GEOCHEMICAL FEATURES AND PETROGENESIS OF MIAOYA CARBONATITES, HUPEH
Li Shi (Geological Laboratory, Hupeh)
The Miaoya carbonatite complex, occuring as lens, is located west of Wudon massif, Hupeh Province, and consists of carbonatites and syenites associated with them. The carbonatites are compositionally classified into four types, i.e.. sovite, alvikite, carbon-bearing alvikite and ankeritic carbonatite. Their average composition is in agreement with the abundance values for carbonatites compiled by Gokd (1966). Three stages can be recognized: the sovite and alvikite types are the earliest followed by carbon-bearing alvikite type, while ankeritic carbonatite type is the latest. Some 'regularities are observed with respect to the distribution of major and rare elements during the evolution of carbonatites. For example, Nb is essentially enriched in sovite type. Except niobite and ilmenorutile, there are also pyrochlore, nioboeschynite and fersmite in it. RE is concentrated mainly in ankeritic carbonatite type, within which bastnasite, parisite and monazite are found. In general, Ca, Nb, and Sr decrease, while Fe, Mg, Mn and RE increase from earlier to later stages. It is suggested that the carbonatites were genetically connected with syenitic magma.