40Ar-39Ar biotite and hornblende dating of Tieshan quartz diorite related to the skarn-type deposits in Daye area, Hubei Province, and its geological significance

Abstract：The Middle-Lower Yangtze River belt is one of the large-scale Mesozoic metallogenic areas in eastern China and also an important Cu-Fe-Au-Mo metallogenic belt in eastern China. The polymetallic Cu-Fe deposits in southeast Hubei area constitute an important part of the Yangtze River belt; nevertheless, studies of rock body chronology and thermal chronology remain very insufficient. Biotite and hornblende of the Tieshan rock body related to the skarn-type Fe deposits in Daye of Hubei Province yield 40Ar-39Ar plateau ages of 133.0±1.0 Ma and 137.0±2.0 Ma and isochronal ages of 133.4±1.5 Ma and 137.3±1.6 Ma respectively. An integrated study of available petrological, geochemical and rock body U-Pb ages led the authors to believe that the rock body ages of southeast Hubei area are the same as the ages of the Yangtze River belt, and the skarn-type Fe mineralization in Daye of Hubei Province was associated with lithospheric extension and thinning during the Late Mesozoic in eastern China. Meanwhile, utilizing the rock body cooling rate theory (the mineralization scale retro-correlation to the rock body cooling rate), the authors found that, although the cooling rate of the Tieshan rock body is rather higher in comparison with the cooling rates of the main mineralization rock bodies in Tongling, small shallow plutons could be complemented by ore-forming fluids and heat energy of deep magma chamber.