**6. Geochemical features of the Late Cenozoic volcanic rocks**

The concentrations of rare and rare earth elements are in rocks of andesitedacite-rhyolite association as a whole regularly changing. Thus, the concentration of lithophile elements increases from andesite to rhyolites (Rb from 44 to 128 ppm, Th 6 to 24 ppm) (**Table 2**). From the coherent elements in increasing the acidity of rocks in general, the content of V, Cr, Co, and Ni decreases. These elements are the same Sr form of silica negative dependence. Positive, but more vague correlation with silica form the content of Y and highly charged elements (HFSE – Nb, Zr, Hf). The above features show the leading role of crystallization differentiation in the association of rocks. As shown Dilek et al. [2] comparison of impurity elements rocks andesite-dacite-rhyolite association and the primitive mantle [23] shows the reduced content of Nb and Ta and elevated levels of lung large ionic lithophile elements (Rb, Ba, Th, La, Ce, and Sr) (LILE). Thus, in relation to the primitive mantle, there is a maximum Rb, Ba, Th, La, Ce, Sr, and negative Ta-Nb anomalies (**Figure 6**).

It is conceivable that this feature brings these rocks with subduction volcanic associations. From the same type of rocks of andesite-dacite-rhyolite association rocks rhyolite associations differ depleted femic components, a lower content of iron group elements, highly charged elements, and enrichment of ore elements in the earth crust, as well as lithophile elements (Pb, Th, U). The distribution of trace elements normalized to primitive mantle for the rhyolite showed that, like the rock of the previous association, rhyolite is enriched in LILE and depleted in highly charged elements. However, the nature of the schedule of rhyolites differs from the schedule of rocks of the previous association and is similar to the composition of the rocks of the earth's crust, which indicates a different genesis of the rocks of this association. In the rocks, trachybasalt-trachyandesite association occurs in about the same pattern as in the rocks of andesite-dacite-rhyolite association, but more clearly. Rocks of this association are inherent to the high content of Rb, Ba, La, Sr, as well as high values of La/Yb, La/Sm relations. Compared with the composition of

primitive mantle [23], alkaline basalts are enriched in most LILE and some highly

*Normalized to the primitive mantle [23] spider diagrams for the trachybasalt-trachyandesite association.*

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

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

tion is due mainly to fractional crystallization. This is evidenced by: (1) with increasing SiO2 content decreases compatible elements (Cr, Ni) and increasing concentrations of incompatible elements (Rb, Th, U) due to fractionation of olivine and clinopyroxene, and (2) revealed clear positive correlation connection LREE with phosphorus, calcium and fluoride, due to the concentration of light rare earth elements in apatite (the distribution coefficients of REE for apatite is 10–100). These data indicate that fractional crystallization is particularly important for trachybasalts and basaltic trachyandesites. In the process of differentiation of the content of trace elements naturally varies depending on the composition of the melt, its temperature, as well as the composition and crystal-chemical properties of rock-forming minerals. Content and types of spectra of these elements of the rock trachybasalt-trachyandesite associations of the Lesser Caucasus are close to the rocks of oceanic islands and the rift zones formed from the enriched mantle source. Similarity of plots, the distribution of elements on the primitive mantle may indi-

**7. Isotopic composition of the Late Cenozoic volcanic rocks**

He/<sup>4</sup>

festations of modern volcanism of the Lesser Caucasus (<sup>3</sup>

For the Neogene-Quaternary rocks of the Lesser Caucasus, we have obtained for the seven samples of volcanic rocks and their nodules isotopic compositions of He

He/<sup>4</sup>

He = 0.93 <sup>10</sup><sup>5</sup>

He/<sup>4</sup>

He = 10<sup>5</sup>

) is characteristic

)

) [24]. A

He (<sup>3</sup>

for alkali olivine basalts, which brings them to the mantle derivatives. Approximately, the same value is obtained for amphibole megacrysts from trachyandesite approaching the isotope ratios of primary helium mantle reservoirs (1–<sup>5</sup> <sup>10</sup><sup>5</sup>

[24] and to the gases carbon sources, the most active areas associated with mani-

fractional difference between the rocks of trachybasalt-trachyandesite association, their nodules, as well as andesite of andesite-dacite-rhyolite association has lower

Geochemical data for this association show that the diversity of species associa-

charged elements: Rb, Ba, Th, La, Ce, Sr, Zr (**Figure 7**).

**Figure 7.**

cate comagmatic members of the association.

(**Table 2**). The highest ratio of <sup>3</sup>

**Figure 6.** *Normalized to the primitive mantle [23] spider diagrams for the andesite-dacite-rhyolite association.*

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

**Figure 7.** *Normalized to the primitive mantle [23] spider diagrams for the trachybasalt-trachyandesite association.*

primitive mantle [23], alkaline basalts are enriched in most LILE and some highly charged elements: Rb, Ba, Th, La, Ce, Sr, Zr (**Figure 7**).

Geochemical data for this association show that the diversity of species association is due mainly to fractional crystallization. This is evidenced by: (1) with increasing SiO2 content decreases compatible elements (Cr, Ni) and increasing concentrations of incompatible elements (Rb, Th, U) due to fractionation of olivine and clinopyroxene, and (2) revealed clear positive correlation connection LREE with phosphorus, calcium and fluoride, due to the concentration of light rare earth elements in apatite (the distribution coefficients of REE for apatite is 10–100). These data indicate that fractional crystallization is particularly important for trachybasalts and basaltic trachyandesites. In the process of differentiation of the content of trace elements naturally varies depending on the composition of the melt, its temperature, as well as the composition and crystal-chemical properties of rock-forming minerals. Content and types of spectra of these elements of the rock trachybasalt-trachyandesite associations of the Lesser Caucasus are close to the rocks of oceanic islands and the rift zones formed from the enriched mantle source. Similarity of plots, the distribution of elements on the primitive mantle may indicate comagmatic members of the association.

## **7. Isotopic composition of the Late Cenozoic volcanic rocks**

For the Neogene-Quaternary rocks of the Lesser Caucasus, we have obtained for the seven samples of volcanic rocks and their nodules isotopic compositions of He (**Table 2**). The highest ratio of <sup>3</sup> He/<sup>4</sup> He (<sup>3</sup> He/<sup>4</sup> He = 0.93 <sup>10</sup><sup>5</sup> ) is characteristic for alkali olivine basalts, which brings them to the mantle derivatives. Approximately, the same value is obtained for amphibole megacrysts from trachyandesite approaching the isotope ratios of primary helium mantle reservoirs (1–<sup>5</sup> <sup>10</sup><sup>5</sup> ) [24] and to the gases carbon sources, the most active areas associated with manifestations of modern volcanism of the Lesser Caucasus (<sup>3</sup> He/<sup>4</sup> He = 10<sup>5</sup> ) [24]. A fractional difference between the rocks of trachybasalt-trachyandesite association, their nodules, as well as andesite of andesite-dacite-rhyolite association has lower

characteristic feature of the association: transition nepheline-normative, olivine containing mildly alkaline rocks to hypersthene-normative, and sometimes quartz-

