THE ORIGIN OF DEVONIAN DOLMITIC ROCKS FROM NINGLANG-LIJIANG REGION, WEST YUNNAN

The; Devonian in Ninglang- Lijiang region of western Chuxiong Basin, Yunnan, is dommanted by a series of carbonate sediments. The dolomitic rocks is one of the major rock types and has largely a forming mechanism of mixed dolomitization. Under microscopy, the fabrics of dolomitic rocks are floating-romb, contact- romb, hypidiotopic mosaic and sutured mosaic fabrics. It is suggested with the results of cathodoluminescence and electronic probe analysis that: the dolomite formed through mixed dolomitization has a tendancey of Fe⁺⁺, Mn⁺⁺becoming rich but K⁺poor fron center to margin. Dolomite grains are characterized by fogged center with clear margin, which display nuclei and girdles under cathodoluminescence microscopy. The very coarsely crystalline dolomite in subsruface and deep burial diagenesis environments display brown girdles under microscopy but lumines dark- red to non- luminescence under .cathodoluminescence microscopy.