**3. Research methods**

This chapter used data from the Neogene-Quaternary volcanism of the Azerbaijan part of Lesser Caucasus based on the authors. Chemical analysis of rocks was determined by the Institute of Geology of Azerbaijan Academy of Sciences X-ray fluorescence method. Rare and rare-earth elements are in Geological and Geochemical Bronitsk expeditions in Russia. Microprobe analysis of mineral composition written in Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Moscow and Russian Geological Research Institute (VSEGEI), St. Petersburg. Measuring the isotopic composition of He performed in Geochemistry Institute of Academy of Sciences Russia, also used the data Sr and Nd [17, 18] performed on the material of Armenia and Georgia.

### **4. Petrography characteristics of the Late Cenozoic volcanic rocks**

The rocks of the *andesite-dacite-rhyolite associations* form thin flows and subvolcanic body in the form of dikes, extrusions and other recent distributed along the Tartar, Lachin-Bashlybel, Istibulag-Agyatak deep faults (**Figure 2**). Texture of porphyritic rocks, with high (25–30%) content of phenocrysts. In andesites, trachyandesites, latites phenocrysts are plagioclase, feldspar, clinopyroxene, and amphibole. In the more acidic varieties (dacites, rhyodacites, rhyolites their varieties), the proportion of dark-colored minerals decreases, leucocratic minerals also increased to 10%, there is quartz, biotite. The bulk of these rocks have hyalopilitic, glass texture (**Figure 3**).

The compositions of plagioclase in the rocks have *An30–<sup>40</sup>* and are paragenesis with amphibole, biotite, clinopyroxene, and feldspar. Plagioclases second generation are relatively acid composition (*An20–30*), crystallized on its own effusive stage. Feldspar in the rocks present in quartz latites, trachyandesites. The composition ranges from *Or55.3Ab26.3An0.3* to *Or73.4Ab44.0 An3.4* (**Table 1**). They belong to an intermediate structural-optical type and are monoclinic, but not homogeneous and presented albite and orthoclase phases. Composition of clinopyroxene varies from medium to acid rocks and the proportion of the component increases Fs: *Wo37.1–41.4 En43.9–40.0 Fs19–19.6* (for andesites), *Wo40.0–44.4 En45.4–44.8 Fs15.2–11.2* (for quartz latites), and *Wo41.7–42.7 En36.3–34.6 Fs22–22.7* (for dacites) (**Table 1**) [13, 19]. The compositions of amphiboles in the classification of B.E. Like [20] are responsible chermakit-, pargasit- and magnesian hornblendes.

Analyses of rock-forming minerals were carried out at the analytical laboratories of the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Moscow State University; Moscow and Russian Geological Research Institute (VSEGEI), St. Petersburg on a Camebax microprobe. Magnetite was analyzed by conventional chemical techniques at Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Analysts A.I. Tsepin, V.K. Garanin, and V.S. Pavshukov.

The rocks of the *rhyolite association* of petrographic composition and structural and textural features are divided into crystallized – rhyolites, trachyrhyolites, rhyodacites and glass – obsidians and perlites. Phenocrysts crystallized rocks are

**2.2 Late Pliocene-quaternary acidic volcanic associations**

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

region based on their stratigraphic position was considered late

varieties, as well as obsidian and perlite (**Figure 2**).

rocks can be considered Quaternary.

**Figure 2.**

**46**

Late Pliocene-quaternary acidic volcanic associations as independent volcanism are widely developed within the Caucasian segment of the Mediterranean belt. Within Azerbaijan, they are confined Kelbajar and Karabakh uplands and form a dome-shaped volcanoes, and a number of small extrusive domes (Kechaldag, Devegezy) with their lava flows composed of rhyolite, rhyodacites their subalkaline

*Geological map of Late Cenozoic volcanic associations in the central part of the Lesser Caucasus (Azerbaijan), scale 1:100,000. Compiled by Imamverdiyev [13].* Volcanic association: Quaternary: 1 – *trachybasalts, basaltic trachyandesites, and trachyandesites; 2 – tuffs, volcanic ashes, tuff breccias;* 3 *– rhyolites, perlite, and obsidian;* Upper Pliocene-Low Quaternary: 4 – *trachybasalts, basaltic trachyandesites, and trachyandesites;* Upper Miocene-Low Pliocene: *5 – dacites, rhyodacites, rhyolites; 6 – andesites, trachyandesites, quartz latites, dacites, trachydacites (Basarkechar formation) 7 – dacites, trachydacites, rhyodacites and rhyolites (Ajagz formation); 8 – diorites, granodiorites, syenites;* Upper Oligocene-Low Miocene: *9 – granodiorites, granites, monsonites, quartz syenites;* Eocene: 10 – *andesites, trachyandesites and their tuffs; 11 – granodiorites, monsonites, quartz diorites;* Base rocks (Cretaceous): *12 – ophiolites; 13 – flysch; limestone's, sandstone's, tuffs; 14 – faults; 15 – Terter deep fault; 16 - largest centers of volcano eruption; 17 – rivers; 18 – lakes.*

