The abundance,distribution,and enrichment mechanism of harmful trace elements in coals from Guizhou,Southwestern China

Coal seams can enrich a variety of harmful trace elements under specific geological conditions.The spatial distribution of harmful trace elements in coal is extremely uneven,and the distribution characteristics of each element content are different.The harmful elements released in the process of coal mining and utilization will cause serious harm to the environment and the human body.It is of great resource significance to study the geochemistry of coal that affects the enrichment and distribution characteristics of harmful trace elements.Based on the domestic and foreign literature on coal geochemistry in Guizhou published by previous investigators,this study counted 1097 sample data from 23 major coal-producing counties in Guizhou Province,systematically summarized the relevant research results of harmful trace elements in the coal of Guizhou,and revealed the overall distribution and enrichment characteristics of harmful trace elements in the coal of Guizhou.The results show that the average contents of Cd,Pb,Se,Cu,Mo,U,V,As,Hg,and Cr in coal of Guizhou are higher than those in Chinese coal and world coal.A variety of harmful trace elements in the coal of Guizhou have high background values,especially in Liupanshui,Xingyi and Qianbei coalfield.The enrichment of various harmful trace elements in the Late Permian coal in Guizhou is mainly related to the combined action of various geological and geochemical factors.The supply of terrigenous debris and sedimentary environment may be the basic background of the enrichment of harmful elements in western Guizhou,while low-temperature hydrothermal activity and volcanic ash deposition may be the main reasons for the enrichment of harmful elements in southwestern Guizhou.

Enriched Constant Elements in the Boundary Element Method for Solving 2D Acoustic Problems at Higher Frequencies

The boundary element method(BEM)is a popular method for solving acoustic wave propagation problems,especially those in exterior domains,owing to its ease in handling radiation conditions at infinity.However,BEM models must meet the requirement of 6–10 elements per wavelength,using the conventional constant,linear,or quadratic elements.Therefore,a large storage size of memory and long solution time are often needed in solving higher-frequency problems.In this work,we propose two new types of enriched elements based on conventional constant boundary elements to improve the computational efficiency of the 2D acoustic BEM.The first one uses a plane wave expansion,which can be used to model scattering problems.The second one uses a special plane wave expansion,which can be used tomodel radiation problems.Five examples are investigated to showthe advantages of the enriched elements.Compared with the conventional constant elements,the new enriched elements can deliver results with the same accuracy and in less computational time.This improvement in the computational efficiency is more evident at higher frequencies(with the nondimensional wave numbers exceeding 100).The paper concludes with the potential of our proposed enriched elements and plans for their further improvement.

Separation and enrichment of elemental sulfur and mercury from hydrometallurgical zinc residue using sodium sulfide

The separation and enrichment of mercury and the recovery of elemental sulfur from flotation sulfur concentrate in zinc pressure leaching process were carried out by sodium sulfide leaching and carbon dioxide precipitating. The results show that the leaching rate of elemental sulfur is more than 98%, and 98.13% of mercury is enriched in the residue, under the optimized conditions of sodium sulfide concentration 1.5 mol/L, liquid/solid ratio 6：1 and leaching time 30 min at room temperature. In addition, the content of mercury is enriched 5.23 times that in the leaching residue. The elemental sulfur is precipitated from leaching solution under conditions of carbon dioxide flow rate 200 mL/min and blowing time 150 min, while solution is stirred adequately. The recovery efficiency of elemental sulfur reaches 97.67%, and the purity of elemental sulfur is 99.75%, meeting the requirements of industrial first-rate product standard according to the national standard of GB/T 2449-2006 （PRC）.

