Table of Content

20 February 2006, Volume 20 Issue 2

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Engineering Geology and Environmental Geology

Tectono-Stratigraphic Analysis of Sedimentary Basins: A Case Study on the Inland Tectonically Active Basins in China

LIN Chang-song

2006, 20(2):  185-194. 

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Comprehensive analysis by combination of basin tectonism during basin formation and evolution with the basin filling and reforming is the key to reveal the configuration of depositional systems and the source, reservoir and seal in the inland tectonically active basins. The development and distribution of different order tectonic unconformities and sequences determined the basic characteristics of the chronstratigraphic framework. The polyphasic and episodic tectonism of these basins usually had a significant influence on the regional depositionerosion cycles and the depositional patterns. It is the key for reconstruction of the basin filling patterns to document the control of the activity of syndepositional structures and the paleostructural framework on the sediment disposal and the variation in tectonic paleogeomorphology. The structural slope break zones usually constrained the development of distinguish facies zones or depositional systems tracts, such as lowstand deltaic or lacustrine fan systems in Mesozoic and Cenozoic rift lacuastrine basins and reef and bank facies zones in the Paleozoic carbonate platform in Tarim Basin, and comprise economically important plays in the basins. The formation and alteration of uplifts and depressions resulted in the complex stratigraphic architecture and unconformity configuration, which significantly constrained the formation and distribution of stratigraphic or structural-stratigraphic traps in the large superimposed basins in the western China.

Sequence-Stratigraphic Frameworks and Their Forming Backgrounds of Paleogeography for the Lower Cambrian of the Upper-Yangtze Region

MEI Ming-xiang, ZHANG Cong, ZHANG Hai, MENG Xiao-qing, CHEN Yong-hong

2006, 20(2):  195-208. 

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In the Upper-Yangtze region, especially in Guizhou Province and its adjacent areas, the Lower Cambrian is well developed and is marked by a succession from black shale to carbonate rocks. And this stratigraphic succession makes up a complex and regular sequence-stratigraphic framework. The Lower Cambrian in the study area constitutes a second-order sequence that can be further subdivided into five third-order sequences, and form a regularly cyclic succession of the transgression-regression. There is a regularly vertical stacking pattern for the third-order sequence in the second-order sequence. From the bottom to the top, third-order sequences that are characterized by the succession of “the CS (condensed section) +HST (high-stand system tract)” are changed into those marked by the succession of “the TST (transgressive system tract)+CS+HST”, correspondingly, the drowning-type sequence boundary is changed into exposure-type one. Therefore, both the second-order and the third-order sequences have a similarity of sedimentary-facies fabric. A concomitant with these temporal changes is that the Lower Cambrian containing five third-order sequences with 1,000 meter thickness is changed into a condensed succession that third-order sequences can not be identified toward the southeast with the deepening of the sedimentary environment. The sequence-stratigraphic framework can demonstrate both the elementary features of the third-order sequence, i.e. the regularity of sedimentary-facies successions in space and the synchronism of sedimentary-environment changes in time, and two kinds of facies-changing surfaces as well as two kinds of diachrononism in the stratigraphic records. And the sequence-stratigraphic framework represents its complex forming-setting of palaeogeography. Third-order sequences with different facies-succession mean particular paleogeographic backgrounds; therefore, five third-order sequences of the Early Cambrian represent a complex paleogeographic variance in the study area. Ultimately, a series of the panel diagrams of sequence-stratigraphic framework shows the temporal and spatial changes of sedimentary-facies succession of the third-order sequence, and a series of the corresponding paleogeographic maps indicates the evolution of paleogeographic setting that forms the third-order sequences.

Study on the Sedimentary Features of High Frequency Cyclothems of the Wumishan Formation at Jixian, Tianjin

ZHOU Hong-rui,MEI Ming-xiang,DU Ben-ming,LUO Zhi-qing,Lv Miao

2006, 20(2):  209-215. 

