【摘要】 <正> 一、区域地质概况 本区碳酸岩位于秦岭纬向褶皱带东南部武当地块的西部边缘,处于次一级复式背斜近轴部的东北翼。区内构造破碎,断裂比较发育,同斜紧密线状褶皱清楚,构造线方向为北西一南东向,倾向北东。 区内出露的主要地层是下震旦统耀令河群浅变质的海相火山岩系,岩性以石英角斑更多还原

【Abstract】 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.更多还原