安哥拉Bonga铌矿床成矿碳酸岩岩石地球化学和C-O同位素研究
发布时间：2018-08-11 12:53
【摘要】：安哥拉Bonga碳酸岩型铌矿床位于Parana'-Angola-Etendeka碱性岩-碳酸岩火成岩省东部,是一个孤立产出的中心式岩栓,侵入于元古宙花岗岩基底中。岩石地球化学研究表明,Bonga岩体由钙碳酸岩和少量的镁碳酸岩组成,岩体成分从钙碳酸岩向镁碳酸岩演化。矿物组合上,钙碳酸岩以方解石为主,副矿物有磷灰石、磁铁矿、烧绿石和少量稀土矿物;镁碳酸岩以白云石为主,烧绿石含量降低,稀土矿物含量增高。富钙碳酸岩(摩尔比值Ca O/Ca O+Mg O+Fe O+Mn O0.83)中Nb含量较高,变化于148.1×10~(-6)~8394×10~(-6),平均为2127×10~(-6),∑REE变化于1441×10~(-6)~9452×10~(-6),平均为2791×10~(-6),LREE/HREE变化于16.7~58.3,平均为25.0;富镁碳酸岩(摩尔比值Ca O/Ca O+Mg O+Fe O+Mn O0.83)Nb含量降低,变化于300.9×10~(-6)~3910×10~(-6),平均为1502×10~(-6),∑REE升高,变化于1659×10~(-6)~18849×10~(-6),平均为7111×10~(-6),轻稀土更加富集,LREE/HREE增大,变化于19.1~114,平均为57.6。铌在碳酸岩浆演化的早期富集,铌矿化主要与富钙碳酸岩有关;稀土元素的富集相对较晚,主要与富镁碳酸岩有关。对碳酸岩碳氧同位素的瑞利分馏模拟计算(RIFMS模型)结果表明,Bonga碳酸岩的铌矿化(烧绿石沉淀)主要受岩浆作用控制,其温度不低于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，
本文编号：2177048
[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，
本文编号：2177048
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