Geochemical Characters And Petrogenesis Of Kalatongke Basic Rock Body In Xinjiang

Kalatongke Cu-Ni ore district lies in east of Saerbulake-Sasekebasitao synclinorium in Junggar fold system, which is the boundary of Altai Caledonian fold system and Junggar Hercynian fold system. This area develops a series of second-order folds and subsidiary fractures, and composed by eleven rock bodies(Y1-Y9,Y10,Y11) and G21,G22 gravity abnormal district and AM16 aeromagnetic anomaly district. Although predecessors make a lot of research about the Kalatongke rock body, there are still some controversial issues. This paper according to systematically research the petrography, crystal chemistry, rare earth elements, trace elements and Sr, Nd, Pb and Re-Os isotopic geochemistry of Kalatongke rock body, scientifically demonstrates its magmatic process, magma nature and mantle source district features. Based on these researches we get some initial understanding as follows:1. The main rock types are diabase-gabbro, gabbro, biotite hornblende olivine norite, gabbro-norite, norite, diorite, the quantity of ultrabasic rock is few, and the main ore-bearing rock is norite, the main rock-forming minerals are olivine, pyroxene, plagioclase, hornblende and biotite. Its formation age is 287±5Ma, belongs to the early Permian.2. The REE partitioning pattern is LREE enrichment, the Eu anomaly is not obvious, and enriches LILE, correspondingly depleted HFSE. The Nd,Sr,Pb isotopes show that it comes from the depleted mantle. The magma source is asthenosphere, and the source matter is composed by asthenosphere matter and metasomatic lithosphere mantle matter. The rock body is formed in post-collision extended environment.3. Kalatongke Y1-Y11 and G21 rock body is the identical rock body troop, it is the result of the same primary magma evolved, AM16 doesn't belong to the identical rock body troop; The rock body can be divided into three group: the first group is the Y1,Y2 rock body, is mainly composed by low evolution degree magma, but they also contain a few upper evolution degree magma; the second group is the Y3,Y5 rock body, is mainly composed by moderate evolved magma, but they also contain a few high evolved degree magma; the third group is the Y7,Y8,Y9,G21 rock body, is mainly composed by evolved magma; The magma channel-way of the rock body should be existed between the Y1 and Y2 rock body. 4. A majority of magma which forms the rock body is not the primary magma, it mainly composed by different evolution degree magma. The parental magma is basaltic magma, and its content of MgO is a little high, the content of MgO is 9.42%. When the magma is in the course of rising it should be hybridized a little by the crust substance, the magma rises from the source to emplacement at least experiences twice magma chamber fractional crystallization process. When the magma is in the course of rising because of the density, it forms deep magma chamber in the deep, and there it takes place the fractional crystallization, the main mineral is olivine and there is a little orthopyroxene. The evolved magma rises into the exalted magma chamber and takes place the fractional crystallization of clinopyroxene and on-spot differentiation, and then forms current Kalatongke basic rock body.