紧闭褶皱翼部的剪切变形作用——五台山绿岩带金矿化的一种构造控矿机制

SHEAR DEFORMATION OF TIGTING FOLD LIMBS-A MECHANISM OF TECTONICS OVER THE DEPOSITS OF GOLD MINERALIZATION IN WUTAISHAN GREENSTONE BELT

五台山绿岩带中 ,与变质火山 沉积岩系直接相关的金矿化分布广泛 ,具有多种成矿和控矿机制。但就两种主要类型金矿———剪切带型金矿和铁建造型金矿的时空分布、地质特征和赋存的构造部位来看 ,它们都明显地与剪切变形 (韧性的或脆性的 )所产生的构造 热液活化作用有关 ,具显著的构造控矿意义。区域构造分析表明 ,五台山绿岩带的构造格架是一个多级和多期褶皱与断裂的组合 ,总的构造样式是一个紧闭程度向中心增强的复式倒转向形。它们是在北西 南东向挤压作用下递进变形的结果。在这一区域应力场作用下 ,处于不同构造部位的岩石发生变形分解作用 ,从而在紧闭褶皱的翼部产生一系列剪切变形带 ,构成了五台山绿岩带构造控矿机制。本文将以两类绿岩金矿的典型矿床为例 ,对这一控矿构造机制进行全面分析。

In Wutaishan greenstone belt, it is widely distribution that gold mineralization is directly related metamorphic volcanic sedimentary rock, and there are a lot of mechanisms of mineralization and tectonics over the deposits. In the light of time and space distributions, geologic features and hosted tectonic settings of two main gold types shear zone type gold deposits and banded iron formation type gold deposits, they are clearly bounded up with the structure-hydrothermal remobilization resulting from shear deformation (ductle or brittle), and marked the significance of tectonics over the deposits. Regional structure analyses have indicated structure frameworks of Wutaishan greenstone belt are an assemblage of multiorder, multiperiod folds and fanlts, general structural styles are an overturned synclinorium of tighting extent increasing towords its centre. They are a result of the progressive deformation in NW SE compression. The rocks of different tectonic settings occured the deformation partition, and tighting fold limbs occured a series of shear deformation belts, so that they formed the mechanisms of tectonics over the deposits of the characteristic themselves in Wutaishan greenstone belt. Taking the typical deposits of two type gold deposits of greenstone belt for example, this paper has the overall analyses for a tectonics mechanism over the deposits.