Hydrothermal Systems Characterized by Crustal Thermally-dominated Structures of Southeastern China

Southeastern China(SE China)is located in the Pacific tectonic domain and has experienced a series of tectono-magmatic events induced by the subduction of the Paleo-Pacific Plate since the late Mesozoic.The subduction formed a series of NE-NNE oriented faults under a NW-SE regional stress field,along which a number of thermal springs occur.Previous studies have focused on the genesis mechanism of specific geothermal fields in SE China,but the general characteristics of hydrothermal systems in SE China remains unclear.In this study,we investigate the correlation between geothermal activity,hydrochemical type and regional faults by studying the distribution of hydrothermal activity and geochemical properties of typical hydrothermal systems in SE China.The hydrothermal systems in SE China have a crustal thermally-dominated structural origin unique to the specific geological and tectonic conditions of the Eurasian Plate margin.The upwelling of the asthenosphere and the widespread granitoids with high radiogenic heat production in SE China provide major heat sources for regional geothermal anomalies.The NE-oriented crustal thermally-dominated faults are critical for the formation of geothermal anomalies and NW-oriented extensional faults have created favorable conditions for meteoric water infiltration,transportation and the formation of thermal springs.

Origin and Evolution of the Hydrothermal System in Namiihu Samlaozhuaiig Molybdenum (Tungsten) Ore Deposit, Luanchuan County, Henan Province

Thoroughgoing studies of the homogenization temperatures, pressures and chendcal compositions offluid inclusions and the stable isotopes of hydrothermal minerals (quartz. calcite, pyrite and molybdenite)have thrown light on the evolution trend of the molybdenum-bearing hydrothermal system which originatedfrom magmatic processus and underwent significant mixing with meteoric waters in the later stages ofhydrothermal activity.

Remnants of an Powerful Ancient “Dynasty”:Material Cycle and Biomineralization in Modern Seafloor Hydrothermal System

The origin of ancient banded iron formation （BIF） has remained unclear for a long time. How the precipitation process occurred and what the environmental condition was have been widely discussed among scientists, because the period when the major BIFs deposited （-2.8 to 1.8Ga） is the same time when biosphere and atmosphere significantly changed. Based on the discovery of modern seafloor hydrothermal vents, it is possible that reductive environment controlled by vent system is related to the environment where BIF was deposited. According to matter source.

PRACTICAL AND PREDICTIVE MODELLING OF ORE DEPOSITS IN HYDROTHERMAL SYSTEMS

Over the pastfive years,we have been making efforts to develop a practical and predic- tive tool to exploreforgiantore deposits in hydrothermal systems. Towards this goal,a sig- nificant progress has been made towards a better understanding of the basic physical and chemical processes behind ore body formation and mineralization in hydrothermal systems. On the scientific developmentside,we have developed analytical solutions to answerthe fol- lowing scientific questions:(1) Can thepore- fluid pressure gradientbemaintained atthe val- ue of the lithostaticpressure gradientin the uppercrustof the Earth?and(2 ) Can convective pore- fluid flow take place in the uppercrustof the Earth ifthere is a fluid/mass leakage from the mantle to the upper crustof the Earth?On the modelling developmentside,we have developed numerical methods to model the following problems:(1) convective pore- fluid flow in two- dimensional hydrothermal systems;(2 ) coupled reactive pore- fluid flow and multiple species transport in porous media;(3) precipitation and dissolution of minerals and rock al- teration in the upper crust of the Earth;(4 ) double diffusion driven reactive flow transport in deformable fluid- saturated porous media with particular consideration of temperature- de- pendentchemical reaction rates;(5 ) pore- fluid flow patterns neargeological lenses in hydro- dynamic and hydrothermal systems;(6 ) dissipative structures for nonequilibrium chemical reactions in fluid- saturated porousmedia;(7) convectivepore- fluid flow and the related min- eralization in three- dimensional hydrothermal systems;(8) fluid- rock interaction problems associated with the rock alteration and metamorphic process in fluid- saturated hydrothermal/ sedimentary basins;and (9) various aspects of the fully coupled problem involving material deformation,pore- fluid flow,heattransferand species transport/ chemical reactionsin pore- fluid saturated porous rock masses. The above- mentioned work has significantly enriched our knowledge about the physical and chemical processes related to ore body formation and mineralization in the upper crustof the

