铜陵石炭纪威宁期沉积相及与黄铁矿矿床的关系

RELATIONSHIP BETWEEN PYRITE DEPOSITS AND SEDIMENTARY FACIES OF THE WEINING AGE OF CARBONIFEROUS PERIOD IN TONGLING AREA

铜陵地区石炭纪威宁期存在潮坪相,泻湖相和浅海陆棚相。白云岩有两种,准同生白云岩分布于潮坪,成岩白云岩分布于泻湖内,本区以成岩白云岩为主。白云岩中赋存了层位稳定的黄铁矿矿床,黄铁矿在泻湖相最易富集,成岩作用是黄铁矿矿床形成的一个重要因素。

The Weining age of Carboniferous period in Tongling area is a trans gressive one. The carbonate sediments were deposited during this age. After solidifying, they formed the stratum of Huanglong formation. The lower part of it is the thick dolomite and the upper of it is the pure limestone. The author thinks that there exsited tidalflat, lagoon and shallow shelf facies during the Weining age according to the sedimentary sequences, sedimentary structure and sedimentary thickness analysis. Among them the lagoon was dominant in this age. Here are two kinds of dolomites in this area, the penecontemporanepus dolomite formed in the tidalflat while the diagenetic dolomite originally deposited in lagoon and then formed during the diagenetic stage. The diagenetic dolomite is dominant in this area. The pyrite deposits exsit constantly in the dolomite. The trace element analysis of dolomites of the different facies shows that the highest content and of the most enriehment of ore elements occurred in the lagoon. In the bottom of the lagoon the sulfates were reduced by sulfur becteria to produce sulfurated hydrogen H2S. FeS and melnicovite were deposited in the lagoon. The crystalline pyrite was formed during the diagenesis stage. A lot of pyrite deposits in Tongling area subjected to the precipitation and diagenesis. The conditions in which the dolomite formed were suitable for the formation of pyrites.