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Magnetotelluric Study of the Hangai Dome, Mongolia: Phase I

Surface deformation in the continental interior, away from active tectonic margins, is enigmatic, with the underlying mechanisms responsible not fully understood. Therefore, it is considered an open and important question in continental dynamics. The Hangai Dome, central Mongolia, is a natural laboratory to explore this question. It is a high-elevation, low-relief, intra-continental region within the Mongolian plateau. It is located between the Siberian and North China cratons and lies within the Central Asian Orogenic Belt. Central Mongolia has a complex tectonic history that is not well understood. It consists of several lithotectonic units that have influenced the formation and development of the region. The Hangai region has a long history of volcanic activity, including Cenozoic episodes of intraplate volcanism, which occurred as recently as the Holocene. It is characterized by dispersed, low-volume, alkali basaltic volcanism. Furthermore, major fault systems bound the Hangai region and large parts of central Mongolia. The processes and driving mechanisms responsible for creating the Hangai region remain largely unexplained. Therefore, we aim to collect high-resolution magnetotelluric data to image the electrical conductivity structure of the crust and upper mantle beneath the Hangai Dome in order to better understand the mechanisms responsible for intracontinental uplift and intraplate volcanism in this unique region. To achieve this objective a project was created, titled “Crust-mantle interactions beneath the Hangai Mountains in western Mongolia - Insights from 3-D magnetotelluric studies and 4-D thermo-mechanical modelling”. The first phase of the project was completed in 2016. Magnetotelluric data were recorded across the Hangai Dome in a grid (~400 by ~200 km), with a nominal site spacing of 50 km. Broadband measurements were acquired at each grid node and, additionally, long period measurements were acquired along two profiles. This data report provides details on the data collection, the measurement site locations, the instrumentation, and the data format. This data publication (https://doi.org/10.5880/GIPP-MT.201613.1) encompasses a detailed report in pdf format with a description of the project, information on the experimental setup, data collection, instrumentation used, recording configuration and data quality. The folder structure and content of the data repository are described in detail in Ritter et al. (2019). Time-series data are provided in EMERALD format (Ritter et al., 2015).

Long-period magnetotelluric data collected on the north-east Greenland Ice Sheet, 2019

The goal of MAGPIE is to improve estimates of present-day ice melting rates in Greenland by accurately correcting observed uplift rates for glacial isostatic adjustment (GIA) from past deglaciation. A key parameter required for constraining uplift rates for GIA is mantle viscosity, which can best be calculated from combined seismic and MT measurements. The data in this repository represent the first year of MAGPIE data collection. This data publication (10.5880/GIPP-MT.201913.1) encompasses a detailed report in pdf format with a description of the project, information on the experimental setup, data collection, instrumentation used, recording configuration and data quality. The folder structure and content of the data repository are described in detail in Ritter et al. (2019). Time-series data are provided in EMERALD format (Ritter et al., 2015).

Geophysical imaging of subsurface properties and magnetostratigraphy of sedimentary records

The Roter Kamm Crater is a 3.7-million-year-old meteoritic impact crater in the Sperrgebiet National Park in southern Namibia. The Sperrgebiet National Park, officially Tsau ǁKhaeb (Sperrgebiet) National Park, is a national park and former diamond mining area in southern Namibia. Since 1908 the public has had no access to the area and even when it was proclaimed a national park in 2008 most of the restrictions remained, leaving the environment mainly undisturbed and unexplored. The geophysical exploration of the Roter Kamm Crater can bring valuable information about its internal structure, as only a very limited number of geophysical studies had been carried out at this site. Prior gravimetry and (airborne-)magnetic measurements indicate a bowl-shaped anomaly underneath the crater with an estimated maximum sedimentary thickness of 400 m or higher. To be able to image the the crater infill appropriatly, two electromagnetic methods were applied: the Transient Electromagnetic (TEM) and the Audiomagnetotelluric (AMT) method. The AMT data set was planned as a complementary data set to the more extensive TEM data set to ensure the imaging of the lower boundary of the sedimentary infill. This data publication (10.5880/GIPP-MT.202127.1) encompasses a detailed report in pdf format with a description of the project, information on the experimental setup, data collection, instrumentation used, recording configuration and data quality. The folder structure and content of the data repository are described in detail in Ritter et al. (2019). Time-series data are provided in EMERALD format (Ritter et al., 2015).

