论西成铅锌矿床的后生成因

A DISCUSSION ON EPIGENESIS OF THE Pb-Zn DEPOSITS IN THE XICHENG ORE FIELD, WESTERN QINLING

以往资料认为西成矿田的铅锌矿床均属泥盆纪热水—喷流沉积或它们的改造型矿床。经笔者研究证实,西成矿田容矿地层除泥盆系外,还有古元古界。超大型厂坝—李家沟矿床产于古元古界地层中。该区矿床不是热水—喷流沉积型或其改造型矿床,而是燕山—喜马拉雅期的后生热液矿床。西成矿田中所有矿床的产出特征、规模和部位完全受抽拉—逆冲岩片构造的控制。为此,原秦岭式或秦岭型铅锌矿床模式的基础已不成立,建议用厂坝式、毕家山式等名称代表西成矿田中两类规模大、经济价值高、特征不同的矿床模式。

It was previously considered that all of the Pb-Zn deposits in the Xicheng orefield belong to Devonian hydrothermal-sedimentary deposits or their reworked ones. Study proves that the host strata, besides the Devonian, include the Lower Proterozoic. The ultra-large Changba-Liji-agou Pb-Zn deposit occurs in the Lower Proterozoic . -The deposits in this region are not hydrothermal-exhalation sedimentary deposits or their reworked ones, but Yanshanian-Himalayan epigenetic-hydrothermal deposits. The occurrence characteristics, size and position of all the deposits in the Xicheng orefield are completely controlled by the Choula (draw)-thrust sheet. Therefore the previous grounds for the model of the Qinling-type Pb-Zn deposits cannot hold good. The writers propose to use Changba-type and Bijiashan-type Pb-Zn deposits to represent the two deposit models with different characteristics which are large in size and of great economic values in the Xicheng orefield.