Browsing by Author "Li, Boxin"

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    The Arxan-Chaihe Volcanic Field of monogenetic volcanism in intracontinental settings in NE China : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2024-02) Li, Boxin
    Pliocene to Recent Arxan-Chaihe Volcanic Field (ACVF) is composed of at least 47 vents, representing various types of volcanism, such as Strombolian style, phreatomagmatic explosive, effusive, and lava-fountaining eruptions. These eruptions produced scoria cones, fissure-aligned spatter cones, and tuff rings with a few surrounding maar craters. Field observations imply that the lava-fountaining eruptions are more common on the western side of ACVF, represented by Yanshan (YS)-the Triple Vent, and Daheigou (DHG). In the southwest part of ACVF, lava flows and loose pyroclastic ejecta, such as scoria, mark the eruption events that took place during the Holocene era about 2000 years ago. Dichi (Earth Pond) Lake, with fissures on its eastern side, formed by lava-effusive eruption styles with spatter rows occurring along a fissure, while the low-lying western side of the vent chain is a maar volcano cut into the pre-eruptive lava sheets. Tianchi (Heaven Lake) Lake and Tuofengling (Camel Hump) Lake on the western side of ACVF preserves a range of well-exposed pyroclastic deposits consistent with edifice-building successions. These are composed of scoriaceous pyroclastic materials, yielding construction histories of complex cones (with both "wet" and "dry" explosive eruptive phases). The most significant and largest vent is in the eastern corner of ACVF, Tongxin Lake, a complex phreatomagmatic eruption-style volcano with a maar crater and thick rim deposits. Tongxin Lake is interpreted to be a maar lake that erupted into an intra-montane basin. Intact pyroclastic deposits are preserved within a km from the crater rim and at least 5 meters thick. Stratigraphic and granulometric analyses from five sites around Tongxin Lake indicate the tuff ring of Tongxin was built by processes associated with magma-water interactions that fueled violent explosive eruptions during distinct syn-eruptive stages. Geochemistry is consistent with at least three magma sources contributing to the formation of the complex eruptive products that build the large tuff ring of the maar edifice. Geomorphology terrain analyses performed through GIS-based applications (QGIS) imply that the diverse range of local geology, especially the pre-eruptive topography, was confined and reshaped by the subsequent Pliocene to Recent volcanism in ACVF. Lava flows within ACVF were emplaced over large areas around the two major fluvial systems: Halaha River in the west and Chaoer River in the east of ACVF. The lava flows in the west of ACVF are generally young and can be modelled using the Q-LavHA plug-in of QGIS. The model has been utilized to simulate lava flow inundation and indicates diverse flow along the flow axis as well as lateral and temporal variations during the evolution of the edifice. Other studies of ACVF, e.g., hazard management, concluded that violent phreatomagmatic explosive events had impacted the fluvial valleys that are commonly associated with structural weakness zones in ACVF. In addition, lava-effusive and lava-fountaining eruptions in urban areas and along major utilities (e.g., roads, geopark facilities or powerlines) also could be heavily impacted by fissure-fed lava flows and potential phreatomagmatic explosions controlled by the local hydrology conditions.
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    Violent phreatomagmatic eruptions that formed maars in an intra-mountain basin at Arxan-Chaihe volcanic field, Inner Mongolia, China : a thesis presented in partial fulfilment of the requirements for the degree of Masters in Earth Science, School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
    (Massey University, 2018) Li, Boxin
    Two large depressions contain Wusulangzi Lake and Tongxin Lake in the Arxan-Chaihe Volcanic Field (ACVF), which preserves at least 27 volcanoes in NE China in about a 1000 km2 area. Due to the preliminary research on both Wusulangzi and Tongxin, two sample groups (Sample 1 and Sample 2) were collected and field observations were held on both sites. Sample 1, representing Wusulangzi, was collected from the SE part of the lake where the lava flow is suspected to cover and preserve medial to distal sections of the tuff ring. Sample 2, representing Tongxin, was collected from the SW rim of the crater from the proximal area, as well as the eastern side in regard to the distal region. Specifically at Tongxin Lake, the pyroclastic successions and beddings contain a series of horizontal and laminated structures, with dune beddings, cross-beddings, as well as a chute-and-pool structure. Pyroclastic deposits of the tuff rings can be traced from the crater rim about 3 km. The various methods of microscopy reveal that glass shards are distributed differently in both sample groups. Mineral diversity is shown to a large extent, and the mineralogical alteration can be observed under petrographic microscopy. SEM and BSE for 2D and 3D images indicate a relatively high fragmentation of juvenile particles. The grain-size distribution also implies medium-to-high explosive energy. Geochemistry data of both major and trace elements reveals a diversity of magma in relation to fractional crystallisation (olivine, clinopyroxene and plagioclase crystallisation) and magma evolution processes, which are depicted by Harker variation diagrams. The AFM plot reveals a primitive stage of magma evolution. The multi-element diagram shows uranium as abnormal, which is suspected to be a U-rich mantle source. Keywords: phreatomagmatic eruption, maar crater, major and trace elements, SEM, BSE, petrographic microscopy, grain-size distribution, ternary plot, Harker diagram