Magnetotelluric Imaging of the Zhangzhou Basin Geothermal Zone, Southeastern China

The geothermal zone of southeast China, which is one of the country’s known geothermal zones, contains significant natural geothermal resources. To understand the formation of geothermal resources, a magnetotelluric (MT) investigation with a site spacing of 1–2 km was carried out around the Zhangzhou Basin. The recorded MT data were processed by robust time series and remote reference processing techniques. The data analysis results revealed that two-dimensional (2-D) modeling can be used to approximately determine the electrical structure. The joint inversions of TE and TM modes have been performed after distortion decomposition. In the inversion models, a low resistivity cap of 200–800 m thickness was observed, which represented the blanketing sediments composed of Quaternary and volcanic rocks of the late Jurassic period. The presence of high resistivity above a depth of 20 km indicates the granites are widely developed in the upper and middle crust. MT measurements have revealed some deep-seated high conductive zones, which were inferred to be partially melting at depth of 8–17 km, which is likely to be reason behind the formation of higher-temperature hot springs. The results also show that there is a shallower Moho, which indicates that the heat from the upper mantle may have a big contribution to the surface heat flow. Fractures-controlled meteoric fluid circulation is the most likely explanation for the hot springs.

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Nisyros Volcanic Island: A Geosite through a Tailored GIS Story

Geosciences ◽

10.3390/geosciences11030132 ◽

2021 ◽

Vol 11 (3) ◽

pp. 132

Author(s):

Varvara Antoniou ◽

Paraskevi Nomikou ◽

Dimitrios Panousis ◽

Effrosyni Zafeirakopoulou

Keyword(s):

Spatial Data ◽

Hot Springs ◽

Volcanic Rocks ◽

Data Communication ◽

Aegean Sea ◽

Volcanic Island ◽

Eastern Aegean ◽

Strongly Connected ◽

Historical Heritage ◽

Available Information

The volcanic island of Nisyros (Greece) is here presented as it presents unique characteristics being a Quaternary volcano in the eastern Aegean Sea, composed of volcanic rocks, and featuring a central caldera that is surrounded by volcanic domes and thick lavas. Its history is strongly connected to the volcano impressing the visitors with steaming hydrothermal craters, intensive smell of sulfur and fumarolic gases, and hot springs. Due to its morphology and geographical position, its cultural and historical heritage has been unchanged in time, bequeath to the island plenty of churches, monasteries with hagiographic frescoes, castles, caves, and spas. To present the geodiversity, the cultural environment, and the biodiversity of this geosite, a relatively new geographic approach was used, ESRI Story Maps. Being web-based applications, they are widespread as an interactive responsive tool used for spatial data communication and dissemination, by combining thematic 2D and 3D webmaps, narrative text, and multimedia content. Such applications can be an ideal way for presenting the available information of places characterized as geosites or protected areas worldwide, providing quick access to the available information to a broader, non-technical audience, developing the interest, and possibly motivating the public to learn more or visit them.

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Phase equilibria in NaAlSiO4–KAlSiO4–SiO2–H2O at 100 MPa pressure: equilibrium leucite composition and the enigma of primary analcime in blairmorites revisited

Mineralogical Magazine ◽

10.1180/minmag.2014.078.1.13 ◽

2014 ◽

Vol 78 (1) ◽

pp. 171-202 ◽

Cited By ~ 6

Author(s):

C. M. B. Henderson ◽

D. L. Hamilton ◽

J. P. Waters

Keyword(s):

