豆荚状铬铁矿豆状结构成因机制探讨——以遵化地区豆荚状铬铁矿为例

豆荚状铬铁矿是蛇绿岩套地幔构造岩中特征的矿产 ,其矿石发育丰富的岩浆 -变形结构构造类型 ,对认识大洋上地幔成因及其成矿过程具有重要意义。对遵化新太古代豆荚状铬铁矿的深入研究 ,发现它们发育了丰富的岩浆结构 (豆状结构、豆壳状结构等 ) ,还保留了大量凝缩标志和旋转特征。对比分析其各种特征结构发现豆状结构是由浸染状结构逐步演化形成的 ,并且旋转和凝缩是形成豆状结构的主要机理。豆荚状铬铁矿以其独特而稳定的物理化学特性 ,记录了大洋地幔深部岩浆活动(特别是扩张中心原始岩浆活动 )以及大洋岩石圈运动过程。因此 ,研究其成因机制能够为研究大洋上地幔动力学机制提供重要线索

RESEARCH ON THE FORMATION MECHANISM OF THE NODULAR TEXTURE OF ARCHEAN PODIFORM CHROMITITE:EVIDENCE FROM PODIFORM CHROMITITE IN ZUNHUA, NORTH CHINA

Podiform chromitite is a characteristic mineral deposit of ophiolitic complex. It has many textural types that are important for the study of its ore-forming process. Thousands of ore samples from the Neoarchean podiform chromitite, Zunhua, not only have the magmatic structures such as nodular and orbicular texture, but also show the textures of condensation and rotation.The nodular texture was evolved from the disseminated texture through the rotation and condensation mechanism. The turbulent flow within the mini-chamber of upper oceanic mantle played an important role in its formation. As podiform chromitite has stable physical and chemical properties, it has recorded the magmatic process of the mantle under the ocean spreading centre and the lateral movement of oceanic lithosphere. Therefore, the study of its formation mechanism may provide an important clue to the dynamic mechanism of oceanic upper mantle.