Loading…

Kimberlite age in the Arkhangelsk Province, Russia: Isotopic geochronologic Rb-Sr and super(40)Ar/ super(39)Ar and mineralogical data on phlogopite

The paper reports detailed data on phlogopite from kimberlite of three facies types in the Arkhangelsk Diamondiferous Province (ADP): (i) massive magmatic kimberlite (Ermakovskaya-7 Pipe), (ii) transitional type between massive volcaniclastic and magmatic kimberlite (Grib Pipe), and (iii) volcanic k...

Full description

Saved in:
Bibliographic Details
Published in:Petrology 2016-11, Vol.24 (6), p.562-593
Main Authors: Larionova, YuO, Sazonova, LV, Lebedeva, N M, Nosova, A A, Tretyachenko, V V, Travin, A V, Kargin, A V, Yudin, D S
Format: Article
Language:English
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The paper reports detailed data on phlogopite from kimberlite of three facies types in the Arkhangelsk Diamondiferous Province (ADP): (i) massive magmatic kimberlite (Ermakovskaya-7 Pipe), (ii) transitional type between massive volcaniclastic and magmatic kimberlite (Grib Pipe), and (iii) volcanic kimberlite (Karpinskii-1 and Karpinskii-2 pipes). Kimberlite from the Ermakovskaya-7 Pipe contains only groundmass phlogopite. Kimberlite from the Grib Pipe contains a number of phlogopite populations: megacrysts, macrocrysts, matrix phlogopite, and this mineral in xenoliths. Phlogopite macrocrysts and matrix phlogopite define a single compositional trend reflecting the evolution of the kimberlite melt. The composition points of phlogopite from the xenoliths lie on a single crystallization trend, i.e., the mineral also crystallized from kimberlite melt, which likely actively metasomatized the host rocks from which the xenoliths were captured. Phlogopite from volcaniclastic kimberlite from the Karpinskii-1 and Karpinskii-2 pipes does not show either any clearly distinct petrographic setting or compositional differentiation. The kimberlite was dated by the Rb-Sr technique on phlogopite and additionally by the super(40)Ar/ super(39)Ar method. Because it is highly probable that phlogopite from all pipes crystallized from kimberlite melt, the crystallization age of the kimberlite can be defined as 376 plus or minus 3 Ma for the Grib Pipe, 380 plus or minus 2 Ma for the Karpinskii-1 pipe, 375 plus or minus 2 Ma for the Karpinskii-2 Pipe, and 377 plus or minus 0.4 Ma for the Ermakovskaya-7 Pipe. The age of the pipes coincides within the error and suggests that the melts of the pipes were emplaced almost simultaneously. Our geochronologic data on kimberlite emplacement in ADP lie within the range of 380 plus or minus 2 to 375 plus or minus Ma and coincide with most age values for Devonian alkaline-ultramafic complexes in the Kola Province: 379 plus or minus 5 Ma; Arzamastsev and Wu, 2014). These data indicate that the kimberlite was formed during the early evolution of the Kola Province, when alkaline-ultramafic complexes (including those with carbonatite) were emplaced.
ISSN:0869-5911
1556-2085
DOI:10.1134/S0869591116040020