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1.
The Mombi bauxite deposit is located in 165 km northwest of Dehdasht city, southwestern Iran. The deposit is situated in the Zagros Simply Fold Belt and developed as discontinuous stratified layers in Upper Cretaceous carbonates (Sarvak Formation). Outcrops of the bauxitic horizons occur in NW-SE trending Bangestan anticline and are situated between the marine neritic limestones of the Ilam and Sarvak Formations. From the bottom to top, the deposit is generally consisting of brown, gray, pink, pisolitic, red, and yellow bauxite horizons. Boehmite, diaspore, kaolinite, and hematite are the major mineral components, while gibbsite, goethite, anatase, rutile, pyrite, chlorite, quartz, as well as feldspar occur to a lesser extent. The Eh–pH conditions during bauxitization in the Mombi bauxite deposit show oxidizing to reducing conditions during the Upper Cretaceous. This feature seems to be general and had a significant effect on the mineral composition of Cretaceous bauxite deposits in the Zagros fold belt. Geochemical data show that Al2O3, SiO2, Fe2O3 and TiO2 are the main components in the bauxite ores at Mombi and immobile elements like Al, Ti, Nb, Zr, Hf, Cr, Ta, Y, and Th were enriched while Rb, Ba, K, Sr, and P were depleted during the bauxitization process. Chondrite-normalized REE pattern in the bauxite ores indicate REE enrichment (ΣREE = 162.8–755.28 ppm, ave. ∼399.36 ppm) relative to argillic limestone (ΣREE = 76.26–84.03 ppm, ave. ∼80.145 ppm) and Sarvak Formation (ΣREE = 40.15 ppm). The REE patterns also reflect enrichment in LREE relative to HREE. Both positive and negative Ce anomalies (0.48–2.0) are observed in the Mombi bauxite horizons. These anomalies are related to the change of oxidation state of Ce (from Ce3+ to Ce4+), ionic potential, and complexation of Ce4+ with carbonate compounds in the studied horizons. It seems that the variations in the chemistry of ore-forming solutions (e.g., Eh and pH), function of carbonate host rock as a geochemical barrier, and leaching degree of lanthanide-bearing minerals are the most important controlling factors in the distribution and concentration of REEs. Several lines of evidences such as Zr/Hf and Nb/Ta ratios as well as similarity in REE patterns indicate that the underlying marly limestone (Sarvak Formation) could be considered as the source of bauxite horizons. Based on mineralogical and geochemical data, it could be inferred that the Mombi deposit has been formed in a karstic environment during karstification and weathering of the Sarvak limy Formation.  相似文献   

2.
《Ore Geology Reviews》2009,35(4):521-532
More than 190 occurrences of bauxitic–lateritic deposits were investigated in seven areas within the Zagros Simply Folded Mountain Belt in southwestern of Iran. The bauxitic horizons are situated in eroded major NW–SE trending anticlines and occur in karst cavities near or at the boundary between the Sarvak and Ilam Formations. Uplift in the Cenomanian–Turanian period had exposed the Sarvak limestone to karst weathering and, during a period of unconformity, layers of ferruginous–argillaceous limestone debris developed and accumulated on its surface. The ferruginous–argillaceous debris was partly converted to bauxite. Folding and faulting in Oligocene–Miocene time, with ensuing erosion, exposed the bauxitic horizons on the limbs and cores of anticlines. The karst bauxite deposits are probably of authigenic origin, as evidenced by their lithologic associations, textural and mineralogy.  相似文献   

3.
The Mandan and Deh-now bauxite deposits are located 40 km northeast of the Dehdasht city in the Zagros simply fold belt. These deposits occur in eroded major NW–SE trending anticlines and occupy karst cavities near or at the boundary between the Sarvak and Ilam Formations. Local uplifts at the end of the Cenomanian and the mid-Turonian caused erosion and karstification of the Sarvak Formation. These unconformities in the Upper Cretaceous favoured the formation and enrichment of bauxite deposits in the Zagros fold belt. The bauxite sequence in the Mandan deposit consists of white, gray, black, pisolitic, red, and yellow bauxites. This sequence was repeated in the Deh-Now area, but without gray and black bauxites. The present mineralogical studies of the Sarvak Formation and the Mandan and Deh-now bauxite deposits indicate oxidizing to reducing conditions during the Upper Cretaceous in the Zagros fold belt, which had a significant effect on the compositions of the bauxites. At least two phases of bauxitization can be distinguished in the study area: (i) an oxidizing phase represented by boehmite, diaspore, hematite and kaolinite; and (ii) a reducing phase represented by pyrite and chlorite. Geochemical data show that trace elements, like Zr, Hf, Nb, Ta, Th, and U, were enriched during bauxitization. The bauxite deposits and carbonate rocks show similar REE patterns, namely they are enriched in REEs although the LREEs are more enriched than the HREEs. Mass change calculations demonstrate that Mg, Mn, Ca, K, and P2O5 were leached out of the weathered system whereas Al, Fe, and Si become concentrated in the residual system. This study indicates that the Mandan and Deh-now deposits are karst-type bauxites formed by karstification and weathering of the Sarvak Formation.  相似文献   

