Laser Raman spectroscopy and cathodoluminescence （CL） images show that most zircon crystals separated from paragneiss in the main drill hole of the Chinese Continental Scientific Drilling Project （CCSD-MH） at Maob...Laser Raman spectroscopy and cathodoluminescence （CL） images show that most zircon crystals separated from paragneiss in the main drill hole of the Chinese Continental Scientific Drilling Project （CCSD-MH） at Maobei, southwestern Sulu terrane, contain low-pressure mineral-bearing detrital cores, coesite-bearing mantles and quartz-bearing or mineral inclusion-free rims. SHRIMP U-Pb dating on these zoned zircons yield three discrete and meaningful age groups. The detrital cores yield a large age span from 659 to 313 Ma, indicating the protolith age for the analyzed paragnelss is Paleozoic rather than Proterozoic. The coesite-bearing mantles yield a weighted mean age of 228 ± 5 Ma for the UHP event. The quartz-bearing outmost rims yield a weighted mean age of 213 ± 6 Ma for the retrogressive event related to the regional amphibolite facies metamorphism in the Sulu UHP terrane. Combined with previous SHRIMP U-Pb dating results from orthogneiss in CCSD-MH, it is suggested that both Neoproterozoic granitic protolith and Paleozoic sedimentary rocks were subducted to mantle depths in the Late Triassic. About 15 million years later, the Sulu UHP metamorphic rocks were exhumed to mid-crustal levels and overprinted by an amphibolite-facies retrogressive metamorphism. The exhumation rate deduced from the SHRIMP data and metamorphic P-T conditions is about 6.7 km/Ma. Such a fast exhumation suggests that the Sulu UHP paragnelss and orthogneiss returned towards the surface as a dominant part of a buoyant sliver, caused as a consequence of slab breakoff.展开更多
The poly-phase orogeny information included in one orogenic belt is the key for studying the regional tectonic evolution at different time period.It also has important significance of understanding the rock associatio...The poly-phase orogeny information included in one orogenic belt is the key for studying the regional tectonic evolution at different time period.It also has important significance of understanding the rock association and展开更多
The petrographic and structural study of Gbowé (Grand-Béréby) formations located in the SASCA domain (South-West of Côte d’Ivoire) revealed migmatitic paragneisses. For an in-depth understandin...The petrographic and structural study of Gbowé (Grand-Béréby) formations located in the SASCA domain (South-West of Côte d’Ivoire) revealed migmatitic paragneisses. For an in-depth understanding of the petrographic, structural and metamorphic characteristics, six (6) thin sections were made from these paragneisses. These gneisses are characterized by paleosomes and neosomes (leucosome and melanosome), consisting of quartz, garnet, plagioclase, biotite, cordierite, sillimanite, myrmekite and microcline. The mineralogical assemblage thus described indicates a retrograde metamorphism (transition from granulitic facies to amphibolitic facies). The structural and microstructural study identified two types of deformation (ductile and brittle). The ductile deformation is characterized by phases D1 (NE-SW flattening) and D2 (NW-SE flattening), materialized by foliations (N140˚, N050˚), folds (asymmetrical folds, similar folds, concentric folds, ptymatic folds) and boudins. Fracture schistosity and fold fracture schistosity are characteristic of the brittle deformation (phase D3). The microstructural study coupled with the metamorphic study shows that the deformations had an impact on the texture of the minerals (recrystallization and mineral reactions). It also allowed giving the paragenesis of phases D1 and D2. The D1 phase is characterized by garnet1, biotite1, quartz1, sillimanite1 and cordierite1 and the D2 phase is characterized by garnet1, quartz2, sillimanite2, biotite2, garnet2 and orthose2. These parageneses thus highlighted bear witness to a polydeformation and polymorphism that affects the study area.展开更多
在柴达木盆地北缘中段的锡铁山地区,夹有榴辉岩或退变榴辉岩透镜体的2个副片麻岩样品的锆石被用于SHRIMP U pb测定。2个片麻岩样品具有类似的特征,主要由石榴子石、夕线石、长石、黑云母和石英组成,这些矿物组合形成的变质条件, 0.6～0....在柴达木盆地北缘中段的锡铁山地区,夹有榴辉岩或退变榴辉岩透镜体的2个副片麻岩样品的锆石被用于SHRIMP U pb测定。2个片麻岩样品具有类似的特征,主要由石榴子石、夕线石、长石、黑云母和石英组成,这些矿物组合形成的变质条件, 0.6～0.9GPa和710～820℃,显示两处片麻岩经历了中压麻粒岩相条件的变质作用。锆石的SHRIMP U-Pb测定显示,2个样品获得近一致的早古生代变质年龄(分别为437Ma±6Ma和441Ma±15Ma),代表早古生代的高温变质作用时代。样品XTS-1还得890Ma±14Ma的年龄,所测定的锆石具有明显的变质作用成因特征,代表了新元古代早期的变质事件,反映了这些副片麻在早古生代造山旋回之前可能还经历了晋宁期的变质作用。展开更多
基金funded by the National Natural Science Foundation of China(grant No.40399143)the National 973 Project of the Chinese Ministry of Science and Technology(grant No.2003CB716502)the Programme of Excellent Youth Scientists of the Ministry of Land and Resources of China.
