Genesis of LCT Pegmatites during Early Paleozoic Orogeny of the North Qinling Orogenic Belt,China:Emplacement Conditions and Structural Control

The Guanpo pegmatite field in the North Qinling orogenic belt(NQB),China,hosts the most abundant LCT pegmatites.However,their emplacement conditions and structural control remain unexplored.In this contribution,we investigated it combining pegmatite orientation measurement with oxygen isotope geothermometry and fluid inclusion study.The orientations of type A1 pegmatites(P_(f)<σ_(2))are predominantly influenced by P-and T-fractures due to simple shearing in Shiziping dextral thrust shear zone during D_(2)deformation,whereas type A2 pegmatites(contemporaneous with D_(4))are governed by hydraulic fractures aligned with S_(0)and S_(0+1)stemming from fluid pressure(P_(f)<σ_(2)).Additionally,type B pegmatites(P_(f)≤σ_(2))exhibit orientations shaped by en echelon extensional fractures in local ductile shear zones(contemporaneous with D_(3)).The albite-quartz oxygen isotope geothermometry and microthermometric analysis of fluid inclusions in elbaites from the latest pegmatites(including types B and A2)suggest that the crystallization P-T for late magmatic and hydrothermal stages are 527.5-559.2℃,320℃,3.1-3.6 kbar and 2.0 kbar,respectively.Our observations along with previous studies suggest that the genesis of the LCT pegmatites was a long-term,multi-stage event during early Paleozoic orogeny(including the collision stage)of the NQB,and was facilitated by various local fractures.

Applications of artificial intelligence in geothermal resource exploration: A review

Artificial intelligence (AI) has become increasingly important in geothermal exploration,significantly improving the efficiency of resource identification.This review examines current AI applications,focusing on the algorithms used,the challenges addressed,and the opportunities created.In addition,the review highlights the growth of machine learning applications in geothermal exploration over the past decade,demonstrating how AI has improved the analysis of subsurface data to identify potential resources.AI techniques such as neural networks,support vector machines,and decision trees are used to estimate subsurface temperatures,predict rock and fluid properties,and identify optimal drilling locations.In particular,neural networks are the most widely used technique,further contributing to improved exploration efficiency.However,the widespread adoption of AI in geothermal exploration is hindered by challenges,such as data accessibility,data quality,and the need for tailored data science training for industry professionals.Furthermore,the review emphasizes the importance of data engineering methodologies,data scaling,and standardization to enable the development of accurate and generalizable AI models for geothermal exploration.It is concluded that the integration of AI into geothermal exploration holds great promise for accelerating the development of geothermal energy resources.By effectively addressing key challenges and leveraging AI technologies,the geothermal industry can unlock cost‐effective and sustainable power generation opportunities.

Isotope and chemical geothermometry and its applications

The Na-K-Mg Geoindicator created by Giggenbach (1988) is convenient to use but it is still based on the empirical geothermometry equations and discrepancy for different cation geo-thermometers is observed. In fact, the location of the curve of 'full equilibrium' is different if a different Na-K geothermometry equation is used. The difference is pronounced for temperatures lower than about 220℃. A case study on the Zhangzhou geothermal field of SE China resulted in a reliable estimate of reservoir temperature of 150℃ by the SO4-H2O pair Oxygen-18 isotope geothermometer. This has provided an example of attained equilibrium of the marine sulphate in the geothermal system in the low-medium temperature range (<150℃). A recent refinement of the theoretical geothermometry was achieved by the FixAl method, which provides the possibility to identify and solve problems such as an erroneous analytical value of Aluminium, and influence of processes such as mixing and degassing, and therefore makes it possible to reconstruct most of the 'lost equilibrium' in geothermal systems.

Chemical geothermometry:application to mud volcanic waters of the Caucasus region

The generation temperatures of gas-water fluids released from mud volcanoes in different provinces of the Caucasian region have been constrained using Mg/Li(T_(Mg/Li))chemical geothermometry.Mud volcanic fluids in the Taman Peninsula(Kerch-Taman mud volcanic province)were generated at temperatures(T_(Mg/Li))from 41℃ to 137℃.The depths of the respective mud reservoirs estimated from T_(Mg/Li) values and local geothermal gradient are in a range of 1.0 to 3.4 km which spans the Maykop Formation of marine shale.For the South Caspian province,the T_(Mg/Li) values of waters vary from 18℃ to 137℃ and the respective root depths HMg/Li of mud volcanoes range from∼0.85 to 6.5 km.The obtained T_(Mg/Li) values for the analyzed mud volcanic waters from Caucasian provinces are in positive correlation with HCO3^(−)contents and water oxygen isotope compositions(δ^(18)OH_(2)O andΔδ^(18)OH_(2)O)and in high negative correlation with Cl^(−).The increase of T_(Mg/Li) toward the Greater Caucasus Range,as well as the lateral T_(Mg/Li) patterns in the Taman and South Caspian mud volcanic provinces,support the idea that mud volcanic fluids generate at temperatures increasing progressively toward the Alpine orogenic belt.

