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1.
【研究目的】不同页岩岩相的矿物组分、含气性和可压性等的差异,决定不同岩相的开发潜力不同,页岩岩相的划分及评价对找寻页岩气勘探开发甜点具有重要指导意义。【研究方法】基于钻井、岩心和分析测试资料,综合利用地质理论结合硅质矿物-黏土矿物-碳酸盐矿物含量三端元图解,对鄂西宜昌斜坡带上奥陶统五峰组—下志留统龙马溪组下段含气页岩岩相进行划分,结合有机碳含量、含气量、岩心镜下特征等划分优势岩相。优选有机质丰度、硅质矿物含量、黏土矿物含量3项指标与页岩含气量进行相关性分析,建立了五峰组—龙马溪组含气页岩优势岩相的分级标准。【研究结果】研究区优势岩相均为II类优势岩相,II1类（最优）优势岩相为S-2混合硅质页岩相和S-3含黏土硅质页岩相,位于龙马溪组一亚段和五峰组上段,厚6 m;II2类（次优）优势岩相为S硅质页岩相,位于五峰组下段,厚4 m。【结论】宜昌斜坡带和涪陵地区具有相似的岩相垂向演化序列,优势岩相均位于五峰组—龙马溪组一亚段,但同一岩相组合的页岩厚度和品质差异较大,发生在鲁丹阶早期的湘鄂西水下隆起和鲁丹阶晚期的水下隆起是造成宜昌地区优势岩相的厚度和品质均要差于涪陵地区的主要原因。创新点：建立五峰组—龙马溪组含气页岩优势岩相的分级标准,提出龙马溪组一亚段和五峰组是优势岩相发育层位。  相似文献   

2.
Nuwaifa Formation is a part of sequence stratigraphy that belongs to the Jurassic system exposed in the western desert of Iraq. The Jurassic system consists of Ubaid, Hussainiyat, Amij, Muhaiwir, and Najmah formations. Each formation is composed of basal clastic unit overlain by upper carbonate unit. Nuwaifa karst bauxite was developed in fossil karsts within the Ubaid Formation in areas where maximum intersection of fractures and faults exist. This bauxitization process affected the upper surface of the Ubaid limestone formation, which directly underlies the Nuwaifa bauxite Formation. Nuwaifa Formation represents karst-filling deposit that consists of a mixture of allochthonous (sandstone, claystone, and mudstone) and autochthonous lithofacies (bauxite kaolinite, kaolinitic bauxite, iron-rich bauxite, and flint clay). Most bauxite bodies occur within the autochthonous lithofacies and are lenticular in shape with maximum thickness ranges from few meters to 35 m and in some place up to 100 m. Petrographically, the bauxite deposit exhibits collomorphic-fluidal, pisolitic, oolitic, nodular, brecciated, and skeletal textures indicative of authigenic origin. Mineralogy boehmite and gibbsite are the only bauxite minerals; the former is dominant in the upper parts of the bauxite profiles, whereas the latter is dominant throughout the lower and middle part of the bauxite. Kaolinite, hematite, goethite, calcite, and anatase occur to a lesser extent. The study bauxites are mainly composed of Al2O3 (33–69.6 wt.%), SiO2 (8.4–42 wt.%), Fe2O3 (0.5–15.9 wt.%), and TiO2 (0.7–6.1 wt.%) with LOI ranging from 13.5 to 19.1 wt.%. Geochemical investigations indicate that the immobile elements like Al2O3, TiO2, Cr, Zr, and Ni were obviously enriched, while SiO2, Fe2O3, CaO, MgO, Zn, Co, Ba, Mn, Cu, and Sr were depleted during bauxitization process. The results of this study strongly suggest that the bauxite deposits of the Nuwaifa Formation are derived from the kaolinite of the Lower Hussainiyat Formation.  相似文献   

