131 resultados para Carbonate rocks

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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Proven by the petroleum exploration activities, the karsts-fissure reservoir in carbonate rocks is significant to find out the large scale oil & gas field. They are made up of the four reservoir types: karsts-cave, karsts-crack, crack-cave and fracture-pore-cave. Each reservoir space and each reservoir bed has different features of reservoir heterogeneity and small scale of pore-crack-cave. The fracture-cave reservoir in carbonate rocks is characteristic by multi-types and long oiliness well. The reservoir shape is controlled by the irregular pore-crack-cave. The development level of fracture and karst-cave is the key element of hydrocarbon enriching, high productivity and stable production. However, most of Carbonate formation are buried deeply and the signal-ration-noise of seismic reflection are very low. It is reason why the fracture-cave reservoir are difficult to be predicted effectively. In terms of surveyed and studied lots of the former research outcome, The author applied the methods of synthetical reservoir geophysical prediction from two ways including macrosopic and microcomic technics in terms of the reservoir-cap condition, geophysics and geology feature and difficulty of prediction in carbonate rocks. It is guiden by the new ideas of stratigraphy, sedimentology, sedimentography, reservoir geology and karst geology. The geophysics technology is key technics. In aspects of macroscopic studies, starting off the three efficiencies of controlling the reservoir distribution including sedimental facies, karst and fracture, by means of comprehensive utilization of geology, geophysics, boring well and well log, the study of reservoir features and karst inside story are developed in terms of data of individual well and multiple well. Through establishing the carbonate deposition model, karstic model and fracture model, the macro-distribution laws of carbonatite are carried out by the study of coherence analysis, seismic reflection feature analysis and palaeotectonics analysis. In aspects of microcosmic studies, starting off analysis in reservoir geophysical response feature of fracture and karst-cave model according to guidance of the macroscopic geological model in carbonate reservoir, the methods of the carbonate reservoir prediction are developed by comprehensively utilization of seismic multi-attribution intersection analysis, seismic inversion restricted by log, seismic discontinuity analysis, seimic spectrum attenuation gradient, moniliform reflection feature analysis and multiparameter karst reservoir appraisement.Through application of carbonate reservoir synthetical geophysics prediction, the author r successfully develops the beneficial reservoir distribution province in Ordovician of Katake block 1in middle Tarim basin. The fracture-cave reservoir distributions are delineated. The prospect direction and favorable aims are demonstrated. There are a set of carbonate reservoir prediction methods in middle Tarim basin. It is the favorable basic technique in predicting reservoir of the Ordovician carbonate in middle Tarim. Proven by exploration drilling, the favorable region of moniliform reflection fracture and pore-cave and cave-fracture in lower-middle Ordovician are coincidence with the region of hydrocarbon show. It’s indicated that the reservoir prediction methods described in the study of Ordovician carbonate formation are feasible practicably.

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The distribution in outcrop of carbonate rocks in China is about 3.44×106km2 and accounts for over one third of the total area of the country, mainly in the Yangtze valley and the Yungui tableland ,and there is a great plenty of Water and hydropower resources in these carbonate area. A large number of projects will be built in order to develop the Water and hydropower resources. They are facing amount of complicated problems of karsts, specially the problem of the depths of karsts below water, which is a key problem that hasn’t been solved well theoretically. So, systematically research in quantitative analysis of the problem is necessary, which is very important to solve the inconsistency between current theories and facts, and is helped to foresee the depth of karsts below water and decrease the expense of the engineering. For the problem mentioned above, the thesis makes a detailed research on the length of corrosion of karsts water, based on the kinetics of corrosion, and founds the primary theory about the processes of four typical geologic elements, which are single fracture, single conduit, porous limestone and fractured limestone. And it has done a deep research upon the characterties and kinetics of corrosion of the four typical geologic elements by simulation using the programme edited by the author. The thesis also makes a discussion on the general model and process of the form of caves by using the founded theory. According to the characteristic of Water Resource and Hydropower engineering, the thesis creates three representative flow-dissolution models for three types of common geologic conditions under the induction of the theory kinetics of corrosion of karsts water. It has done quantitative research upon the process of dissolution and brought out primary theory about quantitative analysis of the depth of karsts below water as well. It found that the depth of karsts below water relates to the specific geologic conditions and the time of dissolution by simulation based on typical parameters and deep analysis of the result. That is to say there are karsts caves in any depths in flow areas of groundwater in specific geologic conditions and appropriate time. The thesis also discourses three basic problems that frequently encountered in the reconnaissance of Water Resource and Hydropower engineering, which are karsts base level, essential conditions of karsts, the comparability of caves and terrace, and indicates the importance of time in karsts. Finally, as an application, the karsts of the scheming Qianzhong water resource engineering is analyzed by the primary theory founded of quantitative analysis. The result of the application comes to a conclusion that the theory accords with the facts properly.

