plagioclase gneiss
1.The Archaean rocks widely exposed in the area studied belong to the Qian-xi Group of granulite facies, including granulite, charnockite, pyroxene(and/or amphibole)-plagioclase gneiss, amphibolite and so on.
2.The zircons (sample No. F103) from biotite plagioclase gneiss of the Lower Fuping Group yield an up intercept age of 2 484 Ma and a concordia age of 2 332 Ma, interpreted as crystallization and anatexis timing, respectively.
3.It is notably different from the Middle Proterozoic Langshan Group on the northern and southern slopes of Mount Langshan. The biotite-plagioclase gneiss has been measured to have a Sm-Nd isochron age of 2735 Ma, which proves it to be of Late Archean age.
4.The complex was previous considered as a uniform stratigraphic sequence named the Fuping Group, and assigned to the uniform Archaean based on the conventional multi grains zircon U Pb age of (2 800 +230 -150 )Ma from the biotite plagioclase gneiss of the Lower Group.
5.Also found in the belt are phlogopite tremolite schist, biotite (-bearing) plagioclase amphibolite, dioritic gneiss, meta-quartz dioritic rock, fine-grained trondhjemite, adamellite, pegmatitic vein.
