地球化学块体的概念及其研究意义

Development and significance of geochemical blocks

地球化学块体是地球上某种或某些元素高含量的巨大岩块,它们是地球从形成与演化至今不均匀性的总显示,为大型至巨型矿床的形成提供了必要的物质供应条件。应用勘查地球化学的方法手段,从元素的角度能够将这些地球化学块体勾绘出来,从中得到这种巨大的地球化学块体能够为大型巨型矿床的形成提供其所必需的足够的物质供应量的新认识。通过对全国区域化探扫面计划(RGNR)所覆盖的全国600多万km2的国土面积上获得的高质量海量元素分析数据的综合研究,发现了比传统意义的分散晕分散流更为宽广的地球化学模式:区域异常、地球化学省、地球化学巨省和地球化学域。这种更为宽广的所谓套合着的地球化学模式谱系实际上是地球上富含各种金属的巨大岩块的内部结构特征在地表的表现,而追索某元素地球化学块体的内部结构则可揭示该元素在地球化学块体中逐步浓集成矿的轨迹。依此思路发展了一整套的矿产勘查新战略:迅速掌握全局,逐步缩小靶区,并应用于国土资源大调查的项目中。尽管地球化学块体的理论与方法学研究尚在初期阶段,但这一概念改变了建立在点源分散模式上的勘查地球化学的基本原理,也为矿床学、成矿学与大地构造学研究开拓了眼界,并提供了新的研究思路。

Geochemical blocks are the giant roc k blocks with high content of one or mo re elements within the upper earths crust,they are the net resul ts of the earths original heterogen eity and the distribution and redistribution of metals during the evolution of the earth up to the present days and provide large metal endowments necessary fo r the formation of large to giant ore deposits.These blocks can be delineated b y the methods of exploration geochem istry.By study the flood of high quality data obtained in Chinas national geoch emical mapping program(RGNR)carried out for 24years over more than 6million km 2 of Chinas territory,it is found more broad geochemical patterns other than dispersion halos and dispersio n trains,e.g.geochemical regions,geochemical provinces,geochemical megaprovinces and geochemical doma ins.They are the surface expression s of large blocks of rock with higher m etal contents.Geochemical blocksmeth ods for finding new large to giant ore deposits of different types of locations within or in the surroundings of larg e geochemical blocks have been developed by which important new discoveries have been already obtained in some re gions in China.Though the developme nt of the geochemical block concept and methodology is still in early stage,but it has already extended the basic principle of exploration geochemis try,and widened the field of vision for ore genesis metallogeny and tectonics,an d provided them with new thought-pro voking approaches.