Magma recharging beneath the Weishan volcano of the intraplate Wudalianchi volcanic field, northeast China, implied from 3-D magnetotelluric imaging

Geology ◽  
2020 ◽  
Vol 48 (9) ◽  
pp. 913-918 ◽  
Author(s):  
Ji Gao ◽  
Haijiang Zhang ◽  
Senqi Zhang ◽  
Hailiang Xin ◽  
Zhiwei Li ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Magma Chamber ◽  
Northeast China ◽  
Volcanic Eruptions ◽  
Volcanic Field ◽  
Magmatic System ◽  
Low Velocity ◽  
Active Monitoring ◽  
Low Resistivity ◽  
Magma Reservoirs

Abstract The last volcanic eruptions at the intraplate Wudalianchi volcanic field in northeast China were ∼300 yr ago. Recent ambient noise tomography (ANT) imaged a potential magma chamber beneath one of its volcanoes, the Weishan volcano, which last erupted at ca. 50 ka. To image the spatial distribution of the magmatic system and estimate the melt fractions beneath the Weishan volcano, we use a dense magnetotelluric (MT) network (average site spacing of ∼1 km) around the Weishan cone to image a three-dimensional (3-D) resistivity structure beneath the volcano. For the first time, 3-D MT inversion illuminates the high-resolution spatial distribution of a very low-resistivity body of ∼0.3–3 Ω·m at depth of ∼2–15 km beneath the Weishan volcano. From the 3-D resistivity model, it can be deduced there exists a magma chamber in the upper and middle crust. From both low-velocity anomalies from ANT and low-resistivity anomalies from MT imaging, melt fractions of magma reservoirs are reliably estimated to be >∼15%. From the morphology of magma reservoirs and the shallow magma chamber, the Weishan volcano can be best described by the model of transcrustal magmatic system. Considering the significant melt fractions and active earthquakes and tremors occurring around magma reservoirs, the Weishan volcano is likely in an active stage with magma recharging. Therefore, it needs more active monitoring for better forecasting of its potential future eruptions.

scholarly journals Supplemental Material: Magma recharging beneath the Weishan volcano of the intraplate Wudalianchi volcanic field, northeast China, implied from 3-D magnetotelluric imaging

2020 ◽  
Author(s):  
Ji Gao ◽  
Haijiang Zhang ◽  
et al.
Keyword(s):  
Northeast China ◽  
Volcanic Field ◽  
Earthquake Activity ◽  
Low Resistivity ◽  
Velocity Anomalies ◽  
Magnetotelluric Inversion ◽  
Magnetotelluric Imaging

Details on the 3-D magnetotelluric inversion, estimating melt fractions based on resistivity and velocity anomalies, earthquake activity, and the interpretation of low-resistivity anomalies by magmas and no apparent hydrothermal alterations for the Weishan volcano.<br>

Understanding Magmatic System of Unzen Volcano (Nagasaki, Southwest Japan) Inferred from Broad-band Magnetotelluric Observation

2021 ◽  
Author(s):  
Agnis Triahadini ◽  
Koki Aizawa ◽  
Tasuku Hashimoto ◽  
Kazunari Uchida ◽  
Yuto Yamamoto ◽  
...  
Keyword(s):  
Magma Chamber ◽  
Broad Band ◽  
Magmatic Fluid ◽  
Volcanic Area ◽  
Resistivity Structure ◽  
Magmatic System ◽  
Magma Chambers ◽  
Unzen Volcano ◽  
Low Resistivity ◽  
Magnetotelluric Method