Magnetotelluric Study of the Hangai Dome, Mongolia: Phase II

Surface deformation in the continental interior, away from active tectonic margins, is enigmatic, with the underlying mechanisms responsible not fully understood. Therefore, it is considered an open and important question in continental dynamics. The Hangai Dome, central Mongolia, is an ideal location to explore this because it is a high-elevation, low-relief, intra-continental region within the Mongolian plateau, between the Siberian and North China cratons, and within the Central Asian Orogenic Belt. The tectonic history of Central Mongolia is not well understood. It consists of several lithotectonic units that have influenced the formation and development of the region. The Hangai region has had intraplate volcanism throughout the Cenozoic, including as recently as the Holocene, in addition to older Mesozoic volcanic activity. It is characterized by dispersed, low-volume, alkali basaltic volcanism. Furthermore, major shear fault systems bound the Hangai region and central Mongolia. Our objective is to collect high-resolution magnetotelluric data to image the electrical resistivity structure of the crust and upper mantle beneath the Hangai Dome in order to better understand the processes and mechanisms responsible for intracontinental uplift and intraplate volcanism in this unique region, helping shed light on the Hangai region. Building on the successful first phase of the project (2016), a second phase was completed in 2017. We expanded our magnetotelluric measurement array: to the west along four new profiles; to the south, across the Gobi-Altai mountains; to the north, across the Bulnay fault segments; filling in the previous profiles for denser site spacing. This new grid of data is ~650 km long and ~400 km wide, with a nominal site spacing of 50 km for broadband measurements. In addition, we completed a small profile across the Tariat/Khorgo region and a reconnaissance profile in Zavkhan. This data report provides details on the data collection, the measurement site locations, the instrumentation, and the data format. This data publication (10.5880/GIPP-MT.201706.1) encompasses a detailed report in pdf format with a description of the project, information on the experimental setup, data collection, instrumentation used, recording configuration and data quality. The folder structure and content of the data repository are described in detail in Ritter et al. (2019). Time-series data are provided in EMERALD format (Ritter et al., 2015).

PCEEJ Equatorial Electrojet Model data for years 2003-2010 and 2014-2018

This dataset comprises the PCEEJ equatorial electrojet model current intensity values (mA/m). The PCEEJ is an empirical model based on the principal component analysis of satellite and ground equatorial electrojet data, described in detail in Soares et al. (2022), to which this data publication is supplement to. The model data is provided as text files (.csv extension) and Matlab-formatted files (.mat extension). For text files, there is one file per year (file name labeled with the corresponding year). For the Matlab format, there is only one Matlab file that contains all years as separate variables (variable name labeled with the corresponding year). Each yearly file/variable corresponds to a matrix: the rows represent local time/longitude bins and the columns represent days of year. The local time/longitude bins (rows) always sum up to 432 (12 local time intervals and 36 longitude intervals). The day of year (columns) always starts in January 1st and ends in December 31st, leading to a total of 365 or 366. The PCEEJ model values of 13 years from 2003 to 2010 and from 2014 to 2018 are provided. The PCEEJ basis functions (principal components) are provided in the text and Matlab files labeled as ‘PC_Functions’. The ‘PC_Functions’ data is given as a 432x10 matrix, in which 432 stands for the aforementioned local time/longitude bins and 10 represents the 10 principal components used to obtain the PCEEJ model (in ascending order). Two additional auxiliary indices, namely ‘lt_index’ and ‘lon_index’ are also contained as text and Matlab files. These indices represent the corresponding local time and longitude values of each row of the PCEEJ yearly files and ‘PC_Functions’ files.

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