Mineral Assemblage ◽

Volcanic Rocks ◽

Stoichiometric Composition ◽

Pressure Equilibrium ◽

Upward Transport ◽

Higher Temperature ◽

Invariant Points ◽

Water Saturated ◽

Low K ◽

Maximum Content

AbstractExperiments in the system NaAlSiO4(Ne)−KAlSiO4(Ks)−SiO2(Qz)−H2O at 100 MPa show that the maximum content of NaAlSi2O6 in leucite is ∼4 wt.% and that analcime is close to the stoichiometric composition (NaAlSi2O6.H2O). Analcime forms metastably on quenching the higher-temperature experiments; it is secondary after leucite in experiments quenched from 780°C, while from 850°C it forms by alteration of leucite, and by devitrification of water-saturated glass. Both processes involve reaction with Na-rich aqueous fluids. Stable analcime forms at 500°C, well below the solidus, and cannot form as phenocrysts in shallow volcanic systems. New data for natural analcime macrocrysts in blairmorites are presented for the Crowsnest volcanics, Alberta, Canada. Other researchers have suggested that primary analcime occurs as yellow-brown, glassy, analcime phenocrysts. Our microprobe analyses show that such primary analcime is close to stoichiometric, with very low K2O (<0.1 wt.%), minor Fe2O3 (0.5−0.8 wt.%) and CaO (∼0.5 wt.%). An extrapolation of published experimental data for Ne−Ks−Qz at >500 MPa PH2O, where Anl + melt coexist, suggests that at >800 MPa two invariant points are present: (1) a reaction point involving Kf + Ab + Anl + melt + vapour; and (2) a eutectic with Kf + Anl + Ne + melt + vapour. We suggest that the nepheline-free equilibrium mineral assemblage for Crowsnest samples is controlled by reaction point (1). In contrast, blairmorites from Lupata Gorge, Mozambique, form at eutectic (2), consistent with the presence of nepheline phenocrysts. Our conclusions, based on high- vs. low-pressure experiments, confirm the suggestion made by other authors, that Crowsnest volcanic rocks must have been erupted explosively to preserve glassy analcime phenocrysts during very rapid, upward transport from deep in the crust (H2O pressures ≫500 MPa). Only rare examples survived the deuteric and hydrothermal alteration that occurred during and after eruption.

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INTERACTION: INTeraction between lifE, Rifting And Caldera Tectonics In OkataiNa

10.5194/egusphere-egu21-1904 ◽

2021 ◽

Author(s):

Cécile Massiot ◽

Craig Miller ◽

Matthew Stott ◽

Pilar Villamor ◽

Hiroshi Asanuma ◽

...

Keyword(s):

Hot Springs ◽

Microbial Community Composition ◽

Volcanic Eruptions ◽

Economic Benefits ◽

Hydrothermal Systems ◽

Seismic Hazards ◽

Geothermal Resources ◽

Ongoing Research ◽

Scientific Drilling ◽

Drill Cores

Calderas are major volcanic features with large volcanic and seismic hazards. They also host diverse microbiota, provide heat, energy, mineral and economic benefits. Despite their scientific and socio-economic importance, we still do not completely understand calderas and the interactions between volcanism, tectonism, fluid circulation and the deep biosphere because in-situ and subsurface observations are sparse.The Okataina Volcanic Centre (OVC) in Aotearoa New Zealand, is one of two active giant calderas of the Taup&#333; Volcanic Zone within the rapidly extending continental intra-arc Taup&#333; Rift. This superb natural laboratory has: 1) numerous past eruptions of varied size and style, 2) documented co-eruptive earthquakes, 3) vigorous hydrothermal manifestations, 4) diverse microbial communities in hot springs but unknown in the subsurface.We propose to establish a scientific drilling programme at the OVC to address:<ul><li>What are the conditions leading to volcanic eruptions; and volcano-tectonic feedbacks in intra-rift calderas?</li> <li>What controls fluid circulations in active calderas/rift regions?</li> <li>Does subsurface microbial community composition vary with tectonic and/or volcanic activity?</li> </ul>High temperatures complicate drillhole design, restrict data collection and prevent exploration of the biosphere. By targeting the cooler parts of the caldera, this project will use conventional engineering to maximise sampling (drill cores and fluids), downhole logging and establish long-term observatories.Two preliminary drill targets are suggested: (1) in the centre of the caldera; (2) through the caldera margin. Drill data will provide a comprehensive record of past activity, establishing eruption frequency-magnitude relationships and precursors. Combined with well-known fault rupture history, the relative timing of tectonic and magmatic activity will be untangled. Drill data will unravel the relationships between the groundwater and hydrothermal systems, magma, faults and stress, informing thermo-hydro-mechanical regional caldera models with findings applicable worldwide. Drill cores and a dedicated fluid sampler triggered by nearby earthquakes will reveal the composition, function and potential change of microbial activity in response to rock and fluid variations.The programme is informed by indigenous M&#257;ori, regulatory authorities and emergency managers to ensure scientific, cultural, regulatory and resilience outcomes. The programme will underpin 1) community resilience to volcanic and seismic hazards; 2) sustainable management of groundwater and geothermal resources, and 3) understanding of subsurface microbial diversity, function and geobiological interactions. At these early stages of planning, we invite the scientific community to contribute to the concept of this project in the exceptional OVC settings and strengthen linkages with other ongoing research and scientific drilling programmes.

