The Qilian Orogen marks the junction of the North China, South China and Tarim cratons. The mechanism of continental growth during the formation of the orogen remains unclear. Based on detailed fieldwork, we present a...The Qilian Orogen marks the junction of the North China, South China and Tarim cratons. The mechanism of continental growth during the formation of the orogen remains unclear. Based on detailed fieldwork, we present a systematic study of petrography, mineral chemistry and phase equilibria of garnet amphibolites from the Hualong Group, which represents the Precambrian basement in the southern accretionary belt of the Qilian Orogen. The garnet amphibolites mainly consist of amphibole, plagioclase, garnet and quartz, with minor pyroxene, biotite and ilmenite. A peak stage of upper amphibolite facies to low-temperature granulite facies metamorphism and retrograde metamorphism in the amphibolite facies affected the samples. Garnet has a homogeneous composition of Alm66-71Grs14-17Prp9_12Sps3-s, amphibole is ferro-hornblende, biotite belongs to the ferro-biotite species and pyroxene is dominated by orthopyroxene with few clinopyroxene. Pseudosection modeling of the garnet amphibolite samples indicates clockwise P-T paths. The samples witness peak metamorphism at conditions of -4.9-6.3 kbar and -755-820 ℃ in the upper amphibolite facies to low- temperature granulite facies, and retrograde cooling and decompression at conditions of-2.5-3.1 kbar and -325-545 ℃. It is inferred that peak metamorphism with high temperature and low pressure occurred at ca. 450 Ma during northward subduction of the South Qilian oceanic crust beneath the central Qilian Block. When continental collision occurred between the central Qilian and the Qaidam blocks, the Hualong Block was aecreted onto the South Qilian accretionary complex and experienced amphibolite facies retrograde metamorphism at ca. 440 Ma.展开更多
IN the Shapingba District in Chongqing, Sichuan Province, there is the Hualong Bridge. During World War Ⅱ, my father ran a bean curd plant near the bridge where he sold bean curd and green vegetables. My mother made ...IN the Shapingba District in Chongqing, Sichuan Province, there is the Hualong Bridge. During World War Ⅱ, my father ran a bean curd plant near the bridge where he sold bean curd and green vegetables. My mother made the bean curd while I helped to tend the kitchen fire. This small bean curd plant witnessed the hard times that my family had undergone in the eight years of the War of Resistance Against the Japanese Aggression. Now I’m over 70 and live together with my children in Hong Kong. Although I now live a peaceful and comfortable life, I cannot forget the past—the long, unstable years by展开更多
基金funded by the National Natural Science Foundation of China (No. 41520104003)the National Key R & D Program of China (No. 2016YFC0600403)+1 种基金the China Geological Survey (No. DD20160201)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (Nos. CUGL170404, CUG160232)
文摘The Qilian Orogen marks the junction of the North China, South China and Tarim cratons. The mechanism of continental growth during the formation of the orogen remains unclear. Based on detailed fieldwork, we present a systematic study of petrography, mineral chemistry and phase equilibria of garnet amphibolites from the Hualong Group, which represents the Precambrian basement in the southern accretionary belt of the Qilian Orogen. The garnet amphibolites mainly consist of amphibole, plagioclase, garnet and quartz, with minor pyroxene, biotite and ilmenite. A peak stage of upper amphibolite facies to low-temperature granulite facies metamorphism and retrograde metamorphism in the amphibolite facies affected the samples. Garnet has a homogeneous composition of Alm66-71Grs14-17Prp9_12Sps3-s, amphibole is ferro-hornblende, biotite belongs to the ferro-biotite species and pyroxene is dominated by orthopyroxene with few clinopyroxene. Pseudosection modeling of the garnet amphibolite samples indicates clockwise P-T paths. The samples witness peak metamorphism at conditions of -4.9-6.3 kbar and -755-820 ℃ in the upper amphibolite facies to low- temperature granulite facies, and retrograde cooling and decompression at conditions of-2.5-3.1 kbar and -325-545 ℃. It is inferred that peak metamorphism with high temperature and low pressure occurred at ca. 450 Ma during northward subduction of the South Qilian oceanic crust beneath the central Qilian Block. When continental collision occurred between the central Qilian and the Qaidam blocks, the Hualong Block was aecreted onto the South Qilian accretionary complex and experienced amphibolite facies retrograde metamorphism at ca. 440 Ma.
文摘IN the Shapingba District in Chongqing, Sichuan Province, there is the Hualong Bridge. During World War Ⅱ, my father ran a bean curd plant near the bridge where he sold bean curd and green vegetables. My mother made the bean curd while I helped to tend the kitchen fire. This small bean curd plant witnessed the hard times that my family had undergone in the eight years of the War of Resistance Against the Japanese Aggression. Now I’m over 70 and live together with my children in Hong Kong. Although I now live a peaceful and comfortable life, I cannot forget the past—the long, unstable years by