文摘Laser Raman spectroscopy and cathodoluminescence （CL） images show that most zircon crystals separated from paragneiss in the main drill hole of the Chinese Continental Scientific Drilling Project （CCSD-MH） at Maobei, southwestern Sulu terrane, contain low-pressure mineral-bearing detrital cores, coesite-bearing mantles and quartz-bearing or mineral inclusion-free rims. SHRIMP U-Pb dating on these zoned zircons yield three discrete and meaningful age groups. The detrital cores yield a large age span from 659 to 313 Ma, indicating the protolith age for the analyzed paragnelss is Paleozoic rather than Proterozoic. The coesite-bearing mantles yield a weighted mean age of 228 ± 5 Ma for the UHP event. The quartz-bearing outmost rims yield a weighted mean age of 213 ± 6 Ma for the retrogressive event related to the regional amphibolite facies metamorphism in the Sulu UHP terrane. Combined with previous SHRIMP U-Pb dating results from orthogneiss in CCSD-MH, it is suggested that both Neoproterozoic granitic protolith and Paleozoic sedimentary rocks were subducted to mantle depths in the Late Triassic. About 15 million years later, the Sulu UHP metamorphic rocks were exhumed to mid-crustal levels and overprinted by an amphibolite-facies retrogressive metamorphism. The exhumation rate deduced from the SHRIMP data and metamorphic P-T conditions is about 6.7 km/Ma. Such a fast exhumation suggests that the Sulu UHP paragnelss and orthogneiss returned towards the surface as a dominant part of a buoyant sliver, caused as a consequence of slab breakoff.
基金funded by the National Science Foundation of China (No. 41572051)the China Geological Survey (No. DD20160022-01)project from Institute of Geology, Chinese Academy of Geological Sciences (J1518)
文摘The poly-phase orogeny information included in one orogenic belt is the key for studying the regional tectonic evolution at different time period.It also has important significance of understanding the rock association and
文摘The petrographic and structural study of Gbowé (Grand-Béréby) formations located in the SASCA domain (South-West of Côte d’Ivoire) revealed migmatitic paragneisses. For an in-depth understanding of the petrographic, structural and metamorphic characteristics, six (6) thin sections were made from these paragneisses. These gneisses are characterized by paleosomes and neosomes (leucosome and melanosome), consisting of quartz, garnet, plagioclase, biotite, cordierite, sillimanite, myrmekite and microcline. The mineralogical assemblage thus described indicates a retrograde metamorphism (transition from granulitic facies to amphibolitic facies). The structural and microstructural study identified two types of deformation (ductile and brittle). The ductile deformation is characterized by phases D1 (NE-SW flattening) and D2 (NW-SE flattening), materialized by foliations (N140˚, N050˚), folds (asymmetrical folds, similar folds, concentric folds, ptymatic folds) and boudins. Fracture schistosity and fold fracture schistosity are characteristic of the brittle deformation (phase D3). The microstructural study coupled with the metamorphic study shows that the deformations had an impact on the texture of the minerals (recrystallization and mineral reactions). It also allowed giving the paragenesis of phases D1 and D2. The D1 phase is characterized by garnet1, biotite1, quartz1, sillimanite1 and cordierite1 and the D2 phase is characterized by garnet1, quartz2, sillimanite2, biotite2, garnet2 and orthose2. These parageneses thus highlighted bear witness to a polydeformation and polymorphism that affects the study area.
文摘在柴达木盆地北缘中段的锡铁山地区,夹有榴辉岩或退变榴辉岩透镜体的2个副片麻岩样品的锆石被用于SHRIMP U pb测定。2个片麻岩样品具有类似的特征,主要由石榴子石、夕线石、长石、黑云母和石英组成,这些矿物组合形成的变质条件, 0.6～0.9GPa和710～820℃,显示两处片麻岩经历了中压麻粒岩相条件的变质作用。锆石的SHRIMP U-Pb测定显示,2个样品获得近一致的早古生代变质年龄(分别为437Ma±6Ma和441Ma±15Ma),代表早古生代的高温变质作用时代。样品XTS-1还得890Ma±14Ma的年龄,所测定的锆石具有明显的变质作用成因特征,代表了新元古代早期的变质事件,反映了这些副片麻在早古生代造山旋回之前可能还经历了晋宁期的变质作用。