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The Mesoproterozoic Wumishan Formation in Jixian, Tianjin represents a succession of carbonate strata with 3,300 m in thick, in which Wumishan cyclothems with approximately symmetrical lithofacies successions are the best developed. They are particularly meter-scale cyclic sequences of peritidal type. Based on the analysis of types and association of genetic units of lithofacies of the Wumishan cyclothems, the general and sedimentary models of the Wumishan cyclothems were established. The magnetic susceptibility of the genetic units and its relationship to the high frequency cyclothems were discussed. It is believed that Wumishan cyclothems were formed in the sedimentary environment change, i.e. water depth changed from shallow to deep,then to shallow, and to be instantaneously exposed at last. So it could be considered as a real sedimentary cycle. According to the vertical stacking patterns of the genetic units of lithofacies of the Wumishan cyclothems, it is concluded that the Wumishan cyclothems were probably formed by autocyclical deposition that was controlled by high frequency sea-level change related to the Milankevitch cycle.

Influence of Late Cretaceous Climate Change to Extinction of Dinosaurs in Jiayin Area of Heilongjiang, Analyzed by Spore and Pollen

ZHAO Hai-bin，YIN Zhi-gang，WAN Xiao-qiao，YU Qing-wen，NIU Yan-hong

2006, 20(2):  216-224. 

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The Jiayin area of Heilongjiang Province is the first fossil dinosaur locality in China. Many fossils have been found from this area but lacking reasonable explanation to the living environment and extinction causes of the dinosaurs. The Late Cretaceous dinosaur-bearing strata have been divided in ascending order as the Yong'an, Taipinglinchang, Yuliangzi and Furao formations. The strata contain abundant dinosaurs and sporopollen fossils, and the Polypodiaceaesporites-Monosulcites-Beaupreaidites, Cyathidites-Taxodiaceaepollenites-Aguilapollenites and Classopollis-Ephedripites-Sphagnumsporites assemblages have been recognized. The fossil assemblages and sedimentary records show that the Jiayin area was generally in subtropical climate during Late Cretaceous. The assemblage variation of spore and pollen indicates a change from warm humid to dry hot climates. Abundance of salt-alkaline megatherm Classopollis-Ephedripites assemblage in a limited time illustrates a short duration of dry hot climate by latest Cretaceous. Such extreme climatic change and ecologic overturn are possible causes of the dinosaur extinction in the study area. Other factors, such as asteroid impact and large volcanic eruption triggering global mass extinction caused the regional climate change.

Facies Architecture of the Reservoir Sandstones within the High-Resolution Sequence Framework of the Pu-1 Oil Layer and Its Significance to
Exploitation in Daqing Oilfield

ZHANG Ying-zhi，LIN Chang-song，MA Li-min，LIU Jing-yan，ZHANG Yu，LIANG Xiu-li

2006, 20(2):  225-231. 

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Pu-1 oil layer of the Upper Cretaceous in the third northern development district of Daqing Oilfield, can be divided into three 4th order and eight 5th order high-resolution sequences, in terms of lacustrine flooding surface. Correlation of these stratigraphic units based on densely-spaced borehole data provides a high resolution correctable stratigraphic framework for the study of the architecture of the reservoir sandbodies. Most of the major reservoir sandbodies are composite sandbodies formed by amalgamation or superimposition of single sandbodies, and include the incised valley-distributary channel, distributary channel superimposed subaqueous distributary channel, distributary channel superimposed delta front mouth bar, crevasse channel superimposed crevasse delta or marginal sand bar composite sandbodies. The complex of the facies architecture of the sandbodies determines the reservoir inhomogeneity of the oil layer. Within the high-resolution sequence stratigraphy framework, three composite sandstone belts have been classified, and their depositional architectures had a significant influence on the remaining oil distribution. The main fluvial channel composite belts are of high porosity, permeability and connectivity, with remaining oil mainly formed by the inhomogeneity of the upper intrabed and obstruct layer. The marginal fluvial channel-mouth bar belts are characteristic of complex amalgamation of sandbodies with more inter obstructs, and the remaining oil are commonly formed by inhomogeneity of the sandbodies with poor permeability and dispreaded areas in development. This is the important facies zone for prediction of remaining oil in the oil field. The marginal sandy bar-crevasse and flooding interbeded fine belt are characterized by limited sandstones and poor permeability, with remaining oil often formed by deficient borehole network or poor connectivity.