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The Huade Group, consisting of low-grade and un-metamorphosed sedimentary rocks with no volcanic interlayer, is located at the northern margin of the North China craton and adjoining the south part of the Central Asian Orogenic Belt. It is east to the Paleo- to Meso-Proterozoic Bayan Obo and Zhaertai-Langshan rifts and northwest to the Paleo- to Neo-proterozoic Yanshan aulacogen, in which the typical Changcheng, Jixian and Qingbaikou systems are developed. The Huade Group are mainly composed of pebbly sandstones, sandstones, greywackes,shales,calc-silicate rocks and limestones, partly undergoing low-grade metamorphism and being changed to meta-sandstones, schists, phyllites, slates and crystalline limestones or marbles. The stratigraphic sequences show several cycles of deposition. Each of them developed coarse clastic rocks – interbedded fine clastic rocks and pelites from bottom upward or from coarse clastic rocks to interbedded fine clastic rocks and pelites to carbonate rocks. The Tumen Group outcrop sporadically around or west to the Tanlu faults in western Shandong. They are mainly composed of pebbly sandstones, sandstones, shales and limestones. This thesis deals with the characteristics of petrology, geochemistry and sedimentary of the Huade Group and the Tumen Group, and discusses the LA-ICP-MS and SIMS U-Pb ages, Hf isotope and trace element composition of the detrital zircons from 5 meta-sandstone samples of the Huade Group and 3 sandstone samples of the Tumen Group. The age populations of the detrital zircons from the Huade Group are mainly ~2.5 Ga and ~1.85 Ga, and there are also minor peaks at ~2.0 Ga, ~1.92 Ga and ~1.73 Ga. Most of the detrital zircon grains of 2.47-2.57 Ga and a few of 1.63-2.03 Ga have Hf crust model ages of 2.7-3.0 Ga, and most of the detrital zircon grains of 1.63-2.03 Ga have Hf crust model ages of 2.35-2.7 Ga, with a peak at 2.54 Ga. The main age peaks of the detrital zircons from the Tumen Group are ~2.5 Ga、~1.85 Ga, 1.57 Ga, 1.5 Ga, 1.33 Ga and 1.2 Ga. Different samples from the Tumen Group have distinct Hf isotopic characteristics. Detrital zircon grains of ~2.52 Ga from one sandstone sample have 2.7-3.2 Ga Hf crust model ages, whereas zircon grains of 1.73-2.02 Ga and 2.31-2.68 Ga from another sample have Hf crust model ages of 2.95-3.55 Ga. Detrital zircon grains of Mesoproterozoic ages have Paleoproterozoic (1.7-2.25 Ga) crust model ages. Through detailed analyses of the detrital zircons from the Huade and Tumen Group and comparison with those from the sedimentary rocks of similar sedimentary ages, the thesis mainly reaches the following conclusions: 1. The youngest age peaks of the detrital zircons of 1.73 Ga constrains the sedimentary time of the Huade Group from late Paleoproterozoic to Mesoproterozoic. 2. The age peaks of detrital zircons of the Huade Group correspond to the significant Precambrian tectonic-thermal events of the North China craton. The basement of the North China craton is the main provenance of the Huade Group, of which the intermediate to high grade metamorphic sedimentary rocks are dominant and provide mainly 1.85-1.92 Ga sediments. 3. The Huade basin belongs to the North China craton and it is suggested that the northern boundary of the North China craton should be north to the Huade basin. 4. The stratigraphic characteristics indicate the Huade Group formed in a stable shallow-hypabyssal sedimentary basin. The rock association and sedimentary time of the Huade Group are similar to those of the Banyan Obo Group and the Zhaertai Group, and they commonly constitute late Paleoproterozoic to Mesoproterozoic continental margin basins along the northern margin of the North China craton. 5. The continental margin basins would have initiated coeval with the Yanshan and Xiong’er aulacogens. 6. The ages of the detrital zircons from the Tumen Group and the Penglai Group at Shandong peninsula and the Yushulazi Group at south Liaoning are similar, so their sedimentary time is suggested to be Neoproterozoic,coeval with the Qingbaikou system. The detrital zircon ages of 1.0-1.2 Ga from the Tumen Group, the Penglai Group and the Yushulazi Group indicate that there have being 1.0-1.2 Ga magmatic activities at the eastern margin of the North China craton. 7. The U-Pb age populations of the detrital zircons from the late Paleoproterozoic to Neoproterozoic sedimentary rocks suggest that the main Precambrian tectonic-thermal events of the North China craton happened at ~2.5 Ga and ~1.85 Ga. But the events at 2.7 Ga and 1.2 Ga are also of great significance. Hf isotope characteristics indicate that the significant crust growth periods of the North China craton are 2.7-3.0 Ga and ~2.5 Ga.

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Ordos Basin is one of the primary bases for petroleum exploration in our country. A series of Ordovician large gas fields were discovered, which suggest that the Lower Paleozoic carbonate, especiallly for Ordovician carbonate rocks, preserve plenty of hydrocarbon resources. Well Longtong 1 is studied as the typical exploration well. Acorrding to the specific research on the type of lithology, texture, structure and sedimentary sequence in Ordovician Majiagou Formation as well as additional data from another 20 wells, the sedimentary model has been built in Majiagou Formation. The sedimentary characteristics for each Member in Majiagou Formaiton and the feature of distribution are well understood as below: It suggests that period of Member 1, Member 3 and Member 5 in Majiagou Formation characterize with dry and hot climate as well as drop of the sea level. The area of Well Longtan 1 in the eastern basin is abundant of platform evaporite lithofacies with the depositional anhyrock and salt rock, whereas yield a suite of dolomite intercalated by the thin layers of anhyrock from the anhyrcok-dolomite platform sediment. It deposits muddy dolomite, dolomitic limestone and fine-grain dolomite in limestone-dolomite platform and restricted sea. During the stage of Member 2 and Member 4 in Majiagou Formation, the climate is wet and hot with increasing sea level. The study region occurs limestone with little dolomite in the open sea environment; but the margin area is the restricted sea settings with interbeding dolomite and limestone. Based on the thin section identification, element and isotope analysis as well as the study of texture and structure, it sugguests that the main reserviors are dolomite while the gypsum are major cap rocks. The Member 2 in Majiagou Formation is both the source rocks and the resveroirs; gypsum rocks widely occur in Member 3 as the better cap; similar to the Member 2, the Member 4 in Majiagou Formation is both the source rocks and the resveroirs; there are two source-reservoir-cap assemblages in the Member 5 alone and the cap is gypsum with high quality and great thickness, which is a favorite source-reservoir-cap assemblage.