Hydrogen and Oxygen Isotope Fractionation Mechanism in the Hydrothermal System and Its Geologic Significance

The geochemical behaviors of hydrogen and oxygen isotopes in the hydrothermal system and their inher-ent relationship with the water / rock exchange are discussed in this paper In addition to the temperature con-ditions, the effective W / R ratio is another factor controlling the changes in H and O isotope compositions ofthe altered rock and hydrothermal water. Besides, the application and geological significance of the water-rockexchange theory are also discussed in the light of the H and O isotope compositions and their variation charac-teristics of the mineralizing hydrothermal water and altered rocks from several mineral deposits. Finally, abrief evolutional model of H and O istotope compositions of meteoric and magmatic hydrothermal waters in ahydrothermal system is given.

Hexagonal and Orthorhombic Perovskite Phases of ErMnO_3 and TmMnO_3 from Hydrothermal Systems

The powder crystals of RMnO3（R=Er, Tm） with hexagonal and orthorhombic structures were prepared under hydrothermal conditions. The different structural phases of the title compounds were controllably formed from different kinds of precursors at different reaction temperatures. All of the samples were characterized by powder X-ray diffraction, scanning electron microscopy, inductively coupled plasma analysis, and variable temperature magnetic susceptibility. Their structures were refined by Rietveld method from powder X-ray diffraction data. The measurement of magnetic behavior shows antiferromagnetic orderings at Neel temperatures around 80 and 40 K for the hexagonal and orthorhombic phases, respectively.

Double Convective Hydrothermal System beneath Massive Sulfide Orebody in Gacun Deposit,Southwestern China

The Gacun Kuroko-type deposit, Southwestern China, is hosted in rhyolitic rocks associated with the underlying mafic rocks occurred in the - 1000 m deep fault - bounded basin within the intra -arc rifting zone which formed on the Triassic Yidun island - arc. Two vertically separated alteration systems are recognized: one is conformable or semiconformable alteration zone developed in - 150 m thick mafic unit 1-1.5 km below the massive sulfide ore body; the other is discordant alteration pipe directly surrounded around stockwork ore within rhyolitic unit. The lower conformable alteration zone extending for several kilometers along strike is characterized by silicification and epidotization which result in the development of quartz vein and quartz-epidote vein systems in mafic lava flows and replacement of primary minerals and groundmass in spilitized mafic volcanics and dikes by quartz, epidote - group minerals and sodic plagioclase. Sulfides often occur in the vein system and altered mafic volcanics. Quartz solubility relation indicates that silicification is a consequence of interaction of Si- saturated fluids with mafic rocks in a higher temperature system (T>340℃), intensifying by intrusion of mafic dike or high-level acidic magma chamber. The alteration pipe of diameter about 2 km shows a similar mineralogical zoning to Kuroko deposits of Japan. The sequence is quartz + hyalophane; sericite + chlorite + quartz and zeolite-like zones from core to margins of the pipe. The chlorite core only occurs in the root part of the alteration pipe and downwards transfers into epidote - chlorite and epidote - quartz vein swarm extending 500 m downwards. The felsic rocks away from the orebody and alteration pipe took place district-scale alteration, which has typical low-temperature mineral association: illite + albite + quartz + calcite. Whole -rock and quartz δ18O values indicate that district - scale alteration is a result of interaction of seawater with rocks at lower temperature (T<200℃)under water-dominated condition. However, the altered rocks from the pipe show remarkably δ18O enrichment, and bulk -rock δ18O values decreased gradually toward stockwork orebody from 15.1‰-l5. 75‰ in zeolite-like zone and 12. 05‰-14. 2‰ in sericite - quartz zone to 11.3 ‰ - 14. 4‰ in quartz - hyalophane zone. The filled temperatures of fluid inclusions in quartz and sphalerite lie in the ranges of 280 -320 ℃ for quartz - hyalophane zone and 250 ℃ to 297 ℃ for sericite-quartz zone. The estimated δ18O values of hydrothermal fluids are 7. 98‰ and3.2‰, respectively, based on quartz δ18O data in the deposit. The lower conformable alteration is considered to be approximately coeval with the alteration pipe, based on the SiO2 concentration in the fluids, which restrict the main fluid - rock reaction zone to be located in mafic horizon by quartz barometer, and metal element flux calculation and sulfide - epidote vein system developed both in alteration systems. High - salinity fluid inclusions in gangue quartz (>8% eq. NaCl) from stockwork ore and in quartz phenocryst (>40% eq. NaCl) in footwall rhyolite strongly suggest the existence of hot-saline brine to react with mafic complex and leach metal components, which probably originates mainly from magmatic fluid derived from high-level acidic magma chamber. The brine layer located in mafic unit possibly heats and drives the overlying single -pass convective seawater reacting with felsic rocks. The 'density window' may be expected to occur on the interface between seawater and brine layer, when the brine becomes to be gravitationally instability by the turbulent entrainment of seawater during magmatic and/or tectonic activities. The sulfide mineralization and alteration pipe is inter preted as an effect of the 'density window' through which the mixed fluids of brine with seawater adiabatically discharges upwards.