4.
The Maltese islands are composed of two limestone aquifers, the Upper and Lower Coralline Limestone separated by an aquitard, the ‘Blue Clay’. The Lower Coralline Limestone is overlain in part by the poorly permeable Globigerina Limestone. The upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall. Frequent detections of coliforms suggest a rapid route to groundwater. However, the unsaturated zone has a considerable thickness in places and the primary porosity of the Upper Coralline Limestone is high, so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures. Measurement of SF6 from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 a. The Main Sea Level aquifers (MSL) on both Malta and Gozo have a large unsaturated thickness as water levels are close to sea level. On Malta, parts of the aquifer are capped by the perched aquifers and more extensively by the Globigerina Limestone. The limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features. Transmissivity is low and 3H and CFC/SF6 data indicate that saturated zone travel times are in the range 15–40 a. On Gozo the aquifer is similar but is more-extensively capped by impermeable Blue Clay. CFC data show the saturated zone travel time is from 25 a to possibly more than 60 a. Groundwater age is clearly related to the extent of low-permeability cover. The δ13C signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence; perched aquifers < Malta MSL < Gozo MSL. The 18O and 2H enriched isotopic signature of post 1983 desalinated water can be seen in more-modern groundwater, particularly the urbanized areas of the perched and Malta MSL aquifers. In all aquifers, movement of solutes from the surface travelling slowly through the matrix provide a long-term source of groundwater contaminants such as NO3.  相似文献   

5.
豫西偃龙煤田深部铝土矿地质特征及矿床成因   总被引：1，自引：0，他引：1  
鲁正清 《地质与勘探》2016,52(4):627-634
偃龙煤田深部铝土矿区位于豫西铝土矿成矿区嵩箕铝土矿成矿小区,是豫西铝土矿成矿区的重要组成部分。区内铝土矿赋存于上石炭统本溪组中上部,下伏具有岩溶特征的寒武—奥陶纪灰岩,沉积相为滨岸泻湖泥岩相区,属海相沉积的一水硬铝石岩溶型矿床,矿体主要填充在岩溶作用形成的负地形之中。本文系统阐述了矿区的含矿岩系、矿床地质及矿石质量特征等,研究了本区铝土矿的成矿地质条件、矿床的展布规律和富集规律,对矿床成因及控矿因素进行了分析,指出铝土矿床分布在坳陷区边部及隆起区的过渡带,铝土矿的厚度和品质与本溪组厚度有着明显的正相关关系,预测深部仍有较好的成矿远景。  相似文献   

6.
祝瑞勤 《地质与勘探》2011,47(3):353-360
广西平果铝矿区主要分布三种岩溶地貌类型,即岩溶丘陵斜坡型、岩溶峰丛洼地型和岩溶峰林洼地型,它们呈现规律性分布而划分为三个地貌带和对应的堆积型铝土矿带.堆积矿的岩溶地貌分带,是在构造地貌的背景下,由原生铝土矿层的暂时性基准面作用,导致矿区岩溶发育程度变化而形成.通过大量矿化数据的统计分析表明,堆积型铝土矿在化学成分、矿块...  相似文献   

7.
桂西岩溶堆积型铝土矿床受地层岩性、构造、岩溶地貌、气候与水文等因素控制。通过对岩溶堆积型铝土矿床地质异常的分析和识别,利用G IS技术圈定铝土矿找矿的有利地段,并预测其资源潜力。  相似文献   