The enhanced element enrichment in the supercritical states of granite–pegmatite systems

In this paper, we show that supercritical fluids have a greater significance in the generation of pegmatites,and for ore-forming processes related to granites than is usually assumed. We show that the supercritical melt or fluid is a silicate phase in which volatiles; principally H_2O are completely miscible in all proportions at magmatic temperatures and pressures. This phase evolves from felsic melts and changes into hydrothermal fluids, and its unique properties are particularly important in sequestering and concentrating low abundance elements, such as metals. In our past research, we have focused on processes observed at upper crustal levels, however extensive work by us and other researchers have demonstrated that supercritical melt/fluids should be abundant in melting zones at deep-crustal levels too. We propose that these fluids may provide a connecting link between lower and upper crustal magmas,and a highly efficient transport mechanism for usually melt incompatible elements. In this paper, we explore the unique features of this fluid which allow the partitioning of variouselements and compounds, potentially up to extreme levels,and may explain various features both of mineralization and the magmas that produced them.

Separation and Enrichment of Rare Earth Elements in Phosphorite in Xinhua,Zhijin,Guizhou

The phosphorite ores-deposits rich in rare earth elements(REE) in Zhijin, Xinhua, Guizhuo occurs in the early Cambrian Meishucun and at the bottom part of Qiongzhusi stage (the upper layer of phosphorites), belonging to Yangzi stratum section. The living creature scraps was proved existent in dolomitic-phosphorites by experiments, The REE could be extracted to provide the worthy data for the further using. Adopting the HNO3 to extract REE, through the ion exchange method, the REE recovery rate could be reached 85.44% , having certain reference value.

Enrichment and Release of Rare Earth Elements during Weathering of Sedimentary Rocks in Wujiang Catchments,Southwest China

Thirteen weathering profiles of sedimentary rocks such as limestone, dolomitic limestone, dolomite, sillicalite, black shale and purple sandrock from Wujiang catchments were selected for study on enrichment and release behavior of rare earth elements （REE） during weathering, and its impact on plant growth and riverine REE distribution in the catchments with methods of hierachical cluster analysis and mass balance calculation in order to set a basis for riverine material source research and agricultural production. The results show that the enrichment degree of REE in calcareous soils from the Wujiang catchments is much higher than that of limestone, yellow soil, upper continental crust （UCC）, China soil （CS） and world soil （WS）. The ability of enrichment and release of REE is partly controlled by distribution of REE in bedrocks, contents and adsorption ability of organic matters, clay minerals and Fe-oxides/hydroxides in weathering profiles. The REE released from weathering of carbonate rocks and clastic rocks can be absorbed and utilized by local plants. The results also reveal that release of REE and Fe mainly from weathering of carbonate rocks and partly from clastic rocks exerts an important control on riverine REE distribution.

STUDY ON ENRICHMENT AND SEPARATION OF TRACE ELEMENTS WITH SILICA GELS MODIFIED BY HETEROCYCLIC AZO DYES

Two types of modified silica gels were prepared by adsorption method and bonding method respectively. Enrichment and separation of trace metal ions have been done by using the column packed with modified silica gels.

Enrichment Characteristics, Occurrence and Origin of Valuable Trace Elements in Lignite from Linchang Coal Mine, Guangxi, China

To evaluate the comprehensive exploitation and utilization values of coal resources in Baise basin of Guangxi, the Paleogene coal of Linchang coal mine were sampled and studied. The enrichment characteristics, occurrence modes, and geochemical origin of valuable trace elements in coal were studied by using X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS), polarizing microscope, X-ray fluorescence spectrometry (XRF), inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrometry (AFS). The results reveal that Linchang coal is ultra-low calorific value lignite with high ash, medium sulfur, medium-high moisture and medium volatilization. The minerals are mainly composed of illite, kaolinite, quartz, pyrite, siderite, bassanite, anhydrite and magnesium-containing calcite. Compared with average values for world low-rank coals, the contents of valuable trace elements in Linchang coal are higher on the whole, which is characterized by the high enrichment of U, the enrichment of elements Li, V and Ag, and the slight enrichment of elements Be, Ga and Se. Lithium, V, Ga and Ag mainly occur in clay minerals including illite and kaolinite, and part of V is related to organic matter. The carriers of Be in coal are clay minerals and organic matter. Selenium is mainly combined with organic matter and a small amount exists in pyrite. Uranium is primarily organically bound in coal. The enrichment of valuable trace elements in Linchang coal is influenced by the sedimentary source, coal-forming environment, underground circulating water and geological structure. The sedimentary environment of the coal seam is an acid-reduced terrestrial peat swamp, and the source is Triassic sedimentary rocks weathered from feldspathic volcanic rocks around Baise basin.