Advances in the microbial mineralization of seafloor hydrothermal systems

Research on the biomineralization in modern seafloor hydrothermal systems is conducive to unveiling the mysteries of the early Earth’s history, life evolution, subsurface biosphere and microbes in outer space. The hydrothermal biomineralization has become a focus of geo-biological research in the last decade, since the introduction of the microelectronic technology and molecular biology technology. Microorganisms play a critical role in the formations of oxide/hydroxides (e.g. Fe, Mn, S and Si oxide/hydroxides) and silicates on the seafloor hydrothermal systems globally. Furthermore, the biomineralization of modern chemolithoautotrophic microorganisms is regarded as a nexus between the geosphere and the biosphere, and as an essential complement of bioscience and geology. In this paper, we summarize the research progress of hydrothermal biomineralization, including the biogenic minerals, the microbial biodiversity, and also the interactions between minerals and microorganisms. In the foreseeable future, the research on hydrothermal biomineralization will inspire the development of geosciences and biosciences and thus enrich our knowledge of the Earth’s history, life evolution and even astrobiology.

Geological characteristics of the Qiaoyue Seamount and associated ultramafic-hosted seafloor hydrothermal system(~52.1°E,Southwest Indian Ridge)

Hydrothermal vent incidence was once thought to be proportional to the spreading rate of the mid-ocean ridges(MORs).However,more and more studies have shown that the ultraslow-spreading ridges(e.g.,Southwest Indian Ridge(SWIR))have a relatively higher incidence of hydrothermal venting fields.The Qiaoyue Seamount(52.1°E)is located at the southern side of segment#25 of the SWIR,to the west of the Gallieni transform fault.The Chinese Dayang cruises conducted eight preliminary deep-towed surveys of hydrothermal activity in the area during 2009 and 2018.Here,through comprehensive analyses of the video and photos obtained by the deep-towed platforms,rock samples,and water column turbidity anomalies,a high-temperature,ultramafic-hosted hydrothermal system is predicted on the northern flank of the Qiaoyue Seamount.We propose that this hydrothermal system is most likely to be driven by gabboric intrusions.Efficient hydrothermal circulation channels appear against a backdrop of high rock permeability related to the detachment fault.

