【摘要】：安哥拉Bonga碳酸巖型鈮礦床位于Parana'-Angola-Etendeka堿性巖-碳酸巖火成巖省東部,是一個孤立產(chǎn)出的中心式巖栓,侵入于元古宙花崗巖基底中。巖石地球化學研究表明,Bonga巖體由鈣碳酸巖和少量的鎂碳酸巖組成,巖體成分從鈣碳酸巖向鎂碳酸巖演化。礦物組合上,鈣碳酸巖以方解石為主,副礦物有磷灰石、磁鐵礦、燒綠石和少量稀土礦物;鎂碳酸巖以白云石為主,燒綠石含量降低,稀土礦物含量增高。富鈣碳酸巖(摩爾比值Ca O/Ca O+Mg O+Fe O+Mn O0.83)中Nb含量較高,變化于148.1×10~(-6)~8394×10~(-6),平均為2127×10~(-6),∑REE變化于1441×10~(-6)~9452×10~(-6),平均為2791×10~(-6),LREE/HREE變化于16.7~58.3,平均為25.0;富鎂碳酸巖(摩爾比值Ca O/Ca O+Mg O+Fe O+Mn O0.83)Nb含量降低,變化于300.9×10~(-6)~3910×10~(-6),平均為1502×10~(-6),∑REE升高,變化于1659×10~(-6)~18849×10~(-6),平均為7111×10~(-6),輕稀土更加富集,LREE/HREE增大,變化于19.1~114,平均為57.6。鈮在碳酸巖漿演化的早期富集,鈮礦化主要與富鈣碳酸巖有關(guān);稀土元素的富集相對較晚,主要與富鎂碳酸巖有關(guān)。對碳酸巖碳氧同位素的瑞利分餾模擬計算(RIFMS模型)結(jié)果表明,Bonga碳酸巖的鈮礦化(燒綠石沉淀)主要受巖漿作用控制,其溫度不低于600℃。
[Abstract]:The Bonga carbonate type niobium deposit in Angola is located in the eastern part of the Parana'-Angola-Etendeka alkaline rock-carbonate igneous province. It is an isolated central plug and intruded into the Proterozoic granite basement. The petrogeochemical study shows that the Bonga rock body is composed of calcium carbonate and a small amount of magnesium carbonate, and the composition of the rock body evolves from the calcium carbonate to the magnesium carbonate. In mineral assemblage, calcite is dominant in calcium carbonate, apatite, magnetite, pyrochlore and a small amount of rare earth minerals are secondary minerals, while dolomite is dominant in mafic carbonate, the content of pyrochlore decreases and the content of rare earth mineral increases. The NB content of calcium-rich carbonatite (molar ratio Ca O/Ca O Mg O Fe O Mn O 0.83) was higher, which varied from 148.1 脳 10 ~ (-6) to 8394 脳 10 ~ (-6) with an average of 2127 脳 10 ~ (-6), 鈭，

本文編號：2177048