8.
The aim of this study is to identify geochemical anomalies using power spectrum–area (S–A) method based on the grade values of Cu, Mo and Au in 2709 soil samples collected from Kahang porphyry-type Cu deposit, Central Iran. S–A log–log plots indicated that there are three stages of Cu, Mo and Au enrichment. The third enrichment was considered as the main stage for the presence of Cu, Mo and Au at the concentrations above 416 ppm, 23 ppm and 71 ppb, respectively. Elemental anomalies are positively associated with monzo–granite–diorite and breccias units which are in the central and western parts of the deposit. The anomalies are located within the potassic, phyllic and argillic alteration types and also there is the positive correlation between the anomalies and nearing faults in the studied area. The results obtained via fractal model were interpreted accordingly to incorporate the information for the mineralized areas including detailed geological map, structural analysis and alterations. The results show that S–A multifractal modeling is applicable for anomalies delineation based on soil data.  相似文献   

9.
In this paper a case study of hydraulic connectivity in a 300–1600 m deep, low temperature, sedimentary geothermal system in Kaifeng area, Henan province, China is presented. Based on lithologic data from 52 geothermal wells and chemical data on geothermal water (GW) from six depth-specific and representative wells, the system was chemically grouped into two main hot reservoirs (300–1300 m and 1300–1600 m deep), which were in turn, divided into six sub-reservoirs (SRs). Data on stable isotope (2H and 18O) ratios, radioactive isotope (14C) radiation in conjunction with computation of mineral–fluid chemical equilibria were used to establish the recharge source (a mountainous region in the southwestern part of Zhengzhou, 60 km away); evaluate groundwater age which varied with well depth from 15630 ± 310 a to 24970 ± 330 a; and assess the chemical equilibrium state within the system. The results of different analysis did not suggest an obvious hydraulic connection between the two main hot reservoirs. The location of the recharge zone and the geohydrologic characteristics of the study area demonstrate that the GW utilized from the system is mainly derived from confined waters of meteoric origin.  相似文献   

10.
For the last 5 a, the authors have been investigating the transport, fate, natural attenuation and ecosystem impacts of inorganic and organic compounds in releases of produced water and associated hydrocarbons at the Osage-Skiatook Petroleum Environmental Research (OSPER) “A” and “B” sites, located in NE Oklahoma. Approximately 1.0 ha of land at OSPER “B”, located within the active Branstetter lease, is visibly affected by salt scarring, tree kills, soil salinization, and brine and petroleum contamination. Site “B” includes an active production tank battery and adjacent large brine pit, two injection well sites, one with an adjacent small pit, and an abandoned brine pit and tank battery site. Oil production in this lease started in 1938, and currently there are 10 wells that produce 0.2–0.5 m3/d (1–3 bbl/d) oil, and 8–16 m3/d (50–100 bbl/d) brine. Geochemical data from nearby oil wells show that the produced water source is a Na–Ca–Cl brine (∼150,000 mg/L TDS), with high Mg, but low SO4 and dissolved organic concentrations. Groundwater impacts are being investigated by detailed chemical analyses of water from repeated sampling of 41 boreholes, 1–71 m deep. The most important results at OSPER “B” are: (1) significant amounts of produced water from the two active brine pits percolate into the surficial rocks and flow towards the adjacent Skiatook reservoir, but only minor amounts of liquid petroleum leave the brine pits; (2) produced-water brine and minor dissolved organics have penetrated the thick (3–7 m) shale and siltstone units resulting in the formation of three interconnected plumes of high-salinity water (5000–30,000 mg/L TDS) that extend towards the Skiatook reservoir from the two active and one abandoned brine pits; and (3) groundwater from the deep section of only one well, BR-01 located 330 m upslope and west of the site, appear not to be impacted by petroleum operations.  相似文献   

11.
张肖 《云南地质》2021,(1):66-69
贵州修文县干坝铝土矿区位于黔中铝土矿带,其矿体形态呈似层状,赋存于下石炭统九架炉组(C1jj)中,铝土矿体的规模与铝土矿岩系的厚度成正比,含矿岩系厚度大,则矿体规模大.而含矿岩系的厚度则受古喀斯特侵蚀面起伏状态控制,低洼处厚度大,凸起处厚度薄.该矿床类型属沉积型铝土矿矿床.  相似文献   

