Distribution and source of elements in Gabbroids of different geochemical types

Abstract

Such gabbroids show an unequal distribution of elements. The contrast of distribution increases with the degree of differentiation and contamination. Gabbroids can be with a different source of elements. Sources of orebearing gabbroids (FeTiV and TiZr) are in the deep mantle. The low ratio, the small range of variance of Sr 87:Sr 86 (0.7035 + 0.7056) and also the absence of presence of a direct connection with petrogenic elements indicate a weak contamination of gabbroids of this type by the Earth's crust matter. The contamination is checked by a quick intrusion of melt. Therefore the content of melt reflects rather the evolution of the deeper stage than the inner chamber one. And the melt there is a product of the pyroxenitic mantle part enriched by Ti, Zr, Nb, TR. Possibly most such melts do originate directly in the mantle. All rocks associations have alkali-ultrabasic features. So the high concentration of Ti and other elements is related to a deep source. Mantle source elements lie with experimental data. On the other hand (gabbroid CrTiAu type—stratiform intrusion), the distribution of most rare elements does not go with the mechanism of fractional crytallization of basaltic magma. The character of mineralization and the distribution of elements because of intermediate chambers is defined by the contamination process. The contamination can be taken as an extraction of rare elements from the substratum. The development of such a process belongs to the deep earth's crust. The role of mass-exchange in situ is very small, since there is a low rare element content in endocontact gabbroid and mother rocks. Gabbroids are magmatic but a part of clinopyroxenites and ore magnetites are metasomatic products. The influence of crust factors produces a higher value and dispersion of incoherent elements (Rb, K, Sr). This leads to an increase of the isotope ratio of Sr (at 0.7096±0.0007) and its correlation with K and Sr. The contamination is wide ranging and eventually produces dioritoids accompanied by, unusual for gabbroids, gold-sulphide mineralization. The new division of gabbroids can explain the difference of the geochemical specialization and the source of ore elements.