The age of acidic volcanic rocks of the Lesser Caucasus in the studied

Pliocene-Akchagyl-Absheron [15]. This is confirmed by the absolute age. Thus, according to [16] age of rhyolite volcanic rocks Devegezy identified 0.61 million years, Kechaldagh 0.7 million years. Based on these data, the age of acidic volcanic

*Upper Pliocene-Quaternary volcanic associations* with a more basic and medium composition, cover the entire Lesser Caucasus, form vast volcanic plateaus and large volcanoes and occupies about 5000 km<sup>2</sup> of surface area. These volcanic associations in the eastern area of Armenia and Azerbaijan within the differentiated form a continuous trachybasalt-basaltic trachyandesite-trachyandesite-trachyte

### **Figure 3.**

*Photomicrographs of the thin sections of rocks of the andesite-dacite-rhyolite association. Plagioclase and hornblende phenocrysts in andesites and trachyandesites, 80, with an analyzer; zoned-plagioclase and quartz phenocrysts in dacites, 80, with an analyzer.*

forsterite-chrysolite (**Table 1**). Olivine in trachyandesites and basaltic

megacrystes sanidine, clinopyroxene, amphibole, phlogopite.

in phenocrysts of clinopyroxene and hornblende, indicating that the earlier

The rocks occur as idiomorphic porphyritic crystals of apatite precipitates; the number of which reaches 0.5–1.25%, and fluoro-apatite. Often present as inclusions

*Chemical composition (wt %) of (1–5) clinopyroxene, (6) olivine, (7–10) amphibole, (11–16) plagioclase,*

**Component 1 2 3 4 5 6 7 8 9 10** SiO2 53.51 50.60 52.28 49.54 48.93 39.57 42.97 42.17 39.32 40.71 TiO2 0.54 0.27 0.64 0.69 1.52 0.08 2.94 3.00 2.91 4.09 Al2O3 3.92 2.34 5.00 4.10 6.98 — 11.56 10.79 13.55 13.87 FeO\* 8.46 12.12 7.63 7.53 7.96 14.94 12.08 14.29 12.77 11.51 MnO 0.22 0.25 0.13 0.18 0.13 0.28 0.14 0.25 0.16 0.10 MgO 14.63 12.81 15.09 15.46 13.72 44.86 13.11 13.06 12.91 14.44 CaO 18.50 20.43 18.65 19.94 19.97 0.22 9.94 10.68 12.06 11.70 Na2O 0.52 0.47 0.56 0.64 0.53 — 2.48 2.76 2.88 2.63 K2O — —— 0.04 0.04 — 0.92 0.92 1.42 1.49 Total 100.27 99.65 100.0 98.11 99.58 99.95 96.14 97.92 97.99 100.54 **Component 11 12 13 14 15 16** SiO2 58.47 64.59 62.87 57.06 52.52 51.39 Al2O3 25.23 19.48 24.02 26.82 28.94 30.62 FeO\* 0.42 0.09 0.22 0.36 0.43 0.75 CaO 7.16 0.17 5.55 8.68 13.17 12.99 Na2O 7.61 4.12 6.96 6.14 4.39 3.79 K2O 0.63 11.22 1.02 0.87 0.12 0.23 Total 99.52 99.66 100.63 99.93 99.52 99.77 **Component 17 18 19 20 21 22** TiO2 1.10 4.14 5.49 6.10 5.41 11.10 Al2O3 0.60 2.71 3.04 4.55 4.23 5.10 Fe2O3 — 65.89 53.62 53.08 60.33 43.22 FeO 91.0 14.02 28.39 19.60 15.68 17.76 MgO 4.0 2.95 1.99 5.97 7.69 4.06 Total 96.70 89.71 82.53 89.30 93.34 81.24 *Note: Rocks:* Andesite-dacite-rhyolite association: *11, 17 – rhyodacite; 1, 7, 12, 18 – dacite; 2, 8, 13, 19 – andesite;* trachybasalt-trachyandesites association: *3, 9, 14, 20 – basaltic trachyandesite; 4, 10, 15, 21 – trachybasalt; 5, 6, 16,*

*Late Cenozoic Collisional Volcanism in the Central Part of the Lesser Caucasus (Azerbaijan)*

*DOI: http://dx.doi.org/10.5772/intechopen.93334*

In the rocks of andesite-dacite-rhyolite and trachybasalt-trachyandesites associations there are two types of inclusions: 1-inclusion, representing cumulates parent rocks, (pyroxenites, gabbro, hornblendites, etc.), 2-crustal inclusion - xenoliths of country rocks, trapped melts of crustal rocks (gabbro-amphibolites, quartz-diorite, quartz-feldspar rocks, etc.). Typical mantle inclusions in rocks associations are absent. Along with the rocks in the rocks of these associations are marked

trachyandesites is more ferruginous *(Fo61–70)*.