Geochemical assessment, mixing behavior and environmental impact of thermal waters in the Guelma geothermal system,Algeria

A study of thirteen geothermal springs located in the geothermal field of Guelma,northeastern Algeria,was conducted.Samples were collected during the period between January 2014 and February 2016.Geochemical processes responsible for the chemical composition of thermal and mineralized water were evaluated.The hydrochemical analysis shows that the thermal waters are characterized by the presence of two different chemical facies,the first type SO4-Ca in the east,west and south of Guelma,the second type HCO3-Ca in the south.This analysis also attributed to sodium,chlorides,and sulfates to an evaporitic terrigenous origin by the molar ratio Sr2+/Ca2+.The thermal spring waters from Guelma geothermal system have a meteoric origin,and all samples are immature with strong mixing between hot and shallow waters with 19-38.5%rate of mixing.The silica geothermometer shows that these thermal waters have a temperature varying from 84 to 122℃and that the water came from a depth of 2100-3000 m through a fault system that limits the pullapart basin of Guelma.Potential environmental effluent from thermal spas could pollute in both the irrigation and drinking waters,and which imposes danger on the health of the inhabitants of the region.

A hydrochemical study of the Hammam Righa geothermal waters in north-central Algeria

This study focuses on the hydrochemical characteristics of 47 water samples collected from thermal and cold springs that emerge from the Hammam Righa geothermal field, located in north-central Algeria. The aquifer that feeds these springs is mainly situated in the deeply fractured Jurassic limestone and dolomite of the Zaccar Mount. Measured discharge temperatures of the cold waters range from 16.0 to 26.5 ℃ and the hot waters from 32.1 to 68.2 ℃. All waters exhibited a near-neutral pH of 6.0-7.6. The thermal waters had a high total dis- solved solids （TDS） content of up to 2527 mg/l, while the TDS for cold waters was 659.0-852.0 mg/l. Chemical analyses suggest that two main types of water exist： hot waters in the upflow area of the Ca-Na-SO4 type （Ham- mam Righa） and cold waters in the recharge zone of the Ca-Na-HCO3 type （Zaccar Mount）. Reservoir tempera- tures were estimated using silica geothermometers and fluid/mineral equilibria at 78, 92, and 95℃ for HR4, HR2, and HRI, respectively. Stable isotopic analyses of the δ18O and δD composition of the waters suggest that the thermal waters of Hammam Righa are of meteoric origin. We conclude that meteoric recharge infiltrates through the fractured dolomitic limestones of the Zaccar Mount and is conductively heated at a depth of 2.1-2.2 km. The hotwaters then interact at depth with Triassic evaporites located in the hydrothermal conduit （fault）, giving rise to the Ca-Na-SO4 water type. As they ascend to the surface, the thermal waters mix with shallower Mg-rich ground- water, resulting in waters that plot in the immature water field in the Na-K-Mg diagram. The mixing trend between cold groundwaters from the recharge zone area （Zaccar Mount） and hot waters in the upflow area （Hammam Righa） is apparent via a chloride-enthalpy diagram that shows a mixing ratio of 22.6 〈 R 〈 29.2 %. We summa- rize these results with a geothermal conceptual model of the Hammam Righa geothermal field.

Ore Controls and Metallogenesis of Au-Ag Deposits at Atalla Mine,Central Eastern Desert of Egypt

