中国铌钽矿成矿规律

A review of niobium and tantalum metallogenic regularity in China

铌、钽是世界新兴产业发展的关键性金属资源.世界上的铌钽资源主要为内生来源,可分为过铝质岩浆系统的花岗伟晶岩型和花岗岩型铌钽矿床、碱性岩-碳酸岩岩浆系统的碳酸岩及其风化壳型和碱性岩型铌钽资源.我国的铌钽资源主要为花岗岩型、花岗伟晶岩型、碱性岩型和碳酸岩型,但资源品位较低,碳酸岩型铌钽资源较少,尚未发现碳酸岩风化壳型资源.我国过铝性岩浆系统的铌钽矿床主要分布在阿尔泰、松潘-甘孜、江南古陆、南岭和滇西-藏南等铌钽成矿带,成矿作用集中在加里东期、印支期和燕山期,并有少量发生在喜山期;碱性系统的铌钽成矿带主要为塔里木-华北北缘、秦岭和扬子西缘成矿带,成矿主要发生在海西-印支期,并有元古宙的成矿作用,两种类型成矿系统的时空分离交替成矿的特征主要归因于二者具有不同的成矿构造背景.前者主要发生在具有巨厚复理石沉积建造的造山带,造山过程中发生铌钽成矿作用;后者主要发生在深大断裂带或裂谷区,成矿物质具有深部来源特征.在今后的找矿工作中,我国应该在松潘-甘孜、阿尔泰、江南古陆、藏南等巨厚复理石沉积建造区,加大寻找高品位花岗伟晶岩型铌钽资源的力度;在塔里木-华北陆块北缘和秦岭等深大断裂发育区,寻找碳酸岩型铌资源;重视南岭、滇西和秦岭地区钨锡矿床中共(伴)生的铌钽资源,加强综合利用研究.

Niobium and tantalum are critical mineral resources in the world. Although they have coherent geochemical behavior, they can be separated to some degree during ore-forming processes. The alkaline property of the host rock is one main factor to control the separation of Nb-Ta. As a result, niobium and tantalum resources can be divided into tantalum-dominated deposits in a peraluminous granitic magma system, including granite-type and granitic pegmatite-type deposits, and into niobium-dominated deposits in alkaline and carbonate magmatic systems, including carbonate-type, carbonate-weathering crust-type and alkaline rock-type deposits. In China, tantalum and niobium resources are mainly present in granite (e.g., the Yichun deposit in Jiangxi), granitic pegmatite (e.g., the Renli deposit in Hunan), alkaline rock (e.g., the Ba'erzhe deposit in Inner Mongolia), and carbonate (e.g., Miaoya in Hubei);however, currently, there are no occurrences of carbonateweathering crust niobium resources. In China, tantalum deposits of the peraluminous granitic magma system are primarily located in the tantalum- metallogenic belts of Altay, Songpan-Ganze, Jiangnan paleocontinent, Nanling, southern Tibet-western Yunnan with mineralizations in the Caledonian, Indosinian and Yanshanian, and few cases in the Himalayas. The niobium deposits of alkaline and carbonate magma systems are primarily located in the niobium-metalogenic belts of Talimu-Northem China, Qinling, and western Yangtze block with mineralizations from Hercynian to Indianian with a few cases from the Proterozoic. Deposits of the peraluminous granitic magma system are primarily located in flysch sedimentary formations with a huge thickness that can be melted into rare metal-rich granitic magma during the orogenic process in a compressional tectonic environment. However, deposits of the alkaline and carbonate magma systems are primarily distributed along deep fractures or rift regions, bearing features of ore-forming material sourced from the mantle. These features show niobium and tantalum mineralization separation and alternation with spatial and temporal distributions, which can be controlled via compression-extension histories of different blocks in China. Although the reserves of niobium and tantalum in China are huge, most niobium and tantalum deposits in China usually bear low grades of Ta5O2 and Nb2O5 and are difficult to utilize. Therefore, in the exploration of niobium and tantalum resources in China, we should pay attention to high-grade granitic pegmatite-type tantalum deposits in the Songpan-Ganze, Jiangnan, Qinling, southern Tibet, and western Yunnan regions. Additionally, we can explore carbonate-type niobium deposits in Talimu-Northem China. The associated niobium and tantalum resources in tungsten and tin deposits may have great potential for exploration in the Nanling, western Yunnan, and Qinling regions.