Teschenite-tephrite, essexite-trachybasalt, sienite-trachytic associations of rocks of Carpathian, Caucasian, North TransBaikal regions

 

Mamedov M.N., Babayeva G.J., Sadygov N.M.

 Geological Institute of  Azerbaijan National Academy of Sciences, Baku, Azerbaijan

 e-mail: musamamedov@rambler.ru

 

Rocks distribution analysis of teschenite-tephrite, essexite-trachybasalt and sienite-trachytic asso­ciations in comparison with differentiates of alkaline and subalkaline series is of limited development. Rocks of studied association are developed in South Wales (Wilkinson, 1955, 1956), in West Car­pathians (Spisak et al., 2004; Grabovski et al., 2003), on north and south slopes of Greater Caucasus (Borsuk, 1979; Dudauri et al., 1989, 2003), in Lesser Caucasus (Mamedov, 1999; Ostraumova et al., 1989), in Talysh (Azizbekov et al., 1979; Ma­medov et al., 1999, 2009), in Araz zone (Rustamov, 2005), in North ТransBaikal (Kazimirovsky, 2001), in sou­theast area of west Syberian platform in Comandor islands (Tsvetkov, 1980), in East Aus­tralia (Martin, 1984).

Analysis of gathered materials of above-mentioned researchers showed that studied associations of rocks formed at three age stages. The first group formed on boundary of late stage of early and early stage of late Cretaceous (80-118 Ma). Second group rocks are of Eocene (43-50 Ma). At last the third group rocks formed in Miocene (17-25 Ma).

Rocks of Cretaceous teschenite-tephrite, essexite-trachybasalt associations can be characterized by great area distribution and pet­ro­gra­phic diversity. They consist of subalkaline tephrites and basanites, trachybasalts in effusive facies on petrographic composition. Intrusive and subvolcanic petrographic rocks types in studied associa­tions are represented by essexites, trachydolerites, teschenites and sometimes by lampophyres.

The following parageneses of minerals are set in rocks composition of effu­sive facies: 1. Phlogopite-chrom­spinel; 2. clinopyroxene-olivine-titano­mag­ne­tite-kaersutite; 3. analcime-orthoclase-sanidine.

However, analcime quantity in tephrites is nearly half of a rock in Khojavend trough (Azerbaijan). In this case studied rock corresponds to analcimite. Rocks of intrusive facies can be characterized by complete crystalline structure. In some cases porphyric diversities are found. It is noteworthy melano -, meso – and leucocratic rocks diversities are found here as well. In melanocratic teschenites olivine and clinopyroxene associations of mine­rals are prevailing signi­ficantly and form teschenite-clinopyroxenite and clinopyro­xene differentiates. By increase of potas­sium feldspar leucocratic teschenites gradually transform into monzoteschenite and in some cases into sienite. Essexite-trachybasalt association of rocks has the more areal development in Khojavend trough (Mamedov at el., 2009) and in North TransBaikal (Kazimirovsky, 2001). Eocene teschenite-tephrites and essexite-trachybasalt associations of rocks are relatively less deve­loped. They can be found in Talysh and in Greater Caucasus (Borsuk, 1979). Miocene teschenite-tephrite and sienite-trachyte associations of rocks are defined in Lesser Caucasus and on Comandor islands.

So, on the base of geological-petrological, mineralogical-geochemical materials one can state that ini­tial melting for studied associations of rocks was subalkaline picrite melting. Evolution of initial mel­ting was subjected to riftogenic structure. Melting differentiation occurred in intrusive chamber and in different-level intermediate focuses. Availability of water (analcime) and hydroxyl (mica, kaersutite, barkevikite) minerals in rocks com­po­sition, studied associations of rocks show that crystallization of subalkaline picrite melting in inter­me­diate focuses and in intrusive chamber was accompanid by water fluid. In this case impregnations of high aluminous titaniferous magnetite crystallized jointly with impregnations of titaniferous salite in tephrites.

 

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