**1. Introduction**

Monogenetic volcanoes are the most common type of subaerial volcanoes on the Earth [1] that occur in any tectonic setting as intraplate, extensional, and subduction [2]. They can be distributed as isolated centers, monogenetic volcanic fields [3], or associated with large volcanic systems as polygenetic volcanoes or calderas [4], displaying a plumbing system relatively simple of a dispersed nature [5]. Monogenetic volcanoes are associated with small eruptions fed from one or multiple magma batches, with volumes typically ≤1 km3 of basic to silicic composition and form over

a short period from hours to decades. Monogenetic centers can build several volcanic landforms in response to their relationship with different environmental settings [6]. They can be produced by different eruptive styles (e.g., Hawaiian, Strombolian, violent Strombolian, phreatomagmatic, Surtseyan, and effusive activity) that are determined by internal- and external- factors [7], and evidencing several magmatic processes (e.g., fractionation, mixing, contamination) [5]. Therefore, each monogenetic volcanic system is different depending on many factors (mentioned above). For this reason, current efforts around the world focus on understanding monogenetic volcanism in different scenarios, in order to provide a better understanding of this variability and to provide tools to estimate possible scenarios of future eruption [8].

The Central Volcanic Zone (CVZ) of the Andes and particularly northern Chile (18–28°S) (**Figure 1**), is an excellent natural laboratory to study monogenetic systems of changing magma compositions in time and space related to the evolution of an active continental margin, and a ~ 70 km thick orogenic crust [12]. Despite this,

### **Figure 1.**

*a) Map showing the location of the Northern, Central, Southern, and Austral Volcanic Zones (NVZ, CVZ, SVZ, and AVZ, respectively) of the Andes defined by Thorpe and Francis [9] (modified from [10]). b) Location map of the CVZ (modified from [10]) showing the central active polygenetic volcanoes [11]. c) Map of northern Chile showing the major morpho-tectonic units of the Central Andes (modified from [12]).*

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*An Overview of the Mafic and Felsic Monogenetic Neogene to Quaternary Volcanism…*

this contribution are available in the supplementary material.

The CVZ is located between 14°S (Quimsachata, Peru) and 28°S (Ojos del Salado, Chile) of the Andean Cordillera, including southern Peru, northern Chile, southwestern Bolivia, and northwestern Argentina (**Figure 1a** and **b**). This volcanic zone is a highly elevated region, reaching a width of 350–400 km at much of it over 4000 m a.s.l., constituting the Western Cordillera and Altiplano-Puna physiographic provinces (**Figure 1c**). It is the second-highest altitude plateau in the world in size (after Tibetan Plateau of Central Asia) [36] built on a thickened continental crust that attains a maximum thickness of ~70 km [37]. The crustal thickening and high elevation of the CVZ are related to the crustal shortening [38], sub-crustal magmatism [39], delamination of eclogitic lower crust and lithosphere [40], and climatically controlled low erosion rates with limited sedimentation on the subduction trench [41]. In addition, this crustal thickness is the reason for the magma composition features that characterize the rocks that make up the CVZ as residual garnet during differentiation, crustal contamination,