12.
The groundwater B concentration in Mesozoic karst, Neogene and alluvial aquifers in the West part of Chalkidiki province in Central Macedonia, Greece reaches 6.45 mg L−1, which exceeds the limit of 1 mg L−1, set by the European Union for drinking water. The high B contents have been detected in this area, not only near the shoreline, where seawater intrusion occurs, but also in the inland part of the basin. Multi isotope (2H, 18O, 34S, 18O(SO4), 11B, 87Sr/86Sr) data from borehole and thermal water springs allow identification of the possible B sources. The B dissolved in groundwater in the Chalkidiki area is mainly geogenic. The low δ11B values, 0–1‰, similar to those of thermal fluids from continental geothermal fields, and the low Cl/B ratio compared to seawater both indicate a geothermal origin for B and reflect deep circulation and interaction with igneous rocks. The 87Sr/86Sr ratio also indicates that the deep-aquifer granodiorite is the predominant rock source of Sr, while the shallow limestone unit has negligible effects on the dissolved Sr budget in these thermal karst waters which O and H isotopes show to be of meteoric origin. The main source of high B in borehole water is mainly mixing with B-rich geothermal water. The mixing between geothermal water and water from the Neogene aquifer is also reflected by isotopic contents of SO4.  相似文献   

13.
To advance understanding of hydrological influences on As concentrations within groundwaters of Southeast Asia, the flow system of an As-rich aquifer on the Mekong Delta in Cambodia where flow patterns have not been disturbed by irrigation well pumping was examined. Monitoring of water levels in a network of installed wells, extending over a 50 km2 area, indicates that groundwater flow is dominated by seasonally-variable gradients developed between the river and the inland wetland basins. While the gradient inverts annually, net groundwater flow is from the wetlands to the river. Hydraulic parameters of the aquifer (K ≈ 10−4 ms−1) and overlying clay aquitard (K ≈ 10−8 ms−1) were determined using grain size, permeameter and slug test analyses; when coupled with observed gradients, they indicate a net groundwater flow velocity of 0.04–0.4 ma−1 downward through the clay and 1–13 ma−1 horizontally within the sand aquifer, producing aquifer residence times on the order 100–1000 a. The results of numerical modeling support this conceptual model of the flow system and, when integrated with observed spatial trends in dissolved As concentrations, reveal that the shallow sediments (upper 2–10 m of fine-grained material) are an important source of As to the underlying aquifer.  相似文献   

14.
遵义铝土矿的分布及对基底的依存关系   总被引：1，自引：0，他引：1  
李克庆  朱成林 《贵州地质》2007,24(4):278-281,286
遵义铝土矿主要分布在乌江两岸,成矿远景区面积3000余km2,包括了后槽、仙人岩等大、中、小型矿床(点)共32处。均为铝土矿底板的粘土页岩经风化后原地堆积或近距离搬运后的产物。其沉积或堆积作用,与基底的古岩溶溶蚀坑、(洼)密切相关,并使铝土矿沉积在平面上或纵向上都具有一定的分带性。其矿床成因类型属于古风化壳型岩溶坑(洼)沉积铝土矿床。根据成矿地质特征分别建立了高铁铝土矿和低铁铝土矿的成矿模式。  相似文献   

15.
The Geysers Valley hydrothermal system is hosted within a system of two permeable faults (revealed by mapping thermal features), located above a suggested partially melted magmatic body and recharged by meteoric water along the outcrops of rhyolite–dacite extrusions. Fast erosion is stimulating the significant discharge rate, the geyser’s cycling mode and landslide events. Natural state thermal hydrodynamic modeling shows that 20–30 ka of high temperature upflow of 250 kg/s and an enthalpy of 900 kJ/kg could build up the hydrothermal system in the Geysers Valley basin with output discharge parameters comparable to those at the current level. Modeling also shows that steam accumulation below an inclined caprock may have hydrothermal eruption potential. The Giant Landslide took place on June 3, 2007, when 20 × 106 m3 of rocks were shifted 2 km downstream, more than 23 geysers were buried or submerged, and Podprudnoe Lake was dammed, injecting cold water into submerged geysers. Possible triggers of the Giant Landslide include the inclination of the sliding plane towards the Geysernaya river basin, a pressure increase in the fluid-magma system, hanging block saturation by water during spring flooding, hydrothermal alteration weakening of the sliding plane, and steam explosions. Recent geysers cycling activity monitoring data (2007–2010), hydrogeochemical sampling, and thermal area infra red (IR) survey data are also discussed.  相似文献   