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The Alytn fault is a huge left-slip fault zone within the Asian continent, and locates such zone that is linked to main tectonic units in the western China, which makes it is very important to the tectonic framework and ore distribution in the western China. Selecting two ophiolite zones (namely Hongliugou-Lapeiquan ophiolite zone and Sulamutage ophiolite zone) respectively located within the southern and northern part of the Altyn fault and based on analysis of field geology characteristics and geochemistry, this paper recognized the rock types (mainly mafic and ultramafic rocks) within the melanges and subdivided each lithological unit based on tectonic environment. At last, this paper rebuilt the paleo-tectonic framework in the Alytn region by the method of tectonic facies and discussed its tectonic evolution with the theory of collision orogens. Combining former results with hard field observation and geochemical analysis, this paper acquired such recognitions to two ophiolte zones within the Altyn fault zone as follows: To the typical regions (Hongliugou, Lapeiquan, Mangya and Sulamutage) within the two ophiolte zones in the Altyn fault zone, this paper offered the field geology profiles. Field geology characteristics show that they are composed of melange bases (mainly abyssal flysch and carbonate rocks) and melange blocks from various tectonic environments, often with fault contact among each lithological units, belonging to typical ophiolitic melange zone. The ultramafic rocks outcropped at the Altyn region are all harzburgites. Remant grains of primary minerals have melted residual texture and elastic deformation texture under high temperature and pressure. The whole-rock analyses show their low TiO_2 contents (0.01~0.04%), low Al, Ca and high MgO contents and wide Mg~# range (89.35~95.57). Rare earth patterns have two types, namely tabacco pipe-shped and LREE-shaped, of which the former is often seen. The chondrite-nomalized Yb values of these analyses are all lower than 1. The spinels have low Ti and high Cr content and most spinels have Cr# higher than 60. All of the above characteristics show that the ultramafic rocks in the Altyn fault zone are components of metmorphic peridotites of ophiolite from depleted mantle source and most ophiolites from this zone belong to supra-subduction zone (SSZ) type ophiolite with a few mid-ocean ridge basalt (MORB) type. Geochemical analyses show that the melange blocks within the Altyn ophiolitic melange zone have different characteristics from various tectonic environments. This paper recognized such tectonic-lithological assemblages as mid-ocean basalts, oceanic island basalts, oceanic island arc tholeiites, island arc calalkaline basalts and island arc granites and inferred that these tectonic-lithological units respectively belongs to such tectonic units as ophiolites, oceanic islands and/or oceanic seamounts, oceanic island arc and a~creting arcs, which show these blocks from oceanic crust and subduction zone for the most part. For the Altyn ophiolites, the chronological data show they become new from the north to the south. Combined with the study on late slip of Altyn fault and North Qilianshan orogeny, the author inferred that the Altyn region had belonged to one part of the North Qilianshan accreting wedge-arc orogeny at paleozoic, and later huge left-slip made it locate modem site.

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Jiyang & Changwei depressions are two neighboring depressions in Bahai Bay Basin, the famous oil rich basin in East China. The exploration activities in the past 40 years has proved that, within the basins, there exists not only plentiful sandstone hydrocarbon reservoirs (conventional), but also abundant special reservoirs as igneous rock, mudstone and conglomerate ones which have been knowing as the unconventional in the past, and with the prospecting activity is getting more and more detailed, the unconventional reservoirs are also getting more and more important for further resources, among which, the igneous lithological reservoir be of significance as a new research and exploration area. The purpose of this paper is, with the historical researches and data as base, the System Theory, Practice Theory and Modern Comprehensive Petroleum Geology Theory as guide, the theoretical and practice break through as the goal, and the existing problems in the past as the break through direction, to explore and establish a valid reservoir formation and distribution models for igneous strata in the profile of the eastern faulted basins. After investigating the distribution of the igneous rocks and review the history of the igneous rocks reservoirs in basins, the author focused on the following issues and correspondingly the following progresses have been made: 1.Come to a new basin evolution and structure model named "Combined-Basin-bodies Model" for Jiyang even Eastern faulted basins based on the study on the origin and evolution of Jiyang & Changwei basins, depending on this model, every faulted basin in the Bo-hai Bay Basin is consisted of three Basin-Bodies including the Lower (Mesozoic), Middle (Early Tertiary) and the Upper (Late Tertiary) Bodies, each evolved in different geo-stress setting and with different basin trend, shape and igneous-sedimentary buildings system, and from this one to next one, the basin experienced a kind of process named "shape changing" and "Style changing". 2. Supposed a serious of new realizations as follows (1) There were "multi-level magma sources" including Upper mantel and the Lower, Middle and even the Upper Shell magma Chambers in the historical Magma Processes in the basins; (2) There were "multi-magma accessing or pass" from the first level (Mantel faults) to the second, third and fourth levels (that is the different levels of fault in the basin sediment strata) worked in the geo-historical and magma processes; (3) Three tectonic magma cycles and more periods have been recognized those are matched with the "Basin -body-Model" and (4)The geo-historical magma processes were non-homogeneous in time and space scale and so the magma rocks distributed in "zones" or "belts". 3. The study of magma process's effect on basin petroleum conditions have been made and the following new conclusions were reached: (1) the eruptive rocks were tend to be matched with the "caped source rock", and the magma process were favorable to the maturing of the source rocks. (2) The magma process were fruitful to the accumulation of the non-hydrocarbon reservoirs however a over magma process may damage the grade of resource rock; (3) Eruptive activity provided a fruitful environment for the formation of such new reservoir rocks as "co-eruptive turbidity sandstones" and "thermal water carbonate rocks" and the intrusive process can lead to the origin of "metamorphism rock reservoir"; (4) even if the intrusive process may cause the cap rock broken, the late Tertiary intrusive rocks may indeed provide the lateral seal and act as the cap rock locally even regionally. All above progresses are valuable for reconstructing the magma-sedimentary process history and enriching the theory system of modem petroleum geology. 4. A systematic classification system has been provided and the dominating factors for the origin and distribution of igneous rock reservoirs have been worked out based on the systematic case studies, which are as follows: (1) The classification is given based on multi-factors as the origin type, litho-phase, type of reservoir pore, reservoir ability etc., (2) Each type of reservoir was characterized in a detailed way; (3) There are 7 factors dominated the intrusive reservoir's characteristics including depth of intrusion, litho-facies of surrounding rocks, thickness of intrusive rock, intrusive facies, frequency and size of the working faults, shape and tectonic deformation of rock, erosion strength of the rock and the time of the intrusion ect., in the contrast, 4 factors are for eruptive rocks as volcanic facies, frequency and size of the working faults, strength of erosion and the thermal water processing. 5. Several new concept including "reservoir litho-facies", "composite-volcanic facies" and "reservoir system" ect. Were suggested, based on which the following models were established: (1) A seven reservoir belts model for a intrusive unit profile and further more, (2) a three layers cubic model consisted of three layer as "metamorphic roe layer", "marginal layer" and "the core"; (3) A five zones vertical reservoir sequence model consisted of five litho-facies named A, B, C, D and E for a original lava unit and furthermore three models respectively for a erosion, subsidence and faulted lava unit; (4) A composite volcanic face model for a lava cone or a composite cone that is consisted of three facies as "crater and nearby face", "middle slope" and "far slope", among which, the middle slope face is the most potential reservoir area and producible for oil & gas. 6. The concept of "igneous reservoir" was redefined as the igneous, and then a new concept of "igneous reservoir system" was supposed which means the reservoir system consisted of igneous and associated non-igneous reservoirs, with non-hydrocarbon reservoir included. 7. The origin and distribution of igneous reservoir system were probed and generalized for the exploration applications, and origin models of the main reservoir sub-systems have been established including those of igneous, related non-igneous and non-hydrocarbon. For intrusive rocks, two reservoir formation models have been suggested, one is called "Original or Primary Model", and the another one is "Secondary Model"; Similarly, the eruptive rock reservoirs were divided in three types including "Highly Produced", "Moderately Produced" and "Lowly Produced" and accordingly their formation models were given off; the related non-igneous reservoir system was considered combination of eight reservoirs, among which some ones like the Above Anticline Trap are highly produced; Also, the non-hydrocarbon. Trap system including five kinds of traps was discussed. 8. The concept models for four reservoir systems were suggested, which include the intrusive system consisted of 7 kinds of traps, the land eruptive system with 6 traps, the under water eruptive system including 6 kinds of traps and the non-hydrocarbon system combined by 5 kinds of traps. In this part, the techniques for exploration of igneous reservoir system were also generalized and probed, and based on which and the geological progresses of this paper, the potential resources and distributions of every reservoir system was evaluated and about 186 millions of reserves and eight most potential non-hydrocarbon areas were predicted and outlined. The author believe that the igneous reservoir system is a very important exploration area and its study is only in its early stage, the framework of this paper should be filled with more detailed studies, and only along way, the exploration of igneous reservoir system can go into it's really effective stage.