The concentrations of rare and rare earth elements are in rocks of andesitedacite-rhyolite association as a whole regularly changing. Thus, the concentration of lithophile elements increases from andesite to rhyolites (Rb from 44 to 128 ppm, Th 6 to 24 ppm) (**Table 2**). From the coherent elements in increasing the acidity of rocks in general, the content of V, Cr, Co, and Ni decreases. These elements are the same Sr form of silica negative dependence. Positive, but more vague correlation with silica form the content of Y and highly charged elements (HFSE – Nb, Zr, Hf). The above features show the leading role of crystallization differentiation in the association of rocks. As shown Dilek et al. [2] comparison of impurity elements rocks andesite-dacite-rhyolite association and the primitive mantle [23] shows the reduced content of Nb and Ta and elevated levels of lung large ionic lithophile elements (Rb, Ba, Th, La, Ce, and Sr) (LILE). Thus, in relation to the primitive mantle, there is a maximum Rb, Ba, Th, La, Ce, Sr, and negative Ta-Nb anomalies

It is conceivable that this feature brings these rocks with subduction volcanic associations. From the same type of rocks of andesite-dacite-rhyolite association rocks rhyolite associations differ depleted femic components, a lower content of iron group elements, highly charged elements, and enrichment of ore elements in the earth crust, as well as lithophile elements (Pb, Th, U). The distribution of trace elements normalized to primitive mantle for the rhyolite showed that, like the rock of the previous association, rhyolite is enriched in LILE and depleted in highly charged elements. However, the nature of the schedule of rhyolites differs from the schedule of rocks of the previous association and is similar to the composition of the rocks of the earth's crust, which indicates a different genesis of the rocks of this association. In the rocks, trachybasalt-trachyandesite association occurs in about the same pattern as in the rocks of andesite-dacite-rhyolite association, but more clearly. Rocks of this association are inherent to the high content of Rb, Ba, La, Sr, as well as high values of La/Yb, La/Sm relations. Compared with the composition of

*Normalized to the primitive mantle [23] spider diagrams for the andesite-dacite-rhyolite association.*

**6. Geochemical features of the Late Cenozoic volcanic rocks**

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

bearing alkaline rocks.

(**Figure 6**).

**Figure 6.**


**Figure 8** (Ce/Yb)MN – Yb MN shows the calculated line of equilibrium partial melting of garnet peridotite with different contents of garnet. Calculated trends melting portions of garnet peridotite, containing 2.5, and 4% garnet, borrowed from [34]. As seen from **Figure 8**, composition points of rocks of andesite-dacite-rhyolite associations are in the range of values with a relatively high degree of melting (3–10%) mantle source containing 4% garnet. Lineups alkali basaltoids trachybasalttrachyandesite association on this chart are in the range of values with a low degree of

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

melting (1–2.5%) garnet peridotite and, apparently, mantle source was more

apatite, amphibole, which are the main carriers of these elements.

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

(eclogite) oceanic plate.

adakites [38] (**Figure 9**).

**Figure 8.**

**59**

*2 – trachybasalt-trachyandesite association.*

metasomatized [13]. It can be assumed that a lower degree of melting of the mantle of the substrate led to the association of basaltic melt at high alkalinity and a significant enrichment of the melt K, P, F, Ba, LREE due priority to the melting of phlogopite,

At present, the association of these volcanic rocks is often associated with the association of subduction "windows" (slab-window) and sees the result of decompression melting of asthenospheric diapir. These volcanics differ from typical subduction magma and have geochemical characteristics of OIB sources. They are described for the active continental margin of North America, Philippines, Kamchatka, East Sikhote-Alin [35, 36]. For collision volcanics, this idea is developed [3–10, 25–26, 30–33, 37]. Such rocks are called adakites. They are characterized by high ratio LREE/HREE and are formed by melting of garnet containing material

Note that we also do not deny the delamination subduction lithospheric slab in the association of Late Cenozoic volcanic rocks of the Lesser Caucasus [2, 7–8, 30–31]. This is evidenced Seismic and some of petrology and geochemistry data. Part of Late Cenozoic andesite and dacite of the Lesser Caucasus can be considered derivatives adakites melts. They (La/Yb)n vary from 17.5 to 26.4, the concentration of Y from 6 to 13 ppm, Yb from 1.2 to 1.8 ppm. Figure Sr/Y-Y majority of species fall into the field

Thus, it is found that the rocks of the Neogene andesite-dacite-rhyolite and Upper Pliocene-Quaternary trachybasalt-trachyandesite association smelt garnet sources at a

*Normalized to primitive mantle [23] the ratio of Ce/Yb-Yb in the Late Cenozoic basalts and andesites of the Lesser Caucasus. Calculated trends melting portions of garnet peridotite, containing 2.5 and 4% garnet [38]. The numbers along the curves – the percentage of melting. Legend: 1 – andesite-dacite-rhyolite association,*

### **Table 3.**

*Isotopic composition He in Late Cenozoic rocks of the Lesser Caucasus.*

values of helium isotopes (**Table 3**). These data indicate that differentiate the first association, incorporation, and andesite second association crystallized in the earth crust.

Unfortunately, Sr and Nd isotope data for Late Cenozoic volcanics in the Azerbaijani part of the Lesser Caucasus are absent. There is anecdotal evidence about the Armenian and Georgian part of the Lesser Caucasus. Chernyshev and his co-workers [17, 18] determined the absolute age of alkali basalts Javakheti Plateau; they proposed a new version of the geochronological scale of the Neogene-Quaternary magmatism of the Caucasus. Dan precises absolute age of rhyolite volcanism for different volcanic highlands of the Lesser Caucasus [16]. Data above authors argue that the dominant role in the petrogenesis of lavas played by processes of fractional crystallization and contamination of the parent melts geochemically distinct from them, crustal matter [17]. A sour rhyolite volcanism developed in the context of tectonic and thermal activity of mantle lesions and relationship with the processes of local anatexis in the lower crust zones of metamorphism [16]. Our petrology and geochemistry data confirm these findings.

### **8. Discussion of results**

This section discusses the nature of the mantle substrate region under study as well as the origin of each of volcanic associations.

### **8.1 Mantle sources of the Late Cenozoic rocks**

These isotopic compositions of Sr and Nd for late Cenozoic volcanic rocks of the Lesser Caucasus show that the primary melts to produce a mantle sources. Acid rock has mostly crustal origin. There have been offset mantle and crustal magmas. In general, this assumption is acceptable for the Azerbaijan part of the region.

A common feature for most of the Neogene-Quaternary volcanic rocks of the Lesser Caucasus is a relative enrichment in light REE and large lithophile elements (Rb, Ba), and weak depletion for heavy rare earth elements, as well as Nb, Ta, Hf [1–3, 7–8, 13, 18, 25–33]. These geochemical data confirm the presence of restite of garnet in the magmatic source for the andesite-dacite-rhyolite and trachybasalttrachyandesite associations. In addition, we believe in the petrogenesis of Late Cenozoic collision basaltoids important role played mantle substance metasomatically processed by previous subduction processes, as evidenced by the relatively high oxidized rocks associations.