3.
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   

4.
The present work assesses the potential industrial uses of Paleocene limestone deposits, Garra Formation in Sinn El-Kaddab Plateau, South Western Desert of Egypt, based on their mineralogy and geochemical characteristics. Eighty-six limestone samples collected from ten stratigraphic columnar sections were analyzed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques. Petrographically, Garra limestone deposits consist dominantly of benthic foraminiferal wackestone and packstone microfacies. The XRD data revealed dominance of low-Mg calcite as essential carbonate mineral in the studied limestone. The bulk rock XRF results revealed CaO (29.28–55.75%) with an average of 52.74%. The CaO exhibits a strong negative correlation with MgO, SiO2, TiO2, Al2O3, and moderate negative correlation with Fe2O3 which indicates that the contribution of these elements is mainly due to detrital input. On the other hand, Al2O3 and Na2O contents exhibit significant negative correlation with loss of ignition (LOI) wt% indicating their incorporation within terrigenous matrix. The average Sr content attains 1297 ppm indicating deposition in temperate marine environment. The average molar CaCO3% values of bulk samples have been computed for individual columnar sections to determine the purity status of Garra limestone deposits. They range from impure (CaCO3%?=?79.92%) to high-pure (CaCO3%?=?97.76%) limestone. Therefore, Garra limestone deposits have extremely valuable uses in a wide spectrum of industrial applications including Portland cement, steel, ceramics, whiting, chemical uses, paper, and feed stuff.  相似文献   

5.
Ammonium feldspar was grown hydrothermally from a gel, having a stöchiometric Al2O3·6SiO2 composition. As a source for NH 4 + , a 25 percent NH3 solution was used. Internal Cr/CrN and graphite/methane buffers fixed the fugacity of NH3 during the experiments. Unit cell parameters of the synthetic ammonium feldspar are a: 0.8824 (5) nm, b: 1.3077 (8) nm, c: 0.7186 (4) nm, β: 116.068 (12)°, V: 0.7448 (34) nm3. the X-ray power diffraction pattern is measured and indexed in accordance to the space group C2/m. Infrared and thermal gravimetric analyses provide no evidence for the presence of structurally bound water molecules in the crystal structure of synthetic ammonium feldspar. Hydrothermally grown anhydrous ammonium feldspar is shown to be identical to the mineral buddingtonite by the similarity of the data between the synthetic and natural materials. There may be justification for considering natural buddingtonite as an anhydrous feldspar with the ideal formula NH4Si3O8. Reexamination of natural specimens is desirable.  相似文献   

6.
The aim of the present research work was to investigate the possibility of adding a jarosite–alunite chemical precipitate, a waste product of a new hydrometallurgical process developed to treat economically low grade nickel oxides ores, in the raw meal for the production of Portland cement clinker. The precipitate was also tested in the production of non-expansive, sulfoaluminate-based cement clinker, as a substitute for gypsum because of its high sulfate content. For the Portland clinker, two samples of raw meals prepared, one with ordinary raw materials (reference sample) and another with 1% jarosite–alunite precipitate. Both raw meals were sintered at 1450 °C. For the sulfoaluminate-based clinker, one raw meal contained 20% gypsum (reference sample) whereas the other contained 11% of the precipitate. Both raw meals were sintered at 1300 °C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the jarosite–alunite precipitate did not affect the mineralogical characteristics of the so produced Portland cement clinker. In the case of sulfoaluminate-based cement clinker, there was confirmed the formation of the sulfoaluminate phase (C4A3S¯), the most typical phase of this cement type.  相似文献   

7.
This work discusses the composition, radioactivity, and possible utilization of the kaolin resources in Sinai which are hosted in thick sandstone sequences belonging to the Carboniferous (Wadi Khaboba) and Early Cretaceous (Wadi Iseila and Abansakar) ages. The characterization of kaolin was done by microscopic and SEM examination, supported by XRD and ICP-MS analyses. The studied kaolin resources consist of kaolinite, as the main constituent, associated with subsidiary dickite and halloysite, and minor contribution of smectite and illite. The most dominant non-clay mineral is quartz, besides minor gypsum, dolomite, and hematite. Ferrugination dominates, in most cases, at the upper boundaries of the kaolin lenses, suggesting possible supergene activity. The high Al2O3/SiO2 ratio for the Cretaceous kaolin (0.54, in average) specifies its better grade relative to the Carboniferous kaolin (0.43, in average). The kaolin of the middle part of lens C in Wadi Iseila contains Si/Al molecular ratio of about unity, suggesting high-grade kaolin. The Carboniferous kaolin has enriched the radionuclides: U, Th, and Ra (at disequilibrium state due to leaching of eU relative to Ra) and the REE, relative to that of the Cretaceous age. The Carboniferous kaolin is characterized by a higher contribution of HREE (zircon signature), whereas LREE seems to be more influential for the Early Cretaceous kaolin (monazite signature). In spite of the very high CIA index (93 to 99), none of the analyzed kaolin deposits displays Ce abnormality. The high radioactivity of some Carboniferous kaolin can be a serious impediment for its utilization or its exportation. The kaolin of Sinai does not satisfy the international standards for paperwork industries and refractory manufacturing, but beneficiation may overcome this challenge. However, some lenses have high-grade kaolin with a low percentage of oxides of iron, magnesium, calcium, sodium, and potassium and a low radioactivity, hence nominated for the local refractory industry. The high-grade kaolin of Sinai fulfills the standards required for ceramics manufacturing in the global market. Grade 3 kaolin (< 30%, Al2O3) can be used in the manufacturing of white Portland cement and red glaze manufacturing on both local and global markets.  相似文献   

