广西离子吸附型重稀土找矿突破方向研究与科研性示范勘查进展

Research on Prospecting Direction of Ion-Adsorption Type Heavy Rare Earth Element Resources in Guangxi and Progresses in Scientific Demonstration Exploration

离子吸附型稀土矿是关乎我国稀土关键矿产国际竞争优势和资源战略安全的重要矿床类型.广西作为中国南方盛产离子吸附型稀土的主要省份之一,矿床数量众多且资源总量丰富,但在配分特征上以轻稀土型为主,重稀土型则相对稀缺.为提高广西重稀土资源储备,在依照江西“足洞式”和广西本地“南安式”重稀土成矿模式找矿效果暂不理想的情况下,提出将近年来新报道的风化壳轻重稀土叠生型矿床作为找矿突破方向.进而选择灵山县佳平地区作为实验基地,开展了集成矿理论研究和找矿勘查为一体的科研性示范勘查工作.结果发现,在示范勘查区内除了常见的轻稀土成矿类型之外,还发育了以“上轻下重”双层结构为标志的轻重稀土叠生类型.内源与外生成矿条件综合研究指示,两种成矿类型的母岩条件类似,均与具有高稀土总量(ΣREE>260×10^(-6))、低度轻稀土配分(1<LREE/HREE<4)且富含易风化稀土副矿物的中粗粒黑云母二长-闪长花岗岩有关.但相比于轻稀土型,轻重稀土叠生型更偏向于在覆盖厚层风化壳和存在强烈土壤水渗流活动的地貌-水文环境中发育.这种特定的外生环境能为稀土元素在风化过程中发生长距离的淋滤-淀积提供更有利的空间和动力条件,增强风化壳内部稀土元素的富集与分异效应,使得活动性更强的重稀土元素比轻稀土元素优先向风化壳下部迁移和富集,最终在持续的分异作用下形成“上轻下重”双层矿化结构.在上述成矿理论认识的指导下,笔者通过对常规勘查方法的调整和优化,采取了整体放稀勘查网度和局部加密钻孔验证相结合的方法,使得科研示范勘查工作取得良好实际找矿效果,探获重稀土资源量达到中型规模,这对指导广西乃至中国南方“上轻下重”叠生型稀土风化矿床的找矿工作具有参考意义.

The ion-adsorption type REE deposit is a critical mineral resource in China that has a great impact on international REE supply.Guangxi,as one of the major provinces in southern China that developing the ion-adsorption type REE,has numerous deposits and abundant reserves.However,when examining the mineralization classification,the majority of the REE deposits in Guangxi is categorized as LREE-type,with fewer of the HREE-type.To bolster Guangxi’s reserves of HREE,it conducted a wide screening of potential prospecting directions and proposed that a newly reported LREE+HREE overlapping type deposit could serve as a breakthrough target.Furthermore,it selected a demonstration district located in Jiaping,Lingshan County,to conduct integrated work encompassing both scientific research and mineral exploration.The results reveal that,in addition to the common LREE-type mineralization,the LREE+HREE overlapping-type mineralization is also found in the demonstration district,characterized by a dual-layer mineralization structure with“upper LREE ore and lower HREE ore”.Both two mineralization types share similar parent rock conditions,which are associated with medium to coarse-grained biotite monzoniticgranodioritic granite with high total REE content(ΣREE>260×10^(-6)),low to moderate LREE distribution(1<LREE/HREE<4),and rich in easily weathered REE-bearing accessory minerals.However,compared to the LREE-type,the LREE+HREE overlapping-type tends to be developed in some special geomorphological-hydrological locations,where thick regolith and strong soil water infiltration exist.This preferred exogenous environment could provide more favorable spatial and dynamic conditions for the happening of long-distance migration of REE,enhancing the differentiation effect between LREE and HREE due to their different behaviors.More mobile HREE,compared to LREE,tend to migrate to the lower part of the regolith profile,ultimately giving rise to the“upper LREE ore and lower HREE ore”dual-layer mineralization structure.Guided by the ore-forming theory mentioned above,it adjusted the conventional prospecting methods through diluting exploration spacing overall and increasing drilling validation locally,which enable to have yielded substantial practical progress.The discovery of HREE resources has reached a medium-sized scale,making it a good reference case for guiding HREE exploration not only in Guangxi but throughout South China.