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

**Figure 8** (Ce/Yb)MN – Yb MN shows the calculated line of equilibrium partial melting of garnet peridotite with different contents of garnet. Calculated trends melting portions of garnet peridotite, containing 2.5, and 4% garnet, borrowed from [34]. As seen from **Figure 8**, composition points of rocks of andesite-dacite-rhyolite associations are in the range of values with a relatively high degree of melting (3–10%) mantle source containing 4% garnet. Lineups alkali basaltoids trachybasalttrachyandesite association on this chart are in the range of values with a low degree of melting (1–2.5%) garnet peridotite and, apparently, mantle source was more metasomatized [13]. It can be assumed that a lower degree of melting of the mantle of the substrate led to the association of basaltic melt at high alkalinity and a significant enrichment of the melt K, P, F, Ba, LREE due priority to the melting of phlogopite, apatite, amphibole, which are the main carriers of these elements.

At present, the association of these volcanic rocks is often associated with the association of subduction "windows" (slab-window) and sees the result of decompression melting of asthenospheric diapir. These volcanics differ from typical subduction magma and have geochemical characteristics of OIB sources. They are described for the active continental margin of North America, Philippines, Kamchatka, East Sikhote-Alin [35, 36]. For collision volcanics, this idea is developed [3–10, 25–26, 30–33, 37]. Such rocks are called adakites. They are characterized by high ratio LREE/HREE and are formed by melting of garnet containing material (eclogite) oceanic plate.

Note that we also do not deny the delamination subduction lithospheric slab in the association of Late Cenozoic volcanic rocks of the Lesser Caucasus [2, 7–8, 30–31]. This is evidenced Seismic and some of petrology and geochemistry data. Part of Late Cenozoic andesite and dacite of the Lesser Caucasus can be considered derivatives adakites melts. They (La/Yb)n vary from 17.5 to 26.4, the concentration of Y from 6 to 13 ppm, Yb from 1.2 to 1.8 ppm. Figure Sr/Y-Y majority of species fall into the field adakites [38] (**Figure 9**).

Thus, it is found that the rocks of the Neogene andesite-dacite-rhyolite and Upper Pliocene-Quaternary trachybasalt-trachyandesite association smelt garnet sources at a

### **Figure 8.**

values of helium isotopes (**Table 3**). These data indicate that differentiate the first association, incorporation, and andesite second association crystallized in the earth

25-b Pyroxsenites 3.33 (0.49) 3.43 (0.03) 13-m Megacryste amphybole 9.39 (1.42) 2.90 (0.03)

 Alkaline olivine basalte 9.29 (1.46) 0.604 (0.006) Trachybasalte 1.76 (0.27) 2.70 (0.03) Trachyandesite 1.05 (0.18) 1.54 (0.02) Andesite 0.924 (0.162) 2.36 (0.02)

**He/<sup>4</sup>**

**He<sup>10</sup>6 4He<sup>10</sup><sup>6</sup>**

Unfortunately, Sr and Nd isotope data for Late Cenozoic volcanics in the Azerbaijani part of the Lesser Caucasus are absent. There is anecdotal evidence about the Armenian and Georgian part of the Lesser Caucasus. Chernyshev and his co-workers [17, 18] determined the absolute age of alkali basalts Javakheti Plateau;

This section discusses the nature of the mantle substrate region under study as

These isotopic compositions of Sr and Nd for late Cenozoic volcanic rocks of the Lesser Caucasus show that the primary melts to produce a mantle sources. Acid rock has mostly crustal origin. There have been offset mantle and crustal magmas. In general, this assumption is acceptable for the Azerbaijan part of the region.

A common feature for most of the Neogene-Quaternary volcanic rocks of the Lesser Caucasus is a relative enrichment in light REE and large lithophile elements (Rb, Ba), and weak depletion for heavy rare earth elements, as well as Nb, Ta, Hf [1–3, 7–8, 13, 18, 25–33]. These geochemical data confirm the presence of restite of garnet in the magmatic source for the andesite-dacite-rhyolite and trachybasalttrachyandesite associations. In addition, we believe in the petrogenesis of Late

metasomatically processed by previous subduction processes, as evidenced by the

Cenozoic collision basaltoids important role played mantle substance

they proposed a new version of the geochronological scale of the Neogene-Quaternary magmatism of the Caucasus. Dan precises absolute age of rhyolite volcanism for different volcanic highlands of the Lesser Caucasus [16]. Data above authors argue that the dominant role in the petrogenesis of lavas played by processes of fractional crystallization and contamination of the parent melts geochemically distinct from them, crustal matter [17]. A sour rhyolite volcanism developed in the context of tectonic and thermal activity of mantle lesions and relationship with the processes of local anatexis in the lower crust zones of metamorphism [16].

Our petrology and geochemistry data confirm these findings.

**No samples Rocks and minerals <sup>3</sup>**

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

*Isotopic composition He in Late Cenozoic rocks of the Lesser Caucasus.*

well as the origin of each of volcanic associations.

**8.1 Mantle sources of the Late Cenozoic rocks**

relatively high oxidized rocks associations.

**58**

**8. Discussion of results**

crust.

**Table 3.**

Nodules

*Normalized to primitive mantle [23] the ratio of Ce/Yb-Yb in the Late Cenozoic basalts and andesites of the Lesser Caucasus. Calculated trends melting portions of garnet peridotite, containing 2.5 and 4% garnet [38]. The numbers along the curves – the percentage of melting. Legend: 1 – andesite-dacite-rhyolite association, 2 – trachybasalt-trachyandesite association.*

the behavior of a number of rock-forming trace elements. For example, a change in slope of trends MgO-SiO2, TiO2-SiO2, and Ni-SiO2 in the field trachyandesite

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

Past balance calculations on a computer showed that the evolution of the melt occurred as a result of changes in the composition and quantity of rock-forming minerals. The results of balance calculation of fractional crystallization of alkaline olivine basalt-trachybasalts showed that the latter is obtained by fractionation of 19.8% Cpx, 57.6% Pl (An65), 15.0% Ol (Fo 84) and 7.6% Mt. As seen from **Table 4**, the absolute and calculated values for major and trace elements in the whole match

Fractionation of the above minerals and amphibole leads to further differentiates associations and the result is a continuous differential series – trachybasalt-basaltic trachyandesite-trachyandesite. Possible further differentiation of the melt to the trachytes, trahyriodasites, that is, for example, in a large polygenic volcano Ishygly. Although, FC simulation of least squares using the basic rock-forming oxides and some trace elements gives good results, the majority of trace elements do not conform to this model. Thus, the content of LREE and HREE for different types of rocks vary in narrow limits. At Harker diagrams micronutrients – SiO2, where not all elements give a clear linear dependence. This suggests their association by other

