Abstract
Yinachang Fe-Cu-Au-REE deposit locates in the central of Yunan province,China,the southern of Kangdian axis,which comprises to the Yangtze block to the 5W edge.Fe-REE ores occur as banded and/or disseminated replacements with in the breccia pipes,whereas Cu-Au ores occur predominantly as massive and veinlets within wallrocks and magnetite ores.According to differences in mineral association,ore structure&texture arid wallrock alterations,we divide the ore-forming process into four stages:Magma stage,metasomatism mineralization stage,hydrothermal mineralization stage and post-mineralization stage.Researches in microphysiography,composition and isotope of fluid inclusions suggest that fluids in magma stage are high salinity fluids,containing alkalis components and volatile phase,which formed in condition of high pressure(150-200 MPa) and high temperature (500-600℃).Irnmiscihility effect happens in these fluids,breeding the magmatic hydrothermal(mid-high temperature170-550℃,mid-high pressure73-155 MPa) in metasomatism mineraIization stage.Replacement between magmatic hydrothermal and carbonaceous wallrock causing the precipitation of Fe and REE,while the dehydration of wallrock produced the metamorphic hydrothermal of hydrothermal mineralization stage.Metamorphic hydrothermal mixed with meteoric water(120-360℃,31-112 MPa),changed the physical&.chemicai conditions,Cu,Au is no longer stable as clathrate in fluid,but precipitated as sulfide (Cu) and substance (Au),In the stage of past-mineralization,with the depletion of metamorphic hydrothermal,dominant fluid became pure meteoric water with fow temperature C95-270℃),low salinity(1.0-17.9% NaCI).The characteristics of fluid inclusions in Yinachang Fe-Cu-Au-REE deposit have many similarities with IOCG deposits,combined with researches in other aspects,it could be concluded as a typical IOCG deposits in central Yunnan province,has important significance in metallogenesis and prospecting.
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