8.
The Euphrates Formation (Lower Miocene) in the Central Iraq consists mainly of shallow marine carbonates. Two hundred ten samples were collected from 21 wells (1E to 21ED) at Bahar Najaf area, and 18 samples were collected at Wadi Asadi in Baghdadi area, from Euphrates Formation. Four microfacies are identified, namely mudstone, wackestone, packstone, and rare grainstone with ten submicrofacies. The allochems in the Euphrates Formation are dominated by bioclasts. Peloids, ooids, and intraclasts are less abundant. The common fossils in the Euphrates Formation are miliolids, algae, ostracods, Miogypsina, and abundant shells of pelecypods and gastropods. Calcite and dolomite are the predominant mineral components of the Euphrates Formation. The carbonates of the Euphrates Formation have been affected by a variety of diagenetic processes such as micritization, dissolution, neomorphism, cementation, stylolitization, dolomitization, dedolomitization, and silicification. The Euphrates Formation was deposited in open to restricted platforms which indicated lagoonal environment with warm and restricted open circulation. In fact, prevalence and abundance of micrite provide an evidence of a shallow marine of low-energy environment and, in some places, may be approaching to be stagnant environment. The average of CaO in Najaf area (51.5 %) is slightly lower than that in Baghdadi area (53.3 %), which was reflected in calcite content found being 91 % in Najaf and 94 % in Baghdadi. Dolomite and gypsum appeared as minor minerals beside calcite, so low concentration of MgO (0.83 % in Najaf; 0.63 in Baghdadi) and SO3 (0.55 % in Najaf; 0.53 % in Baghdadi) was reflected information of small amounts of dolomite (2 % in Najaf; 1.6 % in Baghdadi) and gypsum (0.7 % in Najaf and 0.6 in Baghdadi) in the Euphrates Formation. The insoluble residue in Najaf area (4.37 %) is relatively higher than that in Baghdadi area (1.9 %), indicating that the Euphrates Formation in Najaf Area has deposited in an environment closer to the shoreline. Concentrations of the trace elements Sr, Mn, and Fe which support the conclusion that reminds the Euphrates Formation had been deposited in a shallow marine environment of quiet energy, with the likelihood that the shoreline was the nearest to Najaf rather than to Baghdadi.  相似文献   

