Regional Distribution and Prospects of Potash in China

China was formed by amalgamation of several small continental blocks （cratons）, micro, blocks and orogenic belts in different paleoclimatic settings. It may be correlated with other continental blocks but has its own specific characteristics; therefore the tectonic environments of China＇s marine and continental saline basins and salt, and potash, forming environment have some specific characteristics： multiple phases of salt formation, difference in salt, forming ages, migration and concentration of salt, forming processes and diversity of component materials, as well as small sizes of marine saline basins and great changes of saline basins in the late stage and occurrence of abundant liquid mineral resources. The nature of the tectonic basement exerted a key controlling effect on the formation of potash basins. The stable tectonic region was favorable for potash concentration in a quasi, stable region, and quasi, and the quasi-stable region was favorable for salt concentration and potash formation in a local stable tectonic region. Most China＇s major ancient saline basins occur in ＂quasi, cratons （continental block）＂; especially all the marine saline basins occur in continental blocks with the Precambrian basement. These regions are the key ones for potash search. Most relatively large, scale soluble salt deposits are developed in relatively stable continental nuclei. According to the characteristics of the tectonic domains where China＇s salt, forming basins are located, the North China, Yangtze and Tarim, Qaidam salt minerogenetic domains and the northern Qiangtang, western Yunnan salt minerogenetic belt may be distinguished. Their salt and potash prospects will be discussed separately.

Minerogenic Theory of the Superlarge Lop Nur Potash Deposit, Xinjiang, China

Located in the eastern part of the Tarim basin, Xinjiang, the Lop Nur was an ultimate water catchment area of the Tarim basin during the Quaternary. Through nearly ten years of investigation and research, the authors have found a superlarge brine potash deposit in the Luobei subbasin—a secondary basin of the Lop Nur depression. The deposit has been mined now. On that basis, the authors propose new theories on the genesis of the potash rock deposit. In the tectonic and geomorphologic contexts, the Tarim basin lies in a 'high mountain-deep basin' environment. At the beginning of the Quaternary, influenced by the neotectonic movement, the Lop Nur evolved into a 'deep basin' in the Tarim basin. At the end of the middle Pleistocene, neotectonic migration began to take place in the interior of the Lop Nur and a new secondary deep basin—the Luobei subbasin—formed gradually. Despite its small area, it is actually the deepest subbasin in the Lop Nur depression, where brines of the Lop Nur Salt Lake gather and evaporate, thus providing materials for the formation of a superlarge brine potash rock deposit. With respect to the phenomenon of brine concentration and change with deepening of the lake, the authors propose a model of 'high mountain-deep basin' tectonic migration for potash concentration. In the sedimentological context, the honeycomb-shaped voids developed in glauberite rock in the subbasin are good space for potash-rich brine accumulation. Study indicates that the deposition of glauberite requires recharge of calcium-rich water. In the Tarim area the calcium-rich water might come from deep formation water or oilfield water, and the river water recharging the Lop Nur Salt Lake was rich in sulfate radicals and other components; in addition, the climate in the area was very dry and the brine evaporated steadily, thus resulting in deposition of substantial amount of glauberite, potash accumulation in intercrystal brine and final formation of the potash deposit. Generally, potash formation in a salt lake undergoes a three-stage process of 'carbonates—?sulfates (gypsum and glauberite)—^chlorides (halite etc.)', but in the study area there only occurred a two-stage process of 'carbonates—>sulfates (gypsum and glauberite)'. The authors call this new geological phenomenon the 'two-stage potash formation' model. In conclusion, the superlarge Lop Nur potash deposit is the result of combined 'high mountain-deep basin' tectonism and 'two-stage potash formation'.

The Seismic Response Characteristics of Polyhalite with Shaded Potash Mine in Central Sichuan

Potash deposition is the result of final phase of brine sedimentary evolution,it’s a limited distribution and easily soluble mineral,it is difficult to find the features on the ground,therefore the prospecting is extremely tough.