16.
The Parnassos-Ghiona bauxite deposit in Greece of karst type is the 11th largest bauxite producer in the world. The mineralogical, major and trace-element contents and δ18O, δ12C, δ34S isotopic compositions of bauxite ores from this deposit and associated limestone provide valuable evidence for their origin and biogeochemical processes resulting in the beneficiation of low grade bauxite ores. The organic matter as thin coal layers, overlying the bauxite deposits, within limestone itself (negative δ12C isotopic values) and the negative δ34S values in sulfides within bauxite ores point to the existence of the appropriate circumstances for Fe bio-leaching and bio-mineralization. Furthermore, a consortium of microorganisms of varying morphological forms (filament-like and spherical to lenticular at an average size of 2 μm), either as fossils or presently living and producing enzymes, is a powerful factor to catalyze the redox reactions, expedite the rates of metal extraction and provide alternative pathways for metal leaching processes resulting in the beneficiation of bauxite ore.  相似文献   

17.
Methane microseepage is the result of natural gas migration from subsurface hydrocarbon accumulations to the Earth’s surface, and it is quite common in commercial petroleum fields. While the role of microseepage as a pathfinder in petroleum exploration has been known for about 80 a, its significance as an atmospheric CH4 source has only recently been studied, and flux data are currently available only in the USA and Europe. With the aim of increasing the global data-set and better understanding flux magnitudes and variabilities, microseepage is now being extensively studied in China. A static flux chamber method was recently applied to study microseepage emissions into the atmosphere in four different sectors of the Yakela condensed gas field in Tarim Basin, Xinjiang, China, and specifically in: (a) a faulted sector, across the Luntai fault systems; (b) an oil–water interface sector, at the northern margin of the field; (c) an oil–gas interface sector, in the middle of the field; (d) an external area, outside the northern gas field boundaries. The results show that positive CH4 fluxes are pervasive in all sectors and therefore, only part of the CH4 migrating from the deep oil–gas reservoirs is consumed in the soil by methanotrophic oxidation. The intensity of gas seepage seems to be controlled by subsurface geologic settings and lateral variabilities of natural gas pressure in the condensed gas field. The highest CH4 fluxes, up to ∼14 mg m−2 d−1 (mean of 7.55 mg m−2 d−1) with higher spatial variability (standard deviation, σ: 2.58 mg m−2 d−1), occur in the Luntai fault sector. Merhane flux was lower in the oil–water area (mean of 0.53 mg m−2 d−1) and the external area (mean of 1.55 mg m−2 d−1), and at the intermediate level in the gas–oil sector (mean of 2.89 mg m−2 d−1). These values are consistent with microseepage data reported for petroleum basins in the USA and Europe. The build-up of methane concentration in the flux chambers is always coupled with an enrichment of 13C, from δ13C1 of −46‰ to −42.5‰ (VPDB), which demonstrates that seeping methane is thermogenic, as that occurring in the deep Yakela reservoir. Daily variations of microseepage are very low, with minima in the afternoon, corresponding to higher soil temperature (and higher methanotrophic consumption), and maxima in the early morning (when soil temperatures are lowest). A preliminary and rough estimate of the total amount of CH4 exhaled from the Yakela field is in the order of 102 tonnes a−1.  相似文献   

18.
Short-wave infrared (SWIR) spectral reflectance of hydrothermally altered volcanic rocks in the footwall of the Hellyer massive sulfide deposit was measured with a portable PIMA-II infrared spectrometer. The Al–OH band was used to derive information on the octahedral Al content and the abundance of white mica (sericite) in the hydrothermal alteration and mineralization system. The range of the Al–OH band wavelength from 2192 nm to 2222 nm corresponds to the number of octahedral Al (Alvi) in white mica approximately from 3.9 to 3.0 (based on 4 octahedral cations per formula). This Alvi range represents a significant compositional variation, covering most of the compositional region between muscovite (Alvi = 4.0) and phengite (Alvi = 3.0). Furthermore, the spectral reflectance data show that the compositional variation of white mica is spatially related to hydrothermal alteration zoning, such that phengitic white mica tends to occur in 1) main upflow fluid channel, 2) intensely altered volcanic rocks, and 3) Pb–Zn mineralization, whereas muscovitic white mica was formed preferentially distal to massive sulfide mineralization on the margin of the footwall alteration system. The results suggest that the Al–OH band wavelength, and therefore the octahedral Al content, of white mica can be used as vectors to mineralization to map the hydrothermal system at Hellyer.  相似文献   