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In order to know better about the Phanerozoic lithosphere thinning process of Sino-Korea Plate, four Cretaceous intrusion complexes and their ultramafic xenoliths are investigated by this thesis, which are located in Laiwu, Shandong Province, Eastern China, a region far away from plate margin. The four complexes, Kuanshan, Jiaoyu, Jingniushan and Tietonggou, intruded into Archaeozoic granite gneiss and Paleozoic carbonate rocks with scam iron ore at their contact zone. The four complexes can be divided into two magma series, abyssal rocks for the early and hypabyssal rocks for the later. K-Ar dating show that the abyssal rocks intrusion began with 120 ±2 Ma and the hypabyssal rocks intruded about 113 Ma. Abyssal rocks, mainly made up of augite diorites, amphibole diorites and gabbros for the lesser, are chemically characterized with high-Mg (Mg#>0.5) high-K calcalklic rock, which are depleted with Nb, Ta and Ti related to LILE and extremely enriched with Sr and Pb. Comparatively, augite diorites are the most LREE enriched in abyssal rocks, and they show no Eu abnorrnity or weak positive Eu abnormity. Gabbros show the least LREE enrichment with a strong Eu abnormity relatively. In (~(87)Sr/~(86)Sr)_1 -ε Nd(T) diagram, the abyssal rocks show a mixing trend , a rapid change in ε Nd(T) with a relatively small change in (~(87)Sr/~(86)Sr)_1. Low radiogenic Sr and Pb composition with high radiogeic Nd composition indicate that the mixing processes happened in lower crust Melt-rock interactions in lower crust might be the most possible processes to produce these high-Mg and high-K calcalklic magmas. Hypabyssal rocks, mainly made up of granite porphyry and dioritic porphrite, show much higher ε Nd(T) than abyssal rocks. Granite porphyry are distinct with an adakite geochemical characteristics, high (La/Yb)_N, Sr/Y and low Rb/Sr ratio. The adakitic granite porphyry indicates a new lower crust produced by underplating within plate. Ultramafic xenoliths had been found only in augite diorites and amphibole diorites. Field investigations show that ultramafic xenoliths in augite diorites had been inherited from amphibole diorites, so ultramafic xenoliths had been only entrained by hydrous dioritic magma. Ultramafic xenoliths are mainly made up of dunite and harzburgite, orthopyroxenite and bistangite are the lessor. Coarse olivines in dunite often show many chromite exsolution lamellae. Opx in orthopyroxenite often show dense chromite exsolution lamellae. The presence of exsolution minerals indicates that ultramafic xenoliths had cooled before entraining. Metasomatism phenomenons are popular in dunite and harzburgite xenoliths, including two kinds of assemblage, cpx+phlogapite and opx+pl. The first metasomatism assemblage indicates an ancient enrichment. Rb-Sr dating of xenoliths shows that the ancient enrichment happened in 223 ± 7Ma. The second metasomatism assemblage indicates a recent, relatively not deep melt-rock interaction, which might be related with the genesis of the high-Mg high-K calcalklic rocks. Mineralogy and geochemistry indicate that these ultramafic xenoliths might sample the crust-mante transition zone (or the base of lower crust, moho). Investigation of high-Mg intrusions and their ultramafic xenoliths in Laiwu indicate that the thinning processes of Sino-Korea Plate can be divided into two stages. The first stage is lithosphere mantle thinning with crust thickening by underplating in lower crust. The second stage is that the thickened lower crust delaminated into the underlying mantle.

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Based on the principle and methods of carbonate sedimentology and reservoir geology, and guided by the theories of carbonate reservoir geology, the palaeokarst of Ordovician carbonate rocks in Tarim Basin has been comprehensively studied with multiple methods from different branches of geology. It is indicated that the features and distribution of palaeokarstification have developed in Ordovician carbonates. The controlling of karstification to Ordovician carbonate reservoirs has been discussed. Regional distribution of carbonate reservoirs controlled by karstification has been predicted within this basin. The main consents and conclusions of the this dissertation is as follows: Nine key indicators to the recognition of palaeokarst are proposed in terms of careful observation upon the well cores, lithological and geochemical analyses, and drilling and logging responses to the karst caves and fractures. The time and environment of cave filling are documented from careful research of lithofacies, mineralogy, and geochemistry of the physical and chemical fillings within karst caves. The caves in Ordovician carbonates were filled in Early Carboniferous in Lunnan area. The muddy filling in upper caves was deposited under subaerial fresh-water setting, while the muddy filling in lower caves was formed in the mixed water body of fresh-water and dominated sea water. Although most chemical fillings are suggested being precipated in the burial diagenetic environment after karstification but mineralogic and geochemical characteristics of some chemical fillings indicates they formed in meteoric environment during the karstification. It is obvious that the palaeokarst has been zoned in vertical profile. It can be divided into four units from top to bottom: surface karst, vadose karst, phreatic and tranquil flow zones. Between two types of limestone karst and dolostone karst are firstly differentiated in Tarim Basin, based on the comparison of features of each karst zone in limestone and dolostone regions. In Tabei area, the lowest depth of karstification is approximately 300 m below the Upper Ordovician unconformity interface, while the bottom depth of karstification in Tazhong area ranges commonly from 300 to 400 m, in rare cases may be up to 750 m below the upper Ordovician unconformity interface. In Lunnan and Tazhong areas, the palaeokarst morphology and the surface hydrosystem are firstly reconstructed based on the top of carboniferous "Shuangfeng limestone bed (Double-Peaks limestone)" as basal. According to the palaeomorphologic feature, karst topography can be divided into three units: karst upland, karst slope, and karst valley. Vadose zone was well developed in karst upland, and it can be found in a quite depth. Both vadose and phreatic zones were well developed in karst slope and upstream valley. In downstream valley, the karstification is not strong, the vadose and phreatic zones are thin in thickness. In Tazhong and Yingmaili areas, karstification is also developed in relict carbonate palaeo-hills which existed as isolated blocks admits clastic strata.