&lt;p&gt;Unzen Volcano is located in Shimabara Peninsula, Nagasaki, Japan. After 198 years of dormancy, the volcano erupted throughout 1990-1995 and resulted the emergence of new lava dome called Heisei-Shinzan. Following the eruption, numerous studies have been intensively conducted in Unzen volcano to assess the eruption mechanism and the magma plumbing system. Regarding to the magmatic system, the most preferred model is that the primary supply of magma is stored beneath Chijiwa bay. This magma chamber is located about 15 km west of the active dome at vertical depth approximately 15 km, and followed by subordinate shallower magma chambers beneath the volcano (e.g. Nakamura 1995; Kohno et al 2008). Upon the eruption, the magma ascended obliquely towards the summit in east direction (e.g. Umakoshi et al 2001). However, how main magma chamber&amp;#160; and shallower chambers are connected to the summit via oblique pathway is poorly imaged in terms of structure.&lt;br&gt;As widely known, Magnetotelluric method is highly sensitive to low resistivity zone caused by interconnected fluids. Low resistivity zone detected in the volcanic area usually can be interpreted as hydrothermal/magmatic fluid and or magma chamber containing partial melt (e.g. Aizawa et al 2014; Hill et al 2015). Thus, by using broadband Magnetotelluric method, we aim to investigate resistivity structure of Unzen volcano associated with magmatic system and its controlling structure (e.g. pathway and faults).&lt;br&gt;Although the shallow structures around Unzen volcano are estimated by the 2017-2019 campaigns (Triahadini et al 2019; Hashimoto et al 2020), we are unable to image deeper structure around the proposed location of magma chambers and magma pathway. To achieve our goals, during November-December 2020, we installed 35 new sites to cover whole area in Shimabara Peninsula. In total, deployed 99 Magnetotelluric stations covering Unzen volcano and Shimabara Peninsula. On this meeting, we would like to present our resistivity structure derived from all dataset.&lt;/p&gt;

scholarly journals Supplemental Material: Magma recharging beneath the Weishan volcano of the intraplate Wudalianchi volcanic field, northeast China, implied from 3-D magnetotelluric imaging

2020 ◽  
Author(s):  
Ji Gao ◽  
Haijiang Zhang ◽  
et al.
Keyword(s):  
Northeast China ◽  
Volcanic Field ◽  
Earthquake Activity ◽  
Low Resistivity ◽  
Velocity Anomalies ◽  
Magnetotelluric Inversion ◽  
Magnetotelluric Imaging

Details on the 3-D magnetotelluric inversion, estimating melt fractions based on resistivity and velocity anomalies, earthquake activity, and the interpretation of low-resistivity anomalies by magmas and no apparent hydrothermal alterations for the Weishan volcano.<br>

scholarly journals Studying the Depth Structure of the Kyrgyz Tien Shan by Using the Seismic Tomography and Magnetotelluric Sounding Methods

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 122
Author(s):  
Irina Medved ◽  
Elena Bataleva ◽  
Michael Buslov
Keyword(s):  
Seismic Tomography ◽  
High Velocity ◽  
Fault Zones ◽  
Magnetotelluric Sounding ◽  
Tien Shan ◽  
High Resistivity ◽  
Low Velocity ◽  
Low Resistivity ◽  
Velocity Models ◽  
Fluid Saturation

This paper presents new results of detailed seismic tomography (ST) on the deep structure beneath the Middle Tien Shan to a depth of 60 km. For a better understanding of the detected heterogeneities, the obtained velocity models were compared with the results of magnetotelluric sounding (MTS) along the Kekemeren and Naryn profiles, running parallel to the 74 and 76 meridians, respectively. We found that in the study region the velocity characteristics and geoelectric properties correlate with each other. The high-velocity high-resistivity anomalies correspond to the parts of the Tarim and Kazakhstan-Junggar plates submerged under the Tien Shan. We revealed that the structure of the Middle Tien Shan crust is conditioned by the presence of the Central Tien Shan microcontinent. It manifests itself as two anomalies lying one below the other: the lower low-velocity low-resistivity anomaly, and the upper high-velocity high-resistivity anomaly. The fault zones, limiting the Central Tien Shan microcontinent, appear as low-velocity low-resistivity anomalies. The obtained features indicate the fluid saturation of the fault zones. According to the revealed features of the Central Tien Shan geological structure, it is assumed that the lower-crustal low-velocity layer can play a significant role in the delamination of the mantle part of the submerged plates.

Eruptive frequency of the Bora-Baricha-Tullu Moye (BBTM) volcanic system in the Central Main Ethiopian Rift

2021 ◽  
Author(s):  
Amdemichael Zafu Tadesse ◽  
Karen Fontijn ◽  
Abate Assen Melaku ◽  
Ermias Filfilu Gebru ◽  
Victoria Smith ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Volcanic Eruptions ◽  
Volcanic Field ◽  
Tectonic Activity ◽  
Explosive Eruptions ◽  
Ethiopian Rift ◽  
Rift System ◽  
Diagnostic Features ◽  
Volcanic System ◽  
Main Ethiopian Rift