Gold-silver deposits in the Atalla area occur as hydrothermal quartz veins in NE–SW pre-existing fractures within the Atalla granitic pluton.The orientation of such quartz veins has been attributed to extensional behavior related to the Atalla Shear Zone(ASZ).The Atalla area is covered by a variety of lithologies that are(from oldest to youngest):metasedimentary rocks,metavolcanic rocks,ophiolite assemblage(serpentinites/talc-carbonates),Atalla granite and Dokhan volcanic rocks.Microscopically,Atalla granite ranges in composition from granodiorite to monzogranite.Wholerock geochemistry constrains the calc-alkaine affinity of the Atalla granite that was intruded within an orogenic(syncollision)tectonic regime.The ore minerals are represented by gold/silver(electrum),pyrite(Py1&Py2),arsenopyrite,pyrrhotite,sphalerite,chalcopyrite,galena,covellite and goethite.The temperature of ore formation ranges from 240 to 285℃and the estimated fluid pressure is in the range of 20–100 MPa.Based on the geological setting,ore textures and fluid characteristics;the Atalla Au-Ag deposits are considered to be orogenic in nature,formed from a continental collision(~653-590 Ma),synchronous with the emplacement of calc-alkaline magmatism during the evolutionary history of the Arabian Nubian Shield(ANS).The initial ore-forming fluid was primarily derived from a metamorphic source related to ophiolitic-serpentinite rocks under deep regional conditions of greenschist-amphibolite facies,where the Atalla granitic eruption provided the required temperature conditions for the metamorphic process to take place.Under such conditions,the transportation of ore metals as bisulfide complexes is favoured.The deposition of ore minerals was triggered by fluidwallrock interaction through fracture pathways in conjunction with a temperature-pressure drop that is likely to have been related to uplift into the crustal levels.

Improved Preproduction Conceptual-Numerical Model of the Roosevelt Geothermal Field using Geological, Geochemical and Structural Information

The Roosevelt Hot Springs Known Geothermal Resource Area(KGRA) is a Basin and Range-type geothermal resource, which is located in southwestern Utah. The integrated multicomponent geothermometry(IMG) approach is used to estimate the reservoir temperature at the Roosevelt Hot Springs KGRA. Geothermometric modeling results indicate the deep reservoir temperature is approximately 284.6°C. A conceptual model of the Roosevelt Hot Spring KGRA is provided through integrating the various pieces of exploration information, including the geological data, geothermometric results, temperature well log and field evidence. A two-dimensional cross-sectional model was thus built to quantitatively investigate the coupled thermal-hydraulic processes in the Roosevelt geothermal field. By matching the preproduction temperature log data of deep wells, parameters controlling flow and heat transport are identified. The method and model presented here may be useful for other geothermal fields with similar conditions.

OXYGEN ISOTOPE FRACTIONATION IN URANIUM OXIDES

Thermodynamic oxygen isotope factors for uranium oxides have been calculated by means of the modified increment method. The sequence of 18￣O-enrichment in the uranium oxides with respect to the common rock-forming minerals is predicted as follows: spinel < uraninite brannerite hematite < rutile < pitchblende <cassiterite uranium blacks coffinite sedovite UO3 < illite. Two sets of selfconsistent fractionation factors between the uranium oxides and water and between the uranium oxides and the other minerals have been obtained for 0～ 1200℃. The theoretical results are applicable to the isotopic geothermometry of uranium ores when pairing with other gangue minerals in hydrothermal uranium deposits.

Mineral Chemistry of Wehrlite Xenoliths Hosted in Basalts from the SW of Hossere Dammougalre(Adamawa Plateau,Cameroon):Thermobarometric Implications

Wehrlite samples (size: ~4 cm) hosted in basaltic lavas from the SW of Hosséré Dammougalré are located in the western Adamawa Plateau. Porphyritic and allotriomorphic texture characterize respectively host Basalt and wehrlite xenoliths. The phenocrysts of olivine (Fo68&minus;74), and Ti-magnetite are scattered in host basalt. Wehrlite xenoliths (~4 cm size) contain Cr-rich clinopyroxene (diopise-augite), olivine (Fo76&minus;88) and chromiferous spinel. Equilibrium temperatures calculated from Fe/Mg exchange reaction for olivine/spinel vary between 944&#176;C and 1102&#176;C. The wehrlite olivine crystals with low Fo (<90) indicate a re-equilibration of Fe-Mg in the host basalt at low temperatures. All the analyzed wehrlite clinopyroxenes have crystallized at high pressures as evidenced by the Alvi and Aliv contents. The studied spinel-bearing wehrlite xenoliths represent probably the residual portions of the upper mantle, which are an important source of information about lithospheric composition and thermal evolution beneath the Adamawa Plateau.

