Lamprophyres of Kayla pipe and their mantle xenocrysts, SE Yakutia

The bulk rock and geochemistry of the Kayla and Khatastyr lamproites is similar to other Aldan lamproites and lamprophyres.  The ultramafic varieties are close to cratonic Ol- lamproites and alkaline Al, Si-rich varieties are closer to orogenic type.

Trace element bulk rock trace element (TRE) spider diagrams show inclined patterns with the LILE, Sr, Pb, U, peaks and Ta, Nb minima suggesting melting of originally depleted metasomatized Phl peridotites and mixed ancient (EMII, Nd, Sr isotopes) source (low crust)  and later olivine and clinopyroxene fractionation. They are dated 132-134 Ma (Late Cretaceous plume) similar to Chompolo lamprophyres and many alkaline complexes.

Thermobarometry for the deep-seated xenocrysts gives the low temperature and Sp-Gar and Gar facies for Cr- diopsides and chromites. Low - Cr- clinopyroxenes derived from lamproites give hot 90 mw/m² advective branches. 

The REE patterns for Cr-diopsides are more inclined for deeper varieties and reveal Ba, Th, U, Sr peaks and minima Ta, Nd and smaller in Zr-Hf. The `low Cr diopsides show flatter REE and HFSE minima TRE patterns of parental melts are lamproitic. Salites reveal hot crust conditions.

Lamproites melted from Phl peridotite eclogites mixture in the lithosphere base and interacted with mantle beneath Moho.

The work was supported by the Ministry of Science and Higher Education of the Russian Federation RBRF grants 19-05-00788a, 18-05-00073a;  Government tasks for Institute of Geochemistry SB RAS and Institute of Geology and Mineralogy SB RAS and the governmental assignment in terms of Project IX. 129.1.4