Fluid Regime of the Formation of Late Mesozoic Collisional Granites in Auriferous Districts of the Upper Amur Region

摘要

It is well known that volatile components play an important role in the formation of mineralization associated with granitoid magmatism. Fluid composition, an essential element in the concentration and transport of ore material, significantly governs the evolutionary trend of magmatic melt. There is limited information available concerning the behavior of volatiles in the development of auriferous and other ore-magmatic systems. Therefore, the assessment of crystallization conditions and fluid composition on the basis of biotite data for Late Mesozoic (120-150 Ma) collisional granites of the upper Amur region presents an interesting and important problem. Granitoid domains of the study area are confined to major structures of the upper Amur region (Aldan-Stanovoi, Baikal-Vitim, and Amur superterrains and Mongol-Okhotsk Foldbelt). Late Mesozoic granitoids of the northeastern Amur Super-terrain and southern Mongol-Okhotsk Foldbelt are confined to the Umlekan-Ogodzha volcanoplutonic zone. The granitoids include monzodiorite-granite and granosyenite-granite associations. The monzodiorite-granite association is accompanied by the most productive skarn-hydrothermal types of gold and gold-rare metal mineralizations, whereas the granosyenite-granite association includes the low-productive variety of gold and gold-rare metal mineralizations.