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

10.1130/geol.s.12331124 ◽

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>

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

Geology ◽

10.1130/g47531.1 ◽

2020 ◽

Vol 48 (9) ◽

pp. 913-918 ◽

Cited By ~ 1

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.

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Magnetotelluric Imaging of Subsurface Structure in Rahat Volcanic Field, Madinah City (Saudi Arabia)

On Significant Applications of Geophysical Methods - Advances in Science, Technology & Innovation ◽

10.1007/978-3-030-01656-2_20 ◽

2019 ◽

pp. 89-92

Author(s):

Essam Aboud ◽

Peter Wameyo ◽

Faisal Alqahtani ◽

Mohammed Rashad Moufti

Keyword(s):

Saudi Arabia ◽

Volcanic Field ◽

Subsurface Structure ◽

Magnetotelluric Imaging

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Electrical conductivity of shoshonitic melts with application to magma reservoir beneath the Wudalianchi volcanic field, northeast China

Physics of The Earth and Planetary Interiors ◽

10.1016/j.pepi.2020.106545 ◽

2020 ◽

Vol 306 ◽

pp. 106545

Author(s):

Bin Li ◽

Li Zhang ◽

Xuan Guo ◽

Wan-Cai Li ◽

Huaiwei Ni

Keyword(s):

Electrical Conductivity ◽

Northeast China ◽

Volcanic Field ◽

Magma Reservoir

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

Geophysics ◽

10.1190/geo2018-0876.1 ◽

2020 ◽

Vol 85 (3) ◽

pp. B49-B62 ◽

Cited By ~ 2

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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The first tephra evidence for a Late Glacial explosive volcanic eruption in the Arxan-Chaihe volcanic field (ACVF), northeast China

Quaternary Geochronology ◽

10.1016/j.quageo.2016.10.003 ◽

2017 ◽

Vol 40 ◽

pp. 109-119 ◽

Cited By ~ 7

Author(s):

Chunqing Sun ◽

Qiang Liu ◽

Jing Wu ◽

Károly Németh ◽

Luo Wang ◽

...

Keyword(s):

Volcanic Eruption ◽

Northeast China ◽

Late Glacial ◽

Volcanic Field ◽

Explosive Volcanic Eruption

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Imaging the magmatic system beneath the Krafla geothermal field, Iceland: A new 3-D electrical resistivity model from inversion of magnetotelluric data

Geophysical Journal International ◽

10.1093/gji/ggz427 ◽

2019 ◽

Vol 220 (1) ◽

pp. 541-567 ◽

Cited By ~ 4

Author(s):

Benjamin Lee ◽

Martyn Unsworth ◽

Knútur Árnason ◽

Darcy Cordell

Keyword(s):

