PICRITES OF THE NORTHERN NURATAU (SOUTHERN TIEN SHAN, UZBEKISTAN) Kholboy. D. Ishbaev and A. H. Shukurov National University of Uzbekistan Named after Mirzo Ulugbek, Tashkent, Uzbekistan Authors tor for Correspondence ABSTRACT The composition of the picrites of the Northern Nuratau (Southern Tien Shan) was analyzed. Chemical composition of the picrites and rock-forming minerals is presented here. It is concluded that high content of titanium, iron and chrome minerals picrites in the Northern Nuratau and their diamond-containing matrix points out the deep-mantle nature of original magma chamber nucleation in the Southern Tien Shan. Keywords: Picrites, Dike, Suture Zone, "Spinifex" Structure, Southern Tien Shan, Magmatism, Alkaline, Subalkaline, Mantle, Absolute Age INTRODUCTION Picrites are widespread on the northern slopes of the northern Nurata ridge (Asmansay, Fazilman) north Bukantau and South Fergana (Baubashata, Karachatyr, Aravan, Nadir et al.,). There they form small lenticular bodies, dikes and small stocks (Khamrabaev, 1972; Gamalaeev et al., 1967; Baranov et al., 1978; Mikhailov et al., 1981). It should be noted that all of them are located in Bukantau- Yuzhnoferganskoy suture zone and are closely associated with the host lavas alkaline basalts (eruptive breccia - hyaloclastites, subvolcanic education-gabbro-diabase) and mafic-ultramafic; they are considered the last relics of oceanic crust Turkestan paleooceanic basin. In the area of the Northern area in Asmansay Nuratau (Figure 1) dikes and lenticular bodies picrites are 100-400 m with a capacity up to 30-100 m chain-traced over more than 15 km - from Bagdan (Yangikishlak) to Karakhans. There are about 40 bodies (Golovko et al., 2007). In addition, they are in the form of dikes and low power are met in the upper sais Sentyab and Madzherum (Mushkin, 1979; Golovko et al., 2006). They clearly intrude products like alkaline basalt formation shavasskoy suites. Its age is disputed, ranging from the Ordovician-Silurian to lower Carboniferous (Geology, 1998). Picrites have rather monotonous mineralogical composition: olivine, augite, diopside, plagioclase, and the serpentine accessory minerals - chrome Picota, chromite, titanomagnetite, ilmenite, sulfides, etc. The structure of the porphyritic combined with prismatic-grained microlitic to the bulk. Characteristically, there are needle-like crystals of pyroxene including oval olivine grains (Figure 2, b), indicating "spinifex" structure (Hamrabaev, 1972; Mikhailov and Baranov, 1981). Olivine is 60-70% of the total volume of rocks and has euhedral, round and oval shape of crystals (Figure 2-d-f) with the size of 0.5-4 mm; in the cracks of cleavage widespread veins of chrysotile and lizardite, sometimes there are antigorite and carbonate are seen. The chemical composition of it is similar to olivine-gialosideritu (Table 1). The composition of the olivine closely matches with the composition of the olivine basalt Melilitic in Spiegel Basin, Cape (Africa). It is completely replaced by serpentine, and the chemistry of chrysotile corresponds with lizardite (Figure 2, Table 1). The pyroxene is represented by elongated crystals of augite and titanavgita (Figure 2 a-b) size 0,1h1 mm. The chemical composition (microprobe analysis) corresponds augite and titanavgitu, which are characterized by the fact that they include a very high content of titanium and chromium (Table 1). Titanavgit characterized by intense color and characteristic plehroizmu with a violet hue. In the plagioclase crystals, the nature of picritic basaltic porphyry, differentiate from ultrabasic magma in the magma chamber below the "Moho" border. Accessory minerals are represented as chromespinellids, chromite, titanium-magnetite, sulfide minerals, rare graphite muassonitom, apatite, sphene and diamond. The latter was found by A.V. Golovko and F.K. Divaev while studying picrites Asmansay. Chromite is Centre for Info Bio Technology (CIBTech) 81