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River is a major component of the global surface water and CO2 cycles. The chemistry of river waters reveals the nature of weathering on a basin-wide scale and helps us understand the exogenic cycles of elements in the continent-river-ocean system. In particular, geochemical investigation of large river gives important information on the biogeochemical cycles of the elements, chemical weathering rates, physical erosion rates and CO2 consumption during the weathering of the rocks within the drainage basin. Its importance has led to a number of detailed geochemical studies on some of the world's large and medium-size river systems. Flowing in the south of China, the Xijiang River is the second largest river in the China with respect to its discharge, after the Yangtze River. Its headwaters drain the YunGui Plateau, where altitude is approximately 2000 meters. Geologically, the carbonate rocks are widely spread in the river drainage basin, which covers an area of about 0.17xl06 km2, i.e., 39% of the whole drainage basin. This study focuses on the chemistry of the Xijiang river system and constitutes the first geochemical investigation into major and trace elements concentrations for both suspended and dissolved loads of this river and its main tributaries, and Sr isotopic composition of the dissolved load is also investigated, in order to determine both chemical weathering and mechanical erosion rates. As compared with the other large rivers of the world, the Xijiang River is characterized by higher major element concentration. The dissolved major cations average 1.17, 0.33, 0.15, and 0.04 mmol I"1 for Ca, Mg, Na, and K, respectively. The total cation concentrations (TZ+) in these rivers vary between 2.2 and 4.4 meq I'1. The high concentration of Ca and Mg, high (Ca+Mg)/(Na+K) ratio (7.9), enormous alkalinity and low dissolved SiO2/HCO3 ratio (0.05) in river waters reveal the importance of carbonate weathering and relatively weak silicate weathering over the river drainage basin. The major elements in river water, such as the alkalis and alkaline-earths, are of different origins: from rain water, silicate weathering, carbonate and evaporite weathering. A mixing model based on mass budget equation is used in this study, which allows the proportions of each element derived from the different source to be calculated. The carbonate weathering is the main source of these elements in the Xijiang drainage basin. The contribution of rainwater, especially for Na, reaches to approximately 50% in some tributaries. Dissolved elemental concentration of the river waters are corrected for rain inputs (mainly oceanic salts), the elemental concentrations derived from the different rock weathering are calculated. As a consequence, silicate, carbonate and total rock weathering rates, together with the consumption rates of atmospheric CO2 by weathering of each of these lithologies have been estimated. They provide specific chemical erosion rates varying between 5.1~17.8 t/km2/yr for silicate, 95.5~157.2 t/km2/yr for carbonate, and 100.6-169.1 t/km2/yr for total rock, respectively. CO2 consumptions by silicate and carbonate weathering approach 13><109and 270.5x10 mol/yr. Mechanical denudation rates deduced from the multi-year average of suspended load concentrations range from 92-874 t/km2/yr. The high denudation rates are mainly attributable to high relief and heavy rainfall, and acid rain is very frequent in the drainage basin, may exceed 50% and the pH value of rainwater may be <4.0, result from SO2 pollution in the atmosphere, results in the dissolution of carbonates and aluminosilicates and hence accelerates the chemical erosion rate. The compositions of minerals and elements of suspended particulate matter are also investigated. The most soluble elements (e.g. Ca, Na, Sr, Mg) are strongly depleted in the suspended phase with respect to upper continent crust, which reflects the high intensity of rock weathering in the drainage basin. Some elements (e.g. Pb, Cu, Co, Cr) show positive anomalies, Pb/Th ratios in suspended matter approach 7 times (Liu Jiang) to 10 times (Nanpan Jiang) the crustal value. The enrichment of these elements in suspended matter reflects the intensity both of anthropogenic pollution and adsorption processes onto particles. The contents of the soluble fraction of rare earth elements (REE) in the river are low, and REE mainly reside in particulate phase. In dissolved phase, the PAAS-normalized distribution patterns show significant HREE enrichment with (La/Yb) SN=0.26~0.94 and Ce depletion with (Ce/Ce*) SN=0.31-0.98, and the most pronounced negative Ce anomalies occur in rivers of high pH. In the suspended phase, the rivers have LREE-enriched patterns relative to PAAS, with (La/Yb) SN=1 -00-1 .40. The results suggest that pH is a major factor controlling both the absolute abundances of REE in solution and the fractionation of REE of dissolved phase. Ce depletion in river waters with high pH values results probably from both preferential removal of Ce onto Fe-Mn oxide coating of particles and CeC^ sedimentation. This process is known to occur in the marine environment and may also occur in high pH rivers. Positive correlations are also observed between La/Yb ratio and DOC, HCO3", PO4", suggesting that colloids and (or) adsorption processes play an important role in the control of these elements.

