A detailed survey of 40 Ar/ 39 Ar dating was carried out on basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. All the samples w...A detailed survey of 40 Ar/ 39 Ar dating was carried out on basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. All the samples were analysed in 40 Ar/ 39 Ar isotopic dating laboratory of Salzburg University in Austria. The results of 40 Ar/ 39 Ar dating include: (1) The Jinshuikou Group shows hornblende age of 388 5Ma, muscovite at 233～227Ma, and biotite ages between 232 2 and 208 2Ma. These are interpreted to result from amphibolite\|grade Caledonian orogenic diastrophism and low\|grade metamorphic Indosinian overprint. (2) The Xiaomiao Group is characterized by a 40 Ar/ 39 Ar muscovite age of 413 8Ma. (3) The Wanbaogou Group gives out a muscovite age of ca. 160Ma to the S of the Central Kunlun fault. (4) The Nachitai Group revealed a biotite age of ca. 110Ma that was overprinted by a very\|low\|grade event at 60～40 Ma. (5) The Kuhai basement to the S of the Central Kunlun fault is again characterized by a Caledonian age without detectable late overprint: Hornblende: ca. 405Ma, muscovite 376～357Ma, biotite: ca. 360Ma. The new ages constrain that the Kunlun basement essentially formed during Caledonian tectonic events. The basement was locally overprinted by Indosinian tecto\|thermal event in the north of the Central Kunlun fault, and by Jurassic and Paleogene tecto\|thermal events in the south of the Central Kunlun fault.展开更多
The exposed area of igneous rocks in East Kunlun Mountains is very large and they made a magmatic arc belt broad in scale. The intrusive rocks are mainly of Hercynian—Indo\|Sinian cycle and less of Caledonian and Yan...The exposed area of igneous rocks in East Kunlun Mountains is very large and they made a magmatic arc belt broad in scale. The intrusive rocks are mainly of Hercynian—Indo\|Sinian cycle and less of Caledonian and Yanshanian cycle [1～2] . During the geological mapping of 1∶250000 of Donggeicuonahu area, we firstly found the evidence of intrusive rock of Jinning cycle. Intrusive rocks of Jinning cycle, whose exposed area is about 30km, are located in Waliaoga\|Shaxiong area among East Kunlun magmatic arc belt and are composed of two intrusive bodies. The rock types of Jinning cycle are mainly trondjemite and tonalite. Their wall rocks are Baishahe Group of Paleo\|Proterozoic and was intruded by Hercynian-Indo\|Sinian cycle granodiorite . The wall rock types are mainly banded amphibolite,biotite\|plagioclase schist,leptynite,leptite,banded marble and mica\|schist , their metamorphic condition is overall middle amphibole facies , partly granulite facies , tectonic deformation was mainly of flowage fold and flowage shear in middle and deep levers. Although intrusive rocks of Jinning cycle had undergone intensive metamorphism and deformation, they also preserve the intrusive appearance and are uniform in field. We can see intrusive contacted with wall rock or infolded the basic inclusions. Gneissosity is very common in intrusive rocks of Jinning cycle. Even though intensive metamorphism and deformation lead to interlude between intrusive body and wall rock, most wall rock exists in intrusive rocks as giant roof or inclusions in general, we can see intrusive contacted between intrusive body and wall rock locally. Intrusive rocks are hoar color, meso\|coarse grain lepido\|granoblastic texture , minerals are mainly plagioclase evidence to study the forming and evolution of orogeny of Jinning and Caledonian cycle.展开更多
文摘A detailed survey of 40 Ar/ 39 Ar dating was carried out on basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. All the samples were analysed in 40 Ar/ 39 Ar isotopic dating laboratory of Salzburg University in Austria. The results of 40 Ar/ 39 Ar dating include: (1) The Jinshuikou Group shows hornblende age of 388 5Ma, muscovite at 233～227Ma, and biotite ages between 232 2 and 208 2Ma. These are interpreted to result from amphibolite\|grade Caledonian orogenic diastrophism and low\|grade metamorphic Indosinian overprint. (2) The Xiaomiao Group is characterized by a 40 Ar/ 39 Ar muscovite age of 413 8Ma. (3) The Wanbaogou Group gives out a muscovite age of ca. 160Ma to the S of the Central Kunlun fault. (4) The Nachitai Group revealed a biotite age of ca. 110Ma that was overprinted by a very\|low\|grade event at 60～40 Ma. (5) The Kuhai basement to the S of the Central Kunlun fault is again characterized by a Caledonian age without detectable late overprint: Hornblende: ca. 405Ma, muscovite 376～357Ma, biotite: ca. 360Ma. The new ages constrain that the Kunlun basement essentially formed during Caledonian tectonic events. The basement was locally overprinted by Indosinian tecto\|thermal event in the north of the Central Kunlun fault, and by Jurassic and Paleogene tecto\|thermal events in the south of the Central Kunlun fault.
文摘The exposed area of igneous rocks in East Kunlun Mountains is very large and they made a magmatic arc belt broad in scale. The intrusive rocks are mainly of Hercynian—Indo\|Sinian cycle and less of Caledonian and Yanshanian cycle [1～2] . During the geological mapping of 1∶250000 of Donggeicuonahu area, we firstly found the evidence of intrusive rock of Jinning cycle. Intrusive rocks of Jinning cycle, whose exposed area is about 30km, are located in Waliaoga\|Shaxiong area among East Kunlun magmatic arc belt and are composed of two intrusive bodies. The rock types of Jinning cycle are mainly trondjemite and tonalite. Their wall rocks are Baishahe Group of Paleo\|Proterozoic and was intruded by Hercynian-Indo\|Sinian cycle granodiorite . The wall rock types are mainly banded amphibolite,biotite\|plagioclase schist,leptynite,leptite,banded marble and mica\|schist , their metamorphic condition is overall middle amphibole facies , partly granulite facies , tectonic deformation was mainly of flowage fold and flowage shear in middle and deep levers. Although intrusive rocks of Jinning cycle had undergone intensive metamorphism and deformation, they also preserve the intrusive appearance and are uniform in field. We can see intrusive contacted with wall rock or infolded the basic inclusions. Gneissosity is very common in intrusive rocks of Jinning cycle. Even though intensive metamorphism and deformation lead to interlude between intrusive body and wall rock, most wall rock exists in intrusive rocks as giant roof or inclusions in general, we can see intrusive contacted between intrusive body and wall rock locally. Intrusive rocks are hoar color, meso\|coarse grain lepido\|granoblastic texture , minerals are mainly plagioclase evidence to study the forming and evolution of orogeny of Jinning and Caledonian cycle.