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Detection of a thin layer by seismic reflection with different geophones at a site in Liangzhu, Southeastern China

Arabian Journal of Geosciences ◽

10.1007/s12517-019-4778-1 ◽

2019 ◽

Vol 12 (24) ◽

Author(s):

Abdullah Lizan ◽

Gang Tian ◽

Yimin Wang ◽

Ran Chen ◽

Shahid Shaihk ◽

...

Keyword(s):

Thin Layer ◽

Seismic Reflection ◽

Southeastern China ◽

A Site

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First surface-based estimation of the aerosol indirect effect over a site in southeastern China

Advances in Atmospheric Sciences ◽

10.1007/s00376-017-7106-2 ◽

2018 ◽

Vol 35 (2) ◽

pp. 169-181 ◽

Cited By ~ 6

Author(s):

Jianjun Liu ◽

Zhanqing Li

Keyword(s):

Indirect Effect ◽

Southeastern China ◽

Aerosol Indirect Effect ◽

A Site

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Determination of Hydrothermal Prospects in Paipa Geothermal Region (Boyacá, Colombia) Using Remote Sensing and Field Data

Earth Sciences Research Journal ◽

10.15446/esrj.v23n4.77810 ◽

2019 ◽

Vol 23 (4) ◽

pp. 265-282

Author(s):

Rafael Andrés Calderón-Chaparro ◽

German Vargas-Cuervo

Keyword(s):

Remote Sensing ◽

Soil Temperature ◽

Field Data ◽

Hot Springs ◽

Landsat 8 ◽

Geothermal Resources ◽

Temperature Index ◽

Landsat 7 ◽

Geothermal Region

Geothermal resources (e.g. hot springs) are found with the help of field techniques, such as geological, geochemistry and geophysical. These techniques in some occasions are difficult to apply because of the limit access to the research area, rising operational costs and constrained spatially the exploration areas. The thermal infrared (TIR) remote sensing is an important tool for the exploration of geothermal resources, due to the low cost and high efficiency in the study of large geographic areas. The aim of this study is to use thermal imagery of satellite remote sensing and combined with geological-geophysical data, for spatial determination of exploratory prospects of hot springs in the geothermal region of Paipa, Boyacá. The images used in this study are from satellites Landsat-7 ETM+, Landsat-8 OLI/TIRS, MODIS, ALOS-PALSAR and Pléiades. Also, field data is used, such as soil temperature, surface temperature, air temperature, relative humidity, atmospheric pressure and thermal imagery of surface geothermal manifestations. The Landsat thermal bands were radiometrically calibrated, then atmospherically and surface emissivity corrected, applying single channel and split window algorithms, for Landsat-7 ETM+ and Landsat-8 TIRS, respectively. The field data helped to correct the thermal bands. And the soil temperature data are used to create a subsurface temperature map at 1-meter depth. Once primary and secondary data is had, in a geographic information system (GIS) is implemented an unweighted spatial model, which use four input indicators (satellite temperature index, soil temperature index, structural lineaments index and iso-resistivity index) to determine the areas with higher probability to find geothermal fluids. Six prospects are highlighted for hydrothermal fluid extraction, in which two of them are already known. Results allow to concluded that thermal remote sensing are useful to map geothermal anomalies in the Paipa region, and by using these anomalies plus geological-geophysical information is possible to determine exact exploration areas.

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