**2. Geological settings**

ACVF is located on the eastern side of Inner Mongolia, northeast of China (**Figure 1a**). The Great Xing'an Mountain is the basement holding ACVF's volcanism as a distinctive geomorphological outline, which vastly distracts and draws the interests of both tourism and commercial behaviors.

The volcanism of ACVF is the most targeted element of local interest, not only its rareness but also the value of research. ACVF is a distinctive volcanic field due to its distance away from Japan Subduction Zone, about 200 km. Such a long spatial span indicates that the general background of ACVF is mostly controlled by the intra-continental settings, which are influenced by a distant convergent plate margin [24]. ACVF is located on the western side of Song'liao Graben, which is an enormous geological and structural subsidence in the center of NE China in consideration of a rifting-zone environment. One of the conventional concepts is that the delamination of supracrustal layers takes place on the weak points so that the rifting processes can generate large subsidence areas, that is, grabens, on the local territories [25]. The subduction zone fueled the delamination processes, which manifested the increasing activities of rifting. The basement of ACVF is approximately formed in the middle to late Mesozoic eras. Previous pieces of research show that the major components of the basement of the Great Xing'an Range are composed of Mesozoic volcanic and granitoid materials. The dwelling elements such as zircon, whole-rock elements, and Hf isotopic composition indicate the properties of the Great Xing'an Range. Geochronology (mostly K-Ar and Ar-Ar techniques) shows that there are at least three stages of the evolutionary histories of the ranges. The felsic volcanic rocks were formed in the Middle-Late Jurassic periods about 174–148 Ma; intermediate and intermediate-felsic volcanic

#### **Figure 1.**

*The general morphological aspect of the Arxan-Chaihe volcanic field (a) and its simplified geological architecture (b). Topography is based on SRTM 30 m resolution digital elevation model. Geology information is derived from (Wang et al. 2014). Please note that the young lava flow extent is greatly overestimated. Reconnaissance mapping indicated that many regions shown on this map covered by the youngest lava flows are not accurate and they are rather part of old lava flow fields. Maps are on WGS84 projection using NE China local coordinate system.*

*Eruption Scenario Builder Based on the most Recent Fissure-Feed Lava-Producing Eruptions… DOI: http://dx.doi.org/10.5772/intechopen.109908*

rocks were created in the Early Cretaceous intervals about 142–138 Ma, with no later than 125 Ma; normal felsic volcanic rocks were generated in the Early Cretaceous about 140–120 Ma, with the major volcanic events at 125 Ma. Upwelling mantle movements are the general factor of the compositions of Mesozoic volcanic rocks; this very well corresponds to the methods rifting system of Song'liao Graben [25].

The youngest activities of volcanism at ACVF occurred approximately 2000 years ago. Previous research shows that the lava flows cover the major areas of the Arxan UNESCO Global Geopark with several intervals of the ages. K-Ar method (whole rock) reveals the ages of the bulk lava flows in multiple vent locations of AVCF. Lava flows on both riverbanks of Halaha River erupted at about 0.587 ± 0.18 Ma [21, 26]. Among them, the youngest lava flows were generated from Yanshan's "triple vent" about 1990 to 2000 years ago. All these flow or bulk volcanic rocks are basalt or trachybasalt. The mafic property makes those flows follow the specific rheology and emplacement mechanisms of forming a range of young landforms of volcanism [21, 26, 27].

Up to now, 47 vents have been recognized by various field trips or through satellite images (Li et al. 2021). The ACVF occupies an area of about 2000 km2 in hill country (**Figure 1a**). Those vents are aligned from southwest to northeast, especially along the study area (**Figure 1b**). For instance, on the eastern side of Tianchi Lake, two paralleled fissures indicate the propagation processes during the syn-erupted stages (**Figure 2a**-**d**). This feature is also found on the eastern side of Dichi Lake (**Figure 2a**-**d**). From the satellite images, the two ends of ACVF are marked by Wusulangzi Lake in the southwest corner (**Figure 2a**-**d**) and Tongxin Lake in the northeast corner. Between those two lakes, at least 15 vents are aligned through a distinctive orientation, which is SW-NE. Thus, vent distributions of ACVF show that the local tectonic trends, such as fissure orientations, follow a general direction, which is SW-NE directed trend [23, 24].

#### **Figure 2.**

*Sentinel satellite images of the Arxan – Chaihe volcanic field showing the distinct texture of the young lava flows. a) False color image; b) SWIR image; c) geology – Band 8, 11, 12; d) geology – Band 12, 8, 2. Maps are in WGS84 projection using geographical coordinate systems.*

Present-day geomorphology of the region of ACVF is revealed by a range of post-eruptive landscapes with volcanic products. The currently available geological map (**Figure 1b**) shows an extensive lava-covered region marked as Holocene basalt. Interestingly, in this maps the three volcanic cone complexes, Gaoshan, Yanshan, and Dahei Gou marked as Middle Pleistocene basalts distinctly separated from the young lava flows (**Figure 1b**). The targeted two vent complexes (Yanshan and Dahei Gou) are scoria cones with welded cores and various clastogenic lava units indicating eruptions where Hawaiian and Strombolian style eruptions alternated over the activity. On the present-day Halaha riverbanks, the youngest lava flows extend over 10 km on average and are suspected to reach about 16 km SW from their source following the paleo-Halaha River valley (**Figure 2a**-**d**). The surface structures of the flows represent the two distinctive pāhoehoe and ʻaʻā types. Also, pāhoehoe flows preserve a range of ponded fabrics such as ponded lakes, lave tubes, whalebacks, and tumuli. Lava channels can be observed in a partially collapsed SW side of the Yanshan scoria cones.