The Distribution and Its Controlling Factors of High-Frequency Sequence for Middle Part of Third Member of Shahejie Formation,Guanglidong 3D
 Seismic Survey Region, Dongying Sag，Shandong

YU Jian-cheng，XIN Ren-chen，LIANG Jiang-ping，WANG Shu-heng，QIAO Min

2006, 20(2):  232-238. 

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Based on 3D-seismic and well logging data, ten high-frequency sequences, i.e.A to J, are recognized in middle part of the third member of Shahejie Formation, Guanglidong 3D-seismic survey region, Dongying sag. This work is carried out through careful interpretation and tracing of seismic data. The size and distribution of different high-frequency sequences are changed in space. Integrated well logging and seismic data indicate that five high-frequency sequences (A, D, E, G and I) developed in the area of well Lai10-3. The high-frequency sequences of A, C, D, G, H and I have a big size, but the other high-frequency sequences have a relatively smaller size. Four lake shrinks and two sediment supply transference to west occurred in the study area during the process of these ten high-frequency sequences developed. The size and distribution of high-frequency sequence are controlled by lakelevel fluctuation and sediment supply, but the most important controlling factor is sediment supply.

Numerical Modelling on Migrating Pingo Destructing Bridge Pier  in North Tibetan Plateau

WU Zhen-han, WANG Lian-jie, HU Dao-gong, WU Zhong-hai, YE Pei-sheng

2006, 20(2):  239-251. 

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Migrating pingos formed along fault zone in permafrost north Tibetan Plateau, destructing bridge, culvert and oil pipeline. Here displacement and stress fields caused by migrating pingos and stresses of bended bridge pier were calculated by three dimensional finite element modeling based on field observation and laboratory tests, and breaking mechanism of bridge pier was analyzed after the numerical modeling. It is proved that expansion of migrating pingo can produce axis stress of 11 to -21 MPa, formed concentration of stresses and caused evident displacement and deviation of bridge pier. The bending and deviation further result in extensional stress of 61.9 to 64.6 MPa and compressional stress of -45.0 to -49.0 MPa within the bridge pier, exceeding strength limit of the bridge pier. And stress concentration forms in size change area of upper bridge pier with maximum extensional stress of 26 to 30 MPa and maximum compressional stress of -25 to -28.8 MPa. The maximum extensional stress concentrated in size change area also exceeds strength limit of the bridge pier, formed shear-extensional fractures of the Chumaerhe Bridge. Three dimensional numerical modeling on migrating pingo destructing bridge pier can provide important factors for designing bridge and protecting geological hazard in permafrost.

Budongquan Migrating Pingos and Their Hazard Effects in the Permafrost North Tibetan Plateau

YE Pei-sheng, WU Zhen-han, HU Dao-gong, WU Zhong-hai

2006, 20(2):  252-258. 

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Budongquan migrating pingos form within NE-trending active faults in the permafrost north Tibetan Plateau. Only one small pingo formed in southeast margin of Golmud-Lhasa highway in 2001, and the pingos migrated to northwest of the highway along the buried Budongquan fault zone in 2002. The pingos migrated to northeast section of Budongquan valley and changed to larger-scale pingo groups in 2004-2005. And scale, height and covering area of Budongquan migrating pingos further increased in 2006. Budongquan migrating pingos not only piered and etched the highway, but also destructed the culvert, depressed ground surface, bended oil-pipeline and formed ground fracture zones. Hazards of Budongquan migrating pingos can be decreased or protected by taking engineering measures as building underground water conduits or draining off the upward rushing spring water near ground surface.

Analysis on Late Origin of Overpressure in Bohai Bay Basin

LIU Zhen,XU Xiao-ming,XIE Qi-chao ,ZHAO Yang ,DAI Li-chang

2006, 20(2):  259-267. 