**8.3 The role of crust contamination in the formation of late Cenozoic volcanic**

By Imamverdiyev previously shown that the role of crustal contamination in the genesis of Late Cenozoic volcanic rocks of the Lesser Caucasus is negligible [13]. In other works [12, 18, 39] speculation is about a significant transassociation of the primary magmas of crustal processes. We obtained the last petrogeochemical data suggest involvement in petrogenesis Late Cenozoic volcanic enriched mantle source (lithospheric mantle) and a significant contribution to processes of crustal contamination. The calculations show AFC – a model of crustal material required for the appropriate changes to the source mantle composition of rocks trachybasalttrachyandesite association can be achieved during the fractionation of basalts (degree of fractionation of F = 0.5–0.6) with the absorption of a large number of acid melt (the ratio of assimilation rock and cumulates r = 0.3–0.5) (**Table 5**). A similar pattern is observed for rocks of andesite-dacite-rhyolite association, but this shift is achieved with a high degree of fractionation (F = 0.7–0.9) and with a large

Parental magma 1 51.36 1.05 16.77 7.76 6.29 10.48 3.14 2.10 1.05 Calculated parental magma 2 51.76 0.84 16.68 7.80 6.31 10.46 3.36 1.61 1.14 Daughter magma 3 54.60 1.07 17.13 6.85 4.28 8.57 4.28 2.14 1.07 **Rb Ba Sr V Cr Ni Zr Sc Cu La Ce Sm Eu Yb Y** 1 35 943 1871 105 315 105 240 11 73 63 130 9.8 2.5 2.4 19 2 44 953 1956 2119 575 56 151 22 73 158 112 7.5 1.5 0.8 12 3 64 1392 2821 150 182 46 214 21 101 81 161 10.7 2.1 1.1 17 D 0.01 0.01 0.04 1.99 4.02 1.53 0.08 1.12 0.16 0.03 0.05 0.08 0.09 0.11 0.11

*Balance calculation for alkaline olivine basalt-trachybasalts (petrogenic elements recalculated to 100%).*

*D – Bulk partition coefficient (are taken from [13, 40]).*

**Table 4.**

**61**

**SiO2 TiO2 Al2O3 FeO\* MgO CaO Na2O K2O P2O5**

explained by fractionation of olivine, clinopyroxene, and magnetite.

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

(ΔR<sup>2</sup> = 0.507). The degree of fractionation at the same time is about 61%.

mechanisms, too.

**rocks**

**Figure 9.** *Sr/Y vs. Y in the Neogene andesite-dacite-rhyolite association. The range of adakite and arc magmatic rocks is after [38].*

depth of not less than 60–80 km [8, 33]. Not be excluded on the association of andesite melting subduction oceanic crust [39]. As Upper Pliocene-Quaternary acidic volcanic rocks, as shown by the full range of studies and published isotopic data for the region, the source of rhyolite-dacite magmas could serve as a rock granitemetamorphic layer, metamorphosed to amphibolite, and granulite facies metamorphism. The high concentrations of K, Li, Rb, Cs, U, Th, Rb and low Sr, Ba, Zr, Ti and light lanthanides, the presence of a deep negative Eu – anomalies may indicate relatively low levels of fusion substrate, in which a significant portion of plagioclase and accessories remained in the restite. The eastern part of the Lesser Caucasus (Vardenis and Syunik uplands) (**Figure 1**) 87Sr/86Sr are 0,70,444–0,70,811 [18].

### **8.2 The role of fractional crystallization in the formation of late Cenozoic volcanic rocks**

Petrochemical data show that the association of andesite-dacite-rhyolite and trachybasalt-trachyandesite association of fractional crystallization occurred. Thus, in the rocks of andesite-dacite-rhyolite association with increasing silica content decreases femic rock-forming oxides, increasing the content of incompatible elements due to fractionation of dark-colored minerals and feldspars. However, fuzzy trends show the influence of processes of assimilation and crustal contamination on the association of these rocks. Thus, an attempt to get out of andesitic dacites and from dacitic rhyolites by fractionation of clinopyroxene, amphibole, biotite, magnetite, and feldspar failed [31–33]. Therefore, as will be shown below, apparently, the formation of these rocks is dominated by a single process of AFC, that is, assimilation and fractional crystallization.

We believe that fractional crystallization played a leading role in the association of rocks trachybasalt-trachyandesite association [13, 32–33]. This is evidenced by

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

the behavior of a number of rock-forming trace elements. For example, a change in slope of trends MgO-SiO2, TiO2-SiO2, and Ni-SiO2 in the field trachyandesite explained by fractionation of olivine, clinopyroxene, and magnetite.

Past balance calculations on a computer showed that the evolution of the melt occurred as a result of changes in the composition and quantity of rock-forming minerals. The results of balance calculation of fractional crystallization of alkaline olivine basalt-trachybasalts showed that the latter is obtained by fractionation of 19.8% Cpx, 57.6% Pl (An65), 15.0% Ol (Fo 84) and 7.6% Mt. As seen from **Table 4**, the absolute and calculated values for major and trace elements in the whole match (ΔR<sup>2</sup> = 0.507). The degree of fractionation at the same time is about 61%.

Fractionation of the above minerals and amphibole leads to further differentiates associations and the result is a continuous differential series – trachybasalt-basaltic trachyandesite-trachyandesite. Possible further differentiation of the melt to the trachytes, trahyriodasites, that is, for example, in a large polygenic volcano Ishygly.

Although, FC simulation of least squares using the basic rock-forming oxides and some trace elements gives good results, the majority of trace elements do not conform to this model. Thus, the content of LREE and HREE for different types of rocks vary in narrow limits. At Harker diagrams micronutrients – SiO2, where not all elements give a clear linear dependence. This suggests their association by other mechanisms, too.

## **8.3 The role of crust contamination in the formation of late Cenozoic volcanic rocks**

By Imamverdiyev previously shown that the role of crustal contamination in the genesis of Late Cenozoic volcanic rocks of the Lesser Caucasus is negligible [13]. In other works [12, 18, 39] speculation is about a significant transassociation of the primary magmas of crustal processes. We obtained the last petrogeochemical data suggest involvement in petrogenesis Late Cenozoic volcanic enriched mantle source (lithospheric mantle) and a significant contribution to processes of crustal contamination. The calculations show AFC – a model of crustal material required for the appropriate changes to the source mantle composition of rocks trachybasalttrachyandesite association can be achieved during the fractionation of basalts (degree of fractionation of F = 0.5–0.6) with the absorption of a large number of acid melt (the ratio of assimilation rock and cumulates r = 0.3–0.5) (**Table 5**). A similar pattern is observed for rocks of andesite-dacite-rhyolite association, but this shift is achieved with a high degree of fractionation (F = 0.7–0.9) and with a large


### **Table 4.**

*Balance calculation for alkaline olivine basalt-trachybasalts (petrogenic elements recalculated to 100%).*

depth of not less than 60–80 km [8, 33]. Not be excluded on the association of andesite melting subduction oceanic crust [39]. As Upper Pliocene-Quaternary acidic volcanic rocks, as shown by the full range of studies and published isotopic data for the region, the source of rhyolite-dacite magmas could serve as a rock granitemetamorphic layer, metamorphosed to amphibolite, and granulite facies metamorphism. The high concentrations of K, Li, Rb, Cs, U, Th, Rb and low Sr, Ba, Zr, Ti and light lanthanides, the presence of a deep negative Eu – anomalies may indicate relatively low levels of fusion substrate, in which a significant portion of plagioclase and accessories remained in the restite. The eastern part of the Lesser Caucasus (Vardenis and Syunik uplands) (**Figure 1**) 87Sr/86Sr are 0,70,444–0,70,811 [18].