Features and Formation Mechanism of Faults and Potash-forming Effect in the Lop Nur Salt Lake,Xinjiang,China

The Lop Nur Salt Lake, located in the eastern part of the Tarim Basin, Xinjiang, China, has become a playa in the Quaternary. Rhombic in shape, the Lop Nur depression is mainly controlled by the NE-striking and nearly N-S-striking sets of faults. Since 1995, a superlarge brine potash deposit with potash resources of 2.50×10^8s t has been found in the Luobei subbasin in the northeastern part of the Lop Nur. We intensively studied the features and formation mechanism of faults inside the Lop Nur through satellite images, geomorphologic survey and continuous conductivity imaging and found seven subparallel graben faults formed under the action of nearly N 10° E principal compressional stress during deposition of the Lop Nur Salt Lake. These faults are up to 〉60 km long and 1-4 km wide and may extend downward for 1000 m or more. It is just under the action of these tensional faults that potash subbasius formed. The largest subbasin is the Luobei subbasin and the smaller ones are the Luoxi hollow, Erbei hollow and Tienan hollow. Investigation also indicates that the graben faults in the Lop Nur not only control the origin of the potash subbasins, but they themselves are also good brine reservoir structures, in which abundant potash-rich brines are stored. Therefore, The faults had played an important role in the potash formation of the Lop Nur.

The Impact of the Linked Factors of Provenance,Tectonics and Climate on Potash Formation:An Example from the Potash Deposits of Lop Nur Depression in Tarim Basin,Xinjiang,Western China

Potash deposits commonly accumulate in highly restricted settings at the final stage of brine evaporation. This does not mean that potash deposits are formed simply as a result of the evaporation concentration of seawater or lake water, but rather as a coupling result of particular provenance, tectonics and climate activities. In this paper, we focus on the formative mechanism of the potash deposits of Lop Nur depression in Tarim Basin to interpret the detailed coupling mechanism among provenance, tectonics and climate. In terms of the provenance of Lop Nur Lake, the water of the Tarim River which displays ＂potassium-rich＂ characteristics play an important role. In addition, the Pliocene and Lower-Middle Pleistocene clastic beds surrounding Lop Nur Lake host a certain amount of soluble potassium and thus serves as ＂source beds＂ for potash formation. During the late Pliocene, the Lop Nur region has declined and evolved into a great lake from the previous piedmont and diluvial fan area. Since the mid Pleistocene, the great-united Lop Nur Lake has been separated and has generated a chain system consisting of Taitema Lake, Big Ear Lake and Luobei Lake which has turned into the deepest sag in Lop Nur Lake. Dry climate in Lop Nur region has increased since the Pliocene, and became extreme at the late Pleistocene. The study implies that potash formation in Lop Nur Lake depends on the optimal combination of extreme components of provenance, tectonics and climate during a shorter-term period. The optimal patterns of three factors are generally characterized by the long-term accumulation and preliminary enrichment of potassium, the occurrence of the deepest sub-depression and the appearance of an extremely arid climate in Lop Nur region. These factors have been interacting synergistically since the forming of the saline lake and in the later stages strong ＂vapor extraction＂ caused by extremely arid climate is needed to trigger large scale mineralization of potash deposits.

Degree of Brine Evaporation and Origin of the Mengyejing Potash Deposit：Evidence from Fluid Inclusions in Halite

The Mengyejing potash deposit is located in the southern port of the Simao Basin, Yunnan Province, and is hosted in mid-Cretaceous strata. The chemical compositions of fluid inclusions in halite crystals, collected from the level-610 adit in the deposit, were analysed by laser ablation inductively coupled plasma mass spectrometry（LA-ICP-MS）. The results show that the brine is of the Na-K-Mg-Ca-Cl type and has K concentrations that are distinctly higher than those of Mg and Ca, unlike normal brines associated with Cretaceous halite. The high K concentrations indicate that the degree of evaporation of the ancient Mengyejing saline lake was very high, reaching the sylvite deposition stage but rarely reaching the carnallite deposition stage. The trajectory of the H and O isotopic compositions of the brines in the halite-hosted fluid inclusions corresponds to intense evaporation, indicating that the net evaporation exceeded the net inflow of brines. These brine compositions in halite-hosted fluid inclusions were likely formed by the dissolution of previously deposited K-bearing minerals by fresh continental and/or seawater, forming a type of modified seawater, with deep hydrothermal fluids potentially supplying additional potassium. The basin likely experienced multiple seawater incursion, dissolution and redeposition events in a high-temperature environment with high evaporation rates.