Estimate of the Aquifer Temperature of Assammaqieh Well in Akkar by Geothermometric Equations

This research aims at estimating the temperature of the aquifer that supplies Assammaqieh well at the depth of 550 m, on the basis of chemical analyses and geothermometric techniques which are one of the methods used for searching for the renewable geothermal energy and conserving the environment. In this study, about twenty-two geothermometric indicators have been used. For verifying the results, these results have been compared with data and estimates of temperature of fluids of deep typical wells in New Zealand, and it has been noticed that the theoretical and actual results approach the limits of 95% in many indicators. The study has been restricted to the relations of Cations because they are the most reliable, and the least affected by dissolution and evaporation. Most of the indicators that are based on the four chemical elements: Calcium (Ca), Potassium (K), Sodium (Na), Magnesium (Mg), have been adopted. The laboratory analysis data of Assammaqieh well confirmed that it was hot sulphurous water that acquired its chemical properties from complicated geochemical conditions, underground thermal conditions and volcanic rock nature. It also turned out that the underground heating process was basically due to thermal conductivity and rock adjacency, and that Assammaqieh well was supplied with water from adjacent groundwater tables whose source was the penetration of surface water. It also appeared that most of the equations used in the search for geothermal energy revealed the presence of an aquifer of hot and very hot water, and they were compatible with the high thermal gradient in volcanic rocks. It also tuned out that 86% of the used geothermometric equations estimated the aquifer temperature of Assammaqieh well as being hot and very hot with around 135.5 Celsius (±20). The study concluded with the hypothesis that Akkar possessed a huge geothermal energy, and benefiting from this energy might put an end to the chronic problem of electricity in Lebanon, and opened up many prospects and uses that could participate in a sustainable and comprehensive development of Akkar and Lebanon as a whole.

Evolution of chlorite composition in the Paleogene prototype basin of Jiyang Depression, Shandong, China, and its implication for paleogeothermal gradient

The Dongying Basin, Huimin Basin, and Zhanhua Basin constitute the Jiyang Depression in Shandong Province. They are major oil and gas exploring districts within the depression. Through reconstructions of the paleotemperature of the three basins facilitated with the chlorite geothermometry, the thermal history of the Paleogene prototype basin in Jiyang Depression and its geologic significance were explored. This study reveals that the Si^(4+) component in chlorites reduces gradually as its buried depth increases, while the AI~Ⅳ component increases accordingly. The chlorite type changes from silicon-rich diabantite to silicon-poor ferroamesite and prochlorite. The prochlorite in this district only appears in the deep buried depth, high temperature, and relatively old stratigraphies; while the diabantite appears in the shallower buried, low temperature, and newly formed strata; the ferroamesite exists in the conditions between prochlorite and diabantite formation. The diagenetic temperatures of the chlorites in these Paleogene basins are 171 — 238℃ for the Dongying Basin, 160—202℃ for the Huimin Basin, and 135—180℃ for the Zhanhua Basin. The differences of the chlorite diagenetic temperatures in the three basins were controlled by the duration time of the structural depressing processes. Higher temperature indicates longer depression time. The relationship between the chlorite diagenetic temperature and its buried depth indicates that the average paleogeothermal gradient is about 38.3℃ /km in the Paleogene prototype basin of Jiyang Depression. It was higher than the present geothermal gradient (29—30℃/km). This phenomenon was attributed to the evolution of the structural dynamics in the depression basin.

Paleogeothermal gradient and geologic thermal history of the Turpan-Hami Basin, Xinjiang

Synthetical research has been done on the geological thermal history of the Turpan-Hami Basin by using vitrinite reflectance, fluid inclusion geothermometry and fission track. The geotcmperature of the Turpan-Hami Basin has the character that suggests higher temperature in the past, in the east and south of the basin, and in the areas of large-fracture, and lower temperature in the present day and in the west and north of the basin. This feature is controlled by the difference of burial depth of basement and heat flow values, which made Permian source rock mature in the late Triassic and Jurassic source rock mature at the end of Jurassic and the early Tertiary.

New progresses on geothermal history of Turpan-Hami Basin,Xinjiang,China

A comprehensive study on geothermal history of the Turpan-HamiBasin by vitrinite reflectance, fluid inclusion geothermometry, apatite fission track and 40Ar-39Ar dating displays that the main effects influencing geotemperature distribution are burial depth of the basement, heat flow, magmatic activities, as well as tectonic movement, having a rugulation to be higher in the east and north, lower in the west and south, as well as higher in the past and lower at the present. The heat of the mantle source and the Indo-China tectonic thermal event have extremely influenced matura-tion of source rocks of the upper Lower Permian and the Middle and Upper Triassic in the lndo-China epoch. While, the geothermal gradient and the weak tectonic geothermal event of the Early Yanshan Movement provided necessary heat for the maturation of source rock in coal-bearing strata of the Middle and Lower Jurassic.