内蒙古红彦镇地区山神府花岗岩熔融-流体包裹体特征及其成矿意义

Characteristics and Metallogenic Significance of Melt-Fluid Inclusions of Shanshenfu Granite in the Hongyan Area,Inner Mongolia

通过内蒙古红彦镇地区山神府花岗岩的包裹体研究来探讨岩浆-热液过渡阶段的流体特征和成矿潜力.研究表明,山神府花岗岩包裹体类型可分为熔融包裹体、熔-流包裹体和流体包裹体3大类.熔-流包裹体的存在表明花岗岩经历岩浆-热液过渡阶段,而岩体中心相-边缘相流体包裹体均一温度从281℃变化到大于550℃,盐度从1.1%NaCl eqv变化到大于66.8%NaCl eqv同样指示了这一特征.根据不同温度、盐度包裹体等容线和水饱和花岗质岩浆固相线相交法可计算岩浆出溶流体温压范围,结合CO2三相包裹体对岩体最小侵位压力有较好限制,估算出山神府花岗岩最小侵位深度为7.6-9.5km,出溶温度为580-700℃,出溶深度集中在6.0-14.9km.包裹体拉曼特征表明,熔-流包裹体固相成分含有重晶石、蓝铜矿和赤铁矿等强氧化性物质,说明岩浆-热液体系具有高氧逸度,而在高温高压高盐条件下非常有利于岩浆中Cu等金属向出溶流体中富集,结合野外矿化蚀变特征,分析得出山神府地区具有较好寻找岩浆热液型Cu矿床的成矿潜力.

This study investigates the characteristics of the fluid and its mineralization potential in magmatic-hydrothermal phase by the inclusions study of the Shanshenfu granite located in the Hongyan area, Inner Mongolia. The study shows that the inclusions of the Shanshenfu granite can be divideddevided into three types includingof melt inclusions, melt-fluid inclusions and fluid inclusions. The presence of melt-fluid inclusions indicates that granitic magma has experiencedgot through magmatic-hydro- thermal transition stage, which is confirmed by the large changes in homogenization temperatures （from 281 ℃ to 〉550 ℃） and the salinities（from 1.1% NaCl eqv to 〉66.8 % NaCl eqv） from rock center lithofaciesphase to edge lithofaciesphase. We use inclusion isochors of different homogenization temperatures and salinitiesy together with water-saturated solidus of granitic magma to estimate the temperatures and pressures of exsolved fluids. Considering that the three-phase inclusions containing CO2 have a good limitation to the smallest emplacement pressure, we estimate that the smallest emplacement depth of Shanshenfu granite of range 7.6-9.5 km, exsolution temperature and depth of range 580-700℃ and 6.0-14.9 km, respectively. Laser-Raman characteristics of inclusions show that the solid phases of melt-fluid inclusions contain strong oxidation substances such as barite, azurite and hematite, which indicates the strong oxidation in magmatic-hydrothermal system that is very beneficial for Cu enriched in the exsolved fluids under the conditions of high-pressure, high-temperature and high-salinity. Combined with the wild in situ mineralized alteration characteristics, we conclude that the Shanshenfu area has good mineralization potential to form magmatic-hydrothermal deposit of Cu.