Kinetics of roasting potash feldspar in presence of sodium carbonate

A novel process was proposed for the utilization of potash feldspar by roasting in the presence of sodium carbonate. The effects of roasting temperature, granularity, molar ratio of sodium carbonate to potash feldspar and roasting time on the silica extraction rate were investigated. Under the optimal roasting conditions, the silica extraction rate was 98%. The optimal conditions, determined using an orthogonal experiment, were found to be roasting temperature of 875 A degrees C, potash feldspar granularity of 74-89 mu m, molar ratio of sodium carbonate to potash feldspar of 1.2:1, and roasting time of 80 min. The kinetics of potash feldspar roasting in the presence of sodium carbonate was described by the shrinking core model and the reaction rate was found to be controlled by the chemical reaction at the particle surface. According to the Arrhenius expression, the activation energy was 164.99 kJ/mol, and the process could be expressed as [1-(1-alpha)(1/3)]=2.66x10(5) exp[-164990/(RT)] t.

A Cretaceous Desert-Playa Sedimentary System Controlled the Potash Formation in the Simao Basin

Objective The Simao Basin in Yunnan Province has developed Cretaceous evaporite-bearing clastic deposits, including the Mangang and Mengyejing Formations which were originally interpreted as fluvial and lacustrine deposits. The Mangang Fm. composed of well-rounded quartz sandstones, were commonly considered as the bottom part of the Mengyejing salt series. Dttring last decades,

A Multi–fluid Constrain for the Forming of Potash Deposits in the Savannakhet Basin: Geochemical Evidence from Halite

The Khorat Plateau on the Indochina Terrane is known to have formed during the closure of the Tethys Ocean, although the origin of its potash mineral deposits is a topic of current debate. Data from a borehole on Savannakhet Basin is used in this study to re-define the evaporation processes of the study area. Geochemical analyses of halite from various borehole-derived evaporite strata have elucidated the fluid sources from which these ores formed. Measured δ11B indicated that ore deposits formed primarily due to evaporation of seawater, although non-marine fluids affected the later stages of the evaporation process. Fluctuations in B and Br concentrations in carnallite- and sylvite-rich strata indicate the influence of fresh water. Boron concentration in carnallite unit indicated the influence of hydrothermai fluids. From the relative timings of these various fluid influxes, the evolution of these evaporates can be divided into four stages： （1） an initial marine evaporation at the beginning of the deposit＇s formation, where seawater （and minor fresh water） trapped on the uplifted Khorat Plateau produced sediments and salts with Br contents lower than those of normal marine-derived evaporites; （2） a transgression stage, where seawater recharged the basin; （3） a hydrothermal infiltration stage, which was coeval with the late Yanshan movement; and （4） a stage of fresh water supply, as recorded by fluctuations in B and Br contents, inferring intermittent fresh water influx into the basin. Thus, although evaporites on the Savannakhet Basin primarily formed via marine evaporation, they were also influenced to a significant degree by the addition of non-marine fresh water and hydrothermal fluids.

Benzohydroxamic acid to improve iron removal from potash feldspar ores

The technological mineralogy of the potash feldspar was investigated and a new collector named Yb105 was adopted to remove iron from potash feldspar ores.The technological mineralogy results indicate that the main components of the ore were feldspar,sericite,quartz and kaolinite,and iron mainly existed in limonite and hematite,most of which can be removed by beneficiation.The results show the benzohydroxamic acid can not only increase the recovery of iron and reduce the consumption of oleic acid collector,but also enhance the collecting performance of oleic acid at low temperature,which can realize the flotation of the ores at a low temperature and play an important role in saving energy to some extent.Compared with oleic oil,the benzohydroxamic acid had a great advantage in removing iron from potash feldspar,a potash feldspar concentrate with Fe grade of 0.23%,K2O grade of 12.59%and Na2O grade of 0.26%was obtained by flotation with Yb105 as collector,and the yield of the concentrate was 82.55%.

Spatial Distribution of Halite in Kuqa Basin from Paleogene to Neogene and Signification of Potash Survey

Evaporites with gigantic thickness had been developed in Kuqa Basin from Paleocene to early Miocene,and the sediment thickness changed from tens to thousands of meters.By 3D mine software,spatial distribution model of

Synthesis of Leucite from Potash Feldspar

Leucite particles were synthesized from feldspar mixed with 0% to 52% potassium nitrate fired from 800 ℃ to 1 200 ℃ by solid state method. The X-ray Diffraction （XRD） patterns show that in the temperature range from 800 ℃ to 1 200 ℃, the leucite can be removed as the single crystalline phase. Kalsilite may be crystallized with leucite at 800 ℃, but can be eliminated after prolonged heating. The scanning electron Microscopy （SEM） images clearly display the that crystals of micrometer scale leucite, and the leucite crystals distribute evenly in the matrix. The Thermal expansion coefficient （TEC） of the samples fabricated is as high as 20.52×10^-6 ℃^-1 measured from 20 ℃ to 500 ℃. The mechanism of transformation from feldspar to leucite was proposed.