Super-Enrichment of Dispersed Elements and Associated Ore Deposits

Dispersed elements do not always occur as associated elements in the ore deposits of other elements. Instead, they can constitute independent ore deposits. The focus of this paper is placed on the mechanism of super-enrichment of the four dispersed elements Tl, Ge, Se, and Te under favorable geological conditions, where their enrichment coefficients are so high that their abundances can reach n×10+3-n×10+4, sometimes even up to n×10+6 times (e.g. Te) those of the crust. As a result, they can form their independent ore deposits. Studies have shown that such independent ore deposits are mostly distributed in the southwestern part of China, most of which belong to low-temperature ore deposits, ranging in age from Yanshanian to Himalayan (Cretaceous to Cenozoic), with a significant time gap with the host strata. Moreover, this paper also deals with the existing forms (as independent minerals, occurring isomorphously and being adsorbed) of the dispersed elements in those independent ore deposits. The discovery of independent ore deposits of dispersed elements is a great breakthrough in the study of dispersed element metallogenesis.

Sources, enrichment mechanisms, and resource effects of rare metal elements-enriched geothermal springs in Xizang, China

Rare metals such as lithium(Li), rubidium(Rb), and cesium(Cs) are strategically crucial mineral resources for the development of emerging industries in China. Ensuring a stable long-term supply of these resources is essential. The geothermal systems in Xizang, China are well-developed, with a wide distribution of various types. Most high-temperature geothermal systems in Xizang are exceptionally enriched in rare metal elements(RMEs) and have the potential to become a new source of rare metals to secure China's strategic mineral resource supply in the future. A close relationship also exists between the geothermal system and the special salt lake resources on the Tibetan Plateau. Geothermal springs thus play a key role in the migration and enrichment of RMEs from deep to shallow parts of the crust, in the transition between endogenous and exogenous mineralization, and source-to-sink processes. However, the mechanisms of element enrichment and evolution in these springs have not been systematically discussed, and many theoretical issues remain to be investigated. Based on summarizing and analyzing previous research, this study employs hydrochemical and isotopic geochemistry methods to investigate typical geothermal springs across Xizang and explore the anomalous enrichment mechanism of RMEs, and the resource effects of geothermal springs. Comprehensive analysis shows that the total dissolved solids(TDS) and hydrochemical types of geothermal springs are similar to those of major geothermal fields worldwide, but the Tibetan springs are abnormally rich in Li(averaging5.48 mg/L), Rb(averaging 0.75 mg/L), and Cs(averaging 3.58 mg/L), which are hundreds to thousands of times more concentrated than natural waters. The distribution of these enriched geothermal springs is controlled by the Yarlung Zangbo suture zone and the extended N-S trending rifts, especially in the intersection zone of the two, where the geothermal springs are the most enriched. Based on the spatial distribution, isotopic, and elemental geochemistry, the RMEs enriched in Tibetan geothermal springs are mainly derived from the magmatic-hydrothermal fluids generated by the partial melting of the subducted Indian plate under the Eurasian continent. These fluids not only maintain geothermal activities as a heat source but also participate in the material cycle of the geothermal spring as a material source. Against the background of regional crustal enrichment in RMEs,incompatible elements such as Li, Rb, and Cs are gradually enriched in magmatic-hydrothermal processes including partial melting in the source, magmatic differentiation, and hydrothermal fluid exsolution, and some ore-forming elements are further extracted from surrounding rocks through deep high-temperature water-rock interactions. Eventually, an eruption occurs, and these fluids move to the surface to form a geothermal spring rich in RMEs. With the drainage of geothermal springs, the RMEs are continuously transported to the lake basin by surface runoff and continue to concentrate and evolve into salt lake brines under an extremely arid climate environment, constituting an endogenous source and exogenous accumulation salt lake metallogenic model. This comprehensive explanation of the sources, migration, enrichment mechanisms, and resource effects of geothermal springs will deepen the understanding of rare metal mineralization processes, and aid in the advancement of theoretical models for key rare metal mineral resources in various geological bodies of the Tibetan Plateau, significantly expanding exploration scopes and accurately assessing the resource potential of RMEs.

