Study On Mineral Characteristics Of Segment Ⅱ, Jinchuan Ni-cu (PGE) Sulfide Deposits, Gansu Province

Jinchuan is the world’s third largest deposits of magmatic Cu-Ni sulfide deposit, the researchon the ore-forming processes of it are very popular in deposit scientists at home and abroad.In this paper we studied the mineralogical characteristics of rock-forming and metallicminerals of segment II Jinchuan deposit using microscopy and micro beam test and analysismethod. By doing this, we intend to obtain informative evidence in mineralogy and petrologyand infer processes and conditions of rock-forming and ore-forming. Furtherly, to supply andimprove the metallogenic theory of Jinchuan copper and nickel sulfide magmatic ore deposits.This paper is supported by “Advance research on the scientific drilling location of Jinchuancopper nickel sulfide ore concentration area(SinoProbe05-01)”(Public sector fundproject201011058), and already got some results as follows:1. The olivine of ultrabasic intrusion in segmentⅡof Jinchuan deposits belongs tochrysolite. The beginning crystallization temperature of it are1383-1402℃while the endingtemperature are1258-1272℃, and it has nothing to do with lithology. The type ofclinopyroxene and orthopyroxene are respectively endiopside and bronzite. Thecrystallization temperature and diagenesis pressure are971-1191℃and9.4-10.2Kb.2. the lithofacies of the ultrabasic rocks shows prosodic shape distribution from the centerto the two sides. The main oxides and typical stable trace elements of the rock mass changeregularly and this character is corresponding to the distribution character of lithofacies.3. The Pt, Pd, Au, Ag of Jinchuan deposits mainly exist as independent minerals in bothrock forming and metallic mineral.4. Based on the characteristics of ore output,composition, structure and so on, we devide the mineralization of segmentII of Jinchuandeposits into three periods: magma mineralization period, tectonic-metamorphic hydrothermalmineralization period and supergene oxidation period. And the magma mineralization periodcan be futher devided into four stages: early magmatic liquation-crystallization differen-tiation stage, late magma mineralization stage, ore magma injection mineralization stage, andpostmagmatic hydrothermal mineralization stage.5. The component of olivine and pyroxene indicates the primary magma is high-Mgtholeiitic magma and contains10.9%MgO and11.1%FeO. There was sulfide segregation inthe early magmatic evolution period, and suffered assimilation-contamination by Ca-rich rockduring the process of evolution.