Abstract Ashikule volcanic field, developed in the western Kunlun mountain of north Tibet, is composed of approximately 10 volcanoes, and covers a total area of about 200 km 2 at an average altitude of approximately 5000 m, one of the highest volcanic fields in the world. In this study, we conducted detailed field investigations of the geological and geomorphological features of volcanic rocks and volcanic edifices in Ashikule basin, and compiled a large-scale geological map of the study area for the first time. We also collected a series of samples for petrochemistry analysis, as well as a high-precision 40 Ar/ 39 Ar geochronology study of selected lavas from Ashikule volcanic field. Finally, we refined the eruption history for the volcanic activity in the basin, which provides some new volcanological evidence for the study of the tectonic evolution of the Northern Tibetan Plateau.

Abstract In the West Kunlun Mountains, four volcanic fields (Kangxiwa, Dahongliutan, Qitaidaban and Quanshuigou) are distributed along the Dahongliutan fault, which is c. 180 km long. Based on field investigations, chronological measurements and geochemical analysis of some volcanic fields, the results of geological, geochemical and geophysical research in previous studies in the corresponding study areas are summarized. The volcanic activities in these areas were mainly effusive eruptions, explosive eruptions and phreatomagmatic eruptions. In this study, we discovered the Qitaiyanhu volcanic field for the first time and determined that the 14 C age of the lacustrine strata underlying the Qitaiyanhu lava flows is 13.110 ± 0.04 ka BP, indicating that there may still have been volcanic activities in the late Pleistocene and even the Holocene in the Dahongliutan fault area. Base surge deposits, which are the products of the interaction between magma and water, were found in the Kangxiwa volcanic field. The four shoshonitic rock fields of Kangxiwa, Dahongliutan, Qitaidaban and Quanshuigou are likely to be products of different evolution stages from the same magma source area. The magmatic origin of these volcanic fields may be related to the upwelling of the asthenosphere, triggered by the collision between the Indian and Tarim plates.

Abstract Northern Hainan Island and the Leizhou Peninsula volcanic fields (Leiqiong), the southernmost continental Cenozoic volcanism in China, cover an area of c. 8000 km 2 with 177 volcanoes recognized. Far from the subduction areas, volcanoes in this area provide an ideal opportunity to study the geodynamics of intraplate volcanoes. Here, we review the geochronological and geochemical data of the volcanic rocks in Leiqiong volcanic fields, and discuss their magma sources and geodynamics on the basis of the geological and geophysical observations. Chronological data (34.78–0.01 Ma) show that the volcanic activities started approximately in the Miocene and continued to the Quaternary. These basalts show typical geochemical characteristics of oceanic island basalts, and tomographic images reveal that a mantle plume is situated beneath Hainan Island and extends down to the core–mantle boundary. Thus, we suggest that the Hainan mantle plume is responsible for the Cenozoic volcanism in Leiqiong volcanic fields and this plume is sourced from the lower mantle with additions of dehydrated slab fragments. These mixed plume materials were brought to the upper mantle and produce solid pyroxenites, which are the major source of Leiqiong magmas. Although there is no documental record of volcanic eruptions in Leiqiong volcanic fields, the volcanic danger cannot be neglected.

Abstract Volcanic eruptions, despite causing large-scale disasters, also provide important natural resources and are an effective way to understand the Earth's internal structure and its evolution. Herein, a comprehensive review is presented on recent progress in geophysical imaging of the structure and origin of intraplate volcanoes in Mainland China. We primarily focus on the Changbaishan, Wudalianchi, Tengchong, Hainan and Ashikule volcanoes as they are currently active and hence pose potential hazards during future eruptions, particularly the Changbaishan volcano. The Changbaishan and Wudalianchi volcanoes are widely believed to be caused by the dehydration of the stagnant Pacific slab in the mantle transition zone along with wet upwelling in the big mantle wedge. There are a number of different views regarding the formation mechanism of the Tengchong volcano. Some studies suggest that a big mantle wedge structure is also present under eastern Tibet, and the Tengchong volcano has a deep origin, similar to volcanism in NE China. Others suggest that the Tengchong volcano is caused by a local and shallow process. Most tomographic studies suggest that the Hainan volcano is a hotspot, and its track has been located in SE China by combining seismological, geochemical and numerical modelling data. A gap exists between the subducted Indian Plate and the Tarim lithosphere beneath the Ashikule volcano, which provides a channel for asthenospheric upwelling to give rise to intraplate volcanism in the Ashikule basin. The interactions of lithospheres may produce shear heating of the subcontinental lithospheric mantle, which can generate localized melting. This process has been proposed as an explanation for the intraplate volcanism in Ashikule.

Abstract Following decades of geological surveys and studies, 14 active volcanic fields have been identified in China. Evidence for Holocene volcanism in several of these areas highlights the need to understand and monitor volcanic hazards in those regions. Six volcano observatories have thus been established in the past 40 years. This work reviews China's national capability and history of volcano monitoring, with emphasis on the Changbaishan–Tianchi Volcano Observatory and the Tengchong Volcano Observatory. The Changbaishan–Tianchi Volcano Observatory (CTVO) was constructed in 1996 and began monitoring in 1999, with limited recorded observations dating back to 1973. Currently, CTVO is the largest and most advanced observatories in China. The monitoring network of the CTVO incorporates 11 seismic and 15 GPS stations, two levelling routes and three gas geochemistry sampling points. The Changbaishan–Tianchi Volcano experienced unrest during 2002–05, evidenced in elevated levels of seismicity and ground deformation, as well as shifts in gas geochemistry. After 2006, the volcano returned to quiescence, with activities at background levels as recorded in 1973–2001. The monitoring network of Tengchong Volcano Observatory incorporates eight seismic stations, 20 GPS points, 95 levelling points and three gas geochemistry sampling points. The observations made since 1965 indicate significant seismicity, with more than 3000 events recorded in 2011, mostly related to regional tectonics. Tengchong is known for its widespread hot springs, with temperatures up to 105°C recorded at Dagunguo spring. The four other observatories are Longgang Volcano Observatory, Jingbohu Volcano Observatory, Wudalianchi Volcano Observatory and Qiongbei Volcano Observatory. They are equipped with seismic, geodetic and geochemical monitoring equipment. These areas saw only low levels of activity over the past several decades, but related fault systems are relatively active. In a relatively short time, China has gained considerable experience in observatory design and volcano monitoring and has trained up a sizeable task force, laying the foundation for sustained volcano monitoring at the national level. Future efforts must focus on maintaining and expanding observational capacity, as well as gaining better dynamic understanding to inform volcano hazard assessment.