MAIS IMAGING SPECTROMETER DATA-ANALYSIS FOR NI-CU PROSPECTING IN ULTRAMAFIC ROCKS OF THE JINCHUAN GROUP, CHINA

The Jinchuan intrusion, situated in the Gansu province of China some 3 0 km NE of Yongcang city is an ultramafic dyke-like body emplaced in t he Longshoushan uplifted terrain on the southwest margin of the Sino-K orea platform. The intrusion is 6 km long, 35 m wide and hosts a major Ni-Cu sulfide deposit. The main stratigraphic units include the highl y metamorphosed Lower Proterozoic Longshoushan group and the less exte nsively metamorphosed Dongzigou and Hanmushan groups of Middle and Upp er Proterozoic age. The Longshoushan group consists of serpentine marb le, schist, gneiss and plagioclase amphibolite. The Dongzigou group co mprises schists and granitic rocks. The Hanmushan group basically is r epresented by a large variety of volcanics. Small mafic-ultramafic int rusions are located along faults in the Jinchuan terrain. These ultram afic rock bodies show a concentric zoning with a core of dunites and o livine pyroxenites forming the margins of the bodies. Hydrothermal alt eration (mainly serpentinization) has affected the rocks of the ultram afic bodies to a variable extent; the dunites are extensively altered whereas the pyroxene rich units are relatively fresh. Field spectrosco py is used to spectrally characterize the major rock units. Imaging sp ectrometer data was flown during the end of July until beginning of Au gust of 1993 with a Chinese imaging spectrometer instrument called MAI S: the Modular Airborne Imaging Spectrometer. Feature characterization permits lithologic mapping from MAIS data. This aids in mineral poten tial mapping in the Jinchuan region and permits the identification of areas of possible Ni-Cu deposits.