*and (17–22) magnetite from the late Cenozoic volcanic rocks [13, 19].*

crystallization.

**49**

*22 – alkaline olivine basalt.*

**Table 1.**

plagioclase (*An30–40*), quartz, less feldspar, biotite and hornblende. Number of phenocrysts is 5–10%.

The rocks of the *trachybasalt-trachyandesites associations* form a continuous series of differentiated trachybasalts to trachyandesites, sometimes comes to trachytes. Moderately alkaline olivine basalts are the most mafic rocks of the studied association. They are porphyritic and aphyric and contain phenocrysts of olivine, clinopyroxene, plagioclase, and amphibole. In places, sanidine megacrysts occur. The rock matrix is of pilotaxitic, hyalopilitic, and microlitic textures (**Figure 4**).

Clinopyroxene rock associations more calcium and composition correspond to augite and salite. Plagioclases have relatively basic composition *(An63–75)* (**Table 1**). Olivine in the mafic rocks is more magnesian *(Fo83–87)* and corresponds to


*Late Cenozoic Collisional Volcanism in the Central Part of the Lesser Caucasus (Azerbaijan) DOI: http://dx.doi.org/10.5772/intechopen.93334*

*Note: Rocks:* Andesite-dacite-rhyolite association: *11, 17 – rhyodacite; 1, 7, 12, 18 – dacite; 2, 8, 13, 19 – andesite;* trachybasalt-trachyandesites association: *3, 9, 14, 20 – basaltic trachyandesite; 4, 10, 15, 21 – trachybasalt; 5, 6, 16, 22 – alkaline olivine basalt.*

### **Table 1.**

plagioclase (*An30–40*), quartz, less feldspar, biotite and hornblende. Number of

*Photomicrographs of the thin sections of rocks of the andesite-dacite-rhyolite association. Plagioclase and hornblende phenocrysts in andesites and trachyandesites, 80, with an analyzer; zoned-plagioclase and quartz*

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

The rocks of the *trachybasalt-trachyandesites associations* form a continuous series of differentiated trachybasalts to trachyandesites, sometimes comes to trachytes. Moderately alkaline olivine basalts are the most mafic rocks of the studied association. They are porphyritic and aphyric and contain phenocrysts of olivine, clinopyroxene, plagioclase, and amphibole. In places, sanidine megacrysts occur. The rock matrix is of pilotaxitic,

Clinopyroxene rock associations more calcium and composition correspond to augite and salite. Plagioclases have relatively basic composition *(An63–75)* (**Table 1**).

Olivine in the mafic rocks is more magnesian *(Fo83–87)* and corresponds to

phenocrysts is 5–10%.

*phenocrysts in dacites, 80, with an analyzer.*

**Figure 3.**

**48**

hyalopilitic, and microlitic textures (**Figure 4**).

*Chemical composition (wt %) of (1–5) clinopyroxene, (6) olivine, (7–10) amphibole, (11–16) plagioclase, and (17–22) magnetite from the late Cenozoic volcanic rocks [13, 19].*

forsterite-chrysolite (**Table 1**). Olivine in trachyandesites and basaltic trachyandesites is more ferruginous *(Fo61–70)*.

The rocks occur as idiomorphic porphyritic crystals of apatite precipitates; the number of which reaches 0.5–1.25%, and fluoro-apatite. Often present as inclusions in phenocrysts of clinopyroxene and hornblende, indicating that the earlier crystallization.

In the rocks of andesite-dacite-rhyolite and trachybasalt-trachyandesites associations there are two types of inclusions: 1-inclusion, representing cumulates parent rocks, (pyroxenites, gabbro, hornblendites, etc.), 2-crustal inclusion - xenoliths of country rocks, trapped melts of crustal rocks (gabbro-amphibolites, quartz-diorite, quartz-feldspar rocks, etc.). Typical mantle inclusions in rocks associations are absent. Along with the rocks in the rocks of these associations are marked megacrystes sanidine, clinopyroxene, amphibole, phlogopite.

**1**

**51**

Elements

SiO2 TiO2

Al

Fe

O2 3

FeO

MnO

MgO

CaO

Na O

2

K O

2

P O2 5

LOI

Total

Rb

Li Sr Ba Cr

V Ni Co

20

 30

 35

 16

 34

 24

 3

 15

 9

 5

 3

0.1

 0.2

 31

 29

 50

24

 22

 30

 31

 69

 25

 32

 25

 15

 20

 3

 n.d.

 n.d.

