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

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.

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Hydrothermal alteration, fumarolic deposits and fluids from Lastarria Volcanic Complex: A multidisciplinary study

Andean geology ◽

10.5027/andgeov43n2-a02 ◽

2016 ◽

Vol 43 (2) ◽

pp. 166 ◽

Cited By ~ 13

Author(s):

Felipe Aguilera ◽

Susana Layana ◽

Augusto Rodríguez-Díaz ◽

Cristóbal González ◽

Julio Cortés ◽

...

Keyword(s):

Hydrothermal Alteration ◽

Fluid Inclusions ◽

Alkali Metals ◽

Fumarolic Activity ◽

Volcanic Complex ◽

Main Process ◽

Gaseous Species ◽

Alteration Zones ◽

Multidisciplinary Study ◽

Hydrothermal Alteration Zones

A multidisciplinary study that includes processing of Landsat ETM+ satellite images, chemistry of gas condensed, mineralogy and chemistry of fumarolic deposits, and fluid inclusion data from native sulphur deposits, has been carried out in the Lastarria Volcanic Complex (LVC) with the objective to determine the distribution and characteristics of hydrothermal alteration zones and to establish the relations between gas chemistry and fumarolic deposits. Satellite image processing shows the presence of four hydrothermal alteration zones, characterized by a mineral assemblage constituted mainly by clay minerals, alunite, iron oxides, and more subordinated ferrous minerals and goethite. Hydrothermal alteration zones present in the Lastarria sensu stricto volcano are directly related to the recent fumarolic activity. Geochemistry of fumarolic gas condensed, obtained from two fumaroles at temperatures between 328 and 320 °C, has allowed detecting 37 diverse elements corresponding to halogens, chalcophiles, siderophiles, alkali metals, alkali earth metals and Rare Earth Elements (REE), with concentrations that vary widely between 5,620 ppm (chlorine) and 0.01 ppm (Mo, Ag, Sn, Pb, Se, Mg and Cr). Logarithm of Enrichment Factor (log EFi) for each element present values between 6.35 (iodine) and<1 (K, Na, Ca, Fe and Al). Those elements are originated primarily from a magmatic source, whereas at shallow level a hydrothermal source contributes typical rock-related elements, which are leached from the wall rock by a strong interaction with hyperacid fluids. Mostly of elements detected are transported to the surface in the fumarolic emissions as gaseous species, while very few elements (Mg, Ca and Al) are transported in silicate aerosols. A wide spectrum of minerals are present in the fumarolic deposits, which are constituted by sublimates and incrustations, and the main minerals phases are distributed in six mineral families, corresponding to sulphates, hydrated sulphates, sulphides, halides, carbonates, silicates and native element minerals. The sublimate/incrustation minerals are dominated by the presence of sulphate, sulphur, chlorine and diverse rock-related elements, which are formed by processes that include a. oxidation of gaseous phase; b. strong rock-fluid interaction; c. dissolution of silicate minerals and volcanic glass; d. gas-water interaction; e. deposition/precipitation of saline bearing minerals; f. oxidation of sublimates/incrustations to form secondary minerals and g. remobilization of sulphur deposits by meteoric water. Despite that sublimate/ incrustation minerals are dominated by rock-related elements, its chemistry shows high contents of high-volatile elements as As, Sb, Cd, among others. Fluid inclusions studies carried out in thin pseudobanded native sulphur from fumarolic deposits, by use of Raman and infrared spectroscopy combined with microthermometry analyses, provided evidence of H2O, CO2, H2S, SO4, COS bearing fluids, homogenization temperatures around 110 °C and salinities varying from ~11 to ~7 wt% NaCl. Fluid inclusions data show also evidences of a mixing (dilution) between hot and saline fluid with a cooler fluid (cold groundwater or a steam-heated water) as the main process.

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Clay mineral associations in the clay cap from the Cerro Pabellón blind geothermal system, Andean Cordillera, Northern Chile

Clay Minerals ◽

10.1180/clm.2018.9 ◽

2018 ◽

Vol 53 (2) ◽

pp. 117-141 ◽

Cited By ~ 5

Author(s):

S.N. Maza ◽

G. Collo ◽

D. Morata ◽

C. Lizana ◽

E. Camus ◽

...

