Geochemistry of ultramafic–alkaline rocks of the Ziminsky complex (on the example of the Bol’shetagninsky and Beloziminsky massifs) (Eastern Sayan)

The paper compares the elemental composition of alkaline silicate rocks of the Bol’shetagninsky and Beloziminsky massifs, which are part of the Ziminsky complex of ultrabasic rocks and carbonatites. The rocks of the Bol’shetagninsky massif belong to the potassium series and are distinguished by increased concentrations of large ionic lithophilic elements; in the rocks of the Beloziminsky massif, the rocks of the sodium series predominate and the contents of highly charged elements are increased. Judging by the lack of correlation between the highly charged elements in alkaline and subalkaline rocks of the Bol’shetagninsky massif, their formation, in contrast to the rocks of the Beloziminsky massif, is not associated with the process of fractional crystallization.

Sr-bearing phosphates of the apatite supergroup from the alkaline rocks of the Konder pluton, Khabarovsk Krai

The paper presents a mineralogical description of Sr-bearing phosphates of the apatite supergroup found in eudialyte-aegirine-albite rocks of the Konder pluton, Khabarovsk krai. The Sr-dominant phases are associated with minerals of the lamprophyllite group and titanite, whereas the Ca-dominant phases are associated with calciocatapleite and kainosite-(Y), which are the products of the decomposition of eudialyte. The phosphates probably formed during post-magmatic alteration of host rock in a following sequence: stronadelphite > fuorostrophite > Sr-rich fuorapatite (fuorocaphite) > Na-REE-fuorapatite. Their variable chemical composition indicates decreasing Sr, Ba and F contents and increasing Ca, Na, REE and (OH) contents during crystallization. The crystallization sequence could refect a decrease in alkalinity of the mineral-forming conditions. Keywords: stronadelphite, fuorostrophite, fuorocaphite, Sr-rich fuorapatite, fuorapatite, alkaline rocks, hydrothermal alterations, Konder pluton, alkaline-ultramafc complexes.