The effect of Fe-Mn minerals and seawater interface and enrich-ment mechanism of ore-forming elements of polymetallic crusts and nodules from the South China Sea

Ferromanganese crusts and nodules are important submarine mineral resources that contain various metal elements with significant economic value. In this study, polymetallic crusts and nodules obtained from the South China Sea （SCS） were determined by using X-ray power diffraction （XRD）, Raman spectroscopy （RS）, Fourier transform infrared spectroscopy （FTIR）, and X-ray photoelectron spectroscopy （XPS） to systematically investigate and analyze the mineralogical and spectral characteristics of the Fe-Mn minerals. XRD measurements revealed that the SCS polymetallic crusts and nodules were composed of vernadite, quartz, and plagioclase. The nodules also contained todorokite. The Fe-phase minerals of the SCS crusts and nodules were composed of amorphous Fe oxide/hydroxide, and the Mn- and Fe-phases minerals exhibited relatively poor degrees of crystallization. FTIR results showed that the Fe-Mn minerals in the crusts and nodules included a large number of surface hydroxyl groups. These surface hydroxyl groups contained protons that could provide reactive sites for complexation of ore-forming elements in seawater. XPS results indicated that the surfaces of the Fe-Mn minerals mainly contained Fe, Mn, and O. Fe was present in the trivalent oxidation state, while Mn, which may contain several bivalent oxidation state, was present in the tetravalent and trivalent oxidation states. The SCS polymetallic crusts and nodules were compared with Pacific seamount crusts, and results showed that the surface hydroxyl （-OH） groups of the SCS crusts and nodules numbered more than the lattice oxygen （O^2-）. But the lattice oxygen of Pacific seamount crusts numbered more than the surface hydroxyl groups. This characteristic indicated that the degree of crystallization of Fe-Mn minerals from the Pacific Ocean was higher than that of minerals from the South China Sea. Comprehensive studies showed that ore-forming elements in the interface between seawater and the Fe-Mn minerals in the submarine ferromanganese crusts and nodules employed the following enrichment mechanisms： （1） the metal ion complexed with the surface hydroxyl of Fe-Mn minerals to form hydroxyl complexes, which were connected by coordination bonds or stable inner-sphere complexes that exchanged protons on the mineral surfaces; （2） the charged surfaces of the minerals and metal cations formed outer-sphere complexes, which made up the electrostatic double layer, through electrostatic adsorption; and （3） the metal cations isomorphously exchanged the Mn and Fe ions of the mineral lattice structure.

Enrichment characteristics and sources of the critical metal yttrium in Zhijin rare earth-containing phosphorites, Guizhou Province, China

Yttrium(Y)is a critical metallic element that is used widely in modern scientific,technological,and industrial applications.Phosphorites in the Zhijin area of Guizhou Province,China,are famous for Y enrichment,but the enrichment characteristics and sources remain unclear.Previous studies suggested that the sources of rare earth elements(REEs,La-Lu)and Y(REYs,La-Lu+Y)were related to hydrothermal deposition.However,this study presents evidence refuting that hypothesis,with major and trace elemental data collected with quadrupoleinductively coupled plasma-mass spectrometry(Q-ICPMS)analysis.These data show that Y in Zhijin REYscontaining phosphorites has a normal distribution and is particularly enriched relative to other REYs.The Y enrichment degree is different at different∑REY intervals.Specifically,the Y enrichment degree is higher at lower∑REY values and lower at higher∑REY values.The REYs-containing phosphorites show features of primary phosphorites.Both REEs and Y have good correlations with P2 O5 in the phosphorites with low REYs contents(total REYs<535 ppm),whereas at high REYs contents(total REYs>535 ppm),REEs have a good correlation with P2 O5 but Y does not.Inconsistent enrichment processes of REYs are suggestive of complex sources of Y.Thus,seafloor hydrothermal fluids were not the direct source of Y.Normal seawater mixed with terrestrial sources might have contributed to the origin of Y here.This study could lead to improvements in Y mineral resource explorations and the situation involving the global REYs supply crisis.