Keyword(s):

Clay Mineral ◽

Geothermal Field ◽

Geothermal System ◽

Geothermal Systems ◽

High Enthalpy ◽

Andean Cordillera ◽

Geothermal Fields ◽

Mineral Associations ◽

Hydrothermal Alteration Zones ◽

Clay Cap

ABSTRACTThe occurrence of smectite-illite and smectite-chlorite minerals series was studied along a thick clay cap (~300 m) drilled in the Cerro Pabellón geothermal field (northern Andes, Chile). X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were used to characterize the alteration mineralogy and clay mineral assemblages and their changes with depth. Cerro Pabellón is a high-enthalpy blind geothermal system, with a reservoir zone from ~500 m to 2000 m depth, with temperatures of 200–250°C. Three main hydrothermal alteration zones were identified: (1) argillic; (2) sub-propylitic, and (3) propylitic, with variable amounts of smectite, illite-smectite, chlorite-smectite, mixed-layer chlorite-corrensite, illite and chlorite appearing in the groundmass and filling amygdales and veinlets. Chemical and XRD data of smectites, I-S and illites show, with some exceptions, a progressive illitization with depth. The evolution of I-S with depth, shows a sigmoidal variation in the percentage of illite layers, with the conversion of smectite to R1 I-S at ~180–185°C. These temperatures are greater than those reported for other similar geothermal fields and might indicate, at least in part, the efficiency of the clay cap in terms of restricting the circulation of hydrothermal fluids in low-permeability rocks. Our results highlight the importance of a better understanding of clay-mineral evolution in active geothermal systems, not only as a direct (or indirect) way to control temperature evolution, but also as a control on permeability/porosity efficiency of the clay cap.

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Calibration of Airborne Visible/Infrared Imaging Spectrometer Data (AVIRIS) to reflectance and mineral mapping in hydrothermal alteration zones: An example from the “Cuprite mining district”

Geocarto International ◽

10.1080/10106049409354457 ◽

1994 ◽

Vol 9 (3) ◽

pp. 23-37 ◽

Cited By ~ 10

Author(s):

Freek van der Meer

Keyword(s):

Hydrothermal Alteration ◽

Infrared Imaging ◽

Mining District ◽

Imaging Spectrometer ◽

Alteration Zones ◽

Mineral Mapping ◽

Hydrothermal Alteration Zones ◽

Spectrometer Data

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Integrated geophysical methods for delineating crustal structures and hydrothermal alteration zones for mineral exploration projects in parts of west-central, Nigeria

Modeling Earth Systems and Environment ◽

10.1007/s40808-021-01275-5 ◽

2021 ◽

Author(s):

Leke Sunday Adebiyi ◽

Akinola Bolaji Eluwole ◽

Akindeji Opeyemi Fajana ◽

Naheem Banji Salawu ◽

Sesan Cornelius Falade ◽

...

Keyword(s):

Hydrothermal Alteration ◽

Mineral Exploration ◽

Geophysical Methods ◽

Alteration Zones ◽

West Central ◽

Crustal Structures ◽

Hydrothermal Alteration Zones

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PLUMBIAN "ALUNITES" IN HYDROTHERMAL ALTERATION ZONES OF EPITHERMAL AND PORPHYRY TYPE MINERALIZATIONS IN W. THRACE

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16741 ◽

2004 ◽

Vol 36 (1) ◽

pp. 492 ◽

Cited By ~ 1

Author(s):

Π. Βουδούρης ◽

Κ. Αρίκας ◽

Α. Κατερινόπουλος

Keyword(s):

