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

Abstract

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.