scholarly journals Geochemical Mapping of Sulfur Within Olkaria Geothermal Field, Kenya

2020 ◽  
pp. 55-61
Author(s):  
Muhanga Joel Joseph ◽  
Sang Paul K. Magut ◽  
Onyancha Douglas Okerio
Keyword(s):  
Chemical Species ◽  
Secondary Data ◽  
Ring Structure ◽  
Geothermal Field ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Geochemical Mapping ◽  
Production Wells ◽  
Correlation Parameters ◽  
Different Color

This research paper focuses on the geochemical mapping of Sulfur to characterize the Olkaria geothermal field, a field associated with geothermal power generation in the northeast of Nairobi. The current geochemical methods used are CO<sub>2</sub> and N<sub>2</sub> however, a discrepancy associated with the biogenic sources of CO<sub>2</sub> renders it less reliable. Sulfur in geothermal systems is magmatic, hence its utilization can help solve these discrepancies. The study utilized sulfur present in the geothermal well waters to identify the main features of a magmatic hydrothermal system, their distribution within the Olkaria volcanic complex and how they relate with the Olkaria structures. Secondary data of the concentrations of H<sub>2</sub>S and SO<sub>4 </sub><sup>2-</sup> was used for mapping using ArcMap tool within ArcGIS. The distribution of the magmatic H<sub>2</sub>S facilitated the mapping of the possible up-flow zones and the heat sources within the study area. SO<sub>4 </sub><sup>2-</sup> was used to map possible recharge zones within the study area. The mappings, that is, the up-flow zones, the heat source and the recharge zones are important, because they increase knowledge on where exactly to drill production wells, make up wells and the reinjection wells. Geochemical mapping performed on other fluid chemical species such as CO<sub>2</sub>, Cl<sup>-</sup>, N<sub>2</sub>, as well as the temperature, facilitated the correlation with the sulfur concentration variations. The distribution of various concentrations of sulfur as well as the correlation parameters were shown by different color scales on the geochemical maps. From the maps, the field-scale distributions, enabled the visualization of which faults establish the fluid ascension areas and which are more closely related to recharge zones. The findings indicate that up-flow zones were affiliated to the NW-SE trending faults as well as the Olkaria Fault while the recharge zones were associated with the Gorge farm fault, the ring structure and the Ololbutot fault. Geochemical mapping of Sulfur proved to be an effective method in the characterization of a geothermal field. Its utilization to complement conventional methods, improves precision for well siting. It should therefore, not be ignored during exploration campaign.<

scholarly journals The Hydrothermal Alteration of the Cordón de Inacaliri Volcanic Complex in the Framework of the Hidden Geothermal Systems within the Pabelloncito Graben (Northern Chile)

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1279
Author(s):  
Santiago Nicolás Maza ◽  
Gilda Collo ◽  
Diego Morata ◽  
Carolina Cuña-Rodriguez ◽  
Marco Taussi ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Geothermal Field ◽  
Geothermal System ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Acid Sulfate ◽  
Alteration Zones ◽  
Geological Processes ◽  
Freshwater Bodies ◽  
Hydrothermal Alteration Zones

Detailed mineralogical analyses in areas with surface hydrothermal alteration zones associated with recent volcanism (<1 Ma) in the Central Andean Volcanic Zone could provide key information to unravel the presence of hidden geothermal systems. In the Cordón de Inacaliri Volcanic Complex, a geothermal field with an estimated potential of ~1.08 MWe·km−2 has been recently discovered. In this work, we focus on the hydrothermal alteration zones and discharge products of this area, with the aim to reconstruct the geological processes responsible for the space-time evolution leading to the geothermal records. We identified (1) discharge products associated with acid fluids that could be related to: (i) acid-sulfate alteration with alunite + kaolinite + opal CT + anatase, indicating the presence of a steam-heated blanket with massive fine-grained silica (opal-CT), likely accumulated in mud pots where the intersection of the paleowater table with the surface occurred; (ii) argillic alteration with kaolinite + hematite + halloysite + smectite + I/S + illite in the surrounding of the acid-sulfate alteration; and (2) discharge products associated with neutral-alkaline fluids such as: (i) discontinuous pinnacle-like silica and silica deposits with laterally developed coarse stratification which, together with remaining microorganisms, emphasize a sinter deposit associated with alkaline/freshwater/brackish alkaline-chlorine water bodies and laterally associated with (ii) calcite + aragonite deriving from bicarbonate waters. The scarce presence of relics of sinter deposits, with high degree crystallinity phases and diatom remnants, in addition to alunite + kaolinite + opal CT + anatase assemblages, is consistent with a superimposition of a steam-heated environment to a previous sinter deposit. These characters are also a distinguishing feature of paleosurface deposits associated with the geothermal system of the Cordón de Inacaliri Volcanic Complex. The presence of diatoms in heated freshwater bodies at 5100 m a.s.l. in the Atacama Desert environment could be related with the last documented deglaciation in the area (~20–10 ka), an important factor in the recharge of the hidden geothermal systems of the Pabelloncito graben.