9.
The pegmatite province of the Southeastern Desert (SED) is part of a pegmatite district that extends from Egypt (extends to 1200 km2). Rare metal pegmatites are divided into (1) unzoned, Sn-mineralized; (2) zoned Li, Nb, Ta and Be-bearing; and (3) pegmatites and pegmatites containing colored, gem-quality tourmaline. The Rb/Sr data reflect a crustal origin for the rare metal pegmatites and indicate that the original SED magma was generated during the peak of regional metamorphism and predates the intrusion of post-tectonic leucogranites. These bodies developed an early border zone consisting of coarse to very coarse muscovite quartz alkali feldspar, followed by an intermediate zone of dominant quartz feldspar muscovite rock. Garnet, tourmaline, beryl, galena, pyrite, amblygonite, apatite and monazite are rare accessories in both zones. Cassiterite tends to concentrate in replacement zones and along fractures in albite quartz muscovite-rich portions. The highest concentrations of cassiterite occur in irregular greisenized zones which consist dominantly of micaceous aggregates of green Li-rich muscovite, quartz, albite and coarse-grained cassiterite. The different metasomatic post-solidification alterations include sodic and potassic metasomatism, greisenization and tourmalinization. Geochemically, the pegmatite-generating granites have a metaluminous composition, showing a differentiation trend from coarse-grained, unfractionated plagioclase-rich granite towards highly fractionated fine- to medium-grained, local albite-rich rock. Economically important ore minerals introduced by volatile-rich, rare metal-bearing fluids, either primarily or during the breakdown of the primary mineral assemblages, are niobium-tantalum oxides, Sn-oxides (cassiterite), Li-silicates (petalite, spodumene, euctyptite, and pollucite), Li-phosphates (amblygonite, montebrasite and lithopilite) and minor REE-minerals (Hf-zircon, monazite, xenotime, thorian, loparite and yttrio-fluorite). The pollucite is typically associated with spodumene, petalite, amblygonite, quartz and feldspar. The primary pollucite has Si/Al (at) ratios of 2.53-2.65 and CRK of 79.5- 82.2. Thorian loparite is essentially a member of the loparite (NaLREETi2O6)-lueshite (NaNbO3)-ThTi2O6-ThNb4O12 quaternary system with low or negligible contents of other end-member compositions. The mineral compositionally evolved from niobian loparite to niobian thorian and thorian loparite gave rise to ceriobetafite and belyankinite with high ThO2 contents. Thorian loparite is metamict or partly metamict and upon heating regains a structure close to that of synthetic loparite NaLaTi2O6.  相似文献   

10.
Matrix glass and melt inclusions in phenocrysts from pantellerite lavas of the Boseti volcanic complex, Ethiopia, record extreme fractionation of peralkaline silicic magma, with Al2O3 contents as low as 2.3?wt.%, FeO* contents up to 17?wt.% and SiO2 contents ~65?wt.%. The new data, and published data for natural and experimental glasses, suggest that the effective minimum composition for peralkaline silicic magmas has ~5?wt.% Al2O3, 13?wt.% FeO* and 66?±?2?wt.% SiO2. The dominant fractionating assemblage is alkali feldspar?+?fayalite?+?hedenbergite?+?oxides?±?quartz. Feldspar – melt relationships indicate that the feldspar is close to the minimum on the albite-orthoclase solid solution loop through the entire crystallization history. There is petrographic, mineralogical and geochemical evidence that magma mixing may have been a common process in the Boseti rhyolites.  相似文献   

11.
松辽盆地红岗油田白垩系青山口组发育含片钠铝石砂岩。通过偏光显微镜、扫描电镜、阴极发光 仪、Ｘ射线衍射等多种技术手段,对含片钠铝石砂岩的碎屑成分、胶结物类型及自生矿物共生序列等特征进行 了研究。该区含片钠铝石砂岩为岩屑长石砂岩及长石岩屑砂岩,胶结物有次生加大长石、次生加大石英、自生 石英微晶、黏土矿物、片钠铝石、方解石、铁方解石及铁白云石。方解石的形成分为两期,第１期方解石为原 始生物碎屑颗粒溶蚀溶解的产物,第２期方解石可能与ＣＯ２ 充注后钙长石及早期碳酸盐矿物的溶蚀溶解有关。 含片钠铝石砂岩的自生矿物共生序列为：次生加大长石、早期次生加大石英-自生石英微晶-早期高岭石、第１ 期方解石、片钠铝石-晚期次生加大石英-晚期高岭石、第２期方解石、铁方解石、铁白云石。其中ＣＯ２ 注入 后的矿物共生组合为：片钠铝石-晚期次生加大石英-晚期高岭石、第２期方解石、铁方解石、铁白云石。  相似文献   