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Each sag of Bohai Bay Basin has some comparability on tectonic characteristics and evolution, the overpressure distribution in vertical, the main distribution strata and the origin mechanism of overpressure. Firstly by making a qualitative analysis on the pressure field evolution of Doying, Zhanhua and Liaoxi sags, we discover that the overpressure of the three sags developed late. Then, by making a quantitative analysis on the pressure field evolution of Bonan sub-sag, a typical overpressure sag in Jiyang depression, we discover that the overpressure of Bonan sub-sag developed late as well. The overpressure of the main strata which are the third member and the upper of the fourth member of Shahejie Formation, developed after Dongying episode. From the above we conduct that the overpressure of Bohai Bay Basin developed late.

Characteristics of Structural Evolution in North Yellow Sea Basin

LI Wen-yong,LI Dong-xu1,XIA Bin,BAI Zhi-lin,WANG Liao-liang,CHEN Ling

2006, 20(2):  268-276. 

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Depending on the data of the new oil and gas resources survey, the subsidence history and structural evolution of North Yellow Sea basin are emphatically analyzed in this paper based on the brief discussion on the characteristics of tectonic geology of North Yellow Sea basin. The study results can be summerized as following aspects:(1) The basic settling curve of this basin was broken-line shape of seven sections in which Upper Jurassic, Lower Cretaceous, Eocene, Oligocene and Neogene corresponded with the decline ones representing five episodic clear subsidences of this basin, Late Cretaceous to   Paleocene and Early Miocene corresponded with the rising ones reflecting the uplift and denudation of this basin.(2) The subsidence of this basin migrated from the east to the  west, from Mesozoic to Cenozoic. East depression underwent the most remarkable subsidence in Mesozoic. The main subsidence epoch of middle depression was in Eocene, and the rapid subsidence in west depression occurred in Eocene to Oligocene.(3) The structural evolution of this basin can be approximately divided into three development stages: Mesozoic fault basin stage, Paleogene superimposed fault basin stage and Neogene down-warped basin stage, in which the Mesozoic fault basin developed stage was the study emphasis for oil and gas exploration of North Yellow Sea basin.

Features of Strike-slip Tectonics and Prospecting for Hydrocarbon Exploration in Santanghu Basin，Xinjiang

OUYANG Zheng-jian，ZHOU Ding-wu，FENG Juan-ping，ZHANG Xiao-hao

2006, 20(2):  277-282. 

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Based on drilling-wells and  seismic data, it was proved that there are strike-slip tectonics in Santanghu basin in the following two basic forms：simplified strike-slip faults and positive flower strike-slip faults. Strike-slip tectonics formed possibly in Himalayan Period when the boundary faults thrusted and right lateral strike slipped concurrently,intersect the boundary faults of the central geotectogene and collocate like the en-echelon faults. They play an important role in the generation, migration and accumulation of hydrocarbons

Thermal History and Secondary Hydrocarbon Generation Intensity of Marine Source Rocks in Lower Yangtze Area

YUAN Yu-song，GUO Tong-lou，FU Xiao-yue，LU Qing-zhi，HU Sheng-biao

2006, 20(2):  283-290. 

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Lower Yangtze area is one of the prior marine blocks of petroleum exploration in South China. Aiming at marine petroleum exploration of Mesozoic and Paleozoic, the strategy of the secondary hydrocarbon generation and later formation of petroleum pool was brought forward for petroleum exploration and planning in the study area. Based on thermal history reconstruction, the thermal maturation of the marine source rocks at different geological time is evaluated. In addition, using secondary hydrocarbon generation model based on experiments, the secondary hydrocarbon generation intensity of the four sets of marine source rock is evaluated. The thermal history reconstruction reveals that there are obvious differences among Subei, Sunan and Wannan areas. The study of secondary hydrocarbon generation shows that the Upper Paleozoic and Triassic source rocks have excellent secondary hydrocarbon generation potential. Silurian source rock possesses some secondary hydrocarbon generation. Cambrian source rock, however, nearly cannot provide any secondary hydrocarbon generation. Overall, there are no advantages of secondary hydrocarbon generation in the southern areas of Jiangsu and Anhui. The intensity of secondary hydrocarbon generation in north Jiangsu basin is much stronger than that in the southern areas of Jiangsu and Anhui.