A Novel Particle Swarm Optimization for Optimal Scheduling of Hydrothermal System

A fuzzy adaptive particle swarm optimization (FAPSO) is presented to determine the optimal operation of hydrothermal power system. In order to solve the shortcoming premature and easily local optimum of the standard particle swarm optimization (PSO), the fuzzy adaptive criterion is applied for inertia weight based on the evolution speed factor and square deviation of fitness for the swarm, in each iteration process, the inertia weight is dynamically changed using the fuzzy rules to adapt to nonlinear optimization process. The performance of FAPSO is demonstrated on hydrothermal system comprising 1 thermal unit and 4 hydro plants, the comparison is drawn in PSO, FAPSO and genetic algorithms (GA) in terms of the solution quality and computational efficiency. The experiment showed that the proposed approach has higher quality solutions and strong ability in global search.

Optimal Scheduling of Cascaded Hydrothermal Systems Using a New Improved Particle Swarm Optimization Technique

Optimum scheduling of hydrothermal plants generation is of great importance to electric utilities. Many evolutionary techniques such as particle swarm optimization, differential evolution have been applied to solve these problems and found to perform in a better way in comparison with conventional optimization methods. But often these methods converge to a sub-optimal solution prematurely. This paper presents a new improved particle swarm optimization technique called self-organizing hierarchical particle swarm optimization technique with time-varying acceleration coefficients (SOHPSO_TVAC) for solving short-term economic generation scheduling of hydrothermal systems to avoid premature convergence. A multi-reservoir cascaded hydrothermal system with nonlinear relationship between water discharge rate, power generation and net head is considered here. The performance of the proposed method is demonstrated on two test systems comprising of hydro and thermal units. The results obtained by the proposed methods are compared with other methods. The results show that the proposed technique is capable of producing better results.

Buried Hydrothermal Systems:The Potential Role of Supercritical Water,“ScriW”,in Various Geological Processes and Occurrences in the Sub-Surface

It is well known that seawater that migrates deep into the Earth’s crust will pass into its supercritical domain at temperatures above 407°C and pressures above 298 bars. In the oceanic crust, these pressures are attained at depths of 3 km below sea surface, and sufficiently high temperatures are found near intruding magmas, which have temperatures in the range of 800°C to 1200°C. The physico-chemical behaviour of seawater changes dramatically when passing into the supercritical domain. A supercritical water vapour (ScriW) is formed with a density of 0.3 g/cc and a strongly reduced dipolar character. This change in polarity is causing the ScriW to lose its solubility of the common sea salts (chlorides and sulphates) and a spontaneous precipitation of sea salts takes place in the pore system. However, this is only one of many cases where the very special properties of ScriW affect its surroundings. The objective of this paper is to increase awareness of the many geological processes that are initiated and governed by ScriW. This includes interactions between ScriW and its geological surroundings to initiate and drive processes that are of major importance to the dynamics and livelihood of our planet. ScriW is the driver of volcanism associated with subduction zones, as ScriW deriving from the subduction slab is interacting with the mantle rocks and reducing their melting point. ScriW is also initiating serpentinization processes where olivines in the mantle rocks (e.g. peridotite) are transformed to serpentine minerals upon the uptake of OH-groups from hydrolysed water. The simultaneous oxidation of Fe2+ dissolved from iron-bearing pyroxenes and olivines leads to the formation of magnetite and hydrogen, and consequently, to a very reducing environment. ScriW may also be the potential starter and driver of the poorly understood mud and asphalt volcanism;both submarine and terrestrial. Furthermore, the lack of polarity of the water molecules in ScriW gives the ScriW vapour the potential to dissolve organic matter and petroleum. The same applies to supercritical brines confined in subduction slabs. If these supercritical water vapours migrate upwards to reach the critical point, the supercritical vapour is condensed into steam and dissolved petroleum is partitioned from the water phase to become a separate fluid phase. This opens up the possibility of transporting petroleum long distances when mixed with ScriW. Therefore, we may, popularly, say that ScriW drives a gigantic underground refinery system and also a salt factory. It is suggested that the result of these processes is that ScriW is rejuvenating the world’s ocean waters, as all of the ocean water circulates into the porous oceanic crust and out again in cycles of less than a million years. In summary, we suggest that ScriW participates in and is partly responsible for: 1) Ocean water rejuvenation and formation;2) Fundamental geological processes, such as volcanism, earthquakes, and meta-morphism (including serpentinization);3) Solid salt production, accumulation, transportation, and (salt) dome formation;4) The initiation and driving of mud, serpentine, and asphalt volcanoes;5) Dissolution of organic matter and petroleum, including transportation and phase separation (fractionation), when passing into the subcritical domain of (liquid) water.