12.
The detailed hydro-chemical study of meltwater draining from Khangri glacier Arunachal Pradesh has been carried out to evaluate the major ion chemistry and weathering processes in the drainage basin. The investigative results shows that the meltwater is almost neutral to slightly acidic in nature with Mg–HCO3-dominated hydro-chemical facies. In glacial meltwater, Ca+?2 is the most dominated cation followed by Mg+2, Na+, and K+, while HCO3? is the most dominant anion followed by SO42?, NO3?, and Cl?. The dominant cations such as Ca+2 and Mg+2 show a good relation with the minerals abundance of the rocks. Calcite (CaCO3) and biotite [K(Mg,Fe)3AlSi3O10(F,OH)2] are the most abundant minerals in the deformed carbonate-rich metasedimentary rocks near to the snout with some K feldspar (KAlSi3O8) and quartz (SiO2). This suggests Ca+2 have definitely entered into the water due to the dissolution of calcite and Ca feldspar (CaAl2Si2O8), while one of the source of Mg+2 is biotite. Na feldspar (NaAlSi3O8) has contributed towards the availability of sodium ion, while potassium ion is derived from the chemical weathering of K feldspar and biotite. The chemical weathering is the foremost mechanism controlling the hydro-chemistry of the Khangri glacier because of the least anthropogenic interferences. The mineralogy of surrounding rocks is studied to understand better, the rock–water interaction processes, and their contribution towards ionic concentration of meltwater. The meltwater discharge and individual ion flux of the catchment area have also been calculated, to determine the ionic denudation rate for the ablation season. The high elemental ratio of (Ca?+?Mg)/(Na?+?K) (7.91?±?0.39 mg/l) and low elemental ratio of (Na?+?K)/total cations (0.11?±?0.004) indicate that the chemical composition of meltwater is mainly controlled by carbonate weathering and moderately by silicate weathering. The scatter plot result between (Ca?+?Mg) and total cations confirms that carbonate weathering is a major source of dissolved ions in Khangri glacier meltwater. In addition, the statistical analysis was also used to determine the correlation between physical parameters of glacier meltwater which controlled the solute dynamics.  相似文献   

13.
The Precambrian greywacke of Ribandar‐Chimbel belonging to the Sanvordem Formation of the Goa Group, India, has been studied for petrography and analyzed for major trace elements. The greywacke is characterized by angular to sub‐round grains of quartz, feldspar, biotite, chlorite and clay minerals. The abundance of clay in the matrix seems to have influenced the Al2O3 content and the K2O/Al2O3 ratio. The variation diagrams indicate a decreasing trend of TiO2, Al2O3, Fe2O3 and MgO; whereas Na2O and CaO exhibit a scatter which could be a result of the variable presence of feldspar within the sediments. The immobile elements, vanadium (25 to 144 ppm), nickel (up to 107 ppm) and chromium (up to 184 ppm), reflect abundance of clay minerals. The greywacke shows strongly fractionated REE patterns with LaN/YbN = 8 to 26 and with higher total REE abundances (up to 245 ppm). The low REE enrichment and depletion in heavier REE with prominent negative Eu anomaly (Eu/Eu*= 0.54 to 0.79) suggest a derivation of the greywacke from an old upper continental crust composed chiefly of felsic components. Petrological evidence and geochemical data suggest that the deposition of the greywacke largely took place in a deep to shallow basin that progressively changed from that of a continental island arc to an active continental setting.  相似文献   

14.
The Jiuyishan complex massif, located in the northern section of the Nanling region, is a combination of five plutons, namely, the Xuehuading, Jinjiling, Pangxiemu, Shaziling and Xishan plutons. Whole-rock geochemistry, mineral electron microprobe analysis, zircon U-Pb dating and Hf isotope analysis were carried out for the Jinjiling and Pangxiemu plutons. The zircon U-Pb dating yields weighted mean ages of 152.9±0.9 Ma for the Jinjiling pluton and 151.7±1.5 Ma for the Pangxiemu pluton, with a narrow gap between them. The Jinjiling and Pangxiemu plutons both have geochemical characteristics of high SiO2, Al2O3, Na2O, K2O and low TiO2, MgO, CaO, P2O5 contents, with intense depletionS in Sr, Ba, Ti, Eu and enrichments?in Ga, FeOT and HFSE, and these characteristics reflect an A-type affinity. From the Jinjiling to the Pangxiemu plutons, the mineral composition of mica changes from lepidomelane to zinnwaldite, with increases in F, Li2O and Rb2O contents. The mineral composition of zircon changes from low Zr/Hf to high Zr/Hf, with increasing HfO2, P2O5 and UO2+ThO2+Y2O3 contents. The mineral compositions of feldspar indicate that the Pangxiemu pluton contains more alkali feldspar than the Jinjiling pluton. The whole-rock geochemistry and mineral compositions reveal a higher degree of differentiation for the Pangxiemu pluton. The nearly uniform εHf(t) indicates the same source region for the two plutons: both were derived from partial melting of the lower crust, with small contributions of mantle materials. In addition, higher F, lower Nb/Ta and Zr/Hf ratios in the Pangxiemu Pluton suggest a closer relationship with the rare metal mineralization than for the Jinjiling pluton.  相似文献   