Characteristics of Reef and Beach Facies in the Kangkelin Age from Western Tarim Basin——A Case Study from the Subashi Outcrop Section in the Keping Area

WANG Li-dong，YU Bing-song，ZHANG Yong-wang，MIAO Ji-jun

2006, 20(2):  291-298. 

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Reef-beach bodies of Permo-Carboniferous are well developed in western Tarim Basin, in which there are good oil and gas potentials. Based on the Kangkelin Formation of Subashen outcrop section in Keping country and integrated with Heshenlapu and Sishichang ones, the characteristics and types of reef-beach bodies are discussed, the lithology and lithofacies distribution are studied and the depositional model of carbonate rocks of PermoCarboniferous in western Tarim Basin is established. It is suggested:(1) As primary reef rocks,the reef limestone, which well developed in the Kangkelin Formation of Subashen outcrop section in Keping country, was deposited in the environments from the margin of carbonate platform to the internal of that;(2) In western Tarim Basin, the early and late Kangkelin Age's depositional environments are different, the sea-level change and the paleogeographic condition are reflected by the transfer of the facies zones; (3) The reef-beach bodies of the Kangkelin Age are well developed and have a good spatial continuity. It should be one of the most important reservoirs in western Tarim Basin.

Analysis of Control Factors of Ordovician Karst Reservoir in Ordos Basin

LI Zhen-hong, WANG Xin , YANG Sui-zheng，ZHENG Cong-bin

2006, 20(2):  299-306. 

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Ordovician karst reservoirs of Ordos Basin experienced several superpositions. According to evolutionary periods of paleokarst, three maps are drawn: Ordovician stratum thickness map, Pre-carboniferous karst landform and Ordovician top structure maps of Ordos Basin. Combined with karst development mechanism, the control factors of karst reservoir formation of each period are systematically analyzed, and then the favorable belts of karst reservoirs are comprehensively forecasted, so an advantageous direction of oil and gas exploration of Ordovician is obtained. In syndeposit peroid, there exited three old uplifts in Ordos Basin which controlled the karst reservoir development: Yimeng uplift, Central uplift and Hancheng uplift. The saddle and slope of the uplifts and micro-uplift of the depression are favorable areas of karst reservoir. In naked weathering period, paleokarst landform and paleo-groove distribution were the main control factors of karst reservoir development. Paleokarst sloping field was more favorable for karst evolution. In burial period, the middle part of the Ordovician top surface was high in the west and  low in the east. There was a steep slope between the east uplift and the central depression. Water of compaction migrated and concentrated towards the central uplift and the steep slope was an intensive transition region. This character defined the final distribution of karst reservoirs. As a result, the superimposed position of the uplift slope in syndeposit period, the karst sloping field in naked residue period and the steep slope in burial period should be the favorable areas of karst reservoir development.

Relationship between Uranium Anomaly and Depositional System of  Yan'an Formation, North-east Margin of Ordos Basin

WANG Min-fang,JIAO Yang-quan,YANG Qin,WU Li-qun,ZHANG Cheng-ze,YUAN Hai-tao,XU Z

2006, 20(2):  307-314. 

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Several uranium anomalies in Yan'an Formation, Unit V, have been found in the north-east margin of Ordos Basin, which are important for building the prospective uranium reserve base. According to sedimentology, the depositional system of Unit V, Yan'an Formation, has been reconstructed, it is revealed that there is braided stream system in the northwest of study area, and meandering stream system develops in the southeast. According to successfully extracting and graphing of uranium anomalies, the self-center uranium anomalies and their close relationship with meandering stream systems have been observed. The uranium anomaly always develops in the distributary and turning place of meandering stream system, and is related with thin sand area (whose sand thickness and sand ratio are less than 30 meters and 40% respectively), thicker coal, fine lithology, but the highest value of uranium anomaly exists in middle sandstone.

