Study On The Mineralization Of Basic-ultrabasic Rock Mass In Yueyashan,Inner Mongolia

Yueyashan is located about 130 kilometers south of Ejin Banner in Alxa League,Inner Mongolia,it is also located on the Hongliuhe-Niuquanzi-Yueyashan-Xichangjing fault zone,and the fault structures of the study area is well developed.The basic-ultrabasic rock mass in the area is distributed in the NWW direction,controlled by the fault of NWW direction,and strong alteration and mineralization are visible on the surface.In this paper,the basic geology,petrology and petrogeochemical characteristics of the basic-ultrabasic rock mass of Yueyashan are systematically studied,and the geological and geochemical characteristics of the rock mass are compared with those of the basic-ultrabasic rock mass in Heishan Ni-Cu Deposit.The petrographic characteristics show that the lithology of the rock of Yueyashan mainly includes Pyroxene-peridotite,Olivine-pyroxenolite(strong serpentinization),Pyroxenolite and Gabbro,and the degree of magma differentiation is relatively complete.Overall,the alteration of the rock mass is intense,and the alteration types are mainly Serpentinization,Carbonation and Chloritization.And the rock mass has metal minerals such as pyrrhotite,chalcopyrite and pentlandite.The petrogeochemistry studies have shown that the rock mass shows the characteristics of magnesium,alkali-depleted,aluminum-rich,calcium-rich and titanium-depleted.The average content of Mg O is between 8 and 30,the average m/f ratio is 4.95,and it is an iron-rich ultrabasic rock.The light and heavy rare earth fractionation of the rock mass is obvious,it is shown as a depleted mantle with a significant positive Eu anomaly,and the normalized REE distribution curve of chondrite is left-leaning-flat type.The distribution pattern of trace elements in rock mass is basically consistent,and large ionic lithophile elements(LILE)such as Rb,Ba and Sr are relatively enriched,while Nb,Ta and Th high field strength elements(HFSE)are deficient.These are similar to the rock geochemical characteristics of typical ore-bearing basic-ultrabasic rocks.Based on the ore-bearing evaluation index of basic-ultrabasic rock,the mineralization of Yueyashan rock mass is compared and evaluated by combining the degree of magmatic differentiation,lithofacies zoning,rock alteration and mineralization,lithogeochemistry(Mg Ocontent,m/f ratio,characteristics of rare earth and trace elements),degree of assimilation and contamination and geophysical and geochemical anomaly characteristics.To sum up,the magma differentiation of rock mass in the study area is well,the rock alteration is strong,the rock mass has metal minerals such as pyrrhotite,chalcopyrite and pentlandite,and mineralization of nickel sulfide was also found in drilling samples.And the rock geochemical characteristics are similar to the characteristics of typical ore-bearing basic-ultrabasic rock masses.Moreover,the magnetic anomaly in the exploration area has a high degree of coincidence with IP anomaly,and a number of ore-bearing evaluation indexes show that the basic-ultrabasic rock mass of Yueyashan has the value for further work.