A NEW CONSIDERATION ON THE GENESIS OF MUD MOUND

The genesis of mud mound (also called as micrite mound), which is mainly composed of lime mud, only a few bioclast, has still not been resolved. In explorations on the sea bottom, it is found that a lot of mordern mud mounds are being formed in mid-ocean ridges, hot-spots or back-arc basins by hydrothermal with CO_2 and bio-activeity. Based on the characteristics of the mud mounds in Bayan Obo (i.e. the ore-hosted dolostone), Heilaobao (southeastern 25 km to Bayan Obo) and the Western Hills, Beijing, and considering the discovery of mordern explorations on the sea bottom, writers consider that the mud mounds are formed by hydrothermal (with CO_2), too, while the bio-process is only a companied process; the mud mound in Bayan Obo is formed in passive continental margin, the mud mounds in the Western Hills, Beijing, are formed within continental. This consideration is helpful to study the geneis of the famous Bayan Obo Fe-Nb-REE deposit and the flux limestone and chemical limestone in the Western Hills, Beijing, and its neighbuorhood. Further study is needed.