Episodic hydrothermal alteration on Middle Permian carbonate reservoirs and its geological significance in southwestern Sichuan Basin,SW China

To analyze the episodic alteration of Middle Permian carbonate reservoirs by complex hydrothermal fluid in southwestern Sichuan Basin,petrology,geochemistry,fluid inclusion and U-Pb dating researches are conducted.The fractures and vugs of Middle Permian Qixia–Maokou formations are filled with multi-stage medium-coarse saddle dolomites and associated hydrothermal minerals,which indicates that the early limestone/dolomite episodic alteration was caused by the large-scale,high-temperature,deep magnesium-rich brine along flowing channels such as basement faults or associated fractures under the tectonic compression and napping during the Indosinian.The time of magnesium-rich hydrothermal activity was from the Middle Triassic to the Late Triassic.The siliceous and calcite fillings were triggered by hydrothermal alteration in the Middle and Late Yanshanian Movement and Himalayan Movement.Hydrothermal dolomitization is controlled by fault,hydrothermal property,flowing channel and surrounding rock lithology,which occur as equilibrium effect of porosity and permeability.The thick massive grainstone/dolomites were mainly altered by modification such as hydrothermal dolomitization/recrystallization,brecciation and fracture-vugs filling.Early thin-medium packstones were mainly altered by dissolution and infilling of fracturing,bedding dolomitization,dissolution and associated mineral fillings.The dissolved vugs and fractures are the main reservoir space under hydrothermal conditions,and the connection of dissolved vugs and network fractures is favorable for forming high-quality dolomite reservoir.Hydrothermal dolomite reservoirs are developed within a range of 1 km near faults,with a thickness of 30–60 m.Hydrothermal dolomite reservoirs with local connected pore/vugs and fractures have exploration potential.

Cross-upgrading of biomass hydrothermal carbonization and pyrolysis for high quality blast furnace injection fuel production:Physicochemical characteristics and gasification kinetics analysis

The paper proposes a biomass cross-upgrading process that combines hydrothermal carbonization and pyrolysis to produce high-quality blast furnace injection fuel.The results showed that after upgrading,the volatile content of biochar ranged from 16.19%to 45.35%,and the alkali metal content,ash content,and specific surface area were significantly reduced.The optimal route for biochar pro-duction is hydrothermal carbonization-pyrolysis(P-HC),resulting in biochar with a higher calorific value,C=C structure,and increased graphitization degree.The apparent activation energy(E)of the sample ranges from 199.1 to 324.8 kJ/mol,with P-HC having an E of 277.8 kJ/mol,lower than that of raw biomass,primary biochar,and anthracite.This makes P-HC more suitable for blast furnace injection fuel.Additionally,the paper proposes a path for P-HC injection in blast furnaces and calculates potential environmental benefits.P-HC of-fers the highest potential for carbon emission reduction,capable of reducing emissions by 96.04 kg/t when replacing 40wt%coal injec-tion.

