Research On The Mine-forming Character Of Polymetallic Sulfid Deposits In Langshan District, Proterozoic

Langshan Mountain-Mountain Zha Ertai in Inner Mongolia is one of the important minerals-concentrate districts of our country. The area contains many huge even giant copper deposits , plumbum depostis ,zinc deposits and other polymetallic sulfide ones which have always been the key point of investigation on minerals and their geologic information. Predecessors debated upon the cause of these polymetallic sulfide deposits in the area, but there was no consensus. Therefore , research on these deposits will not only be good for production, but also be helpful to theory-consummating.The thesis mainly discusses the polymetallic sulfide deposits in Langshan district, and chooses three representative deposits Dong Sheng Temple, Tan Yaokou and Huo Geqi. Then it starts with their sediment-ancient environment, analyses their rock-forming environment, and make use of petrology and geochemistry to contrast their geologic-geochemical character; utilize isotope and geochemistry to study the source of ore-forming substance and liquid; analyses the cause of these deposits and summarizes characters. There are the conclusions:(1)The polymetallic sulfide deposits in Langshan Mountain district formed in sub-basiin of marginal rift valley in North China Ancient Land, Proterozoic. As the rift valley evolved, formed clastic rocks-carbonate rocks-clastic rocks sequence, and the deposit formed in mid-late time of the rift valley-evolving, and then was sea-regression phase.(2)When the rift valley developed, syngenetic faultages formed broadly on the margin of basin, caused the change of s??ums and orebodies, and on some extent it controlled the thickness and shape of the stratums and orebodies. At the same time, the syngenetic faultages were not only channels through which ore liquid flowed into ancient rift valley basin but also the site in which the liquid sedimentated.(3)Transmutative lava samdwich developed broadly on the bottom of polymetallic sulfide deposits of Langshan Mountain in Proterozoic, there is a combination of dual-peaks in the south of rift valley. The existence of lava could brought thermal source to deposits and mine-forming substance.(4)The coupling of tension of rift valley, syngenetic breaking and volcanism formed a hydrotherm–sediment ore-forming system. Under the volcanism(hydrotherm), deep volcanic substance and mine-forming liquid constantly flowed into reductive and relatively close basin which formed the ores through syngenetic ruptures, and because of the change of physical and chemical conditions , the liquid sedimentated to form deposits, the cool undersea brine infiltrated, leached ore elements from bottom of ancient land, and as the volcanism the liquid flowed into the proper basin through syngenetic ruptures and sedimentated to form ores.(5)The polymetallic sulfide deposits of Langshan Mountain in Proterozoic belong to undersea lava sedimentary exhalative deposit, and effected by regional metamorphism lately.