationship with folds and their incidental shear and plastic flow structures.Based on tectonic styles and deformation mechanism of the orebodies and their host rocks,the strongly structural deformation in the studied ore deposit can be classified into two phases,which are D1,the early regional-scale synclinorium formation stage and D2,the late fold superimposition and concomitant shear deformation stage.The latter（D2） can be further divided into three uninterrupted stages of D2a,D2b and D2c,and represents dynamic transformation from ductile-brittle shear and high-T（temperature） plastic flow to low-T brittle fracture.The ore-bodies are strictly controlled by the NW-SW trending synclinorium and the superposed folds which were formed due to superposition of the late NE-NNE trending transversal folds on the early synclinorium,whereas the ductile-brittle shear and concomitant high-T plastic flow were main mechanisms for formation of the hematite-rich ore-bodies.Iron-rich ore bodies in the Shilu iron ore deposit often can be found along the synclinorium axis,especially in the positions of the forementioned superposed synclines.