The Extremely Hot and Dry Climatic Events and Potash Enrichment in Salt Lakes of the Jiangling Depression, Jianghan Basin

Objective A total of 820 million tons of potash reserves are predicted to exist in the Palaeocene-Eocene of the Jianghan Basin. However, the basin history is still unclear concerning the potash enriching conditions and mechanism. The Well SKDI is the first exploration well drilled in the Paleogene of Jianghan Basin with continuous coring, which was implemented in the south-central Jiangling Basin in 2013. It is essential to study the Palaeocene-Eocene paleoclimate, to further constrain the extreme draught events and the potash forming conditions.

Isotope Dating of the Potash and Rock Salt Deposit at Bamnet Narong, NE-Thailand

Bamnet Narong is located in northeastern Thailand (Chaiyaphum Province). It is the largest salt mine in the country and has been mined for decades. The landscape in this part of Thailand is characterised by a low plateau, which is called the Khorat Plateau. The plateau is divided into two basins by the Phu Phan Range, the Sakhon Nakhon Basin in the north and the Khorat Basin in the south. The analysed potashes and rock salts are deposited in the Maha Sarakham Formation, which represents the salt-bearing strata of the Khorat Basin. The stratigraphic age of this deposit has been debated since the late 1960’s. The assigned ages range from Mid-Cretaceous to Late Cretaceous and up to the Eocene. In this study different isotopic dating systems (Rb-Sr, Sr-Sr, K-Ar and K-Ca) were applied. The stratigraphic age for the time of deposition was confirmed to be Mid Cretaceous (Cenomanian). Furthermore, the homogeneity of the carnallites was investigated in order to trace a possible redistribution of rubidium.

Chlorination roasting-coupled water leaching process for potash recovery from waste mica scrap using dry marble sludge powder and sodium chloride

The present paper reports the effective utilization of marble sludge powder(MSP)for the recovery of potash values from waste mica scrap using chlorination roasting-water leaching method.Characterization studies indicated the presence of dolomite as the major mineral phase in MSP,whereas muscovite and quartz were observed in the mica sample.The acid leaching studies suggest a maximum of 22%potash recovery under conditions:4 M H2SO4 acid,particle size of^100μm,stirring speed of 600 r/min,leaching temperature of 75℃,and leaching time of 90 min.The chlorination roasting-water leaching process was adopted to achieve the lowest level of 80%-90%potash recovery.The optimum conditions for the recovery of^93%potash from mica(~8.6wt%K2O)requires 900℃ roasting temperature,30 min roasting time,and 1:1:0.75 mass ratio of mica:MSP:NaCl.The roasting temperature and amount of NaCl are found to be the most important factors for the recovery process.The reaction mechanism suggests the formation of different mineral phases,including sylvite(KCl),wollastonite,kyanite,and enstatite,during roasting,which were confirmed by X-ray diffraction(XRD)analyses and scanning electron microscopy(SEM)morphologies.The MSP-blended NaCl additive is more effective for potash recovery compared with the other reported commercial roasting additives.

Progress in the investigation of potash resources in western China

Through the study of the geological conditions of potash deposits in China from recent years,a new understanding of potash theories has arisen that appropriate Chinese geological features.Important progress and substantial breakthroughs have been gained in the direction and management of potash prospecting: (1) Important breakthroughs in continental potassium prospecting:The "Quaternary gravel type deep potassium rich brine metallogenic model in western Qaidam" ensures Quaternary deep potassium rich brine prospecting will grow new KCl resources by 350 Mt,providing a resource guarantee for meeting the Chinese demand for sylvite.(2) The Marine facies potash prospecting shows good prospects: the determination of the new type of Triassic polyhalite potash ore deposits in Sichuan provide an important scientific basis for the establishment of exploration planning and the selection of exploration target areas for polyhalite minerals in the Sichuan Basin;The "two-storey potash deposits model" in southwestern Yunnan has been confirmed,which indicates prospects for the exploration of potash in the deeper Marine facies in southwestern Yunnan are likely to be successful.The discovery of a high concentration of rich bromite salt and potash salt in the Paleogene of the Kuqa depression and the southwestern Tarim region provides strong support for the likelihood large-scale potash deposits exist in these regions.