Rare earth elements-rich phase and enriching mechanism in sediments from CC area, the Pacific Ocean

Compared to North American shale composition (NASC), REE contents of sediments from the CC area in the Pacific Ocean are obviously high except that cerium has equal content to that of NASC. Three-valence rare earth elements were completely enriched in phosphate-phase and cerium in iron-phase. Rare earth elements in the sediments were originally derived from seawater. During lithi- genic and minerogenic processes of metalliferous nodules, three-valence rare earth elements in sediments mobilized and incorporated into sediments as authigenous biogenic-apatite, while cerium had change from Ce3+ to Ce4+ and directly precipitated from seawater and entered metalliferous nodules and caused Ce anomalies in REE pattern in sediments.

Occurrence characteristics and enrichment regularity of indium in pyrite: A case study of Dachang tin ore-field

To reveal the occurrence state and enrichment regularity of the dispersed element indium in pyrite, the petrology,mineralogy, geochemistry, and mineral physics were researched detailedly. The results suggest that the structure of pyrite is mainlycomposed of massive structure, disseminated structure, vein structure, reticular structure, comb structure and so on. Generally, thepyrite coexists with sphalerite, marmatite, pyrrhotite, chalcopyrite, galena, and arsenopyrite. And the texture of pyrite primarilyconsists of the metasomatic texture, solid solution texture, idiomorphic?hypidiomorphic granular texture, and disseminated texture.The content of indium in pyrite ranges from 0.491×10?6 to 65.1×10?6 with an average value of 14.38×10?6. Yet, the indium content inthe Gaofeng deposit is higher than that in the Dafulou and Tongkeng deposit, showing a particularly significant supernormalenrichment. Besides, the cadmium content in pyrite is also higher than other dispersed elements, and similarly the abnormalenrichment of cadmium in the Gaofeng deposit is also very significant. An obvious positive correlation exists between In and Cd, orTl, but a negative correlation between In and Re. It is difficult to find out a positive or negative correlation between In and Ga. Theelement zinc is of great importance to the enrichment of indium, which can possibly facilitate to the migration and crystallization of dispersed element indium.

Enrichment rules and exploration practices of Paleogene shale oil in Jiyang Depression, Bohai Bay Basin, China

Based on formation testing data of more than 40 wells with industrial oil flow, systematic observation of 1 010.26 m long cores taken from 4 wells and test data of over 10 000 core samples combining with drilling and pilot fracturing data of multiple wells, the geological characteristics of the upper submember of the Sha 4 Member to the lower submember of the Sha 3 Member of Paleogene(Es4s-Es3x) in the Jiyang Depression were investigated to find out factors controlling the enrichment of shale oil and the accumulation model of shale oil, and a comprehensive evaluation method for shale oil sweet spots was established. It is found through the study that the target shale layer is characterized by strong heterogeneity, weak diagenesis, low thermal evolution and high content of clay and carbonate minerals. Shale lithofacies, microcrack, thin interlayer and abnormal pressure are the main factors affecting enrichment and stable production of shale oil, the organic rich laminar shale has the best storage and oil-bearing capacity, microcrack network system improve the storage capacity and permeability of the shale, the thin interlayer is the main flow channel for stable shale oil production, and the abnormal high pressure layer is rich in free state shale oil and high in oil content. The shale oil layers in the target section were divided into three types: matrix, interlayer and fracture ones. According to the occurrence state and exploration practice of shale oil at home and abroad, it is concluded that the interlayer shale oil is the most profitable type at present. The selection parameters for the different types of shale oil were determined, and accordingly the favorable areas were pointed out by comprehensive evaluation of multiple factors. Vertical wells in the interlayer shale oil reservoir, such as Fan 159, Fan 143 and GX 26, were stimulated by volume fracturing and high conductivity channel fracturing jointly. After fracturing, they had a daily oil production of over 6 t, up to 44 t, and stable productivity. Shale oil is expected to become an important replacement energy resource in the Jiyang Depression.