Hydrothermal hydrogenation/deoxygenation of palmitic acid to alkanes over Ni/activated carbon catalyst

To produce paraffin from hydrogenation/deoxygenation of palmitic acid,model compound of bio-oil obtained by hydrothermal liquefaction(HTL)of microalgae has been an attractive focus in recent years.In order to avoid energy-intensive separation process of water and bio-oil,it is of importance that deoxygenation upgrading of fatty acids under hydrothermal conditions similar to HTL process.Herein,it is the first time to explore the application of activated carbon(AC)-supported non-noble-metal catalysts,such as Ni,Co,and Mo,and so on,in the hydrothermal hydrogenation/deoxygenation of long-chain fatty acids,and the obtained Ni/AC-H(the Ni/AC was further H_(2)pre-reduced)is one of the best catalysts.In addition,it is found that the catalytic activity can be further improved by H_(2)pre-reduction of catalyst.Characterization results that are more low valences of nickel and oxygen vacancy can be obtained after H_(2)pre-reduction,thus significant promoting the deoxygenation especially the decarbonylation pathway of fatty acids.The total alkanes yield can reaches 95.9%at optimal conditions(280℃,360 min).This work confirmed that the low-priced AC-supported non-noble-metal catalysts have great potential compared with the noble-metal catalyst,in hydrothermal upgrading of bio-oil.

Hydrothermal treatment of pearl millet grains:Effects on nutritional composition,antinutrients and flour properties

Pearl millet(Pennisetum glaucum)is one of the major millets with high nutritional properties.This crop exhibits exceptional resilience to drought and high temperatures.However,the processing of pearl millet poses a significant challenge due to its high lipid content,enzyme activity,and presence of antinutrients.Consequently,it becomes imperative to enhance the quality and prolong the shelf life of pearl millet flour by employing suitable technologies.Hydrothermal treatment in the food industry has long been seen as promising due to its potential to reduce microbial load,inactivate enzymes,and improve nutrient retention.This study aims to investigate the effects of hydrothermal treatment on the quality characteristics of pearl millet.The independent variables of the study were soaking temperature(35,45,55℃),soaking time(2,3,4 h),and steaming time(5,10,15 min).Treatment conditions had a statistically significant effect on nutrient retention.Major antinutrients like tannins and phytates were reduced by 0.99% to 5.94% and 0.36% to 6.00%,respectively,after the treatment.Lipase activity decreased significantly up to 10% with the treatment conditions.The findings of this study could potentially encourage the use of pearl millet flour in the production of various food items and promote the application of hydrothermal treatment in the field of food processing.

A Comparison of Hydrothermal Aging, SO2 and Propene Poisoning Effects on NH3-SCR over Cu-ZSM-5 and Cu-SAPO-34 Catalysts

This study was aimed to investigate the effects of hydrothermal aging, propene and SO2 poisoning on the ammonia-selective catalytic reduction (NH3-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH3-SCR) of NOx conditions. The XRD, TG and N2-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO2 and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO2 or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO2 or propene compared to Cu-SAPO-34 catalyst. The H2-TPR results showed that Cu2 ions could be reduced to Cu and Cu0 for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.

Subaerial hot springs and near-surface hydrothermal mineral systems past and present,and possible extraterrestrial analogues

The principal features,geotectonic settings and association with near-surface hydrothermal mineral systems of ancient and present subaerial hot springs,fumaroles and geysers are herein reviewed.Fumaroles and geysers usually occur in volcanic craters and are in most cases,part and parcel of hot spring environments.Subaerial hot springs are characterised by siliceous-and carbonate-rich chemical sediments,such as sinters and travertines,respectively.Sinters are commonly enriched in various metalliferous elements.Hot springs surface discharges are also characterised by pools,which exhibit bright colours due to the presence of microorganisms.Present-day examples discussed in this paper,include the fumaroles and hot springs of the White Island volcano(New Zealand),the world-renowned Yellowstone caldera(USA)and the Afar region of the East African Rift System.The Afar triangle,in the northern part of East African Rift System,provides a good example of hot springs associated with evaporative deposits.The Tuli-Sabi-Lebombo triple junction rifts were formed during the^180 Ma Karoo igneous event in southern Africa,of which the Tuli arm is the failed rift(aulacogen),as is the Afar region.The Tuli rift is effectively an unusual,if not unique,tectono-thermal setting,because it comprises Karoo-age hot springs systems and associated vein stockworks and breccias,which includes the Messina Cu deposit as well as currently active hot springs with sinter deposits probably due to post-Karoo uplift.Fumarolic pipes in ignimbrites of the Erongo Volcano-Plutonic Complex in Namibia are discussed.This is followed by an example of banded chert rocks in the Killara Formation of the Palaeoproterozoic Capricorn Orogen(Western Australia),interpreted as hot spring chemical sediments,which also show evidence of"fossil"microbial filaments.The paper ends with a brief overview of possible analogues of hot springs on planet Mars.