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

*Sr/Y vs. Y in the Neogene andesite-dacite-rhyolite association. The range of adakite and arc magmatic rocks is*

**8.2 The role of fractional crystallization in the formation of late Cenozoic**

Petrochemical data show that the association of andesite-dacite-rhyolite and trachybasalt-trachyandesite association of fractional crystallization occurred. Thus, in the rocks of andesite-dacite-rhyolite association with increasing silica content decreases femic rock-forming oxides, increasing the content of incompatible elements due to fractionation of dark-colored minerals and feldspars. However, fuzzy trends show the influence of processes of assimilation and crustal contamination on the association of these rocks. Thus, an attempt to get out of andesitic dacites and from dacitic rhyolites by fractionation of clinopyroxene, amphibole, biotite, magnetite, and feldspar failed [31–33]. Therefore, as will be shown below, apparently, the formation of these rocks is dominated by a single process of AFC, that is,

We believe that fractional crystallization played a leading role in the association of rocks trachybasalt-trachyandesite association [13, 32–33]. This is evidenced by

**volcanic rocks**

**60**

**Figure 9.**

*after [38].*

assimilation and fractional crystallization.



*1 – alkaline olivine basalts (initial melt), 2 – rhyolite (assimilation rock), 3 – trachyandesite (hybrid), 4 – calculated composition of trachyandesites, 5 – trachybasalt (initial melt), 6 – rhyolite (assimilation rock), 7 – basaltic trachyandesite (hybrid), 8 – calculated composition (all analyses have been converted to 100%).*

### **Table 5.**

*Results AFC – modeling for rocks trachybasalt-trachyandesite association.*

number of acidic substances (r = 0.6). Obviously, with such volumes of assimilation acidic substances are not stored petrochemical characteristics of the primary rocks (andesites and basalts). Therefore, Harkers figures are not observed clear trends.

Below are the results of AFC – modeling for rocks trachybasalt-trachyandesite association.

As seen from **Table 4**, the intermingling rhyolite and basic rocks (alkaline olivine basalts and trachybasalt) may be formed basaltic trachyandesite and trachyandesite.

Summarizing the above data, the association of Late Cenozoic volcanic series of the Lesser Caucasus can be represented as follows.

Within the Lesser Caucasus in the late Cenozoic volcanism expressed high-K calc-alkaline, mildly alkaline, and partly alkaline associations. In Neogene time (Upper Miocene-Lower Pliocene), with decompression occurs anatexis metasomatized mantle and lower strata of basalt layer at a sufficiently large depth, which determines the enrichment of these melts with alkali, alkaline earth, and light rare earth elements.

This process resulted in association of basaltic melts, enriched in alkalis. Perhaps such a melt was formed at low degrees of partial melting (3–10%) of garnet peridotite or eclogite. We can assume that it corresponds subduction oceanic crust. In the future, as a result of growing tension mantle melts penetrated the upper layers of the earth crust, where it mixes basic and acid magma, with the association of hybrid andesite, andesite-dacite lavas (**Figure 10**). Progressive

cooling of the deep source magma origin may be the cause of education dike fields in the region studied and possibly fractured outpouring mildly alkaline volcanism observed in the other parts of the Lesser Caucasus. Due to additional heating and

*layer; 10 – partially molten material of the upper mantle; 11 – upward mantle fluid flows.*

*Scheme of tectonic development and volcanism of the areas of matium magma formation at the Late Cenozoic stage of development of the Lesser Caucasus [8]. (a) Initial stage of mantle diapir growth; (b) Upper Miocene-Lower Pliocene stage; (c) in the Upper Pliocene is a new stage; (d) Upper Pliocene-Quaternary stage – stage of general extension. 1 – granite layer; 2 – basalt layer; 3 – mantle; 4 – astonesphere; 5 – metasomatized mantle; 6 – region anatexis; 7 – partially molten basalt layer; 8 – dykes; 9 – partially molten granite-metamorphic*

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

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

**Figure 10.**

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

### **Figure 10.**

number of acidic substances (r = 0.6). Obviously, with such volumes of assimilation acidic substances are not stored petrochemical characteristics of the primary rocks (andesites and basalts). Therefore, Harkers figures are not observed clear trends. Below are the results of AFC – modeling for rocks trachybasalt-trachyandesite

*1 – alkaline olivine basalts (initial melt), 2 – rhyolite (assimilation rock), 3 – trachyandesite (hybrid), 4 – calculated composition of trachyandesites, 5 – trachybasalt (initial melt), 6 – rhyolite (assimilation rock), 7 – basaltic trachyandesite (hybrid), 8 – calculated composition (all analyses have been converted to 100%).*

PR<sup>2</sup> = 0.93 r = 0.25 F = 0.68

**Elements 1 2 3 4 5 6 7 8** SiO2 52.46 79.17 64.73 64.94 55.74 79.17 58.76 58.90 TiO2 1.09 0.00 0.00 0.10 1.09 0.00 0.00 0.61 Al2O3 16.39 13.54 17.86 17.87 16.39 13.54 18.16 17.89 FeO\* 7.10 0.00 4.02 4.04 6.01 0.00 5.98 5.99 MgO 6.56 0.00 2.23 2.24 4.37 0.00 3.21 2.96 CaO 9.84 0.00 5.58 5.55 8.74 0.00 7.48 7.51 Na2O 4.37 4.17 3.35 3.34 4.37 4.17 4.27 3.95 K2O 1.09 3.13 2.23 1.87 2.19 3.13 2.14 1.75 P2O5 1.09 0.00 0.00 0.04 1.09 0.00 0.00 0.47 Rb 32 180 59 68 37 174 35 58 Sr 1700 100 1819 1918 2635 16 1543 1306 Ba 1060 100 815 524 1300 26 662 666 Zr 240 80 223 125 250 86 205 152 Ni 110 3 45 28 43 3 43 56 Cr 270 30 180 174 170 3 214 166 V 110 20 78 790 140 20 128 142

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

As seen from **Table 4**, the intermingling rhyolite and basic rocks (alkaline olivine basalts and trachybasalt) may be formed basaltic trachyandesite and

the Lesser Caucasus can be represented as follows.

