The Flow-rock Reaction And Its Relationship With Uranium Mineralization During The Hydrocarbon Escape Process In The Mengqigur Uranium Deposit

In the guide of the hydrogenic sandstone type uranium metallogenic theory,the methods about lithogeochemistry,petroleum geochemistry,isotope geochemistry,isotopic geochronology and a large number of works about field geological investigation,sampling testing and its comprehensive analysis was applied to this thesis.The interaction between fluid and rock and its relationtion with the uranium metallogenic in the process of oil-gas escaping at the Mengqiguer uranium deposit was studied systematically by taking the alteration characteristics of ore-bearing layer sandstone as the breakthrough point.The type of alteration which related to sandstone-type uranium deposit mainly include clayzation,carbonation,silication,metal mineralalization and the clayization dominating in the ore-bearing layer sandstone of Mengqiguer uranium deposit.The geological response of the interaction between fluid and rock in the process of oil-gas escaping mainly contain diagenetic alteration response,element geochemistry response,organic response.The type and genetic of diagenetic alteration and its relationtion with the uranium metallogenic was studied detailedly.Kaolinite was the product of interaction between leaching of meteoric water and organic acid fluid and had something to do with uranium mineralization by the way of adsorption,reduction directly.In addition,kaolinite was on the genesis of uranium mineralization.According to its forming process,pyrite can be divided into framboids of pyrite/colloidal pyrite and cube pyrite and has the characteristics of biogenic.Pyrite was closely associated with uranium mineral on the spatial distribution and provides a reducing agent for the precipitation and enrichment of uranium.Carbonate cement can be divided three phases which were micritic carbonate cement in synsedimentary stage,micritic-sparry carbonate cement relating to sulfate reduction,sparry carbonate cement relating to organic matter decarboxylate role.Carbonate cement was symbiosis with uranium mineral locally and on the genesis of uranium mineral closely.On the basis of above research,the elements migration and its relationship with thealteration minerals was ascertain precisely in the different geochemical zoning in the process of the interaction between fluid and rock by the way of introducing the mass balance theory to the interlayer oxidation zone sandstone type uranium deposit audaciously.The diagenetic stages of the ore-bearing layer of Mengqiguer uranium deposit can be divided into syndiagenetic stage,A and B period of early diagenetic stage,A period of middlediagenetic stage and epidiagenesis stage.the diagenetic environment may experienced weak acid?acid-alkaline transition?acid?alkaline?acid-alkaline transition,oxidation ? weak reduction ? oxidation-reduction transition ? reduction enhancing ? oxidation-reduction transition as a whole,which would control the process of migration and concentrate of uranium.The metallogenic fluid of Mengqiguer uranium deposit has characteristics with the low temperature,large salinity span,medium density and multiple superimposition and so on.The metallogenic fluid was mixed fluid which consists of surface-water stemming frommeteoric waters and organic acid originating from coal measure strata and its concomitant reducing gas?Coal-formed gas?.The effect of diagenetic and uranium mineralization was result from reciprocity of organic-inorganic fluid and fluid-rock.On the basis of above research,the space-time relationship about fluid activities,tectonic evolution,diagenetic alteration and uranium mineralization were stated systematically in the process of ore-bearing layer burial evolution.Apatite fission track research deems that the ore-bearing layer of Mengqiguer uranium deposit experienced roughly six stages of thermal evolution history which was rapid deposition buried and heating stage at Jurassic,rapid uplift denudation and cooling stage at the early cretaceous,rapid deposition buried and heating stage at the late cretaceous – Oligocene,rapid uplift denudation and cooling stage at the early Miocene epoch,slow deposition buried heating stage at the late Miocene,rapid uplift denudation and cooling stage since Pliocene.Based on the temperature test about aqueous inclusions which was symbiosis with hydrocarbon inclusions,the time and period of the coalbed methane dissipation large-scale was ensured preliminary which can be divided three phases.The time was71Ma?15Ma?1 Ma respectively.Then time series of uranium mineralization,tectonic evolution,hydrocarbon dissipation was summarized and the uranium metallogenic was divided into four stages which was preliminary enrichment stage(J_1-2),interlayer oxidation zone large-scale development stage?K₂-E₃?,the main metallogenic stage?N₁?,superposition reconstruction stage?N₂-Q?.On the basis of above research,the tectonic evolution,hydrocarbon dissipation and interlayer oxidation coupling uranium metallogenic model of Mengqiguer uranium deposit was set up.