High-precision double-spike Cd isotopic measurements of seawater by MC-ICP-MS and its application to seawater affected by hydrothermal vent fluids

Cadmium(Cd)isotopes in seawater have been proven as an important geochemical tool for tracing ocean Cd circulation in the modern ocean.In this study,we evaluated a new method to separate Cd(*60 ng)from seawater using Chelex resin(1.0 g)coupled with AG-MP-1M resin.The results show that the Chelex resin is suffi-cient to remove Cd from Na and Mg matrix with Cd recoveries at 98.3±3.5%(2SD,N=6);while AG-MP-1M resin could separate Cd from the residual Na,Mg,and isobaric inferences.The total Cd recoveries of the method are 96.3±1.5%(2SD;N=4)and the salinity of the samples has no significant impacts on Cd recovery.Cd isotope ratios were measured using a Nu PlasmaⅢMC-ICP-MS and^(111)Cd–^(110)Cd double spike technique.By comparing theδ^(114/110)Cd values(0.00±0.06%)of synthetic seawaters doped with Cd isotope standard(NIST-3108;treated by Chelex+AG-MP-1M resin)and the reference value(-0.00%),no variations were observed.We also analyzed the Cd isotope compositions of three deep seawaters from a column at the Southwest Indian Ocean Ridges(SWIR).Theδ^(114/110)Cd values of the col-umn are decreased from 1.05±0.05%at 3200 m to 0.36±0.05%at 2800 m,differing from reportedδ^(114/110)Cd values of deep seawater in other oceans.Considering the spatial distance between the column and active hydrothermal vents in SWIR(-13 km),we propose that such positiveδ^(114/110)Cd values of deep seawater were likely contaminated by vent fluids,which could provide heavy Cd isotope to deep seawaters.This study demon-strates that Cd isotope is more sufficient to distinguish the impact of plumes on deep seawater.

Lessons learned from hydrothermal to hot dry rock exploration and production

In this paper,we investigate geothermal exploration and production in 189 hydrothermal projects and 42 hot dry rock projects around the world.The hydrothermal fields for a working hydrothermal system to generate electricity should have the elements of heat source,water-saturated porous or fractured reservoir,caprock,heat transfer pathway,and good heat preservation condition and geothermal power energy intensity of 10-20 MW per km^(2)within at least 5 km^(2)area in tectonically active region.The hot water or steam flow rate in this hydrothermal system is normally larger than 40 L/s with temperature of 150℃or above.The power generated from enhanced geothermal system(EGS)in hot dry rock projects are generally less than 2 MW because the flow rate in most cases is much less than 40 L/s even with the hydraulic fractures using the modern stimulation technology learned from the oil and gas industry.The natural fracture in the subsurface is generally beneficial to the hydraulic fracturing and heat recovery in the hot dry rock.Moreover,the hydraulic fracture parameters,injection rate and well spacing,drilling strategy should be properly designed to avoid the short-circuit between injector and producer and low heat productivity.In the future,CO^(2)enhanced geothermal recovery associated with CO^(2)sequestration in the high temperature oil,gas,and geothermal fields maybe a good choice.On the other hand,both nearreal-time seismic monitoring to limit the pumping rate and the closed-loop of the Eavor-Loop style system without hydraulic fracture can contribute greatly to heat recovery of hot dry rocks and mitigate the risks of the hydraulic fracturing induced earthquake.Furthermore,the hybrid solar and geothermal system performs better than the stand-alone geothermal system.