Zircon deposit and rare earth element enriched metasomatic alkaline rocks at Kyemyeongsan Formation, Chungju, Korea: Paleozoic magmatism and Zr-REE-Nb mineralization

The zircon ore deposit in metasediments and peralkaline granite of the Kyemyeongsan Formation is located in southwest of Chungju city, Korea. The deposit, closely associated with REE and Nb,is composed of metasomatic alkaline rocks and rare metal alkali granite, and was formed in late Carboniferous (340～343Ma). Zircon occurs in different paragenetic sequence: (1) earlier rare metal alkali granite, (2) later metasomatic zircon ore. The metasomatic zone contains abundant microcline, albite and quartz with minor biotite, magnetite, hornblende, allanite and zircon. The alkali granites have high silica (72.13～74.52wt.% as SiO 2), and total iron content (5.95～6.89%), and are characterized by low Al 2O 3 content (7.12～9.74%). They also show variable K 2O content (3.60～6.98%), and high ratios of K 2O/Na 2O. The REE patterns of rare metal alkali granite are similar to those of felsic volcanics from rifts, or back arc basins in, or near continental crust. Zircon ores are characterized by high iron content and low Al 2O 3, SiO 2, and K 2O content and have unusually high total REE content (0.18～2.33%). REE patterns show relatively flat to somewhat heavy REE (HREE) depleted characteristics (Ce/Yb=0.39～5.17) with large Eu negative anomaly (Eu/Eu *=0.16～0.29). Laser ablation microprobe inductively coupled plasma mass spectrometer (LAM ICP MS) analyses has been carried on zircon. The REE patterns of mineral zircons are almost the same to those of zircon ores and rare metal alkali granites, which may reflect the inability of zircons to effectively fractionated REE at formation of origin. The Sm Nd isochron age of the zircon ore and rare metal alkali granite are 330Ma, and 331Ma, respectively with ε Nd(t) being range from -2.00 to -1.84. This data suggest that the ore forming material came from the mantle. Alkali granite has suffered extensive post magmatic metasomatism of a high temperature to produce zircon ores. Geochemical characteristics show that metasomatism of alkaline fluid was probably the dominant ore forming process in Chungju district.

火电厂燃煤产物中关键微量元素富集特征研究

煤系共伴生战略性关键元素可在燃煤产物中富集,研究燃煤产物中关键元素的富集特点可为元素的预富集和提取利用提供依据。以我国东西部不同火电厂燃煤产物为例,采用波长色散荧光光谱仪(AxiosmAX)、电感耦合等离子体质谱仪(iCAP-Qc)测试了燃煤产物中常量元素和关键微量元素的含量,分析了燃煤产物中关键微量元素分布富集的一般性规律。结果表明:①粉煤灰中主要常量元素为Si、Al、Fe,三者氧化物占比达87.79%;微量元素中稀土元素、锂、镓、铀、锗的含量分别为456.95μg/g、163.58μg/g、49.07μg/g、8.67μg/g、4.59μg/g,除铀、锗外均高于世界煤灰平均值。②常量元素中P趋向富集于细灰中,Fe、Ca更易富集于粗灰中;稀土元素分布模式保持一致,且在细灰中的含量高于粗灰,锂、镓、铀、锗均在细粒燃煤产物中更为富集,分异系数分别为1.17、2.45、1.53、2.14。③数理统计分析表明,煤中稀土元素与无机矿物相关,且富集于燃煤产物的非磁性组分中;锂主要与黏土矿物有关,燃烧后主要以LiAlO2的形式存在;镓、铀赋存形式不单一,与黏土矿物有一定的关系;锗与无机相相关性弱,表明其主要与有机质结合。

