华北地块北缘中段铅锌银矿床成矿作用讨论

华北地块北缘中段分布着许多大中型铅锌银矿床,依据其成因特征可划分为四种类型:沉积喷气型矿床、叠加改造型矿床、与大红峪期碱性火山活动有关的浅成低温热液矿床、与中生代火山-斑岩活动有关的热液矿床.成矿作用具多期多成因的特点:古元古代火山沉积作用不仅可能形成了区内最早的VMS型矿床,而且成为区内最重要的矿源层;中元古代早期形成了本区最古老的浅成热液银多金属矿床;中元古代中期形成了又一期VMS型矿床;而中生代是本区铅锌银最重要的成矿期,成矿显然受基底的制约.

On the Metollogenic Aspects of Pb-Zn-Ag Deposits in the Middle North Margin of North China Block

Many Pb-Zn-Ag deposits are found in the middle north margin of North China Block. According to their metallogenic characteristics, the deposits can be group into four types: sedimentary-exhalative deposits, reformed and superimposed sedimentary (or volcanic)-exhalative deposits, epithermal deposits associated with the alkaline volcanism in the Dahongyu period, hydrothermal deposits associated with the Mesozoic volcanic rocks and porphyries. Thus, the Pb-Zn-Ag mineralizations are of multiple periods and multiple geneses. The volcanism and sedimentation in the Palaeoproterozoic resulted in the formation of not only one of the main metal source beds in this area, but also some Pb-Zn-Ag deposits. The oldest epithermal Pb-Zn-Ag deposits in the area are associated with the mafic alkaline volcanism in the early Mesoproterozoic, and feature high-sulphidation type of Ag-Cu-Au-Pb-Zn mineralization with high Te component. Although the Mesozoic Pb-Zn-Ag mineralizations are dominated in the area, they were controlled by the Precambrian basement, which, with high concentration of metals such as Ag, Cu, Pb, Zn, served as the metal source beds.