15.
全风化花岗岩化学及矿物成份在全土和粘粒中的不同表征   总被引：1，自引：0，他引：1  
对全风化花岗岩化学和矿物成份的测试常用全土和粘粒部分(粒径<2μm)分别进行。业已发现两者由于物质组成和结构特征的差异,对土工程地质性质所起作用不同。本文给出了6个全风化花岗岩样品的全土和粘粒部分筛分法和移液管法测定粒度成份,用X荧光光谱仪做全量化学分析,及XRD矿物学分析的结果。对比这两部分数据发现,属于含砾土的这些样品化学成份的变化同矿物一致,尤其是同粘土矿物成份含量变化很一致。同全岩相比,粘粒化学成份中的SiO2减少了近50%,K2O含量也降低,而Al2O3、Fe2O3和H2O+都明显升高。粘粒中氧化物相对含量升高者居多;全岩矿物成份以石英、粘土矿物和长石为主,粘粒中埃洛石和高岭石占大多数,其次为伊利石;粒度成份、化学成份和矿物含量相关性比较明显的是:石英和角砾正相关,和砂粒负相关,长石和砂粒正相关,粘土矿物含量和Al2O3、烧失量(LOI)和埃洛石含量正相关。  相似文献   

16.
不同产地绿碧玺的产出特征、化学成分、致色机理和形成条件都存在差异.目前关于坦桑尼亚绿碧玺的矿物种属及颜色成因等问题还未得到解决,对其科学鉴定和品质评级造成了一定影响.本文采用红外光谱、拉曼光谱、电子探针、紫外可见光谱等测试技术,对坦桑尼亚绿碧玺宝石矿物学特征及颜色成因进行探究.结果表明:坦桑尼亚绿碧玺呈单晶体产出,无解...  相似文献   

17.
The paper presents mineralogical and geochemical data on clinkers and paralavas and on conditions under which they were formed at the Nyalga combustion metamorphic complex, which was recently discovered in Central Mongolia. Mineral and phase assemblages of the CM rocks do not have analogues in the world. The clinkers contain pyrogenically modified mudstone relics, acid silicate glass, partly molten quartz and feldspar grains, and newly formed indialite microlites (phenocrysts) with a ferroindialite marginal zone. In the paralava melts, spinel microlites with broadly varying Fe concentrations and anorthite–bytownite were the first to crystallize, and were followed by phenocrysts of Al-clinopyroxene ± melilite and Mg–Fe olivine. The next minerals to crystallize were Ca-fayalite, kirschsteinite, pyrrhotite, minerals of the rhönite–kuratite series, K–Ba feldspars (celsian, hyalophane, and Ba-orthoclase, Fe3+-hercynite ± (native iron, wüstite, Al-magnetite, and fresnoite), nepheline ± (kalsilite), and later calcite, siderite, barite, celestine, and gypsum. The paralavas contain rare minerals of the rhönite–kuratite series, a new end-member of the rhönite subgroup Ca4Fe 8 2+ Fe 4 3+ O4 [Si8Al4O36], a tobermorite-like mineral Ca5Si5(Al,Fe)(OH)O16 · 5H2O, and high- Ba F-rich mica (K,Ba)(Mg,Fe)3(Al,Si)4O10F2. The paralavas host quenched relics of microemulsions of immiscible residual silicate melts with broadly varying Si, Al, Fe, Ca, K, Ba, and Sr concentrations, sulfide and calcitic melts, and water-rich silicate–iron ± (Mn) fluid media. The clinkers were formed less than 2 Ma ago in various parts of the Choir–Nyalga basin by melting Early Cretaceous mudstones with bulk composition varies from dacitic to andesitic. The pyrogenic transformations of the mudstones were nearly isochemical, except only for volatile components. The CM melt rocks of basaltic andesitic composition were formed via melting carbonate–silicate sediments at temperatures above 1450°C. The Ca- and Fe-enriched and silicaundersaturated paralavas crystallized near the surface at temperatures higher than 900–1100°C and oxygen fugacity \(f_{O_2 }\) between the IW and QFM buffers. In local melting domains of the carbonate–silicate sedimentary rocks and in isolations of the residual melts among the paralava matrix the fluid pressure was higher than the atmospheric one. The bulk composition, mineral and phase assemblages of CM rocks of the Nyalga complex are very diverse (dacitic, andesitic, basaltic andesitic, basaltic, and silica-undersaturated mafic) because the melts crystallized under unequilibrated conditions and were derived by the complete or partial melting of clayey and carbonate–silicate sediments during natural coal fires.  相似文献   