Relationship between Huashan Granite and Gold Mineralization in Xiongershan Area, Henan

WANG Chang-ming, DENG Jun, ZHANG Shou-ting

2006, 20(2):  315-321. 

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Xiongershan is an important concentration area of gold mineralization in western Henan. By studying geochemical compositions, trace elements, REE, stable isotopes of Huashan granite and its relations with gold deposits, the following research achievements have been obtained: (1)R-clustering spectrum diagram shows that correlations of trace elements such as Au, Ag, Pb, Cu, Ba of granite and gold deposits tend to continuity; (2)REE distribution pattern shows similar right-dipping forms of granite and the altered rocks; (3)Na⁺-K⁺-Ca²⁺+Mg²⁺ composition of fluid inclusions diagram shows intimate relationship between gold metallogenic fluids and magmatic hydrothermal fluids; (4)Space-time distribution of structure-controlled alteration rock type gold deposits and explosion-breccia type gold deposits in Huashan area is controlled by linear structures of Huashan granite; (5)Metallogenic epoch of the gold deposits is Yanshanian period, and the rock-forming age of Huashan granite occured in 81-159 Ma; (6)S, H, O and Pb isotopes show that the ore-forming fluid and metallogenic material come from magmatic hydrothermal fluids

Study on Comprehensive Recovery Technology for Gold Concentrate Containing Copper，Bismuth and Silver by Heap Leaching

CHENG Dong-hui, HE Jiang-tao, WANG Jin-xiang, LI Guo-bing, SHEN Zhao-li

2006, 20(2):  322-328. 

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In this paper, the comprehensive recovery technology for gold concentrate containing Au 140-150 g/t, Ag 900-1,000 g/t, Bi 9.0%-10.0% and Cu 14%-17% was studied by heap-leaching with bacterial oxidation and chemical process. In preliminary test, the technology that bacterial oxidation leaching of Cucyanidation leaching of Au and NaCl-FeCl₃-HCl method leaching of Bi and Ag was found out by the stirred experiment. This technique was applied to leach of Au, Ag, Cu and Bi in the column experiment. The parameters in column experiment were testified to be steady and reliable in scale-up test. The penetrability of concentrate was improved by mixing the coarse sand into concentrate; The copper endurance of the bacterial was increased by acclimation, up to 30 g/L. The leaching solution of NaCl-FeCl₃-HCl system may be used repeatedly because Fe²⁺becomes Fe³⁺ in solution by the H₂O₂ oxidation, and Ag, Bi may be leached simultaneously. The recovery rate of Au, Ag, Cu and Bi is 92.98%, 65.09%, 45.33%, 53.49% respectively.

Chemical Equilibrium in Silicate Systems: Part Ⅰ,Mass Balance Principle

MA Hong-wen, YANG Jing, LIU He, LI He-xiang, BAI Zhi-min, WANG Qing-hua

2006, 20(2):  329-339. 

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The linear programming and the least-squares approximation algorithms for estimating phase proportions in the Phase Mixing Equation (PME), in basis of the mass balance principle, were reviewed in detail by several typical applications, including modal analysis of mineral raw materials and crystalline rocks, estimation of the end members in mineral solid solutions, burden calculations of multi-component silicate ceramics, and calculations of the phase proportions in silicate ceramic products. The data as-resolved are bases for classifying crystalline rocks and industrial rocks, for improving preprocessing techniques of mineral raw materials, and also for thermodynamic analysis of materials processes at high temperatures to approach chemical equilibrium in silicate systems. The accumulated uncertainties in various analytical data must be kept in mind during the Phase Mixing Calculation (PMC) in practice. Both of phase proportions and compositions of mineral solid solutions could be optionally approximated, based upon the principle of mineral crystal chemistry, the law of mineral paragenetic assemblage, and the priority of partitioning of minor components into the solid solution phases.