scholarly journals Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 125-159 ◽  
Author(s):  
Federico Lucci ◽  
Gerardo Carrasco-Núñez ◽  
Federico Rossetti ◽  
Thomas Theye ◽  
John Charles White ◽  
...  
Keyword(s):  
Volcanic Belt ◽  
Mineral Chemistry ◽  
Geothermal Field ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Plumbing System ◽  
Geothermal Fields ◽  
Plumbing Systems ◽  
Magmatic Plumbing System ◽  
Deep Depth

Abstract. Understanding the anatomy of magma plumbing systems of active volcanoes is essential not only for unraveling magma dynamics and eruptive behaviors but also to define the geometry, depth, and temperature of the heat sources for geothermal exploration. The Pleistocene–Holocene Los Humeros volcanic complex is part of the eastern Trans-Mexican Volcanic Belt (central Mexico), and it constitutes one of the most important exploited geothermal fields in Mexico with ca. 90 MW of produced electricity. With the aim to decipher the anatomy (geometry and structure) of the magmatic plumbing system feeding the geothermal field at Los Humeros, we carried out a field-based petrological and thermobarometric study of the exposed Holocene lavas. Textural analysis, whole-rock major-element data, and mineral chemistry are integrated with a suite of mineral-liquid thermobarometric models. Our results support a scenario characterized by a heterogeneous multilayered system, comprising a deep (depth of ca. 30 km) basaltic reservoir feeding progressively shallower and smaller discrete magma stagnation layers and batches, up to shallow-crust conditions (depth of ca. 3 km). The evolution of melts in the feeding system is mainly controlled by differentiation processes through fractional crystallization (plagioclase + clinopyroxene + olivine + spinel). We demonstrate the inadequacy of the existing conceptual models, where a single voluminous melt-controlled magma chamber (or “Standard Model”) at shallow depths was proposed for the magmatic plumbing system at Los Humeros. We instead propose a magmatic plumbing system made of multiple, more or less interconnected, magma transport and storage layers within the crust, feeding small (ephemeral) magma chambers at shallow-crustal conditions. This revised scenario provides a new configuration of the heat source feeding the geothermal reservoir at Los Humeros, and it should be taken into account to drive future exploration and exploitation strategies.

scholarly journals Local earthquake tomography at the Los Humeros geothermal field, Mexico

2020 ◽  
Author(s):  
Tania Toledo ◽  
Philippe Jousset ◽  
Emmanuel Gaucher ◽  
Hansruedi Maurer ◽  
Charlotte Krawzcyzk ◽  
...  
Keyword(s):  
Joint Inversion ◽  
Detection Algorithm ◽  
Geothermal Field ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
The European Union ◽  
Injection Wells ◽  
Geothermal Resources ◽  
Seismic Stations ◽  
Horizon 2020

&lt;p&gt;The GEMex&lt;sup&gt;*&lt;/sup&gt; project is a recently finalized European-Mexican collaboration that aimed to improve the understanding of two geothermal fields: Acoculco and Los Humeros Volcanic Complex . These sites are located in the Trans-Mexican Volcanic Belt, a region that hosts numerous active volcanoes and is favorable for geothermal exploitation. Currently, the &amp;#160;Los Humeros Volcanic Complex is one of Mexico&amp;#8217;s main geothermal systems with an installed capacity of ~95MW. Many studies have been performed at this site since the 70s highlighting several features and characteristics of the shallow subsurface. However a thorough knowledge of structures and behavior of the system at greater depths is still quite sparse. Hence one main objective of the GEMex project was to conduct several geological, geochemical, and geophysical experiments to investigate deeper structures for future development of local and regional geothermal resources.&lt;/p&gt;&lt;p&gt;In this framework, for the period of one year (September 2017 to September 2018), a seismic array consisting of 45 seismic stations was set to record continuously at the Los Humeros Volcanic Complex. In this study we analyzed the continuous seismic records to detect the micro-seismicity mainly related to exploitation activities. After applying a recursive STA/LTA detection algorithm, we assembled and manually picked P- and S- phases of a catalog of about 500 local events. The detected events were mostly clustered around injection wells, with fewer events located close to known structures. We use the retrieved catalog to derive a new minimum 1D velocity model for the Los Humeros site. We then performed a joint inversion to obtain the 3D Vp and Vp/Vs structures of the geothermal field. A post-processing averaging of several inversions was also computed to increase resolution of the investigated region. In this study we will show the derived Vp and Vp/Vs models for the &amp;#160;Los Humeros Volcanic Complex to emphasize various underground structures and potentially identify possible variations due to changes in temperature, fluid content, and rock porosity.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;*This project has received funding from the European Union&amp;#8217;s Horizon 2020 research and innovation programme under grant agreement No. 727550 and the Mexican Energy Sustainability Fund CONACYT-SENER, project 2015-04-68074. We thank the Comisi&amp;#243;n Federal de Electricidad (CFE) for kindly granting the access to the geothermal field for installation and maintenance of seismic stations.&lt;/p&gt;

