构成战略资源的关键元素有56个,大部分关键元素地壳丰度低,需要数十倍至上千倍的超常富集才能成矿,导致其矿产资源分布极不均匀。因此,圈定元素超常富集区是战略资源找矿预测和发现大型矿床的关键。超常富集核心是元素的富集强度,可以用成矿富集系数(m.a.i)、矿床规模吨位指数(t.a.i)和异常富集系数(a.c.i)定量刻画富集强度。对贵金属、有色金属、黑色金属、稀有金属、稀散金属、稀土和放射性等35个战略资源矿种进行统计分析,可以得出:成矿富集系数大于1 000的元素有锑、铋、铼和金,>100~1 000的元素有银、钨、锡、铬、锂、铯、碲、铟、铀和铂族元素(PGE),>10~100的元素有铜、镍、铬、铍、铷、钪、铌、钽、锆和原生稀土矿,≤10的元素有铁、铝、钛和离子吸附型稀土。富集达到大型以上矿床最低矿床规模吨位指数要达到10⁷,一般要达到10¹⁰。异常富集系数要达到2以上。元素超常富集还体现在异常空间分布面积>100~1 000 km²,具有3层以上异常结构,至少存在4个元素组合。元素富集量和潜在资源量,可以用面金属量和体金属量进行定量预测。元素超常富集导致大规模成矿效应,而且在成矿物质背景(源)、成矿过程(运)和最终就位(储)整个富集过程中留下了异常轨迹,可以从定性和定量角度刻画元素超常富集规律,为预测和发现矿床提供找矿标志。

The strategic mineral resources contain 56 critical elements, most of which have low crustal abundance and require 10-1000 folds of enrichment to form ore deposits. This results in extremely uneven distribution of mineral resources. Thus the delineation of super enrichment area is the key to the resource prospecting and discovery of large-sized ore deposits. The enrichment intensity of elements can be quantitatively expressed by the metallogenic acumulatioin index (m.a.i), the tonnagea acumulatioin index (t.a.i) and the anomalous concentration index (a.c.i). Statistical analyses of 35 strategic mineral species, including precious, non-ferrous, ferrous, rare and dispersed elements, rare earth elements and radioactive metals, revealed that (1) elements with a m.a.i greater than 1000 were antimony, bismuth, rhenium and gold; a m.a.i of >100-1000 were silver, tungsten, tin, chromium, lithium, cesium, tellurium, indium, uranium and platinum group elements; and a m.a.i of >10-100 were copper, nickel, chromium, beryllium, rubidium, scandium, niobium, tantalum, zirconium and primary rare earth elements. Iron, aluminium, titanium and ion-adsorbed rare earth elements had a m.a.i ≤10. (2) Large-sized ore deposits should have a t.a.i greater than 10⁷, generally 10¹⁰, and a a.c.i greater than 2.0. Indicators for element super enrichment also included anomaly greater than >100-1000 km², with anomalous hierarchical structure across more than three layers, and with occurence of at least four associated elements. The element enrichment factor and potential resources in a geochemical block may be estimated using areal and cubic metal contents. The qualitative and quantitative geochemical characteritics of element super enrichment provide evaluation criteria for the assessment and discovery of large-sized mineral deposits.