Ym. Puzankov et al., Meso-Cenozoic collision-accretionary volcanic complexes of the Central andSouthern Pamirs (an example of active margin-plume magmatism evolution), GEOL GEOFIZ, 41(5), 2000, pp. 637-654
The paper presents results of a comparative geochemical analysis of the Bar
tang, Kyzylrabat, Pshart, and Dunkel'dyk volcanic complexes in the Central
and Southern Pamirs. The Bartang and Kyzylrabat complexes represent the Cre
taceous-Eocene Tethys active margin, and the age of the other two correspon
ds to the India-Eurasia collision. Volcanism acted upon a thick (60-75 km)
crust that involved Archean sialic plates.
The rock chemistry was studied on 115 representative samples by the XRF, ga
mma- and atomic-absorption spectrometry, INAA, and other methods at the Ins
titute of Geology, Geophysics and Mineralogy (Novosibirsk). The Bartang and
Kyzylrabat complexes are assigned to the margin-continental type on the ba
sis of their petrology and geochemistry, namely, high Al and low Ti content
s, high LILE/HFSE ratios, and a Ta-Nb minimum. The Pshart complex evolved i
n a back-are continental rift, as evidenced by elevated contents of Ti, low
er LILE/HFSE ratios, and a smooth Ta-Nb minimum. The Dunkel'dyk alkali-basa
ltic rocks, apparently related to hotspot activity, are rich in incompatibl
e elements, especially in LREE and RAE, and differ from intraplate magmatic
rocks of the same type in having deep Ti, Ta, and Nb minima. The four volc
anic complexes are derived from primitive or enriched metasomatic mantle, w
ith a great contribution of crustal material.