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在贵州碳酸盐岩风化壳中发现的晶体石英使风化壳及其所发育的地貌面的定年研究成为可能,对这种石英进行裂变径迹尝试性测年工作,发现它们具有很强的研究潜力,是目前为止在碳酸盐岩风化壳剖面中发现的唯一可作为测年对象的矿物。前期工作中进行的风化壳剖面物源判别及石英表面结构观察表明晶体石英是原位形成的,晶体形态指示它们可能是次生的,其裂变径迹测年结果远小于母岩年龄,从另一方面也证明了它们可能是次生的。然而,上述证据只能对贵州碳酸盐岩风化壳中晶体石英的成因进行初步的判定,即次生形成于剖面中,未能揭示其确切的成因。由于,晶体石英成因的确定是利用它们开展测年工作的前提和基础,所以当前急需对这类石英进行成因判别,以明确裂变径迹年龄值的年代学意义。本文在前人成果的基础上,首次对贵州碳酸盐岩风化壳中的晶体石英进行了较系统的研究,通过晶体形态观察、石英粒度分析、包裹体观察来判断其基本成因,利用硅、氧同位素的组成及与其它地质体的对比揭示晶体石英形成的硅质来源、流体性质、沉淀结晶环境等信息,主要获得了以下几方面的认识: 1、 风化壳中石英颗粒的粒度特征 新蒲和大兴剖面中提取出的石英多分布在粉砂(2 ~ 63 μm)和砂粒(>63 μm)粒级范围内,其中以粉砂粒级为主。石英的粒度分布曲线常呈多峰分布,与黄土-古土壤中石英的单峰分布曲线明显不同,说明剖面中的石英不是风成成因的,继而证明两风化壳剖面不是风尘堆积的产物。两剖面中石英颗粒的分选性较差,不同样品之间,石英的粒度分布曲线存在差异,可能是次生石英、母岩中的碎屑石英和燧石团块中的石英以不同比例混合的结果。鉴于以上可能性,与酸不溶物相比,土层的粒度分布曲线表现出较好的一致性,即在碳酸盐岩风化壳物源研究中,石英的粒度分布并不是理想的示踪手段。 2、风化壳中石英颗粒的包裹体观察及均一温度测量 研究剖面中晶体石英的包裹体呈带状分布,多数为单相包体,小于5 μm,无法进行均一温度的测量。在某些次生加大石英或石英胶结物中包裹体很少或未见可供测温的两相包裹体,可能就是由于形成温度低(小于70 ˚C或地表温度),生长缓慢造成的。研究剖面中晶体石英的包裹体特征与某些次生加大石英或石英胶结物中的包裹体类似,暗示晶体石英可能为低温条件下缓慢形成的,与其形态特征一致。 3、风化壳中晶体石英的硅同位素特征及其硅质来源探讨 研究剖面中晶体石英的δ30Si值在0.8‰ ~ 1.7‰之间,与火山作用和热液(水)作用产物具有明显不同的硅同位素组成,表明与火山作用或热液(水)作用无直接关系,而与风化作用有关,可能由风化过程中产生的富30Si流体形成。有研究表明风化过程中溶解的二氧化硅通常来自硅酸盐矿物的化学风化而非石英的溶解,研究剖面中晶体石英的硅质来源以硅酸盐矿物风化释放的硅质流体为主。利用Ge/Si值评估植物作用能否为研究剖面中晶体石英的形成提供物质来源,结果表明植物作用对研究剖面的硅质贡献作用相对较小,在表土层中植物作用的影响可能较大。以Ti作为参比元素来评估风化作用能否为晶体石英提供硅质来源,结果表明剖面中存在稳定且可观的硅的迁出,说明剖面中的晶体石英具有稳定且充足的硅质来源。 4、风化壳中晶体石英的氧同位素特征及其形成条件分析 研究剖面中晶体石英的δ18O值与高温成因石英及高、低温混合来源石英的δ18O值明显不同,在低温石英δ18O值范围内,暗示其形成于低温条件,与晶体石英的形态及包裹体的特征吻合。由于化学风化过程中W/R值很高,研究剖面中母岩以及粘土矿物的同位素组成对晶体石英δ18O值的影响可以忽略,即晶体石英的δ18O值可以粗略地反映大气降水的δ18O值,并可能进一步指示古气候信息。 5、风化壳中不同石英的硅、氧同位素特征及其成因指示 石英的硅、氧同位素分析表明,尽管大兴剖面中圆状石英和棱角状石英具有与晶体石英相似的硅、氧同位素组成特征,但它们的硅-氧同位素相关关系不同,可以明显地将晶体石英与圆状石英和棱角状石英区分开,说明它们具有不同的成因。 6、晶体石英的形成与贵州碳酸盐岩风化成土的关系 风化壳中晶体石英的形成与贵州碳酸盐岩风化成土的两阶段过程密切相关,酸不溶物中长石等硅酸盐矿物的风化能够为晶体生长提供硅质来源,碳酸盐岩风化形成的孔洞,则为晶体石英提供有利的生长环境和充分的生长空间。

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我国西南地区分布有广阔的亚热带潮湿区岩溶,以贵州为中心,总面积达50万km2,是世界上连片分布面积最大的岩溶区。贵州高原地处青藏高原东南缘,云贵高原的东翼,是中国大陆“西高东低”地貌格局中重要的过渡区段,对其新生代地质、地貌演化进行研究无疑具有重要的意义,不仅是对贵州薄弱的新生代地质、地貌研究的补充,而且可以直接通过夷平面展开与青藏高原的对比,探讨青藏高原隆升对贵州高原的直接影响。风化壳作为夷平面的组成部分,在过去没有引起足够的重视,但随着成功实例的不断出现,人们逐渐开始认识到风化壳是夷平面识别和重建的重要依据,也是夷平面环境信息的重要载体。贵州作为碳酸盐岩集中分布区,碳酸盐岩风化壳剖面广泛存在,尤其在黔中、黔北等地区各级夷平面上均发育有红色风化壳,利用碳酸盐岩红色风化壳能为夷平面的识别和形成时代的确立提供可靠的证据,特别是风化壳形成年龄的确定对夷平面时标的建立更具有积极意义。有关贵州地区红色风化壳形成时代的确定,多年来已有一些学者对此展开了研究,但贵州红色风化壳形成时代的确定存在着很大争论。虽然存在其它原因的可能性,但造成这种争论的根本原因在于贵州红色风化壳形成时代是依据其它资料(如夷平面、气候事件等)推断出来的,而不是根据直接测年数据界定的。因此,风化壳直接测年才是解决问题的关键。 