*Results AFC – modeling for rocks trachybasalt-trachyandesite association.*

Summarizing the above data, the association of Late Cenozoic volcanic series of

Within the Lesser Caucasus in the late Cenozoic volcanism expressed high-K calc-alkaline, mildly alkaline, and partly alkaline associations. In Neogene time

metasomatized mantle and lower strata of basalt layer at a sufficiently large depth, which determines the enrichment of these melts with alkali, alkaline earth, and light

This process resulted in association of basaltic melts, enriched in alkalis. Perhaps such a melt was formed at low degrees of partial melting (3–10%) of garnet peridotite or eclogite. We can assume that it corresponds subduction oceanic crust. In the future, as a result of growing tension mantle melts penetrated the upper layers of the earth crust, where it mixes basic and acid magma, with the association of hybrid andesite, andesite-dacite lavas (**Figure 10**). Progressive

(Upper Miocene-Lower Pliocene), with decompression occurs anatexis

association.

**Table 5.**

trachyandesite.

PR2 = 0.154 r = 0.53 F = 0.57

rare earth elements.

**62**

*Scheme of tectonic development and volcanism of the areas of matium magma formation at the Late Cenozoic stage of development of the Lesser Caucasus [8]. (a) Initial stage of mantle diapir growth; (b) Upper Miocene-Lower Pliocene stage; (c) in the Upper Pliocene is a new stage; (d) Upper Pliocene-Quaternary stage – stage of general extension. 1 – granite layer; 2 – basalt layer; 3 – mantle; 4 – astonesphere; 5 – metasomatized mantle; 6 – region anatexis; 7 – partially molten basalt layer; 8 – dykes; 9 – partially molten granite-metamorphic layer; 10 – partially molten material of the upper mantle; 11 – upward mantle fluid flows.*

cooling of the deep source magma origin may be the cause of education dike fields in the region studied and possibly fractured outpouring mildly alkaline volcanism observed in the other parts of the Lesser Caucasus. Due to additional heating and

the flow of volatiles formed fairly large volcanoes of calc-alkaline composition of Neogene age. Then Upper Pliocene-Quaternary formed bimodal volcanism. Thus, the temporal spatial conjugation of crustal and mantle magmatism led to the introduction of mantle melts, under conditions of tension in the lower crust, which resulted in its melting and the association of acidic volcanic rocks rich in radiogenic Sr and Nd (rhyolite association). Simultaneously, in this situation, a change of scenery compression and tensile contributed to the development rifts depressions, arching and exercise slow differentiated and undifferentiated volcanic ( trachybasalt-basaltic trachyandesite-trachyandesite and basanite-tefrite series). Thus, the evolution of the melt in the earth crust is dominated by a single process of AFC (assimilation and fractional crystallization). As the fractionation rare elements, intermediate rocks can be formed by mixing trachybasaltic and rhyolite melts.

crystallization of the inclusions. The incompatible elements content (Rb, Th, Nb,

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

In rocks of formation the light lanthanoids prevail in relation to heavy, and therefore La/Sm, La/Yb relations are high. In medium rocks (quartz latites and andesites), it is defined approaching Eu/Eu\* relation to unit (Eu/Eu\* = 0.94–1.05) and in more acid rocks – Eu-minimum (Eu/Eu\* = 0.58–0.63) that indicates on plagioclase fractionation. It has been established that the content of Ba and Ba/Y, Rb/Y, Th/Yb relations are rapidly increased in the formation's rocks. The formation's rocks enrichment with lithophylous and rare-earth elements caused by

Based on the modeling, it was determined that as a result of high fractionation of the initial melt (F = 0.96) during mixing of 32.4% andesite and 63.4% rhyodacite; it is possible to obtain dacite of hybrid origin. The leading role of single process of Assimilation and Fractional Crystallization (AFC) is responsible for forming the

It has been shown that the enrichment of formation's rock with light rare-earth elements and many incompatible elements indicates on sufficiently important role of the enriched mantle matter in their formation. The high-alumina basalts can be considered as the parental magma for formation's rocks. Their formation is connected with fractionation in the environment of high water pressure from the

Zr, Hf, LREE, etc.) is minimal in the deep-seated inclusions.

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

relatively high degree of fusion melting that enriched by fluids.

initial high-magnesian melt of the olivine-clinopyroxene association.

type are formed due to melts differentiation (**Figure 10**).

assimilation caused the rocks buildup of the formation.

So, the Neogene volcanic series formation of the Lesser Caucasus can be

result of regional compression in the lifting diapir. In the Late Miocene-Early Pliocene anatexis of the metasomatized mantle and lower parts of the basalt layer occurs due to decompression at sufficiently great depth that determines these melts enrichment with alkali, alkaline-earth, light rare-earth elements. As a result of this process, there is formed basalt melts enriched by alkalines. Further evolution of these melts occurs in conditions of continental Earth crust where medium-acidic rocks as steeply dipping dikes and volcanic edifices of the central, central-fractured

At the beginning of the Late Cenozoic, the mantle metasomatism occurred as a

The primary magma evolution was accompanied by fractionation of olivineclinopyroxenic mineral associations and the appearance of high-alumina residual magma in the deep-seated foci. The last ones outcropping are accompanied by a stop at the intermediate foci, fractionation of plagioclase, clinopyroxene, amphibole, surrounding rock melting, crustal material contamination, and by hybrid

The works area can be considered metallogenetically perspective in relation to new Au, Ag, Hg, As, Sb, Cu-Mo with Au, Pb-Zn, Cu-Pb-Zn fields and ore occurrences. The investigated area is also rich by non-metallic raw materials – tuffs,

Therefore, for andesite-dacite-rhyolite formation, developed in the central part of Lesser Caucasus, rocks formation of high-potassium calc-alkaline series is specific unlike the rocks of calc-alkaline series of normal alkalinity. Rocks formation of andesite-dacite-rhyolite formation is caused by fractionation of the rock-forming minerals in the intermediate foci and later due to contamination of the differentiated basaltic melt by the surrounding rocks. Single process of crystallization and

Two volcanic formations of the Late Pliocene-Quaternary age are separated at the end of the collision stage of development of the Azerbaijan part of the Lesser Caucasus, forming a bimodal association: 1 – rhyolite; 2 – trachybasalt-trachyandesite.

igneous rocks of formation.

represented as follows.

magma formation.

scorias, pumices, etc.

**65**

## **9. Conclusions**

A distinctive feature of the investigated Late Miocene-Early Pliocene rocks of the Lesser Caucasus is that they are generally medium and acid. Volcanite composition meets mainly andesites and trachyandesites, dacites and trachydacites and also rhyolites. The volcanism was very powerful in relation to the attic tectonic activity of Late Miocene-Early Pliocene. During this period, there occurs Pre-Mesozoic base uplift and volcanism is mainly manifested in the central parts of the anticlinal zones of the Lesser Caucasus. The andesites and andesidacites with acid pyroclasts dominate in the products' composition at the beginning of the volcanic phase and at its end – andesite lavas. Magmatism of the main composition of high alkalinity has locally been manifested in the extreme parts of the anticlinal zones. Subvolcanic appearings of formation invaded after volcanogenic strata (Basarkechar suite) formation and have more acid composition. After active effusive-explosive activity of Meotian-Pontian-Early Pliocene volcanoes, more acid and viscous magma, cooling at a depth, rising along fractures at shallow depths hardened in the form of dikes and other subvolcanic bodies.