低熔点亲铜元素(LMCE)在金成矿中的作用及促进金富集的机理

低熔点亲铜元素(LMCE),包含As、Sb、Bi、Hg、Pb、Se、Te、Tl、Sn等,在戈尔德斯密特(V·M·Goldschmidt)元素地球化学分类中均属于亲铜元素。它们具有亲铜性、电负性大、低熔点、半金属的特性。在金成矿过程中,这些元素与硫的亲和力强,多形成LMCE的硫化物、硫盐矿物、硒化物、碲化物和金属互化物,甚至形成LMCE与金的互化物和金的化合物。同时,它们在成矿流体中可以形成LMCE熔体,并对金矿床中Au的高效富集沉淀起到一种重要的桥梁作用。作者针对LMCE在金矿床中的赋存状态,总结了金矿床中LMCE富集金的特点,综合归纳了LMCE对金富集的成矿机理,认为在一些大型金矿床中,除了人们熟知的水-岩反应、硫化作用、流体沸腾、流体混合、有机成矿、岩浆脱气、叠加成矿等对热液金矿床的成矿起到重要作用外,流体-熔体分离、溶解-再沉淀、矿物重结晶、矿物表面吸附和元素替代等地质作用,也是LMCE在成矿过程中对金的富集重要机制。

吐哈盆地八仙口地区砂岩型铀矿微量元素的特征

天山造山带上的伊犁和吐哈盆地是中国重要的砂岩型铀矿产区,吐哈盆地八仙口地区是近年来铀矿勘查的重要地段,铀矿化具有矿带窄、厚度不大、品位较低和钙质含量较高等特点。八仙口地区微量元素地球化学变化规律研究薄弱,制约了矿化规模成因的分析。以氧化流体蚀变空间分带研究为基础,开展微量元素分布规律和特征元素在不同蚀变分带的定量迁移富集研究,并通过与伊犁蒙其古尔矿床的对比,揭示八仙口地区氧化流体作用下铀的富集过程与富集规模成因。研究认为,U与Re等变价元素在矿化带内同步富集指示氧化还原是最主要成矿作用;Sc、Co、Ni、Th等不易变价元素和稀土元素(rare earth element,REE)在氧化带内富集而矿带内亏损与地下水性质有关,高矿化度地下水造成的水解和黏土化,增强了氧化带内碎屑颗粒对溶液中离子的吸附;上新世以来天山快速的隆升造成吐哈盆地极端干旱气候出现,造成微量元素和稀土元素在不同蚀变带内再分配。在铀矿化成因分析中可加强对其中变价与不变价元素变化量的表征,在找矿过程中需对氧化带渗入阶段的古气候加以重视。

南堡凹陷油气分布有序性与差异富集主控因素

油气分布有序性是表征油气差异富集规律的重要途径,能够为寻找接替方向提供重要依据。通过开展油气藏类型、油气性质、油气富集程度、油气输导体系和断—盖条件等多角度的系统分析,揭示了南堡凹陷油气分布有序性与差异富集的主要控制因素。研究表明,南堡凹陷从次凹中心向边缘,表现出由岩性油气藏向构造油气藏、原油性质逐渐变差、富集层系逐渐变浅的有序变化。断陷期、坳陷期的构造活动控制了烃源岩的分布与演化,构造演化控制了凹陷沉积体系从而控制储盖组合分布和圈闭类型,其中源下、源内和源上3类储盖组合为多层系油气分布奠定了基础;纵横向输导体系和断—盖配置差异,控制了不同构造带油气运聚过程,形成了凹陷中部源下富集、凹陷边缘源上富集的总体规律。研究成果进一步揭示了该凹陷的油气分布规律性,可为成熟探区的精细勘探提供理论指导和借鉴意义。