HIGH-PRESSURE LOW-TEMPERATURE METAMORPHISM IN NORTHERN HUBEI PROVINCE, CENTRAL CHINA

The Qinling-Dabie accretionary fold belt in east-central China represe nts the E-W trending suture zone between the Sino-Korean and Yangtze c ratons. A portion of the accretionary complex exposed in northern Hube i Province contains a high-pressure/low-temperature metamorphic sequen ce progressively metamorphosed from the blueschist through greenschist to epidote-amphibolite/eclogite facies. The 'Hongan metamorphic belt' can be divided into three metamorphic zones, based on progressive cha nges in mineral assemblages: Zone I, in the south, is characterized by transitional blueschist-greenschist facies; Zone II is characterized by greenschist facies; Zone III, in the northernmost portion of the be lt, is characterized by eclogite and epidote-amphibolite facies sequen ces. Changes in amphibole compositions from south to north as well as the appearance of increasingly higher pressure mineral assemblages tow ard the north document differences in metamorphic P-T conditions durin g formation of this belt. Preliminary P-T estimates for Zone I metamor phism are 5-7 kbar, 350-450-degrees-C; estimates for Zone III eclogite s are 10-22 kbar, 500 +/- 50-degrees-C. The petrographic, chemical and structural characteristics of this metamorphic belt indicate its evol ution in a northward-dipping subduction zone and subsequent uplift pri or to and during the final collision between the Sino-Korean and Yangt ze cratons.