18.
Comparative characteristics of the lithological composition of estuarine incised valley fill, as well as the enclosing and overlying storm-related deltaic sediments (beds VK1, VK2, and VK3), in the productive part of the Vikulovo Formation (upper Aptian), Kamenny area, West Siberia are given. It is shown that the incised valley fill-reservoirs, which are characterized by a coarser structure, inferior sorting, lower mineral maturity, and predominant kaolinitic clayey cement, demonstrate higher filtration properties.  相似文献   

19.
The hydrochemistry of Euphrates River in the study area which extended from Hit to Al-Saqlawia was studied in order to determine the physical, chemical, and biological properties in addition to the radiation level. Thirty-one stations along the Euphrates River were chosen, 17 of them represented the Euphrates River itself, whereas the other stations are considered as point pollution sources which all empty their load directly in the Euphrates River with an average total discharge of 32 m3/s. Twenty-eight samples of the Euphrates water of both high- and low-flow periods were analyzed for cations (Ca2+, Mg2+, Na+, and K+), anions (SO 4 = , Cl?, CO 3 = , HCO 3 ? , NO 3 ? , PO 4 ?3 ), H2S boron, dissolved oxygen, biological oxygen demand, bacteriological tests, radiation levels in addition to physical parameters such as hydrogen number (pH), total dissolved solid, electrical conductivity, total suspended solid, and temperature. This study showed that the cations and anions during periods of high and low flows are within acceptable limit with exceptional Cl?. Hydrochemical formula during the high flow was Na-Ca-Mg-Cl-SO4, then it changed into Na-Ca-Mg-HCO3-SO4-Cl during the low-flow period. The average output cations and anions at downstream (Saqlawiya area) was relatively higher than those of input at upstream (Hit area); this attributed to the natural and anthropogenic activities originated mainly from agricultural activity and population communities around the river. Radiation level for 212Pb, 214Pb, 40k, 220Ac, and 214Bi showed that the higher level of radiation is concentrated within sediment rather than in water, but the radiation in both is within acceptable limit.  相似文献   

20.
A new mineral of the neptunite group, magnesioneptunite KNa2Li(Mg,Fe)2Ti2Si8O24, a Mg-dominant analogue of neptunite and manganoneptunite, has been found in the Upper Chegem caldera near Mount Lakargi, Kabardino-Balkaria, the North Caucasus, Russia in a xenolith of altered sandstone located between skarnified carbonate xenoliths and ignimbrite. Magnesioneptunite occurs as nearly isometric grains and aggregates up to 0.1 mm in size in the cores of some grains of a Mg-rich variety of neptunite with Mg/(Fe + Mn) = 0.7?1.0. The chemical composition of magnesioneptunite with a maximum Mg content is as follows, wt %: 3.63 K2O, 8.21 Na2O, 1.73 Li2O, 6.47 MgO, 0.04 MnO, 5.87 FeO, 0.07 Al2O3, 18.73 TiO2, 56.88 SiO2, 99.62 in total. The empirical formula is (K0.67Na0.32Ca0.01)Σ1.00Na2.06Li1.00 · (Mg1.39Fe 0.71 2+ )Σ2.10(Si7.90Al0.01)Σ7.91O24. Grains of magnesioneptunite are dark brown to red-brown, translucent, with vitreous luster. D calc = 3.15 g/cm3, and the Mohs hardness is 5–6. Cleavage parallel to the (110) is perfect. The new mineral is optically biaxial, positive, α = 1.697(2), β = 1.708 (3), γ = 1.725(3), 2V meas = 45(15)°. The mineral is associated with quartz, alkali feldspar, rutile, aegirine, and neptunite. Magnesioneptunite and the Mg-rich variety of neptunite were formed as products of ilmenite alteration. Magnesioneptunite is monoclinic, C2/c; unit-cell parameters: a = 16.327(7), b = 12.4788(4), c = 9.9666(4) Å, β = 115.6519(5)°, V = 1830.5(1) Å3, Z = 4. The type specimen is deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.  相似文献   

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