Electrical Resistivity ◽

Volcanic Field ◽

Geothermal Field ◽

Fault System ◽

Impedance Tensor ◽

Magnetotelluric Data ◽

Near Surface ◽

Low Resistivity ◽

Rhyolite Magma ◽

Resistivity Model

SUMMARY Krafla is an active volcanic field and a high-temperature geothermal system in northeast Iceland. As part of a program to produce more energy from higher temperature wells, the IDDP-1 well was drilled in 2009 to reach supercritical fluid conditions below the Krafla geothermal field. However, drilling ended prematurely when the well unexpectedly encountered rhyolite magma at a depth of 2.1 km. In this paper we re-examine the magnetotelluric (MT) data that were used to model the electrical resistivity structure at Krafla. We present a new 3-D resistivity model that differs from previous inversions due to (1) using the full impedance tensor data and (2) a finely discretized mesh with horizontal cell dimensions of 100 m by 100 m. We obtained similar resistivity models from using two different prior models: a uniform half-space, and a previously published 1-D resistivity model. Our model contains a near-surface resistive layer of unaltered basalt and a low resistivity layer of hydrothermal alteration (C1). A resistive region (R1) at 1 to 2 km depth corresponds to chlorite-epidote alteration minerals that are stable at temperatures of about 220 to 500 °C. A low resistivity feature (C2) coincides with the Hveragil fault system, a zone of increased permeability allowing interaction of aquifer fluids with magmatic fluids and gases. Our model contains a large, low resistivity zone (C3) below the northern half of the Krafla volcanic field that domes upward to a depth of about 1.6 km b.s.l. C3 is partially coincident with reported low S-wave velocity zones which could be due to partial melt or aqueous fluids. The low resistivity could also be attributed to dehydration and decomposition of chlorite and epidote that occurs above 500 °C. As opposed to previously published resistivity models, our resistivity model shows that IDDP-1 encountered rhyolite magma near the upper edge of C3, where it intersects C2. In order to assess the sensitivity of the MT data to melt at the bottom of IDDP-1, we added hypothetical magma bodies with resistivities of 0.1 to 30 Ωm to our resistivity model and compared the synthetic MT data to the original inversion response. We used two methods to compare the MT data fit: (1) the change in r.m.s. misfit and (2) an asymptotic p-value obtained from the Kolmogorov–Smirnov (K–S) statistical test on the two sets of data residuals. We determined that the MT data can only detect sills that are unrealistically large (2.25 km3) with very low resistivities (0.1 or 0.3 Ωm). Smaller magma bodies (0.125 and 1 km3) were not detected; thus the MT data are not sensitive to small rhyolite magma bodies near the bottom of IDDP-1. Our tests gave similar results when evaluating the changes in r.m.s. misfit and the K–S test p-values, but the K–S test is a more objective method than appraising a relative change in r.m.s. misfit. Our resistivity model and resolution tests are consistent with the idea of rhyolite melt forming by re-melting of hydrothermally altered basalt on the edges of a deeper magma body.

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Tephra evidence for the most recent eruption of Laoheishan volcano, Wudalianchi volcanic field, northeast China

Journal of Volcanology and Geothermal Research ◽

10.1016/j.jvolgeores.2018.03.014 ◽

2019 ◽

Vol 383 ◽

pp. 103-111 ◽

Cited By ~ 1

Author(s):

Chunqing Sun ◽

Károly Németh ◽

Tao Zhan ◽

Haitao You ◽

Guoqiang Chu ◽

...

Keyword(s):

Northeast China ◽

Volcanic Field ◽

Recent Eruption

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Teleseismic Tomography for Imaging the Upper Mantle Beneath Northeast China

Applied Sciences ◽

10.3390/app10134557 ◽

2020 ◽

Vol 10 (13) ◽

pp. 4557

Author(s):

Zhuo Jia ◽

Gongbo Zhang

Keyword(s):

Travel Time ◽

Transition Zone ◽

Upper Mantle ◽

Northeast China ◽

Time Data ◽

Low Velocity ◽

Mantle Transition Zone ◽

Teleseismic Tomography ◽

Travel Time Data ◽

Velocity Anomalies

Tomographic imaging technology is a geophysical inversion method. According to the ray scanning, this method carries on the inversion calculation to the obtained information, and reconstructs the image of the parameter distribution rule of elastic wave and electromagnetic wave in the measured range, so as to delineate the structure of the geological body. In this paper, teleseismic tomography is applied by using seismic travel time data to constrain layered crustal structure where Fast Marching Methods (FMM) and the subspace method are considered as forward and inverse methods, respectively. Based on the travel time data picked up from seismic waveform data in the study region, the P-wave velocity structure beneath Northeast China down to 750 km is obtained. It can be seen that there are low-velocity anomalies penetrating the mantle transition zone under the Changbai volcano group, Jingpohu Volcano, and Arshan Volcano, and these low-velocity anomalies extend to the shallow part. In this paper, it is suggested that the Cenozoic volcanoes in Northeast China were heated by the heat source provided by the dehydration of the subducted Pacific plate and the upwelling of geothermal matter in the lower mantle. The low-velocity anomaly in the north Songliao basin does not penetrate the mantle transition zone, which may be related to mantle convection and basin delamination. According to the low-velocity anomalies widely distributed in the upper mantle and the low-velocity bodies passing through the mantle transition zone beneath the volcanoes, this study suggests that the Cenozoic volcanoes in Northeast China are kindred and have a common formation mechanism.

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