The Dafushan mafic/ultramafic complex and genesis of the related rutile ore deposit at Zaoyang,Hubei
Hong Ji'an1, Ma Bin1, Huang Qi2
1. Key Laboratory of Crest-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026;
2. Institute of Northwest Hubei Geodogy, Bureau of Geology and Minerai Resources of Hubei Prouince, Xdangfan, Hubei 441000
The Dafushan mafic/ultramafic complex at Zaoyang, northern Hubei, located to the south of the Qinling-Tongbai-Dabie orogen.The complex consisted dominantly of not only peridotite arid troctolite,but also garnet amphibolite,garnet saussurite amphibolite and amphibole saussuritite, and surounded by the marble.The hosting ruble ore doposit occurred within metamorphic garnet amphibolite or altered garnet amphiholites.The zircon U-Pb SHRIMP data from the troctolite showed the emplacement age about 600 Ma for the mafic/ultramafic intrusions.All these rocks shared almost the same geoohemical characteristics for the unaltered maficlultramafic intrusive rocks and the metamorphic rocks,which suggested the protoliths of the metamorphic garnet amphibolite being probably troctolite,and all the complex being a differentiated mafic/ ultramafic intrusive body.The ruble occurring within the intersections of two cleavages of amphibote suggested that the primary ore-host rock should be garnet amphibolite rather than garnet pyroxenite,which was thought to be retrograded to later garnet amphibolite.The garnet was andradite rather than Mg and Al-rich one related to high-pressure metamorphism, suggesting none of involvement into the lndosinian ultrahigh pressure metamorphism.The formation of ruble ore deposit and localized metamorphism for the maficluItramafic complex might be resulted from the horizontal thrusting southwards.The energy and fluid by the thrusting combined with the deformation of the mafic/ultramaflc intrusive rocks caused the metasomatic metamorphism between the intrusive body and its wall rock carbonate one, and formed garnet amphibolites and ruble ore deposit.