New Sr Isotope Evidence to Support the Material Source of the Mengyejing Potash Deposit in the Simao Basin from Ancient Marine Halite or Residual Sea

Objective The Mengyejing potash deposit in the Simao Basin is the only producing area of solid potash at present in China. There is still controversy about the material source and distribution of the potash in this deposit （Shen Lijian et al., 2017）, which has influenced not only the prospecting direction and efficiency but also the understanding of the control of Tethys tectonic evolution on the formation and distribution of the mineral resources. This work analyzed the Sr isotope geochemical characteristics of evaporites from core samples in the well MZK-3 in order to further clarify the material source and to explore the potash distribution in the Simao Basin.

The characteristics, formation and exploration progress of the potash deposits on the Khorat Plateau, Thailand and Laos, Southeast Asia

The giant potash deposit on the Khorat Plateau is one of the most promising targets for exploitation of potassium salts.So far,many researches and geologic survey have been conducted on the giant potash deposits.Hence,it is necessary to make an overall review on the potash deposits.The potash deposit on the Khorat Plateau was formed during the Middle to Late Cretaceous,during which seawater was enriched in Ca2+and depleted in SO42-compared with those of modern seawater.In addition to seawater,continental water and hydrothermal fluids could have affected the evaporite basins.The seawater was probably derived from Tethys ocean,and the brine should have evaporated to some extent before entering into the basin systems based on the evidence of absence of carbonates and unproportionate sulphate compared with chloride salts.The paleo-climate during Middle to Late Cretaceous was characterized as high temperature and extremely arid environment,which is favourable for deposition of potassium-magnesium saline minerals.The major saline minerals are of anhydrite,halite,carnallite,sylvite and,tachyhydrite,with trace amounts of borates.The resources of the potash deposit on the Khorat Plateau could be approximately as much as 400×109 t of carnallite and 7×109 t of sylvite.The evaporite sequences have been deformed and altered by postdepositinal processes,including tectonic movements and chemical alteration.Salt domes were formed in the postdepositional processes.Based on the analyses of geophysical surveys and drilling projects,high-quality sylvinite ores are commonly found at the flanks of those salt domes due to incongruent dissolution of carnallite.The furure potential prospecting areas for the highquality sylvinite ores would be on the edges of the Khorat Plateau.

Removing Iron by Magnetic Separation from a Potash Feldspar Ore

A new permanent magnetic separator was introduced to treat the ores with the characteristics of weak magnetic iron minerals and in a fine size range. The new machine was applied to the iron removal from potash feldspar. The effects of the magnetic field intensity, pulp density and grinding fineness on the iron removal were investigated. The optimized operation parameters were achieved and listed as follows： the -0.074 mm content is 85%, the pulp density is 45% and the magnetic field strength is 2T. A close test of middles regrinding was also carried out to improve concentrate yield. The data show that the grade of TFe（total iron） in potash feldspar product decreased from 1.31% to 0.21% and the concentrate yield reached 85.32%. All the results indicated that the traditonal high-intensity electromagnetic separators can be betterly substituted by the new permanent magnetic separator. This study may provide the theoretical evidence for iron removal from potash feldspar.

Effect of Balanced Application of Potash Fertilizer on the Yield of Rice Yongyou 15 and Soil Nutrient Content

By the field experiment,we set up the treatments of non-application of potash fertilizer,conventional fertilization,balanced fertilization and halved application of potash fertilizer,and studied the effect of different treatments on rice yield and soil nutrient content. The results showed that compared with non-application of potash fertilizer,conventional fertilization and balanced fertilization significantly increased the spike length,thousand kernel weight,yield and total potassium content of the stalk,as well as soil organic matter,total nitrogen and available phosphorus content; compared with conventional fertilization,the balanced fertilization did not significantly increase the rice growth and yield,but effectively increased rice grain total nitrogen,stalk total nitrogen and total phosphorus content,as well as soil available phosphorus and available potassium content. It could be found that potash fertilizer played a certain role in increasing rice yield and soil nutrient content,and the balanced fertilization had the most significant effect.