地球历史中矿产资源分布之规律

摘要

Data on the mineral resources distribution are presented. It is shown that the general regularities of the siderophile and chalcophile metallogeny based on the cost of mineral resources probably reflect their evolutionary changes in the Earths history. Iron deposits were mostly developed in the Early Proterozoic after the separation of the Earth core. The distribution of gold reserves is similar to that of iron, except for more prominent metallogenic impulses. The metallogenic potential of siderophile minerals was also mostly developed in the Early Proterozoic, but later it considerably decreased and increased only in the Phanerozoic due to the recycling of the Earths crust and activation of ore substance of older deposits. The behavior of elements was completely different. Their manifestations were moderate during the Precambrian. The total mass of chalcophile mineral deposits was maximal in the Phanerozoic due to recycling. The chalcophile manifestation was stronger than the siderophile one, because sulfides are more mobile than ferrous metal oxides. Cyclicity of the Earth development manifested by the periodicity of the formation of supercontinents fairly corresponded to the distribution of mineral resources. Blooms of the iron ore, siderophile and gold ore metallogeny obviously followed the formation of supercontinents and corresponded to the earliest impulses of their breakup. Maxima of the accumulation of chalcophile elements commonly coincide with the formation of supercontinents, although the third impulse of chalcophile metallogeny coincided with the separation of Laurasia and Gondwana rather than the formation of Mesogea. Such features of ore accumulation can probably be explained by cyclicity of the crust development due to the nonstationary chemical-density convection in the mantle. Judging from the periodicity of the formation of supercontinents, the major period of the mantle convective megacycles is close to 800 Ma. But the same cyclicity was also marked by the processes of the accumulation of siderophile, gold and chalcophile ores with the primary mantle signature. Hence, in addition to the chemical composition of mantle, the mantle cyclicity of convective processes in the geosphere also considerably governed the formation of siderophile and chalcophile mineral deposits.%现有的矿产资源分布资料可以说明地球历史中亲铁和亲铜元素成矿的一般规律.铁矿床在元古宙地核分离之后最为发育.除个别显著成矿高峰外,金的储量分布与铁类似.亲铁元素矿物的成矿潜力在古元古代也最大,以后逐渐降低,只是在显生宙,因地壳的再循环和古老矿床中矿石物质的活化而再次增大.元素的行为则完全不同,在前寒武纪时期它们的活动性为中等.亲铜矿物矿床的总量,在显生宙因再循环而达到最高,亲铜矿物矿床成矿能力较之亲铁矿物强得多,因为硫化物比铁金属氧化物更为活泼.地球演化的旋回性表现为超大陆形成的周期性,它与矿产的分布颇为一致.铁矿、亲铁元素和金成矿作用的突然激增,显然是在超大陆形成之后,并且与其早期裂解的脉动相对应.亲铜元素堆积的高峰期往往与超大陆的形成期相对应.尽管亲铜元素成矿的第三次脉动与中生代古陆(Mesogea)的形成并不一致,但却与劳亚古陆及冈瓦纳古陆的裂解相一致.此种成矿堆积现象可以借助地幔内非稳态化学-密度对流所诱发的地壳发展周期性来解释.根据超大陆形成的周期性推断地幔对流巨旋回的主期应为800 Ma,此种周期性亦反映了具原始地幔印记的亲铁、金和亲铜元素的聚集作用过程.因此,地球圈层中地幔对流作用的周期性亦显著地控制了包括地幔化学成分在内的亲铜和亲铁元素矿床的形成.