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Analyze On The Mineralization And Mineralogical Characteristics Of Kazakhstan Jadeite Jade

Posted on:2015-03-01Degree:MasterType:Thesis
Country:ChinaCandidate:R ZhangFull Text:PDF
GTID:2250330428469286Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
Jadeitite is widespread around the world. Study of Myanmar and Guatemalajadeitite has been well conducted. Kazakhstan is among those poorly studied locations.Petrological and mineralogical study on Kazakhstan jadeitite are discussed in thisstudy, combining chemical composition, microstructure and fluid inclusion features.This study further suggests the formation mechanism of Kazakhstan jadeitite fromrock to jade.Main minerals are jadeite and omphacite. Accessary minerals include zircon,titanite, hyalophane and albite. Omphacite formed earlier than jadeite, then replacedinto islands by fluids rich in Na–Al–Si. Hyalophane formed later than jadeite, fromthe relict fluids. Jadeite has narrow rhythmic zonations. Back-scattered electron (BSE)images and cathodoluminescence (CL) images show oscillaroty variation in chemicalcomposition. Major changes are contents of Na, Ca and Mg. Fluid inclusios inKazakhstan jadeitite are first reported. Micro-Raman spectra shows the fluidinclusions are H2O and CH4,mostly gas-liquid two phase inclusions. A few threephase inclusions with daughter mineral jadeite are found. According to the rhythmiczonation and fluid inclusions, we can infer that Kazakhstan jadeitite are formeddirectly from Na–Al–Si fluids under HP/LT environment. Fluids that formKazakhstan jadeitite is inferred to come from altered ocean crust and deep-seasediments. Kazakhstan jadeitite formed at~1.4GPa,~450℃, i.e., blueschist-faciescondition.Petrographic microstructures of Kazakhstan jadeitite are observed undermicroscope, including euhedral to subhedral grain mosaic texture, medium graingranoblastic texture and semi-oriented to oriented texture. Deformationrecrystallization is apparent. Deformation inside the grains includes micro-fractures,subgrains, mechanical twins and kinking. Deformation among the grains includeshigh angle suture and refinement of jadeite grains. These microstructures show thatjadeitite has experienced varying degrees of metamorphic recrystallization, mainly conducted by deformation of tectonism. Jadeitite formed into jadeite jade through thisstage, after the formation from fluids.
Keywords/Search Tags:jadeitite, microstructure, zonation, fluid inclusion
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