Quaternary monogenetic volcanoes in southern China: eruption styles and controlling factors

Abstract The Hainan Island-Leizhou Peninsula-Beibu Gulf volcanic field (HLBVF) in southern China (covering an area of over 7000 $ km^{2} $) contains at least 50 cinder cones and 12 maar volcanoes. It is one of a few barely studied volcanic fields of Quaternary age in China. The eruption styles, and...
Ausführliche Beschreibung

Abstract The Hainan Island-Leizhou Peninsula-Beibu Gulf volcanic field (HLBVF) in southern China (covering an area of over 7000 $ km^{2} $) contains at least 50 cinder cones and 12 maar volcanoes. It is one of a few barely studied volcanic fields of Quaternary age in China. The eruption styles, and controlling factors that led to the formation of this volcanic field, are thus not yet clear. This study provides a first investigation of the general geology of the HLBVF volcanoes as well as preliminary discussion of the controlling factors affecting the eruption styles. Early Pleistocene (> 1 Ma) and/or earlier (Pliocene) volcanic activity mainly occurred in the form of high-flux magmatic eruptions that formed a large amount of thick lava units and/or cinder cones, which have since experienced intense erosion. The late early Pleistocene to late Pleistocene (~ 1.08–0.03 Ma) phreatomagmatism is represented by maar volcanoes and shows that the initial eruptions were commonly phreatomagmatic events but had increasingly magmatic components in later periods, which reflects sustained, but lower magma fluxes than in the early Pleistocene. The Holocene magmatic eruptions (< 10 ka) primarily formed agglutinate, bomb, and lapilli units, as well as lava flows. These deposits were emplaced mainly by pyroclastic fallout from Hawaiian-style eruptions. This work indicates that eruption styles between magmatic and phreatomagmatic eruptions in the HLBVF were not directly related to fluctuations in annual precipitation and magma compositions. Pre-existing NW-trending faults likely controlled the vent locations, and water fed along fault zones might have supported sustained phreatomagmatism, which formed the large maar volcanoes. The fluctuation of magma fluxes, and water supply linked to long-term tropical climate changes, coupled with regional faults, were likely the three main factors that controlled eruption styles in the HLBVF. Ausführliche Beschreibung