19.
Tissue N contents and δ15N signatures in 175 epilithic mosses were investigated from urban to rural sites in Guiyang (SW China) to determine atmospheric N deposition. Moss N contents (0.85–2.97%) showed a significant decrease from the urban area (mean = 2.24 ± 0.32%, 0–5 km) to the rural area (mean = 1.27 ± 0.13%, 20–25 km), indicating that the level of N deposition decreased away from the urban environment, while slightly higher N contents re-occurred at sites beyond 30 km, suggesting higher N deposition in more remote rural areas. Moss δ15N ranged from −12.50‰ to −1.39‰ and showed a clear bimodal distribution (−12‰ to −6‰ and −5‰ to −2‰), suggesting that there are two main sources for N deposition in the Guiyang area. More negative δ15N (mean = −8.87 ± 1.65‰) of urban mosses mainly indicated NH3 released from excretory wastes and sewage, while the less negative δ15N (from −3.83 ± 0.82‰ to −2.48 ± 0.95‰) of rural mosses were mainly influenced by agricultural NH3. With more negative values in the urban area than in the rural area, the pattern of moss δ15N variation in Guiyang was found to be opposite to cities where N deposition is dominated by NOx–N. Therefore, NHx–N is the dominant N form deposited in the Guiyang area, which is supported by higher NHx–N than NOx–N in local atmospheric deposition. From the data showing that moss is responding to NHx–N/NOx–N in deposition it can be further demonstrated that the variation of moss δ15N from the Guiyang urban to rural area was more likely controlled by the ratio of urban-NHx/agriculture-NHx than the ratio of NHx–N/NOx–N. The results of this study have extended knowledge of atmospheric N sources in city areas, showing that urban sewage discharge could be important in cities co-generic to Guiyang.  相似文献   

20.
The present study focuses on the Late Cretaceous Bidgol bauxite deposit in the Zagros Simply Fold Belt, SW Iran. The orebody is located in the eroded major NW–SE trending Koh-e-Hosseyn anticline and hosted as discontinuous stratified layers and lenses within the upper member of the Cenomanian–Turonian Sarvak Formation. Detailed mineralogical analysis reveals that diaspore, hematite, goethite, anatase, clinochlore, chamosite, and calcite are the major mineral components accompanied by minor amounts of detrital and REE-bearing minerals such as rutile, zircon and parisite. The ore texture suggest that the bauxite material has an authigenic origin but in some parts it has been transported short distances from a primary in situ environment and redeposited in karstic depressions. The spheroidal pisolites of the Bidgol bauxite formed under conditions of low water activity, favouring the formation of large diaspore cores and a single dry-to-wet climatic fluctuation. The mass change calculations relative to the immobile element Ti show that elements such as Si, Fe, Mg, K, Na and Sr are leached out of the weathered system; Al, Ni, Zr, Ga, Cr and Ba are concentrated in the residual system; and Hf, Ta, Co, Rb, Cs, Be, and U are relatively immobile during the bauxitisation processes. The Nb, Th, Y, V, Sc, Sn and ΣREE are relatively immobile in the initial stage of bauxitisation processes in the bauxite ores, but were slightly mobile at the later stage of bauxitisation. Geochemical data reveal progressive enrichment of the REE and intense LREE/HREE fractionation toward the lower parts of the bauxite profile. Cerium behaves differently from the other REEs (especially LREE) and show positive anomalies in the upper horizons that gradually become negative in the deeper parts of the profile. The distribution and fractionation of trace elements and REEs during the bauxitisation process in the Bidgol deposit are mainly controlled by the presence of REE-bearing minerals, fluctuations in soil solution pH, REE ionization potential and the presence of bicarbonates or organic matter. Geochemical analyses confirm a protolith contribution from the bedrock argillaceous limestone and suggest that the source material for the Bidgol bauxite was provided from a siliciclastic material derived from a continental margin. The mid-Turonian uplift led to the formation of karstic topography, rubbly breccia and a layer of ferruginous–argillaceous debris that was affected by lateritic weathering under humid tropical climate. Subsequently, mobile elements are removed from the profiles, while Al, Fe and Ti are enriched, resulting in the formation of the pristine bauxite materials. When the platform subsided into the water again, the pristine bauxitic materials were partly converted to bauxite. During the exposure of bauxite orebodies on the limbs and crests of anticlines and subsequent eroding and accumulation in the karstic depressions during folding and faulting in Oligocene–Miocene, important factors such as intensity of the weathering, drainage and floating flow may have improved the qualities of the bauxite ores.  相似文献   

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