Study On Metamorphism Of Longshoushan Baijiazuizi Group

Jinchuan copper and nickel ore concentration area is China’s largest Ni, Cu and PGEmetals production base, At the same time is also the world’s third largest copper and nickel oreconcentration area. With the development of the jinchuan copper and nickel ore, it’s need todeposit the geological background and deep extension of further exploration. National scienceand technology special continental scientific drilling project in jinchuan Ⅱmining area,establish the scientific research platform for this paper. In the past it has been the importanceof ultramafic rock and Jinchuan nickel-copper deposits in research, while relatively fewstudies on the causes of the Jinchuan deposit rock rock, diagenetic age, tectonic evolution,especially in the area of research metamorphic less. Therefore, this paper order this scientificdeep drilling as platform, combined with surface and drilling core conducted onLongshoushan Baijiazuizi Group petrological, geochemical and zircon U-Pb geochronology,etc studies. There are the following understanding:1.Longshoushanqun group rock group was divided into mixed granite, amphibolite rock,marble, quartz biotite-albite schist, quartz monzonite gneiss.Through field investigation andmicroscopic identification, for it’s detailed classification, and summed up the typical mineralassemblage Namely:Mixed granite: K-feldspar+plagioclase+quartz+chlorite+epidote;Amphibolite rocks: hornblende+plagioclase+biotite+quartz+chlorite+epidote+magnetite;Marble: calcite+muscovite+dolomite+serpentine+antigorite+tremolite+diopside+talc;Schists: biotite+plagioclase+quartz+hornblende+garnet;Gneiss: biotite+plagioclase+K-feldspar+quartz+hornblende.2.With the restoration of the original rock by geochemical method,Most of the samplesare mixed granite and a handful of mafic amphibolite rock is positive metamorphic rocks, theother are vice metamorphic. Migmatite granite alkalinity ratio (AR)=1.97~6.46, cast figureshows alkaline and calc-alkaline; aluminum saturation index (ACNK)=0.82~1.20, asaluminum, metaluminous granite.3.The local metamorphic LREE enrichment relative to heavy rare earth elements, heavyrare earth elements relatively flat. Samples of light rare earth showed typical rightist curve,And there is a significant negative anomalies of Nb and Ta, These features is related to islandarc environment the volcanic. By tectonic discrimination cast chart with mixing granite, we can see its formation after the collision tectonic setting.4.Metamorphism in the study area is mainly regional metamorphism, Studies suggestthat the degree of metamorphism reached amphibolite facies. According to the zircon U-Pbdating amphibolite facies metamorphism age of1899ma (department) and1884ma(edge).Measured mixed granite samples JCB-3and JCB-4cores aged2103Ma and2072Ma,explain its formation in the Paleoproterozoic.