US EPA

7465206 

Journal Article 

Sources of heterogeneous magmatism of the Arkhangelsk diamondiferous province 

Parsadanyan, KS; Kononova, VA; Bogatikov, OA 

1996 

1 

Petrology
ISSN: 0869-5911
EISSN: 1531-8540 

4 

5 

460-479 

English 

WOS:A1996VJ47100003 

The Arkhangelsk diamondiferous province is situated within the Kola-Kuloi craton and Late Proterozoic folded areas of its framing. The province comprises eight fields of Late Devonian-Early Carboniferous ultrabasic and basic magmatism D3-C1 in age (dozens of diatremes and sills of kimberlite, olivine melilitite, and tholeiitic basalt). The kimberlites of the province are comparable to olivine lamproites in some specific features of their mineral composition. These features include relatively low Al2O3 at high TiO2 and BaO concentrations in phlogopites, as well as high FeOtot and Crl2O3 contents and Cr/(Cr + Al) ratio in spinels. Such an affinity to diamondiferous lamproites could be caused by similar conditions of magma evolution. Two groups of rocks that differ in major and trace element chemistry are distinguished among the kimberlites of the province: (a) diamond-rich rocks of the Zolotitsa field and (b) diamond-poor rocks of the other fields. The former are close in some characteristic chemical parameters to group II kimberlites of South Africa (Smith et al., 1985), whereas the latter resemble group I kimberlites of South Africa, Yakutia, and other regions. Systematic analysis of the rock geochemistry and Nd-Sr isotope composition shows that the diversified magmatism of the province is contributed to from three genetically different mantle sources: (a) primitive upper mantle (PUM) or bulk silicate earth (BSE) for diamond-poor group I kimberlites, (b) prevalent mantle (PREMA) for tholeiitic basalts, and (c) type I enriched mantle (EMI) for group II kimberlites of the Zolotitsa field and olivine melilitites of the Izhmozero field. In the course of formation, the parent magmas of kimberlites of the Zolotitsa field mixed with up to 15% magmas of group I kimberlites at the base of the lithosphere. Prior to mixing with group I kimberlites, parent magma of group II kimberlites of the Zolotitsa field had similar isotope composition, but higher Rb, Ba, LREE, and lower CaO, Al2O3, and Na2O compared to olivine melilitites. These differences could be caused by the significant proportion of phlogopite in the kimberlite source, and potassium richterite in the melilitite source. The formation of the lithosphere source of the EMI-type resulted from the metasomatism of the lower part of the old depleted lithosphere involving H2O-, LILE- and LREE-rich fluids-melts, which were derived from a subduction zone in the Late Archean-Early Proterozoic epoch of the cratonic stage of the regional evolution. Copyright © 1996 by MAEe Cyrillic signK Hayκa/Interperiodica Publishing.