scholarly journals Methodology Applied for Thickness Selection and Stored Heat Evaluation in Non-producer Geothermal Wells in Order to Its Investment Rescue

2020 ◽  
pp. 91-111
Author(s):  
Alfonso Aragon- Aguilar ◽  
Georgina Izquierdo- Montalvo ◽  
Dominic A. Becerra- Serrato ◽  
Victor M. Monrroy- Mar
Keyword(s):  
Electric Energy ◽  
Geothermal Field ◽  
Geothermal Systems ◽  
Drainage Radius ◽  
Heterogeneous Behavior ◽  
Water Recharge ◽  
Geothermal Wells ◽  
Using Data ◽  
Heat Calculation ◽  
Heat Store

An assessment methodology of stored heat in rock formation surrounding to wellbore in geothermal systems is shown. Due to geothermal systems generally are nested in volcanic rock, it is characteristic its heterogeneous behavior. Proposed methodology starts since zone selection with possibilities of heat store. This methodology is focused to be applied in geothermal reservoirs with tendency to production decline, due to low permeability and unbalance between exploitation and water recharge. Because the high costs of drilling geothermal wells, methodology shown in this work is proposed to be applied in those with production decline or non-producers, in order to rescue its investment. The objective is to select the thickness with heat, evaluate its storage, design the appropriate instrumentation for its recovery, its energy conversion and rescue its investment done. The different designs for energy recovery using non-conventional methods to those, used habitually are reviewed. Each one of the variables for stored heat calculation was determined using technical tools of reservoir engineering. A parametric analysis about variables sensitivity (porosity and drainage radius) for determining thermal energy and corresponding electric energy of analyzed rock volume is done. Practical application of this methodology was carried out using data of one of wells of Los Humeros Mexican geothermal field.

scholarly journals Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

2019 ◽  
Author(s):  
Federico Lucci ◽  
Gerardo Carrasco-Núñez ◽  
Federico Rossetti ◽  
Thomas Theye ◽  
John C. White ◽  
...  
Keyword(s):  
Volcanic Belt ◽  
Mineral Chemistry ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Plumbing System ◽  
Geothermal Exploration ◽  
Geothermal Fields ◽  
Mexican Volcanic Belt ◽  
Plumbing Systems ◽  
Magmatic Plumbing System

Abstract. Understanding the anatomy of magma plumbing systems of active volcanoes is essential not only for unraveling magma dynamics and eruptive behaviors, but also to define the geometry, depth and temperature of the heat sources for geothermal exploration. The Pleistocene-Holocene Los Humeros volcanic complex is part of the Eastern Trans-Mexican Volcanic Belt (Central Mexico) and it represents one of the most important exploited geothermal fields in Mexico with ca. 90 MW of produced electricity. A field-based petrologic and thermobarometric study of lavas erupted during the Holocene (post-Caldera stage) has been performed with the aim to decipher the anatomy of the magmatic plumbing system existing beneath the caldera. New petrographical, whole rock major element data and mineral chemistry were integrated within a suite of inverse thermobarometric models. Compared with previous studies where a single voluminous melt-controlled magma chamber (or "Standard Model") at shallow depths was proposed, our results support a more complex and realistic scenario characterized by a heterogeneous multilayered system comprising a deep (ca. 30 km) basaltic reservoir feeding progressively shallower and smaller distinct stagnation layers, pockets and batches up to very shallow conditions (1 kbar, ca. 3 km). Evolution of melts in the feeding system is mainly controlled by differentiation processes via fractional crystallization, as recorded by polybaric crystallization of clinopyroxenes and orthopyroxenes. Moreover, this study attempts to emphasize the importance to integrate field-petrography, texture observations and mineral chemistry of primary minerals to unravel the pre-eruptive dynamics and therefore the anatomy of the plumbing system beneath an active volcanic complex, which notwithstanding the numerous existing works is still far to be well understood. A better knowledge of the heat source feeding geothermal systems is very important to improve geothermal exploration strategies.

