The intrusive nature of quartzites of the Makbal complex, Tien-Shan, Kyrgyzstan

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Bakirov, Apas۱; Sakiev, Kadyrbek۲; Tagiri, Michio۳; Takasu, Akira۴
Holding Date 29 September 2008

The Makbal eclogite metamorphic complex is located in the western part of Kyrgyz Ridge, Tien-Shan, Kyrgyzstan. It is compose a bullet of dome and represent by quartzites with horizons of silicious marbles, talk-chloritoid schist of Makbal suite and overlapping their quartz-biotit schists, graphite marbles and quartzites with pyrites mineralize of Neldy suite. Both suites contain lenses of eclogites, albit-winchite rocks, amphibolites, also bodies of carbonate-silicides rocks and albite - biotite - phengite - granate schists. The morphologically this structure whole was considered as brachya-anticline (B. A. Nikolaev), brachyanticlinorium (V. G. Korolev, V. V. Kiselev), but is more than extensively for it used the term "dome". In spite of the visible simple general form of structure of "dome", its internal structure characterized by extreme complexity. In quartzites are strongly developed structures of trend, derive the sharp change thickness of layers from many hundred meters, down to full attenuation. They complicate by lays multistage and diversified structures of crustal folding and more than later strongest foliation.
In granate of talc-chloritoid shists and quartzites which compose the main part of Makbal suite were found microinclusions and quartz pseudomorphs after coesite. Therefore, these rocks were exposed to ultra high pressure metamorphism (~30 kbar). However, the fact that coesite is occur in mineral assemblage of talc + chloritoid, indicate the temperature no more than 600 oC.
Quartzites are composed mainly from quartz, white mica (predominantly phengite), tourmalin and rarely from garnet. Primarily they were presented by feldspar-quartz sandstones with kaolin cement. Talc-chloritoid shists, besides mentioned above minerals, contain garnet and rarely phengite and before metamorphism they were lateritic clays. The transition between these types of rocks are happening due to intercalation.
Apparently, rocks of Makbal suite was exposed to subduction at very low geothermal gradients which are not exceeding 5 °C/km and it was loaded to the depths more than 90-100 km. Then there was a heating that it bring to sharp transition of coesite to quartz.
The rocks steel lighter, and by presence of tangentially compression they suffered to heaving, intrusion. Along the way to uplift the rocks was capture as high pressures (eclogite and albite-wichite schists), so and low pressure (carbonate-silicides: albite + diopside + actinolite + phengite + phlogopite + kalifeldspath + epidote + quartz and albite – biotite - phengite - garnet schists).