**2. Geological background**

prominent active polygenetic volcanoes in Chile such as Parinacota [13], Guallatiri [14], Aucanquilcha [15], Ollagüe [16], Lascar [17], Socompa [18], Lastarria [19], and Ojos del Salado [20] have received priority of research over monogenetic volcanoes (**Figure 1**). Monogenetic volcanism studies in northern Chile have rarely been mentioned, such as Chao dome [21], Tilocálar volcanoes [22], Juan de la Vega maar [23], Corral de Coquena maar [24], SC2 scoria cone [25], or Tinto dome [26]. Monogenetic volcanoes usually have been studied indirectly through i) regional geologic mapping from the Chilean Geological Service (Sernageomin); ii) only previously reported as disaggregated or preliminary data (conference papers and undergraduate thesis); iii) or by researches of a large magmatic system (such as polygenic volcanoes or calderas) mainly associated to petrological knowledge, leaving aside the mechanisms that control eruptive styles (volcanological sense) [27, 28]. Nevertheless, recently, several monogenetic volcanoes have been studied such as Cerro Chascón dome [29], Cerro Overo maar [30], La Poruña scoria cone [31], Chanka, Chac-Inca, and Pabellón domes [32], El País lava flow field [33], Tilocálar monogenetic field [34], Cerro Tujle maar [35], and many others preliminary data reports, which have increased our understanding of the monogenetic volcanism in this part of the Central Andes and provided tools to estimate possible scenarios of future eruptions that could affect the communities of the Altiplano. In this contribution, an overview of the monogenetic volcanism that overlaps spatially and temporally the spectrum of architectures, range of eruptive styles, lithological features, and different magmatic processes of mafic and felsic monogenetic volcanoes of northern Chile (18°S-28°S) is reported. Previous studies, such as research publications and preliminary data reports, were used to assemble the volcanological, petrological, and geochronological information in the framework of this overview. A total of 907 Miocene-Quaternary monogenetic volcanoes (individual and parasite) have been identified, carefully evaluating their distribution in time and space. New stratigraphic and sedimentology data of all monogenetic volcanic center types are presented, which added to compositional and geochronological data, are used to illustrate a plumbing system model. In addition, a general eruptive model for monogenetic volcanoes in northern Chile is proposed, where external (e.g., magma reservoirs or groundwater available) and internal (e.g., magma ascent rate or interaction en-route to the surface) conditions determine the changes in eruptive style, lithofacies, and magmatic processes involved in the formation of monogenetic volcanoes. The methods used and databases generated in

*DOI: http://dx.doi.org/10.5772/intechopen.93959*

### *An Overview of the Mafic and Felsic Monogenetic Neogene to Quaternary Volcanism… DOI: http://dx.doi.org/10.5772/intechopen.93959*

prominent active polygenetic volcanoes in Chile such as Parinacota [13], Guallatiri [14], Aucanquilcha [15], Ollagüe [16], Lascar [17], Socompa [18], Lastarria [19], and Ojos del Salado [20] have received priority of research over monogenetic volcanoes (**Figure 1**). Monogenetic volcanism studies in northern Chile have rarely been mentioned, such as Chao dome [21], Tilocálar volcanoes [22], Juan de la Vega maar [23], Corral de Coquena maar [24], SC2 scoria cone [25], or Tinto dome [26]. Monogenetic volcanoes usually have been studied indirectly through i) regional geologic mapping from the Chilean Geological Service (Sernageomin); ii) only previously reported as disaggregated or preliminary data (conference papers and undergraduate thesis); iii) or by researches of a large magmatic system (such as polygenic volcanoes or calderas) mainly associated to petrological knowledge, leaving aside the mechanisms that control eruptive styles (volcanological sense) [27, 28]. Nevertheless, recently, several monogenetic volcanoes have been studied such as Cerro Chascón dome [29], Cerro Overo maar [30], La Poruña scoria cone [31], Chanka, Chac-Inca, and Pabellón domes [32], El País lava flow field [33], Tilocálar monogenetic field [34], Cerro Tujle maar [35], and many others preliminary data reports, which have increased our understanding of the monogenetic volcanism in this part of the Central Andes and provided tools to estimate possible scenarios of future eruptions that could affect the communities of the Altiplano.

In this contribution, an overview of the monogenetic volcanism that overlaps spatially and temporally the spectrum of architectures, range of eruptive styles, lithological features, and different magmatic processes of mafic and felsic monogenetic volcanoes of northern Chile (18°S-28°S) is reported. Previous studies, such as research publications and preliminary data reports, were used to assemble the volcanological, petrological, and geochronological information in the framework of this overview. A total of 907 Miocene-Quaternary monogenetic volcanoes (individual and parasite) have been identified, carefully evaluating their distribution in time and space. New stratigraphic and sedimentology data of all monogenetic volcanic center types are presented, which added to compositional and geochronological data, are used to illustrate a plumbing system model. In addition, a general eruptive model for monogenetic volcanoes in northern Chile is proposed, where external (e.g., magma reservoirs or groundwater available) and internal (e.g., magma ascent rate or interaction en-route to the surface) conditions determine the changes in eruptive style, lithofacies, and magmatic processes involved in the formation of monogenetic volcanoes. The methods used and databases generated in this contribution are available in the supplementary material.
