Research On Mineralogy Of K-feldspar And Pyrite In Halasu Porphyry Copper Deposit Of Altai Mountain

The Halasu porphyry copper deposit is located at the southern margin of the east section of Altai mountain. The geotectonics is part of the oblique collision and joint between the southwest margin of Siberia plate and the northeast margin of Zungar plate. This district provides good geological ore-forming conditions, especially for the ore-forming of porphyry copper deposit. In this paper based on field geological work,we have done some research on the chemical components, the structure parameters, trace elements, lanthanon of the main minerals, such as K-feldspar, pyrite and biotite, through microscope observation and other modern testing methods, in order to provide some evidence for the genesis and exploration of the mine.Study on chemical components and structure of K-feldspar by EPMA and XRD analysis indicates that K-feldspar is high in degree of order and low in structure; the trademark of plagioclase which coexist with K-feldsper is An3,and the temperature is calculated to be from 300℃to 400℃; The K-feldsper phenocryst is microcline-orthoclase, which is evidence for ore-bearing. The lowest temperature for K-feldspar to reach the state of stability is about 300℃.The data analysis of main elements ,trace elements and lanthanon compositions of pyrites show that there are sulphur deficiency, higher Co,Ni and Co/ Ni (>1),which indicate the genetic of pyrite in this deposit is hydrothermal alteration and the S/Se distribution in 1×104 to 2×104 indicates it is ore-forming fluid deposit.The research of lanthanon in pyrite shows: The content of lanthanon(ΣREE) in theⅢepoch is much more than in theⅠ,Ⅱepochs .The ratios of LREE/HREE in all epochs are more than 1 showing the enrichment of light lanthanon and .TheⅠepoch andⅡepoch are rich in MREE ,TheⅢepoch distribution curve leaning to right that indicates it is rich in light lanthanon.According to the previous studies on the typomorphic components of biotite, Mg / Fe values> 0.5 for Cu-porphyry and Mg / Fe values <0.5 for non-porphyry ore. Mg / Fe values of Biotite are greater than 0.5 in this district, and pertain to the high magnesium biotite, it can reflect that oxygen fugacity is high when granite magma crystallizes, and validate that this deposit pertains to porphyry copper deposit type. The biotite in this area is from the source of mantle according to the illustration of the mantle rocks.