Types and Characteristics of Basic-Ultrabasic Small Intrusions in the Southwest Region of Jinchuan Ni-Cu Deposit

More than 100 basic-ultrabasic small intrusions outcrop in the southwest of Jinchuan Ni-Cu mining area.They mainly distribute in the Lower Proterozoic stratum nearby Tamazi ditch and in the Sininan stratum along Baierquan ditch.Small intrusions are small size,shallow buried in the form of,vein,stock and dike.The attitude in general tends to southwest with a dip angle of about 70 degrees.Base on the characteristics of microscopy and X-ray powder diffraction,these intrusions are roughly divided into two kinds,there are the basic diabase and the ultrabasic josefite.The analysis results of petrochemistry show that the content of Ni and Cr of these intrusions are 58×10^-6-1900.8×10^-6and 65.1×10^-6-4518.2×10^-6,and the content of REE ranges from 22.57×10^-6 to 308.20×10^-6.The enichment of LREE is a typical characteristic of these intrusions,and the differentiation of the HREE is weak.Compared study results show that the josefite in the research area have similar mineral composition,similar content of trace elements and the similar distribution of REE with the ore bearing intrusions,indicating that they are evolved from the same magma activity.