辽西豆荚状铬铁矿的发现及其意义

在辽西建平新太古代变质基底构造混杂带内首次识别出豆荚状铬铁矿。铬铁矿石显示特征的豆荚状构造、褶皱条带、透镜构造、豆状构造、拉长网孔构造等，它们可以与蛇绿岩内典型的豆荚状铬铁矿进行对比。依据同位素年龄制约，辽西豆英状铬铁矿形成于2．50Ga前后。结合该区已报道的新太古变基性火山岩具有大洋拉斑玄武岩成分特点、并广泛发育新太古代高压麻粒岩，可以认为辽西地区新太古代期间曾发生大规模的板块俯冲及碰撞作用过程。

The discovery of podiform chromite in west Liaoning and its implication for plate tectonics

The podiform chromite is identified associated with ultramafic blocks within a structural zone , which cut across a Neoarchean metamorphic terrain, west Liaoning. The characteristic structures of podiform chromite are shown by chromite deposits, such as structural layering, rootless folds, lenses, nodular structures, and antinodular structures etc. The geological occurrence and structures of the chromite ores are evidently comparable to the typical podiform chromites of ophiolites. As constrained by relevant isotopic age dating, the podiform chromite was generated about 2. 50Ga. Furthermore, the Neoarchean metamorphic mafic rocks of this area are chemically similar to MORB, and Neoarchean high-pressures are widely reported along the structural belt. It is suggested that the plate subduction and collision were regionally operated in the Neoarchean.