represented by formations interspersed with rectangular shape, the composition of which corresponds the high-chromites (Table 1) dioxide content of which chromium ranges from 46.70 to 52.79%. Chromite was detected for the first time. Furthermore, a significant content of chromium found in avgite titanium (up to 0.39%). For petrochemical data rocks belonging to normal alkaline-earth series (SiO2 = 38-43%) and have low (by half) contents of lime and alumina and alkali elevated - titanium, total iron, magnesium (in half) as compared with average contents picrites by Daly. From rocks of South Fergana, smaller amount of alumina and total iron were found with identical Severobukantauskimi and Kazakhstan (Table 2). For higher and moderately high chromium - nickel, cobalt, vanadium, and gold (Baranov et al., 1978) was reported. Figure 1: Layout Displays Ophiolite in North Nuratau (Southern Tien Shan) 1-Outputs Ophiolite, 2-Sand and Shale Deposits of the Silurian, 3-Silurian Limestones, Devonian, Carboniferous, 4-Permian Granitoids, 5-Turkestan Suture Zone, 6-Place Study Picritic Dikes а b c d e f Figure 2: The Micrographs of Thin Transparent Picrites of Asmansay (North Nuratau.): A-b- "Spinifex" Structure, Visible Elongated Prismatic Crystals of Augite Among Olivine; in- Porphyritic Texture, Olivine Replaced by Serpentine, the Majority is Composed of Olivine and Pyroxene; Substituted Carbonate Olivine; e-lizardite Mesh (Loop) on Olivine; f-phenocrysts of Olivine among the Basic Masses Centre for Info Bio Technology (CIBTech) 82
Table 1: The Composition of Minerals of Pyrite Ottoman (North Nuratau) Оливин Serpentine Clinopyroxene Chromites Oxides 1 2 3 4 5 6 7 8 9 10 11 SiO 2 40,73 45,46 39,85 42,60 48,27 48,47 48,95 44,72 0,34-0,46 ТiO 2 - - - - 1,53 1,91 1,82 2,92 1,29 2,07 1,72 Аl 2O 3-1,62 1,60 6,22 6,26 6,66 6,26 9,47 9,65 12,61 12,99 Fе 2O 3 13,42 9,35 8,54 12,13 6,89 7,14 6,77 12,95 25,01 26,73 25,05 NiO - - - - - - - - - - 0,31 МgO 44,21 31,57 31,71 31,20 12,99 13,46 13,57 9,66 10,51 11,58 11,71 СаО 0,40 0,23 0,16 0,23 21,57 21,87 22,00 20,57 0,10 - - Na 2O - - - - 0,37 0,52 0,52 - - - - К 2O - 0,08 - - - - - - - - - V 2O 5 - - - - - - - - 0,30 - - Cr 2O 3 - - - - - 0,39 0,32 0,24 52,79 46,70 49,10 Sum 99,12 88,32 81,86 98,38 100,00 100,42 100,00 100,54 100,00 99,70 101,34 Note: 1 - beryl, 2-3 - lizardite, 4-alyuminovy chrysotile, 6-7 chromic augite, 8 titanavgit, 9-11-The high-chromium (?). Table 2: Chemical Composition Picrites Northern Nuratau Oxides 1 2 3 4 5 6 7 8 SiO 2 38,90 39,83 39,88 40,03 40,06 40,51 40,57 41,22 TiO 2 1,06 0,95 0,78 1,10 1,14 0,84 1,10 0,95 Al 2O 3 4,78 5,13 4,97 5,93 5,64 4,66 5,41 5,13 Fe 2O 3 3,20 2,82 2,40 3,48 3,04 3,32 2,37 1,78 FeO 9,35 8,75 8,41 7,87 9,25 8,27 9,30 9,05 MnO 0,17 0,22 0,17 0,05 0,15 0,16 0,22 0,13 MgO 29,69 28,82 28,92 28,22 28,22 29,43 27,52 27,92 CaO 3,79 3,29 4,06 3,79 4,00 3,93 4,35 3,79 Na 2O 0,16 0,36 0,23 0,37 0,33 0,16 0,34 0,27 K 2O 0,17 0,23 0,18 0,08 0,09 0,09 0,10 0,58 П.п.п 8,86 8,34 8,88 8,28 7,78 8,00 7,52 7,69 H 2O - 0,57 0,60 0,60 0,40 0,60 0,51 0,54 0,50 Centre for Info Bio Technology (CIBTech) 83
P 2O 5 0,17 0,15 0,11 0,15 0,18 0,15 0,13 0,15 CO 2 0,20 0,39 0,52 0,20 0,20 0,20 0,20 0,20 SO 3 0,14 0,09 0,17 0,15 0,08 0,13 0,11 0,15 Cr 2O 3-0,19 0,32 0,23 - - 0,28 0,29 NiO - 0,125 0,13 0,16 - - - 0,13 CoO - 0,013 0,009 0,014 - - 0,013 0,013 V 2O 3-0,014 0,02 0,016 - - 0,02 0,02 100,30 99,23 99,47 99,77 99,88 99,52 99,24 99,38 Oxides 9 10 11 12 13 14 15 16 SiO 2 42,50 40,74 40,79 40,28 40,25 40,92 41,25 41,30 TiO 2 0,73 1,18 1,12 0,73 0,84 0,75 1,02 0,81 Al 2O 3 5,13 5,34 5,22 7,59 5,78 6,61 6,13 9,43 Fe 2O 3 1,41 2,88 2,57 6,12 3,72 3,94 5,38 5,30 FeO 8,82 8,65 9,37 6,25 10,04 7,77 8,12 8,86 MnO 0,15 0,08 0,08 0,14 0,19 0,14 0,17 0,29 MgO 27,72 27,59 28,76 27,75 26,67 26,25 27,16 19,94 CaO 3,92 4,89 4,24 5,19 4,95 4,87 4,46 8,01 Na 2O 0,16 0,43 0,43 0,27 0,68 0,39 0,65 1,20 K 2O 0,08 0,08 0,10 0,08 0,19 0,07 0,26 0,39 П.п.п 7,88 - - 5,98 6,02 7,57-4,27 H 2O - 0,62 - - - - 0,46 - - P 2O 5 0,11 0,20 0,20-0,16 0,09 - - CO 2 0,20 0,17 0,20 - - - - - SO 3 0,12 0,25 - - - - - - Cr 2O 3 - - - - - 0,20 - - NiO 0,13 - - - - 0,16 - - CoO 0,013 - - - - - - - V 2O 3 - - - - - - - - 99,75 100,70 100,50 100,39 99,49 100,19 100,50 99,80 Note: 9-1 - Picrites (by Baranov et al., 1978); 10-12 - Picrites (by Gamaleev et al., 1967); 10-11 - Picrites of Asmansay (North Nurata), 12-Picrites of Aravan South Fergana; 13 - Picrites Karachatyr; 14 - Picrites of North Bukantau (by Mikhailov et al., 1981); 15 - Picrites, Kazakhstan; 16 Average Composition Picrites by Daly. Centre for Info Bio Technology (CIBTech) 84