scholarly journals The structural architecture of the Los Humeros volcanic complex and geothermal field

2019 ◽  
Vol 381 ◽  
pp. 312-329 ◽  
Author(s):  
Gianluca Norini ◽  
Gerardo Carrasco-Núñez ◽  
Fernando Corbo-Camargo ◽  
Javier Lermo ◽  
Javier Hernández Rojas ◽  
...  
Keyword(s):  
Geothermal Field ◽  
Volcanic Complex ◽  
Structural Architecture

scholarly journals Chemical and isotopic characterization of the thermal fluids emerging along the North–Northeastern Greece

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
E. Dotsika ◽  
P. Dalampakis ◽  
E. Spyridonos ◽  
G. Diamantopoulos ◽  
P. Karalis ◽  
...  
Keyword(s):  
Geothermal Field ◽  
Chemical Compositions ◽  
Geothermal Systems ◽  
High Enthalpy ◽  
Thermal Fluids ◽  
The North ◽  
Geothermal Fields ◽  
West Part ◽  
Distinct Source ◽  
Isotopic Characterization

AbstractHydrochemical and isotopic characteristics of fluids from major geothermal fields of middle/low temperature in N/NE Greece are examined [basins: Strymon River (SR), Nestos River Delta (ND), Xanthi–Komotini (XK), Loutros–Feres–Soufli (LFS) and Rhodope Massif]. The geodynamic context is reflected to isotopic/chemical composition of fluids, heat flow values and elevated CO2 concentrations in emitted fluids. B and Li are derived from leaching of the geothermal systems hosting rocks. δ18OH2O, δ18OSO4, δ13CCO2 values and chemical compositions of Cl, B and Li of geothermal discharges suggest two distinct source fluids. Fluids in SR exhibit high B/Cl and Li/Cl ratios, suggesting these constituents are derived from associated magmas of intermediate composition (andesitic rocks). Geothermal discharges in LFS exhibit low B/Cl and Li/Cl ratios, implying acid (rhyolitic) magmatism. δ13CCO2 and CO2/(CO2 + 105He) ratios in the west part, suggest fluids affected by addition of volatiles released from subducted marine sediments. For the eastern systems, these ratios suggest gas encountered in systems issued from mixing of crustal and mantle-derived volatiles. Isotopic geothermometers reflect, for the same direction, equilibrium processes more (LFS, XK) or less (SR) pronounced and discriminate the geothermal field from low to middle [SR, ND (Erasmio)] and middle to high enthalpy [ND (Eratino), LFS, XK].

Gold distribution in the Val-d'Or Formation and a model for the formation of the Lamaque–Sigma mines, Val-d'Or, Quebec

1991 ◽  
Vol 28 (5) ◽  
pp. 706-720 ◽  
Author(s):  
Mehmet F. Taner ◽  
Pierre Trudel
Keyword(s):  
Gold Mineralization ◽  
Regional Metamorphism ◽  
Analytical Techniques ◽  
Shear Zones ◽  
Gold Deposits ◽  
Mining District ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Gold Mines ◽  
Geothermal Activity

Recent lithogeochemical studies by accurate analytical techniques (e.g., instrumental and radiochemical neutron-activation analyses) have been used to explore the possibility of using gold distribution in the research for new gold deposits; these show that anomalous gold distribution occurs in some parts of the Val-d'Or Formation in the Val-d'Or mining district of Quebec. Gold lithogeochemistry in the Val-d'Or Formation has shown that it is possible to distinguish: (i) background values (1.4–3.5 ppb Au); (ii) zones of primarily anomalous gold values around the Lamaque–Sigma mines (median: 15 ppb Au); (iii) enrichment halos around gold orebodies (median: 70 ppb Au); and (iv) secondary gold enrichment in shear zones. We conclude that the Val-d'Or Formation is auriferous, i.e., anomalously rich in gold at least in some of its parts and contains the Lamaque – Sigma gold mines, representing 68% of the total gold production in the district. The Val-d'Or Formation is part of a central volcanic complex within an island-arc system. The centre of this complex is located in the main Lamaque plug, and this environment may be compared to high-temperature active geothermal systems that are commonly responsible for the formation of epithermal gold deposits. Gold mineralization at Sigma and Lamaque is considered to be related to a late hydrothermal phase or a retrograde phase of regional metamorphism. For the formation of the gold deposits, two distinct and successive events are postulated: (i) a gold-rich synvolcanic geothermal activity and (ii) a late remobilisation from the host rocks followed by deposition of gold ore within favourable structures.

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