 115

 113

 110

170

 40

 60

 60

 150

 110

 40

 100

 40

 n.d.

 20

 n.d.

 n.d.

 170

 170

 210

120

 180

 180

 180

 n.d.

 n.d.

 180

 100

 n.d.

 30

 n.d.

 3.13

 2.75

 346

 412

 270

1250

 640

 650

 690

 400

 850

 690

 760

 830

 100

 100

 10

 26

 748

 780

 1060

1105

 935

 935

 850

 520

 860

 935

 833

 420

 150

 100

 10

 16

 1190

 1700

 1700

20

 14

 19

 19

 19

 8

 12

 14

 13

 67

 70

 n.d.

 n.d.

 9

 9

 9

83

 66

 63

 74

 42

 51

 86

 72

 97

 160

 180

 209

 174

 23

 34

 32

 98.63

 99.31

 99.08

 98.1

 98.3

 99.21

 100.72

 98.15

 99.23

 99.67

 100.27

 100

 99.99

 99.2

 98.65

 98.1

 0.81

 1.96

 0.54

 0.46

 0.13

 0.83

 0.47

 0.96

 0.27

 0.38

 0.54

 n.d.

 n.d.

 0.7

 1.5

 0.93

0.41

 0.38

 0.28

 0.3

 0.28

 0.35

 0.33

 0.23

 0.06

 0.01

 0.01

 n.d.

 0.01

 0.65

 1.03

 1.18

 3.54

 2.73

 2.95

 3.08

 2.37

 1.87

 3.47

 2.55

 4.14

 4.87

 3.96

 4.59

 4.86

 1.42

 1.96

 1.92

 4.19

 3.93

 4.07

 4.08

 3.37

 3.3

 4.27

 4.05

 4.57

 3.27

 2.92

 4.44

 4.06

 4.22

 3.61

 4

*Late Cenozoic Collisional Volcanism in the Central Part of the Lesser Caucasus (Azerbaijan)*

 4.85

 5.34

 4.24

 4.32

 6.13

 5.25

 3.97

 3.19

 1.32

 0.53

 1.9

 0.44

 0.47

 8.33

 9.8

 9.09

 1.85

 1.77

 1.95

 1.9

 3.18

 1.86

 1.43

 1.31

 0.05

 0.14

 0.36

 0.11

 0.05

 6.04

 6.74

 6.29

 0.06

 0.06

 0.04

 0.09

 0.1

 0.09

 0.03

 0.09

 0.04

 0.01

 0.01

 0.08

 0.06

 0.13

 0.15

 0.14

 1.29

 0.94

 1.01

 1.29

 2.46

 0.43

 0.73

 0.28

 0.43

 1.78

 0.71

 0.66

 0.71

 0.86

 2.16

 2.73

3.47

 2.5

 3.91

 3.28

 3.91

 4.94

 3.38

 3.59

 1.69

 1.2

 0.55

 n.d.

 n.d.

 7.74

 6.38

 5.61

*DOI: http://dx.doi.org/10.5772/intechopen.93334*

O2 3

15.7

 15.41

 16.9

 16.6

 14.81

 17.15

 17.03

 16.41

 15.77

 13.48

 13.79

 12.85

 12.67

 16.49

 15.77

 15.86

0.59

 0.49

 0.58

 0.6

 0.81

 0.75

 0.6

 0.52

 0.27

 0.01

 0.01

 0.08

 0.09

 1.39

 1.2

 1.57

61.09

 62.1

 62.32

 62.99

 63.75

 63.89

 64.81

 65.99

 68.19

 73.99

 75.51

 76.75

 77.01

 51.23

 48.35

 48.88

 40

 8

 15

 100

 190

 194

 106

 74

 96

 12/13

 6/174

 OA 409

 MA 19

 105

 129

 132

 **2**

 **3**

 **4**

 **5**

 **6**

 **7**

 **8**

 **9**

 **10**

 **11**

**12**

 **13**

 **14**

 **15**

 **16**

### **Figure 4.**

*Photomicrographs of the thin sections of rocks of the trachybasalt-trachyandesite association. Trachyandesite (one can see a glomeroporphyritic cluster of clinopyroxenes and opacitized hornblende, plagioclase, and clinopyroxene phenocrysts), 80, with an analyzer; moderately alkaline olivine basalt with olivine, clinopyroxene, and plagioclase phenocsrysts, 80, with an analyzer; crushed olivine in trachybasalt, 80, with an analyzer; trachydolerite, 80, with an analyzer.*