Hydrothermal Alteration ◽

Solid Solutions ◽

Mineral Chemistry ◽

Alteration Zones ◽

Hydrothermal Alteration Zones ◽

Hydrothermal Environment

In this study a new occurrence of Pb-rich members of the alunite supergroup minerals is described. The "alunites" were traced in advanced argilic alteration zones of epithermal and porphyry type mineralizations in W. Thrace/(Greece). These "alunites" are Ca-Sr-Ba-Pb-rich phosphatessulfates and represent solid solutions between members of the alunite, woodhouseite and crandallite group minerals. The highest concentrations of PbO in the Mavrokoryfi and Melitaina alunites are 24.7% and 17.4% respectively. The plumbian phosphates-sulfates occur in the cores of the crystals and are surrounded by common K-Na-rich alunites in Mavrokoryfi and Ba-rich woodhouseite in Melitena, an indication that they were formed in a magmatic-hydrothermal environment after dissolution of apatite and feldspars by phosphate-sulphate rich solutions. The mineral-chemistry of these "alunites" can provide information regarding the genesis of the advanced argilic alteration zones in Greece, and help us in the distinction of the epithermal from deep porphyry style environments.

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Gold content and distribution in hydrothermal alteration zones of the Haenam area, southwestern Korea

Mineral Deposit Research: Meeting the Global Challenge ◽

10.1007/3-540-27946-6_291 ◽

2005 ◽

pp. 1141-1143

Author(s):

Yoon Chung Han

Keyword(s):

Hydrothermal Alteration ◽

Gold Content ◽

Alteration Zones ◽

Hydrothermal Alteration Zones

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A Remote Sensing-Based Application of Bayesian Networks for Epithermal Gold Potential Mapping in Ahar-Arasbaran Area, NW Iran

Remote Sensing ◽

10.3390/rs12010105 ◽

2019 ◽

Vol 12 (1) ◽

pp. 105 ◽

Cited By ~ 9

Author(s):

Seyed Mohammad Bolouki ◽

Hamid Reza Ramazi ◽

Abbas Maghsoudi ◽

Amin Beiranvand Pour ◽

Ghahraman Sohrabi

Keyword(s):

Remote Sensing ◽

Bayesian Network ◽

Hydrothermal Alteration ◽

Gold Mineralization ◽

Epithermal Gold ◽

Alteration Zones ◽

Mineral Potential ◽

Potential Map ◽

Bayesian Network Classifier ◽

Hydrothermal Alteration Zones

Mapping hydrothermal alteration minerals using multispectral remote sensing satellite imagery provides vital information for the exploration of porphyry and epithermal ore mineralizations. The Ahar-Arasbaran region, NW Iran, contains a variety of porphyry, skarn and epithermal ore deposits. Gold mineralization occurs in the form of epithermal veins and veinlets, which is associated with hydrothermal alteration zones. Thus, the identification of hydrothermal alteration zones is one of the key indicators for targeting new prospective zones of epithermal gold mineralization in the Ahar-Arasbaran region. In this study, Landsat Enhanced Thematic Mapper+ (Landsat-7 ETM+), Landsat-8 and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral remote sensing datasets were processed to detect hydrothermal alteration zones associated with epithermal gold mineralization in the Ahar-Arasbaran region. Band ratio techniques and principal component analysis (PCA) were applied on Landsat-7 ETM+ and Landsat-8 data to map hydrothermal alteration zones. Advanced argillic, argillic-phyllic, propylitic and hydrous silica alteration zones were detected and discriminated by implementing band ratio, relative absorption band depth (RBD) and selective PCA to ASTER data. Subsequently, the Bayesian network classifier was used to synthesize the thematic layers of hydrothermal alteration zones. A mineral potential map was generated by the Bayesian network classifier, which shows several new prospective zones of epithermal gold mineralization in the Ahar-Arasbaran region. Besides, comprehensive field surveying and laboratory analysis were conducted to verify the remote sensing results and mineral potential map produced by the Bayesian network classifier. A good rate of agreement with field and laboratory data is achieved for remote sensing results and consequential mineral potential map. It is recommended that the Bayesian network classifier can be broadly used as a valuable model for fusing multi-sensor remote sensing results to generate mineral potential map for reconnaissance stages of epithermal gold exploration in the Ahar-Arasbaran region and other analogous metallogenic provinces around the world.

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