On the basis of nine petrogenic elements oxides (SiO2, TiO2, Al2O3, FeO\*, MgO, CaO, Na2O, K2O, P2O5) such independent groups as andesite-trachyandesite-quartz latites, dacite-trachydatsites and rhyodacite-rhyolites have been defined for andesite-dacite-rhyolite formation using factorial diagram.

It has been shown that with increasing SiO2 content in the rocks composition, the content of TiO2, Al2O3, FeO\*, MgO, CaO, P2O5 decreases due to fractionation of titanomagnetite, clinopyroxene, plagioclase, amphibole, and apatite. The calcalkaline trend of andesite-dacite-rhyolite series is controlled not only by magnetite fractionation but also by the hornblende crystallization, having a high Fe/Mg ratio and by SiO2 under saturation. First, it has been proved that the early hornblende crystallization in the Neogene magmatism evolution is the principal factor in the calc-alkaline series formation. This regularity is especially obvious during change of SiO2 content between 60 and 64%. The slow increase of K2O and Na2O content in the rocks formation is explained by potassium feldspar crystallization.

In formation's volcanites with increasing SiO2 content from andesites to rhyolites and with decreasing MgO quantity the coherent (compatible) elements as macroelements give a linear and sometimes expressed broken dependence. The figurative points of the homogenous inclusions are at the beginning of these dependence trends. These elements distribution in the rocks of formation is controlled by fractionation of rock-forming minerals and accumulative (homogenous)

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

crystallization of the inclusions. The incompatible elements content (Rb, Th, Nb, Zr, Hf, LREE, etc.) is minimal in the deep-seated inclusions.

In rocks of formation the light lanthanoids prevail in relation to heavy, and therefore La/Sm, La/Yb relations are high. In medium rocks (quartz latites and andesites), it is defined approaching Eu/Eu\* relation to unit (Eu/Eu\* = 0.94–1.05) and in more acid rocks – Eu-minimum (Eu/Eu\* = 0.58–0.63) that indicates on plagioclase fractionation. It has been established that the content of Ba and Ba/Y, Rb/Y, Th/Yb relations are rapidly increased in the formation's rocks. The formation's rocks enrichment with lithophylous and rare-earth elements caused by relatively high degree of fusion melting that enriched by fluids.

Based on the modeling, it was determined that as a result of high fractionation of the initial melt (F = 0.96) during mixing of 32.4% andesite and 63.4% rhyodacite; it is possible to obtain dacite of hybrid origin. The leading role of single process of Assimilation and Fractional Crystallization (AFC) is responsible for forming the igneous rocks of formation.

It has been shown that the enrichment of formation's rock with light rare-earth elements and many incompatible elements indicates on sufficiently important role of the enriched mantle matter in their formation. The high-alumina basalts can be considered as the parental magma for formation's rocks. Their formation is connected with fractionation in the environment of high water pressure from the initial high-magnesian melt of the olivine-clinopyroxene association.

So, the Neogene volcanic series formation of the Lesser Caucasus can be represented as follows.

At the beginning of the Late Cenozoic, the mantle metasomatism occurred as a result of regional compression in the lifting diapir. In the Late Miocene-Early Pliocene anatexis of the metasomatized mantle and lower parts of the basalt layer occurs due to decompression at sufficiently great depth that determines these melts enrichment with alkali, alkaline-earth, light rare-earth elements. As a result of this process, there is formed basalt melts enriched by alkalines. Further evolution of these melts occurs in conditions of continental Earth crust where medium-acidic rocks as steeply dipping dikes and volcanic edifices of the central, central-fractured type are formed due to melts differentiation (**Figure 10**).

The primary magma evolution was accompanied by fractionation of olivineclinopyroxenic mineral associations and the appearance of high-alumina residual magma in the deep-seated foci. The last ones outcropping are accompanied by a stop at the intermediate foci, fractionation of plagioclase, clinopyroxene, amphibole, surrounding rock melting, crustal material contamination, and by hybrid magma formation.

The works area can be considered metallogenetically perspective in relation to new Au, Ag, Hg, As, Sb, Cu-Mo with Au, Pb-Zn, Cu-Pb-Zn fields and ore occurrences. The investigated area is also rich by non-metallic raw materials – tuffs, scorias, pumices, etc.

Therefore, for andesite-dacite-rhyolite formation, developed in the central part of Lesser Caucasus, rocks formation of high-potassium calc-alkaline series is specific unlike the rocks of calc-alkaline series of normal alkalinity. Rocks formation of andesite-dacite-rhyolite formation is caused by fractionation of the rock-forming minerals in the intermediate foci and later due to contamination of the differentiated basaltic melt by the surrounding rocks. Single process of crystallization and assimilation caused the rocks buildup of the formation.

Two volcanic formations of the Late Pliocene-Quaternary age are separated at the end of the collision stage of development of the Azerbaijan part of the Lesser Caucasus, forming a bimodal association: 1 – rhyolite; 2 – trachybasalt-trachyandesite.

the flow of volatiles formed fairly large volcanoes of calc-alkaline composition of Neogene age. Then Upper Pliocene-Quaternary formed bimodal volcanism. Thus, the temporal spatial conjugation of crustal and mantle magmatism led to the introduction of mantle melts, under conditions of tension in the lower crust, which resulted in its melting and the association of acidic volcanic rocks rich in radiogenic Sr and Nd (rhyolite association). Simultaneously, in this situation, a change of scenery compression and tensile contributed to the development rifts depressions,

A distinctive feature of the investigated Late Miocene-Early Pliocene rocks of the Lesser Caucasus is that they are generally medium and acid. Volcanite composition meets mainly andesites and trachyandesites, dacites and trachydacites and also rhyolites. The volcanism was very powerful in relation to the attic tectonic activity of Late Miocene-Early Pliocene. During this period, there occurs Pre-Mesozoic base uplift and volcanism is mainly manifested in the central parts of the anticlinal zones of the Lesser Caucasus. The andesites and andesidacites with acid pyroclasts dominate in the products' composition at the beginning of the volcanic phase and at its end – andesite lavas. Magmatism of the main composition of high alkalinity has locally been manifested in the extreme parts of the anticlinal zones.