Indeed, picrites of Southern Tien Shan spatially closely associated with the host alkali basalts, pyroclastic and subvolcanic formations kulkudukskoy, shavazskoy Aravan and suites, as well as with basicultrabasites Nurata, Bukantau and yuzhnoferganskoy series. All these formations are located in the Kyzylkum-South Fergana suture zone. Baranov et al., (1978) stated that picrites Asmansaya is combined with diabase and diabase called asmansayskim picritic complex. Khamrabaev (1972) believed that they were on time and space is autonomous. The authors of this article after Khamrabaev (1972) believe that they are products of a different genesis (Ishbaev et al., 2013). It should be noted that the composition of Aravan (South Fergana) Shavaz (North Nuratau) and Kulkuduk (North Bukantau) suite is identical, they are presented lavas alkaline basalts (60-90%), pyroclastic formations (explosive breccia - hyaloclastites, tuffs) (20-30%), siliceous formations (10-20%), pillow lavas structure and subvolcanic formations - gabbro-diabase, diabase, diabase-porphyries and picrite-porphyries. Conclusion Moderately high chromium - nickel, cobalt, vanadium, and gold was found in the rocks (Baranov et al., 1978). Indeed, picrites of Southern Tien Shan spatially closely associated with the host alkali basalts, pyroclastic and subvolcanic formations kulkudukskoy, shavazskoy Aravan and suites, as well as with basicultrabasites Nurata, Bukantau and yuzhnoferganskoy series. All these formations are located in the Kyzylkum-South Fergana suture zone. Baranov et al., (1978) picrites Asmansaya combined with diabase and diabase-called asmansayskim picritic complex. Khamrabaev (1972) believed that they were on time and space are autonomous. From this can be concluded that the age of the enclosing basalts around the zone to be older (Ordovician- Silurian), as reported by earlier worker. Map of magmatic complexes of the Uzbek SSR (1984), reveals that they really are products of the oceanic crust of the Turkestan paleooceanic basin. It seems to us that they were formed at the same time (under water). As for the age of picrites is concerned, it can be said that they definitely broke through the lower Paleozoic. Some researchers consider the age of shavaz formation to Ordovician-Silurian era. The high content of titanium, iron and chromium minerals in picrites indicate the diamondiferous mantle-deep nature of the source of origin of the magma chamber in the Southern Tien Shan. REFERENCES Baranov VV, Kromskaya KM and Wiśniewski YS (1978). Asmansay diabase-picritic complex (C 1). Gabbroic Complexes Western Part of Southern Tien Shan and Mineragenesis, (Uzbekistan, Tashkent, Fan) 61-69. Gamaleyev IE, Khamrabaev IK, Muminov Sh and Baranov VV (1967). About picritic porphyrites Nuratau North and South Fergana. Uzbekistan Geology Journal 1 3-8. Golovko AV and Divaev FK (2007). Nonkimberlite diamond breed of Uzbekistan and their degree of knowledge. Proceedings of the Scientific Conference "Actual Problems of Geology and Geophysics." Tashkent, Fan 254-261. Ishbaev KJ (2013). The history of mantle magmatism Nurata region. Geology and Mineral Resources 5 12-20. Ishbaev KJ, Ganiev IN and Normamatov Z (2013). About formation type mafic-ultramafic Bukantau- South Fergana suture zone. Vestnik NUU 68-73. Khamrabaev IK (1972). Picritic body of Southern Tien Shan as products mantle. Petrology. Science 39-47. Khamrabaev IK (1998). The nature of the layers and boundaries of the lithosphere of Central Asia. Tashkent: GFNTI 212. Map magmatic complexes of the Uzbek SSR (1984). Tashkent: Fan 345 Mikhailov NP and Baranov VV (1981). About spinifex structures in picrites Southern Tien Shan. Uzbekistan Geology Journal 4 17-24. Mushkhin IV (1979). Petrology of the Upper Mantle of the Southern Tien Shanya, Tashkent: Fan 136. Centre for Info Bio Technology (CIBTech) 85
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