本文在前人工作研究的基础之上,利用扫描电镜手段对贵州碳酸盐岩地区上覆风化壳土层中的石英颗粒进行观察、统计、分析,为风化壳成土的物质来源寻找新的证据;同时,经地球化学分析、测试等手段,判断风化壳土层中的晶体石英颗粒为风化壳形成初期的新生矿物——次生石英颗粒,并利用裂变径迹测年法对这种次生石英颗粒进行测年,最终探讨贵州碳酸盐岩地区上覆风化壳土层的形成年代。主要取得了以下几点认识: 一、石英颗粒蚀刻条件的优选 由于石英颗粒裂变径迹的长度和数量与晶格、铀含量、年龄等因素有关,所以不同地区的石英颗粒样品的裂变径迹蚀刻条件也存在差别;目前国际上有关石英颗粒的裂变径迹测年应用的实例较少,还没有统一的有关石英颗粒蚀刻条件的国际标准;现有的石英颗粒蚀刻条件有多种,但是缺乏对这些方法的优缺点进行对比评价。因此,我们要进行反复的条件实验,对比不同石英蚀刻剂的蚀刻效率,找寻适合石英颗粒的最佳蚀刻剂。实验结果表明,40%的HF溶液为最佳蚀刻剂,最佳蚀刻时间:温度在4℃左右(冬季)时为40min;温度在29℃左右(夏季)时为30min。 二、石英的外形、表面机械作用特征及其指示意义 我们利用扫描电镜对石英颗粒外形特征进行观察、统计、分析,结果表明本次研究的石英颗粒形态类型主要有两种:棱状-次棱状石英颗粒以及圆状、次圆状石英颗粒,其中棱状-次棱状石英颗粒包含了一部分晶体形态较为完整的石英颗粒。 根据石英颗粒表面机械作用特征分析结果,结合剖面区域地质特征,可初步判断剖面中的石英颗粒有三种物质来源:碳酸盐岩中的原生碎屑石英,有长时间长距离搬运特征;燧石团块石英,有短距离搬运或原位沉积特征;晶形较完整的次生石英,无搬运特征。三种石英均具有原位特征,前两种类型的石英是直接对基岩的继承,第三种类型的石英是风化壳剖面的次生矿物。 三、石英颗粒表面的化学作用特征及其风化强度指示意义 我们通过对石英颗粒表面化学作用形态的观察,发现大兴剖面、新蒲剖面和官坝剖面的石英颗粒表面化学溶解作用和化学沉淀作用都非常强烈,这表明三个剖面均处于湿、热环境中,均处于强烈的化学风化阶段。而且大兴剖面中石英颗粒表面的化学作用最强烈,气候较其他两个剖面更湿热,剖面的风化强度也最大,即各剖面的风化强度由强到弱排序为:大兴、新蒲、官坝。这一结果与矿物组成分析、化学风化强度、硅铝、铝铁硅风化系数比以及相对风化强度等的地球化学分析指标相一致,这也再次证明了我们采用石英颗粒表面形态特征分析手段的可行性和可靠性。 四、石英颗粒的裂变径迹年龄 三种类型石英颗粒的裂变径迹测年数据表明:a、同一样点石英颗粒裂变径年龄呈现一定的规律:F.T.AGE圆状、次圆状>F.T.AGE不规则状(棱状、次棱状)>F.T.AGE标准晶形(次生石英)。b、不同剖面的不规则状石英颗粒形成于同一个时期;不同剖面的圆状、次圆状石英颗粒形成于同一个时期。这两种石英颗粒不适于贵州碳酸盐岩风化壳的测年研究。c、不同剖面的标准晶形石英颗粒形成于不同时期,形成于碳酸盐岩酸不溶物原地堆积过程中,即与风化壳剖面同期形成,可用于贵州碳酸盐岩风化壳的测年研究。这一测量结果与我们对石英颗粒表面形态特征的观察、统计、分析结果相一致。 五、风化壳物源的新证据 贵州碳酸盐岩风化壳中的石英颗粒表面形态的分析结果表明,贵州碳酸盐岩风化壳的物质来源于碳酸盐岩中酸不溶物原地风化残积的产物,与其下伏基岩有着明显的继承性。这一分析结果与王世杰等人的碳酸盐岩酸不溶物的提取实验、地球化学、矿物学、粒度特征及区域地质背景等多方面的分析结果相一致,为贵州碳酸盐岩风化壳的物质来源及成因提供新的、更细致的证据。 六、贵州晚新生代地质-环境研究历史轮廓初建 由于目前对贵州及周边地区的风化-气候研究相对缺乏,数据资料较稀少,还没有形成完整的系统,我们本次研究也是建立在对风化壳中次生英颗粒年代学研究的基础上,研究还不是很透彻,因此只能对地质-环境研究历史轮廓进行初建。本文根据本次研究剖面土层中晶体次生石英颗粒的裂变径迹年龄分布情况,结合前人已有资料,对贵州25Ma以来的地质-环境演化历史的轮廓进行初建。从次生石英裂变径迹年龄值来看,中新世以来贵州主要经历了如下构造-风化期:25-19Ma、16-13Ma、10-6.5Ma、5-2Ma、1.7-1Ma。

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为了进一步获得贵州碳酸盐岩风化成土过程的信息,为测定风化成土速率的研究工作奠定基础,本次研究工作通过U-Th的地球化学特征与主量元素、微量元素、稀土元素的地球化学特征的对比研究以及U-Th不平衡来研究贵州两个碳酸盐岩风化剖面的风化成土过程,并得出以下总体认识: 贵州碳酸盐岩风化剖面中的238U-234U-230Th不平衡说明风化剖面中的U-Th不平衡与风化过程密切相关,与风化壳中矿物和铁壳的演化特征密切相关。风化剖面不仅被简单的持续积累或者滤失过程所控制,而且被每一个土层中的复杂的重组过程所影响。U-Th不平衡也说明风化系统的扰动可能与中更新世晚期的气候变化有关。风化剖面中的U-Th不平衡是由母岩碳酸盐岩的风化、风化流体的溶解作用、表土层中的有机质、铁质结核带中的氧化铁矿物以及伊利石、高岭石等粘土矿物对U、Th的吸附作用、α反冲作用以及微生物的还原作用等共同作用的结果。 具体结论如下: (1)两个风化剖面中的U、Th都在半风化层中相对基岩强烈富集,安顺白云岩风化剖面中U、Th在全风化层中下部富集;而遵义石灰岩风化剖面中的U在全风化层中部富集,Th在全风化层上部富集,然后向表土层逐渐减少。 (2)U、Th在半风化层中相对基岩强烈富集,是因为在半风化层中,基岩中的原生矿物发生溶解、蚀变,生成新的次生粘土矿物伊利石,而伊利石对U、Th具有强烈的吸附能力。风化剖面中U、Th的富集主要与地表水的淋滤作用以及铁壳在进一步的风化过程中溶解释放出其中所富集的U、Th,而U、Th向下重新迁移的过程有关。 (3)风化剖面中U、Th的分布特征说明U、Th的含量与风化过程密切相关,与风化壳中的矿物和铁壳的演化特征密切相关。