On the basis of nine petrogenic elements oxides (SiO2, TiO2, Al2O3, FeO\*, MgO, CaO, Na2O, K2O, P2O5) such independent groups as andesite-trachyandesite-quartz

It has been shown that with increasing SiO2 content in the rocks composition, the content of TiO2, Al2O3, FeO\*, MgO, CaO, P2O5 decreases due to fractionation of titanomagnetite, clinopyroxene, plagioclase, amphibole, and apatite. The calcalkaline trend of andesite-dacite-rhyolite series is controlled not only by magnetite fractionation but also by the hornblende crystallization, having a high Fe/Mg ratio and by SiO2 under saturation. First, it has been proved that the early hornblende crystallization in the Neogene magmatism evolution is the principal factor in the calc-alkaline series formation. This regularity is especially obvious during change of SiO2 content between 60 and 64%. The slow increase of K2O and Na2O content in

In formation's volcanites with increasing SiO2 content from andesites to rhyolites and with decreasing MgO quantity the coherent (compatible) elements as macroelements give a linear and sometimes expressed broken dependence. The figurative points of the homogenous inclusions are at the beginning of these dependence trends. These elements distribution in the rocks of formation is controlled by

arching and exercise slow differentiated and undifferentiated volcanic ( trachybasalt-basaltic trachyandesite-trachyandesite and basanite-tefrite series). Thus, the evolution of the melt in the earth crust is dominated by a single process of AFC (assimilation and fractional crystallization). As the fractionation rare elements, intermediate rocks can be formed by mixing trachybasaltic and

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

Subvolcanic appearings of formation invaded after volcanogenic strata (Basarkechar suite) formation and have more acid composition. After active effusive-explosive activity of Meotian-Pontian-Early Pliocene volcanoes, more acid and viscous magma, cooling at a depth, rising along fractures at shallow depths

latites, dacite-trachydatsites and rhyodacite-rhyolites have been defined for

the rocks formation is explained by potassium feldspar crystallization.

fractionation of rock-forming minerals and accumulative (homogenous)

hardened in the form of dikes and other subvolcanic bodies.

andesite-dacite-rhyolite formation using factorial diagram.

rhyolite melts.

**9. Conclusions**

In the mafic volcanics of the behavior of major elements indicate their origin by fractionation of olivine, clinopyroxene, hornblende, basic plagioclase, apatite, magnetite. Acidic volcanic rocks associated with the formation of "dry" high temperature of the melt in the intermediate chambers are not of fractional crystallization.

"Common" with characteristic isotopic 87Sr/86Sr = 0.7041 0.0001,

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

hybrid rocks.

**Author details**

**67**

Nazim Imamverdiyev<sup>1</sup>

and velizade\_anar@yahoo.com

provided the original work is properly cited.

\* and Anar Valiyev<sup>2</sup>

1 Department of Geology, Baku State University, Baku, Azerbaijan

\*Address all correspondence to: inazim17@yahoo.com

\*

2 Azerbaijan National Academy of Sciences, Institute of Geology, Baku, Azerbaijan

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

<sup>∋</sup>Nd = +4.1 0.2; 147Sm/144Nd = 0.105–0.114 and named "Caucasus" [17, 18]. The primary melt composition corresponds to K-Na moderately alkaline olivine basalts. The magma formed by the plume of the Caucasus in the atmosphere of Earth's crust formed the ever-increasing mantle diapir; he's at the very beginning of its process uplift served the development of large volumes of mantle fluids. Due to the hot magma mantle diapir melts the material of Earth's crust, magma is formed, which corresponds to the isotopic composition of the Earth's crust, and subsequently, to varying degrees due to contamination of the mantle and crustal magma formed

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

The distribution of rare earth elements in rocks trachybasalt-trachyandesite formation indicates that the source was the metasomatic alteration of volcanic rocks containing garnet mantle. In the studied volcanics, (Tb/Yb)n = 1.7–3.0 indicates the presence of garnet in the source of the primary magma.

In the rocks of rhyolite formation contents of rare earth elements is low (REE = 66–116 ppm), there is a pronounced low ratio of europium, which indicates that early removal of the molten plagioclase and alkali feldspar.

Trace element composition of the rocks trachybasalt-trachyandesite formation and their relationships complicate the model and determine the fractional crystallization of the magma mantle interaction with the substrate of the crust. In this substrate can be rhyolites, geochemical, and isotopic composition similar to the Earth's crust and forming a spatio-temporal association with the rocks contrast trachybasalt-trachyandesite formation.

The simulation revealed that the evolution of moderately alkaline olivine basalts (considered a primary mantle melt the rocks trachybasalt-trachyandesite formation) occurs due to changes in the composition of the main rock-forming and accessory minerals. Average rock formations formed by the assimilation of poorly differentiated primary magma acidic melt. Geochemical features of moderately alkaline olivine basalts indicate that the source of magma is metasomaticized, phlogopite-garnet-rutile containing lithospheric mantle. It is very possible that the melting of such a source is rutile to a restaurant, and magma is depleted Nb and Ta.

The calculations have shown that the proportion of melting rhyolitic melt separated from andesite substrate close to 15%. After removal of the remaining melt restite entirely consistent with the composition of the lower crust. The typical ratio of rare earth elements is to confirm this.

These fact sheets, model calculations indicate various sources of education salic and mafic melts. Thus, the generation of mafic melt (moderately alkaline olivine basalt composition) came from a differentiated mantle protolith formation of a salic melt occurs during lifting mafic magma by melting of crustal substrate. On the other hand, the salic is going to melt in the top of the magma reservoir and prevents lifting heavier mafic magma, and in a short time in the melt is subjected to intermediate focuses differentiated. During subsequent evolution differentiated mafic melt reacts with rhyolitic melt, which entails the formation of secondary rocks.

Thus, the formation of bimodal volcanism in contrast, the central part of the Lesser Caucasus in the Late Pliocene-Quaternary period is as follows.

Temporary space conjugate crust and mantle magmatism led to the introduction of mantle melts under tension in the lower crust, which led to its melting and the formation of acidic volcanic rocks enriched in radiogenic *Sr* and *Nd* (rhyolite formation). At the same time in this situation, a change of scenery compression tensile contributed to the manifestation of poorly differentiated volcanism. At the same time, the evolution of the melt in the earth's crust is dominated by a single process of AFC (assimilation and fractional crystallization), and intermediate chambers became necessary mixing of mafic (trachybasalt) and salic (rhyolite) melts and created the conditions for the formation of intermediate rocks. However, due to different densities and viscosities of melts, salic mafic and such mixing occurred in small quantities.

Thus, in the petrogenesis of the majority of Caucasian young volcanic rocks has played a significant role lower mantle source material which is close to the tank

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

"Common" with characteristic isotopic 87Sr/86Sr = 0.7041 0.0001, <sup>∋</sup>Nd = +4.1 0.2; 147Sm/144Nd = 0.105–0.114 and named "Caucasus" [17, 18]. The primary melt composition corresponds to K-Na moderately alkaline olivine basalts. The magma formed by the plume of the Caucasus in the atmosphere of Earth's crust formed the ever-increasing mantle diapir; he's at the very beginning of its process uplift served the development of large volumes of mantle fluids. Due to the hot magma mantle diapir melts the material of Earth's crust, magma is formed, which corresponds to the isotopic composition of the Earth's crust, and subsequently, to varying degrees due to contamination of the mantle and crustal magma formed hybrid rocks.