&lt;p&gt;The Main Ethiopian Rift (MER) is the northern portion of the East African Rift System and separates the Eastern and Western plateaus of Ethiopia. The recent volcanic and tectonic activity is largely focused within the rift basin along a 20 km wide zone on the rift floor. Large silicic volcanic complexes are aligned along this central rift axis but their eruptive histories are not well constrained.&lt;/p&gt;&lt;p&gt;The Bora-Baricha-Tullu Moye (BBTM) volcanic field is situated in the central Main Ethiopian Rift and has a different appearance than the other MER volcanic systems. The BBTM constitutes several late Quaternary edifices, the major ones are: Tullu Moye, Bora and Baricha. In addition, there are multiple smaller eruptive vents (e.g. Oda and Dima), cones, and domes across the ca. 20 X 20 km wide area. Currently, there is very little information on the frequency and magnitude of past volcanic eruptions. We present a new dataset of field observations, componentry, petrography, geochronology (&lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;39&lt;/sup&gt;Ar), and glass major and trace element chemistry. The data are assessed as potential fingerprints to assign diagnostic features and correlate units across the area, and establish a tephrostratigraphic framework for the BBTM volcanic field.&lt;/p&gt;&lt;p&gt;Two large-volume and presumably caldera-forming eruptions are identified, the younger of which took place at 100 ka. The volcanic products exposed in the BBTM area show that the volcanic field has undergone at least 20 explosive eruptions since then. The post-caldera eruptions have comenditic (Tullu Moye) and pantelleretic (Bora and Baricha) magma compositions. Other smaller edifices such as Oda and Dima also erupted pantelleritic magmas, and only differ slightly in composition than tephra of Bora and Baricha. Tullu Moye had two distinct explosive eruptions that dispersed tephra up to 14 km away and on to the eastern plateau. Bora and Baricha together had at least 8 explosive eruptions. Their deposits can be distinguished by their light grey color and unique lithic components. Oda had 7 eruptions, the most recent of which generated a pyroclastic density current that travelled up to 10 km away from the vent. Dima experienced at least 3 eruptions, generating tephra with a bluish-grey colour.&lt;/p&gt;&lt;p&gt;This mapping and compositional analysis of the deposits from the BBTM in the MER indicates that the region has been more active in the last 100 ka than previously thought, which has implications for hazards assessments for the region.&lt;/p&gt;

The Christiana–Santorini–Kolumbo Volcanic Field

Elements ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 171-176 ◽  
Author(s):  
Paraskevi Nomikou ◽  
Christian Hübscher ◽  
Steven Carey
Keyword(s):  
Eastern Mediterranean ◽  
Eastern Mediterranean Region ◽  
Aegean Sea ◽  
Volcanic Eruptions ◽  
Volcanic Field ◽  
Explosive Eruptions ◽  
Human Populations ◽  
Mass Wasting ◽  
Geological Processes ◽  
Research Activities

The Christiana–Santorini–Kolumbo volcanic field in the South Aegean Sea (Greece) is one of the most important in Europe, having produced more than 100 explosive eruptions in the last 400,000 years. Its volcanic centers include the extinct Christiana Volcano and associated seamounts, Santorini caldera with its intracaldera Kameni Volcano, Kolumbo Volcano, and 24 other submarine cones of the Kolumbo chain. Earthquakes, volcanic eruptions, submarine mass wasting, neotectonics and gas releases from these centers pose significant geohazards to human populations and infrastructures of the Eastern Mediterranean region. Defining the geological processes and structures that contribute to these geohazards will provide an important framework to guide future monitoring and research activities aimed at hazard mitigation.

Influence of the Bell-Jar Magma Chamber Geometry on a Caldera Formation

2016 ◽  
Vol 825 ◽  
pp. 165-169
Author(s):  
Michael Somr ◽  
Petr Kabele
Keyword(s):  
Numerical Modeling ◽  
Magma Chamber ◽  
Magmatic System ◽  
Caldera Formation

The formation of a caldera poses a serious risk for the society and the environment. There are several established processes (mostly dealing with the conditions inside the reservoir), which must take place in order to reach a collapse leading to the caldera. The role of magma chamber geometry is investigated in this paper, exploiting the numerical modeling. The results indicates that the knowledge of the magmatic system dimensions can provide a helpful factor for an assessment of the caldera formation scenario.

scholarly journals Modeling the Spatial Distribution of Three Typical Dominant Wetland Vegetation Species’ Response to the Hydrological Gradient in a Ramsar Wetland, Honghe National Nature Reserve, Northeast China