遵义石灰岩风化剖面中U、Th的淋失程度比安顺白云岩风化剖面中U、Th的淋失程度弱也说明了遵义石灰岩风化剖面的风化程度要低于安顺白云岩风化剖面的风化程度。 (4)安顺白云岩风化剖面中,234U/238U在<1和>1之间交替变化。除在剖面中部,230Th/238U≈1外,230Th/238U基本上都>1。 (5)安顺白云岩风化剖面中的238U -234U-230Th不平衡表明:安顺白云岩风化剖面中的U-Th不平衡是母岩碳酸盐岩的风化、风化流体的溶解作用、表土层中的有机质、铁质结核带中的氧化铁矿物以及伊利石、高岭石等粘土矿物对234U、230Th的吸附作用、α反冲作用以及微生物的还原作用等共同作用的结果。 (6)遵义石灰岩风化剖面中234U/238U除少数几个点外,大多数采样点的234U/238U都<1。除了少数几个点外,大部分230Th/238U>1。 (7)遵义石灰岩风化剖面中的238U -234U-230Th不平衡表明:234U-238U不平衡主要是由地表水和入渗水的溶解作用以及α反冲作用为主要的控制机制。而风化剖面中230Th-238U不平衡主要是由表土层中的有机质、高岭石、氧化铁矿物以及伊利石对230Th吸附作用和α反冲作用共同作用的结果。 (8)将U的迁移模型应用于本研究中的两个碳酸盐岩风化剖面,说明这两个风化剖面都被U的近期积累或者滤失过程所影响,风化系统处于过渡的不稳定状态,并通过U在风化剖面中的重新迁移将系统带回稳定状态。 (9)由等时线定年法计算出的安顺白云岩风化剖面的年龄范围为:87.0±7.8-479.2±47.9ka;遵义石灰岩风化剖面的年龄范围为:62.3±8.7-353.3±31.8ka。 (10)由等时线定年法可知:两个风化系统将在~1.1Ma达到稳定状态。 (11)碳酸盐岩风化剖面应用U的迁移模型得出的U的迁移过程与风化剖面中主量元素和微量元素的迁移特征相吻合,说明模型的选择是正确的。 (12)整个风化剖面的238U-234U-230Th不平衡说明风化剖面中的U-Th不平衡与风化过程密切相关,与风化壳中矿物和铁壳的演化特征密切相关。风化系统的扰动可能与中更新世晚期的气候变化有关。碳酸盐岩风化剖面被U的近期迁移过程所影响,风化剖面中的每一个单元甚至每一个土样都具有复杂的历史。这些单元或者土样是古老的风化历史和近期的重新迁移过程的叠加。

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真菌在矿物和岩石风化过程中起着不可忽视的作用,岩生真菌对岩石的风化作用研究是微生物风化作用研究的热点问题之一。本研究利用从碳酸盐岩表面分离到一株真菌,开展了岩生真菌对碳酸盐岩风化作用的模拟试验,研究了该真菌对不同碳酸盐岩风化作用的过程和效果,分析了真菌代谢产物,发酵液方解石饱和指数以及风化过程中稀土元素的行为,探讨了该真菌对碳酸盐岩风化作用的机理。 对该岩生真菌GZKM01菌株形态学特征和基于ITS序列的分子鉴定结果表明该菌株隶属真菌界(Kingdom fungi)、半知菌亚门(Deuteromycotina)、腔孢纲(Coelomycetes)、球壳孢目(Sphaeropsidales)、鲜壳孢科 (Nectrioidaceae)座壳孢属(Aschersonia)。 实验条件下显示该真菌对碳酸盐岩具有较强的风化作用,可以大大地提高岩石中Ca2+的溶出量,发酵液上清液Ca2+浓度大大高于培养基对照和纯水对照。以加石灰岩矿粉的发酵液(摇床培养)为例,发酵液上清液最高Ca2+浓度分别是死菌对照和纯水对照处理最高Ca2+浓度的3.98倍和13.73倍。 真菌在生长和风化岩石过程中可以产生有机酸、醇类等挥发性代谢产物;真菌矿物相互作用过程中,真菌与矿物形成菌体-矿物复合体或聚集体,真菌胞外分泌物在矿粉表面形成生物膜结构;真菌对碳酸盐岩的风化作用导致发酵液方解石饱和指数SIc不断增大,溶液处于方解石过饱和状态。真菌对碳酸盐岩的风化作用包括有机酸和其他小分子物质的化学降解作用,机械破坏作用,碳酸酐酶的催化作用,真菌的对矿质元素的吸收作用,次生成矿作用等。 真菌作用下,发酵液上清夜稀土元素的含量普遍高于K2HPO4浸泡液中稀土元素的含量, 与K2HPO4浸泡液相比真菌浸出的稀土元素δCe值较大、δEu值较小,富Ce贫Eu,稀土元素分异现象明显;真菌菌体中富Ce贫Eu的特征更加明显,菌体对Ce有强烈的富集作用。代谢产物的络合作用,真菌产生的代谢产物对pH的调节作用,菌体的直接吸收和吸附作用,有机质的吸附作用,氧化还原作用等是造成稀土元素溶出、迁移和富集的主要原因。 分析认为该真菌对碳酸盐岩风化作用包括一系列的生物化学和生物物理过程,这两个过程相互依赖,相互促进,协同作用,岩生真菌在碳酸盐岩的风化成土过程中起着非常重要的作用。该真菌对岩石中稀土元素溶出、迁移和富集同样起着重要作用。通过综合分析风化壳的风化强度、稀土元素分布特征、微生物活动等可以为评估微生物在岩石风化过程中所起的作用提供依据。上述研究加深了对岩生真菌与碳酸盐岩相互作用过程和机理的理解,为进一步研究碳酸盐岩微生物风化作用提供资料。

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A general formulation of the Helmholtz free energy used in thermodynamics of damage process of rocks is derived within a multi-scale framework. Such a physically-based thermodynamic state potential has a hybrid, discrete/continuum, nature in the sense tha