Mechanism of Polymerization During the Solidification of Flyash-based Geopolymers

NIE Yi-miao，MA Hong-wen，YANG Jing，SU Yu-zhu，LI Ru-chen，GAO Fei

2006, 20(2):  340-346. 

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Geopolymers, with good mechanical properties and resistance to acid attacks, were prepared using flyash and kaolin. Geopolymer could be equivalents of the Portland cement products. The mechanism of polymerization was deduced from the analytical data of XRD, IR, SEM, and NMR of the geopolymeric products cured each for 3 days, 7 days, 14 days, and 28 days, which can be described as follows:(1) the glassy parts of the flyash were dissolved in the high molar alkaline solution and some Si—O, Al—O bonds were broken; (2) at the presence of OH^- and Na⁺, these broken bonds formed aluminosilicate gel and then transformed into zeolitic precursors with changing compositions and concentrations of the solution; (3) by dehydration, these zeolitic precursors were changed into the amorphous phase materials. NMR analysis indicated that in the geopolymeric products cured for 28 days, Q⁴ was the principal form of Si element. The experimental results provided a good basis for understanding the reactive mechanism of polymerization during processing of geopolymer products.

Synthesis of Tobermorite Nano-scale Powder from Potassium Feldspar: Reactive Mechanism Research

LIU He, MA Hong-wen, NIE Yi-miao, WANG Lei

2006, 20(2):  347-353. 

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Potassium feldspar was hydrothermally decomposed with CaO as an additive, and then tobermorite nano-scale powder was synthesized. The effective factors on the synthesizing reaction were the mole ratio of CaO/(SiO₂+AlO_1.5), reaction temperature and reaction time. The experimental results showed the tobermorite was crystallized well with the mole ratio of CaO/(SiO₂+AlO_1.5) in the range of 0.75 to 1.00, at the reaction temperature of 230 to 250 ℃ for 5 to 8 hours. The research data obtained in this study demonstrate that the reactive mechanism of the potassium feldspar's dissolution cannot be explained solely on the basis of ion exchange or aluminosilicate depolymerization reaction. The dissolution of potassium feldspar and the crystallization of tobermorite in hydrothermal system are considered possibly as a three-step process. At first, the potassium feldspar decomposes and gives rise to Si-rich and Al-deficient surface precursor complexes, secondly, the precursor complexes（SiO_2·nH₂O）decompose and further to form C-S-H gel and hydrogarnet phases, and at last, the C-S-H gel and hydrogarnet are converted into the tobermorite.

Preparation of High-strength Mineral Polymer Based on Flyash: An Experimental Study

SU Yu-zhu, YANG Jing, MA Hong-wen, NIE Yi-miao, LI Ru-chen

2006, 20(2):  354-360. 

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The flyash and leached alumino-siliceous residue distilled from a kalisalt from Bayan Obo of Inner Mongolia, with standard sand as aggregate, were used as principal materials to prepare mineral polymer. Quiver moulding method was adopted to manufacture the mineral polymer, and the module was curing at 90 ℃in drying oven. The compressive strength of the products reach up to 78.5 MPa and 89.0 MPa respectively for those cured for 7 days and 28 days. The water content and water absorbability of the representative products were 5.3% and 15.0% respectively, and the mass loss of the product was 2.1% while the specimen was inundated in sulfuric acid solution with a concentration of 1.0 mol/L for 24 hours at 20 ℃. The current experimental results show that the content of leached alumino-siliceous residue distilled from the kalisalt was the primary effective factor on the mechanical properties of the products. High performance mineral polymer can be prepared while the content of sodium silicate in the alkaline liquid and the standard sand in the solid materials are both kept around 70%. During the solidification of the mineral polymer products, both silicate and aluminate oligomers formed by Si—Al materials in the alkaline solution produced aluminosilicate gel by dehydroxy polymerization, then transformed into a three-dimension network structure matrix with Si—O—Al—O bonds, leading to excellent mechanical properties for the mineral polymer products as-prepared in the current study.