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2041
Author(s):  
Dandan Yan ◽  
Zhaoqing Luan ◽  
Dandan Xu ◽  
Yuanyuan Xue ◽  
Dan Shi
Keyword(s):  
Spatial Distribution ◽  
Water Level ◽  
Northeast China ◽  
Nature Reserve ◽  
Wetland Vegetation ◽  
Vegetation Communities ◽  
National Nature Reserve ◽  
Carex Lasiocarpa ◽  
Vegetation Species ◽  
Calamagrostis Angustifolia

Water level fluctuations resulting from natural and anthropogenic factors have been projected to affect the functions and structures of wetland vegetation communities. Therefore, it is important to assess the impact of the hydrological gradient on wetland vegetation. This paper presents a case study on the Honghe National Nature Reserve (HNNR) in the Sanjiang Plain, located in Northeast China. In this study, 210 plots from 18 sampling line transects were sampled in 2011, 2012, and 2014 along the hydrological gradient. Using a Gaussian logistic regression model, we determined a relationship between three wetland plant species and a hydrologic indicator—a combination of the water level and soil moisture—and then applied that relationship to simulate the distribution of plants across a larger landscape by the geographic information system (GIS). The results show that the optimum ecological amplitude of Calamagrostis angustifolia to the hydrological gradient based on the probability of occurrence model was [0.09, 0.41], that of Carex lasiocarpa was [0.35, 0.57], and that of Carex pseudocuraica was [0.49, 0.77]. The optimum of Calamagrostis angustifolia was 0.25, Carex lasiocarpa was 0.46, and Carex pseudocuraica was 0.63. Spatial distribution probability maps were generated, as were maps detailing the distribution of the most suitable habitats for wetland vegetation species. Finally, the model simulation results were verified, showing that this approach can be employed to provide an accurate simulation of the spatial distribution pattern of wetland vegetation communities. Importantly, this study suggests that it may be possible to predict the spatial distribution of different species from the hydrological gradient.

Electromagnetic characterization of epithermal gold deposits: A case study from the Tuoniuhe gold deposit, Northeast China

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. B49-B62 ◽  
Author(s):  
Shan Xu ◽  
Fengming Xu ◽  
Xiangyun Hu ◽  
Qun Zhu ◽  
Yuandong Zhao ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Northeast China ◽  
Depth Interval ◽  
Alteration Zone ◽  
Magnetic Survey ◽  
Depth Range ◽  
Epithermal Gold ◽  
Low Resistivity ◽  
Resistivity Model ◽  
Gold Bearing

A high-resolution electromagnetic study has helped to define the mineralization and alteration system of the Cretaceous volcano-sedimentary hosted epithermal gold (Au) deposit in Tuoniuhe, northeast China. Audio-magnetotelluric (AMT) array data were acquired to map the regional resistivity structure of the Mesozoic volcanic field, whereas an AMT profile and a ground magnetic survey line with denser site spacing were deployed across the deposit to image the alteration and mineralization system. The electrical resistivity model from 2D inversion of the AMT profile data reveals a low-resistivity (approximately [Formula: see text]) cover from the surface to a depth of 0.1 km, which is likely caused by clay and sulfide minerals in the subaerial alteration zone. The magnetic survey and a geologic borehole log assisted in outlining a zone of tonalite and andesite with silicification in the depth interval of 0.1–0.3 km, featuring high resistivity ([Formula: see text]) and high magnetization ([Formula: see text]). This zone is a potential gold target bounded by two channels of moderate resistivity (approximately [Formula: see text]) to its northwest and southeast. The two channels possibly coincide with breccia pipes with fractured stockworks and high permeability to allow gold-bearing fluids to move toward the surface. The 2D and 3D resistivity models reveal regions of low resistivity ([Formula: see text]) at the depth range of 0.5–1.0 km beneath the Cretaceous calderas and the deposit, which might be related to magmatic cryptoexplosion breccia. In the 2D resistivity model, this magmatic cryptoexplosion breccia zone connects to the subaerial alteration zone through the two breccia pipes, indicative of a circulation system of gold-bearing fluids. Given the coincidence of Cretaceous volcanism and the age of mineralization, the Cretaceous magma is inferred to have supplied heat that drove the convective hydrothermal activity and also was a source of magmatic fluids that led to the development of the Tuoniuhe epithermal gold deposit.

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