MULTIPHASE MELT INCLUSIONS IN THE JINCHUAN COMPLEX, CHINA - IMPLICATIONS FOR PETROGENIC AND METALLOGENIC PHYSICOCHEMICAL CONDITIONS

Three types of melt inclusions were identified in pyroxenes, olivine, and chromite from the Jinchuan intrusion-sulfide inclusions (I), cryst allized polyphase inclusions (II), and fluid inclusions (III). Sulfide inclusions in chromite are spherical and occur parallel to chromite g rowth planes. Polyphase inclusions are found in olivine and consist of olivine, orthopyroxene, chrome-spinel, amphibole, and sulfide daughte r minerals. Primary fluid inclusions are usually found in olivine and pyroxene with spherical to tubular shapes. Laser Raman analyses were u sed to identify daughter minerals and fluid phases in the inclusions. The result shows that fluids consist mainly of CO2, with minor amounts of SO2, H2S, and CH4. This indicates that the parental magma of the J inchuan intrusion contains abundant volatiles. Microthermometry shows that Type-II inclusions in dunite and sulfide-rich Iherzolite have hig her trapping temperatures (1000 degrees to 1050 degrees C), whereas tr apping temperatures in sulfide-poor Iherzolite are lower (900 degrees to 950 degrees C). The result of low-temperature microthermomentry ind icates that the CO2 homogenization temperatures of +10 degrees to +15 degrees C correspond to depths of 12.9 to 15 km (deep-level magma cham ber) and the homogenization temperatures of +26 degrees to +29 degrees C correspond to depths of 6.9 to 9.3 km (upper magma chamber). The im miscible sulfide in the inclusions demonstrates that segregation of th e sulfide melt occurs at an early stage during magmatic differentiatio n.